Re: news about IDE PIO HIGHMEM bug (was: Re: 2.6.9-mm1)

[Martin J. Bligh]

--"Martin J. Bligh" <mbligh@xxxxxxxxxxx> wrote (on Wednesday, October 27, 2004 08:52:39 -0700):

>> Bartlomiej Zolnierkiewicz wrote:
>>> We have stuct page of the first page and a offset.
>>> We need to obtain struct page of the current page and map it.
>> 
>> 
>> Opening this question to a wider audience.
>> 
>> struct scatterlist gives us struct page*, and an offset+length pair. The struct page* is the _starting_ page of a potentially multi-page run of data.
>> 
>> The question:  how does one get struct page* for the second, and successive pages in a known-contiguous multi-page run, if one only knows the first page?
> 
> If it's a higher order allocation, just page+1 should be safe. If it just
> happens to be contig, it might cross a discontig boundary, and not obey
> that rule. Very unlikely, but possible.

To repeat what I said in IRC ... ;-)

Actually, you could check this with the pfns being the same when >> MAX_ORDER-1.
We should be aligned on a MAX_ORDER boundary, I think.

However, pfn_to_page(page_to_pfn(page) + 1) might be safer. If rather slower.

M.

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