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From: Stefano Stabellini on 18 May 2010 06:40
From: Don Dutile <ddutile(a)redhat.com>

this way if xenbus isn't configured in a FV xen guest,
loading pv drivers (like netfront) won't crash the guest.

Signed-off-by: Don Dutile <ddutile(a)redhat.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini(a)eu.citrix.com>
---
drivers/xen/xenbus/xenbus_probe.c | 29 +++++++++++++++++++++++++----
drivers/xen/xenbus/xenbus_probe.h | 1 +
2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index f83e083..5e8dae6 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -188,6 +188,11 @@ static struct xen_bus_type xenbus_frontend = {
.levels = 2, /* device/type/<id> */
.get_bus_id = frontend_bus_id,
.probe = xenbus_probe_frontend,
+ /*
+ * to ensure loading pv-on-hvm drivers on FV guest
+ * doesn't blow up trying to use uninit'd xenbus.
+ */
+ .error = -ENODEV,
.bus = {
.name = "xen",
.match = xenbus_match,
@@ -352,6 +357,9 @@ int xenbus_register_driver_common(struct xenbus_driver *drv,
struct module *owner,
const char *mod_name)
{
+ if (bus->error)
+ return bus->error;
+
drv->driver.name = drv->name;
drv->driver.bus = &bus->bus;
drv->driver.owner = owner;
@@ -484,8 +492,12 @@ int xenbus_probe_node(struct xen_bus_type *bus,
struct xenbus_device *xendev;
size_t stringlen;
char *tmpstring;
+ enum xenbus_state state;
+
+ if (bus->error)
+ return bus->error;

- enum xenbus_state state = xenbus_read_driver_state(nodename);
+ state = xenbus_read_driver_state(nodename);

if (state != XenbusStateInitialising) {
/* Device is not new, so ignore it. This can happen if a
@@ -593,6 +605,9 @@ int xenbus_probe_devices(struct xen_bus_type *bus)
char **dir;
unsigned int i, dir_n;

+ if (bus->error)
+ return bus->error;
+
dir = xenbus_directory(XBT_NIL, bus->root, "", &dir_n);
if (IS_ERR(dir))
return PTR_ERR(dir);
@@ -636,7 +651,7 @@ void xenbus_dev_changed(const char *node, struct xen_bus_type *bus)
char type[XEN_BUS_ID_SIZE];
const char *p, *root;

- if (char_count(node, '/') < 2)
+ if (bus->error || char_count(node, '/') < 2)
return;

exists = xenbus_exists(XBT_NIL, node, "");
@@ -829,8 +844,8 @@ int xenbus_probe_init(void)
DPRINTK("");

/* Register ourselves with the kernel bus subsystem */
- err = bus_register(&xenbus_frontend.bus);
- if (err)
+ xenbus_frontend.error = bus_register(&xenbus_frontend.bus);
+ if (xenbus_frontend.error)
goto out_error;

err = xenbus_backend_bus_register();
@@ -923,6 +938,9 @@ static int is_device_connecting(struct device *dev, void *data)

static int exists_connecting_device(struct device_driver *drv)
{
+ if (xenbus_frontend.error)
+ return xenbus_frontend.error;
+
return bus_for_each_dev(&xenbus_frontend.bus, NULL, drv,
is_device_connecting);
}
@@ -1002,6 +1020,9 @@ static void wait_for_devices(struct xenbus_driver *xendrv)
#ifndef MODULE
static int __init boot_wait_for_devices(void)
{
+ if (!xenbus_frontend.error)
+ return xenbus_frontend.error;
+
ready_to_wait_for_devices = 1;
wait_for_devices(NULL);
return 0;
diff --git a/drivers/xen/xenbus/xenbus_probe.h b/drivers/xen/xenbus/xenbus_probe.h
index 6c5e318..15febe4 100644
--- a/drivers/xen/xenbus/xenbus_probe.h
+++ b/drivers/xen/xenbus/xenbus_probe.h
@@ -53,6 +53,7 @@ static inline void xenbus_backend_bus_unregister(void) {}
struct xen_bus_type
{
char *root;
+ int error;
unsigned int levels;
int (*get_bus_id)(char bus_id[XEN_BUS_ID_SIZE], const char *nodename);
int (*probe)(const char *type, const char *dir);
--
1.5.4.3

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Prev: [PATCH 10/12] __setup_vector_irq: handle NULL chip_data
Next: [PATCH] Staging: comedi: quatech_daqp_cs.c Replace eos semaphore with a completion.