2 files changed, 27 insertions, 10 deletions

diff --git a/include/linux/math64.h b/include/linux/math64.h
index c1a5f81501ff..c87f1528703a 100644
--- a/include/linux/math64.h
+++ b/include/linux/math64.h
@@ -81,4 +81,25 @@ static inline s64 div_s64(s64 dividend, s32 divisor)
 }
 #endif
 
+u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder);
+
+static __always_inline u32
+__iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
+{
+        u32 ret = 0;
+
+        while (dividend >= divisor) {
+                /* The following asm() prevents the compiler from
+                   optimising this loop into a modulo operation.  */
+                asm("" : "+rm"(dividend));
+
+                dividend -= divisor;
+                ret++;
+        }
+
+        *remainder = dividend;
+
+        return ret;
+}
+
 #endif /* _LINUX_MATH64_H */
diff --git a/include/linux/time.h b/include/linux/time.h
index d32ef0ad4c0a..e15206a7e82e 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -6,6 +6,7 @@
 #ifdef __KERNEL__
 # include <linux/cache.h>
 # include <linux/seqlock.h>
+# include <linux/math64.h>
 #endif
 
 #ifndef _STRUCT_TIMESPEC
@@ -169,18 +170,13 @@ extern struct timeval ns_to_timeval(const s64 nsec);
  * timespec_add_ns - Adds nanoseconds to a timespec
  * @a:          pointer to timespec to be incremented
  * @ns:         unsigned nanoseconds value to be added
+ *
+ * This must always be inlined because its used from the x86-64 vdso,
+ * which cannot call other kernel functions.
  */
-static inline void timespec_add_ns(struct timespec *a, u64 ns)
+static __always_inline void timespec_add_ns(struct timespec *a, u64 ns)
 {
-        ns += a->tv_nsec;
-        while(unlikely(ns >= NSEC_PER_SEC)) {
-                /* The following asm() prevents the compiler from
-                 * optimising this loop into a modulo operation.  */
-                asm("" : "+r"(ns));
-
-                ns -= NSEC_PER_SEC;
-                a->tv_sec++;
-        }
+        a->tv_sec += __iter_div_u64_rem(a->tv_nsec + ns, NSEC_PER_SEC, &ns);
         a->tv_nsec = ns;
 }
 #endif /* __KERNEL__ */