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Commit 6546bc42 authored by Nadia Derbey's avatar Nadia Derbey Committed by Linus Torvalds
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ipc: re-enable msgmni automatic recomputing msgmni if set to negative 



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: default avatarNadia 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 91cfb2b4

include/linux/ipc_namespace.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/notifier.h

+4 −0
Original line number Diff line number Diff line
@@ -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,

ipc/ipc_sysctl.c

+35 −10
Original line number Diff line number Diff line
@@ -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;

}

ipc/ipcns_notifier.c

+9 −0
Original line number Diff line number Diff line
@@ -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,

kernel/notifier.c

+38 −0
Original line number Diff line number Diff line
@@ -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