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, 2 insertions, 1 deletions

diff --git a/drivers/staging/android/binder.c b/drivers/staging/android/binder.c
index 5d4610babd8..a97bbcd1c9e 100644
--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -33,6 +33,7 @@
 #include <linux/uaccess.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
+#include <linux/pid_namespace.h>
 
 #include "binder.h"
 
@@ -2344,7 +2345,7 @@ retry:
 		if (t->from) {
 			struct task_struct *sender = t->from->proc->tsk;
 			tr.sender_pid = task_tgid_nr_ns(sender,
-							current->nsproxy->pid_ns);
+							task_active_pid_ns(current));
 		} else {
 			tr.sender_pid = 0;
 		}