Revert "cgroup: remove bind() method from cgroup_subsys."

This reverts commit 84cfb6ab484b442d5115eb3baf9db7d74a3ea626.  There
are scheduled changes which make use of the removed callback.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rami Rosen <ramirose@gmail.com>
Cc: Li Zefan <lizefan@huawei.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7bf3ce09c50c..678a22c75fdb 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1091,12 +1091,16 @@ static int rebind_subsystems(struct cgroupfs_root *root,
                         cgrp->subsys[i]->cgroup = cgrp;
                         list_move(&ss->sibling, &root->subsys_list);
                         ss->root = root;
+                        if (ss->bind)
+                                ss->bind(cgrp);
                         /* refcount was already taken, and we're keeping it */
                 } else if (bit & removed_mask) {
                         /* We're removing this subsystem */
                         BUG_ON(ss == NULL);
                         BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
                         BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
+                        if (ss->bind)
+                                ss->bind(dummytop);
                         dummytop->subsys[i]->cgroup = dummytop;
                         cgrp->subsys[i] = NULL;
                         subsys[i]->root = &rootnode;