dm: free table mempools if not used in __bind

With request-based dm, the mempools don't need reloading when switching
tables, but the unused table mempools are not freed until the active
table is finally freed. Free them immediately if they are not needed.

Fixes: 29dec90 ("dm: fix bio_set allocation")
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Tested-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

Author: bmarzins

drivers/md/dm.c

@@ -2461,10 +2461,10 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
 		 * requests in the queue may refer to bio from the old bioset,
 		 * so you must walk through the queue to unprep.
 		 */
-		if (!md->mempools) {
+		if (!md->mempools)
 			md->mempools = t->mempools;
-			t->mempools = NULL;
-		}
+		else
+			dm_free_md_mempools(t->mempools);
 	} else {
 		/*
 		 * The md may already have mempools that need changing.
@@ -2473,8 +2473,8 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
 		 */
 		dm_free_md_mempools(md->mempools);
 		md->mempools = t->mempools;
-		t->mempools = NULL;
 	}
+	t->mempools = NULL;
 
 	old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
 	rcu_assign_pointer(md->map, (void *)t);