[GIT PULL] cgroup fixes for v4.11-rc6

[Tejun Heo]

Hello, Linus.

Unfortunately, the commit to fix the cgroup mount race in the previous
pull request can lead to hangs.  The original bug has been around for
a while and isn't too likely to be triggered in usual use cases.
Revert the commit for now.

Thanks.

The following changes since commit bfb0b80db5f9dca5ac0a5fd0edb765ee555e5a8e:

  cgroup: avoid attaching a cgroup root to two different superblocks (2017-04-11 09:00:57 +0900)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git for-4.11-fixes

for you to fetch changes up to 330c418638612d7658b6314e6a244fcb5f7efac5:

  Revert "cgroup: avoid attaching a cgroup root to two different superblocks" (2017-04-16 23:17:37 +0900)

----------------------------------------------------------------
Tejun Heo (1):
      Revert "cgroup: avoid attaching a cgroup root to two different superblocks"

 kernel/cgroup/cgroup-v1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c
index 12e19f0..1dc22f6 100644
--- 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))