[PATCH] zone handle unaligned zone boundaries (cb2b95e1) · Commits · 戴 / test

The buddy allocator has a requirement that boundaries between contigious zones occur aligned with the the MAX_ORDER ranges. Where they do not we will incorrectly merge pages cross zone boundaries. This can lead to pages from the wrong zone being handed out. Originally the buddy allocator would check that buddies were in the same zone by referencing the zone start and end page frame numbers. This was removed as it became very expensive and the buddy allocator already made the assumption that zones boundaries were aligned. It is clear that not all configurations and architectures are honouring this alignment requirement. Therefore it seems safest to reintroduce support for non-aligned zone boundaries. This patch introduces a new check when considering a page a buddy it compares the zone_table index for the two pages and refuses to merge the pages where they do not match. The zone_table index is unique for each node/zone combination when FLATMEM/DISCONTIGMEM is enabled and for each section/zone combination when SPARSEMEM is enabled (a SPARSEMEM section is at least a MAX_ORDER size). Signed-off-by:

Andy Whitcroft <apw@shadowen.org> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: Yasunori Goto <y-goto@jp.fujitsu.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by:

Andrew Morton <akpm@osdl.org> Signed-off-by:

Linus Torvalds <torvalds@osdl.org>

include/linux/mm.h

+5 −2

Original line number	Diff line number	Diff line
		@@ -465,10 +465,13 @@ static inline unsigned long page_zonenum(struct page *page)
		struct zone;
		extern struct zone *zone_table[];

		static inline int page_zone_id(struct page *page)
		{
		return (page->flags >> ZONETABLE_PGSHIFT) & ZONETABLE_MASK;
		}
		static inline struct zone page_zone(struct page page)
		{
		return zone_table[(page->flags >> ZONETABLE_PGSHIFT) &
		ZONETABLE_MASK];
		return zone_table[page_zone_id(page)];
		}

		static inline unsigned long page_to_nid(struct page *page)

mm/page_alloc.c

+11 −6

Original line number	Diff line number	Diff line
		@@ -286,22 +286,27 @@ __find_combined_index(unsigned long page_idx, unsigned int order)
		* we can do coalesce a page and its buddy if
		* (a) the buddy is not in a hole &&
		* (b) the buddy is in the buddy system &&
		* (c) a page and its buddy have the same order.
		* (c) a page and its buddy have the same order &&
		* (d) a page and its buddy are in the same zone.
		*
		* For recording whether a page is in the buddy system, we use PG_buddy.
		* Setting, clearing, and testing PG_buddy is serialized by zone->lock.
		*
		* For recording page's order, we use page_private(page).
		*/
		static inline int page_is_buddy(struct page *page, int order)
		static inline int page_is_buddy(struct page page, struct page buddy,
		int order)
		{
		#ifdef CONFIG_HOLES_IN_ZONE
		if (!pfn_valid(page_to_pfn(page)))
		if (!pfn_valid(page_to_pfn(buddy)))
		return 0;
		#endif

		if (PageBuddy(page) && page_order(page) == order) {
		BUG_ON(page_count(page) != 0);
		if (page_zone_id(page) != page_zone_id(buddy))
		return 0;

		if (PageBuddy(buddy) && page_order(buddy) == order) {
		BUG_ON(page_count(buddy) != 0);
		return 1;
		}
		return 0;
		@@ -352,7 +357,7 @@ static inline void __free_one_page(struct page *page,
		struct page *buddy;

		buddy = __page_find_buddy(page, page_idx, order);
		if (!page_is_buddy(buddy, order))
		if (!page_is_buddy(page, buddy, order))
		break; /* Move the buddy up one level. */

		list_del(&buddy->lru);

Admin message