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| author | Brian Behlendorf <behlendorf1@llnl.gov> | 2010-10-26 14:23:10 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-26 16:52:19 -0700 |
| commit | 658716d19f8f155c67d4677ba68034b8e492dfbe (patch) | |
| tree | 8743b9a16606a63dc33f93c580367baf36692454 /include/linux | |
| parent | 5d051decfc27cdf33fbbd2bfca958d0d2c903569 (diff) | |
| download | blackbird-op-linux-658716d19f8f155c67d4677ba68034b8e492dfbe.tar.gz blackbird-op-linux-658716d19f8f155c67d4677ba68034b8e492dfbe.zip | |
div64_u64(): improve precision on 32bit platforms
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>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/kernel.h | 5 | ||||
| -rw-r--r-- | include/linux/math64.h | 12 |
2 files changed, 17 insertions, 0 deletions
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 77b04ed037df..450092c1e35f 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -173,6 +173,11 @@ extern int _cond_resched(void); (__x < 0) ? -__x : __x; \ }) +#define abs64(x) ({ \ + s64 __x = (x); \ + (__x < 0) ? -__x : __x; \ + }) + #ifdef CONFIG_PROVE_LOCKING void might_fault(void); #else diff --git a/include/linux/math64.h b/include/linux/math64.h index c87f1528703a..23fcdfcba81b 100644 --- a/include/linux/math64.h +++ b/include/linux/math64.h @@ -35,6 +35,14 @@ static inline u64 div64_u64(u64 dividend, u64 divisor) return dividend / divisor; } +/** + * div64_s64 - signed 64bit divide with 64bit divisor + */ +static inline s64 div64_s64(s64 dividend, s64 divisor) +{ + return dividend / divisor; +} + #elif BITS_PER_LONG == 32 #ifndef div_u64_rem @@ -53,6 +61,10 @@ extern s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder); extern u64 div64_u64(u64 dividend, u64 divisor); #endif +#ifndef div64_s64 +extern s64 div64_s64(s64 dividend, s64 divisor); +#endif + #endif /* BITS_PER_LONG */ /** |
