From 3432a1929ee18e08787ce35476abd74f2c93a17c Mon Sep 17 00:00:00 2001
From: Zhang Haoyu <zhanghy@sangfor.com>
Date: Tue, 21 Oct 2014 16:38:01 +0800
Subject: [PATCH] snapshot: add bdrv_drain_all() to bdrv_snapshot_delete() to
avoid concurrency problem
If there are still pending i/o while deleting snapshot,
because deleting snapshot is done in non-coroutine context, and
the pending i/o read/write (bdrv_co_do_rw) is done in coroutine context,
so it's possible to cause concurrency problem between above two operations.
Add bdrv_drain_all() to bdrv_snapshot_delete() to avoid this problem.
Signed-off-by: Zhang Haoyu <zhanghy@sangfor.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 201410211637596311287@sangfor.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block/snapshot.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/block/snapshot.c b/block/snapshot.c
index 85c52ff455..698e1a1d58 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -236,6 +236,10 @@ int bdrv_snapshot_delete(BlockDriverState *bs,
error_setg(errp, "snapshot_id and name are both NULL");
return -EINVAL;
}
+
+ /* drain all pending i/o before deleting snapshot */
+ bdrv_drain_all();
+
if (drv->bdrv_snapshot_delete) {
return drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
}
--
2.30.2