diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 907c9b1..09ab91a 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -1555,6 +1555,13 @@ static void zs_object_copy(struct size_class *class, unsigned long dst,
 		d_off += size;
 		d_size -= size;
 
+		/*
+		 * Calling kunmap_atomic(d_addr) is necessary. kunmap_atomic()
+		 * calls must occurs in reverse order of calls to kmap_atomic().
+		 * So, to call kunmap_atomic(s_addr) we should first call
+		 * kunmap_atomic(d_addr).  For more details see
+		 * https://lore.kernel.org/linux-mm/5512421D.4000603@samsung.com/
+		 */
 		if (s_off >= PAGE_SIZE) {
 			kunmap_atomic(d_addr);
 			kunmap_atomic(s_addr);