1 files changed, 18 insertions, 4 deletions

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index cd778b1752b5..3db3d242c3ee 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -51,6 +51,7 @@ struct virtio_balloon
         u32 pfns[256];
 
         /* Memory statistics */
+        int need_stats_update;
         struct virtio_balloon_stat stats[VIRTIO_BALLOON_S_NR];
 };
 
@@ -193,20 +194,30 @@ static void update_balloon_stats(struct virtio_balloon *vb)
  * the stats queue operates in reverse.  The driver initializes the virtqueue
  * with a single buffer.  From that point forward, all conversations consist of
  * a hypervisor request (a call to this function) which directs us to refill
- * the virtqueue with a fresh stats buffer.
+ * the virtqueue with a fresh stats buffer.  Since stats collection can sleep,
+ * we notify our kthread which does the actual work via stats_handle_request().
  */
-static void stats_ack(struct virtqueue *vq)
+static void stats_request(struct virtqueue *vq)
 {
         struct virtio_balloon *vb;
         unsigned int len;
-        struct scatterlist sg;
 
         vb = vq->vq_ops->get_buf(vq, &len);
         if (!vb)
                 return;
+        vb->need_stats_update = 1;
+        wake_up(&vb->config_change);
+}
+
+static void stats_handle_request(struct virtio_balloon *vb)
+{
+        struct virtqueue *vq;
+        struct scatterlist sg;
 
+        vb->need_stats_update = 0;
         update_balloon_stats(vb);
 
+        vq = vb->stats_vq;
         sg_init_one(&sg, vb->stats, sizeof(vb->stats));
         if (vq->vq_ops->add_buf(vq, &sg, 1, 0, vb) < 0)
                 BUG();
@@ -249,8 +260,11 @@ static int balloon(void *_vballoon)
                 try_to_freeze();
                 wait_event_interruptible(vb->config_change,
                                          (diff = towards_target(vb)) != 0
+                                         || vb->need_stats_update
                                          || kthread_should_stop()
                                          || freezing(current));
+                if (vb->need_stats_update)
+                        stats_handle_request(vb);
                 if (diff > 0)
                         fill_balloon(vb, diff);
                 else if (diff < 0)
@@ -264,7 +278,7 @@ static int virtballoon_probe(struct virtio_device *vdev)
 {
         struct virtio_balloon *vb;
         struct virtqueue *vqs[3];
-        vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_ack };
+        vq_callback_t *callbacks[] = { balloon_ack, balloon_ack, stats_request };
         const char *names[] = { "inflate", "deflate", "stats" };
         int err, nvqs;