docs: blockdev: convert to ReST

Rename the blockdev documentation files to ReST, add an
index for them and adjust in order to produce a nice html
output via the Sphinx build system.

The drbd sub-directory contains some graphs and data flows.
Add those too to the documentation.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

1 files changed, 42 insertions, 0 deletions

diff --git a/Documentation/blockdev/drbd/data-structure-v9.rst b/Documentation/blockdev/drbd/data-structure-v9.rst
new file mode 100644
index 000000000000..66036b901644
--- /dev/null
+++ b/Documentation/blockdev/drbd/data-structure-v9.rst
@@ -0,0 +1,42 @@
+================================
+kernel data structure for DRBD-9
+================================
+
+This describes the in kernel data structure for DRBD-9. Starting with
+Linux v3.14 we are reorganizing DRBD to use this data structure.
+
+Basic Data Structure
+====================
+
+A node has a number of DRBD resources.  Each such resource has a number of
+devices (aka volumes) and connections to other nodes ("peer nodes"). Each DRBD
+device is represented by a block device locally.
+
+The DRBD objects are interconnected to form a matrix as depicted below; a
+drbd_peer_device object sits at each intersection between a drbd_device and a
+drbd_connection::
+
+  /--------------+---------------+.....+---------------\
+  |   resource   |    device     |     |    device     |
+  +--------------+---------------+.....+---------------+
+  |  connection  |  peer_device  |     |  peer_device  |
+  +--------------+---------------+.....+---------------+
+  :              :               :     :               :
+  :              :               :     :               :
+  +--------------+---------------+.....+---------------+
+  |  connection  |  peer_device  |     |  peer_device  |
+  \--------------+---------------+.....+---------------/
+
+In this table, horizontally, devices can be accessed from resources by their
+volume number.  Likewise, peer_devices can be accessed from connections by
+their volume number.  Objects in the vertical direction are connected by double
+linked lists.  There are back pointers from peer_devices to their connections a
+devices, and from connections and devices to their resource.
+
+All resources are in the drbd_resources double-linked list.  In addition, all
+devices can be accessed by their minor device number via the drbd_devices idr.
+
+The drbd_resource, drbd_connection, and drbd_device objects are reference
+counted.  The peer_device objects only serve to establish the links between
+devices and connections; their lifetime is determined by the lifetime of the
+device and connection which they reference.