io_uring: do build_open_how() only once

to #28736503

commit 25e72d1012b30bdff712b563e6141a4f311d28d6 upstream

build_open_how() is just adjusting open_flags/mode. Do it once during
prep. It looks better than storing raw values for the future.
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Acked-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

fs/io_uring.c

@@ -2984,6 +2984,7 @@ static int io_fallocate(struct io_kiocb *req, bool force_nonblock)
 static int io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	const char __user *fname;
+	u64 flags, mode;
 	int ret;
 
 	if (unlikely(req->ctx->flags & (IORING_SETUP_IOPOLL|IORING_SETUP_SQPOLL)))
@@ -2995,13 +2996,14 @@ static int io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	if (req->flags & REQ_F_NEED_CLEANUP)
 		return 0;
 
-	req->open.dfd = READ_ONCE(sqe->fd);
-	req->open.how.mode = READ_ONCE(sqe->len);
-	fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
-	req->open.how.flags = READ_ONCE(sqe->open_flags);
+	mode = READ_ONCE(sqe->len);
+	flags = READ_ONCE(sqe->open_flags);
 	if (force_o_largefile())
-		req->open.how.flags |= O_LARGEFILE;
+		flags |= O_LARGEFILE;
+	req->open.how = build_open_how(flags, mode);
 
+	req->open.dfd = READ_ONCE(sqe->fd);
+	fname = u64_to_user_ptr(READ_ONCE(sqe->addr));
 	req->open.filename = getname(fname);
 	if (IS_ERR(req->open.filename)) {
 		ret = PTR_ERR(req->open.filename);
@@ -3095,7 +3097,6 @@ static int io_openat2(struct io_kiocb *req, bool force_nonblock)
 
 static int io_openat(struct io_kiocb *req, bool force_nonblock)
 {
-	req->open.how = build_open_how(req->open.how.flags, req->open.how.mode);
 	return io_openat2(req, force_nonblock);
 }