block: Mark bdrv_filter_child() and callers GRAPH_RDLOCK

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

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-12-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -8491,8 +8491,8 @@ BdrvChild *bdrv_primary_child(BlockDriverState *bs)
     return found;
 }
 
-static BlockDriverState *bdrv_do_skip_filters(BlockDriverState *bs,
-                                              bool stop_on_explicit_filter)
+static BlockDriverState * GRAPH_RDLOCK
+bdrv_do_skip_filters(BlockDriverState *bs, bool stop_on_explicit_filter)
 {
     BdrvChild *c;
 

include/block/block_int-io.h

@@ -131,8 +131,8 @@ int co_wrapper_mixed_bdrv_rdlock
 bdrv_refresh_total_sectors(BlockDriverState *bs, int64_t hint);
 
 BdrvChild *bdrv_cow_child(BlockDriverState *bs);
-BdrvChild *bdrv_filter_child(BlockDriverState *bs);
-BdrvChild *bdrv_filter_or_cow_child(BlockDriverState *bs);
+BdrvChild * GRAPH_RDLOCK bdrv_filter_child(BlockDriverState *bs);
+BdrvChild * GRAPH_RDLOCK bdrv_filter_or_cow_child(BlockDriverState *bs);
 BdrvChild * GRAPH_RDLOCK bdrv_primary_child(BlockDriverState *bs);
 BlockDriverState * GRAPH_RDLOCK bdrv_skip_filters(BlockDriverState *bs);
 BlockDriverState * GRAPH_RDLOCK bdrv_backing_chain_next(BlockDriverState *bs);