[patch 3/6] allow reconnects to the backend driver

[Gerd Hoffmann <kraxel@suse.de>]

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  Hi,

The patch below changes the netback and blkback device drivers to allow
and handle frontend state transition from "Closing" to "Initialising".
Instead of destroying the backend device then they wait for a reconnect
from the frontend.  Needed for domU kexec support, to hand over devices
from one kernel instance to the next.

please apply,

  Gerd

-- 
Gerd Hoffmann <kraxel@suse.de>
http://www.suse.de/~kraxel/julika-dora.jpeg

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Signed-off-by: Gerd Hoffmann <kraxel@suse.de>
Index: source-lnx-stable-22813/drivers/xen/blkback/xenbus.c
===================================================================
--- source-lnx-stable-22813.orig/drivers/xen/blkback/xenbus.c	2006-08-17 15:19:20.000000000 +0200
+++ source-lnx-stable-22813/drivers/xen/blkback/xenbus.c	2006-08-17 15:20:17.000000000 +0200
@@ -305,6 +305,11 @@ static void frontend_changed(struct xenb
 
 	switch (frontend_state) {
 	case XenbusStateInitialising:
+		if (dev->state == XenbusStateClosing) {
+			printk("%s: %s: prepare for reconnect\n",
+			       __FUNCTION__, dev->nodename);
+			xenbus_switch_state(dev, XenbusStateInitWait);
+		}
 		break;
 
 	case XenbusStateInitialised:
Index: source-lnx-stable-22813/drivers/xen/netback/xenbus.c
===================================================================
--- source-lnx-stable-22813.orig/drivers/xen/netback/xenbus.c	2006-08-17 15:19:20.000000000 +0200
+++ source-lnx-stable-22813/drivers/xen/netback/xenbus.c	2006-08-17 15:20:17.000000000 +0200
@@ -228,10 +228,25 @@ static void frontend_changed(struct xenb
 
 	switch (frontend_state) {
 	case XenbusStateInitialising:
+		if (dev->state == XenbusStateClosing) {
+			printk("%s: %s: prepare for reconnect\n",
+			       __FUNCTION__, dev->nodename);
+			if (be->netif) {
+				netif_disconnect(be->netif);
+				be->netif = NULL;
+			}
+			xenbus_switch_state(dev, XenbusStateInitWait);
+		}
+		break;
+
 	case XenbusStateInitialised:
 		break;
 
 	case XenbusStateConnected:
+		if (!be->netif) {
+			/* reconnect: setup be->netif */
+			backend_changed(&be->backend_watch, NULL, 0);
+		}
 		maybe_connect(be);
 		break;
 

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