commit 680e0cc40c5830ebcbfa0bce99bf932e1a4cf6c6
author Kevin Wolf <kwolf@redhat.com> Fri Sep 29 16:51:56 2023 +0200
committer Kevin Wolf <kwolf@redhat.com> Thu Oct 12 16:31:33 2023 +0200
tree 25d4599f69d96706708243a273e1a4f37124075e
parent b59b466071391cb76b39584e1558be2d0797c054

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>

block.c

diff --git a/block.c b/block.c
index 2ac7406..f9cf05d 100644
--- a/block.c
+++ b/block.c
@@ -2973,6 +2973,8 @@
 {
     assert(!child->bs);
     GLOBAL_STATE_CODE();
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
+
     assert(!child->next.le_prev); /* not in children list */
 
     g_free(child->name);

block/replication.c

diff --git a/block/replication.c b/block/replication.c
index 3459f50..d522c73 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -430,7 +430,8 @@
     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;
 

include/block/block_int-common.h

diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 0e37acd..b8d9d24 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -1042,7 +1042,7 @@
      */
     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 @@
      * 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;
 

tests/unit/test-bdrv-drain.c

diff --git a/tests/unit/test-bdrv-drain.c b/tests/unit/test-bdrv-drain.c
index d734829..f67e9df 100644
--- a/tests/unit/test-bdrv-drain.c
+++ b/tests/unit/test-bdrv-drain.c
@@ -1034,9 +1034,13 @@
         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;