Merge commit 'v2.6.37-rc1' into kbuild/kbuild

39 files changed, 2607 insertions, 2195 deletions

diff --git a/fs/nilfs2/Makefile b/fs/nilfs2/Makefile
index df3e62c..85c9873 100644
--- a/fs/nilfs2/Makefile
+++ b/fs/nilfs2/Makefile
@@ -2,4 +2,4 @@ obj-$(CONFIG_NILFS2_FS) += nilfs2.o
 nilfs2-y := inode.o file.o dir.o super.o namei.o page.o mdt.o \
 	btnode.o bmap.o btree.o direct.o dat.o recovery.o \
 	the_nilfs.o segbuf.o segment.o cpfile.o sufile.o \
-	ifile.o alloc.o gcinode.o ioctl.o gcdat.o
+	ifile.o alloc.o gcinode.o ioctl.o
diff --git a/fs/nilfs2/bmap.c b/fs/nilfs2/bmap.c
index effdbdb..8b782b0 100644
--- a/fs/nilfs2/bmap.c
+++ b/fs/nilfs2/bmap.c
@@ -26,6 +26,8 @@
 #include "nilfs.h"
 #include "bmap.h"
 #include "sb.h"
+#include "btree.h"
+#include "direct.h"
 #include "btnode.h"
 #include "mdt.h"
 #include "dat.h"
@@ -531,18 +533,20 @@ void nilfs_bmap_init_gc(struct nilfs_bmap *bmap)
 	nilfs_btree_init_gc(bmap);
 }
 
-void nilfs_bmap_init_gcdat(struct nilfs_bmap *gcbmap, struct nilfs_bmap *bmap)
+void nilfs_bmap_save(const struct nilfs_bmap *bmap,
+		     struct nilfs_bmap_store *store)
 {
-	memcpy(gcbmap, bmap, sizeof(union nilfs_bmap_union));
-	init_rwsem(&gcbmap->b_sem);
-	lockdep_set_class(&bmap->b_sem, &nilfs_bmap_dat_lock_key);
-	gcbmap->b_inode = &NILFS_BMAP_I(gcbmap)->vfs_inode;
+	memcpy(store->data, bmap->b_u.u_data, sizeof(store->data));
+	store->last_allocated_key = bmap->b_last_allocated_key;
+	store->last_allocated_ptr = bmap->b_last_allocated_ptr;
+	store->state = bmap->b_state;
 }
 
-void nilfs_bmap_commit_gcdat(struct nilfs_bmap *gcbmap, struct nilfs_bmap *bmap)
+void nilfs_bmap_restore(struct nilfs_bmap *bmap,
+			const struct nilfs_bmap_store *store)
 {
-	memcpy(bmap, gcbmap, sizeof(union nilfs_bmap_union));
-	init_rwsem(&bmap->b_sem);
-	lockdep_set_class(&bmap->b_sem, &nilfs_bmap_dat_lock_key);
-	bmap->b_inode = &NILFS_BMAP_I(bmap)->vfs_inode;
+	memcpy(bmap->b_u.u_data, store->data, sizeof(store->data));
+	bmap->b_last_allocated_key = store->last_allocated_key;
+	bmap->b_last_allocated_ptr = store->last_allocated_ptr;
+	bmap->b_state = store->state;
 }
diff --git a/fs/nilfs2/bmap.h b/fs/nilfs2/bmap.h
index 9980d7d..bde1c0a 100644
--- a/fs/nilfs2/bmap.h
+++ b/fs/nilfs2/bmap.h
@@ -32,11 +32,6 @@
 
 #define NILFS_BMAP_INVALID_PTR	0
 
-#define nilfs_bmap_dkey_to_key(dkey)	le64_to_cpu(dkey)
-#define nilfs_bmap_key_to_dkey(key)	cpu_to_le64(key)
-#define nilfs_bmap_dptr_to_ptr(dptr)	le64_to_cpu(dptr)
-#define nilfs_bmap_ptr_to_dptr(ptr)	cpu_to_le64(ptr)
-
 #define nilfs_bmap_keydiff_abs(diff)	((diff) < 0 ? -(diff) : (diff))
 
 
@@ -71,7 +66,7 @@ struct nilfs_bmap_operations {
 	int (*bop_delete)(struct nilfs_bmap *, __u64);
 	void (*bop_clear)(struct nilfs_bmap *);
 
-	int (*bop_propagate)(const struct nilfs_bmap *, struct buffer_head *);
+	int (*bop_propagate)(struct nilfs_bmap *, struct buffer_head *);
 	void (*bop_lookup_dirty_buffers)(struct nilfs_bmap *,
 					 struct list_head *);
 
@@ -110,6 +105,7 @@ static inline int nilfs_bmap_is_new_ptr(unsigned long ptr)
  * @b_last_allocated_ptr: last allocated ptr for data block
  * @b_ptr_type: pointer type
  * @b_state: state
+ * @b_nchildren_per_block: maximum number of child nodes for non-root nodes
  */
 struct nilfs_bmap {
 	union {
@@ -123,6 +119,7 @@ struct nilfs_bmap {
 	__u64 b_last_allocated_ptr;
 	int b_ptr_type;
 	int b_state;
+	__u16 b_nchildren_per_block;
 };
 
 /* pointer type */
@@ -138,6 +135,12 @@ struct nilfs_bmap {
 /* state */
 #define NILFS_BMAP_DIRTY	0x00000001
 
+struct nilfs_bmap_store {
+	__le64 data[NILFS_BMAP_SIZE / sizeof(__le64)];
+	__u64 last_allocated_key;
+	__u64 last_allocated_ptr;
+	int state;
+};
 
 int nilfs_bmap_test_and_clear_dirty(struct nilfs_bmap *);
 int nilfs_bmap_read(struct nilfs_bmap *, struct nilfs_inode *);
@@ -156,9 +159,9 @@ int nilfs_bmap_lookup_at_level(struct nilfs_bmap *, __u64, int, __u64 *);
 int nilfs_bmap_mark(struct nilfs_bmap *, __u64, int);
 
 void nilfs_bmap_init_gc(struct nilfs_bmap *);
-void nilfs_bmap_init_gcdat(struct nilfs_bmap *, struct nilfs_bmap *);
-void nilfs_bmap_commit_gcdat(struct nilfs_bmap *, struct nilfs_bmap *);
 
+void nilfs_bmap_save(const struct nilfs_bmap *, struct nilfs_bmap_store *);
+void nilfs_bmap_restore(struct nilfs_bmap *, const struct nilfs_bmap_store *);
 
 static inline int nilfs_bmap_lookup(struct nilfs_bmap *bmap, __u64 key,
 				    __u64 *ptr)
@@ -224,6 +227,13 @@ static inline void nilfs_bmap_abort_end_ptr(struct nilfs_bmap *bmap,
 		nilfs_dat_abort_end(dat, &req->bpr_req);
 }
 
+static inline void nilfs_bmap_set_target_v(struct nilfs_bmap *bmap, __u64 key,
+					   __u64 ptr)
+{
+	bmap->b_last_allocated_key = key;
+	bmap->b_last_allocated_ptr = ptr;
+}
+
 __u64 nilfs_bmap_data_get_key(const struct nilfs_bmap *,
 			      const struct buffer_head *);
 
diff --git a/fs/nilfs2/bmap_union.h b/fs/nilfs2/bmap_union.h
deleted file mode 100644
index d41509b..0000000
--- a/fs/nilfs2/bmap_union.h
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * bmap_union.h - NILFS block mapping.
- *
- * Copyright (C) 2006-2008 Nippon Telegraph and Telephone Corporation.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- *
- * Written by Koji Sato <koji@osrg.net>.
- */
-
-#ifndef _NILFS_BMAP_UNION_H
-#define _NILFS_BMAP_UNION_H
-
-#include "bmap.h"
-#include "direct.h"
-#include "btree.h"
-
-/**
- * nilfs_bmap_union -
- * @bi_bmap: bmap structure
- * @bi_btree: direct map structure
- * @bi_direct: B-tree structure
- */
-union nilfs_bmap_union {
-	struct nilfs_bmap bi_bmap;
-	struct nilfs_direct bi_direct;
-	struct nilfs_btree bi_btree;
-};
-
-#endif	/* _NILFS_BMAP_UNION_H */
diff --git a/fs/nilfs2/btnode.c b/fs/nilfs2/btnode.c
index 447ce47..5115814 100644
--- a/fs/nilfs2/btnode.c
+++ b/fs/nilfs2/btnode.c
@@ -37,15 +37,7 @@
 
 void nilfs_btnode_cache_init_once(struct address_space *btnc)
 {
-	memset(btnc, 0, sizeof(*btnc));
-	INIT_RADIX_TREE(&btnc->page_tree, GFP_ATOMIC);
-	spin_lock_init(&btnc->tree_lock);
-	INIT_LIST_HEAD(&btnc->private_list);
-	spin_lock_init(&btnc->private_lock);
-
-	spin_lock_init(&btnc->i_mmap_lock);
-	INIT_RAW_PRIO_TREE_ROOT(&btnc->i_mmap);
-	INIT_LIST_HEAD(&btnc->i_mmap_nonlinear);
+	nilfs_mapping_init_once(btnc);
 }
 
 static const struct address_space_operations def_btnode_aops = {
@@ -55,12 +47,7 @@ static const struct address_space_operations def_btnode_aops = {
 void nilfs_btnode_cache_init(struct address_space *btnc,
 			     struct backing_dev_info *bdi)
 {
-	btnc->host = NULL;  /* can safely set to host inode ? */
-	btnc->flags = 0;
-	mapping_set_gfp_mask(btnc, GFP_NOFS);
-	btnc->assoc_mapping = NULL;
-	btnc->backing_dev_info = bdi;
-	btnc->a_ops = &def_btnode_aops;
+	nilfs_mapping_init(btnc, bdi, &def_btnode_aops);
 }
 
 void nilfs_btnode_cache_clear(struct address_space *btnc)
@@ -96,10 +83,12 @@ nilfs_btnode_create_block(struct address_space *btnc, __u64 blocknr)
 }
 
 int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
-			      sector_t pblocknr, struct buffer_head **pbh)
+			      sector_t pblocknr, int mode,
+			      struct buffer_head **pbh, sector_t *submit_ptr)
 {
 	struct buffer_head *bh;
 	struct inode *inode = NILFS_BTNC_I(btnc);
+	struct page *page;
 	int err;
 
 	bh = nilfs_grab_buffer(inode, btnc, blocknr, 1 << BH_NILFS_Node);
@@ -107,6 +96,7 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
 		return -ENOMEM;
 
 	err = -EEXIST; /* internal code */
+	page = bh->b_page;
 
 	if (buffer_uptodate(bh) || buffer_dirty(bh))
 		goto found;
@@ -125,7 +115,16 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
 			}
 		}
 	}
-	lock_buffer(bh);
+
+	if (mode == READA) {
+		if (pblocknr != *submit_ptr + 1 || !trylock_buffer(bh)) {
+			err = -EBUSY; /* internal code */
+			brelse(bh);
+			goto out_locked;
+		}
+	} else { /* mode == READ */
+		lock_buffer(bh);
+	}
 	if (buffer_uptodate(bh)) {
 		unlock_buffer(bh);
 		err = -EEXIST; /* internal code */
@@ -136,15 +135,16 @@ int nilfs_btnode_submit_block(struct address_space *btnc, __u64 blocknr,
 	bh->b_blocknr = pblocknr; /* set block address for read */
 	bh->b_end_io = end_buffer_read_sync;
 	get_bh(bh);
-	submit_bh(READ, bh);
+	submit_bh(mode, bh);
 	bh->b_blocknr = blocknr; /* set back to the given block address */
+	*submit_ptr = pblocknr;
 	err = 0;
 found:
 	*pbh = bh;
 
 out_locked:
-	unlock_page(bh->b_page);
-	page_cache_release(bh->b_page);
+	unlock_page(page);
+	page_cache_release(page);
 	return err;
 }
 
diff --git a/fs/nilfs2/btnode.h b/fs/nilfs2/btnode.h
index 07da83f..7903749 100644
--- a/fs/nilfs2/btnode.h
+++ b/fs/nilfs2/btnode.h
@@ -42,8 +42,8 @@ void nilfs_btnode_cache_init(struct address_space *, struct backing_dev_info *);
 void nilfs_btnode_cache_clear(struct address_space *);
 struct buffer_head *nilfs_btnode_create_block(struct address_space *btnc,
 					      __u64 blocknr);
-int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t,
-			      struct buffer_head **);
+int nilfs_btnode_submit_block(struct address_space *, __u64, sector_t, int,
+			      struct buffer_head **, sector_t *);
 void nilfs_btnode_delete(struct buffer_head *);
 int nilfs_btnode_prepare_change_key(struct address_space *,
 				    struct nilfs_btnode_chkey_ctxt *);
diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index b27a342..300c2bc 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -66,30 +66,10 @@ static void nilfs_btree_free_path(struct nilfs_btree_path *path)
 /*
  * B-tree node operations
  */
-static int nilfs_btree_get_block(const struct nilfs_btree *btree, __u64 ptr,
-				 struct buffer_head **bhp)
-{
-	struct address_space *btnc =
-		&NILFS_BMAP_I((struct nilfs_bmap *)btree)->i_btnode_cache;
-	int err;
-
-	err = nilfs_btnode_submit_block(btnc, ptr, 0, bhp);
-	if (err)
-		return err == -EEXIST ? 0 : err;
-
-	wait_on_buffer(*bhp);
-	if (!buffer_uptodate(*bhp)) {
-		brelse(*bhp);
-		return -EIO;
-	}
-	return 0;
-}
-
-static int nilfs_btree_get_new_block(const struct nilfs_btree *btree,
+static int nilfs_btree_get_new_block(const struct nilfs_bmap *btree,
 				     __u64 ptr, struct buffer_head **bhp)
 {
-	struct address_space *btnc =
-		&NILFS_BMAP_I((struct nilfs_bmap *)btree)->i_btnode_cache;
+	struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
 	struct buffer_head *bh;
 
 	bh = nilfs_btnode_create_block(btnc, ptr);
@@ -101,71 +81,55 @@ static int nilfs_btree_get_new_block(const struct nilfs_btree *btree,
 	return 0;
 }
 
-static inline int
-nilfs_btree_node_get_flags(const struct nilfs_btree_node *node)
+static int nilfs_btree_node_get_flags(const struct nilfs_btree_node *node)
 {
 	return node->bn_flags;
 }
 
-static inline void
+static void
 nilfs_btree_node_set_flags(struct nilfs_btree_node *node, int flags)
 {
 	node->bn_flags = flags;
 }
 
-static inline int nilfs_btree_node_root(const struct nilfs_btree_node *node)
+static int nilfs_btree_node_root(const struct nilfs_btree_node *node)
 {
 	return nilfs_btree_node_get_flags(node) & NILFS_BTREE_NODE_ROOT;
 }
 
-static inline int
-nilfs_btree_node_get_level(const struct nilfs_btree_node *node)
+static int nilfs_btree_node_get_level(const struct nilfs_btree_node *node)
 {
 	return node->bn_level;
 }
 
-static inline void
+static void
 nilfs_btree_node_set_level(struct nilfs_btree_node *node, int level)
 {
 	node->bn_level = level;
 }
 
-static inline int
-nilfs_btree_node_get_nchildren(const struct nilfs_btree_node *node)
+static int nilfs_btree_node_get_nchildren(const struct nilfs_btree_node *node)
 {
 	return le16_to_cpu(node->bn_nchildren);
 }
 
-static inline void
+static void
 nilfs_btree_node_set_nchildren(struct nilfs_btree_node *node, int nchildren)
 {
 	node->bn_nchildren = cpu_to_le16(nchildren);
 }
 
-static inline int nilfs_btree_node_size(const struct nilfs_btree *btree)
+static int nilfs_btree_node_size(const struct nilfs_bmap *btree)
 {
-	return 1 << btree->bt_bmap.b_inode->i_blkbits;
+	return 1 << btree->b_inode->i_blkbits;
 }
 
-static inline int
-nilfs_btree_node_nchildren_min(const struct nilfs_btree_node *node,
-			       const struct nilfs_btree *btree)
+static int nilfs_btree_nchildren_per_block(const struct nilfs_bmap *btree)
 {
-	return nilfs_btree_node_root(node) ?
-		NILFS_BTREE_ROOT_NCHILDREN_MIN :
-		NILFS_BTREE_NODE_NCHILDREN_MIN(nilfs_btree_node_size(btree));
+	return btree->b_nchildren_per_block;
 }
 
-static inline int
-nilfs_btree_node_nchildren_max(const struct nilfs_btree_node *node,
-			       const struct nilfs_btree *btree)
-{
-	return nilfs_btree_node_root(node) ?
-		NILFS_BTREE_ROOT_NCHILDREN_MAX :
-		NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(btree));
-}
-
-static inline __le64 *
+static __le64 *
 nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)
 {
 	return (__le64 *)((char *)(node + 1) +
@@ -173,45 +137,40 @@ nilfs_btree_node_dkeys(const struct nilfs_btree_node *node)
 			   0 : NILFS_BTREE_NODE_EXTRA_PAD_SIZE));
 }
 
-static inline __le64 *
-nilfs_btree_node_dptrs(const struct nilfs_btree_node *node,
-		       const struct nilfs_btree *btree)
+static __le64 *
+nilfs_btree_node_dptrs(const struct nilfs_btree_node *node, int ncmax)
 {
-	return (__le64 *)(nilfs_btree_node_dkeys(node) +
-			  nilfs_btree_node_nchildren_max(node, btree));
+	return (__le64 *)(nilfs_btree_node_dkeys(node) + ncmax);
 }
 
-static inline __u64
+static __u64
 nilfs_btree_node_get_key(const struct nilfs_btree_node *node, int index)
 {
-	return nilfs_bmap_dkey_to_key(*(nilfs_btree_node_dkeys(node) + index));
+	return le64_to_cpu(*(nilfs_btree_node_dkeys(node) + index));
 }
 
-static inline void
+static void
 nilfs_btree_node_set_key(struct nilfs_btree_node *node, int index, __u64 key)
 {
-	*(nilfs_btree_node_dkeys(node) + index) = nilfs_bmap_key_to_dkey(key);
+	*(nilfs_btree_node_dkeys(node) + index) = cpu_to_le64(key);
 }
 
-static inline __u64
-nilfs_btree_node_get_ptr(const struct nilfs_btree *btree,
-			 const struct nilfs_btree_node *node, int index)
+static __u64
+nilfs_btree_node_get_ptr(const struct nilfs_btree_node *node, int index,
+			 int ncmax)
 {
-	return nilfs_bmap_dptr_to_ptr(*(nilfs_btree_node_dptrs(node, btree) +
-					index));
+	return le64_to_cpu(*(nilfs_btree_node_dptrs(node, ncmax) + index));
 }
 
-static inline void
-nilfs_btree_node_set_ptr(struct nilfs_btree *btree,
-			 struct nilfs_btree_node *node, int index, __u64 ptr)
+static void
+nilfs_btree_node_set_ptr(struct nilfs_btree_node *node, int index, __u64 ptr,
+			 int ncmax)
 {
-	*(nilfs_btree_node_dptrs(node, btree) + index) =
-		nilfs_bmap_ptr_to_dptr(ptr);
+	*(nilfs_btree_node_dptrs(node, ncmax) + index) = cpu_to_le64(ptr);
 }
 
-static void nilfs_btree_node_init(struct nilfs_btree *btree,
-				  struct nilfs_btree_node *node,
-				  int flags, int level, int nchildren,
+static void nilfs_btree_node_init(struct nilfs_btree_node *node, int flags,
+				  int level, int nchildren, int ncmax,
 				  const __u64 *keys, const __u64 *ptrs)
 {
 	__le64 *dkeys;
@@ -223,29 +182,28 @@ static void nilfs_btree_node_init(struct nilfs_btree *btree,
 	nilfs_btree_node_set_nchildren(node, nchildren);
 
 	dkeys = nilfs_btree_node_dkeys(node);
-	dptrs = nilfs_btree_node_dptrs(node, btree);
+	dptrs = nilfs_btree_node_dptrs(node, ncmax);
 	for (i = 0; i < nchildren; i++) {
-		dkeys[i] = nilfs_bmap_key_to_dkey(keys[i]);
-		dptrs[i] = nilfs_bmap_ptr_to_dptr(ptrs[i]);
+		dkeys[i] = cpu_to_le64(keys[i]);
+		dptrs[i] = cpu_to_le64(ptrs[i]);
 	}
 }
 
 /* Assume the buffer heads corresponding to left and right are locked. */
-static void nilfs_btree_node_move_left(struct nilfs_btree *btree,
-				       struct nilfs_btree_node *left,
+static void nilfs_btree_node_move_left(struct nilfs_btree_node *left,
 				       struct nilfs_btree_node *right,
-				       int n)
+				       int n, int lncmax, int rncmax)
 {
 	__le64 *ldkeys, *rdkeys;
 	__le64 *ldptrs, *rdptrs;
 	int lnchildren, rnchildren;
 
 	ldkeys = nilfs_btree_node_dkeys(left);
-	ldptrs = nilfs_btree_node_dptrs(left, btree);
+	ldptrs = nilfs_btree_node_dptrs(left, lncmax);
 	lnchildren = nilfs_btree_node_get_nchildren(left);
 
 	rdkeys = nilfs_btree_node_dkeys(right);
-	rdptrs = nilfs_btree_node_dptrs(right, btree);
+	rdptrs = nilfs_btree_node_dptrs(right, rncmax);
 	rnchildren = nilfs_btree_node_get_nchildren(right);
 
 	memcpy(ldkeys + lnchildren, rdkeys, n * sizeof(*rdkeys));
@@ -260,21 +218,20 @@ static void nilfs_btree_node_move_left(struct nilfs_btree *btree,
 }
 
 /* Assume that the buffer heads corresponding to left and right are locked. */
-static void nilfs_btree_node_move_right(struct nilfs_btree *btree,
-					struct nilfs_btree_node *left,
+static void nilfs_btree_node_move_right(struct nilfs_btree_node *left,
 					struct nilfs_btree_node *right,
-					int n)
+					int n, int lncmax, int rncmax)
 {
 	__le64 *ldkeys, *rdkeys;
 	__le64 *ldptrs, *rdptrs;
 	int lnchildren, rnchildren;
 
 	ldkeys = nilfs_btree_node_dkeys(left);
-	ldptrs = nilfs_btree_node_dptrs(left, btree);
+	ldptrs = nilfs_btree_node_dptrs(left, lncmax);
 	lnchildren = nilfs_btree_node_get_nchildren(left);
 
 	rdkeys = nilfs_btree_node_dkeys(right);
-	rdptrs = nilfs_btree_node_dptrs(right, btree);
+	rdptrs = nilfs_btree_node_dptrs(right, rncmax);
 	rnchildren = nilfs_btree_node_get_nchildren(right);
 
 	memmove(rdkeys + n, rdkeys, rnchildren * sizeof(*rdkeys));
@@ -289,16 +246,15 @@ static void nilfs_btree_node_move_right(struct nilfs_btree *btree,
 }
 
 /* Assume that the buffer head corresponding to node is locked. */
-static void nilfs_btree_node_insert(struct nilfs_btree *btree,
-				    struct nilfs_btree_node *node,
-				    __u64 key, __u64 ptr, int index)
+static void nilfs_btree_node_insert(struct nilfs_btree_node *node, int index,
+				    __u64 key, __u64 ptr, int ncmax)
 {
 	__le64 *dkeys;
 	__le64 *dptrs;
 	int nchildren;
 
 	dkeys = nilfs_btree_node_dkeys(node);
-	dptrs = nilfs_btree_node_dptrs(node, btree);
+	dptrs = nilfs_btree_node_dptrs(node, ncmax);
 	nchildren = nilfs_btree_node_get_nchildren(node);
 	if (index < nchildren) {
 		memmove(dkeys + index + 1, dkeys + index,
@@ -306,16 +262,15 @@ static void nilfs_btree_node_insert(struct nilfs_btree *btree,
 		memmove(dptrs + index + 1, dptrs + index,
 			(nchildren - index) * sizeof(*dptrs));
 	}
-	dkeys[index] = nilfs_bmap_key_to_dkey(key);
-	dptrs[index] = nilfs_bmap_ptr_to_dptr(ptr);
+	dkeys[index] = cpu_to_le64(key);
+	dptrs[index] = cpu_to_le64(ptr);
 	nchildren++;
 	nilfs_btree_node_set_nchildren(node, nchildren);
 }
 
 /* Assume that the buffer head corresponding to node is locked. */
-static void nilfs_btree_node_delete(struct nilfs_btree *btree,
-				    struct nilfs_btree_node *node,
-				    __u64 *keyp, __u64 *ptrp, int index)
+static void nilfs_btree_node_delete(struct nilfs_btree_node *node, int index,
+				    __u64 *keyp, __u64 *ptrp, int ncmax)
 {
 	__u64 key;
 	__u64 ptr;
@@ -324,9 +279,9 @@ static void nilfs_btree_node_delete(struct nilfs_btree *btree,
 	int nchildren;
 
 	dkeys = nilfs_btree_node_dkeys(node);
-	dptrs = nilfs_btree_node_dptrs(node, btree);
-	key = nilfs_bmap_dkey_to_key(dkeys[index]);
-	ptr = nilfs_bmap_dptr_to_ptr(dptrs[index]);
+	dptrs = nilfs_btree_node_dptrs(node, ncmax);
+	key = le64_to_cpu(dkeys[index]);
+	ptr = le64_to_cpu(dptrs[index]);
 	nchildren = nilfs_btree_node_get_nchildren(node);
 	if (keyp != NULL)
 		*keyp = key;
@@ -382,40 +337,92 @@ static int nilfs_btree_node_lookup(const struct nilfs_btree_node *node,
 	return s == 0;
 }
 
-static inline struct nilfs_btree_node *
-nilfs_btree_get_root(const struct nilfs_btree *btree)
+/**
+ * nilfs_btree_node_broken - verify consistency of btree node
+ * @node: btree node block to be examined
+ * @size: node size (in bytes)
+ * @blocknr: block number
+ *
+ * Return Value: If node is broken, 1 is returned. Otherwise, 0 is returned.
+ */
+static int nilfs_btree_node_broken(const struct nilfs_btree_node *node,
+				   size_t size, sector_t blocknr)
 {
-	return (struct nilfs_btree_node *)btree->bt_bmap.b_u.u_data;
+	int level, flags, nchildren;
+	int ret = 0;
+
+	level = nilfs_btree_node_get_level(node);
+	flags = nilfs_btree_node_get_flags(node);
+	nchildren = nilfs_btree_node_get_nchildren(node);
+
+	if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
+		     level >= NILFS_BTREE_LEVEL_MAX ||
+		     (flags & NILFS_BTREE_NODE_ROOT) ||
+		     nchildren < 0 ||
+		     nchildren > NILFS_BTREE_NODE_NCHILDREN_MAX(size))) {
+		printk(KERN_CRIT "NILFS: bad btree node (blocknr=%llu): "
+		       "level = %d, flags = 0x%x, nchildren = %d\n",
+		       (unsigned long long)blocknr, level, flags, nchildren);
+		ret = 1;
+	}
+	return ret;
 }
 
-static inline struct nilfs_btree_node *
+int nilfs_btree_broken_node_block(struct buffer_head *bh)
+{
+	int ret;
+
+	if (buffer_nilfs_checked(bh))
+		return 0;
+
+	ret = nilfs_btree_node_broken((struct nilfs_btree_node *)bh->b_data,
+				       bh->b_size, bh->b_blocknr);
+	if (likely(!ret))
+		set_buffer_nilfs_checked(bh);
+	return ret;
+}
+
+static struct nilfs_btree_node *
+nilfs_btree_get_root(const struct nilfs_bmap *btree)
+{
+	return (struct nilfs_btree_node *)btree->b_u.u_data;
+}
+
+static struct nilfs_btree_node *
 nilfs_btree_get_nonroot_node(const struct nilfs_btree_path *path, int level)
 {
 	return (struct nilfs_btree_node *)path[level].bp_bh->b_data;
 }
 
-static inline struct nilfs_btree_node *
+static struct nilfs_btree_node *
 nilfs_btree_get_sib_node(const struct nilfs_btree_path *path, int level)
 {
 	return (struct nilfs_btree_node *)path[level].bp_sib_bh->b_data;
 }
 
-static inline int nilfs_btree_height(const struct nilfs_btree *btree)
+static int nilfs_btree_height(const struct nilfs_bmap *btree)
 {
 	return nilfs_btree_node_get_level(nilfs_btree_get_root(btree)) + 1;
 }
 
-static inline struct nilfs_btree_node *
-nilfs_btree_get_node(const struct nilfs_btree *btree,
+static struct nilfs_btree_node *
+nilfs_btree_get_node(const struct nilfs_bmap *btree,
 		     const struct nilfs_btree_path *path,
-		     int level)
+		     int level, int *ncmaxp)
 {
-	return (level == nilfs_btree_height(btree) - 1) ?
-		nilfs_btree_get_root(btree) :
-		nilfs_btree_get_nonroot_node(path, level);
+	struct nilfs_btree_node *node;
+
+	if (level == nilfs_btree_height(btree) - 1) {
+		node = nilfs_btree_get_root(btree);
+		*ncmaxp = NILFS_BTREE_ROOT_NCHILDREN_MAX;
+	} else {
+		node = nilfs_btree_get_nonroot_node(path, level);
+		*ncmaxp = nilfs_btree_nchildren_per_block(btree);
+	}
+	return node;
 }
 
-static inline int
+static int
 nilfs_btree_bad_node(struct nilfs_btree_node *node, int level)
 {
 	if (unlikely(nilfs_btree_node_get_level(node) != level)) {
@@ -427,13 +434,83 @@ nilfs_btree_bad_node(struct nilfs_btree_node *node, int level)
 	return 0;
 }
 
-static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
+struct nilfs_btree_readahead_info {
+	struct nilfs_btree_node *node;	/* parent node */
+	int max_ra_blocks;		/* max nof blocks to read ahead */
+	int index;			/* current index on the parent node */
+	int ncmax;			/* nof children in the parent node */
+};
+
+static int __nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
+				   struct buffer_head **bhp,
+				   const struct nilfs_btree_readahead_info *ra)
+{
+	struct address_space *btnc = &NILFS_BMAP_I(btree)->i_btnode_cache;
+	struct buffer_head *bh, *ra_bh;
+	sector_t submit_ptr = 0;
+	int ret;
+
+	ret = nilfs_btnode_submit_block(btnc, ptr, 0, READ, &bh, &submit_ptr);
+	if (ret) {
+		if (ret != -EEXIST)
+			return ret;
+		goto out_check;
+	}
+
+	if (ra) {
+		int i, n;
+		__u64 ptr2;
+
+		/* read ahead sibling nodes */
+		for (n = ra->max_ra_blocks, i = ra->index + 1;
+		     n > 0 && i < ra->ncmax; n--, i++) {
+			ptr2 = nilfs_btree_node_get_ptr(ra->node, i, ra->ncmax);
+
+			ret = nilfs_btnode_submit_block(btnc, ptr2, 0, READA,
+							&ra_bh, &submit_ptr);
+			if (likely(!ret || ret == -EEXIST))
+				brelse(ra_bh);
+			else if (ret != -EBUSY)
+				break;
+			if (!buffer_locked(bh))
+				goto out_no_wait;
+		}
+	}
+
+	wait_on_buffer(bh);
+
+ out_no_wait:
+	if (!buffer_uptodate(bh)) {
+		brelse(bh);
+		return -EIO;
+	}
+
+ out_check:
+	if (nilfs_btree_broken_node_block(bh)) {
+		clear_buffer_uptodate(bh);
+		brelse(bh);
+		return -EINVAL;
+	}
+
+	*bhp = bh;
+	return 0;
+}
+
+static int nilfs_btree_get_block(const struct nilfs_bmap *btree, __u64 ptr,
+				   struct buffer_head **bhp)
+{
+	return __nilfs_btree_get_block(btree, ptr, bhp, NULL);
+}
+
+static int nilfs_btree_do_lookup(const struct nilfs_bmap *btree,
 				 struct nilfs_btree_path *path,
-				 __u64 key, __u64 *ptrp, int minlevel)
+				 __u64 key, __u64 *ptrp, int minlevel,
+				 int readahead)
 {
 	struct nilfs_btree_node *node;
+	struct nilfs_btree_readahead_info p, *ra;
 	__u64 ptr;
-	int level, index, found, ret;
+	int level, index, found, ncmax, ret;
 
 	node = nilfs_btree_get_root(btree);
 	level = nilfs_btree_node_get_level(node);
@@ -441,14 +518,27 @@ static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
 		return -ENOENT;
 
 	found = nilfs_btree_node_lookup(node, key, &index);
-	ptr = nilfs_btree_node_get_ptr(btree, node, index);
+	ptr = nilfs_btree_node_get_ptr(node, index,
+				       NILFS_BTREE_ROOT_NCHILDREN_MAX);
 	path[level].bp_bh = NULL;
 	path[level].bp_index = index;
 
-	for (level--; level >= minlevel; level--) {
-		ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);
+	ncmax = nilfs_btree_nchildren_per_block(btree);
+
+	while (--level >= minlevel) {
+		ra = NULL;
+		if (level == NILFS_BTREE_LEVEL_NODE_MIN && readahead) {
+			p.node = nilfs_btree_get_node(btree, path, level + 1,
+						      &p.ncmax);
+			p.index = index;
+			p.max_ra_blocks = 7;
+			ra = &p;
+		}
+		ret = __nilfs_btree_get_block(btree, ptr, &path[level].bp_bh,
+					      ra);
 		if (ret < 0)
 			return ret;
+
 		node = nilfs_btree_get_nonroot_node(path, level);
 		if (nilfs_btree_bad_node(node, level))
 			return -EINVAL;
@@ -456,9 +546,9 @@ static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
 			found = nilfs_btree_node_lookup(node, key, &index);
 		else
 			index = 0;
-		if (index < nilfs_btree_node_nchildren_max(node, btree))
-			ptr = nilfs_btree_node_get_ptr(btree, node, index);
-		else {
+		if (index < ncmax) {
+			ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
+		} else {
 			WARN_ON(found || level != NILFS_BTREE_LEVEL_NODE_MIN);
 			/* insert */
 			ptr = NILFS_BMAP_INVALID_PTR;
@@ -474,22 +564,24 @@ static int nilfs_btree_do_lookup(const struct nilfs_btree *btree,
 	return 0;
 }
 
-static int nilfs_btree_do_lookup_last(const struct nilfs_btree *btree,
+static int nilfs_btree_do_lookup_last(const struct nilfs_bmap *btree,
 				      struct nilfs_btree_path *path,
 				      __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node;
 	__u64 ptr;
-	int index, level, ret;
+	int index, level, ncmax, ret;
 
 	node = nilfs_btree_get_root(btree);
 	index = nilfs_btree_node_get_nchildren(node) - 1;
 	if (index < 0)
 		return -ENOENT;
 	level = nilfs_btree_node_get_level(node);
-	ptr = nilfs_btree_node_get_ptr(btree, node, index);
+	ptr = nilfs_btree_node_get_ptr(node, index,
+				       NILFS_BTREE_ROOT_NCHILDREN_MAX);
 	path[level].bp_bh = NULL;
 	path[level].bp_index = index;
+	ncmax = nilfs_btree_nchildren_per_block(btree);
 
 	for (level--; level > 0; level--) {
 		ret = nilfs_btree_get_block(btree, ptr, &path[level].bp_bh);
@@ -499,7 +591,7 @@ static int nilfs_btree_do_lookup_last(const struct nilfs_btree *btree,
 		if (nilfs_btree_bad_node(node, level))
 			return -EINVAL;
 		index = nilfs_btree_node_get_nchildren(node) - 1;
-		ptr = nilfs_btree_node_get_ptr(btree, node, index);
+		ptr = nilfs_btree_node_get_ptr(node, index, ncmax);
 		path[level].bp_index = index;
 	}
 
@@ -511,51 +603,45 @@ static int nilfs_btree_do_lookup_last(const struct nilfs_btree *btree,
 	return 0;
 }
 
-static int nilfs_btree_lookup(const struct nilfs_bmap *bmap,
+static int nilfs_btree_lookup(const struct nilfs_bmap *btree,
 			      __u64 key, int level, __u64 *ptrp)
 {
-	struct nilfs_btree *btree;
 	struct nilfs_btree_path *path;
-	__u64 ptr;
 	int ret;
 
-	btree = (struct nilfs_btree *)bmap;
 	path = nilfs_btree_alloc_path();
 	if (path == NULL)
 		return -ENOMEM;
 
-	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level);
-
-	if (ptrp != NULL)
-		*ptrp = ptr;
+	ret = nilfs_btree_do_lookup(btree, path, key, ptrp, level, 0);
 
 	nilfs_btree_free_path(path);
 
 	return ret;
 }
 
-static int nilfs_btree_lookup_contig(const struct nilfs_bmap *bmap,
+static int nilfs_btree_lookup_contig(const struct nilfs_bmap *btree,
 				     __u64 key, __u64 *ptrp, unsigned maxblocks)
 {
-	struct nilfs_btree *btree = (struct nilfs_btree *)bmap;
 	struct nilfs_btree_path *path;
 	struct nilfs_btree_node *node;
 	struct inode *dat = NULL;
 	__u64 ptr, ptr2;
 	sector_t blocknr;
 	int level = NILFS_BTREE_LEVEL_NODE_MIN;
-	int ret, cnt, index, maxlevel;
+	int ret, cnt, index, maxlevel, ncmax;
+	struct nilfs_btree_readahead_info p;
 
 	path = nilfs_btree_alloc_path();
 	if (path == NULL)
 		return -ENOMEM;
 
-	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level);
+	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level, 1);
 	if (ret < 0)
 		goto out;
 
-	if (NILFS_BMAP_USE_VBN(bmap)) {
-		dat = nilfs_bmap_get_dat(bmap);
+	if (NILFS_BMAP_USE_VBN(btree)) {
+		dat = nilfs_bmap_get_dat(btree);
 		ret = nilfs_dat_translate(dat, ptr, &blocknr);
 		if (ret < 0)
 			goto out;
@@ -566,14 +652,14 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *bmap,
 		goto end;
 
 	maxlevel = nilfs_btree_height(btree) - 1;
-	node = nilfs_btree_get_node(btree, path, level);
+	node = nilfs_btree_get_node(btree, path, level, &ncmax);
 	index = path[level].bp_index + 1;
 	for (;;) {
 		while (index < nilfs_btree_node_get_nchildren(node)) {
 			if (nilfs_btree_node_get_key(node, index) !=
 			    key + cnt)
 				goto end;
-			ptr2 = nilfs_btree_node_get_ptr(btree, node, index);
+			ptr2 = nilfs_btree_node_get_ptr(node, index, ncmax);
 			if (dat) {
 				ret = nilfs_dat_translate(dat, ptr2, &blocknr);
 				if (ret < 0)
@@ -589,20 +675,24 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *bmap,
 			break;
 
 		/* look-up right sibling node */
-		node = nilfs_btree_get_node(btree, path, level + 1);
-		index = path[level + 1].bp_index + 1;
-		if (index >= nilfs_btree_node_get_nchildren(node) ||
-		    nilfs_btree_node_get_key(node, index) != key + cnt)
+		p.node = nilfs_btree_get_node(btree, path, level + 1, &p.ncmax);
+		p.index = path[level + 1].bp_index + 1;
+		p.max_ra_blocks = 7;
+		if (p.index >= nilfs_btree_node_get_nchildren(p.node) ||
+		    nilfs_btree_node_get_key(p.node, p.index) != key + cnt)
 			break;
-		ptr2 = nilfs_btree_node_get_ptr(btree, node, index);
-		path[level + 1].bp_index = index;
+		ptr2 = nilfs_btree_node_get_ptr(p.node, p.index, p.ncmax);
+		path[level + 1].bp_index = p.index;
 
 		brelse(path[level].bp_bh);
 		path[level].bp_bh = NULL;
-		ret = nilfs_btree_get_block(btree, ptr2, &path[level].bp_bh);
+
+		ret = __nilfs_btree_get_block(btree, ptr2, &path[level].bp_bh,
+					      &p);
 		if (ret < 0)
 			goto out;
 		node = nilfs_btree_get_nonroot_node(path, level);
+		ncmax = nilfs_btree_nchildren_per_block(btree);
 		index = 0;
 		path[level].bp_index = index;
 	}
@@ -614,7 +704,7 @@ static int nilfs_btree_lookup_contig(const struct nilfs_bmap *bmap,
 	return ret;
 }
 
-static void nilfs_btree_promote_key(struct nilfs_btree *btree,
+static void nilfs_btree_promote_key(struct nilfs_bmap *btree,
 				    struct nilfs_btree_path *path,
 				    int level, __u64 key)
 {
@@ -636,16 +726,18 @@ static void nilfs_btree_promote_key(struct nilfs_btree *btree,
 	}
 }
 
-static void nilfs_btree_do_insert(struct nilfs_btree *btree,
+static void nilfs_btree_do_insert(struct nilfs_bmap *btree,
 				  struct nilfs_btree_path *path,
 				  int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node;
+	int ncblk;
 
 	if (level < nilfs_btree_height(btree) - 1) {
 		node = nilfs_btree_get_nonroot_node(path, level);
-		nilfs_btree_node_insert(btree, node, *keyp, *ptrp,
-					path[level].bp_index);
+		ncblk = nilfs_btree_nchildren_per_block(btree);
+		nilfs_btree_node_insert(node, path[level].bp_index,
+					*keyp, *ptrp, ncblk);
 		if (!buffer_dirty(path[level].bp_bh))
 			nilfs_btnode_mark_dirty(path[level].bp_bh);
 
@@ -655,22 +747,24 @@ static void nilfs_btree_do_insert(struct nilfs_btree *btree,
 									 0));
 	} else {
 		node = nilfs_btree_get_root(btree);
-		nilfs_btree_node_insert(btree, node, *keyp, *ptrp,
-					path[level].bp_index);
+		nilfs_btree_node_insert(node, path[level].bp_index,
+					*keyp, *ptrp,
+					NILFS_BTREE_ROOT_NCHILDREN_MAX);
 	}
 }
 
-static void nilfs_btree_carry_left(struct nilfs_btree *btree,
+static void nilfs_btree_carry_left(struct nilfs_bmap *btree,
 				   struct nilfs_btree_path *path,
 				   int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node, *left;
-	int nchildren, lnchildren, n, move;
+	int nchildren, lnchildren, n, move, ncblk;
 
 	node = nilfs_btree_get_nonroot_node(path, level);
 	left = nilfs_btree_get_sib_node(path, level);
 	nchildren = nilfs_btree_node_get_nchildren(node);
 	lnchildren = nilfs_btree_node_get_nchildren(left);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 	move = 0;
 
 	n = (nchildren + lnchildren + 1) / 2 - lnchildren;
@@ -680,7 +774,7 @@ static void nilfs_btree_carry_left(struct nilfs_btree *btree,
 		move = 1;
 	}
 
-	nilfs_btree_node_move_left(btree, left, node, n);
+	nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);
 
 	if (!buffer_dirty(path[level].bp_bh))
 		nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -705,17 +799,18 @@ static void nilfs_btree_carry_left(struct nilfs_btree *btree,
 	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
 }
 
-static void nilfs_btree_carry_right(struct nilfs_btree *btree,
+static void nilfs_btree_carry_right(struct nilfs_bmap *btree,
 				    struct nilfs_btree_path *path,
 				    int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node, *right;
-	int nchildren, rnchildren, n, move;
+	int nchildren, rnchildren, n, move, ncblk;
 
 	node = nilfs_btree_get_nonroot_node(path, level);
 	right = nilfs_btree_get_sib_node(path, level);
 	nchildren = nilfs_btree_node_get_nchildren(node);
 	rnchildren = nilfs_btree_node_get_nchildren(right);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 	move = 0;
 
 	n = (nchildren + rnchildren + 1) / 2 - rnchildren;
@@ -725,7 +820,7 @@ static void nilfs_btree_carry_right(struct nilfs_btree *btree,
 		move = 1;
 	}
 
-	nilfs_btree_node_move_right(btree, node, right, n);
+	nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);
 
 	if (!buffer_dirty(path[level].bp_bh))
 		nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -751,18 +846,19 @@ static void nilfs_btree_carry_right(struct nilfs_btree *btree,
 	nilfs_btree_do_insert(btree, path, level, keyp, ptrp);
 }
 
-static void nilfs_btree_split(struct nilfs_btree *btree,
+static void nilfs_btree_split(struct nilfs_bmap *btree,
 			      struct nilfs_btree_path *path,
 			      int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node, *right;
 	__u64 newkey;
 	__u64 newptr;
-	int nchildren, n, move;
+	int nchildren, n, move, ncblk;
 
 	node = nilfs_btree_get_nonroot_node(path, level);
 	right = nilfs_btree_get_sib_node(path, level);
 	nchildren = nilfs_btree_node_get_nchildren(node);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 	move = 0;
 
 	n = (nchildren + 1) / 2;
@@ -771,7 +867,7 @@ static void nilfs_btree_split(struct nilfs_btree *btree,
 		move = 1;
 	}
 
-	nilfs_btree_node_move_right(btree, node, right, n);
+	nilfs_btree_node_move_right(node, right, n, ncblk, ncblk);
 
 	if (!buffer_dirty(path[level].bp_bh))
 		nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -783,8 +879,8 @@ static void nilfs_btree_split(struct nilfs_btree *btree,
 
 	if (move) {
 		path[level].bp_index -= nilfs_btree_node_get_nchildren(node);
-		nilfs_btree_node_insert(btree, right, *keyp, *ptrp,
-					path[level].bp_index);
+		nilfs_btree_node_insert(right, path[level].bp_index,
+					*keyp, *ptrp, ncblk);
 
 		*keyp = nilfs_btree_node_get_key(right, 0);
 		*ptrp = path[level].bp_newreq.bpr_ptr;
@@ -805,19 +901,21 @@ static void nilfs_btree_split(struct nilfs_btree *btree,
 	path[level + 1].bp_index++;
 }
 
-static void nilfs_btree_grow(struct nilfs_btree *btree,
+static void nilfs_btree_grow(struct nilfs_bmap *btree,
 			     struct nilfs_btree_path *path,
 			     int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *root, *child;
-	int n;
+	int n, ncblk;
 
 	root = nilfs_btree_get_root(btree);
 	child = nilfs_btree_get_sib_node(path, level);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 
 	n = nilfs_btree_node_get_nchildren(root);
 
-	nilfs_btree_node_move_right(btree, root, child, n);
+	nilfs_btree_node_move_right(root, child, n,
+				    NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);
 	nilfs_btree_node_set_level(root, level + 1);
 
 	if (!buffer_dirty(path[level].bp_sib_bh))
@@ -832,11 +930,11 @@ static void nilfs_btree_grow(struct nilfs_btree *btree,
 	*ptrp = path[level].bp_newreq.bpr_ptr;
 }
 
