1 files changed, 132 insertions, 140 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index c630e02836a8..c8cc1cbb6370 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -76,14 +76,42 @@ static void blkg_free(struct blkcg_gq *blkg)
 		if (blkg->pd[i])
 			blkcg_policy[i]->pd_free_fn(blkg->pd[i]);
 
-	if (blkg->blkcg != &blkcg_root)
-		blk_exit_rl(blkg->q, &blkg->rl);
-
 	blkg_rwstat_exit(&blkg->stat_ios);
 	blkg_rwstat_exit(&blkg->stat_bytes);
 	kfree(blkg);
 }
 
+static void __blkg_release(struct rcu_head *rcu)
+{
+	struct blkcg_gq *blkg = container_of(rcu, struct blkcg_gq, rcu_head);
+
+	percpu_ref_exit(&blkg->refcnt);
+
+	/* release the blkcg and parent blkg refs this blkg has been holding */
+	css_put(&blkg->blkcg->css);
+	if (blkg->parent)
+		blkg_put(blkg->parent);
+
+	wb_congested_put(blkg->wb_congested);
+
+	blkg_free(blkg);
+}
+
+/*
+ * A group is RCU protected, but having an rcu lock does not mean that one
+ * can access all the fields of blkg and assume these are valid.  For
+ * example, don't try to follow throtl_data and request queue links.
+ *
+ * Having a reference to blkg under an rcu allows accesses to only values
+ * local to groups like group stats and group rate limits.
+ */
+static void blkg_release(struct percpu_ref *ref)
+{
+	struct blkcg_gq *blkg = container_of(ref, struct blkcg_gq, refcnt);
+
+	call_rcu(&blkg->rcu_head, __blkg_release);
+}
+
 /**
  * blkg_alloc - allocate a blkg
  * @blkcg: block cgroup the new blkg is associated with
@@ -110,14 +138,6 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 	blkg->q = q;
 	INIT_LIST_HEAD(&blkg->q_node);
 	blkg->blkcg = blkcg;
-	atomic_set(&blkg->refcnt, 1);
-
-	/* root blkg uses @q->root_rl, init rl only for !root blkgs */
-	if (blkcg != &blkcg_root) {
-		if (blk_init_rl(&blkg->rl, q, gfp_mask))
-			goto err_free;
-		blkg->rl.blkg = blkg;
-	}
 
 	for (i = 0; i < BLKCG_MAX_POLS; i++) {
 		struct blkcg_policy *pol = blkcg_policy[i];
@@ -157,7 +177,7 @@ struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
 	blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
 	if (blkg && blkg->q == q) {
 		if (update_hint) {
-			lockdep_assert_held(q->queue_lock);
+			lockdep_assert_held(&q->queue_lock);
 			rcu_assign_pointer(blkcg->blkg_hint, blkg);
 		}
 		return blkg;
@@ -180,7 +200,13 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 	int i, ret;
 
 	WARN_ON_ONCE(!rcu_read_lock_held());
-	lockdep_assert_held(q->queue_lock);
+	lockdep_assert_held(&q->queue_lock);
+
+	/* request_queue is dying, do not create/recreate a blkg */
+	if (blk_queue_dying(q)) {
+		ret = -ENODEV;
+		goto err_free_blkg;
+	}
 
 	/* blkg holds a reference to blkcg */
 	if (!css_tryget_online(&blkcg->css)) {
@@ -217,6 +243,11 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 		blkg_get(blkg->parent);
 	}
 
+	ret = percpu_ref_init(&blkg->refcnt, blkg_release, 0,
+			      GFP_NOWAIT | __GFP_NOWARN);
+	if (ret)
+		goto err_cancel_ref;
+
 	/* invoke per-policy init */
 	for (i = 0; i < BLKCG_MAX_POLS; i++) {
 		struct blkcg_policy *pol = blkcg_policy[i];
@@ -249,6 +280,8 @@ static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
 	blkg_put(blkg);
 	return ERR_PTR(ret);
 
+err_cancel_ref:
+	percpu_ref_exit(&blkg->refcnt);
 err_put_congested:
 	wb_congested_put(wb_congested);
 err_put_css:
@@ -259,7 +292,7 @@ err_free_blkg:
 }
 
