Commit 06961c48 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm: split discards further if target sets max_discard_granularity 



The block core (bio_split_discard) will already split discards based
on the 'discard_granularity' and 'max_discard_sectors' queue_limits.
But the DM thin target also needs to ensure that it doesn't receive a
discard that spans a 'max_discard_sectors' boundary.

Introduce a dm_target 'max_discard_granularity' flag that if set will
cause DM core to split discard bios relative to 'max_discard_sectors'.
This treats 'discard_granularity' as a "min_discard_granularity" and
'max_discard_sectors' as a "max_discard_granularity".

Requested-by: default avatarJoe Thornber <ejt@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent bb46c561

drivers/md/dm.c

+19 −6
Original line number Diff line number Diff line
@@ -1162,7 +1162,8 @@ static inline sector_t max_io_len_target_boundary(struct dm_target *ti, 
	return ti->len - target_offset;

}



static sector_t max_io_len(struct dm_target *ti, sector_t sector)

static sector_t __max_io_len(struct dm_target *ti, sector_t sector,

			     unsigned int max_granularity)

{

	sector_t target_offset = dm_target_offset(ti, sector);

	sector_t len = max_io_len_target_boundary(ti, target_offset);
@@ -1173,11 +1174,16 @@ static sector_t max_io_len(struct dm_target *ti, sector_t sector) 
	 *   explains why stacked chunk_sectors based splitting via

	 *   bio_split_to_limits() isn't possible here.

	 */

	if (!ti->max_io_len)

	if (!max_granularity)

		return len;

	return min_t(sector_t, len,

		min(queue_max_sectors(ti->table->md->queue),

		    blk_chunk_sectors_left(target_offset, ti->max_io_len)));

		    blk_chunk_sectors_left(target_offset, max_granularity)));

}



static inline sector_t max_io_len(struct dm_target *ti, sector_t sector)

{

	return __max_io_len(ti, sector, ti->max_io_len);

}



int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
@@ -1565,12 +1571,13 @@ static void __send_empty_flush(struct clone_info *ci) 
}



static void __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,

					unsigned int num_bios)

					unsigned int num_bios,

					unsigned int max_granularity)

{

	unsigned int len, bios;



	len = min_t(sector_t, ci->sector_count,

		    max_io_len_target_boundary(ti, dm_target_offset(ti, ci->sector)));

		    __max_io_len(ti, ci->sector, max_granularity));



	atomic_add(num_bios, &ci->io->io_count);

	bios = __send_duplicate_bios(ci, ti, num_bios, &len);
@@ -1606,10 +1613,16 @@ static blk_status_t __process_abnormal_io(struct clone_info *ci, 
					  struct dm_target *ti)

{

	unsigned int num_bios = 0;

	unsigned int max_granularity = 0;



	switch (bio_op(ci->bio)) {

	case REQ_OP_DISCARD:

		num_bios = ti->num_discard_bios;

		if (ti->max_discard_granularity) {

			struct queue_limits *limits =

				dm_get_queue_limits(ti->table->md);

			max_granularity = limits->max_discard_sectors;

		}

		break;

	case REQ_OP_SECURE_ERASE:

		num_bios = ti->num_secure_erase_bios;
@@ -1630,7 +1643,7 @@ static blk_status_t __process_abnormal_io(struct clone_info *ci, 
	if (unlikely(!num_bios))

		return BLK_STS_NOTSUPP;



	__send_changing_extent_only(ci, ti, num_bios);

	__send_changing_extent_only(ci, ti, num_bios, max_granularity);

	return BLK_STS_OK;

}

include/linux/device-mapper.h

+6 −0
Original line number Diff line number Diff line
@@ -358,6 +358,12 @@ struct dm_target { 
	 */

	bool discards_supported:1;



	/*

	 * Set if this target requires that discards be split on both

	 * 'discard_granularity' and 'max_discard_sectors' boundaries.

	 */

	bool max_discard_granularity:1;



	/*

	 * Set if we need to limit the number of in-flight bios when swapping.

	 */

include/uapi/linux/dm-ioctl.h

+2 −2
Original line number Diff line number Diff line
@@ -286,9 +286,9 @@ enum { 
#define DM_DEV_SET_GEOMETRY	_IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)



#define DM_VERSION_MAJOR	4

#define DM_VERSION_MINOR	47

#define DM_VERSION_MINOR	48

#define DM_VERSION_PATCHLEVEL	0

#define DM_VERSION_EXTRA	"-ioctl (2022-07-28)"

#define DM_VERSION_EXTRA	"-ioctl (2023-03-01)"



/* Status bits */

#define DM_READONLY_FLAG	(1 << 0) /* In/Out */