Re: [PATCH v19 2/3] scsi: ufs: L2P map management for HPB read

[Can Guo]

On 2021-02-08 16:03, Daejun Park wrote:
> > @@ -342,13 +1208,14 @@ void ufshpb_suspend(struct ufs_hba *hba)
> > >  	struct scsi_device *sdev;
> > >
> > >  	shost_for_each_device(sdev, hba->host) {
> > > -		hpb = sdev->hostdata;
> > > +		hpb = ufshpb_get_hpb_data(sdev);
> > >  		if (!hpb)
> > >  			continue;
> > >
> > >  		if (ufshpb_get_state(hpb) != HPB_PRESENT)
> > >  			continue;
> > >  		ufshpb_set_state(hpb, HPB_SUSPEND);
> > > +		ufshpb_cancel_jobs(hpb);
> >
> > Here may have a dead lock problem - in the case of runtime suspend,
> > when ufshpb_suspend() is invoked, all of hba's children scsi devices
> > are in RPM_SUSPENDED state. When this line tries to cancel a running
> > map work, i.e. when ufshpb_get_map_req() calls below lines, it will
> > be stuck at blk_queue_enter().
> >
> > req = blk_get_request(hpb->sdev_ufs_lu->request_queue,
> > 		      REQ_OP_SCSI_IN, 0);
> >
> > Please check block layer power management, and see also commit 
> > d55d15a33
> > ("scsi: block: Do not accept any requests while suspended").
>
> I am agree with your comment.
> How about add BLK_MQ_REQ_NOWAIT flag on blk_get_request() to avoid 
> hang?

That won't work - BLK_MQ_REQ_NOWAIT allows one to fast fail from 
blk_mq_get_tag(),
but blk_queue_enter() comes before __blk_mq_alloc_request();

Regards,

Can Guo.

> Thanks,
> Daejun