// SPDX-License-Identifier: GPL-2.0

  /*
   * Shared Memory Communications over RDMA (SMC-R) and RoCE
   *
   * Connection Data Control (CDC)
   * handles flow control
   *
   * Copyright IBM Corp. 2016
   *
   * Author(s):  Ursula Braun <ubraun@linux.vnet.ibm.com>
   */
  
  #include <linux/spinlock.h>
  
  #include "smc.h"
  #include "smc_wr.h"
  #include "smc_cdc.h"

  #include "smc_tx.h"

  #include "smc_rx.h"

  #include "smc_close.h"

  
  /********************************** send *************************************/

  /* handler for send/transmission completion of a CDC msg */
  static void smc_cdc_tx_handler(struct smc_wr_tx_pend_priv *pnd_snd,
  			       struct smc_link *link,
  			       enum ib_wc_status wc_status)
  {
  	struct smc_cdc_tx_pend *cdcpend = (struct smc_cdc_tx_pend *)pnd_snd;

  	struct smc_connection *conn = cdcpend->conn;

  	struct smc_sock *smc;
  	int diff;

  	if (!conn)

  		/* already dismissed */
  		return;

  	smc = container_of(conn, struct smc_sock, conn);

  	bh_lock_sock(&smc->sk);
  	if (!wc_status) {

  		diff = smc_curs_diff(cdcpend->conn->sndbuf_desc->len,

  				     &cdcpend->conn->tx_curs_fin,
  				     &cdcpend->cursor);
  		/* sndbuf_space is decreased in smc_sendmsg */
  		smp_mb__before_atomic();
  		atomic_add(diff, &cdcpend->conn->sndbuf_space);

  		/* guarantee 0 <= sndbuf_space <= sndbuf_desc->len */

  		smp_mb__after_atomic();

  		smc_curs_copy(&conn->tx_curs_fin, &cdcpend->cursor, conn);

  		smc_curs_copy(&conn->local_tx_ctrl_fin, &cdcpend->p_cursor,
  			      conn);
  		conn->tx_cdc_seq_fin = cdcpend->ctrl_seq;

  	}

  	smc_tx_sndbuf_nonfull(smc);

  	bh_unlock_sock(&smc->sk);
  }

  int smc_cdc_get_free_slot(struct smc_connection *conn,

  			  struct smc_link *link,

  			  struct smc_wr_buf **wr_buf,

  			  struct smc_rdma_wr **wr_rdma_buf,

  			  struct smc_cdc_tx_pend **pend)
  {

  	int rc;

  	rc = smc_wr_tx_get_free_slot(link, smc_cdc_tx_handler, wr_buf,

  				     wr_rdma_buf,

  				     (struct smc_wr_tx_pend_priv **)pend);

  	if (conn->killed) {

  		/* abnormal termination */

  		if (!rc)
  			smc_wr_tx_put_slot(link,
  					   (struct smc_wr_tx_pend_priv *)pend);

  		rc = -EPIPE;

  	}

  	return rc;

  }
  
  static inline void smc_cdc_add_pending_send(struct smc_connection *conn,
  					    struct smc_cdc_tx_pend *pend)
  {
  	BUILD_BUG_ON_MSG(
  		sizeof(struct smc_cdc_msg) > SMC_WR_BUF_SIZE,
  		"must increase SMC_WR_BUF_SIZE to at least sizeof(struct smc_cdc_msg)");
  	BUILD_BUG_ON_MSG(

  		offsetofend(struct smc_cdc_msg, reserved) > SMC_WR_TX_SIZE,

  		"must adapt SMC_WR_TX_SIZE to sizeof(struct smc_cdc_msg); if not all smc_wr upper layer protocols use the same message size any more, must start to set link->wr_tx_sges[i].length on each individual smc_wr_tx_send()");
  	BUILD_BUG_ON_MSG(
  		sizeof(struct smc_cdc_tx_pend) > SMC_WR_TX_PEND_PRIV_SIZE,
  		"must increase SMC_WR_TX_PEND_PRIV_SIZE to at least sizeof(struct smc_cdc_tx_pend)");
  	pend->conn = conn;
  	pend->cursor = conn->tx_curs_sent;
  	pend->p_cursor = conn->local_tx_ctrl.prod;
  	pend->ctrl_seq = conn->tx_cdc_seq;
  }
  
