linux-kernel - Re: new procfs memory analysis feature

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Date:	Thu, 7 Dec 2006 17:53:06 -0800
From:	david singleton <dsingleton@...sta.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: new procfs memory analysis feature


On Dec 7, 2006, at 5:46 PM, Andrew Morton wrote:

> On Thu, 7 Dec 2006 17:07:22 -0800
> david singleton <dsingleton@...sta.com> wrote:
>
>> Attached is the 2.6.19 patch.
>
> It still has the overflow bug.
>> +       do {
>> +               ptent = *pte;
>> +               if (pte_present(ptent)) {
>> +                       page = vm_normal_page(vma, addr, ptent);
>> +                       if (page) {
>> +                               if (pte_dirty(ptent))
>> +                                       mapcount = 
>> -page_mapcount(page);
>> +                               else
>> +                                       mapcount = 
>> page_mapcount(page);
>> +                       } else {
>> +                               mapcount = 1;
>> +                       }
>> +               }
>> +               seq_printf(m, " %d", mapcount);
>> +
>> +       } while (pte++, addr += PAGE_SIZE, addr != end);
>
> Well that's cute.  As long as both seq_file and pte-pages are of size
> PAGE_SIZE, and as long as pte's are more than three bytes, this will 
> not
> overflow the seq_file output buffer.
>
> hm.  Unless the pages are all dirty and the mapcounts are all 10000.  I
> think it will overflow then?
>

I guess that could happen?    Any suggestions?

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