block: Let blk_drain_queue() caller obtain the queue lock

Let the caller of blk_drain_queue() obtain the queue lock to improve
readability of the patch called "Avoid that request_fn is invoked on
a dead queue".

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: James Bottomley <JBottomley@Parallels.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Chanho Min <chanho.min@lge.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 18 insertions, 12 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 1a95272cca50..a182b586b06a 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -349,7 +349,7 @@ void blk_put_queue(struct request_queue *q)
 EXPORT_SYMBOL(blk_put_queue);
 
 /**
- * blk_drain_queue - drain requests from request_queue
+ * __blk_drain_queue - drain requests from request_queue
  * @q: queue to drain
  * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
  *
@@ -357,15 +357,17 @@ EXPORT_SYMBOL(blk_put_queue);
  * If not, only ELVPRIV requests are drained.  The caller is responsible
  * for ensuring that no new requests which need to be drained are queued.
  */
-void blk_drain_queue(struct request_queue *q, bool drain_all)
+static void __blk_drain_queue(struct request_queue *q, bool drain_all)
+        __releases(q->queue_lock)
+        __acquires(q->queue_lock)
 {
         int i;
 
+        lockdep_assert_held(q->queue_lock);
+
         while (true) {
                 bool drain = false;
 
-                spin_lock_irq(q->queue_lock);
-
                 /*
                  * The caller might be trying to drain @q before its
                  * elevator is initialized.
@@ -401,11 +403,14 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
                         }
                 }
 
-                spin_unlock_irq(q->queue_lock);
-
                 if (!drain)
                         break;
+
+                spin_unlock_irq(q->queue_lock);
+
                 msleep(10);
+
+                spin_lock_irq(q->queue_lock);
         }
 
         /*
@@ -416,13 +421,9 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
         if (q->request_fn) {
                 struct request_list *rl;
 
-                spin_lock_irq(q->queue_lock);
-
                 blk_queue_for_each_rl(rl, q)
                         for (i = 0; i < ARRAY_SIZE(rl->wait); i++)
                                 wake_up_all(&rl->wait[i]);
-
-                spin_unlock_irq(q->queue_lock);
         }
 }
 
@@ -446,7 +447,10 @@ void blk_queue_bypass_start(struct request_queue *q)
         spin_unlock_irq(q->queue_lock);
 
         if (drain) {
-                blk_drain_queue(q, false);
+                spin_lock_irq(q->queue_lock);
+                __blk_drain_queue(q, false);
+                spin_unlock_irq(q->queue_lock);
+
                 /* ensure blk_queue_bypass() is %true inside RCU read lock */
                 synchronize_rcu();
         }
@@ -504,7 +508,9 @@ void blk_cleanup_queue(struct request_queue *q)
         mutex_unlock(&q->sysfs_lock);
 
         /* drain all requests queued before DYING marking */
-        blk_drain_queue(q, true);
+        spin_lock_irq(lock);
+        __blk_drain_queue(q, true);
+        spin_unlock_irq(lock);
 
         /* @q won't process any more request, flush async actions */
         del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);