This patch proposes an alternative to the "magical positive-versus-negative number trick" Andrew complained about last week in http://lkml.org/lkml/2008/6/24/418. This had been introduced with the patches that scale msgmni to the amount of lowmem. With these patches, msgmni has a registered notification routine that recomputes msgmni value upon memory add/remove or ipc namespace creation/ removal. When msgmni is changed from user space (i.e. value written to the proc file), that notification routine is unregistered, and the way to make it registered back is to write a negative value into the proc file. This is the "magical positive-versus-negative number trick". To fix this, a new proc file is introduced: /proc/sys/kernel/auto_msgmni. This file acts as ON/OFF for msgmni automatic recomputing. With this patch, the process is the following: 1) kernel boots in "automatic recomputing mode" /proc/sys/kernel/msgmni contains the value that has been computed (depends on lowmem) /proc/sys/kernel/automatic_msgmni contains "1" 2) echo <val> > /proc/sys/kernel/msgmni . sets msg_ctlmni to <val> . de-activates automatic recomputing (i.e. if, say, some memory is added msgmni won't be recomputed anymore) . /proc/sys/kernel/automatic_msgmni now contains "0" 3) echo "0" > /proc/sys/kernel/automatic_msgmni . de-activates msgmni automatic recomputing this has the same effect as 2) except that msg_ctlmni's value stays blocked at its current value) 3) echo "1" > /proc/sys/kernel/automatic_msgmni . recomputes msgmni's value based on the current available memory size and number of ipc namespaces . re-activates automatic recomputing for msgmni. Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net> Cc: Solofo Ramangalahy <Solofo.Ramangalahy@bull.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
291 lines
7 KiB
C
291 lines
7 KiB
C
/*
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* Copyright (C) 2007
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*
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* Author: Eric Biederman <ebiederm@xmision.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation, version 2 of the
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* License.
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*/
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#include <linux/module.h>
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#include <linux/ipc.h>
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#include <linux/nsproxy.h>
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#include <linux/sysctl.h>
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#include <linux/uaccess.h>
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#include <linux/ipc_namespace.h>
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#include <linux/msg.h>
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#include "util.h"
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static void *get_ipc(ctl_table *table)
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{
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char *which = table->data;
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struct ipc_namespace *ipc_ns = current->nsproxy->ipc_ns;
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which = (which - (char *)&init_ipc_ns) + (char *)ipc_ns;
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return which;
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}
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/*
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* Routine that is called when the file "auto_msgmni" has successfully been
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* written.
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* Two values are allowed:
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* 0: unregister msgmni's callback routine from the ipc namespace notifier
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* chain. This means that msgmni won't be recomputed anymore upon memory
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* add/remove or ipc namespace creation/removal.
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* 1: register back the callback routine.
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*/
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static void ipc_auto_callback(int val)
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{
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if (!val)
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unregister_ipcns_notifier(current->nsproxy->ipc_ns);
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else {
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/*
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* Re-enable automatic recomputing only if not already
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* enabled.
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*/
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recompute_msgmni(current->nsproxy->ipc_ns);
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cond_register_ipcns_notifier(current->nsproxy->ipc_ns);
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}
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}
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#ifdef CONFIG_PROC_FS
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static int proc_ipc_dointvec(ctl_table *table, int write, struct file *filp,
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void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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struct ctl_table ipc_table;
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memcpy(&ipc_table, table, sizeof(ipc_table));
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ipc_table.data = get_ipc(table);
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return proc_dointvec(&ipc_table, write, filp, buffer, lenp, ppos);
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}
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static int proc_ipc_callback_dointvec(ctl_table *table, int write,
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struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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struct ctl_table ipc_table;
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size_t lenp_bef = *lenp;
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int rc;
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memcpy(&ipc_table, table, sizeof(ipc_table));
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ipc_table.data = get_ipc(table);
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rc = proc_dointvec(&ipc_table, write, filp, buffer, lenp, ppos);
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if (write && !rc && lenp_bef == *lenp)
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/*
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* Tunable has successfully been changed by hand. Disable its
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* automatic adjustment. This simply requires unregistering
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* the notifiers that trigger recalculation.
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*/
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unregister_ipcns_notifier(current->nsproxy->ipc_ns);
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return rc;
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}
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static int proc_ipc_doulongvec_minmax(ctl_table *table, int write,
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struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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struct ctl_table ipc_table;
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memcpy(&ipc_table, table, sizeof(ipc_table));
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ipc_table.data = get_ipc(table);
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return proc_doulongvec_minmax(&ipc_table, write, filp, buffer,
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lenp, ppos);
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}
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static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write,
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struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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struct ctl_table ipc_table;
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size_t lenp_bef = *lenp;
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int oldval;
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int rc;
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memcpy(&ipc_table, table, sizeof(ipc_table));
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ipc_table.data = get_ipc(table);
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oldval = *((int *)(ipc_table.data));
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rc = proc_dointvec_minmax(&ipc_table, write, filp, buffer, lenp, ppos);
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if (write && !rc && lenp_bef == *lenp) {
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int newval = *((int *)(ipc_table.data));
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/*
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* The file "auto_msgmni" has correctly been set.
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* React by (un)registering the corresponding tunable, if the
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* value has changed.
