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authorMing Lei <ming.lei@redhat.com>2017-06-06 18:22:09 +0300
committerJens Axboe <axboe@kernel.dk>2017-06-18 23:24:48 +0300
commit39a70c76b89b81db91a72a86b6c6a9b239013417 (patch)
tree8fa5baf83a330c9e38df72270484d6e41e5a1fa6 /block/blk-mq.c
parent1d9e9bc6b56e1bb7e33e7e2e1b99d7088356c006 (diff)
downloadlinux-39a70c76b89b81db91a72a86b6c6a9b239013417.tar.xz
blk-mq: clarify dispatch may not be drained/blocked by stopping queue
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 <ming.lei@redhat.com> Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.c')
-rw-r--r--block/blk-mq.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c
index dbae586602f6..89cbd022b1eb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1204,6 +1204,15 @@ static void __blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx, bool sync)
set_bit(BLK_MQ_S_STOPPED, &hctx->state);
}
+/*
+ * This function is often used for pausing .queue_rq() by driver when
+ * there isn't enough resource or some conditions aren't satisfied, and
+ * BLK_MQ_RQ_QUEUE_BUSY is usually returned.
+ *
+ * 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);
@@ -1219,6 +1228,15 @@ static void __blk_mq_stop_hw_queues(struct request_queue *q, bool sync)
__blk_mq_stop_hw_queue(hctx, sync);
}
+/*
+ * This function is often used for pausing .queue_rq() by driver when
+ * there isn't enough resource or some conditions aren't satisfied, and
+ * BLK_MQ_RQ_QUEUE_BUSY is usually returned.
+ *
+ * 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);