virtio-balloon: Fix memory leak when unloading while hinting is in progress

commit 6c22dc61c76b7e7d355f1697ba0ecf26d1334ba6 upstream.

When unloading the driver while hinting is in progress, we will not
release the free page blocks back to MM, resulting in a memory leak.

Fixes: 86a559787e6f ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT")
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Wei Wang <wei.w.wang@intel.com>
Cc: Liang Li <liang.z.li@intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20200205163402.42627-2-david@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 246b7b5..90dd87c 100644 (file)
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -967,6 +967,10 @@ static void remove_common(struct virtio_balloon *vb)
                leak_balloon(vb, vb->num_pages);
        update_balloon_size(vb);
 
+       /* There might be free pages that are being reported: release them. */
+       if (virtio_has_feature(vb->vdev, VIRTIO_BALLOON_F_FREE_PAGE_HINT))
+               return_free_pages_to_mm(vb, ULONG_MAX);
+
        /* Now we reset the device so we can clean up the queues. */
        vb->vdev->config->reset(vb->vdev);