x86: Assert non-zero refcount on entry to put_page().

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 4f58720fed402c785390bec687f98feca5ddc8ec..7752d1a3a08d49f4b111be56ebc831789b10593a 100644 (file)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -1929,6 +1929,7 @@ void put_page(struct page_info *page)
     unsigned long nx, x, y = page->count_info;
 
     do {
+        ASSERT((y & PGC_count_mask) != 0);
         x  = y;
         nx = x - 1;
     }