ext4: delayed allocation ENOSPC handling

This patch does block reservation for delayed
allocation, to avoid ENOSPC later at page flush time.

Blocks(data and metadata) are reserved at da_write_begin()
time, the freeblocks counter is updated by then, and the number of
reserved blocks is store in per inode counter.
        
At the writepage time, the unused reserved meta blocks are returned
back. At unlink/truncate time, reserved blocks are properly released.

Updated fix from  Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
to fix the oldallocator block reservation accounting with delalloc, added
lock to guard the counters and also fix the reservation for meta blocks.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 156 insertions, 28 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2bef4f87..a6b800c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -39,6 +39,7 @@
 #include "ext4_jbd2.h"
 #include "xattr.h"
 #include "acl.h"
+#include "ext4_extents.h"
 
 static inline int ext4_begin_ordered_truncate(struct inode *inode,
 					      loff_t new_size)
@@ -982,7 +983,7 @@ out:
  */
 int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
 			unsigned long max_blocks, struct buffer_head *bh,
-			int create, int extend_disksize)
+			int create, int extend_disksize, int flag)
 {
 	int retval;
 
@@ -1023,6 +1024,15 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
 	 * with create == 1 flag.
 	 */
 	down_write((&EXT4_I(inode)->i_data_sem));
+
+	/*
+	 * if the caller is from delayed allocation writeout path
+	 * we have already reserved fs blocks for allocation
+	 * let the underlying get_block() function know to
+	 * avoid double accounting
+	 */
+	if (flag)
+		EXT4_I(inode)->i_delalloc_reserved_flag = 1;
 	/*
 	 * We need to check for EXT4 here because migrate
 	 * could have changed the inode type in between
@@ -1044,6 +1054,18 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
 							~EXT4_EXT_MIGRATE;
 		}
 	}
+
+	if (flag) {
+		EXT4_I(inode)->i_delalloc_reserved_flag = 0;
+		/*
+		 * Update reserved blocks/metadata blocks
+		 * after successful block allocation
+		 * which were deferred till now
+		 */
+		if ((retval > 0) && buffer_delay(bh))
+			ext4_da_release_space(inode, retval, 0);
+	}
+
 	up_write((&EXT4_I(inode)->i_data_sem));
 	return retval;
 }
@@ -1069,7 +1091,7 @@ static int ext4_get_block(struct inode *inode, sector_t iblock,
 	}
 
 	ret = ext4_get_blocks_wrap(handle, inode, iblock,
-					max_blocks, bh_result, create, 0);
+					max_blocks, bh_result, create, 0, 0);
 	if (ret > 0) {
 		bh_result->b_size = (ret << inode->i_blkbits);
 		ret = 0;
@@ -1095,7 +1117,7 @@ struct buffer_head *ext4_getblk(handle_t *handle, struct inode *inode,
 	dummy.b_blocknr = -1000;
 	buffer_trace_init(&dummy.b_history);
 	err = ext4_get_blocks_wrap(handle, inode, block, 1,
-					&dummy, create, 1);
+					&dummy, create, 1, 0);
 	/*
 	 * ext4_get_blocks_handle() returns number of blocks
 	 * mapped. 0 in case of a HOLE.
@@ -1409,6 +1431,122 @@ static int ext4_journalled_write_end(struct file *file,
 
 	return ret ? ret : copied;
 }
+/*
+ * Calculate the number of metadata blocks need to reserve
+ * to allocate @blocks for non extent file based file
+ */
+static int ext4_indirect_calc_metadata_amount(struct inode *inode, int blocks)
+{
+	int icap = EXT4_ADDR_PER_BLOCK(inode->i_sb);
+	int ind_blks, dind_blks, tind_blks;
+
+	/* number of new indirect blocks needed */
+	ind_blks = (blocks + icap - 1) / icap;
+
+	dind_blks = (ind_blks + icap - 1) / icap;
+
+	tind_blks = 1;
+
+	return ind_blks + dind_blks + tind_blks;
+}
+
+/*
+ * Calculate the number of metadata blocks need to reserve
+ * to allocate given number of blocks
+ */
+static int ext4_calc_metadata_amount(struct inode *inode, int blocks)
+{
+	if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL)
+		return ext4_ext_calc_metadata_amount(inode, blocks);
+
+	return ext4_indirect_calc_metadata_amount(inode, blocks);
+}
+
+static int ext4_da_reserve_space(struct inode *inode, int nrblocks)
+{
+       struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+       unsigned long md_needed, mdblocks, total = 0;
+
+	/*
+	 * recalculate the amount of metadata blocks to reserve
+	 * in order to allocate nrblocks
+	 * worse case is one extent per block
+	 */
+	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
+	total = EXT4_I(inode)->i_reserved_data_blocks + nrblocks;
+	mdblocks = ext4_calc_metadata_amount(inode, total);
+	BUG_ON(mdblocks < EXT4_I(inode)->i_reserved_meta_blocks);
+
+	md_needed = mdblocks - EXT4_I(inode)->i_reserved_meta_blocks;
+	total = md_needed + nrblocks;
+
+	if (ext4_has_free_blocks(sbi, total) < total) {
+		spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
+		return -ENOSPC;
+	}
+
+	/* reduce fs free blocks counter */
+	percpu_counter_sub(&sbi->s_freeblocks_counter, total);
+
+	EXT4_I(inode)->i_reserved_data_blocks += nrblocks;
+	EXT4_I(inode)->i_reserved_meta_blocks = mdblocks;
+
+	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
+	return 0;       /* success */
+}
+
+void ext4_da_release_space(struct inode *inode, int used, int to_free)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+	int total, mdb, mdb_free, release;
+
+	spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
+	/* recalculate the number of metablocks still need to be reserved */
+	total = EXT4_I(inode)->i_reserved_data_blocks - used - to_free;
+	mdb = ext4_calc_metadata_amount(inode, total);
+
+	/* figure out how many metablocks to release */
+	BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
+	mdb_free = EXT4_I(inode)->i_reserved_meta_blocks - mdb;
+
+	/* Account for allocated meta_blocks */
+	mdb_free -= EXT4_I(inode)->i_allocated_meta_blocks;
+
+	release = to_free + mdb_free;
+
+	/* update fs free blocks counter for truncate case */
+	percpu_counter_add(&sbi->s_freeblocks_counter, release);
+
+	/* update per-inode reservations */
+	BUG_ON(used + to_free > EXT4_I(inode)->i_reserved_data_blocks);
+	EXT4_I(inode)->i_reserved_data_blocks -= (used + to_free);
+
+	BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
+	EXT4_I(inode)->i_reserved_meta_blocks = mdb;
+	EXT4_I(inode)->i_allocated_meta_blocks = 0;
+	spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
+}
+
+static void ext4_da_page_release_reservation(struct page *page,
+						unsigned long offset)
+{
+	int to_release = 0;
+	struct buffer_head *head, *bh;
+	unsigned int curr_off = 0;
+
+	head = page_buffers(page);
+	bh = head;
+	do {
+		unsigned int next_off = curr_off + bh->b_size;
+
+		if ((offset <= curr_off) && (buffer_delay(bh))) {
+			to_release++;
+			clear_buffer_delay(bh);
+		}
+		curr_off = next_off;
+	} while ((bh = bh->b_this_page) != head);
+	ext4_da_release_space(page->mapping->host, 0, to_release);
+}
 
