[Qemu-devel] [PATCH 06/12] block/dirty-bitmap: add bdrv_dirty_bitmap_claim

[John Snow <jsnow@redhat.com>]

This function can claim an hbitmap to replace its own current hbitmap.
In the case that the granularities do not match, it will use
hbitmap_merge to copy the bit data instead.

Signed-off-by: John Snow <jsnow@redhat.com>
---
 include/block/block_int.h |  1 +
 include/qemu/hbitmap.h    |  8 ++++++++
 block/dirty-bitmap.c      | 14 ++++++++++++++
 util/hbitmap.c            |  5 +++++
 4 files changed, 28 insertions(+)

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 89370c1b9b..7348ea8e78 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -1240,6 +1240,7 @@ void bdrv_set_dirty(BlockDriverState *bs, int64_t offset, int64_t bytes);
 
 void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap **out);
 void bdrv_restore_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap *backup);
+void bdrv_dirty_bitmap_claim(BdrvDirtyBitmap *bitmap, HBitmap **hbitmap);
 
 void bdrv_inc_in_flight(BlockDriverState *bs);
 void bdrv_dec_in_flight(BlockDriverState *bs);
diff --git a/include/qemu/hbitmap.h b/include/qemu/hbitmap.h
index 4afbe6292e..c74519042a 100644
--- a/include/qemu/hbitmap.h
+++ b/include/qemu/hbitmap.h
@@ -82,6 +82,14 @@ void hbitmap_truncate(HBitmap *hb, uint64_t size);
  */
 bool hbitmap_merge(const HBitmap *a, const HBitmap *b, HBitmap *result);
 
+/**
+ * hbitmap_same_conf:
+ *
+ * Compares the configuration for HBitmaps A and B.
+ * Return true if they are identical, false otherwise.
+ */
+bool hbitmap_same_conf(const HBitmap *a, const HBitmap *b);
+
 /**
  * hbitmap_can_merge:
  *
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 95a9c2a5d8..15c857e445 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -632,6 +632,20 @@ void bdrv_restore_dirty_bitmap(BdrvDirtyBitmap *bitmap, HBitmap *backup)
     hbitmap_free(tmp);
 }
 
+/* claim ownership of an hbitmap */
+void bdrv_dirty_bitmap_claim(BdrvDirtyBitmap *bitmap, HBitmap **hbitmap)
+{
+    if (hbitmap_same_conf(bitmap->bitmap, *hbitmap)) {
+        bdrv_restore_dirty_bitmap(bitmap, *hbitmap);
+    } else {
+        assert(hbitmap_can_merge(bitmap->bitmap, *hbitmap));
+        bdrv_clear_dirty_bitmap(bitmap, NULL);
+        hbitmap_merge(bitmap->bitmap, *hbitmap, bitmap->bitmap);
+        hbitmap_free(*hbitmap);
+    }
+    *hbitmap = NULL;
+}
+
 uint64_t bdrv_dirty_bitmap_serialization_size(const BdrvDirtyBitmap *bitmap,
                                               uint64_t offset, uint64_t bytes)
 {
diff --git a/util/hbitmap.c b/util/hbitmap.c
index 0d6724b7bc..a2abd425b5 100644
--- a/util/hbitmap.c
+++ b/util/hbitmap.c
@@ -775,6 +775,11 @@ void hbitmap_truncate(HBitmap *hb, uint64_t size)
     }
 }
 
+bool hbitmap_same_conf(const HBitmap *a, const HBitmap *b)
+{
+    return (a->size == b->size) && (a->granularity == b->granularity);
+}
+
 bool hbitmap_can_merge(const HBitmap *a, const HBitmap *b)
 {
     return (a->size == b->size);
-- 
2.21.0