Re: [Qemu-block] [PATCH] nbd: Flip qemu-nbd to prefer newstyle; add -O for old behavior

[Eric Blake]

On 10/3/18 12:38 PM, Vladimir Sementsov-Ogievskiy wrote:
> 03.10.2018 20:19, Eric Blake wrote:
> > Oldstyle NBD negotiation cannot perform any of the extensions that
> > we have recently been relying on.  While you can always pass -x ""
> > to get newstyle negotiation, these days, it is better to just default
> > to newstyle (with an empty export name) and fall back to oldstyle
> > only on an explicit request.

> > +    if (oldstyle && (export_name || export_description)) {
> > +        error_report("oldstyle negotiation cannot set export details");
> > +        exit(EXIT_FAILURE);
> > +    }
> >       if (export_name) {
> >           nbd_export_set_name(exp, export_name);
> >           nbd_export_set_description(exp, export_description);
> >           newproto = true;
>
> a bit strange, to have both newproto and oldstyle variables which are 
> opposite by value.

Yeah. I added a function-local 'oldstyle' before noticing that there was 
a file static 'newproto'. We could squash this in:

diff --git i/qemu-nbd.c w/qemu-nbd.c
index 8571a4f93d8..2b0f7de86d0 100644
--- i/qemu-nbd.c
+++ w/qemu-nbd.c
@@ -56,7 +56,7 @@
 #define MBR_SIZE 512

 static NBDExport *exp;
-static bool newproto;
+static bool oldstyle;
 static int verbose;
 static char *srcpath;
 static SocketAddress *saddr;
@@ -355,7 +355,7 @@ static void nbd_accept(QIONetListener *listener, 
QIOChannelSocket *cioc,

     nb_fds++;
     nbd_update_server_watch();
-    nbd_client_new(newproto ? NULL : exp, cioc,
+    nbd_client_new(oldstyle ? exp : NULL, cioc,
                    tlscreds, NULL, nbd_client_closed);
 }

@@ -553,7 +553,6 @@ int main(int argc, char **argv)
     QDict *options = NULL;
     const char *export_name = NULL;
     const char *export_description = NULL;
-    bool oldstyle = false;
     const char *tlscredsid = NULL;
     bool imageOpts = false;
     bool writethrough = true;
@@ -1030,7 +1029,6 @@ int main(int argc, char **argv)
     if (export_name) {
         nbd_export_set_name(exp, export_name);
         nbd_export_set_description(exp, export_description);
-        newproto = true;
     }

     if (device) {


--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org