linux.git/net/tipc/link.h, branch v4.3

tipc: clean up link creation

2015-07-31T00:25:15+00:00

We simplify the link creation function tipc_link_create() and the way
the link struct it is connected to the node struct. In particular, we
remove the duplicate initialization of some fields which are anyway set
in tipc_link_reset().

Tested-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: merge link->exec_mode and link->state into one FSM

2015-07-31T00:25:14+00:00

Until now, we have been handling link failover and synchronization
by using an additional link state variable, "exec_mode". This variable
is not independent of the link FSM state, something causing a risk of
inconsistencies, apart from the fact that it clutters the code.

The conditions are now in place to define a new link FSM that covers
all existing use cases, including failover and synchronization, and
eliminate the "exec_mode" field altogether. The FSM must also support
non-atomic resetting of links, which will be introduced later.

The new link FSM is shown below, with 7 states and 8 events.
Only events leading to state change are shown as edges.

+------------------------------------+
|RESET_EVT                           |
|                                    |
|                             +--------------+
|           +-----------------|   SYNCHING   |-----------------+
|           |FAILURE_EVT      +--------------+   PEER_RESET_EVT|
|           |                  A            |                  |
|           |                  |            |                  |
|           |                  |            |                  |
|           |                  |SYNCH_      |SYNCH_            |
|           |                  |BEGIN_EVT   |END_EVT           |
|           |                  |            |                  |
|           V                  |            V                  V
|    +-------------+          +--------------+          +------------+
|    |  RESETTING  |<---------|  ESTABLISHED |--------->| PEER_RESET |
|    +-------------+ FAILURE_ +--------------+ PEER_    +------------+
|           |        EVT        |    A         RESET_EVT       |
|           |                   |    |                         |
|           |                   |    |                         |
|           |    +--------------+    |                         |
|  RESET_EVT|    |RESET_EVT          |ESTABLISH_EVT            |
|           |    |                   |                         |
|           |    |                   |                         |
|           V    V                   |                         |
|    +-------------+          +--------------+        RESET_EVT|
+--->|    RESET    |--------->| ESTABLISHING |<----------------+
     +-------------+ PEER_    +--------------+
      |           A  RESET_EVT       |
      |           |                  |
      |           |                  |
      |FAILOVER_  |FAILOVER_         |FAILOVER_
      |BEGIN_EVT  |END_EVT           |BEGIN_EVT
      |           |                  |
      V           |                  |
     +-------------+                 |
     | FAILINGOVER |<----------------+
     +-------------+

These changes are fully backwards compatible.

Tested-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: move protocol message sending away from link FSM

2015-07-31T00:25:14+00:00

The implementation of the link FSM currently takes decisions about and
sends out link protocol messages. This is unnecessary, since such
actions are not the result of any link state change, and are even
decided based on non-FSM state information ("silent_intv_cnt").

We now move the sending of unicast link protocol messages to the
function tipc_link_timeout(), and the initial broadcast synchronization
message to tipc_node_link_up(). The latter is done because a link
instance should not need to know whether it is the first or second
link to a destination. Such information is now restricted to and
handled by the link aggregation layer in node.c

Tested-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: move link synch and failover to link aggregation level

2015-07-31T00:25:14+00:00

Link failover and synchronization have until now been handled by the
links themselves, forcing them to have knowledge about and to access
parallel links in order to make the two algorithms work correctly.

In this commit, we move the control part of this functionality to the
link aggregation level in node.c, which is the right location for this.
As a result, the two algorithms become easier to follow, and the link
implementation becomes simpler.

Tested-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: move all link_reset() calls to link aggregation level

2015-07-31T00:25:13+00:00

In line with our effort to let the node level have full control over
its links, we want to move all link reset calls from link.c to node.c.
Some of the calls can be moved by simply moving the calling function,
when this is the right thing to do. For the remaining calls we use
the now established technique of returning a TIPC_LINK_DOWN_EVT
flag from tipc_link_rcv(), whereafter we perform the reset call when
the call returns.

This change serves as a preparation for the coming commits.

Tested-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: eliminate function tipc_link_activate()

2015-07-31T00:25:13+00:00

The function tipc_link_activate() is redundant, since it mostly performs
settings that have already been done in a preceding tipc_link_reset().

There are three exceptions to this:
- The actual state change to TIPC_LINK_WORKING. This should anyway be done
  in the FSM, and not in a separate function.
- Registration of the link with the bearer. This should be done by the
  node, since we don't want the link to have any knowledge about its
  specific bearer.
- Call to tipc_node_link_up() for user access registration. With the new
  role distribution between link aggregation and link level this becomes
  the wrong call order; tipc_node_link_up() should instead be called
  directly as a result of a TIPC_LINK_UP event, hence by the node itself.

This commit implements those changes.

Tested-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: reduce locking scope during packet reception

2015-07-21T03:41:16+00:00

We convert packet/message reception according to the same principle
we have been using for message sending and timeout handling:

We move the function tipc_rcv() to node.c, hence handling the initial
packet reception at the link aggregation level. The function grabs
the node lock, selects the receiving link, and accesses it via a new
call tipc_link_rcv(). This function appends buffers to the input
queue for delivery upwards, but it may also append outgoing packets
to the xmit queue, just as we do during regular message sending. The
latter will happen when buffers are forwarded from the link backlog,
or when retransmission is requested.

Upon return of this function, and after having released the node lock,
tipc_rcv() delivers/tranmsits the contents of those queues, but it may
also perform actions such as link activation or reset, as indicated by
the return flags from the link.

This reduces the number of cpu cycles spent inside the node spinlock,
and reduces contention on that lock.

Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: move link supervision timer to node level

2015-07-21T03:41:16+00:00

In our effort to move control of the links to the link aggregation
layer, we move the perodic link supervision timer to struct tipc_node.
The new timer is shared between all links belonging to the node, thus
saving resources, while still kicking the FSM on both its pertaining
links at each expiration.

The current link timer and corresponding functions are removed.

Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: simplify link timer implementation

2015-07-21T03:41:16+00:00

We create a second, simpler, link timer function, tipc_link_timeout().
The new function  makes use of the new FSM function introduced in the
previous commit, and just like it, takes a buffer queue as parameter.
It returns an event bit field and potentially a link protocol packet
to the caller.

The existing timer function, link_timeout(), is still needed for a
while, so we redesign it to become a wrapper around the new function.

Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller

tipc: improve link FSM implementation

2015-07-21T03:41:15+00:00

The link FSM implementation is currently unnecessarily complex.
It sometimes checks for conditional state outside the FSM data
before deciding next state, and often performs actions directly
inside the FSM logics.

In this commit, we create a second, simpler FSM implementation,
that as far as possible acts only on states and events that it is
strictly defined for, and postpone any actions until it is finished
with its decisions. It also returns an event flag field and an a
buffer queue which may potentially contain a protocol message to
be sent by the caller.

Unfortunately, we cannot yet make the FSM "clean", in the sense
that its decisions are only based on FSM state and event, and that
state changes happen only here. That will have to wait until the
activate/reset logics has been cleaned up in a future commit.

We also rename the link states as follows:

WORKING_WORKING -> TIPC_LINK_WORKING
WORKING_UNKNOWN -> TIPC_LINK_PROBING
RESET_UNKNOWN   -> TIPC_LINK_RESETTING
RESET_RESET     -> TIPC_LINK_ESTABLISHING

The existing FSM function, link_state_event(), is still needed for
a while, so we redesign it to make use of the new function.

Reviewed-by: Ying Xue 
Signed-off-by: Jon Maloy 
Signed-off-by: David S. Miller