2024-05-29 02:01:08

by Zhang Yi

Subject: [RFC PATCH v4 2/8] math64: add rem_u64() to just return the remainder

From: Zhang Yi <[email protected]>

Add a new helper rem_u64() to only get the remainder of unsigned 64bit
divide with 32bit divisor.

Signed-off-by: Zhang Yi <[email protected]>
---
include/linux/math64.h | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/include/linux/math64.h b/include/linux/math64.h
index d34def7f9a8c..618df4862091 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -3,6 +3,7 @@
#define _LINUX_MATH64_H

#include <linux/types.h>
+#include <linux/log2.h>
#include <linux/math.h>
#include <asm/div64.h>
#include <vdso/math64.h>
@@ -12,6 +13,20 @@
#define div64_long(x, y) div64_s64((x), (y))
#define div64_ul(x, y) div64_u64((x), (y))

+/**
+ * rem_u64 - remainder of unsigned 64bit divide with 32bit divisor
+ * @dividend: unsigned 64bit dividend
+ * @divisor: unsigned 32bit divisor
+ *
+ * Return: dividend % divisor
+ */
+static inline u32 rem_u64(u64 dividend, u32 divisor)
+{
+ if (is_power_of_2(divisor))
+ return dividend & (divisor - 1);
+ return dividend % divisor;
+}
+
/**
* div_u64_rem - unsigned 64bit divide with 32bit divisor with remainder
* @dividend: unsigned 64bit dividend
@@ -86,6 +101,15 @@ static inline s64 div64_s64(s64 dividend, s64 divisor)
#define div64_long(x, y) div_s64((x), (y))
#define div64_ul(x, y) div_u64((x), (y))

+#ifndef rem_u64
+static inline u32 rem_u64(u64 dividend, u32 divisor)
+{
+ if (is_power_of_2(divisor))
+ return dividend & (divisor - 1);
+ return do_div(dividend, divisor);
+}
+#endif
+
#ifndef div_u64_rem
static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
{
--
2.39.2

2024-05-31 14:20:38

by Darrick J. Wong

Subject: Re: [RFC PATCH v4 2/8] math64: add rem_u64() to just return the remainder

On Wed, May 29, 2024 at 05:52:00PM +0800, Zhang Yi wrote:
> From: Zhang Yi <[email protected]>
>
> Add a new helper rem_u64() to only get the remainder of unsigned 64bit
> divide with 32bit divisor.
>
> Signed-off-by: Zhang Yi <[email protected]>

Modulo hch's comments,
Reviewed-by: Darrick J. Wong <[email protected]>

--D

> ---
> include/linux/math64.h | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/include/linux/math64.h b/include/linux/math64.h
> index d34def7f9a8c..618df4862091 100644
> --- a/include/linux/math64.h
> +++ b/include/linux/math64.h
> @@ -3,6 +3,7 @@
> #define _LINUX_MATH64_H
>
> #include <linux/types.h>
> +#include <linux/log2.h>
> #include <linux/math.h>
> #include <asm/div64.h>
> #include <vdso/math64.h>
> @@ -12,6 +13,20 @@
> #define div64_long(x, y) div64_s64((x), (y))
> #define div64_ul(x, y) div64_u64((x), (y))
>
> +/**
> + * rem_u64 - remainder of unsigned 64bit divide with 32bit divisor
> + * @dividend: unsigned 64bit dividend
> + * @divisor: unsigned 32bit divisor
> + *
> + * Return: dividend % divisor
> + */
> +static inline u32 rem_u64(u64 dividend, u32 divisor)
> +{
> + if (is_power_of_2(divisor))
> + return dividend & (divisor - 1);
> + return dividend % divisor;
> +}
> +
> /**
> * div_u64_rem - unsigned 64bit divide with 32bit divisor with remainder
> * @dividend: unsigned 64bit dividend
> @@ -86,6 +101,15 @@ static inline s64 div64_s64(s64 dividend, s64 divisor)
> #define div64_long(x, y) div_s64((x), (y))
> #define div64_ul(x, y) div_u64((x), (y))
>
> +#ifndef rem_u64
> +static inline u32 rem_u64(u64 dividend, u32 divisor)
> +{
> + if (is_power_of_2(divisor))
> + return dividend & (divisor - 1);
> + return do_div(dividend, divisor);
> +}
> +#endif
> +
> #ifndef div_u64_rem
> static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
> {
> --
> 2.39.2
>
>

2024-05-31 15:08:01

by Christoph Hellwig

Subject: Re: [RFC PATCH v4 2/8] math64: add rem_u64() to just return the remainder

> +#ifndef rem_u64
> +static inline u32 rem_u64(u64 dividend, u32 divisor)
> +{
> + if (is_power_of_2(divisor))
> + return dividend & (divisor - 1);
> + return do_div(dividend, divisor);
> +}
> +#endif

This ifndef seems superflous.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <[email protected]>