[PATCH v2 7/8] blk-mq: clarify dispatch may not be drained/blocked by stopping queue
From: Ming Lei <hidden>
Date: 2017-05-27 14:22:49
Subsystem:
block layer, the rest · Maintainers:
Jens Axboe, Linus Torvalds
BLK_MQ_S_STOPPED may not be observed in other concurrent I/O paths, we can't guarantee that dispatching won't happen after returning from the APIs of stopping queue. So clarify the fact and avoid potential misuse. Signed-off-by: Ming Lei <redacted> --- block/blk-mq.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 84cce67caee3..73e07bc074a6 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c@@ -1240,6 +1240,11 @@ static void __blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx, bool sync) set_bit(BLK_MQ_S_STOPPED, &hctx->state); } +/* + * We do not guarantee that dispatch can be drained or blocked + * after blk_mq_stop_hw_queue() returns. Please use + * blk_mq_quiesce_queue() for that requirement. + */ void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx) { __blk_mq_stop_hw_queue(hctx, false);
@@ -1255,6 +1260,11 @@ static void __blk_mq_stop_hw_queues(struct request_queue *q, bool sync) __blk_mq_stop_hw_queue(hctx, sync); } +/* + * We do not guarantee that dispatch can be drained or blocked + * after blk_mq_stop_hw_queues() returns. Please use + * blk_mq_quiesce_queue() for that requirement. + */ void blk_mq_stop_hw_queues(struct request_queue *q) { __blk_mq_stop_hw_queues(q, false);
--
2.9.4