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

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Date:	Tue, 26 Jan 2010 15:08:59 -0800
From:	Paul Menage <menage@...gle.com>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ben Blum <bblum@...rew.cmu.edu>,
	LKML <linux-kernel@...r.kernel.org>,
	"containers@...ts.osdl.org" <containers@...ts.osdl.org>
Subject: Re: [PATCH 2/2] cgroups: Clean up cgroup_pidlist_find() a bit

On Tue, Jan 26, 2010 at 12:17 AM, Li Zefan <lizf@...fujitsu.com> wrote:
> Don't Call get_pid_ns() before we locate/alloc the ns.
>
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>

Acked-by: Paul Menage <menage@...gle.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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