1 files changed, 646 insertions, 0 deletions

diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
new file mode 100644
index 000000000..2429f9fc7
--- /dev/null
+++ b/net/smc/smc_tx.c
@@ -0,0 +1,646 @@
+// 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"
+
+#define SMC_TX_WORK_DELAY	0
+#define SMC_TX_CORK_DELAY	(HZ >> 2)	/* 250 ms */
+
+/***************************** 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) {
+		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;
+}
+
+/* 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;
+	}
+
+	while (msg_data_left(msg)) {
+		if (sk->sk_state == SMC_INIT)
+			return -ENOTCONN;
+		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;
+		smc_sndbuf_sync_sg_for_cpu(conn);
+		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 ((msg->msg_flags & MSG_MORE || smc_tx_is_corked(smc)) &&
+		    (atomic_read(&conn->sndbuf_space) >
+						(conn->sndbuf_desc->len >> 1)))
+			/* for a corked socket defer the RDMA writes if there
+			 * is still sufficient sndbuf_space available
+			 */
+			queue_delayed_work(conn->lgr->tx_wq, &conn->tx_work,
+					   SMC_TX_CORK_DELAY);
+		else
+			smc_tx_sndbuf_nonempty(conn);
+	} /* 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)
+{
+	struct smc_ism_position pos;
+	int rc;
+
+	memset(&pos, 0, sizeof(pos));
+	pos.token = conn->peer_token;
+	pos.index = conn->peer_rmbe_idx;
+	pos.offset = conn->tx_off + offset;
+	pos.signal = signal;
+	rc = smc_ism_write(conn->lgr->smcd, &pos, 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);
+	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_sge *sge =
+			wr_rdma_buf->wr_tx_rdma[dstchunk].wr.sg_list;
+
+		num_sges = 0;
+		for (srcchunk = 0; srcchunk < 2; srcchunk++) {
+			sge[srcchunk].addr = dma_addr + src_off;
+			sge[srcchunk].length = src_len;
+			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_rdma_buf->wr_tx_rdma[dstchunk]);
+		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;
+
+	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)
+		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)
+{
+	int rc;
+
+	if (conn->killed ||
+	    conn->local_rx_ctrl.conn_state_flags.peer_conn_abort)
+		return -EPIPE;	/* connection being aborted */
+	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 */
+		struct smc_sock *smc = container_of(conn, struct smc_sock,
+						    conn);
+		smc_close_wake_tx_prepared(smc);
+	}
+	return rc;
+}
+
+/* Wakeup sndbuf consumers from process context
+ * since there is more data to transmit
+ */
+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);
+	int rc;
+
+	lock_sock(&smc->sk);
+	if (smc->sk.sk_err)
+		goto out;
+
+	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;
+
+out:
+	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;
+}