[PATCH 4/5] io_uring: send/recv with registered buffer

[Pavel Begunkov <asml.silence@gmail.com>]

Add support of registered buffers to send() and recv(). Done by
exploiting last bit of send/recv flags, IO_MSG_FIXED, which is cleared
before going into net stack.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7703291617f3..390495170fb0 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -104,6 +104,8 @@
 #define IORING_MAX_RESTRICTIONS	(IORING_RESTRICTION_LAST + \
 				 IORING_REGISTER_LAST + IORING_OP_LAST)
 
+#define IO_MSG_FIXED		(1U << 31)
+
 struct io_uring {
 	u32 head ____cacheline_aligned_in_smp;
 	u32 tail ____cacheline_aligned_in_smp;
@@ -4689,18 +4691,25 @@ static int io_send(struct io_kiocb *req, bool force_nonblock,
 		   struct io_comp_state *cs)
 {
 	struct io_sr_msg *sr = &req->sr_msg;
+	unsigned int flags = sr->msg_flags;
 	struct msghdr msg;
 	struct iovec iov;
 	struct socket *sock;
-	unsigned flags;
 	int ret;
 
 	sock = sock_from_file(req->file, &ret);
 	if (unlikely(!sock))
 		return ret;
 
-	ret = import_single_range(WRITE, sr->buf, sr->len, &iov, &msg.msg_iter);
-	if (unlikely(ret))
+	if (flags & IO_MSG_FIXED) {
+		ret = io_import_fixed(req, WRITE, (u64)sr->buf, sr->len,
+				      &msg.msg_iter);
+		flags &= ~IO_MSG_FIXED;
+	} else {
+		ret = import_single_range(WRITE, sr->buf, sr->len, &iov,
+					  &msg.msg_iter);
+	}
+	if (unlikely(ret < 0))
 		return ret;
 
 	msg.msg_name = NULL;
@@ -4708,7 +4717,6 @@ static int io_send(struct io_kiocb *req, bool force_nonblock,
 	msg.msg_controllen = 0;
 	msg.msg_namelen = 0;
 
-	flags = req->sr_msg.msg_flags;
 	if (flags & MSG_DONTWAIT)
 		req->flags |= REQ_F_NOWAIT;
 	else if (force_nonblock)
@@ -4821,15 +4829,22 @@ static int io_recv(struct io_kiocb *req, bool force_nonblock,
 	if (unlikely(!sock))
 		return ret;
 
-	if (req->flags & REQ_F_BUFFER_SELECT) {
-		kbuf = io_recv_buffer_select(req, !force_nonblock);
-		if (IS_ERR(kbuf))
-			return PTR_ERR(kbuf);
-		buf = u64_to_user_ptr(kbuf->addr);
-	}
+	if (flags & IO_MSG_FIXED) {
+		ret = io_import_fixed(req, READ, (u64)buf, sr->len,
+				      &msg.msg_iter);
+		flags &= ~IO_MSG_FIXED;
+	} else {
+		if (req->flags & REQ_F_BUFFER_SELECT) {
+			kbuf = io_recv_buffer_select(req, !force_nonblock);
+			if (IS_ERR(kbuf))
+				return PTR_ERR(kbuf);
+			buf = u64_to_user_ptr(kbuf->addr);
+		}
 
-	ret = import_single_range(READ, buf, sr->len, &iov, &msg.msg_iter);
-	if (unlikely(ret))
+		ret = import_single_range(READ, buf, sr->len, &iov,
+					  &msg.msg_iter);
+	}
+	if (unlikely(ret < 0))
 		goto out_free;
 
 	msg.msg_name = NULL;
-- 
2.24.0