On Sat, May 15, 2021 at 10:55:19AM +0000, William Kucharski wrote: > > +/** > > + * folio_page - Return a page from a folio. > > + * @folio: The folio. > > + * @n: The page number to return. > > + * > > + * @n is relative to the start of the folio. It should be between > > + * 0 and folio_nr_pages(@folio) - 1, but this is not checked for. > > Please add a statement noting WHY @n isn't checked since you state it > should be. Something like "...but this is not checked for because this is > a hot path." Hmm ... how about this: /** * folio_page - Return a page from a folio. * @folio: The folio. * @n: The page number to return. * * @n is relative to the start of the folio. This function does not * check that the page number lies within @folio; the caller is presumed * to have a reference to the page. */ #define folio_page(folio, n) nth_page(&(folio)->page, n) It occurred to me that it is actually useful (under some circumstances) for referring to a page outside the base folio. For example when dealing with bios that have merged consecutive pages together into a single bvec (ok, bios don't use folios, but it would be reasonable if they did in future).
