Re: [PATCH v1 4/4] mm/mmu_gather: Store and process pages in contig ranges

[Ryan Roberts]

>>>
>>> Also, struct page (memmap) might not be always contiguous, using struct page
>>> points to represent folio range might not give the result you want.
>>> See nth_page() and folio_page_idx() in include/linux/mm.h.
>>
>> Is that true for pages within the same folio too? Or are all pages in a folio
>> guarranteed contiguous? Perhaps I'm better off using pfn?
> 
> folio_page_idx() says not all pages in a folio is guaranteed to be contiguous.
> PFN might be a better choice.

Hi Zi, Matthew,

Zi made this comment a couple of months back that it is incorrect to assume that
`struct page`s within a folio are (virtually) contiguous. I'm not sure if that's
really the case though? I see other sites in the source that do page++ when
iterating over a folio. e.g. smaps_account(), splice_folio_into_pipe(),
__collapse_huge_page_copy(), etc.

Any chance someone could explain the rules?

Thanks,
Ryan