 /**
- * blkg_lookup_create - lookup blkg, try to create one if not there
+ * __blkg_lookup_create - lookup blkg, try to create one if not there
  * @blkcg: blkcg of interest
  * @q: request_queue of interest
  *
@@ -268,24 +301,16 @@ err_free_blkg:
  * that all non-root blkg's have access to the parent blkg.  This function
  * should be called under RCU read lock and @q->queue_lock.
  *
- * Returns pointer to the looked up or created blkg on success, ERR_PTR()
- * value on error.  If @q is dead, returns ERR_PTR(-EINVAL).  If @q is not
- * dead and bypassing, returns ERR_PTR(-EBUSY).
+ * Returns the blkg or the closest blkg if blkg_create() fails as it walks
+ * down from root.
  */
-struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
-				    struct request_queue *q)
+struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
+				      struct request_queue *q)
 {
 	struct blkcg_gq *blkg;
 
 	WARN_ON_ONCE(!rcu_read_lock_held());
-	lockdep_assert_held(q->queue_lock);
-
-	/*
-	 * This could be the first entry point of blkcg implementation and
-	 * we shouldn't allow anything to go through for a bypassing queue.
-	 */
-	if (unlikely(blk_queue_bypass(q)))
-		return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY);
+	lockdep_assert_held(&q->queue_lock);
 
 	blkg = __blkg_lookup(blkcg, q, true);
 	if (blkg)
@@ -293,30 +318,64 @@ struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
 
 	/*
 	 * Create blkgs walking down from blkcg_root to @blkcg, so that all
-	 * non-root blkgs have access to their parents.
+	 * non-root blkgs have access to their parents.  Returns the closest
+	 * blkg to the intended blkg should blkg_create() fail.
 	 */
 	while (true) {
 		struct blkcg *pos = blkcg;
 		struct blkcg *parent = blkcg_parent(blkcg);
-
-		while (parent && !__blkg_lookup(parent, q, false)) {
+		struct blkcg_gq *ret_blkg = q->root_blkg;
+
+		while (parent) {
+			blkg = __blkg_lookup(parent, q, false);
+			if (blkg) {
+				/* remember closest blkg */
+				ret_blkg = blkg;
+				break;
+			}
 			pos = parent;
 			parent = blkcg_parent(parent);
 		}
 
 		blkg = blkg_create(pos, q, NULL);
-		if (pos == blkcg || IS_ERR(blkg))
+		if (IS_ERR(blkg))
+			return ret_blkg;
+		if (pos == blkcg)
 			return blkg;
 	}
 }
 
+/**
+ * blkg_lookup_create - find or create a blkg
+ * @blkcg: target block cgroup
+ * @q: target request_queue
+ *
+ * This looks up or creates the blkg representing the unique pair
+ * of the blkcg and the request_queue.
+ */
+struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
+				    struct request_queue *q)
+{
+	struct blkcg_gq *blkg = blkg_lookup(blkcg, q);
+
+	if (unlikely(!blkg)) {
+		unsigned long flags;
+
+		spin_lock_irqsave(&q->queue_lock, flags);
+		blkg = __blkg_lookup_create(blkcg, q);
+		spin_unlock_irqrestore(&q->queue_lock, flags);
+	}
+
+	return blkg;
+}
+
 static void blkg_destroy(struct blkcg_gq *blkg)
 {
 	struct blkcg *blkcg = blkg->blkcg;
 	struct blkcg_gq *parent = blkg->parent;
 	int i;
 
-	lockdep_assert_held(blkg->q->queue_lock);
+	lockdep_assert_held(&blkg->q->queue_lock);
 	lockdep_assert_held(&blkcg->lock);
 
 	/* Something wrong if we are trying to remove same group twice */
@@ -353,7 +412,7 @@ static void blkg_destroy(struct blkcg_gq *blkg)
 	 * Put the reference taken at the time of creation so that when all
 	 * queues are gone, group can be destroyed.
 	 */
-	blkg_put(blkg);
+	percpu_ref_kill(&blkg->refcnt);
 }
 
 /**
@@ -366,8 +425,7 @@ static void blkg_destroy_all(struct request_queue *q)
 {
 	struct blkcg_gq *blkg, *n;
 
-	lockdep_assert_held(q->queue_lock);
-
+	spin_lock_irq(&q->queue_lock);
 	list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
 		struct blkcg *blkcg = blkg->blkcg;
 
@@ -377,7 +435,7 @@ static void blkg_destroy_all(struct request_queue *q)
 	}
 
 	q->root_blkg = NULL;
-	q->root_rl.blkg = NULL;
+	spin_unlock_irq(&q->queue_lock);
 }
 
 /*
@@ -403,41 +461,6 @@ void __blkg_release_rcu(struct rcu_head *rcu_head)
 }
 EXPORT_SYMBOL_GPL(__blkg_release_rcu);
 
