linux-kernel - Re: [patch 08/11 -mmotm] oom: invoke oom killer for __GFP

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Message-ID: <alpine.DEB.2.00.0905111529090.2234@chino.kir.corp.google.com>
Date:	Mon, 11 May 2009 15:31:04 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	gregkh@...e.de, npiggin@...e.de, mel@....ul.ie,
	a.p.zijlstra@...llo.nl, cl@...ux-foundation.org,
	dave@...ux.vnet.ibm.com, san@...roid.com, arve@...roid.com,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 08/11 -mmotm] oom: invoke oom killer for __GFP_NOFAIL

On Mon, 11 May 2009, Andrew Morton wrote:

> __GFP_NOFAIL is a bad fiction.  Allocations _can_ fail, and callers should
> detect and suitably handle this (and not by lamely moving the infinite
> loop up to the caller level either).
> 
> Attempting to use __GFP_NOFAIL for a higher-order allocation is even
> worse, so add a once-off runtime check for this to slap people around for
> even thinking about trying it.
> 
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Mel Gorman <mel@....ul.ie>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>

This only emits a warning when you have CONFIG_DEBUG_KERNEL, 
CONFIG_FAULT_INJECTION, and CONFIG_FAIL_PAGE_ALLOC, which is all related 
to fault injection (since we never want to inject a fault into anything 
using __GFP_NOFAIL).  So it may be helpful in tracking down such callers, 
but is unrelated to the config options that enable it and it may not get 
the best coverage.
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