From c1f98a666c5f159c505494ebb1581bee61fbe510 Mon Sep 17 00:00:00 2001
From: Filippos Giannakos <philipgian@grnet.gr>
Date: Fri, 30 Jun 2017 11:20:28 +0300
Subject: [PATCH] Enhance cache settings for userspace URI
---
ext_scripts/ext_rbd.py | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/ext_scripts/ext_rbd.py b/ext_scripts/ext_rbd.py
index dce1c74..38f576a 100755
--- a/ext_scripts/ext_rbd.py
+++ b/ext_scripts/ext_rbd.py
@@ -301,9 +301,17 @@ def format_qemu_uri(name, pool=None, cephx=None, conf_file=None, cache=None,
extra_conf += ':id=%s' % cephx['id']
if conf_file:
extra_conf += ':conf=%s' % conf_file
- # TODO: we need to revisit this, to support more caching modes correctly.
- if cache in ['writeback']:
+ # We need to set these here to override the settings in 'ceph.conf'
+ # They are consistent with how QEMU treats the cache settings for an RBD
+ # drive.
+ if cache in ['writeback', 'writethrough', 'unsafe']:
extra_conf += ':rbd_cache=true'
+ if cache == 'writethrough':
+ # To ensure that the cache is set in writethrough mode.
+ # QEMU alone, does not set this value when 'cache=writethrough' is set,
+ # although if 'ceph.conf' does not says otherwise, 'rbd_cache' is set
+ # to true.
+ extra_conf += ':rbd_cache_max_dirty=0'
for k, v in kwargs.iteritems():
extra_conf += ':%s=%s' % (k, v)
--
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