linux-kernel - Re: [patch -mmotm] mm: invoke oom killer for __GFP

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Message-ID: <20090512164934.GC31131@wotan.suse.de>
Date:	Tue, 12 May 2009 18:49:34 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>, mel@....ul.ie,
	a.p.zijlstra@...llo.nl, cl@...ux-foundation.org,
	dave@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	Divy Le Ray <divy@...lsio.com>
Subject: Re: [patch -mmotm] mm: invoke oom killer for __GFP_NOFAIL

On Tue, May 12, 2009 at 06:37:30PM +0200, Jens Axboe wrote:
> On Tue, May 12 2009, Nick Piggin wrote:
> > On Tue, May 12, 2009 at 02:42:02PM +0200, Jens Axboe wrote:
> > > On Mon, May 11 2009, Andrew Morton wrote:
> > > > On Sat, 9 May 2009 15:46:39 -0700 (PDT)
> > > > David Rientjes <rientjes@...gle.com> wrote:
> > > > 
> > > > > The oom killer must be invoked regardless of the order if the allocation
> > > > > is __GFP_NOFAIL, otherwise it will loop forever when reclaim fails to
> > > > > free some memory.
> > > > 
> > > > Sigh.  We're supposed to be deleting __GFP_NOFAIL.  I added it as a way
> > > > of easily finding lame error-handling-challenged callers which need to
> > > > be fixed up.  So of course we went and added lots more callers.
> > > > 
> > > > y:/usr/src/linux-2.6.30-rc5> grep -rl GFP_NOFAIL . 
> > > > ./fs/bio-integrity.c
> > 
> > This is no good either, it seems to be in the bio submission path.
> > 
> > It needs a mempool or something.
> 
> mempool cannot help here, since the allocation is tied to the process
> (and IO) life time.

Oh, I was talking about bio-integrity.c...

 
> > It has a dead code "fallback" that returns an error, but I suspect that's
> > not really acceptable.
> 
> It's not that difficult to handle an error there, it just means that we
> lose any process association with that request. It's mostly making sure
> that all the bits and pieces deal with that correctly, but it should not
> be very hard.


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