linux-kernel - Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3

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Date:	Wed, 3 Jun 2009 11:35:46 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Wu Fengguang <fengguang.wu@...el.com>,
	"hugh@...itas.com" <hugh@...itas.com>,
	"riel@...hat.com" <riel@...hat.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"chris.mason@...cle.com" <chris.mason@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH] [13/16] HWPOISON: The high level memory error handler in the VM v3

On Tue, Jun 02, 2009 at 07:27:15PM +0200, Andi Kleen wrote:
> > Hmm, if you're handling buffercache here then possibly yes.
> 
> Good question, will check.

BTW. now that I think about it, buffercache is probably not a good
idea to truncate (truncate, as-in: remove from pagecache). Because
filesystems can assume that with just a reference on the page, then
it will not be truncated.

This code will cause ext2 (as the first one I looked at), to go
oops.

And this is not predicated on PagePrivate or page_has_buffers,
because filesystems are free to directly operate on their own
metadata buffercache pages.

So I think it would be a good idea to exclude buffercache from
here completely until it can be shown to be safe. Actually you
*can* use the invalidate_mapping_pages path, which will check
refcounts etc (or a derivative thereof, similarly to my truncate
patch).

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