1. I ask for not setting your authorship/copyright on the code which you just copied
   from other places. Just doesn't look polite IMHO.
2. please don't name files like ipc/ipc_sysctl.c
   ipc/sysctl.c sounds better IMHO.
3. any reason to introduce CONFIG_SYSVIPC_SYSCTL?
   why not simply do
   > +obj-$(CONFIG_SYSCTL) += sysctl.o
   instead?

Kirill

> From: Eric W. Biederman <ebiederm@xmission.com> - unquoted
> 
> This is just a simple cleanup to keep kernel/sysctl.c
> from getting to crowded with special cases, and by
> keeping all of the ipc logic to together it makes
> the code a little more readable.
> 
> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
> ---
>  init/Kconfig     |    6 ++
>  ipc/Makefile     |    1 +
>  ipc/ipc_sysctl.c |  182 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  kernel/sysctl.c  |  174 ---------------------------------------------------
>  4 files changed, 189 insertions(+), 174 deletions(-)
> 
> diff --git a/init/Kconfig b/init/Kconfig
> index a3f83e2..33bc38d 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -116,6 +116,12 @@ config SYSVIPC
>  	  section 6.4 of the Linux Programmer's Guide, available from
>  	  <http://www.tldp.org/guides.html>.
>  
> +config SYSVIPC_SYSCTL
> +	bool
> +	depends on SYSVIPC
> +	depends on SYSCTL
> +	default y
> +
>  config IPC_NS
>  	bool "IPC Namespaces"
>  	depends on SYSVIPC
> diff --git a/ipc/Makefile b/ipc/Makefile
> index 0a6d626..b93bba6 100644
> --- a/ipc/Makefile
> +++ b/ipc/Makefile
> @@ -4,6 +4,7 @@
>  
>  obj-$(CONFIG_SYSVIPC_COMPAT) += compat.o
>  obj-$(CONFIG_SYSVIPC) += util.o msgutil.o msg.o sem.o shm.o
> +obj-$(CONFIG_SYSVIPC_SYSCTL) += ipc_sysctl.o
>  obj_mq-$(CONFIG_COMPAT) += compat_mq.o
>  obj-$(CONFIG_POSIX_MQUEUE) += mqueue.o msgutil.o $(obj_mq-y)
>  
> diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
> new file mode 100644
> index 0000000..9018009
> --- /dev/null
> +++ b/ipc/ipc_sysctl.c
> @@ -0,0 +1,182 @@
> +/*
> + *  Copyright (C) 2007
> + *
> + *  Author: Eric Biederman <ebiederm@xmision.com>
> + *
> + *  This program is free software; you can redistribute it and/or
> + *  modify it under the terms of the GNU General Public License as
> + *  published by the Free Software Foundation, version 2 of the
> + *  License.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/ipc.h>
> +#include <linux/nsproxy.h>
> +#include <linux/sysctl.h>
> +
> +#ifdef CONFIG_IPC_NS
> +static void *get_ipc(ctl_table *table)
> +{
> +	char *which = table->data;
> +	struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
> +	which = (which - (char *)&init_ipc_ns) + (char *)ipc_ns;
> +	return which;
> +}
> +#else
> +#define get_ipc(T) ((T)->data)
> +#endif
> +
> +#ifdef CONFIG_PROC_FS
> +static int proc_ipc_dointvec(ctl_table *table, int write, struct file *filp,
> +	void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	struct ctl_table ipc_table;
> +	memcpy(&ipc_table, table, sizeof(ipc_table));
