pids: kill signal_struct-> __pgrp/__session and friends

We are wasting 2 words in signal_struct without any reason to implement
task_pgrp_nr() and task_session_nr().

task_session_nr() has no callers since
2e2ba22ea4fd4bb85f0fa37c521066db6775cbef, we can remove it.

task_pgrp_nr() is still (I believe wrongly) used in fs/autofsX and
fs/coda.

This patch reimplements task_pgrp_nr() via task_pgrp_nr_ns(), and kills
__pgrp/__session and the related helpers.

The change in drivers/char/tty_io.c is cosmetic, but hopefully makes sense
anyway.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Alan Cox <number6@the-village.bc.nu>		[tty parts]
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 4 insertions, 12 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 384f09caf2ef..3bec141c82f6 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -357,16 +357,12 @@ static void reparent_to_kthreadd(void)
 void __set_special_pids(struct pid *pid)
 {
         struct task_struct *curr = current->group_leader;
-        pid_t nr = pid_nr(pid);
 
-        if (task_session(curr) != pid) {
+        if (task_session(curr) != pid)
                 change_pid(curr, PIDTYPE_SID, pid);
-                set_task_session(curr, nr);
-        }
-        if (task_pgrp(curr) != pid) {
+
+        if (task_pgrp(curr) != pid)
                 change_pid(curr, PIDTYPE_PGID, pid);
-                set_task_pgrp(curr, nr);
-        }
 }
 
 static void set_special_pids(struct pid *pid)
diff --git a/kernel/fork.c b/kernel/fork.c
index adbea16ec649..f74458231449 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1265,8 +1265,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                         p->signal->leader_pid = pid;
                         tty_kref_put(p->signal->tty);
                         p->signal->tty = tty_kref_get(current->signal->tty);
-                        set_task_pgrp(p, task_pgrp_nr(current));
-                        set_task_session(p, task_session_nr(current));
                         attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
                         attach_pid(p, PIDTYPE_SID, task_session(current));
                         list_add_tail_rcu(&p->tasks, &init_task.tasks);
diff --git a/kernel/sys.c b/kernel/sys.c
index 37f458e6882a..742cefa527e6 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1013,10 +1013,8 @@ SYSCALL_DEFINE2(setpgid, pid_t, pid, pid_t, pgid)
         if (err)
                 goto out;
 
-        if (task_pgrp(p) != pgrp) {
+        if (task_pgrp(p) != pgrp)
                 change_pid(p, PIDTYPE_PGID, pgrp);
-                set_task_pgrp(p, pid_nr(pgrp));
-        }
 
         err = 0;
 out: