[PATCH v2 1/8] lib/find: add find_next_and_andnot_bit()

[Yury Norov]

Similarly to find_nth_and_andnot_bit(), find_next_and_andnot_bit() is
a convenient helper that allows traversing bitmaps without storing
intermediate results in a temporary bitmap.

In the following patches the function is used to implement NUMA-aware
CPUs enumeration.

Signed-off-by: Yury Norov <yury.norov@xxxxxxxxx>
---
 include/linux/find.h | 43 +++++++++++++++++++++++++++++++++++++++++++
 lib/find_bit.c       | 12 ++++++++++++
 2 files changed, 55 insertions(+)

diff --git a/include/linux/find.h b/include/linux/find.h
index 5e4f39ef2e72..90b68d76c073 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -16,6 +16,9 @@ unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned l
 					unsigned long nbits, unsigned long start);
 unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
 					unsigned long nbits, unsigned long start);
+unsigned long _find_next_and_andnot_bit(const unsigned long *addr1, const unsigned long *addr2,
+					const unsigned long *addr3, unsigned long nbits,
+					unsigned long start);
 unsigned long _find_next_zero_bit(const unsigned long *addr, unsigned long nbits,
 					 unsigned long start);
 extern unsigned long _find_first_bit(const unsigned long *addr, unsigned long size);
@@ -159,6 +162,40 @@ unsigned long find_next_or_bit(const unsigned long *addr1,
 }
 #endif
 
+#ifndef find_next_and_andnot_bit
+/**
+ * find_next_and_andnot_bit - find the next bit set in *addr1 and *addr2,
+ *			      excluding all the bits in *addr3
+ * @addr1: The first address to base the search on
+ * @addr2: The second address to base the search on
+ * @addr3: The third address to base the search on
+ * @size: The bitmap size in bits
+ * @offset: The bitnumber to start searching at
+ *
+ * Return: the bit number for the next set bit
+ * If no bits are set, returns @size.
+ */
+static __always_inline
+unsigned long find_next_and_andnot_bit(const unsigned long *addr1,
+				   const unsigned long *addr2,
+				   const unsigned long *addr3,
+				   unsigned long size,
+				   unsigned long offset)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val;
+
+		if (unlikely(offset >= size))
+			return size;
+
+		val = *addr1 & *addr2 & ~*addr3 & GENMASK(size - 1, offset);
+		return val ? __ffs(val) : size;
+	}
+
+	return _find_next_and_andnot_bit(addr1, addr2, addr3, size, offset);
+}
+#endif
+
 #ifndef find_next_zero_bit
 /**
  * find_next_zero_bit - find the next cleared bit in a memory region
@@ -568,6 +605,12 @@ unsigned long find_next_bit_le(const void *addr, unsigned
 	     (bit) = find_next_andnot_bit((addr1), (addr2), (size), (bit)), (bit) < (size);\
 	     (bit)++)
 
+#define for_each_and_andnot_bit(bit, addr1, addr2, addr3, size) \
+	for ((bit) = 0;									\
+	     (bit) = find_next_and_andnot_bit((addr1), (addr2), (addr3), (size), (bit)),\
+	     (bit) < (size);								\
+	     (bit)++)
+
 #define for_each_or_bit(bit, addr1, addr2, size) \
 	for ((bit) = 0;									\
 	     (bit) = find_next_or_bit((addr1), (addr2), (size), (bit)), (bit) < (size);\
diff --git a/lib/find_bit.c b/lib/find_bit.c
index 32f99e9a670e..4403e00890b1 100644
--- a/lib/find_bit.c
+++ b/lib/find_bit.c
@@ -182,6 +182,18 @@ unsigned long _find_next_andnot_bit(const unsigned long *addr1, const unsigned l
 EXPORT_SYMBOL(_find_next_andnot_bit);
 #endif
 
+#ifndef find_next_and_andnot_bit
+unsigned long _find_next_and_andnot_bit(const unsigned long *addr1,
+					const unsigned long *addr2,
+					const unsigned long *addr3,
+					unsigned long nbits,
+					unsigned long start)
+{
+	return FIND_NEXT_BIT(addr1[idx] & addr2[idx] & ~addr3[idx], /* nop */, nbits, start);
+}
+EXPORT_SYMBOL(_find_next_and_andnot_bit);
+#endif
+
 #ifndef find_next_or_bit
 unsigned long _find_next_or_bit(const unsigned long *addr1, const unsigned long *addr2,
 					unsigned long nbits, unsigned long start)
-- 
2.34.1