diff --git a/lib/bitmap.c b/lib/bitmap.c
index a2348d19c8b5e9ac2999c9cd5e279ff4828db995..5ade00d4219a56ec49b797dfd3e273ca15721383 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -13,6 +13,7 @@
 #include <linux/bitops.h>
 #include <linux/bug.h>
 #include <linux/kernel.h>
+#include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/uaccess.h>
@@ -461,14 +462,15 @@ EXPORT_SYMBOL(bitmap_parse_user);
  * ranges if list is specified or hex digits grouped into comma-separated
  * sets of 8 digits/set. Returns the number of characters written to buf.
  *
- * It is assumed that @buf is a pointer into a PAGE_SIZE area and that
- * sufficient storage remains at @buf to accommodate the
- * bitmap_print_to_pagebuf() output.
+ * It is assumed that @buf is a pointer into a PAGE_SIZE, page-aligned
+ * area and that sufficient storage remains at @buf to accommodate the
+ * bitmap_print_to_pagebuf() output. Returns the number of characters
+ * actually printed to @buf, excluding terminating '\0'.
  */
 int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp,
 			    int nmaskbits)
 {
-	ptrdiff_t len = PTR_ALIGN(buf + PAGE_SIZE - 1, PAGE_SIZE) - buf;
+	ptrdiff_t len = PAGE_SIZE - offset_in_page(buf);
 	int n = 0;
 
 	if (len > 1)