Re: [PATCH 13/16] block/virtio-blk: Fix missing ERRP_GUARD() for error_prepend()

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Feb 29, 2024 at 12:37:20AM +0800, Zhao Liu wrote:
> From: Zhao Liu <zhao1.liu@intel.com>
> 
> As the comment in qapi/error, passing @errp to error_prepend() requires
> ERRP_GUARD():
> 
> * = Why, when and how to use ERRP_GUARD() =
> *
> * Without ERRP_GUARD(), use of the @errp parameter is restricted:
> ...
> * - It should not be passed to error_prepend(), error_vprepend() or
> *   error_append_hint(), because that doesn't work with &error_fatal.
> * ERRP_GUARD() lifts these restrictions.
> *
> * To use ERRP_GUARD(), add it right at the beginning of the function.
> * @errp can then be used without worrying about the argument being
> * NULL or &error_fatal.
> 
> ERRP_GUARD() could avoid the case when @errp is the pointer of
> error_fatal, the user can't see this additional information, because
> exit() happens in error_setg earlier than information is added [1].
> 
> The virtio_blk_vq_aio_context_init() passes @errp to error_prepend().
> 
> Though its @errp points its caller's local @err variable, to follow the
> requirement of @errp, add missing ERRP_GUARD() at the beginning of
> virtio_blk_vq_aio_context_init().
> 
> [1]: Issue description in the commit message of commit ae7c80a7bd73
>      ("error: New macro ERRP_GUARD()").
> 
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Hanna Reitz <hreitz@redhat.com>
> Signed-off-by: Zhao Liu <zhao1.liu@intel.com>


Acked-by: Michael S. Tsirkin <mst@redhat.com>

merge with other things please.

> ---
>  hw/block/virtio-blk.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index 738cb2ac367d..92de315f17f7 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -1682,6 +1682,7 @@ static bool apply_iothread_vq_mapping(
>  /* Context: BQL held */
>  static bool virtio_blk_vq_aio_context_init(VirtIOBlock *s, Error **errp)
>  {
> +    ERRP_GUARD();
>      VirtIODevice *vdev = VIRTIO_DEVICE(s);
>      VirtIOBlkConf *conf = &s->conf;
>      BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
> -- 
> 2.34.1