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Subject[RFC][v7][PATCH 3/9] Make pid_max a pid_ns property


From: Serge Hallyn <serue@us.ibm.com>
Subject: [RFC][v7][PATCH 3/9] 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,

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