new helper: iov_iter_rw()

Get either READ or WRITE out of iter->type.

Signed-off-by: Omar Sandoval <[e-mail]>
Signed-off-by: Al Viro <[e-mail]>

include/linux/uio.h

···
 }
 
 /*
+ * Get one of READ or WRITE out of iter->type without any other flags OR'd in
+ * with it.
+ *
+ * The ?: is just for type safety.
+ */
+#define iov_iter_rw(i) ((0 ? (struct iov_iter *)0 : (i))->type & RW_MASK)
+
+/*
  * Cap the iov_iter by given limit; note that the second argument is
  * *not* the new size - it's upper limit for such.  Passing it a value
  * greater than the amount of data in iov_iter is fine - it'll just do