/lib/udev/rules.d/80-btrfs-lvm.rules is in btrfs-tools 3.17-1.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 | SUBSYSTEM!="block", GOTO="btrfs_lvm_end"
ENV{DM_UUID}!="LVM-?*", GOTO="btrfs_lvm_end"
RUN+="/sbin/modprobe btrfs"
RUN+="/sbin/btrfs device scan $env{DEVNAME}"
LABEL="btrfs_lvm_end"
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