math64: New div64_u64_rem helper

Provide an extended version of div64_u64() that
also returns the remainder of the division.

We are going to need this to refine the cputime
scaling code.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/math64.h b/include/linux/math64.h
index b8ba85544721fd911ce52c61e08a8ba88328ecfe..931a619407bfc477b1ceabe06487a7537f10baba 100644 (file)
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -29,6 +29,15 @@ static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
        return dividend / divisor;
 }
 
+/**
+ * div64_u64_rem - unsigned 64bit divide with 64bit divisor
+ */
+static inline u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
+{
+       *remainder = dividend % divisor;
+       return dividend / divisor;
+}
+
 /**
  * div64_u64 - unsigned 64bit divide with 64bit divisor
  */
@@ -61,8 +70,16 @@ static inline u64 div_u64_rem(u64 dividend, u32 divisor, u32 *remainder)
 extern s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder);
 #endif
 
+#ifndef div64_u64_rem
+extern u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder);
+#endif
+
 #ifndef div64_u64
-extern u64 div64_u64(u64 dividend, u64 divisor);
+static inline u64 div64_u64(u64 dividend, u64 divisor)
+{
+       u64 remainder;
+       return div64_u64_rem(dividend, divisor, &remainder);
+}
 #endif
 
 #ifndef div64_s64

diff --git a/lib/div64.c b/lib/div64.c
index a163b6caef73fdc26e19f8d18ef66604a03b1cf8..3af5728d95fda3c2aa740deec3f6de69cc847e94 100644 (file)
--- a/lib/div64.c
+++ b/lib/div64.c
@@ -79,9 +79,10 @@ EXPORT_SYMBOL(div_s64_rem);
 #endif
 
 /**
- * div64_u64 - unsigned 64bit divide with 64bit divisor
+ * div64_u64_rem - unsigned 64bit divide with 64bit divisor and 64bit remainder
  * @dividend:  64bit dividend
  * @divisor:   64bit divisor
+ * @remainder:  64bit remainder
  *
  * This implementation is a modified version of the algorithm proposed
  * by the book 'Hacker's Delight'.  The original source and full proof
@@ -89,27 +90,33 @@ EXPORT_SYMBOL(div_s64_rem);
  *
  * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt'
  */
-#ifndef div64_u64
-u64 div64_u64(u64 dividend, u64 divisor)
+#ifndef div64_u64_rem
+u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
 {
        u32 high = divisor >> 32;
        u64 quot;
 
        if (high == 0) {
-               quot = div_u64(dividend, divisor);
+               u32 rem32;
+               quot = div_u64_rem(dividend, divisor, &rem32);
+               *remainder = rem32;
        } else {
                int n = 1 + fls(high);
                quot = div_u64(dividend >> n, divisor >> n);
 
                if (quot != 0)
                        quot--;
-               if ((dividend - quot * divisor) >= divisor)
+
+               *remainder = dividend - quot * divisor;
+               if (*remainder >= divisor) {
                        quot++;
+                       *remainder -= divisor;
+               }
        }
 
        return quot;
 }
-EXPORT_SYMBOL(div64_u64);
+EXPORT_SYMBOL(div64_u64_rem);
 #endif
 
 /**