-static __u64 nilfs_btree_find_near(const struct nilfs_btree *btree,
+static __u64 nilfs_btree_find_near(const struct nilfs_bmap *btree,
 				   const struct nilfs_btree_path *path)
 {
 	struct nilfs_btree_node *node;
-	int level;
+	int level, ncmax;
 
 	if (path == NULL)
 		return NILFS_BMAP_INVALID_PTR;
@@ -844,29 +942,30 @@ static __u64 nilfs_btree_find_near(const struct nilfs_btree *btree,
 	/* left sibling */
 	level = NILFS_BTREE_LEVEL_NODE_MIN;
 	if (path[level].bp_index > 0) {
-		node = nilfs_btree_get_node(btree, path, level);
-		return nilfs_btree_node_get_ptr(btree, node,
-						path[level].bp_index - 1);
+		node = nilfs_btree_get_node(btree, path, level, &ncmax);
+		return nilfs_btree_node_get_ptr(node,
+						path[level].bp_index - 1,
+						ncmax);
 	}
 
 	/* parent */
 	level = NILFS_BTREE_LEVEL_NODE_MIN + 1;
 	if (level <= nilfs_btree_height(btree) - 1) {
-		node = nilfs_btree_get_node(btree, path, level);
-		return nilfs_btree_node_get_ptr(btree, node,
-						path[level].bp_index);
+		node = nilfs_btree_get_node(btree, path, level, &ncmax);
+		return nilfs_btree_node_get_ptr(node, path[level].bp_index,
+						ncmax);
 	}
 
 	return NILFS_BMAP_INVALID_PTR;
 }
 
-static __u64 nilfs_btree_find_target_v(const struct nilfs_btree *btree,
+static __u64 nilfs_btree_find_target_v(const struct nilfs_bmap *btree,
 				       const struct nilfs_btree_path *path,
 				       __u64 key)
 {
 	__u64 ptr;
 
-	ptr = nilfs_bmap_find_target_seq(&btree->bt_bmap, key);
+	ptr = nilfs_bmap_find_target_seq(btree, key);
 	if (ptr != NILFS_BMAP_INVALID_PTR)
 		/* sequential access */
 		return ptr;
@@ -877,17 +976,10 @@ static __u64 nilfs_btree_find_target_v(const struct nilfs_btree *btree,
 			return ptr;
 	}
 	/* block group */
-	return nilfs_bmap_find_target_in_group(&btree->bt_bmap);
-}
-
-static void nilfs_btree_set_target_v(struct nilfs_btree *btree, __u64 key,
-				     __u64 ptr)
-{
-	btree->bt_bmap.b_last_allocated_key = key;
-	btree->bt_bmap.b_last_allocated_ptr = ptr;
+	return nilfs_bmap_find_target_in_group(btree);
 }
 
-static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
+static int nilfs_btree_prepare_insert(struct nilfs_bmap *btree,
 				      struct nilfs_btree_path *path,
 				      int *levelp, __u64 key, __u64 ptr,
 				      struct nilfs_bmap_stats *stats)
@@ -895,79 +987,78 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 	struct buffer_head *bh;
 	struct nilfs_btree_node *node, *parent, *sib;
 	__u64 sibptr;
-	int pindex, level, ret;
+	int pindex, level, ncmax, ncblk, ret;
 	struct inode *dat = NULL;
 
 	stats->bs_nblocks = 0;
 	level = NILFS_BTREE_LEVEL_DATA;
 
 	/* allocate a new ptr for data block */
-	if (NILFS_BMAP_USE_VBN(&btree->bt_bmap)) {
+	if (NILFS_BMAP_USE_VBN(btree)) {
 		path[level].bp_newreq.bpr_ptr =
 			nilfs_btree_find_target_v(btree, path, key);
-		dat = nilfs_bmap_get_dat(&btree->bt_bmap);
+		dat = nilfs_bmap_get_dat(btree);
 	}
 
-	ret = nilfs_bmap_prepare_alloc_ptr(&btree->bt_bmap,
-					   &path[level].bp_newreq, dat);
+	ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);
 	if (ret < 0)
 		goto err_out_data;
 
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
 	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
 	     level < nilfs_btree_height(btree) - 1;
 	     level++) {
 		node = nilfs_btree_get_nonroot_node(path, level);
-		if (nilfs_btree_node_get_nchildren(node) <
-		    nilfs_btree_node_nchildren_max(node, btree)) {
+		if (nilfs_btree_node_get_nchildren(node) < ncblk) {
 			path[level].bp_op = nilfs_btree_do_insert;
 			stats->bs_nblocks++;
 			goto out;
 		}
 
-		parent = nilfs_btree_get_node(btree, path, level + 1);
+		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
 		pindex = path[level + 1].bp_index;
 
 		/* left sibling */
 		if (pindex > 0) {
-			sibptr = nilfs_btree_node_get_ptr(btree, parent,
-							  pindex - 1);
+			sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
+							  ncmax);
 			ret = nilfs_btree_get_block(btree, sibptr, &bh);
 			if (ret < 0)
 				goto err_out_child_node;
 			sib = (struct nilfs_btree_node *)bh->b_data;
-			if (nilfs_btree_node_get_nchildren(sib) <
-			    nilfs_btree_node_nchildren_max(sib, btree)) {
+			if (nilfs_btree_node_get_nchildren(sib) < ncblk) {
 				path[level].bp_sib_bh = bh;
 				path[level].bp_op = nilfs_btree_carry_left;
 				stats->bs_nblocks++;
 				goto out;
-			} else
+			} else {
 				brelse(bh);
+			}
 		}
 
 		/* right sibling */
-		if (pindex <
-		    nilfs_btree_node_get_nchildren(parent) - 1) {
-			sibptr = nilfs_btree_node_get_ptr(btree, parent,
-							  pindex + 1);
+		if (pindex < nilfs_btree_node_get_nchildren(parent) - 1) {
+			sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
+							  ncmax);
 			ret = nilfs_btree_get_block(btree, sibptr, &bh);
 			if (ret < 0)
 				goto err_out_child_node;
 			sib = (struct nilfs_btree_node *)bh->b_data;
-			if (nilfs_btree_node_get_nchildren(sib) <
-			    nilfs_btree_node_nchildren_max(sib, btree)) {
+			if (nilfs_btree_node_get_nchildren(sib) < ncblk) {
 				path[level].bp_sib_bh = bh;
 				path[level].bp_op = nilfs_btree_carry_right;
 				stats->bs_nblocks++;
 				goto out;
-			} else
+			} else {
 				brelse(bh);
+			}
 		}
 
 		/* split */
 		path[level].bp_newreq.bpr_ptr =
 			path[level - 1].bp_newreq.bpr_ptr + 1;
-		ret = nilfs_bmap_prepare_alloc_ptr(&btree->bt_bmap,
+		ret = nilfs_bmap_prepare_alloc_ptr(btree,
 						   &path[level].bp_newreq, dat);
 		if (ret < 0)
 			goto err_out_child_node;
@@ -979,9 +1070,8 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 
 		stats->bs_nblocks++;
 
-		nilfs_btree_node_init(btree,
-				      (struct nilfs_btree_node *)bh->b_data,
-				      0, level, 0, NULL, NULL);
+		sib = (struct nilfs_btree_node *)bh->b_data;
+		nilfs_btree_node_init(sib, 0, level, 0, ncblk, NULL, NULL);
 		path[level].bp_sib_bh = bh;
 		path[level].bp_op = nilfs_btree_split;
 	}
@@ -989,7 +1079,7 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 	/* root */
 	node = nilfs_btree_get_root(btree);
 	if (nilfs_btree_node_get_nchildren(node) <
-	    nilfs_btree_node_nchildren_max(node, btree)) {
+	    NILFS_BTREE_ROOT_NCHILDREN_MAX) {
 		path[level].bp_op = nilfs_btree_do_insert;
 		stats->bs_nblocks++;
 		goto out;
@@ -997,8 +1087,7 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 
 	/* grow */
 	path[level].bp_newreq.bpr_ptr = path[level - 1].bp_newreq.bpr_ptr + 1;
-	ret = nilfs_bmap_prepare_alloc_ptr(&btree->bt_bmap,
-					   &path[level].bp_newreq, dat);
+	ret = nilfs_bmap_prepare_alloc_ptr(btree, &path[level].bp_newreq, dat);
 	if (ret < 0)
 		goto err_out_child_node;
 	ret = nilfs_btree_get_new_block(btree, path[level].bp_newreq.bpr_ptr,
@@ -1006,8 +1095,8 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 	if (ret < 0)
 		goto err_out_curr_node;
 
-	nilfs_btree_node_init(btree, (struct nilfs_btree_node *)bh->b_data,
-			      0, level, 0, NULL, NULL);
+	nilfs_btree_node_init((struct nilfs_btree_node *)bh->b_data,
+			      0, level, 0, ncblk, NULL, NULL);
 	path[level].bp_sib_bh = bh;
 	path[level].bp_op = nilfs_btree_grow;
 
@@ -1024,25 +1113,22 @@ static int nilfs_btree_prepare_insert(struct nilfs_btree *btree,
 
 	/* error */
  err_out_curr_node:
-	nilfs_bmap_abort_alloc_ptr(&btree->bt_bmap, &path[level].bp_newreq,
-				   dat);
+	nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
  err_out_child_node:
 	for (level--; level > NILFS_BTREE_LEVEL_DATA; level--) {
 		nilfs_btnode_delete(path[level].bp_sib_bh);
-		nilfs_bmap_abort_alloc_ptr(&btree->bt_bmap,
-					   &path[level].bp_newreq, dat);
+		nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
 
 	}
 
-	nilfs_bmap_abort_alloc_ptr(&btree->bt_bmap, &path[level].bp_newreq,
-				   dat);
+	nilfs_bmap_abort_alloc_ptr(btree, &path[level].bp_newreq, dat);
  err_out_data:
 	*levelp = level;
 	stats->bs_nblocks = 0;
 	return ret;
 }
 
-static void nilfs_btree_commit_insert(struct nilfs_btree *btree,
+static void nilfs_btree_commit_insert(struct nilfs_bmap *btree,
 				      struct nilfs_btree_path *path,
 				      int maxlevel, __u64 key, __u64 ptr)
 {
@@ -1051,35 +1137,33 @@ static void nilfs_btree_commit_insert(struct nilfs_btree *btree,
 
 	set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
 	ptr = path[NILFS_BTREE_LEVEL_DATA].bp_newreq.bpr_ptr;
-	if (NILFS_BMAP_USE_VBN(&btree->bt_bmap)) {
-		nilfs_btree_set_target_v(btree, key, ptr);
-		dat = nilfs_bmap_get_dat(&btree->bt_bmap);
+	if (NILFS_BMAP_USE_VBN(btree)) {
+		nilfs_bmap_set_target_v(btree, key, ptr);
+		dat = nilfs_bmap_get_dat(btree);
 	}
 
 	for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
-		nilfs_bmap_commit_alloc_ptr(&btree->bt_bmap,
+		nilfs_bmap_commit_alloc_ptr(btree,
 					    &path[level - 1].bp_newreq, dat);
 		path[level].bp_op(btree, path, level, &key, &ptr);
 	}
 
-	if (!nilfs_bmap_dirty(&btree->bt_bmap))
-		nilfs_bmap_set_dirty(&btree->bt_bmap);
+	if (!nilfs_bmap_dirty(btree))
+		nilfs_bmap_set_dirty(btree);
 }
 
-static int nilfs_btree_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
+static int nilfs_btree_insert(struct nilfs_bmap *btree, __u64 key, __u64 ptr)
 {
-	struct nilfs_btree *btree;
 	struct nilfs_btree_path *path;
 	struct nilfs_bmap_stats stats;
 	int level, ret;
 
-	btree = (struct nilfs_btree *)bmap;
 	path = nilfs_btree_alloc_path();
 	if (path == NULL)
 		return -ENOMEM;
 
 	ret = nilfs_btree_do_lookup(btree, path, key, NULL,
-				    NILFS_BTREE_LEVEL_NODE_MIN);
+				    NILFS_BTREE_LEVEL_NODE_MIN, 0);
 	if (ret != -ENOENT) {
 		if (ret == 0)
 			ret = -EEXIST;
@@ -1090,23 +1174,25 @@ static int nilfs_btree_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
 	if (ret < 0)
 		goto out;
 	nilfs_btree_commit_insert(btree, path, level, key, ptr);
-	nilfs_bmap_add_blocks(bmap, stats.bs_nblocks);
+	nilfs_bmap_add_blocks(btree, stats.bs_nblocks);
 
  out:
 	nilfs_btree_free_path(path);
 	return ret;
 }
 
-static void nilfs_btree_do_delete(struct nilfs_btree *btree,
+static void nilfs_btree_do_delete(struct nilfs_bmap *btree,
 				  struct nilfs_btree_path *path,
 				  int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node;
+	int ncblk;
 
 	if (level < nilfs_btree_height(btree) - 1) {
 		node = nilfs_btree_get_nonroot_node(path, level);
-		nilfs_btree_node_delete(btree, node, keyp, ptrp,
-					path[level].bp_index);
+		ncblk = nilfs_btree_nchildren_per_block(btree);
+		nilfs_btree_node_delete(node, path[level].bp_index,
+					keyp, ptrp, ncblk);
 		if (!buffer_dirty(path[level].bp_bh))
 			nilfs_btnode_mark_dirty(path[level].bp_bh);
 		if (path[level].bp_index == 0)
@@ -1114,17 +1200,18 @@ static void nilfs_btree_do_delete(struct nilfs_btree *btree,
 				nilfs_btree_node_get_key(node, 0));
 	} else {
 		node = nilfs_btree_get_root(btree);
-		nilfs_btree_node_delete(btree, node, keyp, ptrp,
-					path[level].bp_index);
+		nilfs_btree_node_delete(node, path[level].bp_index,
+					keyp, ptrp,
+					NILFS_BTREE_ROOT_NCHILDREN_MAX);
 	}
 }
 
-static void nilfs_btree_borrow_left(struct nilfs_btree *btree,
+static void nilfs_btree_borrow_left(struct nilfs_bmap *btree,
 				    struct nilfs_btree_path *path,
 				    int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node, *left;
-	int nchildren, lnchildren, n;
+	int nchildren, lnchildren, n, ncblk;
 
 	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
 
@@ -1132,10 +1219,11 @@ static void nilfs_btree_borrow_left(struct nilfs_btree *btree,
 	left = nilfs_btree_get_sib_node(path, level);
 	nchildren = nilfs_btree_node_get_nchildren(node);
 	lnchildren = nilfs_btree_node_get_nchildren(left);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 
 	n = (nchildren + lnchildren) / 2 - nchildren;
 
-	nilfs_btree_node_move_right(btree, left, node, n);
+	nilfs_btree_node_move_right(left, node, n, ncblk, ncblk);
 
 	if (!buffer_dirty(path[level].bp_bh))
 		nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -1150,12 +1238,12 @@ static void nilfs_btree_borrow_left(struct nilfs_btree *btree,
 	path[level].bp_index += n;
 }
 
-static void nilfs_btree_borrow_right(struct nilfs_btree *btree,
+static void nilfs_btree_borrow_right(struct nilfs_bmap *btree,
 				     struct nilfs_btree_path *path,
 				     int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node, *right;
-	int nchildren, rnchildren, n;
+	int nchildren, rnchildren, n, ncblk;
 
 	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
 
@@ -1163,10 +1251,11 @@ static void nilfs_btree_borrow_right(struct nilfs_btree *btree,
 	right = nilfs_btree_get_sib_node(path, level);
 	nchildren = nilfs_btree_node_get_nchildren(node);
 	rnchildren = nilfs_btree_node_get_nchildren(right);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 
 	n = (nchildren + rnchildren) / 2 - nchildren;
 
-	nilfs_btree_node_move_left(btree, node, right, n);
+	nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);
 
 	if (!buffer_dirty(path[level].bp_bh))
 		nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -1182,21 +1271,22 @@ static void nilfs_btree_borrow_right(struct nilfs_btree *btree,
 	path[level].bp_sib_bh = NULL;
 }
 
-static void nilfs_btree_concat_left(struct nilfs_btree *btree,
+static void nilfs_btree_concat_left(struct nilfs_bmap *btree,
 				    struct nilfs_btree_path *path,
 				    int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node, *left;
-	int n;
+	int n, ncblk;
 
 	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
 
 	node = nilfs_btree_get_nonroot_node(path, level);
 	left = nilfs_btree_get_sib_node(path, level);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 
 	n = nilfs_btree_node_get_nchildren(node);
 
-	nilfs_btree_node_move_left(btree, left, node, n);
+	nilfs_btree_node_move_left(left, node, n, ncblk, ncblk);
 
 	if (!buffer_dirty(path[level].bp_sib_bh))
 		nilfs_btnode_mark_dirty(path[level].bp_sib_bh);
@@ -1207,21 +1297,22 @@ static void nilfs_btree_concat_left(struct nilfs_btree *btree,
 	path[level].bp_index += nilfs_btree_node_get_nchildren(left);
 }
 
-static void nilfs_btree_concat_right(struct nilfs_btree *btree,
+static void nilfs_btree_concat_right(struct nilfs_bmap *btree,
 				     struct nilfs_btree_path *path,
 				     int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *node, *right;
-	int n;
+	int n, ncblk;
 
 	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
 
 	node = nilfs_btree_get_nonroot_node(path, level);
 	right = nilfs_btree_get_sib_node(path, level);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 
 	n = nilfs_btree_node_get_nchildren(right);
 
-	nilfs_btree_node_move_left(btree, node, right, n);
+	nilfs_btree_node_move_left(node, right, n, ncblk, ncblk);
 
 	if (!buffer_dirty(path[level].bp_bh))
 		nilfs_btnode_mark_dirty(path[level].bp_bh);
@@ -1231,29 +1322,32 @@ static void nilfs_btree_concat_right(struct nilfs_btree *btree,
 	path[level + 1].bp_index++;
 }
 
-static void nilfs_btree_shrink(struct nilfs_btree *btree,
+static void nilfs_btree_shrink(struct nilfs_bmap *btree,
 			       struct nilfs_btree_path *path,
 			       int level, __u64 *keyp, __u64 *ptrp)
 {
 	struct nilfs_btree_node *root, *child;
-	int n;
+	int n, ncblk;
 
 	nilfs_btree_do_delete(btree, path, level, keyp, ptrp);
 
 	root = nilfs_btree_get_root(btree);
 	child = nilfs_btree_get_nonroot_node(path, level);
+	ncblk = nilfs_btree_nchildren_per_block(btree);
 
-	nilfs_btree_node_delete(btree, root, NULL, NULL, 0);
+	nilfs_btree_node_delete(root, 0, NULL, NULL,
+				NILFS_BTREE_ROOT_NCHILDREN_MAX);
 	nilfs_btree_node_set_level(root, level);
 	n = nilfs_btree_node_get_nchildren(child);
-	nilfs_btree_node_move_left(btree, root, child, n);
+	nilfs_btree_node_move_left(root, child, n,
+				   NILFS_BTREE_ROOT_NCHILDREN_MAX, ncblk);
 
 	nilfs_btnode_delete(path[level].bp_bh);
 	path[level].bp_bh = NULL;
 }
 
 
-static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
+static int nilfs_btree_prepare_delete(struct nilfs_bmap *btree,
 				      struct nilfs_btree_path *path,
 				      int *levelp,
 				      struct nilfs_bmap_stats *stats,
@@ -1262,42 +1356,43 @@ static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
 	struct buffer_head *bh;
 	struct nilfs_btree_node *node, *parent, *sib;
 	__u64 sibptr;
-	int pindex, level, ret;
+	int pindex, level, ncmin, ncmax, ncblk, ret;
 
 	ret = 0;
 	stats->bs_nblocks = 0;
+	ncmin = NILFS_BTREE_NODE_NCHILDREN_MIN(nilfs_btree_node_size(btree));
+	ncblk = nilfs_btree_nchildren_per_block(btree);
+
 	for (level = NILFS_BTREE_LEVEL_NODE_MIN;
 	     level < nilfs_btree_height(btree) - 1;
 	     level++) {
 		node = nilfs_btree_get_nonroot_node(path, level);
 		path[level].bp_oldreq.bpr_ptr =
-			nilfs_btree_node_get_ptr(btree, node,
-						 path[level].bp_index);
-		ret = nilfs_bmap_prepare_end_ptr(&btree->bt_bmap,
+			nilfs_btree_node_get_ptr(node, path[level].bp_index,
+						 ncblk);
+		ret = nilfs_bmap_prepare_end_ptr(btree,
 						 &path[level].bp_oldreq, dat);
 		if (ret < 0)
 			goto err_out_child_node;
 
-		if (nilfs_btree_node_get_nchildren(node) >
-		    nilfs_btree_node_nchildren_min(node, btree)) {
+		if (nilfs_btree_node_get_nchildren(node) > ncmin) {
 			path[level].bp_op = nilfs_btree_do_delete;
 			stats->bs_nblocks++;
 			goto out;
 		}
 
-		parent = nilfs_btree_get_node(btree, path, level + 1);
+		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
 		pindex = path[level + 1].bp_index;
 
 		if (pindex > 0) {
 			/* left sibling */
-			sibptr = nilfs_btree_node_get_ptr(btree, parent,
-							  pindex - 1);
+			sibptr = nilfs_btree_node_get_ptr(parent, pindex - 1,
+							  ncmax);
 			ret = nilfs_btree_get_block(btree, sibptr, &bh);
 			if (ret < 0)
 				goto err_out_curr_node;
 			sib = (struct nilfs_btree_node *)bh->b_data;
-			if (nilfs_btree_node_get_nchildren(sib) >
-			    nilfs_btree_node_nchildren_min(sib, btree)) {
+			if (nilfs_btree_node_get_nchildren(sib) > ncmin) {
 				path[level].bp_sib_bh = bh;
 				path[level].bp_op = nilfs_btree_borrow_left;
 				stats->bs_nblocks++;
@@ -1311,14 +1406,13 @@ static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
 		} else if (pindex <
 			   nilfs_btree_node_get_nchildren(parent) - 1) {
 			/* right sibling */
-			sibptr = nilfs_btree_node_get_ptr(btree, parent,
-							  pindex + 1);
+			sibptr = nilfs_btree_node_get_ptr(parent, pindex + 1,
+							  ncmax);
 			ret = nilfs_btree_get_block(btree, sibptr, &bh);
 			if (ret < 0)
 				goto err_out_curr_node;
 			sib = (struct nilfs_btree_node *)bh->b_data;
-			if (nilfs_btree_node_get_nchildren(sib) >
-			    nilfs_btree_node_nchildren_min(sib, btree)) {
+			if (nilfs_btree_node_get_nchildren(sib) > ncmin) {
 				path[level].bp_sib_bh = bh;
 				path[level].bp_op = nilfs_btree_borrow_right;
 				stats->bs_nblocks++;
@@ -1349,10 +1443,10 @@ static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
 
 	node = nilfs_btree_get_root(btree);
 	path[level].bp_oldreq.bpr_ptr =
-		nilfs_btree_node_get_ptr(btree, node, path[level].bp_index);
+		nilfs_btree_node_get_ptr(node, path[level].bp_index,
+					 NILFS_BTREE_ROOT_NCHILDREN_MAX);
 
-	ret = nilfs_bmap_prepare_end_ptr(&btree->bt_bmap,
-					 &path[level].bp_oldreq, dat);
+	ret = nilfs_bmap_prepare_end_ptr(btree, &path[level].bp_oldreq, dat);
 	if (ret < 0)
 		goto err_out_child_node;
 
@@ -1367,75 +1461,68 @@ static int nilfs_btree_prepare_delete(struct nilfs_btree *btree,
 
 	/* error */
  err_out_curr_node:
-	nilfs_bmap_abort_end_ptr(&btree->bt_bmap, &path[level].bp_oldreq, dat);
+	nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);
  err_out_child_node:
 	for (level--; level >= NILFS_BTREE_LEVEL_NODE_MIN; level--) {
 		brelse(path[level].bp_sib_bh);
-		nilfs_bmap_abort_end_ptr(&btree->bt_bmap,
-					 &path[level].bp_oldreq, dat);
+		nilfs_bmap_abort_end_ptr(btree, &path[level].bp_oldreq, dat);
 	}
 	*levelp = level;
 	stats->bs_nblocks = 0;
 	return ret;
 }
 
-static void nilfs_btree_commit_delete(struct nilfs_btree *btree,
+static void nilfs_btree_commit_delete(struct nilfs_bmap *btree,
 				      struct nilfs_btree_path *path,
 				      int maxlevel, struct inode *dat)
 {
 	int level;
 
 	for (level = NILFS_BTREE_LEVEL_NODE_MIN; level <= maxlevel; level++) {
-		nilfs_bmap_commit_end_ptr(&btree->bt_bmap,
-					  &path[level].bp_oldreq, dat);
+		nilfs_bmap_commit_end_ptr(btree, &path[level].bp_oldreq, dat);
 		path[level].bp_op(btree, path, level, NULL, NULL);
 	}
 
-	if (!nilfs_bmap_dirty(&btree->bt_bmap))
-		nilfs_bmap_set_dirty(&btree->bt_bmap);
+	if (!nilfs_bmap_dirty(btree))
+		nilfs_bmap_set_dirty(btree);
 }
 
-static int nilfs_btree_delete(struct nilfs_bmap *bmap, __u64 key)
+static int nilfs_btree_delete(struct nilfs_bmap *btree, __u64 key)
 
 {
-	struct nilfs_btree *btree;
 	struct nilfs_btree_path *path;
 	struct nilfs_bmap_stats stats;
 	struct inode *dat;
 	int level, ret;
 
-	btree = (struct nilfs_btree *)bmap;
 	path = nilfs_btree_alloc_path();
 	if (path == NULL)
 		return -ENOMEM;
 
 	ret = nilfs_btree_do_lookup(btree, path, key, NULL,
-				    NILFS_BTREE_LEVEL_NODE_MIN);
+				    NILFS_BTREE_LEVEL_NODE_MIN, 0);
 	if (ret < 0)
 		goto out;
 
 
-	dat = NILFS_BMAP_USE_VBN(&btree->bt_bmap) ?
-		nilfs_bmap_get_dat(&btree->bt_bmap) : NULL;
+	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
 
 	ret = nilfs_btree_prepare_delete(btree, path, &level, &stats, dat);
 	if (ret < 0)
 		goto out;
 	nilfs_btree_commit_delete(btree, path, level, dat);
-	nilfs_bmap_sub_blocks(bmap, stats.bs_nblocks);
+	nilfs_bmap_sub_blocks(btree, stats.bs_nblocks);
 
 out:
 	nilfs_btree_free_path(path);
 	return ret;
 }
 
-static int nilfs_btree_last_key(const struct nilfs_bmap *bmap, __u64 *keyp)
+static int nilfs_btree_last_key(const struct nilfs_bmap *btree, __u64 *keyp)
 {
-	struct nilfs_btree *btree;
 	struct nilfs_btree_path *path;
 	int ret;
 
-	btree = (struct nilfs_btree *)bmap;
 	path = nilfs_btree_alloc_path();
 	if (path == NULL)
 		return -ENOMEM;
@@ -1447,16 +1534,14 @@ static int nilfs_btree_last_key(const struct nilfs_bmap *bmap, __u64 *keyp)
 	return ret;
 }
 
-static int nilfs_btree_check_delete(struct nilfs_bmap *bmap, __u64 key)
+static int nilfs_btree_check_delete(struct nilfs_bmap *btree, __u64 key)
 {
 	struct buffer_head *bh;
-	struct nilfs_btree *btree;
 	struct nilfs_btree_node *root, *node;
 	__u64 maxkey, nextmaxkey;
 	__u64 ptr;
 	int nchildren, ret;
 
-	btree = (struct nilfs_btree *)bmap;
 	root = nilfs_btree_get_root(btree);
 	switch (nilfs_btree_height(btree)) {
 	case 2:
@@ -1467,7 +1552,8 @@ static int nilfs_btree_check_delete(struct nilfs_bmap *bmap, __u64 key)
 		nchildren = nilfs_btree_node_get_nchildren(root);
 		if (nchildren > 1)
 			return 0;
-		ptr = nilfs_btree_node_get_ptr(btree, root, nchildren - 1);
+		ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
+					       NILFS_BTREE_ROOT_NCHILDREN_MAX);
 		ret = nilfs_btree_get_block(btree, ptr, &bh);
 		if (ret < 0)
 			return ret;
@@ -1487,32 +1573,33 @@ static int nilfs_btree_check_delete(struct nilfs_bmap *bmap, __u64 key)
 	return (maxkey == key) && (nextmaxkey < NILFS_BMAP_LARGE_LOW);
 }
 
-static int nilfs_btree_gather_data(struct nilfs_bmap *bmap,
+static int nilfs_btree_gather_data(struct nilfs_bmap *btree,
 				   __u64 *keys, __u64 *ptrs, int nitems)
 {
 	struct buffer_head *bh;
-	struct nilfs_btree *btree;
 	struct nilfs_btree_node *node, *root;
 	__le64 *dkeys;
 	__le64 *dptrs;
 	__u64 ptr;
-	int nchildren, i, ret;
+	int nchildren, ncmax, i, ret;
 
-	btree = (struct nilfs_btree *)bmap;
 	root = nilfs_btree_get_root(btree);
 	switch (nilfs_btree_height(btree)) {
 	case 2:
 		bh = NULL;
 		node = root;
+		ncmax = NILFS_BTREE_ROOT_NCHILDREN_MAX;
 		break;
 	case 3:
 		nchildren = nilfs_btree_node_get_nchildren(root);
 		WARN_ON(nchildren > 1);
-		ptr = nilfs_btree_node_get_ptr(btree, root, nchildren - 1);
+		ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
+					       NILFS_BTREE_ROOT_NCHILDREN_MAX);
 		ret = nilfs_btree_get_block(btree, ptr, &bh);
 		if (ret < 0)
 			return ret;
 		node = (struct nilfs_btree_node *)bh->b_data;
+		ncmax = nilfs_btree_nchildren_per_block(btree);
 		break;
 	default:
 		node = NULL;
@@ -1523,10 +1610,10 @@ static int nilfs_btree_gather_data(struct nilfs_bmap *bmap,
 	if (nchildren < nitems)
 		nitems = nchildren;
 	dkeys = nilfs_btree_node_dkeys(node);
-	dptrs = nilfs_btree_node_dptrs(node, btree);
+	dptrs = nilfs_btree_node_dptrs(node, ncmax);
 	for (i = 0; i < nitems; i++) {
-		keys[i] = nilfs_bmap_dkey_to_key(dkeys[i]);
-		ptrs[i] = nilfs_bmap_dptr_to_ptr(dptrs[i]);
+		keys[i] = le64_to_cpu(dkeys[i]);
+		ptrs[i] = le64_to_cpu(dptrs[i]);
 	}
 
 	if (bh != NULL)
@@ -1536,14 +1623,13 @@ static int nilfs_btree_gather_data(struct nilfs_bmap *bmap,
 }
 
 static int
-nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
+nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *btree, __u64 key,
 				       union nilfs_bmap_ptr_req *dreq,
 				       union nilfs_bmap_ptr_req *nreq,
 				       struct buffer_head **bhp,
 				       struct nilfs_bmap_stats *stats)
 {
 	struct buffer_head *bh;
-	struct nilfs_btree *btree = (struct nilfs_btree *)bmap;
 	struct inode *dat = NULL;
 	int ret;
 
@@ -1551,12 +1637,12 @@ nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
 
 	/* for data */
 	/* cannot find near ptr */
-	if (NILFS_BMAP_USE_VBN(bmap)) {
+	if (NILFS_BMAP_USE_VBN(btree)) {
 		dreq->bpr_ptr = nilfs_btree_find_target_v(btree, NULL, key);
-		dat = nilfs_bmap_get_dat(bmap);
+		dat = nilfs_bmap_get_dat(btree);
 	}
 
-	ret = nilfs_bmap_prepare_alloc_ptr(bmap, dreq, dat);
+	ret = nilfs_bmap_prepare_alloc_ptr(btree, dreq, dat);
 	if (ret < 0)
 		return ret;
 
@@ -1564,7 +1650,7 @@ nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
 	stats->bs_nblocks++;
 	if (nreq != NULL) {
 		nreq->bpr_ptr = dreq->bpr_ptr + 1;
-		ret = nilfs_bmap_prepare_alloc_ptr(bmap, nreq, dat);
+		ret = nilfs_bmap_prepare_alloc_ptr(btree, nreq, dat);
 		if (ret < 0)
 			goto err_out_dreq;
 
@@ -1581,16 +1667,16 @@ nilfs_btree_prepare_convert_and_insert(struct nilfs_bmap *bmap, __u64 key,
 
 	/* error */
  err_out_nreq:
-	nilfs_bmap_abort_alloc_ptr(bmap, nreq, dat);
+	nilfs_bmap_abort_alloc_ptr(btree, nreq, dat);
  err_out_dreq:
-	nilfs_bmap_abort_alloc_ptr(bmap, dreq, dat);
+	nilfs_bmap_abort_alloc_ptr(btree, dreq, dat);
 	stats->bs_nblocks = 0;
 	return ret;
 
 }
 
 static void
-nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *bmap,
+nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *btree,
 				      __u64 key, __u64 ptr,
 				      const __u64 *keys, const __u64 *ptrs,
 				      int n,
@@ -1598,57 +1684,59 @@ nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *bmap,
 				      union nilfs_bmap_ptr_req *nreq,
 				      struct buffer_head *bh)
 {
-	struct nilfs_btree *btree = (struct nilfs_btree *)bmap;
 	struct nilfs_btree_node *node;
 	struct inode *dat;
 	__u64 tmpptr;
+	int ncblk;
 
 	/* free resources */
-	if (bmap->b_ops->bop_clear != NULL)
-		bmap->b_ops->bop_clear(bmap);
+	if (btree->b_ops->bop_clear != NULL)
+		btree->b_ops->bop_clear(btree);
 
 	/* ptr must be a pointer to a buffer head. */
 	set_buffer_nilfs_volatile((struct buffer_head *)((unsigned long)ptr));
 
 	/* convert and insert */
-	dat = NILFS_BMAP_USE_VBN(bmap) ? nilfs_bmap_get_dat(bmap) : NULL;
-	nilfs_btree_init(bmap);
+	dat = NILFS_BMAP_USE_VBN(btree) ? nilfs_bmap_get_dat(btree) : NULL;
+	nilfs_btree_init(btree);
 	if (nreq != NULL) {
-		nilfs_bmap_commit_alloc_ptr(bmap, dreq, dat);
-		nilfs_bmap_commit_alloc_ptr(bmap, nreq, dat);
+		nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
+		nilfs_bmap_commit_alloc_ptr(btree, nreq, dat);
 
 		/* create child node at level 1 */
 		node = (struct nilfs_btree_node *)bh->b_data;
-		nilfs_btree_node_init(btree, node, 0, 1, n, keys, ptrs);
-		nilfs_btree_node_insert(btree, node,
-					key, dreq->bpr_ptr, n);
+		ncblk = nilfs_btree_nchildren_per_block(btree);
+		nilfs_btree_node_init(node, 0, 1, n, ncblk, keys, ptrs);
+		nilfs_btree_node_insert(node, n, key, dreq->bpr_ptr, ncblk);
 		if (!buffer_dirty(bh))
 			nilfs_btnode_mark_dirty(bh);
-		if (!nilfs_bmap_dirty(bmap))
-			nilfs_bmap_set_dirty(bmap);
+		if (!nilfs_bmap_dirty(btree))
+			nilfs_bmap_set_dirty(btree);
 
 		brelse(bh);
 
 		/* create root node at level 2 */
 		node = nilfs_btree_get_root(btree);
 		tmpptr = nreq->bpr_ptr;
-		nilfs_btree_node_init(btree, node, NILFS_BTREE_NODE_ROOT,
-				      2, 1, &keys[0], &tmpptr);
+		nilfs_btree_node_init(node, NILFS_BTREE_NODE_ROOT, 2, 1,
+				      NILFS_BTREE_ROOT_NCHILDREN_MAX,
+				      &keys[0], &tmpptr);
 	} else {
-		nilfs_bmap_commit_alloc_ptr(bmap, dreq, dat);
+		nilfs_bmap_commit_alloc_ptr(btree, dreq, dat);
 
 		/* create root node at level 1 */
 		node = nilfs_btree_get_root(btree);
-		nilfs_btree_node_init(btree, node, NILFS_BTREE_NODE_ROOT,
-				      1, n, keys, ptrs);
-		nilfs_btree_node_insert(btree, node,
-					key, dreq->bpr_ptr, n);
-		if (!nilfs_bmap_dirty(bmap))
-			nilfs_bmap_set_dirty(bmap);
+		nilfs_btree_node_init(node, NILFS_BTREE_NODE_ROOT, 1, n,
+				      NILFS_BTREE_ROOT_NCHILDREN_MAX,
+				      keys, ptrs);
+		nilfs_btree_node_insert(node, n, key, dreq->bpr_ptr,
+					NILFS_BTREE_ROOT_NCHILDREN_MAX);
+		if (!nilfs_bmap_dirty(btree))
+			nilfs_bmap_set_dirty(btree);
 	}
 
-	if (NILFS_BMAP_USE_VBN(bmap))
-		nilfs_btree_set_target_v(btree, key, dreq->bpr_ptr);
+	if (NILFS_BMAP_USE_VBN(btree))
+		nilfs_bmap_set_target_v(btree, key, dreq->bpr_ptr);
 }
 
 /**
@@ -1660,7 +1748,7 @@ nilfs_btree_commit_convert_and_insert(struct nilfs_bmap *bmap,
  * @ptrs:
  * @n:
  */
-int nilfs_btree_convert_and_insert(struct nilfs_bmap *bmap,
+int nilfs_btree_convert_and_insert(struct nilfs_bmap *btree,
 				   __u64 key, __u64 ptr,
 				   const __u64 *keys, const __u64 *ptrs, int n)
 {
@@ -1673,7 +1761,7 @@ int nilfs_btree_convert_and_insert(struct nilfs_bmap *bmap,
 		di = &dreq;
 		ni = NULL;
 	} else if ((n + 1) <= NILFS_BTREE_NODE_NCHILDREN_MAX(
-			   1 << bmap->b_inode->i_blkbits)) {
+			   1 << btree->b_inode->i_blkbits)) {
 		di = &dreq;
 		ni = &nreq;
 	} else {
@@ -1682,17 +1770,17 @@ int nilfs_btree_convert_and_insert(struct nilfs_bmap *bmap,
 		BUG();
 	}
 
-	ret = nilfs_btree_prepare_convert_and_insert(bmap, key, di, ni, &bh,
+	ret = nilfs_btree_prepare_convert_and_insert(btree, key, di, ni, &bh,
 						     &stats);
 	if (ret < 0)
 		return ret;
-	nilfs_btree_commit_convert_and_insert(bmap, key, ptr, keys, ptrs, n,
+	nilfs_btree_commit_convert_and_insert(btree, key, ptr, keys, ptrs, n,
 					      di, ni, bh);
-	nilfs_bmap_add_blocks(bmap, stats.bs_nblocks);
+	nilfs_bmap_add_blocks(btree, stats.bs_nblocks);
 	return 0;
 }
 
-static int nilfs_btree_propagate_p(struct nilfs_btree *btree,
+static int nilfs_btree_propagate_p(struct nilfs_bmap *btree,
 				   struct nilfs_btree_path *path,
 				   int level,
 				   struct buffer_head *bh)
@@ -1704,17 +1792,17 @@ static int nilfs_btree_propagate_p(struct nilfs_btree *btree,
 	return 0;
 }
 
-static int nilfs_btree_prepare_update_v(struct nilfs_btree *btree,
+static int nilfs_btree_prepare_update_v(struct nilfs_bmap *btree,
 					struct nilfs_btree_path *path,
 					int level, struct inode *dat)
 {
 	struct nilfs_btree_node *parent;
-	int ret;
+	int ncmax, ret;
 
-	parent = nilfs_btree_get_node(btree, path, level + 1);
+	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
 	path[level].bp_oldreq.bpr_ptr =
-		nilfs_btree_node_get_ptr(btree, parent,
-					 path[level + 1].bp_index);
+		nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
+					 ncmax);
 	path[level].bp_newreq.bpr_ptr = path[level].bp_oldreq.bpr_ptr + 1;
 	ret = nilfs_dat_prepare_update(dat, &path[level].bp_oldreq.bpr_req,
 				       &path[level].bp_newreq.bpr_req);
@@ -1726,7 +1814,7 @@ static int nilfs_btree_prepare_update_v(struct nilfs_btree *btree,
 		path[level].bp_ctxt.newkey = path[level].bp_newreq.bpr_ptr;
 		path[level].bp_ctxt.bh = path[level].bp_bh;
 		ret = nilfs_btnode_prepare_change_key(
-			&NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+			&NILFS_BMAP_I(btree)->i_btnode_cache,
 			&path[level].bp_ctxt);
 		if (ret < 0) {
 			nilfs_dat_abort_update(dat,
@@ -1739,30 +1827,31 @@ static int nilfs_btree_prepare_update_v(struct nilfs_btree *btree,
 	return 0;
 }
 
-static void nilfs_btree_commit_update_v(struct nilfs_btree *btree,
+static void nilfs_btree_commit_update_v(struct nilfs_bmap *btree,
 					struct nilfs_btree_path *path,
 					int level, struct inode *dat)
 {
 	struct nilfs_btree_node *parent;
+	int ncmax;
 
 	nilfs_dat_commit_update(dat, &path[level].bp_oldreq.bpr_req,
 				&path[level].bp_newreq.bpr_req,
-				btree->bt_bmap.b_ptr_type == NILFS_BMAP_PTR_VS);
+				btree->b_ptr_type == NILFS_BMAP_PTR_VS);
 
 	if (buffer_nilfs_node(path[level].bp_bh)) {
 		nilfs_btnode_commit_change_key(
-			&NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+			&NILFS_BMAP_I(btree)->i_btnode_cache,
 			&path[level].bp_ctxt);
 		path[level].bp_bh = path[level].bp_ctxt.bh;
 	}
 	set_buffer_nilfs_volatile(path[level].bp_bh);
 
-	parent = nilfs_btree_get_node(btree, path, level + 1);
-	nilfs_btree_node_set_ptr(btree, parent, path[level + 1].bp_index,
-				 path[level].bp_newreq.bpr_ptr);
+	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+	nilfs_btree_node_set_ptr(parent, path[level + 1].bp_index,
+				 path[level].bp_newreq.bpr_ptr, ncmax);
 }
 
-static void nilfs_btree_abort_update_v(struct nilfs_btree *btree,
+static void nilfs_btree_abort_update_v(struct nilfs_bmap *btree,
 				       struct nilfs_btree_path *path,
 				       int level, struct inode *dat)
 {
@@ -1770,11 +1859,11 @@ static void nilfs_btree_abort_update_v(struct nilfs_btree *btree,
 			       &path[level].bp_newreq.bpr_req);
 	if (buffer_nilfs_node(path[level].bp_bh))
 		nilfs_btnode_abort_change_key(
-			&NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+			&NILFS_BMAP_I(btree)->i_btnode_cache,
 			&path[level].bp_ctxt);
 }
 
-static int nilfs_btree_prepare_propagate_v(struct nilfs_btree *btree,
+static int nilfs_btree_prepare_propagate_v(struct nilfs_bmap *btree,
 					   struct nilfs_btree_path *path,
 					   int minlevel, int *maxlevelp,
 					   struct inode *dat)
@@ -1809,7 +1898,7 @@ static int nilfs_btree_prepare_propagate_v(struct nilfs_btree *btree,
 	return ret;
 }
 
-static void nilfs_btree_commit_propagate_v(struct nilfs_btree *btree,
+static void nilfs_btree_commit_propagate_v(struct nilfs_bmap *btree,
 					   struct nilfs_btree_path *path,
 					   int minlevel, int maxlevel,
 					   struct buffer_head *bh,
@@ -1824,14 +1913,15 @@ static void nilfs_btree_commit_propagate_v(struct nilfs_btree *btree,
 		nilfs_btree_commit_update_v(btree, path, level, dat);
 }
 
-static int nilfs_btree_propagate_v(struct nilfs_btree *btree,
+static int nilfs_btree_propagate_v(struct nilfs_bmap *btree,
 				   struct nilfs_btree_path *path,
 				   int level, struct buffer_head *bh)
 {
 	int maxlevel = 0, ret;
 	struct nilfs_btree_node *parent;
-	struct inode *dat = nilfs_bmap_get_dat(&btree->bt_bmap);
+	struct inode *dat = nilfs_bmap_get_dat(btree);
 	__u64 ptr;
+	int ncmax;
 
 	get_bh(bh);
 	path[level].bp_bh = bh;
@@ -1841,9 +1931,10 @@ static int nilfs_btree_propagate_v(struct nilfs_btree *btree,
 		goto out;
 
 	if (buffer_nilfs_volatile(path[level].bp_bh)) {
-		parent = nilfs_btree_get_node(btree, path, level + 1);
-		ptr = nilfs_btree_node_get_ptr(btree, parent,
-					       path[level + 1].bp_index);
+		parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+		ptr = nilfs_btree_node_get_ptr(parent,
+					       path[level + 1].bp_index,
+					       ncmax);
 		ret = nilfs_dat_mark_dirty(dat, ptr);
 		if (ret < 0)
 			goto out;
@@ -1857,10 +1948,9 @@ static int nilfs_btree_propagate_v(struct nilfs_btree *btree,
 	return ret;
 }
 
-static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
+static int nilfs_btree_propagate(struct nilfs_bmap *btree,
 				 struct buffer_head *bh)
 {
-	struct nilfs_btree *btree;
 	struct nilfs_btree_path *path;
 	struct nilfs_btree_node *node;
 	__u64 key;
@@ -1868,7 +1958,6 @@ static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
 
 	WARN_ON(!buffer_dirty(bh));
 
-	btree = (struct nilfs_btree *)bmap;
 	path = nilfs_btree_alloc_path();
 	if (path == NULL)
 		return -ENOMEM;
@@ -1878,11 +1967,11 @@ static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
 		key = nilfs_btree_node_get_key(node, 0);
 		level = nilfs_btree_node_get_level(node);
 	} else {
-		key = nilfs_bmap_data_get_key(bmap, bh);
+		key = nilfs_bmap_data_get_key(btree, bh);
 		level = NILFS_BTREE_LEVEL_DATA;
 	}
 
-	ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1);
+	ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1, 0);
 	if (ret < 0) {
 		if (unlikely(ret == -ENOENT))
 			printk(KERN_CRIT "%s: key = %llu, level == %d\n",
@@ -1890,7 +1979,7 @@ static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
 		goto out;
 	}
 
-	ret = NILFS_BMAP_USE_VBN(bmap) ?
+	ret = NILFS_BMAP_USE_VBN(btree) ?
 		nilfs_btree_propagate_v(btree, path, level, bh) :
 		nilfs_btree_propagate_p(btree, path, level, bh);
 
@@ -1900,13 +1989,13 @@ static int nilfs_btree_propagate(const struct nilfs_bmap *bmap,
 	return ret;
 }
 
-static int nilfs_btree_propagate_gc(const struct nilfs_bmap *bmap,
+static int nilfs_btree_propagate_gc(struct nilfs_bmap *btree,
 				    struct buffer_head *bh)
 {
-	return nilfs_dat_mark_dirty(nilfs_bmap_get_dat(bmap), bh->b_blocknr);
+	return nilfs_dat_mark_dirty(nilfs_bmap_get_dat(btree), bh->b_blocknr);
 }
 
