dm table: stack 'chunk_sectors' limit to account for target-specific splitting

If target set ti->max_io_len it must be used when stacking
DM device's queue_limits to establish a 'chunk_sectors' that is
compatible with the IO stack.

By using lcm_not_zero() care is taken to avoid blindly overriding the
chunk_sectors limit stacked up by blk_stack_limits().

Depends-on: 07d098e6 ("block: allow 'chunk_sectors' to be non-power-of-2")
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-table.c

@@ -18,6 +18,7 @@
 #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>
@@ -1506,6 +1507,10 @@ 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);