Memory returned 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.szyprow...@samsung.com>
Reviewed-by: Kyungmin Park <kyungmin.p...@samsung.com>
CC: Michal Nazarewicz <min...@mina86.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 count = 0;
+       for (; nr_pages--; page++) {
+               count += page_count(page) != 1;
+               __free_page(page);
+       }
+       WARN(count != 0, "%d pages are still in use!\n", count);
 }
 #endif
 
-- 
1.7.9.5

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