Re: [PATCH v4 4/9] xfs: clamp a pNFS LAYOUTCOMMIT extent before computing its end

["Pankaj Raghav (Samsung)" <pankaj.raghav@linux.dev>]

On Tue, Oct 20, 2026 at 12:08:47PM +0900, Daejun Park wrote:
> xfs_fs_commit_blocks() clamps the end of each committed extent to the
> file size, but computes the end as offset + length first. A length
> from the client can make that sum wrap around, and the loop then
> passes the client's length, unclamped, to xfs_iomap_write_unwritten().
> The range wraps there as well, and xfs_bmapi_write() maps nothing.
> Before the previous two patches, that failed an assertion on XFS_DEBUG
> kernels, which is a BUG with XFS_ASSERT_FATAL, and otherwise returned
> -ENOSR, which nfsd warns about as a non-standard errno. With
> XFS_BMAPI_CONVERT_ONLY, the LAYOUTCOMMIT fails with -EIO and converts
> nothing, even when every block up to the size is allocated.
> 
> With pynfs as the client and an RW layout for the first 64 KiB of a
> 2 MiB sparse file, a LAYOUTCOMMIT of 2^64 - 4 KiB at 4 KiB got
> NFS4ERR_IO, "nfsd: non-standard errno: -63" and a WARNING, or the
> assertion on XFS_DEBUG. With the previous two patches, it gets
> NFS4ERR_IO and the laid-out range stays unwritten.
> 
> Clamp the length to what is left below the size before adding it to
> the offset. The extent then ends at the size, its allocated part is
> converted, and the LAYOUTCOMMIT gets NFS4ERR_IO at the hole after it.
> 
> Fixes: 527851124d10 ("xfs: implement pNFS export operations")
> Cc: stable@vger.kernel.org
> Signed-off-by: Daejun Park <daejun7.park@samsung.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_pnfs.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
Looks good.
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>

-- 
Pankaj