Our hosts use local md arrays as LVM2 PVs in a very straightforward way.
They also have lots of slower iscsi devices which LVM shouldn't scan or
touch, so we use a simple filter in lvm.conf:
devices {
filter = [ "a|^/dev/md.*|", "r|.*|" ]
}
Upon upgrading from lvm-2.02.106 to 2.02.129, commands like lvdisplay and
lvs dramatically slowed down. Investigating, we found the filter wasn't
excluding the unwanted devices anymore: they were being scanned despite
being explicitly excluded.
A simple way to reproduce this in a VM is
# cat /etc/lvm/lvm.conf
devices {
filter = [ "r|.*|" ]
}
# lvm-2.02.129 pvscan -vv 2>&1 | grep /dev/
/dev/md0: size is 0 sectors
/dev/vda: size is 2147483648 sectors
/dev/vda: size is 2147483648 sectors
# lvm-2.02.106 pvscan -vv 2>&1 | grep /dev/
#
If I replace filter with global_filter, both versions behave identically:
# cat /etc/lvm/lvm.conf
devices {
global_filter = [ "r|.*|" ]
}
# lvm-2.02.129 pvscan -vv 2>&1 | grep /dev/
# lvm-2.02.106 pvscan -vv 2>&1 | grep /dev/
#
Deleting /etc/lvm/cache before running each pvscan doesn't affect the result.
A quick git bisect finds the behaviour changed with the following:
commit 80ac8f37d6ac5f8c5228678d4ee07187b5d4db7b
Author: Peter Rajnoha <prajnoha@redhat.com>
Date: Thu Sep 11 09:30:03 2014 +0200
filters: fix incorrect filter indexing in composite filter array
Caused by recent changes - a7be3b12dfe7388d1648595e6cc4c7a1379bb8a7.
If global filter was not defined, then part of the code
creating composite filter (the cmd->lvmetad_filter) incorrectly
increased index value even if this global filter was not created
as part of the composite filter. This caused a gap with "NULL"
value in the composite filter array which ended up with the rest
of the filters after the gap to be ignored and also it caused a mem
leak when destroying the composite filter.
Presumably this change in the behaviour of devices.filter is an
unintentional consequence rather than deliberate? Our use is copied
more-or-less directly from the example in conf/example.conf.
Best wishes,
Chris.
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