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blk-mq: update comments on blk_mq_quiesce_queue() 

Actually what we want to get from blk_mq_quiesce_queue()
isn't only to wait for completion of all ongoing .queue_rq().

In the typical context of canceling requests, we need to
make sure that the following is done in the dispatch path
before starting to cancel requests:

	- failed dispatched request is finished
	- busy dispatched request is requeued, and the STARTED
	flag is cleared

So update comment to keep code, doc and our expection consistent.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2017-06-06 23:22:07 +08:00 committed by Jens Axboe
parent f4560ffe8c
commit 69e07c4adb
1 changed files with 4 additions and 3 deletions
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7
block/blk-mq.c
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@ -155,12 +155,13 @@ void blk_mq_unfreeze_queue(struct request_queue *q)
EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue); EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
/** /**
* blk_mq_quiesce_queue() - wait until all ongoing queue_rq calls have finished * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
* @q: request queue. * @q: request queue.
* *
* Note: this function does not prevent that the struct request end_io() * Note: this function does not prevent that the struct request end_io()
* callback function is invoked. Additionally, it is not prevented that * callback function is invoked. Once this function is returned, we make
* new queue_rq() calls occur unless the queue has been stopped first. * sure no dispatch can happen until the queue is unquiesced via
* blk_mq_unquiesce_queue().
*/ */
void blk_mq_quiesce_queue(struct request_queue *q) void blk_mq_quiesce_queue(struct request_queue *q)
{ {