Re: [PATCH v2 5/4] virtio_balloon: warn on failed buffer add in stats_handle_request()

[David Hildenbrand (Arm)]

On 6/24/26 17:40, Denis V. Lunev wrote:
> Like tell_host(), stats_handle_request() ignores the return value of
> virtqueue_add_outbuf() and kicks the queue regardless. The same "we
> should always be able to add one buffer to an empty queue" assumption
> does not hold once the virtqueue has been broken (e.g. on device
> shutdown), where the add fails with -EIO. Unlike tell_host() it does
> not wait_event() afterwards so it cannot hang, but it still kicks a
> queue with nothing queued.
> 
> Warn and bail out on failure, mirroring tell_host() and
> virtballoon_free_page_report().
> 
> Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Denis V. Lunev <den@xxxxxxxxxx>
> ---
>  drivers/virtio/virtio_balloon.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 0866a8781f0b..454bbb77331d 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -445,6 +445,7 @@ static void stats_handle_request(struct virtio_balloon *vb)
>  	struct virtqueue *vq;
>  	struct scatterlist sg;
>  	unsigned int len, num_stats;
> +	int err;
>  
>  	num_stats = update_balloon_stats(vb);
>  
> @@ -452,7 +453,9 @@ static void stats_handle_request(struct virtio_balloon *vb)
>  	if (!virtqueue_get_buf(vq, &len))
>  		return;
>  	sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats);
> -	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> +	err = virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> +	if (WARN_ON_ONCE(err))
> +		return;
>  	virtqueue_kick(vq);
>  }
>  

Reviewed-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

Although I would just squash #4 and #5.

-- 
Cheers,

David