[Qemu-block] [PULL 06/36] block/backup: add 'never' policy to bitmap sync mode

[John Snow]

This adds a "never" policy for bitmap synchronization. Regardless of if
the job succeeds or fails, we never update the bitmap. This can be used
to perform differential backups, or simply to avoid the job modifying a
bitmap.

Signed-off-by: John Snow <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Message-id: address@hidden
Signed-off-by: John Snow <address@hidden>
---
 block/backup.c       | 7 +++++--
 qapi/block-core.json | 5 ++++-
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/block/backup.c b/block/backup.c
index 2b4c5c23e4e..d07b838930f 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -274,8 +274,11 @@ static void backup_cleanup_sync_bitmap(BackupBlockJob 
*job, int ret)
     BdrvDirtyBitmap *bm;
     BlockDriverState *bs = blk_bs(job->common.blk);
 
-    if (ret < 0) {
-        /* Merge the successor back into the parent, delete nothing. */
+    if (ret < 0 || job->bitmap_mode == BITMAP_SYNC_MODE_NEVER) {
+        /*
+         * Failure, or we don't want to synchronize the bitmap.
+         * Merge the successor back into the parent, delete nothing.
+         */
         bm = bdrv_reclaim_dirty_bitmap(bs, job->sync_bitmap, NULL);
         assert(bm);
     } else {
diff --git a/qapi/block-core.json b/qapi/block-core.json
index dd926f78285..06e34488a30 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1146,10 +1146,13 @@
 # @on-success: The bitmap is only synced when the operation is successful.
 #              This is the behavior always used for 'INCREMENTAL' backups.
 #
+# @never: The bitmap is never synchronized with the operation, and is
+#         treated solely as a read-only manifest of blocks to copy.
+#
 # Since: 4.2
 ##
 { 'enum': 'BitmapSyncMode',
-  'data': ['on-success'] }
+  'data': ['on-success', 'never'] }
 
 ##
 # @MirrorCopyMode:
-- 
2.21.0