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 23:51:33 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Nick Piggin <npiggin@...e.de>,
	"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 02:32:25AM +0800, Andi Kleen wrote:
[snip]
> > > > > Clean swap cache pages can be directly isolated. A later page fault will bring
> > > > > in the known good data from disk.
> > > > 
> > > > OK, but why do you ClearPageUptodate if it is just to be deleted from
> > > > swapcache anyway?
> > > 
> > > The ClearPageUptodate() is kind of a careless addition, in the hope
> > > that it will stop some random readers. Need more investigations.
> > 
> > OK. But it just muddies the waters in the meantime, so maybe take
> > such things out until there is a case for them.
> 
> It's gone

Andi, I'd recommend to re-add ClearPageUptodate() for dirty swap cache
pages. It will then make shmem_getpage() return EIO for
- shmem_fault()        => kill app with VM_FAULT_SIGBUS
- shmem_readpage()     => fail splice()/sendfile() etc.
- shmem_write_begin()  => fail splice()/sendfile() etc.
which is exactly what we wanted. Note that the EIO here is permanent.

I'll continue to do some experiments on its normal read/write behaviors.

Thanks,
Fengguang
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