Btrfs: fix bad extent logging

A user sent me a btrfs-image of a file system that was panicing on mount during
the log recovery.  I had originally thought these problems were from a bug in
the free space cache code, but that was just a symptom of the problem.  The
problem is if your application does something like this

[prealloc][prealloc][prealloc]

the internal extent maps will merge those all together into one extent map, even
though on disk they are 3 separate extents.  So if you go to write into one of
these ranges the extent map will be right since we use the physical extent when
doing the write, but when we log the extents they will use the wrong sizes for
the remainder prealloc space.  If this doesn't happen to trip up the free space
cache (which it won't in a lot of cases) then you will get bogus entries in your
extent tree which will screw stuff up later.  The data and such will still work,
but everything else is broken.  This patch fixes this by not allowing extents
that are on the modified list to be merged.  This has the side effect that we
are no longer adding everything to the modified list all the time, which means
we now have to call btrfs_drop_extents every time we log an extent into the
tree.  So this allows me to drop all this speciality code I was using to get
around calling btrfs_drop_extents.  With this patch the testcase I've created no
longer creates a bogus file system after replaying the log.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 6 insertions, 138 deletions

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 592aa65..b069faf 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -3209,115 +3209,6 @@ static int extent_cmp(void *priv, struct list_head *a, struct list_head *b)
 	return 0;
 }
 
-static int drop_adjacent_extents(struct btrfs_trans_handle *trans,
-				 struct btrfs_root *root, struct inode *inode,
-				 struct extent_map *em,
-				 struct btrfs_path *path)
-{
-	struct btrfs_file_extent_item *fi;
-	struct extent_buffer *leaf;
-	struct btrfs_key key, new_key;
-	struct btrfs_map_token token;
-	u64 extent_end;
-	u64 extent_offset = 0;
-	int extent_type;
-	int del_slot = 0;
-	int del_nr = 0;
-	int ret = 0;
-
-	while (1) {
-		btrfs_init_map_token(&token);
-		leaf = path->nodes[0];
-		path->slots[0]++;
-		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
-			if (del_nr) {
-				ret = btrfs_del_items(trans, root, path,
-						      del_slot, del_nr);
-				if (ret)
-					return ret;
-				del_nr = 0;
-			}
-
-			ret = btrfs_next_leaf_write(trans, root, path, 1);
-			if (ret < 0)
-				return ret;
-			if (ret > 0)
-				return 0;
-			leaf = path->nodes[0];
-		}
-
-		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
-		if (key.objectid != btrfs_ino(inode) ||
-		    key.type != BTRFS_EXTENT_DATA_KEY ||
-		    key.offset >= em->start + em->len)
-			break;
-
-		fi = btrfs_item_ptr(leaf, path->slots[0],
-				    struct btrfs_file_extent_item);
-		extent_type = btrfs_token_file_extent_type(leaf, fi, &token);
-		if (extent_type == BTRFS_FILE_EXTENT_REG ||
-		    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
-			extent_offset = btrfs_token_file_extent_offset(leaf,
-								fi, &token);
-			extent_end = key.offset +
-				btrfs_token_file_extent_num_bytes(leaf, fi,
-								  &token);
-		} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
-			extent_end = key.offset +
-				btrfs_file_extent_inline_len(leaf, fi);
-		} else {
-			BUG();
-		}
-
-		if (extent_end <= em->len + em->start) {
-			if (!del_nr) {
-				del_slot = path->slots[0];
-			}
-			del_nr++;
-			continue;
-		}
-
-		/*
-		 * Ok so we'll ignore previous items if we log a new extent,
-		 * which can lead to overlapping extents, so if we have an
-		 * existing extent we want to adjust we _have_ to check the next
-		 * guy to make sure we even need this extent anymore, this keeps
-		 * us from panicing in set_item_key_safe.
-		 */
-		if (path->slots[0] < btrfs_header_nritems(leaf) - 1) {
-			struct btrfs_key tmp_key;
-
-			btrfs_item_key_to_cpu(leaf, &tmp_key,
-					      path->slots[0] + 1);
-			if (tmp_key.objectid == btrfs_ino(inode) &&
-			    tmp_key.type == BTRFS_EXTENT_DATA_KEY &&
-			    tmp_key.offset <= em->start + em->len) {
-				if (!del_nr)
-					del_slot = path->slots[0];
-				del_nr++;
-				continue;
-			}
-		}
-
-		BUG_ON(extent_type == BTRFS_FILE_EXTENT_INLINE);
-		memcpy(&new_key, &key, sizeof(new_key));
-		new_key.offset = em->start + em->len;
-		btrfs_set_item_key_safe(trans, root, path, &new_key);
-		extent_offset += em->start + em->len - key.offset;
-		btrfs_set_token_file_extent_offset(leaf, fi, extent_offset,
-						   &token);
-		btrfs_set_token_file_extent_num_bytes(leaf, fi, extent_end -
-						      (em->start + em->len),
-						      &token);
-		btrfs_mark_buffer_dirty(leaf);
-	}
-
-	if (del_nr)
-		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
-
-	return ret;
-}
-
 static int log_one_extent(struct btrfs_trans_handle *trans,
 			  struct inode *inode, struct btrfs_root *root,
 			  struct extent_map *em, struct btrfs_path *path)
@@ -3339,39 +3230,24 @@ static int log_one_extent(struct btrfs_trans_handle *trans,
 	int index = log->log_transid % 2;
 	bool skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
 
-insert:
+	ret = __btrfs_drop_extents(trans, log, inode, path, em->start,
+				   em->start + em->len, NULL, 0);
+	if (ret)
+		return ret;
+
 	INIT_LIST_HEAD(&ordered_sums);
 	btrfs_init_map_token(&token);
 	key.objectid = btrfs_ino(inode);
 	key.type = BTRFS_EXTENT_DATA_KEY;
 	key.offset = em->start;
-	path->really_keep_locks = 1;
 
 	ret = btrfs_insert_empty_item(trans, log, path, &key, sizeof(*fi));
-	if (ret && ret != -EEXIST) {
-		path->really_keep_locks = 0;
+	if (ret)
 		return ret;
-	}
 	leaf = path->nodes[0];
 	fi = btrfs_item_ptr(leaf, path->slots[0],
 			    struct btrfs_file_extent_item);
 
-	/*
-	 * If we are overwriting an inline extent with a real one then we need
-	 * to just delete the inline extent as it may not be large enough to
-	 * have the entire file_extent_item.
-	 */
-	if (ret && btrfs_token_file_extent_type(leaf, fi, &token) ==
-	    BTRFS_FILE_EXTENT_INLINE) {
-		ret = btrfs_del_item(trans, log, path);
-		btrfs_release_path(path);
-		if (ret) {
-			path->really_keep_locks = 0;
-			return ret;
-		}
-		goto insert;
-	}
-
 	btrfs_set_token_file_extent_generation(leaf, fi, em->generation,
 					       &token);
 	if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags)) {
@@ -3417,15 +3293,7 @@ insert:
 	btrfs_set_token_file_extent_other_encoding(leaf, fi, 0, &token);
 	btrfs_mark_buffer_dirty(leaf);
 
-	/*
-	 * Have to check the extent to the right of us to make sure it doesn't
-	 * fall in our current range.  We're ok if the previous extent is in our
-	 * range since the recovery stuff will run us in key order and thus just
-	 * drop the part we overwrote.
-	 */
-	ret = drop_adjacent_extents(trans, log, inode, em, path);
 	btrfs_release_path(path);
-	path->really_keep_locks = 0;
 	if (ret) {
 		return ret;
 	}