block: Drop permissions when migration completes

With image locking, permissions affect other qemu processes as well. We
want to be sure that the destination can run, so let's drop permissions
on the source when migration completes.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/block/block-backend.c b/block/block-backend.c
index a7ce72b..f3a6008 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -156,6 +156,30 @@ static void blk_root_activate(BdrvChild *child, Error **errp)
     }
 }
 
+static int blk_root_inactivate(BdrvChild *child)
+{
+    BlockBackend *blk = child->opaque;
+
+    if (blk->disable_perm) {
+        return 0;
+    }
+
+    /* Only inactivate BlockBackends for guest devices (which are inactive at
+     * this point because the VM is stopped) and unattached monitor-owned
+     * BlockBackends. If there is still any other user like a block job, then
+     * we simply can't inactivate the image. */
+    if (!blk->dev && !blk->name[0]) {
+        return -EPERM;
+    }
+
+    blk->disable_perm = true;
+    if (blk->root) {
+        bdrv_child_try_set_perm(blk->root, 0, BLK_PERM_ALL, &error_abort);
+    }
+
+    return 0;
+}
+
 static const BdrvChildRole child_root = {
     .inherit_options    = blk_root_inherit_options,
 
@@ -168,6 +192,7 @@ static const BdrvChildRole child_root = {
     .drained_end        = blk_root_drained_end,
 
     .activate           = blk_root_activate,
+    .inactivate         = blk_root_inactivate,
 };
 
 /*