[Qemu-devel] [PATCH 04/13] block: add meta bitmaps

[Vladimir Sementsov-Ogievskiy]

Meta bitmap is a 'dirty bitmap' for the BdrvDirtyBitmap. It tracks
changes (set/unset) of this BdrvDirtyBitmap. It is needed for live
migration of block dirty bitmaps.

Reviewed-by: John Snow <address@hidden>
Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
 block.c               | 44 ++++++++++++++++++++++++++++++++++++++++++++
 include/block/block.h |  7 +++++++
 2 files changed, 51 insertions(+)

diff --git a/block.c b/block.c
index 1171dbb..05307bc 100644
--- a/block.c
+++ b/block.c
@@ -61,9 +61,15 @@
  * (3) successor is set: frozen mode.
  *     A frozen bitmap cannot be renamed, deleted, anonymized, cleared, set,
  *     or enabled. A frozen bitmap can only abdicate() or reclaim().
+ *
+ * Meta bitmap:
+ * Meta bitmap is a 'dirty bitmap' for the BdrvDirtyBitmap. It tracks changes
+ * (set/unset) of this BdrvDirtyBitmap. It is needed for live migration of
+ * block dirty bitmaps.
  */
 struct BdrvDirtyBitmap {
     HBitmap *bitmap;            /* Dirty sector bitmap implementation */
+    HBitmap *meta_bitmap;       /* Meta bitmap */
     BdrvDirtyBitmap *successor; /* Anonymous child; implies frozen status */
     char *name;                 /* Optional non-empty unique ID */
     int64_t size;               /* Size of the bitmap (Number of sectors) */
@@ -3145,6 +3151,35 @@ void bdrv_dirty_bitmap_make_anon(BdrvDirtyBitmap *bitmap)
     bitmap->name = NULL;
 }
 
+HBitmap *bdrv_create_meta_bitmap(BdrvDirtyBitmap *bitmap,
+                                 uint64_t chunk_size)
+{
+    uint64_t sector_granularity;
+
+    assert((chunk_size & (chunk_size - 1)) == 0);
+
+    /* one chunk is corresponding to one bit of the meta bitmap, and each bit
+     * of the chunk is corresponding to 'bdrv_dirty_bitmap_granularity(bitmap)'
+     * bytes of the node */
+    sector_granularity =
+        (chunk_size * 8 * bdrv_dirty_bitmap_granularity(bitmap))
+        >> BDRV_SECTOR_BITS;
+    assert(sector_granularity);
+
+    bitmap->meta_bitmap =
+        hbitmap_alloc(bitmap->size, ctz64(sector_granularity));
+
+    return bitmap->meta_bitmap;
+}
+
+void bdrv_release_meta_bitmap(BdrvDirtyBitmap *bitmap)
+{
+    if (bitmap->meta_bitmap) {
+        hbitmap_free(bitmap->meta_bitmap);
+        bitmap->meta_bitmap = NULL;
+    }
+}
+
 BdrvDirtyBitmap *bdrv_create_dirty_bitmap(BlockDriverState *bs,
                                           uint32_t granularity,
                                           const char *name,
@@ -3305,6 +3340,9 @@ void bdrv_release_dirty_bitmap(BlockDriverState *bs, 
BdrvDirtyBitmap *bitmap)
             assert(!bdrv_dirty_bitmap_frozen(bm));
             QLIST_REMOVE(bitmap, list);
             hbitmap_free(bitmap->bitmap);
+            if (bitmap->meta_bitmap) {
+                hbitmap_free(bitmap->meta_bitmap);
+            }
             g_free(bitmap->name);
             g_free(bitmap);
             return;
@@ -3390,6 +3428,9 @@ void bdrv_set_dirty_bitmap(BdrvDirtyBitmap *bitmap,
 {
     assert(bdrv_dirty_bitmap_enabled(bitmap));
     hbitmap_set(bitmap->bitmap, cur_sector, nr_sectors);
+    if (bitmap->meta_bitmap) {
+        hbitmap_set(bitmap->meta_bitmap, cur_sector, nr_sectors);
+    }
 }
 
 void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
@@ -3397,6 +3438,9 @@ void bdrv_reset_dirty_bitmap(BdrvDirtyBitmap *bitmap,
 {
     assert(bdrv_dirty_bitmap_enabled(bitmap));
     hbitmap_reset(bitmap->bitmap, cur_sector, nr_sectors);
+    if (bitmap->meta_bitmap) {
+        hbitmap_set(bitmap->meta_bitmap, cur_sector, nr_sectors);
+    }
 }
 
 void bdrv_clear_dirty_bitmap(BdrvDirtyBitmap *bitmap)
diff --git a/include/block/block.h b/include/block/block.h
index 5b9c2d6..7deb8e8 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -5,6 +5,7 @@
 #include "qemu-common.h"
 #include "qemu/option.h"
 #include "qemu/coroutine.h"
+#include "qemu/hbitmap.h"
 #include "block/accounting.h"
 #include "qapi/qmp/qobject.h"
 #include "qapi-types.h"
@@ -511,6 +512,12 @@ void bdrv_dirty_bitmap_deserialize_zeroes(BdrvDirtyBitmap 
*bitmap,
                                           uint64_t start, uint64_t count);
 void bdrv_dirty_bitmap_deserialize_finish(BdrvDirtyBitmap *bitmap);
 
+/* chunk size here is number of bytes of the @bitmap data per one bit of the
+ * meta bitmap being created */
+HBitmap *bdrv_create_meta_bitmap(BdrvDirtyBitmap *bitmap,
+                                 uint64_t granularity);
+void bdrv_release_meta_bitmap(BdrvDirtyBitmap *bitmap);
+
 void bdrv_enable_copy_on_read(BlockDriverState *bs);
 void bdrv_disable_copy_on_read(BlockDriverState *bs);
 
-- 
2.1.4