1 files changed, 41 insertions, 55 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index c3226ce..2a4f77f 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -235,13 +235,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 	blkg->online = true;
 	spin_unlock(&blkcg->lock);
 
-	if (!ret) {
-		if (blkcg == &blkcg_root) {
-			q->root_blkg = blkg;
-			q->root_rl.blkg = blkg;
-		}
+	if (!ret)
 		return blkg;
-	}
 
 	/* @blkg failed fully initialized, use the usual release path */
 	blkg_put(blkg);
@@ -340,15 +335,6 @@ static void blkg_destroy(struct blkcg_gq *blkg)
 		rcu_assign_pointer(blkcg->blkg_hint, NULL);
 
 	/*
-	 * If root blkg is destroyed.  Just clear the pointer since root_rl
-	 * does not take reference on root blkg.
-	 */
-	if (blkcg == &blkcg_root) {
-		blkg->q->root_blkg = NULL;
-		blkg->q->root_rl.blkg = NULL;
-	}
-
-	/*
 	 * Put the reference taken at the time of creation so that when all
 	 * queues are gone, group can be destroyed.
 	 */
@@ -855,9 +841,45 @@ done:
  */
 int blkcg_init_queue(struct request_queue *q)
 {
-	might_sleep();
+	struct blkcg_gq *new_blkg, *blkg;
+	bool preloaded;
+	int ret;
+
+	new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
+	if (!new_blkg)
+		return -ENOMEM;
+
+	preloaded = !radix_tree_preload(GFP_KERNEL);
 
-	return blk_throtl_init(q);
+	/*
+	 * Make sure the root blkg exists and count the existing blkgs.  As
+	 * @q is bypassing at this point, blkg_lookup_create() can't be
+	 * used.  Open code insertion.
+	 */
+	rcu_read_lock();
+	spin_lock_irq(q->queue_lock);
+	blkg = blkg_create(&blkcg_root, q, new_blkg);
+	spin_unlock_irq(q->queue_lock);
+	rcu_read_unlock();
+
+	if (preloaded)
+		radix_tree_preload_end();
+
+	if (IS_ERR(blkg)) {
+		kfree(new_blkg);
+		return PTR_ERR(blkg);
+	}
+
+	q->root_blkg = blkg;
+	q->root_rl.blkg = blkg;
+
+	ret = blk_throtl_init(q);
+	if (ret) {
+		spin_lock_irq(q->queue_lock);
+		blkg_destroy_all(q);
+		spin_unlock_irq(q->queue_lock);
+	}
+	return ret;
 }
 
 /**
@@ -958,52 +980,20 @@ int blkcg_activate_policy(struct request_queue *q,
 			  const struct blkcg_policy *pol)
 {
 	LIST_HEAD(pds);
-	struct blkcg_gq *blkg, *new_blkg;
+	struct blkcg_gq *blkg;
 	struct blkg_policy_data *pd, *n;
 	int cnt = 0, ret;
-	bool preloaded;
 
 	if (blkcg_policy_enabled(q, pol))
 		return 0;
 
-	/* preallocations for root blkg */
-	new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
-	if (!new_blkg)
-		return -ENOMEM;
-
+	/* count and allocate policy_data for all existing blkgs */
 	blk_queue_bypass_start(q);
-
-	preloaded = !radix_tree_preload(GFP_KERNEL);
-
-	/*
-	 * Make sure the root blkg exists and count the existing blkgs.  As
-	 * @q is bypassing at this point, blkg_lookup_create() can't be
-	 * used.  Open code it.
-	 */
 	spin_lock_irq(q->queue_lock);
-
-	rcu_read_lock();
-	blkg = __blkg_lookup(&blkcg_root, q, false);
-	if (blkg)
-		blkg_free(new_blkg);
-	else
-		blkg = blkg_create(&blkcg_root, q, new_blkg);
-	rcu_read_unlock();
-
-	if (preloaded)
-		radix_tree_preload_end();
-
-	if (IS_ERR(blkg)) {
-		ret = PTR_ERR(blkg);
-		goto out_unlock;
-	}
-
 	list_for_each_entry(blkg, &q->blkg_list, q_node)
 		cnt++;
-
 	spin_unlock_irq(q->queue_lock);
 
-	/* allocate policy_data for all existing blkgs */
 	while (cnt--) {
 		pd = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);
 		if (!pd) {
@@ -1072,10 +1062,6 @@ 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);