On Tue, Oct 13, 2015 at 7:06 PM, Chris Mason <c...@fb.com> wrote:
> The code for btrfs inode-resolve has never worked properly for
> files with enough hard links to trigger extrefs.  It was trying to
> get the leaf out of a path after freeing the path:
>
>         btrfs_release_path(path);
>         leaf = path->nodes[0];
>         item_size = btrfs_item_size_nr(leaf, slot);
>
> The fix here is to use the extent buffer we cloned just a little higher
> up to avoid deadlocks caused by using the leaf in the path.
>
> Signed-off-by: Chris Mason <c...@fb.com>
> cc: sta...@vger.kernel.org # v3.7+
> cc: Mark Fasheh <mfas...@suse.de>
Reviewed-by: Filipe Manana <fdman...@suse.com>

Looks good to me.
I failed to notice that problem at commit [1]

[1] 
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=3fe81ce206f3805e0eb5d886aabbf91064655144

> ---
>  fs/btrfs/backref.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
> index ecbc63d..9a2ec79 100644
> --- a/fs/btrfs/backref.c
> +++ b/fs/btrfs/backref.c
> @@ -1828,7 +1828,6 @@ static int iterate_inode_extrefs(u64 inum, struct 
> btrfs_root *fs_root,
>         int found = 0;
>         struct extent_buffer *eb;
>         struct btrfs_inode_extref *extref;
> -       struct extent_buffer *leaf;
>         u32 item_size;
>         u32 cur_offset;
>         unsigned long ptr;
> @@ -1856,9 +1855,8 @@ static int iterate_inode_extrefs(u64 inum, struct 
> btrfs_root *fs_root,
>                 btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
>                 btrfs_release_path(path);
>
> -               leaf = path->nodes[0];
> -               item_size = btrfs_item_size_nr(leaf, slot);
> -               ptr = btrfs_item_ptr_offset(leaf, slot);
> +               item_size = btrfs_item_size_nr(eb, slot);
> +               ptr = btrfs_item_ptr_offset(eb, slot);
>                 cur_offset = 0;
>
>                 while (cur_offset < item_size) {
> @@ -1872,7 +1870,7 @@ static int iterate_inode_extrefs(u64 inum, struct 
> btrfs_root *fs_root,
>                         if (ret)
>                                 break;
>
> -                       cur_offset += btrfs_inode_extref_name_len(leaf, 
> extref);
> +                       cur_offset += btrfs_inode_extref_name_len(eb, extref);
>                         cur_offset += sizeof(*extref);
>                 }
>                 btrfs_tree_read_unlock_blocking(eb);
> --
> 2.4.6
>
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-- 
Filipe David Manana,

"Reasonable men adapt themselves to the world.
 Unreasonable men adapt the world to themselves.
 That's why all progress depends on unreasonable men."
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