From: Chao Leng <lengchao@huawei.com>
To: Sagi Grimberg <sagi@grimberg.me>, Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Yi Zhang <yi.zhang@redhat.com>,
linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
Keith Busch <kbusch@kernel.org>, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH] block: re-introduce blk_mq_complete_request_sync
Date: Wed, 14 Oct 2020 09:25:43 +0800 [thread overview]
Message-ID: <dba6f24d-7d4f-a89e-047d-9d63837084dd@huawei.com> (raw)
In-Reply-To: <0b5bfc44-d925-960d-b2a2-d0ba88b51111@grimberg.me>
On 2020/10/14 6:31, Sagi Grimberg wrote:
>
>>>>>>> --
>>>>>>> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
>>>>>>> index 629b025685d1..46428ff0b0fc 100644
>>>>>>> --- a/drivers/nvme/host/tcp.c
>>>>>>> +++ b/drivers/nvme/host/tcp.c
>>>>>>> @@ -2175,7 +2175,7 @@ static void nvme_tcp_complete_timed_out(struct request *rq)
>>>>>>> /* fence other contexts that may complete the command */
>>>>>>> mutex_lock(&to_tcp_ctrl(ctrl)->teardown_lock);
>>>>>>> nvme_tcp_stop_queue(ctrl, nvme_tcp_queue_id(req->queue));
>>>>>>> - if (!blk_mq_request_completed(rq)) {
>>>>>>> + if (blk_mq_request_started(rq) && !blk_mq_request_completed(rq)) {
>>>>>>> nvme_req(rq)->status = NVME_SC_HOST_ABORTED_CMD;
>>>>>>> blk_mq_complete_request_sync(rq);
>>>>>>> }
>>> This may just reduce the probability. The concurrency of timeout and teardown will cause the same request
>>> be treated repeatly, this is not we expected.
>>
>> That is right, not like SCSI, NVME doesn't apply atomic request completion, so
>> request may be completed/freed from both timeout & nvme_cancel_request().
>>
>> .teardown_lock still may cover the race with Sagi's patch because teardown
>> actually cancels requests in sync style.
>>
>>> In the teardown process, after quiesced queues delete the timer and cancel the timeout work maybe a better option.
>>
>> Seems better solution, given it is aligned with NVME PCI's reset
>> handling. nvme_sync_queues() may be called in nvme_tcp_teardown_io_queues() to
>> avoid this race.
>
> We can't call nvme_sync_queues, that flushes the timeout work that is
> serializing with the teardown, it will deadlock.
yes, the teardown_lock is not needed if we sync_queue. We is testing the patch with nvme over roce.
> .
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next prev parent reply other threads:[~2020-10-14 1:26 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-08 21:37 [PATCH] block: re-introduce blk_mq_complete_request_sync Sagi Grimberg
2020-10-09 4:39 ` Ming Lei
2020-10-09 5:03 ` Yi Zhang
2020-10-09 8:09 ` Sagi Grimberg
2020-10-09 13:55 ` Yi Zhang
2020-10-09 18:29 ` Sagi Grimberg
2020-10-10 6:08 ` Yi Zhang
2020-10-12 3:59 ` Chao Leng
2020-10-12 8:13 ` Ming Lei
2020-10-12 9:06 ` Chao Leng
2020-10-13 22:36 ` Sagi Grimberg
2020-10-14 1:08 ` Ming Lei
2020-10-14 1:37 ` Chao Leng
2020-10-14 2:02 ` Ming Lei
2020-10-14 2:32 ` Chao Leng
2020-10-14 2:41 ` Chao Leng
2020-10-14 3:34 ` Ming Lei
2020-10-14 9:39 ` Chao Leng
2020-10-14 9:56 ` Ming Lei
2020-10-15 6:05 ` Chao Leng
2020-10-15 7:50 ` Ming Lei
2020-10-15 10:05 ` Chao Leng
2020-10-14 1:32 ` Chao Leng
2020-10-13 22:31 ` Sagi Grimberg
2020-10-14 1:25 ` Chao Leng [this message]
2020-10-09 8:11 ` Sagi Grimberg
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