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, 4 insertions, 0 deletions

diff --git a/block/blk-exec.c b/block/blk-exec.c
index c3edf9dff566..bbfc072a79c2 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -60,6 +60,10 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
         rq->rq_disk = bd_disk;
         rq->end_io = done;
 
+        /*
+         * don't check dying flag for MQ because the request won't
+         * be resued after dying flag is set
+         */
         if (q->mq_ops) {
                 blk_mq_insert_request(q, rq, true);
                 return;