[rulkc] [PATCH v1] vsock/virtio: rework MSG_ZEROCOPY flag handling

[Arseniy Krasnov]

Logically it was based on TCP implementation, so to make further
support easier, rewrite it in the TCP way.

Signed-off-by: Arseniy Krasnov <avkrasnov at rulkc.org>
---
 net/vmw_vsock/virtio_transport_common.c | 64 ++++++++++++-------------
 1 file changed, 32 insertions(+), 32 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 2fd9eaaf5ca6..00caeeaa5590 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -73,10 +73,13 @@ static bool virtio_transport_can_zcopy(const struct virtio_transport *t_ops,
 static int virtio_transport_fill_skb(struct sk_buff *skb,
 				     struct virtio_vsock_pkt_info *info,
 				     size_t len,
-				     bool zcopy)
+				     bool zcopy, struct ubuf_info *uarg)
 {
 	struct msghdr *msg = info->msg;
 
+	/* We have completion - attach it to 'skb'. */
+	skb_zcopy_set(skb, uarg, NULL);
+
 	if (zcopy)
 		return __zerocopy_sg_from_iter(msg, NULL, skb,
 					       &msg->msg_iter, len, NULL);
@@ -208,7 +211,8 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *
 						  u32 src_cid,
 						  u32 src_port,
 						  u32 dst_cid,
-						  u32 dst_port)
+						  u32 dst_port,
+						  struct ubuf_info *uarg)
 {
 	struct vsock_sock *vsk;
 	struct sk_buff *skb;
@@ -245,7 +249,7 @@ static struct sk_buff *virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *
 	if (info->msg && payload_len > 0) {
 		int err;
 
-		err = virtio_transport_fill_skb(skb, info, payload_len, zcopy);
+		err = virtio_transport_fill_skb(skb, info, payload_len, zcopy, uarg);
 		if (err)
 			goto out;
 
@@ -321,38 +325,36 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 	if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
 		return pkt_len;
 
-	if (info->msg) {
-		/* If zerocopy is not enabled by 'setsockopt()', we behave as
-		 * there is no MSG_ZEROCOPY flag set.
+	if (info->msg && (info->msg->msg_flags & MSG_ZEROCOPY)) {
+		/* If 'info->msg' is not NULL, this is only VIRTIO_VSOCK_OP_RW.
+		 * 'MSG_ZEROCOPY' flag handling here is based on the same flag
+		 * handling from 'tcp_sendmsg_locked()'.
 		 */
-		if (!sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY))
-			info->msg->msg_flags &= ~MSG_ZEROCOPY;
+		if (info->msg->msg_ubuf) {
+			uarg = info->msg->msg_ubuf;
+			can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len);
+		} else if (sock_flag(sk_vsock(vsk), SOCK_ZEROCOPY)) {
+			uarg = msg_zerocopy_realloc(sk_vsock(vsk), pkt_len,
+						    NULL, false);
+			if (!uarg) {
+				virtio_transport_put_credit(vvs, pkt_len);
+				return -ENOMEM;
+			}
 
-		if (info->msg->msg_flags & MSG_ZEROCOPY)
 			can_zcopy = virtio_transport_can_zcopy(t_ops, info, pkt_len);
 
+			if (!can_zcopy)
+				uarg_to_msgzc(uarg)->zerocopy = 0;
+
+			have_uref = true;
+		}
+
+		/* 'can_zcopy' means that this transmission will be
+		 * in zerocopy way (e.g. using 'frags' array).
+		 */
 		if (can_zcopy)
 			max_skb_len = min_t(u32, VIRTIO_VSOCK_MAX_PKT_BUF_SIZE,
 					    (MAX_SKB_FRAGS * PAGE_SIZE));
-
-		if (info->msg->msg_flags & MSG_ZEROCOPY &&
-		    info->op == VIRTIO_VSOCK_OP_RW) {
-			uarg = info->msg->msg_ubuf;
-
-			if (!uarg) {
-				uarg = msg_zerocopy_realloc(sk_vsock(vsk),
-							    pkt_len, NULL, false);
-				if (!uarg) {
-					virtio_transport_put_credit(vvs, pkt_len);
-					return -ENOMEM;
-				}
-
-				if (!can_zcopy)
-					uarg_to_msgzc(uarg)->zerocopy = 0;
-
-				have_uref = true;
-			}
-		}
 	}
 
 	rest_len = pkt_len;
@@ -365,14 +367,12 @@ static int virtio_transport_send_pkt_info(struct vsock_sock *vsk,
 
 		skb = virtio_transport_alloc_skb(info, skb_len, can_zcopy,
 						 src_cid, src_port,
-						 dst_cid, dst_port);
+						 dst_cid, dst_port, uarg);
 		if (!skb) {
 			ret = -ENOMEM;
 			break;
 		}
 
-		skb_zcopy_set(skb, uarg, NULL);
-
 		virtio_transport_inc_tx_pkt(vvs, skb);
 
 		ret = t_ops->send_pkt(skb, info->net);
@@ -1178,7 +1178,7 @@ static int virtio_transport_reset_no_sock(const struct virtio_transport *t,
 					   le64_to_cpu(hdr->dst_cid),
 					   le32_to_cpu(hdr->dst_port),
 					   le64_to_cpu(hdr->src_cid),
-					   le32_to_cpu(hdr->src_port));
+					   le32_to_cpu(hdr->src_port), NULL);
 	if (!reply)
 		return -ENOMEM;
 
-- 
2.25.1