Bug 460846

Summary: Deadlock possibility with nested LVMs with snapshots
Product: Red Hat Enterprise Linux 5 Reporter: Mikuláš Patočka <mpatocka>
Component: kernelAssignee: Mikuláš Patočka <mpatocka>
Status: CLOSED ERRATA QA Contact: Martin Jenner <mjenner>
Severity: low Docs Contact:
Priority: medium    
Version: 5.3CC: agk, christophe.varoqui, cmarthal, dwysocha, edamato, egoggin, heinzm, jbrassow, junichi.nomura, kueda, lmb, mbroz, prockai, tranlan
Target Milestone: rc   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2009-01-20 20:17:25 UTC Type: ---
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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patch none

Description Mikuláš Patočka 2008-09-01 22:20:21 UTC 
When using nested LVMs (volume group built from physical devices that are logical devices in another volume group), there is possibility of deadlock in snapshot target because it uses shared mempool. If the upper-layer LVM drains the mempool, the lower layer can deadlock unable to allocate any memory.

It nees to be changed to per-device mempools.

This deadlocky configuration is very unusual, but supported by Red Hat, so it should be fixed.
Comment 1 RHEL Program Management 2008-09-01 22:22:05 UTC 
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release.  Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products.  This request is not yet committed for inclusion in an Update
release.
Comment 2 Mikuláš Patočka 2008-09-01 22:48:29 UTC 
Created attachment 315497 [details]
patch

A patch for the problem. Use per-snapshot mempools.
Comment 3 Don Zickus 2008-09-11 19:44:20 UTC 
in kernel-2.6.18-111.el5
You can download this test kernel from http://people.redhat.com/dzickus/el5
Comment 7 errata-xmlrpc 2009-01-20 20:17:25 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-2009-0225.html