linux-kernel - Re: [PATCH] cma: use unsigned type for count argument

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Message-ID: <xa1tzk10ntaa.fsf@mina86.com>
Date:	Thu, 27 Dec 2012 03:05:49 +0100
From:	Michal Nazarewicz <mpn@...gle.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cma: use unsigned type for count argument

> On Sat, 22 Dec 2012, Michal Nazarewicz wrote:
>> So I think just adding the following, should be sufficient to make
>> everyone happy:
>> 
>> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
>> index e34e3e0..e91743b 100644
>> --- a/drivers/base/dma-contiguous.c
>> +++ b/drivers/base/dma-contiguous.c
>> @@ -320,7 +320,7 @@ struct page *dma_alloc_from_contiguous(struct device *dev, unsigned int count,
>>  	pr_debug("%s(cma %p, count %u, align %u)\n", __func__, (void *)cma,
>>  		 count, align);
>>  
>> -	if (!count)
>> +	if (!count || count > INT_MAX)
>>  		return NULL;
>>  
>>  	mask = (1 << align) - 1;
>
On Thu, Dec 27 2012, David Rientjes <rientjes@...gle.com> wrote:
> How is this different than leaving the formal to have a signed type, i.e. 
> drop your patch, and testing for count <= 0 instead?

Not much different I guess.  I don't have strong opinions to be honest,
except that I feel unsigned is the proper type to use, on top of which
I think bitmap_set() should use unsigned, so in case anyone ever bothers
to change it, CMA will be ready. :P

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
ooo +----<email/xmpp: mpn@...gle.com>--------------ooO--(_)--Ooo--

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