[PATCH 0/3] avoid race between time out and tear down

[Chao Leng]

On 2020/10/21 12:59, Sagi Grimberg wrote:
> 
>>>> Avoid race between time out and tear down for rdma and tcp.
>>>
>>> This patchset overall looks good, but we still need the patch that
>>> avoids double completion:
>>>
>>> -- 
>>> 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)) {
>> Yes, this patch is need. and samely for nvme_cancel_request.
>> This will fix the race with asynchronous completion.
>>
>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>> index e85f6304efd7..1e838d952096 100644
>> --- a/drivers/nvme/host/core.c
>> +++ b/drivers/nvme/host/core.c
>> @@ -338,7 +338,7 @@ bool nvme_cancel_request(struct request *req, void *data, bool reserved)
>>                                  "Cancelling I/O %d", req->tag);
>>
>>          /* don't abort one completed request */
>> -       if (blk_mq_request_completed(req))
>> +       if (blk_mq_request_completed(req) || !blk_mq_request_started(rq))
>>                  return true;
>>
>>          nvme_req(req)->status = NVME_SC_HOST_ABORTED_CMD;
> 
> This one is unneeded because blk_mq_tagset_busy_iter checks that the
> request has started...
Yes, it is already checked.
> .