// SPDX-License-Identifier: GPL-2.0
/*
 * Shared Memory Communications over RDMA (SMC-R) and RoCE
 *
 * Manage send buffer.
 * Producer:
 * Copy user space data into send buffer, if send buffer space available.
 * Consumer:
 * Trigger RDMA write into RMBE of peer and send CDC, if RMBE space available.
 *
 * Copyright IBM Corp. 2016
 *
 * Author(s):  Ursula Braun <ubraun@linux.vnet.ibm.com>
 */

#include <linux/net.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
#include <linux/sched/signal.h>

#include <net/sock.h>
#include <net/tcp.h>

#include "smc.h"
#include "smc_wr.h"
#include "smc_cdc.h"
#include "smc_close.h"
#include "smc_ism.h"
#include "smc_tx.h"
#include "smc_stats.h"
#include "smc_tracepoint.h"

#define SMC_TX_WORK_DELAY       0

/***************************** sndbuf producer *******************************/

/* callback implementation for sk.sk_write_space()
 * to wakeup sndbuf producers that blocked with smc_tx_wait().
 * called under sk_socket lock.
 */
static void smc_tx_write_space(struct sock *sk)
{
        struct socket *sock = sk->sk_socket;
        struct smc_sock *smc = smc_sk(sk);
        struct socket_wq *wq;

        /* similar to sk_stream_write_space */
        if (atomic_read(&smc->conn.sndbuf_space) && sock) {
                if (test_bit(SOCK_NOSPACE, &sock->flags))
                        SMC_STAT_RMB_TX_FULL(smc, !smc->conn.lnk);
                clear_bit(SOCK_NOSPACE, &sock->flags);
                rcu_read_lock();
                wq = rcu_dereference(sk->sk_wq);
                if (skwq_has_sleeper(wq))
                        wake_up_interruptible_poll(&wq->wait,
                                                   EPOLLOUT | EPOLLWRNORM |
                                                   EPOLLWRBAND);
                if (wq && wq->fasync_list && !(sk->sk_shutdown & SEND_SHUTDOWN))
                        sock_wake_async(wq, SOCK_WAKE_SPACE, POLL_OUT);
                rcu_read_unlock();
        }
}

/* Wakeup sndbuf producers that blocked with smc_tx_wait().
 * Cf. tcp_data_snd_check()=>tcp_check_space()=>tcp_new_space().
 */
void smc_tx_sndbuf_nonfull(struct smc_sock *smc)
{
        if (smc->sk.sk_socket &&
            test_bit(SOCK_NOSPACE, &smc->sk.sk_socket->flags))
                smc->sk.sk_write_space(&smc->sk);
}

/* blocks sndbuf producer until at least one byte of free space available
 * or urgent Byte was consumed
 */
static int smc_tx_wait(struct smc_sock *smc, int flags)
{
        DEFINE_WAIT_FUNC(wait, woken_wake_function);
        struct smc_connection *conn = &smc->conn;
        struct sock *sk = &smc->sk;
        long timeo;
        int rc = 0;

        /* similar to sk_stream_wait_memory */
        timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
        add_wait_queue(sk_sleep(sk), &wait);
        while (1) {
                sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
                if (sk->sk_err ||
                    (sk->sk_shutdown & SEND_SHUTDOWN) ||
                    conn->killed ||
                    conn->local_tx_ctrl.conn_state_flags.peer_done_writing) {
                        rc = -EPIPE;
                        break;
                }
                if (smc_cdc_rxed_any_close(conn)) {
                        rc = -ECONNRESET;
                        break;
                }
                if (!timeo) {
                        /* ensure EPOLLOUT is subsequently generated */
                        set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
                        rc = -EAGAIN;
                        break;
                }
                if (signal_pending(current)) {
                        rc = sock_intr_errno(timeo);
                        break;
                }
                sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
                if (atomic_read(&conn->sndbuf_space) && !conn->urg_tx_pend)
                        break; /* at least 1 byte of free & no urgent data */
                set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
                sk_wait_event(sk, &timeo,
                              READ_ONCE(sk->sk_err) ||
                              (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN) ||
                              smc_cdc_rxed_any_close(conn) ||
                              (atomic_read(&conn->sndbuf_space) &&
                               !conn->urg_tx_pend),
                              &wait);
        }
        remove_wait_queue(sk_sleep(sk), &wait);
        return rc;
}

