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dm rq: fix the starting and stopping of blk-mq queues 

Improve dm_stop_queue() to cancel any requeue_work.  Also, have
dm_start_queue() and dm_stop_queue() clear/set the QUEUE_FLAG_STOPPED
for the blk-mq request_queue.

On suspend dm_stop_queue() handles stopping the blk-mq request_queue
BUT: even though the hw_queues are marked BLK_MQ_S_STOPPED at that point
there is still a race that is allowing block/blk-mq.c to call ->queue_rq
against a hctx that it really shouldn't.  Add a check to
dm_mq_queue_rq() that guards against this rarity (albeit _not_
race-free).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # must patch dm.c on < 4.8 kernels
This commit is contained in:
Mike Snitzer 2016-08-02 12:51:11 -04:00
parent 1814f2e3fb
commit 7d9595d848
1 changed files with 19 additions and 1 deletions
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20
drivers/md/dm-rq.c
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@ -78,6 +78,7 @@ void dm_start_queue(struct request_queue *q)
if (!q->mq_ops)
dm_old_start_queue(q);
else {
queue_flag_clear_unlocked(QUEUE_FLAG_STOPPED, q);
blk_mq_start_stopped_hw_queues(q, true);
blk_mq_kick_requeue_list(q);
}
@ -101,8 +102,14 @@ void dm_stop_queue(struct request_queue *q)
{
if (!q->mq_ops)
dm_old_stop_queue(q);
else
else {
spin_lock_irq(q->queue_lock);
queue_flag_set(QUEUE_FLAG_STOPPED, q);
spin_unlock_irq(q->queue_lock);
blk_mq_cancel_requeue_work(q);
blk_mq_stop_hw_queues(q);
}
}
static struct dm_rq_target_io *alloc_old_rq_tio(struct mapped_device *md,
@ -864,6 +871,17 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
dm_put_live_table(md, srcu_idx);
}
/*
* On suspend dm_stop_queue() handles stopping the blk-mq
* request_queue BUT: even though the hw_queues are marked
* BLK_MQ_S_STOPPED at that point there is still a race that
* is allowing block/blk-mq.c to call ->queue_rq against a
* hctx that it really shouldn't. The following check guards
* against this rarity (albeit _not_ race-free).
*/
if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state)))
return BLK_MQ_RQ_QUEUE_BUSY;
if (ti->type->busy && ti->type->busy(ti))
return BLK_MQ_RQ_QUEUE_BUSY;