[PATCH 08/11] block: Fix AioContext locking in bdrv_open_backing_file()

[Kevin Wolf]

bdrv_set_backing() requires the caller to hold the AioContext lock for
@backing_hd. Take it in bdrv_open_backing_file() before calling the
function.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block.c b/block.c
index 954b9923d9..d5f8231f31 100644
--- a/block.c
+++ b/block.c
@@ -3526,6 +3526,7 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict 
*parent_options,
     int ret = 0;
     bool implicit_backing = false;
     BlockDriverState *backing_hd;
+    AioContext *backing_hd_ctx;
     QDict *options;
     QDict *tmp_parent_options = NULL;
     Error *local_err = NULL;
@@ -3610,8 +3611,12 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict 
*parent_options,
 
     /* Hook up the backing file link; drop our reference, bs owns the
      * backing_hd reference now */
+    backing_hd_ctx = bdrv_get_aio_context(backing_hd);
+    aio_context_acquire(backing_hd_ctx);
     ret = bdrv_set_backing_hd(bs, backing_hd, errp);
     bdrv_unref(backing_hd);
+    aio_context_release(backing_hd_ctx);
+
     if (ret < 0) {
         goto free_exit;
     }
-- 
2.40.1