[linux-lvm] rc4 can't take snaphots of 0.9.1_beta7 lvs

[Chris Mason]

Hello everyone,

Looks like the compatibility code in rc4 doesn't properly snapshot beta7
logical volumes (2.4.10 kernel).

To reproduce, I did this:

Install 0.9.1 beta7 tools

pvcreate /dev/sdb2
vgcreate big /dev/sdb2
lvcreate --size 6G -n lv1 big
vgchange -a n
rmmod lvm-mod

Install rc4 tools
vgscan
vchange -a y
mkfs /dev/big/lv1
mount /dev/big/lv1 /data
lvcreate --size 1G -n snap --snapshot /dev/big/lv1
(trigger COW to snapshot)

And I get these messages:

lvm -- _pv_get_number failed for rdev = 0
lvm -- giving up to snapshot /dev/big/lv1 on /dev/big/snap: couldn't
prepare kiovec blocks (start probably isn't block aligned).

Now that I can reliably reproduce on stock kernels/tools, I'm trying to
trace it further.  If anyone has ideas I'd love to hear them.

-chris