Re: [PATCH] xen-blkback: Switch to closed state after releasing the backing device

From: Valentin Vidic
Date: Fri Sep 07 2018 - 06:20:37 EST


On Fri, Sep 07, 2018 at 09:54:55AM +0200, Roger Pau Monné wrote:
> Then I'm afraid you will have to look into the vbd_free/create fix.

Yes, here is a first draft for that idea, let me know if you see some
problems there:

--- xenbus.c.orig 2018-09-07 12:11:57.798071485 +0200
+++ xenbus.c 2018-09-07 12:14:23.536077992 +0200
@@ -758,6 +759,7 @@
enum xenbus_state frontend_state)
{
struct backend_info *be = dev_get_drvdata(&dev->dev);
+ struct block_device *bdev;
int err;

pr_debug("%s %p %s\n", __func__, dev, xenbus_strstate(frontend_state));
@@ -772,6 +774,22 @@

case XenbusStateInitialised:
case XenbusStateConnected:
+ if (!be->blkif->vbd.bdev) {
+ printk("blkdev_get");
+ bdev = blkdev_get_by_dev(be->blkif->vbd.pdevice,
+ be->blkif->vbd.readonly ?
+ FMODE_READ : FMODE_WRITE, NULL);
+
+ if (IS_ERR(bdev)) {
+ pr_warn("frontend_changed: device %08x could not be opened\n",
+ be->blkif->vbd.pdevice);
+ break;
+ }
+
+ printk("blkdev_get good");
+ be->blkif->vbd.bdev = bdev;
+ }
+
/*
* Ensure we connect even when two watches fire in
* close succession and we miss the intermediate value
@@ -808,6 +826,7 @@

case XenbusStateClosed:
xen_blkif_disconnect(be->blkif);
+ xen_vbd_free(&be->blkif->vbd);
xenbus_switch_state(dev, XenbusStateClosed);
if (xenbus_dev_is_online(dev))
break;

--
Valentin