Re: [PATCH] ibmvscsis: Initial commit of IBM VSCSI Tgt Driver

[Bart Van Assche]

On 05/24/2016 01:00 PM, Bryant G Ly wrote:
> Quoting Bart Van Assche <bart.vanassche@xxxxxxxxxxx>:
> > On 05/24/2016 06:52 AM, Bryant G. Ly wrote:
> > > +static uint64_t ibmvscsis_unpack_lun(const uint8_t *lun, int len)
> > > +{
> > > +    uint64_t res = NO_SUCH_LUN;
> > > +    int addressing_method;
> > > +
> > > +    if (unlikely(len < 2)) {
> > > +        pr_err("Illegal LUN length %d, expected 2 bytes or more\n",
> > > +            len);
> > > +        goto out;
> > > +    }
> > > +
> > > +    switch (len) {
> > > +    case 8:
> > > +        if ((*((__be64 *)lun) & cpu_to_be64(0x0000FFFFFFFFFFFFLL))
> > > != 0)
> > > +            goto out_err;
> > > +        break;
> > > +    case 4:
> > > +        if (*((__be16 *)&lun[2]) != 0)
> > > +            goto out_err;
> > > +        break;
> > > +    case 6:
> > > +        if (*((__be32 *)&lun[2]) != 0)
> > > +            goto out_err;
> > > +        break;
> > > +    case 2:
> > > +        break;
> > > +    default:
> > > +        goto out_err;
> > > +    }
> > > +
> > > +    addressing_method = (*lun) >> 6; /* highest two bits of byte 0 */
> > > +    switch (addressing_method) {
> > > +    case SCSI_LUN_ADDR_METHOD_PERIPHERAL:
> > > +    case SCSI_LUN_ADDR_METHOD_FLAT:
> > > +    case SCSI_LUN_ADDR_METHOD_LUN:
> > > +        res = *(lun + 1) | (((*lun) & 0x3f) << 8);
> > > +        break;
> > > +
> > > +    case SCSI_LUN_ADDR_METHOD_EXTENDED_LUN:
> > > +    default:
> > > +        pr_err("Unimplemented LUN addressing method %u\n",
> > > +            addressing_method);
> > > +        break;
> > > +    }
> > > +
> > > +out:
> > > +    return res;
> > > +out_err:
> > > +    pr_err("Support for multi-level LUNs has not yet been
> > > implemented\n");
> > > +    goto out;
> > > +}
> >
> > In the above function there is nothing that is specific to the VIO
> > mechanism. Please consider to merge this function with
> > scsilun_to_int(), e.g. by introducing a new function that accepts a
> > SCSI LUN and the addressing method as arguments and by making
> > scsilun_to_int() call that function with
> > SCSI_LUN_ADDR_METHOD_PERIPHERAL as one of its arguments.
>
> We are going to keep this here atm, until we can make sure canonical can
> pick up
> these changes, since we have a deliverable for a 3rd party vendor who is
> going to
> fully utilize this driver. Once they can pick it up in 4.4 kernel I will
> make the
> change you recommended / move the scsi_lun_addr_method addressed below.
> I will also
> address the changes that ib_srpt needs to utilize this new function too.

A much better approach would be to move this function into the SCSI core 
and to add a copy of that function to the backported driver that will be 
provided to Canonical.

Thanks,

Bart.