kernel/linux.git/fs/dlm/lowcomms.h, branch v6.6.141

fs: dlm: remove socket shutdown handling

2022-11-21T15:45:49+00:00

Since commit 489d8e559c65 ("fs: dlm: add reliable connection if reconnect") we have functionality like TCP offers for half-closed sockets on dlm application protocol layer. This feature is required because the cluster manager events about leaving resource memberships can be locally already occurred but other cluster nodes having a pending leaving membership over the cluster manager protocol happening. In this time the local dlm node already shutdown it's connection and don't transmit anymore any new dlm messages, but however it still needs to be able to accept dlm messages because the pending leave membership request of the cluster manager protocol which the dlm kernel implementation has no control about it. We have this functionality on the application for two reasons, the main reason is that SCTP does not support such functionality on socket layer. But we can do it inside application layer. Another small issue is that this feature is broken in the TCP world because some NAT devices does not implement such functionality correctly. This is the same reason why the reliable connection session layer in DLM exists. We give up on middle devices in the networking which sends e.g. TCP resets out. In DLM we cannot have any message dropping and we ensure it over a session layer that it can't happen. Back to the half-closed grace shutdown handling. It's not necessary anymore to do it on socket layer (which is only support for TCP sockets) because we do it on application layer. This patch removes this handling, if there are still issues then we have a problem on the application layer for such handling. Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: use listen sock as dlm running indicator

2022-11-21T15:45:49+00:00

This patch will switch from dlm_allow_conn to check if dlm lowcomms is running or not to if we actually have a listen socket set or not. The list socket will be set and unset in lowcomms start and shutdown functionality. To synchronize with data_ready() callback we will set the socket callback to NULL while socket lock is held. Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: add midcomms init/start functions

2022-11-21T15:45:49+00:00

This patch introduces leftovers of init, start, stop and exit functionality. The dlm application layer should always call the midcomms layer which getting aware of such event and redirect it to the lowcomms layer. Some functionality which is currently handled inside the start functionality of midcomms and lowcomms should be handled in the init functionality as it only need to be initialized once when dlm is loaded. Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: memory cache for lowcomms hotpath

2021-12-07T18:42:26+00:00

This patch introduces a kmem cache for dlm_msg handles which are used always if dlm sends a message out. Even if their are covered by midcomms layer or not. Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: memory cache for writequeue_entry

2021-12-07T18:42:26+00:00

This patch introduces a kmem cache for writequeue entry. A writequeue entry get quite a lot allocated if dlm transmit messages. Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: let handle callback data as void

2021-11-02T19:39:20+00:00

This patch changes the dlm_lowcomms_new_msg() function pointer private data from "struct mhandle *" to "void *" to provide different structures than just "struct mhandle". Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: implement delayed ack handling

2021-08-19T16:33:03+00:00

This patch changes that we don't ack each message. Lowcomms will take care about to send an ack back after a bulk of messages was processed. Currently it's only when the whole receive buffer was processed, there might better positions to send an ack back but only the lowcomms implementation know when there are more data to receive. This patch has also disadvantages that we might retransmit more on errors, however this is a very rare case. Tested with make_panic on gfs2 with three nodes by running: trace-cmd record -p function -l 'dlm_send_ack' sleep 100 and trace-cmd report | wc -l Before patch: - 20548 - 21376 - 21398 After patch: - 18338 - 20679 - 19949 Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: rename socket and app buffer defines

2021-06-02T16:53:04+00:00

This patch renames DEFAULT_BUFFER_SIZE to DLM_MAX_SOCKET_BUFSIZE and LOWCOMMS_MAX_TX_BUFFER_LEN to DLM_MAX_APP_BUFSIZE as they are proper names to define what's behind those values. The DLM_MAX_SOCKET_BUFSIZE defines the maximum size of buffer which can be handled on socket layer, the DLM_MAX_APP_BUFSIZE defines the maximum size of buffer which can be handled by the DLM application layer. Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: add reliable connection if reconnect

2021-05-25T14:22:20+00:00

This patch introduce to make a tcp lowcomms connection reliable even if reconnects occurs. This is done by an application layer re-transmission handling and sequence numbers in dlm protocols. There are three new dlm commands: DLM_OPTS: This will encapsulate an existing dlm message (and rcom message if they don't have an own application side re-transmission handling). As optional handling additional tlv's (type length fields) can be appended. This can be for example a sequence number field. However because in DLM_OPTS the lockspace field is unused and a sequence number is a mandatory field it isn't made as a tlv and we put the sequence number inside the lockspace id. The possibility to add optional options are still there for future purposes. DLM_ACK: Just a dlm header to acknowledge the receive of a DLM_OPTS message to it's sender. DLM_FIN: This provides a 4 way handshake for connection termination inclusive support for half-closed connections. It's provided on application layer because SCTP doesn't support half-closed sockets, the shutdown() call can interrupted by e.g. TCP resets itself and a hard logic to implement it because the othercon paradigm in lowcomms. The 4-way termination handshake also solve problems to synchronize peer EOF arrival and that the cluster manager removes the peer in the node membership handling of DLM. In some cases messages can be still transmitted in this time and we need to wait for the node membership event. To provide a reliable connection the node will retransmit all unacknowledges message to it's peer on reconnect. The receiver will then filtering out the next received message and drop all messages which are duplicates. As RCOM_STATUS and RCOM_NAMES messages are the first messages which are exchanged and they have they own re-transmission handling, there exists logic that these messages must be first. If these messages arrives we store the dlm version field. This handling is on DLM 3.1 and after this patch 3.2 the same. A backwards compatibility handling has been added which seems to work on tests without tcpkill, however it's not recommended to use DLM 3.1 and 3.2 at the same time, because DLM 3.2 tries to fix long term bugs in the DLM protocol. Signed-off-by: Alexander Aring Signed-off-by: David Teigland

fs: dlm: move out some hash functionality

2021-05-25T14:22:20+00:00

This patch moves out some lowcomms hash functionality into lowcomms header to provide them to other layers like midcomms as well. Signed-off-by: Alexander Aring Signed-off-by: David Teigland