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The DM support describes lots of aspects related to mapped disk partitions from the userspace PoV. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
111 lines
2.9 KiB
ReStructuredText
111 lines
2.9 KiB
ReStructuredText
====================
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device-mapper uevent
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====================
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The device-mapper uevent code adds the capability to device-mapper to create
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and send kobject uevents (uevents). Previously device-mapper events were only
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available through the ioctl interface. The advantage of the uevents interface
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is the event contains environment attributes providing increased context for
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the event avoiding the need to query the state of the device-mapper device after
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the event is received.
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There are two functions currently for device-mapper events. The first function
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listed creates the event and the second function sends the event(s)::
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void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
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const char *path, unsigned nr_valid_paths)
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void dm_send_uevents(struct list_head *events, struct kobject *kobj)
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The variables added to the uevent environment are:
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Variable Name: DM_TARGET
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------------------------
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:Uevent Action(s): KOBJ_CHANGE
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:Type: string
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:Description:
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:Value: Name of device-mapper target that generated the event.
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Variable Name: DM_ACTION
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------------------------
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:Uevent Action(s): KOBJ_CHANGE
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:Type: string
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:Description:
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:Value: Device-mapper specific action that caused the uevent action.
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PATH_FAILED - A path has failed;
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PATH_REINSTATED - A path has been reinstated.
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Variable Name: DM_SEQNUM
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------------------------
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:Uevent Action(s): KOBJ_CHANGE
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:Type: unsigned integer
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:Description: A sequence number for this specific device-mapper device.
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:Value: Valid unsigned integer range.
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Variable Name: DM_PATH
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----------------------
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:Uevent Action(s): KOBJ_CHANGE
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:Type: string
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:Description: Major and minor number of the path device pertaining to this
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event.
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:Value: Path name in the form of "Major:Minor"
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Variable Name: DM_NR_VALID_PATHS
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--------------------------------
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:Uevent Action(s): KOBJ_CHANGE
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:Type: unsigned integer
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:Description:
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:Value: Valid unsigned integer range.
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Variable Name: DM_NAME
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----------------------
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:Uevent Action(s): KOBJ_CHANGE
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:Type: string
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:Description: Name of the device-mapper device.
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:Value: Name
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Variable Name: DM_UUID
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----------------------
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:Uevent Action(s): KOBJ_CHANGE
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:Type: string
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:Description: UUID of the device-mapper device.
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:Value: UUID. (Empty string if there isn't one.)
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An example of the uevents generated as captured by udevmonitor is shown
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below
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1.) Path failure::
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UEVENT[1192521009.711215] change@/block/dm-3
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ACTION=change
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DEVPATH=/block/dm-3
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SUBSYSTEM=block
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DM_TARGET=multipath
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DM_ACTION=PATH_FAILED
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DM_SEQNUM=1
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DM_PATH=8:32
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DM_NR_VALID_PATHS=0
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DM_NAME=mpath2
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DM_UUID=mpath-35333333000002328
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MINOR=3
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MAJOR=253
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SEQNUM=1130
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2.) Path reinstate::
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UEVENT[1192521132.989927] change@/block/dm-3
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ACTION=change
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DEVPATH=/block/dm-3
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SUBSYSTEM=block
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DM_TARGET=multipath
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DM_ACTION=PATH_REINSTATED
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DM_SEQNUM=2
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DM_PATH=8:32
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DM_NR_VALID_PATHS=1
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DM_NAME=mpath2
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DM_UUID=mpath-35333333000002328
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MINOR=3
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MAJOR=253
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SEQNUM=1131
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