mm, page_alloc: avoid page_to_pfn() when merging buddies
On architectures that allow memory holes, page_is_buddy() has to perform
page_to_pfn() to check for the memory hole. After the previous patch,
we have the pfn already available in __free_one_page(), which is the
only caller of page_is_buddy(), so move the check there and avoid
page_to_pfn().
Link: http://lkml.kernel.org/r/20161216120009.20064-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 49d4026..af65c4e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -714,7 +714,7 @@
/*
* This function checks whether a page is free && is the buddy
* we can do coalesce a page and its buddy if
- * (a) the buddy is not in a hole &&
+ * (a) the buddy is not in a hole (check before calling!) &&
* (b) the buddy is in the buddy system &&
* (c) a page and its buddy have the same order &&
* (d) a page and its buddy are in the same zone.
@@ -729,9 +729,6 @@
static inline int page_is_buddy(struct page *page, struct page *buddy,
unsigned int order)
{
- if (!pfn_valid_within(page_to_pfn(buddy)))
- return 0;
-
if (page_is_guard(buddy) && page_order(buddy) == order) {
if (page_zone_id(page) != page_zone_id(buddy))
return 0;
@@ -808,6 +805,9 @@
while (order < max_order - 1) {
buddy_pfn = __find_buddy_pfn(pfn, order);
buddy = page + (buddy_pfn - pfn);
+
+ if (!pfn_valid_within(buddy_pfn))
+ goto done_merging;
if (!page_is_buddy(page, buddy, order))
goto done_merging;
/*
@@ -862,7 +862,7 @@
* so it's less likely to be used soon and more likely to be merged
* as a higher order page
*/
- if ((order < MAX_ORDER-2) && pfn_valid_within(page_to_pfn(buddy))) {
+ if ((order < MAX_ORDER-2) && pfn_valid_within(buddy_pfn)) {
struct page *higher_page, *higher_buddy;
combined_pfn = buddy_pfn & pfn;
higher_page = page + (combined_pfn - pfn);