[PATCH] add process_session() helper routine

Replace occurences of task->signal->session by a new process_session() helper
routine.

It will be useful for pid namespaces to abstract the session pid number.

Signed-off-by: Cedric Le Goater <clg@fr.ibm.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/fork.c b/kernel/fork.c
index 5977078..298c4d6 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1259,9 +1259,9 @@
 		if (thread_group_leader(p)) {
 			p->signal->tty = current->signal->tty;
 			p->signal->pgrp = process_group(current);
-			p->signal->session = current->signal->session;
+			p->signal->session = process_session(current);
 			attach_pid(p, PIDTYPE_PGID, process_group(p));
-			attach_pid(p, PIDTYPE_SID, p->signal->session);
+			attach_pid(p, PIDTYPE_SID, process_session(p));
 
 			list_add_tail_rcu(&p->tasks, &init_task.tasks);
 			__get_cpu_var(process_counts)++;