linux-kernel - Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct truncating of page v2

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Date:	Thu, 6 Aug 2009 13:48:30 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	fengguang.wu@...el.com, hidehiro.kawai.ez@...achi.com,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH] [11/19] HWPOISON: Refactor truncate to allow direct
 truncating of page v2

On Wed, 5 Aug 2009 16:16:42 +0200
Nick Piggin <npiggin@...e.de> wrote:

> On Wed, Aug 05, 2009 at 04:10:01PM +0200, Andi Kleen wrote:
> > > I haven't brought up the caller at this point, but IIRC you had
> > > the page locked and mapping confirmed at this point anyway so
> > > it would never be an error for your code.
> > > 
> > > Probably it would be nice to just force callers to verify the page.
> > > Normally IMO it is much nicer and clearer to do it at the time the
> > > page gets locked, unless there is good reason otherwise.
> > 
> > Ok. I think I'll just keep it as it is for now.
> > 
> > The only reason I added the error code was to make truncate_inode_page
> > fit into .error_remove_page, but then latter I did another wrapper
> > so it could be removed again. But it won't hurt to have it either.
> 
> OK, it's more of a cleanup/nit.
> 
> One question I had for the others (Andrew? other mm guys?) what is the
> feelings of merging this feature? Leaving aside exact implementation
> and just considering the high level design and cost/benefit. Last time
> there were some people objecting, so I wonder the situation now? So
> does anybody need more convincing? :)
> 
> Also I will just cc linux-arch. It would be interesting to know whether
> powerpc, ia64, or s390 or others would be interested to use this feature?

This is not relevant for s390, as current machines do transparent memory
sparing if a memory module goes bad. Really old machines reported bad
memory to the OS by means of a machine check (storage error uncorrected
and storage error corrected). I have never seen this happen, the level
below the OS deals with these errors for us.

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

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