From 7b973b9cb7b890eaf9a31c99f5c272b513322ac1 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 3 Feb 2022 15:05:33 +0100
Subject: [PATCH 1/8] block: Lock AioContext for drain_end in blockdev-reopen

RH-Author: Kevin Wolf <kwolf@redhat.com>
RH-MergeRequest: 73: block: Lock AioContext for drain_end in blockdev-reopen
RH-Commit: [1/2] db25e999152b0e4f09decade1ac76b9f56cd9706 (kmwolf/centos-qemu-kvm)
RH-Bugzilla: 2046659
RH-Acked-by: Sergio Lopez <None>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Hanna Reitz <hreitz@redhat.com>

bdrv_subtree_drained_end() requires the caller to hold the AioContext
lock for the drained node. Not doing this for nodes outside of the main
AioContext leads to crashes when AIO_WAIT_WHILE() needs to wait and
tries to temporarily release the lock.

Fixes: 3908b7a8994fa5ef7a89aa58cd5a02fc58141592
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2046659
Reported-by: Qing Wang <qinwang@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20220203140534.36522-2-kwolf@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit aba8205be0707b9d108e32254e186ba88107a869)
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 blockdev.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/blockdev.c b/blockdev.c
index b35072644e..565f6a81fd 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3562,6 +3562,7 @@ void qmp_blockdev_reopen(BlockdevOptionsList *reopen_list, Error **errp)
 {
     BlockReopenQueue *queue = NULL;
     GSList *drained = NULL;
+    GSList *p;
 
     /* Add each one of the BDS that we want to reopen to the queue */
     for (; reopen_list != NULL; reopen_list = reopen_list->next) {
@@ -3611,7 +3612,15 @@ void qmp_blockdev_reopen(BlockdevOptionsList *reopen_list, Error **errp)
 
 fail:
     bdrv_reopen_queue_free(queue);
-    g_slist_free_full(drained, (GDestroyNotify) bdrv_subtree_drained_end);
+    for (p = drained; p; p = p->next) {
+        BlockDriverState *bs = p->data;
+        AioContext *ctx = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(ctx);
+        bdrv_subtree_drained_end(bs);
+        aio_context_release(ctx);
+    }
+    g_slist_free(drained);
 }
 
 void qmp_blockdev_del(const char *node_name, Error **errp)
-- 
2.27.0