static bool smc_tx_is_corked(struct smc_sock *smc)
{
        struct tcp_sock *tp = tcp_sk(smc->clcsock->sk);

        return (tp->nonagle & TCP_NAGLE_CORK) ? true : false;
}

/* If we have pending CDC messages, do not send:
 * Because CQE of this CDC message will happen shortly, it gives
 * a chance to coalesce future sendmsg() payload in to one RDMA Write,
 * without need for a timer, and with no latency trade off.
 * Algorithm here:
 *  1. First message should never cork
 *  2. If we have pending Tx CDC messages, wait for the first CDC
 *     message's completion
 *  3. Don't cork to much data in a single RDMA Write to prevent burst
 *     traffic, total corked message should not exceed sendbuf/2
 */
static bool smc_should_autocork(struct smc_sock *smc)
{
        struct smc_connection *conn = &smc->conn;
        int corking_size;

        corking_size = min_t(unsigned int, conn->sndbuf_desc->len >> 1,
                             sock_net(&smc->sk)->smc.sysctl_autocorking_size);

        if (atomic_read(&conn->cdc_pend_tx_wr) == 0 ||
            smc_tx_prepared_sends(conn) > corking_size)
                return false;
        return true;
}

static bool smc_tx_should_cork(struct smc_sock *smc, struct msghdr *msg)
{
        struct smc_connection *conn = &smc->conn;

        if (smc_should_autocork(smc))
                return true;

        /* for a corked socket defer the RDMA writes if
         * sndbuf_space is still available. The applications
         * should known how/when to uncork it.
         */
        if ((msg->msg_flags & MSG_MORE ||
             smc_tx_is_corked(smc)) &&
            atomic_read(&conn->sndbuf_space))
                return true;

        return false;
}

/* sndbuf producer: main API called by socket layer.
 * called under sock lock.
 */
int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len)
{
        size_t copylen, send_done = 0, send_remaining = len;
        size_t chunk_len, chunk_off, chunk_len_sum;
        struct smc_connection *conn = &smc->conn;
        union smc_host_cursor prep;
        struct sock *sk = &smc->sk;
        char *sndbuf_base;
        int tx_cnt_prep;
        int writespace;
        int rc, chunk;

        /* This should be in poll */
        sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);

        if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) {
                rc = -EPIPE;
                goto out_err;
        }

        if (sk->sk_state == SMC_INIT)
                return -ENOTCONN;

        if (len > conn->sndbuf_desc->len)
                SMC_STAT_RMB_TX_SIZE_SMALL(smc, !conn->lnk);

        if (len > conn->peer_rmbe_size)
                SMC_STAT_RMB_TX_PEER_SIZE_SMALL(smc, !conn->lnk);

        if (msg->msg_flags & MSG_OOB)
                SMC_STAT_INC(smc, urg_data_cnt);

        while (msg_data_left(msg)) {
                if (smc->sk.sk_shutdown & SEND_SHUTDOWN ||
                    (smc->sk.sk_err == ECONNABORTED) ||
                    conn->killed)
                        return -EPIPE;
                if (smc_cdc_rxed_any_close(conn))
                        return send_done ?: -ECONNRESET;

                if (msg->msg_flags & MSG_OOB)
                        conn->local_tx_ctrl.prod_flags.urg_data_pending = 1;

                if (!atomic_read(&conn->sndbuf_space) || conn->urg_tx_pend) {
                        if (send_done)
                                return send_done;
                        rc = smc_tx_wait(smc, msg->msg_flags);
                        if (rc)
                                goto out_err;
                        continue;
                }

