On 23.8.2016 16:10, zhongjiang wrote: > From: zhong jiang <zhongjiang@xxxxxxxxxx> > > At present, page aligned with MAX_ORDER make no sense. Is it a bug that manifests... how? Does it make more sense with max_order? why? I think we could just drop the page_idx masking and use pfn directly. __find_buddy_index() only looks at the 1 << order bit. Then there are operations such as (buddy_idx & page_idx) and (combined_idx - page_idx), none of these should care about the bits higher than MAX_ORDER/max_order as the subtraction cancels them out. That's also why the "mistake" you point out doesn't result in a bug IMHO. > > Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx> > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ff726f94..a178b1d 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -786,7 +786,7 @@ static inline void __free_one_page(struct page *page, > if (likely(!is_migrate_isolate(migratetype))) > __mod_zone_freepage_state(zone, 1 << order, migratetype); > > - page_idx = pfn & ((1 << MAX_ORDER) - 1); > + page_idx = pfn & ((1 << max_order) - 1); > > VM_BUG_ON_PAGE(page_idx & ((1 << order) - 1), page); > VM_BUG_ON_PAGE(bad_range(zone, page), page); > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>