pidns: Use task_active_pid_ns where appropriate

The expressions tsk->nsproxy->pid_ns and task_active_pid_ns
aka ns_of_pid(task_pid(tsk)) should have the same number of
cache line misses with the practical difference that
ns_of_pid(task_pid(tsk)) is released later in a processes life.

Furthermore by using task_active_pid_ns it becomes trivial
to write an unshare implementation for the the pid namespace.

So I have used task_active_pid_ns everywhere I can.

In fork since the pid has not yet been attached to the
process I use ns_of_pid, to achieve the same effect.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index f24f724620dd..0dbfba2efa77 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3390,7 +3390,7 @@ 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 = current->nsproxy->pid_ns;
+        struct pid_namespace *ns = task_active_pid_ns(current);
 
         /*
          * We can't drop the pidlist_mutex before taking the l->mutex in case