+/*
+ * Some copy_from_user() implementations do not return the exact number of
+ * bytes remaining to copy on a fault. But copy_mount_options() requires that.
+ * Note that this function differs from copy_from_user() in that it will oops
+ * on bad values of `to', rather than returning a short copy.
+ */
+static long
+exact_copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+ char *t = to;
+ const char __user *f = from;
+ char c;
+
+ if (!access_ok(VERIFY_READ, from, n))
+ return n;
+
+ while (n) {
+ if (__get_user(c, f)) {
+ memset(t, 0, n);
+ break;
+ }
+ *t++ = c;
+ f++;
+ n--;
+ }
+ return n;
+}
+
+int copy_mount_options(const void __user *data, unsigned long *where)