The names of the two struct cgroup_subsys_state accessors -
cgroup_subsys_state() and task_subsys_state() - are somewhat awkward.
The former clashes with the type name and the latter doesn't even
indicate it's somehow related to cgroup.

We're about to revamp large portion of cgroup API, so, let's rename
them so that they're less awkward.  Most per-controller usages of the
accessors are localized in accessor wrappers and given the amount of
scheduled changes, this isn't gonna add any noticeable headache.

Rename cgroup_subsys_state() to cgroup_css() and task_subsys_state()
to task_css().  This patch is pure rename.
Signed-off-by: NTejun Heo <tj@kernel.org>
Acked-by: NLi Zefan <lizefan@huawei.com>

The cpuacct split caused this build failure on UML:

  kernel/sched/cpuacct.c:94:2: error: implicit declaration of  function 'ERR_PTR'

Cc: Li Zefan <lizefan@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Now we're guaranteed when cpuacct_charge() and
cpuacct_account_field() are called, cpuacct has already been
properly initialized, so we no longer need those checks.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5155384C.7000508@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Initialize cpuacct before the scheduler is functioning, so when
cpuacct_charge() and cpuacct_account_field() are called,
task_ca() won't return NULL.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5155383F.8000005@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Now we don't need cpuacct_init(), and instead we just initialize
root_cpuacct when it's defined.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51553834.9090701@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This is a preparation, so later we can initialize cpuacct
earlier.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51553822.5000403@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Now most of the code in cpuacct.h can be moved to cpuacct.c
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/515536D5.2080401@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This is a micro optimazation for a hot path.

- We don't need to check if @CA returned from task_ca() is NULL.
- We don't need to check if @CA returned from parent_ca() is NULL.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/515536B7.6060602@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This is a micro optimization for the hot path.

- We don't need to check if @CA is NULL in parent_ca().
- We don't need to check if @CA is NULL in the beginning of the for loop.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/515536A9.5000700@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

So we can remove open-coded cpuacct code in cputime.c.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51553692.9060008@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

So we don't open-coded initialization of cpuacct in core.c.
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/51553687.1060906@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5155366F.5060404@huawei.comSigned-off-by: NIngo Molnar <mingo@kernel.org>