lvm/device-mapper weirdness

Spent almost an hour trying to figure out why logical volume doesn't want to be activated on NetApp iSCSI LUN. Turned out that the answer is pretty simple: the lun is in readonly mode.

# vgchange -ay "vg"
device-mapper: reload ioctl failed: Invalid argument
1 logical volume(s) in volume group "" now active

# dmesg
device-mapper: table: 253:2: linear: dm-linear: Device lookup failed
device-mapper: ioctl: error adding target to table

filer>lun show
/vol/test_vol/test_lun 99g (106300440576) (r/o, online, mapped)