Re: [PATCH] btrfs: fix incorrect return value after crossing leaf boundary in lookup_extent_data_ref

[Filipe Manana <fdmanana@kernel.org>]

On Wed, Mar 25, 2026 at 10:28 AM robbieko <robbieko@synology.com> wrote:
>
> After commit 1618aa3c2e01 ("btrfs: simplify return variables in
> lookup_extent_data_ref()"), the err and ret variables were merged into
> a single ret variable. However, when btrfs_next_leaf() returns 0
> (success), ret is overwritten from -ENOENT to 0. If the first key in
> the next leaf does not match (different objectid or type), the function
> returns 0 instead of -ENOENT, making the caller believe the lookup
> succeeded when it did not. This can lead to operations on the wrong
> extent tree item, potentially causing extent tree corruption.
>
> Fix this by returning -ENOENT directly when the key does not match,
> instead of relying on the ret variable.
>
> Fixes: 1618aa3c2e01 ("btrfs: simplify return variables in lookup_extent_data_ref()")
> Signed-off-by: robbieko <robbieko@synology.com>

Reviewed-by: Filipe Manana <fdmanana@suse.com>

Looks good, thanks.

> ---
>  fs/btrfs/extent-tree.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 85ee5c79759d..098e64106d02 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -495,7 +495,7 @@ static noinline int lookup_extent_data_ref(struct btrfs_trans_handle *trans,
>                 btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
>                 if (key.objectid != bytenr ||
>                     key.type != BTRFS_EXTENT_DATA_REF_KEY)
> -                       return ret;
> +                       return -ENOENT;
>
>                 ref = btrfs_item_ptr(leaf, path->slots[0],
>                                      struct btrfs_extent_data_ref);
> --
> 2.43.0
>
>
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