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From: Christoph Lameter <clameter@sgi.com>
To: Andrea Arcangeli <andrea@qumranet.com>
Cc: Robin Holt <holt@sgi.com>, Avi Kivity <avi@qumranet.com>,
	Izik Eidus <izike@qumranet.com>, Nick Piggin <npiggin@suse.de>,
	kvm-devel@lists.sourceforge.net,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	steiner@sgi.com, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, daniel.blueman@quadrics.com,
	Hugh Dickins <hugh@veritas.com>
Subject: Re: [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges
Date: Tue, 29 Jan 2008 12:30:06 -0800 (PST)	[thread overview]
Message-ID: <Pine.LNX.4.64.0801291219030.25629@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <20080129182831.GS7233@v2.random>

On Tue, 29 Jan 2008, Andrea Arcangeli wrote:

> diff --git a/mm/fremap.c b/mm/fremap.c
> --- a/mm/fremap.c
> +++ b/mm/fremap.c
> @@ -212,8 +212,8 @@ asmlinkage long sys_remap_file_pages(uns
>  		spin_unlock(&mapping->i_mmap_lock);
>  	}
>  
> +	err = populate_range(mm, vma, start, size, pgoff);
>  	mmu_notifier(invalidate_range, mm, start, start + size, 0);
> -	err = populate_range(mm, vma, start, size, pgoff);
>  	if (!err && !(flags & MAP_NONBLOCK)) {
>  		if (unlikely(has_write_lock)) {
>  			downgrade_write(&mm->mmap_sem);

We invalidate the range *after* populating it? Isnt it okay to establish 
references while populate_range() runs?

> diff --git a/mm/memory.c b/mm/memory.c
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1639,8 +1639,6 @@ gotten:
>  	/*
>  	 * Re-check the pte - we dropped the lock
>  	 */
> -	mmu_notifier(invalidate_range, mm, address,
> -				address + PAGE_SIZE - 1, 0);
>  	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
>  	if (likely(pte_same(*page_table, orig_pte))) {
>  		if (old_page) {

What we did is to invalidate the page (?!) before taking the pte lock. In 
the lock we replace the pte to point to another page. This means that we 
need to clear stale information. So we zap it before. If another reference 
is established after taking the spinlock then the pte contents have 
changed at the cirtical section fails.

Before the critical section starts we have gotten an extra refcount on the 
original page so the page cannot vanish from under us.

> @@ -1676,6 +1674,8 @@ gotten:
>  		page_cache_release(old_page);
>  unlock:
>  	pte_unmap_unlock(page_table, ptl);
> +	mmu_notifier(invalidate_range, mm, address,
> +				address + PAGE_SIZE - 1, 0);
>  	if (dirty_page) {
>  		if (vma->vm_file)
>  			file_update_time(vma->vm_file);

Now we invalidate the page after the transaction is complete. This means 
external pte can persist while we change the pte? Possibly even dirty the 
page?




  reply	other threads:[~2008-01-29 20:30 UTC|newest]

