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cgroup: add/update accessors which obtain subsys specific data from css

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css (cgroup_subsys_state) is usually embedded in a subsys specific
data structure.  Subsystems either use container_of() directly to cast
from css to such data structure or has an accessor function wrapping
such cast.  As cgroup as whole is moving towards using css as the main
interface handle, add and update such accessors to ease dealing with
css's.

All accessors explicitly handle NULL input and return NULL in those
cases.  While this looks like an extra branch in the code, as all
controllers specific data structures have css as the first field, the
casting doesn't involve any offsetting and the compiler can trivially
optimize out the branch.

* blkio, freezer, cpuset, cpu, cpuacct and net_cls didn't have such
  accessor.  Added.

* memory, hugetlb and devices already had one but didn't explicitly
  handle NULL input.  Updated.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo
2013-08-08 20:11:23 -04:00
parent 72c97e54e0
commit a7c6d554aa
9 changed files with 45 additions and 25 deletions
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8
kernel/sched/core.c
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@@ -7083,11 +7083,15 @@ int sched_rt_handler(struct ctl_table *table, int write,
#ifdef CONFIG_CGROUP_SCHED
static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
{
return css ? container_of(css, struct task_group, css) : NULL;
}
/* return corresponding task_group object of a cgroup */
static inline struct task_group *cgroup_tg(struct cgroup *cgrp)
{
return container_of(cgroup_css(cgrp, cpu_cgroup_subsys_id),
struct task_group, css);
return css_tg(cgroup_css(cgrp, cpu_cgroup_subsys_id));
}
static struct cgroup_subsys_state *cpu_cgroup_css_alloc(struct cgroup *cgrp)