[Qemu-devel] [RFC PATCH 07/16] block: Only swap non-persistent dirty bitmaps

[Fam Zheng]

Persistent dirty bitmaps are special because they're tightly associated
with, or even belonging to the driver, swapping them doesn't make much
sense. Because this has nothing to do with backward compatibility, it's
okay to just let them stay with the old BDS.

Signed-off-by: Fam Zheng <address@hidden>
---
 block.c                      | 11 +++++------
 block/dirty-bitmap.c         | 25 +++++++++++++++++++++++++
 include/block/dirty-bitmap.h |  1 +
 3 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/block.c b/block.c
index 78db342..3a29de2 100644
--- a/block.c
+++ b/block.c
@@ -2274,9 +2274,6 @@ static void bdrv_move_feature_fields(BlockDriverState 
*bs_dest,
     bs_dest->copy_on_read       = bs_src->copy_on_read;
 
     bs_dest->enable_write_cache = bs_src->enable_write_cache;
-
-    /* dirty bitmap */
-    bs_dest->dirty_bitmaps      = bs_src->dirty_bitmaps;
 }
 
 static void change_parent_backing_link(BlockDriverState *from,
@@ -2302,10 +2299,12 @@ static void change_parent_backing_link(BlockDriverState 
*from,
 }
 
 static void swap_feature_fields(BlockDriverState *bs_top,
-                                BlockDriverState *bs_new)
+                                BlockDriverState *bs_new,
+                                Error **errp)
 {
     BlockDriverState tmp;
 
+    bdrv_dirty_bitmap_swap(bs_top, bs_new);
     bdrv_move_feature_fields(&tmp, bs_top);
     bdrv_move_feature_fields(bs_top, bs_new);
     bdrv_move_feature_fields(bs_new, &tmp);
@@ -2343,7 +2342,7 @@ void bdrv_append(BlockDriverState *bs_new, 
BlockDriverState *bs_top)
     change_parent_backing_link(bs_top, bs_new);
 
     /* Some fields always stay on top of the backing file chain */
-    swap_feature_fields(bs_top, bs_new);
+    swap_feature_fields(bs_top, bs_new, NULL);
 
     bdrv_set_backing_hd(bs_new, bs_top);
     bdrv_unref(bs_top);
@@ -2368,7 +2367,7 @@ void bdrv_replace_in_backing_chain(BlockDriverState *old, 
BlockDriverState *new)
          * swap instead so that pointers aren't duplicated and cause trouble.
          * (Also, bdrv_swap() used to do the same.) */
         assert(!new->blk);
-        swap_feature_fields(old, new);
+        swap_feature_fields(old, new, NULL);
     }
     change_parent_backing_link(old, new);
 
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 882a0db..a3a401f 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -65,6 +65,31 @@ BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState 
*bs, const char *name)
     return NULL;
 }
 
+/* Swap non-persistent dirty bitmaps. */
+void bdrv_dirty_bitmap_swap(BlockDriverState *bs1, BlockDriverState *bs2)
+{
+    BdrvDirtyBitmap *bm, *next;
+    QLIST_HEAD(, BdrvDirtyBitmap) tmp = QLIST_HEAD_INITIALIZER(&tmp);
+
+    QLIST_FOREACH_SAFE(bm, &bs1->dirty_bitmaps, list, next) {
+        if (bm->persistent) {
+            continue;
+        }
+        QLIST_REMOVE(bm, list);
+        QLIST_INSERT_HEAD(&tmp, bm, list);
+    }
+    QLIST_FOREACH_SAFE(bm, &bs2->dirty_bitmaps, list, next) {
+        if (bm->persistent) {
+            continue;
+        }
+        QLIST_REMOVE(bm, list);
+        QLIST_INSERT_HEAD(&bs1->dirty_bitmaps, bm, list);
+    }
+    QLIST_FOREACH_SAFE(bm, &tmp, list, next) {
+        QLIST_INSERT_HEAD(&bs2->dirty_bitmaps, bm, list);
+    }
+}
+
 void bdrv_dirty_bitmap_make_anon(BdrvDirtyBitmap *bitmap)
 {
     assert(!bdrv_dirty_bitmap_frozen(bitmap));
diff --git a/include/block/dirty-bitmap.h b/include/block/dirty-bitmap.h
index 5885720..a4de9c7 100644
--- a/include/block/dirty-bitmap.h
+++ b/include/block/dirty-bitmap.h
@@ -23,6 +23,7 @@ BdrvDirtyBitmap *bdrv_reclaim_dirty_bitmap(BlockDriverState 
*bs,
                                            Error **errp);
 BdrvDirtyBitmap *bdrv_find_dirty_bitmap(BlockDriverState *bs,
                                         const char *name);
+void bdrv_dirty_bitmap_swap(BlockDriverState *bs1, BlockDriverState *bs2);
 void bdrv_dirty_bitmap_make_anon(BdrvDirtyBitmap *bitmap);
 int bdrv_dirty_bitmap_set_persistent(BlockDriverState *bs,
                                      BdrvDirtyBitmap *bitmap,
-- 
2.4.3