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memory cgroup enhancements: add- pre_destroy() handler

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Add a handler "pre_destroy" to cgroup_subsys.  It is called before
cgroup_rmdir() checks all subsys's refcnt.

I think this is useful for subsys which have some extra refs even if there
are no tasks in cgroup.  By adding pre_destroy(), the kernel keeps the rule
"destroy() against subsystem is called only when refcnt=0." and allows css
ref to be used by other objects than tasks.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Paul Menage <menage@google.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki 2008-02-07 00:14:27 -08:00 committed by Linus Torvalds
parent d2ceb9b7dd
commit 4fca88c87b
2 changed files with 23 additions and 0 deletions
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1
include/linux/cgroup.h
View file

@ -233,6 +233,7 @@ int cgroup_is_descendant(const struct cgroup *cont);
struct cgroup_subsys {
struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
struct cgroup *cont);
void (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cont);
void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cont);
int (*can_attach)(struct cgroup_subsys *ss,
struct cgroup *cont, struct task_struct *tsk);

22
kernel/cgroup.c
View file

@ -586,6 +586,21 @@ static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
return inode;
}
/*
* Call subsys's pre_destroy handler.
* This is called before css refcnt check.
*/
static void cgroup_call_pre_destroy(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
for_each_subsys(cgrp->root, ss)
if (ss->pre_destroy && cgrp->subsys[ss->subsys_id])
ss->pre_destroy(ss, cgrp);
return;
}
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
/* is dentry a directory ? if so, kfree() associated cgroup */
@ -2160,6 +2175,13 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
parent = cgrp->parent;
root = cgrp->root;
sb = root->sb;
/*
* Call pre_destroy handlers of subsys
*/
cgroup_call_pre_destroy(cgrp);
/*
* Notify subsyses that rmdir() request comes.
*/
if (cgroup_has_css_refs(cgrp)) {
mutex_unlock(&cgroup_mutex);