Hi Ming
On 06/15/2018 11:20 AM, Ming Lei wrote:
> On Fri, Jun 15, 2018 at 11:04 AM, jianchao.wang
> <jianchao.w.wang@xxxxxxxxxx> wrote:
>> Hi Ming
>>
>> Thanks for your kindly response.
>>
>> On 06/15/2018 10:56 AM, Ming Lei wrote:
>>>>> IMO, ref-counter is just to fix the blk-mq req life recycle issue.
>>>>> It cannot replace the blk_mark_rq_complete which could avoid the race between
>>>>> timeout and io completion path.
>>>> The .timeout return BLK_EH_DONE doesn't always mean the request has been completed.
>>>> Such as scsi-mid layer, its .timeout callback return BLK_EH_DONE but the timed out
>>>> request is still in abort or eh process. What if a completion irq come during that ?
>>> For blk-mq, it is avoided by the atomic state change in
>>> __blk_mq_complete_request(),
>>> that is why I mentioned the question in my last reply.
>>>
>>
>> but blk_mq_check_expired doesn't do that.
>> do I miss anything ?
>
> Right, that is the difference between blk-mq and legacy now,
Sorry, I cannot follow your point.
blk_mq_check_expired doesn't do a atmoc state change from IN-FLIGHT to COMPLETE.
__blk_mq_complete_request could still proceed to complete a timed out request
which is in scsi abort or eh process. Is it really OK ?
Thanks
Jianchao
> then if scsi-mq
> drivers can work well, they should work well with the following change in the
> non-mq mode:
>
> diff --git a/block/blk-timeout.c b/block/blk-timeout.c
> index 4b8a48d48ba1..9fce09d55652 100644
> --- a/block/blk-timeout.c
> +++ b/block/blk-timeout.c
> @@ -88,7 +88,6 @@ static void blk_rq_timed_out(struct request *req)
> switch (ret) {
> case BLK_EH_RESET_TIMER:
> blk_add_timer(req);
> - blk_clear_rq_complete(req);
> break;
> case BLK_EH_DONE:
> /*
> @@ -115,8 +114,7 @@ static void blk_rq_check_expired(struct request
> *rq, unsigned long *next_timeout
> /*
> * Check if we raced with end io completion
> */
> - if (!blk_mark_rq_complete(rq))
> - blk_rq_timed_out(rq);
> + blk_rq_timed_out(rq);
> } else if (!*next_set || time_after(*next_timeout, deadline)) {
> *next_timeout = deadline;
> *next_set = 1;
>
>
> Thanks,
> Ming Lei
>
