From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 29 Sep 2023 14:51:56 +0000 (+0200)
Subject: block: Protect bs->children with graph_lock
X-Git-Tag: v8.2.0-rc0~72^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=680e0cc40c5830ebcbfa0bce99bf932e1a4cf6c6;p=thirdparty%2Fqemu.git

block: Protect bs->children with graph_lock

Almost all functions that access the child links 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: <20230929145157.45443-22-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---

diff --git a/block.c b/block.c
index 2ac7406c779..f9cf05ddcfc 100644
--- a/block.c
+++ b/block.c
@@ -2973,6 +2973,8 @@ static void bdrv_child_free(BdrvChild *child)
 {
     assert(!child->bs);
     GLOBAL_STATE_CODE();
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
+
     assert(!child->next.le_prev); /* not in children list */
 
     g_free(child->name);
diff --git a/block/replication.c b/block/replication.c
index 3459f506690..d522c7396f2 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -430,7 +430,8 @@ static void backup_job_completed(void *opaque, int ret)
     backup_job_cleanup(bs);
 }
 
-static bool check_top_bs(BlockDriverState *top_bs, BlockDriverState *bs)
+static bool GRAPH_RDLOCK
+check_top_bs(BlockDriverState *top_bs, BlockDriverState *bs)
 {
     BdrvChild *child;
 
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 0e37acd976c..b8d9d24f397 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -1042,7 +1042,7 @@ struct BdrvChild {
      */
     bool quiesced_parent;
 
-    QLIST_ENTRY(BdrvChild) next;
+    QLIST_ENTRY(BdrvChild GRAPH_RDLOCK_PTR) next;
     QLIST_ENTRY(BdrvChild GRAPH_RDLOCK_PTR) next_parent;
 };
 
@@ -1176,7 +1176,7 @@ struct BlockDriverState {
      * See also comment in include/block/block.h, to learn how backing and file
      * are connected with BdrvChildRole.
      */
-    QLIST_HEAD(, BdrvChild) children;
+    QLIST_HEAD(, BdrvChild GRAPH_RDLOCK_PTR) children;
     BdrvChild *backing;
     BdrvChild *file;
 
diff --git a/tests/unit/test-bdrv-drain.c b/tests/unit/test-bdrv-drain.c
index d734829778b..f67e9df01cd 100644
--- a/tests/unit/test-bdrv-drain.c
+++ b/tests/unit/test-bdrv-drain.c
@@ -1034,9 +1034,13 @@ static void coroutine_fn test_co_delete_by_drain(void *opaque)
         blk_co_unref(blk);
     } else {
         BdrvChild *c, *next_c;
+        bdrv_graph_co_rdlock();
         QLIST_FOREACH_SAFE(c, &bs->children, next, next_c) {
+            bdrv_graph_co_rdunlock();
             bdrv_co_unref_child(bs, c);
+            bdrv_graph_co_rdlock();
         }
+        bdrv_graph_co_rdunlock();
     }
 
     dbdd->done = true;