linux-ext4 - Re: ftruncate-mmap: pages are lost after writing to mmaped file.

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Date:	Thu, 2 Apr 2009 22:24:29 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Ying Han <yinghan@...gle.com>
Cc:	Jan Kara <jack@...e.cz>, "Martin J. Bligh" <mbligh@...igh.org>,
	linux-ext4@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"linux-mm" <linux-mm@...ck.org>, guichaz@...il.com,
	Alex Khesin <alexk@...gle.com>,
	Mike Waychison <mikew@...gle.com>,
	Rohit Seth <rohitseth@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: ftruncate-mmap: pages are lost after writing to mmaped file.

On Thursday 02 April 2009 09:36:13 Ying Han wrote:
> Hi Jan:
>     I feel that the problem you saw is kind of differnt than mine. As
> you mentioned that you saw the PageError() message, which i don't see
> it on my system. I tried you patch(based on 2.6.21) on my system and
> it runs ok for 2 days, Still, since i don't see the same error message
> as you saw, i am not convineced this is the root cause at least for
> our problem. I am still looking into it.
>     So, are you seeing the PageError() every time the problem happened?

So I asked if you could test with my workaround of taking truncate_mutex
at the start of ext2_get_blocks, and report back. I never heard of any
response after that.

To reiterate: I was able to reproduce a problem with ext2 (I was testing
on brd to get IO rates high enough to reproduce it quite frequently).
I think I narrowed the problem down to block allocation or inode block
tree corruption because I was unable to reproduce it with that hack in
place.

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