Commit a1317f45 authored Dec 15, 2014 by Filipe Manana Committed by Chris Mason Jan 02, 2015

Btrfs: correctly get tree level in tree_backref_for_extent

If we are using skinny metadata, the block's tree level is in the offset
of the key and not in a btrfs_tree_block_info structure following the
extent item (it doesn't exist). Therefore fix it.

Besides returning the correct level in the tree, this also prevents reading
past the leaf's end in the case where the extent item is the last item in
the leaf (eb) and it has only 1 inline reference - this is because
sizeof(struct btrfs_tree_block_info) is greater than
sizeof(struct btrfs_extent_inline_ref).

Got it while running a scrub which produced the following warning:

BTRFS: checksum error at logical 42123264 on dev /dev/sde, sector 15840: metadata node (level 24) in tree 5

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Signed-off-by: Chris Mason <clm@fb.com>

parent c7cfb8a5

fs/btrfs/backref.c

+10 −3

Original line number	Diff line number	Diff line
		@@ -1552,7 +1552,6 @@ int tree_backref_for_extent(unsigned long ptr, struct extent_buffer eb,
		{
		int ret;
		int type;
		struct btrfs_tree_block_info *info;
		struct btrfs_extent_inline_ref *eiref;

		if (*ptr == (unsigned long)-1)
		@@ -1573,9 +1572,17 @@ int tree_backref_for_extent(unsigned long ptr, struct extent_buffer eb,
		}

		/* we can treat both ref types equally here */
		info = (struct btrfs_tree_block_info *)(ei + 1);
		*out_root = btrfs_extent_inline_ref_offset(eb, eiref);

		if (key->type == BTRFS_EXTENT_ITEM_KEY) {
		struct btrfs_tree_block_info *info;

		info = (struct btrfs_tree_block_info *)(ei + 1);
		*out_level = btrfs_tree_block_level(eb, info);
		} else {
		ASSERT(key->type == BTRFS_METADATA_ITEM_KEY);
		*out_level = (u8)key->offset;
		}

		if (ret == 1)
		*ptr = (unsigned long)-1;

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