dm cache: set minimum_io_size to cache's data block size

Before, if the block layer's limit stacking didn't establish an
optimal_io_size that was compatible with the cache's data block size
we'd set optimal_io_size to the data block size and minimum_io_size to 0
(which the block layer adjusts to be physical_block_size).

Update cache_io_hints() to set both minimum_io_size and optimal_io_size
to the cache's data block size.  This fixes an issue where mkfs.xfs
would create more XFS Allocation Groups on cache volumes than on a
normal linear LV of comparable size.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index a54108e..1af40ee 100644 (file)
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -3094,7 +3094,7 @@ static void cache_io_hints(struct dm_target *ti, struct queue_limits *limits)
         */
        if (io_opt_sectors < cache->sectors_per_block ||
            do_div(io_opt_sectors, cache->sectors_per_block)) {
-               blk_limits_io_min(limits, 0);
+               blk_limits_io_min(limits, cache->sectors_per_block << SECTOR_SHIFT);
                blk_limits_io_opt(limits, cache->sectors_per_block << SECTOR_SHIFT);
        }
        set_discard_limits(cache, limits);