On Mon, Sep 30, 2024 at 12:54:36PM +0000, John Garry wrote:
> Support providing info on atomic write unit min and max for an inode.
>
> For simplicity, currently we limit the min at the FS block size. As for
> max, we limit also at FS block size, as there is no current method to
> guarantee extent alignment or granularity for regular files.
>
> Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
> ---
> fs/xfs/xfs_inode.h | 17 +++++++++++++++++
> fs/xfs/xfs_iops.c | 24 ++++++++++++++++++++++++
> 2 files changed, 41 insertions(+)
>
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index 1c62ee294a5a..1ea73402d592 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -332,6 +332,23 @@ static inline bool xfs_inode_has_atomicwrites(struct xfs_inode *ip)
> return ip->i_diflags2 & XFS_DIFLAG2_ATOMICWRITES;
> }
>
> +static inline bool
> +xfs_inode_can_atomicwrite(
> + struct xfs_inode *ip)
> +{
> + struct xfs_mount *mp = ip->i_mount;
> + struct xfs_buftarg *target = xfs_inode_buftarg(ip);
> +
> + if (!xfs_inode_has_atomicwrites(ip))
> + return false;
> + if (mp->m_sb.sb_blocksize < target->bt_bdev_awu_min)
> + return false;
> + if (mp->m_sb.sb_blocksize > target->bt_bdev_awu_max)
> + return false;
> +
> + return true;
> +}
> +
> /*
> * In-core inode flags.
> */
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index ee79cf161312..915d057db9bb 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -570,6 +570,23 @@ xfs_stat_blksize(
> return max_t(uint32_t, PAGE_SIZE, mp->m_sb.sb_blocksize);
> }
>
> +static void
> +xfs_get_atomic_write_attr(
> + struct xfs_inode *ip,
> + unsigned int *unit_min,
> + unsigned int *unit_max)
> +{
> + struct xfs_mount *mp = ip->i_mount;
> + struct xfs_sb *sbp = &mp->m_sb;
> +
> + if (!xfs_inode_can_atomicwrite(ip)) {
> + *unit_min = *unit_max = 0;
> + return;
> + }
> +
> + *unit_min = *unit_max = sbp->sb_blocksize;
Ok, so we're only supporting untorn writes if they're exactly the fs
blocksize, and 1 fsblock is between awu_min/max. That simplifies a lot
of things. :)
Not supporting sub-fsblock atomic writes means that we'll never hit the
directio COW fallback code, which uses the pagecache.
Not supporting multi-fsblock atomic writes means that you don't have to
figure out how to ensure that we always do cow on forcealign
granularity. Though as I pointed out elsewhere in this thread, that's a
forcealign problem.
Yay! ;)
> +}
> +
> STATIC int
> xfs_vn_getattr(
> struct mnt_idmap *idmap,
> @@ -643,6 +660,13 @@ xfs_vn_getattr(
> stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
> stat->dio_offset_align = bdev_logical_block_size(bdev);
> }
> + if (request_mask & STATX_WRITE_ATOMIC) {
> + unsigned int unit_min, unit_max;
> +
> + xfs_get_atomic_write_attr(ip, &unit_min, &unit_max);
> + generic_fill_statx_atomic_writes(stat,
> + unit_min, unit_max);
Consistent indenting and wrapping, please:
xfs_get_atomic_write_attr(ip, &unit_min,
&unit_max);
generic_fill_statx_atomic_writes(stat,
unit_min, unit_max);
With that fixed,
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> + }
> fallthrough;
> default:
> stat->blksize = xfs_stat_blksize(ip);
> --
> 2.31.1
>
>
