Bug 537646 – backports of qemu barrier support

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Bug 537646 - backports of qemu barrier support

Summary:	backports of qemu barrier support

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 5
Classification:	Red Hat
Component:	kvm (Show other bugs)
Sub Component:
Version:	5.4
Hardware:	All Linux

Priority	low Severity medium
Target Milestone:	rc
Target Release:	---
Assigned To:	Kevin Wolf
QA Contact:	Virtualization Bugs
Docs Contact:

URL:
Whiteboard:
Keywords:	OtherQA

Depends On:
Blocks:	572825
	Show dependency tree / graph

Reported:	2009-11-15 07:54 EST by Dor Laor
Modified:	2013-01-09 16:16 EST (History)
CC List:	7 users (show)

See Also:
Fixed In Version:	kvm-83-136.el5
Doc Type:	Bug Fix
Doc Text:
Story Points:	---
Clone Of:
Clones:	571735 572825 (view as bug list)
Environment:
Last Closed:	2010-03-30 03:56:37 EDT
Type:	---
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2010:0271	normal	SHIPPED_LIVE	Important: kvm security, bug fix and enhancement update	2010-03-29 09:19:48 EDT

Groups: None (edit)

Description Dor Laor 2009-11-15 07:54:41 EST

block: use fdatasync instead of fsync if possible
    
If we are flushing the caches for our image files we only care about the
data (including the metadata required for accessing it) but not things
like timestamp updates.  So try to use fdatasync instead of fsync to
implement the flush operations.

Comment 1 Dor Laor 2009-11-15 08:12:49 EST

The bug now scopes all the patch set of exposing write cache flags to the guest and flush aio when the guest orders to do so:

[PATCH 0/5] RHEL 5.4.z / 5.5 backports of qemu barrier support
[PATCH 1/5] block: add enable_write_cache flag
[PATCH 2/5] block: use fdatasync instead of fsync if possible
[PATCH 3/5] block: add aio_flush operation
[PATCH 4/5] ide: use bdrv_aio_flush
[PATCH 5/5] virtio-blk: add volatile writecache feature

Comment 6 lihuang 2010-01-26 13:31:31 EST

Hi Dor
 could you please tell me how to test this bug ?

 thanks

Comment 7 Dor Laor 2010-01-26 17:34:29 EST

We only managed to reproduce it on Cisco's compiler, probably impossible here.

Comment 8 Chris Ward 2010-02-08 06:50:06 EST

Dor, would you be able to test for QE then to verify the fix? Or provide QE with access to "cisco's compiler" ? Thanks!

Comment 9 Dor Laor 2010-02-08 07:35:27 EST

I'm sorry, I was wrong about the #c7, it is mostly an optimization and not a bug, you can check the patch descriptions. I was fooled by another 'qemu barrier' BZ

Comment 22 Dor Laor 2010-03-08 07:03:35 EST

It seems that this is a qcow issue so I reassign it to Kevin. We did have a problem with the ref-count code. Note that cache=wb is not supported if rhel5 for the time being so it's less painful but might indeed impose a general issue

Comment 28 lihuang 2010-03-11 03:34:45 EST

I will close this bug with above results and comments

lihuang->kwolf
Do we already have BZ for the qcow2 issue ?


Thanks
Lijun Huang

Comment 29 Kevin Wolf 2010-03-11 04:02:22 EST

I'm not aware of any.

Comment 30 lihuang 2010-03-12 01:15:25 EST

(In reply to comment #29)
> I'm not aware of any.    

I have cloned to bug 572825.

Comment 33 errata-xmlrpc 2010-03-30 03:56:37 EDT

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2010-0271.html

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