On Wed, Aug 28, 2024 at 08:11:03AM +0300, Christoph Hellwig wrote:
> For I/O to reflinked blocks we always need to write an entire new
> file system block, and the code enforces the file system block alignment
> for the entire file if it has any reflinked blocks.
>
> Use the new STATX_DIO_READ_ALIGN flag to report the asymmetric read
> vs write alignments for reflinked files.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/xfs/xfs_iops.c | 37 +++++++++++++++++++++++++++++--------
> 1 file changed, 29 insertions(+), 8 deletions(-)
>
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 1cdc8034f54d93..de2fc12688dc23 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -570,6 +570,33 @@ xfs_stat_blksize(
> return PAGE_SIZE;
> }
>
> +static void
> +xfs_report_dioalign(
> + struct xfs_inode *ip,
> + struct kstat *stat)
> +{
> + struct xfs_buftarg *target = xfs_inode_buftarg(ip);
> + struct block_device *bdev = target->bt_bdev;
> +
> + stat->result_mask |= STATX_DIOALIGN | STATX_DIO_READ_ALIGN;
> + stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
> + stat->dio_read_offset_align = bdev_logical_block_size(bdev);
> +
> + /*
> + * On COW inodes we are forced to always rewrite an entire file system
> + * block.
> + *
> + * Because applications assume they can do sector sized direct writes
> + * on XFS we provide an emulation by doing a read-modify-write cycle
> + * through the cache, but that is highly inefficient. Thus report the
> + * natively supported size here.
> + */
> + if (xfs_is_cow_inode(ip))
> + stat->dio_offset_align = ip->i_mount->m_sb.sb_blocksize;
xfs_inode_alloc_unitsize(), since we can only cow full allocation units.
(Not necessary today, but we might as well make it work for rtreflink
from the start.)
--D
> + else
> + stat->dio_offset_align = stat->dio_read_offset_align;
> +}
> +
> STATIC int
> xfs_vn_getattr(
> struct mnt_idmap *idmap,
> @@ -635,14 +662,8 @@ xfs_vn_getattr(
> stat->rdev = inode->i_rdev;
> break;
> case S_IFREG:
> - if (request_mask & STATX_DIOALIGN) {
> - struct xfs_buftarg *target = xfs_inode_buftarg(ip);
> - struct block_device *bdev = target->bt_bdev;
> -
> - stat->result_mask |= STATX_DIOALIGN;
> - stat->dio_mem_align = bdev_dma_alignment(bdev) + 1;
> - stat->dio_offset_align = bdev_logical_block_size(bdev);
> - }
> + if (request_mask & (STATX_DIOALIGN | STATX_DIO_READ_ALIGN))
> + xfs_report_dioalign(ip, stat);
> fallthrough;
> default:
> stat->blksize = xfs_stat_blksize(ip);
> --
> 2.43.0
>
>
