blk-mq: use QUEUE_FLAG_QUIESCED to quiesce queue

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It is required that no dispatch can happen any more once
blk_mq_quiesce_queue() returns, and we don't have such requirement
on APIs of stopping queue.

But blk_mq_quiesce_queue() still may not block/drain dispatch in the
the case of BLK_MQ_S_START_ON_RUN, so use the new introduced flag of
QUEUE_FLAG_QUIESCED and evaluate it inside RCU read-side critical
sections for fixing this issue.

Also blk_mq_quiesce_queue() is implemented via stopping queue, which
limits its uses, and easy to cause race, because any queue restart in
other paths may break blk_mq_quiesce_queue(). With the introduced
flag of QUEUE_FLAG_QUIESCED, we don't need to depend on stopping queue
for quiescing any more.

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>

...

This commit is contained in:

Ming Lei 2017-06-18 14:24:27 -06:00 • committed by Jens Axboe

parent f660174e8b

commit f4560ffe8c

4 changed files with 18 additions and 2 deletions

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3

block/blk-mq-sched.c

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11

block/blk-mq.c

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4

include/linux/blk-mq.h

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2

include/linux/blkdev.h

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