Re: [Qemu-devel] [PATCH] Fix iSCSI crash on SG_IO with an iovector

[Laszlo Ersek <lersek@redhat.com>]

On 06/22/13 03:37, Ronnie Sahlberg wrote:
> Don't assume that SG_IO is always invoked with a simple buffer,
> check the iovec_count and if it is > 1 then we need to pass an array
> of iovectors to libiscsi instead of just a plain buffer.
> 
> Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> ---
>  block/iscsi.c |   56 +++++++++++++++++++++++++++++++++++++++++++++++++-------
>  1 files changed, 49 insertions(+), 7 deletions(-)

Looks okay to me, but of course I'm not too familiar with this code.

You (or the maintainer with jurisdiction) might want to change the
commit message:

- check the iovec_count and if it is > 1 then we need to pass an array
+ check the iovec_count and if it is >= 1 then we need to pass an array

But I won't insist on a repost naturally!

I assume you tested the code for both definednesses of
LIBISCSI_FEATURE_IOVECTOR.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo

> 
> diff --git a/block/iscsi.c b/block/iscsi.c
> index 0bbf0b1..cbe2e8f 100644
> --- a/block/iscsi.c
> +++ b/block/iscsi.c
> @@ -651,6 +651,9 @@ iscsi_aio_ioctl_cb(struct iscsi_context *iscsi, int status,
>  {
>      IscsiAIOCB *acb = opaque;
>  
> +    g_free(acb->buf);
> +    acb->buf = NULL;
> +
>      if (acb->canceled != 0) {
>          return;
>      }
> @@ -727,14 +730,36 @@ static BlockDriverAIOCB *iscsi_aio_ioctl(BlockDriverState *bs,
>      memcpy(&acb->task->cdb[0], acb->ioh->cmdp, acb->ioh->cmd_len);
>      acb->task->expxferlen = acb->ioh->dxfer_len;
>  
> +    data.size = 0;
>      if (acb->task->xfer_dir == SCSI_XFER_WRITE) {
> -        data.data = acb->ioh->dxferp;
> -        data.size = acb->ioh->dxfer_len;
> +        if (acb->ioh->iovec_count == 0) {
> +            data.data = acb->ioh->dxferp;
> +            data.size = acb->ioh->dxfer_len;
> +        } else {
> +#if defined(LIBISCSI_FEATURE_IOVECTOR)
> +             scsi_task_set_iov_out(acb->task,
> +                                  (struct scsi_iovec *) acb->ioh->dxferp,
> +                                  acb->ioh->iovec_count);
> + #else
> +            int i;
> +            char *buf;
> +            struct scsi_iovec *iov = (struct scsi_iovec *)acb->ioh->dxferp;
> +
> +            acb->buf = g_malloc(acb->ioh->dxfer_len);
> +            buf = acb->buf;
> +            for (i = 0; i < acb->ioh->iovec_count; i++) {
> +                memcpy(buf, iov[i].iov_base, iov[i].iov_len);
> +                buf += iov[i].iov_len;
> +            }
> +            data.data = acb->buf;
> +            data.size = acb->ioh->dxfer_len;
> +#endif
> +        }
>      }
> +
>      if (iscsi_scsi_command_async(iscsi, iscsilun->lun, acb->task,
>                                   iscsi_aio_ioctl_cb,
> -                                 (acb->task->xfer_dir == SCSI_XFER_WRITE) ?
> -                                     &data : NULL,
> +                                 (data.size > 0) ? &data : NULL,
>                                   acb) != 0) {
>          scsi_free_scsi_task(acb->task);
>          qemu_aio_release(acb);
> @@ -743,9 +768,26 @@ static BlockDriverAIOCB *iscsi_aio_ioctl(BlockDriverState *bs,
>  
>      /* tell libiscsi to read straight into the buffer we got from ioctl */
>      if (acb->task->xfer_dir == SCSI_XFER_READ) {
> -        scsi_task_add_data_in_buffer(acb->task,
> -                                     acb->ioh->dxfer_len,
> -                                     acb->ioh->dxferp);
> +        if (acb->ioh->iovec_count == 0) {
> +            scsi_task_add_data_in_buffer(acb->task,
> +                                         acb->ioh->dxfer_len,
> +                                         acb->ioh->dxferp);
> +        } else {
> +#if defined(LIBISCSI_FEATURE_IOVECTOR)
> +            scsi_task_set_iov_in(acb->task,
> +                                 (struct scsi_iovec *) acb->ioh->dxferp,
> +                                 acb->ioh->iovec_count);
> +#else
> +            int i;
> +            for (i = 0; i < acb->ioh->iovec_count; i++) {
> +                struct scsi_iovec *iov = (struct scsi_iovec *)acb->ioh->dxferp;
> +
> +                scsi_task_add_data_in_buffer(acb->task,
> +                    iov[i].iov_len,
> +                    iov[i].iov_base);
> +            }
> +#endif
> +        }
>      }
>  
>      iscsi_set_events(iscsilun);
>