Re: [Xen-devel] [PATCH 0001/001] xen: multi page ring support for block devices

On Mar 6, 2012, at 1:34 AM, Jan Beulich wrote:

quoted

quoted

quoted

On 05.03.12 at 22:49, Santosh Jodh [off-list ref] wrote:

…

quoted

+       }
+
       /* Create shared ring, alloc event channel. */
       err = setup_blkring(dev, info);
       if (err)

@@ -889,12 +916,35 @@ again:
               goto destroy_blkring;
       }

-       err = xenbus_printf(xbt, dev->nodename,
-                           "ring-ref", "%u", info->ring_ref);
-       if (err) {
-               message = "writing ring-ref";
-               goto abort_transaction;
+       if (legacy_backend) {

Why not use the simpler interface always when info->ring_order == 0?

Because, as I just found out today via a FreeBSD bug report, that's
not how XenServer works.  If the front-end publishes "ring-page-order",
the backend assumes the "ring-refNN" XenStore nodes are in effect,
even if the order is 0.

I'm working on a documentation update for blkif.h now.

<sigh>

--
Justin