Ugly netdev sysfs errors handling

[Kirill Korotaev <dev@sw.ru>]

Hello,

During debug I faced oops in 
netdev_unregister_sysfs()->sysfs_remove_group(),
since kobj->dentry == NULL.

The problem is that netdev code doesn't handle errors from sysfs 
correctly - it calls netdev_unregister_sysfs() in any case, even if 
netdev_register_sysfs() failed on registering:

void netdev_run_todo(void)
...
                 case NETREG_REGISTERING:
                         err = netdev_register_sysfs(dev);
                         if (err)
                                 printk(KERN_ERR "%s: failed sysfs 
registration (%d)\n",
                                        dev->name, err);
                         dev->reg_state = NETREG_REGISTERED;
                         break;
                 case NETREG_UNREGISTERING:
                         netdev_unregister_sysfs(dev); <<<< OOPS here,
					<<<< if netdev_register_sysfs()
					<<<<< failed
...

I tried to fix it in netdev code, but it's impossible to do it in a 
fashioned manner. Since there are some kobject manipulations in 
destructors (e.g. free_netdev() oopses as well if workaround the above 
code).
Another approach can be to check kobj->dentry and other fields in sysfs.

Maybe someone has any ideas on this? Except for "no errors should 
normally happen" :)

Kirill