[linux-lvm] dmsetup -split is buggy

Linda A. Walsh lvm at tlinx.org
Mon Aug 15 09:34:20 UTC 2011

I'm told that /dev/VG/LV is the official LVM syntax for a devname,

so I passed a /dev/VG/LV, name to LVM, and it mangled the LV name,
splitting it into a LVLayer.

I gave it:


Which corresponds to a /home/snapdir/@GMT-2011.08.08-03.29.58
(@GMT-date-time is a required name format), so my volumes
for such snapdirs have the base-LV and the date-time.

There is nothing in the lvm spec that or device name spec, that says
"-" is to be interpreted as some layer.... 

The problem is that when this routine gets a device name, it might be
/dev/mapper/<encoded value>
or /dev/VG/LV

dmsetup splitname, should, I believe, know how to split
names in the only 'supported' name format  i.e. /dev/VG/LV -- but
instead, it's treating it as though it were under /dev/mapper and using 
that for

I can hack around the bug, but its surprising that dmsetup doesn't support
the only official LVM names (/dev/VG/LV).

Is this bug a 'feature', or is it something that should be fixed?

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