linux-kernel - Re: [PATCH] mmu notifiers #v3

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Message-Id: <1201030127.6341.39.camel@lappy>
Date:	Tue, 22 Jan 2008 20:28:47 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrea Arcangeli <andrea@...ranet.com>
Cc:	Izik Eidus <izike@...ranet.com>, Rik van Riel <riel@...hat.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	kvm-devel@...ts.sourceforge.net, Avi Kivity <avi@...ranet.com>,
	clameter@....com, daniel.blueman@...drics.com, holt@....com,
	steiner@....com, Andrew Morton <akpm@...l.org>,
	Hugh Dickins <hugh@...itas.com>, Nick Piggin <npiggin@...e.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH] mmu notifiers #v3


On Mon, 2008-01-21 at 13:52 +0100, Andrea Arcangeli wrote:

> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> new file mode 100644
> --- /dev/null
> +++ b/include/linux/mmu_notifier.h
> @@ -0,0 +1,79 @@
> +#ifndef _LINUX_MMU_NOTIFIER_H
> +#define _LINUX_MMU_NOTIFIER_H
> +
> +#include <linux/list.h>
> +#include <linux/spinlock.h>
> +
> +#ifdef CONFIG_MMU_NOTIFIER
> +
> +struct mmu_notifier;
> +
> +struct mmu_notifier_ops {
> +	void (*release)(struct mmu_notifier *mn,
> +			struct mm_struct *mm);
> +	void (*age_page)(struct mmu_notifier *mn,
> +			 struct mm_struct *mm,
> +			 unsigned long address);
> +	void (*invalidate_page)(struct mmu_notifier *mn,
> +				struct mm_struct *mm,
> +				unsigned long address);
> +	void (*invalidate_range)(struct mmu_notifier *mn,
> +				 struct mm_struct *mm,
> +				 unsigned long start, unsigned long end);
> +};
> +
> +struct mmu_notifier_head {
> +	struct hlist_head head;
> +	rwlock_t lock;

	spinlock_t lock;

I think we can get rid of this rwlock as I think this will seriously
hurt larger machines.

> +};
> +
> +struct mmu_notifier {
> +	struct hlist_node hlist;
> +	const struct mmu_notifier_ops *ops;
> +};
> +
> +#include <linux/mm_types.h>
> +
> +extern void mmu_notifier_register(struct mmu_notifier *mn,
> +				  struct mm_struct *mm);
> +extern void mmu_notifier_unregister(struct mmu_notifier *mn,
> +				    struct mm_struct *mm);
> +extern void mmu_notifier_release(struct mm_struct *mm);
> +
> +static inline void mmu_notifier_head_init(struct mmu_notifier_head *mnh)
> +{
> +	INIT_HLIST_HEAD(&mnh->head);
> +	rwlock_init(&mnh->lock);
> +}
> +
> +#define mmu_notifier(function, mm, args...)				\
> +	do {								\
> +		struct mmu_notifier *__mn;				\
> +		struct hlist_node *__n;					\
> +									\
> +		if (unlikely(!hlist_empty(&(mm)->mmu_notifier.head))) { \
> +			read_lock(&(mm)->mmu_notifier.lock);		\
			rcu_read_lock();
> +			hlist_for_each_entry(__mn, __n,			\
			hlist_for_each_entry_rcu
> +					     &(mm)->mmu_notifier.head,	\
> +					     hlist)			\
> +				if (__mn->ops->function)		\
> +					__mn->ops->function(__mn,	\
> +							    mm,		\
> +							    args);	\
> +			read_unlock(&(mm)->mmu_notifier.lock);		\
			rcu_read_unlock();
> +		}							\
> +	} while (0)
> +
> +#else /* CONFIG_MMU_NOTIFIER */
> +
> +#define mmu_notifier_register(mn, mm) do {} while(0)
> +#define mmu_notifier_unregister(mn, mm) do {} while (0)
> +#define mmu_notifier_release(mm) do {} while (0)
> +#define mmu_notifier_head_init(mmh) do {} while (0)
> +
> +#define mmu_notifier(function, mm, args...)	\
> +	do { } while (0)
> +
> +#endif /* CONFIG_MMU_NOTIFIER */
> +
> +#endif /* _LINUX_MMU_NOTIFIER_H */


> diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
> new file mode 100644
> --- /dev/null
> +++ b/mm/mmu_notifier.c
> @@ -0,0 +1,44 @@
> +/*
> + *  linux/mm/mmu_notifier.c
> + *
> + *  Copyright (C) 2008  Qumranet, Inc.
> + *
> + *  This work is licensed under the terms of the GNU GPL, version 2. See
> + *  the COPYING file in the top-level directory.
> + */
> +
> +#include <linux/mmu_notifier.h>
> +#include <linux/module.h>
> +
> +void mmu_notifier_release(struct mm_struct *mm)
> +{
> +	struct mmu_notifier *mn;
> +	struct hlist_node *n, *tmp;
> +
> +	if (unlikely(!hlist_empty(&mm->mmu_notifier.head))) {
> +		read_lock(&mm->mmu_notifier.lock);
		rcu_read_lock();
> +		hlist_for_each_entry_safe(mn, n, tmp,
		hlist_for_each_entry_safe_rcu
> +					  &mm->mmu_notifier.head, hlist) {
> +			if (mn->ops->release)
> +				mn->ops->release(mn, mm);
> +			hlist_del(&mn->hlist);
			hlist_del_rcu
> +		}
> +		read_unlock(&mm->mmu_notifier.lock);
		rcu_read_unlock();
> +	}
> +}
> +
> +void mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
> +{
> +	write_lock(&mm->mmu_notifier.lock);
	spin_lock
> +	hlist_add_head(&mn->hlist, &mm->mmu_notifier.head);
	hlist_add_head_rcu
> +	write_unlock(&mm->mmu_notifier.lock);
	spin_unlock
> +}
> +EXPORT_SYMBOL_GPL(mmu_notifier_register);
> +
> +void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
> +{
> +	write_lock(&mm->mmu_notifier.lock);
	spin_lock
> +	hlist_del(&mn->hlist);
	hlist_del_rcu
> +	write_unlock(&mm->mmu_notifier.lock);
	spin_unlock
> +}
> +EXPORT_SYMBOL_GPL(mmu_notifier_unregister);


#define hlist_for_each_entry_safe(tpos, pos, n, head, member) 		 \
	for (pos = (head)->first;					 \
	     rcu_dereference(pos) && ({ n = pos->next; 1; }) && 	 \
		({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \
	     pos = n)



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