mm: cma: WARN if freed memory is still in use

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.

[rientjes@google.com: support sparsemem]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 2 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2ad2ad168efe..4ba5e37127fc 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5978,8 +5978,15 @@ done:
 
 void free_contig_range(unsigned long pfn, unsigned nr_pages)
 {
-        for (; nr_pages--; ++pfn)
-                __free_page(pfn_to_page(pfn));
+        unsigned int count = 0;
+
+        for (; nr_pages--; pfn++) {
+                struct page *page = pfn_to_page(pfn);
+
+                count += page_count(page) != 1;
+                __free_page(page);
+        }
+        WARN(count != 0, "%d pages are still in use!\n", count);
 }
 #endif