linux-kernel - Re: [PATCH] adjust gfp mask passed on nested vmalloc() invocation

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Message-Id: <4ACC749602000078000186ED@vpn.id2.novell.com>
Date:	Wed, 07 Oct 2009 09:59:34 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"Hugh Dickins" <hugh.dickins@...cali.co.uk>
Cc:	<linux-mm@...ck.org>, "Andrew Morton" <akpm@...ux-foundation.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] adjust gfp mask passed on nested vmalloc()
	 invocation

>>> Hugh Dickins <hugh.dickins@...cali.co.uk> 06.10.09 23:58 >>>
>On Mon, 5 Oct 2009, Jan Beulich wrote:
>
>> - fix a latent bug resulting from blindly or-ing in __GFP_ZERO, since
>>   the combination of this and __GFP_HIGHMEM (possibly passed into the
>>   function) is forbidden in interrupt context
>> - avoid wasting more precious resources (DMA or DMA32 pools), when
>>   being called through vmalloc_32{,_user}()
>> - explicitly allow using high memory here even if the outer allocation
>>   request doesn't allow it, unless is collides with __GFP_ZERO
>> 
>> Signed-off-by: Jan Beulich <jbeulich@...ell.com>
>
>I thought vmalloc.c was a BUG_ON(in_interrupt()) zone?
>The locking is all spin_lock stuff, not spin_lock_irq stuff.
>That's probably why your "bug" has remained "latent".

Actually, my previous reply to this was bogus, and I agree with your
statement. Hence, from a second version of the patch (depending on
your response on my question regarding the other part of your reply),
I should drop that part of the description.

Jan

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