[PATCH V2 net-next 12/15] smc: send data (through RDMA)

Ursula Braun
2016-09-27T16:41:53Z

copy data to kernel send buffer, and trigger RDMA write

Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
---
net/smc/Makefile | 2 +-
net/smc/af_smc.c | 13 +-
net/smc/smc.h | 1 +
net/smc/smc_cdc.c | 7 +-
net/smc/smc_tx.c | 437 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
net/smc/smc_tx.h | 34 +++++
6 files changed, 490 insertions(+), 4 deletions(-)
create mode 100644 net/smc/smc_tx.c
create mode 100644 net/smc/smc_tx.h

diff --git a/net/smc/Makefile b/net/smc/Makefile
index ec0fd03..fc28d79 100644
--- a/net/smc/Makefile
+++ b/net/smc/Makefile
@@ -1,3 +1,3 @@
obj-$(CONFIG_SMC) += smc.o
smc-y := af_smc.o smc_pnet.o smc_ib.o smc_clc.o smc_core.o smc_wr.o smc_llc.o
-smc-y += smc_cdc.o
+smc-y += smc_cdc.o smc_tx.o
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index af82d28..c96a234 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -36,6 +36,7 @@
#include "smc_core.h"
#include "smc_ib.h"
#include "smc_pnet.h"
+#include "smc_tx.h"

static DEFINE_MUTEX(smc_create_lgr_pending); /* serialize link group
* creation
@@ -420,6 +421,8 @@ static int smc_connect_rdma(struct smc_sock *smc)
}

mutex_unlock(&smc_create_lgr_pending);
+ smc_tx_init(smc);
+
out_connected:
smc_copy_sock_settings_to_clc(smc);
smc->sk.sk_state = SMC_ACTIVE;
@@ -761,6 +764,8 @@ static void smc_listen_work(struct work_struct *work)
goto decline_rdma;
}

+ smc_tx_init(new_smc);
+
out_connected:
sk_refcnt_debug_inc(newsmcsk);
newsmcsk->sk_state = SMC_ACTIVE;
@@ -934,7 +939,7 @@ static int smc_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
if (smc->use_fallback)
rc = smc->clcsock->ops->sendmsg(smc->clcsock, msg, len);
else
- rc = sock_no_sendmsg(sock, msg, len);
+ rc = smc_tx_sendmsg(smc, msg, len);
out:
release_sock(sk);
return rc;
@@ -1015,6 +1020,12 @@ static unsigned int smc_poll(struct file *file, struct socket *sock,
mask |= smc_accept_poll(sk);
if (sk->sk_err)
mask |= POLLERR;
+ if (atomic_read(&smc->conn.sndbuf_space)) {
+ mask |= POLLOUT | POLLWRNORM;
+ } else {
+ sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
+ set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+ }
/* for now - to be enhanced in follow-on patch */
}

diff --git a/net/smc/smc.h b/net/smc/smc.h
index 65147da..191e913 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -130,6 +130,7 @@ struct smc_connection {
atomic_t sndbuf_space; /* remaining space in sndbuf */
u16 tx_cdc_seq; /* sequence # for CDC send */
spinlock_t send_lock; /* protect wr_sends */
+ struct work_struct tx_work; /* retry of smc_cdc_msg_send */

struct smc_host_cdc_msg local_rx_ctrl; /* filled during event_handl.
* .prod cf. TCP rcv_nxt
diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index ddd6a2d..d5e4a24 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -14,6 +14,7 @@
#include "smc.h"
#include "smc_wr.h"
#include "smc_cdc.h"
+#include "smc_tx.h"

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

@@ -52,7 +53,7 @@ static void smc_cdc_tx_handler(struct smc_wr_tx_pend_priv *pnd_snd,
smc_curs_read(&cdcpend->cursor, cdcpend->conn),
cdcpend->conn);
}
- /* subsequent patch: wake if send buffer space available */
+ smc_tx_sndbuf_nonfull(smc);
bh_unlock_sock(&smc->sk);
}

