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authorBrian Behlendorf <behlendorf1@llnl.gov>2010-10-26 14:23:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-26 16:52:19 -0700
commit658716d19f8f155c67d4677ba68034b8e492dfbe (patch)
tree8743b9a16606a63dc33f93c580367baf36692454 /include
parent5d051decfc27cdf33fbbd2bfca958d0d2c903569 (diff)
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')
-rw-r--r--include/linux/kernel.h5
-rw-r--r--include/linux/math64.h12
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 */
/**

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