On Wed, Jun 14, 2023 at 01:13:05PM -0700, Andrew Morton wrote: > On Tue, 13 Jun 2023 19:13:09 -0700 "Vishal Moola (Oracle)" <vishal.moola@xxxxxxxxx> wrote: > > > Introduce folio_migratetype() as a folio equivalent for > > get_pageblock_migratetype(). This function intends to return the > > migratetype the folio is located in, hence the name choice. > > > > ... > > > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -105,6 +105,9 @@ extern int page_group_by_mobility_disabled; > > #define get_pageblock_migratetype(page) \ > > get_pfnblock_flags_mask(page, page_to_pfn(page), MIGRATETYPE_MASK) > > > > +#define folio_migratetype(folio) \ > > + get_pfnblock_flags_mask(&folio->page, folio_pfn(folio), \ > > + MIGRATETYPE_MASK) > > Theoretically this is risky because it evaluates its argument more than > once. Although folio_migratetype(folio++) seems an unlikely thing to do. folio++ is always an unsafe thing to do. folios are not consecutive in memory (unless we know they're order-0). > An inlined C function is always preferable. My quick attempt at that > reveals that the header files are All Messed Up As Usual. The page-equivalent of this also evaluates its arguments more than once, so it doesn't see too risky for now?