-static void nilfs_btree_add_dirty_buffer(struct nilfs_btree *btree,
+static void nilfs_btree_add_dirty_buffer(struct nilfs_bmap *btree,
 					 struct list_head *lists,
 					 struct buffer_head *bh)
 {
@@ -1920,6 +2009,18 @@ static void nilfs_btree_add_dirty_buffer(struct nilfs_btree *btree,
 	node = (struct nilfs_btree_node *)bh->b_data;
 	key = nilfs_btree_node_get_key(node, 0);
 	level = nilfs_btree_node_get_level(node);
+	if (level < NILFS_BTREE_LEVEL_NODE_MIN ||
+	    level >= NILFS_BTREE_LEVEL_MAX) {
+		dump_stack();
+		printk(KERN_WARNING
+		       "%s: invalid btree level: %d (key=%llu, ino=%lu, "
+		       "blocknr=%llu)\n",
+		       __func__, level, (unsigned long long)key,
+		       NILFS_BMAP_I(btree)->vfs_inode.i_ino,
+		       (unsigned long long)bh->b_blocknr);
+		return;
+	}
+
 	list_for_each(head, &lists[level]) {
 		cbh = list_entry(head, struct buffer_head, b_assoc_buffers);
 		cnode = (struct nilfs_btree_node *)cbh->b_data;
@@ -1930,11 +2031,10 @@ static void nilfs_btree_add_dirty_buffer(struct nilfs_btree *btree,
 	list_add_tail(&bh->b_assoc_buffers, head);
 }
 
-static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *bmap,
+static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *btree,
 					     struct list_head *listp)
 {
-	struct nilfs_btree *btree = (struct nilfs_btree *)bmap;
-	struct address_space *btcache = &NILFS_BMAP_I(bmap)->i_btnode_cache;
+	struct address_space *btcache = &NILFS_BMAP_I(btree)->i_btnode_cache;
 	struct list_head lists[NILFS_BTREE_LEVEL_MAX];
 	struct pagevec pvec;
 	struct buffer_head *bh, *head;
@@ -1968,7 +2068,7 @@ static void nilfs_btree_lookup_dirty_buffers(struct nilfs_bmap *bmap,
 		list_splice_tail(&lists[level], listp);
 }
 
-static int nilfs_btree_assign_p(struct nilfs_btree *btree,
+static int nilfs_btree_assign_p(struct nilfs_bmap *btree,
 				struct nilfs_btree_path *path,
 				int level,
 				struct buffer_head **bh,
@@ -1978,38 +2078,38 @@ static int nilfs_btree_assign_p(struct nilfs_btree *btree,
 	struct nilfs_btree_node *parent;
 	__u64 key;
 	__u64 ptr;
-	int ret;
+	int ncmax, ret;
 
-	parent = nilfs_btree_get_node(btree, path, level + 1);
-	ptr = nilfs_btree_node_get_ptr(btree, parent,
-				       path[level + 1].bp_index);
+	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+	ptr = nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
+				       ncmax);
 	if (buffer_nilfs_node(*bh)) {
 		path[level].bp_ctxt.oldkey = ptr;
 		path[level].bp_ctxt.newkey = blocknr;
 		path[level].bp_ctxt.bh = *bh;
 		ret = nilfs_btnode_prepare_change_key(
-			&NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+			&NILFS_BMAP_I(btree)->i_btnode_cache,
 			&path[level].bp_ctxt);
 		if (ret < 0)
 			return ret;
 		nilfs_btnode_commit_change_key(
-			&NILFS_BMAP_I(&btree->bt_bmap)->i_btnode_cache,
+			&NILFS_BMAP_I(btree)->i_btnode_cache,
 			&path[level].bp_ctxt);
 		*bh = path[level].bp_ctxt.bh;
 	}
 
-	nilfs_btree_node_set_ptr(btree, parent,
-				 path[level + 1].bp_index, blocknr);
+	nilfs_btree_node_set_ptr(parent, path[level + 1].bp_index, blocknr,
+				 ncmax);
 
 	key = nilfs_btree_node_get_key(parent, path[level + 1].bp_index);
 	/* on-disk format */
-	binfo->bi_dat.bi_blkoff = nilfs_bmap_key_to_dkey(key);
+	binfo->bi_dat.bi_blkoff = cpu_to_le64(key);
 	binfo->bi_dat.bi_level = level;
 
 	return 0;
 }
 
-static int nilfs_btree_assign_v(struct nilfs_btree *btree,
+static int nilfs_btree_assign_v(struct nilfs_bmap *btree,
 				struct nilfs_btree_path *path,
 				int level,
 				struct buffer_head **bh,
@@ -2017,15 +2117,15 @@ static int nilfs_btree_assign_v(struct nilfs_btree *btree,
 				union nilfs_binfo *binfo)
 {
 	struct nilfs_btree_node *parent;
-	struct inode *dat = nilfs_bmap_get_dat(&btree->bt_bmap);
+	struct inode *dat = nilfs_bmap_get_dat(btree);
 	__u64 key;
 	__u64 ptr;
 	union nilfs_bmap_ptr_req req;
-	int ret;
+	int ncmax, ret;
 
-	parent = nilfs_btree_get_node(btree, path, level + 1);
-	ptr = nilfs_btree_node_get_ptr(btree, parent,
-				       path[level + 1].bp_index);
+	parent = nilfs_btree_get_node(btree, path, level + 1, &ncmax);
+	ptr = nilfs_btree_node_get_ptr(parent, path[level + 1].bp_index,
+				       ncmax);
 	req.bpr_ptr = ptr;
 	ret = nilfs_dat_prepare_start(dat, &req.bpr_req);
 	if (ret < 0)
@@ -2034,24 +2134,22 @@ static int nilfs_btree_assign_v(struct nilfs_btree *btree,
 
 	key = nilfs_btree_node_get_key(parent, path[level + 1].bp_index);
 	/* on-disk format */
-	binfo->bi_v.bi_vblocknr = nilfs_bmap_ptr_to_dptr(ptr);
-	binfo->bi_v.bi_blkoff = nilfs_bmap_key_to_dkey(key);
+	binfo->bi_v.bi_vblocknr = cpu_to_le64(ptr);
+	binfo->bi_v.bi_blkoff = cpu_to_le64(key);
 
 	return 0;
 }
 
-static int nilfs_btree_assign(struct nilfs_bmap *bmap,
+static int nilfs_btree_assign(struct nilfs_bmap *btree,
 			      struct buffer_head **bh,
 			      sector_t blocknr,
 			      union nilfs_binfo *binfo)
 {
-	struct nilfs_btree *btree;
 	struct nilfs_btree_path *path;
 	struct nilfs_btree_node *node;
 	__u64 key;
 	int level, ret;
 
-	btree = (struct nilfs_btree *)bmap;
 	path = nilfs_btree_alloc_path();
 	if (path == NULL)
 		return -ENOMEM;
@@ -2061,17 +2159,17 @@ static int nilfs_btree_assign(struct nilfs_bmap *bmap,
 		key = nilfs_btree_node_get_key(node, 0);
 		level = nilfs_btree_node_get_level(node);
 	} else {
-		key = nilfs_bmap_data_get_key(bmap, *bh);
+		key = nilfs_bmap_data_get_key(btree, *bh);
 		level = NILFS_BTREE_LEVEL_DATA;
 	}
 
-	ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1);
+	ret = nilfs_btree_do_lookup(btree, path, key, NULL, level + 1, 0);
 	if (ret < 0) {
 		WARN_ON(ret == -ENOENT);
 		goto out;
 	}
 
-	ret = NILFS_BMAP_USE_VBN(bmap) ?
+	ret = NILFS_BMAP_USE_VBN(btree) ?
 		nilfs_btree_assign_v(btree, path, level, bh, blocknr, binfo) :
 		nilfs_btree_assign_p(btree, path, level, bh, blocknr, binfo);
 
@@ -2081,7 +2179,7 @@ static int nilfs_btree_assign(struct nilfs_bmap *bmap,
 	return ret;
 }
 
-static int nilfs_btree_assign_gc(struct nilfs_bmap *bmap,
+static int nilfs_btree_assign_gc(struct nilfs_bmap *btree,
 				 struct buffer_head **bh,
 				 sector_t blocknr,
 				 union nilfs_binfo *binfo)
@@ -2090,7 +2188,7 @@ static int nilfs_btree_assign_gc(struct nilfs_bmap *bmap,
 	__u64 key;
 	int ret;
 
-	ret = nilfs_dat_move(nilfs_bmap_get_dat(bmap), (*bh)->b_blocknr,
+	ret = nilfs_dat_move(nilfs_bmap_get_dat(btree), (*bh)->b_blocknr,
 			     blocknr);
 	if (ret < 0)
 		return ret;
@@ -2099,29 +2197,27 @@ static int nilfs_btree_assign_gc(struct nilfs_bmap *bmap,
 		node = (struct nilfs_btree_node *)(*bh)->b_data;
 		key = nilfs_btree_node_get_key(node, 0);
 	} else
-		key = nilfs_bmap_data_get_key(bmap, *bh);
+		key = nilfs_bmap_data_get_key(btree, *bh);
 
 	/* on-disk format */
 	binfo->bi_v.bi_vblocknr = cpu_to_le64((*bh)->b_blocknr);
-	binfo->bi_v.bi_blkoff = nilfs_bmap_key_to_dkey(key);
+	binfo->bi_v.bi_blkoff = cpu_to_le64(key);
 
 	return 0;
 }
 
-static int nilfs_btree_mark(struct nilfs_bmap *bmap, __u64 key, int level)
+static int nilfs_btree_mark(struct nilfs_bmap *btree, __u64 key, int level)
 {
 	struct buffer_head *bh;
-	struct nilfs_btree *btree;
 	struct nilfs_btree_path *path;
 	__u64 ptr;
 	int ret;
 
-	btree = (struct nilfs_btree *)bmap;
 	path = nilfs_btree_alloc_path();
 	if (path == NULL)
 		return -ENOMEM;
 
-	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level + 1);
+	ret = nilfs_btree_do_lookup(btree, path, key, &ptr, level + 1, 0);
 	if (ret < 0) {
 		WARN_ON(ret == -ENOENT);
 		goto out;
@@ -2135,8 +2231,8 @@ static int nilfs_btree_mark(struct nilfs_bmap *bmap, __u64 key, int level)
 	if (!buffer_dirty(bh))
 		nilfs_btnode_mark_dirty(bh);
 	brelse(bh);
-	if (!nilfs_bmap_dirty(&btree->bt_bmap))
-		nilfs_bmap_set_dirty(&btree->bt_bmap);
+	if (!nilfs_bmap_dirty(btree))
+		nilfs_bmap_set_dirty(btree);
 
  out:
 	nilfs_btree_free_path(path);
@@ -2186,10 +2282,14 @@ static const struct nilfs_bmap_operations nilfs_btree_ops_gc = {
 int nilfs_btree_init(struct nilfs_bmap *bmap)
 {
 	bmap->b_ops = &nilfs_btree_ops;
+	bmap->b_nchildren_per_block =
+		NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
 	return 0;
 }
 
 void nilfs_btree_init_gc(struct nilfs_bmap *bmap)
 {
 	bmap->b_ops = &nilfs_btree_ops_gc;
+	bmap->b_nchildren_per_block =
+		NILFS_BTREE_NODE_NCHILDREN_MAX(nilfs_btree_node_size(bmap));
 }
diff --git a/fs/nilfs2/btree.h b/fs/nilfs2/btree.h
index 43c8c5b..22c02e3 100644
--- a/fs/nilfs2/btree.h
+++ b/fs/nilfs2/btree.h
@@ -31,14 +31,6 @@
 #include "bmap.h"
 
 /**
- * struct nilfs_btree - B-tree structure
- * @bt_bmap: bmap base structure
- */
-struct nilfs_btree {
-	struct nilfs_bmap bt_bmap;
-};
-
-/**
  * struct nilfs_btree_path - A path on which B-tree operations are executed
  * @bp_bh: buffer head of node block
  * @bp_sib_bh: buffer head of sibling node block
@@ -54,7 +46,7 @@ struct nilfs_btree_path {
 	union nilfs_bmap_ptr_req bp_oldreq;
 	union nilfs_bmap_ptr_req bp_newreq;
 	struct nilfs_btnode_chkey_ctxt bp_ctxt;
-	void (*bp_op)(struct nilfs_btree *, struct nilfs_btree_path *,
+	void (*bp_op)(struct nilfs_bmap *, struct nilfs_btree_path *,
 		      int, __u64 *, __u64 *);
 };
 
@@ -80,4 +72,6 @@ int nilfs_btree_convert_and_insert(struct nilfs_bmap *, __u64, __u64,
 				   const __u64 *, const __u64 *, int);
 void nilfs_btree_init_gc(struct nilfs_bmap *);
 
+int nilfs_btree_broken_node_block(struct buffer_head *bh);
+
 #endif	/* _NILFS_BTREE_H */
diff --git a/fs/nilfs2/cpfile.c b/fs/nilfs2/cpfile.c
index 1873781..5ff15a8 100644
--- a/fs/nilfs2/cpfile.c
+++ b/fs/nilfs2/cpfile.c
@@ -863,26 +863,19 @@ int nilfs_cpfile_is_snapshot(struct inode *cpfile, __u64 cno)
  */
 int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode)
 {
-	struct the_nilfs *nilfs;
 	int ret;
 
-	nilfs = NILFS_MDT(cpfile)->mi_nilfs;
-
 	switch (mode) {
 	case NILFS_CHECKPOINT:
-		/*
-		 * Check for protecting existing snapshot mounts:
-		 * ns_mount_mutex is used to make this operation atomic and
-		 * exclusive with a new mount job.  Though it doesn't cover
-		 * umount, it's enough for the purpose.
-		 */
-		if (nilfs_checkpoint_is_mounted(nilfs, cno, 1)) {
-			/* Current implementation does not have to protect
-			   plain read-only mounts since they are exclusive
-			   with a read/write mount and are protected from the
-			   cleaner. */
+		if (nilfs_checkpoint_is_mounted(cpfile->i_sb, cno))
+			/*
+			 * Current implementation does not have to protect
+			 * plain read-only mounts since they are exclusive
+			 * with a read/write mount and are protected from the
+			 * cleaner.
+			 */
 			ret = -EBUSY;
-		} else
+		else
 			ret = nilfs_cpfile_clear_snapshot(cpfile, cno);
 		return ret;
 	case NILFS_SNAPSHOT:
@@ -933,27 +926,40 @@ int nilfs_cpfile_get_stat(struct inode *cpfile, struct nilfs_cpstat *cpstat)
 }
 
 /**
- * nilfs_cpfile_read - read cpfile inode
- * @cpfile: cpfile inode
- * @raw_inode: on-disk cpfile inode
- */
-int nilfs_cpfile_read(struct inode *cpfile, struct nilfs_inode *raw_inode)
-{
-	return nilfs_read_inode_common(cpfile, raw_inode);
-}
-
-/**
- * nilfs_cpfile_new - create cpfile
- * @nilfs: nilfs object
+ * nilfs_cpfile_read - read or get cpfile inode
+ * @sb: super block instance
  * @cpsize: size of a checkpoint entry
+ * @raw_inode: on-disk cpfile inode
+ * @inodep: buffer to store the inode
  */
-struct inode *nilfs_cpfile_new(struct the_nilfs *nilfs, size_t cpsize)
+int nilfs_cpfile_read(struct super_block *sb, size_t cpsize,
+		      struct nilfs_inode *raw_inode, struct inode **inodep)
 {
 	struct inode *cpfile;
+	int err;
+
+	cpfile = nilfs_iget_locked(sb, NULL, NILFS_CPFILE_INO);
+	if (unlikely(!cpfile))
+		return -ENOMEM;
+	if (!(cpfile->i_state & I_NEW))
+		goto out;
+
+	err = nilfs_mdt_init(cpfile, NILFS_MDT_GFP, 0);
+	if (err)
+		goto failed;
 
-	cpfile = nilfs_mdt_new(nilfs, NULL, NILFS_CPFILE_INO, 0);
-	if (cpfile)
-		nilfs_mdt_set_entry_size(cpfile, cpsize,
-					 sizeof(struct nilfs_cpfile_header));
-	return cpfile;
+	nilfs_mdt_set_entry_size(cpfile, cpsize,
+				 sizeof(struct nilfs_cpfile_header));
+
+	err = nilfs_read_inode_common(cpfile, raw_inode);
+	if (err)
+		goto failed;
+
+	unlock_new_inode(cpfile);
+ out:
+	*inodep = cpfile;
+	return 0;
+ failed:
+	iget_failed(cpfile);
+	return err;
 }
diff --git a/fs/nilfs2/cpfile.h b/fs/nilfs2/cpfile.h
index bc0809e..a242b9a 100644
--- a/fs/nilfs2/cpfile.h
+++ b/fs/nilfs2/cpfile.h
@@ -40,7 +40,7 @@ int nilfs_cpfile_get_stat(struct inode *, struct nilfs_cpstat *);
 ssize_t nilfs_cpfile_get_cpinfo(struct inode *, __u64 *, int, void *, unsigned,
 				size_t);
 
-int nilfs_cpfile_read(struct inode *cpfile, struct nilfs_inode *raw_inode);
-struct inode *nilfs_cpfile_new(struct the_nilfs *nilfs, size_t cpsize);
+int nilfs_cpfile_read(struct super_block *sb, size_t cpsize,
+		      struct nilfs_inode *raw_inode, struct inode **inodep);
 
 #endif	/* _NILFS_CPFILE_H */
diff --git a/fs/nilfs2/dat.c b/fs/nilfs2/dat.c
index 0131467..49c844d 100644
--- a/fs/nilfs2/dat.c
+++ b/fs/nilfs2/dat.c
@@ -36,6 +36,7 @@
 struct nilfs_dat_info {
 	struct nilfs_mdt_info mi;
 	struct nilfs_palloc_cache palloc_cache;
+	struct nilfs_shadow_map shadow;
 };
 
 static inline struct nilfs_dat_info *NILFS_DAT_I(struct inode *dat)
@@ -102,7 +103,8 @@ void nilfs_dat_abort_alloc(struct inode *dat, struct nilfs_palloc_req *req)
 	nilfs_palloc_abort_alloc_entry(dat, req);
 }
 
-void nilfs_dat_commit_free(struct inode *dat, struct nilfs_palloc_req *req)
+static void nilfs_dat_commit_free(struct inode *dat,
+				  struct nilfs_palloc_req *req)
 {
 	struct nilfs_dat_entry *entry;
 	void *kaddr;
@@ -327,6 +329,23 @@ int nilfs_dat_move(struct inode *dat, __u64 vblocknr, sector_t blocknr)
 	ret = nilfs_palloc_get_entry_block(dat, vblocknr, 0, &entry_bh);
 	if (ret < 0)
 		return ret;
+
+	/*
+	 * The given disk block number (blocknr) is not yet written to
+	 * the device at this point.
+	 *
+	 * To prevent nilfs_dat_translate() from returning the
+	 * uncommited block number, this makes a copy of the entry
+	 * buffer and redirects nilfs_dat_translate() to the copy.
+	 */
+	if (!buffer_nilfs_redirected(entry_bh)) {
+		ret = nilfs_mdt_freeze_buffer(dat, entry_bh);
+		if (ret) {
+			brelse(entry_bh);
+			return ret;
+		}
+	}
+
 	kaddr = kmap_atomic(entry_bh->b_page, KM_USER0);
 	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
 	if (unlikely(entry->de_blocknr == cpu_to_le64(0))) {
@@ -371,7 +390,7 @@ int nilfs_dat_move(struct inode *dat, __u64 vblocknr, sector_t blocknr)
  */
 int nilfs_dat_translate(struct inode *dat, __u64 vblocknr, sector_t *blocknrp)
 {
-	struct buffer_head *entry_bh;
+	struct buffer_head *entry_bh, *bh;
 	struct nilfs_dat_entry *entry;
 	sector_t blocknr;
 	void *kaddr;
@@ -381,6 +400,15 @@ int nilfs_dat_translate(struct inode *dat, __u64 vblocknr, sector_t *blocknrp)
 	if (ret < 0)
 		return ret;
 
+	if (!nilfs_doing_gc() && buffer_nilfs_redirected(entry_bh)) {
+		bh = nilfs_mdt_get_frozen_buffer(dat, entry_bh);
+		if (bh) {
+			WARN_ON(!buffer_uptodate(bh));
+			brelse(entry_bh);
+			entry_bh = bh;
+		}
+	}
+
 	kaddr = kmap_atomic(entry_bh->b_page, KM_USER0);
 	entry = nilfs_palloc_block_get_entry(dat, vblocknr, entry_bh, kaddr);
 	blocknr = le64_to_cpu(entry->de_blocknr);
@@ -436,38 +464,48 @@ ssize_t nilfs_dat_get_vinfo(struct inode *dat, void *buf, unsigned visz,
 }
 
 /**
- * nilfs_dat_read - read dat inode
- * @dat: dat inode
- * @raw_inode: on-disk dat inode
- */
-int nilfs_dat_read(struct inode *dat, struct nilfs_inode *raw_inode)
-{
-	return nilfs_read_inode_common(dat, raw_inode);
-}
-
-/**
- * nilfs_dat_new - create dat file
- * @nilfs: nilfs object
+ * nilfs_dat_read - read or get dat inode
+ * @sb: super block instance
  * @entry_size: size of a dat entry
+ * @raw_inode: on-disk dat inode
+ * @inodep: buffer to store the inode
  */
-struct inode *nilfs_dat_new(struct the_nilfs *nilfs, size_t entry_size)
+int nilfs_dat_read(struct super_block *sb, size_t entry_size,
+		   struct nilfs_inode *raw_inode, struct inode **inodep)
 {
 	static struct lock_class_key dat_lock_key;
 	struct inode *dat;
 	struct nilfs_dat_info *di;
 	int err;
 
-	dat = nilfs_mdt_new(nilfs, NULL, NILFS_DAT_INO, sizeof(*di));
-	if (dat) {
-		err = nilfs_palloc_init_blockgroup(dat, entry_size);
-		if (unlikely(err)) {
-			nilfs_mdt_destroy(dat);
-			return NULL;
-		}
+	dat = nilfs_iget_locked(sb, NULL, NILFS_DAT_INO);
+	if (unlikely(!dat))
+		return -ENOMEM;
+	if (!(dat->i_state & I_NEW))
+		goto out;
 
-		di = NILFS_DAT_I(dat);
-		lockdep_set_class(&di->mi.mi_sem, &dat_lock_key);
-		nilfs_palloc_setup_cache(dat, &di->palloc_cache);
-	}
-	return dat;
+	err = nilfs_mdt_init(dat, NILFS_MDT_GFP, sizeof(*di));
+	if (err)
+		goto failed;
+
+	err = nilfs_palloc_init_blockgroup(dat, entry_size);
+	if (err)
+		goto failed;
+
+	di = NILFS_DAT_I(dat);
+	lockdep_set_class(&di->mi.mi_sem, &dat_lock_key);
+	nilfs_palloc_setup_cache(dat, &di->palloc_cache);
+	nilfs_mdt_setup_shadow_map(dat, &di->shadow);
+
+	err = nilfs_read_inode_common(dat, raw_inode);
+	if (err)
+		goto failed;
+
+	unlock_new_inode(dat);
+ out:
+	*inodep = dat;
+	return 0;
+ failed:
+	iget_failed(dat);
+	return err;
 }
diff --git a/fs/nilfs2/dat.h b/fs/nilfs2/dat.h
index d31c3aa..cbd8e97 100644
--- a/fs/nilfs2/dat.h
+++ b/fs/nilfs2/dat.h
@@ -53,7 +53,7 @@ int nilfs_dat_freev(struct inode *, __u64 *, size_t);
 int nilfs_dat_move(struct inode *, __u64, sector_t);
 ssize_t nilfs_dat_get_vinfo(struct inode *, void *, unsigned, size_t);
 
-int nilfs_dat_read(struct inode *dat, struct nilfs_inode *raw_inode);
-struct inode *nilfs_dat_new(struct the_nilfs *nilfs, size_t entry_size);
+int nilfs_dat_read(struct super_block *sb, size_t entry_size,
+		   struct nilfs_inode *raw_inode, struct inode **inodep);
 
 #endif	/* _NILFS_DAT_H */
diff --git a/fs/nilfs2/dir.c b/fs/nilfs2/dir.c
index 85c89df..cb003c8 100644
--- a/fs/nilfs2/dir.c
+++ b/fs/nilfs2/dir.c
@@ -80,23 +80,10 @@ static unsigned nilfs_last_byte(struct inode *inode, unsigned long page_nr)
 	return last_byte;
 }
 
-static int nilfs_prepare_chunk_uninterruptible(struct page *page,
-					       struct address_space *mapping,
-					       unsigned from, unsigned to)
+static int nilfs_prepare_chunk(struct page *page, unsigned from, unsigned to)
 {
 	loff_t pos = page_offset(page) + from;
-	return block_write_begin(NULL, mapping, pos, to - from,
-				 AOP_FLAG_UNINTERRUPTIBLE, &page,
-				 NULL, nilfs_get_block);
-}
-
-static int nilfs_prepare_chunk(struct page *page,
-			       struct address_space *mapping,
-			       unsigned from, unsigned to)
-{
-	loff_t pos = page_offset(page) + from;
-	return block_write_begin(NULL, mapping, pos, to - from, 0, &page,
-				 NULL, nilfs_get_block);
+	return __block_write_begin(page, pos, to - from, nilfs_get_block);
 }
 
 static void nilfs_commit_chunk(struct page *page,
@@ -141,7 +128,7 @@ static void nilfs_check_page(struct page *page)
 	}
 	for (offs = 0; offs <= limit - NILFS_DIR_REC_LEN(1); offs += rec_len) {
 		p = (struct nilfs_dir_entry *)(kaddr + offs);
-		rec_len = le16_to_cpu(p->rec_len);
+		rec_len = nilfs_rec_len_from_disk(p->rec_len);
 
 		if (rec_len < NILFS_DIR_REC_LEN(1))
 			goto Eshort;
@@ -199,13 +186,10 @@ fail:
 static struct page *nilfs_get_page(struct inode *dir, unsigned long n)
 {
 	struct address_space *mapping = dir->i_mapping;
-	struct page *page = read_cache_page(mapping, n,
-				(filler_t *)mapping->a_ops->readpage, NULL);
+	struct page *page = read_mapping_page(mapping, n, NULL);
+
 	if (!IS_ERR(page)) {
-		wait_on_page_locked(page);
 		kmap(page);
-		if (!PageUptodate(page))
-			goto fail;
 		if (!PageChecked(page))
 			nilfs_check_page(page);
 		if (PageError(page))
@@ -238,7 +222,8 @@ nilfs_match(int len, const unsigned char *name, struct nilfs_dir_entry *de)
  */
 static struct nilfs_dir_entry *nilfs_next_entry(struct nilfs_dir_entry *p)
 {
-	return (struct nilfs_dir_entry *)((char *)p + le16_to_cpu(p->rec_len));
+	return (struct nilfs_dir_entry *)((char *)p +
+					  nilfs_rec_len_from_disk(p->rec_len));
 }
 
 static unsigned char
@@ -329,7 +314,7 @@ static int nilfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
 					goto success;
 				}
 			}
-			filp->f_pos += le16_to_cpu(de->rec_len);
+			filp->f_pos += nilfs_rec_len_from_disk(de->rec_len);
 		}
 		nilfs_put_page(page);
 	}
@@ -444,12 +429,12 @@ void nilfs_set_link(struct inode *dir, struct nilfs_dir_entry *de,
 		    struct page *page, struct inode *inode)
 {
 	unsigned from = (char *) de - (char *) page_address(page);
-	unsigned to = from + le16_to_cpu(de->rec_len);
+	unsigned to = from + nilfs_rec_len_from_disk(de->rec_len);
 	struct address_space *mapping = page->mapping;
 	int err;
 
 	lock_page(page);
-	err = nilfs_prepare_chunk_uninterruptible(page, mapping, from, to);
+	err = nilfs_prepare_chunk(page, from, to);
 	BUG_ON(err);
 	de->inode = cpu_to_le64(inode->i_ino);
 	nilfs_set_de_type(de, inode);
@@ -500,7 +485,7 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
 				/* We hit i_size */
 				name_len = 0;
 				rec_len = chunk_size;
-				de->rec_len = cpu_to_le16(chunk_size);
+				de->rec_len = nilfs_rec_len_to_disk(chunk_size);
 				de->inode = 0;
 				goto got_it;
 			}
@@ -514,7 +499,7 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
 			if (nilfs_match(namelen, name, de))
 				goto out_unlock;
 			name_len = NILFS_DIR_REC_LEN(de->name_len);
-			rec_len = le16_to_cpu(de->rec_len);
+			rec_len = nilfs_rec_len_from_disk(de->rec_len);
 			if (!de->inode && rec_len >= reclen)
 				goto got_it;
 			if (rec_len >= name_len + reclen)
@@ -530,15 +515,15 @@ int nilfs_add_link(struct dentry *dentry, struct inode *inode)
 got_it:
 	from = (char *)de - (char *)page_address(page);
 	to = from + rec_len;
-	err = nilfs_prepare_chunk(page, page->mapping, from, to);
+	err = nilfs_prepare_chunk(page, from, to);
 	if (err)
 		goto out_unlock;
 	if (de->inode) {
 		struct nilfs_dir_entry *de1;
 
 		de1 = (struct nilfs_dir_entry *)((char *)de + name_len);
-		de1->rec_len = cpu_to_le16(rec_len - name_len);
-		de->rec_len = cpu_to_le16(name_len);
+		de1->rec_len = nilfs_rec_len_to_disk(rec_len - name_len);
+		de->rec_len = nilfs_rec_len_to_disk(name_len);
 		de = de1;
 	}
 	de->name_len = namelen;
@@ -569,7 +554,8 @@ int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
 	struct inode *inode = mapping->host;
 	char *kaddr = page_address(page);
 	unsigned from = ((char *)dir - kaddr) & ~(nilfs_chunk_size(inode) - 1);
-	unsigned to = ((char *)dir - kaddr) + le16_to_cpu(dir->rec_len);
+	unsigned to = ((char *)dir - kaddr) +
+		nilfs_rec_len_from_disk(dir->rec_len);
 	struct nilfs_dir_entry *pde = NULL;
 	struct nilfs_dir_entry *de = (struct nilfs_dir_entry *)(kaddr + from);
 	int err;
@@ -587,10 +573,10 @@ int nilfs_delete_entry(struct nilfs_dir_entry *dir, struct page *page)
 	if (pde)
 		from = (char *)pde - (char *)page_address(page);
 	lock_page(page);
-	err = nilfs_prepare_chunk(page, mapping, from, to);
+	err = nilfs_prepare_chunk(page, from, to);
 	BUG_ON(err);
 	if (pde)
-		pde->rec_len = cpu_to_le16(to - from);
+		pde->rec_len = nilfs_rec_len_to_disk(to - from);
 	dir->inode = 0;
 	nilfs_commit_chunk(page, mapping, from, to);
 	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
@@ -615,7 +601,7 @@ int nilfs_make_empty(struct inode *inode, struct inode *parent)
 	if (!page)
 		return -ENOMEM;
 
-	err = nilfs_prepare_chunk(page, mapping, 0, chunk_size);
+	err = nilfs_prepare_chunk(page, 0, chunk_size);
 	if (unlikely(err)) {
 		unlock_page(page);
 		goto fail;
@@ -624,14 +610,14 @@ int nilfs_make_empty(struct inode *inode, struct inode *parent)
 	memset(kaddr, 0, chunk_size);
 	de = (struct nilfs_dir_entry *)kaddr;
 	de->name_len = 1;
-	de->rec_len = cpu_to_le16(NILFS_DIR_REC_LEN(1));
+	de->rec_len = nilfs_rec_len_to_disk(NILFS_DIR_REC_LEN(1));
 	memcpy(de->name, ".\0\0", 4);
 	de->inode = cpu_to_le64(inode->i_ino);
 	nilfs_set_de_type(de, inode);
 
 	de = (struct nilfs_dir_entry *)(kaddr + NILFS_DIR_REC_LEN(1));
 	de->name_len = 2;
-	de->rec_len = cpu_to_le16(chunk_size - NILFS_DIR_REC_LEN(1));
+	de->rec_len = nilfs_rec_len_to_disk(chunk_size - NILFS_DIR_REC_LEN(1));
 	de->inode = cpu_to_le64(parent->i_ino);
 	memcpy(de->name, "..\0", 4);
 	nilfs_set_de_type(de, inode);
diff --git a/fs/nilfs2/direct.c b/fs/nilfs2/direct.c
index 236753d..324d80c 100644
--- a/fs/nilfs2/direct.c
+++ b/fs/nilfs2/direct.c
@@ -27,47 +27,43 @@
 #include "alloc.h"
 #include "dat.h"
 
-static inline __le64 *nilfs_direct_dptrs(const struct nilfs_direct *direct)
+static inline __le64 *nilfs_direct_dptrs(const struct nilfs_bmap *direct)
 {
 	return (__le64 *)
-		((struct nilfs_direct_node *)direct->d_bmap.b_u.u_data + 1);
+		((struct nilfs_direct_node *)direct->b_u.u_data + 1);
 }
 
 static inline __u64
-nilfs_direct_get_ptr(const struct nilfs_direct *direct, __u64 key)
+nilfs_direct_get_ptr(const struct nilfs_bmap *direct, __u64 key)
 {
-	return nilfs_bmap_dptr_to_ptr(*(nilfs_direct_dptrs(direct) + key));
+	return le64_to_cpu(*(nilfs_direct_dptrs(direct) + key));
 }
 
-static inline void nilfs_direct_set_ptr(struct nilfs_direct *direct,
+static inline void nilfs_direct_set_ptr(struct nilfs_bmap *direct,
 					__u64 key, __u64 ptr)
 {
-	*(nilfs_direct_dptrs(direct) + key) = nilfs_bmap_ptr_to_dptr(ptr);
+	*(nilfs_direct_dptrs(direct) + key) = cpu_to_le64(ptr);
 }
 
-static int nilfs_direct_lookup(const struct nilfs_bmap *bmap,
+static int nilfs_direct_lookup(const struct nilfs_bmap *direct,
 			       __u64 key, int level, __u64 *ptrp)
 {
-	struct nilfs_direct *direct;
 	__u64 ptr;
 
-	direct = (struct nilfs_direct *)bmap;  /* XXX: use macro for level 1 */
 	if (key > NILFS_DIRECT_KEY_MAX || level != 1)
 		return -ENOENT;
 	ptr = nilfs_direct_get_ptr(direct, key);
 	if (ptr == NILFS_BMAP_INVALID_PTR)
 		return -ENOENT;
 
-	if (ptrp != NULL)
-		*ptrp = ptr;
+	*ptrp = ptr;
 	return 0;
 }
 
-static int nilfs_direct_lookup_contig(const struct nilfs_bmap *bmap,
+static int nilfs_direct_lookup_contig(const struct nilfs_bmap *direct,
 				      __u64 key, __u64 *ptrp,
 				      unsigned maxblocks)
 {
-	struct nilfs_direct *direct = (struct nilfs_direct *)bmap;
 	struct inode *dat = NULL;
 	__u64 ptr, ptr2;
 	sector_t blocknr;
@@ -79,8 +75,8 @@ static int nilfs_direct_lookup_contig(const struct nilfs_bmap *bmap,
 	if (ptr == NILFS_BMAP_INVALID_PTR)
 		return -ENOENT;
 
-	if (NILFS_BMAP_USE_VBN(bmap)) {
-		dat = nilfs_bmap_get_dat(bmap);
+	if (NILFS_BMAP_USE_VBN(direct)) {
+		dat = nilfs_bmap_get_dat(direct);
 		ret = nilfs_dat_translate(dat, ptr, &blocknr);
 		if (ret < 0)
 			return ret;
@@ -106,29 +102,21 @@ static int nilfs_direct_lookup_contig(const struct nilfs_bmap *bmap,
 }
 
 static __u64
-nilfs_direct_find_target_v(const struct nilfs_direct *direct, __u64 key)
+nilfs_direct_find_target_v(const struct nilfs_bmap *direct, __u64 key)
 {
 	__u64 ptr;
 
-	ptr = nilfs_bmap_find_target_seq(&direct->d_bmap, key);
+	ptr = nilfs_bmap_find_target_seq(direct, key);
 	if (ptr != NILFS_BMAP_INVALID_PTR)
 		/* sequential access */
 		return ptr;
 	else
 		/* block group */
-		return nilfs_bmap_find_target_in_group(&direct->d_bmap);
-}
-
-static void nilfs_direct_set_target_v(struct nilfs_direct *direct,
-				      __u64 key, __u64 ptr)
-{
-	direct->d_bmap.b_last_allocated_key = key;
-	direct->d_bmap.b_last_allocated_ptr = ptr;
+		return nilfs_bmap_find_target_in_group(direct);
 }
 
 static int nilfs_direct_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
 {
-	struct nilfs_direct *direct = (struct nilfs_direct *)bmap;
 	union nilfs_bmap_ptr_req req;
 	struct inode *dat = NULL;
 	struct buffer_head *bh;
@@ -136,11 +124,11 @@ static int nilfs_direct_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
 
 	if (key > NILFS_DIRECT_KEY_MAX)
 		return -ENOENT;
-	if (nilfs_direct_get_ptr(direct, key) != NILFS_BMAP_INVALID_PTR)
+	if (nilfs_direct_get_ptr(bmap, key) != NILFS_BMAP_INVALID_PTR)
 		return -EEXIST;
 
 	if (NILFS_BMAP_USE_VBN(bmap)) {
-		req.bpr_ptr = nilfs_direct_find_target_v(direct, key);
+		req.bpr_ptr = nilfs_direct_find_target_v(bmap, key);
 		dat = nilfs_bmap_get_dat(bmap);
 	}
 	ret = nilfs_bmap_prepare_alloc_ptr(bmap, &req, dat);
@@ -150,13 +138,13 @@ static int nilfs_direct_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
 		set_buffer_nilfs_volatile(bh);
 
 		nilfs_bmap_commit_alloc_ptr(bmap, &req, dat);
-		nilfs_direct_set_ptr(direct, key, req.bpr_ptr);
+		nilfs_direct_set_ptr(bmap, key, req.bpr_ptr);
 
 		if (!nilfs_bmap_dirty(bmap))
 			nilfs_bmap_set_dirty(bmap);
 
 		if (NILFS_BMAP_USE_VBN(bmap))
-			nilfs_direct_set_target_v(direct, key, req.bpr_ptr);
+			nilfs_bmap_set_target_v(bmap, key, req.bpr_ptr);
 
 		nilfs_bmap_add_blocks(bmap, 1);
 	}
@@ -165,33 +153,30 @@ static int nilfs_direct_insert(struct nilfs_bmap *bmap, __u64 key, __u64 ptr)
 
 static int nilfs_direct_delete(struct nilfs_bmap *bmap, __u64 key)
 {
-	struct nilfs_direct *direct = (struct nilfs_direct *)bmap;
 	union nilfs_bmap_ptr_req req;
 	struct inode *dat;
 	int ret;
 
 	if (key > NILFS_DIRECT_KEY_MAX ||
-	    nilfs_direct_get_ptr(direct, key) == NILFS_BMAP_INVALID_PTR)
+	    nilfs_direct_get_ptr(bmap, key) == NILFS_BMAP_INVALID_PTR)
 		return -ENOENT;
 
 	dat = NILFS_BMAP_USE_VBN(bmap) ? nilfs_bmap_get_dat(bmap) : NULL;
-	req.bpr_ptr = nilfs_direct_get_ptr(direct, key);
+	req.bpr_ptr = nilfs_direct_get_ptr(bmap, key);
 
 	ret = nilfs_bmap_prepare_end_ptr(bmap, &req, dat);
 	if (!ret) {
 		nilfs_bmap_commit_end_ptr(bmap, &req, dat);
-		nilfs_direct_set_ptr(direct, key, NILFS_BMAP_INVALID_PTR);
+		nilfs_direct_set_ptr(bmap, key, NILFS_BMAP_INVALID_PTR);
 		nilfs_bmap_sub_blocks(bmap, 1);
 	}
 	return ret;
 }
 
-static int nilfs_direct_last_key(const struct nilfs_bmap *bmap, __u64 *keyp)
+static int nilfs_direct_last_key(const struct nilfs_bmap *direct, __u64 *keyp)
 {
-	struct nilfs_direct *direct;
 	__u64 key, lastkey;
 
-	direct = (struct nilfs_direct *)bmap;
 	lastkey = NILFS_DIRECT_KEY_MAX + 1;
 	for (key = NILFS_DIRECT_KEY_MIN; key <= NILFS_DIRECT_KEY_MAX; key++)
 		if (nilfs_direct_get_ptr(direct, key) !=
@@ -211,15 +196,13 @@ static int nilfs_direct_check_insert(const struct nilfs_bmap *bmap, __u64 key)
 	return key > NILFS_DIRECT_KEY_MAX;
 }
 
-static int nilfs_direct_gather_data(struct nilfs_bmap *bmap,
+static int nilfs_direct_gather_data(struct nilfs_bmap *direct,
 				    __u64 *keys, __u64 *ptrs, int nitems)
 {
-	struct nilfs_direct *direct;
 	__u64 key;
 	__u64 ptr;
 	int n;
 
-	direct = (struct nilfs_direct *)bmap;
 	if (nitems > NILFS_DIRECT_NBLOCKS)
 		nitems = NILFS_DIRECT_NBLOCKS;
 	n = 0;
@@ -237,7 +220,6 @@ static int nilfs_direct_gather_data(struct nilfs_bmap *bmap,
 int nilfs_direct_delete_and_convert(struct nilfs_bmap *bmap,
 				    __u64 key, __u64 *keys, __u64 *ptrs, int n)
 {
-	struct nilfs_direct *direct;
 	__le64 *dptrs;
 	int ret, i, j;
 
@@ -253,12 +235,11 @@ int nilfs_direct_delete_and_convert(struct nilfs_bmap *bmap,
 		bmap->b_ops->bop_clear(bmap);
 
 	/* convert */
-	direct = (struct nilfs_direct *)bmap;
-	dptrs = nilfs_direct_dptrs(direct);
+	dptrs = nilfs_direct_dptrs(bmap);
 	for (i = 0, j = 0; i < NILFS_DIRECT_NBLOCKS; i++) {
 		if ((j < n) && (i == keys[j])) {
 			dptrs[i] = (i != key) ?
-				nilfs_bmap_ptr_to_dptr(ptrs[j]) :
+				cpu_to_le64(ptrs[j]) :
 				NILFS_BMAP_INVALID_PTR;
 			j++;
 		} else
@@ -269,10 +250,9 @@ int nilfs_direct_delete_and_convert(struct nilfs_bmap *bmap,
 	return 0;
 }
 
-static int nilfs_direct_propagate(const struct nilfs_bmap *bmap,
+static int nilfs_direct_propagate(struct nilfs_bmap *bmap,
 				  struct buffer_head *bh)
 {
-	struct nilfs_direct *direct = (struct nilfs_direct *)bmap;
 	struct nilfs_palloc_req oldreq, newreq;
 	struct inode *dat;
 	__u64 key;
@@ -284,7 +264,7 @@ static int nilfs_direct_propagate(const struct nilfs_bmap *bmap,
 
 	dat = nilfs_bmap_get_dat(bmap);
 	key = nilfs_bmap_data_get_key(bmap, bh);
-	ptr = nilfs_direct_get_ptr(direct, key);
+	ptr = nilfs_direct_get_ptr(bmap, key);
 	if (!buffer_nilfs_volatile(bh)) {
 		oldreq.pr_entry_nr = ptr;
 		newreq.pr_entry_nr = ptr;
@@ -294,20 +274,20 @@ static int nilfs_direct_propagate(const struct nilfs_bmap *bmap,
 		nilfs_dat_commit_update(dat, &oldreq, &newreq,
 					bmap->b_ptr_type == NILFS_BMAP_PTR_VS);
 		set_buffer_nilfs_volatile(bh);
-		nilfs_direct_set_ptr(direct, key, newreq.pr_entry_nr);
+		nilfs_direct_set_ptr(bmap, key, newreq.pr_entry_nr);
 	} else
 		ret = nilfs_dat_mark_dirty(dat, ptr);
 
 	return ret;
 }
 
-static int nilfs_direct_assign_v(struct nilfs_direct *direct,
+static int nilfs_direct_assign_v(struct nilfs_bmap *direct,
 				 __u64 key, __u64 ptr,
 				 struct buffer_head **bh,
 				 sector_t blocknr,
 				 union nilfs_binfo *binfo)
 {
-	struct inode *dat = nilfs_bmap_get_dat(&direct->d_bmap);
+	struct inode *dat = nilfs_bmap_get_dat(direct);
 	union nilfs_bmap_ptr_req req;
 	int ret;
 
@@ -315,13 +295,13 @@ static int nilfs_direct_assign_v(struct nilfs_direct *direct,
 	ret = nilfs_dat_prepare_start(dat, &req.bpr_req);
 	if (!ret) {
 		nilfs_dat_commit_start(dat, &req.bpr_req, blocknr);
-		binfo->bi_v.bi_vblocknr = nilfs_bmap_ptr_to_dptr(ptr);
-		binfo->bi_v.bi_blkoff = nilfs_bmap_key_to_dkey(key);
+		binfo->bi_v.bi_vblocknr = cpu_to_le64(ptr);
+		binfo->bi_v.bi_blkoff = cpu_to_le64(key);
 	}
 	return ret;
 }
 
-static int nilfs_direct_assign_p(struct nilfs_direct *direct,
+static int nilfs_direct_assign_p(struct nilfs_bmap *direct,
 				 __u64 key, __u64 ptr,
 				 struct buffer_head **bh,
 				 sector_t blocknr,
@@ -329,7 +309,7 @@ static int nilfs_direct_assign_p(struct nilfs_direct *direct,
 {
 	nilfs_direct_set_ptr(direct, key, blocknr);
 
-	binfo->bi_dat.bi_blkoff = nilfs_bmap_key_to_dkey(key);
+	binfo->bi_dat.bi_blkoff = cpu_to_le64(key);
 	binfo->bi_dat.bi_level = 0;
 
 	return 0;
@@ -340,18 +320,16 @@ static int nilfs_direct_assign(struct nilfs_bmap *bmap,
 			       sector_t blocknr,
 			       union nilfs_binfo *binfo)
 {
-	struct nilfs_direct *direct;
 	__u64 key;
 	__u64 ptr;
 
