[PATCH V2 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 <m...@redhat.com>
Fixes: 7f466032dc9e ("vhost: access vq metadata through kernel virtual address")
Signed-off-by: Jason Wang <jasow...@redhat.com>
---
 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 db2c81cb1e90..fc2da8a0c671 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -414,14 +414,13 @@ static void vhost_invalidate_vq_start(struct 
vhost_virtqueue *vq,
        ++vq->invalidate_count;
 
        map = vq->maps[index];
-       if (map) {
-               vhost_set_map_dirty(vq, map, index);
+       if (map)
                vq->maps[index] = NULL;
-       }
        spin_unlock(&vq->mmu_lock);
 
        if (map) {
                vhost_vq_sync_access(vq);
+               vhost_set_map_dirty(vq, map, index);
                vhost_map_unprefetch(map);
        }
 }
-- 
2.18.1