[PATCH v5 3/6] remus: resume immediately if libxl__xc_domain_save_done() completes

[Wen Congyang <wency@cn.fujitsu.com>]

For example: if the secondary host is down, and we fail to send the data to
the secondary host. xc_domain_save() returns 0. So in the function
libxl__xc_domain_save_done(), rc is 0 (the helper program exits normally),
and retval is 0 (it is xc_domain_save()'s return value). In such case, we
just need to complete the stream.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
 tools/libxl/libxl.h              |  4 ++++
 tools/libxl/libxl_stream_write.c | 14 ++++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 7114491..df6c7a3 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -1215,6 +1215,10 @@ int libxl_domain_resume(libxl_ctx *ctx, uint32_t domid, int suspend_cancel,
                         const libxl_asyncop_how *ao_how)
                         LIBXL_EXTERNAL_CALLERS_ONLY;
 
+/*
+ * This function doesn't return until something is wrong, and we need to
+ * do failover from secondary.
+ */
 int libxl_domain_remus_start(libxl_ctx *ctx, libxl_domain_remus_info *info,
                              uint32_t domid, int send_fd, int recv_fd,
                              const libxl_asyncop_how *ao_how)
diff --git a/tools/libxl/libxl_stream_write.c b/tools/libxl/libxl_stream_write.c
index 80d9208..21b4b51 100644
--- a/tools/libxl/libxl_stream_write.c
+++ b/tools/libxl/libxl_stream_write.c
@@ -354,8 +354,18 @@ void libxl__xc_domain_save_done(libxl__egc *egc, void *dss_void,
      * alive, and check_all_finished() may have torn it down around us.
      * If the stream is not still alive, we must not continue any work.
      */
-    if (libxl__stream_write_inuse(stream))
-        write_emulator_xenstore_record(egc, stream);
+    if (libxl__stream_write_inuse(stream)) {
+        if (dss->remus)
+            /*
+             * For remus, if libxl__xc_domain_save_done() completes,
+             * there was an error sending data to the secondary.
+             * Resume the primary ASAP. The caller doesn't care of the
+             * return value (Please refer to libxl__remus_teardown())
+             */
+            stream_complete(egc, stream, 0);
+        else
+            write_emulator_xenstore_record(egc, stream);
+    }
 }
 
 static void write_emulator_xenstore_record(libxl__egc *egc,
-- 
2.5.0