[PATCH V6 2/9] blk-mq: move cancel of requeue_work into blk_mq_release

[ming.lei@redhat.com (Ming Lei)]

With holding queue's kobject refcount, it is safe for driver
to schedule requeue. However, blk_mq_kick_requeue_list() may
be called after blk_sync_queue() is done because of concurrent
requeue activities, then requeue work may not be completed when
freeing queue, and kernel oops is triggered.

So moving the cancel of requeue_work into blk_mq_release() for
avoiding race between requeue and freeing queue.

Cc: Dongli Zhang <dongli.zhang at oracle.com>
Cc: James Smart <james.smart at broadcom.com>
Cc: Bart Van Assche <bart.vanassche at wdc.com>
Cc: linux-scsi at vger.kernel.org,
Cc: Martin K . Petersen <martin.petersen at oracle.com>,
Cc: Christoph Hellwig <hch at lst.de>,
Cc: James E . J . Bottomley <jejb at linux.vnet.ibm.com>,
Cc: jianchao wang <jianchao.w.wang at oracle.com>
Reviewed-by: Bart Van Assche <bvanassche at acm.org>
Reviewed-by: Johannes Thumshirn <jthumshirn at suse.de>
Signed-off-by: Ming Lei <ming.lei at redhat.com>
---
 block/blk-core.c | 1 -
 block/blk-mq.c   | 2 ++
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index a55389ba8779..93dc588fabe2 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -237,7 +237,6 @@ void blk_sync_queue(struct request_queue *q)
 		struct blk_mq_hw_ctx *hctx;
 		int i;
 
-		cancel_delayed_work_sync(&q->requeue_work);
 		queue_for_each_hw_ctx(q, hctx, i)
 			cancel_delayed_work_sync(&hctx->run_work);
 	}
diff --git a/block/blk-mq.c b/block/blk-mq.c
index ef5a16a2d6fb..55776a6e2586 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2640,6 +2640,8 @@ void blk_mq_release(struct request_queue *q)
 	struct blk_mq_hw_ctx *hctx;
 	unsigned int i;
 
+	cancel_delayed_work_sync(&q->requeue_work);
+
 	/* hctx kobj stays in hctx */
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (!hctx)
-- 
2.9.5