linux-kernel - Re: [PATCH] [16/19] HWPOISON: Enable .remove_error

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Date:	Wed, 12 Aug 2009 12:16:58 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
Cc:	Andi Kleen <andi@...stfloor.org>, tytso@....edu, hch@...radead.org,
	mfasheh@...e.com, aia21@...tab.net, hugh.dickins@...cali.co.uk,
	swhiteho@...hat.com, akpm@...ux-foundation.org, npiggin@...e.de,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	fengguang.wu@...el.com,
	Satoshi OSHIMA <satoshi.oshima.fk@...achi.com>,
	Taketoshi Sakuraba <taketoshi.sakuraba.hc@...achi.com>
Subject: Re: [PATCH] [16/19] HWPOISON: Enable .remove_error_page for
	migration aware file systems

On Wed, Aug 12, 2009 at 06:52:14PM +0900, Hidehiro Kawai wrote:
> Andi Kleen wrote:
> 
> >>Generally, dropping unwritten dirty page caches is considered to be
> >>risky.  So the "panic on IO error" policy has been used as usual
> >>practice for some systems.  I just suggested that we adopted
> >>this policy into machine check errors. 
> > 
> > Hmm, what we could possibly do -- as followon patches -- would be to
> > let error_remove_page check the per file system panic-on-io-error
> > super block setting for dirty pages and panic in this case too.  
> > Unfortunately this setting is currently per file system, not generic,
> > so it would need to be a fs specific check (or the flag would need
> > to be moved into a generic fs superblock field first)
> 
> A generic setting would be better, so I suggested
> panic_on_dirty_page_cache_corruption flag which would be checked
> before invoking error_remove_page().  If we check per-filesystem
> settings, we might want to notify EIO to the filesystem.

You mean remounting ro if that is set?
That makes sense, but I'm not sure how complicated it would be.
I still would prefer to unify it with the file system settings.

> > The problem is memory_failure() would then need to start distingushing
> > between AR=1 and AR=0 which it doesn't today.
> > 
> > It could be done, but would need some more work. 
> 
> It's my understanding that memory_failure() are never called in
> AR=1 case.  Is it wrong?

Today yes, but we don't want to hardcode that assumption. e.g. for IA64
they will definitely need the equivalent of AR=1 handling.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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