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/sysctl_binary.c b/kernel/sysctl_binary.c
index 65bdcf198d4e..5a6384450501 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -1344,7 +1344,7 @@ static ssize_t binary_sysctl(const int *name, int nlen,
                 goto out_putname;
         }
 
-        mnt = current->nsproxy->pid_ns->proc_mnt;
+        mnt = task_active_pid_ns(current)->proc_mnt;
         file = file_open_root(mnt->mnt_root, mnt, pathname, flags);
         result = PTR_ERR(file);
         if (IS_ERR(file))