virtqueue_add_outbuf() can fail, when it fails, there is no need
to call the funciont virtqueue_kick().

Signed-off-by: Bo Liu <liubo03@inspur.com>
---
 drivers/virtio/virtio_balloon.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index b9737da6c4dd..0d7da4d95e1e 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -153,16 +153,18 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
 {
 	struct scatterlist sg;
 	unsigned int len;
+	int err;
 
 	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
 
 	/* We should always be able to add one buffer to an empty queue. */
-	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
-	virtqueue_kick(vq);
-
-	/* When host has read buffer, this completes via balloon_ack */
-	wait_event(vb->acked, virtqueue_get_buf(vq, &len));
+	err = virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
+	if (!err) {
+		virtqueue_kick(vq);
 
+		/* When host has read buffer, this completes via balloon_ack */
+		wait_event(vb->acked, virtqueue_get_buf(vq, &len));
+	}
 }
 
 static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
@@ -382,6 +384,7 @@ 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);
 
@@ -389,8 +392,9 @@ 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);
-	virtqueue_kick(vq);
+	err = virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
+	if (!err)
+		virtqueue_kick(vq);
 }
 
 static inline s64 towards_target(struct virtio_balloon *vb)
-- 
2.27.0

On Thu, May 26, 2022 at 09:34:01PM -0400, Bo Liu wrote:
> virtqueue_add_outbuf() can fail, when it fails, there is no need
> to call the funciont virtqueue_kick().
> Signed-off-by: Bo Liu <liubo03@inspur.com>

Sorry don't get it.
What's the point of this patch really?

> ---
>  drivers/virtio/virtio_balloon.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index b9737da6c4dd..0d7da4d95e1e 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -153,16 +153,18 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq)
>  {
>  	struct scatterlist sg;
>  	unsigned int len;
> +	int err;
>  
>  	sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns);
>  
>  	/* We should always be able to add one buffer to an empty queue. */
> -	virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> -	virtqueue_kick(vq);
> -
> -	/* When host has read buffer, this completes via balloon_ack */
> -	wait_event(vb->acked, virtqueue_get_buf(vq, &len));
> +	err = virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> +	if (!err) {
> +		virtqueue_kick(vq);
>  
> +		/* When host has read buffer, this completes via balloon_ack */
> +		wait_event(vb->acked, virtqueue_get_buf(vq, &len));
> +	}
>  }
>  
>  static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info,
> @@ -382,6 +384,7 @@ 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);
>  
> @@ -389,8 +392,9 @@ 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);
> -	virtqueue_kick(vq);
> +	err = virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL);
> +	if (!err)
> +		virtqueue_kick(vq);
>  }
>  
>  static inline s64 towards_target(struct virtio_balloon *vb)
> -- 
> 2.27.0