-	direct = (struct nilfs_direct *)bmap;
 	key = nilfs_bmap_data_get_key(bmap, *bh);
 	if (unlikely(key > NILFS_DIRECT_KEY_MAX)) {
 		printk(KERN_CRIT "%s: invalid key: %llu\n", __func__,
 		       (unsigned long long)key);
 		return -EINVAL;
 	}
-	ptr = nilfs_direct_get_ptr(direct, key);
+	ptr = nilfs_direct_get_ptr(bmap, key);
 	if (unlikely(ptr == NILFS_BMAP_INVALID_PTR)) {
 		printk(KERN_CRIT "%s: invalid pointer: %llu\n", __func__,
 		       (unsigned long long)ptr);
@@ -359,8 +337,8 @@ static int nilfs_direct_assign(struct nilfs_bmap *bmap,
 	}
 
 	return NILFS_BMAP_USE_VBN(bmap) ?
-		nilfs_direct_assign_v(direct, key, ptr, bh, blocknr, binfo) :
-		nilfs_direct_assign_p(direct, key, ptr, bh, blocknr, binfo);
+		nilfs_direct_assign_v(bmap, key, ptr, bh, blocknr, binfo) :
+		nilfs_direct_assign_p(bmap, key, ptr, bh, blocknr, binfo);
 }
 
 static const struct nilfs_bmap_operations nilfs_direct_ops = {
diff --git a/fs/nilfs2/direct.h b/fs/nilfs2/direct.h
index a5ffd66..dc643de 100644
--- a/fs/nilfs2/direct.h
+++ b/fs/nilfs2/direct.h
@@ -28,8 +28,6 @@
 #include "bmap.h"
 
 
-struct nilfs_direct;
-
 /**
  * struct nilfs_direct_node - direct node
  * @dn_flags: flags
@@ -40,15 +38,6 @@ struct nilfs_direct_node {
 	__u8 pad[7];
 };
 
-/**
- * struct nilfs_direct - direct mapping
- * @d_bmap: bmap structure
- */
-struct nilfs_direct {
-	struct nilfs_bmap d_bmap;
-};
-
-
 #define NILFS_DIRECT_NBLOCKS	(NILFS_BMAP_SIZE / sizeof(__le64) - 1)
 #define NILFS_DIRECT_KEY_MIN	0
 #define NILFS_DIRECT_KEY_MAX	(NILFS_DIRECT_NBLOCKS - 1)
diff --git a/fs/nilfs2/export.h b/fs/nilfs2/export.h
new file mode 100644
index 0000000..a71cc41
--- /dev/null
+++ b/fs/nilfs2/export.h
@@ -0,0 +1,17 @@
+#ifndef NILFS_EXPORT_H
+#define NILFS_EXPORT_H
+
+#include <linux/exportfs.h>
+
+extern const struct export_operations nilfs_export_ops;
+
+struct nilfs_fid {
+	u64 cno;
+	u64 ino;
+	u32 gen;
+
+	u32 parent_gen;
+	u64 parent_ino;
+} __attribute__ ((packed));
+
+#endif
diff --git a/fs/nilfs2/gcdat.c b/fs/nilfs2/gcdat.c
deleted file mode 100644
index dd5f7e0..0000000
--- a/fs/nilfs2/gcdat.c
+++ /dev/null
@@ -1,87 +0,0 @@
-/*
- * gcdat.c - NILFS shadow DAT inode for GC
- *
- * Copyright (C) 2005-2008 Nippon Telegraph and Telephone Corporation.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
- *
- * Written by Seiji Kihara <kihara@osrg.net>, Amagai Yoshiji <amagai@osrg.net>,
- *            and Ryusuke Konishi <ryusuke@osrg.net>.
- *
- */
-
-#include <linux/buffer_head.h>
-#include "nilfs.h"
-#include "page.h"
-#include "mdt.h"
-
-int nilfs_init_gcdat_inode(struct the_nilfs *nilfs)
-{
-	struct inode *dat = nilfs->ns_dat, *gcdat = nilfs->ns_gc_dat;
-	struct nilfs_inode_info *dii = NILFS_I(dat), *gii = NILFS_I(gcdat);
-	int err;
-
-	gcdat->i_state = 0;
-	gcdat->i_blocks = dat->i_blocks;
-	gii->i_flags = dii->i_flags;
-	gii->i_state = dii->i_state | (1 << NILFS_I_GCDAT);
-	gii->i_cno = 0;
-	nilfs_bmap_init_gcdat(gii->i_bmap, dii->i_bmap);
-	err = nilfs_copy_dirty_pages(gcdat->i_mapping, dat->i_mapping);
-	if (unlikely(err))
-		return err;
-
-	return nilfs_copy_dirty_pages(&gii->i_btnode_cache,
-				      &dii->i_btnode_cache);
-}
-
-void nilfs_commit_gcdat_inode(struct the_nilfs *nilfs)
-{
-	struct inode *dat = nilfs->ns_dat, *gcdat = nilfs->ns_gc_dat;
-	struct nilfs_inode_info *dii = NILFS_I(dat), *gii = NILFS_I(gcdat);
-	struct address_space *mapping = dat->i_mapping;
-	struct address_space *gmapping = gcdat->i_mapping;
-
-	down_write(&NILFS_MDT(dat)->mi_sem);
-	dat->i_blocks = gcdat->i_blocks;
-	dii->i_flags = gii->i_flags;
-	dii->i_state = gii->i_state & ~(1 << NILFS_I_GCDAT);
-
-	nilfs_bmap_commit_gcdat(gii->i_bmap, dii->i_bmap);
-
-	nilfs_palloc_clear_cache(dat);
-	nilfs_palloc_clear_cache(gcdat);
-	nilfs_clear_dirty_pages(mapping);
-	nilfs_copy_back_pages(mapping, gmapping);
-	/* note: mdt dirty flags should be cleared by segctor. */
-
-	nilfs_clear_dirty_pages(&dii->i_btnode_cache);
-	nilfs_copy_back_pages(&dii->i_btnode_cache, &gii->i_btnode_cache);
-
-	up_write(&NILFS_MDT(dat)->mi_sem);
-}
-
-void nilfs_clear_gcdat_inode(struct the_nilfs *nilfs)
-{
-	struct inode *gcdat = nilfs->ns_gc_dat;
-	struct nilfs_inode_info *gii = NILFS_I(gcdat);
-
-	gcdat->i_state = I_CLEAR;
-	gii->i_flags = 0;
-
-	nilfs_palloc_clear_cache(gcdat);
-	truncate_inode_pages(gcdat->i_mapping, 0);
-	truncate_inode_pages(&gii->i_btnode_cache, 0);
-}
diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c
index 145f03c..33ad25d 100644
--- a/fs/nilfs2/gcinode.c
+++ b/fs/nilfs2/gcinode.c
@@ -28,13 +28,6 @@
  * gcinodes), and this file provides lookup function of the dummy
  * inodes and their buffer read function.
  *
- * Since NILFS2 keeps up multiple checkpoints/snapshots across GC, it
- * has to treat blocks that belong to a same file but have different
- * checkpoint numbers.  To avoid interference among generations, dummy
- * inodes are managed separately from actual inodes, and their lookup
- * function (nilfs_gc_iget) is designed to be specified with a
- * checkpoint number argument as well as an inode number.
- *
  * Buffers and pages held by the dummy inodes will be released each
  * time after they are copied to a new log.  Dirty blocks made on the
  * current generation and the blocks to be moved by GC never overlap
@@ -48,6 +41,8 @@
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include "nilfs.h"
+#include "btree.h"
+#include "btnode.h"
 #include "page.h"
 #include "mdt.h"
 #include "dat.h"
@@ -149,8 +144,10 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
 int nilfs_gccache_submit_read_node(struct inode *inode, sector_t pbn,
 				   __u64 vbn, struct buffer_head **out_bh)
 {
-	int ret = nilfs_btnode_submit_block(&NILFS_I(inode)->i_btnode_cache,
-					    vbn ? : pbn, pbn, out_bh);
+	int ret;
+
+	ret = nilfs_btnode_submit_block(&NILFS_I(inode)->i_btnode_cache,
+					vbn ? : pbn, pbn, READ, out_bh, &pbn);
 	if (ret == -EEXIST) /* internal code (cache hit) */
 		ret = 0;
 	return ret;
@@ -164,127 +161,53 @@ int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *bh)
 	if (buffer_dirty(bh))
 		return -EEXIST;
 
-	if (buffer_nilfs_node(bh))
+	if (buffer_nilfs_node(bh)) {
+		if (nilfs_btree_broken_node_block(bh)) {
+			clear_buffer_uptodate(bh);
+			return -EIO;
+		}
 		nilfs_btnode_mark_dirty(bh);
-	else
-		nilfs_mdt_mark_buffer_dirty(bh);
-	return 0;
-}
-
-/*
- * nilfs_init_gccache() - allocate and initialize gc_inode hash table
- * @nilfs - the_nilfs
- *
- * Return Value: On success, 0.
- * On error, a negative error code is returned.
- */
-int nilfs_init_gccache(struct the_nilfs *nilfs)
-{
-	int loop;
-
-	BUG_ON(nilfs->ns_gc_inodes_h);
-
-	INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
-
-	nilfs->ns_gc_inodes_h =
-		kmalloc(sizeof(struct hlist_head) * NILFS_GCINODE_HASH_SIZE,
-			GFP_NOFS);
-	if (nilfs->ns_gc_inodes_h == NULL)
-		return -ENOMEM;
-
-	for (loop = 0; loop < NILFS_GCINODE_HASH_SIZE; loop++)
-		INIT_HLIST_HEAD(&nilfs->ns_gc_inodes_h[loop]);
-	return 0;
-}
-
-/*
- * nilfs_destroy_gccache() - free gc_inode hash table
- * @nilfs - the nilfs
- */
-void nilfs_destroy_gccache(struct the_nilfs *nilfs)
-{
-	if (nilfs->ns_gc_inodes_h) {
-		nilfs_remove_all_gcinode(nilfs);
-		kfree(nilfs->ns_gc_inodes_h);
-		nilfs->ns_gc_inodes_h = NULL;
+	} else {
+		nilfs_mark_buffer_dirty(bh);
 	}
+	return 0;
 }
 
-static struct inode *alloc_gcinode(struct the_nilfs *nilfs, ino_t ino,
-				   __u64 cno)
+int nilfs_init_gcinode(struct inode *inode)
 {
-	struct inode *inode;
-	struct nilfs_inode_info *ii;
-
-	inode = nilfs_mdt_new_common(nilfs, NULL, ino, GFP_NOFS, 0);
-	if (!inode)
-		return NULL;
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct the_nilfs *nilfs = NILFS_SB(inode->i_sb)->s_nilfs;
 
-	inode->i_op = NULL;
-	inode->i_fop = NULL;
+	inode->i_mode = S_IFREG;
+	mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
 	inode->i_mapping->a_ops = &def_gcinode_aops;
+	inode->i_mapping->backing_dev_info = inode->i_sb->s_bdi;
 
-	ii = NILFS_I(inode);
-	ii->i_cno = cno;
 	ii->i_flags = 0;
-	ii->i_state = 1 << NILFS_I_GCINODE;
-	ii->i_bh = NULL;
 	nilfs_bmap_init_gc(ii->i_bmap);
 
-	return inode;
-}
-
-static unsigned long ihash(ino_t ino, __u64 cno)
-{
-	return hash_long((unsigned long)((ino << 2) + cno),
-			 NILFS_GCINODE_HASH_BITS);
-}
-
-/*
- * nilfs_gc_iget() - find or create gc inode with specified (ino,cno)
- */
-struct inode *nilfs_gc_iget(struct the_nilfs *nilfs, ino_t ino, __u64 cno)
-{
-	struct hlist_head *head = nilfs->ns_gc_inodes_h + ihash(ino, cno);
-	struct hlist_node *node;
-	struct inode *inode;
-
-	hlist_for_each_entry(inode, node, head, i_hash) {
-		if (inode->i_ino == ino && NILFS_I(inode)->i_cno == cno)
-			return inode;
-	}
-
-	inode = alloc_gcinode(nilfs, ino, cno);
-	if (likely(inode)) {
-		hlist_add_head(&inode->i_hash, head);
-		list_add(&NILFS_I(inode)->i_dirty, &nilfs->ns_gc_inodes);
-	}
-	return inode;
-}
+	/*
+	 * Add the inode to GC inode list. Garbage Collection
+	 * is serialized and no two processes manipulate the
+	 * list simultaneously.
+	 */
+	igrab(inode);
+	list_add(&NILFS_I(inode)->i_dirty, &nilfs->ns_gc_inodes);
 
-/*
- * nilfs_clear_gcinode() - clear and free a gc inode
- */
-void nilfs_clear_gcinode(struct inode *inode)
-{
-	nilfs_mdt_destroy(inode);
+	return 0;
 }
 
-/*
- * nilfs_remove_all_gcinode() - remove all inodes from the_nilfs
+/**
+ * nilfs_remove_all_gcinodes() - remove all unprocessed gc inodes
  */
-void nilfs_remove_all_gcinode(struct the_nilfs *nilfs)
+void nilfs_remove_all_gcinodes(struct the_nilfs *nilfs)
 {
-	struct hlist_head *head = nilfs->ns_gc_inodes_h;
-	struct hlist_node *node, *n;
-	struct inode *inode;
-	int loop;
+	struct list_head *head = &nilfs->ns_gc_inodes;
+	struct nilfs_inode_info *ii;
 
-	for (loop = 0; loop < NILFS_GCINODE_HASH_SIZE; loop++, head++) {
-		hlist_for_each_entry_safe(inode, node, n, head, i_hash) {
-			hlist_del_init(&inode->i_hash);
-			list_del_init(&NILFS_I(inode)->i_dirty);
-			nilfs_clear_gcinode(inode); /* might sleep */
-		}
+	while (!list_empty(head)) {
+		ii = list_first_entry(head, struct nilfs_inode_info, i_dirty);
+		list_del_init(&ii->i_dirty);
+		iput(&ii->vfs_inode);
 	}
 }
diff --git a/fs/nilfs2/ifile.c b/fs/nilfs2/ifile.c
index 922d9dd..9f8a2da 100644
--- a/fs/nilfs2/ifile.c
+++ b/fs/nilfs2/ifile.c
@@ -161,25 +161,46 @@ int nilfs_ifile_get_inode_block(struct inode *ifile, ino_t ino,
 }
 
 /**
- * nilfs_ifile_new - create inode file
- * @sbi: nilfs_sb_info struct
+ * nilfs_ifile_read - read or get ifile inode
+ * @sb: super block instance
+ * @root: root object
  * @inode_size: size of an inode
+ * @raw_inode: on-disk ifile inode
+ * @inodep: buffer to store the inode
  */
-struct inode *nilfs_ifile_new(struct nilfs_sb_info *sbi, size_t inode_size)
+int nilfs_ifile_read(struct super_block *sb, struct nilfs_root *root,
+		     size_t inode_size, struct nilfs_inode *raw_inode,
+		     struct inode **inodep)
 {
 	struct inode *ifile;
 	int err;
 
-	ifile = nilfs_mdt_new(sbi->s_nilfs, sbi->s_super, NILFS_IFILE_INO,
-			      sizeof(struct nilfs_ifile_info));
-	if (ifile) {
-		err = nilfs_palloc_init_blockgroup(ifile, inode_size);
-		if (unlikely(err)) {
-			nilfs_mdt_destroy(ifile);
-			return NULL;
-		}
-		nilfs_palloc_setup_cache(ifile,
-					 &NILFS_IFILE_I(ifile)->palloc_cache);
-	}
-	return ifile;
+	ifile = nilfs_iget_locked(sb, root, NILFS_IFILE_INO);
+	if (unlikely(!ifile))
+		return -ENOMEM;
+	if (!(ifile->i_state & I_NEW))
+		goto out;
+
+	err = nilfs_mdt_init(ifile, NILFS_MDT_GFP,
+			     sizeof(struct nilfs_ifile_info));
+	if (err)
+		goto failed;
+
+	err = nilfs_palloc_init_blockgroup(ifile, inode_size);
+	if (err)
+		goto failed;
+
+	nilfs_palloc_setup_cache(ifile, &NILFS_IFILE_I(ifile)->palloc_cache);
+
+	err = nilfs_read_inode_common(ifile, raw_inode);
+	if (err)
+		goto failed;
+
+	unlock_new_inode(ifile);
+ out:
+	*inodep = ifile;
+	return 0;
+ failed:
+	iget_failed(ifile);
+	return err;
 }
diff --git a/fs/nilfs2/ifile.h b/fs/nilfs2/ifile.h
index cbca32e..59b6f2b 100644
--- a/fs/nilfs2/ifile.h
+++ b/fs/nilfs2/ifile.h
@@ -49,6 +49,8 @@ int nilfs_ifile_create_inode(struct inode *, ino_t *, struct buffer_head **);
 int nilfs_ifile_delete_inode(struct inode *, ino_t);
 int nilfs_ifile_get_inode_block(struct inode *, ino_t, struct buffer_head **);
 
-struct inode *nilfs_ifile_new(struct nilfs_sb_info *sbi, size_t inode_size);
+int nilfs_ifile_read(struct super_block *sb, struct nilfs_root *root,
+		     size_t inode_size, struct nilfs_inode *raw_inode,
+		     struct inode **inodep);
 
 #endif	/* _NILFS_IFILE_H */
diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 39e038a..71d4bc8 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -27,12 +27,19 @@
 #include <linux/writeback.h>
 #include <linux/uio.h>
 #include "nilfs.h"
+#include "btnode.h"
 #include "segment.h"
 #include "page.h"
 #include "mdt.h"
 #include "cpfile.h"
 #include "ifile.h"
 
+struct nilfs_iget_args {
+	u64 ino;
+	__u64 cno;
+	struct nilfs_root *root;
+	int for_gc;
+};
 
 /**
  * nilfs_get_block() - get a file block on the filesystem (callback function)
@@ -197,11 +204,15 @@ static int nilfs_write_begin(struct file *file, struct address_space *mapping,
 	if (unlikely(err))
 		return err;
 
-	*pagep = NULL;
-	err = block_write_begin(file, mapping, pos, len, flags, pagep,
-				fsdata, nilfs_get_block);
-	if (unlikely(err))
+	err = block_write_begin(mapping, pos, len, flags, pagep,
+				nilfs_get_block);
+	if (unlikely(err)) {
+		loff_t isize = mapping->host->i_size;
+		if (pos + len > isize)
+			vmtruncate(mapping->host, isize);
+
 		nilfs_transaction_abort(inode->i_sb);
+	}
 	return err;
 }
 
@@ -237,6 +248,19 @@ nilfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
 	/* Needs synchronization with the cleaner */
 	size = blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev, iov,
 				  offset, nr_segs, nilfs_get_block, NULL);
+
+	/*
+	 * In case of error extending write may have instantiated a few
+	 * blocks outside i_size. Trim these off again.
+	 */
+	if (unlikely((rw & WRITE) && size < 0)) {
+		loff_t isize = i_size_read(inode);
+		loff_t end = offset + iov_length(iov, nr_segs);
+
+		if (end > isize)
+			vmtruncate(inode, isize);
+	}
+
 	return size;
 }
 
@@ -261,6 +285,7 @@ struct inode *nilfs_new_inode(struct inode *dir, int mode)
 	struct nilfs_sb_info *sbi = NILFS_SB(sb);
 	struct inode *inode;
 	struct nilfs_inode_info *ii;
+	struct nilfs_root *root;
 	int err = -ENOMEM;
 	ino_t ino;
 
@@ -271,15 +296,17 @@ struct inode *nilfs_new_inode(struct inode *dir, int mode)
 	mapping_set_gfp_mask(inode->i_mapping,
 			     mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
 
+	root = NILFS_I(dir)->i_root;
 	ii = NILFS_I(inode);
 	ii->i_state = 1 << NILFS_I_NEW;
+	ii->i_root = root;
 
-	err = nilfs_ifile_create_inode(sbi->s_ifile, &ino, &ii->i_bh);
+	err = nilfs_ifile_create_inode(root->ifile, &ino, &ii->i_bh);
 	if (unlikely(err))
 		goto failed_ifile_create_inode;
 	/* reference count of i_bh inherits from nilfs_mdt_read_block() */
 
-	atomic_inc(&sbi->s_inodes_count);
+	atomic_inc(&root->inodes_count);
 	inode_init_owner(inode, dir, mode);
 	inode->i_ino = ino;
 	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
@@ -302,7 +329,6 @@ struct inode *nilfs_new_inode(struct inode *dir, int mode)
 	/* ii->i_file_acl = 0; */
 	/* ii->i_dir_acl = 0; */
 	ii->i_dir_start_lookup = 0;
-	ii->i_cno = 0;
 	nilfs_set_inode_flags(inode);
 	spin_lock(&sbi->s_next_gen_lock);
 	inode->i_generation = sbi->s_next_generation++;
@@ -332,17 +358,6 @@ struct inode *nilfs_new_inode(struct inode *dir, int mode)
 	return ERR_PTR(err);
 }
 
-void nilfs_free_inode(struct inode *inode)
-{
-	struct super_block *sb = inode->i_sb;
-	struct nilfs_sb_info *sbi = NILFS_SB(sb);
-
-	clear_inode(inode);
-	/* XXX: check error code? Is there any thing I can do? */
-	(void) nilfs_ifile_delete_inode(sbi->s_ifile, inode->i_ino);
-	atomic_dec(&sbi->s_inodes_count);
-}
-
 void nilfs_set_inode_flags(struct inode *inode)
 {
 	unsigned int flags = NILFS_I(inode)->i_flags;
@@ -393,7 +408,6 @@ int nilfs_read_inode_common(struct inode *inode,
 		0 : le32_to_cpu(raw_inode->i_dir_acl);
 #endif
 	ii->i_dir_start_lookup = 0;
-	ii->i_cno = 0;
 	inode->i_generation = le32_to_cpu(raw_inode->i_generation);
 
 	if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
@@ -407,7 +421,8 @@ int nilfs_read_inode_common(struct inode *inode,
 	return 0;
 }
 
-static int __nilfs_read_inode(struct super_block *sb, unsigned long ino,
+static int __nilfs_read_inode(struct super_block *sb,
+			      struct nilfs_root *root, unsigned long ino,
 			      struct inode *inode)
 {
 	struct nilfs_sb_info *sbi = NILFS_SB(sb);
@@ -417,11 +432,11 @@ static int __nilfs_read_inode(struct super_block *sb, unsigned long ino,
 	int err;
 
 	down_read(&NILFS_MDT(dat)->mi_sem);	/* XXX */
-	err = nilfs_ifile_get_inode_block(sbi->s_ifile, ino, &bh);
+	err = nilfs_ifile_get_inode_block(root->ifile, ino, &bh);
 	if (unlikely(err))
 		goto bad_inode;
 
-	raw_inode = nilfs_ifile_map_inode(sbi->s_ifile, ino, bh);
+	raw_inode = nilfs_ifile_map_inode(root->ifile, ino, bh);
 
 	err = nilfs_read_inode_common(inode, raw_inode);
 	if (err)
@@ -444,14 +459,14 @@ static int __nilfs_read_inode(struct super_block *sb, unsigned long ino,
 			inode, inode->i_mode,
 			huge_decode_dev(le64_to_cpu(raw_inode->i_device_code)));
 	}
-	nilfs_ifile_unmap_inode(sbi->s_ifile, ino, bh);
+	nilfs_ifile_unmap_inode(root->ifile, ino, bh);
 	brelse(bh);
 	up_read(&NILFS_MDT(dat)->mi_sem);	/* XXX */
 	nilfs_set_inode_flags(inode);
 	return 0;
 
  failed_unmap:
-	nilfs_ifile_unmap_inode(sbi->s_ifile, ino, bh);
+	nilfs_ifile_unmap_inode(root->ifile, ino, bh);
 	brelse(bh);
 
  bad_inode:
@@ -459,18 +474,95 @@ static int __nilfs_read_inode(struct super_block *sb, unsigned long ino,
 	return err;
 }
 
-struct inode *nilfs_iget(struct super_block *sb, unsigned long ino)
+static int nilfs_iget_test(struct inode *inode, void *opaque)
+{
+	struct nilfs_iget_args *args = opaque;
+	struct nilfs_inode_info *ii;
+
+	if (args->ino != inode->i_ino || args->root != NILFS_I(inode)->i_root)
+		return 0;
+
+	ii = NILFS_I(inode);
+	if (!test_bit(NILFS_I_GCINODE, &ii->i_state))
+		return !args->for_gc;
+
+	return args->for_gc && args->cno == ii->i_cno;
+}
+
+static int nilfs_iget_set(struct inode *inode, void *opaque)
+{
+	struct nilfs_iget_args *args = opaque;
+
+	inode->i_ino = args->ino;
+	if (args->for_gc) {
+		NILFS_I(inode)->i_state = 1 << NILFS_I_GCINODE;
+		NILFS_I(inode)->i_cno = args->cno;
+		NILFS_I(inode)->i_root = NULL;
+	} else {
+		if (args->root && args->ino == NILFS_ROOT_INO)
+			nilfs_get_root(args->root);
+		NILFS_I(inode)->i_root = args->root;
+	}
+	return 0;
+}
+
+struct inode *nilfs_ilookup(struct super_block *sb, struct nilfs_root *root,
+			    unsigned long ino)
+{
+	struct nilfs_iget_args args = {
+		.ino = ino, .root = root, .cno = 0, .for_gc = 0
+	};
+
+	return ilookup5(sb, ino, nilfs_iget_test, &args);
+}
+
+struct inode *nilfs_iget_locked(struct super_block *sb, struct nilfs_root *root,
+				unsigned long ino)
+{
+	struct nilfs_iget_args args = {
+		.ino = ino, .root = root, .cno = 0, .for_gc = 0
+	};
+
+	return iget5_locked(sb, ino, nilfs_iget_test, nilfs_iget_set, &args);
+}
+
+struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root,
+			 unsigned long ino)
+{
+	struct inode *inode;
+	int err;
+
+	inode = nilfs_iget_locked(sb, root, ino);
+	if (unlikely(!inode))
+		return ERR_PTR(-ENOMEM);
+	if (!(inode->i_state & I_NEW))
+		return inode;
+
+	err = __nilfs_read_inode(sb, root, ino, inode);
+	if (unlikely(err)) {
+		iget_failed(inode);
+		return ERR_PTR(err);
+	}
+	unlock_new_inode(inode);
+	return inode;
+}
+
+struct inode *nilfs_iget_for_gc(struct super_block *sb, unsigned long ino,
+				__u64 cno)
 {
+	struct nilfs_iget_args args = {
+		.ino = ino, .root = NULL, .cno = cno, .for_gc = 1
+	};
 	struct inode *inode;
 	int err;
 
-	inode = iget_locked(sb, ino);
+	inode = iget5_locked(sb, ino, nilfs_iget_test, nilfs_iget_set, &args);
 	if (unlikely(!inode))
 		return ERR_PTR(-ENOMEM);
 	if (!(inode->i_state & I_NEW))
 		return inode;
 
-	err = __nilfs_read_inode(sb, ino, inode);
+	err = nilfs_init_gcinode(inode);
 	if (unlikely(err)) {
 		iget_failed(inode);
 		return ERR_PTR(err);
@@ -511,21 +603,20 @@ void nilfs_update_inode(struct inode *inode, struct buffer_head *ibh)
 {
 	ino_t ino = inode->i_ino;
 	struct nilfs_inode_info *ii = NILFS_I(inode);
-	struct super_block *sb = inode->i_sb;
-	struct nilfs_sb_info *sbi = NILFS_SB(sb);
+	struct inode *ifile = ii->i_root->ifile;
 	struct nilfs_inode *raw_inode;
 
-	raw_inode = nilfs_ifile_map_inode(sbi->s_ifile, ino, ibh);
+	raw_inode = nilfs_ifile_map_inode(ifile, ino, ibh);
 
 	if (test_and_clear_bit(NILFS_I_NEW, &ii->i_state))
-		memset(raw_inode, 0, NILFS_MDT(sbi->s_ifile)->mi_entry_size);
+		memset(raw_inode, 0, NILFS_MDT(ifile)->mi_entry_size);
 	set_bit(NILFS_I_INODE_DIRTY, &ii->i_state);
 
 	nilfs_write_inode_common(inode, raw_inode, 0);
 		/* XXX: call with has_bmap = 0 is a workaround to avoid
 		   deadlock of bmap. This delays update of i_bmap to just
 		   before writing */
-	nilfs_ifile_unmap_inode(sbi->s_ifile, ino, ibh);
+	nilfs_ifile_unmap_inode(ifile, ino, ibh);
 }
 
 #define NILFS_MAX_TRUNCATE_BLOCKS	16384  /* 64MB for 4KB block */
@@ -597,16 +688,41 @@ void nilfs_truncate(struct inode *inode)
 	   But truncate has no return value. */
 }
 
-void nilfs_delete_inode(struct inode *inode)
+static void nilfs_clear_inode(struct inode *inode)
+{
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
+
+	/*
+	 * Free resources allocated in nilfs_read_inode(), here.
+	 */
+	BUG_ON(!list_empty(&ii->i_dirty));
+	brelse(ii->i_bh);
+	ii->i_bh = NULL;
+
+	if (mdi && mdi->mi_palloc_cache)
+		nilfs_palloc_destroy_cache(inode);
+
+	if (test_bit(NILFS_I_BMAP, &ii->i_state))
+		nilfs_bmap_clear(ii->i_bmap);
+
+	nilfs_btnode_cache_clear(&ii->i_btnode_cache);
+
+	if (ii->i_root && inode->i_ino == NILFS_ROOT_INO)
+		nilfs_put_root(ii->i_root);
+}
+
+void nilfs_evict_inode(struct inode *inode)
 {
 	struct nilfs_transaction_info ti;
 	struct super_block *sb = inode->i_sb;
 	struct nilfs_inode_info *ii = NILFS_I(inode);
 
-	if (unlikely(is_bad_inode(inode))) {
+	if (inode->i_nlink || !ii->i_root || unlikely(is_bad_inode(inode))) {
 		if (inode->i_data.nrpages)
 			truncate_inode_pages(&inode->i_data, 0);
-		clear_inode(inode);
+		end_writeback(inode);
+		nilfs_clear_inode(inode);
 		return;
 	}
 	nilfs_transaction_begin(sb, &ti, 0); /* never fails */
@@ -614,10 +730,16 @@ void nilfs_delete_inode(struct inode *inode)
 	if (inode->i_data.nrpages)
 		truncate_inode_pages(&inode->i_data, 0);
 
+	/* TODO: some of the following operations may fail.  */
 	nilfs_truncate_bmap(ii, 0);
 	nilfs_mark_inode_dirty(inode);
-	nilfs_free_inode(inode);
-	/* nilfs_free_inode() marks inode buffer dirty */
+	end_writeback(inode);
+
+	nilfs_ifile_delete_inode(ii->i_root->ifile, inode->i_ino);
+	atomic_dec(&ii->i_root->inodes_count);
+
+	nilfs_clear_inode(inode);
+
 	if (IS_SYNC(inode))
 		nilfs_set_transaction_flag(NILFS_TI_SYNC);
 	nilfs_transaction_commit(sb);
@@ -639,17 +761,41 @@ int nilfs_setattr(struct dentry *dentry, struct iattr *iattr)
 	err = nilfs_transaction_begin(sb, &ti, 0);
 	if (unlikely(err))
 		return err;
-	err = inode_setattr(inode, iattr);
-	if (!err && (iattr->ia_valid & ATTR_MODE))
+
+	if ((iattr->ia_valid & ATTR_SIZE) &&
+	    iattr->ia_size != i_size_read(inode)) {
+		err = vmtruncate(inode, iattr->ia_size);
+		if (unlikely(err))
+			goto out_err;
+	}
+
+	setattr_copy(inode, iattr);
+	mark_inode_dirty(inode);
+
+	if (iattr->ia_valid & ATTR_MODE) {
 		err = nilfs_acl_chmod(inode);
-	if (likely(!err))
-		err = nilfs_transaction_commit(sb);
-	else
-		nilfs_transaction_abort(sb);
+		if (unlikely(err))
+			goto out_err;
+	}
+
+	return nilfs_transaction_commit(sb);
 
+out_err:
+	nilfs_transaction_abort(sb);
 	return err;
 }
 
+int nilfs_permission(struct inode *inode, int mask)
+{
+	struct nilfs_root *root = NILFS_I(inode)->i_root;
+
+	if ((mask & MAY_WRITE) && root &&
+	    root->cno != NILFS_CPTREE_CURRENT_CNO)
+		return -EROFS; /* snapshot is not writable */
+
+	return generic_permission(inode, mask, NULL);
+}
+
 int nilfs_load_inode_block(struct nilfs_sb_info *sbi, struct inode *inode,
 			   struct buffer_head **pbh)
 {
@@ -659,8 +805,8 @@ int nilfs_load_inode_block(struct nilfs_sb_info *sbi, struct inode *inode,
 	spin_lock(&sbi->s_inode_lock);
 	if (ii->i_bh == NULL) {
 		spin_unlock(&sbi->s_inode_lock);
-		err = nilfs_ifile_get_inode_block(sbi->s_ifile, inode->i_ino,
-						  pbh);
+		err = nilfs_ifile_get_inode_block(ii->i_root->ifile,
+						  inode->i_ino, pbh);
 		if (unlikely(err))
 			return err;
 		spin_lock(&sbi->s_inode_lock);
@@ -740,7 +886,7 @@ int nilfs_mark_inode_dirty(struct inode *inode)
 	}
 	nilfs_update_inode(inode, ibh);
 	nilfs_mdt_mark_buffer_dirty(ibh);
-	nilfs_mdt_mark_dirty(sbi->s_ifile);
+	nilfs_mdt_mark_dirty(NILFS_I(inode)->i_root->ifile);
 	brelse(ibh);
 	return 0;
 }
@@ -758,6 +904,7 @@ int nilfs_mark_inode_dirty(struct inode *inode)
 void nilfs_dirty_inode(struct inode *inode)
 {
 	struct nilfs_transaction_info ti;
+	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
 
 	if (is_bad_inode(inode)) {
 		nilfs_warning(inode->i_sb, __func__,
@@ -765,6 +912,10 @@ void nilfs_dirty_inode(struct inode *inode)
 		dump_stack();
 		return;
 	}
+	if (mdi) {
+		nilfs_mdt_mark_dirty(inode);
+		return;
+	}
 	nilfs_transaction_begin(inode->i_sb, &ti, 0);
 	nilfs_mark_inode_dirty(inode);
 	nilfs_transaction_commit(inode->i_sb); /* never fails */
diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index f90a33d..3e90f86 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -22,7 +22,6 @@
 
 #include <linux/fs.h>
 #include <linux/wait.h>
-#include <linux/smp_lock.h>	/* lock_kernel(), unlock_kernel() */
 #include <linux/slab.h>
 #include <linux/capability.h>	/* capable() */
 #include <linux/uaccess.h>	/* copy_from_user(), copy_to_user() */
@@ -118,7 +117,7 @@ static int nilfs_ioctl_change_cpmode(struct inode *inode, struct file *filp,
 	if (copy_from_user(&cpmode, argp, sizeof(cpmode)))
 		goto out;
 
-	mutex_lock(&nilfs->ns_mount_mutex);
+	down_read(&inode->i_sb->s_umount);
 
 	nilfs_transaction_begin(inode->i_sb, &ti, 0);
 	ret = nilfs_cpfile_change_cpmode(
@@ -128,7 +127,7 @@ static int nilfs_ioctl_change_cpmode(struct inode *inode, struct file *filp,
 	else
 		nilfs_transaction_commit(inode->i_sb); /* never fails */
 
-	mutex_unlock(&nilfs->ns_mount_mutex);
+	up_read(&inode->i_sb->s_umount);
 out:
 	mnt_drop_write(filp->f_path.mnt);
 	return ret;
@@ -334,7 +333,7 @@ static int nilfs_ioctl_move_inode_block(struct inode *inode,
 	return 0;
 }
 
-static int nilfs_ioctl_move_blocks(struct the_nilfs *nilfs,
+static int nilfs_ioctl_move_blocks(struct super_block *sb,
 				   struct nilfs_argv *argv, void *buf)
 {
 	size_t nmembs = argv->v_nmembs;
@@ -349,7 +348,7 @@ static int nilfs_ioctl_move_blocks(struct the_nilfs *nilfs,
 	for (i = 0, vdesc = buf; i < nmembs; ) {
 		ino = vdesc->vd_ino;
 		cno = vdesc->vd_cno;
-		inode = nilfs_gc_iget(nilfs, ino, cno);
+		inode = nilfs_iget_for_gc(sb, ino, cno);
 		if (unlikely(inode == NULL)) {
 			ret = -ENOMEM;
 			goto failed;
@@ -357,11 +356,15 @@ static int nilfs_ioctl_move_blocks(struct the_nilfs *nilfs,
 		do {
 			ret = nilfs_ioctl_move_inode_block(inode, vdesc,
 							   &buffers);
-			if (unlikely(ret < 0))
+			if (unlikely(ret < 0)) {
+				iput(inode);
 				goto failed;
+			}
 			vdesc++;
 		} while (++i < nmembs &&
 			 vdesc->vd_ino == ino && vdesc->vd_cno == cno);
+
+		iput(inode); /* The inode still remains in GC inode list */
 	}
 
 	list_for_each_entry_safe(bh, n, &buffers, b_assoc_buffers) {
@@ -567,7 +570,7 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
 	}
 
 	/*
-	 * nilfs_ioctl_move_blocks() will call nilfs_gc_iget(),
+	 * nilfs_ioctl_move_blocks() will call nilfs_iget_for_gc(),
 	 * which will operates an inode list without blocking.
 	 * To protect the list from concurrent operations,
 	 * nilfs_ioctl_move_blocks should be atomic operation.
@@ -577,15 +580,16 @@ static int nilfs_ioctl_clean_segments(struct inode *inode, struct file *filp,
 		goto out_free;
 	}
 
-	ret = nilfs_ioctl_move_blocks(nilfs, &argv[0], kbufs[0]);
+	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
+
+	ret = nilfs_ioctl_move_blocks(inode->i_sb, &argv[0], kbufs[0]);
 	if (ret < 0)
 		printk(KERN_ERR "NILFS: GC failed during preparation: "
 			"cannot read source blocks: err=%d\n", ret);
 	else
 		ret = nilfs_clean_segments(inode->i_sb, argv, kbufs);
 
-	if (ret < 0)
-		nilfs_remove_all_gcinode(nilfs);
+	nilfs_remove_all_gcinodes(nilfs);
 	clear_nilfs_gc_running(nilfs);
 
 out_free:
diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
index 024be8c..39a5b84 100644
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -28,6 +28,7 @@
 #include <linux/swap.h>
 #include <linux/slab.h>
 #include "nilfs.h"
+#include "btnode.h"
 #include "segment.h"
 #include "page.h"
 #include "mdt.h"
@@ -35,7 +36,6 @@
 
 #define NILFS_MDT_MAX_RA_BLOCKS		(16 - 1)
 
-#define INIT_UNUSED_INODE_FIELDS
 
 static int
 nilfs_mdt_insert_new_block(struct inode *inode, unsigned long block,
@@ -77,25 +77,11 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
 						     struct buffer_head *,
 						     void *))
 {
-	struct the_nilfs *nilfs = NILFS_MDT(inode)->mi_nilfs;
 	struct super_block *sb = inode->i_sb;
 	struct nilfs_transaction_info ti;
 	struct buffer_head *bh;
 	int err;
 
-	if (!sb) {
-		/*
-		 * Make sure this function is not called from any
-		 * read-only context.
-		 */
-		if (!nilfs->ns_writer) {
-			WARN_ON(1);
-			err = -EROFS;
-			goto out;
-		}
-		sb = nilfs->ns_writer->s_super;
-	}
-
 	nilfs_transaction_begin(sb, &ti, 0);
 
 	err = -ENOMEM;
@@ -111,7 +97,7 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
 	if (buffer_uptodate(bh))
 		goto failed_bh;
 
-	bh->b_bdev = nilfs->ns_bdev;
+	bh->b_bdev = sb->s_bdev;
 	err = nilfs_mdt_insert_new_block(inode, block, bh, init_block);
 	if (likely(!err)) {
 		get_bh(bh);
@@ -128,7 +114,7 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
 		err = nilfs_transaction_commit(sb);
 	else
 		nilfs_transaction_abort(sb);
- out:
+
 	return err;
 }
 
@@ -166,9 +152,7 @@ nilfs_mdt_submit_block(struct inode *inode, unsigned long blkoff,
 		unlock_buffer(bh);
 		goto failed_bh;
 	}
-	bh->b_bdev = NILFS_MDT(inode)->mi_nilfs->ns_bdev;
-	bh->b_blocknr = (sector_t)blknum;
-	set_buffer_mapped(bh);
+	map_bh(bh, inode->i_sb, (sector_t)blknum);
 
 	bh->b_end_io = end_buffer_read_sync;
 	get_bh(bh);
@@ -397,35 +381,24 @@ int nilfs_mdt_fetch_dirty(struct inode *inode)
 static int
 nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
 {
-	struct inode *inode = container_of(page->mapping,
-					   struct inode, i_data);
-	struct super_block *sb = inode->i_sb;
-	struct the_nilfs *nilfs = NILFS_MDT(inode)->mi_nilfs;
-	struct nilfs_sb_info *writer = NULL;
+	struct inode *inode;
+	struct super_block *sb;
 	int err = 0;
 
 	redirty_page_for_writepage(wbc, page);
 	unlock_page(page);
 
-	if (page->mapping->assoc_mapping)
-		return 0; /* Do not request flush for shadow page cache */
-	if (!sb) {
-		down_read(&nilfs->ns_writer_sem);
-		writer = nilfs->ns_writer;
-		if (!writer) {
-			up_read(&nilfs->ns_writer_sem);
-			return -EROFS;
-		}
-		sb = writer->s_super;
-	}
+	inode = page->mapping->host;
+	if (!inode)
+		return 0;
+
+	sb = inode->i_sb;
 
 	if (wbc->sync_mode == WB_SYNC_ALL)
 		err = nilfs_construct_segment(sb);
 	else if (wbc->for_reclaim)
 		nilfs_flush_segment(sb, inode->i_ino);
 
-	if (writer)
-		up_read(&nilfs->ns_writer_sem);
 	return err;
 }
 
@@ -438,105 +411,27 @@ static const struct address_space_operations def_mdt_aops = {
 static const struct inode_operations def_mdt_iops;
 static const struct file_operations def_mdt_fops;
 
-/*
- * NILFS2 uses pseudo inodes for meta data files such as DAT, cpfile, sufile,
- * ifile, or gcinodes.  This allows the B-tree code and segment constructor
- * to treat them like regular files, and this helps to simplify the
- * implementation.
- *   On the other hand, some of the pseudo inodes have an irregular point:
- * They don't have valid inode->i_sb pointer because their lifetimes are
- * longer than those of the super block structs; they may continue for
- * several consecutive mounts/umounts.  This would need discussions.
- */
-/**
- * nilfs_mdt_new_common - allocate a pseudo inode for metadata file
- * @nilfs: nilfs object
- * @sb: super block instance the metadata file belongs to
- * @ino: inode number
- * @gfp_mask: gfp mask for data pages
- * @objsz: size of the private object attached to inode->i_private
- */
-struct inode *
-nilfs_mdt_new_common(struct the_nilfs *nilfs, struct super_block *sb,
-		     ino_t ino, gfp_t gfp_mask, size_t objsz)
+
+int nilfs_mdt_init(struct inode *inode, gfp_t gfp_mask, size_t objsz)
 {
-	struct inode *inode = nilfs_alloc_inode_common(nilfs);
+	struct nilfs_mdt_info *mi;
 
-	if (!inode)
-		return NULL;
-	else {
-		struct address_space * const mapping = &inode->i_data;
-		struct nilfs_mdt_info *mi;
-
-		mi = kzalloc(max(sizeof(*mi), objsz), GFP_NOFS);
-		if (!mi) {
-			nilfs_destroy_inode(inode);
-			return NULL;
-		}
-		mi->mi_nilfs = nilfs;
-		init_rwsem(&mi->mi_sem);
-
-		inode->i_sb = sb; /* sb may be NULL for some meta data files */
-		inode->i_blkbits = nilfs->ns_blocksize_bits;
-		inode->i_flags = 0;
-		atomic_set(&inode->i_count, 1);
-		inode->i_nlink = 1;
-		inode->i_ino = ino;
-		inode->i_mode = S_IFREG;
-		inode->i_private = mi;
-
-#ifdef INIT_UNUSED_INODE_FIELDS
-		atomic_set(&inode->i_writecount, 0);
-		inode->i_size = 0;
-		inode->i_blocks = 0;
-		inode->i_bytes = 0;
-		inode->i_generation = 0;
-#ifdef CONFIG_QUOTA
-		memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
-#endif
-		inode->i_pipe = NULL;
-		inode->i_bdev = NULL;
-		inode->i_cdev = NULL;
-		inode->i_rdev = 0;
-#ifdef CONFIG_SECURITY
-		inode->i_security = NULL;
-#endif
-		inode->dirtied_when = 0;
-
-		INIT_LIST_HEAD(&inode->i_list);
-		INIT_LIST_HEAD(&inode->i_sb_list);
-		inode->i_state = 0;
-#endif
-
-		spin_lock_init(&inode->i_lock);
-		mutex_init(&inode->i_mutex);
-		init_rwsem(&inode->i_alloc_sem);
-
-		mapping->host = NULL;  /* instead of inode */
-		mapping->flags = 0;
-		mapping_set_gfp_mask(mapping, gfp_mask);
-		mapping->assoc_mapping = NULL;
-		mapping->backing_dev_info = nilfs->ns_bdi;
-
-		inode->i_mapping = mapping;
-	}
+	mi = kzalloc(max(sizeof(*mi), objsz), GFP_NOFS);
+	if (!mi)
+		return -ENOMEM;
 
-	return inode;
-}
+	init_rwsem(&mi->mi_sem);
+	inode->i_private = mi;
 
-struct inode *nilfs_mdt_new(struct the_nilfs *nilfs, struct super_block *sb,
-			    ino_t ino, size_t objsz)
-{
-	struct inode *inode;
-
-	inode = nilfs_mdt_new_common(nilfs, sb, ino, NILFS_MDT_GFP, objsz);
-	if (!inode)
-		return NULL;
+	inode->i_mode = S_IFREG;
+	mapping_set_gfp_mask(inode->i_mapping, gfp_mask);
+	inode->i_mapping->backing_dev_info = inode->i_sb->s_bdi;
 
 	inode->i_op = &def_mdt_iops;
 	inode->i_fop = &def_mdt_fops;
 	inode->i_mapping->a_ops = &def_mdt_aops;
-	return inode;
+
+	return 0;
 }
 
 void nilfs_mdt_set_entry_size(struct inode *inode, unsigned entry_size,
@@ -549,34 +444,159 @@ void nilfs_mdt_set_entry_size(struct inode *inode, unsigned entry_size,
 	mi->mi_first_entry_offset = DIV_ROUND_UP(header_size, entry_size);
 }
 
-void nilfs_mdt_set_shadow(struct inode *orig, struct inode *shadow)
+static const struct address_space_operations shadow_map_aops = {
+	.sync_page		= block_sync_page,
+};
+
+/**
+ * nilfs_mdt_setup_shadow_map - setup shadow map and bind it to metadata file
+ * @inode: inode of the metadata file
+ * @shadow: shadow mapping
+ */
+int nilfs_mdt_setup_shadow_map(struct inode *inode,
+			       struct nilfs_shadow_map *shadow)
 {
-	shadow->i_mapping->assoc_mapping = orig->i_mapping;
-	NILFS_I(shadow)->i_btnode_cache.assoc_mapping =
-		&NILFS_I(orig)->i_btnode_cache;
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+	struct backing_dev_info *bdi = inode->i_sb->s_bdi;
+
+	INIT_LIST_HEAD(&shadow->frozen_buffers);
+	nilfs_mapping_init_once(&shadow->frozen_data);
+	nilfs_mapping_init(&shadow->frozen_data, bdi, &shadow_map_aops);
+	nilfs_mapping_init_once(&shadow->frozen_btnodes);
+	nilfs_mapping_init(&shadow->frozen_btnodes, bdi, &shadow_map_aops);
+	mi->mi_shadow = shadow;
+	return 0;
 }
 