Thread overview: 113+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-28 20:28 [patch 0/6] [RFC] MMU Notifiers V2 Christoph Lameter
2008-01-28 20:28 ` [patch 1/6] mmu_notifier: Core code Christoph Lameter
2008-01-28 22:06   ` Christoph Lameter
2008-01-29  0:05   ` Robin Holt
2008-01-29  1:19     ` Christoph Lameter
2008-01-29 13:59   ` Andrea Arcangeli
2008-01-29 14:34     ` Andrea Arcangeli
2008-01-29 19:49     ` Christoph Lameter
2008-01-29 20:41       ` Avi Kivity
2008-01-29 16:07   ` Robin Holt
2008-02-05 18:05   ` Andy Whitcroft
2008-02-05 18:17     ` Peter Zijlstra
2008-02-05 18:19     ` Christoph Lameter
2008-01-28 20:28 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-01-29 16:20   ` Andrea Arcangeli
2008-01-29 18:28     ` Andrea Arcangeli
2008-01-29 20:30       ` Christoph Lameter [this message]
2008-01-29 21:36         ` Andrea Arcangeli
2008-01-29 21:53           ` Christoph Lameter
2008-01-29 22:35             ` Andrea Arcangeli
2008-01-29 22:55               ` Christoph Lameter
2008-01-29 23:43                 ` Andrea Arcangeli
2008-01-30  0:34                   ` Christoph Lameter
2008-01-29 19:55     ` Christoph Lameter
2008-01-29 21:17       ` Andrea Arcangeli
2008-01-29 21:35         ` Christoph Lameter
2008-01-29 22:02           ` Andrea Arcangeli
2008-01-29 22:39             ` Christoph Lameter
2008-01-30  0:00               ` Andrea Arcangeli
2008-01-30  0:05                 ` Andrea Arcangeli
2008-01-30  0:22                   ` Christoph Lameter
2008-01-30  0:59                     ` Andrea Arcangeli
2008-01-30  8:26                       ` Peter Zijlstra
2008-01-30  0:20                 ` Christoph Lameter
2008-01-30  0:28                   ` Jack Steiner
2008-01-30  0:35                     ` Christoph Lameter
2008-01-30 13:37                     ` Andrea Arcangeli
2008-01-30 14:43                       ` Jack Steiner
2008-01-30 19:41                         ` Christoph Lameter
2008-01-30 20:29                           ` Jack Steiner
2008-01-30 20:55                             ` Christoph Lameter
2008-01-30 16:11                 ` Robin Holt
2008-01-30 17:04                   ` Andrea Arcangeli
2008-01-30 17:30                     ` Robin Holt
2008-01-30 18:25                       ` Andrea Arcangeli
2008-01-30 19:50                         ` Christoph Lameter
2008-01-30 22:18                           ` Robin Holt
2008-01-30 23:52                           ` Andrea Arcangeli
2008-01-31  0:01                             ` Christoph Lameter
2008-01-31  0:34                               ` [kvm-devel] " Andrea Arcangeli
2008-01-31  1:46                                 ` Christoph Lameter
2008-01-31  2:34                                   ` Robin Holt
2008-01-31  2:37                                     ` Christoph Lameter
2008-01-31  2:56                                     ` [kvm-devel] mmu_notifier: invalidate_range_start with lock=1 Christoph Lameter
2008-01-31 10:52                                   ` [kvm-devel] [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Andrea Arcangeli
2008-01-31  2:08                                 ` Christoph Lameter
2008-01-31  2:42                                   ` Andrea Arcangeli
2008-01-31  2:51                                     ` Christoph Lameter
2008-01-31 13:39                                       ` Andrea Arcangeli
2008-01-30 19:35                   ` Christoph Lameter
2008-01-28 20:28 ` [patch 3/6] mmu_notifier: invalidate_page callbacks for subsystems with rmap Christoph Lameter
2008-01-29 16:28   ` Robin Holt
2008-01-28 20:28 ` [patch 4/6] MMU notifier: invalidate_page callbacks using Linux rmaps Christoph Lameter
2008-01-29 14:03   ` Andrea Arcangeli
2008-01-29 14:24     ` Andrea Arcangeli
2008-01-29 19:51       ` Christoph Lameter
2008-01-28 20:28 ` [patch 5/6] mmu_notifier: Callbacks for xip_filemap.c Christoph Lameter
2008-01-28 20:28 ` [patch 6/6] mmu_notifier: Add invalidate_all() Christoph Lameter
2008-01-29 16:31   ` Robin Holt
2008-01-29 20:02     ` Christoph Lameter
2008-01-30  2:29 [patch 0/6] [RFC] MMU Notifiers V3 Christoph Lameter
2008-01-30  2:29 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-02-08 22:06 [patch 0/6] MMU Notifiers V6 Christoph Lameter
2008-02-08 22:06 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-02-15  6:48 [patch 0/6] MMU Notifiers V7 Christoph Lameter
2008-02-15  6:49 ` [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges Christoph Lameter
2008-02-16  3:37   ` Andrew Morton
2008-02-16 19:26     ` Christoph Lameter
2008-02-19  8:54   ` Nick Piggin
2008-02-19 13:34     ` Andrea Arcangeli
2008-02-27 22:23       ` Christoph Lameter
2008-02-27 23:57         ` Andrea Arcangeli
2008-02-19 23:08   ` Nick Piggin
2008-02-20  1:00     ` Andrea Arcangeli
2008-02-20  3:00       ` Robin Holt
2008-02-20  3:11         ` Nick Piggin
2008-02-20  3:19           ` Robin Holt
2008-02-27 22:39       ` Christoph Lameter
2008-02-28  0:38         ` Andrea Arcangeli
2008-02-27 22:35     ` Christoph Lameter
2008-02-27 22:42       ` Jack Steiner
2008-02-28  0:10       ` Christoph Lameter
2008-02-28  0:11       ` Andrea Arcangeli
2008-02-28  0:14         ` Christoph Lameter
2008-02-28  0:52           ` Andrea Arcangeli
2008-02-28  1:03             ` Christoph Lameter
2008-02-28  1:10               ` Andrea Arcangeli
2008-02-28 18:43                 ` Christoph Lameter
2008-02-29  0:55                   ` Andrea Arcangeli
2008-02-29  0:59                     ` Christoph Lameter
2008-02-29 13:13                       ` Andrea Arcangeli
2008-02-29 19:55                         ` Christoph Lameter
2008-02-29 20:17                           ` Andrea Arcangeli
2008-02-29 21:03                             ` Christoph Lameter
2008-02-29 21:23                               ` Andrea Arcangeli
2008-02-29 21:29                                 ` Christoph Lameter
2008-02-29 21:34                                 ` Christoph Lameter
2008-02-29 21:48                                   ` Andrea Arcangeli
2008-02-29 22:12                                     ` Christoph Lameter
2008-02-29 22:41                                       ` Andrea Arcangeli
2008-02-28 10:53             ` Robin Holt
2008-03-03  5:11       ` Nick Piggin
2008-03-03 19:28         ` Christoph Lameter
2008-03-03 19:50           ` Nick Piggin
2008-03-04 18:58             ` Christoph Lameter
2008-03-05  0:52               ` Nick Piggin

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