On 6/15/19 2:49 PM, Jordan Glover wrote:
One question: does reencryption allows changing block size?
For example: old size:512, new size:4096
Hi,
new reencryption code indeed supports change of encryption block size
(both ways), even in online mode. But user has to ask for it explicitly
by specifying --sector-size parameter when initializing device
reencryption. By default we retain original encryption sector size (from
luksFormat action).
But I strongly recommend to be careful with it. Changing encryption
sector size on devices underneath existing filesystem is tricky. See my
post on pvmove of existing fs from dm-crypt with 512 sector size to
dm-crypt with 4K sector size:
https://www.saout.de/pipermail/dm-crypt/2019-February/006078.html
You have to ensure the filesystem can handle device limits increase to
4K (that's what encryption sector size increase actually does). It's
safe for fs formatted with blocksize set to 4K. But if fs was formatted
with blocksize < 4K do not try do not try to increase encryption sector
size beyond filesystem block size.
Kind regards
O.
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