-/*
- * The next function used by blk_queue_for_each_rl().  It's a bit tricky
- * because the root blkg uses @q->root_rl instead of its own rl.
- */
-struct request_list *__blk_queue_next_rl(struct request_list *rl,
-					 struct request_queue *q)
-{
-	struct list_head *ent;
-	struct blkcg_gq *blkg;
-
-	/*
-	 * Determine the current blkg list_head.  The first entry is
-	 * root_rl which is off @q->blkg_list and mapped to the head.
-	 */
-	if (rl == &q->root_rl) {
-		ent = &q->blkg_list;
-		/* There are no more block groups, hence no request lists */
-		if (list_empty(ent))
-			return NULL;
-	} else {
-		blkg = container_of(rl, struct blkcg_gq, rl);
-		ent = &blkg->q_node;
-	}
-
-	/* walk to the next list_head, skip root blkcg */
-	ent = ent->next;
-	if (ent == &q->root_blkg->q_node)
-		ent = ent->next;
-	if (ent == &q->blkg_list)
-		return NULL;
-
-	blkg = container_of(ent, struct blkcg_gq, q_node);
-	return &blkg->rl;
-}
-
 static int blkcg_reset_stats(struct cgroup_subsys_state *css,
 			     struct cftype *cftype, u64 val)
 {
@@ -477,7 +500,6 @@ const char *blkg_dev_name(struct blkcg_gq *blkg)
 		return dev_name(blkg->q->backing_dev_info->dev);
 	return NULL;
 }
-EXPORT_SYMBOL_GPL(blkg_dev_name);
 
 /**
  * blkcg_print_blkgs - helper for printing per-blkg data
@@ -508,10 +530,10 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
 
 	rcu_read_lock();
 	hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
-		spin_lock_irq(blkg->q->queue_lock);
+		spin_lock_irq(&blkg->q->queue_lock);
 		if (blkcg_policy_enabled(blkg->q, pol))
 			total += prfill(sf, blkg->pd[pol->plid], data);
-		spin_unlock_irq(blkg->q->queue_lock);
+		spin_unlock_irq(&blkg->q->queue_lock);
 	}
 	rcu_read_unlock();
 
@@ -709,7 +731,7 @@ u64 blkg_stat_recursive_sum(struct blkcg_gq *blkg,
 	struct cgroup_subsys_state *pos_css;
 	u64 sum = 0;
 
-	lockdep_assert_held(blkg->q->queue_lock);
+	lockdep_assert_held(&blkg->q->queue_lock);
 
 	rcu_read_lock();
 	blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
@@ -752,7 +774,7 @@ struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkcg_gq *blkg,
 	struct blkg_rwstat sum = { };
 	int i;
 
-	lockdep_assert_held(blkg->q->queue_lock);
+	lockdep_assert_held(&blkg->q->queue_lock);
 
 	rcu_read_lock();
 	blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
@@ -783,18 +805,10 @@ static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg,
 					  struct request_queue *q)
 {
 	WARN_ON_ONCE(!rcu_read_lock_held());
-	lockdep_assert_held(q->queue_lock);
+	lockdep_assert_held(&q->queue_lock);
 
 	if (!blkcg_policy_enabled(q, pol))
 		return ERR_PTR(-EOPNOTSUPP);
-
-	/*
-	 * This could be the first entry point of blkcg implementation and
-	 * we shouldn't allow anything to go through for a bypassing queue.
-	 */
-	if (unlikely(blk_queue_bypass(q)))
-		return ERR_PTR(blk_queue_dying(q) ? -ENODEV : -EBUSY);
-
 	return __blkg_lookup(blkcg, q, true /* update_hint */);
 }
 
@@ -812,7 +826,7 @@ static struct blkcg_gq *blkg_lookup_check(struct blkcg *blkcg,
  */
 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		   char *input, struct blkg_conf_ctx *ctx)
-	__acquires(rcu) __acquires(disk->queue->queue_lock)
+	__acquires(rcu) __acquires(&disk->queue->queue_lock)
 {
 	struct gendisk *disk;
 	struct request_queue *q;
@@ -840,7 +854,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 	q = disk->queue;
 
 	rcu_read_lock();
-	spin_lock_irq(q->queue_lock);
+	spin_lock_irq(&q->queue_lock);
 
 	blkg = blkg_lookup_check(blkcg, pol, q);
 	if (IS_ERR(blkg)) {
@@ -867,7 +881,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		}
 
