On 8/25/22 00:09, Gu Mi wrote: > The problem occurs in two async processes, One is when a new IO calls > the blk_mq_start_request() interface to start sending,The other is > that the block layer timer process calls the blk_mq_req_expired > interface to check whether there is an IO timeout. > > When an instruction out of sequence occurs between blk_add_timer and > WRITE_ONCE(rq->state,MQ_RQ_IN_FLIGHT) in the interface > blk_mq_start_request,at this time, the block timer is checking the new > IO timeout, Since the req status has been set to MQ_RQ_IN_FLIGHT and > req->deadline is 0 at this time, the new IO will be misjudged as a > timeout. > > Our repair plan is for the deadline to be 0, and we do not think that > a timeout occurs. At the same time, because the jiffies of the 32-bit > system will be reversed shortly after the system is turned on, we will > add 1 jiffies to the deadline at this time. > > Signed-off-by: Gu Mi <gumi@xxxxxxxxxxxxxxxxx> > --- > v1->v2: > > time_after_eq() can handle the overflow, so remove the change on > 32-bit in blk_add_timer(). > > block/blk-mq.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/block/blk-mq.c b/block/blk-mq.c index 4b90d2d..6defaa1 > 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -1451,6 +1451,8 @@ static bool blk_mq_req_expired(struct request *rq, unsigned long *next) > return false; > > deadline = READ_ONCE(rq->deadline); > + if (unlikely(deadline == 0)) > + return false; > if (time_after_eq(jiffies, deadline)) > return true; > rq->deadline == 0 can be a valid deadline value so the above patch doesn't look right to me. Thanks, Bart. --- in patch 1, I added another modification in blk_add_timer(). As follows, > +#ifndef CONFIG_64BIT > +/* In case INITIAL_JIFFIES wraps on 32-bit */ > + expiry |= 1UL; The purpose of this modification is to ensure that rq->deadline is 0 means that it is initialized to 0 in blk_mq_req_expired(). In this case, make sure rq->deadline is an invalid value in blk_mq_req_expired(). Please review my workaround again. Thanks, Gu Mi.
