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.
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.
Created attachment 315497 [details] patch A patch for the problem. Use per-snapshot mempools.
in kernel-2.6.18-111.el5 You can download this test kernel from http://people.redhat.com/dzickus/el5
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