                /* initialize variables for 1st iteration of subsequent loop */
                /* could be just 1 byte, even after smc_tx_wait above */
                writespace = atomic_read(&conn->sndbuf_space);
                /* not more than what user space asked for */
                copylen = min_t(size_t, send_remaining, writespace);
                /* determine start of sndbuf */
                sndbuf_base = conn->sndbuf_desc->cpu_addr;
                smc_curs_copy(&prep, &conn->tx_curs_prep, conn);
                tx_cnt_prep = prep.count;
                /* determine chunks where to write into sndbuf */
                /* either unwrapped case, or 1st chunk of wrapped case */
                chunk_len = min_t(size_t, copylen, conn->sndbuf_desc->len -
                                  tx_cnt_prep);
                chunk_len_sum = chunk_len;
                chunk_off = tx_cnt_prep;
                for (chunk = 0; chunk < 2; chunk++) {
                        rc = memcpy_from_msg(sndbuf_base + chunk_off,
                                             msg, chunk_len);
                        if (rc) {
                                smc_sndbuf_sync_sg_for_device(conn);
                                if (send_done)
                                        return send_done;
                                goto out_err;
                        }
                        send_done += chunk_len;
                        send_remaining -= chunk_len;

                        if (chunk_len_sum == copylen)
                                break; /* either on 1st or 2nd iteration */
                        /* prepare next (== 2nd) iteration */
                        chunk_len = copylen - chunk_len; /* remainder */
                        chunk_len_sum += chunk_len;
                        chunk_off = 0; /* modulo offset in send ring buffer */
                }
                smc_sndbuf_sync_sg_for_device(conn);
                /* update cursors */
                smc_curs_add(conn->sndbuf_desc->len, &prep, copylen);
                smc_curs_copy(&conn->tx_curs_prep, &prep, conn);
                /* increased in send tasklet smc_cdc_tx_handler() */
                smp_mb__before_atomic();
                atomic_sub(copylen, &conn->sndbuf_space);
                /* guarantee 0 <= sndbuf_space <= sndbuf_desc->len */
                smp_mb__after_atomic();
                /* since we just produced more new data into sndbuf,
                 * trigger sndbuf consumer: RDMA write into peer RMBE and CDC
                 */
                if ((msg->msg_flags & MSG_OOB) && !send_remaining)
                        conn->urg_tx_pend = true;
                /* If we need to cork, do nothing and wait for the next
                 * sendmsg() call or push on tx completion
                 */
                if (!smc_tx_should_cork(smc, msg))
                        smc_tx_sndbuf_nonempty(conn);

                trace_smc_tx_sendmsg(smc, copylen);
        } /* while (msg_data_left(msg)) */

        return send_done;

out_err:
        rc = sk_stream_error(sk, msg->msg_flags, rc);
        /* make sure we wake any epoll edge trigger waiter */
        if (unlikely(rc == -EAGAIN))
                sk->sk_write_space(sk);
        return rc;
}

/***************************** sndbuf consumer *******************************/

/* sndbuf consumer: actual data transfer of one target chunk with ISM write */
int smcd_tx_ism_write(struct smc_connection *conn, void *data, size_t len,
                      u32 offset, int signal)
{
        int rc;

        rc = smc_ism_write(conn->lgr->smcd, conn->peer_token,
                           conn->peer_rmbe_idx, signal, conn->tx_off + offset,
                           data, len);
        if (rc)
                conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
        return rc;
}

/* sndbuf consumer: actual data transfer of one target chunk with RDMA write */
static int smc_tx_rdma_write(struct smc_connection *conn, int peer_rmbe_offset,
                             int num_sges, struct ib_rdma_wr *rdma_wr)
{
        struct smc_link_group *lgr = conn->lgr;
        struct smc_link *link = conn->lnk;
        int rc;

        rdma_wr->wr.wr_id = smc_wr_tx_get_next_wr_id(link);
        rdma_wr->wr.num_sge = num_sges;
        rdma_wr->remote_addr =
                lgr->rtokens[conn->rtoken_idx][link->link_idx].dma_addr +
                /* RMBE within RMB */
                conn->tx_off +
                /* offset within RMBE */
                peer_rmbe_offset;
        rdma_wr->rkey = lgr->rtokens[conn->rtoken_idx][link->link_idx].rkey;
        rc = ib_post_send(link->roce_qp, &rdma_wr->wr, NULL);
        if (rc)
                smcr_link_down_cond_sched(link);
        return rc;
}

