Uninline find_task_by_xxx set of functions

The find_task_by_something is a set of macros are used to find task by pid
depending on what kind of pid is proposed - global or virtual one.  All of
them are wrappers above the most generic one - find_task_by_pid_type_ns() -
and just substitute some args for it.

It turned out, that dereferencing the current->nsproxy->pid_ns construction
and pushing one more argument on the stack inline cause kernel text size to
grow.

This patch moves all this stuff out-of-line into kernel/pid.c.  Together
with the next patch it saves a bit less than 400 bytes from the .text
section.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Paul Menage <menage@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/futex.c b/kernel/futex.c
index 86b26003..3271045 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -446,9 +446,7 @@
 	struct task_struct *p;
 
 	rcu_read_lock();
-	p = find_task_by_pid_ns(pid,
-			current->nsproxy->pid_ns);
-
+	p = find_task_by_vpid(pid);
 	if (!p || ((current->euid != p->euid) && (current->euid != p->uid)))
 		p = ERR_PTR(-ESRCH);
 	else
@@ -1858,8 +1856,7 @@
 
 		ret = -ESRCH;
 		rcu_read_lock();
-		p = find_task_by_pid_ns(pid,
-				current->nsproxy->pid_ns);
+		p = find_task_by_vpid(pid);
 		if (!p)
 			goto err_unlock;
 		ret = -EPERM;