Grab math.h from kernel source tree

This gets us round_up() and round_down()

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 151 insertions, 0 deletions

diff --git a/include/linux/math.h b/include/linux/math.h
new file mode 100644
index 00000000..3cf6726d
--- /dev/null
+++ b/include/linux/math.h
@@ -0,0 +1,151 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MATH_H
+#define _LINUX_MATH_H
+
+/*
+ * This looks more complex than it should be. But we need to
+ * get the type for the ~ right in round_down (it needs to be
+ * as wide as the result!), and we want to evaluate the macro
+ * arguments just once each.
+ */
+#define __round_mask(x, y) ((__typeof__(x))((y)-1))
+
+/**
+ * round_up - round up to next specified power of 2
+ * @x: the value to round
+ * @y: multiple to round up to (must be a power of 2)
+ *
+ * Rounds @x up to next multiple of @y (which must be a power of 2).
+ * To perform arbitrary rounding up, use roundup() below.
+ */
+#define round_up(x, y) ((((x)-1) | __round_mask(x, y))+1)
+
+/**
+ * round_down - round down to next specified power of 2
+ * @x: the value to round
+ * @y: multiple to round down to (must be a power of 2)
+ *
+ * Rounds @x down to next multiple of @y (which must be a power of 2).
+ * To perform arbitrary rounding down, use rounddown() below.
+ */
+#define round_down(x, y) ((x) & ~__round_mask(x, y))
+
+#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
+
+#define DIV_ROUND_DOWN_ULL(ll, d) \
+	({ unsigned long long _tmp = (ll); do_div(_tmp, d); _tmp; })
+
+#define DIV_ROUND_UP_ULL(ll, d) \
+	DIV_ROUND_DOWN_ULL((unsigned long long)(ll) + (d) - 1, (d))
+
+#if BITS_PER_LONG == 32
+# define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP_ULL(ll, d)
+#else
+# define DIV_ROUND_UP_SECTOR_T(ll,d) DIV_ROUND_UP(ll,d)
+#endif
+
+/**
+ * roundup - round up to the next specified multiple
+ * @x: the value to up
+ * @y: multiple to round up to
+ *
+ * Rounds @x up to next multiple of @y. If @y will always be a power
+ * of 2, consider using the faster round_up().
+ */
+#define roundup(x, y) (					\
+{							\
+	typeof(y) __y = y;				\
+	(((x) + (__y - 1)) / __y) * __y;		\
+}							\
+)
+/**
+ * rounddown - round down to next specified multiple
+ * @x: the value to round
+ * @y: multiple to round down to
+ *
+ * Rounds @x down to next multiple of @y. If @y will always be a power
+ * of 2, consider using the faster round_down().
+ */
+#define rounddown(x, y) (				\
+{							\
+	typeof(x) __x = (x);				\
+	__x - (__x % (y));				\
+}							\
+)
+
+/*
+ * Divide positive or negative dividend by positive or negative divisor
+ * and round to closest integer. Result is undefined for negative
+ * divisors if the dividend variable type is unsigned and for negative
+ * dividends if the divisor variable type is unsigned.
+ */
+#define DIV_ROUND_CLOSEST(x, divisor)(			\
+{							\
+	typeof(x) __x = x;				\
+	typeof(divisor) __d = divisor;			\
+	(((typeof(x))-1) > 0 ||				\
+	 ((typeof(divisor))-1) > 0 ||			\
+	 (((__x) > 0) == ((__d) > 0))) ?		\
+		(((__x) + ((__d) / 2)) / (__d)) :	\
+		(((__x) - ((__d) / 2)) / (__d));	\
+}							\
+)
+/*
+ * Same as above but for u64 dividends. divisor must be a 32-bit
+ * number.
+ */
+#define DIV_ROUND_CLOSEST_ULL(x, divisor)(		\
+{							\
+	typeof(divisor) __d = divisor;			\
+	unsigned long long _tmp = (x) + (__d) / 2;	\
+	do_div(_tmp, __d);				\
+	_tmp;						\
+}							\
+)
+
+/*
+ * Multiplies an integer by a fraction, while avoiding unnecessary
+ * overflow or loss of precision.
+ */
+#define mult_frac(x, numer, denom)(			\
+{							\
+	typeof(x) quot = (x) / (denom);			\
+	typeof(x) rem  = (x) % (denom);			\
+	(quot * (numer)) + ((rem * (numer)) / (denom));	\
+}							\
+)
+
+#define sector_div(a, b) do_div(a, b)
+
+/**
+ * reciprocal_scale - "scale" a value into range [0, ep_ro)
+ * @val: value
+ * @ep_ro: right open interval endpoint
+ *
+ * Perform a "reciprocal multiplication" in order to "scale" a value into
+ * range [0, @ep_ro), where the upper interval endpoint is right-open.
+ * This is useful, e.g. for accessing a index of an array containing
+ * @ep_ro elements, for example. Think of it as sort of modulus, only that
+ * the result isn't that of modulo. ;) Note that if initial input is a
+ * small value, then result will return 0.
+ *
+ * Return: a result based on @val in interval [0, @ep_ro).
+ */
+static inline u32 reciprocal_scale(u32 val, u32 ep_ro)
+{
+	return (u32)(((u64) val * ep_ro) >> 32);
+}
+
+u64 int_pow(u64 base, unsigned int exp);
+unsigned long int_sqrt(unsigned long);
+
+#if BITS_PER_LONG < 64
+u32 int_sqrt64(u64 x);
+#else
+static inline u32 int_sqrt64(u64 x)
+{
+	return (u32)int_sqrt(x);
+}
+#endif
+
+#endif	/* _LINUX_MATH_H */