  int smc_cdc_msg_send(struct smc_connection *conn,
  		     struct smc_wr_buf *wr_buf,
  		     struct smc_cdc_tx_pend *pend)
  {

  	struct smc_link *link = conn->lnk;

  	union smc_host_cursor cfed;

  	int rc;

  	smc_cdc_add_pending_send(conn, pend);
  
  	conn->tx_cdc_seq++;
  	conn->local_tx_ctrl.seqno = conn->tx_cdc_seq;

  	smc_host_msg_to_cdc((struct smc_cdc_msg *)wr_buf, conn, &cfed);

  	rc = smc_wr_tx_send(link, (struct smc_wr_tx_pend_priv *)pend);

  	if (!rc) {

  		smc_curs_copy(&conn->rx_curs_confirmed, &cfed, conn);

  		conn->local_rx_ctrl.prod_flags.cons_curs_upd_req = 0;

  	} else {
  		conn->tx_cdc_seq--;
  		conn->local_tx_ctrl.seqno = conn->tx_cdc_seq;

  	}

  
  	return rc;
  }

  /* send a validation msg indicating the move of a conn to an other QP link */

  int smcr_cdc_msg_send_validation(struct smc_connection *conn,
  				 struct smc_cdc_tx_pend *pend,
  				 struct smc_wr_buf *wr_buf)

  {
  	struct smc_host_cdc_msg *local = &conn->local_tx_ctrl;
  	struct smc_link *link = conn->lnk;

  	struct smc_cdc_msg *peer;
  	int rc;

  	peer = (struct smc_cdc_msg *)wr_buf;
  	peer->common.type = local->common.type;
  	peer->len = local->len;
  	peer->seqno = htons(conn->tx_cdc_seq_fin); /* seqno last compl. tx */
  	peer->token = htonl(local->token);
  	peer->prod_flags.failover_validation = 1;
  
  	rc = smc_wr_tx_send(link, (struct smc_wr_tx_pend_priv *)pend);
  	return rc;
  }

  static int smcr_cdc_get_slot_and_msg_send(struct smc_connection *conn)

  {
  	struct smc_cdc_tx_pend *pend;
  	struct smc_wr_buf *wr_buf;

  	struct smc_link *link;
  	bool again = false;

  	int rc;

  again:
  	link = conn->lnk;
  	rc = smc_cdc_get_free_slot(conn, link, &wr_buf, NULL, &pend);

  	if (rc)
  		return rc;

  	spin_lock_bh(&conn->send_lock);

  	if (link != conn->lnk) {
  		/* link of connection changed, try again one time*/
  		spin_unlock_bh(&conn->send_lock);
  		smc_wr_tx_put_slot(link,
  				   (struct smc_wr_tx_pend_priv *)pend);
  		if (again)
  			return -ENOLINK;
  		again = true;
  		goto again;
  	}

  	rc = smc_cdc_msg_send(conn, wr_buf, pend);
  	spin_unlock_bh(&conn->send_lock);
  	return rc;

  }

  int smc_cdc_get_slot_and_msg_send(struct smc_connection *conn)
  {
  	int rc;

  	if (!conn->lgr || (conn->lgr->is_smcd && conn->lgr->peer_shutdown))
  		return -EPIPE;

  	if (conn->lgr->is_smcd) {
  		spin_lock_bh(&conn->send_lock);
  		rc = smcd_cdc_msg_send(conn);
  		spin_unlock_bh(&conn->send_lock);
  	} else {
  		rc = smcr_cdc_get_slot_and_msg_send(conn);
  	}
  
  	return rc;
  }

  static bool smc_cdc_tx_filter(struct smc_wr_tx_pend_priv *tx_pend,
  			      unsigned long data)
  {
  	struct smc_connection *conn = (struct smc_connection *)data;
  	struct smc_cdc_tx_pend *cdc_pend =
  		(struct smc_cdc_tx_pend *)tx_pend;
  
