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

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Message-Id: <1413400805-15547-1-git-send-email-yuzhao@google.com>
Date:	Wed, 15 Oct 2014 12:20:04 -0700
From:	Yu Zhao <yuzhao@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Hugh Dickins <hughd@...gle.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Bob Liu <lliubbo@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	David Rientjes <rientjes@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org, Yu Zhao <yuzhao@...gle.com>
Subject: [PATCH v2 1/2] mm: free compound page with correct order

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@...ux.intel.com>
Fixes: 97ae17497e99 ("thp: implement refcounting for huge zero page")
Cc: stable@...r.kernel.org (v3.8+)
Signed-off-by: Yu Zhao <yuzhao@...gle.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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