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From:   Michael Kelley <mikelley@microsoft.com>
To:     Long Li <longli@microsoft.com>, KY Srinivasan <kys@microsoft.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        "jejb@linux.ibm.com" <jejb@linux.ibm.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>
Subject: RE: [PATCH 3/3] scsi: storvsc: Correctly handle multiple flags in
 srb_status
Thread-Topic: [PATCH 3/3] scsi: storvsc: Correctly handle multiple flags in
 srb_status
Thread-Index: AQHXWWYJfm7T4x/P7ECmgJNN1E96wasJJSuAgAEQpHA=
Date:   Tue, 8 Jun 2021 14:48:44 +0000
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From: Long Li <longli@microsoft.com> Sent: Monday, June 7, 2021 3:25 PM
> >
> > Hyper-V is observed to sometimes set multiple flags in the srb_status, =
such
> > as ABORTED and ERROR. Current code in
> > storvsc_handle_error() handles only a single flag being set, and does n=
othing
> > when multiple flags are set.  Fix this by changing the case statement i=
nto a
> > series of "if" statements testing individual flags. The functionality f=
or handling
> > each flag is unchanged.
> >
> > Signed-off-by: Michael Kelley <mikelley@microsoft.com>
> > ---
> >  drivers/scsi/storvsc_drv.c | 61 +++++++++++++++++++++++++-------------=
---
> > -----
> >  1 file changed, 33 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c in=
dex
> > fff9441..e96d2aa 100644
> > --- a/drivers/scsi/storvsc_drv.c
> > +++ b/drivers/scsi/storvsc_drv.c
> > @@ -1009,17 +1009,40 @@ static void storvsc_handle_error(struct
> > vmscsi_request *vm_srb,
> >  	struct storvsc_scan_work *wrk;
> >  	void (*process_err_fn)(struct work_struct *work);
> >  	struct hv_host_device *host_dev =3D shost_priv(host);
> > -	bool do_work =3D false;
> >
> > -	switch (SRB_STATUS(vm_srb->srb_status)) {
> > -	case SRB_STATUS_ERROR:
> > +	/*
> > +	 * In some situations, Hyper-V sets multiple bits in the
> > +	 * srb_status, such as ABORTED and ERROR. So process them
> > +	 * individually, with the most specific bits first.
> > +	 */
> > +
> > +	if (vm_srb->srb_status & SRB_STATUS_INVALID_LUN) {
> > +		set_host_byte(scmnd, DID_NO_CONNECT);
> > +		process_err_fn =3D storvsc_remove_lun;
> > +		goto do_work;
> > +	}
> > +
> > +	if (vm_srb->srb_status & SRB_STATUS_ABORTED) {
> > +		if (vm_srb->srb_status & SRB_STATUS_AUTOSENSE_VALID &&
> > +		    /* Capacity data has changed */
> > +		    (asc =3D=3D 0x2a) && (ascq =3D=3D 0x9)) {
> > +			process_err_fn =3D storvsc_device_scan;
> > +			/*
> > +			 * Retry the I/O that triggered this.
> > +			 */
> > +			set_host_byte(scmnd, DID_REQUEUE);
> > +			goto do_work;
> > +		}
> > +	}
> > +
> > +	if (vm_srb->srb_status & SRB_STATUS_ERROR) {
>=20
> I'm curious on SRB_STATUS_INVALID_LUN and SRB_STATUS_ABORTED, the actions=
 on
> those two codes are different.
>=20
> It doesn't look like we can get those two in the same status code.

Agreed.  I've only observed having ERROR and ABORTED in the same status cod=
e.
That happens when a bad PFN is passed on a I/O request, which can be easily
tested.  With the old code, having ERROR and ABORTED together resulted in d=
oing
nothing.

The behavior of INVALID_LUN is unchanged by this patch.  But with this patc=
h,
if INVALID_LUN and ABORTED should ever occur together, we would process the
INVALID_LUN error, and ignore ABORTED, which I think makes sense.=20
INVALID_LUN is the most serious error, so we process it first.  Then ABORTE=
D is
next in priority for the specific case of "Capacity data has changed".  Fin=
ally we
handle ERROR.

Michael

>=20
> >  		/*
> >  		 * Let upper layer deal with error when
> >  		 * sense message is present.
> >  		 */
> > -
> >  		if (vm_srb->srb_status & SRB_STATUS_AUTOSENSE_VALID)
> > -			break;
> > +			return;
> > +
> >  		/*
> >  		 * If there is an error; offline the device since all
> >  		 * error recovery strategies would have already been @@ -
> > 1032,37 +1055,19 @@ static void storvsc_handle_error(struct vmscsi_requ=
est *vm_srb,
> >  			set_host_byte(scmnd, DID_PASSTHROUGH);
> >  			break;
> >  		/*
> > -		 * On Some Windows hosts TEST_UNIT_READY command can
> > return
> > -		 * SRB_STATUS_ERROR, let the upper level code deal with it
> > -		 * based on the sense information.
> > +		 * On some Hyper-V hosts TEST_UNIT_READY command can
> > +		 * return SRB_STATUS_ERROR. Let the upper level code
> > +		 * deal with it based on the sense information.
> >  		 */
> >  		case TEST_UNIT_READY:
> >  			break;
> >  		default:
> >  			set_host_byte(scmnd, DID_ERROR);
> >  		}
> > -		break;
> > -	case SRB_STATUS_INVALID_LUN:
> > -		set_host_byte(scmnd, DID_NO_CONNECT);
> > -		do_work =3D true;
> > -		process_err_fn =3D storvsc_remove_lun;
> > -		break;
> > -	case SRB_STATUS_ABORTED:
> > -		if (vm_srb->srb_status & SRB_STATUS_AUTOSENSE_VALID &&
> > -		    (asc =3D=3D 0x2a) && (ascq =3D=3D 0x9)) {
> > -			do_work =3D true;
> > -			process_err_fn =3D storvsc_device_scan;
> > -			/*
> > -			 * Retry the I/O that triggered this.
> > -			 */
> > -			set_host_byte(scmnd, DID_REQUEUE);
> > -		}
> > -		break;
> >  	}
> > +	return;
> >
> > -	if (!do_work)
> > -		return;
> > -
> > +do_work:
> >  	/*
> >  	 * We need to schedule work to process this error; schedule it.
> >  	 */
> > --
> > 1.8.3.1