attach_pid() with struct pid parameter

attach_pid() currently takes a pid_t and then uses find_pid() to find the
corresponding struct pid.  Sometimes we already have the struct pid.  We can
then skip find_pid() if attach_pid() were to take a struct pid parameter.

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: <containers@lists.osdl.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/pid.h b/include/linux/pid.h
index 2ac27f9..33d3438 100644
--- a/include/linux/pid.h
+++ b/include/linux/pid.h
@@ -76,8 +76,7 @@
  * write-held.
  */
 extern int FASTCALL(attach_pid(struct task_struct *task,
-				enum pid_type type, int nr));
-
+				enum pid_type type, struct pid *pid));
 extern void FASTCALL(detach_pid(struct task_struct *task, enum pid_type));
 extern void FASTCALL(transfer_pid(struct task_struct *old,
 				  struct task_struct *new, enum pid_type));