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Date: Mon, 12 May 2014 15:16:54 +0200
From: Michal Hocko <mhocko@...e.cz>
To: Tejun Heo <tj@...nel.org>
Cc: lizefan@...wei.com, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org, hannes@...xchg.org,
Vivek Goyal <vgoyal@...hat.com>, Jens Axboe <axboe@...nel.dk>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Neil Horman <nhorman@...driver.com>,
"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 01/14] cgroup: remove css_parent()
On Fri 09-05-14 17:31:18, Tejun Heo wrote:
> cgroup in general is moving towards using cgroup_subsys_state as the
> fundamental structural component and css_parent() was introduced to
> convert from using cgroup->parent to css->parent. It was quite some
> time ago and we're moving forward with making css more prominent.
>
> This patch drops the trivial wrapper css_parent() and let the users
> dereference css->parent. While at it, explicitly mark fields of css
> which are public and immutable.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Li Zefan <lizefan@...wei.com>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...e.cz>
> Cc: Neil Horman <nhorman@...driver.com>
> Cc: "David S. Miller" <davem@...emloft.net>
For memcg part
Acked-by: Michal Hocko <mhocko@...e.cz>
> ---
> block/blk-cgroup.h | 2 +-
> include/linux/cgroup.h | 29 +++++++++++------------------
> kernel/cgroup.c | 8 ++++----
> kernel/cgroup_freezer.c | 2 +-
> kernel/cpuset.c | 2 +-
> kernel/sched/core.c | 2 +-
> kernel/sched/cpuacct.c | 2 +-
> mm/hugetlb_cgroup.c | 2 +-
> mm/memcontrol.c | 14 +++++++-------
> net/core/netclassid_cgroup.c | 2 +-
> net/core/netprio_cgroup.c | 2 +-
> security/device_cgroup.c | 6 +++---
> 12 files changed, 33 insertions(+), 40 deletions(-)
>
> diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
> index 371fe8e..d692b29 100644
> --- a/block/blk-cgroup.h
> +++ b/block/blk-cgroup.h
> @@ -204,7 +204,7 @@ static inline struct blkcg *bio_blkcg(struct bio *bio)
> */
> static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
> {
> - return css_to_blkcg(css_parent(&blkcg->css));
> + return css_to_blkcg(blkcg->css.parent);
> }
>
> /**
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index 76dadd77..88c4d03 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -48,22 +48,28 @@ enum cgroup_subsys_id {
> };
> #undef SUBSYS
>
> -/* Per-subsystem/per-cgroup state maintained by the system. */
> +/*
> + * Per-subsystem/per-cgroup state maintained by the system. This is the
> + * fundamental structural building block that controllers deal with.
> + *
> + * Fields marked with "PI:" are public and immutable and may be accessed
> + * directly without synchronization.
> + */
> struct cgroup_subsys_state {
> - /* the cgroup that this css is attached to */
> + /* PI: the cgroup that this css is attached to */
> struct cgroup *cgroup;
>
> - /* the cgroup subsystem that this css is attached to */
> + /* PI: the cgroup subsystem that this css is attached to */
> struct cgroup_subsys *ss;
>
> /* reference count - access via css_[try]get() and css_put() */
> struct percpu_ref refcnt;
>
> - /* the parent css */
> + /* PI: the parent css */
> struct cgroup_subsys_state *parent;
>
> /*
> - * Subsys-unique ID. 0 is unused and root is always 1. The
> + * PI: Subsys-unique ID. 0 is unused and root is always 1. The
> * matching css can be looked up using css_from_id().
> */
> int id;
> @@ -665,19 +671,6 @@ struct cgroup_subsys {
> #undef SUBSYS
>
> /**
> - * css_parent - find the parent css
> - * @css: the target cgroup_subsys_state
> - *
> - * Return the parent css of @css. This function is guaranteed to return
> - * non-NULL parent as long as @css isn't the root.
