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@cn.fujitsu.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Acked-by: Paul Menage <menage@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 521591d..1bf4d6d 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2597,7 +2597,8 @@ static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
 {
        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
@@ -2607,8 +2608,6 @@ static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
        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);
@@ -2619,13 +2618,12 @@ static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
        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;