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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20090602135324.GB21338@localhost>
Date:	Tue, 2 Jun 2009 21:53:24 +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 09:41:26PM +0800, Andi Kleen wrote:
> On Tue, Jun 02, 2009 at 03:24:41PM +0200, Nick Piggin wrote:
> > On Tue, Jun 02, 2009 at 03:25:38PM +0200, Andi Kleen wrote:
> > > On Tue, Jun 02, 2009 at 02:57:13PM +0200, Nick Piggin wrote:
> > > > > > not a big deal and just avoids duplicating code. I attached an
> > > > > > (untested) patch.
> > > > > 
> > > > > Thanks. But the function in the patch is not doing the same what
> > > > > the me_pagecache_clean/dirty are doing. For once there is no error
> > > > > checking, as in the second try_to_release_page()
> > > > > 
> > > > > Then it doesn't do all the IO error and missing mapping handling.
> > > > 
> > > > Obviously I don't mean just use that single call for the entire
> > > > handler. You can set the EIO bit or whatever you like. The
> > > > "error handling" you have there also seems strange. You could
> > > > retain it, but the page is assured to be removed from pagecache.
> > > 
> > > The reason this code double checks is that someone could have 
> > > a reference (remember we can come in any time) we cannot kill immediately.
> > 
> > Can't kill what? The page is gone from pagecache. It may remain
> > other kernel references, but I don't see why this code will
> > consider this as a failure (and not, for example, a raised error
> > count).
> 
> It's a failure because the page was still used and not successfully
> isolated.
> 
> > +        * remove_from_page_cache assumes (mapping && !mapped)
> > +        */
> > +       if (page_mapping(p) && !page_mapped(p)) {
> 
> Ok you're right. That one is not needed. I will remove it.

No! Please read the comment. In fact __remove_from_page_cache() has a

                BUG_ON(page_mapped(page));

Or, at least correct that BUG_ON() line together.

Thanks,
Fengguang

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/