From 7ffbff485e40bc3f36542f2892877adc5241accf Mon Sep 17 00:00:00 2001
From: Pádraig Brady <pbrady@redhat.com>
Date: Wed, 15 Feb 2012 10:05:23 +0000
Subject: improve injection diagnostics when nbd unavailable. Bug 755854

It's better to fail immediately with this improved diagnostic.
Relying on qemu-nbd to detect the issue (no device), is inefficient.

Change-Id: Ib124f6b83d8f04f0b4791c98912603f3499a9d2a
---
 nova/virt/disk/nbd.py | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/nova/virt/disk/nbd.py b/nova/virt/disk/nbd.py
index 029fecaf2..1839b2d90 100644
--- a/nova/virt/disk/nbd.py
+++ b/nova/virt/disk/nbd.py
@@ -54,6 +54,9 @@ class Mount(mount.Mount):
     _DEVICES = ['/dev/nbd%s' % i for i in range(FLAGS.max_nbd_devices)]
 
     def _allocate_nbd(self):
+        if not os.path.exists("/sys/block/nbd0"):
+            self.error = _('nbd unavailable: module not loaded')
+            return None
         while True:
             if not self._DEVICES:
                 # really want to log this info, not raise
-- 
cgit