  	return cdc_pend->conn == conn;
  }
  
  static void smc_cdc_tx_dismisser(struct smc_wr_tx_pend_priv *tx_pend)
  {
  	struct smc_cdc_tx_pend *cdc_pend =
  		(struct smc_cdc_tx_pend *)tx_pend;
  
  	cdc_pend->conn = NULL;
  }
  
  void smc_cdc_tx_dismiss_slots(struct smc_connection *conn)
  {

  	struct smc_link *link = conn->lnk;

  
  	smc_wr_tx_dismiss_slots(link, SMC_CDC_MSG_TYPE,
  				smc_cdc_tx_filter, smc_cdc_tx_dismisser,
  				(unsigned long)conn);
  }

  /* Send a SMC-D CDC header.
   * This increments the free space available in our send buffer.
   * Also update the confirmed receive buffer with what was sent to the peer.
   */
  int smcd_cdc_msg_send(struct smc_connection *conn)
  {
  	struct smc_sock *smc = container_of(conn, struct smc_sock, conn);

  	union smc_host_cursor curs;

  	struct smcd_cdc_msg cdc;
  	int rc, diff;
  
  	memset(&cdc, 0, sizeof(cdc));
  	cdc.common.type = SMC_CDC_MSG_TYPE;

  	curs.acurs.counter = atomic64_read(&conn->local_tx_ctrl.prod.acurs);
  	cdc.prod.wrap = curs.wrap;
  	cdc.prod.count = curs.count;
  	curs.acurs.counter = atomic64_read(&conn->local_tx_ctrl.cons.acurs);
  	cdc.cons.wrap = curs.wrap;
  	cdc.cons.count = curs.count;
  	cdc.cons.prod_flags = conn->local_tx_ctrl.prod_flags;
  	cdc.cons.conn_state_flags = conn->local_tx_ctrl.conn_state_flags;

  	rc = smcd_tx_ism_write(conn, &cdc, sizeof(cdc), 0, 1);
  	if (rc)
  		return rc;

  	smc_curs_copy(&conn->rx_curs_confirmed, &curs, conn);

  	conn->local_rx_ctrl.prod_flags.cons_curs_upd_req = 0;

  	/* Calculate transmitted data and increment free send buffer space */
  	diff = smc_curs_diff(conn->sndbuf_desc->len, &conn->tx_curs_fin,
  			     &conn->tx_curs_sent);
  	/* increased by confirmed number of bytes */
  	smp_mb__before_atomic();
  	atomic_add(diff, &conn->sndbuf_space);
  	/* guarantee 0 <= sndbuf_space <= sndbuf_desc->len */
  	smp_mb__after_atomic();

  	smc_curs_copy(&conn->tx_curs_fin, &conn->tx_curs_sent, conn);

  
  	smc_tx_sndbuf_nonfull(smc);
  	return rc;
  }

  /********************************* receive ***********************************/
  
  static inline bool smc_cdc_before(u16 seq1, u16 seq2)
  {
  	return (s16)(seq1 - seq2) < 0;
  }

  static void smc_cdc_handle_urg_data_arrival(struct smc_sock *smc,
  					    int *diff_prod)
  {
  	struct smc_connection *conn = &smc->conn;
  	char *base;
  
  	/* new data included urgent business */

  	smc_curs_copy(&conn->urg_curs, &conn->local_rx_ctrl.prod, conn);

  	conn->urg_state = SMC_URG_VALID;
  	if (!sock_flag(&smc->sk, SOCK_URGINLINE))
  		/* we'll skip the urgent byte, so don't account for it */
  		(*diff_prod)--;

  	base = (char *)conn->rmb_desc->cpu_addr + conn->rx_off;

  	if (conn->urg_curs.count)
  		conn->urg_rx_byte = *(base + conn->urg_curs.count - 1);
  	else
  		conn->urg_rx_byte = *(base + conn->rmb_desc->len - 1);
  	sk_send_sigurg(&smc->sk);
  }

  static void smc_cdc_msg_validate(struct smc_sock *smc, struct smc_cdc_msg *cdc,
  				 struct smc_link *link)
  {
  	struct smc_connection *conn = &smc->conn;
  	u16 recv_seq = ntohs(cdc->seqno);
  	s16 diff;
  
