[PATCH V5 8/9] vhost: correctly set dirty pages in MMU notifiers callback

[Jason Wang]

We need make sure there's no reference on the map before trying to
mark set dirty pages.

Reported-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address")
Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
---
 drivers/vhost/vhost.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 29e8abe694f7..d8863aaaf0f6 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -386,13 +386,12 @@ static void vhost_invalidate_vq_start(struct vhost_virtqueue *vq,
 	++vq->invalidate_count;
 
 	map = vq->maps[index];
-	if (map) {
+	if (map)
 		vq->maps[index] = NULL;
-		vhost_set_map_dirty(vq, map, index);
-	}
 	spin_unlock(&vq->mmu_lock);
 
 	if (map) {
+		vhost_set_map_dirty(vq, map, index);
 		vhost_map_unprefetch(map);
 	}
 }
-- 
2.18.1