block: mark bdrv_open_child_common() and its callers GRAPH_UNLOCKED

The function bdrv_open_child_common() calls
bdrv_graph_wrlock_drained(), which must be called with the graph
unlocked. Mark it and its two callers bdrv_open_file_child() and
bdrv_open_child() as GRAPH_UNLOCKED. This requires temporarily
unlocking in vmdk_parse_extents() and making the locked section
shorter in vmdk_open().

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-48-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -3766,13 +3766,12 @@ done:
     return bs;
 }
 
-static BdrvChild *bdrv_open_child_common(const char *filename,
-                                         QDict *options, const char *bdref_key,
-                                         BlockDriverState *parent,
-                                         const BdrvChildClass *child_class,
-                                         BdrvChildRole child_role,
-                                         bool allow_none, bool parse_filename,
-                                         Error **errp)
+static BdrvChild * GRAPH_UNLOCKED
+bdrv_open_child_common(const char *filename, QDict *options,
+                       const char *bdref_key, BlockDriverState *parent,
+                       const BdrvChildClass *child_class,
+                       BdrvChildRole child_role, bool allow_none,
+                       bool parse_filename, Error **errp)
 {
     BlockDriverState *bs;
     BdrvChild *child;

block/vmdk.c

@@ -1229,9 +1229,11 @@ vmdk_parse_extents(const char *desc, BlockDriverState *bs, QDict *options,
             extent_role |= BDRV_CHILD_METADATA;
         }
 
+        bdrv_graph_rdunlock_main_loop();
         extent_file = bdrv_open_child(extent_path, options, extent_opt_prefix,
                                       bs, &child_of_bds, extent_role, false,
                                       &local_err);
+        bdrv_graph_rdlock_main_loop();
         g_free(extent_path);
         if (!extent_file) {
             error_propagate(errp, local_err);
@@ -1352,13 +1354,13 @@ static int vmdk_open(BlockDriverState *bs, QDict *options, int flags,
     BDRVVmdkState *s = bs->opaque;
     uint32_t magic;
 
-    GRAPH_RDLOCK_GUARD_MAINLOOP();
-
     ret = bdrv_open_file_child(NULL, options, "file", bs, errp);
     if (ret < 0) {
         return ret;
     }
 
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
+
     buf = vmdk_read_desc(bs->file, 0, errp);
     if (!buf) {
         return -EINVAL;

include/block/block-global-state.h

@@ -81,7 +81,7 @@ bdrv_insert_node(BlockDriverState *bs, QDict *node_options, int flags,
                  Error **errp);
 int bdrv_drop_filter(BlockDriverState *bs, Error **errp);
 
-BdrvChild * no_coroutine_fn
+BdrvChild * no_coroutine_fn GRAPH_UNLOCKED
 bdrv_open_child(const char *filename, QDict *options, const char *bdref_key,
                 BlockDriverState *parent, const BdrvChildClass *child_class,
                 BdrvChildRole child_role, bool allow_none, Error **errp);
@@ -91,9 +91,10 @@ bdrv_co_open_child(const char *filename, QDict *options, const char *bdref_key,
                 BlockDriverState *parent, const BdrvChildClass *child_class,
                 BdrvChildRole child_role, bool allow_none, Error **errp);
 
-int bdrv_open_file_child(const char *filename,
-                         QDict *options, const char *bdref_key,
-                         BlockDriverState *parent, Error **errp);
+int GRAPH_UNLOCKED
+bdrv_open_file_child(const char *filename, QDict *options,
+                     const char *bdref_key, BlockDriverState *parent,
+                     Error **errp);
 
 BlockDriverState * no_coroutine_fn
 bdrv_open_blockdev_ref(BlockdevRef *ref, Error **errp);