/* sndbuf consumer */
static inline void smc_tx_advance_cursors(struct smc_connection *conn,
                                          union smc_host_cursor *prod,
                                          union smc_host_cursor *sent,
                                          size_t len)
{
        smc_curs_add(conn->peer_rmbe_size, prod, len);
        /* increased in recv tasklet smc_cdc_msg_rcv() */
        smp_mb__before_atomic();
        /* data in flight reduces usable snd_wnd */
        atomic_sub(len, &conn->peer_rmbe_space);
        /* guarantee 0 <= peer_rmbe_space <= peer_rmbe_size */
        smp_mb__after_atomic();
        smc_curs_add(conn->sndbuf_desc->len, sent, len);
}

/* SMC-R helper for smc_tx_rdma_writes() */
static int smcr_tx_rdma_writes(struct smc_connection *conn, size_t len,
                               size_t src_off, size_t src_len,
                               size_t dst_off, size_t dst_len,
                               struct smc_rdma_wr *wr_rdma_buf)
{
        struct smc_link *link = conn->lnk;

        dma_addr_t dma_addr =
                sg_dma_address(conn->sndbuf_desc->sgt[link->link_idx].sgl);
        u64 virt_addr = (uintptr_t)conn->sndbuf_desc->cpu_addr;
        int src_len_sum = src_len, dst_len_sum = dst_len;
        int sent_count = src_off;
        int srcchunk, dstchunk;
        int num_sges;
        int rc;

        for (dstchunk = 0; dstchunk < 2; dstchunk++) {
                struct ib_rdma_wr *wr = &wr_rdma_buf->wr_tx_rdma[dstchunk];
                struct ib_sge *sge = wr->wr.sg_list;
                u64 base_addr = dma_addr;

                if (dst_len < link->qp_attr.cap.max_inline_data) {
                        base_addr = virt_addr;
                        wr->wr.send_flags |= IB_SEND_INLINE;
                } else {
                        wr->wr.send_flags &= ~IB_SEND_INLINE;
                }

                num_sges = 0;
                for (srcchunk = 0; srcchunk < 2; srcchunk++) {
                        sge[srcchunk].addr = conn->sndbuf_desc->is_vm ?
                                (virt_addr + src_off) : (base_addr + src_off);
                        sge[srcchunk].length = src_len;
                        if (conn->sndbuf_desc->is_vm)
                                sge[srcchunk].lkey =
                                        conn->sndbuf_desc->mr[link->link_idx]->lkey;
                        num_sges++;

                        src_off += src_len;
                        if (src_off >= conn->sndbuf_desc->len)
                                src_off -= conn->sndbuf_desc->len;
                                                /* modulo in send ring */
                        if (src_len_sum == dst_len)
                                break; /* either on 1st or 2nd iteration */
                        /* prepare next (== 2nd) iteration */
                        src_len = dst_len - src_len; /* remainder */
                        src_len_sum += src_len;
                }
                rc = smc_tx_rdma_write(conn, dst_off, num_sges, wr);
                if (rc)
                        return rc;
                if (dst_len_sum == len)
                        break; /* either on 1st or 2nd iteration */
                /* prepare next (== 2nd) iteration */
                dst_off = 0; /* modulo offset in RMBE ring buffer */
                dst_len = len - dst_len; /* remainder */
                dst_len_sum += dst_len;
                src_len = min_t(int, dst_len, conn->sndbuf_desc->len -
                                sent_count);
                src_len_sum = src_len;
        }
        return 0;
}

