blkcg: shoot down blkgs if all policies are deactivated

There's no reason to keep blkgs around if no policy is activated for the queue. This patch moves queue locking out of blkg_destroy_all() and call it from blkg_deactivate_policy() on deactivation of the last policy on the queue. This change was suggested by Vivek. Signed-off-by: Tejun Heo <[email protected]> Cc: Vivek Goyal <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
Chm · Apr 20, 2012 · 6d18b00 · 6d18b00
1 parent 3c96cb3
commit 6d18b00
Showing 1 changed file with 8 additions and 3 deletions.
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
@@ -258,7 +258,7 @@ static void blkg_destroy_all(struct request_queue *q)
 {
 	struct blkio_group *blkg, *n;
 
-	spin_lock_irq(q->queue_lock);
+	lockdep_assert_held(q->queue_lock);
 
 	list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
 		struct blkio_cgroup *blkcg = blkg->blkcg;
@@ -267,8 +267,6 @@ static void blkg_destroy_all(struct request_queue *q)
 		blkg_destroy(blkg);
 		spin_unlock(&blkcg->lock);
 	}
-
-	spin_unlock_irq(q->queue_lock);
 }
 
 static void blkg_rcu_free(struct rcu_head *rcu_head)
@@ -646,7 +644,10 @@ void blkcg_drain_queue(struct request_queue *q)
  */
 void blkcg_exit_queue(struct request_queue *q)
 {
+	spin_lock_irq(q->queue_lock);
 	blkg_destroy_all(q);
+	spin_unlock_irq(q->queue_lock);
+
 	blk_throtl_exit(q);
 }
 
@@ -802,6 +803,10 @@ void blkcg_deactivate_policy(struct request_queue *q,
 
 	__clear_bit(pol->plid, q->blkcg_pols);
 
+	/* if no policy is left, no need for blkgs - shoot them down */
+	if (bitmap_empty(q->blkcg_pols, BLKCG_MAX_POLS))
+		blkg_destroy_all(q);
+
 	list_for_each_entry(blkg, &q->blkg_list, q_node) {
 		/* grab blkcg lock too while removing @pd from @blkg */
 		spin_lock(&blkg->blkcg->lock);