Re: [PATCH v2] btrfs: send: fix is_current_inode_path() to avoid path resets for common prefixes

On Mon, 15 Jun 2026 at 19:15, <[email protected]> wrote:
> From: Filipe Manana <[email protected]>
>
> In case the current inode's path is a prefix of the given path, the helper
> is_current_inode_path() will return true, which causes the single caller
> to reset the current inode's path. While this is not a functional issue,
> it makes the caller recompute the current inode's path later. It could
> also become a problem in the future in case get new callers for
> is_current_inode_path() in more sensitive contexts.
>
> Example: the current inode path is "/foo/bar" and the path we compare
> against is "/foo/bar_xyz".
>
> Fix this by returning true only if we have exact matches.
>
> Signed-off-by: Filipe Manana <[email protected]>

This version looks good.

Reviewed-by: Daniel Vacek <[email protected]>

> ---
>
> V2: Simplify and avoid false positives in case of something like
>     "/foo/bar" vs "foo/bar/xyz".
>
>  fs/btrfs/send.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index a3c8f2d889bb..d664e470fd77 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -627,7 +627,14 @@ static inline bool is_current_inode_path(const struct send_ctx *sctx,
>  {
>         const struct fs_path *cur = &sctx->cur_inode_path;
>
> -       return (strncmp(path->start, cur->start, fs_path_len(cur)) == 0);
> +       /*
> +        * Path may be a prefix of the current inode's path, so return false if
> +        * the lengths are different.
> +        */
> +       if (fs_path_len(path) != fs_path_len(cur))
> +               return false;
> +
> +       return (strcmp(path->start, cur->start) == 0);
>  }
>
>  static struct btrfs_path *alloc_path_for_send(void)
> --
> 2.47.2
>
>