/* SMC-D helper for smc_tx_rdma_writes() */
static int smcd_tx_rdma_writes(struct smc_connection *conn, size_t len,
                               size_t src_off, size_t src_len,
                               size_t dst_off, size_t dst_len)
{
        int src_len_sum = src_len, dst_len_sum = dst_len;
        int srcchunk, dstchunk;
        int rc;

        if (conn->sndbuf_desc->is_attached)
                return 0;

        for (dstchunk = 0; dstchunk < 2; dstchunk++) {
                for (srcchunk = 0; srcchunk < 2; srcchunk++) {
                        void *data = conn->sndbuf_desc->cpu_addr + src_off;

                        rc = smcd_tx_ism_write(conn, data, src_len, dst_off +
                                               sizeof(struct smcd_cdc_msg), 0);
                        if (rc)
                                return rc;
                        dst_off += src_len;
                        src_off += src_len;
                        if (src_off >= conn->sndbuf_desc->len)
                                src_off -= conn->sndbuf_desc->len;
                                                /* modulo in send ring */
                        if (src_len_sum == dst_len)
                                break; /* either on 1st or 2nd iteration */
                        /* prepare next (== 2nd) iteration */
                        src_len = dst_len - src_len; /* remainder */
                        src_len_sum += src_len;
                }
                if (dst_len_sum == len)
                        break; /* either on 1st or 2nd iteration */
                /* prepare next (== 2nd) iteration */
                dst_off = 0; /* modulo offset in RMBE ring buffer */
                dst_len = len - dst_len; /* remainder */
                dst_len_sum += dst_len;
                src_len = min_t(int, dst_len, conn->sndbuf_desc->len - src_off);
                src_len_sum = src_len;
        }
        return 0;
}

/* sndbuf consumer: prepare all necessary (src&dst) chunks of data transmit;
 * usable snd_wnd as max transmit
 */
static int smc_tx_rdma_writes(struct smc_connection *conn,
                              struct smc_rdma_wr *wr_rdma_buf)
{
        size_t len, src_len, dst_off, dst_len; /* current chunk values */
        union smc_host_cursor sent, prep, prod, cons;
        struct smc_cdc_producer_flags *pflags;
        int to_send, rmbespace;
        int rc;

        /* source: sndbuf */
        smc_curs_copy(&sent, &conn->tx_curs_sent, conn);
        smc_curs_copy(&prep, &conn->tx_curs_prep, conn);
        /* cf. wmem_alloc - (snd_max - snd_una) */
        to_send = smc_curs_diff(conn->sndbuf_desc->len, &sent, &prep);
        if (to_send <= 0)
                return 0;

        /* destination: RMBE */
        /* cf. snd_wnd */
        rmbespace = atomic_read(&conn->peer_rmbe_space);
        if (rmbespace <= 0) {
                struct smc_sock *smc = container_of(conn, struct smc_sock,
                                                    conn);
                SMC_STAT_RMB_TX_PEER_FULL(smc, !conn->lnk);
                return 0;
        }
        smc_curs_copy(&prod, &conn->local_tx_ctrl.prod, conn);
        smc_curs_copy(&cons, &conn->local_rx_ctrl.cons, conn);

        /* if usable snd_wnd closes ask peer to advertise once it opens again */
        pflags = &conn->local_tx_ctrl.prod_flags;
        pflags->write_blocked = (to_send >= rmbespace);
        /* cf. usable snd_wnd */
        len = min(to_send, rmbespace);

