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Date: Tue, 24 Aug 2010 18:35:00 -0700
From: Paul Menage <menage@...gle.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: linux-mm@...ck.org,
"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
gthelen@...gle.com, m-ikeda@...jp.nec.com,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
kamezawa.hiroyuki@...il.com,
"lizf@...fujitsu.com" <lizf@...fujitsu.com>
Subject: Re: [PATCH 1/5] cgroup: ID notification call back
On Tue, Aug 24, 2010 at 6:03 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
>
> Hmm. How this pseudo code looks like ? This passes "new id" via
> cgroup->subsys[array] at creation. (Using union will be better, maybe).
>
That's rather ugly. I was thinking of something more like this. (Not
even compiled yet, and the only subsystem updated is cpuset).
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ed3e92e..063d9f2 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -458,8 +458,7 @@ void cgroup_release_and_wakeup_rmdir(struct
cgroup_subsys_state *css);
*/
struct cgroup_subsys {
- struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
- struct cgroup *cgrp);
+ int (*create)(struct cgroup_subsys *ss, struct cgroup *cgrp);
int (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
@@ -513,6 +512,12 @@ struct cgroup_subsys {
/* should be defined only by modular subsystems */
struct module *module;
+
+ /* Total size of the subsystem's CSS object */
+ size_t css_size;
+
+ /* If non-NULL, the CSS to use for the root cgroup */
+ struct cgroup_subsys_state *root_css;
};
#define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 192f88c..c589a41 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3307,6 +3307,7 @@ static long cgroup_create(struct cgroup *parent,
struct dentry *dentry,
mode_t mode)
{
struct cgroup *cgrp;
+ struct cgroup_subsys_state *new_css[CGROUP_SUBSYS_COUNT] = {};
struct cgroupfs_root *root = parent->root;
int err = 0;
struct cgroup_subsys *ss;
@@ -3325,6 +3326,16 @@ static long cgroup_create(struct cgroup
*parent, struct dentry *dentry,
mutex_lock(&cgroup_mutex);
+ for_each_subsys(root, ss) {
+ int id = ss->subsys_id;
+ new_css[id] = kzalloc(ss->css_size, GFP_KERNEL);
+ if (!new_css) {
+ /* Failed to allocate memory */
+ err = -ENOMEM;
+ goto err_destroy;
+ }
+ }
+
init_cgroup_housekeeping(cgrp);
cgrp->parent = parent;
@@ -3335,19 +3346,19 @@ static long cgroup_create(struct cgroup
*parent, struct dentry *dentry,
set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
for_each_subsys(root, ss) {
- struct cgroup_subsys_state *css = ss->create(ss, cgrp);
-
- if (IS_ERR(css)) {
- err = PTR_ERR(css);
- goto err_destroy;
- }
- init_cgroup_css(css, ss, cgrp);
+ int id = ss->subsys_id;
+ init_cgroup_css(new_css[id], ss, cgrp);
if (ss->use_id) {
err = alloc_css_id(ss, parent, cgrp);
if (err)
goto err_destroy;
}
- /* At error, ->destroy() callback has to free assigned ID. */
+ err = ss->create(ss, cgrp);
+ if (err) {
+ free_css_id(ss, css->id);
+ goto err_destroy;
+ }
+ new_css[id] = NULL;
}
cgroup_lock_hierarchy(root);
@@ -3380,7 +3391,10 @@ static long cgroup_create(struct cgroup
*parent, struct dentry *dentry,
err_destroy:
for_each_subsys(root, ss) {
- if (cgrp->subsys[ss->subsys_id])
+ int id = ss->subsys_id;
+ if (new_css[id])
+ kfree(new_css[id]);
+ else if (cgrp->subsys[id])
ss->destroy(ss, cgrp);
}
@@ -3607,11 +3621,16 @@ static void __init cgroup_init_subsys(struct
cgroup_subsys *ss)
/* Create the top cgroup state for this subsystem */
list_add(&ss->sibling, &rootnode.subsys_list);
ss->root = &rootnode;
- css = ss->create(ss, dummytop);
+ if (ss->root_css)
+ css = ss->root_css;
+ else
+ css = kzalloc(ss->css_size, GFP_KERNEL);
/* We don't handle early failures gracefully */
- BUG_ON(IS_ERR(css));
+ BUG_ON(!css);
init_cgroup_css(css, ss, dummytop);
+ BUG_ON(ss->create(ss, dummytop));
+
/* Update the init_css_set to contain a subsys
* pointer to this state - since the subsystem is
* newly registered, all tasks and hence the
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index b23c097..7720a79 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1871,24 +1871,12 @@ static void cpuset_post_clone(struct cgroup_subsys *ss,
* cont: control group that the new cpuset will be part of
*/
-static struct cgroup_subsys_state *cpuset_create(
- struct cgroup_subsys *ss,
- struct cgroup *cont)
+static int cpuset_create(struct cgroup_subsys *ss, struct cgroup *cont)
{
- struct cpuset *cs;
- struct cpuset *parent;
-
- if (!cont->parent) {
- return &top_cpuset.css;
- }
- parent = cgroup_cs(cont->parent);
- cs = kmalloc(sizeof(*cs), GFP_KERNEL);
- if (!cs)
- return ERR_PTR(-ENOMEM);
- if (!alloc_cpumask_var(&cs->cpus_allowed, GFP_KERNEL)) {
- kfree(cs);
- return ERR_PTR(-ENOMEM);
- }
+ struct cpuset *cs = cgroup_cs(cont);
+ struct cpuset *parent = cgroup_cs(cont->parent);
+ if (!alloc_cpumask_var(&cs->cpus_allowed, GFP_KERNEL))
+ return -ENOMEM;
cs->flags = 0;
if (is_spread_page(parent))
@@ -1903,7 +1891,7 @@ static struct cgroup_subsys_state *cpuset_create(
cs->parent = parent;
number_of_cpusets++;
- return &cs->css ;
+ return 0;
}
/*
@@ -1934,6 +1922,8 @@ struct cgroup_subsys cpuset_subsys = {
.post_clone = cpuset_post_clone,
.subsys_id = cpuset_subsys_id,
.early_init = 1,
+ .css_size = sizeof(struct cpuset),
+ .root_css = &top_cpuset.css;
};
/**
--
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