From 99167f6d66e509389c51732b763abd03a8187e56 Mon Sep 17 00:00:00 2001
From: Zach Brown <zab@versity.com>
Date: Wed, 27 Jul 2016 13:50:22 -0700
Subject: [PATCH] Expand little endian bitops functions

We had the start of functions that operated on little endian bitmaps.
This adds more operations and uses __packed to support unaligned bitmaps
on platforms where unaligned accesses are a problem.

Signed-off-by: Zach Brown <zab@versity.com>
---
 utils/src/bitops.h | 64 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 61 insertions(+), 3 deletions(-)

diff --git a/utils/src/bitops.h b/utils/src/bitops.h
index 5ac429fc..abfa3755 100644
--- a/utils/src/bitops.h
+++ b/utils/src/bitops.h
@@ -1,6 +1,13 @@
 #ifndef _BITOPS_H_
 #define _BITOPS_H_
 
+/*
+ * Implement little endian bitmaps in terms of native longs.  __packed
+ * is used to avoid unaligned accesses.
+ */
+
+typedef unsigned long * __packed ulong_ptr;
+
 #define BITS_PER_LONG (sizeof(long) * 8)
 #if __BYTE_ORDER == __LITTLE_ENDIAN
 #define BITOP_LE_SWIZZLE        0
@@ -8,13 +15,64 @@
 #define BITOP_LE_SWIZZLE        ((BITS_PER_LONG-1) & ~0x7)
 #endif
 
-static inline void set_bit_le(int nr, void *addr)
+static inline ulong_ptr nr_word(int nr, ulong_ptr longs)
 {
-	unsigned long *longs = addr;
+	return &longs[nr / BITS_PER_LONG];
+}
+
+static inline unsigned long nr_mask(int nr)
+{
+	return 1UL << (nr % BITS_PER_LONG);
+}
+
+static inline int test_bit(int nr, ulong_ptr longs)
+{
+	return !!(*nr_word(nr, longs) & nr_mask(nr));
+}
+
+static inline void set_bit(int nr, ulong_ptr longs)
+{
+	*nr_word(nr, longs) |= nr_mask(nr);
+}
+
+static inline void clear_bit(int nr, ulong_ptr longs)
+{
+	*nr_word(nr, longs) &= ~nr_mask(nr);
+}
+
+static inline int test_bit_le(int nr, void *addr)
+{
+	return test_bit(nr ^ BITOP_LE_SWIZZLE, addr);
+}
+
+static inline int test_and_set_bit_le(int nr, void *addr)
+{
+	int ret;
 
 	nr ^= BITOP_LE_SWIZZLE;
+	ret = test_bit(nr, addr);
+	set_bit(nr, addr);
+	return ret;
+}
 
-	longs[nr / BITS_PER_LONG] |= 1UL << (nr & (BITS_PER_LONG - 1));
+static inline void set_bit_le(int nr, void *addr)
+{
+	set_bit(nr ^ BITOP_LE_SWIZZLE, addr);
+}
+
+static inline void clear_bit_le(int nr, void *addr)
+{
+	clear_bit(nr ^ BITOP_LE_SWIZZLE, addr);
+}
+
+static inline int test_and_clear_bit_le(int nr, void *addr)
+{
+	int ret;
+
+	nr ^= BITOP_LE_SWIZZLE;
+	ret = test_bit(nr, addr);
+	clear_bit(nr, addr);
+	return ret;
 }
 
 #endif