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Bug 1558034

Summary:	Creating a partial child snapshot in a VM with an existing snapshot containing a cinder snapshot breaks the snapshot
Product:	[oVirt] ovirt-engine	Reporter:	Benny Zlotnik <bzlotnik>
Component:	BLL.Storage	Assignee:	Benny Zlotnik <bzlotnik>
Status:	CLOSED CURRENTRELEASE	QA Contact:	Natalie Gavrielov <ngavrilo>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	future	CC:	bugs, bzlotnik, derez, tnisan
Target Milestone:	ovirt-4.2.3	Flags:	rule-engine: ovirt-4.2+
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2018-05-10 06:30:57 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	Storage	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Benny Zlotnik 2018-03-19 13:20:34 UTC

Description of problem:


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. Create a VM with a regular disk (either block or file), and a cinder disk
2. Take a snapshot of both disks - s1
3. Take a second snapshot of only the regular disk - s2

Actual results:
Multiple problems occur: The cinder disk in the first snapshot appears illegal, the active snapshot only contains the cinder disk.
According to the DB, the cinder snapshot is part of s2 and no longer a part of s1.

This has additional side effects, such as removing the snapshot s2 will also remove cinder disk

Expected results:
s1 should contain the cinder disk and the regular disk
s2 should contain only the regular disk
and the active snapshot should contain both without the additional side-effects

Additional info:

Comment 1 Natalie Gavrielov 2018-04-23 19:36:27 UTC

Performed scenario described in comment 0.
* First snapshot contains the cinder disk and the regular disk.
* Second snapshot contains only the regular disk.

Cinder disk id was: 7b81c8b5-7f75-4560-9f0b-b193316ca558
Cinder disk snapshot id (s1) was: cc84dcae-5e60-4782-ab2a-1b2eec858b2c

When looking at the active vm:

Status Up
Alias cinder_disk
Virtual Size 5 GiB
Actual Size < 1 GiB
Allocation Policy Unassigned
Interface N/A
Creation Date Apr 23, 2018, 9:34:26 PM
Disk Snapshot ID 7b81c8b5-7f75-4560-9f0b-b193316ca558    <-- HERE
Type CINDER
Description N/A

It shows the original cinder disk id, I expected to see the first snapshot id: cc84dcae-5e60-4782-ab2a-1b2eec858b2c

Benny, is this part of the fix? or another bug?

Comment 2 Benny Zlotnik 2018-04-24 07:24:18 UTC

This is the expected behavior: In Cinder we always write to the "active image" and snapshots are created separately, unlike in regular images where when creating a snapshot we take the current active image and create a new "active image"

Daniel, can you confirm?

Comment 3 Daniel Erez 2018-04-24 08:38:24 UTC

(In reply to Benny Zlotnik from comment #2)
> This is the expected behavior: In Cinder we always write to the "active
> image" and snapshots are created separately, unlike in regular images where
> when creating a snapshot we take the current active image and create a new
> "active image"
> 
> Daniel, can you confirm?

Indeed, the id shouldn't change as we keep the active layer intact for cinder disks when creating snapshots.

Comment 4 Natalie Gavrielov 2018-04-24 10:56:11 UTC

Verified (including delete snapshot operations), used builds:
rhvm-4.2.3.2-0.1.el7.noarch
vdsm-4.20.26-1.el7ev.x86_64

Comment 5 Sandro Bonazzola 2018-05-10 06:30:57 UTC

This bugzilla is included in oVirt 4.2.3 release, published on May 4th 2018.

Since the problem described in this bug report should be
resolved in oVirt 4.2.3 release, it has been closed with a resolution of CURRENT RELEASE.

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