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Subject: [PATCH RFC 2/4] SUNRPC: Convert svc_udp_sendto() to use the
 per-socket bio_vec array
From:   Chuck Lever <cel@kernel.org>
To:     linux-nfs@vger.kernel.org
Cc:     Chuck Lever <chuck.lever@oracle.com>, dhowells@redhat.com
Date:   Sun, 09 Jul 2023 16:05:05 -0400
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From: Chuck Lever <chuck.lever@oracle.com>

Commit da1661b93bf4 ("SUNRPC: Teach server to use xprt_sock_sendmsg
for socket sends") modified svc_udp_sendto() to use xprt_sock_sendmsg()
because we originally believed xprt_sock_sendmsg() would be needed
for TLS support. That does not actually appear to be the case.

In addition, the linkage between the client and server send code has
been a bit of a maintenance headache because of the distinct ways
that the client and server handle memory allocation.

Going forward, eventually the XDR layer will deal with its buffers
in the form of bio_vec arrays, so convert this function accordingly.
Once the use of bio_vecs is ubiquitous, the xdr_buf-to-bio_vec array
code can be hoisted into a path that is common for all transports.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/svcsock.c |   22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index d3c5f1a07979..ae7143f68343 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -729,7 +729,7 @@ static int svc_udp_sendto(struct svc_rqst *rqstp)
 		.msg_control	= cmh,
 		.msg_controllen	= sizeof(buffer),
 	};
-	unsigned int sent;
+	unsigned int count;
 	int err;
 
 	svc_udp_release_ctxt(xprt, rqstp->rq_xprt_ctxt);
@@ -742,22 +742,22 @@ static int svc_udp_sendto(struct svc_rqst *rqstp)
 	if (svc_xprt_is_dead(xprt))
 		goto out_notconn;
 
-	err = xdr_alloc_bvec(xdr, GFP_KERNEL);
-	if (err < 0)
-		goto out_unlock;
+	count = svc_sock_xdr_to_bvecs(svsk->sk_send_bvec, xdr);
 
-	err = xprt_sock_sendmsg(svsk->sk_sock, &msg, xdr, 0, 0, &sent);
+	iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, svsk->sk_send_bvec,
+		      count, 0);
+	err = sock_sendmsg(svsk->sk_sock, &msg);
 	if (err == -ECONNREFUSED) {
 		/* ICMP error on earlier request. */
-		err = xprt_sock_sendmsg(svsk->sk_sock, &msg, xdr, 0, 0, &sent);
+		iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, svsk->sk_send_bvec,
+			      count, 0);
+		err = sock_sendmsg(svsk->sk_sock, &msg);
 	}
-	xdr_free_bvec(xdr);
+
 	trace_svcsock_udp_send(xprt, err);
-out_unlock:
+
 	mutex_unlock(&xprt->xpt_mutex);
-	if (err < 0)
-		return err;
-	return sent;
+	return err;
 
 out_notconn:
 	mutex_unlock(&xprt->xpt_mutex);