migration: add qemu_file_update_transfer interface

Add qemu_file_update_transfer for just update bytes_xfer for speed
limitation. This will be used for further migration feature such as
multifd migration.
Signed-off-by: NIvan Ren <ivanren@tencent.com>
Reviewed-by: NWei Yang <richardw.yang@linux.intel.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Message-Id: <1564464816-21804-2-git-send-email-ivanren@tencent.com>
Signed-off-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

migration/qemu-file.c

@@ -654,6 +654,11 @@ void qemu_file_reset_rate_limit(QEMUFile *f)
     f->bytes_xfer = 0;
 }
 
+void qemu_file_update_transfer(QEMUFile *f, int64_t len)
+{
+    f->bytes_xfer += len;
+}
+
 void qemu_put_be16(QEMUFile *f, unsigned int v)
 {
     qemu_put_byte(f, v >> 8);

migration/qemu-file.h

@@ -150,6 +150,7 @@ int qemu_peek_byte(QEMUFile *f, int offset);
 void qemu_file_skip(QEMUFile *f, int size);
 void qemu_update_position(QEMUFile *f, size_t size);
 void qemu_file_reset_rate_limit(QEMUFile *f);
+void qemu_file_update_transfer(QEMUFile *f, int64_t len);
 void qemu_file_set_rate_limit(QEMUFile *f, int64_t new_rate);
 int64_t qemu_file_get_rate_limit(QEMUFile *f);
 int qemu_file_get_error_obj(QEMUFile *f, Error **errp);