(2014/12/16 1:04), Filipe Manana wrote:
> 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.
Yes, this key type is introduced by commit 3173a18.
fs/btrfs/ctree.h
======================
/*
* The same as the BTRFS_EXTENT_ITEM_KEY, except it's metadata we already know
* the length, so we save the level in key->offset instead of the length.
*/
#define BTRFS_METADATA_ITEM_KEY 169
======================
>
> 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@xxxxxxxx>
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
In addition, build v3.18 + this patch succeeded without any warning.
Thanks,
Satoru
> ---
> fs/btrfs/backref.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
> index 2d3e32e..8729cf6 100644
> --- a/fs/btrfs/backref.c
> +++ b/fs/btrfs/backref.c
> @@ -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);
> - *out_level = btrfs_tree_block_level(eb, info);
> +
> + 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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