[linux-lvm] Creation of snapshots failing with `in use' errors

[Alasdair G Kergon]

On Sun, Aug 27, 2006 at 06:57:37PM +0100, Nix wrote:
> Specifically, snapshot creation randomly fails if you've recently done
> another LVM command. 

See if it's the usual udev problem: completely disable udev for your
lvm devices.  [Common problem is udev causing the device to be opened to
look for a label - then lvm command fails because it needs exclusive
access.]

> original filesystem, since LVM maintains a snapshot percentage counter

lvm2 doesn't maintain it, but while a device is active, kernel dm tells
userspace lvm2 the percentage full.

> This has not only not worked for no good reason (it's not in use! it's
> brand new!) 

udev is probably using it.
Old udev packages used to work OK, but something got changed - we never
discovered what (ref. an old debian bug) - and this started to break.

Some people at suse are working on a proper fix for this problem (so kernel
will inform udev when device is usable, instead of udev running too early as
it can now; udev will inform lvm2 when it has finished whatever pointless
things it wants to do and lvm2 will wait for that message).

Alasdair
-- 
agk at redhat.com