scsi: vmw_pvscsi: Set residual data length conditionally

scsi: vmw_pvscsi: Set residual data length conditionally

The PVSCSI implementation in the VMware hypervisor under specific
configuration ("SCSI Bus Sharing" set to "Physical") returns zero dataLen
in the completion descriptor for READ CAPACITY(16). As a result, the kernel
can not detect proper disk geometry. This can be recognized by the kernel
message:

  [ 0.776588] sd 1:0:0:0: [sdb] Sector size 0 reported, assuming 512.

The PVSCSI implementation in QEMU does not set dataLen at all, keeping it
zeroed. This leads to a boot hang as was reported by Shmulik Ladkani.

It is likely that the controller returns the garbage at the end of the
buffer. Residual length should be set by the driver in that case. The SCSI
layer will erase corresponding data. See commit bdb2b8cab439 ("[SCSI] erase
invalid data returned by device") for details.

Commit e662502b3a78 ("scsi: vmw_pvscsi: Set correct residual data length")
introduced the issue by setting residual length unconditionally, causing
the SCSI layer to erase the useful payload beyond dataLen when this value
is returned as 0.

As a result, considering existing issues in implementations of PVSCSI
controllers, we do not want to call scsi_set_resid() when dataLen ==
0. Calling scsi_set_resid() has no effect if dataLen equals buffer length.

Link: https://lore.kernel.org/lkml/20210824120028.30d9c071@blondie/
Link: https://lore.kernel.org/r/20211220190514.55935-1-amakhalov@vmware.com
Fixes: e662502b3a78 ("scsi: vmw_pvscsi: Set correct residual data length")
Cc: Matt Wang <wwentao@vmware.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Vishal Bhakta <vbhakta@vmware.com>
Cc: VMware PV-Drivers <pv-drivers@vmware.com>
Cc: James E.J. Bottomley <jejb@linux.ibm.com>
Cc: linux-scsi@vger.kernel.org
Cc: stable@vger.kernel.org
Reported-and-suggested-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>