blk-mq: add timer in blk_mq_start_request

This way will become consistent with non-mq case, also
avoid to update rq->deadline twice for mq.

The comment said: "We do this early, to ensure we are on
the right CPU.", but no percpu stuff is used in blk_add_timer(),
so it isn't necessary. Even when inserting from plug list, there
is no such guarantee at all.

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

diff --git a/block/blk-mq.c b/block/blk-mq.c
index a5ea37d..e11f5f8 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -411,16 +411,7 @@ static void blk_mq_start_request(struct request *rq, bool last)
        if (unlikely(blk_bidi_rq(rq)))
                rq->next_rq->resid_len = blk_rq_bytes(rq->next_rq);
 
-       /*
-        * Just mark start time and set the started bit. Due to memory
-        * ordering, we know we'll see the correct deadline as long as
-        * REQ_ATOMIC_STARTED is seen. Use the default queue timeout,
-        * unless one has been set in the request.
-        */
-       if (!rq->timeout)
-               rq->deadline = jiffies + q->rq_timeout;
-       else
-               rq->deadline = jiffies + rq->timeout;
+       blk_add_timer(rq);
 
        /*
         * Mark us as started and clear complete. Complete might have been
@@ -972,11 +963,6 @@ static void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx,
                list_add_tail(&rq->queuelist, &ctx->rq_list);
 
        blk_mq_hctx_mark_pending(hctx, ctx);
-
-       /*
-        * We do this early, to ensure we are on the right CPU.
-        */
-       blk_add_timer(rq);
 }
 
 void blk_mq_insert_request(struct request *rq, bool at_head, bool run_queue,
@@ -1219,7 +1205,6 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio)
 
                blk_mq_bio_to_request(rq, bio);
                blk_mq_start_request(rq, true);
-               blk_add_timer(rq);
 
                /*
                 * For OK queue, we are done. For error, kill it. Any other