lib/bitmap: add bitmap_weight_and()

The function calculates Hamming weight of (bitmap1 & bitmap2). Now we
have to do like this:
	tmp = bitmap_alloc(nbits);
	bitmap_and(tmp, map1, map2, nbits);
	weight = bitmap_weight(tmp, nbits);
	bitmap_free(tmp);

This requires additional memory, adds pressure on alloc subsystem, and
way less cache-friendly than just:
	weight = bitmap_weight_and(map1, map2, nbits);

The following patches apply it for cpumask functions.

Signed-off-by: Yury Norov <yury.norov@gmail.com>

2 files changed, 23 insertions, 0 deletions

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index f65410a49fda..b2aef45af0db 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -51,6 +51,7 @@ struct device;
  *  bitmap_empty(src, nbits)                    Are all bits zero in *src?
  *  bitmap_full(src, nbits)                     Are all bits set in *src?
  *  bitmap_weight(src, nbits)                   Hamming Weight: number set bits
+ *  bitmap_weight_and(src1, src2, nbits)        Hamming Weight of and'ed bitmap
  *  bitmap_set(dst, pos, nbits)                 Set specified bit area
  *  bitmap_clear(dst, pos, nbits)               Clear specified bit area
  *  bitmap_find_next_zero_area(buf, len, pos, n, mask)  Find bit free area
@@ -164,6 +165,8 @@ bool __bitmap_intersects(const unsigned long *bitmap1,
 bool __bitmap_subset(const unsigned long *bitmap1,
 		     const unsigned long *bitmap2, unsigned int nbits);
 unsigned int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
+unsigned int __bitmap_weight_and(const unsigned long *bitmap1,
+				 const unsigned long *bitmap2, unsigned int nbits);
 void __bitmap_set(unsigned long *map, unsigned int start, int len);
 void __bitmap_clear(unsigned long *map, unsigned int start, int len);
 
@@ -439,6 +442,15 @@ unsigned int bitmap_weight(const unsigned long *src, unsigned int nbits)
 	return __bitmap_weight(src, nbits);
 }
 
+static __always_inline
+unsigned long bitmap_weight_and(const unsigned long *src1,
+				const unsigned long *src2, unsigned int nbits)
+{
+	if (small_const_nbits(nbits))
+		return hweight_long(*src1 & *src2 & BITMAP_LAST_WORD_MASK(nbits));
+	return __bitmap_weight_and(src1, src2, nbits);
+}
+
 static __always_inline void bitmap_set(unsigned long *map, unsigned int start,
 		unsigned int nbits)
 {
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 1b442fb2001f..9a71af8097ca 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -587,6 +587,17 @@ static inline unsigned int cpumask_weight(const struct cpumask *srcp)
 }
 
 /**
+ * cpumask_weight_and - Count of bits in (*srcp1 & *srcp2)
+ * @srcp1: the cpumask to count bits (< nr_cpu_ids) in.
+ * @srcp2: the cpumask to count bits (< nr_cpu_ids) in.
+ */
+static inline unsigned int cpumask_weight_and(const struct cpumask *srcp1,
+						const struct cpumask *srcp2)
+{
+	return bitmap_weight_and(cpumask_bits(srcp1), cpumask_bits(srcp2), nr_cpumask_bits);
+}
+
+/**
  * cpumask_shift_right - *dstp = *srcp >> n
  * @dstp: the cpumask result
  * @srcp: the input to shift