@@ -208,7 +209,9 @@ static void smc_cdc_msg_recv_action(struct smc_sock *smc,
}

/* piggy backed tx info */
- /* subsequent patch: wake receivers if receive buffer space available */
+ /* trigger sndbuf consumer: RDMA write into peer RMBE and CDC */
+ if (diff_cons && smc_tx_prepared_sends(conn))
+ smc_tx_sndbuf_nonempty(conn);

/* subsequent patch: trigger socket release if connection closed */

diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
new file mode 100644
index 0000000..368d27b
--- /dev/null
+++ b/net/smc/smc_tx.c
@@ -0,0 +1,437 @@
+/*
+ * 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 <ursula.braun@linux.vnet.ibm.com>
+ */
+
+#include <linux/net.h>
+#include <linux/rcupdate.h>
+#include <linux/workqueue.h>
+#include <net/sock.h>
+
+#include "smc.h"
+#include "smc_wr.h"
+#include "smc_cdc.h"
+#include "smc_tx.h"
+
+/***************************** sndbuf producer *******************************/
+
+/* callback implementation for sk.sk_write_space()
+ * to wakeup sndbuf producers that blocked with smc_tx_wait_memory().
+ * 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,
+ POLLOUT | POLLWRNORM |
+ POLLWRBAND);
+ 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_memory().
+ * 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 */
+static int smc_tx_wait_memory(struct smc_sock *smc, int flags)
+{
+ struct smc_connection *conn = &smc->conn;
+ struct sock *sk = &smc->sk;
+ DEFINE_WAIT(wait);
+ bool noblock;
+ long timeo;
+ int rc = 0;
+
+ /* similar to sk_stream_wait_memory */
+ timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
+ noblock = timeo ? false : true;
+ while (1) {
+ sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
+ prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+ if (sk->sk_err ||
+ (sk->sk_shutdown & SEND_SHUTDOWN) ||
+ conn->local_tx_ctrl.conn_state_flags.peer_done_writing) {
+ rc = -EPIPE;
+ break;
+ }
+ if (conn->local_rx_ctrl.conn_state_flags.peer_conn_abort) {
+ rc = -ECONNRESET;
+ break;
+ }
+ if (!timeo) {
+ if (noblock)
+ 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))
+ break; /* at least 1 byte of free space available */
+ set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
+ sk->sk_write_pending++;
+ sk_wait_event(sk, &timeo,
+ sk->sk_err ||
+ (sk->sk_shutdown & SEND_SHUTDOWN) ||
+ smc_cdc_rxed_any_close_or_senddone(conn) ||
+ atomic_read(&conn->sndbuf_space));
+ sk->sk_write_pending--;
+ }
+ finish_wait(sk_sleep(sk), &wait);
+ return rc;
+}
+
+/* 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 ||
+ conn->local_tx_ctrl.conn_state_flags.peer_conn_abort)
+ return -EPIPE;
+ if (smc_cdc_rxed_any_close(conn))
+ return send_done ?: -ECONNRESET;
+
+ if (!atomic_read(&conn->sndbuf_space)) {
+ rc = smc_tx_wait_memory(smc, msg->msg_flags);
+ if (rc) {
+ if (send_done)
+ return send_done;
+ goto out_err;
+ }
+ continue;
+ }
+
+ /* initialize variables for 1st iteration of subsequent loop */
+ /* could be just 1 byte, even after smc_tx_wait_memory 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_write(&prep,
+ smc_curs_read(&conn->tx_curs_prep, conn),
+ 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_size - 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) {
