[Engine-patches] Change in ovirt-hosted-engine-ha[master]: don't use direct io on block devices

[jmoskovc at redhat.com]

Jiří Moskovčák has uploaded a new change for review.

Change subject: don't use direct io on block devices
......................................................................

don't use direct io on block devices

In python the O_DIRECT flag doesn't work properly,
because it needs the buffer alligned to 512B to read into and
in python it's not possible to control the size so the attempt
to read from file using O_DIRECT fails with an os exception.
It's also doubtful if it ever worked as intended because the
code used direct_io only to read, but not write.

Change-Id: Ie5264e1757e43f22e860af3869495ebab15e0d85
Signed-off-by: Jiri Moskovcak <jmoskovc at redhat.com>
---
M ovirt_hosted_engine_ha/broker/storage_broker.py
M ovirt_hosted_engine_ha/env/constants.py.in
M ovirt_hosted_engine_ha/lib/storage_backends.py
3 files changed, 4 insertions(+), 2 deletions(-)


  git pull ssh://gerrit.ovirt.org:29418/ovirt-hosted-engine-ha refs/changes/71/27971/1

diff --git a/ovirt_hosted_engine_ha/broker/storage_broker.py b/ovirt_hosted_engine_ha/broker/storage_broker.py
index 5ffe238..5ee8660 100644
--- a/ovirt_hosted_engine_ha/broker/storage_broker.py
+++ b/ovirt_hosted_engine_ha/broker/storage_broker.py
@@ -112,7 +112,7 @@
         # from hiding metadata file updates from other hosts.  For NFS, we
         # don't have to worry about alignment; see man open(2) for details.
         # TODO it would be better if this was configurable
-        direct_flag = (os.O_DIRECT if constants.USE_DIRECT_IO else 0)
+        direct_flag = (os.O_DIRECT if self._backends[client].direct_io else 0)
 
         bs = constants.HOST_SEGMENT_BYTES
         # TODO it would be better if this was configurable
diff --git a/ovirt_hosted_engine_ha/env/constants.py.in b/ovirt_hosted_engine_ha/env/constants.py.in
index 3fefd40..1a3064a 100644
--- a/ovirt_hosted_engine_ha/env/constants.py.in
+++ b/ovirt_hosted_engine_ha/env/constants.py.in
@@ -26,7 +26,6 @@
 HOST_SEGMENT_BYTES = 4096
 METADATA_BLOCK_BYTES = 512
 SERVICE_TYPE = 'hosted-engine'
-USE_DIRECT_IO = True
 HOST_ALIVE_TIMEOUT_SECS = 60
 
 # See http://www.gnu.org/software/automake/manual/html_node/Scripts.html
diff --git a/ovirt_hosted_engine_ha/lib/storage_backends.py b/ovirt_hosted_engine_ha/lib/storage_backends.py
index b6c1305..37db6f7 100644
--- a/ovirt_hosted_engine_ha/lib/storage_backends.py
+++ b/ovirt_hosted_engine_ha/lib/storage_backends.py
@@ -31,6 +31,7 @@
     __metaclass__ = ABCMeta
 
     def __init__(self):
+        self.direct_io = True
         # the atomic block size of the underlying storage
         self._blocksize = constants.METADATA_BLOCK_BYTES
 
@@ -317,6 +318,8 @@
 
     def __init__(self, block_dev_name, dm_prefix):
         super(BlockBackend, self).__init__()
+        # direct io doesn't work for block devices
+        self.direct_io = False
         self._block_dev_name = block_dev_name
         self._dm_prefix = dm_prefix.replace("-", "--")
         self._services = {}


-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: Ie5264e1757e43f22e860af3869495ebab15e0d85
Gerrit-PatchSet: 1
Gerrit-Project: ovirt-hosted-engine-ha
Gerrit-Branch: master
Gerrit-Owner: Jiří Moskovčák <jmoskovc at redhat.com>