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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-dataAssignee: LVM and device-mapper development team <lvm-team>
Status: CLOSED ERRATA QA Contact: Jakub Krysl <jkrysl>
Severity: high Docs Contact:
Priority: high    
Version: 7.5CC: agk, heinzm, jkrysl, lmiksik, lvm-team, msnitzer, rhandlin, thornber
Target Milestone: rcKeywords: 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:
: 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: ---
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