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Bug 1512844

Summary:	cache_restore tool may corrupt cache metadata
Product:	Red Hat Enterprise Linux 7	Reporter:	Marian Csontos <mcsontos>
Component:	device-mapper-persistent-data	Assignee:	LVM and device-mapper development team <lvm-team>
Status:	CLOSED ERRATA	QA Contact:	Jakub Krysl <jkrysl>
Severity:	high	Docs Contact:
Priority:	high
Version:	7.5	CC:	agk, heinzm, jkrysl, lmiksik, lvm-team, msnitzer, rhandlin, thornber
Target Milestone:	rc	Keywords:	ZStream
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	device-mapper-persistent-data-0.7.3-3.el7	Doc Type:	If docs needed, set a value
Doc Text:	Previously, the cache_restore utility passed incorrect arguments to a function. Additionally, it missed a call to flush dirty bits when version 2 metadata of the cache was used. As a consequence, the utility corrupted the cache metadata. With this update, cache_restore now handles the arguments correctly and adds the missing call. As a result, the utility no longer corrupts version 2 metadata.	Story Points:	---
Clone Of:
Clones:	1515109 (view as bug list)		Environment:
Last Closed:	2018-04-10 13:18:38 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:
Bug Depends On:
Bug Blocks:	1515109

Description Marian Csontos 2017-11-14 09:36:38 UTC

Description of problem:
Under some circumstances cache_restore tool corrupts metadata.

Version-Release number of selected component (if applicable):
device-mapper-persistent-data-0.7.3

Sorry for being so vague. Waiting for devel to fill in reproducer.

Comment 2 Joe Thornber 2017-11-14 09:43:31 UTC

v0.7.0 of the tools introduced support for cache metadata v2.

However cache restore was not writing a crucial field to the superblock.  So the kernel cannot load the metadata.

This patch fixes it:

https://github.com/jthornber/thin-provisioning-tools/commit/e3b7d825696c23c23f6bd867de4dbda69be38db8

The bug wasn't discovered for a long time because a separate bug meant v1 metadata was always being written even if v2 was requested.

v0.7.5 behaves correctly.

Comment 5 Jakub Krysl 2017-11-20 13:30:10 UTC

before:
# cache_restore -V
0.7.0-0.1.rc6.el7
# cache_restore -i metadata -o /dev/mapper/vgtest-swapvol --debug-override-metadata-version 2
cache_restore: /usr/include/boost/optional/optional.hpp:631: boost::optional<T>::reference_type boost::optional<T>::get() [with T = long unsigned int; boost::optional<T>::reference_type = long unsigned int&]: Assertion `this->is_initialized()' failed.
Aborted (core dumped)

with this patch:
# cache_restore -V
0.7.0-0.1.rc6.el7_4.1
# cache_restore -i metadata -o /dev/mapper/vgtest-swapvol --debug-override-metadata-version 2
Restoring: [==================================================]   100%

Comment 8 errata-xmlrpc 2018-04-10 13:18:38 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://access.redhat.com/errata/RHEA-2018:0776