[PATCH spice-server v2 1/4] spicevmc: Do not use RedCharDevice pipe items handling

[Frediano Ziglio <fziglio@xxxxxxxxxx>]

As we don't use any token there's no reason to not queue directly instead
of passing through RedCharDevice.
This will make easier to limit the queue which currently is unlimited.

RedCharDevice flow control has some problems:
- it's really designed with VDI in mind. This for SpiceVMC would cause
  code implementation to be confusing having to satisfy the agent token
  handling;
- it's using items as unit not allowing counting bytes;
- it duplicates some queue management between RedChannelClient;
- it's broken (see comments in char-device.h);
- it forces "clients" to behave in some way not altering for instance the
  queued items (which is very useful if items can be collapsed together);
- it replicates the token handling on the device queue too. This could
  seems right but is not that if you have a network card going @ 1 GBit/s
  you are able to upload more than 1 Gbit/s just using multiple
  connections. The kernel will use a single queue for the network interface
  limiting and sharing de facto the various buffers between the multiple
  connections.

Signed-off-by: Frediano Ziglio <fziglio@xxxxxxxxxx>
---
Changes in v2:
- more commit message comments
---
 server/spicevmc.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/server/spicevmc.c b/server/spicevmc.c
index 84bbb73c2..8c41573ae 100644
--- a/server/spicevmc.c
+++ b/server/spicevmc.c
@@ -360,29 +360,24 @@ static RedPipeItem *spicevmc_chardev_read_msg_from_dev(RedCharDevice *self,
 
         msg_item_compressed = try_compress_lz4(channel, n, msg_item);
         if (msg_item_compressed != NULL) {
-            return &msg_item_compressed->base;
+            red_channel_client_pipe_add_push(channel->rcc, &msg_item_compressed->base);
+            return NULL;
         }
 #endif
         stat_inc_counter(channel->out_data, n);
         msg_item->uncompressed_data_size = n;
         msg_item->buf_used = n;
-        return &msg_item->base;
-    } else {
-        channel->pipe_item = msg_item;
+        red_channel_client_pipe_add_push(channel->rcc, &msg_item->base);
         return NULL;
     }
+    channel->pipe_item = msg_item;
+    return NULL;
 }
 
 static void spicevmc_chardev_send_msg_to_client(RedCharDevice *self,
                                                 RedPipeItem *msg,
                                                 RedClient *client)
 {
-    RedCharDeviceSpiceVmc *vmc = RED_CHAR_DEVICE_SPICEVMC(self);
-    RedVmcChannel *channel = RED_VMC_CHANNEL(vmc->channel);
-
-    spice_assert(red_channel_client_get_client(channel->rcc) == client);
-    red_pipe_item_ref(msg);
-    red_channel_client_pipe_add_push(channel->rcc, msg);
 }
 
 static void red_port_init_item_free(struct RedPipeItem *base)
-- 
2.20.1

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