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

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Message-Id: <20100823132315.6906ddbe.akpm@linux-foundation.org>
Date:	Mon, 23 Aug 2010 13:23:15 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	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

On Mon, 23 Aug 2010 13:08:53 -0700 (PDT)
David Rientjes <rientjes@...gle.com> wrote:

> On Mon, 23 Aug 2010, Andrew Morton 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?
> > 
> 
> That would only serve as documentation

Is that bad?

> of a caller that could potentially 
> loop forever waiting for memory (which I did by adding "/* FIXME: this may 
> potentially loop forever */")

A helper function could check that appropriate gfp flags are being set.

> since all of the allocations in this 
> patchset never loop in the code that was added, they already loop forever 
> in the page allocator doing the same thing.  The hope is that kswapd will 
> eventually be able to free memory since direct reclaim will usually fail 
> for GFP_NOFS and we simply need to wait long enough for there to be 
> memory.

While holding locks which will prevent kswapd from doing anything useful.

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