cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach()

Currently, there's no way to pass multiple tasks to cgroup_subsys
methods necessitating the need for separate per-process and per-task
methods.  This patch introduces cgroup_taskset which can be used to
pass multiple tasks and their associated cgroups to cgroup_subsys
methods.

Three methods - can_attach(), cancel_attach() and attach() - are
converted to use cgroup_taskset.  This unifies passed parameters so
that all methods have access to all information.  Conversions in this
patchset are identical and don't introduce any behavior change.

-v2: documentation updated as per Paul Menage's suggestion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul Menage <paul@paulmenage.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: James Morris <jmorris@namei.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index e411a60..e95c6fb 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -159,7 +159,7 @@ static void freezer_destroy(struct cgroup_subsys *ss,
  */
 static int freezer_can_attach(struct cgroup_subsys *ss,
 			      struct cgroup *new_cgroup,
-			      struct task_struct *task)
+			      struct cgroup_taskset *tset)
 {
 	struct freezer *freezer;