cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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dm-uevent.rst (2964B)

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