On Wed, Aug 06, 2014 at 04:18:30PM +0900, Joonsoo Kim wrote: > In __free_one_page(), we check the buddy page if it is guard page. > And, if so, we should clear guard attribute on the buddy page. But, > currently, we clear original page's order rather than buddy one's. > This doesn't have any problem, because resetting buddy's order > is useless and the original page's order is re-assigned soon. > But, it is better to correct code. > > Additionally, I change (set/clear)_page_guard_flag() to > (set/clear)_page_guard() and makes these functions do all works > needed for guard page. This may make code more understandable. > > One more thing, I did in this patch, is that fixing freepage accounting. > If we clear guard page and link it onto isolate buddy list, we should > not increase freepage count.
You are saying just "shouldn't do that" but don't say "why" and "result" I know the reason but as you know, I'm one of the person who is rather familiar with this part but I guess others should spend some time to get. Kind detail description is never to look down on person. :) > Nice catch, Joonsoo! But what make me worry is is this patch makes 3 thing all at once. 1. fix - no candidate for stable 2. clean up 3. fix - candidate for stable. Could you separate 3 and (1,2) in next spin? > Acked-by: Vlastimil Babka <[email protected]> > Signed-off-by: Joonsoo Kim <[email protected]> > --- > mm/page_alloc.c | 29 ++++++++++++++++------------- > 1 file changed, 16 insertions(+), 13 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 44672dc..3e1e344 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -441,18 +441,28 @@ static int __init debug_guardpage_minorder_setup(char > *buf) > } > __setup("debug_guardpage_minorder=", debug_guardpage_minorder_setup); > > -static inline void set_page_guard_flag(struct page *page) > +static inline void set_page_guard(struct zone *zone, struct page *page, > + unsigned int order, int migratetype) > { > __set_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); > + set_page_private(page, order); > + /* Guard pages are not available for any usage */ > + __mod_zone_freepage_state(zone, -(1 << order), migratetype); > } > > -static inline void clear_page_guard_flag(struct page *page) > +static inline void clear_page_guard(struct zone *zone, struct page *page, > + unsigned int order, int migratetype) > { > __clear_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); > + set_page_private(page, 0); > + if (!is_migrate_isolate(migratetype)) > + __mod_zone_freepage_state(zone, (1 << order), migratetype); > } > #else > -static inline void set_page_guard_flag(struct page *page) { } > -static inline void clear_page_guard_flag(struct page *page) { } > +static inline void set_page_guard(struct zone *zone, struct page *page, > + unsigned int order, int migratetype) {} > +static inline void clear_page_guard(struct zone *zone, struct page *page, > + unsigned int order, int migratetype) {} > #endif > > static inline void set_page_order(struct page *page, unsigned int order) > @@ -594,10 +604,7 @@ static inline void __free_one_page(struct page *page, > * merge with it and move up one order. > */ > if (page_is_guard(buddy)) { > - clear_page_guard_flag(buddy); > - set_page_private(page, 0); > - __mod_zone_freepage_state(zone, 1 << order, > - migratetype); > + clear_page_guard(zone, buddy, order, migratetype); > } else { > list_del(&buddy->lru); > zone->free_area[order].nr_free--; > @@ -876,11 +883,7 @@ static inline void expand(struct zone *zone, struct page > *page, > * pages will stay not present in virtual address space > */ > INIT_LIST_HEAD(&page[size].lru); > - set_page_guard_flag(&page[size]); > - set_page_private(&page[size], high); > - /* Guard pages are not available for any usage */ > - __mod_zone_freepage_state(zone, -(1 << high), > - migratetype); > + set_page_guard(zone, &page[size], high, migratetype); > continue; > } > #endif > -- > 1.7.9.5 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
