Commit 0ba8f2d5 authored Sep 17, 2012 by Li Haifeng Committed by Linus Torvalds Sep 17, 2012

mm/page_alloc: fix the page address of higher page's buddy calculation



The heuristic method for buddy has been introduced since commit
43506fad ("mm/page_alloc.c: simplify calculation of combined index
of adjacent buddy lists").  But the page address of higher page's buddy
was wrongly calculated, which will lead page_is_buddy to fail for ever.
IOW, the heuristic method would be disabled with the wrong page address
of higher page's buddy.

Calculating the page address of higher page's buddy should be based
higher_page with the offset between index of higher page and index of
higher page's buddy.

Signed-off-by: Haifeng Li <omycle@gmail.com>
Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: KyongHo Cho <pullip.cho@samsung.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: <stable@vger.kernel.org>	[2.6.38+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 8dcebaa9

mm/page_alloc.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -584,7 +584,7 @@ static inline void __free_one_page(struct page *page,
		combined_idx = buddy_idx & page_idx;
		higher_page = page + (combined_idx - page_idx);
		buddy_idx = __find_buddy_index(combined_idx, order + 1);
		higher_buddy = page + (buddy_idx - combined_idx);
		higher_buddy = higher_page + (buddy_idx - combined_idx);
		if (page_is_buddy(higher_page, higher_buddy, order + 1)) {
		list_add_tail(&page->lru,
		&zone->free_area[order].free_list[migratetype]);

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