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Date: Wed, 25 Mar 2009 12:43:16 +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:
>>> 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.

> 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?