Re: [Qemu-devel] [PATCH v2 20/20] scsi-disk: correctly implement WRITE SAME

[Stefan Hajnoczi]

On Tue, Nov 19, 2013 at 06:07:43PM +0100, Paolo Bonzini wrote:
> +static void scsi_disk_emulate_write_same(SCSIDiskReq *r, uint8_t *inbuf)
> +{
> +    SCSIRequest *req = &r->req;
> +    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, req->dev);
> +    uint32_t nb_sectors = scsi_data_cdb_length(r->req.cmd.buf);
> +    WriteSameCBData *data;
> +    uint8_t *buf;
> +    int i;
> +
> +    /* Fail if PBDATA=1 or LBDATA=1 or ANCHOR=1.  */
> +    if (nb_sectors == 0 || (req->cmd.buf[1] & 0x16)) {
> +        scsi_check_condition(r, SENSE_CODE(INVALID_FIELD));
> +        return;
> +    }
> +
> +    if (bdrv_is_read_only(s->qdev.conf.bs)) {
> +        scsi_check_condition(r, SENSE_CODE(WRITE_PROTECTED));
> +        return;
> +    }
> +    if (!check_lba_range(s, r->req.cmd.lba, nb_sectors)) {
> +        scsi_check_condition(r, SENSE_CODE(LBA_OUT_OF_RANGE));
> +        return;
> +    }
> +
> +    if (buffer_is_zero(inbuf, s->qdev.blocksize)) {

Where is inbuf's size checked?  It must be s->qdev.blocksize for this
code to be correct.

> +        int flags = (req->cmd.buf[1] & 0x8) ? BDRV_REQ_MAY_UNMAP : 0;
> +
> +        /* The request is used as the AIO opaque value, so add a ref.  */
> +        scsi_req_ref(&r->req);
> +        bdrv_acct_start(s->qdev.conf.bs, &r->acct, nb_sectors * 
> s->qdev.blocksize,
> +                        BDRV_ACCT_WRITE);
> +        r->req.aiocb = bdrv_aio_write_zeroes(s->qdev.conf.bs,
> +                                             r->req.cmd.lba * 
> (s->qdev.blocksize / 512),
> +                                             nb_sectors * (s->qdev.blocksize 
> / 512),
> +                                             flags, scsi_aio_complete, r);
> +        return;
> +    }
> +
> +    data = g_new0(WriteSameCBData, 1);
> +    data->r = r;
> +    data->sector = r->req.cmd.lba * (s->qdev.blocksize / 512);
> +    data->nb_sectors = nb_sectors * (s->qdev.blocksize / 512);
> +    data->iov.iov_len = MIN(data->nb_sectors * 512, SCSI_WRITE_SAME_MAX);
> +    data->iov.iov_base = buf = g_malloc(data->iov.iov_len);

qemu_blockalign() so the buffer is aligned for O_DIRECT.