Comment 14 for bug 1481536

This problem is caused by a race condition, which is why only some people are experiencing it.

At /usr/share/initramfs-tools/scripts/local-top/cryptsetup line 322, the setup_mapping() function in the cryptroot script calls the activate_vg() function, which runs 'lvm vgchange -a y'. At line 340, without waiting for udev to finish creating the device links for the newly activated volume group, 'blkid' is invoked to get the filesystem type of the logical volume. This fails if udev hasn't yet finished creating the device links, which causes the script to log "cryptsetup: unknown fstype, bad password or options?" at line 345 and run 'cryptsetup remove' at line 347. Fortunately 'cryptsetup remove' fails because the volume group was successfully activated (the crypt device is now busy), which allows the next iteration through the loop to succeed.

The attached patch fixes this bug for me.