        /* initialize variables for first iteration of subsequent nested loop */
        dst_off = prod.count;
        if (prod.wrap == cons.wrap) {
                /* the filled destination area is unwrapped,
                 * hence the available free destination space is wrapped
                 * and we need 2 destination chunks of sum len; start with 1st
                 * which is limited by what's available in sndbuf
                 */
                dst_len = min_t(size_t,
                                conn->peer_rmbe_size - prod.count, len);
        } else {
                /* the filled destination area is wrapped,
                 * hence the available free destination space is unwrapped
                 * and we need a single destination chunk of entire len
                 */
                dst_len = len;
        }
        /* dst_len determines the maximum src_len */
        if (sent.count + dst_len <= conn->sndbuf_desc->len) {
                /* unwrapped src case: single chunk of entire dst_len */
                src_len = dst_len;
        } else {
                /* wrapped src case: 2 chunks of sum dst_len; start with 1st: */
                src_len = conn->sndbuf_desc->len - sent.count;
        }

        if (conn->lgr->is_smcd)
                rc = smcd_tx_rdma_writes(conn, len, sent.count, src_len,
                                         dst_off, dst_len);
        else
                rc = smcr_tx_rdma_writes(conn, len, sent.count, src_len,
                                         dst_off, dst_len, wr_rdma_buf);
        if (rc)
                return rc;

        if (conn->urg_tx_pend && len == to_send)
                pflags->urg_data_present = 1;
        smc_tx_advance_cursors(conn, &prod, &sent, len);
        /* update connection's cursors with advanced local cursors */
        smc_curs_copy(&conn->local_tx_ctrl.prod, &prod, conn);
                                                        /* dst: peer RMBE */
        smc_curs_copy(&conn->tx_curs_sent, &sent, conn);/* src: local sndbuf */

        return 0;
}

/* Wakeup sndbuf consumers from any context (IRQ or process)
 * since there is more data to transmit; usable snd_wnd as max transmit
 */
static int smcr_tx_sndbuf_nonempty(struct smc_connection *conn)
{
        struct smc_cdc_producer_flags *pflags = &conn->local_tx_ctrl.prod_flags;
        struct smc_link *link = conn->lnk;
        struct smc_rdma_wr *wr_rdma_buf;
        struct smc_cdc_tx_pend *pend;
        struct smc_wr_buf *wr_buf;
        int rc;

        if (!link || !smc_wr_tx_link_hold(link))
                return -ENOLINK;
        rc = smc_cdc_get_free_slot(conn, link, &wr_buf, &wr_rdma_buf, &pend);
        if (rc < 0) {
                smc_wr_tx_link_put(link);
                if (rc == -EBUSY) {
                        struct smc_sock *smc =
                                container_of(conn, struct smc_sock, conn);

                        if (smc->sk.sk_err == ECONNABORTED)
                                return sock_error(&smc->sk);
                        if (conn->killed)
                                return -EPIPE;
                        rc = 0;
                        mod_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
                                         SMC_TX_WORK_DELAY);
                }
                return rc;
        }

        spin_lock_bh(&conn->send_lock);
        if (link != conn->lnk) {
                /* link of connection changed, tx_work will restart */
                smc_wr_tx_put_slot(link,
                                   (struct smc_wr_tx_pend_priv *)pend);
                rc = -ENOLINK;
                goto out_unlock;
        }
        if (!pflags->urg_data_present) {
                rc = smc_tx_rdma_writes(conn, wr_rdma_buf);
                if (rc) {
                        smc_wr_tx_put_slot(link,
                                           (struct smc_wr_tx_pend_priv *)pend);
                        goto out_unlock;
                }
        }

        rc = smc_cdc_msg_send(conn, wr_buf, pend);
        if (!rc && pflags->urg_data_present) {
                pflags->urg_data_pending = 0;
                pflags->urg_data_present = 0;
        }

out_unlock:
        spin_unlock_bh(&conn->send_lock);
        smc_wr_tx_link_put(link);
        return rc;
}

static int smcd_tx_sndbuf_nonempty(struct smc_connection *conn)
{
        struct smc_cdc_producer_flags *pflags = &conn->local_tx_ctrl.prod_flags;
        int rc = 0;

        spin_lock_bh(&conn->send_lock);
        if (!pflags->urg_data_present)
                rc = smc_tx_rdma_writes(conn, NULL);
        if (!rc)
                rc = smcd_cdc_msg_send(conn);

        if (!rc && pflags->urg_data_present) {
                pflags->urg_data_pending = 0;
                pflags->urg_data_present = 0;
        }
        spin_unlock_bh(&conn->send_lock);
        return rc;
}

int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
{
        struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
        int rc = 0;

