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Diffstat (limited to 'Documentation/device-mapper/dm-uevent.txt')
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diff --git a/Documentation/device-mapper/dm-uevent.txt b/Documentation/device-mapper/dm-uevent.txt new file mode 100644 index 00000000000..07edbd85c71 --- /dev/null +++ b/Documentation/device-mapper/dm-uevent.txt @@ -0,0 +1,97 @@ +The device-mapper uevent code adds the capability to device-mapper to create +and send kobject uevents (uevents). Previously device-mapper events were only +available through the ioctl interface. The advantage of the uevents interface +is the event contains environment attributes providing increased context for +the event avoiding the need to query the state of the device-mapper device after +the event is received. + +There are two functions currently for device-mapper events. The first function +listed creates the event and the second function sends the event(s). + +void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti, + const char *path, unsigned nr_valid_paths) + +void dm_send_uevents(struct list_head *events, struct kobject *kobj) + + +The variables added to the uevent environment are: + +Variable Name: DM_TARGET +Uevent Action(s): KOBJ_CHANGE +Type: string +Description: +Value: Name of device-mapper target that generated the event. + +Variable Name: DM_ACTION +Uevent Action(s): KOBJ_CHANGE +Type: string +Description: +Value: Device-mapper specific action that caused the uevent action. + PATH_FAILED - A path has failed. + PATH_REINSTATED - A path has been reinstated. + +Variable Name: DM_SEQNUM +Uevent Action(s): KOBJ_CHANGE +Type: unsigned integer +Description: A sequence number for this specific device-mapper device. +Value: Valid unsigned integer range. + +Variable Name: DM_PATH +Uevent Action(s): KOBJ_CHANGE +Type: string +Description: Major and minor number of the path device pertaining to this +event. +Value: Path name in the form of "Major:Minor" + +Variable Name: DM_NR_VALID_PATHS +Uevent Action(s): KOBJ_CHANGE +Type: unsigned integer +Description: +Value: Valid unsigned integer range. + +Variable Name: DM_NAME +Uevent Action(s): KOBJ_CHANGE +Type: string +Description: Name of the device-mapper device. +Value: Name + +Variable Name: DM_UUID +Uevent Action(s): KOBJ_CHANGE +Type: string +Description: UUID of the device-mapper device. +Value: UUID. (Empty string if there isn't one.) + +An example of the uevents generated as captured by udevmonitor is shown +below. + +1.) Path failure. +UEVENT[1192521009.711215] change@/block/dm-3 +ACTION=change +DEVPATH=/block/dm-3 +SUBSYSTEM=block +DM_TARGET=multipath +DM_ACTION=PATH_FAILED +DM_SEQNUM=1 +DM_PATH=8:32 +DM_NR_VALID_PATHS=0 +DM_NAME=mpath2 +DM_UUID=mpath-35333333000002328 +MINOR=3 +MAJOR=253 +SEQNUM=1130 + +2.) Path reinstate. +UEVENT[1192521132.989927] change@/block/dm-3 +ACTION=change +DEVPATH=/block/dm-3 +SUBSYSTEM=block +DM_TARGET=multipath +DM_ACTION=PATH_REINSTATED +DM_SEQNUM=2 +DM_PATH=8:32 +DM_NR_VALID_PATHS=1 +DM_NAME=mpath2 +DM_UUID=mpath-35333333000002328 +MINOR=3 +MAJOR=253 +SEQNUM=1131 |