Re: [EXTERNAL] [PATCH] scsi: storvsc: Handle PERSISTENT_RESERVE_IN truncation for Hyper-V vFC

[Laurence Oberman <loberman@redhat.com>]

On Tue, 2026-04-07 at 22:30 +0000, Long Li wrote:
> 
> 
> > -----Original Message-----
> > From: Li Tian <litian@redhat.com>
> > Sent: Sunday, April 5, 2026 6:54 PM
> > To: linux-scsi@vger.kernel.org
> > Cc: Li Tian <litian@redhat.com>; KY Srinivasan <kys@microsoft.com>;
> > Haiyang
> > Zhang <haiyangz@microsoft.com>; Wei Liu <wei.liu@kernel.org>;
> > Dexuan Cui
> > <DECUI@microsoft.com>; Long Li <longli@microsoft.com>; James E.J.
> > Bottomley
> > <James.Bottomley@HansenPartnership.com>; Martin K. Petersen
> > <martin.petersen@oracle.com>; linux-hyperv@vger.kernel.org; linux-
> > kernel@vger.kernel.org
> > Subject: [EXTERNAL] [PATCH] scsi: storvsc: Handle
> > PERSISTENT_RESERVE_IN
> > truncation for Hyper-V vFC
> > 
> > The storvsc driver has become stricter in handling SRB status codes
> > returned by
> > the Hyper-V host. When using Virtual Fibre Channel (vFC)
> > passthrough, the host
> > may return SRB_STATUS_DATA_OVERRUN for PERSISTENT_RESERVE_IN
> > commands if the allocation length in the CDB does not match the
> > host's expected
> > response size.
> > 
> > Currently, this status is treated as a fatal error, propagating
> > Host_status=0x07 [DID_ERROR] to the SCSI mid-layer. This causes
> > userspace
> > storage utilities (such as sg_persist) to fail with transport
> > errors, even when the
> > host has actually returned the requested reservation data in the
> > buffer.
> > 
> > Refactor the existing command-specific workarounds into a new
> > helper function,
> > storvsc_host_mishandles_cmd(), and add PERSISTENT_RESERVE_IN to the
> > list of
> > commands where SRB status errors should be suppressed for vFC
> > devices. This
> > ensures that the SCSI mid-layer processes the returned data buffer
> > instead of
> > terminating the command.
> > 
> > Signed-off-by: Li Tian <litian@redhat.com>
> 
> Reviewed-by: Long Li <longli@microsoft.com>
> 
> 
> > ---
> >  drivers/scsi/storvsc_drv.c | 32 +++++++++++++++++++++-----------
> >  1 file changed, 21 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/scsi/storvsc_drv.c
> > b/drivers/scsi/storvsc_drv.c index
> > ae1abab97835..6977ca8a0658 100644
> > --- a/drivers/scsi/storvsc_drv.c
> > +++ b/drivers/scsi/storvsc_drv.c
> > @@ -1131,6 +1131,26 @@ static void
> > storvsc_command_completion(struct
> > storvsc_cmd_request *cmd_request,
> >  		kfree(payload);
> >  }
> > 
> > +/*
> > + * The current SCSI handling on the host side does not correctly
> > handle:
> > + * INQUIRY with page code 0x80, MODE_SENSE / MODE_SENSE_10 with
> > cmd[2]
> > +== 0x1c,
> > + * and (for FC) MAINTENANCE_IN / PERSISTENT_RESERVE_IN
> > passthrough.
> > + */
> > +static bool storvsc_host_mishandles_cmd(u8 opcode, struct
> > hv_device
> > +*device) {
> > +	switch (opcode) {
> > +	case INQUIRY:
> > +	case MODE_SENSE:
> > +	case MODE_SENSE_10:
> > +		return true;
> > +	case MAINTENANCE_IN:
> > +	case PERSISTENT_RESERVE_IN:
> > +		return hv_dev_is_fc(device);
> > +	default:
> > +		return false;
> > +	}
> > +}
> > +
> >  static void storvsc_on_io_completion(struct storvsc_device
> > *stor_device,
> >  				  struct vstor_packet
> > *vstor_packet,
> >  				  struct storvsc_cmd_request
> > *request) @@ -
> > 1141,22 +1161,12 @@ 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 and MODE_SENSE_10 command with cmd[2] ==
> > 0x1c
> > -	 * MAINTENANCE_IN is not supported by HyperV FC
> > passthrough
> > -	 *
> >  	 * 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) ||
> > -	   (stor_pkt->vm_srb.cdb[0] == MODE_SENSE_10) ||
> > -	   (stor_pkt->vm_srb.cdb[0] == MAINTENANCE_IN &&
> > -	   hv_dev_is_fc(device))) {
> > +	if (storvsc_host_mishandles_cmd(stor_pkt->vm_srb.cdb[0],
> > device)) {
> >  		vstor_packet->vm_srb.scsi_status = 0;
> >  		vstor_packet->vm_srb.srb_status =
> > SRB_STATUS_SUCCESS;
> >  	}
> > --
> > 2.53.0
> 

Looks good, rewrite of how it was done before but will achieve the same
behavior we wanted for the new addition for PR.

Reviewed-by: Laurence Oberman <loberman@redhat.com>