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658716d19f
The current implementation of div64_u64 for 32bit systems returns an approximately correct result when the divisor exceeds 32bits. Since doing 64bit division using 32bit hardware is a long since solved problem we just use one of the existing proven methods. Additionally, add a div64_s64 function to correctly handle doing signed 64bit division. Addresses https://bugzilla.redhat.com/show_bug.cgi?id=616105 Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Ben Woodard <bwoodard@llnl.gov> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Mark Grondona <mgrondona@llnl.gov> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
118 lines
2.4 KiB
C
118 lines
2.4 KiB
C
#ifndef _LINUX_MATH64_H
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#define _LINUX_MATH64_H
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#include <linux/types.h>
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#include <asm/div64.h>
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#if BITS_PER_LONG == 64
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/**
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* div_u64_rem - unsigned 64bit divide with 32bit divisor with remainder
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*
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* This is commonly provided by 32bit archs to provide an optimized 64bit
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* divide.
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*/
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static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
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{
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*remainder = dividend % divisor;
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return dividend / divisor;
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}
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/**
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* div_s64_rem - signed 64bit divide with 32bit divisor with remainder
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*/
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static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
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{
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*remainder = dividend % divisor;
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return dividend / divisor;
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}
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/**
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* div64_u64 - unsigned 64bit divide with 64bit divisor
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*/
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static inline u64 div64_u64(u64 dividend, u64 divisor)
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{
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return dividend / divisor;
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}
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/**
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* div64_s64 - signed 64bit divide with 64bit divisor
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*/
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static inline s64 div64_s64(s64 dividend, s64 divisor)
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{
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return dividend / divisor;
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}
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#elif BITS_PER_LONG == 32
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#ifndef div_u64_rem
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static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
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{
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*remainder = do_div(dividend, divisor);
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return dividend;
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}
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#endif
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#ifndef div_s64_rem
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extern s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder);
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#endif
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#ifndef div64_u64
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extern u64 div64_u64(u64 dividend, u64 divisor);
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#endif
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#ifndef div64_s64
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extern s64 div64_s64(s64 dividend, s64 divisor);
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#endif
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#endif /* BITS_PER_LONG */
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/**
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* div_u64 - unsigned 64bit divide with 32bit divisor
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*
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* This is the most common 64bit divide and should be used if possible,
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* as many 32bit archs can optimize this variant better than a full 64bit
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* divide.
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*/
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#ifndef div_u64
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static inline u64 div_u64(u64 dividend, u32 divisor)
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{
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u32 remainder;
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return div_u64_rem(dividend, divisor, &remainder);
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}
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#endif
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/**
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* div_s64 - signed 64bit divide with 32bit divisor
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*/
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#ifndef div_s64
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static inline s64 div_s64(s64 dividend, s32 divisor)
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{
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s32 remainder;
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return div_s64_rem(dividend, divisor, &remainder);
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}
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#endif
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u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder);
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static __always_inline u32
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__iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
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{
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u32 ret = 0;
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while (dividend >= divisor) {
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/* The following asm() prevents the compiler from
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optimising this loop into a modulo operation. */
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asm("" : "+rm"(dividend));
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dividend -= divisor;
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ret++;
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}
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*remainder = dividend;
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return ret;
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}
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#endif /* _LINUX_MATH64_H */
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