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

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Message-ID: <alpine.DEB.2.10.1703161104210.14378@sstabellini-ThinkPad-X260>
Date:   Thu, 16 Mar 2017 11:04:28 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Juergen Gross <jgross@...e.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        groug@...d.org, Stefano Stabellini <stefano@...reto.com>,
        boris.ostrovsky@...cle.com, Eric Van Hensbergen <ericvh@...il.com>,
        Ron Minnich <rminnich@...dia.gov>,
        Latchesar Ionkov <lucho@...kov.net>,
        v9fs-developer@...ts.sourceforge.net
Subject: Re: [PATCH v4 4/7] xen/9pfs: connect to the backend

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@...reto.com>
> > CC: groug@...d.org
> > CC: boris.ostrovsky@...cle.com
> > CC: jgross@...e.com
> > CC: Eric Van Hensbergen <ericvh@...il.com>
> > CC: Ron Minnich <rminnich@...dia.gov>
> > CC: Latchesar Ionkov <lucho@...kov.net>
> > CC: v9fs-developer@...ts.sourceforge.net
> > ---
> >  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!