linux-kernel - Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3)

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Message-ID: <4BBBDD64.9030800@redhat.com>
Date:	Tue, 06 Apr 2010 21:18:28 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Borislav Petkov <bp@...en8.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan.kim@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	sgunderson@...foot.com
Subject: Re: Ugly rmap NULL ptr deref oopsie on hibernate (was Linux 2.6.34-rc3)

On 04/06/2010 08:10 PM, Linus Torvalds wrote:

> That said, the code that _really_ confuses me is the stuff that uses
> "anon_vma_clone()". Could you please also explain the code flow of
> vma_adjust() to mere mortals, please?

That's easier said than done.  I spent 3 days with pen and paper,
going over that code before I made the anon_vma changes, first
verifying that the code is indeed correct and then figuring out
how I could make the anon_vma changes safely.

I am not happy with the complexity of the code around vma_adjust,
but could not find a way to simplify it and still keep merging
VMAs the way we do.

My largest change to vma_adjust was moving some code closer to
the beginning of the function, so I could bail out if the
allocation failed, without making change to the vma...

> I suspect Borislav is sleeping. But at least we have a patch for him to
> test when he wakes up ;)

I am looking forward to the test results.

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