Bug 537646 - backports of qemu barrier support
Summary: backports of qemu barrier support
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: kvm
Version: 5.4
Hardware: All
OS: Linux
low
medium
Target Milestone: rc
: ---
Assignee: Kevin Wolf
QA Contact: Virtualization Bugs
URL:
Whiteboard:
Depends On:
Blocks: 572825
TreeView+ depends on / blocked
 
Reported: 2009-11-15 12:54 UTC by Dor Laor
Modified: 2013-01-09 21:16 UTC (History)
7 users (show)

Fixed In Version: kvm-83-136.el5
Doc Type: Bug Fix
Doc Text:
Clone Of:
: 571735 572825 (view as bug list)
Environment:
Last Closed: 2010-03-30 07:56:37 UTC
Target Upstream Version:
Embargoed:


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2010:0271 0 normal SHIPPED_LIVE Important: kvm security, bug fix and enhancement update 2010-03-29 13:19:48 UTC

Description Dor Laor 2009-11-15 12:54:41 UTC
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 13:12:49 UTC
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 18:31:31 UTC
Hi Dor
 could you please tell me how to test this bug ?

 thanks

Comment 7 Dor Laor 2010-01-26 22:34:29 UTC
We only managed to reproduce it on Cisco's compiler, probably impossible here.

Comment 8 Chris Ward 2010-02-08 11:50:06 UTC
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 12:35:27 UTC
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 12:03:35 UTC
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 08:34:45 UTC
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 09:02:22 UTC
I'm not aware of any.

Comment 30 lihuang 2010-03-12 06:15:25 UTC
(In reply to comment #29)
> I'm not aware of any.    

I have cloned to bug 572825.

Comment 33 errata-xmlrpc 2010-03-30 07:56:37 UTC
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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