io_uring: deduplicate open iopoll check

Move IORING_SETUP_IOPOLL check into __io_openat_prep(), so both openat
and openat2 reuse it.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9a73ce83e4ee60d011180ef177eecef8e87ff2a2.1628471125.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3789,6 +3789,8 @@ static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
 	const char __user *fname;
 	int ret;
 
+	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
+		return -EINVAL;
 	if (unlikely(sqe->ioprio || sqe->buf_index))
 		return -EINVAL;
 	if (unlikely(req->flags & REQ_F_FIXED_FILE))
@@ -3813,12 +3815,9 @@ static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
 
 static int io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
-	u64 flags, mode;
+	u64 mode = READ_ONCE(sqe->len);
+	u64 flags = READ_ONCE(sqe->open_flags);
 
-	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
-		return -EINVAL;
-	mode = READ_ONCE(sqe->len);
-	flags = READ_ONCE(sqe->open_flags);
 	req->open.how = build_open_how(flags, mode);
 	return __io_openat_prep(req, sqe);
 }
@@ -3829,8 +3828,6 @@ static int io_openat2_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	size_t len;
 	int ret;
 
-	if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
-		return -EINVAL;
 	how = u64_to_user_ptr(READ_ONCE(sqe->addr2));
 	len = READ_ONCE(sqe->len);
 	if (len < OPEN_HOW_SIZE_VER0)