/lib/udev/rules.d/ Current File: //lib/udev/rules.d/56-dm-mpath.rules
ACTION!="add|change", GOTO="mpath_end"
ENV{DM_UDEV_RULES}!="?*", GOTO="mpath_end"
ENV{DM_UUID}!="mpath-?*", GOTO="mpath_end"

IMPORT{db}="DM_DISABLE_OTHER_RULES_FLAG_OLD"
IMPORT{db}="MPATH_DEVICE_READY"

# If this uevent didn't come from dm, don't try to update the
# device state
ENV{DM_COOKIE}!="?*", ENV{DM_ACTION}!="PATH_*", IMPORT{db}="DM_UDEV_DISABLE_OTHER_RULES_FLAG", IMPORT{db}="DM_NOSCAN", GOTO="scan_import"

ENV{.MPATH_DEVICE_READY_OLD}="$env{MPATH_DEVICE_READY}"

# multipath sets DM_SUBSYSTEM_UDEV_FLAG2 when it reloads a
# table with no active devices. If this happens, mark the
# device not ready
ENV{DM_SUBSYSTEM_UDEV_FLAG2}=="1", ENV{MPATH_DEVICE_READY}="0",\
	GOTO="mpath_action"

# If the last path has failed mark the device not ready
# Note that DM_NR_VALID_PATHS is only set for PATH_FAILED|PATH_REINSTATED
# events.
# This may not be reliable, as events aren't necessarily received in order.
ENV{DM_NR_VALID_PATHS}=="0", ENV{MPATH_DEVICE_READY}="0", GOTO="mpath_action"

ENV{MPATH_SBIN_PATH}="/sbin"
TEST!="$env{MPATH_SBIN_PATH}/multipath", ENV{MPATH_SBIN_PATH}="/usr/sbin"

# Don't run multipath -U during "coldplug" after switching root,
# because paths are just being added to the udev db.
ACTION=="add", ENV{.MPATH_DEVICE_READY_OLD}=="1", GOTO="paths_ok"

# Check the map state directly with multipath -U.
# This doesn't attempt I/O on the device.
PROGRAM=="$env{MPATH_SBIN_PATH}/multipath -U %k", GOTO="paths_ok"
ENV{MPATH_DEVICE_READY}="0", GOTO="mpath_action"
LABEL="paths_ok"

# Don't mark a device ready on a PATH_FAILED event. even if
# DM_NR_VALID_PATHS is greater than 0. Just keep the existing
# value
ENV{DM_ACTION}=="PATH_FAILED", GOTO="mpath_action"

# This event is either a PATH_REINSTATED or a table reload where
# there are active paths. Mark the device ready
ENV{MPATH_DEVICE_READY}="1"

LABEL="mpath_action"
# DM_SUBSYSTEM_UDEV_FLAG0 is the "RELOAD" flag for multipath subsystem.
# Drop the DM_ACTIVATION flag here as mpath reloads tables if any of its
# paths are lost/recovered. For any stack above the mpath device, this is not
# something that should be reacted upon since it would be useless extra work.
# It's exactly mpath's job to provide *seamless* device access to any of the
# paths that are available underneath.
ENV{DM_SUBSYSTEM_UDEV_FLAG0}=="1", \
	ENV{DM_ACTIVATION}="0", ENV{MPATH_UNCHANGED}="1"

# For path failed or reinstated events, unset DM_ACTIVATION.
# This is similar to the DM_SUBSYSTEM_UDEV_FLAG0 case above.
ENV{DM_ACTION}=="PATH_FAILED|PATH_REINSTATED", \
	ENV{DM_ACTIVATION}="0", ENV{MPATH_UNCHANGED}="1"

# Do not initiate scanning if no path is available,
# otherwise there would be a hang or IO error on access.
# We'd like to avoid this, especially within udev processing.
ENV{MPATH_DEVICE_READY}=="0", ENV{DM_NOSCAN}="1"

# Also skip all foreign rules if no path is available.
# Remember the original value of DM_DISABLE_OTHER_RULES_FLAG
# and restore it back once we have at least one path available.
ENV{MPATH_DEVICE_READY}=="0", ENV{.MPATH_DEVICE_READY_OLD}=="1",\
	ENV{DM_DISABLE_OTHER_RULES_FLAG_OLD}=="",\
	ENV{DM_DISABLE_OTHER_RULES_FLAG_OLD}="$env{DM_UDEV_DISABLE_OTHER_RULES_FLAG}"
ENV{MPATH_DEVICE_READY}=="0", ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}="1"
ENV{MPATH_DEVICE_READY}!="0", ENV{.MPATH_DEVICE_READY_OLD}=="0",\
	ENV{DM_UDEV_DISABLE_OTHER_RULES_FLAG}="$env{DM_DISABLE_OTHER_RULES_FLAG_OLD}",\
	ENV{DM_DISABLE_OTHER_RULES_FLAG_OLD}="",\
	ENV{DM_ACTIVATION}="1"

# The code to check multipath state ends here. We need to set
# properties and symlinks regardless whether the map is usable or
# not. If symlinks get lost, systemd may auto-unmount file systems.

LABEL="scan_import"
ENV{DM_NOSCAN}!="1", GOTO="import_end"
IMPORT{db}="ID_FS_TYPE"
IMPORT{db}="ID_FS_USAGE"
IMPORT{db}="ID_FS_UUID"
IMPORT{db}="ID_FS_UUID_ENC"
IMPORT{db}="ID_FS_LABEL"
IMPORT{db}="ID_FS_LABEL_ENC"
IMPORT{db}="ID_FS_VERSION"

LABEL="import_end"

# Multipath maps should take precedence over their members.
ENV{DM_UDEV_LOW_PRIORITY_FLAG}!="1", OPTIONS+="link_priority=50"

# Set some additional symlinks that typically exist for mpath
# path members, too, and should be overridden.

# kpartx_id is very robust, it works for suspended maps and maps
# with 0 dependencies. It sets DM_TYPE, DM_PART, DM_WWN
TEST=="/lib/udev/kpartx_id", \
	IMPORT{program}=="kpartx_id %M %m $env{DM_UUID}"

ENV{DM_TYPE}=="?*", ENV{DM_SERIAL}=="?*", \
	SYMLINK+="disk/by-id/$env{DM_TYPE}-$env{DM_SERIAL}"
ENV{DM_WWN}=="?*", SYMLINK+="disk/by-id/wwn-$env{DM_WWN}"

LABEL="mpath_end"