Re: [PATCH] block: don't decrement flush request refcount if it's state is idle in flush_end_io()

[yukuai (C)]

Please ignore this email, I reply to the wrong wmail.

Sincerely apologize
Kuai

在 2021/08/13 17:40, yukuai (C) 写道:
> Hi, jens
>
> Can you please consider to apply this patch?
>
> Thanks
> Kuai
>
> On 2021/08/08 15:03, Yu Kuai wrote:
> > flush_end_io() currently decrement request refcount unconditionally.
> > However, it's possible that the request is already idle and it's
> > refcount is zero since that flush_end_io() can be called concurrently.
> >
> > For example, nbd_clear_que() can be called concurrently with normal
> > io completion or io timeout.
> >
> > Thus check idle before decrement to avoid refcount_t underflow
> > warning.
> >
> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
> > ---
> >   block/blk-flush.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/block/blk-flush.c b/block/blk-flush.c
> > index 1002f6c58181..9b65dc43702c 100644
> > --- a/block/blk-flush.c
> > +++ b/block/blk-flush.c
> > @@ -222,7 +222,8 @@ static void flush_end_io(struct request *flush_rq, 
> > blk_status_t error)
> >       /* release the tag's ownership to the req cloned from */
> >       spin_lock_irqsave(&fq->mq_flush_lock, flags);
> > -    if (!refcount_dec_and_test(&flush_rq->ref)) {
> > +    if (blk_mq_rq_state(flush_rq) == MQ_RQ_IDLE ||
> > +        !refcount_dec_and_test(&flush_rq->ref)) {
> >           fq->rq_status = error;
> >           spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
> >           return;
> .