 		/* Drop locks to do new blkg allocation with GFP_KERNEL. */
-		spin_unlock_irq(q->queue_lock);
+		spin_unlock_irq(&q->queue_lock);
 		rcu_read_unlock();
 
 		new_blkg = blkg_alloc(pos, q, GFP_KERNEL);
@@ -877,7 +891,7 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		}
 
 		rcu_read_lock();
-		spin_lock_irq(q->queue_lock);
+		spin_lock_irq(&q->queue_lock);
 
 		blkg = blkg_lookup_check(pos, pol, q);
 		if (IS_ERR(blkg)) {
@@ -905,7 +919,7 @@ success:
 	return 0;
 
 fail_unlock:
-	spin_unlock_irq(q->queue_lock);
+	spin_unlock_irq(&q->queue_lock);
 	rcu_read_unlock();
 fail:
 	put_disk_and_module(disk);
@@ -921,7 +935,6 @@ fail:
 	}
 	return ret;
 }
-EXPORT_SYMBOL_GPL(blkg_conf_prep);
 
 /**
  * blkg_conf_finish - finish up per-blkg config update
@@ -931,13 +944,12 @@ EXPORT_SYMBOL_GPL(blkg_conf_prep);
  * with blkg_conf_prep().
  */
 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
-	__releases(ctx->disk->queue->queue_lock) __releases(rcu)
+	__releases(&ctx->disk->queue->queue_lock) __releases(rcu)
 {
-	spin_unlock_irq(ctx->disk->queue->queue_lock);
+	spin_unlock_irq(&ctx->disk->queue->queue_lock);
 	rcu_read_unlock();
 	put_disk_and_module(ctx->disk);
 }
-EXPORT_SYMBOL_GPL(blkg_conf_finish);
 
 static int blkcg_print_stat(struct seq_file *sf, void *v)
 {
@@ -967,7 +979,7 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 		 */
 		off += scnprintf(buf+off, size-off, "%s ", dname);
 
-		spin_lock_irq(blkg->q->queue_lock);
+		spin_lock_irq(&blkg->q->queue_lock);
 
 		rwstat = blkg_rwstat_recursive_sum(blkg, NULL,
 					offsetof(struct blkcg_gq, stat_bytes));
@@ -981,7 +993,7 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
 		wios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_WRITE]);
 		dios = atomic64_read(&rwstat.aux_cnt[BLKG_RWSTAT_DISCARD]);
 
-		spin_unlock_irq(blkg->q->queue_lock);
+		spin_unlock_irq(&blkg->q->queue_lock);
 
 		if (rbytes || wbytes || rios || wios) {
 			has_stats = true;
@@ -1102,9 +1114,9 @@ void blkcg_destroy_blkgs(struct blkcg *blkcg)
 						struct blkcg_gq, blkcg_node);
 		struct request_queue *q = blkg->q;
 
-		if (spin_trylock(q->queue_lock)) {
+		if (spin_trylock(&q->queue_lock)) {
 			blkg_destroy(blkg);
-			spin_unlock(q->queue_lock);
+			spin_unlock(&q->queue_lock);
 		} else {
 			spin_unlock_irq(&blkcg->lock);
 			cpu_relax();
@@ -1225,36 +1237,31 @@ int blkcg_init_queue(struct request_queue *q)
 
 	/* Make sure the root blkg exists. */
 	rcu_read_lock();
-	spin_lock_irq(q->queue_lock);
+	spin_lock_irq(&q->queue_lock);
 	blkg = blkg_create(&blkcg_root, q, new_blkg);
 	if (IS_ERR(blkg))
 		goto err_unlock;
 	q->root_blkg = blkg;
-	q->root_rl.blkg = blkg;
-	spin_unlock_irq(q->queue_lock);
+	spin_unlock_irq(&q->queue_lock);
 	rcu_read_unlock();
 
 	if (preloaded)
 		radix_tree_preload_end();
 
 	ret = blk_iolatency_init(q);
-	if (ret) {
-		spin_lock_irq(q->queue_lock);
-		blkg_destroy_all(q);
-		spin_unlock_irq(q->queue_lock);
-		return ret;
-	}
+	if (ret)
+		goto err_destroy_all;
 
 	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;
+	if (ret)
+		goto err_destroy_all;
+	return 0;
 
+err_destroy_all:
+	blkg_destroy_all(q);
+	return ret;
 err_unlock:
-	spin_unlock_irq(q->queue_lock);
+	spin_unlock_irq(&q->queue_lock);
 	rcu_read_unlock();
 	if (preloaded)
 		radix_tree_preload_end();
@@ -1269,7 +1276,7 @@ err_unlock:
  */
 void blkcg_drain_queue(struct request_queue *q)
 {
-	lockdep_assert_held(q->queue_lock);
+	lockdep_assert_held(&q->queue_lock);
 
