linux-kernel - Re: VM: Fix nasty and subtle race in shared mmap'ed page writeback

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Date:	Wed, 10 Jan 2007 14:54:53 +0100
From:	Andrea Gelmini <gelma@...ma.net>
To:	Nick Piggin <nickpiggin@...oo.com.au>
Cc:	Andrew Morton <akpm@...l.org>, Linus Torvalds <torvalds@...l.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: VM: Fix nasty and subtle race in shared mmap'ed page writeback

On Fri, Jan 05, 2007 at 04:36:06PM +1100, Nick Piggin wrote:
> I was thinking like a 100 line C program that I can reproduce here ;)
not soon, but I'll try to produce it.

> If you can even describe the steps it does: (eg. mmap file A, write(2) to
> it, truncate it, ...., should contain 1s but it contains 0s!), then we
> might have some suggestions to try.
I ignore this... I mean, BerkelyDB does all this on its own (we just
talk with the library). we never touch directly the DB.

> One obvious thing is change filesystems or filesystem block sizes, try
> ext2 or even tmpfs. Another is to try using write(2) instead of mmap to
> write data.
well, I tried all filesystems, tmpfs also. I know BDB use a lot mmap.

thanks,
gelma

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