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Message-ID: <4C03932F.8000303@cesarb.net>
Date: Mon, 31 May 2010 07:45:03 -0300
From: Cesar Eduardo Barros <cesarb@cesarb.net>
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To: Rusty Russell <rusty@rustcorp.com.au>
CC: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org, Russell King <linux@arm.linux.org.uk>,
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       "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
       Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH] Make kunmap_atomic() harder to misuse
References: <1275043993-26557-1-git-send-email-cesarb@cesarb.net> <20100529204256.b92b1ff6.akpm@linux-foundation.org> <201005311945.19784.rusty@rustcorp.com.au>
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Em 31-05-2010 07:15, Rusty Russell escreveu:
> On Sun, 30 May 2010 01:12:56 pm Andrew Morton wrote:
>> On Fri, 28 May 2010 07:53:13 -0300 Cesar Eduardo Barros<cesarb@cesarb.net>  wrote:
>>> +/* Prevent people trying to call kunmap_atomic() as if it were kunmap() */
>>> +struct __kunmap_atomic_dummy {};
>>> +#define kunmap_atomic(addr, idx) do { \
>>> +		BUILD_BUG_ON( \
>>> +			__builtin_types_compatible_p(typeof(addr), struct page *)&&  \
>>> +			!__builtin_types_compatible_p(typeof(addr), struct __kunmap_atomic_dummy *)); \
>>> +		kunmap_atomic_notypecheck((addr), (idx)); \
>>> +	} while (0)
>>
>> We have a little __same_type() helper for this.  __must_be_array()
>> should be using it, too.
>
> Yep... but I think BUILD_BUG_ON(__same_type((addr), struct page *)); is
> sufficient; void * is not compatible in my quick tests here.

That is what I get for only reading the manual instead of testing :(

(I only tested the completed patch, not each step along the way.)

I will try it later today and make a new patch if it works as expected.

-- 
Cesar Eduardo Barros
cesarb@cesarb.net
cesar.barros@gmail.com