 /*
  * Delayed allocation stuff
@@ -1829,14 +1967,18 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 	 * preallocated blocks are unmapped but should treated
 	 * the same as allocated blocks.
 	 */
-	ret = ext4_get_blocks_wrap(NULL, inode, iblock, 1,  bh_result, 0, 0);
-	if (ret == 0) {
-		/* the block isn't allocated yet, let's reserve space */
-		/* XXX: call reservation here */
+	ret = ext4_get_blocks_wrap(NULL, inode, iblock, 1,  bh_result, 0, 0, 0);
+	if ((ret == 0) && !buffer_delay(bh_result)) {
+		/* the block isn't (pre)allocated yet, let's reserve space */
 		/*
 		 * XXX: __block_prepare_write() unmaps passed block,
 		 * is it OK?
 		 */
+		ret = ext4_da_reserve_space(inode, 1);
+		if (ret)
+			/* not enough space to reserve */
+			return ret;
+
 		map_bh(bh_result, inode->i_sb, 0);
 		set_buffer_new(bh_result);
 		set_buffer_delay(bh_result);
@@ -1847,7 +1989,7 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 
 	return ret;
 }
-
+#define		EXT4_DELALLOC_RSVED	1
 static int ext4_da_get_block_write(struct inode *inode, sector_t iblock,
 				   struct buffer_head *bh_result, int create)
 {
@@ -1865,7 +2007,7 @@ static int ext4_da_get_block_write(struct inode *inode, sector_t iblock,
 	}
 
 	ret = ext4_get_blocks_wrap(handle, inode, iblock, max_blocks,
-				   bh_result, create, 0);
+				   bh_result, create, 0, EXT4_DELALLOC_RSVED);
 	if (ret > 0) {
 		bh_result->b_size = (ret << inode->i_blkbits);
 
@@ -1952,7 +2094,7 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
 				loff_t pos, unsigned len, unsigned flags,
 				struct page **pagep, void **fsdata)
 {
-	int ret;
+	int ret, retries = 0;
 	struct page *page;
 	pgoff_t index;
 	unsigned from, to;
@@ -1963,6 +2105,7 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
 	from = pos & (PAGE_CACHE_SIZE - 1);
 	to = from + len;
 
+retry:
 	/*
 	 * With delayed allocation, we don't log the i_disksize update
 	 * if there is delayed block allocation. But we still need
@@ -1988,6 +2131,8 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
 		page_cache_release(page);
 	}
 
+	if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
+		goto retry;
 out:
 	return ret;
 }
@@ -2040,9 +2185,6 @@ static int ext4_da_write_end(struct file *file,
 
 static void ext4_da_invalidatepage(struct page *page, unsigned long offset)
 {
-	struct buffer_head *head, *bh;
-	unsigned int curr_off = 0;
-
 	/*
 	 * Drop reserved blocks
 	 */
@@ -2050,21 +2192,7 @@ static void ext4_da_invalidatepage(struct page *page, unsigned long offset)
 	if (!page_has_buffers(page))
 		goto out;
 
-	head = page_buffers(page);
-	bh = head;
-	do {
-		unsigned int next_off = curr_off + bh->b_size;
-
-		/*
-		 * is this block fully invalidated?
-		 */
-		if (offset <= curr_off && buffer_delay(bh)) {
-			clear_buffer_delay(bh);
-			/* XXX: add real stuff here */
-		}
-		curr_off = next_off;
-		bh = bh->b_this_page;
-	} while (bh != head);
+	ext4_da_page_release_reservation(page, offset);
 
 out:
 	ext4_invalidatepage(page, offset);