linux-kernel - [PATCH] mm: cma: WARN if freed memory is still in use

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Date:	Mon, 12 Nov 2012 12:07:26 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	linux-mm@...ck.org, linaro-mm-sig@...ts.linaro.org,
	linux-kernel@...r.kernel.org
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	Michal Nazarewicz <mina86@...a86.com>,
	Minchan Kim <minchan@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: [PATCH] mm: cma: WARN if freed memory is still in use

Memory return to free_contig_range() must have no other references. Let
kernel to complain loudly if page reference count is not equal to 1.

Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
Reviewed-by: Kyungmin Park <kyungmin.park@...sung.com>
CC: Michal Nazarewicz <mina86@...a86.com>
---
 mm/page_alloc.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 022e4ed..290c2eb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5888,8 +5888,13 @@ done:
 
 void free_contig_range(unsigned long pfn, unsigned nr_pages)
 {
-	for (; nr_pages--; ++pfn)
-		__free_page(pfn_to_page(pfn));
+	struct page *page = pfn_to_page(pfn);
+	int refcount = nr_pages;
+	for (; nr_pages--; page++) {
+		refcount -= page_count(page) == 1;
+		__free_page(page);
+	}
+	WARN(refcount != 0, "some pages are still in use!\n");
 }
 #endif
 
-- 
1.7.9.5

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