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>

1 files changed, 17 insertions, 20 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 6a9cc0d22a61..1905aaba49fb 100644
--- 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;
 }