block: Mark bdrv_co_debug_event() GRAPH_RDLOCK

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

Unfortunately we cannot use a co_wrapper_bdrv_rdlock (i.e. make the
coroutine wrapper a no_coroutine_fn), because the function is called
(using the BLKDBG_EVENT macro) by mixed functions that run both in
coroutine and non-coroutine context (for example many of the functions
in qcow2-cluster.c and qcow2-refcount.c).

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20230504115750.54437-16-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

@@ -6399,6 +6399,8 @@ BlockStatsSpecific *bdrv_get_specific_stats(BlockDriverState *bs)
 void coroutine_fn bdrv_co_debug_event(BlockDriverState *bs, BlkdebugEvent event)
 {
     IO_CODE();
+    assert_bdrv_graph_readable();
+
     if (!bs || !bs->drv || !bs->drv->bdrv_co_debug_event) {
         return;
     }

include/block/block-io.h

@@ -205,10 +205,11 @@ void *qemu_try_blockalign0(BlockDriverState *bs, size_t size);
 void bdrv_enable_copy_on_read(BlockDriverState *bs);
 void bdrv_disable_copy_on_read(BlockDriverState *bs);
 
-void coroutine_fn bdrv_co_debug_event(BlockDriverState *bs,
-                                      BlkdebugEvent event);
-void co_wrapper_mixed bdrv_debug_event(BlockDriverState *bs,
-                                       BlkdebugEvent event);
+void coroutine_fn GRAPH_RDLOCK
+bdrv_co_debug_event(BlockDriverState *bs, BlkdebugEvent event);
+
+void co_wrapper_mixed_bdrv_rdlock
+bdrv_debug_event(BlockDriverState *bs, BlkdebugEvent event);
 
 #define BLKDBG_EVENT(child, evt) \
     do { \

include/block/block_int-common.h

@@ -735,8 +735,8 @@ struct BlockDriver {
     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_check)(
         BlockDriverState *bs, BdrvCheckResult *result, BdrvCheckMode fix);
 
-    void coroutine_fn (*bdrv_co_debug_event)(BlockDriverState *bs,
-                                             BlkdebugEvent event);
+    void coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_debug_event)(
+        BlockDriverState *bs, BlkdebugEvent event);
 
     /* io queue for linux-aio */
     void coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_io_plug)(BlockDriverState *bs);