Re: [Xen-devel] [PATCH v4 4/7] xen/9pfs: connect to the backend

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 16 Mar 2017, Juergen Gross wrote:
> On 15/03/17 20:23, Stefano Stabellini wrote:
> > Implement functions to handle the xenbus handshake. Upon connection,
> > allocate the rings according to the protocol specification.
> > 
> > Initialize a work_struct and a wait_queue. The work_struct will be used
> > to schedule work upon receiving an event channel notification from the
> > backend. The wait_queue will be used to wait when the ring is full and
> > we need to send a new request.
> > 
> > Signed-off-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
> > CC: groug@xxxxxxxx
> > CC: boris.ostrovsky@xxxxxxxxxx
> > CC: jgross@xxxxxxxx
> > CC: Eric Van Hensbergen <ericvh@xxxxxxxxx>
> > CC: Ron Minnich <rminnich@xxxxxxxxxx>
> > CC: Latchesar Ionkov <lucho@xxxxxxxxxx>
> > CC: v9fs-developer@xxxxxxxxxxxxxxxxxxxxx
> > ---
> >  net/9p/trans_xen.c | 248 
> > +++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 248 insertions(+)
> > 
> > diff --git a/net/9p/trans_xen.c b/net/9p/trans_xen.c
> > index b1333b2..ada2b0c 100644
> > --- a/net/9p/trans_xen.c
> > +++ b/net/9p/trans_xen.c
> >  static int xen_9pfs_front_probe(struct xenbus_device *dev,
> >             const struct xenbus_device_id *id)
> >  {
> > +   int ret, i;
> > +   struct xenbus_transaction xbt;
> > +   struct xen_9pfs_front_priv *priv = NULL;
> > +   char *versions;
> > +   unsigned int max_rings, max_ring_order, len;
> > +
> > +   versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
> > +   if (!len)
> > +           return -EINVAL;
> > +   if (strcmp(versions, "1")) {
> > +           kfree(versions);
> > +           return -EINVAL;
> > +   }
> > +   kfree(versions);
> > +   max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
> > +   if (max_rings < XEN_9PFS_NUM_RINGS)
> > +           return -EINVAL;
> > +   max_ring_order = xenbus_read_unsigned(dev->otherend, 
> > "max-ring-page-order", 0);
> > +   if (max_ring_order < XEN_9PFS_RING_ORDER)
> > +           return -EINVAL;
> > +
> > +
> > +   priv = kzalloc(sizeof(struct xen_9pfs_front_priv), GFP_KERNEL);
> > +   if (!priv)
> > +           return -ENOMEM;
> > +
> > +   priv->dev = dev;
> > +   priv->num_rings = XEN_9PFS_NUM_RINGS;
> > +   priv->rings = kzalloc(sizeof(struct xen_9pfs_dataring) * 
> > priv->num_rings,
> > +                         GFP_KERNEL);
> > +   if (!priv->rings) {
> > +           kfree(priv);
> > +           return -ENOMEM;
> > +   }
> > +
> > +   for (i = 0; i < priv->num_rings; i++) {
> > +           priv->rings[i].priv = priv;
> > +           ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i]);
> > +           if (ret < 0)
> > +                   goto error;
> > +   }
> > +
> > + again:
> > +   ret = xenbus_transaction_start(&xbt);
> > +   if (ret) {
> > +           xenbus_dev_fatal(dev, ret, "starting transaction");
> > +           goto error;
> > +   }
> > +   ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
> > +   if (ret)
> > +           goto error_xenbus;
> > +   ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u", 
> > priv->num_rings);
> > +   if (ret)
> > +           goto error_xenbus;
> > +   for (i = 0; i < priv->num_rings; i++) {
> > +           char str[16];
> > +
> > +           BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
> > +           sprintf(str, "ring-ref%u", i);
> > +           ret = xenbus_printf(xbt, dev->nodename, str, "%d", 
> > priv->rings[i].ref);
> > +           if (ret)
> > +                   goto error_xenbus;
> > +
> > +           sprintf(str, "event-channel-%u", i);
> > +           ret = xenbus_printf(xbt, dev->nodename, str, "%u", 
> > priv->rings[i].evtchn);
> > +           if (ret)
> > +                   goto error_xenbus;
> > +   }
> > +   priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
> > +   if (ret)
> > +           goto error_xenbus;
> 
> Shouldn't you test priv->tag instead?

well spotted, thanks!

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