Bug 1177062

Summary:	The error messages are not accurate enough when do blockcommit passing target[index] to base and top
Product:	Red Hat Enterprise Linux 7	Reporter:	Yang Yang <yanyang>
Component:	libvirt	Assignee:	Peter Krempa <pkrempa>
Status:	CLOSED ERRATA	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	low	Docs Contact:
Priority:	low
Version:	7.1	CC:	dyuan, eblake, mzhan, pkrempa, rbalakri, shyu, xuzhang
Target Milestone:	rc
Target Release:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Fixed In Version:	libvirt-1.2.15-1.el7	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-11-19 06:05:44 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Yang Yang 2014-12-24 02:20:41 UTC

Description of problem:
As described in comment #4 in bug 1110212, file a low priority bug.
https://bugzilla.redhat.com/show_bug.cgi?id=1110212#c4

Version-Release number of selected component (if applicable):
libvirt-1.2.8-10.el7.x86_64
qemu-kvm-rhev-2.1.2-16.el7.x86_64
kernel-3.10.0-212.el7.x86_64


How reproducible:
100%

Steps to Reproduce:
1. create 4 external disk-only snapshots
# for i in {1..4}; do virsh snapshot-create-as vm2 s$i --disk-only --diskspec hda,file=/tmp/vm2.s$i; done
Domain snapshot s1 created
Domain snapshot s2 created
Domain snapshot s3 created
Domain snapshot s4 created

# virsh domblklist vm2
Target     Source
------------------------------------------------
hda        /tmp/vm2.s4

2.blockcommit passing hda[x] to base and top
# virsh blockcommit vm2 hda --base hda[2] --top hda[2] --wait --verbose
error: invalid argument: could not find backing store 2 in chain for '/tmp/vm2.s4'

# virsh blockcommit vm2 hda --base hda[1] --top hda[2] --wait --verbose
error: invalid argument: could not find backing store 1 in chain for '/tmp/vm2.s4'


# virsh blockcommit vm2 hda --base hda[1] --top /tmp/vm2.s1 --wait --verbose
error: invalid argument: could not find backing store 1 in chain for '/tmp/vm2.s4'


Actual results:


Expected results:
Libvirt should provide a proper error info 

Additional info:

Comment 1 Peter Krempa 2015-04-22 12:31:48 UTC

Following upstream commit improves the error message:

commit dff92b3f2fe63da63391f929134b06d3be992a40
Author: Peter Krempa <pkrempa>
Date:   Tue Apr 21 17:38:08 2015 +0200

    util: storage: Improve error message when requesting image above 'start'
    
    When a user would specify a backing chain index that is above the start
    point libvirt would report a rather unhelpful error:
    
    invalid argument: could not find backing store 1 in chain for 'sub/link2'
    
    This patch adds an explicit check that the index is below start point in
    the backing store and reports the following error if not:
    
    invalid argument: requested backing store index 1 is above 'sub/../qcow2' in chain for 'sub/link2'

v1.2.14-260-gdff92b3

Comment 3 Yang Yang 2015-05-25 10:15:44 UTC

Hi Peter
I found a tiny issue that error message is not accurate when passing an invalid path to base when using gluster as storage backend

# virsh blockcommit vm3 vda --top vda[2] --base xx --wait --verbose 
error: invalid argument: top '/rhel7.qcow2' in chain for 'vda' has no backing file

# virsh blockcommit vm3 vda --top vda[2] --base vda[] --wait --verbose --bandwidth 1
error: invalid argument: top '/rhel7.qcow2' in chain for 'vda' has no backing file

==============================================
The following test scenarios have passed.
Tested with libvirt-1.2.15-2.el7.x86_64

Steps

<disk type='network' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source protocol='gluster' name='gluster-vol1/rhel7.s3'>
        <host name='10.66.4.164' port='24007'/>
      </source>
      <backingStore type='network' index='1'>
        <format type='qcow2'/>
        <source protocol='gluster' name='gluster-vol1/rhel7.s2'>
          <host name='10.66.4.164'/>
        </source>
        <backingStore type='network' index='2'>
          <format type='qcow2'/>
          <source protocol='gluster' name='gluster-vol1/rhel7.s1'>
            <host name='10.66.4.164'/>
          </source>
          <backingStore type='network' index='3'>
            <format type='qcow2'/>
            <source protocol='gluster' name='gluster-vol1/rhel7.qcow2'>
              <host name='10.66.4.164'/>
            </source>
            <backingStore/>
          </backingStore>
        </backingStore>
      </backingStore>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </disk>


# virsh blockcommit vm3 vda --top vda[2] --base vda[1] --wait --verbose
error: invalid argument: requested backing store index 1 is above '/rhel7.s1' in chain for '/rhel7.s3'

# virsh blockcommit vm3 vda --top vda[2] --base vda[2] --wait --verbose
error: invalid argument: requested backing store index 2 is above '/rhel7.s1' in chain for '/rhel7.s3'

# virsh blockcommit vm3 vda --top xx --base vda[1] --wait --verbose --bandwidth 1
error: invalid argument: could not find image 'xx' in chain for '/rhel7.s3'

Comment 4 Peter Krempa 2015-06-03 08:07:15 UTC

Yes that's a known issue. Network disk strings in error messages need to be fixed at some time. Here as long as it works for local files it's good enough.

Comment 5 Yang Yang 2015-06-03 08:42:07 UTC

Thanks Peter.

Also verified it with local file

libvirt-1.2.15-2.el7.x86_64

Steps as following

# virsh blockcommit simple vda --top vda[2] --base xx --wait --verbose
error: invalid argument: could not find image 'xx' beneath '/tmp/simple.s2' in chain for '/tmp/simple.s4'

# virsh blockcommit simple vda --top vda[2] --base vda[] --wait --verbose
error: invalid argument: could not find image 'vda[]' beneath '/tmp/simple.s2' in chain for '/tmp/simple.s4'

# virsh blockcommit simple vda --top vda[] --base vda[] --wait --verbose
error: invalid argument: could not find image 'vda[]' in chain for '/tmp/simple.s4'


# virsh blockcommit simple vda --top vda[2] --base vda[1] --wait --verbose
error: invalid argument: requested backing store index 1 is above '/tmp/simple.s2' in chain for '/tmp/simple.s4'

# virsh blockcommit simple vda --top vda[2] --base vda[2] --wait --verbose
error: invalid argument: requested backing store index 2 is above '/tmp/simple.s2' in chain for '/tmp/simple.s4'

Per comment #2 and comment #4, move it to verified status.

Comment 7 errata-xmlrpc 2015-11-19 06:05:44 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2202.html