diff --git a/drivers/s390/cio/idset.c b/drivers/s390/cio/idset.c
index 835de44dbbccd0ad5f1fbac5a7001dad8a7cef8e..b98526d3ddfdc8d97920681e92649004d75638a0 100644
--- a/drivers/s390/cio/idset.c
+++ b/drivers/s390/cio/idset.c
@@ -16,20 +16,21 @@ struct idset {
 	unsigned long bitmap[0];
 };
 
-static inline unsigned long bitmap_size(int num_ssid, int num_id)
+static inline unsigned long idset_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)
 {
 	struct idset *set;
 
-	set = vmalloc(sizeof(struct idset) + bitmap_size(num_ssid, num_id));
+	set = vmalloc(sizeof(struct idset) +
+		      idset_bitmap_size(num_ssid, num_id));
 	if (set) {
 		set->num_ssid = num_ssid;
 		set->num_id = num_id;
-		memset(set->bitmap, 0, bitmap_size(num_ssid, num_id));
+		memset(set->bitmap, 0, idset_bitmap_size(num_ssid, num_id));
 	}
 	return set;
 }
@@ -41,7 +42,8 @@ void idset_free(struct idset *set)
 
 void idset_fill(struct idset *set)
 {
-	memset(set->bitmap, 0xff, bitmap_size(set->num_ssid, set->num_id));
+	memset(set->bitmap, 0xff,
+	       idset_bitmap_size(set->num_ssid, set->num_id));
 }
 
 static inline void idset_add(struct idset *set, int ssid, int id)
diff --git a/fs/file.c b/fs/file.c
index 4c192bc684949ccc9f3e3e92d1113ee3fa1e03b5..545f9c5bd2debf48711672a661ca7de16507a10f 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -44,27 +44,23 @@ static void free_fdtable_rcu(struct rcu_head *rcu)
 #define BITBIT_NR(nr)	BITS_TO_LONGS(BITS_TO_LONGS(nr))
 #define BITBIT_SIZE(nr)	(BITBIT_NR(nr) * sizeof(long))
 
+#define fdt_words(fdt) ((fdt)->max_fds / BITS_PER_LONG) // words in ->open_fds
 /*
  * Copy 'count' fd bits from the old table to the new table and clear the extra
  * space if any.  This does not copy the file pointers.  Called with the files
  * spinlock held for write.
  */
-static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
-			    unsigned int count)
+static inline void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
+			    unsigned int copy_words)
 {
-	unsigned int cpy, set;
-
-	cpy = count / BITS_PER_BYTE;
-	set = (nfdt->max_fds - count) / BITS_PER_BYTE;
-	memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
-	memset((char *)nfdt->open_fds + cpy, 0, set);
-	memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
-	memset((char *)nfdt->close_on_exec + cpy, 0, set);
-
-	cpy = BITBIT_SIZE(count);
-	set = BITBIT_SIZE(nfdt->max_fds) - cpy;
-	memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
-	memset((char *)nfdt->full_fds_bits + cpy, 0, set);
+	unsigned int nwords = fdt_words(nfdt);
+
+	bitmap_copy_and_extend(nfdt->open_fds, ofdt->open_fds,
+			copy_words * BITS_PER_LONG, nwords * BITS_PER_LONG);
+	bitmap_copy_and_extend(nfdt->close_on_exec, ofdt->close_on_exec,
+			copy_words * BITS_PER_LONG, nwords * BITS_PER_LONG);
+	bitmap_copy_and_extend(nfdt->full_fds_bits, ofdt->full_fds_bits,
+			copy_words, nwords);
 }
 
 /*
@@ -82,7 +78,7 @@ static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
 	memcpy(nfdt->fd, ofdt->fd, cpy);
 	memset((char *)nfdt->fd + cpy, 0, set);
 
-	copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
+	copy_fd_bitmaps(nfdt, ofdt, fdt_words(ofdt));
 }
 
 static struct fdtable * alloc_fdtable(unsigned int nr)
@@ -337,7 +333,7 @@ struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 		open_files = count_open_files(old_fdt);
 	}
 
-	copy_fd_bitmaps(new_fdt, old_fdt, open_files);
+	copy_fd_bitmaps(new_fdt, old_fdt, open_files / BITS_PER_LONG);
 
 	old_fds = old_fdt->fd;
 	new_fds = new_fdt->fd;
diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index b71a033c781efef8cb586f1706fd20059baec70e..3c942d9a8639c4bf4cae96de3d869061ad3c414d 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);
 	}
 }
@@ -254,6 +256,18 @@ static inline void bitmap_copy_clear_tail(unsigned long *dst,
 		dst[nbits / BITS_PER_LONG] &= BITMAP_LAST_WORD_MASK(nbits);
 }
 
+static inline void bitmap_copy_and_extend(unsigned long *to,
+					  const unsigned long *from,
+					  unsigned int count, unsigned int size)
+{
+	unsigned int copy = BITS_TO_LONGS(count);
+
+	memcpy(to, from, copy * sizeof(long));
+	if (count % BITS_PER_LONG)
+		to[copy - 1] &= BITMAP_LAST_WORD_MASK(count);
+	memset(to + copy, 0, bitmap_size(size) - copy * sizeof(long));
+}
+
 /*
  * On 32-bit systems bitmaps are represented as u32 arrays internally, and
  * therefore conversion is not needed when copying data from/to arrays of u32.
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 147bdec42215d54f6f17686492bbdcc6162f1c8b..e4467240eb86c00a22a5ec2f0f56253c92aea29c 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 e63662db131ba525c36e79232150fc5f62e2f758..3aeeb60f1988231d36bd6afbf5d4dee841cdc654 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));
 }
 
 /*