What:		/sys/block/dm-<num>/dm/name
Date:		January 2009
KernelVersion:	2.6.29
Contact:	dm-devel@redhat.com
Description:	Device-mapper device name.
		Read-only string containing mapped device name.
Users:		util-linux, device-mapper udev rules

What:		/sys/block/dm-<num>/dm/uuid
Date:		January 2009
KernelVersion:	2.6.29
Contact:	dm-devel@redhat.com
Description:	Device-mapper device UUID.
		Read-only string containing DM-UUID or empty string
		if DM-UUID is not set.
Users:		util-linux, device-mapper udev rules

What:		/sys/block/dm-<num>/dm/suspended
Date:		June 2009
KernelVersion:	2.6.31
Contact:	dm-devel@redhat.com
Description:	Device-mapper device suspend state.
		Contains the value 1 while the device is suspended.
		Otherwise it contains 0. Read-only attribute.
Users:		util-linux, device-mapper udev rules

What:		/sys/block/dm-<num>/dm/rq_based_seq_io_merge_deadline
Date:		March 2015
KernelVersion:	4.1
Contact:	dm-devel@redhat.com
Description:	Allow control over how long a request that is a
		reasonable merge candidate can be queued on the request
		queue.  The resolution of this deadline is in
		microseconds (ranging from 1 to 100000 usecs).
		Setting this attribute to 0 (the default) will disable
		request-based DM's merge heuristic and associated extra
		accounting.  This attribute is not applicable to
		bio-based DM devices so it will only ever report 0 for
		them.

What:		/sys/block/dm-<num>/dm/use_blk_mq
Date:		March 2015
KernelVersion:	4.1
Contact:	dm-devel@redhat.com
Description:	Request-based Device-mapper blk-mq I/O path mode.
		Contains the value 1 if the device is using blk-mq.
		Otherwise it contains 0. Read-only attribute.
