linux-kernel - [PATCH 2/2] cgroups: Clean up cgroup_pidlist

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Message-ID: <4B5EA500.5040802@cn.fujitsu.com>
Date:	Tue, 26 Jan 2010 16:17:04 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Li Zefan <lizf@...fujitsu.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <menage@...gle.com>,
	Ben Blum <bblum@...rew.cmu.edu>,
	LKML <linux-kernel@...r.kernel.org>,
	"containers@...ts.osdl.org" <containers@...ts.osdl.org>
Subject: [PATCH 2/2] cgroups: Clean up cgroup_pidlist_find() a bit

Don't Call get_pid_ns() before we locate/alloc the ns.

Signed-off-by: Li Zefan <lizf@...fujitsu.com>
---
 cgroup.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/kernel/cgroup.c.orig	2010-01-26 14:24:29.000000000 +0800
+++ a/kernel/cgroup.c	2010-01-26 14:24:44.000000000 +0800
@@ -2643,7 +2643,8 @@ static struct cgroup_pidlist *cgroup_pid
 {
 	struct cgroup_pidlist *l;
 	/* don't need task_nsproxy() if we're looking at ourself */
-	struct pid_namespace *ns = get_pid_ns(current->nsproxy->pid_ns);
+	struct pid_namespace *ns = current->nsproxy->pid_ns;
+
 	/*
 	 * We can't drop the pidlist_mutex before taking the l->mutex in case
 	 * the last ref-holder is trying to remove l from the list at the same
@@ -2653,8 +2654,6 @@ static struct cgroup_pidlist *cgroup_pid
 	mutex_lock(&cgrp->pidlist_mutex);
 	list_for_each_entry(l, &cgrp->pidlists, links) {
 		if (l->key.type == type && l->key.ns == ns) {
-			/* found a matching list - drop the extra refcount */
-			put_pid_ns(ns);
 			/* make sure l doesn't vanish out from under us */
 			down_write(&l->mutex);
 			mutex_unlock(&cgrp->pidlist_mutex);
@@ -2665,13 +2664,12 @@ static struct cgroup_pidlist *cgroup_pid
 	l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
 	if (!l) {
 		mutex_unlock(&cgrp->pidlist_mutex);
-		put_pid_ns(ns);
 		return l;
 	}
 	init_rwsem(&l->mutex);
 	down_write(&l->mutex);
 	l->key.type = type;
-	l->key.ns = ns;
+	l->key.ns = get_pid_ns(ns);
 	l->use_count = 0; /* don't increment here */
 	l->list = NULL;
 	l->owner = cgrp;
--
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