block: Let blk_drain_queue() caller obtain the queue lock
Bart Van Assche [Wed, 28 Nov 2012 12:43:38 +0000 (13:43 +0100)]
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>

block/blk-core.c

index 1a95272..a182b58 100644 (file)
@@ -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);