On Fri, Feb 04, Olaf Hering wrote:
Ping?
Can this and the reset_devices patch be applied to the 2.6.18 tree?
Olaf
>
> After triggering a crash dump in a HVM guest, the PV backend drivers
> will remain in connected state. When the kdump kernel starts the PV
> drivers will skip such devices. As a result, no root device is found
> and the vmcore cant be saved.
>
> With this change all frontend devices with state XenbusStateConnected
> will be reset by changing the state file to Closing/Closed/Initializing.
> This will trigger a disconnect in the backend drivers. Now the frontend
> drivers will find the backend drivers in state Initwait and can connect.
>
> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
>
> ---
> drivers/xen/xenbus/xenbus_comms.c | 4 +
> drivers/xen/xenbus/xenbus_probe.c | 96
> ++++++++++++++++++++++++++++++++++++++
> 2 files changed, 99 insertions(+), 1 deletion(-)
>
> --- linux-2.6.18-xen.hg.orig/drivers/xen/xenbus/xenbus_comms.c
> +++ linux-2.6.18-xen.hg/drivers/xen/xenbus/xenbus_comms.c
> @@ -234,7 +234,9 @@ int xb_init_comms(void)
> printk(KERN_WARNING "XENBUS response ring is not quiescent "
> "(%08x:%08x): fixing up\n",
> intf->rsp_cons, intf->rsp_prod);
> - intf->rsp_cons = intf->rsp_prod;
> + /* breaks kdump */
> + if (!reset_devices)
> + intf->rsp_cons = intf->rsp_prod;
> }
>
> if (xenbus_irq)
> --- linux-2.6.18-xen.hg.orig/drivers/xen/xenbus/xenbus_probe.c
> +++ linux-2.6.18-xen.hg/drivers/xen/xenbus/xenbus_probe.c
> @@ -854,11 +854,107 @@ void unregister_xenstore_notifier(struct
> }
> EXPORT_SYMBOL_GPL(unregister_xenstore_notifier);
>
> +#ifdef CONFIG_CRASH_DUMP
> +static DECLARE_WAIT_QUEUE_HEAD(be_state_wq);
> +static int be_state;
> +
> +static void xenbus_reset_state_changed(struct xenbus_watch *w, const char
> **v, unsigned int l)
> +{
> + xenbus_scanf(XBT_NIL, v[XS_WATCH_PATH], "", "%i", &be_state);
> + printk(KERN_INFO "XENBUS: %s %s", v[XS_WATCH_PATH],
> xenbus_strstate(be_state));
> + wake_up(&be_state_wq);
> +}
> +
> +static int xenbus_reset_check_final(int *st)
> +{
> + return *st == XenbusStateInitialising || *st == XenbusStateInitWait;
> +}
> +
> +static void xenbus_reset_frontend_state(char *backend, char *frontend)
> +{
> + struct xenbus_watch watch;
> +
> + memset(&watch, 0, sizeof(watch));
> + watch.node = kasprintf(GFP_NOIO | __GFP_HIGH, "%s/state", backend);
> + if (!watch.node)
> + return;
> +
> + watch.callback = xenbus_reset_state_changed;
> + be_state = XenbusStateUnknown;
> +
> + printk(KERN_INFO "triggering reconnect on %s", backend);
> + register_xenbus_watch(&watch);
> +
> + xenbus_printf(XBT_NIL, frontend, "state", "%d", XenbusStateClosing);
> + wait_event_interruptible(be_state_wq, be_state == XenbusStateClosing);
> +
> + xenbus_printf(XBT_NIL, frontend, "state", "%d", XenbusStateClosed);
> + wait_event_interruptible(be_state_wq, be_state == XenbusStateClosed);
> +
> + xenbus_printf(XBT_NIL, frontend, "state", "%d",
> XenbusStateInitialising);
> + wait_event_interruptible(be_state_wq,
> xenbus_reset_check_final(&be_state));
> +
> + unregister_xenbus_watch(&watch);
> + printk(KERN_INFO "reconnect done on %s", backend);
> + kfree(watch.node);
> +}
> +
> +static void xenbus_reset_check_state(char *frontend)
> +{
> + int state, err;
> + char *backend;
> +
> + err = xenbus_scanf(XBT_NIL, frontend, "state", "%i", &state);
> + /* frontend connected? */
> + if (err == 1 && state == XenbusStateConnected) {
> + backend = xenbus_read(XBT_NIL, frontend, "backend", NULL);
> + if (!backend || IS_ERR(backend))
> + return;
> + err = xenbus_scanf(XBT_NIL, backend, "state", "%i", &state);
> + /* backend connected? */
> + if (err == 1 && state == XenbusStateConnected)
> + xenbus_reset_frontend_state(backend, frontend);
> + kfree(backend);
> + }
> +}
> +
> +static void xenbus_reset_state(void)
> +{
> + char *frontend;
> + char **devclass, **dev;
> + int devclass_n, dev_n;
> + int i, j;
> +
> + devclass = xenbus_directory(XBT_NIL, "device", "", &devclass_n);
> + if (IS_ERR(devclass))
> + return;
> +
> + for (i = 0; i < devclass_n; i++) {
> + dev = xenbus_directory(XBT_NIL, "device", devclass[i], &dev_n);
> + if (IS_ERR(dev))
> + continue;
> + for (j = 0; j < dev_n; j++) {
> + frontend = kasprintf(GFP_NOIO|__GFP_HIGH,
> "device/%s/%s", devclass[i], dev[j]);
> + if (!frontend)
> + continue;
> + xenbus_reset_check_state(frontend);
> + kfree(frontend);
> + }
> + kfree(dev);
> + }
> + kfree(devclass);
> +}
> +#endif
>
> void xenbus_probe(void *unused)
> {
> BUG_ON(!is_xenstored_ready());
>
> +#ifdef CONFIG_CRASH_DUMP
> + /* reset devices in XenbusStateConnected state */
> + if (!is_initial_xendomain() && reset_devices)
> + xenbus_reset_state();
> +#endif
> /* Enumerate devices in xenstore and watch for changes. */
> xenbus_probe_devices(&xenbus_frontend);
> register_xenbus_watch(&fe_watch);
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