  	/* check that seqnum was seen before */
  	diff = conn->local_rx_ctrl.seqno - recv_seq;
  	if (diff < 0) { /* diff larger than 0x7fff */
  		/* drop connection */
  		conn->out_of_sync = 1;	/* prevent any further receives */
  		spin_lock_bh(&conn->send_lock);
  		conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
  		conn->lnk = link;
  		spin_unlock_bh(&conn->send_lock);
  		sock_hold(&smc->sk); /* sock_put in abort_work */

  		if (!queue_work(smc_close_wq, &conn->abort_work))

  			sock_put(&smc->sk);
  	}
  }

  static void smc_cdc_msg_recv_action(struct smc_sock *smc,

  				    struct smc_cdc_msg *cdc)
  {
  	union smc_host_cursor cons_old, prod_old;
  	struct smc_connection *conn = &smc->conn;
  	int diff_cons, diff_prod;

  	smc_curs_copy(&prod_old, &conn->local_rx_ctrl.prod, conn);
  	smc_curs_copy(&cons_old, &conn->local_rx_ctrl.cons, conn);

  	smc_cdc_msg_to_host(&conn->local_rx_ctrl, cdc, conn);
  
  	diff_cons = smc_curs_diff(conn->peer_rmbe_size, &cons_old,
  				  &conn->local_rx_ctrl.cons);
  	if (diff_cons) {
  		/* peer_rmbe_space is decreased during data transfer with RDMA
  		 * write
  		 */
  		smp_mb__before_atomic();
  		atomic_add(diff_cons, &conn->peer_rmbe_space);
  		/* guarantee 0 <= peer_rmbe_space <= peer_rmbe_size */
  		smp_mb__after_atomic();
  	}

  	diff_prod = smc_curs_diff(conn->rmb_desc->len, &prod_old,

  				  &conn->local_rx_ctrl.prod);
  	if (diff_prod) {

  		if (conn->local_rx_ctrl.prod_flags.urg_data_present)
  			smc_cdc_handle_urg_data_arrival(smc, &diff_prod);

  		/* bytes_to_rcv is decreased in smc_recvmsg */
  		smp_mb__before_atomic();
  		atomic_add(diff_prod, &conn->bytes_to_rcv);

  		/* guarantee 0 <= bytes_to_rcv <= rmb_desc->len */

  		smp_mb__after_atomic();

  		smc->sk.sk_data_ready(&smc->sk);

  	} else {

  		if (conn->local_rx_ctrl.prod_flags.write_blocked)
  			smc->sk.sk_data_ready(&smc->sk);
  		if (conn->local_rx_ctrl.prod_flags.urg_data_pending)
  			conn->urg_state = SMC_URG_NOTYET;

  	}

  	/* trigger sndbuf consumer: RDMA write into peer RMBE and CDC */

  	if ((diff_cons && smc_tx_prepared_sends(conn)) ||
  	    conn->local_rx_ctrl.prod_flags.cons_curs_upd_req ||
  	    conn->local_rx_ctrl.prod_flags.urg_data_pending)

  		smc_tx_sndbuf_nonempty(conn);

  	if (diff_cons && conn->urg_tx_pend &&
  	    atomic_read(&conn->peer_rmbe_space) == conn->peer_rmbe_size) {
  		/* urg data confirmed by peer, indicate we're ready for more */
  		conn->urg_tx_pend = false;
  		smc->sk.sk_write_space(&smc->sk);
  	}

  	if (conn->local_rx_ctrl.conn_state_flags.peer_conn_abort) {

  		smc->sk.sk_err = ECONNRESET;

  		conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
  	}

  	if (smc_cdc_rxed_any_close_or_senddone(conn)) {
  		smc->sk.sk_shutdown |= RCV_SHUTDOWN;
  		if (smc->clcsock && smc->clcsock->sk)
  			smc->clcsock->sk->sk_shutdown |= RCV_SHUTDOWN;
  		sock_set_flag(&smc->sk, SOCK_DONE);

  		sock_hold(&smc->sk); /* sock_put in close_work */

  		if (!queue_work(smc_close_wq, &conn->close_work))

  			sock_put(&smc->sk);

