block: add bdrv_can_store_new_dirty_bitmap

This will be needed to check some restrictions before making bitmap
persistent in qmp-block-dirty-bitmap-add (this functionality will be
added by future patch)

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20170628120530.31251-22-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>

block.c

@@ -4880,3 +4880,25 @@ void bdrv_del_child(BlockDriverState *parent_bs, BdrvChild *child, Error **errp)
 
     parent_bs->drv->bdrv_del_child(parent_bs, child, errp);
 }
+
+bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                     uint32_t granularity, Error **errp)
+{
+    BlockDriver *drv = bs->drv;
+
+    if (!drv) {
+        error_setg_errno(errp, ENOMEDIUM,
+                         "Can't store persistent bitmaps to %s",
+                         bdrv_get_device_or_node_name(bs));
+        return false;
+    }
+
+    if (!drv->bdrv_can_store_new_dirty_bitmap) {
+        error_setg_errno(errp, ENOTSUP,
+                         "Can't store persistent bitmaps to %s",
+                         bdrv_get_device_or_node_name(bs));
+        return false;
+    }
+
+    return drv->bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp);
+}

include/block/block.h

@@ -617,4 +617,7 @@ void bdrv_add_child(BlockDriverState *parent, BlockDriverState *child,
                     Error **errp);
 void bdrv_del_child(BlockDriverState *parent, BdrvChild *child, Error **errp);
 
+bool bdrv_can_store_new_dirty_bitmap(BlockDriverState *bs, const char *name,
+                                     uint32_t granularity, Error **errp);
+
 #endif

include/block/block_int.h

@@ -387,6 +387,10 @@ struct BlockDriver {
      * field of BlockDirtyBitmap's in case of success.
      */
     int (*bdrv_reopen_bitmaps_rw)(BlockDriverState *bs, Error **errp);
+    bool (*bdrv_can_store_new_dirty_bitmap)(BlockDriverState *bs,
+                                            const char *name,
+                                            uint32_t granularity,
+                                            Error **errp);
 
     QLIST_ENTRY(BlockDriver) list;
 };