Re: [Qemu-devel] [PATCH v2 1/2] virtio-blk: Factor out virtio_blk_handle_scsi_req from virtio_blk_handle_scsi

[Paolo Bonzini <pbonzini@redhat.com>]

Il 22/05/2014 09:37, Fam Zheng ha scritto:
> -static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
> +int virtio_blk_handle_scsi_req(BlockDriverState *bs,
> +                               VirtIOBlkConf *conf,
> +                               VirtQueueElement *elem)

Two more comments...

please pass the VirtIOBlock * instead of bs/conf here.

>  {
> +    int status = VIRTIO_BLK_S_OK;
> +    struct virtio_scsi_inhdr *scsi = NULL;
>  #ifdef __linux__
> -    int ret;
>      int i;
> +    struct sg_io_hdr hdr;
>  #endif
> -    int status = VIRTIO_BLK_S_OK;
>
>      /*
>       * We require at least one output segment each for the virtio_blk_outhdr
> @@ -140,63 +142,61 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
>       * We also at least require the virtio_blk_inhdr, the virtio_scsi_inhdr
>       * and the sense buffer pointer in the input segments.
>       */
> -    if (req->elem.out_num < 2 || req->elem.in_num < 3) {
> -        virtio_blk_req_complete(req, VIRTIO_BLK_S_IOERR);
> -        g_free(req);
> -        return;
> +    if (elem->out_num < 2 || elem->in_num < 3) {
> +        status = VIRTIO_BLK_S_IOERR;
> +        goto fail;
>      }
>
>      /*
>       * The scsi inhdr is placed in the second-to-last input segment, just
>       * before the regular inhdr.
>       */
> -    req->scsi = (void *)req->elem.in_sg[req->elem.in_num - 2].iov_base;
> +    scsi = (void *)elem->in_sg[elem->in_num - 2].iov_base;
>
> -    if (!req->dev->blk.scsi) {
> +    /*
> +     * No support for bidirection commands yet.
> +     */
> +    if (elem->out_num > 2 && elem->in_num > 3) {
>          status = VIRTIO_BLK_S_UNSUPP;
>          goto fail;
>      }
>
> -    /*
> -     * No support for bidirection commands yet.
> -     */
> -    if (req->elem.out_num > 2 && req->elem.in_num > 3) {
> +    if (!conf->scsi) {
>          status = VIRTIO_BLK_S_UNSUPP;
>          goto fail;
>      }

Swapping the two conditionals unnecessarily makes the patch bigger.

Paolo

>  #ifdef __linux__
> -    struct sg_io_hdr hdr;
>      memset(&hdr, 0, sizeof(struct sg_io_hdr));
>      hdr.interface_id = 'S';
> -    hdr.cmd_len = req->elem.out_sg[1].iov_len;
> -    hdr.cmdp = req->elem.out_sg[1].iov_base;
> +    hdr.cmd_len = elem->out_sg[1].iov_len;
> +    hdr.cmdp = elem->out_sg[1].iov_base;
>      hdr.dxfer_len = 0;
>
> -    if (req->elem.out_num > 2) {
> +    if (elem->out_num > 2) {
>          /*
>           * If there are more than the minimally required 2 output segments
>           * there is write payload starting from the third iovec.
>           */
>          hdr.dxfer_direction = SG_DXFER_TO_DEV;
> -        hdr.iovec_count = req->elem.out_num - 2;
> +        hdr.iovec_count = elem->out_num - 2;
>
>          for (i = 0; i < hdr.iovec_count; i++)
> -            hdr.dxfer_len += req->elem.out_sg[i + 2].iov_len;
> +            hdr.dxfer_len += elem->out_sg[i + 2].iov_len;
>
> -        hdr.dxferp = req->elem.out_sg + 2;
> +        hdr.dxferp = elem->out_sg + 2;
>
> -    } else if (req->elem.in_num > 3) {
> +    } else if (elem->in_num > 3) {
>          /*
>           * If we have more than 3 input segments the guest wants to actually
>           * read data.
>           */
>          hdr.dxfer_direction = SG_DXFER_FROM_DEV;
> -        hdr.iovec_count = req->elem.in_num - 3;
> +        hdr.iovec_count = elem->in_num - 3;
>          for (i = 0; i < hdr.iovec_count; i++)
> -            hdr.dxfer_len += req->elem.in_sg[i].iov_len;
> +            hdr.dxfer_len += elem->in_sg[i].iov_len;
>
> -        hdr.dxferp = req->elem.in_sg;
> +        hdr.dxferp = elem->in_sg;
>      } else {
>          /*
>           * Some SCSI commands don't actually transfer any data.
> @@ -204,11 +204,11 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
>          hdr.dxfer_direction = SG_DXFER_NONE;
>      }
>
> -    hdr.sbp = req->elem.in_sg[req->elem.in_num - 3].iov_base;
> -    hdr.mx_sb_len = req->elem.in_sg[req->elem.in_num - 3].iov_len;
> +    hdr.sbp = elem->in_sg[elem->in_num - 3].iov_base;
> +    hdr.mx_sb_len = elem->in_sg[elem->in_num - 3].iov_len;
>
> -    ret = bdrv_ioctl(req->dev->bs, SG_IO, &hdr);
> -    if (ret) {
> +    status = bdrv_ioctl(bs, SG_IO, &hdr);
> +    if (status) {
>          status = VIRTIO_BLK_S_UNSUPP;
>          goto fail;
>      }
> @@ -224,23 +224,32 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
>          hdr.status = CHECK_CONDITION;
>      }
>
> -    stl_p(&req->scsi->errors,
> +    stl_p(&scsi->errors,
>            hdr.status | (hdr.msg_status << 8) |
>            (hdr.host_status << 16) | (hdr.driver_status << 24));
> -    stl_p(&req->scsi->residual, hdr.resid);
> -    stl_p(&req->scsi->sense_len, hdr.sb_len_wr);
> -    stl_p(&req->scsi->data_len, hdr.dxfer_len);
> +    stl_p(&scsi->residual, hdr.resid);
> +    stl_p(&scsi->sense_len, hdr.sb_len_wr);
> +    stl_p(&scsi->data_len, hdr.dxfer_len);
>
> -    virtio_blk_req_complete(req, status);
> -    g_free(req);
> -    return;
> +    return status;
>  #else
>      abort();
>  #endif
>
>  fail:
>      /* Just put anything nonzero so that the ioctl fails in the guest.  */
> -    stl_p(&req->scsi->errors, 255);
> +    if (scsi) {
> +        stl_p(&scsi->errors, 255);
> +    }
> +    return status;
> +}
> +
> +static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
> +{
> +    int status;
> +
> +    status = virtio_blk_handle_scsi_req(req->dev->bs, &req->dev->blk,
> +                                        &req->elem);
>      virtio_blk_req_complete(req, status);
>      g_free(req);
>  }
> diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
> index e4c41ff..1b00b48 100644
> --- a/include/hw/virtio/virtio-blk.h
> +++ b/include/hw/virtio/virtio-blk.h
> @@ -155,4 +155,8 @@ typedef struct VirtIOBlock {
>
>  void virtio_blk_set_conf(DeviceState *dev, VirtIOBlkConf *blk);
>
> +int virtio_blk_handle_scsi_req(BlockDriverState *bs,
> +                               VirtIOBlkConf *conf,
> +                               VirtQueueElement *elem);
> +
>  #endif
>