block: Mark bdrv_skip_implicit_filters() and callers GRAPH_RDLOCK

This adds GRAPH_RDLOCK annotations to declare that callers of
bdrv_skip_implicit_filters() need to hold a reader lock for the graph
because it calls bdrv_filter_child(), which accesses bs->file/backing.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-8-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/blockdev.c b/blockdev.c
index 4cb8e1d..6cdf48b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1746,10 +1746,10 @@ static void drive_backup_action(DriveBackup *backup,
         assert(format);
         if (source) {
             /* Implicit filters should not appear in the filename */
-            BlockDriverState *explicit_backing =
-                bdrv_skip_implicit_filters(source);
+            BlockDriverState *explicit_backing;
 
             bdrv_graph_rdlock_main_loop();
+            explicit_backing = bdrv_skip_implicit_filters(source);
             bdrv_refresh_filename(explicit_backing);
             bdrv_graph_rdunlock_main_loop();
 
@@ -3108,16 +3108,18 @@ void qmp_drive_mirror(DriveMirror *arg, Error **errp)
         bdrv_img_create(arg->target, format,
                         NULL, NULL, NULL, size, flags, false, &local_err);
     } else {
-        /* Implicit filters should not appear in the filename */
-        BlockDriverState *explicit_backing =
-            bdrv_skip_implicit_filters(target_backing_bs);
+        BlockDriverState *explicit_backing;
 
         switch (arg->mode) {
         case NEW_IMAGE_MODE_EXISTING:
             break;
         case NEW_IMAGE_MODE_ABSOLUTE_PATHS:
-            /* create new image with backing file */
+            /*
+             * Create new image with backing file.
+             * Implicit filters should not appear in the filename.
+             */
             bdrv_graph_rdlock_main_loop();
+            explicit_backing = bdrv_skip_implicit_filters(target_backing_bs);
             bdrv_refresh_filename(explicit_backing);
             bdrv_graph_rdunlock_main_loop();