commit 32a8aba37eaae54d3a0a7ae5e93e3e157525660a
author Kevin Wolf <kwolf@redhat.com> Mon Sep 11 11:46:19 2023 +0200
committer Kevin Wolf <kwolf@redhat.com> Wed Sep 20 17:46:01 2023 +0200
tree c310d966906d71c635c89425f2e1f314dfafdba9
parent ede01e4635050a395eacd57b7d7fbea8ea208704

block: Mark bdrv_unref_child() GRAPH_WRLOCK

Instead of taking the writer lock internally, require callers to already
hold it when calling bdrv_unref_child(). These callers will typically
already hold the graph lock once the locking work is completed, which
means that they can't call functions that take it internally.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230911094620.45040-21-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

block.c

diff --git a/block.c b/block.c
index 9ea8333..e7f349b 100644
--- a/block.c
+++ b/block.c
@@ -1701,7 +1701,9 @@
 open_failed:
     bs->drv = NULL;
     if (bs->file != NULL) {
+        bdrv_graph_wrlock(NULL);
         bdrv_unref_child(bs, bs->file);
+        bdrv_graph_wrunlock();
         assert(!bs->file);
     }
     g_free(bs->opaque);
@@ -3331,8 +3333,9 @@
  * @root that point to @root, where necessary.
  * @tran is allowed to be NULL. In this case no rollback is possible
  */
-static void bdrv_unset_inherits_from(BlockDriverState *root, BdrvChild *child,
-                                     Transaction *tran)
+static void GRAPH_WRLOCK
+bdrv_unset_inherits_from(BlockDriverState *root, BdrvChild *child,
+                         Transaction *tran)
 {
     BdrvChild *c;
 
@@ -3364,10 +3367,8 @@
         return;
     }
 
-    bdrv_graph_wrlock(NULL);
     bdrv_unset_inherits_from(parent, child, NULL);
     bdrv_root_unref_child(child);
-    bdrv_graph_wrunlock();
 }
 
 
@@ -5164,9 +5165,11 @@
         bs->drv = NULL;
     }
 
+    bdrv_graph_wrlock(NULL);
     QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
         bdrv_unref_child(bs, child);
     }
+    bdrv_graph_wrunlock();
 
     assert(!bs->backing);
     assert(!bs->file);