linux/net/tipc/msg.h, branch v3.18

tipc: use pseudo message to wake up sockets after link congestion

2014-08-23T18:18:33Z

The current link implementation keeps a linked list of blocked ports/ sockets that is populated when there is link congestion. The purpose of this is to let the link know which users to wake up when the congestion abates. This adds unnecessary complexity to the data structure and the code, since it forces us to involve the link each time we want to delete a socket. It also forces us to grab the spinlock port_lock within the scope of node_lock. We want to get rid of this direct dependence, as well as the deadlock hazard resulting from the usage of port_lock. In this commit, we instead let the link keep list of a "wakeup" pseudo messages for use in such situations. Those messages are sent to the pending sockets via the ordinary message reception path, and wake up the socket's owner when they are received. This enables us to get rid of the 'waiting_ports' linked lists in struct tipc_port that manifest this direct reference. As a consequence, we can eliminate another BH entry into the socket, and hence the need to grab port_lock. This is a further step in our effort to remove port_lock altogether. Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: introduce new function tipc_msg_create()

2014-08-23T18:18:33Z

The function tipc_msg_init() has turned out to be of limited value in many cases. It take too few parameters to be usable for creating a complete message, it makes too many assumptions about what the message should be used for, and it does not allocate any buffer to be returned to the caller. Therefore, we now introduce the new function tipc_msg_create(), which takes all the parameters needed to create a full message, and returns a buffer of the requested size. The new function will be very useful for the changes we will be doing in later commits in this series. Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: rename temporarily named functions

2014-07-17T04:38:19Z

After the previous commit, we can now give the functions with temporary names, such as tipc_link_xmit2(), tipc_msg_build2() etc., their proper names. There are no functional changes in this commit. Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: remove unreferenced functions

2014-07-17T04:38:19Z

We can now remove a number of functions which have become obsolete and unreferenced through this commit series. There are no functional changes in this commit. Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: add new functions for multicast and broadcast distribution

2014-07-17T04:38:18Z

We add a new broadcast link transmit function in bclink.c and a new receive function in socket.c. The purpose is to move the branching between external and internal destination down to the link layer, just as we have done with unicast in earlier commits. We also make use of the new link-independent fragmentation support that was introduced in an earlier commit series. This gives a shorter and simpler code path, and makes it possible to obtain copy-free buffer delivery to all node local destination sockets. The new transmission code is added in parallel with the existing one, and will be used by the socket multicast send function in the next commit in this series. Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: introduce message evaluation function

2014-06-27T19:50:55Z

When a message arrives in a node and finds no destination socket, we may need to drop it, reject it, or forward it after a secondary destination lookup. The latter two cases currently results in a code path that is perceived as complex, because it follows a deep call chain via obscure functions such as net_route_named_msg() and net_route_msg(). We now introduce a function, tipc_msg_eval(), that takes the decision about whether such a message should be rejected or forwarded, but leaves it to the caller to actually perform the indicated action. If the decision is 'reject', it is still the task of the recently introduced function tipc_msg_reverse() to take the final decision about whether the message is rejectable or not. In the latter case it drops the message. As a result of this change, we can finally eliminate the function net_route_named_msg(), and hence become independent of net_route_msg(). Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: separate building and sending of rejected messages

2014-06-27T19:50:55Z

The way we build and send rejected message is currenty perceived as hard to follow, partly because we let the transmission go via deep call chains through functions such as tipc_reject_msg() and net_route_msg(). We want to remove those functions, and make the call sequences shallower and simpler. For this purpose, we separate building and sending of rejected messages. We build the reject message using the new function tipc_msg_reverse(), and let the transmission go via the newly introduced tipc_link_xmit2() function, as all transmission eventually will do. We also ensure that all calls to tipc_link_xmit2() are made outside port_lock/bh_lock_sock. Finally, we replace all calls to tipc_reject_msg() with the two new calls at all locations in the code that we want to keep. The remaining calls are made from code that we are planning to remove, along with tipc_reject_msg() itself. Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: introduce direct iovec to buffer chain fragmentation function

2014-06-27T19:50:55Z

Fragmentation at message sending is currently performed in two places in link.c, depending on whether data to be transmitted is delivered in the form of an iovec or as a big sk_buff. Those functions are also tightly entangled with the send functions that are using them. We now introduce a re-entrant, standalone function, tipc_msg_build2(), that builds a packet chain directly from an iovec. Each fragment is sized according to the MTU value given by the caller, and is prepended with a correctly built fragment header, when needed. The function is independent from who is calling and where the chain will be delivered, as long as the caller is able to indicate a correct MTU. The function is tested, but not called by anybody yet. Since it is incompatible with the existing tipc_msg_build(), and we cannot yet remove that function, we have given it a temporary name. Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: introduce send functions for chained buffers in link

2014-06-27T19:50:54Z

The current link implementation provides several different transmit functions, depending on the characteristics of the message to be sent: if it is an iovec or an sk_buff, if it needs fragmentation or not, if the caller holds the node_lock or not. The permutation of these options gives us an unwanted amount of unnecessarily complex code. As a first step towards simplifying the send path for all messages, we introduce two new send functions at link level, tipc_link_xmit2() and __tipc_link_xmit2(). The former looks up a link to the message destination, and if one is found, it grabs the node lock and calls the second function, which works exclusively inside the node lock protection. If no link is found, and the destination is on the same node, it delivers the message directly to the local destination socket. The new functions take a buffer chain where all packet headers are already prepared, and the correct MTU has been used. These two functions will later replace all other link-level transmit functions. The functions are not backwards compatible, so we have added them as new functions with temporary names. They are tested, but have no users yet. Those will be added later in this series. Signed-off-by: Jon Maloy Reviewed-by: Erik Hugne Reviewed-by: Ying Xue Signed-off-by: David S. Miller

tipc: rename and move message reassembly function

2014-05-14T19:19:48Z

The function tipc_link_frag_rcv() is in reality a re-entrant generic message reassemby function that has nothing in particular to do with the link, where it is defined now. This becomes obvious when we see the need to call the function from other places in the code. In this commit rename it to tipc_buf_append() and move it to the file msg.c. We also simplify its signature by moving the tail pointer to the control block of the head buffer, hence making the head buffer self-contained. Signed-off-by: Jon Maloy Reviewed-by: Ying Xue Signed-off-by: David S. Miller