cgroup: add/update accessors which obtain subsys specific data from css
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>
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 9d3f615..1db686e 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -45,16 +45,19 @@
spinlock_t lock;
};
+static inline struct freezer *css_freezer(struct cgroup_subsys_state *css)
+{
+ return css ? container_of(css, struct freezer, css) : NULL;
+}
+
static inline struct freezer *cgroup_freezer(struct cgroup *cgroup)
{
- return container_of(cgroup_css(cgroup, freezer_subsys_id),
- struct freezer, css);
+ return css_freezer(cgroup_css(cgroup, freezer_subsys_id));
}
static inline struct freezer *task_freezer(struct task_struct *task)
{
- return container_of(task_css(task, freezer_subsys_id),
- struct freezer, css);
+ return css_freezer(task_css(task, freezer_subsys_id));
}
static struct freezer *parent_freezer(struct freezer *freezer)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index f737134..6e9cbdd 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -114,18 +114,21 @@
int relax_domain_level;
};
+static inline struct cpuset *css_cs(struct cgroup_subsys_state *css)
+{
+ return css ? container_of(css, struct cpuset, css) : NULL;
+}
+
/* Retrieve the cpuset for a cgroup */
static inline struct cpuset *cgroup_cs(struct cgroup *cgrp)
{
- return container_of(cgroup_css(cgrp, cpuset_subsys_id),
- struct cpuset, css);
+ return css_cs(cgroup_css(cgrp, cpuset_subsys_id));
}
/* Retrieve the cpuset for a task */
static inline struct cpuset *task_cs(struct task_struct *task)
{
- return container_of(task_css(task, cpuset_subsys_id),
- struct cpuset, css);
+ return css_cs(task_css(task, cpuset_subsys_id));
}
static inline struct cpuset *parent_cs(struct cpuset *cs)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 323d907..5bccb02 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7083,11 +7083,15 @@
#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)
diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
index 4a210fa..8ccfa10 100644
--- a/kernel/sched/cpuacct.c
+++ b/kernel/sched/cpuacct.c
@@ -33,18 +33,21 @@
struct kernel_cpustat __percpu *cpustat;
};
+static inline struct cpuacct *css_ca(struct cgroup_subsys_state *css)
+{
+ return css ? container_of(css, struct cpuacct, css) : NULL;
+}
+
/* return cpu accounting group corresponding to this container */
static inline struct cpuacct *cgroup_ca(struct cgroup *cgrp)
{
- return container_of(cgroup_css(cgrp, cpuacct_subsys_id),
- struct cpuacct, css);
+ return css_ca(cgroup_css(cgrp, cpuacct_subsys_id));
}
/* return cpu accounting group to which this task belongs */
static inline struct cpuacct *task_ca(struct task_struct *tsk)
{
- return container_of(task_css(tsk, cpuacct_subsys_id),
- struct cpuacct, css);
+ return css_ca(task_css(tsk, cpuacct_subsys_id));
}
static inline struct cpuacct *__parent_ca(struct cpuacct *ca)