From 1405a6440d646524d41adfed4fc1344948e2871f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <pbrady@redhat.com>
Date: Fri, 23 Nov 2012 11:24:44 +0000
Subject: [PATCH] use O_DIRECT when copying from /dev/zero too

We need to avoid trying O_DIRECT with virtual
devices like /dev/zero and /dev/urandom etc.
as it's not supported there, which because of
our later check, would cause O_DIRECT to be
not applied to the output device either.

Related to bug 937694
Possibly related to bug 1023755
Change-Id: I034d8345c3d00689c1f1fffcc2c110735c49ee01
---
 cinder/volume/driver.py | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/cinder/volume/driver.py b/cinder/volume/driver.py
index 35af0993534..0dacacfcd01 100644
--- a/cinder/volume/driver.py
+++ b/cinder/volume/driver.py
@@ -22,6 +22,7 @@
 
 import os
 import re
+import stat
 import time
 
 from cinder import exception
@@ -105,7 +106,15 @@ def _create_volume(self, volume_name, sizestr):
 
     def _copy_volume(self, srcstr, deststr, size_in_g):
         # Use O_DIRECT to avoid thrashing the system buffer cache
-        direct_flags = ('iflag=direct', 'oflag=direct')
+        direct_flags = ['oflag=direct']
+        try:
+            # Avoid trying O_DIRECT on virtual inputs like /dev/zero
+            # as it's not supported with such devices.
+            if not stat.S_ISCHR(os.stat(srcstr).st_mode):
+                direct_flags += ['iflag=direct']
+        except OSError:
+            # Deal with any access issues below
+            pass
 
         # Check whether O_DIRECT is supported
         try: