block: Protect bs->backing with graph_lock

Almost all functions that access bs->backing already take the graph
lock now. Add locking to the remaining users and finally annotate the
struct field itself as protected by the graph lock.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20231027155333.420094-18-kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

2 files changed, 22 insertions, 5 deletions

diff --git a/tests/unit/test-bdrv-drain.c b/tests/unit/test-bdrv-drain.c
index b16f831c23..ba4e42b197 100644
--- a/tests/unit/test-bdrv-drain.c
+++ b/tests/unit/test-bdrv-drain.c
@@ -218,8 +218,14 @@ static void do_drain_end_unlocked(enum drain_type drain_type, BlockDriverState *
     }
 }
 
-static void test_drv_cb_common(BlockBackend *blk, enum drain_type drain_type,
-                               bool recursive)
+/*
+ * Locking the block graph would be a bit cumbersome here because this function
+ * is called both in coroutine and non-coroutine context. We know this is a test
+ * and nothing else is running, so don't bother with TSA.
+ */
+static void coroutine_mixed_fn TSA_NO_TSA
+test_drv_cb_common(BlockBackend *blk, enum drain_type drain_type,
+                   bool recursive)
 {
     BlockDriverState *bs = blk_bs(blk);
     BlockDriverState *backing = bs->backing->bs;
@@ -307,8 +313,14 @@ static void test_drv_cb_co_drain(void)
     blk_unref(blk);
 }
 
-static void test_quiesce_common(BlockBackend *blk, enum drain_type drain_type,
-                                bool recursive)
+/*
+ * Locking the block graph would be a bit cumbersome here because this function
+ * is called both in coroutine and non-coroutine context. We know this is a test
+ * and nothing else is running, so don't bother with TSA.
+ */
+static void coroutine_mixed_fn TSA_NO_TSA
+test_quiesce_common(BlockBackend *blk, enum drain_type drain_type,
+                    bool recursive)
 {
     BlockDriverState *bs = blk_bs(blk);
     BlockDriverState *backing = bs->backing->bs;
@@ -1868,6 +1880,8 @@ static void bdrv_replace_test_drain_end(BlockDriverState *bs)
 {
     BDRVReplaceTestState *s = bs->opaque;
 
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
+
     if (!s->setup_completed) {
         return;
     }
diff --git a/tests/unit/test-bdrv-graph-mod.c b/tests/unit/test-bdrv-graph-mod.c
index 22d4cd83f6..878544dbd5 100644
--- a/tests/unit/test-bdrv-graph-mod.c
+++ b/tests/unit/test-bdrv-graph-mod.c
@@ -206,15 +206,18 @@ static void test_should_update_child(void)
 
     bdrv_set_backing_hd(target, bs, &error_abort);
 
-    g_assert(target->backing->bs == bs);
     bdrv_graph_wrlock(NULL);
+    g_assert(target->backing->bs == bs);
     bdrv_attach_child(filter, target, "target", &child_of_bds,
                       BDRV_CHILD_DATA, &error_abort);
     bdrv_graph_wrunlock();
     aio_context_acquire(qemu_get_aio_context());
     bdrv_append(filter, bs, &error_abort);
     aio_context_release(qemu_get_aio_context());
+
+    bdrv_graph_rdlock_main_loop();
     g_assert(target->backing->bs == bs);
+    bdrv_graph_rdunlock_main_loop();
 
     bdrv_unref(filter);
     bdrv_unref(bs);