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

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Message-ID: <20090528134848.GI1065@one.firstfloor.org>
Date:	Thu, 28 May 2009 15:48:48 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	"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 Thu, May 28, 2009 at 02:15:41PM +0200, Nick Piggin wrote:
> For correctness for what? You can't remove a page from swapcache or
> pagecache under writeback because then the mm thinks that location
> is not being used.

I'm adding wait_on_page_writeback() to memory_failure(), so 
it will be out of the picture hopefully

> 
>  
> > I'm mainly interested in correctness (as in not crashing) of this
> > version now.
> > 
> > Also writeback seems to be only used by nfs/afs/nilfs2, not in
> > the normal case, unless I'm misreading the code. 
> 
> I don't follow. What writeback are you talking about?

Sorry I misread the code, it's indeed used more commonly.


> > > Then the writeback pages simply won't reach here. And it won't
> > > magically go into writeback state, since the page has been locked.
> > 
> > But since we take the page lock they should not be in writeback anyways,
> > no?
> 
> No. PG_writeback was introduced so as to reduce page lock hold
> times (most of writeback runs without page lock held).

Ok. Then the wait_on_page_writeback() will take care of that.

Thanks for the feedback,

-Andi

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