From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: kosaki.motohiro@jp.fujitsu.com, Rik van Riel <riel@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Borislav Petkov <bp@alien8.de>,
Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
Minchan Kim <minchan.kim@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
Nick Piggin <npiggin@suse.de>,
Andrea Arcangeli <aarcange@redhat.com>,
Hugh Dickins <hugh.dickins@tiscali.co.uk>,
sgunderson@bigfoot.com
Subject: Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA
Date: Tue, 13 Apr 2010 21:00:36 +0900 (JST) [thread overview]
Message-ID: <20100413204149.D11C.A69D9226@jp.fujitsu.com> (raw)
In-Reply-To: <1271158226.4807.1107.camel@twins>
> On Tue, 2010-04-13 at 19:53 +0900, KOSAKI Motohiro wrote:
> > > struct anon_vma *page_lock_anon_vma(struct page *page)
> > > {
> > > @@ -294,14 +309,24 @@ struct anon_vma *page_lock_anon_vma(struct page *page)
> > > unsigned long anon_mapping;
> > >
> > > rcu_read_lock();
> > > - anon_mapping = (unsigned long) ACCESS_ONCE(page->mapping);
> > > + anon_mapping = (unsigned long)rcu_dereference(page->mapping);
> > > if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON)
> > > goto out;
> > > - if (!page_mapped(page))
> > > - goto out;
> > >
> > > anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
> > > spin_lock(&anon_vma->lock);
> >
> > Does anon->lock dereference is guranteed if page->_mapcount==-1?
> > It can be freed miliseconds ago, rcu_read_lock() doesn't provide such
> > gurantee.
> >
> > perhaps, I'm missing your point.
>
> No you're right, I got my head hopelessly twisted up trying to make
> page_lock_anon_vma() do something reliable, but there really isn't much
> that can be done.
>
> Luckily most users (with exception of the memory-failure.c one) don't
> really care and all take steps to verify the page is indeed in any of
> the vmas it might find.
>
> So I've given up on this and will only submit a patch like the below,
> which hopefully does still make sense...
>
> I do think there's a missing barrier in there as well, but I've made
> enough of a fool of myself.
>
> [ with the preemptible mmu_gather patches I introduce a refcount to
> the anon_vma, and then with atomic_inc_not_zero() we can add a
> guarantee that the returned anon_vma is alive ]
Indeed. refcount is best way. anon_vma DESTROY_BY_RCU stuff seems
overengineering, I think. this is fastest, but anon_vma allocation is not
(and was not) fork/exit bottleneck point. So, I guess most simply way is
best.
Also following patch looks good to me.
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Thanks for that. I've thought this is really necessary. but my (very) poor
english skill make hesitate it to me. sorry my laziness ;)
>
> ---
> mm/rmap.c | 18 ++++++++++++++++--
> 1 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index eaa7a09..49a2533 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -285,8 +285,22 @@ void __init anon_vma_init(void)
> }
>
> /*
> - * Getting a lock on a stable anon_vma from a page off the LRU is
> - * tricky: page_lock_anon_vma rely on RCU to guard against the races.
> + * Getting a lock on a stable anon_vma from a page off the LRU is tricky!
> + *
> + * Since there is no serialization what so ever against page_remove_rmap()
> + * the best this function can do is return a locked anon_vma that might
> + * have been relevant to this page.
> + *
> + * The page might have been remapped to a different anon_vma or the anon_vma
> + * returned may already be freed (and even reused).
> + *
> + * All users of this function must be very careful when walking the anon_vma
> + * chain and verify that the page in question is indeed mapped in it
> + * [ something equivalent to page_mapped_in_vma() ].
> + *
> + * Since anon_vma's slab is DESTROY_BY_RCU and we know from page_remove_rmap()
> + * that the anon_vma pointer from page->mapping is valid if there is a
> + * mapcount, we can dereference the anon_vma after observing those.