-static void nilfs_mdt_clear(struct inode *inode)
+/**
+ * nilfs_mdt_save_to_shadow_map - copy bmap and dirty pages to shadow map
+ * @inode: inode of the metadata file
+ */
+int nilfs_mdt_save_to_shadow_map(struct inode *inode)
 {
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
 	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct nilfs_shadow_map *shadow = mi->mi_shadow;
+	int ret;
 
-	invalidate_mapping_pages(inode->i_mapping, 0, -1);
-	truncate_inode_pages(inode->i_mapping, 0);
+	ret = nilfs_copy_dirty_pages(&shadow->frozen_data, inode->i_mapping);
+	if (ret)
+		goto out;
+
+	ret = nilfs_copy_dirty_pages(&shadow->frozen_btnodes,
+				     &ii->i_btnode_cache);
+	if (ret)
+		goto out;
 
-	if (test_bit(NILFS_I_BMAP, &ii->i_state))
-		nilfs_bmap_clear(ii->i_bmap);
-	nilfs_btnode_cache_clear(&ii->i_btnode_cache);
+	nilfs_bmap_save(ii->i_bmap, &shadow->bmap_store);
+ out:
+	return ret;
 }
 
-void nilfs_mdt_destroy(struct inode *inode)
+int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh)
 {
-	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
+	struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
+	struct buffer_head *bh_frozen;
+	struct page *page;
+	int blkbits = inode->i_blkbits;
+	int ret = -ENOMEM;
+
+	page = grab_cache_page(&shadow->frozen_data, bh->b_page->index);
+	if (!page)
+		return ret;
+
+	if (!page_has_buffers(page))
+		create_empty_buffers(page, 1 << blkbits, 0);
+
+	bh_frozen = nilfs_page_get_nth_block(page, bh_offset(bh) >> blkbits);
+	if (bh_frozen) {
+		if (!buffer_uptodate(bh_frozen))
+			nilfs_copy_buffer(bh_frozen, bh);
+		if (list_empty(&bh_frozen->b_assoc_buffers)) {
+			list_add_tail(&bh_frozen->b_assoc_buffers,
+				      &shadow->frozen_buffers);
+			set_buffer_nilfs_redirected(bh);
+		} else {
+			brelse(bh_frozen); /* already frozen */
+		}
+		ret = 0;
+	}
+	unlock_page(page);
+	page_cache_release(page);
+	return ret;
+}
+
+struct buffer_head *
+nilfs_mdt_get_frozen_buffer(struct inode *inode, struct buffer_head *bh)
+{
+	struct nilfs_shadow_map *shadow = NILFS_MDT(inode)->mi_shadow;
+	struct buffer_head *bh_frozen = NULL;
+	struct page *page;
+	int n;
+
+	page = find_lock_page(&shadow->frozen_data, bh->b_page->index);
+	if (page) {
+		if (page_has_buffers(page)) {
+			n = bh_offset(bh) >> inode->i_blkbits;
+			bh_frozen = nilfs_page_get_nth_block(page, n);
+		}
+		unlock_page(page);
+		page_cache_release(page);
+	}
+	return bh_frozen;
+}
+
+static void nilfs_release_frozen_buffers(struct nilfs_shadow_map *shadow)
+{
+	struct list_head *head = &shadow->frozen_buffers;
+	struct buffer_head *bh;
+
+	while (!list_empty(head)) {
+		bh = list_first_entry(head, struct buffer_head,
+				      b_assoc_buffers);
+		list_del_init(&bh->b_assoc_buffers);
+		brelse(bh); /* drop ref-count to make it releasable */
+	}
+}
+
+/**
+ * nilfs_mdt_restore_from_shadow_map - restore dirty pages and bmap state
+ * @inode: inode of the metadata file
+ */
+void nilfs_mdt_restore_from_shadow_map(struct inode *inode)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+	struct nilfs_inode_info *ii = NILFS_I(inode);
+	struct nilfs_shadow_map *shadow = mi->mi_shadow;
+
+	down_write(&mi->mi_sem);
 
-	if (mdi->mi_palloc_cache)
-		nilfs_palloc_destroy_cache(inode);
-	nilfs_mdt_clear(inode);
+	if (mi->mi_palloc_cache)
+		nilfs_palloc_clear_cache(inode);
+
+	nilfs_clear_dirty_pages(inode->i_mapping);
+	nilfs_copy_back_pages(inode->i_mapping, &shadow->frozen_data);
+
+	nilfs_clear_dirty_pages(&ii->i_btnode_cache);
+	nilfs_copy_back_pages(&ii->i_btnode_cache, &shadow->frozen_btnodes);
+
+	nilfs_bmap_restore(ii->i_bmap, &shadow->bmap_store);
+
+	up_write(&mi->mi_sem);
+}
+
+/**
+ * nilfs_mdt_clear_shadow_map - truncate pages in shadow map caches
+ * @inode: inode of the metadata file
+ */
+void nilfs_mdt_clear_shadow_map(struct inode *inode)
+{
+	struct nilfs_mdt_info *mi = NILFS_MDT(inode);
+	struct nilfs_shadow_map *shadow = mi->mi_shadow;
 
-	kfree(mdi->mi_bgl); /* kfree(NULL) is safe */
-	kfree(mdi);
-	nilfs_destroy_inode(inode);
+	down_write(&mi->mi_sem);
+	nilfs_release_frozen_buffers(shadow);
+	truncate_inode_pages(&shadow->frozen_data, 0);
+	truncate_inode_pages(&shadow->frozen_btnodes, 0);
+	up_write(&mi->mi_sem);
 }
diff --git a/fs/nilfs2/mdt.h b/fs/nilfs2/mdt.h
index 6c4bbb0..b13734b 100644
--- a/fs/nilfs2/mdt.h
+++ b/fs/nilfs2/mdt.h
@@ -28,26 +28,33 @@
 #include "nilfs.h"
 #include "page.h"
 
+struct nilfs_shadow_map {
+	struct nilfs_bmap_store bmap_store;
+	struct address_space frozen_data;
+	struct address_space frozen_btnodes;
+	struct list_head frozen_buffers;
+};
+
 /**
  * struct nilfs_mdt_info - on-memory private data of meta data files
- * @mi_nilfs: back pointer to the_nilfs struct
  * @mi_sem: reader/writer semaphore for meta data operations
  * @mi_bgl: per-blockgroup locking
  * @mi_entry_size: size of an entry
  * @mi_first_entry_offset: offset to the first entry
  * @mi_entries_per_block: number of entries in a block
  * @mi_palloc_cache: persistent object allocator cache
+ * @mi_shadow: shadow of bmap and page caches
  * @mi_blocks_per_group: number of blocks in a group
  * @mi_blocks_per_desc_block: number of blocks per descriptor block
  */
 struct nilfs_mdt_info {
-	struct the_nilfs       *mi_nilfs;
 	struct rw_semaphore	mi_sem;
 	struct blockgroup_lock *mi_bgl;
 	unsigned		mi_entry_size;
 	unsigned		mi_first_entry_offset;
 	unsigned long		mi_entries_per_block;
 	struct nilfs_palloc_cache *mi_palloc_cache;
+	struct nilfs_shadow_map *mi_shadow;
 	unsigned long		mi_blocks_per_group;
 	unsigned long		mi_blocks_per_desc_block;
 };
@@ -59,9 +66,7 @@ static inline struct nilfs_mdt_info *NILFS_MDT(const struct inode *inode)
 
 static inline struct the_nilfs *NILFS_I_NILFS(struct inode *inode)
 {
-	struct super_block *sb = inode->i_sb;
-
-	return sb ? NILFS_SB(sb)->s_nilfs : NILFS_MDT(inode)->mi_nilfs;
+	return NILFS_SB(inode->i_sb)->s_nilfs;
 }
 
 /* Default GFP flags using highmem */
@@ -76,14 +81,17 @@ int nilfs_mdt_forget_block(struct inode *, unsigned long);
 int nilfs_mdt_mark_block_dirty(struct inode *, unsigned long);
 int nilfs_mdt_fetch_dirty(struct inode *);
 
-struct inode *nilfs_mdt_new(struct the_nilfs *, struct super_block *, ino_t,
-			    size_t);
-struct inode *nilfs_mdt_new_common(struct the_nilfs *, struct super_block *,
-				   ino_t, gfp_t, size_t);
-void nilfs_mdt_destroy(struct inode *);
+int nilfs_mdt_init(struct inode *inode, gfp_t gfp_mask, size_t objsz);
 void nilfs_mdt_set_entry_size(struct inode *, unsigned, unsigned);
-void nilfs_mdt_set_shadow(struct inode *, struct inode *);
 
+int nilfs_mdt_setup_shadow_map(struct inode *inode,
+			       struct nilfs_shadow_map *shadow);
+int nilfs_mdt_save_to_shadow_map(struct inode *inode);
+void nilfs_mdt_restore_from_shadow_map(struct inode *inode);
+void nilfs_mdt_clear_shadow_map(struct inode *inode);
+int nilfs_mdt_freeze_buffer(struct inode *inode, struct buffer_head *bh);
+struct buffer_head *nilfs_mdt_get_frozen_buffer(struct inode *inode,
+						struct buffer_head *bh);
 
 #define nilfs_mdt_mark_buffer_dirty(bh)	nilfs_mark_buffer_dirty(bh)
 
@@ -100,7 +108,7 @@ static inline void nilfs_mdt_clear_dirty(struct inode *inode)
 
 static inline __u64 nilfs_mdt_cno(struct inode *inode)
 {
-	return NILFS_MDT(inode)->mi_nilfs->ns_cno;
+	return NILFS_I_NILFS(inode)->ns_cno;
 }
 
 #define nilfs_mdt_bgl_lock(inode, bg) \
diff --git a/fs/nilfs2/namei.c b/fs/nilfs2/namei.c
index ad6ed2c..6e9557e 100644
--- a/fs/nilfs2/namei.c
+++ b/fs/nilfs2/namei.c
@@ -40,7 +40,11 @@
 
 #include <linux/pagemap.h>
 #include "nilfs.h"
+#include "export.h"
 
+#define NILFS_FID_SIZE_NON_CONNECTABLE \
+	(offsetof(struct nilfs_fid, parent_gen) / 4)
+#define NILFS_FID_SIZE_CONNECTABLE	(sizeof(struct nilfs_fid) / 4)
 
 static inline int nilfs_add_nondir(struct dentry *dentry, struct inode *inode)
 {
@@ -70,29 +74,13 @@ nilfs_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd)
 	ino = nilfs_inode_by_name(dir, &dentry->d_name);
 	inode = NULL;
 	if (ino) {
-		inode = nilfs_iget(dir->i_sb, ino);
+		inode = nilfs_iget(dir->i_sb, NILFS_I(dir)->i_root, ino);
 		if (IS_ERR(inode))
 			return ERR_CAST(inode);
 	}
 	return d_splice_alias(inode, dentry);
 }
 
-struct dentry *nilfs_get_parent(struct dentry *child)
-{
-	unsigned long ino;
-	struct inode *inode;
-	struct qstr dotdot = {.name = "..", .len = 2};
-
-	ino = nilfs_inode_by_name(child->d_inode, &dotdot);
-	if (!ino)
-		return ERR_PTR(-ENOENT);
-
-	inode = nilfs_iget(child->d_inode->i_sb, ino);
-	if (IS_ERR(inode))
-		return ERR_CAST(inode);
-	return d_obtain_alias(inode);
-}
-
 /*
  * By the time this is called, we already have created
  * the directory cache entry for the new file, but it
@@ -219,7 +207,7 @@ static int nilfs_link(struct dentry *old_dentry, struct inode *dir,
 
 	inode->i_ctime = CURRENT_TIME;
 	inode_inc_link_count(inode);
-	atomic_inc(&inode->i_count);
+	ihold(inode);
 
 	err = nilfs_add_nondir(dentry, inode);
 	if (!err)
@@ -468,6 +456,115 @@ out:
 	return err;
 }
 
+/*
+ * Export operations
+ */
+static struct dentry *nilfs_get_parent(struct dentry *child)
+{
+	unsigned long ino;
+	struct inode *inode;
+	struct qstr dotdot = {.name = "..", .len = 2};
+	struct nilfs_root *root;
+
+	ino = nilfs_inode_by_name(child->d_inode, &dotdot);
+	if (!ino)
+		return ERR_PTR(-ENOENT);
+
+	root = NILFS_I(child->d_inode)->i_root;
+
+	inode = nilfs_iget(child->d_inode->i_sb, root, ino);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+
+	return d_obtain_alias(inode);
+}
+
+static struct dentry *nilfs_get_dentry(struct super_block *sb, u64 cno,
+				       u64 ino, u32 gen)
+{
+	struct nilfs_root *root;
+	struct inode *inode;
+
+	if (ino < NILFS_FIRST_INO(sb) && ino != NILFS_ROOT_INO)
+		return ERR_PTR(-ESTALE);
+
+	root = nilfs_lookup_root(NILFS_SB(sb)->s_nilfs, cno);
+	if (!root)
+		return ERR_PTR(-ESTALE);
+
+	inode = nilfs_iget(sb, root, ino);
+	nilfs_put_root(root);
+
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+	if (gen && inode->i_generation != gen) {
+		iput(inode);
+		return ERR_PTR(-ESTALE);
+	}
+	return d_obtain_alias(inode);
+}
+
+static struct dentry *nilfs_fh_to_dentry(struct super_block *sb, struct fid *fh,
+					 int fh_len, int fh_type)
+{
+	struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+
+	if ((fh_len != NILFS_FID_SIZE_NON_CONNECTABLE &&
+	     fh_len != NILFS_FID_SIZE_CONNECTABLE) ||
+	    (fh_type != FILEID_NILFS_WITH_PARENT &&
+	     fh_type != FILEID_NILFS_WITHOUT_PARENT))
+		return NULL;
+
+	return nilfs_get_dentry(sb, fid->cno, fid->ino, fid->gen);
+}
+
+static struct dentry *nilfs_fh_to_parent(struct super_block *sb, struct fid *fh,
+					 int fh_len, int fh_type)
+{
+	struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+
+	if (fh_len != NILFS_FID_SIZE_CONNECTABLE ||
+	    fh_type != FILEID_NILFS_WITH_PARENT)
+		return NULL;
+
+	return nilfs_get_dentry(sb, fid->cno, fid->parent_ino, fid->parent_gen);
+}
+
+static int nilfs_encode_fh(struct dentry *dentry, __u32 *fh, int *lenp,
+			   int connectable)
+{
+	struct nilfs_fid *fid = (struct nilfs_fid *)fh;
+	struct inode *inode = dentry->d_inode;
+	struct nilfs_root *root = NILFS_I(inode)->i_root;
+	int type;
+
+	if (*lenp < NILFS_FID_SIZE_NON_CONNECTABLE ||
+	    (connectable && *lenp < NILFS_FID_SIZE_CONNECTABLE))
+		return 255;
+
+	fid->cno = root->cno;
+	fid->ino = inode->i_ino;
+	fid->gen = inode->i_generation;
+
+	if (connectable && !S_ISDIR(inode->i_mode)) {
+		struct inode *parent;
+
+		spin_lock(&dentry->d_lock);
+		parent = dentry->d_parent->d_inode;
+		fid->parent_ino = parent->i_ino;
+		fid->parent_gen = parent->i_generation;
+		spin_unlock(&dentry->d_lock);
+
+		type = FILEID_NILFS_WITH_PARENT;
+		*lenp = NILFS_FID_SIZE_CONNECTABLE;
+	} else {
+		type = FILEID_NILFS_WITHOUT_PARENT;
+		*lenp = NILFS_FID_SIZE_NON_CONNECTABLE;
+	}
+
+	return type;
+}
+
 const struct inode_operations nilfs_dir_inode_operations = {
 	.create		= nilfs_create,
 	.lookup		= nilfs_lookup,
@@ -491,4 +588,12 @@ const struct inode_operations nilfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.follow_link	= page_follow_link_light,
 	.put_link	= page_put_link,
+	.permission     = nilfs_permission,
+};
+
+const struct export_operations nilfs_export_ops = {
+	.encode_fh = nilfs_encode_fh,
+	.fh_to_dentry = nilfs_fh_to_dentry,
+	.fh_to_parent = nilfs_fh_to_parent,
+	.get_parent = nilfs_get_parent,
 };
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index 47d6d79..f7560da 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -32,7 +32,6 @@
 #include "the_nilfs.h"
 #include "sb.h"
 #include "bmap.h"
-#include "bmap_union.h"
 
 /*
  * nilfs inode data in memory
@@ -41,7 +40,7 @@ struct nilfs_inode_info {
 	__u32 i_flags;
 	unsigned long  i_state;		/* Dynamic state flags */
 	struct nilfs_bmap *i_bmap;
-	union nilfs_bmap_union i_bmap_union;
+	struct nilfs_bmap i_bmap_data;
 	__u64 i_xattr;	/* sector_t ??? */
 	__u32 i_dir_start_lookup;
 	__u64 i_cno;		/* check point number for GC inode */
@@ -60,6 +59,7 @@ struct nilfs_inode_info {
 #endif
 	struct buffer_head *i_bh;	/* i_bh contains a new or dirty
 					   disk inode */
+	struct nilfs_root *i_root;
 	struct inode vfs_inode;
 };
 
@@ -71,9 +71,7 @@ static inline struct nilfs_inode_info *NILFS_I(const struct inode *inode)
 static inline struct nilfs_inode_info *
 NILFS_BMAP_I(const struct nilfs_bmap *bmap)
 {
-	return container_of((union nilfs_bmap_union *)bmap,
-			    struct nilfs_inode_info,
-			    i_bmap_union);
+	return container_of(bmap, struct nilfs_inode_info, i_bmap_data);
 }
 
 static inline struct inode *NILFS_BTNC_I(struct address_space *btnc)
@@ -103,7 +101,14 @@ enum {
 	NILFS_I_INODE_DIRTY,		/* write_inode is requested */
 	NILFS_I_BMAP,			/* has bmap and btnode_cache */
 	NILFS_I_GCINODE,		/* inode for GC, on memory only */
-	NILFS_I_GCDAT,			/* shadow DAT, on memory only */
+};
+
+/*
+ * commit flags for nilfs_commit_super and nilfs_sync_super
+ */
+enum {
+	NILFS_SB_COMMIT = 0,	/* Commit a super block alternately */
+	NILFS_SB_COMMIT_ALL	/* Commit both super blocks */
 };
 
 /*
@@ -187,7 +192,7 @@ static inline int nilfs_doing_construction(void)
 
 static inline struct inode *nilfs_dat_inode(const struct the_nilfs *nilfs)
 {
-	return nilfs_doing_gc() ? nilfs->ns_gc_dat : nilfs->ns_dat;
+	return nilfs->ns_dat;
 }
 
 /*
@@ -195,12 +200,9 @@ static inline struct inode *nilfs_dat_inode(const struct the_nilfs *nilfs)
  */
 #ifdef CONFIG_NILFS_POSIX_ACL
 #error "NILFS: not yet supported POSIX ACL"
-extern int nilfs_permission(struct inode *, int, struct nameidata *);
 extern int nilfs_acl_chmod(struct inode *);
 extern int nilfs_init_acl(struct inode *, struct inode *);
 #else
-#define nilfs_permission   NULL
-
 static inline int nilfs_acl_chmod(struct inode *inode)
 {
 	return 0;
@@ -242,11 +244,19 @@ extern int nilfs_get_block(struct inode *, sector_t, struct buffer_head *, int);
 extern void nilfs_set_inode_flags(struct inode *);
 extern int nilfs_read_inode_common(struct inode *, struct nilfs_inode *);
 extern void nilfs_write_inode_common(struct inode *, struct nilfs_inode *, int);
-extern struct inode *nilfs_iget(struct super_block *, unsigned long);
+struct inode *nilfs_ilookup(struct super_block *sb, struct nilfs_root *root,
+			    unsigned long ino);
+struct inode *nilfs_iget_locked(struct super_block *sb, struct nilfs_root *root,
+				unsigned long ino);
+struct inode *nilfs_iget(struct super_block *sb, struct nilfs_root *root,
+			 unsigned long ino);
+extern struct inode *nilfs_iget_for_gc(struct super_block *sb,
+				       unsigned long ino, __u64 cno);
 extern void nilfs_update_inode(struct inode *, struct buffer_head *);
 extern void nilfs_truncate(struct inode *);
-extern void nilfs_delete_inode(struct inode *);
+extern void nilfs_evict_inode(struct inode *);
 extern int nilfs_setattr(struct dentry *, struct iattr *);
+int nilfs_permission(struct inode *inode, int mask);
 extern int nilfs_load_inode_block(struct nilfs_sb_info *, struct inode *,
 				  struct buffer_head **);
 extern int nilfs_inode_dirty(struct inode *);
@@ -255,11 +265,7 @@ extern int nilfs_set_file_dirty(struct nilfs_sb_info *, struct inode *,
 extern int nilfs_mark_inode_dirty(struct inode *);
 extern void nilfs_dirty_inode(struct inode *);
 
-/* namei.c */
-extern struct dentry *nilfs_get_parent(struct dentry *);
-
 /* super.c */
-extern struct inode *nilfs_alloc_inode_common(struct the_nilfs *);
 extern struct inode *nilfs_alloc_inode(struct super_block *);
 extern void nilfs_destroy_inode(struct inode *);
 extern void nilfs_error(struct super_block *, const char *, const char *, ...)
@@ -270,9 +276,17 @@ extern struct nilfs_super_block *
 nilfs_read_super_block(struct super_block *, u64, int, struct buffer_head **);
 extern int nilfs_store_magic_and_option(struct super_block *,
 					struct nilfs_super_block *, char *);
+extern int nilfs_check_feature_compatibility(struct super_block *,
+					     struct nilfs_super_block *);
+extern void nilfs_set_log_cursor(struct nilfs_super_block *,
+				 struct the_nilfs *);
+extern struct nilfs_super_block **nilfs_prepare_super(struct nilfs_sb_info *,
+						      int flip);
 extern int nilfs_commit_super(struct nilfs_sb_info *, int);
-extern int nilfs_attach_checkpoint(struct nilfs_sb_info *, __u64);
-extern void nilfs_detach_checkpoint(struct nilfs_sb_info *);
+extern int nilfs_cleanup_super(struct nilfs_sb_info *);
+int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno, int curr_mnt,
+			    struct nilfs_root **root);
+int nilfs_checkpoint_is_mounted(struct super_block *sb, __u64 cno);
 
 /* gcinode.c */
 int nilfs_gccache_submit_read_data(struct inode *, sector_t, sector_t, __u64,
@@ -280,16 +294,8 @@ int nilfs_gccache_submit_read_data(struct inode *, sector_t, sector_t, __u64,
 int nilfs_gccache_submit_read_node(struct inode *, sector_t, __u64,
 				   struct buffer_head **);
 int nilfs_gccache_wait_and_mark_dirty(struct buffer_head *);
-int nilfs_init_gccache(struct the_nilfs *);
-void nilfs_destroy_gccache(struct the_nilfs *);
-void nilfs_clear_gcinode(struct inode *);
-struct inode *nilfs_gc_iget(struct the_nilfs *, ino_t, __u64);
-void nilfs_remove_all_gcinode(struct the_nilfs *);
-
-/* gcdat.c */
-int nilfs_init_gcdat_inode(struct the_nilfs *);
-void nilfs_commit_gcdat_inode(struct the_nilfs *);
-void nilfs_clear_gcdat_inode(struct the_nilfs *);
+int nilfs_init_gcinode(struct inode *inode);
+void nilfs_remove_all_gcinodes(struct the_nilfs *nilfs);
 
 /*
  * Inodes and files operations
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 8de3e1e..a6c3c2e8 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -37,7 +37,8 @@
 
 #define NILFS_BUFFER_INHERENT_BITS  \
 	((1UL << BH_Uptodate) | (1UL << BH_Mapped) | (1UL << BH_NILFS_Node) | \
-	 (1UL << BH_NILFS_Volatile) | (1UL << BH_NILFS_Allocated))
+	 (1UL << BH_NILFS_Volatile) | (1UL << BH_NILFS_Allocated) | \
+	 (1UL << BH_NILFS_Checked))
 
 static struct buffer_head *
 __nilfs_get_page_block(struct page *page, unsigned long block, pgoff_t index,
@@ -78,8 +79,8 @@ struct buffer_head *nilfs_grab_buffer(struct inode *inode,
 {
 	int blkbits = inode->i_blkbits;
 	pgoff_t index = blkoff >> (PAGE_CACHE_SHIFT - blkbits);
-	struct page *page, *opage;
-	struct buffer_head *bh, *obh;
+	struct page *page;
+	struct buffer_head *bh;
 
 	page = grab_cache_page(mapping, index);
 	if (unlikely(!page))
@@ -91,30 +92,6 @@ struct buffer_head *nilfs_grab_buffer(struct inode *inode,
 		page_cache_release(page);
 		return NULL;
 	}
-	if (!buffer_uptodate(bh) && mapping->assoc_mapping != NULL) {
-		/*
-		 * Shadow page cache uses assoc_mapping to point its original
-		 * page cache.  The following code tries the original cache
-		 * if the given cache is a shadow and it didn't hit.
-		 */
-		opage = find_lock_page(mapping->assoc_mapping, index);
-		if (!opage)
-			return bh;
-
-		obh = __nilfs_get_page_block(opage, blkoff, index, blkbits,
-					     b_state);
-		if (buffer_uptodate(obh)) {
-			nilfs_copy_buffer(bh, obh);
-			if (buffer_dirty(obh)) {
-				nilfs_mark_buffer_dirty(bh);
-				if (!buffer_nilfs_node(bh) && NILFS_MDT(inode))
-					nilfs_mdt_mark_dirty(inode);
-			}
-		}
-		brelse(obh);
-		unlock_page(opage);
-		page_cache_release(opage);
-	}
 	return bh;
 }
 
@@ -129,6 +106,8 @@ void nilfs_forget_buffer(struct buffer_head *bh)
 
 	lock_buffer(bh);
 	clear_buffer_nilfs_volatile(bh);
+	clear_buffer_nilfs_checked(bh);
+	clear_buffer_nilfs_redirected(bh);
 	clear_buffer_dirty(bh);
 	if (nilfs_page_buffers_clean(page))
 		__nilfs_clear_page_dirty(page);
@@ -480,6 +459,8 @@ void nilfs_clear_dirty_pages(struct address_space *mapping)
 				lock_buffer(bh);
 				clear_buffer_dirty(bh);
 				clear_buffer_nilfs_volatile(bh);
+				clear_buffer_nilfs_checked(bh);
+				clear_buffer_nilfs_redirected(bh);
 				clear_buffer_uptodate(bh);
 				clear_buffer_mapped(bh);
 				unlock_buffer(bh);
@@ -510,6 +491,31 @@ unsigned nilfs_page_count_clean_buffers(struct page *page,
 	}
 	return nc;
 }
+ 
+void nilfs_mapping_init_once(struct address_space *mapping)
+{
+	memset(mapping, 0, sizeof(*mapping));
+	INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC);
+	spin_lock_init(&mapping->tree_lock);
+	INIT_LIST_HEAD(&mapping->private_list);
+	spin_lock_init(&mapping->private_lock);
+
+	spin_lock_init(&mapping->i_mmap_lock);
+	INIT_RAW_PRIO_TREE_ROOT(&mapping->i_mmap);
+	INIT_LIST_HEAD(&mapping->i_mmap_nonlinear);
+}
+
+void nilfs_mapping_init(struct address_space *mapping,
+			struct backing_dev_info *bdi,
+			const struct address_space_operations *aops)
+{
+	mapping->host = NULL;
+	mapping->flags = 0;
+	mapping_set_gfp_mask(mapping, GFP_NOFS);
+	mapping->assoc_mapping = NULL;
+	mapping->backing_dev_info = bdi;
+	mapping->a_ops = aops;
+}
 
 /*
  * NILFS2 needs clear_page_dirty() in the following two cases:
diff --git a/fs/nilfs2/page.h b/fs/nilfs2/page.h
index 8abca4d..fb9e8a8 100644
--- a/fs/nilfs2/page.h
+++ b/fs/nilfs2/page.h
@@ -34,11 +34,15 @@ enum {
 	BH_NILFS_Allocated = BH_PrivateStart,
 	BH_NILFS_Node,
 	BH_NILFS_Volatile,
+	BH_NILFS_Checked,
+	BH_NILFS_Redirected,
 };
 
 BUFFER_FNS(NILFS_Allocated, nilfs_allocated)	/* nilfs private buffers */
 BUFFER_FNS(NILFS_Node, nilfs_node)		/* nilfs node buffers */
 BUFFER_FNS(NILFS_Volatile, nilfs_volatile)
+BUFFER_FNS(NILFS_Checked, nilfs_checked)	/* buffer is verified */
+BUFFER_FNS(NILFS_Redirected, nilfs_redirected)	/* redirected to a copy */
 
 
 void nilfs_mark_buffer_dirty(struct buffer_head *bh);
@@ -57,6 +61,10 @@ void nilfs_free_private_page(struct page *);
 int nilfs_copy_dirty_pages(struct address_space *, struct address_space *);
 void nilfs_copy_back_pages(struct address_space *, struct address_space *);
 void nilfs_clear_dirty_pages(struct address_space *);
+void nilfs_mapping_init_once(struct address_space *mapping);
+void nilfs_mapping_init(struct address_space *mapping,
+			struct backing_dev_info *bdi,
+			const struct address_space_operations *aops);
 unsigned nilfs_page_count_clean_buffers(struct page *, unsigned, unsigned);
 
 #define NILFS_PAGE_BUG(page, m, a...) \
diff --git a/fs/nilfs2/recovery.c b/fs/nilfs2/recovery.c
index bae2a51..5d2711c2 100644
--- a/fs/nilfs2/recovery.c
+++ b/fs/nilfs2/recovery.c
@@ -91,27 +91,9 @@ static int nilfs_warn_segment_error(int err)
 	return -EINVAL;
 }
 
-static void store_segsum_info(struct nilfs_segsum_info *ssi,
-			      struct nilfs_segment_summary *sum,
-			      unsigned int blocksize)
-{
-	ssi->flags = le16_to_cpu(sum->ss_flags);
-	ssi->seg_seq = le64_to_cpu(sum->ss_seq);
-	ssi->ctime = le64_to_cpu(sum->ss_create);
-	ssi->next = le64_to_cpu(sum->ss_next);
-	ssi->nblocks = le32_to_cpu(sum->ss_nblocks);
-	ssi->nfinfo = le32_to_cpu(sum->ss_nfinfo);
-	ssi->sumbytes = le32_to_cpu(sum->ss_sumbytes);
-
-	ssi->nsumblk = DIV_ROUND_UP(ssi->sumbytes, blocksize);
-	ssi->nfileblk = ssi->nblocks - ssi->nsumblk - !!NILFS_SEG_HAS_SR(ssi);
-
-	/* need to verify ->ss_bytes field if read ->ss_cno */
-}
-
 /**
- * calc_crc_cont - check CRC of blocks continuously
- * @sbi: nilfs_sb_info
+ * nilfs_compute_checksum - compute checksum of blocks continuously
+ * @nilfs: nilfs object
  * @bhs: buffer head of start block
  * @sum: place to store result
  * @offset: offset bytes in the first block
@@ -119,23 +101,25 @@ static void store_segsum_info(struct nilfs_segsum_info *ssi,
  * @start: DBN of start block
  * @nblock: number of blocks to be checked
  */
-static int calc_crc_cont(struct nilfs_sb_info *sbi, struct buffer_head *bhs,
-			 u32 *sum, unsigned long offset, u64 check_bytes,
-			 sector_t start, unsigned long nblock)
+static int nilfs_compute_checksum(struct the_nilfs *nilfs,
+				  struct buffer_head *bhs, u32 *sum,
+				  unsigned long offset, u64 check_bytes,
+				  sector_t start, unsigned long nblock)
 {
-	unsigned long blocksize = sbi->s_super->s_blocksize;
+	unsigned int blocksize = nilfs->ns_blocksize;
 	unsigned long size;
 	u32 crc;
 
 	BUG_ON(offset >= blocksize);
 	check_bytes -= offset;
 	size = min_t(u64, check_bytes, blocksize - offset);
-	crc = crc32_le(sbi->s_nilfs->ns_crc_seed,
+	crc = crc32_le(nilfs->ns_crc_seed,
 		       (unsigned char *)bhs->b_data + offset, size);
 	if (--nblock > 0) {
 		do {
-			struct buffer_head *bh
-				= sb_bread(sbi->s_super, ++start);
+			struct buffer_head *bh;
+
+			bh = __bread(nilfs->ns_bdev, ++start, blocksize);
 			if (!bh)
 				return -EIO;
 			check_bytes -= size;
@@ -150,12 +134,12 @@ static int calc_crc_cont(struct nilfs_sb_info *sbi, struct buffer_head *bhs,
 
 /**
  * nilfs_read_super_root_block - read super root block
- * @sb: super_block
+ * @nilfs: nilfs object
  * @sr_block: disk block number of the super root block
  * @pbh: address of a buffer_head pointer to return super root buffer
  * @check: CRC check flag
  */
-int nilfs_read_super_root_block(struct super_block *sb, sector_t sr_block,
+int nilfs_read_super_root_block(struct the_nilfs *nilfs, sector_t sr_block,
 				struct buffer_head **pbh, int check)
 {
 	struct buffer_head *bh_sr;
@@ -164,7 +148,7 @@ int nilfs_read_super_root_block(struct super_block *sb, sector_t sr_block,
 	int ret;
 
 	*pbh = NULL;
-	bh_sr = sb_bread(sb, sr_block);
+	bh_sr = __bread(nilfs->ns_bdev, sr_block, nilfs->ns_blocksize);
 	if (unlikely(!bh_sr)) {
 		ret = NILFS_SEG_FAIL_IO;
 		goto failed;
@@ -174,12 +158,13 @@ int nilfs_read_super_root_block(struct super_block *sb, sector_t sr_block,
 	if (check) {
 		unsigned bytes = le16_to_cpu(sr->sr_bytes);
 
-		if (bytes == 0 || bytes > sb->s_blocksize) {
+		if (bytes == 0 || bytes > nilfs->ns_blocksize) {
 			ret = NILFS_SEG_FAIL_CHECKSUM_SUPER_ROOT;
 			goto failed_bh;
 		}
-		if (calc_crc_cont(NILFS_SB(sb), bh_sr, &crc,
-				  sizeof(sr->sr_sum), bytes, sr_block, 1)) {
+		if (nilfs_compute_checksum(
+			    nilfs, bh_sr, &crc, sizeof(sr->sr_sum), bytes,
+			    sr_block, 1)) {
 			ret = NILFS_SEG_FAIL_IO;
 			goto failed_bh;
 		}
@@ -199,64 +184,76 @@ int nilfs_read_super_root_block(struct super_block *sb, sector_t sr_block,
 }
 
 /**
- * load_segment_summary - read segment summary of the specified partial segment
- * @sbi: nilfs_sb_info
- * @pseg_start: start disk block number of partial segment
- * @seg_seq: sequence number requested
- * @ssi: pointer to nilfs_segsum_info struct to store information
+ * nilfs_read_log_header - read summary header of the specified log
+ * @nilfs: nilfs object
+ * @start_blocknr: start block number of the log
+ * @sum: pointer to return segment summary structure
  */
-static int
-load_segment_summary(struct nilfs_sb_info *sbi, sector_t pseg_start,
-		     u64 seg_seq, struct nilfs_segsum_info *ssi)
+static struct buffer_head *
+nilfs_read_log_header(struct the_nilfs *nilfs, sector_t start_blocknr,
+		      struct nilfs_segment_summary **sum)
 {
 	struct buffer_head *bh_sum;
-	struct nilfs_segment_summary *sum;
+
+	bh_sum = __bread(nilfs->ns_bdev, start_blocknr, nilfs->ns_blocksize);
+	if (bh_sum)
+		*sum = (struct nilfs_segment_summary *)bh_sum->b_data;
+	return bh_sum;
+}
+
+/**
+ * nilfs_validate_log - verify consistency of log
+ * @nilfs: nilfs object
+ * @seg_seq: sequence number of segment
+ * @bh_sum: buffer head of summary block
+ * @sum: segment summary struct
+ */
+static int nilfs_validate_log(struct the_nilfs *nilfs, u64 seg_seq,
+			      struct buffer_head *bh_sum,
+			      struct nilfs_segment_summary *sum)
+{
 	unsigned long nblock;
 	u32 crc;
-	int ret = NILFS_SEG_FAIL_IO;
+	int ret;
 
-	bh_sum = sb_bread(sbi->s_super, pseg_start);
-	if (!bh_sum)
+	ret = NILFS_SEG_FAIL_MAGIC;
+	if (le32_to_cpu(sum->ss_magic) != NILFS_SEGSUM_MAGIC)
 		goto out;
 
-	sum = (struct nilfs_segment_summary *)bh_sum->b_data;
-
-	/* Check consistency of segment summary */
-	if (le32_to_cpu(sum->ss_magic) != NILFS_SEGSUM_MAGIC) {
-		ret = NILFS_SEG_FAIL_MAGIC;
-		goto failed;
-	}
-	store_segsum_info(ssi, sum, sbi->s_super->s_blocksize);
-	if (seg_seq != ssi->seg_seq) {
-		ret = NILFS_SEG_FAIL_SEQ;
-		goto failed;
-	}
+	ret = NILFS_SEG_FAIL_SEQ;
+	if (le64_to_cpu(sum->ss_seq) != seg_seq)
+		goto out;
 
-	nblock = ssi->nblocks;
-	if (unlikely(nblock == 0 ||
-		     nblock > sbi->s_nilfs->ns_blocks_per_segment)) {
+	nblock = le32_to_cpu(sum->ss_nblocks);
+	ret = NILFS_SEG_FAIL_CONSISTENCY;
+	if (unlikely(nblock == 0 || nblock > nilfs->ns_blocks_per_segment))
 		/* This limits the number of blocks read in the CRC check */
-		ret = NILFS_SEG_FAIL_CONSISTENCY;
-		goto failed;
-	}
-	if (calc_crc_cont(sbi, bh_sum, &crc, sizeof(sum->ss_datasum),
-			  ((u64)nblock << sbi->s_super->s_blocksize_bits),
-			  pseg_start, nblock)) {
-		ret = NILFS_SEG_FAIL_IO;
-		goto failed;
-	}
-	if (crc == le32_to_cpu(sum->ss_datasum))
-		ret = 0;
-	else
-		ret = NILFS_SEG_FAIL_CHECKSUM_FULL;
- failed:
-	brelse(bh_sum);
- out:
+		goto out;
+
+	ret = NILFS_SEG_FAIL_IO;
+	if (nilfs_compute_checksum(nilfs, bh_sum, &crc, sizeof(sum->ss_datasum),
+				   ((u64)nblock << nilfs->ns_blocksize_bits),
+				   bh_sum->b_blocknr, nblock))
+		goto out;
+
+	ret = NILFS_SEG_FAIL_CHECKSUM_FULL;
+	if (crc != le32_to_cpu(sum->ss_datasum))
+		goto out;
+	ret = 0;
+out:
 	return ret;
 }
 
-static void *segsum_get(struct super_block *sb, struct buffer_head **pbh,
-			unsigned int *offset, unsigned int bytes)
+/**
+ * nilfs_read_summary_info - read an item on summary blocks of a log
+ * @nilfs: nilfs object
+ * @pbh: the current buffer head on summary blocks [in, out]
+ * @offset: the current byte offset on summary blocks [in, out]
+ * @bytes: byte size of the item to be read
+ */
+static void *nilfs_read_summary_info(struct the_nilfs *nilfs,
+				     struct buffer_head **pbh,
+				     unsigned int *offset, unsigned int bytes)
 {
 	void *ptr;
 	sector_t blocknr;
@@ -265,7 +262,8 @@ static void *segsum_get(struct super_block *sb, struct buffer_head **pbh,
 	if (bytes > (*pbh)->b_size - *offset) {
 		blocknr = (*pbh)->b_blocknr;
 		brelse(*pbh);
-		*pbh = sb_bread(sb, blocknr + 1);
+		*pbh = __bread(nilfs->ns_bdev, blocknr + 1,
+			       nilfs->ns_blocksize);
 		if (unlikely(!*pbh))
 			return NULL;
 		*offset = 0;
@@ -275,9 +273,18 @@ static void *segsum_get(struct super_block *sb, struct buffer_head **pbh,
 	return ptr;
 }
 
-static void segsum_skip(struct super_block *sb, struct buffer_head **pbh,
-			unsigned int *offset, unsigned int bytes,
-			unsigned long count)
+/**
+ * nilfs_skip_summary_info - skip items on summary blocks of a log
+ * @nilfs: nilfs object
+ * @pbh: the current buffer head on summary blocks [in, out]
+ * @offset: the current byte offset on summary blocks [in, out]
+ * @bytes: byte size of the item to be skipped
+ * @count: number of items to be skipped
+ */
+static void nilfs_skip_summary_info(struct the_nilfs *nilfs,
+				    struct buffer_head **pbh,
+				    unsigned int *offset, unsigned int bytes,
+				    unsigned long count)
 {
 	unsigned int rest_item_in_current_block
 		= ((*pbh)->b_size - *offset) / bytes;
@@ -294,36 +301,46 @@ static void segsum_skip(struct super_block *sb, struct buffer_head **pbh,
 		*offset = bytes * (count - (bcnt - 1) * nitem_per_block);
 
 		brelse(*pbh);
-		*pbh = sb_bread(sb, blocknr + bcnt);
+		*pbh = __bread(nilfs->ns_bdev, blocknr + bcnt,
+			       nilfs->ns_blocksize);
 	}
 }
 
-static int
-collect_blocks_from_segsum(struct nilfs_sb_info *sbi, sector_t sum_blocknr,
-			   struct nilfs_segsum_info *ssi,
-			   struct list_head *head)
+/**
+ * nilfs_scan_dsync_log - get block information of a log written for data sync
+ * @nilfs: nilfs object
+ * @start_blocknr: start block number of the log
+ * @sum: log summary information
+ * @head: list head to add nilfs_recovery_block struct
+ */
+static int nilfs_scan_dsync_log(struct the_nilfs *nilfs, sector_t start_blocknr,
+				struct nilfs_segment_summary *sum,
+				struct list_head *head)
 {
 	struct buffer_head *bh;
 	unsigned int offset;
-	unsigned long nfinfo = ssi->nfinfo;
-	sector_t blocknr = sum_blocknr + ssi->nsumblk;
+	u32 nfinfo, sumbytes;
+	sector_t blocknr;
 	ino_t ino;
 	int err = -EIO;
 
+	nfinfo = le32_to_cpu(sum->ss_nfinfo);
 	if (!nfinfo)
 		return 0;
 
-	bh = sb_bread(sbi->s_super, sum_blocknr);
+	sumbytes = le32_to_cpu(sum->ss_sumbytes);
+	blocknr = start_blocknr + DIV_ROUND_UP(sumbytes, nilfs->ns_blocksize);
+	bh = __bread(nilfs->ns_bdev, start_blocknr, nilfs->ns_blocksize);
 	if (unlikely(!bh))
 		goto out;
 
-	offset = le16_to_cpu(
-		((struct nilfs_segment_summary *)bh->b_data)->ss_bytes);
+	offset = le16_to_cpu(sum->ss_bytes);
 	for (;;) {
 		unsigned long nblocks, ndatablk, nnodeblk;
 		struct nilfs_finfo *finfo;
 
-		finfo = segsum_get(sbi->s_super, &bh, &offset, sizeof(*finfo));
+		finfo = nilfs_read_summary_info(nilfs, &bh, &offset,
+						sizeof(*finfo));
 		if (unlikely(!finfo))
 			goto out;
 
@@ -336,8 +353,8 @@ collect_blocks_from_segsum(struct nilfs_sb_info *sbi, sector_t sum_blocknr,
 			struct nilfs_recovery_block *rb;
 			struct nilfs_binfo_v *binfo;
 
-			binfo = segsum_get(sbi->s_super, &bh, &offset,
-					   sizeof(*binfo));
+			binfo = nilfs_read_summary_info(nilfs, &bh, &offset,
+							sizeof(*binfo));
 			if (unlikely(!binfo))
 				goto out;
 
@@ -355,9 +372,9 @@ collect_blocks_from_segsum(struct nilfs_sb_info *sbi, sector_t sum_blocknr,
 		}
 		if (--nfinfo == 0)
 			break;
-		blocknr += nnodeblk; /* always 0 for the data sync segments */
-		segsum_skip(sbi->s_super, &bh, &offset, sizeof(__le64),
-			    nnodeblk);
+		blocknr += nnodeblk; /* always 0 for data sync logs */
+		nilfs_skip_summary_info(nilfs, &bh, &offset, sizeof(__le64),
+					nnodeblk);
 		if (unlikely(!bh))
 			goto out;
 	}
@@ -423,7 +440,6 @@ static int nilfs_prepare_segment_for_recovery(struct the_nilfs *nilfs,
 	segnum[2] = ri->ri_segnum;
 	segnum[3] = ri->ri_nextnum;
 
-	nilfs_attach_writer(nilfs, sbi);
 	/*
 	 * Releasing the next segment of the latest super root.
 	 * The next segment is invalidated by this recovery.
@@ -463,18 +479,17 @@ static int nilfs_prepare_segment_for_recovery(struct the_nilfs *nilfs,
 
  failed:
 	/* No need to recover sufile because it will be destroyed on error */
-	nilfs_detach_writer(nilfs, sbi);
 	return err;
 }
 
-static int nilfs_recovery_copy_block(struct nilfs_sb_info *sbi,
+static int nilfs_recovery_copy_block(struct the_nilfs *nilfs,
 				     struct nilfs_recovery_block *rb,
 				     struct page *page)
 {
 	struct buffer_head *bh_org;
 	void *kaddr;
 
-	bh_org = sb_bread(sbi->s_super, rb->blocknr);
+	bh_org = __bread(nilfs->ns_bdev, rb->blocknr, nilfs->ns_blocksize);
 	if (unlikely(!bh_org))
 		return -EIO;
 
@@ -485,19 +500,21 @@ static int nilfs_recovery_copy_block(struct nilfs_sb_info *sbi,
 	return 0;
 }
 