> +	ipc_table.data = get_ipc(table);
> +
> +	return proc_dointvec(&ipc_table, write, filp, buffer, lenp, ppos);
> +}
> +
> +static int proc_ipc_doulongvec_minmax(ctl_table *table, int write,
> +	struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	struct ctl_table ipc_table;
> +	memcpy(&ipc_table, table, sizeof(ipc_table));
> +	ipc_table.data = get_ipc(table);
> +
> +	return proc_doulongvec_minmax(&ipc_table, write, filp, buffer,
> +					lenp, ppos);
> +}
> +
> +#else
> +#define proc_ipc_do_ulongvec_minmax NULL
> +#define proc_ipc_do_intvec	    NULL
> +#endif
> +
> +#ifdef CONFIG_SYSCTL_SYSCALL
> +/* The generic sysctl ipc data routine. */
> +static int sysctl_ipc_data(ctl_table *table, int __user *name, int nlen,
> +		void __user *oldval, size_t __user *oldlenp,
> +		void __user *newval, size_t newlen)
> +{
> +	size_t len;
> +	void *data;
> +
> +	/* Get out of I don't have a variable */
> +	if (!table->data || !table->maxlen)
> +		return -ENOTDIR;
> +
> +	data = get_ipc(table);
> +	if (!data)
> +		return -ENOTDIR;
> +
> +	if (oldval && oldlenp) {
> +		if (get_user(len, oldlenp))
> +			return -EFAULT;
> +		if (len) {
> +			if (len > table->maxlen)
> +				len = table->maxlen;
> +			if (copy_to_user(oldval, data, len))
> +				return -EFAULT;
> +			if (put_user(len, oldlenp))
> +				return -EFAULT;
> +		}
> +	}
> +
> +	if (newval && newlen) {
> +		if (newlen > table->maxlen)
> +			newlen = table->maxlen;
> +
> +		if (copy_from_user(data, newval, newlen))
> +			return -EFAULT;
> +	}
> +	return 1;
> +}
> +#else
> +#define sysctl_ipc_data NULL
> +#endif
> +
> +static struct ctl_table ipc_kern_table[] = {
> +	{
> +		.ctl_name	= KERN_SHMMAX,
> +		.procname	= "shmmax",
> +		.data		= &init_ipc_ns.shm_ctlmax,
> +		.maxlen		= sizeof (init_ipc_ns.shm_ctlmax),
> +		.mode		= 0644,
> +		.proc_handler	= proc_ipc_doulongvec_minmax,
> +		.strategy	= sysctl_ipc_data,
> +	},
> +	{
> +		.ctl_name	= KERN_SHMALL,
> +		.procname	= "shmall",
> +		.data		= &init_ipc_ns.shm_ctlall,
> +		.maxlen		= sizeof (init_ipc_ns.shm_ctlall),
> +		.mode		= 0644,
> +		.proc_handler	= proc_ipc_doulongvec_minmax,
> +		.strategy	= sysctl_ipc_data,
> +	},
> +	{
> +		.ctl_name	= KERN_SHMMNI,
> +		.procname	= "shmmni",
> +		.data		= &init_ipc_ns.shm_ctlmni,
> +		.maxlen		= sizeof (init_ipc_ns.shm_ctlmni),
> +		.mode		= 0644,
> +		.proc_handler	= proc_ipc_dointvec,
> +		.strategy	= sysctl_ipc_data,
> +	},
> +	{
> +		.ctl_name	= KERN_MSGMAX,
> +		.procname	= "msgmax",
> +		.data		= &init_ipc_ns.msg_ctlmax,
> +		.maxlen		= sizeof (init_ipc_ns.msg_ctlmax),
> +		.mode		= 0644,
> +		.proc_handler	= proc_ipc_dointvec,
> +		.strategy	= sysctl_ipc_data,
> +	},
> +	{
> +		.ctl_name	= KERN_MSGMNI,
> +		.procname	= "msgmni",
> +		.data		= &init_ipc_ns.msg_ctlmni,
> +		.maxlen		= sizeof (init_ipc_ns.msg_ctlmni),
> +		.mode		= 0644,
> +		.proc_handler	= proc_ipc_dointvec,
> +		.strategy	= sysctl_ipc_data,
> +	},
