Message-ID: <51A77FF7.5090908@linux.vnet.ibm.com>
Date: Thu, 30 May 2013 09:36:07 -0700
From: Cody P Schafer <cody@linux.vnet.ibm.com>
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To: Jiang Liu <liuj97@gmail.com>
CC: LKML <linux-kernel@vger.kernel.org>, Linux MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] mm: sparse: use __aligned() instead of manual padding
 in mem_section
References: <1369869279-20155-1-git-send-email-cody@linux.vnet.ibm.com> <51A6A34B.6020907@gmail.com>
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On 05/29/2013 05:54 PM, Jiang Liu wrote:
> On Thu 30 May 2013 07:14:39 AM CST, Cody P Schafer wrote:
>> Also, does anyone know what causes this alignment to be required here? I found
>> this was breaking things in a patchset I'm working on (WARNs in sysfs code
>> about duplicate filenames when initing mem_sections). Adding some documentation
>> for the reason would be appreciated.
> Hi Cody,
>          I think the alignment requirement is caused by the way the
> mem_section array is
> organized. Basically it requires that PAGE_SIZE could be divided by
> sizeof(struct mem_section).
> So your change seems risky too because it should be aligned to power of
> two instead
> of 2 * sizeof(long).

Well, if that's the case then this patch is wrong, and manual padding 
may be the only way to go. :(

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