On 01/21/2014 05:46 PM, Eric Sandeen wrote:
> Some time ago, mkfs.xfs started picking the storage physical
> sector size as the default filesystem "sector size" in order
> to avoid RMW costs incurred by doing IOs at logical sector
> size alignments.
>
> However, this means that for a filesystem made with i.e.
> a 4k sector size on an "advanced format" 4k/512 disk,
> 512-byte direct IOs are no longer allowed. This means
> that XFS has essentially turned this AF drive into a hard
> 4K device, from the filesystem on up.
>
> XFS's mkfs-specified "sector size" is really just controlling
> the minimum size & alignment of filesystem metadata.
>
> There is no real need to tightly couple XFS's minimal
> metadata size to the minimum allowed direct IO size;
> XFS can continue doing metadata in optimal sizes, but
> still allow smaller DIOs for apps which issue them,
> for whatever reason.
>
> This patch adds a new field to the xfs_buftarg, so that
> we now track 2 sizes:
>
> 1) The metadata sector size, which is the minimum unit and
> alignment of IO which will be performed by metadata operations.
> 2) The device logical sector size
>
> The first is used internally by the file system for metadata
> alignment and IOs.
> The second is used for the minimum allowed direct IO alignment.
>
> This has passed xfstests on filesystems made with 4k sectors,
> including when run under the patch I sent to ignore
> XFS_IOC_DIOINFO, and issue 512 DIOs anyway. I also directly
> tested end of block behavior on preallocated, sparse, and
> existing files when we do a 512 IO into a 4k file on a
> 4k-sector filesystem, to be sure there were no unexpected
> behaviors.
>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
Looks good to me...
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index a526f8d..5175711 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -1599,6 +1599,7 @@ xfs_setsize_buftarg(
> unsigned int blocksize,
> unsigned int sectorsize)
> {
> + /* Set up metadata sector size info */
> btp->bt_meta_sectorsize = sectorsize;
> btp->bt_meta_sectormask = sectorsize - 1;
>
> @@ -1613,6 +1614,10 @@ xfs_setsize_buftarg(
> return EINVAL;
> }
>
> + /* Set up device logical sector size mask */
> + btp->bt_logical_sectorsize = bdev_logical_block_size(btp->bt_bdev);
> + btp->bt_logical_sectormask = bdev_logical_block_size(btp->bt_bdev) - 1;
> +
> return 0;
> }
>
> diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
> index d5d88dd..9953395 100644
> --- a/fs/xfs/xfs_buf.h
> +++ b/fs/xfs/xfs_buf.h
> @@ -88,6 +88,19 @@ typedef unsigned int xfs_buf_flags_t;
> */
> #define XFS_BSTATE_DISPOSE (1 << 0) /* buffer being discarded */
>
> +/*
> + * The xfs_buftarg contains 2 notions of "sector size" -
> + *
> + * 1) The metadata sector size, which is the minimum unit and
> + * alignment of IO which will be performed by metadata operations.
> + * 2) The device logical sector size
> + *
> + * The first is specified at mkfs time, and is stored on-disk in the
> + * superblock's sb_sectsize.
> + *
> + * The latter is derived from the underlying device, and controls direct IO
> + * alignment constraints.
> + */
> typedef struct xfs_buftarg {
> dev_t bt_dev;
> struct block_device *bt_bdev;
> @@ -95,6 +108,8 @@ typedef struct xfs_buftarg {
> struct xfs_mount *bt_mount;
> unsigned int bt_meta_sectorsize;
> size_t bt_meta_sectormask;
> + size_t bt_logical_sectorsize;
> + size_t bt_logical_sectormask;
>
> /* LRU control structures */
> struct shrinker bt_shrinker;
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index ef0c933..57725b4 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -261,7 +261,8 @@ xfs_file_aio_read(
> xfs_buftarg_t *target =
> XFS_IS_REALTIME_INODE(ip) ?
> mp->m_rtdev_targp : mp->m_ddev_targp;
> - if ((pos | size) & target->bt_meta_sectormask) {
> + /* DIO must be aligned to device logical sector size */
> + if ((pos | size) & target->bt_logical_sectormask) {
> if (pos == i_size_read(inode))
> return 0;
> return -XFS_ERROR(EINVAL);
> @@ -641,9 +642,11 @@ xfs_file_dio_aio_write(
> struct xfs_buftarg *target = XFS_IS_REALTIME_INODE(ip) ?
> mp->m_rtdev_targp : mp->m_ddev_targp;
>
> - if ((pos | count) & target->bt_meta_sectormask)
> + /* DIO must be aligned to device logical sector size */
> + if ((pos | count) & target->bt_logical_sectormask)
> return -XFS_ERROR(EINVAL);
>
> + /* "unaligned" here means not aligned to a filesystem block */
> if ((pos & mp->m_blockmask) || ((pos + count) & mp->m_blockmask))
> unaligned_io = 1;
>
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 64ca8e9..f7ac335 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1587,7 +1587,7 @@ xfs_file_ioctl(
> XFS_IS_REALTIME_INODE(ip) ?
> mp->m_rtdev_targp : mp->m_ddev_targp;
>
> - da.d_mem = da.d_miniosz = target->bt_meta_sectorsize;
> + da.d_mem = da.d_miniosz = target->bt_logical_sectorsize;
> da.d_maxiosz = INT_MAX & ~(da.d_miniosz - 1);
>
> if (copy_to_user(arg, &da, sizeof(da)))
>
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> http://oss.sgi.com/mailman/listinfo/xfs
>
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