[RFC][v8][PATCH 3/10]: Make pid_max a pid_ns property

[Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>]

From: Serge Hallyn <serue@us.ibm.com>
Subject: [RFC][v8][PATCH 3/10]: Make pid_max a pid_ns property

Remove the pid_max global, and make it a property of the
pid_namespace.  When a pid_ns is created, it inherits
the parent's pid_ns.

Fixing up sysctl (trivial akin to ipc version, but
potentially tedious to get right for all CONFIG*
combinations) is left for later.

Changelog[v2]:
	- Port to newer kernel
	- Make pid_max a local variable in alloc_pidmap() to simplify code/patch

Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
---
 include/linux/pid_namespace.h |    1 +
 kernel/pid.c                  |    4 ++--
 kernel/pid_namespace.c        |    1 +
 kernel/sysctl.c               |    4 ++--
 4 files changed, 6 insertions(+), 4 deletions(-)

Index: linux-2.6/include/linux/pid_namespace.h
===================================================================
--- linux-2.6.orig/include/linux/pid_namespace.h	2009-09-09 19:06:21.000000000 -0700
+++ linux-2.6/include/linux/pid_namespace.h	2009-09-09 19:07:20.000000000 -0700
@@ -30,6 +30,7 @@ struct pid_namespace {
 #ifdef CONFIG_BSD_PROCESS_ACCT
 	struct bsd_acct_struct *bacct;
 #endif
+	int pid_max;
 };
 
 extern struct pid_namespace init_pid_ns;
Index: linux-2.6/kernel/pid.c
===================================================================
--- linux-2.6.orig/kernel/pid.c	2009-09-09 19:06:46.000000000 -0700
+++ linux-2.6/kernel/pid.c	2009-09-09 19:07:20.000000000 -0700
@@ -43,8 +43,6 @@ static struct hlist_head *pid_hash;
 static int pidhash_shift;
 struct pid init_struct_pid = INIT_STRUCT_PID;
 
-int pid_max = PID_MAX_DEFAULT;
-
 #define RESERVED_PIDS		300
 
 int pid_max_min = RESERVED_PIDS + 1;
@@ -78,6 +76,7 @@ struct pid_namespace init_pid_ns = {
 	.last_pid = 0,
 	.level = 0,
 	.child_reaper = &init_task,
+	.pid_max = PID_MAX_DEFAULT,
 };
 EXPORT_SYMBOL_GPL(init_pid_ns);
 
@@ -151,6 +150,7 @@ static int alloc_pidmap(struct pid_names
 {
 	int i, offset, max_scan, pid, last = pid_ns->last_pid;
 	int rc = -EAGAIN;
+	int pid_max = pid_ns->pid_max;
 	struct pidmap *map;
 
 	pid = last + 1;
Index: linux-2.6/kernel/pid_namespace.c
===================================================================
--- linux-2.6.orig/kernel/pid_namespace.c	2009-09-09 19:06:21.000000000 -0700
+++ linux-2.6/kernel/pid_namespace.c	2009-09-09 19:07:20.000000000 -0700
@@ -87,6 +87,7 @@ static struct pid_namespace *create_pid_
 
 	kref_init(&ns->kref);
 	ns->level = level;
+	ns->pid_max = parent_pid_ns->pid_max;
 	ns->parent = get_pid_ns(parent_pid_ns);
 
 	set_bit(0, ns->pidmap[0].page);
Index: linux-2.6/kernel/sysctl.c
===================================================================
--- linux-2.6.orig/kernel/sysctl.c	2009-09-09 19:06:21.000000000 -0700
+++ linux-2.6/kernel/sysctl.c	2009-09-09 19:07:20.000000000 -0700
@@ -55,6 +55,7 @@
 
 #include <asm/uaccess.h>
 #include <asm/processor.h>
+#include <linux/pid_namespace.h>
 
 #ifdef CONFIG_X86
 #include <asm/nmi.h>
@@ -78,7 +79,6 @@ extern int max_threads;
 extern int core_uses_pid;
 extern int suid_dumpable;
 extern char core_pattern[];
-extern int pid_max;
 extern int min_free_kbytes;
 extern int pid_max_min, pid_max_max;
 extern int sysctl_drop_caches;
@@ -670,7 +670,7 @@ static struct ctl_table kern_table[] = {
 	{
 		.ctl_name	= KERN_PIDMAX,
 		.procname	= "pid_max",
-		.data		= &pid_max,
+		.data		= &init_pid_ns.pid_max,
 		.maxlen		= sizeof (int),
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec_minmax,