linux/net/smc/smc_tx.c
Ursula Braun 6b5771aa3c smc: no consumer update in tasklet context
The SMC protocol requires to send a separate consumer cursor update,
if it cannot be piggybacked to updates of the producer cursor.
When receiving a blocked signal from the sender, this update is sent
already in tasklet context. In addition consumer cursor updates are
sent after data receival.
Sending of cursor updates is controlled by sequence numbers.
Assuming receiving stray messages the receiver drops updates with older
sequence numbers than an already received cursor update with a higher
sequence number.
Sending consumer cursor updates in tasklet context may result in
wrong order sends and its corresponding drops at the receiver. Since
it is sufficient to send consumer cursor updates once the data is
received, this patch gets rid of the consumer cursor update in tasklet
context to guarantee in-sequence arrival of cursor updates.

Signed-off-by: Ursula Braun <ubraun@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-12-07 15:03:12 -05:00

489 lines
14 KiB
C

// 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 "smc.h"
#include "smc_wr.h"
#include "smc_cdc.h"
#include "smc_tx.h"
#define SMC_TX_WORK_DELAY HZ
/***************************** 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)
{
DEFINE_WAIT_FUNC(wait, woken_wake_function);
struct smc_connection *conn = &smc->conn;
struct sock *sk = &smc->sk;
bool noblock;
long timeo;
int rc = 0;
/* similar to sk_stream_wait_memory */
timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
noblock = timeo ? false : true;
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->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_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),
&wait);
}
remove_wait_queue(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 ||
(smc->sk.sk_err == ECONNABORTED) ||
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;
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_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_size) +
/* 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_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_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;
dma_addr_t dma_addr;
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_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_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;
dma_addr = sg_dma_address(conn->sndbuf_desc->sgt[SMC_SINGLE_LINK].sgl);
for (dstchunk = 0; dstchunk < 2; dstchunk++) {
num_sges = 0;
for (srcchunk = 0; srcchunk < 2; srcchunk++) {
sges[srcchunk].addr = dma_addr + src_off;
sges[srcchunk].length = src_len;
sges[srcchunk].lkey = link->roce_pd->local_dma_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, &wr_buf, &pend);
if (rc < 0) {
if (rc == -EBUSY) {
struct smc_sock *smc =
container_of(conn, struct smc_sock, conn);
if (smc->sk.sk_err == ECONNABORTED) {
rc = sock_error(&smc->sk);
goto out_unlock;
}
rc = 0;
schedule_delayed_work(&conn->tx_work,
SMC_TX_WORK_DELAY);
}
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(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);
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;
release_sock(&smc->sk);
}
void smc_tx_consumer_update(struct smc_connection *conn)
{
union smc_host_cursor cfed, cons;
int to_confirm;
smc_curs_write(&cons,
smc_curs_read(&conn->local_tx_ctrl.cons, conn),
conn);
smc_curs_write(&cfed,
smc_curs_read(&conn->rx_curs_confirmed, conn),
conn);
to_confirm = smc_curs_diff(conn->rmbe_size, &cfed, &cons);
if (conn->local_rx_ctrl.prod_flags.cons_curs_upd_req ||
((to_confirm > conn->rmbe_update_limit) &&
((to_confirm > (conn->rmbe_size / 2)) ||
conn->local_rx_ctrl.prod_flags.write_blocked))) {
if (smc_cdc_get_slot_and_msg_send(conn) < 0) {
schedule_delayed_work(&conn->tx_work,
SMC_TX_WORK_DELAY);
return;
}
smc_curs_write(&conn->rx_curs_confirmed,
smc_curs_read(&conn->local_tx_ctrl.cons, conn),
conn);
conn->local_rx_ctrl.prod_flags.cons_curs_upd_req = 0;
}
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;
INIT_DELAYED_WORK(&smc->conn.tx_work, smc_tx_work);
spin_lock_init(&smc->conn.send_lock);
}