+ 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 */
+ }
+ /* update cursors */
+ smc_curs_add(conn->sndbuf_size, &prep, copylen);
+ smc_curs_write(&conn->tx_curs_prep,
+ smc_curs_read(&prep, conn),
+ conn);
+ /* increased in send tasklet smc_cdc_tx_handler() */
+ smp_mb__before_atomic();
+ atomic_sub(copylen, &conn->sndbuf_space);
+ /* guarantee 0 <= sndbuf_space <= sndbuf_size */
+ smp_mb__after_atomic();
+ /* since we just produced more new data into sndbuf,
+ * trigger sndbuf consumer: RDMA write into peer RMBE and CDC
+ */
+ 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 RDMA write */
+static int smc_tx_rdma_write(struct smc_connection *conn, int peer_rmbe_offset,
+ int num_sges, struct ib_sge sges[])
+{
+ struct smc_link_group *lgr = conn->lgr;
+ struct ib_send_wr *failed_wr = NULL;
+ struct ib_rdma_wr rdma_wr;
+ struct smc_link *link;
+ int rc;
+
+ memset(&rdma_wr, 0, sizeof(rdma_wr));
+ link = &lgr->lnk[SMC_SINGLE_LINK];
+ rdma_wr.wr.wr_id = smc_wr_tx_get_next_wr_id(link);
+ rdma_wr.wr.sg_list = sges;
+ rdma_wr.wr.num_sge = num_sges;
+ rdma_wr.wr.opcode = IB_WR_RDMA_WRITE;
+ rdma_wr.remote_addr =
+ lgr->rtokens[conn->rtoken_idx][SMC_SINGLE_LINK].dma_addr +
+ /* RMBE within RMB */
+ ((conn->peer_conn_idx - 1) * conn->peer_rmbe_len) +
+ /* offset within RMBE */
+ peer_rmbe_offset;
+ rdma_wr.rkey = lgr->rtokens[conn->rtoken_idx][SMC_SINGLE_LINK].rkey;
+ rc = ib_post_send(link->roce_qp, &rdma_wr.wr, &failed_wr);
+ if (rc)
+ conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
+ 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_len, 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_len */
+ smp_mb__after_atomic();
+ smc_curs_add(conn->sndbuf_size, sent, len);
+}
+
+/* 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)
+{
+ size_t src_off, src_len, dst_off, dst_len; /* current chunk values */
+ size_t len, dst_len_sum, src_len_sum, dstchunk, srcchunk;
+ union smc_host_cursor sent, prep, prod, cons;
+ struct ib_sge sges[SMC_IB_MAX_SEND_SGE];
+ struct smc_link_group *lgr = conn->lgr;
+ int to_send, rmbespace;
+ struct smc_link *link;
+ int num_sges;
+ int rc;
+
+ /* source: sndbuf */
+ smc_curs_write(&sent, smc_curs_read(&conn->tx_curs_sent, conn), conn);
+ smc_curs_write(&prep, smc_curs_read(&conn->tx_curs_prep, conn), conn);
+ /* cf. wmem_alloc - (snd_max - snd_una) */
+ to_send = smc_curs_diff(conn->sndbuf_size, &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_write(&prod,
+ smc_curs_read(&conn->local_tx_ctrl.prod, conn),
+ conn);
+ smc_curs_write(&cons,
+ smc_curs_read(&conn->local_rx_ctrl.cons, conn),
+ conn);
+
+ /* if usable snd_wnd closes ask peer to advertise once it opens again */
+ conn->local_tx_ctrl.prod_flags.write_blocked = (to_send >= rmbespace);
+ /* cf. usable snd_wnd */
+ len = min(to_send, rmbespace);
+
+ /* initialize variables for first iteration of subsequent nested loop */
+ link = &lgr->lnk[SMC_SINGLE_LINK];
+ 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_len - 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_sum = dst_len;
+ src_off = sent.count;
+ /* dst_len determines the maximum src_len */
+ if (sent.count + dst_len <= conn->sndbuf_size) {
