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
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 7a96618..1ca7463 100644
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -78,6 +78,7 @@
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 @@
{
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 @@
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;