qcow2-bitmap: add qcow2_reopen_bitmaps_rw_hint()

Add version of qcow2_reopen_bitmaps_rw, which do the same work but
also return a hint about was header updated or not. This will be
used in the following fix for bitmaps reloading after migration.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20180320170521.32152-2-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

block/qcow2-bitmap.c

@@ -1004,14 +1004,19 @@ bool qcow2_load_dirty_bitmaps(BlockDriverState *bs, Error **errp)
     return false;
 }
 
-int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp)
+int qcow2_reopen_bitmaps_rw_hint(BlockDriverState *bs, bool *header_updated,
+                                 Error **errp)
 {
     BDRVQcow2State *s = bs->opaque;
     Qcow2BitmapList *bm_list;
     Qcow2Bitmap *bm;
     GSList *ro_dirty_bitmaps = NULL;
     int ret = 0;
 
+    if (header_updated != NULL) {
+        *header_updated = false;
+    }
+
     if (s->nb_bitmaps == 0) {
         /* No bitmaps - nothing to do */
         return 0;
@@ -1055,6 +1060,9 @@ int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp)
             error_setg_errno(errp, -ret, "Can't update bitmap directory");
             goto out;
         }
+        if (header_updated != NULL) {
+            *header_updated = true;
+        }
         g_slist_foreach(ro_dirty_bitmaps, set_readonly_helper, false);
     }
 
@@ -1065,6 +1073,11 @@ int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp)
     return ret;
 }
 
+int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp)
+{
+    return qcow2_reopen_bitmaps_rw_hint(bs, NULL, errp);
+}
+
 /* store_bitmap_data()
  * Store bitmap to image, filling bitmap table accordingly.
  */

block/qcow2.h

@@ -671,6 +671,8 @@ int qcow2_check_bitmaps_refcounts(BlockDriverState *bs, BdrvCheckResult *res,
                                   void **refcount_table,
                                   int64_t *refcount_table_size);
 bool qcow2_load_dirty_bitmaps(BlockDriverState *bs, Error **errp);
+int qcow2_reopen_bitmaps_rw_hint(BlockDriverState *bs, bool *header_updated,
+                                 Error **errp);
 int qcow2_reopen_bitmaps_rw(BlockDriverState *bs, Error **errp);
 void qcow2_store_persistent_dirty_bitmaps(BlockDriverState *bs, Error **errp);
 int qcow2_reopen_bitmaps_ro(BlockDriverState *bs, Error **errp);