-static int recover_dsync_blocks(struct nilfs_sb_info *sbi,
-				struct list_head *head,
-				unsigned long *nr_salvaged_blocks)
+static int nilfs_recover_dsync_blocks(struct the_nilfs *nilfs,
+				      struct nilfs_sb_info *sbi,
+				      struct nilfs_root *root,
+				      struct list_head *head,
+				      unsigned long *nr_salvaged_blocks)
 {
 	struct inode *inode;
 	struct nilfs_recovery_block *rb, *n;
-	unsigned blocksize = sbi->s_super->s_blocksize;
+	unsigned blocksize = nilfs->ns_blocksize;
 	struct page *page;
 	loff_t pos;
 	int err = 0, err2 = 0;
 
 	list_for_each_entry_safe(rb, n, head, list) {
-		inode = nilfs_iget(sbi->s_super, rb->ino);
+		inode = nilfs_iget(sbi->s_super, root, rb->ino);
 		if (IS_ERR(inode)) {
 			err = PTR_ERR(inode);
 			inode = NULL;
@@ -505,13 +522,16 @@ static int recover_dsync_blocks(struct nilfs_sb_info *sbi,
 		}
 
 		pos = rb->blkoff << inode->i_blkbits;
-		page = NULL;
-		err = block_write_begin(NULL, inode->i_mapping, pos, blocksize,
-					0, &page, NULL, nilfs_get_block);
-		if (unlikely(err))
+		err = block_write_begin(inode->i_mapping, pos, blocksize,
+					0, &page, nilfs_get_block);
+		if (unlikely(err)) {
+			loff_t isize = inode->i_size;
+			if (pos + blocksize > isize)
+				vmtruncate(inode, isize);
 			goto failed_inode;
+		}
 
-		err = nilfs_recovery_copy_block(sbi, rb, page);
+		err = nilfs_recovery_copy_block(nilfs, rb, page);
 		if (unlikely(err))
 			goto failed_page;
 
@@ -551,18 +571,21 @@ static int recover_dsync_blocks(struct nilfs_sb_info *sbi,
 /**
  * nilfs_do_roll_forward - salvage logical segments newer than the latest
  * checkpoint
+ * @nilfs: nilfs object
  * @sbi: nilfs_sb_info
- * @nilfs: the_nilfs
  * @ri: pointer to a nilfs_recovery_info
  */
 static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
 				 struct nilfs_sb_info *sbi,
+				 struct nilfs_root *root,
 				 struct nilfs_recovery_info *ri)
 {
-	struct nilfs_segsum_info ssi;
+	struct buffer_head *bh_sum = NULL;
+	struct nilfs_segment_summary *sum;
 	sector_t pseg_start;
 	sector_t seg_start, seg_end;  /* Starting/ending DBN of full segment */
 	unsigned long nsalvaged_blocks = 0;
+	unsigned int flags;
 	u64 seg_seq;
 	__u64 segnum, nextnum = 0;
 	int empty_seg = 0;
@@ -574,15 +597,20 @@ static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
 	};
 	int state = RF_INIT_ST;
 
-	nilfs_attach_writer(nilfs, sbi);
 	pseg_start = ri->ri_lsegs_start;
 	seg_seq = ri->ri_lsegs_start_seq;
 	segnum = nilfs_get_segnum_of_block(nilfs, pseg_start);
 	nilfs_get_segment_range(nilfs, segnum, &seg_start, &seg_end);
 
 	while (segnum != ri->ri_segnum || pseg_start <= ri->ri_pseg_start) {
+		brelse(bh_sum);
+		bh_sum = nilfs_read_log_header(nilfs, pseg_start, &sum);
+		if (!bh_sum) {
+			err = -EIO;
+			goto failed;
+		}
 
-		ret = load_segment_summary(sbi, pseg_start, seg_seq, &ssi);
+		ret = nilfs_validate_log(nilfs, seg_seq, bh_sum, sum);
 		if (ret) {
 			if (ret == NILFS_SEG_FAIL_IO) {
 				err = -EIO;
@@ -590,33 +618,38 @@ static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
 			}
 			goto strayed;
 		}
-		if (unlikely(NILFS_SEG_HAS_SR(&ssi)))
+
+		flags = le16_to_cpu(sum->ss_flags);
+		if (flags & NILFS_SS_SR)
 			goto confused;
 
 		/* Found a valid partial segment; do recovery actions */
-		nextnum = nilfs_get_segnum_of_block(nilfs, ssi.next);
+		nextnum = nilfs_get_segnum_of_block(nilfs,
+						    le64_to_cpu(sum->ss_next));
 		empty_seg = 0;
-		nilfs->ns_ctime = ssi.ctime;
-		if (!(ssi.flags & NILFS_SS_GC))
-			nilfs->ns_nongc_ctime = ssi.ctime;
+		nilfs->ns_ctime = le64_to_cpu(sum->ss_create);
+		if (!(flags & NILFS_SS_GC))
+			nilfs->ns_nongc_ctime = nilfs->ns_ctime;
 
 		switch (state) {
 		case RF_INIT_ST:
-			if (!NILFS_SEG_LOGBGN(&ssi) || !NILFS_SEG_DSYNC(&ssi))
+			if (!(flags & NILFS_SS_LOGBGN) ||
+			    !(flags & NILFS_SS_SYNDT))
 				goto try_next_pseg;
 			state = RF_DSYNC_ST;
 			/* Fall through */
 		case RF_DSYNC_ST:
-			if (!NILFS_SEG_DSYNC(&ssi))
+			if (!(flags & NILFS_SS_SYNDT))
 				goto confused;
 
-			err = collect_blocks_from_segsum(
-				sbi, pseg_start, &ssi, &dsync_blocks);
+			err = nilfs_scan_dsync_log(nilfs, pseg_start, sum,
+						   &dsync_blocks);
 			if (unlikely(err))
 				goto failed;
-			if (NILFS_SEG_LOGEND(&ssi)) {
-				err = recover_dsync_blocks(
-					sbi, &dsync_blocks, &nsalvaged_blocks);
+			if (flags & NILFS_SS_LOGEND) {
+				err = nilfs_recover_dsync_blocks(
+					nilfs, sbi, root, &dsync_blocks,
+					&nsalvaged_blocks);
 				if (unlikely(err))
 					goto failed;
 				state = RF_INIT_ST;
@@ -627,7 +660,7 @@ static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
  try_next_pseg:
 		if (pseg_start == ri->ri_lsegs_end)
 			break;
-		pseg_start += ssi.nblocks;
+		pseg_start += le32_to_cpu(sum->ss_nblocks);
 		if (pseg_start < seg_end)
 			continue;
 		goto feed_segment;
@@ -652,8 +685,8 @@ static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
 		ri->ri_need_recovery = NILFS_RECOVERY_ROLLFORWARD_DONE;
 	}
  out:
+	brelse(bh_sum);
 	dispose_recovery_list(&dsync_blocks);
-	nilfs_detach_writer(sbi->s_nilfs, sbi);
 	return err;
 
  confused:
@@ -667,7 +700,6 @@ static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
 }
 
 static void nilfs_finish_roll_forward(struct the_nilfs *nilfs,
-				      struct nilfs_sb_info *sbi,
 				      struct nilfs_recovery_info *ri)
 {
 	struct buffer_head *bh;
@@ -677,7 +709,7 @@ static void nilfs_finish_roll_forward(struct the_nilfs *nilfs,
 	    nilfs_get_segnum_of_block(nilfs, ri->ri_super_root))
 		return;
 
-	bh = sb_getblk(sbi->s_super, ri->ri_lsegs_start);
+	bh = __getblk(nilfs->ns_bdev, ri->ri_lsegs_start, nilfs->ns_blocksize);
 	BUG_ON(!bh);
 	memset(bh->b_data, 0, bh->b_size);
 	set_buffer_dirty(bh);
@@ -690,9 +722,8 @@ static void nilfs_finish_roll_forward(struct the_nilfs *nilfs,
 }
 
 /**
- * nilfs_recover_logical_segments - salvage logical segments written after
- * the latest super root
- * @nilfs: the_nilfs
+ * nilfs_salvage_orphan_logs - salvage logs written after the latest checkpoint
+ * @nilfs: nilfs object
  * @sbi: nilfs_sb_info
  * @ri: pointer to a nilfs_recovery_info struct to store search results.
  *
@@ -709,23 +740,24 @@ static void nilfs_finish_roll_forward(struct the_nilfs *nilfs,
  *
  * %-ENOMEM - Insufficient memory available.
  */
-int nilfs_recover_logical_segments(struct the_nilfs *nilfs,
-				   struct nilfs_sb_info *sbi,
-				   struct nilfs_recovery_info *ri)
+int nilfs_salvage_orphan_logs(struct the_nilfs *nilfs,
+			      struct nilfs_sb_info *sbi,
+			      struct nilfs_recovery_info *ri)
 {
+	struct nilfs_root *root;
 	int err;
 
 	if (ri->ri_lsegs_start == 0 || ri->ri_lsegs_end == 0)
 		return 0;
 
-	err = nilfs_attach_checkpoint(sbi, ri->ri_cno);
+	err = nilfs_attach_checkpoint(sbi, ri->ri_cno, true, &root);
 	if (unlikely(err)) {
 		printk(KERN_ERR
 		       "NILFS: error loading the latest checkpoint.\n");
 		return err;
 	}
 
-	err = nilfs_do_roll_forward(nilfs, sbi, ri);
+	err = nilfs_do_roll_forward(nilfs, sbi, root, ri);
 	if (unlikely(err))
 		goto failed;
 
@@ -737,7 +769,7 @@ int nilfs_recover_logical_segments(struct the_nilfs *nilfs,
 			goto failed;
 		}
 
-		err = nilfs_attach_segment_constructor(sbi);
+		err = nilfs_attach_segment_constructor(sbi, root);
 		if (unlikely(err))
 			goto failed;
 
@@ -751,18 +783,17 @@ int nilfs_recover_logical_segments(struct the_nilfs *nilfs,
 			goto failed;
 		}
 
-		nilfs_finish_roll_forward(nilfs, sbi, ri);
+		nilfs_finish_roll_forward(nilfs, ri);
 	}
 
  failed:
-	nilfs_detach_checkpoint(sbi);
+	nilfs_put_root(root);
 	return err;
 }
 
 /**
  * nilfs_search_super_root - search the latest valid super root
  * @nilfs: the_nilfs
- * @sbi: nilfs_sb_info
  * @ri: pointer to a nilfs_recovery_info struct to store search results.
  *
  * nilfs_search_super_root() looks for the latest super-root from a partial
@@ -775,14 +806,19 @@ int nilfs_recover_logical_segments(struct the_nilfs *nilfs,
  * %-EINVAL - No valid segment found
  *
  * %-EIO - I/O error
+ *
+ * %-ENOMEM - Insufficient memory available.
  */
-int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
+int nilfs_search_super_root(struct the_nilfs *nilfs,
 			    struct nilfs_recovery_info *ri)
 {
-	struct nilfs_segsum_info ssi;
+	struct buffer_head *bh_sum = NULL;
+	struct nilfs_segment_summary *sum;
 	sector_t pseg_start, pseg_end, sr_pseg_start = 0;
 	sector_t seg_start, seg_end; /* range of full segment (block number) */
 	sector_t b, end;
+	unsigned long nblocks;
+	unsigned int flags;
 	u64 seg_seq;
 	__u64 segnum, nextnum = 0;
 	__u64 cno;
@@ -801,17 +837,24 @@ int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
 	/* Read ahead segment */
 	b = seg_start;
 	while (b <= seg_end)
-		sb_breadahead(sbi->s_super, b++);
+		__breadahead(nilfs->ns_bdev, b++, nilfs->ns_blocksize);
 
 	for (;;) {
-		/* Load segment summary */
-		ret = load_segment_summary(sbi, pseg_start, seg_seq, &ssi);
+		brelse(bh_sum);
+		ret = NILFS_SEG_FAIL_IO;
+		bh_sum = nilfs_read_log_header(nilfs, pseg_start, &sum);
+		if (!bh_sum)
+			goto failed;
+
+		ret = nilfs_validate_log(nilfs, seg_seq, bh_sum, sum);
 		if (ret) {
 			if (ret == NILFS_SEG_FAIL_IO)
 				goto failed;
 			goto strayed;
 		}
-		pseg_end = pseg_start + ssi.nblocks - 1;
+
+		nblocks = le32_to_cpu(sum->ss_nblocks);
+		pseg_end = pseg_start + nblocks - 1;
 		if (unlikely(pseg_end > seg_end)) {
 			ret = NILFS_SEG_FAIL_CONSISTENCY;
 			goto strayed;
@@ -821,11 +864,13 @@ int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
 		ri->ri_pseg_start = pseg_start;
 		ri->ri_seq = seg_seq;
 		ri->ri_segnum = segnum;
-		nextnum = nilfs_get_segnum_of_block(nilfs, ssi.next);
+		nextnum = nilfs_get_segnum_of_block(nilfs,
+						    le64_to_cpu(sum->ss_next));
 		ri->ri_nextnum = nextnum;
 		empty_seg = 0;
 
-		if (!NILFS_SEG_HAS_SR(&ssi) && !scan_newer) {
+		flags = le16_to_cpu(sum->ss_flags);
+		if (!(flags & NILFS_SS_SR) && !scan_newer) {
 			/* This will never happen because a superblock
 			   (last_segment) always points to a pseg
 			   having a super root. */
@@ -836,14 +881,15 @@ int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
 		if (pseg_start == seg_start) {
 			nilfs_get_segment_range(nilfs, nextnum, &b, &end);
 			while (b <= end)
-				sb_breadahead(sbi->s_super, b++);
+				__breadahead(nilfs->ns_bdev, b++,
+					     nilfs->ns_blocksize);
 		}
-		if (!NILFS_SEG_HAS_SR(&ssi)) {
-			if (!ri->ri_lsegs_start && NILFS_SEG_LOGBGN(&ssi)) {
+		if (!(flags & NILFS_SS_SR)) {
+			if (!ri->ri_lsegs_start && (flags & NILFS_SS_LOGBGN)) {
 				ri->ri_lsegs_start = pseg_start;
 				ri->ri_lsegs_start_seq = seg_seq;
 			}
-			if (NILFS_SEG_LOGEND(&ssi))
+			if (flags & NILFS_SS_LOGEND)
 				ri->ri_lsegs_end = pseg_start;
 			goto try_next_pseg;
 		}
@@ -854,12 +900,12 @@ int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
 		ri->ri_lsegs_start = ri->ri_lsegs_end = 0;
 
 		nilfs_dispose_segment_list(&segments);
-		nilfs->ns_pseg_offset = (sr_pseg_start = pseg_start)
-			+ ssi.nblocks - seg_start;
+		sr_pseg_start = pseg_start;
+		nilfs->ns_pseg_offset = pseg_start + nblocks - seg_start;
 		nilfs->ns_seg_seq = seg_seq;
 		nilfs->ns_segnum = segnum;
 		nilfs->ns_cno = cno;  /* nilfs->ns_cno = ri->ri_cno + 1 */
-		nilfs->ns_ctime = ssi.ctime;
+		nilfs->ns_ctime = le64_to_cpu(sum->ss_create);
 		nilfs->ns_nextnum = nextnum;
 
 		if (scan_newer)
@@ -870,15 +916,9 @@ int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
 			scan_newer = 1;
 		}
 
-		/* reset region for roll-forward */
-		pseg_start += ssi.nblocks;
-		if (pseg_start < seg_end)
-			continue;
-		goto feed_segment;
-
  try_next_pseg:
 		/* Standing on a course, or met an inconsistent state */
-		pseg_start += ssi.nblocks;
+		pseg_start += nblocks;
 		if (pseg_start < seg_end)
 			continue;
 		goto feed_segment;
@@ -909,6 +949,7 @@ int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
 
  super_root_found:
 	/* Updating pointers relating to the latest checkpoint */
+	brelse(bh_sum);
 	list_splice_tail(&segments, &ri->ri_used_segments);
 	nilfs->ns_last_pseg = sr_pseg_start;
 	nilfs->ns_last_seq = nilfs->ns_seg_seq;
@@ -916,6 +957,7 @@ int nilfs_search_super_root(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi,
 	return 0;
 
  failed:
+	brelse(bh_sum);
 	nilfs_dispose_segment_list(&segments);
 	return (ret < 0) ? ret : nilfs_warn_segment_error(ret);
 }
diff --git a/fs/nilfs2/sb.h b/fs/nilfs2/sb.h
index 0776ccc..35a0715 100644
--- a/fs/nilfs2/sb.h
+++ b/fs/nilfs2/sb.h
@@ -42,11 +42,6 @@ struct nilfs_sc_info;
  * NILFS super-block data in memory
  */
 struct nilfs_sb_info {
-	/* Snapshot status */
-	__u64 s_snapshot_cno;		/* Checkpoint number */
-	atomic_t s_inodes_count;
-	atomic_t s_blocks_count;	/* Reserved (might be deleted) */
-
 	/* Mount options */
 	unsigned long s_mount_opt;
 	uid_t s_resuid;
@@ -59,8 +54,6 @@ struct nilfs_sb_info {
 	/* Fundamental members */
 	struct super_block *s_super;	/* reverse pointer to super_block */
 	struct the_nilfs *s_nilfs;
-	struct list_head s_list;	/* list head for nilfs->ns_supers */
-	atomic_t s_count;		/* reference count */
 
 	/* Segment constructor */
 	struct list_head s_dirty_files;	/* dirty files list */
@@ -68,9 +61,6 @@ struct nilfs_sb_info {
 	spinlock_t s_inode_lock;	/* Lock for the nilfs inode.
 					   It covers s_dirty_files list */
 
-	/* Metadata files */
-	struct inode *s_ifile;		/* index file inode */
-
 	/* Inode allocator */
 	spinlock_t s_next_gen_lock;
 	u32 s_next_generation;
diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
index 2e6a272..0f83e93 100644
--- a/fs/nilfs2/segbuf.c
+++ b/fs/nilfs2/segbuf.c
@@ -371,7 +371,8 @@ static int nilfs_segbuf_submit_bio(struct nilfs_segment_buffer *segbuf,
 	struct bio *bio = wi->bio;
 	int err;
 
-	if (segbuf->sb_nbio > 0 && bdi_write_congested(wi->nilfs->ns_bdi)) {
+	if (segbuf->sb_nbio > 0 &&
+	    bdi_write_congested(segbuf->sb_super->s_bdi)) {
 		wait_for_completion(&segbuf->sb_bio_event);
 		segbuf->sb_nbio--;
 		if (unlikely(atomic_read(&segbuf->sb_err))) {
@@ -508,7 +509,7 @@ static int nilfs_segbuf_write(struct nilfs_segment_buffer *segbuf,
 		 * Last BIO is always sent through the following
 		 * submission.
 		 */
-		rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
+		rw |= REQ_SYNC | REQ_UNPLUG;
 		res = nilfs_segbuf_submit_bio(segbuf, &wi, rw);
 	}
 
diff --git a/fs/nilfs2/segbuf.h b/fs/nilfs2/segbuf.h
index 85fbb66..b04f08c 100644
--- a/fs/nilfs2/segbuf.h
+++ b/fs/nilfs2/segbuf.h
@@ -54,17 +54,6 @@ struct nilfs_segsum_info {
 	sector_t		next;
 };
 
-/* macro for the flags */
-#define NILFS_SEG_HAS_SR(sum)    ((sum)->flags & NILFS_SS_SR)
-#define NILFS_SEG_LOGBGN(sum)    ((sum)->flags & NILFS_SS_LOGBGN)
-#define NILFS_SEG_LOGEND(sum)    ((sum)->flags & NILFS_SS_LOGEND)
-#define NILFS_SEG_DSYNC(sum)     ((sum)->flags & NILFS_SS_SYNDT)
-#define NILFS_SEG_SIMPLEX(sum) \
-	(((sum)->flags & (NILFS_SS_LOGBGN | NILFS_SS_LOGEND)) == \
-	 (NILFS_SS_LOGBGN | NILFS_SS_LOGEND))
-
-#define NILFS_SEG_EMPTY(sum)	((sum)->nblocks == (sum)->nsumblk)
-
 /**
  * struct nilfs_segment_buffer - Segment buffer
  * @sb_super: back pointer to a superblock struct
@@ -141,6 +130,19 @@ int nilfs_segbuf_extend_payload(struct nilfs_segment_buffer *,
 				struct buffer_head **);
 void nilfs_segbuf_fill_in_segsum(struct nilfs_segment_buffer *);
 
+static inline int nilfs_segbuf_simplex(struct nilfs_segment_buffer *segbuf)
+{
+	unsigned int flags = segbuf->sb_sum.flags;
+
+	return (flags & (NILFS_SS_LOGBGN | NILFS_SS_LOGEND)) ==
+		(NILFS_SS_LOGBGN | NILFS_SS_LOGEND);
+}
+
+static inline int nilfs_segbuf_empty(struct nilfs_segment_buffer *segbuf)
+{
+	return segbuf->sb_sum.nblocks == segbuf->sb_sum.nsumblk;
+}
+
 static inline void
 nilfs_segbuf_add_segsum_buffer(struct nilfs_segment_buffer *segbuf,
 			       struct buffer_head *bh)
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index c920164..687d090 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -191,6 +191,8 @@ int nilfs_transaction_begin(struct super_block *sb,
 	if (ret > 0)
 		return 0;
 
+	vfs_check_frozen(sb, SB_FREEZE_WRITE);
+
 	sbi = NILFS_SB(sb);
 	nilfs = sbi->s_nilfs;
 	down_read(&nilfs->ns_segctor_sem);
@@ -366,8 +368,7 @@ static int nilfs_segctor_reset_segment_buffer(struct nilfs_sc_info *sci)
 
 	if (nilfs_doing_gc())
 		flags = NILFS_SS_GC;
-	err = nilfs_segbuf_reset(segbuf, flags, sci->sc_seg_ctime,
-				 sci->sc_sbi->s_nilfs->ns_cno);
+	err = nilfs_segbuf_reset(segbuf, flags, sci->sc_seg_ctime, sci->sc_cno);
 	if (unlikely(err))
 		return err;
 
@@ -440,17 +441,26 @@ static void nilfs_segctor_end_finfo(struct nilfs_sc_info *sci,
 	struct nilfs_finfo *finfo;
 	struct nilfs_inode_info *ii;
 	struct nilfs_segment_buffer *segbuf;
+	__u64 cno;
 
 	if (sci->sc_blk_cnt == 0)
 		return;
 
 	ii = NILFS_I(inode);
+
+	if (test_bit(NILFS_I_GCINODE, &ii->i_state))
+		cno = ii->i_cno;
+	else if (NILFS_ROOT_METADATA_FILE(inode->i_ino))
+		cno = 0;
+	else
+		cno = sci->sc_cno;
+
 	finfo = nilfs_segctor_map_segsum_entry(sci, &sci->sc_finfo_ptr,
 						 sizeof(*finfo));
 	finfo->fi_ino = cpu_to_le64(inode->i_ino);
 	finfo->fi_nblocks = cpu_to_le32(sci->sc_blk_cnt);
 	finfo->fi_ndatablk = cpu_to_le32(sci->sc_datablk_cnt);
-	finfo->fi_cno = cpu_to_le64(ii->i_cno);
+	finfo->fi_cno = cpu_to_le64(cno);
 
 	segbuf = sci->sc_curseg;
 	segbuf->sb_sum.sumbytes = sci->sc_binfo_ptr.offset +
@@ -755,12 +765,12 @@ static void nilfs_dispose_list(struct nilfs_sb_info *sbi,
 	}
 }
 
-static int nilfs_test_metadata_dirty(struct nilfs_sb_info *sbi)
+static int nilfs_test_metadata_dirty(struct the_nilfs *nilfs,
+				     struct nilfs_root *root)
 {
-	struct the_nilfs *nilfs = sbi->s_nilfs;
 	int ret = 0;
 
-	if (nilfs_mdt_fetch_dirty(sbi->s_ifile))
+	if (nilfs_mdt_fetch_dirty(root->ifile))
 		ret++;
 	if (nilfs_mdt_fetch_dirty(nilfs->ns_cpfile))
 		ret++;
@@ -785,7 +795,7 @@ static int nilfs_segctor_confirm(struct nilfs_sc_info *sci)
 	struct nilfs_sb_info *sbi = sci->sc_sbi;
 	int ret = 0;
 
-	if (nilfs_test_metadata_dirty(sbi))
+	if (nilfs_test_metadata_dirty(sbi->s_nilfs, sci->sc_root))
 		set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
 
 	spin_lock(&sbi->s_inode_lock);
@@ -801,7 +811,7 @@ static void nilfs_segctor_clear_metadata_dirty(struct nilfs_sc_info *sci)
 	struct nilfs_sb_info *sbi = sci->sc_sbi;
 	struct the_nilfs *nilfs = sbi->s_nilfs;
 
-	nilfs_mdt_clear_dirty(sbi->s_ifile);
+	nilfs_mdt_clear_dirty(sci->sc_root->ifile);
 	nilfs_mdt_clear_dirty(nilfs->ns_cpfile);
 	nilfs_mdt_clear_dirty(nilfs->ns_sufile);
 	nilfs_mdt_clear_dirty(nilfs_dat_inode(nilfs));
@@ -848,9 +858,9 @@ static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
 	raw_cp->cp_snapshot_list.ssl_next = 0;
 	raw_cp->cp_snapshot_list.ssl_prev = 0;
 	raw_cp->cp_inodes_count =
-		cpu_to_le64(atomic_read(&sbi->s_inodes_count));
+		cpu_to_le64(atomic_read(&sci->sc_root->inodes_count));
 	raw_cp->cp_blocks_count =
-		cpu_to_le64(atomic_read(&sbi->s_blocks_count));
+		cpu_to_le64(atomic_read(&sci->sc_root->blocks_count));
 	raw_cp->cp_nblk_inc =
 		cpu_to_le64(sci->sc_nblk_inc + sci->sc_nblk_this_inc);
 	raw_cp->cp_create = cpu_to_le64(sci->sc_seg_ctime);
@@ -861,7 +871,8 @@ static int nilfs_segctor_fill_in_checkpoint(struct nilfs_sc_info *sci)
 	else
 		nilfs_checkpoint_set_minor(raw_cp);
 
-	nilfs_write_inode_common(sbi->s_ifile, &raw_cp->cp_ifile_inode, 1);
+	nilfs_write_inode_common(sci->sc_root->ifile,
+				 &raw_cp->cp_ifile_inode, 1);
 	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, nilfs->ns_cno, bh_cp);
 	return 0;
 
@@ -886,13 +897,12 @@ static void nilfs_fill_in_file_bmap(struct inode *ifile,
 	}
 }
 
-static void nilfs_segctor_fill_in_file_bmap(struct nilfs_sc_info *sci,
-					    struct inode *ifile)
+static void nilfs_segctor_fill_in_file_bmap(struct nilfs_sc_info *sci)
 {
 	struct nilfs_inode_info *ii;
 
 	list_for_each_entry(ii, &sci->sc_dirty_files, i_dirty) {
-		nilfs_fill_in_file_bmap(ifile, ii);
+		nilfs_fill_in_file_bmap(sci->sc_root->ifile, ii);
 		set_bit(NILFS_I_COLLECTED, &ii->i_state);
 	}
 }
@@ -1135,7 +1145,7 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
 		sci->sc_stage.flags |= NILFS_CF_IFILE_STARTED;
 		/* Fall through */
 	case NILFS_ST_IFILE:
-		err = nilfs_segctor_scan_file(sci, sbi->s_ifile,
+		err = nilfs_segctor_scan_file(sci, sci->sc_root->ifile,
 					      &nilfs_sc_file_ops);
 		if (unlikely(err))
 			break;
@@ -1599,7 +1609,7 @@ nilfs_copy_replace_page_buffers(struct page *page, struct list_head *out)
 	kunmap_atomic(kaddr, KM_USER0);
 
 	if (!TestSetPageWriteback(clone_page))
-		inc_zone_page_state(clone_page, NR_WRITEBACK);
+		account_page_writeback(clone_page);
 	unlock_page(clone_page);
 
 	return 0;
@@ -1900,6 +1910,7 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 			set_buffer_uptodate(bh);
 			clear_buffer_dirty(bh);
 			clear_buffer_nilfs_volatile(bh);
+			clear_buffer_nilfs_redirected(bh);
 			if (bh == segbuf->sb_super_root) {
 				if (bh->b_page != bd_page) {
 					end_page_writeback(bd_page);
@@ -1914,12 +1925,12 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 			}
 		}
 
-		if (!NILFS_SEG_SIMPLEX(&segbuf->sb_sum)) {
-			if (NILFS_SEG_LOGBGN(&segbuf->sb_sum)) {
+		if (!nilfs_segbuf_simplex(segbuf)) {
+			if (segbuf->sb_sum.flags & NILFS_SS_LOGBGN) {
 				set_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
 				sci->sc_lseg_stime = jiffies;
 			}
-			if (NILFS_SEG_LOGEND(&segbuf->sb_sum))
+			if (segbuf->sb_sum.flags & NILFS_SS_LOGEND)
 				clear_bit(NILFS_SC_UNCLOSED, &sci->sc_flags);
 		}
 	}
@@ -1936,11 +1947,9 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 
 	nilfs_drop_collected_inodes(&sci->sc_dirty_files);
 
-	if (nilfs_doing_gc()) {
+	if (nilfs_doing_gc())
 		nilfs_drop_collected_inodes(&sci->sc_gc_inodes);
-		if (update_sr)
-			nilfs_commit_gcdat_inode(nilfs);
-	} else
+	else
 		nilfs->ns_nongc_ctime = sci->sc_seg_ctime;
 
 	sci->sc_nblk_inc += sci->sc_nblk_this_inc;
@@ -1951,7 +1960,6 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 	if (update_sr) {
 		nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
 				       segbuf->sb_sum.seg_seq, nilfs->ns_cno++);
-		set_nilfs_sb_dirty(nilfs);
 
 		clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
 		clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
@@ -1977,7 +1985,7 @@ static int nilfs_segctor_check_in_files(struct nilfs_sc_info *sci,
 					struct nilfs_sb_info *sbi)
 {
 	struct nilfs_inode_info *ii, *n;
-	__u64 cno = sbi->s_nilfs->ns_cno;
+	struct inode *ifile = sci->sc_root->ifile;
 
 	spin_lock(&sbi->s_inode_lock);
  retry:
@@ -1988,14 +1996,14 @@ static int nilfs_segctor_check_in_files(struct nilfs_sc_info *sci,
 
 			spin_unlock(&sbi->s_inode_lock);
 			err = nilfs_ifile_get_inode_block(
-				sbi->s_ifile, ii->vfs_inode.i_ino, &ibh);
+				ifile, ii->vfs_inode.i_ino, &ibh);
 			if (unlikely(err)) {
 				nilfs_warning(sbi->s_super, __func__,
 					      "failed to get inode block.\n");
 				return err;
 			}
 			nilfs_mdt_mark_buffer_dirty(ibh);
-			nilfs_mdt_mark_dirty(sbi->s_ifile);
+			nilfs_mdt_mark_dirty(ifile);
 			spin_lock(&sbi->s_inode_lock);
 			if (likely(!ii->i_bh))
 				ii->i_bh = ibh;
@@ -2003,7 +2011,6 @@ static int nilfs_segctor_check_in_files(struct nilfs_sc_info *sci,
 				brelse(ibh);
 			goto retry;
 		}
-		ii->i_cno = cno;
 
 		clear_bit(NILFS_I_QUEUED, &ii->i_state);
 		set_bit(NILFS_I_BUSY, &ii->i_state);
@@ -2012,8 +2019,6 @@ static int nilfs_segctor_check_in_files(struct nilfs_sc_info *sci,
 	}
 	spin_unlock(&sbi->s_inode_lock);
 
-	NILFS_I(sbi->s_ifile)->i_cno = cno;
-
 	return 0;
 }
 
@@ -2022,19 +2027,13 @@ static void nilfs_segctor_check_out_files(struct nilfs_sc_info *sci,
 {
 	struct nilfs_transaction_info *ti = current->journal_info;
 	struct nilfs_inode_info *ii, *n;
-	__u64 cno = sbi->s_nilfs->ns_cno;
 
 	spin_lock(&sbi->s_inode_lock);
 	list_for_each_entry_safe(ii, n, &sci->sc_dirty_files, i_dirty) {
 		if (!test_and_clear_bit(NILFS_I_UPDATED, &ii->i_state) ||
-		    test_bit(NILFS_I_DIRTY, &ii->i_state)) {
-			/* The current checkpoint number (=nilfs->ns_cno) is
-			   changed between check-in and check-out only if the
-			   super root is written out.  So, we can update i_cno
-			   for the inodes that remain in the dirty list. */
-			ii->i_cno = cno;
+		    test_bit(NILFS_I_DIRTY, &ii->i_state))
 			continue;
-		}
+
 		clear_bit(NILFS_I_BUSY, &ii->i_state);
 		brelse(ii->i_bh);
 		ii->i_bh = NULL;
@@ -2055,12 +2054,13 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
 	int err;
 
 	sci->sc_stage.scnt = NILFS_ST_INIT;
+	sci->sc_cno = nilfs->ns_cno;
 
 	err = nilfs_segctor_check_in_files(sci, sbi);
 	if (unlikely(err))
 		goto out;
 
-	if (nilfs_test_metadata_dirty(sbi))
+	if (nilfs_test_metadata_dirty(nilfs, sci->sc_root))
 		set_bit(NILFS_SC_DIRTY, &sci->sc_flags);
 
 	if (nilfs_segctor_clean(sci))
@@ -2082,7 +2082,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
 
 		/* Avoid empty segment */
 		if (sci->sc_stage.scnt == NILFS_ST_DONE &&
-		    NILFS_SEG_EMPTY(&sci->sc_curseg->sb_sum)) {
+		    nilfs_segbuf_empty(sci->sc_curseg)) {
 			nilfs_segctor_abort_construction(sci, nilfs, 1);
 			goto out;
 		}
@@ -2092,7 +2092,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
 			goto failed;
 
 		if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
-			nilfs_segctor_fill_in_file_bmap(sci, sbi->s_ifile);
+			nilfs_segctor_fill_in_file_bmap(sci);
 
 		if (mode == SC_LSEG_SR &&
 		    sci->sc_stage.scnt >= NILFS_ST_CPFILE) {
@@ -2408,6 +2408,7 @@ static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
 {
 	struct nilfs_sb_info *sbi = sci->sc_sbi;
 	struct the_nilfs *nilfs = sbi->s_nilfs;
+	struct nilfs_super_block **sbp;
 	int err = 0;
 
 	nilfs_segctor_accept(sci);
@@ -2423,8 +2424,13 @@ static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
 		if (test_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags) &&
 		    nilfs_discontinued(nilfs)) {
 			down_write(&nilfs->ns_sem);
-			err = nilfs_commit_super(
-				sbi, nilfs_altsb_need_update(nilfs));
+			err = -EIO;
+			sbp = nilfs_prepare_super(sbi,
+						  nilfs_sb_will_flip(nilfs));
+			if (likely(sbp)) {
+				nilfs_set_log_cursor(sbp[0], nilfs);
+				err = nilfs_commit_super(sbi, NILFS_SB_COMMIT);
+			}
 			up_write(&nilfs->ns_sem);
 		}
 	}
@@ -2447,9 +2453,8 @@ nilfs_remove_written_gcinodes(struct the_nilfs *nilfs, struct list_head *head)
 	list_for_each_entry_safe(ii, n, head, i_dirty) {
 		if (!test_bit(NILFS_I_UPDATED, &ii->i_state))
 			continue;
-		hlist_del_init(&ii->vfs_inode.i_hash);
 		list_del_init(&ii->i_dirty);
-		nilfs_clear_gcinode(&ii->vfs_inode);
+		iput(&ii->vfs_inode);
 	}
 }
 
@@ -2467,13 +2472,15 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
 
 	nilfs_transaction_lock(sbi, &ti, 1);
 
-	err = nilfs_init_gcdat_inode(nilfs);
+	err = nilfs_mdt_save_to_shadow_map(nilfs->ns_dat);
 	if (unlikely(err))
 		goto out_unlock;
 
 	err = nilfs_ioctl_prepare_clean_segments(nilfs, argv, kbufs);
-	if (unlikely(err))
+	if (unlikely(err)) {
+		nilfs_mdt_restore_from_shadow_map(nilfs->ns_dat);
 		goto out_unlock;
+	}
 
 	sci->sc_freesegs = kbufs[4];
 	sci->sc_nfreesegs = argv[4].v_nmembs;
@@ -2505,7 +2512,7 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
  out_unlock:
 	sci->sc_freesegs = NULL;
 	sci->sc_nfreesegs = 0;
-	nilfs_clear_gcdat_inode(nilfs);
+	nilfs_mdt_clear_shadow_map(nilfs->ns_dat);
 	nilfs_transaction_unlock(sbi);
 	return err;
 }
@@ -2667,6 +2674,8 @@ static int nilfs_segctor_start_thread(struct nilfs_sc_info *sci)
 }
 
 static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
+	__acquires(&sci->sc_state_lock)
+	__releases(&sci->sc_state_lock)
 {
 	sci->sc_state |= NILFS_SEGCTOR_QUIT;
 
@@ -2681,7 +2690,8 @@ static void nilfs_segctor_kill_thread(struct nilfs_sc_info *sci)
 /*
  * Setup & clean-up functions
  */
-static struct nilfs_sc_info *nilfs_segctor_new(struct nilfs_sb_info *sbi)
+static struct nilfs_sc_info *nilfs_segctor_new(struct nilfs_sb_info *sbi,
+					       struct nilfs_root *root)
 {
 	struct nilfs_sc_info *sci;
 
@@ -2692,6 +2702,9 @@ static struct nilfs_sc_info *nilfs_segctor_new(struct nilfs_sb_info *sbi)
 	sci->sc_sbi = sbi;
 	sci->sc_super = sbi->s_super;
 
+	nilfs_get_root(root);
+	sci->sc_root = root;
+
 	init_waitqueue_head(&sci->sc_wait_request);
 	init_waitqueue_head(&sci->sc_wait_daemon);
 	init_waitqueue_head(&sci->sc_wait_task);
@@ -2766,6 +2779,8 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
 	WARN_ON(!list_empty(&sci->sc_segbufs));
 	WARN_ON(!list_empty(&sci->sc_write_logs));
 
+	nilfs_put_root(sci->sc_root);
+
 	down_write(&sbi->s_nilfs->ns_segctor_sem);
 
 	del_timer_sync(&sci->sc_timer);
@@ -2775,6 +2790,7 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
 /**
  * nilfs_attach_segment_constructor - attach a segment constructor
  * @sbi: nilfs_sb_info
+ * @root: root object of the current filesystem tree
  *
  * nilfs_attach_segment_constructor() allocates a struct nilfs_sc_info,
  * initializes it, and starts the segment constructor.
@@ -2784,9 +2800,9 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
  *
  * %-ENOMEM - Insufficient memory available.
  */
-int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi)
+int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi,
+				     struct nilfs_root *root)
 {
-	struct the_nilfs *nilfs = sbi->s_nilfs;
 	int err;
 
 	if (NILFS_SC(sbi)) {
@@ -2798,14 +2814,12 @@ int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi)
 		nilfs_detach_segment_constructor(sbi);
 	}
 
-	sbi->s_sc_info = nilfs_segctor_new(sbi);
+	sbi->s_sc_info = nilfs_segctor_new(sbi, root);
 	if (!sbi->s_sc_info)
 		return -ENOMEM;
 
-	nilfs_attach_writer(nilfs, sbi);
 	err = nilfs_segctor_start_thread(NILFS_SC(sbi));
 	if (err) {
-		nilfs_detach_writer(nilfs, sbi);
 		kfree(sbi->s_sc_info);
 		sbi->s_sc_info = NULL;
 	}
@@ -2842,5 +2856,4 @@ void nilfs_detach_segment_constructor(struct nilfs_sb_info *sbi)
 	up_write(&nilfs->ns_segctor_sem);
 
 	nilfs_dispose_list(sbi, &garbage_list, 1);
-	nilfs_detach_writer(nilfs, sbi);
 }
diff --git a/fs/nilfs2/segment.h b/fs/nilfs2/segment.h
index 01e20db..cd8056e 100644
--- a/fs/nilfs2/segment.h
+++ b/fs/nilfs2/segment.h
@@ -29,6 +29,8 @@
 #include <linux/nilfs2_fs.h>
 #include "sb.h"
 
+struct nilfs_root;
+
 /**
  * struct nilfs_recovery_info - Recovery information
  * @ri_need_recovery: Recovery status
@@ -87,6 +89,7 @@ struct nilfs_segsum_pointer {
  * struct nilfs_sc_info - Segment constructor information
  * @sc_super: Back pointer to super_block struct
  * @sc_sbi: Back pointer to nilfs_sb_info struct
+ * @sc_root: root object of the current filesystem tree
  * @sc_nblk_inc: Block count of current generation
  * @sc_dirty_files: List of files to be written
  * @sc_gc_inodes: List of GC inodes having blocks to be written
@@ -107,6 +110,7 @@ struct nilfs_segsum_pointer {
  * @sc_datablk_cnt: Data block count of a file
  * @sc_nblk_this_inc: Number of blocks included in the current logical segment
  * @sc_seg_ctime: Creation time
+ * @sc_cno: checkpoint number of current log
  * @sc_flags: Internal flags
  * @sc_state_lock: spinlock for sc_state and so on
  * @sc_state: Segctord state flags
@@ -128,6 +132,7 @@ struct nilfs_segsum_pointer {
 struct nilfs_sc_info {
 	struct super_block     *sc_super;
 	struct nilfs_sb_info   *sc_sbi;
+	struct nilfs_root      *sc_root;
 
 	unsigned long		sc_nblk_inc;
 
@@ -156,7 +161,7 @@ struct nilfs_sc_info {
 	unsigned long		sc_datablk_cnt;
 	unsigned long		sc_nblk_this_inc;
 	time_t			sc_seg_ctime;
-
+	__u64			sc_cno;
 	unsigned long		sc_flags;
 
 	spinlock_t		sc_state_lock;
@@ -230,17 +235,18 @@ extern void nilfs_flush_segment(struct super_block *, ino_t);
 extern int nilfs_clean_segments(struct super_block *, struct nilfs_argv *,
 				void **);
 
-extern int nilfs_attach_segment_constructor(struct nilfs_sb_info *);
+int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi,
+				     struct nilfs_root *root);
 extern void nilfs_detach_segment_constructor(struct nilfs_sb_info *);
 
 /* recovery.c */
-extern int nilfs_read_super_root_block(struct super_block *, sector_t,
+extern int nilfs_read_super_root_block(struct the_nilfs *, sector_t,
 				       struct buffer_head **, int);
-extern int nilfs_search_super_root(struct the_nilfs *, struct nilfs_sb_info *,
+extern int nilfs_search_super_root(struct the_nilfs *,
 				   struct nilfs_recovery_info *);
-extern int nilfs_recover_logical_segments(struct the_nilfs *,
-					  struct nilfs_sb_info *,
-					  struct nilfs_recovery_info *);
+extern int nilfs_salvage_orphan_logs(struct the_nilfs *,
+				     struct nilfs_sb_info *,
+				     struct nilfs_recovery_info *);
 extern void nilfs_dispose_segment_list(struct list_head *);
 
 #endif /* _NILFS_SEGMENT_H */
diff --git a/fs/nilfs2/sufile.c b/fs/nilfs2/sufile.c
index 3c6cc60..1d6f488 100644
--- a/fs/nilfs2/sufile.c
+++ b/fs/nilfs2/sufile.c
@@ -505,7 +505,7 @@ int nilfs_sufile_get_stat(struct inode *sufile, struct nilfs_sustat *sustat)
 {
 	struct buffer_head *header_bh;
 	struct nilfs_sufile_header *header;
-	struct the_nilfs *nilfs = NILFS_MDT(sufile)->mi_nilfs;
+	struct the_nilfs *nilfs = NILFS_I_NILFS(sufile);
 	void *kaddr;
 	int ret;
 
@@ -583,7 +583,7 @@ ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
 	struct nilfs_segment_usage *su;
 	struct nilfs_suinfo *si = buf;
 	size_t susz = NILFS_MDT(sufile)->mi_entry_size;
-	struct the_nilfs *nilfs = NILFS_MDT(sufile)->mi_nilfs;
+	struct the_nilfs *nilfs = NILFS_I_NILFS(sufile);
 	void *kaddr;
 	unsigned long nsegs, segusages_per_block;
 	ssize_t n;
@@ -635,46 +635,55 @@ ssize_t nilfs_sufile_get_suinfo(struct inode *sufile, __u64 segnum, void *buf,
 }
 
 /**
- * nilfs_sufile_read - read sufile inode
- * @sufile: sufile inode
+ * nilfs_sufile_read - read or get sufile inode
+ * @sb: super block instance
+ * @susize: size of a segment usage entry
  * @raw_inode: on-disk sufile inode
+ * @inodep: buffer to store the inode
  */
-int nilfs_sufile_read(struct inode *sufile, struct nilfs_inode *raw_inode)
+int nilfs_sufile_read(struct super_block *sb, size_t susize,
+		      struct nilfs_inode *raw_inode, struct inode **inodep)
 {
-	struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
+	struct inode *sufile;
+	struct nilfs_sufile_info *sui;
 	struct buffer_head *header_bh;
 	struct nilfs_sufile_header *header;
 	void *kaddr;
-	int ret;
+	int err;
 
-	ret = nilfs_read_inode_common(sufile, raw_inode);
-	if (ret < 0)
-		return ret;
+	sufile = nilfs_iget_locked(sb, NULL, NILFS_SUFILE_INO);
+	if (unlikely(!sufile))
+		return -ENOMEM;
+	if (!(sufile->i_state & I_NEW))
+		goto out;
 
-	ret = nilfs_sufile_get_header_block(sufile, &header_bh);
-	if (!ret) {
-		kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
-		header = kaddr + bh_offset(header_bh);
-		sui->ncleansegs = le64_to_cpu(header->sh_ncleansegs);
-		kunmap_atomic(kaddr, KM_USER0);
-		brelse(header_bh);
-	}
-	return ret;
-}
+	err = nilfs_mdt_init(sufile, NILFS_MDT_GFP, sizeof(*sui));
+	if (err)
+		goto failed;
 
-/**
- * nilfs_sufile_new - create sufile
- * @nilfs: nilfs object
- * @susize: size of a segment usage entry
- */
-struct inode *nilfs_sufile_new(struct the_nilfs *nilfs, size_t susize)
-{
-	struct inode *sufile;
+	nilfs_mdt_set_entry_size(sufile, susize,
+				 sizeof(struct nilfs_sufile_header));
+
+	err = nilfs_read_inode_common(sufile, raw_inode);
+	if (err)
+		goto failed;
+
+	err = nilfs_sufile_get_header_block(sufile, &header_bh);
+	if (err)
+		goto failed;
 
-	sufile = nilfs_mdt_new(nilfs, NULL, NILFS_SUFILE_INO,
-			       sizeof(struct nilfs_sufile_info));
-	if (sufile)
-		nilfs_mdt_set_entry_size(sufile, susize,
-					 sizeof(struct nilfs_sufile_header));
-	return sufile;
+	sui = NILFS_SUI(sufile);
+	kaddr = kmap_atomic(header_bh->b_page, KM_USER0);
+	header = kaddr + bh_offset(header_bh);
+	sui->ncleansegs = le64_to_cpu(header->sh_ncleansegs);
+	kunmap_atomic(kaddr, KM_USER0);
+	brelse(header_bh);
+
+	unlock_new_inode(sufile);
+ out:
+	*inodep = sufile;
+	return 0;
+ failed:
+	iget_failed(sufile);
+	return err;
 }
diff --git a/fs/nilfs2/sufile.h b/fs/nilfs2/sufile.h
index 15163b8..a943fba 100644
--- a/fs/nilfs2/sufile.h
+++ b/fs/nilfs2/sufile.h
@@ -31,7 +31,7 @@
 
 static inline unsigned long nilfs_sufile_get_nsegments(struct inode *sufile)
 {
-	return NILFS_MDT(sufile)->mi_nilfs->ns_nsegments;
+	return NILFS_I_NILFS(sufile)->ns_nsegments;
 }
 
 unsigned long nilfs_sufile_get_ncleansegs(struct inode *sufile);
@@ -61,8 +61,8 @@ void nilfs_sufile_do_cancel_free(struct inode *, __u64, struct buffer_head *,
 void nilfs_sufile_do_set_error(struct inode *, __u64, struct buffer_head *,
 			       struct buffer_head *);
 
