Documentation/device-mapper/dm-uevent.txt

   1 The device-mapper uevent code adds the capability to device-mapper to create
   2 and send kobject uevents (uevents).  Previously device-mapper events were only
   3 available through the ioctl interface.  The advantage of the uevents interface
   4 is the event contains environment attributes providing increased context for
   5 the event avoiding the need to query the state of the device-mapper device after
   6 the event is received.
   7
   8 There are two functions currently for device-mapper events.  The first function
   9 listed creates the event and the second function sends the event(s).
  10
  11 void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
  12                     const char *path, unsigned nr_valid_paths)
  13
  14 void dm_send_uevents(struct list_head *events, struct kobject *kobj)
  15
  16
  17 The variables added to the uevent environment are:
  18
  19 Variable Name: DM_TARGET
  20 Uevent Action(s): KOBJ_CHANGE
  21 Type: string
  22 Description:
  23 Value: Name of device-mapper target that generated the event.
  24
  25 Variable Name: DM_ACTION
  26 Uevent Action(s): KOBJ_CHANGE
  27 Type: string
  28 Description:
  29 Value: Device-mapper specific action that caused the uevent action.
  30         PATH_FAILED - A path has failed.
  31         PATH_REINSTATED - A path has been reinstated.
  32
  33 Variable Name: DM_SEQNUM
  34 Uevent Action(s): KOBJ_CHANGE
  35 Type: unsigned integer
  36 Description: A sequence number for this specific device-mapper device.
  37 Value: Valid unsigned integer range.
  38
  39 Variable Name: DM_PATH
  40 Uevent Action(s): KOBJ_CHANGE
  41 Type: string
  42 Description: Major and minor number of the path device pertaining to this
  43 event.
  44 Value: Path name in the form of "Major:Minor"
  45
  46 Variable Name: DM_NR_VALID_PATHS
  47 Uevent Action(s): KOBJ_CHANGE
  48 Type: unsigned integer
  49 Description:
  50 Value: Valid unsigned integer range.
  51
  52 Variable Name: DM_NAME
  53 Uevent Action(s): KOBJ_CHANGE
  54 Type: string
  55 Description: Name of the device-mapper device.
  56 Value: Name
  57
  58 Variable Name: DM_UUID
  59 Uevent Action(s): KOBJ_CHANGE
  60 Type: string
  61 Description: UUID of the device-mapper device.
  62 Value: UUID. (Empty string if there isn't one.)
  63
  64 An example of the uevents generated as captured by udevmonitor is shown
  65 below.
  66
  67 1.) Path failure.
  68 UEVENT[1192521009.711215] change@/block/dm-3
  69 ACTION=change
  70 DEVPATH=/block/dm-3
  71 SUBSYSTEM=block
  72 DM_TARGET=multipath
  73 DM_ACTION=PATH_FAILED
  74 DM_SEQNUM=1
  75 DM_PATH=8:32
  76 DM_NR_VALID_PATHS=0
  77 DM_NAME=mpath2
  78 DM_UUID=mpath-35333333000002328
  79 MINOR=3
  80 MAJOR=253
  81 SEQNUM=1130
  82
  83 2.) Path reinstate.
  84 UEVENT[1192521132.989927] change@/block/dm-3
  85 ACTION=change
  86 DEVPATH=/block/dm-3
  87 SUBSYSTEM=block
  88 DM_TARGET=multipath
  89 DM_ACTION=PATH_REINSTATED
  90 DM_SEQNUM=2
  91 DM_PATH=8:32
  92 DM_NR_VALID_PATHS=1
  93 DM_NAME=mpath2
  94 DM_UUID=mpath-35333333000002328
  95 MINOR=3
  96 MAJOR=253
  97 SEQNUM=1131