RE: [RFC] hv_storvsc: error handling.

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> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@xxxxxxxxxxxxxxxxxx]
> Sent: Monday, March 6, 2017 8:36 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>
> Cc: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>; Hannes
> Reinecke <hare@xxxxxxx>; Christoph Hellwig <hch@xxxxxx>; James
> Bottomley <jejb@xxxxxxxxxxxxxxxxxx>; Jens Axboe <axboe@xxxxxxxxx>;
> Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>; Martin K. Petersen
> <martin.petersen@xxxxxxxxxx>; Dexuan Cui <decui@xxxxxxxxxxxxx>; Long
> Li <longli@xxxxxxxxxxxxx>; Josh Poulson <jopoulso@xxxxxxxxxxxxx>; Adrian
> Suhov (Cloudbase Solutions SRL) <v-adsuho@xxxxxxxxxxxxx>; linux-
> scsi@xxxxxxxxxxxxxxx; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> Subject: Re: [RFC] hv_storvsc: error handling.
> 
> On Sat, 4 Mar 2017 21:03:41 +0000
> KY Srinivasan <kys@xxxxxxxxxxxxx> wrote:
> 
> > > -----Original Message-----
> > > From: Stephen Hemminger [mailto:stephen@xxxxxxxxxxxxxxxxxx]
> > > Sent: Friday, March 3, 2017 4:50 PM
> > > To: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> > > Cc: Hannes Reinecke <hare@xxxxxxx>; Christoph Hellwig <hch@xxxxxx>;
> > > James Bottomley <jejb@xxxxxxxxxxxxxxxxxx>; Jens Axboe
> > > <axboe@xxxxxxxxx>; Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>;
> > > Martin K. Petersen <martin.petersen@xxxxxxxxxx>; KY Srinivasan
> > > <kys@xxxxxxxxxxxxx>; Dexuan Cui <decui@xxxxxxxxxxxxx>; Long Li
> > > <longli@xxxxxxxxxxxxx>; Josh Poulson <jopoulso@xxxxxxxxxxxxx>;
> Adrian
> > > Suhov (Cloudbase Solutions SRL) <v-adsuho@xxxxxxxxxxxxx>; linux-
> > > scsi@xxxxxxxxxxxxxxx; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
> > > Subject: [RFC] hv_storvsc: error handling.
> > >
> > > Needs more testing but this does fix the observed problem.
> > >
> > > From: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
> > >
> > > Subject: [PATCH] hv_storvsc: fix error handling
> > >
> > > The Hyper-V storvsc SCSI driver was hiding all errors in INQUIRY and
> > > MODE_SENSE commands. This caused the scan process to incorrectly
> think
> > > devices were present and online.  Also invalid LUN errors were not
> > > being handled correctly.
> > >
> > > This fixes problems booting a GEN2 VM on Hyper-V. It effectively
> > > reverts commit 4ed51a21c0f69 ("Staging: hv: storvsc: Fixup
> > > srb and scsi status for INQUIRY and MODE_SENSE")
> > >
> > > Signed-off-by: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
> > > ---
> > >  drivers/scsi/storvsc_drv.c | 48 ++++------------------------------------------
> > >  1 file changed, 4 insertions(+), 44 deletions(-)
> > >
> > > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> > > index 638e5f427c90..8cc241fc54b8 100644
> > > --- a/drivers/scsi/storvsc_drv.c
> > > +++ b/drivers/scsi/storvsc_drv.c
> > > @@ -543,28 +543,6 @@ static void storvsc_host_scan(struct work_struct
> > > *work)
> > >  	kfree(wrk);
> > >  }
> > >
> > > -static void storvsc_remove_lun(struct work_struct *work)
> > > -{
> > > -	struct storvsc_scan_work *wrk;
> > > -	struct scsi_device *sdev;
> > > -
> > > -	wrk = container_of(work, struct storvsc_scan_work, work);
> > > -	if (!scsi_host_get(wrk->host))
> > > -		goto done;
> > > -
> > > -	sdev = scsi_device_lookup(wrk->host, 0, wrk->tgt_id, wrk->lun);
> > > -
> > > -	if (sdev) {
> > > -		scsi_remove_device(sdev);
> > > -		scsi_device_put(sdev);
> > > -	}
> > > -	scsi_host_put(wrk->host);
> > > -
> > > -done:
> > > -	kfree(wrk);
> > > -}
> > > -
> > > -
> > >  /*
> > >   * We can get incoming messages from the host that are not in response
> to
> > >   * messages that we have sent out. An example of this would be
> messages
> > > @@ -955,8 +933,7 @@ static void storvsc_handle_error(struct
> > > vmscsi_request *vm_srb,
> > >  		}
> > >  		break;
> > >  	case SRB_STATUS_INVALID_LUN:
> > > -		do_work = true;
> > > -		process_err_fn = storvsc_remove_lun;
> > > +		set_host_byte(scmnd, DID_NO_CONNECT);
> > >  		break;
> > >  	case SRB_STATUS_ABORTED:
> > >  		if (vm_srb->srb_status & SRB_STATUS_AUTOSENSE_VALID
> > > &&
> > > @@ -1050,32 +1027,15 @@ static void storvsc_on_io_completion(struct
> > > storvsc_device *stor_device,
> > >
> > >  	stor_pkt = &request->vstor_packet;
> > >
