md,rcu: Convert call_rcu(free_conf) to kfree_rcu()

The rcu callback free_conf() just calls a kfree(),
so we use kfree_rcu() instead of the call_rcu(free_conf).
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: NeilBrown <neilb@suse.de>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

drivers/md/linear.c

@@ -213,12 +213,6 @@ static int linear_run (mddev_t *mddev)
 	return md_integrity_register(mddev);
 }
 
-static void free_conf(struct rcu_head *head)
-{
-	linear_conf_t *conf = container_of(head, linear_conf_t, rcu);
-	kfree(conf);
-}
-
 static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
 {
 	/* Adding a drive to a linear array allows the array to grow.
@@ -247,7 +241,7 @@ static int linear_add(mddev_t *mddev, mdk_rdev_t *rdev)
 	md_set_array_sectors(mddev, linear_size(mddev, 0, 0));
 	set_capacity(mddev->gendisk, mddev->array_sectors);
 	revalidate_disk(mddev->gendisk);
-	call_rcu(&oldconf->rcu, free_conf);
+	kfree_rcu(oldconf, rcu);
 	return 0;
 }