Before commit 780db2071a(blk-mq: decouble blk-mq freezing
from generic bypassing), the dying flag is checked before
entering queue, and Tejun converts the checking into .mq_freeze_depth,
and assumes the counter is increased just after dying flag
is set. Unfortunately we doesn't do that in blk_set_queue_dying().
This patch calls blk_freeze_queue_start() in blk_set_queue_dying(),
so that we can block new I/O coming once the queue is set as dying.
Given blk_set_queue_dying() is always called in remove path
of block device, and queue will be cleaned up later, we don't
need to worry about undoing the counter.
Cc: Bart Van Assche <bart.vanassche@xxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Signed-off-by: Ming Lei <tom.leiming@xxxxxxxxx>
---
block/blk-core.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index 60f364e1d36b..e22c4ea002ec 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -500,6 +500,13 @@ void blk_set_queue_dying(struct request_queue *q)
queue_flag_set(QUEUE_FLAG_DYING, q);
spin_unlock_irq(q->queue_lock);
+ /*
+ * When queue DYING flag is set, we need to block new req
+ * entering queue, so we call blk_freeze_queue_start() to
+ * prevent I/O from crossing blk_queue_enter().
+ */
+ blk_freeze_queue_start(q);
+
if (q->mq_ops)
blk_mq_wake_waiters(q);
else {
@@ -672,9 +679,9 @@ int blk_queue_enter(struct request_queue *q, bool nowait)
/*
* read pair of barrier in blk_freeze_queue_start(),
* we need to order reading __PERCPU_REF_DEAD flag of
- * .q_usage_counter and reading .mq_freeze_depth,
- * otherwise the following wait may never return if the
- * two reads are reordered.
+ * .q_usage_counter and reading .mq_freeze_depth or
+ * queue dying flag, otherwise the following wait may
+ * never return if the two reads are reordered.
*/
smp_rmb();
--
2.9.3
