✏ EDIT: 69-dm-lvm-metad.rules

# Copyright (C) 2012 Red Hat, Inc. All rights reserved.
#
# This file is part of LVM2.

# Udev rules for LVM.
#
# This rule requires blkid to be called on block devices before so only devices
# used as LVM PVs are processed (ID_FS_TYPE="LVM2_member" or "LVM1_member").

SUBSYSTEM!="block", GOTO="lvm_end"

ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}=="1", GOTO="lvm_end"

# Detect removed PV label by comparing previous ID_FS_TYPE value with current one.
ENV{.ID_FS_TYPE_NEW}="$env{ID_FS_TYPE}"
IMPORT{db}="ID_FS_TYPE"
ENV{ID_FS_TYPE}=="LVM2_member|LVM1_member", ENV{.ID_FS_TYPE_NEW}!="LVM2_member|LVM1_member", ENV{LVM_PV_GONE}="1"
ENV{ID_FS_TYPE}="$env{.ID_FS_TYPE_NEW}"
ENV{LVM_PV_GONE}=="1", GOTO="lvm_scan"

# Only process devices already marked as a PV - this requires blkid to be called before.
ENV{ID_FS_TYPE}!="LVM2_member|LVM1_member", GOTO="lvm_end"
ENV{DM_MULTIPATH_DEVICE_PATH}=="1", GOTO="lvm_end"

ACTION=="remove", GOTO="lvm_scan"

# Create /dev/disk/by-id/lvm-pv-uuid-<PV_UUID> symlink for each PV
ENV{ID_FS_UUID_ENC}=="?*", SYMLINK+="disk/by-id/lvm-pv-uuid-$env{ID_FS_UUID_ENC}"

# If the PV is a special device listed below, scan only if the device is
# properly activated. These devices are not usable after an ADD event,
# but they require an extra setup and they are ready after a CHANGE event.
# Also support coldplugging with ADD event but only if the device is already
# properly activated.
# This logic should be eventually moved to rules where those particular
# devices are processed primarily (MD and loop).

# DM device:
KERNEL!="dm-[0-9]*", GOTO="next"
ENV{DM_UDEV_PRIMARY_SOURCE_FLAG}=="1", ENV{DM_ACTIVATION}=="1", GOTO="lvm_scan"
GOTO="lvm_end"

# MD device:
LABEL="next"
KERNEL!="md[0-9]*", GOTO="next"
IMPORT{db}="LVM_MD_PV_ACTIVATED"
ACTION=="add", ENV{LVM_MD_PV_ACTIVATED}=="1", GOTO="lvm_scan"
ACTION=="change", ENV{LVM_MD_PV_ACTIVATED}!="1", TEST=="md/array_state", ENV{LVM_MD_PV_ACTIVATED}="1", GOTO="lvm_scan"
ACTION=="add", KERNEL=="md[0-9]*p[0-9]*", GOTO="lvm_scan"
ENV{LVM_MD_PV_ACTIVATED}!="1", ENV{SYSTEMD_READY}="0"
GOTO="lvm_end"

# Loop device:
LABEL="next"
KERNEL!="loop[0-9]*", GOTO="next"
ACTION=="add", ENV{LVM_LOOP_PV_ACTIVATED}=="1", GOTO="lvm_scan"
ACTION=="change", ENV{LVM_LOOP_PV_ACTIVATED}!="1", TEST=="loop/backing_file", ENV{LVM_LOOP_PV_ACTIVATED}="1", GOTO="lvm_scan"
ENV{LVM_LOOP_PV_ACTIVATED}!="1", ENV{SYSTEMD_READY}="0"
GOTO="lvm_end"

# If the PV is not a special device listed above, scan only if necessary.
# For "systemd_background" mode, systemd takes care of this by activating
# the lvm2-pvscan@.service only once.
LABEL="next"
ACTION!="add|change", GOTO="lvm_end"

LABEL="lvm_scan"

ENV{SYSTEMD_READY}="1"

# The method for invoking pvscan is selected at build time with the option
# --(enable|disable)-udev-systemd-background-jobs to "configure".
# On modern distributions with recent systemd, it's "systemd_background";
# on others, "direct_pvscan".
GOTO="systemd_background"

LABEL="systemd_background"

# The table below summarises the situations in which we reach the LABEL="lvm_scan"
# in the "systemd_background" case.
# Marked by X, X* means only if the special dev is properly set up.
# The artificial ADD is supported for coldplugging. We avoid running the pvscan
# on artificial CHANGE so there's no unexpected autoactivation when WATCH rule fires.
# N.B. MD and loop never actually  reaches lvm_scan on REMOVE as the PV label is gone
# within a CHANGE event (these are caught by the "LVM_PV_GONE" rule at the beginning).
#
# In this case, we simply set up the dependency between the device and the pvscan
# job using SYSTEMD_ALIAS (which sets up a simplified device identifier that
# allows using "BindsTo" in the systemd unit file) and SYSTEMD_WANTS (which tells
# systemd to start the pvscan job once the device is ready).
# We need to set these variables for both "add" and "change" events, otherwise
# systemd may loose information about the device/unit dependencies.
#
#        | real ADD | real CHANGE | artificial ADD | artificial CHANGE | REMOVE
# =============================================================================
#  DM    |          |      X      |       X*       |                   |   X
#  MD    |          |      X      |       X*       |                   |
#  loop  |          |      X      |       X*       |                   |
#  other |    X     |      X      |       X        |                   |   X
ACTION!="remove", ENV{LVM_PV_GONE}=="1", RUN+="/usr/bin/systemd-run /usr/sbin/lvm pvscan --cache $major:$minor", GOTO="lvm_end"
ENV{SYSTEMD_ALIAS}="/dev/block/$major:$minor"
ENV{SYSTEMD_WANTS}+="lvm2-pvscan@$major:$minor.service"
GOTO="lvm_end"

# FIXME: this mode is not used and should be removed.
LABEL="direct_pvscan"

# The table below summarises the situations in which we reach the LABEL="lvm_scan"
# for the "direct_pvscan" case.
# Marked by X, X* means only if the special dev is properly set up.
# The artificial ADD is supported for coldplugging. We avoid running the pvscan
# on artificial CHANGE so there's no unexpected autoactivation when WATCH rule fires.
#
# In this case, we need to make sure that pvscan is not invoked spuriously, therefore
# we invoke it only for "add" events for "other" devices.
#
#        | real ADD | real CHANGE | artificial ADD | artificial CHANGE | REMOVE
# =============================================================================
#  DM    |          |      X      |       X*       |                   |   X
#  MD    |          |      X      |       X*       |                   |
#  loop  |          |      X      |       X*       |                   |
#  other |    X     |             |       X        |                   |   X
RUN+="/usr/sbin/lvm pvscan --background --cache --activate ay --major $major --minor $minor", ENV{LVM_SCANNED}="1"

LABEL="lvm_end"

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