dirty-bitmaps: clean-up bitmaps loading and migration logic

This patch aims to bring the following behavior:

1. We don't load bitmaps, when started in inactive mode. It's the case
of incoming migration. In this case we wait for bitmaps migration
through migration channel (if 'dirty-bitmaps' capability is enabled) or
for invalidation (to load bitmaps from the image).

2. We don't remove persistent bitmaps on inactivation. Instead, we only
remove bitmaps after storing. This is the only way to restore bitmaps,
if we decided to resume source after [failed] migration with
'dirty-bitmaps' capability enabled (which means, that bitmaps were not
stored).

3. We load bitmaps on open and any invalidation, it's ok for all cases:
  - normal open
  - migration target invalidation with dirty-bitmaps capability
    (bitmaps are migrating through migration channel, the are not
     stored, so they should have IN_USE flag set and will be skipped
     when loading. However, it would fail if bitmaps are read-only[1])
  - migration target invalidation without dirty-bitmaps capability
    (normal load of the bitmaps, if migrated with shared storage)
  - source invalidation with dirty-bitmaps capability
    (skip because IN_USE)
  - source invalidation without dirty-bitmaps capability
    (bitmaps were dropped, reload them)

[1]: to accurately handle this, migration of read-only bitmaps is
     explicitly forbidden in this patch.

New mechanism for not storing bitmaps when migrate with dirty-bitmaps
capability is introduced: migration filed in BdrvDirtyBitmap.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: John Snow <jsnow@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index 14639439a2..8f38a3dec1 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -26,7 +26,6 @@ BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState *bs,
                                         const char *name);
 void bdrv_release_dirty_bitmap(BlockDriverState *bs, BdrvDirtyBitmap *bitmap);
 void bdrv_release_named_dirty_bitmaps(BlockDriverState *bs);
-void bdrv_release_persistent_dirty_bitmaps(BlockDriverState *bs);
 void bdrv_remove_persistent_dirty_bitmap(BlockDriverState *bs,
                                          const char *name,
                                          Error **errp);
@@ -72,6 +71,7 @@ void bdrv_dirty_bitmap_set_persistance(BdrvDirtyBitmap *bitmap,
 void bdrv_dirty_bitmap_set_qmp_locked(BdrvDirtyBitmap *bitmap, bool qmp_locked);
 void bdrv_merge_dirty_bitmap(BdrvDirtyBitmap *dest, const BdrvDirtyBitmap *src,
                              HBitmap **backup, Error **errp);
+void bdrv_dirty_bitmap_set_migration(BdrvDirtyBitmap *bitmap, bool migration);
 
 /* Functions that require manual locking.  */
 void bdrv_dirty_bitmap_lock(BdrvDirtyBitmap *bitmap);