 	/*
 	 * @q could be exiting and already have destroyed all blkgs as
@@ -1289,10 +1296,7 @@ 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);
 }
 
@@ -1396,10 +1400,8 @@ int blkcg_activate_policy(struct request_queue *q,
 	if (blkcg_policy_enabled(q, pol))
 		return 0;
 
-	if (q->mq_ops)
+	if (queue_is_mq(q))
 		blk_mq_freeze_queue(q);
-	else
-		blk_queue_bypass_start(q);
 pd_prealloc:
 	if (!pd_prealloc) {
 		pd_prealloc = pol->pd_alloc_fn(GFP_KERNEL, q->node);
@@ -1409,7 +1411,7 @@ pd_prealloc:
 		}
 	}
 
-	spin_lock_irq(q->queue_lock);
+	spin_lock_irq(&q->queue_lock);
 
 	list_for_each_entry(blkg, &q->blkg_list, q_node) {
 		struct blkg_policy_data *pd;
@@ -1421,7 +1423,7 @@ pd_prealloc:
 		if (!pd)
 			swap(pd, pd_prealloc);
 		if (!pd) {
-			spin_unlock_irq(q->queue_lock);
+			spin_unlock_irq(&q->queue_lock);
 			goto pd_prealloc;
 		}
 
@@ -1435,12 +1437,10 @@ pd_prealloc:
 	__set_bit(pol->plid, q->blkcg_pols);
 	ret = 0;
 
-	spin_unlock_irq(q->queue_lock);
+	spin_unlock_irq(&q->queue_lock);
 out_bypass_end:
-	if (q->mq_ops)
+	if (queue_is_mq(q))
 		blk_mq_unfreeze_queue(q);
-	else
-		blk_queue_bypass_end(q);
 	if (pd_prealloc)
 		pol->pd_free_fn(pd_prealloc);
 	return ret;
@@ -1463,12 +1463,10 @@ void blkcg_deactivate_policy(struct request_queue *q,
 	if (!blkcg_policy_enabled(q, pol))
 		return;
 
-	if (q->mq_ops)
+	if (queue_is_mq(q))
 		blk_mq_freeze_queue(q);
-	else
-		blk_queue_bypass_start(q);
 
-	spin_lock_irq(q->queue_lock);
+	spin_lock_irq(&q->queue_lock);
 
 	__clear_bit(pol->plid, q->blkcg_pols);
 
@@ -1481,12 +1479,10 @@ void blkcg_deactivate_policy(struct request_queue *q,
 		}
 	}
 
-	spin_unlock_irq(q->queue_lock);
+	spin_unlock_irq(&q->queue_lock);
 
-	if (q->mq_ops)
+	if (queue_is_mq(q))
 		blk_mq_unfreeze_queue(q);
-	else
-		blk_queue_bypass_end(q);
 }
 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
 
@@ -1748,8 +1744,7 @@ void blkcg_maybe_throttle_current(void)
 	blkg = blkg_lookup(blkcg, q);
 	if (!blkg)
 		goto out;
-	blkg = blkg_try_get(blkg);
-	if (!blkg)
+	if (!blkg_tryget(blkg))
 		goto out;
 	rcu_read_unlock();
 
@@ -1761,7 +1756,6 @@ out:
 	rcu_read_unlock();
 	blk_put_queue(q);
 }
-EXPORT_SYMBOL_GPL(blkcg_maybe_throttle_current);
 
 /**
  * blkcg_schedule_throttle - this task needs to check for throttling
@@ -1795,7 +1789,6 @@ void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay)
 		current->use_memdelay = use_memdelay;
 	set_notify_resume(current);
 }
-EXPORT_SYMBOL_GPL(blkcg_schedule_throttle);
 
 /**
  * blkcg_add_delay - add delay to this blkg
@@ -1810,7 +1803,6 @@ void blkcg_add_delay(struct blkcg_gq *blkg, u64 now, u64 delta)
 	blkcg_scale_delay(blkg, now);
 	atomic64_add(delta, &blkg->delay_nsec);
 }
-EXPORT_SYMBOL_GPL(blkcg_add_delay);
 
 module_param(blkcg_debug_stats, bool, 0644);
 MODULE_PARM_DESC(blkcg_debug_stats, "True if you want debug stats, false if not");