linux-kernel - Re: [patch 1/6] md: remove dependency on __GFP

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Message-ID: <AANLkTi=HxY6w2iJme3qW_J_sbXedu7JSSECBEFPM1d_c@mail.gmail.com>
Date:	Mon, 23 Aug 2010 23:29:13 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Neil Brown <neilb@...e.de>, Alasdair G Kergon <agk@...hat.com>,
	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/6] md: remove dependency on __GFP_NOFAIL

Hi David,

On Mon, 23 Aug 2010, Pekka Enberg wrote:
>> > Hows about you add a helper function
>> >
>> >        void *[kmalloc|alloc_page]_retrying_forever_because_i_suck(lots of args)
>> >
>> > then convert the callsites to use that, then nuke __GFP_NOFAIL?
>>
>> I'd prefer killing off __GFP_NOFAIL properly :-)

On Mon, Aug 23, 2010 at 11:13 PM, David Rientjes <rientjes@...gle.com> wrote:
> And how is this not done properly if it's not even needed for any of the
> allocations in this patchset since the page allocator loops forever for
> their orders and context?  (This is why we don't need to add __GFP_NOWARN
> in its place.)
>
> This is a cleanup patchset to remove the unnecessary use of __GFP_NOFAIL,
> there _are_ GFP_KERNEL | __GFP_NOFAIL allocations that need to be
> addressed in phase three.

My point is that I don't think Andrew's helper will change all that
much. Fixing the actual callers is the hard part and I don't see your
patches helping that either. Hiding the looping in filesystem code is
only going to make problematic callers harder to find (e.g
kmem_alloc() in XFS code).

FWIW, I'd just add a nasty WARN_ON in the page allocator and put a big
fat "fix your shit" comment on top of it to motivate people to fix
their code.

                         Pekka
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