Re: [PATCH v5 8/8] xfs: support STATX_DIOALIGN

[Darrick J. Wong]

On Fri, Aug 26, 2022 at 11:58:51PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
> 
> Add support for STATX_DIOALIGN to xfs, so that direct I/O alignment
> restrictions are exposed to userspace in a generic way.
> 
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>

Looks good to me; I particularly like the adjustment to report the
device's DMA alignment.  Someone should probably fix DIONINFO, or
perhaps turn it into a getattr wrapper and hoist it?  IMHO none of those
suggestions are necessary to land this patch, though.

Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>

--D

> ---
>  fs/xfs/xfs_iops.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 45518b8c613c9a..f51c60d7e2054a 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -604,6 +604,16 @@ xfs_vn_getattr(
>  		stat->blksize = BLKDEV_IOSIZE;
>  		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);
> +		}
> +		fallthrough;
>  	default:
>  		stat->blksize = xfs_stat_blksize(ip);
>  		stat->rdev = 0;
> -- 
> 2.37.2
>