// 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(struct tasklet_struct *t)
{
        struct smc_connection *conn = from_tasklet(conn, t, rx_tsklet);
        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_setup(&conn->rx_tsklet, smcd_cdc_rx_tsklet);
}

/***************************** 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;
}