FAILED: patch "[PATCH] blk-mq: move cancel of requeue_work to the front of" failed to apply to 4.19-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e26cc08265dda37d2acc8394604f220ef412299d Mon Sep 17 00:00:00 2001
From: zhengbin <zhengbin13@huawei.com>
Date: Mon, 12 Aug 2019 20:36:55 +0800
Subject: [PATCH] blk-mq: move cancel of requeue_work to the front of
 blk_exit_queue

blk_exit_queue will free elevator_data, while blk_mq_requeue_work
will access it. Move cancel of requeue_work to the front of
blk_exit_queue to avoid use-after-free.

blk_exit_queue                blk_mq_requeue_work
  __elevator_exit               blk_mq_run_hw_queues
    blk_mq_exit_sched             blk_mq_run_hw_queue
      dd_exit_queue                 blk_mq_hctx_has_pending
        kfree(elevator_data)          blk_mq_sched_has_work
                                        dd_has_work

Fixes: fbc2a15e3433 ("blk-mq: move cancel of requeue_work into blk_mq_release")
Cc: stable@vger.kernel.org
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f78d3287dd82..a8e6a58f5f28 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2666,8 +2666,6 @@ void blk_mq_release(struct request_queue *q)
 	struct blk_mq_hw_ctx *hctx, *next;
 	int i;
 
-	cancel_delayed_work_sync(&q->requeue_work);
-
 	queue_for_each_hw_ctx(q, hctx, i)
 		WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));
 
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 977c659dcd18..9bfa3ea4ed63 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -892,6 +892,9 @@ static void __blk_release_queue(struct work_struct *work)
 
 	blk_free_queue_stats(q->stats);
 
+	if (queue_is_mq(q))
+		cancel_delayed_work_sync(&q->requeue_work);
+
 	blk_exit_queue(q);
 
 	blk_queue_free_zone_bitmaps(q);