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Date: Thu, 26 Mar 2009 10:13:44 +0200
From: Adrian Hunter <adrian.hunter@nokia.com>
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To: "Singh, Vimal" <vimalsingh@ti.com>
Subject: Re: Is high_memory check in omap2.c for OneNAND is sufficient?
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Singh, Vimal wrote:
> From: Adrian Hunter [adrian.hunter@nokia.com]
>> Singh, Vimal wrote:
>>> From: Adrian Hunter [adrian.hunter@nokia.com]
>>>> Singh, Vimal wrote:
>>>>> There is check for 'high_memory' in 'drivers/mtd/onenand/omap2.c', always before doing 'dma_map_single'.
>>>>> Snippet:
>>>>> ----------------------
>>>>>         if (buf >= high_memory) {
>>>>>                 struct page *p1;
>>>>> ----------------------
>>>>> This check seems not sufficient. There should be a check for upper boundary too.
>>>>> Thinking scenario when 'buf' is less than 'high_memory', but somewhere near to it, and 'count' is big enough to beyond 'high_memory'.
>>>> AFAIK it is not possible to allocate memory that crosses the high_memory boundary.
>>> Do you mean 'buf' can not cross 'high_memory' boundary?
>> Yes.
> If so, then I wonder why above check is present in code...
> 

Which check?

>>> But then I have seen a case where it was crossing that and BUG was reported by function 'dma_cache_maint'.
>> Is it possible that 'buf' or 'count' is wrong?
> I do not think so...
>