pids: clean up find_task_by_pid variants

find_task_by_pid_type_ns is only used to implement find_task_by_vpid and
find_task_by_pid_ns, but both of them pass PIDTYPE_PID as first argument.
So just fold find_task_by_pid_type_ns into find_task_by_pid_ns and use
find_task_by_pid_ns to implement find_task_by_vpid.

While we're at it also remove the exports for find_task_by_pid_ns and
find_task_by_vpid - we don't have any modular callers left as the only
modular caller of he old pre pid namespace find_task_by_pid (gfs2) was
switched to pid_task which operates on a struct pid pointer instead of a
pid_t.  Given the confusion about pid_t values vs namespace that's
generally the better option anyway and I think we're better of restricting
modules to do it that way.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/sched.h

@@ -1878,9 +1878,6 @@ extern struct pid_namespace init_pid_ns;
 /*
  * find a task by one of its numerical ids
  *
- * find_task_by_pid_type_ns():
- *      it is the most generic call - it finds a task by all id,
- *      type and namespace specified
  * find_task_by_pid_ns():
  *      finds a task by its pid in the specified namespace
  * find_task_by_vpid():
@@ -1889,9 +1886,6 @@ extern struct pid_namespace init_pid_ns;
  * see also find_vpid() etc in include/linux/pid.h
  */
 
-extern struct task_struct *find_task_by_pid_type_ns(int type, int pid,
-		struct pid_namespace *ns);
-
 extern struct task_struct *find_task_by_vpid(pid_t nr);
 extern struct task_struct *find_task_by_pid_ns(pid_t nr,
 		struct pid_namespace *ns);