        /* No data in the send queue */
        if (unlikely(smc_tx_prepared_sends(conn) <= 0))
                goto out;

        /* Peer don't have RMBE space */
        if (unlikely(atomic_read(&conn->peer_rmbe_space) <= 0)) {
                SMC_STAT_RMB_TX_PEER_FULL(smc, !conn->lnk);
                goto out;
        }

        if (conn->killed ||
            conn->local_rx_ctrl.conn_state_flags.peer_conn_abort) {
                rc = -EPIPE;    /* connection being aborted */
                goto out;
        }
        if (conn->lgr->is_smcd)
                rc = smcd_tx_sndbuf_nonempty(conn);
        else
                rc = smcr_tx_sndbuf_nonempty(conn);

        if (!rc) {
                /* trigger socket release if connection is closing */
                smc_close_wake_tx_prepared(smc);
        }

out:
        return rc;
}

/* Wakeup sndbuf consumers from process context
 * since there is more data to transmit. The caller
 * must hold sock lock.
 */
void smc_tx_pending(struct smc_connection *conn)
{
        struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
        int rc;

        if (smc->sk.sk_err)
                return;

        rc = smc_tx_sndbuf_nonempty(conn);
        if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked &&
            !atomic_read(&conn->bytes_to_rcv))
                conn->local_rx_ctrl.prod_flags.write_blocked = 0;
}

/* Wakeup sndbuf consumers from process context
 * since there is more data to transmit in locked
 * sock.
 */
void smc_tx_work(struct work_struct *work)
{
        struct smc_connection *conn = container_of(to_delayed_work(work),
                                                   struct smc_connection,
                                                   tx_work);
        struct smc_sock *smc = container_of(conn, struct smc_sock, conn);

        lock_sock(&smc->sk);
        smc_tx_pending(conn);
        release_sock(&smc->sk);
}

void smc_tx_consumer_update(struct smc_connection *conn, bool force)
{
        union smc_host_cursor cfed, cons, prod;
        int sender_free = conn->rmb_desc->len;
        int to_confirm;

        smc_curs_copy(&cons, &conn->local_tx_ctrl.cons, conn);
        smc_curs_copy(&cfed, &conn->rx_curs_confirmed, conn);
        to_confirm = smc_curs_diff(conn->rmb_desc->len, &cfed, &cons);
        if (to_confirm > conn->rmbe_update_limit) {
                smc_curs_copy(&prod, &conn->local_rx_ctrl.prod, conn);
                sender_free = conn->rmb_desc->len -
                              smc_curs_diff_large(conn->rmb_desc->len,
                                                  &cfed, &prod);
        }

        if (conn->local_rx_ctrl.prod_flags.cons_curs_upd_req ||
            force ||
            ((to_confirm > conn->rmbe_update_limit) &&
             ((sender_free <= (conn->rmb_desc->len / 2)) ||
              conn->local_rx_ctrl.prod_flags.write_blocked))) {
                if (conn->killed ||
                    conn->local_rx_ctrl.conn_state_flags.peer_conn_abort)
                        return;
                if ((smc_cdc_get_slot_and_msg_send(conn) < 0) &&
                    !conn->killed) {
                        queue_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
                                           SMC_TX_WORK_DELAY);
                        return;
                }
        }
        if (conn->local_rx_ctrl.prod_flags.write_blocked &&
            !atomic_read(&conn->bytes_to_rcv))
                conn->local_rx_ctrl.prod_flags.write_blocked = 0;
}

/***************************** send initialize *******************************/

/* Initialize send properties on connection establishment. NB: not __init! */
void smc_tx_init(struct smc_sock *smc)
{
        smc->sk.sk_write_space = smc_tx_write_space;
}