We are going to publish copy-before-write filter to be used in separate
of backup. Future step would support bitmap for the filter. But let's
start from full set bitmap.

We have to modify backup, as bitmap is first initialized by
copy-before-write filter, and then backup modifies it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 block/backup.c            | 16 +++++++---------
 block/copy-before-write.c |  4 ++++
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/block/backup.c b/block/backup.c
index af17149f22..14652ac98a 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -233,18 +233,16 @@ static void backup_init_bcs_bitmap(BackupBlockJob *job)
     BdrvDirtyBitmap *bcs_bitmap = block_copy_dirty_bitmap(job->bcs);
 
     if (job->sync_mode == MIRROR_SYNC_MODE_BITMAP) {
+        bdrv_clear_dirty_bitmap(bcs_bitmap, NULL);
         ret = bdrv_dirty_bitmap_merge_internal(bcs_bitmap, job->sync_bitmap,
                                                NULL, true);
         assert(ret);
-    } else {
-        if (job->sync_mode == MIRROR_SYNC_MODE_TOP) {
-            /*
-             * We can't hog the coroutine to initialize this thoroughly.
-             * Set a flag and resume work when we are able to yield safely.
-             */
-            block_copy_set_skip_unallocated(job->bcs, true);
-        }
-        bdrv_set_dirty_bitmap(bcs_bitmap, 0, job->len);
+    } else if (job->sync_mode == MIRROR_SYNC_MODE_TOP) {
+        /*
+         * We can't hog the coroutine to initialize this thoroughly.
+         * Set a flag and resume work when we are able to yield safely.
+         */
+        block_copy_set_skip_unallocated(job->bcs, true);
     }
 
     estimate = bdrv_get_dirty_count(bcs_bitmap);
diff --git a/block/copy-before-write.c b/block/copy-before-write.c
index e889af7b80..ba2466a328 100644
--- a/block/copy-before-write.c
+++ b/block/copy-before-write.c
@@ -147,6 +147,7 @@ static void cbw_child_perm(BlockDriverState *bs, BdrvChild *c,
 static int cbw_init(BlockDriverState *bs, QDict *options, Error **errp)
 {
     BDRVCopyBeforeWriteState *s = bs->opaque;
+    BdrvDirtyBitmap *copy_bitmap;
     bool compress;
 
     bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
@@ -184,6 +185,9 @@ static int cbw_init(BlockDriverState *bs, QDict *options, Error **errp)
         return -EINVAL;
     }
 
+    copy_bitmap = block_copy_dirty_bitmap(s->bcs);
+    bdrv_set_dirty_bitmap(copy_bitmap, 0, bdrv_dirty_bitmap_size(copy_bitmap));
+
     return 0;
 }
 
-- 
2.29.2

On 20.05.21 16:21, Vladimir Sementsov-Ogievskiy wrote:
> We are going to publish copy-before-write filter to be used in separate
> of backup. Future step would support bitmap for the filter. But let's
> start from full set bitmap.
>
> We have to modify backup, as bitmap is first initialized by
> copy-before-write filter, and then backup modifies it.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>   block/backup.c            | 16 +++++++---------
>   block/copy-before-write.c |  4 ++++
>   2 files changed, 11 insertions(+), 9 deletions(-)
>

Reviewed-by: Max Reitz <mreitz@redhat.com>