migration: remove the QEMUFileOps 'get_return_path' callback

This directly implements the get_return_path logic using QIOChannel APIs.

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

migration/qemu-file-channel.c

@@ -32,27 +32,11 @@
 #include "yank_functions.h"
 
 
-static QEMUFile *channel_get_input_return_path(void *opaque)
-{
-    QIOChannel *ioc = QIO_CHANNEL(opaque);
-
-    return qemu_fopen_channel_output(ioc);
-}
-
-static QEMUFile *channel_get_output_return_path(void *opaque)
-{
-    QIOChannel *ioc = QIO_CHANNEL(opaque);
-
-    return qemu_fopen_channel_input(ioc);
-}
-
 static const QEMUFileOps channel_input_ops = {
-    .get_return_path = channel_get_input_return_path,
 };
 
 
 static const QEMUFileOps channel_output_ops = {
-    .get_return_path = channel_get_output_return_path,
 };
 
 

migration/qemu-file.c

@@ -95,18 +95,6 @@ int qemu_file_shutdown(QEMUFile *f)
     return ret;
 }
 
-/*
- * Result: QEMUFile* for a 'return path' for comms in the opposite direction
- *         NULL if not available
- */
-QEMUFile *qemu_file_get_return_path(QEMUFile *f)
-{
-    if (!f->ops->get_return_path) {
-        return NULL;
-    }
-    return f->ops->get_return_path(f->ioc);
-}
-
 bool qemu_file_mode_is_not_valid(const char *mode)
 {
     if (mode == NULL ||
@@ -134,6 +122,16 @@ static QEMUFile *qemu_file_new_impl(QIOChannel *ioc,
     return f;
 }
 
+/*
+ * Result: QEMUFile* for a 'return path' for comms in the opposite direction
+ *         NULL if not available
+ */
+QEMUFile *qemu_file_get_return_path(QEMUFile *f)
+{
+    object_ref(f->ioc);
+    return qemu_file_new_impl(f->ioc, f->ops, !f->is_writable);
+}
+
 QEMUFile *qemu_file_new_output(QIOChannel *ioc, const QEMUFileOps *ops)
 {
     return qemu_file_new_impl(ioc, ops, true);

migration/qemu-file.h

@@ -55,13 +55,7 @@ typedef size_t (QEMURamSaveFunc)(QEMUFile *f,
                                  size_t size,
                                  uint64_t *bytes_sent);
 
-/*
- * Return a QEMUFile for comms in the opposite direction
- */
-typedef QEMUFile *(QEMURetPathFunc)(void *opaque);
-
 typedef struct QEMUFileOps {
-    QEMURetPathFunc *get_return_path;
 } QEMUFileOps;
 
 typedef struct QEMUFileHooks {