Commit 825d8bbd authored by Mike Snitzer's avatar Mike Snitzer
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dm: always manage discard support in terms of max_hw_discard_sectors 



Commit 4f563a64 ("block: add a max_user_discard_sectors queue
limit") changed block core to set max_discard_sectors to:
 min(lim->max_hw_discard_sectors, lim->max_user_discard_sectors)

Since commit 1c0e7202 ("dm: use queue_limits_set") it was reported
dm-thinp was failing in a few fstests (generic/347 and generic/405)
with the first WARN_ON_ONCE in dm_cell_key_has_valid_range() being
reported, e.g.:
WARNING: CPU: 1 PID: 30 at drivers/md/dm-bio-prison-v1.c:128 dm_cell_key_has_valid_range+0x3d/0x50

blk_set_stacking_limits() sets max_user_discard_sectors to UINT_MAX,
so given how block core now sets max_discard_sectors (detailed above)
it follows that blk_stack_limits() stacks up the underlying device's
max_hw_discard_sectors and max_discard_sectors is set to match it. If
max_hw_discard_sectors exceeds dm's BIO_PRISON_MAX_RANGE, then
dm_cell_key_has_valid_range() will trigger the warning with:
WARN_ON_ONCE(key->block_end - key->block_begin > BIO_PRISON_MAX_RANGE)

Aside from this warning, the discard will fail.  Fix this and other DM
issues by governing discard support in terms of max_hw_discard_sectors
instead of max_discard_sectors.

Reported-by: default avatarTheodore Ts'o <tytso@mit.edu>
Fixes: 1c0e7202 ("dm: use queue_limits_set")
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent 69381cf8

drivers/md/dm-cache-target.c

+2 −3
Original line number Diff line number Diff line
@@ -3394,7 +3394,7 @@ static void set_discard_limits(struct cache *cache, struct queue_limits *limits) 


	if (!cache->features.discard_passdown) {

		/* No passdown is done so setting own virtual limits */

		limits->max_discard_sectors = min_t(sector_t, cache->discard_block_size * 1024,

		limits->max_hw_discard_sectors = min_t(sector_t, cache->discard_block_size * 1024,

						       cache->origin_sectors);

		limits->discard_granularity = cache->discard_block_size << SECTOR_SHIFT;

		return;
@@ -3404,7 +3404,6 @@ static void set_discard_limits(struct cache *cache, struct queue_limits *limits) 
	 * cache_iterate_devices() is stacking both origin and fast device limits

	 * but discards aren't passed to fast device, so inherit origin's limits.

	 */

	limits->max_discard_sectors = origin_limits->max_discard_sectors;

	limits->max_hw_discard_sectors = origin_limits->max_hw_discard_sectors;

	limits->discard_granularity = origin_limits->discard_granularity;

	limits->discard_alignment = origin_limits->discard_alignment;

drivers/md/dm-clone-target.c

+2 −2
Original line number Diff line number Diff line
@@ -2050,7 +2050,8 @@ static void set_discard_limits(struct clone *clone, struct queue_limits *limits) 
	if (!test_bit(DM_CLONE_DISCARD_PASSDOWN, &clone->flags)) {

		/* No passdown is done so we set our own virtual limits */

		limits->discard_granularity = clone->region_size << SECTOR_SHIFT;

		limits->max_discard_sectors = round_down(UINT_MAX >> SECTOR_SHIFT, clone->region_size);

		limits->max_hw_discard_sectors = round_down(UINT_MAX >> SECTOR_SHIFT,

							    clone->region_size);

		return;

	}
@@ -2059,7 +2060,6 @@ static void set_discard_limits(struct clone *clone, struct queue_limits *limits) 
	 * device limits but discards aren't passed to the source device, so

	 * inherit destination's limits.

	 */

	limits->max_discard_sectors = dest_limits->max_discard_sectors;

	limits->max_hw_discard_sectors = dest_limits->max_hw_discard_sectors;

	limits->discard_granularity = dest_limits->discard_granularity;

	limits->discard_alignment = dest_limits->discard_alignment;

drivers/md/dm-log-writes.c

+1 −1
Original line number Diff line number Diff line
@@ -871,7 +871,7 @@ static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limit 
	if (!bdev_max_discard_sectors(lc->dev->bdev)) {

		lc->device_supports_discard = false;

		limits->discard_granularity = lc->sectorsize;

		limits->max_discard_sectors = (UINT_MAX >> SECTOR_SHIFT);

		limits->max_hw_discard_sectors = (UINT_MAX >> SECTOR_SHIFT);

	}

	limits->logical_block_size = bdev_logical_block_size(lc->dev->bdev);

	limits->physical_block_size = bdev_physical_block_size(lc->dev->bdev);

drivers/md/dm-snap.c

+1 −1
Original line number Diff line number Diff line
@@ -2410,7 +2410,7 @@ static void snapshot_io_hints(struct dm_target *ti, struct queue_limits *limits) 


		/* All discards are split on chunk_size boundary */

		limits->discard_granularity = snap->store->chunk_size;

		limits->max_discard_sectors = snap->store->chunk_size;

		limits->max_hw_discard_sectors = snap->store->chunk_size;



		up_read(&_origins_lock);

	}

drivers/md/dm-target.c

+0 −1
Original line number Diff line number Diff line
@@ -249,7 +249,6 @@ static int io_err_iterate_devices(struct dm_target *ti, 


static void io_err_io_hints(struct dm_target *ti, struct queue_limits *limits)

{

	limits->max_discard_sectors = UINT_MAX;

	limits->max_hw_discard_sectors = UINT_MAX;

	limits->discard_granularity = 512;

}