Re: [PATCH 1/2] virtio-blk: Acquire context while switching them on dataplane start

[Eric Blake]

On 12/4/20 10:53 AM, Sergio Lopez wrote:
> On dataplane start, acquire the new AIO context before calling
> 'blk_set_aio_context', releasing it immediately afterwards. This
> prevents reaching the AIO context attach/detach notifier functions
> without having acquired it first.
> 
> It was also the only place where 'blk_set_aio_context' was called with
> an unprotected AIO context.
> 
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> ---
>  hw/block/dataplane/virtio-blk.c | 2 ++
>  1 file changed, 2 insertions(+)

Reviewed-by: Eric Blake <eblake@redhat.com>

I'll queue through my NBD tree, but will wait a couple days to see if
other block developers want to add review comments.

> 
> diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
> index 37499c5564..034e43cb1f 100644
> --- a/hw/block/dataplane/virtio-blk.c
> +++ b/hw/block/dataplane/virtio-blk.c
> @@ -214,7 +214,9 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
>      vblk->dataplane_started = true;
>      trace_virtio_blk_data_plane_start(s);
>  
> +    aio_context_acquire(s->ctx);
>      r = blk_set_aio_context(s->conf->conf.blk, s->ctx, &local_err);
> +    aio_context_release(s->ctx);
>      if (r < 0) {
>          error_report_err(local_err);
>          goto fail_guest_notifiers;
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org