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*/
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if (newval != oldval)
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ipc_auto_callback(newval);
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}
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return rc;
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}
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#else
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#define proc_ipc_doulongvec_minmax NULL
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#define proc_ipc_dointvec NULL
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#define proc_ipc_callback_dointvec NULL
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#define proc_ipcauto_dointvec_minmax NULL
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#endif
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#ifdef CONFIG_SYSCTL_SYSCALL
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/* The generic sysctl ipc data routine. */
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static int sysctl_ipc_data(ctl_table *table, int __user *name, int nlen,
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void __user *oldval, size_t __user *oldlenp,
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void __user *newval, size_t newlen)
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{
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size_t len;
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void *data;
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/* Get out of I don't have a variable */
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if (!table->data || !table->maxlen)
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return -ENOTDIR;
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data = get_ipc(table);
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if (!data)
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return -ENOTDIR;
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if (oldval && oldlenp) {
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if (get_user(len, oldlenp))
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return -EFAULT;
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if (len) {
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if (len > table->maxlen)
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len = table->maxlen;
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if (copy_to_user(oldval, data, len))
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return -EFAULT;
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if (put_user(len, oldlenp))
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return -EFAULT;
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}
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}
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if (newval && newlen) {
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if (newlen > table->maxlen)
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newlen = table->maxlen;
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if (copy_from_user(data, newval, newlen))
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return -EFAULT;
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}
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return 1;
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}
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static int sysctl_ipc_registered_data(ctl_table *table, int __user *name,
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int nlen, void __user *oldval, size_t __user *oldlenp,
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void __user *newval, size_t newlen)
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{
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int rc;
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rc = sysctl_ipc_data(table, name, nlen, oldval, oldlenp, newval,
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newlen);
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if (newval && newlen && rc > 0)
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/*
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* Tunable has successfully been changed from userland
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*/
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unregister_ipcns_notifier(current->nsproxy->ipc_ns);
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return rc;
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}
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#else
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#define sysctl_ipc_data NULL
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#define sysctl_ipc_registered_data NULL
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#endif
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static int zero;
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static int one = 1;
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static struct ctl_table ipc_kern_table[] = {
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{
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.ctl_name = KERN_SHMMAX,
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.procname = "shmmax",
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.data = &init_ipc_ns.shm_ctlmax,
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.maxlen = sizeof (init_ipc_ns.shm_ctlmax),
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.mode = 0644,
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.proc_handler = proc_ipc_doulongvec_minmax,
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.strategy = sysctl_ipc_data,
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},
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{
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.ctl_name = KERN_SHMALL,
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.procname = "shmall",
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.data = &init_ipc_ns.shm_ctlall,
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.maxlen = sizeof (init_ipc_ns.shm_ctlall),
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.mode = 0644,
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.proc_handler = proc_ipc_doulongvec_minmax,
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.strategy = sysctl_ipc_data,
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},
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{
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.ctl_name = KERN_SHMMNI,
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.procname = "shmmni",
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.data = &init_ipc_ns.shm_ctlmni,
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.maxlen = sizeof (init_ipc_ns.shm_ctlmni),
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.mode = 0644,
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.proc_handler = proc_ipc_dointvec,
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.strategy = sysctl_ipc_data,
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},
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{
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.ctl_name = KERN_MSGMAX,
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.procname = "msgmax",
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.data = &init_ipc_ns.msg_ctlmax,
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.maxlen = sizeof (init_ipc_ns.msg_ctlmax),
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.mode = 0644,
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.proc_handler = proc_ipc_dointvec,
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.strategy = sysctl_ipc_data,
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},
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{
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.ctl_name = KERN_MSGMNI,
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.procname = "msgmni",
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.data = &init_ipc_ns.msg_ctlmni,
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.maxlen = sizeof (init_ipc_ns.msg_ctlmni),
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.mode = 0644,
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.proc_handler = proc_ipc_callback_dointvec,
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.strategy = sysctl_ipc_registered_data,
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},
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{
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.ctl_name = KERN_MSGMNB,
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.procname = "msgmnb",
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.data = &init_ipc_ns.msg_ctlmnb,
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.maxlen = sizeof (init_ipc_ns.msg_ctlmnb),
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.mode = 0644,
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.proc_handler = proc_ipc_dointvec,
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.strategy = sysctl_ipc_data,
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},
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{
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.ctl_name = KERN_SEM,
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.procname = "sem",
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.data = &init_ipc_ns.sem_ctls,
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.maxlen = 4*sizeof (int),
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.mode = 0644,
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.proc_handler = proc_ipc_dointvec,
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.strategy = sysctl_ipc_data,
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},
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{
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.ctl_name = CTL_UNNUMBERED,
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.procname = "auto_msgmni",
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.data = &init_ipc_ns.auto_msgmni,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_ipcauto_dointvec_minmax,
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.extra1 = &zero,
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.extra2 = &one,
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},
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{}
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};
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static struct ctl_table ipc_root_table[] = {
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{
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.ctl_name = CTL_KERN,
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.procname = "kernel",
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.mode = 0555,
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.child = ipc_kern_table,
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},
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{}
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};
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static int __init ipc_sysctl_init(void)
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{
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register_sysctl_table(ipc_root_table);
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return 0;
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}
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__initcall(ipc_sysctl_init);
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