[2/7] scsi-disk: support WRITE SAME (16) with unmap bit

Support discards via the WRITE SAME command with the unmap bit set, and
tell the initiator about the support for it via the block limit and the
new thin provisioning EVPD pages.  Also fix the comment which incorrectly
describedthe block limits EVPD page.

Signed-off-by: Christoph Hellwig <hch@lst.de>

Am 10.12.2010 16:00, schrieb Christoph Hellwig:
> Support discards via the WRITE SAME command with the unmap bit set, and
> tell the initiator about the support for it via the block limit and the
> new thin provisioning EVPD pages.  Also fix the comment which incorrectly
> describedthe block limits EVPD page.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Index: qemu/hw/scsi-disk.c
> ===================================================================
> --- qemu.orig/hw/scsi-disk.c	2010-12-07 09:35:44.203009851 +0100
> +++ qemu/hw/scsi-disk.c	2010-12-07 09:42:07.984255141 +0100
> @@ -424,7 +424,8 @@ static int scsi_disk_emulate_inquiry(SCS
>              outbuf[buflen++] = 0x80; // unit serial number
>              outbuf[buflen++] = 0x83; // device identification
>              if (bdrv_get_type_hint(s->bs) != BDRV_TYPE_CDROM) {
> -                outbuf[buflen++] = 0xb0; // block device characteristics
> +                outbuf[buflen++] = 0xb0; // block limits
> +                outbuf[buflen++] = 0xb2; // thin provisioning
>              }
>              outbuf[pages] = buflen - pages - 1; // number of pages
>              break;
> @@ -466,8 +467,10 @@ static int scsi_disk_emulate_inquiry(SCS
>              buflen += id_len;
>              break;
>          }
> -        case 0xb0: /* block device characteristics */
> +        case 0xb0: /* block limits */
>          {
> +            unsigned int unmap_sectors =
> +                    s->qdev.conf.discard_granularity / s->qdev.blocksize;
>              unsigned int min_io_size =
>                      s->qdev.conf.min_io_size / s->qdev.blocksize;
>              unsigned int opt_io_size =
> @@ -492,6 +495,21 @@ static int scsi_disk_emulate_inquiry(SCS
>              outbuf[13] = (opt_io_size >> 16) & 0xff;
>              outbuf[14] = (opt_io_size >> 8) & 0xff;
>              outbuf[15] = opt_io_size & 0xff;
> +
> +            /* optimal unmap granularity */
> +            outbuf[28] = (unmap_sectors >> 24) & 0xff;
> +            outbuf[29] = (unmap_sectors >> 16) & 0xff;
> +            outbuf[30] = (unmap_sectors >> 8) & 0xff;
> +            outbuf[31] = unmap_sectors & 0xff;
> +            break;
> +        }
> +        case 0xb2: /* thin provisioning */
> +        {
> +            outbuf[3] = buflen = 8;
> +            outbuf[4] = 0;
> +            outbuf[5] = 0x40; /* write same with unmap supported */
> +            outbuf[6] = 0;
> +            outbuf[7] = 0;
>              break;
>          }
>          default:
> @@ -959,6 +977,11 @@ static int scsi_disk_emulate_command(SCS
>              outbuf[11] = 0;
>              outbuf[12] = 0;
>              outbuf[13] = get_physical_block_exp(&s->qdev.conf);
> +
> +            /* set TPE bit if the format supports discard */
> +            if (s->qdev.conf.discard_granularity)
> +                outbuf[14] = 0x80;

Missing braces.

> +
>              /* Protection, exponent and lowest lba field left blank. */
>              buflen = req->cmd.xfer;
>              break;
> @@ -1123,6 +1146,34 @@ static int32_t scsi_send_command(SCSIDev
>              goto illegal_lba;
>          }
>          break;
> +    case WRITE_SAME_16:
> +        len = r->req.cmd.xfer / d->blocksize;
> +
> +        DPRINTF("WRITE SAME(16) (sector %" PRId64 ", count %d)\n",
> +                r->req.cmd.lba, len);
> +
> +        if (r->req.cmd.lba > s->max_lba) {
> +            goto illegal_lba;
> +        }
> +
> +        /*
> +         * We only support WRITE SAME with the unmap bit set for now.
> +         */
> +        if (!(buf[1] & 0x8)) {
> +            goto fail;
> +        }
> +
> +        rc = bdrv_discard(s->bs, r->req.cmd.lba * s->cluster_size,
> +                          len * s->cluster_size);
> +        if (rc < 0) {
> +            /* XXX: better error code ?*/
> +            goto fail;
> +        }
> +
> +        scsi_req_set_status(r, GOOD, NO_SENSE);
> +        scsi_req_complete(&r->req);
> +        scsi_remove_request(r);

Isn't this the same as scsi_command_complete()?

> +        return 0;

And if you break; here instead of returning (like all other commands)
and remove the three lines above completely, I think it would just do
the right thing.

Kevin

On Thu, Dec 16, 2010 at 04:48:15PM +0100, Kevin Wolf wrote:
> > +        scsi_req_set_status(r, GOOD, NO_SENSE);
> > +        scsi_req_complete(&r->req);
> > +        scsi_remove_request(r);
> 
> Isn't this the same as scsi_command_complete()?

Yes.

> 
> > +        return 0;
> 
> And if you break; here instead of returning (like all other commands)
> and remove the three lines above completely, I think it would just do
> the right thing.

Yes, that looks doable.