block: Move the second call to get_request to the end of the loop

In function get_request_wait, the second call to get_request could be
moved to the end of the while loop, because if the first call to
get_request fails, the second call will fail without sleep.

Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

diff --git a/block/blk-core.c b/block/blk-core.c
index 6a9cc0d22a61c1aa2300d18c9728a7546c15cf0a..1905aaba49fb2cd1d999bce222949c938fa3e9e5 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -806,35 +806,32 @@ static struct request *get_request_wait(struct request_queue *q, int rw_flags,
        rq = get_request(q, rw_flags, bio, GFP_NOIO);
        while (!rq) {
                DEFINE_WAIT(wait);
+               struct io_context *ioc;
                struct request_list *rl = &q->rq;
 
                prepare_to_wait_exclusive(&rl->wait[rw], &wait,
                                TASK_UNINTERRUPTIBLE);
 
-               rq = get_request(q, rw_flags, bio, GFP_NOIO);
-
-               if (!rq) {
-                       struct io_context *ioc;
+               blk_add_trace_generic(q, bio, rw, BLK_TA_SLEEPRQ);
 
-                       blk_add_trace_generic(q, bio, rw, BLK_TA_SLEEPRQ);
-
-                       __generic_unplug_device(q);
-                       spin_unlock_irq(q->queue_lock);
-                       io_schedule();
+               __generic_unplug_device(q);
+               spin_unlock_irq(q->queue_lock);
+               io_schedule();
 
-                       /*
-                        * After sleeping, we become a "batching" process and
-                        * will be able to allocate at least one request, and
-                        * up to a big batch of them for a small period time.
-                        * See ioc_batching, ioc_set_batching
-                        */
-                       ioc = current_io_context(GFP_NOIO, q->node);
-                       ioc_set_batching(q, ioc);
+               /*
+                * After sleeping, we become a "batching" process and
+                * will be able to allocate at least one request, and
+                * up to a big batch of them for a small period time.
+                * See ioc_batching, ioc_set_batching
+                */
+               ioc = current_io_context(GFP_NOIO, q->node);
+               ioc_set_batching(q, ioc);
 
-                       spin_lock_irq(q->queue_lock);
-               }
+               spin_lock_irq(q->queue_lock);
                finish_wait(&rl->wait[rw], &wait);
-       }
+
+               rq = get_request(q, rw_flags, bio, GFP_NOIO);
+       };
 
        return rq;
 }