> - */
> -static inline
> -struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css)
> -{
> - return css->parent;
> -}
> -
> -/**
> * task_css_set_check - obtain a task's css_set with extra access conditions
> * @task: the task to obtain css_set for
> * @__c: extra condition expression to be passed to rcu_dereference_check()
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 64ff413..dab8f35 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -3175,10 +3175,10 @@ css_next_descendant_pre(struct cgroup_subsys_state *pos,
>
> /* no child, visit my or the closest ancestor's next sibling */
> while (pos != root) {
> - next = css_next_child(pos, css_parent(pos));
> + next = css_next_child(pos, pos->parent);
> if (next)
> return next;
> - pos = css_parent(pos);
> + pos = pos->parent;
> }
>
> return NULL;
> @@ -3260,12 +3260,12 @@ css_next_descendant_post(struct cgroup_subsys_state *pos,
> return NULL;
>
> /* if there's an unvisited sibling, visit its leftmost descendant */
> - next = css_next_child(pos, css_parent(pos));
> + next = css_next_child(pos, pos->parent);
> if (next)
> return css_leftmost_descendant(next);
>
> /* no sibling left, visit parent */
> - return css_parent(pos);
> + return pos->parent;
> }
>
> static bool cgroup_has_live_children(struct cgroup *cgrp)
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index f52c443..fee1ae63 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -59,7 +59,7 @@ static inline struct freezer *task_freezer(struct task_struct *task)
>
> static struct freezer *parent_freezer(struct freezer *freezer)
> {
> - return css_freezer(css_parent(&freezer->css));
> + return css_freezer(freezer->css.parent);
> }
>
> bool cgroup_freezing(struct task_struct *task)
> diff --git a/kernel/cpuset.c b/kernel/cpuset.c
> index 2f4b08b..5b2a310 100644
> --- a/kernel/cpuset.c
> +++ b/kernel/cpuset.c
> @@ -124,7 +124,7 @@ static inline struct cpuset *task_cs(struct task_struct *task)
>
> static inline struct cpuset *parent_cs(struct cpuset *cs)
> {
> - return css_cs(css_parent(&cs->css));
> + return css_cs(cs->css.parent);
> }
>
> #ifdef CONFIG_NUMA
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 268a45e..ac61ad1 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7586,7 +7586,7 @@ cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
> static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
> {
> struct task_group *tg = css_tg(css);
> - struct task_group *parent = css_tg(css_parent(css));
> + struct task_group *parent = css_tg(css->parent);
>
> if (parent)
> sched_online_group(tg, parent);
> diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c
> index c143ee3..9cf350c 100644
> --- a/kernel/sched/cpuacct.c
> +++ b/kernel/sched/cpuacct.c
> @@ -46,7 +46,7 @@ static inline struct cpuacct *task_ca(struct task_struct *tsk)
>
> static inline struct cpuacct *parent_ca(struct cpuacct *ca)
> {
> - return css_ca(css_parent(&ca->css));
> + return css_ca(ca->css.parent);
> }
>
> static DEFINE_PER_CPU(u64, root_cpuacct_cpuusage);
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
> index a380681..493f758 100644
> --- a/mm/hugetlb_cgroup.c
> +++ b/mm/hugetlb_cgroup.c
> @@ -52,7 +52,7 @@ static inline bool hugetlb_cgroup_is_root(struct hugetlb_cgroup *h_cg)
> static inline struct hugetlb_cgroup *
> parent_hugetlb_cgroup(struct hugetlb_cgroup *h_cg)
> {
> - return hugetlb_cgroup_from_css(css_parent(&h_cg->css));
> + return hugetlb_cgroup_from_css(h_cg->css.parent);
> }
>
> static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index b638a79..a5e0417 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1540,7 +1540,7 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
> int mem_cgroup_swappiness(struct mem_cgroup *memcg)
> {
> /* root ? */
> - if (!css_parent(&memcg->css))
> + if (!memcg->css.parent)
> return vm_swappiness;
>
> return memcg->swappiness;
> @@ -4909,7 +4909,7 @@ static int mem_cgroup_hierarchy_write(struct cgroup_subsys_state *css,
> {
> int retval = 0;
> struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> - struct mem_cgroup *parent_memcg = mem_cgroup_from_css(css_parent(&memcg->css));
