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6546bc4279
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>
82 lines
2.1 KiB
C
82 lines
2.1 KiB
C
/*
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* linux/ipc/ipcns_notifier.c
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* Copyright (C) 2007 BULL SA. Nadia Derbey
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*
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* Notification mechanism for ipc namespaces:
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* The callback routine registered in the memory chain invokes the ipcns
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* notifier chain with the IPCNS_MEMCHANGED event.
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* Each callback routine registered in the ipcns namespace recomputes msgmni
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* for the owning namespace.
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*/
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#include <linux/msg.h>
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#include <linux/rcupdate.h>
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#include <linux/notifier.h>
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#include <linux/nsproxy.h>
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#include <linux/ipc_namespace.h>
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#include "util.h"
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static BLOCKING_NOTIFIER_HEAD(ipcns_chain);
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static int ipcns_callback(struct notifier_block *self,
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unsigned long action, void *arg)
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{
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struct ipc_namespace *ns;
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switch (action) {
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case IPCNS_MEMCHANGED: /* amount of lowmem has changed */
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case IPCNS_CREATED:
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case IPCNS_REMOVED:
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/*
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* It's time to recompute msgmni
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*/
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ns = container_of(self, struct ipc_namespace, ipcns_nb);
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/*
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* No need to get a reference on the ns: the 1st job of
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* free_ipc_ns() is to unregister the callback routine.
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* blocking_notifier_chain_unregister takes the wr lock to do
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* it.
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* When this callback routine is called the rd lock is held by
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* blocking_notifier_call_chain.
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* So the ipc ns cannot be freed while we are here.
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*/
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recompute_msgmni(ns);
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break;
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default:
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break;
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}
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return NOTIFY_OK;
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}
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int register_ipcns_notifier(struct ipc_namespace *ns)
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{
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memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
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ns->ipcns_nb.notifier_call = ipcns_callback;
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ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
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return blocking_notifier_chain_register(&ipcns_chain, &ns->ipcns_nb);
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}
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int cond_register_ipcns_notifier(struct ipc_namespace *ns)
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{
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memset(&ns->ipcns_nb, 0, sizeof(ns->ipcns_nb));
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ns->ipcns_nb.notifier_call = ipcns_callback;
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ns->ipcns_nb.priority = IPCNS_CALLBACK_PRI;
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return blocking_notifier_chain_cond_register(&ipcns_chain,
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&ns->ipcns_nb);
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}
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int unregister_ipcns_notifier(struct ipc_namespace *ns)
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{
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return blocking_notifier_chain_unregister(&ipcns_chain,
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&ns->ipcns_nb);
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}
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int ipcns_notify(unsigned long val)
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{
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return blocking_notifier_call_chain(&ipcns_chain, val, NULL);
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}
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