cgroup: don't use subsys->can_attach_task() or ->attach_task()

Now that subsys->can_attach() and attach() take @tset instead of
@task, they can handle per-task operations.  Convert
->can_attach_task() and ->attach_task() users to use ->can_attach()
and attach() instead.  Most converions are straight-forward.
Noteworthy changes are,

* In cgroup_freezer, remove unnecessary NULL assignments to unused
  methods.  It's useless and very prone to get out of sync, which
  already happened.

* In cpuset, PF_THREAD_BOUND test is checked for each task.  This
  doesn't make any practical difference but is conceptually cleaner.

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: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <paul@paulmenage.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: James Morris <jmorris@namei.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>

1 files changed, 4 insertions, 10 deletions

diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index e95c6fb65cc0..0e748059ba87 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -162,10 +162,14 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
                               struct cgroup_taskset *tset)
 {
         struct freezer *freezer;
+        struct task_struct *task;
 
         /*
          * Anything frozen can't move or be moved to/from.
          */
+        cgroup_taskset_for_each(task, new_cgroup, tset)
+                if (cgroup_freezing(task))
+                        return -EBUSY;
 
         freezer = cgroup_freezer(new_cgroup);
         if (freezer->state != CGROUP_THAWED)
@@ -174,11 +178,6 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
         return 0;
 }
 
-static int freezer_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
-{
-        return cgroup_freezing(tsk) ? -EBUSY : 0;
-}
-
 static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
 {
         struct freezer *freezer;
@@ -374,10 +373,5 @@ struct cgroup_subsys freezer_subsys = {
         .populate       = freezer_populate,
         .subsys_id      = freezer_subsys_id,
         .can_attach     = freezer_can_attach,
-        .can_attach_task = freezer_can_attach_task,
-        .pre_attach     = NULL,
-        .attach_task    = NULL,
-        .attach         = NULL,
         .fork           = freezer_fork,
-        .exit           = NULL,
 };