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cgroup: remove cgroup->name

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cgroup->name handling became quite complicated over time involving
dedicated struct cgroup_name for RCU protection.  Now that cgroup is
on kernfs, we can drop all of it and simply use kernfs_name/path() and
friends.  Replace cgroup->name and all related code with kernfs
name/path constructs.

* Reimplement cgroup_name() and cgroup_path() as thin wrappers on top
  of kernfs counterparts, which involves semantic changes.
  pr_cont_cgroup_name() and pr_cont_cgroup_path() added.

* cgroup->name handling dropped from cgroup_rename().

* All users of cgroup_name/path() updated to the new semantics.  Users
  which were formatting the string just to printk them are converted
  to use pr_cont_cgroup_name/path() instead, which simplifies things
  quite a bit.  As cgroup_name() no longer requires RCU read lock
  around it, RCU lockings which were protecting only cgroup_name() are
  removed.

v2: Comment above oom_info_lock updated as suggested by Michal.

v3: dummy_top doesn't have a kn associated and
    pr_cont_cgroup_name/path() ended up calling the matching kernfs
    functions with NULL kn leading to oops.  Test for NULL kn and
    print "/" if so.  This issue was reported by Fengguang Wu.

v4: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
    cgroup_idr with cgroup_mutex").

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
This commit is contained in:
Tejun Heo 2014-02-12 09:29:50 -05:00
parent 6f30558f37
commit e61734c55c
7 changed files with 110 additions and 210 deletions
Download patch file Download diff file Expand all files Collapse all files

63
include/linux/cgroup.h
View file

@ -138,11 +138,6 @@ enum {
CGRP_SANE_BEHAVIOR,
};
struct cgroup_name {
struct rcu_head rcu_head;
char name[];
};
struct cgroup {
unsigned long flags; /* "unsigned long" so bitops work */
@ -179,19 +174,6 @@ struct cgroup {
*/
u64 serial_nr;
/*
* This is a copy of dentry->d_name, and it's needed because
* we can't use dentry->d_name in cgroup_path().
*
* You must acquire rcu_read_lock() to access cgrp->name, and
* the only place that can change it is rename(), which is
* protected by parent dir's i_mutex.
*
* Normally you should use cgroup_name() wrapper rather than
* access it directly.
*/
struct cgroup_name __rcu *name;
/* Private pointers for each registered subsystem */
struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
@ -479,12 +461,6 @@ static inline bool cgroup_sane_behavior(const struct cgroup *cgrp)
return cgrp->root->flags & CGRP_ROOT_SANE_BEHAVIOR;
}
/* Caller should hold rcu_read_lock() */
static inline const char *cgroup_name(const struct cgroup *cgrp)
{
return rcu_dereference(cgrp->name)->name;
}
/* returns ino associated with a cgroup, 0 indicates unmounted root */
static inline ino_t cgroup_ino(struct cgroup *cgrp)
{
@ -503,14 +479,47 @@ static inline struct cftype *seq_cft(struct seq_file *seq)
struct cgroup_subsys_state *seq_css(struct seq_file *seq);
/*
* Name / path handling functions. All are thin wrappers around the kernfs
* counterparts and can be called under any context.
*/
static inline int cgroup_name(struct cgroup *cgrp, char *buf, size_t buflen)
{
return kernfs_name(cgrp->kn, buf, buflen);
}
static inline char * __must_check cgroup_path(struct cgroup *cgrp, char *buf,
size_t buflen)
{
return kernfs_path(cgrp->kn, buf, buflen);
}
static inline void pr_cont_cgroup_name(struct cgroup *cgrp)
{
/* dummy_top doesn't have a kn associated */
if (cgrp->kn)
pr_cont_kernfs_name(cgrp->kn);
else
pr_cont("/");
}
static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
{
/* dummy_top doesn't have a kn associated */
if (cgrp->kn)
pr_cont_kernfs_path(cgrp->kn);
else
pr_cont("/");
}
char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_rm_cftypes(struct cftype *cfts);
bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen);
int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
int cgroup_task_count(const struct cgroup *cgrp);
/*