> */
> struct anon_vma *page_lock_anon_vma(struct page *page)
> {
>
next prev parent reply other threads:[~2010-04-13 12:00 UTC|newest]
Thread overview: 231+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-30 17:50 Linux 2.6.34-rc3 Linus Torvalds
2010-03-30 21:16 ` [Regression, post-rc2] Commit a5ee4eb7541 breaks OpenGL on RS780 (was: Re: Linux 2.6.34-rc3) Rafael J. Wysocki
2010-03-31 20:34 ` [stable] " Greg KH
2010-04-01 1:13 ` Rafael J. Wysocki
2010-04-01 2:19 ` Alex Deucher
2010-04-01 6:36 ` Clemens Ladisch
2010-04-01 15:01 ` Alex Deucher
2010-04-01 20:28 ` Rafael J. Wysocki
2010-04-01 20:39 ` Alex Deucher
2010-04-01 20:48 ` Rafael J. Wysocki
2010-04-01 21:00 ` Alex Deucher
2010-04-01 21:01 ` Alex Deucher
2010-04-01 21:08 ` Rafael J. Wysocki
2010-04-01 21:13 ` Alex Deucher
2010-04-01 21:46 ` Rafael J. Wysocki
2010-04-01 22:07 ` Alex Deucher
2010-04-01 23:20 ` Rafael J. Wysocki
2010-04-02 0:23 ` Linus Torvalds
2010-04-02 16:46 ` Rafael J. Wysocki
2010-04-03 18:08 ` Clemens Ladisch
2010-04-03 19:33 ` Rafael J. Wysocki
2010-04-01 16:29 ` Linus Torvalds
2010-04-01 17:07 ` Alex Deucher
2010-04-01 17:24 ` Linus Torvalds
2010-04-01 17:50 ` [Regression, post-rc2] Commit a5ee4eb7541 breaks OpenGL on RS780 Clemens Ladisch
2010-04-01 17:53 ` [Regression, post-rc2] Commit a5ee4eb7541 breaks OpenGL on RS780 (was: Re: Linux 2.6.34-rc3) Alex Deucher
2010-04-01 20:17 ` Linus Torvalds
2010-04-01 20:23 ` Alex Deucher
2010-04-01 19:46 ` Rafael J. Wysocki
2010-04-01 22:48 ` Jesse Barnes
2010-04-01 23:23 ` Rafael J. Wysocki
2010-04-02 17:59 ` Ugly rmap NULL ptr deref oopsie on hibernate (was " Borislav Petkov
2010-04-02 18:09 ` Linus Torvalds
2010-04-02 15:24 ` Andrew Morton
2010-04-02 18:37 ` Linus Torvalds
2010-04-02 22:01 ` Rik van Riel
2010-04-03 0:19 ` Linus Torvalds
2010-04-04 16:12 ` Minchan Kim
2010-04-04 17:24 ` Rik van Riel
2010-04-04 23:09 ` [PATCH] rmap: fix anon_vma_fork() memory leak Rik van Riel
2010-04-04 23:56 ` Minchan Kim
2010-04-05 15:37 ` Linus Torvalds
2010-04-05 15:48 ` Minchan Kim
2010-04-05 16:04 ` Rik van Riel
2010-04-05 16:13 ` [PATCH -v2] " Rik van Riel
2010-04-06 8:53 ` Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3) KOSAKI Motohiro
2010-04-06 10:09 ` KOSAKI Motohiro
2010-04-06 14:34 ` Rik van Riel
2010-04-06 14:38 ` Rik van Riel
2010-04-06 15:34 ` Minchan Kim
2010-04-06 15:40 ` Rik van Riel
2010-04-06 15:58 ` Minchan Kim
2010-04-06 15:55 ` Linus Torvalds
2010-04-06 16:23 ` Minchan Kim
2010-04-06 16:28 ` Linus Torvalds
2010-04-06 16:45 ` Minchan Kim
2010-04-06 16:53 ` Linus Torvalds
2010-04-06 17:04 ` Rik van Riel
2010-04-06 18:28 ` Linus Torvalds
2010-04-06 19:03 ` Andrew Morton
2010-04-06 19:10 ` Steinar H. Gunderson
2010-04-06 19:10 ` Linus Torvalds
2010-04-06 19:35 ` Linus Torvalds
2010-04-06 19:42 ` Borislav Petkov
2010-04-06 20:02 ` Linus Torvalds
2010-04-06 20:46 ` Steinar H. Gunderson
2010-04-06 20:56 ` Linus Torvalds
2010-04-06 21:05 ` Steinar H. Gunderson
2010-04-06 20:51 ` Borislav Petkov
2010-04-06 21:27 ` Linus Torvalds
2010-04-06 22:59 ` Borislav Petkov
2010-04-06 23:27 ` Linus Torvalds
2010-04-06 23:54 ` [PATCH] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA Rik van Riel
2010-04-07 7:00 ` KOSAKI Motohiro
2010-04-07 14:48 ` Rik van Riel
2010-04-07 14:54 ` [PATCH -v2] " Rik van Riel
2010-04-07 15:30 ` Linus Torvalds
2010-04-07 15:52 ` Rik van Riel
2010-04-07 16:56 ` Linus Torvalds
2010-04-07 21:19 ` Linus Torvalds
2010-04-07 21:52 ` Rik van Riel
2010-04-07 22:09 ` Linus Torvalds
2010-04-07 22:15 ` Linus Torvalds
2010-04-08 0:38 ` Rik van Riel
2010-04-07 23:37 ` Linus Torvalds
2010-04-08 2:03 ` KOSAKI Motohiro
2010-04-08 2:33 ` Linus Torvalds
2010-04-08 5:47 ` Borislav Petkov
2010-04-08 14:11 ` Linus Torvalds
2010-04-08 18:25 ` Rik van Riel
2010-04-08 18:32 ` Linus Torvalds
2010-04-08 20:31 ` Borislav Petkov
2010-04-08 21:00 ` Borislav Petkov
2010-04-08 23:16 ` Linus Torvalds
2010-04-08 23:47 ` Borislav Petkov
2010-04-09 0:50 ` Linus Torvalds
2010-04-09 1:30 ` Borislav Petkov
2010-04-09 9:21 ` Borislav Petkov
2010-04-09 16:35 ` Linus Torvalds
2010-04-09 17:40 ` Borislav Petkov
2010-04-09 17:50 ` Linus Torvalds
2010-04-09 19:14 ` Borislav Petkov
2010-04-09 19:32 ` Linus Torvalds
2010-04-09 20:03 ` Rik van Riel
2010-04-09 20:43 ` Johannes Weiner
2010-04-09 20:57 ` Rik van Riel
2010-04-09 21:33 ` Borislav Petkov
2010-04-09 23:22 ` Linus Torvalds
2010-04-09 23:45 ` Rik van Riel
2010-04-10 0:03 ` Linus Torvalds
2010-04-10 0:11 ` Rik van Riel
2010-04-09 23:54 ` Johannes Weiner
2010-04-09 23:56 ` Linus Torvalds
2010-04-10 0:19 ` Rik van Riel
2010-04-10 0:31 ` Johannes Weiner
2010-04-10 0:32 ` Linus Torvalds
2010-04-10 7:27 ` Borislav Petkov
2010-04-10 11:26 ` Borislav Petkov
2010-04-10 14:45 ` Rik van Riel
2010-04-10 15:24 ` Linus Torvalds
2010-04-10 16:38 ` Borislav Petkov
2010-04-10 17:05 ` Linus Torvalds
2010-04-10 18:21 ` Linus Torvalds
2010-04-10 18:26 ` Linus Torvalds
2010-04-10 18:51 ` Borislav Petkov
2010-04-10 18:58 ` Borislav Petkov
2010-04-10 20:05 ` Linus Torvalds
2010-04-10 20:12 ` Linus Torvalds
2010-04-10 20:36 ` Borislav Petkov
2010-04-10 20:40 ` Linus Torvalds
2010-04-10 21:25 ` Borislav Petkov
2010-04-10 21:30 ` Linus Torvalds
2010-04-10 21:51 ` Borislav Petkov
2010-04-11 13:08 ` Borislav Petkov
2010-04-11 13:19 ` [PATCH 1/3] mm: make page freeing path RCU-safe Borislav Petkov
2010-04-11 13:19 ` [PATCH 2/3] mm: cleanup find_mergeable_anon_vma complexity Borislav Petkov
2010-04-11 13:19 ` [PATCH 3/3] mm: fixup vma_adjust Borislav Petkov
2010-04-11 13:25 ` [PATCH 2/3] mm: cleanup find_mergeable_anon_vma complexity Borislav Petkov
2010-04-11 17:07 ` [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA Linus Torvalds
2010-04-11 17:16 ` Linus Torvalds
2010-04-11 18:55 ` Borislav Petkov
2010-04-12 0:13 ` Linus Torvalds
2010-04-12 1:04 ` Linus Torvalds
2010-04-12 7:20 ` Borislav Petkov
2010-04-12 16:02 ` Linus Torvalds
2010-04-12 16:26 ` Linus Torvalds
2010-04-12 18:40 ` Rik van Riel
2010-04-12 19:00 ` Borislav Petkov
2010-04-12 19:17 ` Linus Torvalds
2010-04-12 20:22 ` [PATCH 1/4] Simplify and comment on anon_vma re-use for anon_vma_prepare() Linus Torvalds
2010-04-12 20:23 ` [PATCH 2/4] vma_adjust: fix the copying of anon_vma chains Linus Torvalds
2010-04-12 20:23 ` [PATCH 3/4] anon_vma: clone the anon_vma chain in the right order Linus Torvalds
2010-04-12 20:23 ` [PATCH 4/4] anonvma: when setting up page->mapping, we need to pick the _oldest_ anonvma Linus Torvalds
2010-04-12 21:03 ` Rik van Riel
2010-04-13 0:41 ` Johannes Weiner
2010-04-13 1:08 ` Linus Torvalds
2010-04-13 4:23 ` Minchan Kim
2010-04-13 4:26 ` Minchan Kim
2010-04-12 20:57 ` [PATCH 3/4] anon_vma: clone the anon_vma chain in the right order Rik van Riel
2010-04-13 0:18 ` Johannes Weiner
2010-04-13 4:16 ` Minchan Kim
2010-04-12 20:54 ` [PATCH 2/4] vma_adjust: fix the copying of anon_vma chains Rik van Riel
2010-04-12 23:59 ` Johannes Weiner
2010-04-13 4:15 ` Minchan Kim
2010-04-12 20:54 ` [PATCH 1/4] Simplify and comment on anon_vma re-use for anon_vma_prepare() Rik van Riel
2010-04-12 23:54 ` Johannes Weiner
2010-04-13 4:04 ` Minchan Kim
2010-04-13 9:51 ` Peter Zijlstra
2010-04-12 21:50 ` [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA Borislav Petkov
2010-04-12 22:11 ` Linus Torvalds
2010-04-12 22:18 ` Linus Torvalds
2010-04-12 22:29 ` Borislav Petkov
2010-04-13 9:38 ` Borislav Petkov
2010-04-14 21:59 ` [PATCH] rmap: add exclusively owned pages to the newest anon_vma Rik van Riel
2010-04-14 23:20 ` Johannes Weiner
2010-04-15 8:34 ` Borislav Petkov
2010-04-15 16:02 ` Minchan Kim
2010-04-15 20:01 ` Linus Torvalds
2010-04-16 6:09 ` Felipe Balbi
2010-04-16 14:48 ` Linus Torvalds
2010-04-11 19:49 ` [PATCH -v2] rmap: make anon_vma_prepare link in all the anon_vmas of a mergeable VMA Rik van Riel
2010-04-12 15:44 ` Linus Torvalds
2010-04-12 15:51 ` Rik van Riel
2010-04-11 21:45 ` Rik van Riel
2010-04-12 15:51 ` Linus Torvalds
2010-04-13 10:36 ` KOSAKI Motohiro
2010-04-10 20:24 ` Rik van Riel
2010-04-10 20:34 ` Linus Torvalds
2010-04-10 20:43 ` Rik van Riel
2010-04-10 20:32 ` Rik van Riel
2010-04-10 19:36 ` Rik van Riel
2010-04-12 14:40 ` Peter Zijlstra
2010-04-12 15:17 ` Minchan Kim
2010-04-12 15:33 ` Peter Zijlstra
2010-04-12 15:19 ` Rik van Riel
2010-04-12 16:01 ` Peter Zijlstra
2010-04-12 16:06 ` Rik van Riel
2010-04-12 16:46 ` Linus Torvalds
2010-04-12 18:40 ` Peter Zijlstra
2010-04-12 19:30 ` Peter Zijlstra
2010-04-12 19:44 ` Peter Zijlstra
2010-04-13 10:53 ` KOSAKI Motohiro
2010-04-13 11:30 ` Peter Zijlstra
2010-04-13 12:00 ` KOSAKI Motohiro [this message]
2010-04-14 14:27 ` Peter Zijlstra
2010-04-10 17:07 ` Borislav Petkov
2010-04-10 16:41 ` Linus Torvalds
2010-04-10 22:49 ` Johannes Weiner
2010-04-10 23:31 ` Linus Torvalds
2010-04-09 1:45 ` KOSAKI Motohiro
2010-04-07 15:55 ` Minchan Kim
2010-04-07 7:29 ` Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3) Borislav Petkov
2010-04-07 14:05 ` Paulo Marques
2010-04-07 14:13 ` Borislav Petkov
2010-04-06 23:37 ` Linus Torvalds
2010-04-06 23:22 ` Rik van Riel
2010-04-07 0:10 ` Linus Torvalds
2010-04-07 1:18 ` Rik van Riel
2010-04-07 7:22 ` Borislav Petkov
2010-04-07 10:09 ` Pekka Enberg
2010-04-07 10:12 ` KOSAKI Motohiro
2010-04-07 8:41 ` Peter Zijlstra
2010-04-07 8:36 ` Peter Zijlstra
2010-04-07 9:16 ` Johannes Weiner
2010-04-07 9:37 ` Peter Zijlstra
2010-04-07 14:12 ` Rik van Riel
2010-04-07 15:46 ` Linus Torvalds
2010-04-06 16:32 ` Linus Torvalds
2010-04-06 16:54 ` Minchan Kim
2010-04-07 8:37 ` Peter Zijlstra
2010-04-06 17:05 ` Borislav Petkov
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