block: blk-mq: support draining mq queue

blk_mq_drain_queue() is introduced so that we can drain
mq queue inside blk_cleanup_queue().

Also don't accept new requests any more if queue is marked
as dying.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 27 insertions, 16 deletions

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 3929f43d0b03..e2f811cba417 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -106,10 +106,13 @@ static int blk_mq_queue_enter(struct request_queue *q)
 
         spin_lock_irq(q->queue_lock);
         ret = wait_event_interruptible_lock_irq(q->mq_freeze_wq,
-                !blk_queue_bypass(q), *q->queue_lock);
+                !blk_queue_bypass(q) || blk_queue_dying(q),
+                *q->queue_lock);
         /* inc usage with lock hold to avoid freeze_queue runs here */
-        if (!ret)
+        if (!ret && !blk_queue_dying(q))
                 __percpu_counter_add(&q->mq_usage_counter, 1, 1000000);
+        else if (blk_queue_dying(q))
+                ret = -ENODEV;
         spin_unlock_irq(q->queue_lock);
 
         return ret;
@@ -120,6 +123,22 @@ static void blk_mq_queue_exit(struct request_queue *q)
         __percpu_counter_add(&q->mq_usage_counter, -1, 1000000);
 }
 
+static void __blk_mq_drain_queue(struct request_queue *q)
+{
+        while (true) {
+                s64 count;
+
+                spin_lock_irq(q->queue_lock);
+                count = percpu_counter_sum(&q->mq_usage_counter);
+                spin_unlock_irq(q->queue_lock);
+
+                if (count == 0)
+                        break;
+                blk_mq_run_queues(q, false);
+                msleep(10);
+        }
+}
+
 /*
  * Guarantee no request is in use, so we can change any data structure of
  * the queue afterward.
@@ -133,21 +152,13 @@ static void blk_mq_freeze_queue(struct request_queue *q)
         queue_flag_set(QUEUE_FLAG_BYPASS, q);
         spin_unlock_irq(q->queue_lock);
 
-        if (!drain)
-                return;
-
-        while (true) {
-                s64 count;
-
-                spin_lock_irq(q->queue_lock);
-                count = percpu_counter_sum(&q->mq_usage_counter);
-                spin_unlock_irq(q->queue_lock);
+        if (drain)
+                __blk_mq_drain_queue(q);
+}
 
-                if (count == 0)
-                        break;
-                blk_mq_run_queues(q, false);
-                msleep(10);
-        }
+void blk_mq_drain_queue(struct request_queue *q)
+{
+        __blk_mq_drain_queue(q);
 }
 
 static void blk_mq_unfreeze_queue(struct request_queue *q)