[Xen-devel] [PATCH v8 --for 4.6 COLO 05/25] tools/libxl: add back channel support to write stream

[Yang Hongyang <yanghy@xxxxxxxxxxxxxx>]

Add back channel support to write stream. If the write stream is
a back channel stream, this means the write stream is used by
Secondary to send some records back.

Signed-off-by: Yang Hongyang <yanghy@xxxxxxxxxxxxxx>
---
 tools/libxl/libxl_dom_save.c     |  1 +
 tools/libxl/libxl_internal.h     |  1 +
 tools/libxl/libxl_stream_write.c | 16 ++++++++++++++++
 3 files changed, 18 insertions(+)

diff --git a/tools/libxl/libxl_dom_save.c b/tools/libxl/libxl_dom_save.c
index 9b7159f..25813ce 100644
--- a/tools/libxl/libxl_dom_save.c
+++ b/tools/libxl/libxl_dom_save.c
@@ -445,6 +445,7 @@ void libxl__domain_save(libxl__egc *egc, 
libxl__domain_save_state *dss)
     dss->sws.ao  = dss->ao;
     dss->sws.dss = dss;
     dss->sws.fd  = dss->fd;
+    dss->sws.back_channel = false;
     dss->sws.completion_callback = stream_done;
 
     libxl__stream_write_start(egc, &dss->sws);
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 9c81d8d..a83d6a5 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -2989,6 +2989,7 @@ struct libxl__stream_write_state {
     libxl__ao *ao;
     libxl__domain_save_state *dss;
     int fd;
+    bool back_channel;
     void (*completion_callback)(libxl__egc *egc,
                                 libxl__stream_write_state *sws,
                                 int rc);
diff --git a/tools/libxl/libxl_stream_write.c b/tools/libxl/libxl_stream_write.c
index 16f667a..df55277 100644
--- a/tools/libxl/libxl_stream_write.c
+++ b/tools/libxl/libxl_stream_write.c
@@ -47,6 +47,13 @@
  *  - Toolstack record
  *  - if (hvm), Qemu record
  *  - Checkpoint end record
+ *
+ * For back channel stream:
+ * - libxl__stream_write_start()
+ *    - Set up the stream to running state
+ *
+ * - Add a new API to write the record. When the record is written
+ *   out, call stream->checkpoint_callback() to return.
  */
 
 /* Success/error/cleanup handling. */
@@ -178,6 +185,9 @@ void libxl__stream_write_start(libxl__egc *egc,
 
     stream->running = true;
 
+    if (stream->back_channel)
+        return;
+
     dc->ao        = ao;
     dc->readfd    = -1;
     dc->writewhat = "save/migration stream";
@@ -207,6 +217,7 @@ void libxl__stream_write_start_checkpoint(libxl__egc *egc,
 {
     assert(stream->running);
     assert(!stream->in_checkpoint);
+    assert(!stream->back_channel);
     stream->in_checkpoint = true;
 
     write_toolstack_record(egc, stream);
@@ -500,6 +511,11 @@ static void stream_done(libxl__egc *egc,
     assert(stream->running);
     stream->running = false;
 
+    if (stream->back_channel) {
+        stream->completion_callback(egc, stream, stream->rc);
+        return;
+    }
+
     if (stream->emu_carefd)
         libxl__carefd_close(stream->emu_carefd);
     free(stream->emu_body);
-- 
1.9.1


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