[PATCH v2 1/2] mm: free compound page with correct order

[Yu Zhao <yuzhao@google.com>]

Compound page should be freed by put_page() or free_pages() with
correct order. Not doing so will cause tail pages leaked.

The compound order can be obtained by compound_order() or use
HPAGE_PMD_ORDER in our case. Some people would argue the latter
is faster but I prefer the former which is more general.

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Fixes: 97ae17497e99 ("thp: implement refcounting for huge zero page")
Cc: stable@vger.kernel.org (v3.8+)
Signed-off-by: Yu Zhao <yuzhao@google.com>
---
 mm/huge_memory.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 74c78aa..780d12c 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -200,7 +200,7 @@ retry:
 	preempt_disable();
 	if (cmpxchg(&huge_zero_page, NULL, zero_page)) {
 		preempt_enable();
-		__free_page(zero_page);
+		__free_pages(zero_page, compound_order(zero_page));
 		goto retry;
 	}
 
@@ -232,7 +232,7 @@ static unsigned long shrink_huge_zero_page_scan(struct shrinker *shrink,
 	if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) {
 		struct page *zero_page = xchg(&huge_zero_page, NULL);
 		BUG_ON(zero_page == NULL);
-		__free_page(zero_page);
+		__free_pages(zero_page, compound_order(zero_page));
 		return HPAGE_PMD_NR;
 	}
 
-- 
2.1.0.rc2.206.gedb03e5

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