qapi: support external bitmaps in block-dirty-bitmap-merge

Add new optional parameter making possible to merge bitmaps from
different nodes. It is needed to maintain external snapshots during
incremental backup chain history.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20190517152111.206494-2-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>

block/dirty-bitmap.c

@@ -816,10 +816,10 @@ void bdrv_merge_dirty_bitmap(BdrvDirtyBitmap *dest, const BdrvDirtyBitmap *src,
 {
     bool ret;
 
-    /* only bitmaps from one bds are supported */
-    assert(dest->mutex == src->mutex);
-
     qemu_mutex_lock(dest->mutex);
+    if (src->mutex != dest->mutex) {
+        qemu_mutex_lock(src->mutex);
+    }
 
     if (bdrv_dirty_bitmap_check(dest, BDRV_BITMAP_DEFAULT, errp)) {
         goto out;
@@ -845,4 +845,7 @@ void bdrv_merge_dirty_bitmap(BdrvDirtyBitmap *dest, const BdrvDirtyBitmap *src,
 
 out:
     qemu_mutex_unlock(dest->mutex);
+    if (src->mutex != dest->mutex) {
+        qemu_mutex_unlock(src->mutex);
+    }
 }

blockdev.c

@@ -2112,11 +2112,10 @@ static void block_dirty_bitmap_disable_abort(BlkActionState *common)
     }
 }
 
-static BdrvDirtyBitmap *do_block_dirty_bitmap_merge(const char *node,
-                                                    const char *target,
-                                                    strList *bitmaps,
-                                                    HBitmap **backup,
-                                                    Error **errp);
+static BdrvDirtyBitmap *do_block_dirty_bitmap_merge(
+        const char *node, const char *target,
+        BlockDirtyBitmapMergeSourceList *bitmaps,
+        HBitmap **backup, Error **errp);
 
 static void block_dirty_bitmap_merge_prepare(BlkActionState *common,
                                              Error **errp)
@@ -2965,15 +2964,14 @@ void qmp_block_dirty_bitmap_disable(const char *node, const char *name,
     bdrv_disable_dirty_bitmap(bitmap);
 }
 
-static BdrvDirtyBitmap *do_block_dirty_bitmap_merge(const char *node,
-                                                    const char *target,
-                                                    strList *bitmaps,
-                                                    HBitmap **backup,
-                                                    Error **errp)
+static BdrvDirtyBitmap *do_block_dirty_bitmap_merge(
+        const char *node, const char *target,
+        BlockDirtyBitmapMergeSourceList *bitmaps,
+        HBitmap **backup, Error **errp)
 {
     BlockDriverState *bs;
     BdrvDirtyBitmap *dst, *src, *anon;
-    strList *lst;
+    BlockDirtyBitmapMergeSourceList *lst;
     Error *local_err = NULL;
 
     dst = block_dirty_bitmap_lookup(node, target, &bs, errp);
@@ -2988,11 +2986,28 @@ static BdrvDirtyBitmap *do_block_dirty_bitmap_merge(const char *node,
     }
 
     for (lst = bitmaps; lst; lst = lst->next) {
-        src = bdrv_find_dirty_bitmap(bs, lst->value);
-        if (!src) {
-            error_setg(errp, "Dirty bitmap '%s' not found", lst->value);
-            dst = NULL;
-            goto out;
+        switch (lst->value->type) {
+            const char *name, *node;
+        case QTYPE_QSTRING:
+            name = lst->value->u.local;
+            src = bdrv_find_dirty_bitmap(bs, name);
+            if (!src) {
+                error_setg(errp, "Dirty bitmap '%s' not found", name);
+                dst = NULL;
+                goto out;
+            }
+            break;
+        case QTYPE_QDICT:
+            node = lst->value->u.external.node;
+            name = lst->value->u.external.name;
+            src = block_dirty_bitmap_lookup(node, name, NULL, errp);
+            if (!src) {
+                dst = NULL;
+                goto out;
+            }
+            break;
+        default:
+            abort();
         }
 
         bdrv_merge_dirty_bitmap(anon, src, NULL, &local_err);
@@ -3012,7 +3027,8 @@ static BdrvDirtyBitmap *do_block_dirty_bitmap_merge(const char *node,
 }
 
 void qmp_block_dirty_bitmap_merge(const char *node, const char *target,
-                                  strList *bitmaps, Error **errp)
+                                  BlockDirtyBitmapMergeSourceList *bitmaps,
+                                  Error **errp)
 {
     do_block_dirty_bitmap_merge(node, target, bitmaps, NULL, errp);
 }

qapi/block-core.json

@@ -2003,19 +2003,35 @@
   'data': { 'node': 'str', 'name': 'str', '*granularity': 'uint32',
             '*persistent': 'bool', '*autoload': 'bool', '*disabled': 'bool' } }
 
+##
+# @BlockDirtyBitmapMergeSource:
+#
+# @local: name of the bitmap, attached to the same node as target bitmap.
+#
+# @external: bitmap with specified node
+#
+# Since: 4.1
+##
+{ 'alternate': 'BlockDirtyBitmapMergeSource',
+  'data': { 'local': 'str',
+            'external': 'BlockDirtyBitmap' } }
+
 ##
 # @BlockDirtyBitmapMerge:
 #
-# @node: name of device/node which the bitmap is tracking
+# @node: name of device/node which the @target bitmap is tracking
 #
 # @target: name of the destination dirty bitmap
 #
-# @bitmaps: name(s) of the source dirty bitmap(s)
+# @bitmaps: name(s) of the source dirty bitmap(s) at @node and/or fully
+#           specifed BlockDirtyBitmap elements. The latter are supported
+#           since 4.1.
 #
 # Since: 4.0
 ##
 { 'struct': 'BlockDirtyBitmapMerge',
-  'data': { 'node': 'str', 'target': 'str', 'bitmaps': ['str'] } }
+  'data': { 'node': 'str', 'target': 'str',
+            'bitmaps': ['BlockDirtyBitmapMergeSource'] } }
 
 ##
 # @block-dirty-bitmap-add: