block: fix drain_all condition in blk_drain_queue()

When trying to drain all requests, blk_drain_queue() checked only
q->rq.count[]; however, this only tracks REQ_ALLOCED requests.  This
patch updates blk_drain_queue() such that it looks at all the counters
and queues so that request_queue is actually empty on completion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index b5ed4f4..c37e9e7 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -358,7 +358,8 @@ EXPORT_SYMBOL(blk_put_queue);
 void blk_drain_queue(struct request_queue *q, bool drain_all)
 {
        while (true) {
-               int nr_rqs;
+               bool drain = false;
+               int i;
 
                spin_lock_irq(q->queue_lock);
 
@@ -368,14 +369,25 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
 
                __blk_run_queue(q);
 
-               if (drain_all)
-                       nr_rqs = q->rq.count[0] + q->rq.count[1];
-               else
-                       nr_rqs = q->rq.elvpriv;
+               drain |= q->rq.elvpriv;
+
+               /*
+                * Unfortunately, requests are queued at and tracked from
+                * multiple places and there's no single counter which can
+                * be drained.  Check all the queues and counters.
+                */
+               if (drain_all) {
+                       drain |= !list_empty(&q->queue_head);
+                       for (i = 0; i < 2; i++) {
+                               drain |= q->rq.count[i];
+                               drain |= q->in_flight[i];
+                               drain |= !list_empty(&q->flush_queue[i]);
+                       }
+               }
 
                spin_unlock_irq(q->queue_lock);
 
-               if (!nr_rqs)
+               if (!drain)
                        break;
                msleep(10);
        }