/* * linux/ipc/ipcns_notifier.c * Copyright (C) 2007 BULL SA. Nadia Derbey * * Notification mechanism for ipc namespaces: * The callback routine registered in the memory chain invokes the ipcns * notifier chain with the IPCNS_MEMCHANGED event. * Each callback routine registered in the ipcns namespace recomputes msgmni * for the owning namespace. */ #include <linux/msg.h>#include <linux/rcupdate.h>#include <linux/notifier.h>#include <linux/nsproxy.h>#include <linux/ipc_namespace.h> #include "util.h"   static BLOCKING_NOTIFIER_HEAD(ipcns_chain);  static int ipcns_callback(struct notifier_block *self,				unsigned long action, void *arg){	struct ipc_namespace *ns; 	switch (action) {	case IPCNS_MEMCHANGED:   /* amount of lowmem has changed */	case IPCNS_CREATED:	case IPCNS_REMOVED:		/*		 * It's time to recompute msgmni		 */		ns = container_of(self, struct ipc_namespace, ipcns_nb);		/*		 * No need to get a reference on the ns: the 1st job of		 * free_ipc_ns() is to unregister the callback routine.		 * blocking_notifier_chain_unregister takes the wr lock to do		 * it.		 * When this callback routine is called the rd lock is held by		 * blocking_notifier_call_chain.		 * So the ipc ns cannot be freed while we are here.		 */		recompute_msgmni(ns);		break;	default:		break;	} 	return NOTIFY_OK;} int register_ipcns_notifier(struct ipc_namespace *ns){	int rc; 	memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));	ns->ipcns_nb.notifier_call = ipcns_callback;	ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;	rc = blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);	if (!rc)		ns->auto_msgmni = 1;	return rc;} int cond_register_ipcns_notifier(struct ipc_namespace *ns){	int rc; 	memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));	ns->ipcns_nb.notifier_call = ipcns_callback;	ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;	rc = blocking_notifier_chain_cond_register(&ipcns_chain,							&ns->ipcns_nb);	if (!rc)		ns->auto_msgmni = 1;	return rc;} void unregister_ipcns_notifier(struct ipc_namespace *ns){	blocking_notifier_chain_unregister(&ipcns_chain, &ns->ipcns_nb);	ns->auto_msgmni = 0;} int ipcns_notify(unsigned long val){	return blocking_notifier_call_chain(&ipcns_chain, val, NULL);}