Package: lsof Version: 4.95.0-1 Followup-For: Bug #1040373 This seems to be related to upstream issue:
https://github.com/lsof-org/lsof/issues/152 "LTlock fails on btrfs" Small test-case: SUBVOL_FILE="/mnt/machines_old/test"; sudo findmnt -oTARGET,SOURCE,FSTYPE,MAJ:MIN "${SUBVOL_FILE%/*}" sudo stat --format="%n %Hd:%Ld" "$SUBVOL_FILE" flock "$SUBVOL_FILE" grep ":$(stat --format="%i" "$SUBVOL_FILE")" /proc/locks | tee >(bc <<< "ibase=16; $(cut -d: -f 3)") TARGET SOURCE FSTYPE MAJ:MIN /mnt/machines_old /dev/mapper/SUNNY-machines_old btrfs 0:100 /mnt/machines_old/test 0:101 20: FLOCK ADVISORY WRITE 378526 00:64:395 0 EOF 100