[PATCH v2] mm, page_alloc: Add missing check for memory holes

From: Luck, Tony
Date: Wed Mar 08 2017 - 12:42:04 EST

From: Tony Luck <tony.luck@xxxxxxxxx>

commit 13ad59df67f19788f6c22985b1a33e466eceb643
("mm, page_alloc: avoid page_to_pfn() when merging buddies")
moved the check for memory holes out of page_is_buddy() and
had the callers do the check.

But this wasn't done correctly in one place which caused
ia64 to crash very early in boot.

Update to fix that and make ia64 boot again.

Fixes: 13ad59df67f1 ("avoid page_to_pfn() when merging buddies")
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: LKML <linux-kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>

v2: Vlastimil pointed out we don't need to call page_to_pfn() we already
have the result of that in "buddy_pfn"

mm/page_alloc.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index eaa64d2ffdc5..6cbde310abed 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -873,7 +873,8 @@ static inline void __free_one_page(struct page *page,
higher_page = page + (combined_pfn - pfn);
buddy_pfn = __find_buddy_pfn(combined_pfn, order + 1);
higher_buddy = higher_page + (buddy_pfn - combined_pfn);
- if (page_is_buddy(higher_page, higher_buddy, order + 1)) {
+ if (pfn_valid_within(buddy_pfn) &&
+ page_is_buddy(higher_page, higher_buddy, order + 1)) {
goto out;