[PATCH -next] md/raid10: fix a 'conf->barrier' leakage in raid10_takeover()

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

After commit 4d27e927344a ("md: don't quiesce in mddev_suspend()"),
'conf->barrier' will be leaked in the case that raid10 takeover raid0:

level_store
 pers->takeover -> raid10_takeover
  raid10_takeover_raid0
   WRITE_ONCE(conf->barrier, 1)

mddev_suspend
// still raid0
mddev->pers = pers
// switch to raid10
mddev_resume
// resume without suspend

After the above commit, mddev_resume() will not decrease 'conf->barrier'
that is set in raid10_takeover_raid0().

Fix this problem by remove the setting of 'conf->barrier' from
raid10_takeover_raid0().

By the way, this problem is found while I'm trying to make
mddev_suspend/resume() to be independent from raid personalities. rai10
is the only personality to use reference count in the quiesce() callback
and this problem is only related to raid10.

Fixes: 4d27e927344a ("md: don't quiesce in mddev_suspend()")
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/raid10.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 16aa9d735880..7704a4c7f469 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4417,7 +4417,6 @@ static void *raid10_takeover_raid0(struct mddev *mddev, sector_t size, int devs)
 				rdev->new_raid_disk = rdev->raid_disk * 2;
 				rdev->sectors = size;
 			}
-		WRITE_ONCE(conf->barrier, 1);
 	}
 
 	return conf;
-- 
2.39.2