Instead of implying a locked status, make it explicit.
Now, bitmaps in use by migration, NBD or backup operations
are all treated the same way with the same code paths.
---
 block/dirty-bitmap.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 1a433130ff..22c4a9e0fe 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -188,10 +188,8 @@ bool bdrv_dirty_bitmap_has_successor(BdrvDirtyBitmap *bitmap)
     return bitmap->successor;
 }
 
-/* Both conditions disallow user-modification via QMP. */
 bool bdrv_dirty_bitmap_user_locked(BdrvDirtyBitmap *bitmap) {
-    return bdrv_dirty_bitmap_has_successor(bitmap) ||
-           bdrv_dirty_bitmap_qmp_locked(bitmap);
+    return bdrv_dirty_bitmap_qmp_locked(bitmap);
 }
 
 void bdrv_dirty_bitmap_set_qmp_locked(BdrvDirtyBitmap *bitmap, bool qmp_locked)
@@ -266,8 +264,9 @@ int bdrv_dirty_bitmap_create_successor(BlockDriverState *bs,
     child->disabled = bitmap->disabled;
     bitmap->disabled = true;
 
-    /* Install the successor and freeze the parent */
+    /* Install the successor and lock the parent */
     bitmap->successor = child;
+    bitmap->qmp_locked = true;
     return 0;
 }
 
@@ -321,6 +320,7 @@ BdrvDirtyBitmap *bdrv_dirty_bitmap_abdicate(BlockDriverState *bs,
     bitmap->successor = NULL;
     successor->persistent = bitmap->persistent;
     bitmap->persistent = false;
+    bitmap->qmp_locked = false;
     bdrv_release_dirty_bitmap(bs, bitmap);
 
     return successor;
@@ -349,6 +349,7 @@ BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap_locked(BlockDriverState *bs,
     }
 
     parent->disabled = successor->disabled;
+    parent->qmp_locked = false;
     bdrv_release_dirty_bitmap_locked(successor);
     parent->successor = NULL;
 
-- 
2.17.2

On 2/11/19 7:02 PM, John Snow wrote:
> Instead of implying a locked status, make it explicit.
> Now, bitmaps in use by migration, NBD or backup operations
> are all treated the same way with the same code paths.
> ---
>  block/dirty-bitmap.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org