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>

1 files changed, 3 insertions, 5 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 521591dbab2f..1bf4d6db54ab 100644
--- 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;