[PATCH v3 4/4] block: block new I/O just after queue is set as dying
From: Ming Lei <tom.leiming@gmail.com>
Date: 2017-03-27 12:07:41
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
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 <redacted> Cc: Tejun Heo <tj@kernel.org> Reviewed-by: Hannes Reinecke <hare@suse.com> Signed-off-by: Ming Lei <tom.leiming@gmail.com> --- 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