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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 |
98 |
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