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

Signed-off-by: Arseniy Krasnov <[email protected]>
---
 Changelog v1->v2:
 * Rebase on last 'net-next'. Don't need 'skb_zcopy_set()' now - it was
   already added.

 net/vmw_vsock/virtio_transport_common.c | 48 ++++++++++++-------------
 1 file changed, 23 insertions(+), 25 deletions(-)

diff --git a/net/vmw_vsock/virtio_transport_common.c 
b/net/vmw_vsock/virtio_transport_common.c
index 09475007165b..787524b8cb44 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -328,38 +328,36 @@ 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;
-- 
2.25.1


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