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>

1 files changed, 11 insertions, 0 deletions

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