linux-kernel - Re: [PATCH] Fix kunmap() argument in sg_miter

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Message-ID: <20081117182650.GY26778@kernel.dk>
Date:	Mon, 17 Nov 2008 19:26:50 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>, Ingo Molnar <mingo@...e.hu>,
	Tejun Heo <htejun@...il.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Hugh Dickins <hugh@...itas.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] Fix kunmap() argument in sg_miter_stop

On Mon, Nov 17 2008, Linus Torvalds wrote:
> 
> 
> On Mon, 17 Nov 2008, Jens Axboe wrote:
> > 
> > Any opinions on the kunmap/kunmap_atomic pointer checking? It's a bit
> > ugly that we have to enforce a void * rule for kunmap_atomic(),
> 
> I don't think that's a "bit ugly". I think it's unacceptable.
> 
> Making sure we pass in "struct page" to kunmap() sounds good, but the 
> kunmap_atomic() part just sounds insane.

It's been the primary source of bugs that I have seen. The xen and sg
iter bug were kunmap() variants though, but otherwise I've mostly seen
the opposite. But it is ugly, no doubt about it. I can't think of a
better way to attempt to warn about it though, so if you really dislike
it I'll just drop the _atomic() bits.

-- 
Jens Axboe

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