[RFC PATCH v2 3/9] migration/multifd: Introduce MultiFDSendData

[Fabiano Rosas]

Add a new data structure to replace p->pages in the multifd
channel. This new structure will hide the multifd payload type behind
an union, so we don't need to add a new field to the channel each time
we want to handle a different data type.

This also allow us to keep multifd_send_pages() as is, without needing
to complicate the pointer switching.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 migration/multifd.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/migration/multifd.h b/migration/multifd.h
index 0ecd6f47d7..c7b1ebe099 100644
--- a/migration/multifd.h
+++ b/migration/multifd.h
@@ -16,6 +16,7 @@
 #include "ram.h"
 
 typedef struct MultiFDRecvData MultiFDRecvData;
+typedef struct MultiFDSendData MultiFDSendData;
 
 bool multifd_send_setup(void);
 void multifd_send_shutdown(void);
@@ -89,6 +90,29 @@ struct MultiFDRecvData {
     off_t file_offset;
 };
 
+typedef enum {
+    MULTIFD_PAYLOAD_NONE,
+    MULTIFD_PAYLOAD_RAM,
+} MultiFDPayloadType;
+
+struct MultiFDSendData {
+    MultiFDPayloadType type;
+    union {
+        MultiFDPages_t ram;
+    } u;
+};
+
+static inline bool multifd_payload_empty(MultiFDSendData *data)
+{
+    return data->type == MULTIFD_PAYLOAD_NONE;
+}
+
+static inline void multifd_set_payload_type(MultiFDSendData *data,
+                                            MultiFDPayloadType type)
+{
+    data->type = type;
+}
+
 typedef struct {
     /* Fields are only written at creating/deletion time */
     /* No lock required for them, they are read only */
-- 
2.35.3