Re: [PATCH] btrfs: fix inline reflink deadlock at non-zero offset

[Filipe Manana]

On Mon, Jun 1, 2026 at 3:23 PM Guangshuo Li <lgs201920130244@xxxxxxxxx> wrote:
>
> clone_copy_inline_extent() can copy an inline extent into a page of the
> destination inode before starting a transaction. If that page is beyond
> EOF, writeback started by a transaction commit with flushoncommit can
> invalidate the folio and block on the same extent range lock held by the
> reflink task, while the reflink task waits to start a transaction.
>
> The copy_to_page path already updates i_size after copy_inline_to_page(),
> so writeback no longer treats the copied page as beyond EOF. However,
> clone_copy_inline_extent() has an earlier new_key->offset > 0 path that
> also calls copy_inline_to_page() and then goes to out, where it starts a
> transaction. That path still leaves i_size unchanged before starting the
> transaction.
>
> Update i_size after a successful copy_inline_to_page() in the early
> non-zero offset path as well, matching the existing copy_to_page path.
>
> Fixes: 05a5a7621ce66 ("Btrfs: implement full reflink support for inline extents")
> Signed-off-by: Guangshuo Li <lgs201920130244@xxxxxxxxx>
> ---
>  fs/btrfs/reflink.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
> index 49865a463780..5722cccb53eb 100644
> --- a/fs/btrfs/reflink.c
> +++ b/fs/btrfs/reflink.c
> @@ -185,6 +185,8 @@ static int clone_copy_inline_extent(struct btrfs_inode *inode,
>         if (new_key->offset > 0) {
>                 ret = copy_inline_to_page(inode, new_key->offset,
>                                           inline_data, size, datal, comp_type);
> +               if (ret == 0 && new_key->offset + datal > i_size_read(&inode->vfs_inode))
> +                       i_size_write(&inode->vfs_inode, new_key->offset + datal);

Please don't copy code without an explanation.

This was already fixed here:

https://lore.kernel.org/linux-btrfs/cbaede508d12a0bd0ef9ec1b49f8338fc46a07fb.1779803705.git.fdmanana@xxxxxxxx/

Thanks.

>                 goto out;
>         }
>
> --
> 2.43.0
>
>