Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  1) ================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  2) kernel data structure for DRBD-9
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  3) ================================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  4) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  5) This describes the in kernel data structure for DRBD-9. Starting with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  6) Linux v3.14 we are reorganizing DRBD to use this data structure.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  7) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  8) Basic Data Structure
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  9) ====================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) A node has a number of DRBD resources.  Each such resource has a number of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) devices (aka volumes) and connections to other nodes ("peer nodes"). Each DRBD
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) device is represented by a block device locally.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) The DRBD objects are interconnected to form a matrix as depicted below; a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16) drbd_peer_device object sits at each intersection between a drbd_device and a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) drbd_connection::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19)   /--------------+---------------+.....+---------------\
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20)   |   resource   |    device     |     |    device     |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21)   +--------------+---------------+.....+---------------+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22)   |  connection  |  peer_device  |     |  peer_device  |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23)   +--------------+---------------+.....+---------------+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24)   :              :               :     :               :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25)   :              :               :     :               :
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26)   +--------------+---------------+.....+---------------+
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27)   |  connection  |  peer_device  |     |  peer_device  |
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28)   \--------------+---------------+.....+---------------/
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) In this table, horizontally, devices can be accessed from resources by their
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) volume number.  Likewise, peer_devices can be accessed from connections by
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) their volume number.  Objects in the vertical direction are connected by double
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33) linked lists.  There are back pointers from peer_devices to their connections a
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) devices, and from connections and devices to their resource.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) All resources are in the drbd_resources double-linked list.  In addition, all
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) devices can be accessed by their minor device number via the drbd_devices idr.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) The drbd_resource, drbd_connection, and drbd_device objects are reference
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) counted.  The peer_device objects only serve to establish the links between
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41) devices and connections; their lifetime is determined by the lifetime of the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) device and connection which they reference.