-int nilfs_sufile_read(struct inode *sufile, struct nilfs_inode *raw_inode);
-struct inode *nilfs_sufile_new(struct the_nilfs *nilfs, size_t susize);
+int nilfs_sufile_read(struct super_block *sb, size_t susize,
+		      struct nilfs_inode *raw_inode, struct inode **inodep);
 
 /**
  * nilfs_sufile_scrap - make a segment garbage
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 414ef68..f804d41 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -45,16 +45,17 @@
 #include <linux/parser.h>
 #include <linux/random.h>
 #include <linux/crc32.h>
-#include <linux/smp_lock.h>
 #include <linux/vfs.h>
 #include <linux/writeback.h>
 #include <linux/kobject.h>
-#include <linux/exportfs.h>
 #include <linux/seq_file.h>
 #include <linux/mount.h>
 #include "nilfs.h"
+#include "export.h"
 #include "mdt.h"
 #include "alloc.h"
+#include "btree.h"
+#include "btnode.h"
 #include "page.h"
 #include "cpfile.h"
 #include "ifile.h"
@@ -67,13 +68,33 @@ MODULE_DESCRIPTION("A New Implementation of the Log-structured Filesystem "
 		   "(NILFS)");
 MODULE_LICENSE("GPL");
 
-struct kmem_cache *nilfs_inode_cachep;
+static struct kmem_cache *nilfs_inode_cachep;
 struct kmem_cache *nilfs_transaction_cachep;
 struct kmem_cache *nilfs_segbuf_cachep;
 struct kmem_cache *nilfs_btree_path_cache;
 
+static int nilfs_setup_super(struct nilfs_sb_info *sbi, int is_mount);
 static int nilfs_remount(struct super_block *sb, int *flags, char *data);
 
+static void nilfs_set_error(struct nilfs_sb_info *sbi)
+{
+	struct the_nilfs *nilfs = sbi->s_nilfs;
+	struct nilfs_super_block **sbp;
+
+	down_write(&nilfs->ns_sem);
+	if (!(nilfs->ns_mount_state & NILFS_ERROR_FS)) {
+		nilfs->ns_mount_state |= NILFS_ERROR_FS;
+		sbp = nilfs_prepare_super(sbi, 0);
+		if (likely(sbp)) {
+			sbp[0]->s_state |= cpu_to_le16(NILFS_ERROR_FS);
+			if (sbp[1])
+				sbp[1]->s_state |= cpu_to_le16(NILFS_ERROR_FS);
+			nilfs_commit_super(sbi, NILFS_SB_COMMIT_ALL);
+		}
+	}
+	up_write(&nilfs->ns_sem);
+}
+
 /**
  * nilfs_error() - report failure condition on a filesystem
  *
@@ -99,16 +120,7 @@ void nilfs_error(struct super_block *sb, const char *function,
 	va_end(args);
 
 	if (!(sb->s_flags & MS_RDONLY)) {
-		struct the_nilfs *nilfs = sbi->s_nilfs;
-
-		down_write(&nilfs->ns_sem);
-		if (!(nilfs->ns_mount_state & NILFS_ERROR_FS)) {
-			nilfs->ns_mount_state |= NILFS_ERROR_FS;
-			nilfs->ns_sbp[0]->s_state |=
-				cpu_to_le16(NILFS_ERROR_FS);
-			nilfs_commit_super(sbi, 1);
-		}
-		up_write(&nilfs->ns_sem);
+		nilfs_set_error(sbi);
 
 		if (nilfs_test_opt(sbi, ERRORS_RO)) {
 			printk(KERN_CRIT "Remounting filesystem read-only\n");
@@ -135,7 +147,7 @@ void nilfs_warning(struct super_block *sb, const char *function,
 }
 
 
-struct inode *nilfs_alloc_inode_common(struct the_nilfs *nilfs)
+struct inode *nilfs_alloc_inode(struct super_block *sb)
 {
 	struct nilfs_inode_info *ii;
 
@@ -144,70 +156,55 @@ struct inode *nilfs_alloc_inode_common(struct the_nilfs *nilfs)
 		return NULL;
 	ii->i_bh = NULL;
 	ii->i_state = 0;
+	ii->i_cno = 0;
 	ii->vfs_inode.i_version = 1;
-	nilfs_btnode_cache_init(&ii->i_btnode_cache, nilfs->ns_bdi);
+	nilfs_btnode_cache_init(&ii->i_btnode_cache, sb->s_bdi);
 	return &ii->vfs_inode;
 }
 
-struct inode *nilfs_alloc_inode(struct super_block *sb)
-{
-	return nilfs_alloc_inode_common(NILFS_SB(sb)->s_nilfs);
-}
-
 void nilfs_destroy_inode(struct inode *inode)
 {
-	kmem_cache_free(nilfs_inode_cachep, NILFS_I(inode));
-}
-
-static void nilfs_clear_inode(struct inode *inode)
-{
-	struct nilfs_inode_info *ii = NILFS_I(inode);
-
-	/*
-	 * Free resources allocated in nilfs_read_inode(), here.
-	 */
-	BUG_ON(!list_empty(&ii->i_dirty));
-	brelse(ii->i_bh);
-	ii->i_bh = NULL;
-
-	if (test_bit(NILFS_I_BMAP, &ii->i_state))
-		nilfs_bmap_clear(ii->i_bmap);
+	struct nilfs_mdt_info *mdi = NILFS_MDT(inode);
 
-	nilfs_btnode_cache_clear(&ii->i_btnode_cache);
+	if (mdi) {
+		kfree(mdi->mi_bgl); /* kfree(NULL) is safe */
+		kfree(mdi);
+	}
+	kmem_cache_free(nilfs_inode_cachep, NILFS_I(inode));
 }
 
-static int nilfs_sync_super(struct nilfs_sb_info *sbi, int dupsb)
+static int nilfs_sync_super(struct nilfs_sb_info *sbi, int flag)
 {
 	struct the_nilfs *nilfs = sbi->s_nilfs;
 	int err;
-	int barrier_done = 0;
 
-	if (nilfs_test_opt(sbi, BARRIER)) {
-		set_buffer_ordered(nilfs->ns_sbh[0]);
-		barrier_done = 1;
-	}
  retry:
 	set_buffer_dirty(nilfs->ns_sbh[0]);
-	err = sync_dirty_buffer(nilfs->ns_sbh[0]);
-	if (err == -EOPNOTSUPP && barrier_done) {
-		nilfs_warning(sbi->s_super, __func__,
-			      "barrier-based sync failed. "
-			      "disabling barriers\n");
-		nilfs_clear_opt(sbi, BARRIER);
-		barrier_done = 0;
-		clear_buffer_ordered(nilfs->ns_sbh[0]);
-		goto retry;
+	if (nilfs_test_opt(sbi, BARRIER)) {
+		err = __sync_dirty_buffer(nilfs->ns_sbh[0],
+					  WRITE_SYNC | WRITE_FLUSH_FUA);
+	} else {
+		err = sync_dirty_buffer(nilfs->ns_sbh[0]);
 	}
+
 	if (unlikely(err)) {
 		printk(KERN_ERR
 		       "NILFS: unable to write superblock (err=%d)\n", err);
 		if (err == -EIO && nilfs->ns_sbh[1]) {
+			/*
+			 * sbp[0] points to newer log than sbp[1],
+			 * so copy sbp[0] to sbp[1] to take over sbp[0].
+			 */
+			memcpy(nilfs->ns_sbp[1], nilfs->ns_sbp[0],
+			       nilfs->ns_sbsize);
 			nilfs_fall_back_super_block(nilfs);
 			goto retry;
 		}
 	} else {
 		struct nilfs_super_block *sbp = nilfs->ns_sbp[0];
 
+		nilfs->ns_sbwcount++;
+
 		/*
 		 * The latest segment becomes trailable from the position
 		 * written in superblock.
@@ -216,66 +213,122 @@ static int nilfs_sync_super(struct nilfs_sb_info *sbi, int dupsb)
 
 		/* update GC protection for recent segments */
 		if (nilfs->ns_sbh[1]) {
-			sbp = NULL;
-			if (dupsb) {
+			if (flag == NILFS_SB_COMMIT_ALL) {
 				set_buffer_dirty(nilfs->ns_sbh[1]);
-				if (!sync_dirty_buffer(nilfs->ns_sbh[1]))
-					sbp = nilfs->ns_sbp[1];
+				if (sync_dirty_buffer(nilfs->ns_sbh[1]) < 0)
+					goto out;
 			}
+			if (le64_to_cpu(nilfs->ns_sbp[1]->s_last_cno) <
+			    le64_to_cpu(nilfs->ns_sbp[0]->s_last_cno))
+				sbp = nilfs->ns_sbp[1];
 		}
-		if (sbp) {
-			spin_lock(&nilfs->ns_last_segment_lock);
-			nilfs->ns_prot_seq = le64_to_cpu(sbp->s_last_seq);
-			spin_unlock(&nilfs->ns_last_segment_lock);
-		}
-	}
 
+		spin_lock(&nilfs->ns_last_segment_lock);
+		nilfs->ns_prot_seq = le64_to_cpu(sbp->s_last_seq);
+		spin_unlock(&nilfs->ns_last_segment_lock);
+	}
+ out:
 	return err;
 }
 
-int nilfs_commit_super(struct nilfs_sb_info *sbi, int dupsb)
+void nilfs_set_log_cursor(struct nilfs_super_block *sbp,
+			  struct the_nilfs *nilfs)
+{
+	sector_t nfreeblocks;
+
+	/* nilfs->ns_sem must be locked by the caller. */
+	nilfs_count_free_blocks(nilfs, &nfreeblocks);
+	sbp->s_free_blocks_count = cpu_to_le64(nfreeblocks);
+
+	spin_lock(&nilfs->ns_last_segment_lock);
+	sbp->s_last_seq = cpu_to_le64(nilfs->ns_last_seq);
+	sbp->s_last_pseg = cpu_to_le64(nilfs->ns_last_pseg);
+	sbp->s_last_cno = cpu_to_le64(nilfs->ns_last_cno);
+	spin_unlock(&nilfs->ns_last_segment_lock);
+}
+
+struct nilfs_super_block **nilfs_prepare_super(struct nilfs_sb_info *sbi,
+					       int flip)
 {
 	struct the_nilfs *nilfs = sbi->s_nilfs;
 	struct nilfs_super_block **sbp = nilfs->ns_sbp;
-	sector_t nfreeblocks;
-	time_t t;
-	int err;
 
-	/* nilfs->sem must be locked by the caller. */
+	/* nilfs->ns_sem must be locked by the caller. */
 	if (sbp[0]->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
-		if (sbp[1] && sbp[1]->s_magic == cpu_to_le16(NILFS_SUPER_MAGIC))
-			nilfs_swap_super_block(nilfs);
-		else {
+		if (sbp[1] &&
+		    sbp[1]->s_magic == cpu_to_le16(NILFS_SUPER_MAGIC)) {
+			memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
+		} else {
 			printk(KERN_CRIT "NILFS: superblock broke on dev %s\n",
 			       sbi->s_super->s_id);
-			return -EIO;
+			return NULL;
 		}
+	} else if (sbp[1] &&
+		   sbp[1]->s_magic != cpu_to_le16(NILFS_SUPER_MAGIC)) {
+			memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
 	}
-	err = nilfs_count_free_blocks(nilfs, &nfreeblocks);
-	if (unlikely(err)) {
-		printk(KERN_ERR "NILFS: failed to count free blocks\n");
-		return err;
-	}
-	spin_lock(&nilfs->ns_last_segment_lock);
-	sbp[0]->s_last_seq = cpu_to_le64(nilfs->ns_last_seq);
-	sbp[0]->s_last_pseg = cpu_to_le64(nilfs->ns_last_pseg);
-	sbp[0]->s_last_cno = cpu_to_le64(nilfs->ns_last_cno);
-	spin_unlock(&nilfs->ns_last_segment_lock);
 
+	if (flip && sbp[1])
+		nilfs_swap_super_block(nilfs);
+
+	return sbp;
+}
+
+int nilfs_commit_super(struct nilfs_sb_info *sbi, int flag)
+{
+	struct the_nilfs *nilfs = sbi->s_nilfs;
+	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	time_t t;
+
+	/* nilfs->ns_sem must be locked by the caller. */
 	t = get_seconds();
-	nilfs->ns_sbwtime[0] = t;
-	sbp[0]->s_free_blocks_count = cpu_to_le64(nfreeblocks);
+	nilfs->ns_sbwtime = t;
 	sbp[0]->s_wtime = cpu_to_le64(t);
 	sbp[0]->s_sum = 0;
 	sbp[0]->s_sum = cpu_to_le32(crc32_le(nilfs->ns_crc_seed,
 					     (unsigned char *)sbp[0],
 					     nilfs->ns_sbsize));
-	if (dupsb && sbp[1]) {
-		memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
-		nilfs->ns_sbwtime[1] = t;
+	if (flag == NILFS_SB_COMMIT_ALL && sbp[1]) {
+		sbp[1]->s_wtime = sbp[0]->s_wtime;
+		sbp[1]->s_sum = 0;
+		sbp[1]->s_sum = cpu_to_le32(crc32_le(nilfs->ns_crc_seed,
+					    (unsigned char *)sbp[1],
+					    nilfs->ns_sbsize));
 	}
 	clear_nilfs_sb_dirty(nilfs);
-	return nilfs_sync_super(sbi, dupsb);
+	return nilfs_sync_super(sbi, flag);
+}
+
+/**
+ * nilfs_cleanup_super() - write filesystem state for cleanup
+ * @sbi: nilfs_sb_info to be unmounted or degraded to read-only
+ *
+ * This function restores state flags in the on-disk super block.
+ * This will set "clean" flag (i.e. NILFS_VALID_FS) unless the
+ * filesystem was not clean previously.
+ */
+int nilfs_cleanup_super(struct nilfs_sb_info *sbi)
+{
+	struct nilfs_super_block **sbp;
+	int flag = NILFS_SB_COMMIT;
+	int ret = -EIO;
+
+	sbp = nilfs_prepare_super(sbi, 0);
+	if (sbp) {
+		sbp[0]->s_state = cpu_to_le16(sbi->s_nilfs->ns_mount_state);
+		nilfs_set_log_cursor(sbp[0], sbi->s_nilfs);
+		if (sbp[1] && sbp[0]->s_last_cno == sbp[1]->s_last_cno) {
+			/*
+			 * make the "clean" flag also to the opposite
+			 * super block if both super blocks point to
+			 * the same checkpoint.
+			 */
+			sbp[1]->s_state = sbp[0]->s_state;
+			flag = NILFS_SB_COMMIT_ALL;
+		}
+		ret = nilfs_commit_super(sbi, flag);
+	}
+	return ret;
 }
 
 static void nilfs_put_super(struct super_block *sb)
@@ -283,34 +336,29 @@ static void nilfs_put_super(struct super_block *sb)
 	struct nilfs_sb_info *sbi = NILFS_SB(sb);
 	struct the_nilfs *nilfs = sbi->s_nilfs;
 
-	lock_kernel();
-
 	nilfs_detach_segment_constructor(sbi);
 
 	if (!(sb->s_flags & MS_RDONLY)) {
 		down_write(&nilfs->ns_sem);
-		nilfs->ns_sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
-		nilfs_commit_super(sbi, 1);
+		nilfs_cleanup_super(sbi);
 		up_write(&nilfs->ns_sem);
 	}
-	down_write(&nilfs->ns_super_sem);
-	if (nilfs->ns_current == sbi)
-		nilfs->ns_current = NULL;
-	up_write(&nilfs->ns_super_sem);
 
-	nilfs_detach_checkpoint(sbi);
-	put_nilfs(sbi->s_nilfs);
+	iput(nilfs->ns_sufile);
+	iput(nilfs->ns_cpfile);
+	iput(nilfs->ns_dat);
+
+	destroy_nilfs(nilfs);
 	sbi->s_super = NULL;
 	sb->s_fs_info = NULL;
-	nilfs_put_sbinfo(sbi);
-
-	unlock_kernel();
+	kfree(sbi);
 }
 
 static int nilfs_sync_fs(struct super_block *sb, int wait)
 {
 	struct nilfs_sb_info *sbi = NILFS_SB(sb);
 	struct the_nilfs *nilfs = sbi->s_nilfs;
+	struct nilfs_super_block **sbp;
 	int err = 0;
 
 	/* This function is called when super block should be written back */
@@ -318,27 +366,34 @@ static int nilfs_sync_fs(struct super_block *sb, int wait)
 		err = nilfs_construct_segment(sb);
 
 	down_write(&nilfs->ns_sem);
-	if (nilfs_sb_dirty(nilfs))
-		nilfs_commit_super(sbi, 1);
+	if (nilfs_sb_dirty(nilfs)) {
+		sbp = nilfs_prepare_super(sbi, nilfs_sb_will_flip(nilfs));
+		if (likely(sbp)) {
+			nilfs_set_log_cursor(sbp[0], nilfs);
+			nilfs_commit_super(sbi, NILFS_SB_COMMIT);
+		}
+	}
 	up_write(&nilfs->ns_sem);
 
 	return err;
 }
 
-int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno)
+int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno, int curr_mnt,
+			    struct nilfs_root **rootp)
 {
 	struct the_nilfs *nilfs = sbi->s_nilfs;
+	struct nilfs_root *root;
 	struct nilfs_checkpoint *raw_cp;
 	struct buffer_head *bh_cp;
-	int err;
+	int err = -ENOMEM;
 
-	down_write(&nilfs->ns_super_sem);
-	list_add(&sbi->s_list, &nilfs->ns_supers);
-	up_write(&nilfs->ns_super_sem);
+	root = nilfs_find_or_create_root(
+		nilfs, curr_mnt ? NILFS_CPTREE_CURRENT_CNO : cno);
+	if (!root)
+		return err;
 
-	sbi->s_ifile = nilfs_ifile_new(sbi, nilfs->ns_inode_size);
-	if (!sbi->s_ifile)
-		return -ENOMEM;
+	if (root->ifile)
+		goto reuse; /* already attached checkpoint */
 
 	down_read(&nilfs->ns_segctor_sem);
 	err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, cno, 0, &raw_cp,
@@ -354,44 +409,64 @@ int nilfs_attach_checkpoint(struct nilfs_sb_info *sbi, __u64 cno)
 		}
 		goto failed;
 	}
-	err = nilfs_read_inode_common(sbi->s_ifile, &raw_cp->cp_ifile_inode);
-	if (unlikely(err))
+
+	err = nilfs_ifile_read(sbi->s_super, root, nilfs->ns_inode_size,
+			       &raw_cp->cp_ifile_inode, &root->ifile);
+	if (err)
 		goto failed_bh;
-	atomic_set(&sbi->s_inodes_count, le64_to_cpu(raw_cp->cp_inodes_count));
-	atomic_set(&sbi->s_blocks_count, le64_to_cpu(raw_cp->cp_blocks_count));
+
+	atomic_set(&root->inodes_count, le64_to_cpu(raw_cp->cp_inodes_count));
+	atomic_set(&root->blocks_count, le64_to_cpu(raw_cp->cp_blocks_count));
 
 	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
+
+ reuse:
+	*rootp = root;
 	return 0;
 
  failed_bh:
 	nilfs_cpfile_put_checkpoint(nilfs->ns_cpfile, cno, bh_cp);
  failed:
-	nilfs_mdt_destroy(sbi->s_ifile);
-	sbi->s_ifile = NULL;
+	nilfs_put_root(root);
 
-	down_write(&nilfs->ns_super_sem);
-	list_del_init(&sbi->s_list);
-	up_write(&nilfs->ns_super_sem);
+	return err;
+}
 
+static int nilfs_freeze(struct super_block *sb)
+{
+	struct nilfs_sb_info *sbi = NILFS_SB(sb);
+	struct the_nilfs *nilfs = sbi->s_nilfs;
+	int err;
+
+	if (sb->s_flags & MS_RDONLY)
+		return 0;
+
+	/* Mark super block clean */
+	down_write(&nilfs->ns_sem);
+	err = nilfs_cleanup_super(sbi);
+	up_write(&nilfs->ns_sem);
 	return err;
 }
 
-void nilfs_detach_checkpoint(struct nilfs_sb_info *sbi)
+static int nilfs_unfreeze(struct super_block *sb)
 {
+	struct nilfs_sb_info *sbi = NILFS_SB(sb);
 	struct the_nilfs *nilfs = sbi->s_nilfs;
 
-	nilfs_mdt_destroy(sbi->s_ifile);
-	sbi->s_ifile = NULL;
-	down_write(&nilfs->ns_super_sem);
-	list_del_init(&sbi->s_list);
-	up_write(&nilfs->ns_super_sem);
+	if (sb->s_flags & MS_RDONLY)
+		return 0;
+
+	down_write(&nilfs->ns_sem);
+	nilfs_setup_super(sbi, false);
+	up_write(&nilfs->ns_sem);
+	return 0;
 }
 
 static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 {
 	struct super_block *sb = dentry->d_sb;
-	struct nilfs_sb_info *sbi = NILFS_SB(sb);
-	struct the_nilfs *nilfs = sbi->s_nilfs;
+	struct nilfs_root *root = NILFS_I(dentry->d_inode)->i_root;
+	struct the_nilfs *nilfs = root->nilfs;
 	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 	unsigned long long blocks;
 	unsigned long overhead;
@@ -427,7 +502,7 @@ static int nilfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_bfree = nfreeblocks;
 	buf->f_bavail = (buf->f_bfree >= nrsvblocks) ?
 		(buf->f_bfree - nrsvblocks) : 0;
-	buf->f_files = atomic_read(&sbi->s_inodes_count);
+	buf->f_files = atomic_read(&root->inodes_count);
 	buf->f_ffree = 0; /* nilfs_count_free_inodes(sb); */
 	buf->f_namelen = NILFS_NAME_LEN;
 	buf->f_fsid.val[0] = (u32)id;
@@ -440,22 +515,22 @@ static int nilfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
 {
 	struct super_block *sb = vfs->mnt_sb;
 	struct nilfs_sb_info *sbi = NILFS_SB(sb);
+	struct nilfs_root *root = NILFS_I(vfs->mnt_root->d_inode)->i_root;
 
 	if (!nilfs_test_opt(sbi, BARRIER))
-		seq_printf(seq, ",nobarrier");
-	if (nilfs_test_opt(sbi, SNAPSHOT))
-		seq_printf(seq, ",cp=%llu",
-			   (unsigned long long int)sbi->s_snapshot_cno);
+		seq_puts(seq, ",nobarrier");
+	if (root->cno != NILFS_CPTREE_CURRENT_CNO)
+		seq_printf(seq, ",cp=%llu", (unsigned long long)root->cno);
 	if (nilfs_test_opt(sbi, ERRORS_PANIC))
-		seq_printf(seq, ",errors=panic");
+		seq_puts(seq, ",errors=panic");
 	if (nilfs_test_opt(sbi, ERRORS_CONT))
-		seq_printf(seq, ",errors=continue");
+		seq_puts(seq, ",errors=continue");
 	if (nilfs_test_opt(sbi, STRICT_ORDER))
-		seq_printf(seq, ",order=strict");
+		seq_puts(seq, ",order=strict");
 	if (nilfs_test_opt(sbi, NORECOVERY))
-		seq_printf(seq, ",norecovery");
+		seq_puts(seq, ",norecovery");
 	if (nilfs_test_opt(sbi, DISCARD))
-		seq_printf(seq, ",discard");
+		seq_puts(seq, ",discard");
 
 	return 0;
 }
@@ -467,85 +542,45 @@ static const struct super_operations nilfs_sops = {
 	/* .write_inode    = nilfs_write_inode, */
 	/* .put_inode      = nilfs_put_inode, */
 	/* .drop_inode	  = nilfs_drop_inode, */
-	.delete_inode   = nilfs_delete_inode,
+	.evict_inode    = nilfs_evict_inode,
 	.put_super      = nilfs_put_super,
 	/* .write_super    = nilfs_write_super, */
 	.sync_fs        = nilfs_sync_fs,
+	.freeze_fs	= nilfs_freeze,
+	.unfreeze_fs	= nilfs_unfreeze,
 	/* .write_super_lockfs */
 	/* .unlockfs */
 	.statfs         = nilfs_statfs,
 	.remount_fs     = nilfs_remount,
-	.clear_inode    = nilfs_clear_inode,
 	/* .umount_begin */
 	.show_options = nilfs_show_options
 };
 
-static struct inode *
-nilfs_nfs_get_inode(struct super_block *sb, u64 ino, u32 generation)
-{
-	struct inode *inode;
-
-	if (ino < NILFS_FIRST_INO(sb) && ino != NILFS_ROOT_INO &&
-	    ino != NILFS_SKETCH_INO)
-		return ERR_PTR(-ESTALE);
-
-	inode = nilfs_iget(sb, ino);
-	if (IS_ERR(inode))
-		return ERR_CAST(inode);
-	if (generation && inode->i_generation != generation) {
-		iput(inode);
-		return ERR_PTR(-ESTALE);
-	}
-
-	return inode;
-}
-
-static struct dentry *
-nilfs_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len,
-		   int fh_type)
-{
-	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
-				    nilfs_nfs_get_inode);
-}
-
-static struct dentry *
-nilfs_fh_to_parent(struct super_block *sb, struct fid *fid, int fh_len,
-		   int fh_type)
-{
-	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
-				    nilfs_nfs_get_inode);
-}
-
-static const struct export_operations nilfs_export_ops = {
-	.fh_to_dentry = nilfs_fh_to_dentry,
-	.fh_to_parent = nilfs_fh_to_parent,
-	.get_parent = nilfs_get_parent,
-};
-
 enum {
 	Opt_err_cont, Opt_err_panic, Opt_err_ro,
-	Opt_nobarrier, Opt_snapshot, Opt_order, Opt_norecovery,
-	Opt_discard, Opt_err,
+	Opt_barrier, Opt_nobarrier, Opt_snapshot, Opt_order, Opt_norecovery,
+	Opt_discard, Opt_nodiscard, Opt_err,
 };
 
 static match_table_t tokens = {
 	{Opt_err_cont, "errors=continue"},
 	{Opt_err_panic, "errors=panic"},
 	{Opt_err_ro, "errors=remount-ro"},
+	{Opt_barrier, "barrier"},
 	{Opt_nobarrier, "nobarrier"},
 	{Opt_snapshot, "cp=%u"},
 	{Opt_order, "order=%s"},
 	{Opt_norecovery, "norecovery"},
 	{Opt_discard, "discard"},
+	{Opt_nodiscard, "nodiscard"},
 	{Opt_err, NULL}
 };
 
-static int parse_options(char *options, struct super_block *sb)
+static int parse_options(char *options, struct super_block *sb, int is_remount)
 {
 	struct nilfs_sb_info *sbi = NILFS_SB(sb);
 	char *p;
 	substring_t args[MAX_OPT_ARGS];
-	int option;
 
 	if (!options)
 		return 1;
@@ -557,6 +592,9 @@ static int parse_options(char *options, struct super_block *sb)
 
 		token = match_token(p, tokens, args);
 		switch (token) {
+		case Opt_barrier:
+			nilfs_set_opt(sbi, BARRIER);
+			break;
 		case Opt_nobarrier:
 			nilfs_clear_opt(sbi, BARRIER);
 			break;
@@ -580,12 +618,12 @@ static int parse_options(char *options, struct super_block *sb)
 			nilfs_write_opt(sbi, ERROR_MODE, ERRORS_CONT);
 			break;
 		case Opt_snapshot:
-			if (match_int(&args[0], &option) || option <= 0)
-				return 0;
-			if (!(sb->s_flags & MS_RDONLY))
+			if (is_remount) {
+				printk(KERN_ERR
+				       "NILFS: \"%s\" option is invalid "
+				       "for remount.\n", p);
 				return 0;
-			sbi->s_snapshot_cno = option;
-			nilfs_set_opt(sbi, SNAPSHOT);
+			}
 			break;
 		case Opt_norecovery:
 			nilfs_set_opt(sbi, NORECOVERY);
@@ -593,6 +631,9 @@ static int parse_options(char *options, struct super_block *sb)
 		case Opt_discard:
 			nilfs_set_opt(sbi, DISCARD);
 			break;
+		case Opt_nodiscard:
+			nilfs_clear_opt(sbi, DISCARD);
+			break;
 		default:
 			printk(KERN_ERR
 			       "NILFS: Unrecognized mount option \"%s\"\n", p);
@@ -610,14 +651,24 @@ nilfs_set_default_options(struct nilfs_sb_info *sbi,
 		NILFS_MOUNT_ERRORS_RO | NILFS_MOUNT_BARRIER;
 }
 
-static int nilfs_setup_super(struct nilfs_sb_info *sbi)
+static int nilfs_setup_super(struct nilfs_sb_info *sbi, int is_mount)
 {
 	struct the_nilfs *nilfs = sbi->s_nilfs;
-	struct nilfs_super_block *sbp = nilfs->ns_sbp[0];
-	int max_mnt_count = le16_to_cpu(sbp->s_max_mnt_count);
-	int mnt_count = le16_to_cpu(sbp->s_mnt_count);
+	struct nilfs_super_block **sbp;
+	int max_mnt_count;
+	int mnt_count;
+
+	/* nilfs->ns_sem must be locked by the caller. */
+	sbp = nilfs_prepare_super(sbi, 0);
+	if (!sbp)
+		return -EIO;
+
+	if (!is_mount)
+		goto skip_mount_setup;
+
+	max_mnt_count = le16_to_cpu(sbp[0]->s_max_mnt_count);
+	mnt_count = le16_to_cpu(sbp[0]->s_mnt_count);
 
-	/* nilfs->sem must be locked by the caller. */
 	if (nilfs->ns_mount_state & NILFS_ERROR_FS) {
 		printk(KERN_WARNING
 		       "NILFS warning: mounting fs with errors\n");
@@ -628,12 +679,17 @@ static int nilfs_setup_super(struct nilfs_sb_info *sbi)
 #endif
 	}
 	if (!max_mnt_count)
-		sbp->s_max_mnt_count = cpu_to_le16(NILFS_DFL_MAX_MNT_COUNT);
+		sbp[0]->s_max_mnt_count = cpu_to_le16(NILFS_DFL_MAX_MNT_COUNT);
+
+	sbp[0]->s_mnt_count = cpu_to_le16(mnt_count + 1);
+	sbp[0]->s_mtime = cpu_to_le64(get_seconds());
 
-	sbp->s_mnt_count = cpu_to_le16(mnt_count + 1);
-	sbp->s_state = cpu_to_le16(le16_to_cpu(sbp->s_state) & ~NILFS_VALID_FS);
-	sbp->s_mtime = cpu_to_le64(get_seconds());
-	return nilfs_commit_super(sbi, 1);
+skip_mount_setup:
+	sbp[0]->s_state =
+		cpu_to_le16(le16_to_cpu(sbp[0]->s_state) & ~NILFS_VALID_FS);
+	/* synchronize sbp[1] with sbp[0] */
+	memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
+	return nilfs_commit_super(sbi, NILFS_SB_COMMIT_ALL);
 }
 
 struct nilfs_super_block *nilfs_read_super_block(struct super_block *sb,
@@ -670,7 +726,165 @@ int nilfs_store_magic_and_option(struct super_block *sb,
 	sbi->s_interval = le32_to_cpu(sbp->s_c_interval);
 	sbi->s_watermark = le32_to_cpu(sbp->s_c_block_max);
 
-	return !parse_options(data, sb) ? -EINVAL : 0 ;
+	return !parse_options(data, sb, 0) ? -EINVAL : 0 ;
+}
+
+int nilfs_check_feature_compatibility(struct super_block *sb,
+				      struct nilfs_super_block *sbp)
+{
+	__u64 features;
+
+	features = le64_to_cpu(sbp->s_feature_incompat) &
+		~NILFS_FEATURE_INCOMPAT_SUPP;
+	if (features) {
+		printk(KERN_ERR "NILFS: couldn't mount because of unsupported "
+		       "optional features (%llx)\n",
+		       (unsigned long long)features);
+		return -EINVAL;
+	}
+	features = le64_to_cpu(sbp->s_feature_compat_ro) &
+		~NILFS_FEATURE_COMPAT_RO_SUPP;
+	if (!(sb->s_flags & MS_RDONLY) && features) {
+		printk(KERN_ERR "NILFS: couldn't mount RDWR because of "
+		       "unsupported optional features (%llx)\n",
+		       (unsigned long long)features);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int nilfs_get_root_dentry(struct super_block *sb,
+				 struct nilfs_root *root,
+				 struct dentry **root_dentry)
+{
+	struct inode *inode;
+	struct dentry *dentry;
+	int ret = 0;
+
+	inode = nilfs_iget(sb, root, NILFS_ROOT_INO);
+	if (IS_ERR(inode)) {
+		printk(KERN_ERR "NILFS: get root inode failed\n");
+		ret = PTR_ERR(inode);
+		goto out;
+	}
+	if (!S_ISDIR(inode->i_mode) || !inode->i_blocks || !inode->i_size) {
+		iput(inode);
+		printk(KERN_ERR "NILFS: corrupt root inode.\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	if (root->cno == NILFS_CPTREE_CURRENT_CNO) {
+		dentry = d_find_alias(inode);
+		if (!dentry) {
+			dentry = d_alloc_root(inode);
+			if (!dentry) {
+				iput(inode);
+				ret = -ENOMEM;
+				goto failed_dentry;
+			}
+		} else {
+			iput(inode);
+		}
+	} else {
+		dentry = d_obtain_alias(inode);
+		if (IS_ERR(dentry)) {
+			ret = PTR_ERR(dentry);
+			goto failed_dentry;
+		}
+	}
+	*root_dentry = dentry;
+ out:
+	return ret;
+
+ failed_dentry:
+	printk(KERN_ERR "NILFS: get root dentry failed\n");
+	goto out;
+}
+
+static int nilfs_attach_snapshot(struct super_block *s, __u64 cno,
+				 struct dentry **root_dentry)
+{
+	struct the_nilfs *nilfs = NILFS_SB(s)->s_nilfs;
+	struct nilfs_root *root;
+	int ret;
+
+	down_read(&nilfs->ns_segctor_sem);
+	ret = nilfs_cpfile_is_snapshot(nilfs->ns_cpfile, cno);
+	up_read(&nilfs->ns_segctor_sem);
+	if (ret < 0) {
+		ret = (ret == -ENOENT) ? -EINVAL : ret;
+		goto out;
+	} else if (!ret) {
+		printk(KERN_ERR "NILFS: The specified checkpoint is "
+		       "not a snapshot (checkpoint number=%llu).\n",
+		       (unsigned long long)cno);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = nilfs_attach_checkpoint(NILFS_SB(s), cno, false, &root);
+	if (ret) {
+		printk(KERN_ERR "NILFS: error loading snapshot "
+		       "(checkpoint number=%llu).\n",
+	       (unsigned long long)cno);
+		goto out;
+	}
+	ret = nilfs_get_root_dentry(s, root, root_dentry);
+	nilfs_put_root(root);
+ out:
+	return ret;
+}
+
+static int nilfs_tree_was_touched(struct dentry *root_dentry)
+{
+	return atomic_read(&root_dentry->d_count) > 1;
+}
+
+/**
+ * nilfs_try_to_shrink_tree() - try to shrink dentries of a checkpoint
+ * @root_dentry: root dentry of the tree to be shrunk
+ *
+ * This function returns true if the tree was in-use.
+ */
+static int nilfs_try_to_shrink_tree(struct dentry *root_dentry)
+{
+	if (have_submounts(root_dentry))
+		return true;
+	shrink_dcache_parent(root_dentry);
+	return nilfs_tree_was_touched(root_dentry);
+}
+
+int nilfs_checkpoint_is_mounted(struct super_block *sb, __u64 cno)
+{
+	struct the_nilfs *nilfs = NILFS_SB(sb)->s_nilfs;
+	struct nilfs_root *root;
+	struct inode *inode;
+	struct dentry *dentry;
+	int ret;
+
+	if (cno < 0 || cno > nilfs->ns_cno)
+		return false;
+
+	if (cno >= nilfs_last_cno(nilfs))
+		return true;	/* protect recent checkpoints */
+
+	ret = false;
+	root = nilfs_lookup_root(NILFS_SB(sb)->s_nilfs, cno);
+	if (root) {
+		inode = nilfs_ilookup(sb, root, NILFS_ROOT_INO);
+		if (inode) {
+			dentry = d_find_alias(inode);
+			if (dentry) {
+				if (nilfs_tree_was_touched(dentry))
+					ret = nilfs_try_to_shrink_tree(dentry);
+				dput(dentry);
+			}
+			iput(inode);
+		}
+		nilfs_put_root(root);
+	}
+	return ret;
 }
 
 /**
@@ -678,17 +892,17 @@ int nilfs_store_magic_and_option(struct super_block *sb,
  * @sb: super_block
  * @data: mount options
  * @silent: silent mode flag
- * @nilfs: the_nilfs struct
  *
  * This function is called exclusively by nilfs->ns_mount_mutex.
  * So, the recovery process is protected from other simultaneous mounts.
  */
 static int
-nilfs_fill_super(struct super_block *sb, void *data, int silent,
-		 struct the_nilfs *nilfs)
+nilfs_fill_super(struct super_block *sb, void *data, int silent)
 {
+	struct the_nilfs *nilfs;
 	struct nilfs_sb_info *sbi;
-	struct inode *root;
+	struct nilfs_root *fsroot;
+	struct backing_dev_info *bdi;
 	__u64 cno;
 	int err;
 
@@ -697,19 +911,21 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
 		return -ENOMEM;
 
 	sb->s_fs_info = sbi;
+	sbi->s_super = sb;
 
-	get_nilfs(nilfs);
+	nilfs = alloc_nilfs(sb->s_bdev);
+	if (!nilfs) {
+		err = -ENOMEM;
+		goto failed_sbi;
+	}
 	sbi->s_nilfs = nilfs;
-	sbi->s_super = sb;
-	atomic_set(&sbi->s_count, 1);
 
 	err = init_nilfs(nilfs, sbi, (char *)data);
 	if (err)
-		goto failed_sbi;
+		goto failed_nilfs;
 
 	spin_lock_init(&sbi->s_inode_lock);
 	INIT_LIST_HEAD(&sbi->s_dirty_files);
-	INIT_LIST_HEAD(&sbi->s_list);
 
 	/*
 	 * Following initialization is overlapped because
@@ -725,141 +941,80 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent,
 	sb->s_export_op = &nilfs_export_ops;
 	sb->s_root = NULL;
 	sb->s_time_gran = 1;
-	sb->s_bdi = nilfs->ns_bdi;
+
+	bdi = sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
+	sb->s_bdi = bdi ? : &default_backing_dev_info;
 
 	err = load_nilfs(nilfs, sbi);
 	if (err)
-		goto failed_sbi;
+		goto failed_nilfs;
 
 	cno = nilfs_last_cno(nilfs);
-
-	if (sb->s_flags & MS_RDONLY) {
-		if (nilfs_test_opt(sbi, SNAPSHOT)) {
-			down_read(&nilfs->ns_segctor_sem);
-			err = nilfs_cpfile_is_snapshot(nilfs->ns_cpfile,
-						       sbi->s_snapshot_cno);
-			up_read(&nilfs->ns_segctor_sem);
-			if (err < 0) {
-				if (err == -ENOENT)
-					err = -EINVAL;
-				goto failed_sbi;
-			}
-			if (!err) {
-				printk(KERN_ERR
-				       "NILFS: The specified checkpoint is "
-				       "not a snapshot "
-				       "(checkpoint number=%llu).\n",
-				       (unsigned long long)sbi->s_snapshot_cno);
-				err = -EINVAL;
-				goto failed_sbi;
-			}
-			cno = sbi->s_snapshot_cno;
-		}
-	}
-
-	err = nilfs_attach_checkpoint(sbi, cno);
+	err = nilfs_attach_checkpoint(sbi, cno, true, &fsroot);
 	if (err) {
-		printk(KERN_ERR "NILFS: error loading a checkpoint"
-		       " (checkpoint number=%llu).\n", (unsigned long long)cno);
-		goto failed_sbi;
+		printk(KERN_ERR "NILFS: error loading last checkpoint "
+		       "(checkpoint number=%llu).\n", (unsigned long long)cno);
+		goto failed_unload;
 	}
 
 	if (!(sb->s_flags & MS_RDONLY)) {
-		err = nilfs_attach_segment_constructor(sbi);
+		err = nilfs_attach_segment_constructor(sbi, fsroot);
 		if (err)
 			goto failed_checkpoint;
 	}
 
-	root = nilfs_iget(sb, NILFS_ROOT_INO);
-	if (IS_ERR(root)) {
-		printk(KERN_ERR "NILFS: get root inode failed\n");
-		err = PTR_ERR(root);
-		goto failed_segctor;
-	}
-	if (!S_ISDIR(root->i_mode) || !root->i_blocks || !root->i_size) {
-		iput(root);
-		printk(KERN_ERR "NILFS: corrupt root inode.\n");
-		err = -EINVAL;
-		goto failed_segctor;
-	}
-	sb->s_root = d_alloc_root(root);
-	if (!sb->s_root) {
-		iput(root);
-		printk(KERN_ERR "NILFS: get root dentry failed\n");
-		err = -ENOMEM;
+	err = nilfs_get_root_dentry(sb, fsroot, &sb->s_root);
+	if (err)
 		goto failed_segctor;
-	}
+
+	nilfs_put_root(fsroot);
 
 	if (!(sb->s_flags & MS_RDONLY)) {
 		down_write(&nilfs->ns_sem);
-		nilfs_setup_super(sbi);
+		nilfs_setup_super(sbi, true);
 		up_write(&nilfs->ns_sem);
 	}
 
-	down_write(&nilfs->ns_super_sem);
-	if (!nilfs_test_opt(sbi, SNAPSHOT))
-		nilfs->ns_current = sbi;
-	up_write(&nilfs->ns_super_sem);
-
 	return 0;
 
  failed_segctor:
 	nilfs_detach_segment_constructor(sbi);
 
  failed_checkpoint:
-	nilfs_detach_checkpoint(sbi);
+	nilfs_put_root(fsroot);
+
+ failed_unload:
+	iput(nilfs->ns_sufile);
+	iput(nilfs->ns_cpfile);
+	iput(nilfs->ns_dat);
+
+ failed_nilfs:
+	destroy_nilfs(nilfs);
 
  failed_sbi:
-	put_nilfs(nilfs);
 	sb->s_fs_info = NULL;
-	nilfs_put_sbinfo(sbi);
+	kfree(sbi);
 	return err;
 }
 
 static int nilfs_remount(struct super_block *sb, int *flags, char *data)
 {
 	struct nilfs_sb_info *sbi = NILFS_SB(sb);
-	struct nilfs_super_block *sbp;
 	struct the_nilfs *nilfs = sbi->s_nilfs;
 	unsigned long old_sb_flags;
 	struct nilfs_mount_options old_opts;
-	int was_snapshot, err;
-
-	lock_kernel();
+	int err;
 
-	down_write(&nilfs->ns_super_sem);
 	old_sb_flags = sb->s_flags;
 	old_opts.mount_opt = sbi->s_mount_opt;
-	old_opts.snapshot_cno = sbi->s_snapshot_cno;
-	was_snapshot = nilfs_test_opt(sbi, SNAPSHOT);
 
-	if (!parse_options(data, sb)) {
+	if (!parse_options(data, sb, 1)) {
 		err = -EINVAL;
 		goto restore_opts;
 	}
 	sb->s_flags = (sb->s_flags & ~MS_POSIXACL);
 
 	err = -EINVAL;
-	if (was_snapshot) {
-		if (!(*flags & MS_RDONLY)) {
-			printk(KERN_ERR "NILFS (device %s): cannot remount "
-			       "snapshot read/write.\n",
-			       sb->s_id);
-			goto restore_opts;
-		} else if (sbi->s_snapshot_cno != old_opts.snapshot_cno) {
-			printk(KERN_ERR "NILFS (device %s): cannot "
-			       "remount to a different snapshot.\n",
-			       sb->s_id);
-			goto restore_opts;
-		}
-	} else {
-		if (nilfs_test_opt(sbi, SNAPSHOT)) {
-			printk(KERN_ERR "NILFS (device %s): cannot change "
-			       "a regular mount to a snapshot.\n",
-			       sb->s_id);
-			goto restore_opts;
-		}
-	}
 
 	if (!nilfs_valid_fs(nilfs)) {
 		printk(KERN_WARNING "NILFS (device %s): couldn't "
@@ -880,40 +1035,47 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data)
 		 * the RDONLY flag and then mark the partition as valid again.
 		 */
 		down_write(&nilfs->ns_sem);
-		sbp = nilfs->ns_sbp[0];
-		if (!(sbp->s_state & le16_to_cpu(NILFS_VALID_FS)) &&
-		    (nilfs->ns_mount_state & NILFS_VALID_FS))
-			sbp->s_state = cpu_to_le16(nilfs->ns_mount_state);
-		sbp->s_mtime = cpu_to_le64(get_seconds());
-		nilfs_commit_super(sbi, 1);
+		nilfs_cleanup_super(sbi);
 		up_write(&nilfs->ns_sem);
 	} else {
+		__u64 features;
+		struct nilfs_root *root;
+
 		/*
 		 * Mounting a RDONLY partition read-write, so reread and
 		 * store the current valid flag.  (It may have been changed
 		 * by fsck since we originally mounted the partition.)
 		 */
+		down_read(&nilfs->ns_sem);
+		features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
+			~NILFS_FEATURE_COMPAT_RO_SUPP;
+		up_read(&nilfs->ns_sem);
+		if (features) {
+			printk(KERN_WARNING "NILFS (device %s): couldn't "
+			       "remount RDWR because of unsupported optional "
+			       "features (%llx)\n",
+			       sb->s_id, (unsigned long long)features);
+			err = -EROFS;
+			goto restore_opts;
+		}
+
 		sb->s_flags &= ~MS_RDONLY;
 
-		err = nilfs_attach_segment_constructor(sbi);
+		root = NILFS_I(sb->s_root->d_inode)->i_root;
+		err = nilfs_attach_segment_constructor(sbi, root);
 		if (err)
 			goto restore_opts;
 
 		down_write(&nilfs->ns_sem);
-		nilfs_setup_super(sbi);
+		nilfs_setup_super(sbi, true);
 		up_write(&nilfs->ns_sem);
 	}
  out:
-	up_write(&nilfs->ns_super_sem);
-	unlock_kernel();
 	return 0;
 
  restore_opts:
 	sb->s_flags = old_sb_flags;
 	sbi->s_mount_opt = old_opts.mount_opt;
-	sbi->s_snapshot_cno = old_opts.snapshot_cno;
-	up_write(&nilfs->ns_super_sem);
-	unlock_kernel();
 	return err;
 }
 
