net/filter: Optimize filter_send to coroutine

This patch is to improve the logic of QEMU main thread sleep code in
qemu_chr_write_buffer() where it can be blocked and can't run other
coroutines during COLO IO stress test.

Our approach is to put filter_send() in a coroutine. In this way,
filter_send() will call qemu_coroutine_yield() in qemu_co_sleep_ns(),
so that it can be scheduled out and QEMU main thread has opportunity to
run other tasks.

Signed-off-by: Lei Rao <lei.rao@intel.com>
Signed-off-by: Zhang Chen <chen.zhang@intel.com>
Reviewed-by: Li Zhijian <lizhijian@fujitsu.com>
Reviewed-by: Zhang Chen <chen.zhang@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

net/filter-mirror.c

@@ -20,6 +20,7 @@
 #include "chardev/char-fe.h"
 #include "qemu/iov.h"
 #include "qemu/sockets.h"
+#include "block/aio-wait.h"
 
 #define TYPE_FILTER_MIRROR "filter-mirror"
 typedef struct MirrorState MirrorState;
@@ -42,20 +43,21 @@ struct MirrorState {
     bool vnet_hdr;
 };
 
-static int filter_send(MirrorState *s,
-                       const struct iovec *iov,
-                       int iovcnt)
+typedef struct FilterSendCo {
+    MirrorState *s;
+    char *buf;
+    ssize_t size;
+    bool done;
+    int ret;
+} FilterSendCo;
+
+static int _filter_send(MirrorState *s,
+                       char *buf,
+                       ssize_t size)
 {
     NetFilterState *nf = NETFILTER(s);
     int ret = 0;
-    ssize_t size = 0;
     uint32_t len = 0;
-    char *buf;
-
-    size = iov_size(iov, iovcnt);
-    if (!size) {
-        return 0;
-    }
 
     len = htonl(size);
     ret = qemu_chr_fe_write_all(&s->chr_out, (uint8_t *)&len, sizeof(len));
@@ -80,10 +82,7 @@ static int filter_send(MirrorState *s,
         }
     }
 
-    buf = g_malloc(size);
-    iov_to_buf(iov, iovcnt, 0, buf, size);
     ret = qemu_chr_fe_write_all(&s->chr_out, (uint8_t *)buf, size);
-    g_free(buf);
     if (ret != size) {
         goto err;
     }
@@ -94,6 +93,47 @@ err:
     return ret < 0 ? ret : -EIO;
 }
 
+static void coroutine_fn filter_send_co(void *opaque)
+{
+    FilterSendCo *data = opaque;
+
+    data->ret = _filter_send(data->s, data->buf, data->size);
+    data->done = true;
+    g_free(data->buf);
+    aio_wait_kick();
+}
+
+static int filter_send(MirrorState *s,
+                       const struct iovec *iov,
+                       int iovcnt)
+{
+    ssize_t size = iov_size(iov, iovcnt);
+    char *buf = NULL;
+
+    if (!size) {
+        return 0;
+    }
+
+    buf = g_malloc(size);
+    iov_to_buf(iov, iovcnt, 0, buf, size);
+
+    FilterSendCo data = {
+        .s = s,
+        .size = size,
+        .buf = buf,
+        .ret = 0,
+    };
+
+    Coroutine *co = qemu_coroutine_create(filter_send_co, &data);
+    qemu_coroutine_enter(co);
+
+    while (!data.done) {
+        aio_poll(qemu_get_aio_context(), true);
+    }
+
+    return data.ret;
+}
+
 static void redirector_to_filter(NetFilterState *nf,
                                  const uint8_t *buf,
                                  int len)