diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index 1a53d49..963b703 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -120,6 +120,9 @@
 
 	atomic_add((int) count - PCPU_COUNT_BIAS, &ref->count);
 
+	WARN_ONCE(atomic_read(&ref->count) <= 0, "percpu ref <= 0 (%i)",
+		  atomic_read(&ref->count));
+
 	/* @ref is viewed as dead on all CPUs, send out kill confirmation */
 	if (ref->confirm_kill)
 		ref->confirm_kill(ref);
diff --git a/mm/percpu.c b/mm/percpu.c
index 0d10def..afbf352 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1686,10 +1686,10 @@
 	max_distance += ai->unit_size;
 
 	/* warn if maximum distance is further than 75% of vmalloc space */
-	if (max_distance > (VMALLOC_END - VMALLOC_START) * 3 / 4) {
+	if (max_distance > VMALLOC_TOTAL * 3 / 4) {
 		pr_warning("PERCPU: max_distance=0x%zx too large for vmalloc "
 			   "space 0x%lx\n", max_distance,
-			   (unsigned long)(VMALLOC_END - VMALLOC_START));
+			   VMALLOC_TOTAL);
 #ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
 		/* and fail if we have fallback */
 		rc = -EINVAL;