+ /* 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_size - sent.count;
+ }
+ src_len_sum = src_len;
+ for (dstchunk = 0; dstchunk < 2; dstchunk++) {
+ num_sges = 0;
+ for (srcchunk = 0; srcchunk < 2; srcchunk++) {
+ sges[srcchunk].addr =
+ conn->sndbuf_desc->dma_addr[SMC_SINGLE_LINK] +
+ src_off;
+ sges[srcchunk].length = src_len;
+ sges[srcchunk].lkey = link->mr_tx->lkey;
+ num_sges++;
+ src_off += src_len;
+ if (src_off >= conn->sndbuf_size)
+ src_off -= conn->sndbuf_size;
+ /* 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, sges);
+ 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_size - sent.count);
+ src_len_sum = src_len;
+ }
+
+ smc_tx_advance_cursors(conn, &prod, &sent, len);
+ /* update connection's cursors with advanced local cursors */
+ smc_curs_write(&conn->local_tx_ctrl.prod,
+ smc_curs_read(&prod, conn),
+ conn);
+ /* dst: peer RMBE */
+ smc_curs_write(&conn->tx_curs_sent,
+ smc_curs_read(&sent, conn),
+ 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
+ */
+int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
+{
+ struct smc_cdc_tx_pend *pend;
+ struct smc_wr_buf *wr_buf;
+ int rc;
+
+ spin_lock_bh(&conn->send_lock);
+ rc = smc_cdc_get_free_slot(&conn->lgr->lnk[SMC_SINGLE_LINK], &wr_buf,
+ &pend);
+ if (rc < 0) {
+ if (rc == -EBUSY) {
+ rc = 0;
+ schedule_work(&conn->tx_work);
+ }
+ goto out_unlock;
+ }
+
+ rc = smc_tx_rdma_writes(conn);
+ if (rc) {
+ smc_wr_tx_put_slot(&conn->lgr->lnk[SMC_SINGLE_LINK],
+ (struct smc_wr_tx_pend_priv *)pend);
+ goto out_unlock;
+ }
+
+ rc = smc_cdc_msg_send(conn, wr_buf, pend);
+
+out_unlock:
+ spin_unlock_bh(&conn->send_lock);
+ return rc;
+}
+
+/* Wakeup sndbuf consumers from process context
+ * since there is more data to transmit
+ */
+static void smc_tx_work(struct work_struct *work)
+{
+ struct smc_connection *conn = container_of(work,
+ struct smc_connection,
+ tx_work);
+ struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
+
+ lock_sock(&smc->sk);
+ smc_tx_sndbuf_nonempty(conn);
+ release_sock(&smc->sk);
+}
+
+/***************************** 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;
+ INIT_WORK(&smc->conn.tx_work, smc_tx_work);
+ spin_lock_init(&smc->conn.send_lock);
+}
diff --git a/net/smc/smc_tx.h b/net/smc/smc_tx.h
new file mode 100644
index 0000000..27db7b2
--- /dev/null
+++ b/net/smc/smc_tx.h
@@ -0,0 +1,34 @@
+/*
+ * Shared Memory Communications over RDMA (SMC-R) and RoCE
+ *
+ * Manage send buffer
+ *
+ * Copyright IBM Corp. 2016
+ *
+ * Author(s): Ursula Braun <ubraun@linux.vnet.ibm.com>
+ */
+
+#ifndef SMC_TX_H
+#define SMC_TX_H
+
+#include <linux/socket.h>
+#include <linux/types.h>
+
+#include "smc.h"
+#include "smc_cdc.h"
+
+static inline int smc_tx_prepared_sends(struct smc_connection *conn)
+{
+ union smc_host_cursor sent, prep;
+
+ smc_curs_write(&sent, smc_curs_read(&conn->tx_curs_sent, conn), conn);
+ smc_curs_write(&prep, smc_curs_read(&conn->tx_curs_prep, conn), conn);
+ return smc_curs_diff(conn->sndbuf_size, &sent, &prep);
+}
+
+void smc_tx_init(struct smc_sock *);
+int smc_tx_sendmsg(struct smc_sock *, struct msghdr *, size_t);
+int smc_tx_sndbuf_nonempty(struct smc_connection *);
+void smc_tx_sndbuf_nonfull(struct smc_sock *);
+
+#endif /* SMC_TX_H */
--
2.8.4