kernel/net/tipc/server.h, branch linux-rolling-stable

tipc: rename tipc_server to tipc_topsrv

2018-02-16T20:26:34Z

We rename struct tipc_server to struct tipc_topsrv. This reflect its now specialized role as topology server. Accoringly, we change or add function prefixes to make it clearer which functionality those belong to. There are no functional changes in this commit. Acked-by: Ying.Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: make struct tipc_server private for server.c

2018-02-16T20:26:34Z

In order to narrow the interface and dependencies between the topology server and the subscription/binding table functionality we move struct tipc_server inside the file server.c. This requires some code adaptations in other files, but those are mostly minor. The most important change is that we have to move the start/stop functions for the topology server to server.c, where they logically belong anyway. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: collapse subscription creation functions

2018-02-16T20:26:34Z

After the previous changes it becomes logical to collapse the two-level creation of subscription instances into one. We do that here. We also rename the creation and deletion functions for more consistency. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: simplify interaction between subscription and topology connection

2018-02-16T20:26:33Z

The message transmission and reception in the topology server is more generic than is currently necessary. By basing the funtionality on the fact that we only send items of type struct tipc_event and always receive items of struct tipc_subcr we can make several simplifications, and also get rid of some unnecessary dynamic memory allocations. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: eliminate struct tipc_subscriber

2018-02-16T20:26:33Z

It is unnecessary to keep two structures, struct tipc_conn and struct tipc_subscriber, with a one-to-one relationship and still with different life cycles. The fact that the two often run in different contexts, and still may access each other via direct pointers constitutes an additional hazard, something we have experienced at several occasions, and still see happening. We have identified at least two remaining problems that are easier to fix if we simplify the topology server data structure somewhat. - When there is a race between a subscription up/down event and a timeout event, it is fully possible that the former might be delivered after the latter, leading to confusion for the receiver. - The function tipc_subcrp_timeout() is executing in interrupt context, while the following call chain is at least theoretically possible: tipc_subscrp_timeout() tipc_subscrp_send_event() tipc_conn_sendmsg() conn_put() tipc_conn_kref_release() sock_release(sock) I.e., we end up calling a function that might try to sleep in interrupt context. To eliminate this, we need to ensure that the tipc_conn structure and the socket, as well as the subscription instances, only are deleted in work queue context, i.e., after the timeout event really has been sent out. We now remove this unnecessary complexity, by merging data and functionality of the subscriber structure into struct tipc_conn and the associated file server.c. We thereafter add a spinlock and a new 'inactive' state to the subscription structure. Using those, both problems described above can be easily solved. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: remove unnecessary function pointers

2018-02-16T20:26:33Z

Interaction between the functionality in server.c and subscr.c is done via function pointers installed in struct server. This makes the code harder to follow, and doesn't serve any obvious purpose. Here, we replace the function pointers with direct function calls. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: remove redundant code in topology server

2018-02-16T20:26:33Z

The socket handling in the topology server is unnecessarily generic. It is prepared to handle both SOCK_RDM, SOCK_DGRAM and SOCK_STREAM type sockets, as well as the only socket type which is really used, SOCK_SEQPACKET. We now remove this redundant code to make the code more readable. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: fix race condition at topology server receive

2018-01-16T19:42:41Z

We have identified a race condition during reception of socket events and messages in the topology server. - The function tipc_close_conn() is releasing the corresponding struct tipc_subscriber instance without considering that there may still be items in the receive work queue. When those are scheduled, in the function tipc_receive_from_work(), they are using the subscriber pointer stored in struct tipc_conn, without first checking if this is valid or not. This will sometimes lead to crashes, as the next call of tipc_conn_recvmsg() will access the now deleted item. We fix this by making the usage of this pointer conditional on whether the connection is active or not. I.e., we check the condition test_bit(CF_CONNECTED) before making the call tipc_conn_recvmsg(). - Since the two functions may be running on different cores, the condition test described above is not enough. tipc_close_conn() may come in between and delete the subscriber item after the condition test is done, but before tipc_conn_recv_msg() is finished. This happens less frequently than the problem described above, but leads to the same symptoms. We fix this by using the existing sk_callback_lock for mutual exclusion in the two functions. In addition, we have to move a call to tipc_conn_terminate() outside the mentioned lock to avoid deadlock. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: improve groupcast scope handling

2018-01-09T17:35:58Z

When a member joins a group, it also indicates a binding scope. This makes it possible to create both node local groups, invisible to other nodes, as well as cluster global groups, visible everywhere. In order to avoid that different members end up having permanently differing views of group size and memberhip, we must inhibit locally and globally bound members from joining the same group. We do this by using the binding scope as an additional separator between groups. I.e., a member must ignore all membership events from sockets using a different scope than itself, and all lookups for message destinations must require an exact match between the message's lookup scope and the potential target's binding scope. Apart from making it possible to create local groups using the same identity on different nodes, a side effect of this is that it now also becomes possible to create a cluster global group with the same identity across the same nodes, without interfering with the local groups. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller

tipc: add option to suppress PUBLISH events for pre-existing publications

2018-01-09T17:35:58Z

Currently, when a user is subscribing for binding table publications, he will receive a PUBLISH event for all already existing matching items in the binding table. However, a group socket making a subscriptions doesn't need this initial status update from the binding table, because it has already scanned it during the join operation. Worse, the multiplicatory effect of issuing mutual events for dozens or hundreds group members within a short time frame put a heavy load on the topology server, with the end result that scale out operations on a big group tend to take much longer than needed. We now add a new filter option, TIPC_SUB_NO_STATUS, for topology server subscriptions, so that this initial avalanche of events is suppressed. This change, along with the previous commit, significantly improves the range and speed of group scale out operations. We keep the new option internal for the tipc driver, at least for now. Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller