From: Nick Piggin <npiggin@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: Mel Gorman <mel@csn.ul.ie>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, Dave Chinner <david@fromorbit.com>,
Chris Mason <chris.mason@oracle.com>,
Rik van Riel <riel@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 11/12] vmscan: Write out dirty pages in batch
Date: Tue, 15 Jun 2010 21:13:37 +1000 [thread overview]
Message-ID: <20100615111337.GK6138@laptop> (raw)
In-Reply-To: <20100615105341.GB31051@infradead.org>
On Tue, Jun 15, 2010 at 06:53:41AM -0400, Christoph Hellwig wrote:
> > + /*
> > + * XXX: This is the Holy Hand Grenade of PotentiallyInvalidMapping. As
> > + * the page lock has been dropped by ->writepage, that mapping could
> > + * be anything
> > + */
>
> Why is this an XXX comment?
It's just a pretty simple use-after-free. Maybe people forget it because
->writepage is an asynchronous API.
> > + *
> > + * XXX: Is there a problem with holding multiple page locks like this?
>
> I think there is. There's quite a few places that do hold multiple
> pages locked, but they always lock pages in increasing page->inxex order.
> Given that this locks basically in random order it could cause problems
> for those places.
There shouldn't be a problem _holding_ the locks, but there is a problem
waiting for multiple locks out of page->index order.
But there is a problem with holding the lock of a lot of pages while
calling ->writepage on them. So yeah, you can't do that.
Hmm, I should rediff that lockdep page_lock patch and get it merged.
(although I don't know if that can catch these all these problems easily)
WARNING: multiple messages have this Message-ID (diff)
From: Nick Piggin <npiggin@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: Mel Gorman <mel@csn.ul.ie>,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, Dave Chinner <david@fromorbit.com>,
Chris Mason <chris.mason@oracle.com>,
Rik van Riel <riel@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 11/12] vmscan: Write out dirty pages in batch
Date: Tue, 15 Jun 2010 21:13:37 +1000 [thread overview]
Message-ID: <20100615111337.GK6138@laptop> (raw)
In-Reply-To: <20100615105341.GB31051@infradead.org>
On Tue, Jun 15, 2010 at 06:53:41AM -0400, Christoph Hellwig wrote:
> > + /*
> > + * XXX: This is the Holy Hand Grenade of PotentiallyInvalidMapping. As
> > + * the page lock has been dropped by ->writepage, that mapping could
> > + * be anything
> > + */
>
> Why is this an XXX comment?
It's just a pretty simple use-after-free. Maybe people forget it because
->writepage is an asynchronous API.
> > + *
> > + * XXX: Is there a problem with holding multiple page locks like this?
>
> I think there is. There's quite a few places that do hold multiple
> pages locked, but they always lock pages in increasing page->inxex order.
> Given that this locks basically in random order it could cause problems
> for those places.
There shouldn't be a problem _holding_ the locks, but there is a problem
waiting for multiple locks out of page->index order.
But there is a problem with holding the lock of a lot of pages while
calling ->writepage on them. So yeah, you can't do that.
Hmm, I should rediff that lockdep page_lock patch and get it merged.
(although I don't know if that can catch these all these problems easily)
--
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next prev parent reply other threads:[~2010-06-15 11:13 UTC|newest]
Thread overview: 198+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-14 11:17 [PATCH 0/12] Avoid overflowing of stack during page reclaim V2 Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 11:17 ` [PATCH 01/12] tracing, vmscan: Add trace events for kswapd wakeup, sleeping and direct reclaim Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 15:45 ` Rik van Riel
2010-06-14 15:45 ` Rik van Riel
2010-06-14 21:01 ` Larry Woodman
2010-06-14 21:01 ` Larry Woodman
2010-06-14 11:17 ` [PATCH 02/12] tracing, vmscan: Add trace events for LRU page isolation Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 16:47 ` Rik van Riel
2010-06-14 16:47 ` Rik van Riel
2010-06-14 21:02 ` Larry Woodman
2010-06-14 21:02 ` Larry Woodman
2010-06-14 11:17 ` [PATCH 03/12] tracing, vmscan: Add trace event when a page is written Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 16:48 ` Rik van Riel
2010-06-14 16:48 ` Rik van Riel
2010-06-14 21:02 ` Larry Woodman
2010-06-14 21:02 ` Larry Woodman
2010-06-14 11:17 ` [PATCH 04/12] tracing, vmscan: Add a postprocessing script for reclaim-related ftrace events Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 17:55 ` Rik van Riel
2010-06-14 17:55 ` Rik van Riel
2010-06-14 21:03 ` Larry Woodman
2010-06-14 21:03 ` Larry Woodman
2010-06-14 11:17 ` [PATCH 05/12] vmscan: kill prev_priority completely Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 18:04 ` Rik van Riel
2010-06-14 18:04 ` Rik van Riel
2010-06-16 23:37 ` Andrew Morton
2010-06-16 23:37 ` Andrew Morton
2010-06-16 23:45 ` Rik van Riel
2010-06-16 23:45 ` Rik van Riel
2010-06-17 0:18 ` Andrew Morton
2010-06-17 0:18 ` Andrew Morton
2010-06-17 0:34 ` Rik van Riel
2010-06-17 0:34 ` Rik van Riel
2010-06-25 8:29 ` KOSAKI Motohiro
2010-06-25 8:29 ` KOSAKI Motohiro
2010-06-28 10:35 ` Mel Gorman
2010-06-28 10:35 ` Mel Gorman
2010-06-14 11:17 ` [PATCH 06/12] vmscan: simplify shrink_inactive_list() Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 18:06 ` Rik van Riel
2010-06-14 18:06 ` Rik van Riel
2010-06-15 10:13 ` Mel Gorman
2010-06-15 10:13 ` Mel Gorman
2010-06-14 11:17 ` [PATCH 07/12] vmscan: Remove unnecessary temporary vars in do_try_to_free_pages Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 18:14 ` Rik van Riel
2010-06-14 18:14 ` Rik van Riel
2010-06-14 11:17 ` [PATCH 08/12] vmscan: Setup pagevec as late as possible in shrink_inactive_list() Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 18:59 ` Rik van Riel
2010-06-14 18:59 ` Rik van Riel
2010-06-15 10:47 ` Christoph Hellwig
2010-06-15 10:47 ` Christoph Hellwig
2010-06-15 15:56 ` Mel Gorman
2010-06-15 15:56 ` Mel Gorman
2010-06-16 23:43 ` Andrew Morton
2010-06-16 23:43 ` Andrew Morton
2010-06-17 10:30 ` Mel Gorman
2010-06-17 10:30 ` Mel Gorman
2010-06-14 11:17 ` [PATCH 09/12] vmscan: Setup pagevec as late as possible in shrink_page_list() Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 19:24 ` Rik van Riel
2010-06-14 19:24 ` Rik van Riel
2010-06-16 23:48 ` Andrew Morton
2010-06-16 23:48 ` Andrew Morton
2010-06-17 10:46 ` Mel Gorman
2010-06-17 10:46 ` Mel Gorman
2010-06-14 11:17 ` [PATCH 10/12] vmscan: Update isolated page counters outside of main path in shrink_inactive_list() Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 19:42 ` Rik van Riel
2010-06-14 19:42 ` Rik van Riel
2010-06-14 11:17 ` [PATCH 11/12] vmscan: Write out dirty pages in batch Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 21:13 ` Rik van Riel
2010-06-14 21:13 ` Rik van Riel
2010-06-15 10:18 ` Mel Gorman
2010-06-15 10:18 ` Mel Gorman
2010-06-14 23:11 ` Dave Chinner
2010-06-14 23:11 ` Dave Chinner
2010-06-14 23:21 ` Andrew Morton
2010-06-14 23:21 ` Andrew Morton
2010-06-15 0:39 ` Dave Chinner
2010-06-15 0:39 ` Dave Chinner
2010-06-15 1:16 ` Rik van Riel
2010-06-15 1:16 ` Rik van Riel
2010-06-15 1:45 ` Andrew Morton
2010-06-15 1:45 ` Andrew Morton
2010-06-15 4:08 ` Rik van Riel
2010-06-15 4:08 ` Rik van Riel
2010-06-15 4:37 ` Andrew Morton
