Re: [PATCH 21/43] xfs: don't call xfs_can_free_eofblocks from ->release for zoned inodes

Darrick J. Wong
2024-12-12T22:15:24Z

On Wed, Dec 11, 2024 at 09:54:46AM +0100, Christoph Hellwig wrote:
> Zoned file systems require out of place writes and thus can't support
> post-EOF speculative preallocations. Avoid the pointless ilock critical
> section to find out that none can be freed.

I wonder if this is true of alwayscow inodes in general, not just zoned
inodes?

> Signed-off-by: Christoph Hellwig <hch@lst.de>

Anyway that makes sense to me, so
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
> fs/xfs/xfs_file.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 27301229011b..827f7819df6a 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1356,15 +1356,22 @@ xfs_file_release(
> * blocks. This avoids open/read/close workloads from removing EOF
> * blocks that other writers depend upon to reduce fragmentation.
> *
> + * Inodes on the zoned RT device never have preallocations, so skip
> + * taking the locks below.
> + */
> + if (!inode->i_nlink ||
> + !(file->f_mode & FMODE_WRITE) ||
> + (ip->i_diflags & XFS_DIFLAG_APPEND) ||
> + xfs_is_zoned_inode(ip))
> + return 0;
> +
> + /*
> * If we can't get the iolock just skip truncating the blocks past EOF
> * because we could deadlock with the mmap_lock otherwise. We'll get
> * another chance to drop them once the last reference to the inode is
> * dropped, so we'll never leak blocks permanently.
> */
> - if (inode->i_nlink &&
> - (file->f_mode & FMODE_WRITE) &&
> - !(ip->i_diflags & XFS_DIFLAG_APPEND) &&
> - !xfs_iflags_test(ip, XFS_EOFBLOCKS_RELEASED) &&
> + if (!xfs_iflags_test(ip, XFS_EOFBLOCKS_RELEASED) &&
> xfs_ilock_nowait(ip, XFS_IOLOCK_EXCL)) {
> if (xfs_can_free_eofblocks(ip) &&
> !xfs_iflags_test_and_set(ip, XFS_EOFBLOCKS_RELEASED))
> --
> 2.45.2
>
>