2 files changed, 53 insertions, 0 deletions

diff --git a/include/linux/math64.h b/include/linux/math64.h
index 2913b86eb12a..69ed5f5e9f6e 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -31,6 +31,15 @@ static inline s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
 }
 
 /**
+ * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
+ */
+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
  */
 static inline u64 div64_u64(u64 dividend, u64 divisor)
@@ -63,6 +72,10 @@ 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);
 #endif
diff --git a/lib/div64.c b/lib/div64.c
index a163b6caef73..4382ad77777e 100644
--- a/lib/div64.c
+++ b/lib/div64.c
@@ -79,6 +79,46 @@ EXPORT_SYMBOL(div_s64_rem);
 #endif
 
 /**
+ * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
+ * @dividend:   64bit dividend
+ * @divisor:    64bit divisor
+ * @remainder:  64bit remainder
+ *
+ * This implementation is a comparable to algorithm used by div64_u64.
+ * But this operation, which includes math for calculating the remainder,
+ * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
+ * systems.
+ */
+#ifndef div64_u64_rem
+u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
+{
+        u32 high = divisor >> 32;
+        u64 quot;
+
+        if (high == 0) {
+                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--;
+
+                *remainder = dividend - quot * divisor;
+                if (*remainder >= divisor) {
+                        quot++;
+                        *remainder -= divisor;
+                }
+        }
+
+        return quot;
+}
+EXPORT_SYMBOL(div64_u64_rem);
+#endif
+
+/**
  * div64_u64 - unsigned 64bit divide with 64bit divisor
  * @dividend:   64bit dividend
  * @divisor:    64bit divisor