> +	{
> +		.ctl_name	= KERN_MSGMNB,
> +		.procname	=  "msgmnb",
> +		.data		= &init_ipc_ns.msg_ctlmnb,
> +		.maxlen		= sizeof (init_ipc_ns.msg_ctlmnb),
> +		.mode		= 0644,
> +		.proc_handler	= proc_ipc_dointvec,
> +		.strategy	= sysctl_ipc_data,
> +	},
> +	{
> +		.ctl_name	= KERN_SEM,
> +		.procname	= "sem",
> +		.data		= &init_ipc_ns.sem_ctls,
> +		.maxlen		= 4*sizeof (int),
> +		.mode		= 0644,
> +		.proc_handler	= proc_ipc_dointvec,
> +		.strategy	= sysctl_ipc_data,
> +	},
> +	{}
> +};
> +
> +static struct ctl_table ipc_root_table[] = {
> +	{
> +		.ctl_name	= CTL_KERN,
> +		.procname	= "kernel",
> +		.mode		= 0555,
> +		.child		= ipc_kern_table,
> +	},
> +	{}
> +};
> +
> +static int __init ipc_sysctl_init(void)
> +{
> +	register_sysctl_table(ipc_root_table, 0);
> +	return 0;
> +}
> +
> +__initcall(ipc_sysctl_init);
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index a8c0a03..6e2e608 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -90,12 +90,6 @@ extern char modprobe_path[];
>  #ifdef CONFIG_CHR_DEV_SG
>  extern int sg_big_buff;
>  #endif
> -#ifdef CONFIG_SYSVIPC
> -static int proc_ipc_dointvec(ctl_table *table, int write, struct file *filp,
> -		void __user *buffer, size_t *lenp, loff_t *ppos);
> -static int proc_ipc_doulongvec_minmax(ctl_table *table, int write, struct file *filp,
> -		void __user *buffer, size_t *lenp, loff_t *ppos);
> -#endif
>  
>  #ifdef __sparc__
>  extern char reboot_command [];
> @@ -135,11 +129,6 @@ static int parse_table(int __user *, int, void __user *, size_t __user *,
>  		void __user *, size_t, ctl_table *);
>  #endif
>  
> -#ifdef CONFIG_SYSVIPC
> -static int sysctl_ipc_data(ctl_table *table, int __user *name, int nlen,
> -		  void __user *oldval, size_t __user *oldlenp,
> -		  void __user *newval, size_t newlen);
> -#endif
>  
>  #ifdef CONFIG_PROC_SYSCTL
>  static int proc_do_cad_pid(ctl_table *table, int write, struct file *filp,
> @@ -168,17 +157,6 @@ int sysctl_legacy_va_layout;
>  #endif
>  
>  
> -#ifdef CONFIG_SYSVIPC
> -static void *get_ipc(ctl_table *table, int write)
> -{
> -	char *which = table->data;
> -	struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
> -	which = (which - (char *)&init_ipc_ns) + (char *)ipc_ns;
> -	return which;
> -}
> -#else
> -#define get_ipc(T,W) ((T)->data)
> -#endif
>  
>  /* /proc declarations: */
>  
> @@ -400,71 +378,6 @@ static ctl_table kern_table[] = {
>  		.proc_handler	= &proc_dointvec,
>  	},
>  #endif
> -#ifdef CONFIG_SYSVIPC
> -	{
> -		.ctl_name	= KERN_SHMMAX,
> -		.procname	= "shmmax",
> -		.data		= &init_ipc_ns.shm_ctlmax,
> -		.maxlen		= sizeof (init_ipc_ns.shm_ctlmax),
> -		.mode		= 0644,
> -		.proc_handler	= &proc_ipc_doulongvec_minmax,
> -		.strategy	= sysctl_ipc_data,
> -	},
> -	{
> -		.ctl_name	= KERN_SHMALL,
> -		.procname	= "shmall",
> -		.data		= &init_ipc_ns.shm_ctlall,
> -		.maxlen		= sizeof (init_ipc_ns.shm_ctlall),
> -		.mode		= 0644,
> -		.proc_handler	= &