Revert "cgroup: avoid attaching a cgroup root to two different superblocks"

This reverts commit ebe5ea64e0b5b9526fc66fa712ab5f5ebb5227ef.

Andrei reports CRIU test hangs with the patch applied.  The bug fixed
by the patch isn't too likely to trigger in actual uses.  Revert the
patch for now.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Andrei Vagin <avagin@virtuozzo.com>
Link: http://lkml.kernel.org/r/20170414232737.GC20350@outlook.office365.com

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 12e19f0636ea8366b190ab2ef41a0de84e0829f5..1dc22f6b49f5e06c4af22222dfb1b32c885ce16a 100644 (file)
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -1146,7 +1146,7 @@ struct dentry *cgroup1_mount(struct file_system_type *fs_type, int flags,
                 * path is super cold.  Let's just sleep a bit and retry.
                 */
                pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
-               if (IS_ERR_OR_NULL(pinned_sb) ||
+               if (IS_ERR(pinned_sb) ||
                    !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
                        mutex_unlock(&cgroup_mutex);
                        if (!IS_ERR_OR_NULL(pinned_sb))