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authorMike Snitzer <snitzer@redhat.com>2020-11-30 18:57:43 +0300
committerMike Snitzer <snitzer@redhat.com>2020-12-04 22:53:15 +0300
commit3ee16db390b42b8a21f2ad2ea2518f3469c6e532 (patch)
tree2a34d72f6ef06b6708c8ae56577baa2c9506002b /drivers/md/dm-table.c
parent857c4c0a8b2888d806f4308c58f59a6a81a1dee9 (diff)
downloadlinux-3ee16db390b42b8a21f2ad2ea2518f3469c6e532.tar.xz
dm: fix IO splitting
Commit 882ec4e609c1 ("dm table: stack 'chunk_sectors' limit to account for target-specific splitting") caused a couple regressions: 1) Using lcm_not_zero() when stacking chunk_sectors was a bug because chunk_sectors must reflect the most limited of all devices in the IO stack. 2) DM targets that set max_io_len but that do _not_ provide an .iterate_devices method no longer had there IO split properly. And commit 5091cdec56fa ("dm: change max_io_len() to use blk_max_size_offset()") also caused a regression where DM no longer supported varied (per target) IO splitting. The implication being the potential for severely reduced performance for IO stacks that use a DM target like dm-cache to hide performance limitations of a slower device (e.g. one that requires 4K IO splitting). Coming full circle: Fix all these issues by discontinuing stacking chunk_sectors up using ti->max_io_len in dm_calculate_queue_limits(), add optional chunk_sectors override argument to blk_max_size_offset() and update DM's max_io_len() to pass ti->max_io_len to its blk_max_size_offset() call. Passing in an optional chunk_sectors override to blk_max_size_offset() allows for code reuse of block's centralized calculation for max IO size based on provided offset and split boundary. Fixes: 882ec4e609c1 ("dm table: stack 'chunk_sectors' limit to account for target-specific splitting") Fixes: 5091cdec56fa ("dm: change max_io_len() to use blk_max_size_offset()") Cc: stable@vger.kernel.org Reported-by: John Dorminy <jdorminy@redhat.com> Reported-by: Bruce Johnston <bjohnsto@redhat.com> Reported-by: Kirill Tkhai <ktkhai@virtuozzo.com> Reviewed-by: John Dorminy <jdorminy@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Reviewed-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/md/dm-table.c')
-rw-r--r--drivers/md/dm-table.c5
1 files changed, 0 insertions, 5 deletions
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 2073ee8d18f4..7eeb7c4169c9 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -18,7 +18,6 @@
#include <linux/mutex.h>
#include <linux/delay.h>
#include <linux/atomic.h>
-#include <linux/lcm.h>
#include <linux/blk-mq.h>
#include <linux/mount.h>
#include <linux/dax.h>
@@ -1449,10 +1448,6 @@ int dm_calculate_queue_limits(struct dm_table *table,
zone_sectors = ti_limits.chunk_sectors;
}
- /* Stack chunk_sectors if target-specific splitting is required */
- if (ti->max_io_len)
- ti_limits.chunk_sectors = lcm_not_zero(ti->max_io_len,
- ti_limits.chunk_sectors);
/* Set I/O hints portion of queue limits */
if (ti->type->io_hints)
ti->type->io_hints(ti, &ti_limits);