Commit 57cbc87e authored Nov 13, 2014 by Joonsoo Kim Committed by Linus Torvalds Nov 13, 2014

mm/debug-pagealloc: correct freepage accounting and order resetting



One thing I did in this patch is fixing freepage accounting.  If we
clear guard page and link it onto isolate buddy list, we should not
increase freepage count.  This patch adds conditional branch to skip
counting in this case.  Without this patch, this overcounting happens
frequently if guard order is set and CMA is used.

Another thing fixed in this patch is the target to reset order.  In
__free_one_page(), we check the buddy page whether it is a guard page or
not.  And, if so, we should clear guard attribute on the buddy page and
reset order of it to 0.  But, current code resets original page's order
rather than buddy one's.  Maybe, this doesn't have any problem, because
whole merged page's order will be re-assigned soon.  But, it is better
to correct code.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Gioh Kim <gioh.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 8edc6e16

mm/page_alloc.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -583,9 +583,11 @@ static inline void __free_one_page(struct page *page,
		*/
		if (page_is_guard(buddy)) {
		clear_page_guard_flag(buddy);
		set_page_private(page, 0);
		set_page_private(buddy, 0);
		if (!is_migrate_isolate(migratetype)) {
		__mod_zone_freepage_state(zone, 1 << order,
		migratetype);
		}
		} else {
		list_del(&buddy->lru);
		zone->free_area[order].nr_free--;

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