From: Bart Van Assche <bart.vanassche@sandisk.com>
Date: Wed, 26 Apr 2017 20:47:48 +0000 (-0700)
Subject: blk-mq: Register <dev>/queue/mq after having registered <dev>/queue
X-Git-Tag: accepted/tizen/unified/20230406.165743~1
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=4a4595d3b13017cbd600f18b1c0ff2e2cd7082ec;p=platform%2Fkernel%2Flinux-amlogic.git

blk-mq: Register <dev>/queue/mq after having registered <dev>/queue

A later patch in this series will modify blk_mq_debugfs_register()
such that it uses q->kobj.parent to determine the name of a
request queue. Hence make sure that that pointer is initialized
before blk_mq_debugfs_register() is called. To avoid lock inversion,
protect sysfs / debugfs registration with the queue sysfs_lock
instead of the global mutex all_q_mutex.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

[sw0312.kim: backport mainline commit 2d0364c8c1a9 to fix possible deadlock in blk-mq for cpu hotplug]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>

Change-Id: Id43aae4f67f6aa43b5ad0ccd19b8f40baab337b8
---

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
index 5b64d9d7d147..1e69db2bdfcf 100644
--- a/block/blk-mq-sysfs.c
+++ b/block/blk-mq-sysfs.c
@@ -404,6 +404,8 @@ static void __blk_mq_unregister_dev(struct device *dev, struct request_queue *q)
 	struct blk_mq_ctx *ctx;
 	int i, j;
 
+	lockdep_assert_held(&q->sysfs_lock);
+
 	queue_for_each_hw_ctx(q, hctx, i) {
 		blk_mq_unregister_hctx(hctx);
 
@@ -424,9 +426,9 @@ static void __blk_mq_unregister_dev(struct device *dev, struct request_queue *q)
 
 void blk_mq_unregister_dev(struct device *dev, struct request_queue *q)
 {
-	blk_mq_disable_hotplug();
+	mutex_lock(&q->sysfs_lock);
 	__blk_mq_unregister_dev(dev, q);
-	blk_mq_enable_hotplug();
+	mutex_unlock(&q->sysfs_lock);
 }
 
 void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx)
@@ -447,12 +449,13 @@ void blk_mq_sysfs_init(struct request_queue *q)
 	}
 }
 
-int blk_mq_register_dev(struct device *dev, struct request_queue *q)
+int __blk_mq_register_dev(struct device *dev, struct request_queue *q)
 {
 	struct blk_mq_hw_ctx *hctx;
 	int ret, i;
 
-	blk_mq_disable_hotplug();
+	WARN_ON_ONCE(!q->kobj.parent);
+	lockdep_assert_held(&q->sysfs_lock);
 
 	ret = kobject_add(&q->mq_kobj, kobject_get(&dev->kobj), "%s", "mq");
 	if (ret < 0)
@@ -470,8 +473,18 @@ int blk_mq_register_dev(struct device *dev, struct request_queue *q)
 		__blk_mq_unregister_dev(dev, q);
 	else
 		q->mq_sysfs_init_done = true;
+
 out:
-	blk_mq_enable_hotplug();
+	return ret;
+}
+
+int blk_mq_register_dev(struct device *dev, struct request_queue *q)
+{
+	int ret;
+
+	mutex_lock(&q->sysfs_lock);
+	ret = __blk_mq_register_dev(dev, q);
+	mutex_unlock(&q->sysfs_lock);
 
 	return ret;
 }
@@ -482,11 +495,15 @@ void blk_mq_sysfs_unregister(struct request_queue *q)
 	struct blk_mq_hw_ctx *hctx;
 	int i;
 
+	mutex_lock(&q->sysfs_lock);
 	if (!q->mq_sysfs_init_done)
-		return;
+		goto unlock;
 
 	queue_for_each_hw_ctx(q, hctx, i)
 		blk_mq_unregister_hctx(hctx);
+
+unlock:
+	mutex_unlock(&q->sysfs_lock);
 }
 
 int blk_mq_sysfs_register(struct request_queue *q)
@@ -494,8 +511,9 @@ int blk_mq_sysfs_register(struct request_queue *q)
 	struct blk_mq_hw_ctx *hctx;
 	int i, ret = 0;
 
+	mutex_lock(&q->sysfs_lock);
 	if (!q->mq_sysfs_init_done)
-		return ret;
+		goto unlock;
 
 	queue_for_each_hw_ctx(q, hctx, i) {
 		ret = blk_mq_register_hctx(hctx);
@@ -503,5 +521,8 @@ int blk_mq_sysfs_register(struct request_queue *q)
 			break;
 	}
 
+unlock:
+	mutex_unlock(&q->sysfs_lock);
+
 	return ret;
 }
diff --git a/block/blk-mq.h b/block/blk-mq.h
index c26a84d44cc4..a2cc41a984bf 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -51,6 +51,7 @@ static inline struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q,
  * sysfs helpers
  */
 extern void blk_mq_sysfs_init(struct request_queue *q);
+extern int __blk_mq_register_dev(struct device *dev, struct request_queue *q);
 extern int blk_mq_sysfs_register(struct request_queue *q);
 extern void blk_mq_sysfs_unregister(struct request_queue *q);
 extern void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx);
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 88c13e58c6e9..d26937ac33db 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -695,9 +695,6 @@ int blk_register_queue(struct gendisk *disk)
 	if (ret)
 		return ret;
 
-	if (q->mq_ops)
-		blk_mq_register_dev(dev, q);
-
 	/* Prevent changes through sysfs until registration is completed. */
 	mutex_lock(&q->sysfs_lock);
 
@@ -707,6 +704,9 @@ int blk_register_queue(struct gendisk *disk)
 		goto unlock;
 	}
 
+	if (q->mq_ops)
+		__blk_mq_register_dev(dev, q);
+
 	kobject_uevent(&q->kobj, KOBJ_ADD);
 
 	if (!q->request_fn) {