pid namespaces: round up the API

The set of functions process_session, task_session, process_group and
task_pgrp is confusing, as the names can be mixed with each other when looking
at the code for a long time.

The proposals are to
* equip the functions that return the integer with _nr suffix to
  represent that fact,
* and to make all functions work with task (not process) by making
  the common prefix of the same name.

For monotony the routines signal_session() and set_signal_session() are
replaced with task_session_nr() and set_task_session(), especially since they
are only used with the explicit task->signal dereference.

Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Acked-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Kirill Korotaev <dev@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/mips/kernel/irixsig.c b/arch/mips/kernel/irixsig.c
index 85c2e38..a0a9105 100644
--- a/arch/mips/kernel/irixsig.c
+++ b/arch/mips/kernel/irixsig.c
@@ -609,7 +609,7 @@
 		p = list_entry(_p, struct task_struct, sibling);
 		if ((type == IRIX_P_PID) && p->pid != pid)
 			continue;
-		if ((type == IRIX_P_PGID) && process_group(p) != pid)
+		if ((type == IRIX_P_PGID) && task_pgrp_nr(p) != pid)
 			continue;
 		if ((p->exit_signal != SIGCHLD))
 			continue;