linux-kernel - [RFC PATCH v2 07/11] lib: implement find_{first,next}_{zero,one}_and_zero

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Message-Id: <20220218210633.23345-8-mathieu.desnoyers@efficios.com>
Date:   Fri, 18 Feb 2022 16:06:29 -0500
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        "H . Peter Anvin" <hpa@...or.com>, Paul Turner <pjt@...gle.com>,
        linux-api@...r.kernel.org,
        Christian Brauner <christian.brauner@...ntu.com>,
        Florian Weimer <fw@...eb.enyo.de>, David.Laight@...LAB.COM,
        carlos@...hat.com, Peter Oskolkov <posk@...k.io>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [RFC PATCH v2 07/11] lib: implement find_{first,next}_{zero,one}_and_zero_bit

Allow finding the first or next bit within two input bitmasks which is
either:

- both zero and zero,
- respectively one and zero.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
---
 include/linux/find.h | 110 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)

diff --git a/include/linux/find.h b/include/linux/find.h
index 41941cb9cad7..9b6edd00b45e 100644
--- a/include/linux/find.h
+++ b/include/linux/find.h
@@ -76,6 +76,66 @@ unsigned long find_next_and_bit(const unsigned long *addr1,
 }
 #endif
 
+#ifndef find_next_one_and_zero_bit
+/**
+ * find_next_one_and_zero_bit - find the next bit which is one in addr1 and zero in addr2
+ * @addr1: The first address to base the search on
+ * @addr2: The second address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number for the next bit set in addr1 and cleared in addr2
+ * If no corresponding bits meet this criterion, returns @size.
+ */
+static inline
+unsigned long find_next_one_and_zero_bit(const unsigned long *addr1,
+		const unsigned long *addr2, unsigned long size,
+		unsigned long offset)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val;
+
+		if (unlikely(offset >= size))
+			return size;
+
+		val = *addr1 & ~*addr2 & GENMASK(size - 1, offset);
+		return val ? __ffs(val) : size;
+	}
+
+	return _find_next_bit(addr1, addr2, size, offset, 0UL, ~0UL, 0);
+}
+#endif
+
+#ifndef find_next_zero_and_zero_bit
+/**
+ * find_next_zero_and_zero_bit - find the next bit which is zero in addr1 and addr2
+ * @addr1: The first address to base the search on
+ * @addr2: The second address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number for the next bit cleared in addr1 and addr2
+ * If no corresponding bits meet this criterion, returns @size.
+ */
+static inline
+unsigned long find_next_zero_and_zero_bit(const unsigned long *addr1,
+		const unsigned long *addr2, unsigned long size,
+		unsigned long offset)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val;
+
+		if (unlikely(offset >= size))
+			return size;
+
+		val = ~*addr1 & ~*addr2 & GENMASK(size - 1, offset);
+		return val ? __ffs(val) : size;
+	}
+
+	return _find_next_bit(addr1, addr2, size, offset, ~0UL, ~0UL, 0);
+}
+#endif
+
 #ifndef find_next_zero_bit
 /**
  * find_next_zero_bit - find the next cleared bit in a memory region
@@ -173,6 +233,56 @@ unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
 }
 #endif
 
+#ifndef find_first_one_and_zero_bit
+/**
+ * find_first_one_and_zero_bit - find the first bit which is one in addr1 and zero in addr2
+ * @addr1: The first address to base the search on
+ * @addr2: The second address to base the search on
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number for the first bit set in addr1 and cleared in addr2
+ * If no corresponding bits meet this criterion, returns @size.
+ */
+static inline
+unsigned long find_first_one_and_zero_bit(const unsigned long *addr1,
+				 const unsigned long *addr2,
+				 unsigned long size)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val = *addr1 & ~*addr2 & GENMASK(size - 1, 0);
+
+		return val ? __ffs(val) : size;
+	}
+
+	return _find_next_bit(addr1, addr2, size, 0, 0UL, ~0UL, 0);
+}
+#endif
+
+#ifndef find_first_zero_and_zero_bit
+/**
+ * find_first_zero_and_zero_bit - find the first bit which is zero in addr1 and addr2
+ * @addr1: The first address to base the search on
+ * @addr2: The second address to base the search on
+ * @size: The bitmap size in bits
+ *
+ * Returns the bit number for the first bit cleared in addr1 and addr2
+ * If no corresponding bits meet this criterion, returns @size.
+ */
+static inline
+unsigned long find_first_zero_and_zero_bit(const unsigned long *addr1,
+				 const unsigned long *addr2,
+				 unsigned long size)
+{
+	if (small_const_nbits(size)) {
+		unsigned long val = ~*addr1 & ~*addr2 & GENMASK(size - 1, 0);
+
+		return val ? __ffs(val) : size;
+	}
+
+	return _find_next_bit(addr1, addr2, size, 0, ~0UL, ~0UL, 0);
+}
+#endif
+
 #ifndef find_last_bit
 /**
  * find_last_bit - find the last set bit in a memory region
-- 
2.17.1