From e790b4c20a5124239fe93e91fbc87745e5f2cea6 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Fri, 18 Nov 2022 18:41:01 +0100
Subject: [PATCH 19/31] block: Fix locking for bdrv_reopen_queue_child()

RH-Author: Stefano Garzarella <sgarzare@redhat.com>
RH-MergeRequest: 135: block: Simplify drain to prevent QEMU from crashing during snapshot
RH-Bugzilla: 2155112
RH-Acked-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-Acked-by: Hanna Czenczek <hreitz@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Commit: [7/16] 46bb54506c4400b9a1bf66b6bd7987ff67260003 (sgarzarella/qemu-kvm-c-9-s)

Callers don't agree whether bdrv_reopen_queue_child() should be called
with the AioContext lock held or not. Standardise on holding the lock
(as done by QMP blockdev-reopen and the replication block driver) and
fix bdrv_reopen() to do the same.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20221118174110.55183-7-kwolf@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 2e117866d7c96cc17e84cd2946fee1bf3292d814)
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 block.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/block.c b/block.c
index 7999fd08c5..46df410b07 100644
--- a/block.c
+++ b/block.c
@@ -4151,6 +4151,8 @@ static bool bdrv_recurse_has_child(BlockDriverState *bs,
  * bs_queue, or the existing bs_queue being used.
  *
  * bs must be drained between bdrv_reopen_queue() and bdrv_reopen_multiple().
+ *
+ * To be called with bs->aio_context locked.
  */
 static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
                                                  BlockDriverState *bs,
@@ -4309,6 +4311,7 @@ static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
     return bs_queue;
 }
 
+/* To be called with bs->aio_context locked */
 BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
                                     BlockDriverState *bs,
                                     QDict *options, bool keep_old_opts)
@@ -4473,11 +4476,11 @@ int bdrv_reopen(BlockDriverState *bs, QDict *opts, bool keep_old_opts,
     GLOBAL_STATE_CODE();
 
     bdrv_subtree_drained_begin(bs);
+    queue = bdrv_reopen_queue(NULL, bs, opts, keep_old_opts);
+
     if (ctx != qemu_get_aio_context()) {
         aio_context_release(ctx);
     }
-
-    queue = bdrv_reopen_queue(NULL, bs, opts, keep_old_opts);
     ret = bdrv_reopen_multiple(queue, errp);
 
     if (ctx != qemu_get_aio_context()) {
-- 
2.31.1