linux-kernel - Re: [PATCH v3 1/2] memblock: add assertion for zero allocation alignment

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Date:	Mon, 4 Mar 2013 16:45:25 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Tejun Heo <tj@...nel.org>, Yinghai Lu <yinghai@...nel.org>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] memblock: add assertion for zero allocation alignment

Hi Andrew,

On Friday 22 February 2013 02:23 AM, Tejun Heo wrote:
> On Thu, Feb 21, 2013 at 12:52 PM, Vineet Gupta
> <Vineet.Gupta1@...opsys.com> wrote:
>> This came to light when calling memblock allocator from arc port (for
>> copying flattended DT). If a "0" alignment is passed, the allocator
>> round_up() call incorrectly rounds up the size to 0.
>>
>> round_up(num, alignto) => ((num - 1) | (alignto -1)) + 1
>>
>> While the obvious allocation failure causes kernel to panic, it is
>> better to warn the caller to fix the code.
>>
>> Tejun suggested that instead of BUG_ON(!align) - which might be
>> ineffective due to pending console init and such, it is better to
>> WARN_ON, and continue the boot with a reasonable default align.
>>
>> Caller passing @size need not be handled similarly as the subsequent
>> panic will indicate that anyhow.
>>
>> Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Tejun Heo <tj@...nel.org>
>> Cc: Yinghai Lu <yinghai@...nel.org>
>> Cc: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
>> Cc: Ingo Molnar <mingo@...nel.org>
>> Cc: linux-mm@...ck.org
>> Cc: linux-kernel@...r.kernel.org
> 
> Acked-by: Tejun Heo <tj@...nel.org>
> 
> Thanks.
> 

I'm hoping this will be routed via the mm tree.

Thx,
-Vineet
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