io_uring: don't assign write hint in the read path

Move this out of the generic read/write prep path, and place it in the
write specific kiocb setup instead.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -2825,7 +2825,6 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		req->flags |= REQ_F_CUR_POS;
 		kiocb->ki_pos = file->f_pos;
 	}
-	kiocb->ki_hint = ki_hint_validate(file_write_hint(file));
 	kiocb->ki_flags = iocb_flags(file);
 	ret = kiocb_set_rw_flags(kiocb, READ_ONCE(sqe->rw_flags));
 	if (unlikely(ret))
@@ -3568,6 +3567,7 @@ static int io_write_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	if (unlikely(!(req->file->f_mode & FMODE_WRITE)))
 		return -EBADF;
+	req->rw.kiocb.ki_hint = ki_hint_validate(file_write_hint(req->file));
 	return io_prep_rw(req, sqe);
 }