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Nathel

Member

Registered: 2014-07-11

Posts: 4

[SOLVED]Opening a LUKS encrypted USB SSD changes its provisioning_mode

By "opening" I mean running cryptsetup luksOpen.

I want to use TRIM on the drive, so I made a udev rule according to the wiki:

cat /sys/block/sda/../../../../../../idVendor
04e8

cat /sys/block/sda/../../../../../../idProduct
61fb

cat /etc/udev/rules.d/10-uas-discard.rules 
ACTION=="add|change", ATTRS{idVendor}=="04e8", ATTRS{idProduct}=="61fb", SUBSYSTEM=="scsi_disk", ATTR{provisioning_mode}="unmap"

It used to work just fine back then, in March 2024. I could run fstrim without any issues.

Now, however, cryptsetup for some reason causes provisioning_mode to revert back to full. And changing it when the drive is already unlocked sadly achieves nothing.

cat /sys/block/sda/device/scsi_disk/*/provisioning_mode
unmap

sudo cryptsetup luksOpen /dev/sda external
Enter passphrase for /dev/sda: 

cat /sys/block/sda/device/scsi_disk/*/provisioning_mode
full

sudo su

echo "unmap" > /sys/block/sda/device/scsi_disk/*/provisioning_mode

^D

cat /sys/block/sda/device/scsi_disk/*/provisioning_mode
unmap

sudo cryptsetup luksDump /dev/sda | grep Flags
Flags:          allow-discards

mkdir test && sudo mount /dev/mapper/external ./test

sudo fstrim ./test
fstrim: ./test: the discard operation is not supported

I'm at a loss at what's going on, could use some input.

Last edited by Nathel (2025-09-12 19:10:40)

Nathel

Member

Registered: 2014-07-11

Posts: 4

Re: [SOLVED]Opening a LUKS encrypted USB SSD changes its provisioning_mode

Two kernel updates later the issue went away.