releases/4.8.5/dm-rq-take-request_queue-lock-while-clearing-queue_flag_stopped.patch

   1 From 9dbeaeabacb26260d1621fe58f0f6fdedc8860d4 Mon Sep 17 00:00:00 2001
   2 From: Mike Snitzer <snitzer@redhat.com>
   3 Date: Thu, 1 Sep 2016 11:59:33 -0400
   4 Subject: dm rq: take request_queue lock while clearing QUEUE_FLAG_STOPPED
   5
   6 From: Mike Snitzer <snitzer@redhat.com>
   7
   8 commit 9dbeaeabacb26260d1621fe58f0f6fdedc8860d4 upstream.
   9
  10 Every call of queue_flag_clear_unlocked() after block device
  11 initialization has finished is wrong if blk_cleanup_queue() can be
  12 called concurrently.  Convert queue_flag_clear_unlocked() into
  13 queue_flag_clear() and protect it by the block layer queue lock.
  14
  15 Also, factor out dm_mq_start_queue().
  16
  17 Reported-by: Bart Van Assche <bart.vanassche@sandisk.com>
  18 Signed-off-by: Mike Snitzer <snitzer@redhat.com>
  19 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  20
  21 ---
  22  drivers/md/dm-rq.c |   19 ++++++++++++++-----
  23  1 file changed, 14 insertions(+), 5 deletions(-)
  24
  25 --- a/drivers/md/dm-rq.c
  26 +++ b/drivers/md/dm-rq.c
  27 @@ -73,15 +73,24 @@ static void dm_old_start_queue(struct re
  28         spin_unlock_irqrestore(q->queue_lock, flags);
  29  }
  30
  31 +static void dm_mq_start_queue(struct request_queue *q)
  32 +{
  33 +       unsigned long flags;
  34 +
  35 +       spin_lock_irqsave(q->queue_lock, flags);
  36 +       queue_flag_clear(QUEUE_FLAG_STOPPED, q);
  37 +       spin_unlock_irqrestore(q->queue_lock, flags);
  38 +
  39 +       blk_mq_start_stopped_hw_queues(q, true);
  40 +       blk_mq_kick_requeue_list(q);
  41 +}
  42 +
  43  void dm_start_queue(struct request_queue *q)
  44  {
  45         if (!q->mq_ops)
  46                 dm_old_start_queue(q);
  47 -       else {
  48 -               queue_flag_clear_unlocked(QUEUE_FLAG_STOPPED, q);
  49 -               blk_mq_start_stopped_hw_queues(q, true);
  50 -               blk_mq_kick_requeue_list(q);
  51 -       }
  52 +       else
  53 +               dm_mq_start_queue(q);
  54  }
  55
  56  static void dm_old_stop_queue(struct request_queue *q)