Is high_memory check in omap2.c for OneNAND is sufficient?

[Singh, Vimal]

From: Adrian Hunter [adrian.hunter at nokia.com]
>Singh, Vimal wrote:
>> From: Adrian Hunter [adrian.hunter at 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...

>
>> 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...