  	}

  }
  
  /* called under tasklet context */

  static void smc_cdc_msg_recv(struct smc_sock *smc, struct smc_cdc_msg *cdc)

  {

  	sock_hold(&smc->sk);

  	bh_lock_sock(&smc->sk);

  	smc_cdc_msg_recv_action(smc, cdc);

  	bh_unlock_sock(&smc->sk);
  	sock_put(&smc->sk); /* no free sk in softirq-context */
  }

  /* Schedule a tasklet for this connection. Triggered from the ISM device IRQ
   * handler to indicate update in the DMBE.
   *
   * Context:
   * - tasklet context
   */
  static void smcd_cdc_rx_tsklet(unsigned long data)
  {
  	struct smc_connection *conn = (struct smc_connection *)data;

  	struct smcd_cdc_msg *data_cdc;

  	struct smcd_cdc_msg cdc;
  	struct smc_sock *smc;

  	if (!conn || conn->killed)

  		return;

  	data_cdc = (struct smcd_cdc_msg *)conn->rmb_desc->cpu_addr;
  	smcd_curs_copy(&cdc.prod, &data_cdc->prod, conn);
  	smcd_curs_copy(&cdc.cons, &data_cdc->cons, conn);

  	smc = container_of(conn, struct smc_sock, conn);
  	smc_cdc_msg_recv(smc, (struct smc_cdc_msg *)&cdc);
  }
  
  /* Initialize receive tasklet. Called from ISM device IRQ handler to start
   * receiver side.
   */
  void smcd_cdc_rx_init(struct smc_connection *conn)
  {
  	tasklet_init(&conn->rx_tsklet, smcd_cdc_rx_tsklet, (unsigned long)conn);
  }

  /***************************** init, exit, misc ******************************/
  
  static void smc_cdc_rx_handler(struct ib_wc *wc, void *buf)
  {
  	struct smc_link *link = (struct smc_link *)wc->qp->qp_context;
  	struct smc_cdc_msg *cdc = buf;

  	struct smc_connection *conn;
  	struct smc_link_group *lgr;
  	struct smc_sock *smc;

  
  	if (wc->byte_len < offsetof(struct smc_cdc_msg, reserved))
  		return; /* short message */

  	if (cdc->len != SMC_WR_TX_SIZE)

  		return; /* invalid message */

  
  	/* lookup connection */

  	lgr = smc_get_lgr(link);

  	read_lock_bh(&lgr->conns_lock);
  	conn = smc_lgr_find_conn(ntohl(cdc->token), lgr);
  	read_unlock_bh(&lgr->conns_lock);

  	if (!conn || conn->out_of_sync)

  		return;
  	smc = container_of(conn, struct smc_sock, conn);

  	if (cdc->prod_flags.failover_validation) {
  		smc_cdc_msg_validate(smc, cdc, link);
  		return;

  	}

  	if (smc_cdc_before(ntohs(cdc->seqno),
  			   conn->local_rx_ctrl.seqno))
  		/* received seqno is old */
  		return;

  	smc_cdc_msg_recv(smc, cdc);

  }
  
  static struct smc_wr_rx_handler smc_cdc_rx_handlers[] = {
  	{
  		.handler	= smc_cdc_rx_handler,
  		.type		= SMC_CDC_MSG_TYPE
  	},
  	{
  		.handler	= NULL,
  	}
  };
  
  int __init smc_cdc_init(void)
  {
  	struct smc_wr_rx_handler *handler;
  	int rc = 0;
  
  	for (handler = smc_cdc_rx_handlers; handler->handler; handler++) {
  		INIT_HLIST_NODE(&handler->list);
  		rc = smc_wr_rx_register_handler(handler);
  		if (rc)
  			break;
  	}
  	return rc;
  }