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

[Kevin Wolf]

Am 04.12.2020 um 17:53 hat Sergio Lopez geschrieben:
> 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(+)
> 
> 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);

bdrv_set_aio_context_ignore() is documented like this:

 * The caller must own the AioContext lock for the old AioContext of bs, but it
 * must not own the AioContext lock for new_context (unless new_context is the
 * same as the current context of bs).

Doesn't this patch lock the new context instead of the old one?

Kevin