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| author |   Mike Snitzer <snitzer@redhat.com> | 2020-11-30 10:57:43 -0500 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2020-12-04 14:53:15 -0500 |
| commit | 3ee16db390b42b8a21f2ad2ea2518f3469c6e532 (patch) | |
| tree | 2a34d72f6ef06b6708c8ae56577baa2c9506002b /drivers/md/dm-table.c | |
| parent | dm writecache: remove BUG() and fail gracefully instead (diff) | |
| download | linux-dev-3ee16db390b42b8a21f2ad2ea2518f3469c6e532.tar.xz linux-dev-3ee16db390b42b8a21f2ad2ea2518f3469c6e532.zip | |
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.c | 5 |
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); |