From: Yury Norov <ynorov@nvidia.com>
Date: Mon, 2 Mar 2026 01:11:55 +0000 (-0500)
Subject: bitmap: introduce bitmap_weighted_xor()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d57e74f10461b80c77d1678f646720f616fb8553;p=thirdparty%2Fkernel%2Flinux.git

bitmap: introduce bitmap_weighted_xor()

The function helps to XOR bitmaps and calculate Hamming weight of
the result in one pass.

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Yury Norov <ynorov@nvidia.com>
---

diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
index 9c0d1de443500..b007d54a9036a 100644
--- a/include/linux/bitmap.h
+++ b/include/linux/bitmap.h
@@ -46,6 +46,7 @@ struct device;
  *  bitmap_and(dst, src1, src2, nbits)          *dst = *src1 & *src2
  *  bitmap_or(dst, src1, src2, nbits)           *dst = *src1 | *src2
  *  bitmap_weighted_or(dst, src1, src2, nbits)	*dst = *src1 | *src2. Returns Hamming Weight of dst
+ *  bitmap_weighted_xor(dst, src1, src2, nbits)	*dst = *src1 ^ *src2. Returns Hamming Weight of dst
  *  bitmap_xor(dst, src1, src2, nbits)          *dst = *src1 ^ *src2
  *  bitmap_andnot(dst, src1, src2, nbits)       *dst = *src1 & ~(*src2)
  *  bitmap_complement(dst, src, nbits)          *dst = ~(*src)
@@ -169,6 +170,8 @@ void __bitmap_or(unsigned long *dst, const unsigned long *bitmap1,
 		 const unsigned long *bitmap2, unsigned int nbits);
 unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitmap1,
 				  const unsigned long *bitmap2, unsigned int nbits);
+unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1,
+				  const unsigned long *bitmap2, unsigned int nbits);
 void __bitmap_xor(unsigned long *dst, const unsigned long *bitmap1,
 		  const unsigned long *bitmap2, unsigned int nbits);
 bool __bitmap_andnot(unsigned long *dst, const unsigned long *bitmap1,
@@ -353,6 +356,18 @@ unsigned int bitmap_weighted_or(unsigned long *dst, const unsigned long *src1,
 	}
 }
 
+static __always_inline
+unsigned int bitmap_weighted_xor(unsigned long *dst, const unsigned long *src1,
+				const unsigned long *src2, unsigned int nbits)
+{
+	if (small_const_nbits(nbits)) {
+		*dst = *src1 ^ *src2;
+		return hweight_long(*dst & BITMAP_LAST_WORD_MASK(nbits));
+	} else {
+		return __bitmap_weighted_xor(dst, src1, src2, nbits);
+	}
+}
+
 static __always_inline
 void bitmap_xor(unsigned long *dst, const unsigned long *src1,
 		const unsigned long *src2, unsigned int nbits)
diff --git a/lib/bitmap.c b/lib/bitmap.c
index 1b897f94e0ffd..b9bfa157e0950 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -363,6 +363,13 @@ unsigned int __bitmap_weighted_or(unsigned long *dst, const unsigned long *bitma
 }
 EXPORT_SYMBOL(__bitmap_weighted_or);
 
+unsigned int __bitmap_weighted_xor(unsigned long *dst, const unsigned long *bitmap1,
+				  const unsigned long *bitmap2, unsigned int bits)
+{
+	return BITMAP_WEIGHT(({dst[idx] = bitmap1[idx] ^ bitmap2[idx]; dst[idx]; }), bits);
+}
+EXPORT_SYMBOL(__bitmap_weighted_xor);
+
 void __bitmap_set(unsigned long *map, unsigned int start, int len)
 {
 	unsigned long *p = map + BIT_WORD(start);