docs: networking: convert rds.txt to ReST

- add SPDX header;
- add a document title;
- mark code blocks and literals as such;
- mark tables as such;
- mark lists as such;
- adjust identation, whitespaces and blank lines where needed;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/index.rst

@@ -97,6 +97,7 @@ Contents:
    proc_net_tcp
    radiotap-headers
    ray_cs
+   rds
 
 .. only::  subproject and html
 

Documentation/networking/rds.rst

@@ -1,3 +1,8 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==
+RDS
+===
 
 Overview
 ========
@@ -24,6 +29,7 @@ as IB.
 The high-level semantics of RDS from the application's point of view are
 
  *	Addressing
+
 	RDS uses IPv4 addresses and 16bit port numbers to identify
 	the end point of a connection. All socket operations that involve
 	passing addresses between kernel and user space generally
@@ -38,6 +44,7 @@ The high-level semantics of RDS from the application's point of view are
 	protocol.
 
  *	Socket interface
+
 	RDS sockets work *mostly* as you would expect from a BSD
 	socket. The next section will cover the details. At any rate,
 	all I/O is performed through the standard BSD socket API.
@@ -53,6 +60,7 @@ The high-level semantics of RDS from the application's point of view are
 	doesn't move to a different transport.
 
  *	sysctls
+
 	RDS supports a number of sysctls in /proc/sys/net/rds
 
 
@@ -147,8 +155,7 @@ Socket Interface
 	operation. In this case, it would use RDS_CANCEL_SENT_TO to
 	nuke any pending messages.
 
-  setsockopt(fd, SOL_RDS, SO_RDS_TRANSPORT, (int *)&transport ..)
+  ``setsockopt(fd, SOL_RDS, SO_RDS_TRANSPORT, (int *)&transport ..), getsockopt(fd, SOL_RDS, SO_RDS_TRANSPORT, (int *)&transport ..)``
-  getsockopt(fd, SOL_RDS, SO_RDS_TRANSPORT, (int *)&transport ..)
 	Set or read an integer defining  the underlying
 	encapsulating transport to be used for RDS packets on the
 	socket. When setting the option, integer argument may be
@@ -180,7 +187,9 @@ RDS Protocol
   Message header
 
     The message header is a 'struct rds_header' (see rds.h):
+
     Fields:
+
       h_sequence:
 	  per-packet sequence number
       h_ack:
@@ -192,9 +201,14 @@ RDS Protocol
       h_dport:
 	  destination port
       h_flags:
-          CONG_BITMAP - this is a congestion update bitmap
+	  Can be:
-          ACK_REQUIRED - receiver must ack this packet
+
-          RETRANSMITTED - packet has previously been sent
+	  =============  ==================================
+	  CONG_BITMAP    this is a congestion update bitmap
+	  ACK_REQUIRED   receiver must ack this packet
+	  RETRANSMITTED  packet has previously been sent
+	  =============  ==================================
+
       h_credit:
 	  indicate to other end of connection that
 	  it has more credits available (i.e. there is
@@ -260,7 +274,7 @@ RDS Protocol
 
 
 RDS Transport Layer
-==================
+===================
 
   As mentioned above, RDS is not IB-specific. Its code is divided
   into a general RDS layer and a transport layer.
@@ -281,19 +295,25 @@ RDS Kernel Structures
     be sent and sets header fields as needed, based on the socket API.
     This is then queued for the individual connection and sent by the
     connection's transport.
+
   struct rds_incoming
     a generic struct referring to incoming data that can be handed from
     the transport to the general code and queued by the general code
     while the socket is awoken. It is then passed back to the transport
     code to handle the actual copy-to-user.
+
   struct rds_socket
     per-socket information
+
   struct rds_connection
     per-connection information
+
   struct rds_transport
     pointers to transport-specific functions
+
   struct rds_statistics
     non-transport-specific statistics
+
   struct rds_cong_map
     wraps the raw congestion bitmap, contains rbnode, waitq, etc.
 
@@ -317,53 +337,58 @@ The send path
 =============
 
   rds_sendmsg()
-    struct rds_message built from incoming data
+    - struct rds_message built from incoming data
-    CMSGs parsed (e.g. RDMA ops)
+    - CMSGs parsed (e.g. RDMA ops)
-    transport connection alloced and connected if not already
+    - transport connection alloced and connected if not already
-    rds_message placed on send queue
+    - rds_message placed on send queue
-    send worker awoken
+    - send worker awoken
+
   rds_send_worker()
-    calls rds_send_xmit() until queue is empty
+    - calls rds_send_xmit() until queue is empty
+
   rds_send_xmit()
-    transmits congestion map if one is pending
+    - transmits congestion map if one is pending
-    may set ACK_REQUIRED
+    - may set ACK_REQUIRED
-    calls transport to send either non-RDMA or RDMA message
+    - calls transport to send either non-RDMA or RDMA message
       (RDMA ops never retransmitted)
+
   rds_ib_xmit()
-    allocs work requests from send ring
+    - allocs work requests from send ring
-    adds any new send credits available to peer (h_credits)
+    - adds any new send credits available to peer (h_credits)
-    maps the rds_message's sg list
+    - maps the rds_message's sg list
-    piggybacks ack
+    - piggybacks ack
-    populates work requests
+    - populates work requests
-    post send to connection's queue pair
+    - post send to connection's queue pair
 
 The recv path
 =============
 
   rds_ib_recv_cq_comp_handler()
-    looks at write completions
+    - looks at write completions
-    unmaps recv buffer from device
+    - unmaps recv buffer from device
-    no errors, call rds_ib_process_recv()
+    - no errors, call rds_ib_process_recv()
-    refill recv ring
+    - refill recv ring
+
   rds_ib_process_recv()
-    validate header checksum
+    - validate header checksum
-    copy header to rds_ib_incoming struct if start of a new datagram
+    - copy header to rds_ib_incoming struct if start of a new datagram
-    add to ibinc's fraglist
+    - add to ibinc's fraglist
-    if competed datagram:
+    - if competed datagram:
-      update cong map if datagram was cong update
+	 - update cong map if datagram was cong update
-      call rds_recv_incoming() otherwise
+	 - call rds_recv_incoming() otherwise
-      note if ack is required
+	 - note if ack is required
+
   rds_recv_incoming()
-    drop duplicate packets
+    - drop duplicate packets
-    respond to pings
+    - respond to pings
-    find the sock associated with this datagram
+    - find the sock associated with this datagram
-    add to sock queue
+    - add to sock queue
-    wake up sock
+    - wake up sock
-    do some congestion calculations
+    - do some congestion calculations
   rds_recvmsg
-    copy data into user iovec
+    - copy data into user iovec
-    handle CMSGs
+    - handle CMSGs
-    return to application
+    - return to application
 
 Multipath RDS (mprds)
 =====================

MAINTAINERS

@@ -14219,7 +14219,7 @@ L:	linux-rdma@vger.kernel.org
 L:	rds-devel@oss.oracle.com (moderated for non-subscribers)
 S:	Supported
 W:	https://oss.oracle.com/projects/rds/
-F:	Documentation/networking/rds.txt
+F:	Documentation/networking/rds.rst
 F:	net/rds/
 
 RDT - RESOURCE ALLOCATION