[Devel] [PATCH rh7 2/2] block: fix leak of q->rq_wb

[Andrey Ryabinin]

From: Omar Sandoval <osandov at fb.com>

CONFIG_DEBUG_TEST_DRIVER_REMOVE found a possible leak of q->rq_wb when a
request queue is reregistered. This has been a problem since wbt was
introduced, but the WARN_ON(!list_empty(&stats->callbacks)) in the
blk-stat rework exposed it. Fix it by cleaning up wbt when we unregister
the queue.

Fixes: 87760e5eef35 ("block: hook up writeback throttling")
Signed-off-by: Omar Sandoval <osandov at fb.com>
Signed-off-by: Jens Axboe <axboe at fb.com>

(cherry picked from commit 02ba8893ac9aa34fcb4ce2a9baef5615b190335a)
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
---
 block/blk-sysfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index ed5c71a8e84f..7aebab0ced19 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -587,7 +587,6 @@ static void blk_release_queue(struct kobject *kobj)
 	struct request_queue *q =
 		container_of(kobj, struct request_queue, kobj);
 
-	wbt_exit(q);
 	if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags))
 		blk_stat_remove_callback(q, q->poll_cb);
 	blk_stat_free_callback(q->poll_cb);
@@ -753,6 +752,8 @@ void blk_unregister_queue(struct gendisk *disk)
 	queue_flag_clear(QUEUE_FLAG_REGISTERED, q);
 	spin_unlock_irq(q->queue_lock);
 
+	wbt_exit(q);
+
 	/*
 	 * Remove the sysfs attributes before unregistering the queue data
 	 * structures that can be modified through sysfs.
-- 
2.23.0