The patch titled
zone handle unaligned zone boundaries
has been added to the -mm tree. Its filename is
zone-handle-unaligned-zone-boundaries.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: zone handle unaligned zone boundaries
From: Andy Whitcroft <apw@xxxxxxxxxxxx>
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@xxxxxxxxxxxx>
Cc: Dave Hansen <haveblue@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Yasunori Goto <y-goto@xxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/mm.h | 7 +++++--
mm/page_alloc.c | 17 +++++++++++------
2 files changed, 16 insertions(+), 8 deletions(-)
diff -puN include/linux/mm.h~zone-handle-unaligned-zone-boundaries include/linux/mm.h
--- a/include/linux/mm.h~zone-handle-unaligned-zone-boundaries
+++ a/include/linux/mm.h
@@ -473,10 +473,13 @@ static inline unsigned long page_zonenum
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)
diff -puN mm/page_alloc.c~zone-handle-unaligned-zone-boundaries mm/page_alloc.c
--- a/mm/page_alloc.c~zone-handle-unaligned-zone-boundaries
+++ a/mm/page_alloc.c
@@ -285,22 +285,27 @@ __find_combined_index(unsigned long page
* 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;
@@ -351,7 +356,7 @@ static inline void __free_one_page(struc
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);
_
Patches currently in -mm which might be from apw@xxxxxxxxxxxx are
zone-handle-unaligned-zone-boundaries.patch
zone-init-check-and-report-unaligned-zone-boundaries.patch
x86-align-highmem-zone-boundaries-with-numa.patch
zone-allow-unaligned-zone-boundaries.patch
zone-allow-unaligned-zone-boundaries-x86-add-zone-alignment-qualifier.patch
pg_uncached-is-ia64-only.patch
squash-duplicate-page_to_pfn-and-pfn_to_page.patch
flatmem-relax-requirement-for-memory-to-start-at-pfn-0.patch
sparsemem-record-nid-during-memory-present.patch
-
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