block: Mark bdrv_co_pwrite_zeroes() and callers GRAPH_RDLOCK

This adds GRAPH_RDLOCK annotations to declare that callers of
bdrv_co_pwrite_zeroes() need to hold a reader lock for the graph.

For some places, we know that they will hold the lock, but we don't have
the GRAPH_RDLOCK annotations yet. In this case, add assume_graph_lock()
with a FIXME comment. These places will be removed once everything is
properly annotated.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230203152202.49054-10-kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block/throttle.c b/block/throttle.c
index b07d853..3db4fa3 100644
--- a/block/throttle.c
+++ b/block/throttle.c
@@ -134,9 +134,9 @@
     return bdrv_co_pwritev(bs->file, offset, bytes, qiov, flags);
 }
 
-static int coroutine_fn throttle_co_pwrite_zeroes(BlockDriverState *bs,
-                                                  int64_t offset, int64_t bytes,
-                                                  BdrvRequestFlags flags)
+static int coroutine_fn GRAPH_RDLOCK
+throttle_co_pwrite_zeroes(BlockDriverState *bs, int64_t offset, int64_t bytes,
+                          BdrvRequestFlags flags)
 {
     ThrottleGroupMember *tgm = bs->opaque;
     throttle_group_co_io_limits_intercept(tgm, bytes, true);