We have a reproducer now:
$ uname -a Linux ln-sv-infr01 4.15.0-42-generic #45-Ubuntu SMP Thu Nov 15 19:32:57 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 3.7T 0 disk ├─sda1 8:1 0 512M 0 part /boot/efi └─sda2 8:2 0 3.7T 0 part ├─ln--sv--infr01--vg-root 253:0 0 301G 0 lvm / ├─ln--sv--infr01--vg-swap_1 │ 253:1 0 976M 0 lvm [SWAP] └─ln--sv--infr01--vg-var 253:2 0 3.4T 0 lvm └─bcache0 252:0 0 3.4T 0 disk /var nvme0n1 259:0 0 1.5T 0 disk └─bcache0 252:0 0 3.4T 0 disk /var
$ sudo fstrim /var # at this point it will immediately fail to kernel panic ... oops
We have a reproducer now:
$ uname -a
Linux ln-sv-infr01 4.15.0-42-generic #45-Ubuntu SMP Thu Nov 15 19:32:57 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
$ lsblk -sv--infr01- -vg-root 253:0 0 301G 0 lvm / -sv--infr01- -vg-swap_ 1 -sv--infr01- -vg-var 253:2 0 3.4T 0 lvm
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 3.7T 0 disk
├─sda1 8:1 0 512M 0 part /boot/efi
└─sda2 8:2 0 3.7T 0 part
├─ln-
├─ln-
│ 253:1 0 976M 0 lvm [SWAP]
└─ln-
└─bcache0 252:0 0 3.4T 0 disk /var
nvme0n1 259:0 0 1.5T 0 disk
└─bcache0 252:0 0 3.4T 0 disk /var
$ sudo fstrim /var
# at this point it will immediately fail to kernel panic ... oops