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Date: Mon, 11 May 2009 15:31:04 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
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To: Andrew Morton <akpm@linux-foundation.org>
cc: gregkh@suse.de, npiggin@suse.de, mel@csn.ul.ie, a.p.zijlstra@chello.nl,
       cl@linux-foundation.org, dave@linux.vnet.ibm.com, san@android.com,
       arve@android.com, linux-kernel@vger.kernel.org
Subject: Re: [patch 08/11 -mmotm] oom: invoke oom killer for __GFP_NOFAIL
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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@google.com>
> Cc: Mel Gorman <mel@csn.ul.ie>
> Signed-off-by: Andrew Morton <akpm@linux-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.