Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Sep 22, 2022 at 12:57:01PM -0400, Michael S. Tsirkin wrote:
> On Thu, Sep 22, 2022 at 11:45:15PM +0900, Suwan Kim wrote:
> > Hi Michael,
> > 
> > Can this patch be merged to the next rc?
> > We received two bug reports about this issue and need to fix it.
> > 
> > Regards,
> > Suwan Kim
> > 
> > 
> > On Wed, Aug 31, 2022 at 9:44 PM Pankaj Raghav <pankydev8@gmail.com> wrote:
> > >
> > > On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> > > > If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> > > > and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> > > > again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> > > > request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> > > > despite the failure.
> > > >
> > > > To avoid calling blk_mq_start_request() twice, This patch moves the
> > > > execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> > > > And instead of requeuing failed request to plug list in the error path of
> > > > virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> > > > request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> > > > on the next trial.
> > > >
> > > > Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> > > > Reported-by: Alexandre Courbot <acourbot@chromium.org>
> > > > Tested-by: Alexandre Courbot <acourbot@chromium.org>
> > > > Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> > > > ---
> > > Looks good.
> > > Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
> 
> Stefan, Paolo, any feedback here?

Oh, Stefan acked. Sorry. Will queue now.


> -- 
> MST