io_uring: never call io_buffer_select() for a buffer re-select

Callers already have room to store the addr and length information,
clean it up by having the caller just assign the previously provided
data.
Signed-off-by: Jens Axboe <axboe@kernel.dk>

fs/io_uring.c

@@ -3455,9 +3455,6 @@ static void __user *io_buffer_select(struct io_kiocb *req, size_t *len,
 	struct io_ring_ctx *ctx = req->ctx;
 	struct io_buffer_list *bl;
 
-	if (req->flags & REQ_F_BUFFER_SELECTED)
-		return u64_to_user_ptr(kbuf->addr);
-
 	io_ring_submit_lock(req->ctx, issue_flags);
 
 	bl = io_buffer_get_list(ctx, req->buf_index);
@@ -3497,8 +3494,9 @@ static ssize_t io_compat_import(struct io_kiocb *req, struct iovec *iov,
 	buf = io_buffer_select(req, &len, issue_flags);
 	if (IS_ERR(buf))
 		return PTR_ERR(buf);
+	req->rw.addr = (unsigned long) buf;
 	iov[0].iov_base = buf;
-	iov[0].iov_len = (compat_size_t) len;
+	req->rw.len = iov[0].iov_len = (compat_size_t) len;
 	return 0;
 }
 #endif
@@ -3519,8 +3517,9 @@ static ssize_t __io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
 	buf = io_buffer_select(req, &len, issue_flags);
 	if (IS_ERR(buf))
 		return PTR_ERR(buf);
+	req->rw.addr = (unsigned long) buf;
 	iov[0].iov_base = buf;
-	iov[0].iov_len = len;
+	req->rw.len = iov[0].iov_len = len;
 	return 0;
 }
 
@@ -3528,10 +3527,8 @@ static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
 				    unsigned int issue_flags)
 {
 	if (req->flags & REQ_F_BUFFER_SELECTED) {
-		struct io_buffer *kbuf = req->kbuf;
-
-		iov[0].iov_base = u64_to_user_ptr(kbuf->addr);
-		iov[0].iov_len = kbuf->len;
+		iov[0].iov_base = u64_to_user_ptr(req->rw.addr);
+		iov[0].iov_len = req->rw.len;
 		return 0;
 	}
 	if (req->rw.len != 1)
@@ -3545,6 +3542,13 @@ static ssize_t io_iov_buffer_select(struct io_kiocb *req, struct iovec *iov,
 	return __io_iov_buffer_select(req, iov, issue_flags);
 }
 
+static inline bool io_do_buffer_select(struct io_kiocb *req)
+{
+	if (!(req->flags & REQ_F_BUFFER_SELECT))
+		return false;
+	return !(req->flags & REQ_F_BUFFER_SELECTED);
+}
+
 static struct iovec *__io_import_iovec(int rw, struct io_kiocb *req,
 				       struct io_rw_state *s,
 				       unsigned int issue_flags)
@@ -3567,10 +3571,11 @@ static struct iovec *__io_import_iovec(int rw, struct io_kiocb *req,
 	sqe_len = req->rw.len;
 
 	if (opcode == IORING_OP_READ || opcode == IORING_OP_WRITE) {
-		if (req->flags & REQ_F_BUFFER_SELECT) {
+		if (io_do_buffer_select(req)) {
 			buf = io_buffer_select(req, &sqe_len, issue_flags);
 			if (IS_ERR(buf))
 				return ERR_CAST(buf);
+			req->rw.addr = (unsigned long) buf;
 			req->rw.len = sqe_len;
 		}
 
@@ -5555,7 +5560,7 @@ static int io_recvmsg(struct io_kiocb *req, unsigned int issue_flags)
 	    (sr->flags & IORING_RECVSEND_POLL_FIRST))
 		return io_setup_async_msg(req, kmsg);
 
-	if (req->flags & REQ_F_BUFFER_SELECT) {
+	if (io_do_buffer_select(req)) {
 		void __user *buf;
 
 		buf = io_buffer_select(req, &sr->len, issue_flags);
@@ -5619,7 +5624,7 @@ static int io_recv(struct io_kiocb *req, unsigned int issue_flags)
 	if (unlikely(!sock))
 		return -ENOTSOCK;
 
-	if (req->flags & REQ_F_BUFFER_SELECT) {
+	if (io_do_buffer_select(req)) {
 		void __user *buf;
 
 		buf = io_buffer_select(req, &sr->len, issue_flags);