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ipc: re-enable msgmni automatic recomputing msgmni if set to negative

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The enhancement as asked for by Yasunori: if msgmni is set to a negative
value, register it back into the ipcns notifier chain.

A new interface has been added to the notification mechanism:
notifier_chain_cond_register() registers a notifier block only if not already
registered.  With that new interface we avoid taking care of the states
changes in procfs.

Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Mingming Cao <cmm@us.ibm.com>
Cc: Pierre Peiffer <pierre.peiffer@bull.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nadia Derbey 2008-04-29 01:00:45 -07:00 committed by Linus Torvalds
parent 91cfb2b4b5
commit 6546bc4279
5 changed files with 87 additions and 10 deletions
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1
include/linux/ipc_namespace.h
View file

@ -52,6 +52,7 @@ extern atomic_t nr_ipc_ns;
#define INIT_IPC_NS(ns) .ns = &init_ipc_ns,
extern int register_ipcns_notifier(struct ipc_namespace *);
extern int cond_register_ipcns_notifier(struct ipc_namespace *);
extern int unregister_ipcns_notifier(struct ipc_namespace *);
extern int ipcns_notify(unsigned long);

4
include/linux/notifier.h
View file

@ -121,6 +121,10 @@ extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
struct notifier_block *nb);
extern int blocking_notifier_chain_cond_register(
struct blocking_notifier_head *nh,
struct notifier_block *nb);
extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
struct notifier_block *nb);
extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,

45
ipc/ipc_sysctl.c
View file

@ -15,6 +15,8 @@
#include <linux/sysctl.h>
#include <linux/uaccess.h>
#include <linux/ipc_namespace.h>
#include <linux/msg.h>
#include "util.h"
static void *get_ipc(ctl_table *table)
{
@ -24,6 +26,27 @@ static void *get_ipc(ctl_table *table)
return which;
}
/*
* Routine that is called when a tunable has successfully been changed by
* hand and it has a callback routine registered on the ipc namespace notifier
* chain: we don't want such tunables to be recomputed anymore upon memory
* add/remove or ipc namespace creation/removal.
* They can come back to a recomputable state by being set to a <0 value.
*/
static void tunable_set_callback(int val)
{
if (val >= 0)
unregister_ipcns_notifier(current->nsproxy->ipc_ns);
else {
/*
* Re-enable automatic recomputing only if not already
* enabled.
*/
recompute_msgmni(current->nsproxy->ipc_ns);
cond_register_ipcns_notifier(current->nsproxy->ipc_ns);
}
}
#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)
@ -38,17 +61,17 @@ static int proc_ipc_dointvec(ctl_table *table, int write, struct file *filp,
static int proc_ipc_callback_dointvec(ctl_table *table, int write,
struct file *filp, void __user *buffer, size_t *lenp, loff_t *ppos)
{
struct ctl_table ipc_table;
size_t lenp_bef = *lenp;
int rc;
rc = proc_ipc_dointvec(table, write, filp, buffer, lenp, ppos);
memcpy(&ipc_table, table, sizeof(ipc_table));
ipc_table.data = get_ipc(table);
rc = proc_dointvec(&ipc_table, write, filp, buffer, lenp, ppos);
if (write && !rc && lenp_bef == *lenp)
/*
* Tunable has successfully been changed from userland:
* disable its automatic recomputing.
*/
unregister_ipcns_notifier(current->nsproxy->ipc_ns);
tunable_set_callback(*((int *)(ipc_table.data)));
return rc;
}
@ -119,12 +142,14 @@ static int sysctl_ipc_registered_data(ctl_table *table, int __user *name,
rc = sysctl_ipc_data(table, name, nlen, oldval, oldlenp, newval,
newlen);
if (newval && newlen && rc > 0)
if (newval && newlen && rc > 0) {
/*
* Tunable has successfully been changed from userland:
* disable its automatic recomputing.
* Tunable has successfully been changed from userland
*/
unregister_ipcns_notifier(current->nsproxy->ipc_ns);
int *data = get_ipc(table);
tunable_set_callback(*data);
}
return rc;
}

9
ipc/ipcns_notifier.c
View file

@ -61,6 +61,15 @@ int register_ipcns_notifier(struct ipc_namespace *ns)
return blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
}
int cond_register_ipcns_notifier(struct ipc_namespace *ns)
{
memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
ns->ipcns_nb.notifier_call = ipcns_callback;
ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
return blocking_notifier_chain_cond_register(&ipcns_chain,
&ns->ipcns_nb);
}
int unregister_ipcns_notifier(struct ipc_namespace *ns)
{
return blocking_notifier_chain_unregister(&ipcns_chain,

38
kernel/notifier.c
View file

@ -31,6 +31,21 @@ static int notifier_chain_register(struct notifier_block **nl,
return 0;
}
static int notifier_chain_cond_register(struct notifier_block **nl,
struct notifier_block *n)
{
while ((*nl) != NULL) {
if ((*nl) == n)
return 0;
if (n->priority > (*nl)->priority)
break;
nl = &((*nl)->next);
}
n->next = *nl;
rcu_assign_pointer(*nl, n);
return 0;
}
static int notifier_chain_unregister(struct notifier_block **nl,
struct notifier_block *n)
{
@ -204,6 +219,29 @@ int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
}
EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
/**
* blocking_notifier_chain_cond_register - Cond add notifier to a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain
* @n: New entry in notifier chain
*
* Adds a notifier to a blocking notifier chain, only if not already
* present in the chain.
* Must be called in process context.
*
* Currently always returns zero.
*/
int blocking_notifier_chain_cond_register(struct blocking_notifier_head *nh,
struct notifier_block *n)
{
int ret;
down_write(&nh->rwsem);
ret = notifier_chain_cond_register(&nh->head, n);
up_write(&nh->rwsem);
return ret;
}
EXPORT_SYMBOL_GPL(blocking_notifier_chain_cond_register);
/**
* blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain