diff --git a/drivers/s390/cio/idset.c b/drivers/s390/cio/idset.c
index 835de44dbbcc..2137aa23c664 100644
--- a/drivers/s390/cio/idset.c
+++ b/drivers/s390/cio/idset.c
@@ -18,7 +18,7 @@ struct idset {
 
 static inline unsigned long bitmap_size(int num_ssid, int num_id)
 {
-	return BITS_TO_LONGS(num_ssid * num_id) * sizeof(unsigned long);
+	return bitmap_size(size_mul(num_ssid, num_id));
 }
 
 static struct idset *idset_new(int num_ssid, int num_id)
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index b71a033c781e..6bcc7e72bc5a 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -212,12 +212,14 @@ extern int bitmap_print_to_pagebuf(bool list, char *buf,
 #define small_const_nbits(nbits) \
 	(__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG && (nbits) > 0)
 
+#define bitmap_size(nbits)	(ALIGN(nbits, BITS_PER_LONG) / BITS_PER_BYTE)
+
 static inline void bitmap_zero(unsigned long *dst, unsigned int nbits)
 {
 	if (small_const_nbits(nbits))
 		*dst = 0UL;
 	else {
-		unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
+		unsigned int len = bitmap_size(nbits);
 		memset(dst, 0, len);
 	}
 }
@@ -227,7 +229,7 @@ static inline void bitmap_fill(unsigned long *dst, unsigned int nbits)
 	if (small_const_nbits(nbits))
 		*dst = ~0UL;
 	else {
-		unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
+		unsigned int len = bitmap_size(nbits);
 		memset(dst, 0xff, len);
 	}
 }
@@ -238,7 +240,7 @@ static inline void bitmap_copy(unsigned long *dst, const unsigned long *src,
 	if (small_const_nbits(nbits))
 		*dst = *src;
 	else {
-		unsigned int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
+		unsigned int len = bitmap_size(nbits);
 		memcpy(dst, src, len);
 	}
 }
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 147bdec42215..e4467240eb86 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -656,7 +656,7 @@ static inline int cpulist_parse(const char *buf, struct cpumask *dstp)
  */
 static inline unsigned int cpumask_size(void)
 {
-	return BITS_TO_LONGS(nr_cpumask_bits) * sizeof(long);
+	return bitmap_size(nr_cpumask_bits);
 }
 
 /*
diff --git a/tools/include/linux/bitmap.h b/tools/include/linux/bitmap.h
index e63662db131b..3aeeb60f1988 100644
--- a/tools/include/linux/bitmap.h
+++ b/tools/include/linux/bitmap.h
@@ -27,13 +27,14 @@ int __bitmap_and(unsigned long *dst, const unsigned long *bitmap1,
 #define small_const_nbits(nbits) \
 	(__builtin_constant_p(nbits) && (nbits) <= BITS_PER_LONG)
 
+#define bitmap_size(nbits)	(ALIGN(nbits, BITS_PER_LONG) / BITS_PER_BYTE)
+
 static inline void bitmap_zero(unsigned long *dst, int nbits)
 {
 	if (small_const_nbits(nbits))
 		*dst = 0UL;
 	else {
-		int len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
-		memset(dst, 0, len);
+		memset(dst, 0, bitmap_size(nbits));
 	}
 }
 
@@ -119,7 +120,7 @@ static inline int test_and_clear_bit(int nr, unsigned long *addr)
  */
 static inline unsigned long *bitmap_alloc(int nbits)
 {
-	return calloc(1, BITS_TO_LONGS(nbits) * sizeof(unsigned long));
+	return calloc(1, bitmap_size(nbits));
 }
 
 /*