qcow2: Mark qcow2_inactivate() and callers GRAPH_RDLOCK

This adds GRAPH_RDLOCK annotations to declare that callers of
qcow2_inactivate() need to hold a reader lock for the graph because it
calls bdrv_get_device_or_node_name(), which accesses the parents list of
a node.

qcow2_do_close() is a bit strange because it is called from different
contexts. If close_data_file = true, we know that we were called from
non-coroutine main loop context (more specifically, we're coming from
qcow2_close()) and can safely drop the reader lock temporarily with
bdrv_graph_rdunlock_main_loop() and acquire the writer lock.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20230929145157.45443-16-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 10 insertions, 5 deletions

diff --git a/block/qcow2.c b/block/qcow2.c
index 137c036..aa01d9e 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2737,14 +2737,12 @@ fail_nometa:
     return ret;
 }
 
-static int qcow2_inactivate(BlockDriverState *bs)
+static int GRAPH_RDLOCK qcow2_inactivate(BlockDriverState *bs)
 {
     BDRVQcow2State *s = bs->opaque;
     int ret, result = 0;
     Error *local_err = NULL;
 
-    assume_graph_lock(); /* FIXME */
-
     qcow2_store_persistent_dirty_bitmaps(bs, true, &local_err);
     if (local_err != NULL) {
         result = -EINVAL;
@@ -2774,7 +2772,8 @@ static int qcow2_inactivate(BlockDriverState *bs)
     return result;
 }
 
-static void qcow2_do_close(BlockDriverState *bs, bool close_data_file)
+static void coroutine_mixed_fn GRAPH_RDLOCK
+qcow2_do_close(BlockDriverState *bs, bool close_data_file)
 {
     BDRVQcow2State *s = bs->opaque;
     qemu_vfree(s->l1_table);
@@ -2801,18 +2800,24 @@ static void qcow2_do_close(BlockDriverState *bs, bool close_data_file)
     g_free(s->image_backing_format);
 
     if (close_data_file && has_data_file(bs)) {
+        GLOBAL_STATE_CODE();
+        bdrv_graph_rdunlock_main_loop();
         bdrv_graph_wrlock(NULL);
         bdrv_unref_child(bs, s->data_file);
         bdrv_graph_wrunlock();
         s->data_file = NULL;
+        bdrv_graph_rdlock_main_loop();
     }
 
     qcow2_refcount_close(bs);
     qcow2_free_snapshots(bs);
 }
 
-static void qcow2_close(BlockDriverState *bs)
+static void GRAPH_UNLOCKED qcow2_close(BlockDriverState *bs)
 {
+    GLOBAL_STATE_CODE();
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
+
     qcow2_do_close(bs, true);
 }