[PATCH] cgroup: fix top cgroup refcnt leak

[Andrei Vagin <avagin@gmail.com>]

It looks like the c6b3d5bcd67c ("cgroup: fix top cgroup refcnt leak")
commit was reverted by mistake.

$ mkdir /tmp/cgroup
$ mkdir /tmp/cgroup2
$ mount -t cgroup -o none,name=test test /tmp/cgroup
$ mount -t cgroup -o none,name=test test /tmp/cgroup2
$ umount /tmp/cgroup
$ umount /tmp/cgroup2
$ cat /proc/self/cgroup | grep test
12:name=test:/

You can see the test cgroup was not freed.

Cc: Li Zefan <lizefan@huawei.com>
Fixes: aea3f2676c83 ("kernfs, sysfs, cgroup, intel_rdt: Support fs_context")
Signed-off-by: Andrei Vagin <avagin@gmail.com>
---
 kernel/cgroup/cgroup.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index fb0717696895..dbb8805bf66c 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2045,8 +2045,11 @@ int cgroup_do_get_tree(struct fs_context *fc)
 	}
 
 	ret = 0;
-	if (ctx->kfc.new_sb_created)
+	if (ctx->kfc.new_sb_created) {
 		goto out_cgrp;
+	} else {
+		cgroup_put(&ctx->root->cgrp);
+	}
 	apply_cgroup_root_flags(ctx->flags);
 	return 0;
 
-- 
2.17.2