linux-kernel - Re: [PATCH 00/22] HWPOISON: Intro (v5)

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Date:	Mon, 15 Jun 2009 12:36:19 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Balbir Singh <balbir@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Mel Gorman <mel@....ul.ie>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andi Kleen <andi@...stfloor.org>,
	"riel@...hat.com" <riel@...hat.com>,
	"chris.mason@...cle.com" <chris.mason@...cle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 00/22] HWPOISON: Intro (v5)

On Mon, Jun 15, 2009 at 06:09:54PM +0800, Wu Fengguang wrote:
> On Mon, Jun 15, 2009 at 04:14:53PM +0800, Nick Piggin wrote:
> > On Mon, Jun 15, 2009 at 08:44:47AM +0200, Nick Piggin wrote:
> > > Did we verify with filesystem maintainers (eg. btrfs) that the
> > > !ISREG test will be enough to prevent oopses?
> > 
> > BTW. this is quite a significant change I think and not
> > really documented well enough. Previously a filesystem
> > will know exactly when and why pagecache in a mapping
> > under its control will be truncated (as opposed to
> > invalidated).
> > 
> > They even have opportunity to hold locks such as i_mutex.
> > 
> > And depending on what they do, they could do interesting
> > things even with ISREG files.
> > 
> > So, I really think this needs review by filesystem
> > maintainers and it would be far safer to use invalidate
> > until it is known to be safe.
> 
> Nick, we are doing invalidate_complete_page() for !S_ISREG inodes now.
> Do you mean to do invalidate_complete_page() for all inodes for now?

That would make me a lot happier. It is obviously correct because
that is basically what page reclaim and inode reclaim and drop
caches etc does.

Note that I still don't like exporting invalidate_complete_page
fro the same reasons I don't like exporting truncate_complete_page,
so I will ask if you can do an invalidate_inode_page function
along the same lines of the truncate_inode_page one please.


> That's a good suggestion, it shall be able to do the job for most
> pages indeed.

Yes I think it will be far far safer while only introducing
another small class of pages which cannot be recovered (probably
a much smaller set most of the time than the size of the existing
set of pages which cannot be recovered).


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