Re: [dm-crypt] luks2 and discard/trim not working

[Nikolay Kichukov <hijacker@oldum.net>]

Hello Chris,

On Sat, 9 May 2020 09:45:13 -0600
Chris Murphy <lists@colorremedies.com> wrote:

> On Sat, May 9, 2020 at 8:28 AM Nikolay Kichukov <hijacker@oldum.net>
> wrote:
> >
> > Hello folks,
> >
> > Recently, I upgraded to LUKS2 on a NVME SSD disk and noticed that
> > fstrim does not work. Surely it was running fine with LUKS1.  
> 
> ...
> 
> > dmsetup table /dev/mapper/root | grep allow
> > 0 947028136 crypt capi:rfc7539(chacha20,poly1305)-random
> > :32:logon:cryptsetup:6ae40ec7-1b4c-40ea-871b-d13c9ae66b92-d0 0
> > 254:0 0 2 allow_discards integrity:28:aead  
> 
> Was the original luksFormat command combined with --integrity option?

yes

> From man cryptsetup: Since dm-integrity doesn't support discards
> (TRIM), dm-crypt device on top of it inherits this, so integrity
> protection mode doesn't support discards either.

Thanks for the direction! It seems like, this is in the pipeline for
dm-integrity, which is to arrive in version 1.6.0 in kernel 5.7:

"allow_discards
Allow block discard requests (a.k.a. TRIM) for the integrity device.
Discards are only allowed to devices using internal hash.
The default is to ignore discard requests.
Available since: 1.6.0 (kernel 5.7)"

source: https://gitlab.com/cryptsetup/cryptsetup/-/wikis/DMIntegrity
 
Does mine use an internal hash?

Thanks,
-Nik