> > > -	/*
> > > -	 * The current SCSI handling on the host side does
> > > -	 * not correctly handle:
> > > -	 * INQUIRY command with page code parameter set to 0x80
> > > -	 * MODE_SENSE command with cmd[2] == 0x1c
> > > -	 *
> > > -	 * Setup srb and scsi status so this won't be fatal.
> > > -	 * We do this so we can distinguish truly fatal failues
> > > -	 * (srb status == 0x4) and off-line the device in that case.
> > > -	 */
> > > -
> > > -	if ((stor_pkt->vm_srb.cdb[0] == INQUIRY) ||
> > > -	   (stor_pkt->vm_srb.cdb[0] == MODE_SENSE)) {
> > > -		vstor_packet->vm_srb.scsi_status = 0;
> > > -		vstor_packet->vm_srb.srb_status = SRB_STATUS_SUCCESS;
> > > -	}
> > > -
> > > -
> > >  	/* Copy over the status...etc */
> > >  	stor_pkt->vm_srb.scsi_status = vstor_packet->vm_srb.scsi_status;
> > >  	stor_pkt->vm_srb.srb_status = vstor_packet->vm_srb.srb_status;
> > >  	stor_pkt->vm_srb.sense_info_length =
> > >  	vstor_packet->vm_srb.sense_info_length;
> > >
> > > -	if (vstor_packet->vm_srb.scsi_status != 0 ||
> > > -	    vstor_packet->vm_srb.srb_status != SRB_STATUS_SUCCESS)
> > > +	if (stor_pkt->vm_srb.cdb[0] != INQUIRY &&
> > > +	    (vstor_packet->vm_srb.scsi_status != 0 ||
> > > +	     vstor_packet->vm_srb.srb_status != SRB_STATUS_SUCCESS))
> > >  		storvsc_log(device, STORVSC_LOGGING_WARN,
> > >  			"cmd 0x%x scsi status 0x%x srb status 0x%x\n",
> > >  			stor_pkt->vm_srb.cdb[0],
> > > --
> >
> > This patch gets rid of the ability to "hot remove" LUNs. I don't think that can
> be part of any
> > solution. The INQUIRY hack I put in a long time ago was to deal with host
> bugs on prior versions of
> > Windows server. WS2016 should not be trigerring this code. Stephen, could
> you please test this patch -
> > a quick hack:
> >
> > From b97f24f224a71a6e745c42e5640045a553eb407c Mon Sep 17 00:00:00
> 2001
> > From: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> > Date: Sat, 4 Mar 2017 14:00:46 -0700
> > Subject: [PATCH 1/1] scsi: storvsc: Fix a bug in LUN removal code
> > Reply-To: kys@xxxxxxxxxxxxx
> >
> > Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> > ---
> >  drivers/scsi/storvsc_drv.c |   13 +++++++++++++
> >  1 files changed, 13 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> > index 05526b7..27eb682 100644
> > --- a/drivers/scsi/storvsc_drv.c
> > +++ b/drivers/scsi/storvsc_drv.c
> > @@ -885,6 +885,7 @@ static void storvsc_handle_error(struct
> vmscsi_request *vm_srb,
> >         struct storvsc_scan_work *wrk;
> >         void (*process_err_fn)(struct work_struct *work);
> >         bool do_work = false;
> > +       struct scsi_device *sdev;
> >
> >         switch (SRB_STATUS(vm_srb->srb_status)) {
> >         case SRB_STATUS_ERROR:
> > @@ -911,6 +912,18 @@ static void storvsc_handle_error(struct
> vmscsi_request *vm_srb,
> >                 }
> >                 break;
> >         case SRB_STATUS_INVALID_LUN:
> > +               if (!scsi_host_get(host)) {
> > +                       set_host_byte(scmnd, DID_NO_CONNECT);
> > +                       break;
> > +               }
> > +
> > +               sdev = scsi_device_lookup(wrk->host, 0, wrk->tgt_id, wrk->lun);
> > +
> > +               if (!sdev) {
> > +                       set_host_byte(scmnd, DID_NO_CONNECT);
> > +                       break;
> > +               }
> > +
> >                 do_work = true;
> >                 process_err_fn = storvsc_remove_lun;
> >                 break;
> 
> I will try it, but it can't work for two reasons.
> First, the INVALID_LUN error is masked off on INQUIRY in current code.
> Second, the scsi_device is instantiated already as part of scan probe process
> before it gets here.

Was the invalid LUN in the LUN0 position. Inquiry of LUN0 support (when LUN0 is not populated)
was added only recently to address host side issue.

> 
> The best solution so far is:
> 	- remove old INQUIRY/SENSE error masking
> 	+ add new workaround for INQUIRY of device id on LUN 0
> 	  which appears to be the reason for old masking
> 	+ return errors on missing LUN
> 	+ provide better transport services for hot remove (rather
>           than detecting by failed I/O).

This the mechanism used by the host for notifying LUN removal - invalid LUN error code.

K. Y
> 





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