cgroup: introduce cancel_attach()

Add cancel_attach() operation to struct cgroup_subsys.  cancel_attach()
can be used when can_attach() operation prepares something for the subsys,
but we should rollback what can_attach() operation has prepared if attach
task fails after we've succeeded in can_attach().

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Reviewed-by: Paul Menage <menage@google.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c9bbcb2a75ae..d08cfe7e12e5 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -428,6 +428,8 @@ struct cgroup_subsys {
         void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
         int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
                           struct task_struct *tsk, bool threadgroup);
+        void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
+                          struct task_struct *tsk, bool threadgroup);
         void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
                         struct cgroup *old_cgrp, struct task_struct *tsk,
                         bool threadgroup);