2010-06-15 4:37 ` Andrew Morton
2010-06-15 5:12 ` Nick Piggin
2010-06-15 5:12 ` Nick Piggin
2010-06-15 5:43 ` [patch] mm: vmscan fix mapping use after free Nick Piggin
2010-06-15 5:43 ` Nick Piggin
2010-06-15 13:23 ` Mel Gorman
2010-06-15 13:23 ` Mel Gorman
2010-06-15 11:01 ` [PATCH 11/12] vmscan: Write out dirty pages in batch Christoph Hellwig
2010-06-15 11:01 ` Christoph Hellwig
2010-06-15 13:32 ` Rik van Riel
2010-06-15 13:32 ` Rik van Riel
2010-06-15 1:39 ` Andrew Morton
2010-06-15 1:39 ` Andrew Morton
2010-06-15 3:20 ` Dave Chinner
2010-06-15 3:20 ` Dave Chinner
2010-06-15 4:15 ` Andrew Morton
2010-06-15 4:15 ` Andrew Morton
2010-06-15 6:36 ` Dave Chinner
2010-06-15 6:36 ` Dave Chinner
2010-06-15 10:28 ` Evgeniy Polyakov
2010-06-15 10:28 ` Evgeniy Polyakov
2010-06-15 10:55 ` Nick Piggin
2010-06-15 10:55 ` Nick Piggin
2010-06-15 11:10 ` Christoph Hellwig
2010-06-15 11:10 ` Christoph Hellwig
2010-06-15 11:20 ` Nick Piggin
2010-06-15 11:20 ` Nick Piggin
2010-06-15 23:20 ` Dave Chinner
2010-06-15 23:20 ` Dave Chinner
2010-06-16 6:04 ` Nick Piggin
2010-06-16 6:04 ` Nick Piggin
2010-06-15 11:08 ` Christoph Hellwig
2010-06-15 11:08 ` Christoph Hellwig
2010-06-15 11:43 ` Mel Gorman
2010-06-15 11:43 ` Mel Gorman
2010-06-15 13:07 ` tytso
2010-06-15 13:07 ` tytso
2010-06-15 15:44 ` Mel Gorman
2010-06-15 15:44 ` Mel Gorman
2010-06-15 10:57 ` Christoph Hellwig
2010-06-15 10:57 ` Christoph Hellwig
2010-06-15 10:53 ` Christoph Hellwig
2010-06-15 10:53 ` Christoph Hellwig
2010-06-15 11:11 ` Mel Gorman
2010-06-15 11:11 ` Mel Gorman
2010-06-15 11:13 ` Nick Piggin [this message]
2010-06-15 11:13 ` Nick Piggin
2010-06-14 11:17 ` [PATCH 12/12] vmscan: Do not writeback pages in direct reclaim Mel Gorman
2010-06-14 11:17 ` Mel Gorman
2010-06-14 21:55 ` Rik van Riel
2010-06-14 21:55 ` Rik van Riel
2010-06-15 11:45 ` Mel Gorman
2010-06-15 11:45 ` Mel Gorman
2010-06-15 13:34 ` Rik van Riel
2010-06-15 13:34 ` Rik van Riel
2010-06-15 13:37 ` Christoph Hellwig
2010-06-15 13:37 ` Christoph Hellwig
2010-06-15 13:54 ` Mel Gorman
2010-06-15 13:54 ` Mel Gorman
2010-06-16 0:30 ` KAMEZAWA Hiroyuki
2010-06-16 0:30 ` KAMEZAWA Hiroyuki
2010-06-15 14:02 ` Rik van Riel
2010-06-15 14:02 ` Rik van Riel
2010-06-15 13:59 ` Mel Gorman
2010-06-15 13:59 ` Mel Gorman
2010-06-15 14:04 ` Rik van Riel
2010-06-15 14:04 ` Rik van Riel
2010-06-15 14:16 ` Mel Gorman
2010-06-15 14:16 ` Mel Gorman
2010-06-16 0:17 ` KAMEZAWA Hiroyuki
2010-06-16 0:17 ` KAMEZAWA Hiroyuki
2010-06-16 0:29 ` Rik van Riel
2010-06-16 0:29 ` Rik van Riel
2010-06-16 0:39 ` KAMEZAWA Hiroyuki
2010-06-16 0:39 ` KAMEZAWA Hiroyuki
2010-06-16 0:53 ` Rik van Riel
2010-06-16 0:53 ` Rik van Riel
2010-06-16 1:40 ` KAMEZAWA Hiroyuki
2010-06-16 1:40 ` KAMEZAWA Hiroyuki
2010-06-16 2:20 ` KAMEZAWA Hiroyuki
2010-06-16 2:20 ` KAMEZAWA Hiroyuki
2010-06-16 5:11 ` Christoph Hellwig
2010-06-16 5:11 ` Christoph Hellwig
2010-06-16 10:51 ` Jens Axboe
2010-06-16 10:51 ` Jens Axboe
2010-06-16 5:07 ` Christoph Hellwig
2010-06-16 5:07 ` Christoph Hellwig
2010-06-16 5:06 ` Christoph Hellwig
2010-06-16 5:06 ` Christoph Hellwig
2010-06-17 0:25 ` KAMEZAWA Hiroyuki
2010-06-17 0:25 ` KAMEZAWA Hiroyuki
2010-06-17 6:16 ` Christoph Hellwig
2010-06-17 6:16 ` Christoph Hellwig
2010-06-17 6:23 ` KAMEZAWA Hiroyuki
2010-06-17 6:23 ` KAMEZAWA Hiroyuki
2010-06-14 15:10 ` [PATCH 0/12] Avoid overflowing of stack during page reclaim V2 Christoph Hellwig
2010-06-14 15:10 ` Christoph Hellwig
2010-06-15 11:45 ` Mel Gorman
2010-06-15 11:45 ` Mel Gorman
2010-06-15 0:08 ` KAMEZAWA Hiroyuki
2010-06-15 0:08 ` KAMEZAWA Hiroyuki
2010-06-15 11:49 ` Mel Gorman
2010-06-15 11:49 ` Mel Gorman
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