@@ -933,7 +1095,7 @@ static int nilfs_identify(char *data, struct nilfs_super_data *sd)
 {
 	char *p, *options = data;
 	substring_t args[MAX_OPT_ARGS];
-	int option, token;
+	int token;
 	int ret = 0;
 
 	do {
@@ -941,16 +1103,18 @@ static int nilfs_identify(char *data, struct nilfs_super_data *sd)
 		if (p != NULL && *p) {
 			token = match_token(p, tokens, args);
 			if (token == Opt_snapshot) {
-				if (!(sd->flags & MS_RDONLY))
+				if (!(sd->flags & MS_RDONLY)) {
 					ret++;
-				else {
-					ret = match_int(&args[0], &option);
-					if (!ret) {
-						if (option > 0)
-							sd->cno = option;
-						else
-							ret++;
-					}
+				} else {
+					sd->cno = simple_strtoull(args[0].from,
+								  NULL, 0);
+					/*
+					 * No need to see the end pointer;
+					 * match_token() has done syntax
+					 * checking.
+					 */
+					if (sd->cno == 0)
+						ret++;
 				}
 			}
 			if (ret)
@@ -967,43 +1131,33 @@ static int nilfs_identify(char *data, struct nilfs_super_data *sd)
 
 static int nilfs_set_bdev_super(struct super_block *s, void *data)
 {
-	struct nilfs_super_data *sd = data;
-
-	s->s_bdev = sd->bdev;
+	s->s_bdev = data;
 	s->s_dev = s->s_bdev->bd_dev;
 	return 0;
 }
 
 static int nilfs_test_bdev_super(struct super_block *s, void *data)
 {
-	struct nilfs_super_data *sd = data;
-
-	return sd->sbi && s->s_fs_info == (void *)sd->sbi;
+	return (void *)s->s_bdev == data;
 }
 
-static int
-nilfs_get_sb(struct file_system_type *fs_type, int flags,
-	     const char *dev_name, void *data, struct vfsmount *mnt)
+static struct dentry *
+nilfs_mount(struct file_system_type *fs_type, int flags,
+	     const char *dev_name, void *data)
 {
 	struct nilfs_super_data sd;
 	struct super_block *s;
 	fmode_t mode = FMODE_READ;
-	struct the_nilfs *nilfs;
-	int err, need_to_close = 1;
+	struct dentry *root_dentry;
+	int err, s_new = false;
 
 	if (!(flags & MS_RDONLY))
 		mode |= FMODE_WRITE;
 
 	sd.bdev = open_bdev_exclusive(dev_name, mode, fs_type);
 	if (IS_ERR(sd.bdev))
-		return PTR_ERR(sd.bdev);
+		return ERR_CAST(sd.bdev);
 
-	/*
-	 * To get mount instance using sget() vfs-routine, NILFS needs
-	 * much more information than normal filesystems to identify mount
-	 * instance.  For snapshot mounts, not only a mount type (ro-mount
-	 * or rw-mount) but also a checkpoint number is required.
-	 */
 	sd.cno = 0;
 	sd.flags = flags;
 	if (nilfs_identify((char *)data, &sd)) {
@@ -1011,101 +1165,91 @@ nilfs_get_sb(struct file_system_type *fs_type, int flags,
 		goto failed;
 	}
 
-	nilfs = find_or_create_nilfs(sd.bdev);
-	if (!nilfs) {
-		err = -ENOMEM;
-		goto failed;
-	}
-
-	mutex_lock(&nilfs->ns_mount_mutex);
-
-	if (!sd.cno) {
-		/*
-		 * Check if an exclusive mount exists or not.
-		 * Snapshot mounts coexist with a current mount
-		 * (i.e. rw-mount or ro-mount), whereas rw-mount and
-		 * ro-mount are mutually exclusive.
-		 */
-		down_read(&nilfs->ns_super_sem);
-		if (nilfs->ns_current &&
-		    ((nilfs->ns_current->s_super->s_flags ^ flags)
-		     & MS_RDONLY)) {
-			up_read(&nilfs->ns_super_sem);
-			err = -EBUSY;
-			goto failed_unlock;
-		}
-		up_read(&nilfs->ns_super_sem);
-	}
-
 	/*
-	 * Find existing nilfs_sb_info struct
+	 * once the super is inserted into the list by sget, s_umount
+	 * will protect the lockfs code from trying to start a snapshot
+	 * while we are mounting
 	 */
-	sd.sbi = nilfs_find_sbinfo(nilfs, !(flags & MS_RDONLY), sd.cno);
-
-	/*
-	 * Get super block instance holding the nilfs_sb_info struct.
-	 * A new instance is allocated if no existing mount is present or
-	 * existing instance has been unmounted.
-	 */
-	s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, &sd);
-	if (sd.sbi)
-		nilfs_put_sbinfo(sd.sbi);
-
+	mutex_lock(&sd.bdev->bd_fsfreeze_mutex);
+	if (sd.bdev->bd_fsfreeze_count > 0) {
+		mutex_unlock(&sd.bdev->bd_fsfreeze_mutex);
+		err = -EBUSY;
+		goto failed;
+	}
+	s = sget(fs_type, nilfs_test_bdev_super, nilfs_set_bdev_super, sd.bdev);
+	mutex_unlock(&sd.bdev->bd_fsfreeze_mutex);
 	if (IS_ERR(s)) {
 		err = PTR_ERR(s);
-		goto failed_unlock;
+		goto failed;
 	}
 
 	if (!s->s_root) {
 		char b[BDEVNAME_SIZE];
 
+		s_new = true;
+
 		/* New superblock instance created */
 		s->s_flags = flags;
 		s->s_mode = mode;
 		strlcpy(s->s_id, bdevname(sd.bdev, b), sizeof(s->s_id));
 		sb_set_blocksize(s, block_size(sd.bdev));
 
-		err = nilfs_fill_super(s, data, flags & MS_SILENT ? 1 : 0,
-				       nilfs);
+		err = nilfs_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
 		if (err)
-			goto cancel_new;
+			goto failed_super;
 
 		s->s_flags |= MS_ACTIVE;
-		need_to_close = 0;
+	} else if (!sd.cno) {
+		int busy = false;
+
+		if (nilfs_tree_was_touched(s->s_root)) {
+			busy = nilfs_try_to_shrink_tree(s->s_root);
+			if (busy && (flags ^ s->s_flags) & MS_RDONLY) {
+				printk(KERN_ERR "NILFS: the device already "
+				       "has a %s mount.\n",
+				       (s->s_flags & MS_RDONLY) ?
+				       "read-only" : "read/write");
+				err = -EBUSY;
+				goto failed_super;
+			}
+		}
+		if (!busy) {
+			/*
+			 * Try remount to setup mount states if the current
+			 * tree is not mounted and only snapshots use this sb.
+			 */
+			err = nilfs_remount(s, &flags, data);
+			if (err)
+				goto failed_super;
+		}
 	}
 
-	mutex_unlock(&nilfs->ns_mount_mutex);
-	put_nilfs(nilfs);
-	if (need_to_close)
-		close_bdev_exclusive(sd.bdev, mode);
-	simple_set_mnt(mnt, s);
-	return 0;
+	if (sd.cno) {
+		err = nilfs_attach_snapshot(s, sd.cno, &root_dentry);
+		if (err)
+			goto failed_super;
+	} else {
+		root_dentry = dget(s->s_root);
+	}
 
- failed_unlock:
-	mutex_unlock(&nilfs->ns_mount_mutex);
-	put_nilfs(nilfs);
- failed:
-	close_bdev_exclusive(sd.bdev, mode);
+	if (!s_new)
+		close_bdev_exclusive(sd.bdev, mode);
 
-	return err;
+	return root_dentry;
 
- cancel_new:
-	/* Abandoning the newly allocated superblock */
-	mutex_unlock(&nilfs->ns_mount_mutex);
-	put_nilfs(nilfs);
+ failed_super:
 	deactivate_locked_super(s);
-	/*
-	 * deactivate_locked_super() invokes close_bdev_exclusive().
-	 * We must finish all post-cleaning before this call;
-	 * put_nilfs() needs the block device.
-	 */
-	return err;
+
+ failed:
+	if (!s_new)
+		close_bdev_exclusive(sd.bdev, mode);
+	return ERR_PTR(err);
 }
 
 struct file_system_type nilfs_fs_type = {
 	.owner    = THIS_MODULE,
 	.name     = "nilfs2",
-	.get_sb   = nilfs_get_sb,
+	.mount    = nilfs_mount,
 	.kill_sb  = kill_block_super,
 	.fs_flags = FS_REQUIRES_DEV,
 };
@@ -1119,7 +1263,7 @@ static void nilfs_inode_init_once(void *obj)
 	init_rwsem(&ii->xattr_sem);
 #endif
 	nilfs_btnode_cache_init_once(&ii->i_btnode_cache);
-	ii->i_bmap = (struct nilfs_bmap *)&ii->i_bmap_union;
+	ii->i_bmap = &ii->i_bmap_data;
 	inode_init_once(&ii->vfs_inode);
 }
 
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 8c10973..0254be2 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -35,8 +35,7 @@
 #include "segbuf.h"
 
 
-static LIST_HEAD(nilfs_objects);
-static DEFINE_SPINLOCK(nilfs_lock);
+static int nilfs_valid_sb(struct nilfs_super_block *sbp);
 
 void nilfs_set_last_segment(struct the_nilfs *nilfs,
 			    sector_t start_blocknr, u64 seq, __u64 cno)
@@ -45,20 +44,27 @@ void nilfs_set_last_segment(struct the_nilfs *nilfs,
 	nilfs->ns_last_pseg = start_blocknr;
 	nilfs->ns_last_seq = seq;
 	nilfs->ns_last_cno = cno;
+
+	if (!nilfs_sb_dirty(nilfs)) {
+		if (nilfs->ns_prev_seq == nilfs->ns_last_seq)
+			goto stay_cursor;
+
+		set_nilfs_sb_dirty(nilfs);
+	}
+	nilfs->ns_prev_seq = nilfs->ns_last_seq;
+
+ stay_cursor:
 	spin_unlock(&nilfs->ns_last_segment_lock);
 }
 
 /**
- * alloc_nilfs - allocate the_nilfs structure
+ * alloc_nilfs - allocate a nilfs object
  * @bdev: block device to which the_nilfs is related
  *
- * alloc_nilfs() allocates memory for the_nilfs and
- * initializes its reference count and locks.
- *
  * Return Value: On success, pointer to the_nilfs is returned.
  * On error, NULL is returned.
  */
-static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
+struct the_nilfs *alloc_nilfs(struct block_device *bdev)
 {
 	struct the_nilfs *nilfs;
 
@@ -67,92 +73,25 @@ static struct the_nilfs *alloc_nilfs(struct block_device *bdev)
 		return NULL;
 
 	nilfs->ns_bdev = bdev;
-	atomic_set(&nilfs->ns_count, 1);
 	atomic_set(&nilfs->ns_ndirtyblks, 0);
 	init_rwsem(&nilfs->ns_sem);
-	init_rwsem(&nilfs->ns_super_sem);
-	mutex_init(&nilfs->ns_mount_mutex);
-	init_rwsem(&nilfs->ns_writer_sem);
-	INIT_LIST_HEAD(&nilfs->ns_list);
-	INIT_LIST_HEAD(&nilfs->ns_supers);
+	INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
 	spin_lock_init(&nilfs->ns_last_segment_lock);
-	nilfs->ns_gc_inodes_h = NULL;
+	nilfs->ns_cptree = RB_ROOT;
+	spin_lock_init(&nilfs->ns_cptree_lock);
 	init_rwsem(&nilfs->ns_segctor_sem);
 
 	return nilfs;
 }
 
 /**
- * find_or_create_nilfs - find or create nilfs object
- * @bdev: block device to which the_nilfs is related
- *
- * find_nilfs() looks up an existent nilfs object created on the
- * device and gets the reference count of the object.  If no nilfs object
- * is found on the device, a new nilfs object is allocated.
- *
- * Return Value: On success, pointer to the nilfs object is returned.
- * On error, NULL is returned.
+ * destroy_nilfs - destroy nilfs object
+ * @nilfs: nilfs object to be released
  */
-struct the_nilfs *find_or_create_nilfs(struct block_device *bdev)
+void destroy_nilfs(struct the_nilfs *nilfs)
 {
-	struct the_nilfs *nilfs, *new = NULL;
-
- retry:
-	spin_lock(&nilfs_lock);
-	list_for_each_entry(nilfs, &nilfs_objects, ns_list) {
-		if (nilfs->ns_bdev == bdev) {
-			get_nilfs(nilfs);
-			spin_unlock(&nilfs_lock);
-			if (new)
-				put_nilfs(new);
-			return nilfs; /* existing object */
-		}
-	}
-	if (new) {
-		list_add_tail(&new->ns_list, &nilfs_objects);
-		spin_unlock(&nilfs_lock);
-		return new; /* new object */
-	}
-	spin_unlock(&nilfs_lock);
-
-	new = alloc_nilfs(bdev);
-	if (new)
-		goto retry;
-	return NULL; /* insufficient memory */
-}
-
-/**
- * put_nilfs - release a reference to the_nilfs
- * @nilfs: the_nilfs structure to be released
- *
- * put_nilfs() decrements a reference counter of the_nilfs.
- * If the reference count reaches zero, the_nilfs is freed.
- */
-void put_nilfs(struct the_nilfs *nilfs)
-{
-	spin_lock(&nilfs_lock);
-	if (!atomic_dec_and_test(&nilfs->ns_count)) {
-		spin_unlock(&nilfs_lock);
-		return;
-	}
-	list_del_init(&nilfs->ns_list);
-	spin_unlock(&nilfs_lock);
-
-	/*
-	 * Increment of ns_count never occurs below because the caller
-	 * of get_nilfs() holds at least one reference to the_nilfs.
-	 * Thus its exclusion control is not required here.
-	 */
-
 	might_sleep();
-	if (nilfs_loaded(nilfs)) {
-		nilfs_mdt_destroy(nilfs->ns_sufile);
-		nilfs_mdt_destroy(nilfs->ns_cpfile);
-		nilfs_mdt_destroy(nilfs->ns_dat);
-		nilfs_mdt_destroy(nilfs->ns_gc_dat);
-	}
 	if (nilfs_init(nilfs)) {
-		nilfs_destroy_gccache(nilfs);
 		brelse(nilfs->ns_sbh[0]);
 		brelse(nilfs->ns_sbh[1]);
 	}
@@ -160,16 +99,17 @@ void put_nilfs(struct the_nilfs *nilfs)
 }
 
 static int nilfs_load_super_root(struct the_nilfs *nilfs,
-				 struct nilfs_sb_info *sbi, sector_t sr_block)
+				 struct super_block *sb, sector_t sr_block)
 {
 	struct buffer_head *bh_sr;
 	struct nilfs_super_root *raw_sr;
 	struct nilfs_super_block **sbp = nilfs->ns_sbp;
+	struct nilfs_inode *rawi;
 	unsigned dat_entry_size, segment_usage_size, checkpoint_size;
 	unsigned inode_size;
 	int err;
 
-	err = nilfs_read_super_root_block(sbi->s_super, sr_block, &bh_sr, 1);
+	err = nilfs_read_super_root_block(nilfs, sr_block, &bh_sr, 1);
 	if (unlikely(err))
 		return err;
 
@@ -181,40 +121,22 @@ static int nilfs_load_super_root(struct the_nilfs *nilfs,
 
 	inode_size = nilfs->ns_inode_size;
 
-	err = -ENOMEM;
-	nilfs->ns_dat = nilfs_dat_new(nilfs, dat_entry_size);
-	if (unlikely(!nilfs->ns_dat))
+	rawi = (void *)bh_sr->b_data + NILFS_SR_DAT_OFFSET(inode_size);
+	err = nilfs_dat_read(sb, dat_entry_size, rawi, &nilfs->ns_dat);
+	if (err)
 		goto failed;
 
-	nilfs->ns_gc_dat = nilfs_dat_new(nilfs, dat_entry_size);
-	if (unlikely(!nilfs->ns_gc_dat))
+	rawi = (void *)bh_sr->b_data + NILFS_SR_CPFILE_OFFSET(inode_size);
+	err = nilfs_cpfile_read(sb, checkpoint_size, rawi, &nilfs->ns_cpfile);
+	if (err)
 		goto failed_dat;
 
-	nilfs->ns_cpfile = nilfs_cpfile_new(nilfs, checkpoint_size);
-	if (unlikely(!nilfs->ns_cpfile))
-		goto failed_gc_dat;
-
-	nilfs->ns_sufile = nilfs_sufile_new(nilfs, segment_usage_size);
-	if (unlikely(!nilfs->ns_sufile))
+	rawi = (void *)bh_sr->b_data + NILFS_SR_SUFILE_OFFSET(inode_size);
+	err = nilfs_sufile_read(sb, segment_usage_size, rawi,
+				&nilfs->ns_sufile);
+	if (err)
 		goto failed_cpfile;
 
-	nilfs_mdt_set_shadow(nilfs->ns_dat, nilfs->ns_gc_dat);
-
-	err = nilfs_dat_read(nilfs->ns_dat, (void *)bh_sr->b_data +
-			     NILFS_SR_DAT_OFFSET(inode_size));
-	if (unlikely(err))
-		goto failed_sufile;
-
-	err = nilfs_cpfile_read(nilfs->ns_cpfile, (void *)bh_sr->b_data +
-				NILFS_SR_CPFILE_OFFSET(inode_size));
-	if (unlikely(err))
-		goto failed_sufile;
-
-	err = nilfs_sufile_read(nilfs->ns_sufile, (void *)bh_sr->b_data +
-				NILFS_SR_SUFILE_OFFSET(inode_size));
-	if (unlikely(err))
-		goto failed_sufile;
-
 	raw_sr = (struct nilfs_super_root *)bh_sr->b_data;
 	nilfs->ns_nongc_ctime = le64_to_cpu(raw_sr->sr_nongc_ctime);
 
@@ -222,17 +144,11 @@ static int nilfs_load_super_root(struct the_nilfs *nilfs,
 	brelse(bh_sr);
 	return err;
 
- failed_sufile:
-	nilfs_mdt_destroy(nilfs->ns_sufile);
-
  failed_cpfile:
-	nilfs_mdt_destroy(nilfs->ns_cpfile);
-
- failed_gc_dat:
-	nilfs_mdt_destroy(nilfs->ns_gc_dat);
+	iput(nilfs->ns_cpfile);
 
  failed_dat:
-	nilfs_mdt_destroy(nilfs->ns_dat);
+	iput(nilfs->ns_dat);
 	goto failed;
 }
 
@@ -248,6 +164,37 @@ static void nilfs_clear_recovery_info(struct nilfs_recovery_info *ri)
 }
 
 /**
+ * nilfs_store_log_cursor - load log cursor from a super block
+ * @nilfs: nilfs object
+ * @sbp: buffer storing super block to be read
+ *
+ * nilfs_store_log_cursor() reads the last position of the log
+ * containing a super root from a given super block, and initializes
+ * relevant information on the nilfs object preparatory for log
+ * scanning and recovery.
+ */
+static int nilfs_store_log_cursor(struct the_nilfs *nilfs,
+				  struct nilfs_super_block *sbp)
+{
+	int ret = 0;
+
+	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
+	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
+	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);
+
+	nilfs->ns_prev_seq = nilfs->ns_last_seq;
+	nilfs->ns_seg_seq = nilfs->ns_last_seq;
+	nilfs->ns_segnum =
+		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
+	nilfs->ns_cno = nilfs->ns_last_cno + 1;
+	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
+		printk(KERN_ERR "NILFS invalid last segment number.\n");
+		ret = -EINVAL;
+	}
+	return ret;
+}
+
+/**
  * load_nilfs - load and recover the nilfs
  * @nilfs: the_nilfs structure to be released
  * @sbi: nilfs_sb_info used to recover past segment
@@ -264,15 +211,6 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 	int valid_fs = nilfs_valid_fs(nilfs);
 	int err;
 
-	if (nilfs_loaded(nilfs)) {
-		if (valid_fs ||
-		    ((s_flags & MS_RDONLY) && nilfs_test_opt(sbi, NORECOVERY)))
-			return 0;
-		printk(KERN_ERR "NILFS: the filesystem is in an incomplete "
-		       "recovery state.\n");
-		return -EINVAL;
-	}
-
 	if (!valid_fs) {
 		printk(KERN_WARNING "NILFS warning: mounting unchecked fs\n");
 		if (s_flags & MS_RDONLY) {
@@ -285,13 +223,55 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 
 	nilfs_init_recovery_info(&ri);
 
-	err = nilfs_search_super_root(nilfs, sbi, &ri);
+	err = nilfs_search_super_root(nilfs, &ri);
 	if (unlikely(err)) {
-		printk(KERN_ERR "NILFS: error searching super root.\n");
-		goto failed;
+		struct nilfs_super_block **sbp = nilfs->ns_sbp;
+		int blocksize;
+
+		if (err != -EINVAL)
+			goto scan_error;
+
+		if (!nilfs_valid_sb(sbp[1])) {
+			printk(KERN_WARNING
+			       "NILFS warning: unable to fall back to spare"
+			       "super block\n");
+			goto scan_error;
+		}
+		printk(KERN_INFO
+		       "NILFS: try rollback from an earlier position\n");
+
+		/*
+		 * restore super block with its spare and reconfigure
+		 * relevant states of the nilfs object.
+		 */
+		memcpy(sbp[0], sbp[1], nilfs->ns_sbsize);
+		nilfs->ns_crc_seed = le32_to_cpu(sbp[0]->s_crc_seed);
+		nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
+
+		/* verify consistency between two super blocks */
+		blocksize = BLOCK_SIZE << le32_to_cpu(sbp[0]->s_log_block_size);
+		if (blocksize != nilfs->ns_blocksize) {
+			printk(KERN_WARNING
+			       "NILFS warning: blocksize differs between "
+			       "two super blocks (%d != %d)\n",
+			       blocksize, nilfs->ns_blocksize);
+			goto scan_error;
+		}
+
+		err = nilfs_store_log_cursor(nilfs, sbp[0]);
+		if (err)
+			goto scan_error;
+
+		/* drop clean flag to allow roll-forward and recovery */
+		nilfs->ns_mount_state &= ~NILFS_VALID_FS;
+		valid_fs = 0;
+
+		err = nilfs_search_super_root(nilfs, &ri);
+		if (err)
+			goto scan_error;
 	}
 
-	err = nilfs_load_super_root(nilfs, sbi, ri.ri_super_root);
+	err = nilfs_load_super_root(nilfs, sbi->s_super, ri.ri_super_root);
 	if (unlikely(err)) {
 		printk(KERN_ERR "NILFS: error loading super root.\n");
 		goto failed;
@@ -301,11 +281,23 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 		goto skip_recovery;
 
 	if (s_flags & MS_RDONLY) {
+		__u64 features;
+
 		if (nilfs_test_opt(sbi, NORECOVERY)) {
 			printk(KERN_INFO "NILFS: norecovery option specified. "
 			       "skipping roll-forward recovery\n");
 			goto skip_recovery;
 		}
+		features = le64_to_cpu(nilfs->ns_sbp[0]->s_feature_compat_ro) &
+			~NILFS_FEATURE_COMPAT_RO_SUPP;
+		if (features) {
+			printk(KERN_ERR "NILFS: couldn't proceed with "
+			       "recovery because of unsupported optional "
+			       "features (%llx)\n",
+			       (unsigned long long)features);
+			err = -EROFS;
+			goto failed_unload;
+		}
 		if (really_read_only) {
 			printk(KERN_ERR "NILFS: write access "
 			       "unavailable, cannot proceed.\n");
@@ -320,14 +312,13 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 		goto failed_unload;
 	}
 
-	err = nilfs_recover_logical_segments(nilfs, sbi, &ri);
+	err = nilfs_salvage_orphan_logs(nilfs, sbi, &ri);
 	if (err)
 		goto failed_unload;
 
 	down_write(&nilfs->ns_sem);
-	nilfs->ns_mount_state |= NILFS_VALID_FS;
-	nilfs->ns_sbp[0]->s_state = cpu_to_le16(nilfs->ns_mount_state);
-	err = nilfs_commit_super(sbi, 1);
+	nilfs->ns_mount_state |= NILFS_VALID_FS; /* set "clean" flag */
+	err = nilfs_cleanup_super(sbi);
 	up_write(&nilfs->ns_sem);
 
 	if (err) {
@@ -343,10 +334,14 @@ int load_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
 	sbi->s_super->s_flags = s_flags;
 	return 0;
 
+ scan_error:
+	printk(KERN_ERR "NILFS: error searching super root.\n");
+	goto failed;
+
  failed_unload:
-	nilfs_mdt_destroy(nilfs->ns_cpfile);
-	nilfs_mdt_destroy(nilfs->ns_sufile);
-	nilfs_mdt_destroy(nilfs->ns_dat);
+	iput(nilfs->ns_cpfile);
+	iput(nilfs->ns_sufile);
+	iput(nilfs->ns_dat);
 
  failed:
 	nilfs_clear_recovery_info(&ri);
@@ -368,8 +363,8 @@ static unsigned long long nilfs_max_size(unsigned int blkbits)
 static int nilfs_store_disk_layout(struct the_nilfs *nilfs,
 				   struct nilfs_super_block *sbp)
 {
-	if (le32_to_cpu(sbp->s_rev_level) != NILFS_CURRENT_REV) {
-		printk(KERN_ERR "NILFS: revision mismatch "
+	if (le32_to_cpu(sbp->s_rev_level) < NILFS_MIN_SUPP_REV) {
+		printk(KERN_ERR "NILFS: unsupported revision "
 		       "(superblock rev.=%d.%d, current rev.=%d.%d). "
 		       "Please check the version of mkfs.nilfs.\n",
 		       le32_to_cpu(sbp->s_rev_level),
@@ -509,14 +504,14 @@ static int nilfs_load_super_block(struct the_nilfs *nilfs,
 		return -EINVAL;
 	}
 
-	if (swp) {
+	if (!valid[!swp])
 		printk(KERN_WARNING "NILFS warning: broken superblock. "
 		       "using spare superblock.\n");
+	if (swp)
 		nilfs_swap_super_block(nilfs);
-	}
 
-	nilfs->ns_sbwtime[0] = le64_to_cpu(sbp[0]->s_wtime);
-	nilfs->ns_sbwtime[1] = valid[!swp] ? le64_to_cpu(sbp[1]->s_wtime) : 0;
+	nilfs->ns_sbwcount = 0;
+	nilfs->ns_sbwtime = le64_to_cpu(sbp[0]->s_wtime);
 	nilfs->ns_prot_seq = le64_to_cpu(sbp[valid[1] & !swp]->s_last_seq);
 	*sbpp = sbp[0];
 	return 0;
@@ -531,12 +526,7 @@ static int nilfs_load_super_block(struct the_nilfs *nilfs,
  *
  * init_nilfs() performs common initialization per block device (e.g.
  * reading the super block, getting disk layout information, initializing
- * shared fields in the_nilfs). It takes on some portion of the jobs
- * typically done by a fill_super() routine. This division arises from
- * the nature that multiple NILFS instances may be simultaneously
- * mounted on a device.
- * For multiple mounts on the same device, only the first mount
- * invokes these tasks.
+ * shared fields in the_nilfs).
  *
  * Return Value: On success, 0 is returned. On error, a negative error
  * code is returned.
@@ -545,30 +535,12 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 {
 	struct super_block *sb = sbi->s_super;
 	struct nilfs_super_block *sbp;
-	struct backing_dev_info *bdi;
 	int blocksize;
 	int err;
 
 	down_write(&nilfs->ns_sem);
-	if (nilfs_init(nilfs)) {
-		/* Load values from existing the_nilfs */
-		sbp = nilfs->ns_sbp[0];
-		err = nilfs_store_magic_and_option(sb, sbp, data);
-		if (err)
-			goto out;
-
-		blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
-		if (sb->s_blocksize != blocksize &&
-		    !sb_set_blocksize(sb, blocksize)) {
-			printk(KERN_ERR "NILFS: blocksize %d unfit to device\n",
-			       blocksize);
-			err = -EINVAL;
-		}
-		sb->s_maxbytes = nilfs_max_size(sb->s_blocksize_bits);
-		goto out;
-	}
 
-	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
+	blocksize = sb_min_blocksize(sb, NILFS_MIN_BLOCK_SIZE);
 	if (!blocksize) {
 		printk(KERN_ERR "NILFS: unable to set blocksize\n");
 		err = -EINVAL;
@@ -582,7 +554,18 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 	if (err)
 		goto failed_sbh;
 
+	err = nilfs_check_feature_compatibility(sb, sbp);
+	if (err)
+		goto failed_sbh;
+
 	blocksize = BLOCK_SIZE << le32_to_cpu(sbp->s_log_block_size);
+	if (blocksize < NILFS_MIN_BLOCK_SIZE ||
+	    blocksize > NILFS_MAX_BLOCK_SIZE) {
+		printk(KERN_ERR "NILFS: couldn't mount because of unsupported "
+		       "filesystem blocksize %d\n", blocksize);
+		err = -EINVAL;
+		goto failed_sbh;
+	}
 	if (sb->s_blocksize != blocksize) {
 		int hw_blocksize = bdev_logical_block_size(sb->s_bdev);
 
@@ -604,6 +587,7 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 			   when reloading fails. */
 	}
 	nilfs->ns_blocksize_bits = sb->s_blocksize_bits;
+	nilfs->ns_blocksize = blocksize;
 
 	err = nilfs_store_disk_layout(nilfs, sbp);
 	if (err)
@@ -613,29 +597,7 @@ int init_nilfs(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi, char *data)
 
 	nilfs->ns_mount_state = le16_to_cpu(sbp->s_state);
 
-	bdi = nilfs->ns_bdev->bd_inode->i_mapping->backing_dev_info;
-	nilfs->ns_bdi = bdi ? : &default_backing_dev_info;
-
-	/* Finding last segment */
-	nilfs->ns_last_pseg = le64_to_cpu(sbp->s_last_pseg);
-	nilfs->ns_last_cno = le64_to_cpu(sbp->s_last_cno);
-	nilfs->ns_last_seq = le64_to_cpu(sbp->s_last_seq);
-
-	nilfs->ns_seg_seq = nilfs->ns_last_seq;
-	nilfs->ns_segnum =
-		nilfs_get_segnum_of_block(nilfs, nilfs->ns_last_pseg);
-	nilfs->ns_cno = nilfs->ns_last_cno + 1;
-	if (nilfs->ns_segnum >= nilfs->ns_nsegments) {
-		printk(KERN_ERR "NILFS invalid last segment number.\n");
-		err = -EINVAL;
-		goto failed_sbh;
-	}
-	/* Dummy values  */
-	nilfs->ns_free_segments_count =
-		nilfs->ns_nsegments - (nilfs->ns_segnum + 1);
-
-	/* Initialize gcinode cache */
-	err = nilfs_init_gccache(nilfs);
+	err = nilfs_store_log_cursor(nilfs, sbp);
 	if (err)
 		goto failed_sbh;
 
@@ -673,8 +635,7 @@ int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
 			ret = blkdev_issue_discard(nilfs->ns_bdev,
 						   start * sects_per_block,
 						   nblocks * sects_per_block,
-						   GFP_NOFS,
-						   BLKDEV_IFL_BARRIER);
+						   GFP_NOFS, 0);
 			if (ret < 0)
 				return ret;
 			nblocks = 0;
@@ -684,7 +645,7 @@ int nilfs_discard_segments(struct the_nilfs *nilfs, __u64 *segnump,
 		ret = blkdev_issue_discard(nilfs->ns_bdev,
 					   start * sects_per_block,
 					   nblocks * sects_per_block,
-					   GFP_NOFS, BLKDEV_IFL_BARRIER);
+					   GFP_NOFS, 0);
 	return ret;
 }
 
@@ -711,79 +672,92 @@ int nilfs_near_disk_full(struct the_nilfs *nilfs)
 	return ncleansegs <= nilfs->ns_nrsvsegs + nincsegs;
 }
 
-/**
- * nilfs_find_sbinfo - find existing nilfs_sb_info structure
- * @nilfs: nilfs object
- * @rw_mount: mount type (non-zero value for read/write mount)
- * @cno: checkpoint number (zero for read-only mount)
- *
- * nilfs_find_sbinfo() returns the nilfs_sb_info structure which
- * @rw_mount and @cno (in case of snapshots) matched.  If no instance
- * was found, NULL is returned.  Although the super block instance can
- * be unmounted after this function returns, the nilfs_sb_info struct
- * is kept on memory until nilfs_put_sbinfo() is called.
- */
-struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *nilfs,
-					int rw_mount, __u64 cno)
+struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno)
 {
-	struct nilfs_sb_info *sbi;
-
-	down_read(&nilfs->ns_super_sem);
-	/*
-	 * The SNAPSHOT flag and sb->s_flags are supposed to be
-	 * protected with nilfs->ns_super_sem.
-	 */
-	sbi = nilfs->ns_current;
-	if (rw_mount) {
-		if (sbi && !(sbi->s_super->s_flags & MS_RDONLY))
-			goto found; /* read/write mount */
-		else
-			goto out;
-	} else if (cno == 0) {
-		if (sbi && (sbi->s_super->s_flags & MS_RDONLY))
-			goto found; /* read-only mount */
-		else
-			goto out;
+	struct rb_node *n;
+	struct nilfs_root *root;
+
+	spin_lock(&nilfs->ns_cptree_lock);
+	n = nilfs->ns_cptree.rb_node;
+	while (n) {
+		root = rb_entry(n, struct nilfs_root, rb_node);
+
+		if (cno < root->cno) {
+			n = n->rb_left;
+		} else if (cno > root->cno) {
+			n = n->rb_right;
+		} else {
+			atomic_inc(&root->count);
+			spin_unlock(&nilfs->ns_cptree_lock);
+			return root;
+		}
 	}
+	spin_unlock(&nilfs->ns_cptree_lock);
 
-	list_for_each_entry(sbi, &nilfs->ns_supers, s_list) {
-		if (nilfs_test_opt(sbi, SNAPSHOT) &&
-		    sbi->s_snapshot_cno == cno)
-			goto found; /* snapshot mount */
-	}
- out:
-	up_read(&nilfs->ns_super_sem);
 	return NULL;
-
- found:
-	atomic_inc(&sbi->s_count);
-	up_read(&nilfs->ns_super_sem);
-	return sbi;
 }
 
-int nilfs_checkpoint_is_mounted(struct the_nilfs *nilfs, __u64 cno,
-				int snapshot_mount)
+struct nilfs_root *
+nilfs_find_or_create_root(struct the_nilfs *nilfs, __u64 cno)
 {
-	struct nilfs_sb_info *sbi;
-	int ret = 0;
+	struct rb_node **p, *parent;
+	struct nilfs_root *root, *new;
+
+	root = nilfs_lookup_root(nilfs, cno);
+	if (root)
+		return root;
+
+	new = kmalloc(sizeof(*root), GFP_KERNEL);
+	if (!new)
+		return NULL;
+
+	spin_lock(&nilfs->ns_cptree_lock);
 
-	down_read(&nilfs->ns_super_sem);
-	if (cno == 0 || cno > nilfs->ns_cno)
-		goto out_unlock;
+	p = &nilfs->ns_cptree.rb_node;
+	parent = NULL;
 
-	list_for_each_entry(sbi, &nilfs->ns_supers, s_list) {
-		if (sbi->s_snapshot_cno == cno &&
-		    (!snapshot_mount || nilfs_test_opt(sbi, SNAPSHOT))) {
-					/* exclude read-only mounts */
-			ret++;
-			break;
+	while (*p) {
+		parent = *p;
+		root = rb_entry(parent, struct nilfs_root, rb_node);
+
+		if (cno < root->cno) {
+			p = &(*p)->rb_left;
+		} else if (cno > root->cno) {
+			p = &(*p)->rb_right;
+		} else {
+			atomic_inc(&root->count);
+			spin_unlock(&nilfs->ns_cptree_lock);
+			kfree(new);
+			return root;
 		}
 	}
-	/* for protecting recent checkpoints */
-	if (cno >= nilfs_last_cno(nilfs))
-		ret++;
 
- out_unlock:
-	up_read(&nilfs->ns_super_sem);
-	return ret;
+	new->cno = cno;
+	new->ifile = NULL;
+	new->nilfs = nilfs;
+	atomic_set(&new->count, 1);
+	atomic_set(&new->inodes_count, 0);
+	atomic_set(&new->blocks_count, 0);
+
+	rb_link_node(&new->rb_node, parent, p);
+	rb_insert_color(&new->rb_node, &nilfs->ns_cptree);
+
+	spin_unlock(&nilfs->ns_cptree_lock);
+
+	return new;
+}
+
+void nilfs_put_root(struct nilfs_root *root)
+{
+	if (atomic_dec_and_test(&root->count)) {
+		struct the_nilfs *nilfs = root->nilfs;
+
+		spin_lock(&nilfs->ns_cptree_lock);
+		rb_erase(&root->rb_node, &nilfs->ns_cptree);
+		spin_unlock(&nilfs->ns_cptree_lock);
+		if (root->ifile)
+			iput(root->ifile);
+
+		kfree(root);
+	}
 }
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index 1ab9745..69226e1 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -26,6 +26,7 @@
 
 #include <linux/types.h>
 #include <linux/buffer_head.h>
+#include <linux/rbtree.h>
 #include <linux/fs.h>
 #include <linux/blkdev.h>
 #include <linux/backing-dev.h>
@@ -45,21 +46,13 @@ enum {
 /**
  * struct the_nilfs - struct to supervise multiple nilfs mount points
  * @ns_flags: flags
- * @ns_count: reference count
- * @ns_list: list head for nilfs_list
  * @ns_bdev: block device
- * @ns_bdi: backing dev info
- * @ns_writer: back pointer to writable nilfs_sb_info
  * @ns_sem: semaphore for shared states
- * @ns_super_sem: semaphore for global operations across super block instances
- * @ns_mount_mutex: mutex protecting mount process of nilfs
- * @ns_writer_sem: semaphore protecting ns_writer attach/detach
- * @ns_current: back pointer to current mount
  * @ns_sbh: buffer heads of on-disk super blocks
  * @ns_sbp: pointers to super block data
- * @ns_sbwtime: previous write time of super blocks
+ * @ns_sbwtime: previous write time of super block
+ * @ns_sbwcount: write count of super block
  * @ns_sbsize: size of valid data in super block
- * @ns_supers: list of nilfs super block structs
  * @ns_seg_seq: segment sequence counter
  * @ns_segnum: index number of the latest full segment.
  * @ns_nextnum: index number of the full segment index to be used next
@@ -73,15 +66,16 @@ enum {
  * @ns_last_seq: sequence value of the latest segment
  * @ns_last_cno: checkpoint number of the latest segment
  * @ns_prot_seq: least sequence number of segments which must not be reclaimed
- * @ns_free_segments_count: counter of free segments
+ * @ns_prev_seq: base sequence number used to decide if advance log cursor
  * @ns_segctor_sem: segment constructor semaphore
  * @ns_dat: DAT file inode
  * @ns_cpfile: checkpoint file inode
  * @ns_sufile: segusage file inode
- * @ns_gc_dat: shadow inode of the DAT file inode for GC
+ * @ns_cptree: rb-tree of all mounted checkpoints (nilfs_root)
+ * @ns_cptree_lock: lock protecting @ns_cptree
  * @ns_gc_inodes: dummy inodes to keep live blocks
- * @ns_gc_inodes_h: hash list to keep dummy inode holding live blocks
  * @ns_blocksize_bits: bit length of block size
+ * @ns_blocksize: block size
  * @ns_nsegments: number of segments in filesystem
  * @ns_blocks_per_segment: number of blocks per segment
  * @ns_r_segments_percentage: reserved segments percentage
@@ -93,22 +87,9 @@ enum {
  */
 struct the_nilfs {
 	unsigned long		ns_flags;
-	atomic_t		ns_count;
-	struct list_head	ns_list;
 
 	struct block_device    *ns_bdev;
-	struct backing_dev_info *ns_bdi;
-	struct nilfs_sb_info   *ns_writer;
 	struct rw_semaphore	ns_sem;
-	struct rw_semaphore	ns_super_sem;
-	struct mutex		ns_mount_mutex;
-	struct rw_semaphore	ns_writer_sem;
-
-	/*
-	 * components protected by ns_super_sem
-	 */
-	struct nilfs_sb_info   *ns_current;
-	struct list_head	ns_supers;
 
 	/*
 	 * used for
@@ -119,7 +100,8 @@ struct the_nilfs {
 	 */
 	struct buffer_head     *ns_sbh[2];
 	struct nilfs_super_block *ns_sbp[2];
-	time_t			ns_sbwtime[2];
+	time_t			ns_sbwtime;
+	unsigned		ns_sbwcount;
 	unsigned		ns_sbsize;
 	unsigned		ns_mount_state;
 
@@ -149,7 +131,7 @@ struct the_nilfs {
 	u64			ns_last_seq;
 	__u64			ns_last_cno;
 	u64			ns_prot_seq;
-	unsigned long		ns_free_segments_count;
+	u64			ns_prev_seq;
 
 	struct rw_semaphore	ns_segctor_sem;
 
@@ -160,14 +142,17 @@ struct the_nilfs {
 	struct inode	       *ns_dat;
 	struct inode	       *ns_cpfile;
 	struct inode	       *ns_sufile;
-	struct inode	       *ns_gc_dat;
 
-	/* GC inode list and hash table head */
+	/* Checkpoint tree */
+	struct rb_root		ns_cptree;
+	spinlock_t		ns_cptree_lock;
+
+	/* GC inode list */
 	struct list_head	ns_gc_inodes;
-	struct hlist_head      *ns_gc_inodes_h;
 
 	/* Disk layout information (static) */
 	unsigned int		ns_blocksize_bits;
+	unsigned int		ns_blocksize;
 	unsigned long		ns_nsegments;
 	unsigned long		ns_blocks_per_segment;
 	unsigned long		ns_r_segments_percentage;
@@ -178,9 +163,6 @@ struct the_nilfs {
 	u32			ns_crc_seed;
 };
 
-#define NILFS_GCINODE_HASH_BITS		8
-#define NILFS_GCINODE_HASH_SIZE		(1<<NILFS_GCINODE_HASH_BITS)
-
 #define THE_NILFS_FNS(bit, name)					\
 static inline void set_nilfs_##name(struct the_nilfs *nilfs)		\
 {									\
@@ -201,65 +183,67 @@ THE_NILFS_FNS(DISCONTINUED, discontinued)
 THE_NILFS_FNS(GC_RUNNING, gc_running)
 THE_NILFS_FNS(SB_DIRTY, sb_dirty)
 
+/**
+ * struct nilfs_root - nilfs root object
+ * @cno: checkpoint number
+ * @rb_node: red-black tree node
+ * @count: refcount of this structure
+ * @nilfs: nilfs object
+ * @ifile: inode file
+ * @root: root inode
+ * @inodes_count: number of inodes
+ * @blocks_count: number of blocks (Reserved)
+ */
+struct nilfs_root {
+	__u64 cno;
+	struct rb_node rb_node;
+
+	atomic_t count;
+	struct the_nilfs *nilfs;
+	struct inode *ifile;
+
+	atomic_t inodes_count;
+	atomic_t blocks_count;
+};
+
+/* Special checkpoint number */
+#define NILFS_CPTREE_CURRENT_CNO	0
+
 /* Minimum interval of periodical update of superblocks (in seconds) */
 #define NILFS_SB_FREQ		10
-#define NILFS_ALTSB_FREQ	60  /* spare superblock */
 
 static inline int nilfs_sb_need_update(struct the_nilfs *nilfs)
 {
 	u64 t = get_seconds();
-	return t < nilfs->ns_sbwtime[0] ||
-		 t > nilfs->ns_sbwtime[0] + NILFS_SB_FREQ;
+	return t < nilfs->ns_sbwtime || t > nilfs->ns_sbwtime + NILFS_SB_FREQ;
 }
 
-static inline int nilfs_altsb_need_update(struct the_nilfs *nilfs)
+static inline int nilfs_sb_will_flip(struct the_nilfs *nilfs)
 {
-	u64 t = get_seconds();
-	struct nilfs_super_block **sbp = nilfs->ns_sbp;
-	return sbp[1] && t > nilfs->ns_sbwtime[1] + NILFS_ALTSB_FREQ;
+	int flip_bits = nilfs->ns_sbwcount & 0x0FL;
+	return (flip_bits != 0x08 && flip_bits != 0x0F);
 }
 
 void nilfs_set_last_segment(struct the_nilfs *, sector_t, u64, __u64);
-struct the_nilfs *find_or_create_nilfs(struct block_device *);
-void put_nilfs(struct the_nilfs *);
+struct the_nilfs *alloc_nilfs(struct block_device *bdev);
+void destroy_nilfs(struct the_nilfs *nilfs);
 int init_nilfs(struct the_nilfs *, struct nilfs_sb_info *, char *);
 int load_nilfs(struct the_nilfs *, struct nilfs_sb_info *);
 int nilfs_discard_segments(struct the_nilfs *, __u64 *, size_t);
 int nilfs_count_free_blocks(struct the_nilfs *, sector_t *);
+struct nilfs_root *nilfs_lookup_root(struct the_nilfs *nilfs, __u64 cno);
+struct nilfs_root *nilfs_find_or_create_root(struct the_nilfs *nilfs,
+					     __u64 cno);
+void nilfs_put_root(struct nilfs_root *root);
 struct nilfs_sb_info *nilfs_find_sbinfo(struct the_nilfs *, int, __u64);
-int nilfs_checkpoint_is_mounted(struct the_nilfs *, __u64, int);
 int nilfs_near_disk_full(struct the_nilfs *);
 void nilfs_fall_back_super_block(struct the_nilfs *);
 void nilfs_swap_super_block(struct the_nilfs *);
 
 
-static inline void get_nilfs(struct the_nilfs *nilfs)
-{
-	/* Caller must have at least one reference of the_nilfs. */
-	atomic_inc(&nilfs->ns_count);
-}
-
-static inline void
-nilfs_attach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
-{
-	down_write(&nilfs->ns_writer_sem);
-	nilfs->ns_writer = sbi;
-	up_write(&nilfs->ns_writer_sem);
-}
-
-static inline void
-nilfs_detach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
-{
-	down_write(&nilfs->ns_writer_sem);
-	if (sbi == nilfs->ns_writer)
-		nilfs->ns_writer = NULL;
-	up_write(&nilfs->ns_writer_sem);
-}
-
-static inline void nilfs_put_sbinfo(struct nilfs_sb_info *sbi)
+static inline void nilfs_get_root(struct nilfs_root *root)
 {
-	if (atomic_dec_and_test(&sbi->s_count))
-		kfree(sbi);
+	atomic_inc(&root->count);
 }
 
 static inline int nilfs_valid_fs(struct the_nilfs *nilfs)