xenbus: limit when state is forced to closed

If a driver probe() fails then leave the xenstore state alone. There is no
reason to modify it as the failure may be due to transient resource
allocation issues and hence a subsequent probe() may succeed.

If the driver supports re-binding then only force state to closed during
remove() only in the case when the toolstack may need to clean up. This can
be detected by checking whether the state in xenstore has been set to
closing prior to device removal.

NOTE: Re-bind support is indicated by new boolean in struct xenbus_driver,
      which defaults to false. Subsequent patches will add support to
      some backend drivers.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 5aa29396c9e39e5d83e5451f7ff8bc0089ae4d22..378486b79f96aeec8e308f5630f9ffc168ae16a6 100644 (file)
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -255,7 +255,6 @@ fail_put:
        module_put(drv->driver.owner);
 fail:
        xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
-       xenbus_switch_state(dev, XenbusStateClosed);
        return err;
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_probe);
@@ -276,7 +275,16 @@ int xenbus_dev_remove(struct device *_dev)
 
        free_otherend_details(dev);
 
-       xenbus_switch_state(dev, XenbusStateClosed);
+       /*
+        * If the toolstack has forced the device state to closing then set
+        * the state to closed now to allow it to be cleaned up.
+        * Similarly, if the driver does not support re-bind, set the
+        * closed.
+        */
+       if (!drv->allow_rebind ||
+           xenbus_read_driver_state(dev->nodename) == XenbusStateClosing)
+               xenbus_switch_state(dev, XenbusStateClosed);
+
        return 0;
 }
 EXPORT_SYMBOL_GPL(xenbus_dev_remove);

diff --git a/include/xen/xenbus.h b/include/xen/xenbus.h
index 869c816d5f8c3097b09298a9d086e7f75fff540e..24228a102141e3981911bba20712ca53dcb2b219 100644 (file)
--- a/include/xen/xenbus.h
+++ b/include/xen/xenbus.h
@@ -93,6 +93,7 @@ struct xenbus_device_id
 struct xenbus_driver {
        const char *name;       /* defaults to ids[0].devicetype */
        const struct xenbus_device_id *ids;
+       bool allow_rebind; /* avoid setting xenstore closed during remove */
        int (*probe)(struct xenbus_device *dev,
                     const struct xenbus_device_id *id);
        void (*otherend_changed)(struct xenbus_device *dev,