| Mike Anderson | 7a8c3d3 | 2007-10-19 22:48:01 +0100 | [diff] [blame] | 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 |