> + struct mem_cgroup *parent_memcg = mem_cgroup_from_css(memcg->css.parent);
>
> mutex_lock(&memcg_create_mutex);
>
> @@ -5207,8 +5207,8 @@ static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
> if (!memcg->use_hierarchy)
> goto out;
>
> - while (css_parent(&memcg->css)) {
> - memcg = mem_cgroup_from_css(css_parent(&memcg->css));
> + while (memcg->css.parent) {
> + memcg = mem_cgroup_from_css(memcg->css.parent);
> if (!memcg->use_hierarchy)
> break;
> tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
> @@ -5443,7 +5443,7 @@ static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css,
> struct cftype *cft, u64 val)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> - struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));
> + struct mem_cgroup *parent = mem_cgroup_from_css(memcg->css.parent);
>
> if (val > 100 || !parent)
> return -EINVAL;
> @@ -5790,7 +5790,7 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
> struct cftype *cft, u64 val)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> - struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));
> + struct mem_cgroup *parent = mem_cgroup_from_css(memcg->css.parent);
>
> /* cannot set to root cgroup and only 0 and 1 are allowed */
> if (!parent || !((val == 0) || (val == 1)))
> @@ -6407,7 +6407,7 @@ static int
> mem_cgroup_css_online(struct cgroup_subsys_state *css)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> - struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(css));
> + struct mem_cgroup *parent = mem_cgroup_from_css(css->parent);
>
> if (css->id > MEM_CGROUP_ID_MAX)
> return -ENOSPC;
> diff --git a/net/core/netclassid_cgroup.c b/net/core/netclassid_cgroup.c
> index 22931e1..30d903b 100644
> --- a/net/core/netclassid_cgroup.c
> +++ b/net/core/netclassid_cgroup.c
> @@ -42,7 +42,7 @@ cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
> static int cgrp_css_online(struct cgroup_subsys_state *css)
> {
> struct cgroup_cls_state *cs = css_cls_state(css);
> - struct cgroup_cls_state *parent = css_cls_state(css_parent(css));
> + struct cgroup_cls_state *parent = css_cls_state(css->parent);
>
> if (parent)
> cs->classid = parent->classid;
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> index b990cef..2f385b9 100644
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -140,7 +140,7 @@ cgrp_css_alloc(struct cgroup_subsys_state *parent_css)
>
> static int cgrp_css_online(struct cgroup_subsys_state *css)
> {
> - struct cgroup_subsys_state *parent_css = css_parent(css);
> + struct cgroup_subsys_state *parent_css = css->parent;
> struct net_device *dev;
> int ret = 0;
>
> diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> index 82d6b4f..3116015 100644
> --- a/security/device_cgroup.c
> +++ b/security/device_cgroup.c
> @@ -182,7 +182,7 @@ static inline bool is_devcg_online(const struct dev_cgroup *devcg)
> static int devcgroup_online(struct cgroup_subsys_state *css)
> {
> struct dev_cgroup *dev_cgroup = css_to_devcgroup(css);
> - struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css_parent(css));
> + struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css->parent);
> int ret = 0;
>
> mutex_lock(&devcgroup_mutex);
> @@ -374,7 +374,7 @@ static bool may_access(struct dev_cgroup *dev_cgroup,
> static int parent_has_perm(struct dev_cgroup *childcg,
> struct dev_exception_item *ex)
> {
> - struct dev_cgroup *parent = css_to_devcgroup(css_parent(&childcg->css));
> + struct dev_cgroup *parent = css_to_devcgroup(childcg->css.parent);
>
> if (!parent)
> return 1;
> @@ -502,7 +502,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
> char temp[12]; /* 11 + 1 characters needed for a u32 */
> int count, rc = 0;
> struct dev_exception_item ex;
> - struct dev_cgroup *parent = css_to_devcgroup(css_parent(&devcgroup->css));
> + struct dev_cgroup *parent = css_to_devcgroup(devcgroup->css.parent);
>
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
> --
> 1.9.0
>
--
Michal Hocko
SUSE Labs
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