LXR linux/net/smc/smc

   1/*
   2 * Shared Memory Communications over RDMA (SMC-R) and RoCE
   3 *
   4 * Manage send buffer.
   5 * Producer:
   6 * Copy user space data into send buffer, if send buffer space available.
   7 * Consumer:
   8 * Trigger RDMA write into RMBE of peer and send CDC, if RMBE space available.
   9 *
  10 * Copyright IBM Corp. 2016
  11 *
  12 * Author(s):  Ursula Braun <ubraun@linux.vnet.ibm.com>
  13 */
  14
  15#include <linux/net.h>
  16#include <linux/rcupdate.h>
  17#include <linux/workqueue.h>
  18#include <linux/sched/signal.h>
  19
  20#include <net/sock.h>
  21
  22#include "smc.h"
  23#include "smc_wr.h"
  24#include "smc_cdc.h"
  25#include "smc_tx.h"
  26
  27/***************************** sndbuf producer *******************************/
  28
  29/* callback implementation for sk.sk_write_space()
  30 * to wakeup sndbuf producers that blocked with smc_tx_wait_memory().
  31 * called under sk_socket lock.
  32 */
  33static void smc_tx_write_space(struct sock *sk)
  34{
  35        struct socket *sock = sk->sk_socket;
  36        struct smc_sock *smc = smc_sk(sk);
  37        struct socket_wq *wq;
  38
  39        /* similar to sk_stream_write_space */
  40        if (atomic_read(&smc->conn.sndbuf_space) && sock) {
  41                clear_bit(SOCK_NOSPACE, &sock->flags);
  42                rcu_read_lock();
  43                wq = rcu_dereference(sk->sk_wq);
  44                if (skwq_has_sleeper(wq))
  45                        wake_up_interruptible_poll(&wq->wait,
  46                                                   POLLOUT | POLLWRNORM |
  47                                                   POLLWRBAND);
  48                if (wq && wq->fasync_list && !(sk->sk_shutdown & SEND_SHUTDOWN))
  49                        sock_wake_async(wq, SOCK_WAKE_SPACE, POLL_OUT);
  50                rcu_read_unlock();
  51        }
  52}
  53
  54/* Wakeup sndbuf producers that blocked with smc_tx_wait_memory().
  55 * Cf. tcp_data_snd_check()=>tcp_check_space()=>tcp_new_space().
  56 */
  57void smc_tx_sndbuf_nonfull(struct smc_sock *smc)
  58{
  59        if (smc->sk.sk_socket &&
  60            test_bit(SOCK_NOSPACE, &smc->sk.sk_socket->flags))
  61                smc->sk.sk_write_space(&smc->sk);
  62}
  63
  64/* blocks sndbuf producer until at least one byte of free space available */
  65static int smc_tx_wait_memory(struct smc_sock *smc, int flags)
  66{
  67        DEFINE_WAIT_FUNC(wait, woken_wake_function);
  68        struct smc_connection *conn = &smc->conn;
  69        struct sock *sk = &smc->sk;
  70        bool noblock;
  71        long timeo;
  72        int rc = 0;
  73
  74        /* similar to sk_stream_wait_memory */
  75        timeo = sock_sndtimeo(sk, flags & MSG_DONTWAIT);
  76        noblock = timeo ? false : true;
  77        add_wait_queue(sk_sleep(sk), &wait);
  78        while (1) {
  79                sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
  80                if (sk->sk_err ||
  81                    (sk->sk_shutdown & SEND_SHUTDOWN) ||
  82                    conn->local_tx_ctrl.conn_state_flags.peer_done_writing) {
  83                        rc = -EPIPE;
  84                        break;
  85                }
  86                if (conn->local_rx_ctrl.conn_state_flags.peer_conn_abort) {
  87                        rc = -ECONNRESET;
  88                        break;
  89                }
  90                if (!timeo) {
  91                        if (noblock)
  92                                set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
  93                        rc = -EAGAIN;
  94                        break;
  95                }
  96                if (signal_pending(current)) {
  97                        rc = sock_intr_errno(timeo);
  98                        break;
  99                }
 100                sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 101                if (atomic_read(&conn->sndbuf_space))
 102                        break; /* at least 1 byte of free space available */
 103                set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
 104                sk->sk_write_pending++;
 105                sk_wait_event(sk, &timeo,
 106                              sk->sk_err ||
 107                              (sk->sk_shutdown & SEND_SHUTDOWN) ||
 108                              smc_cdc_rxed_any_close_or_senddone(conn) ||
 109                              atomic_read(&conn->sndbuf_space),
 110                              &wait);
 111                sk->sk_write_pending--;
 112        }
 113        remove_wait_queue(sk_sleep(sk), &wait);
 114        return rc;
 115}
 116
 117/* sndbuf producer: main API called by socket layer.
 118 * called under sock lock.
 119 */
 120int smc_tx_sendmsg(struct smc_sock *smc, struct msghdr *msg, size_t len)
 121{
 122        size_t copylen, send_done = 0, send_remaining = len;
 123        size_t chunk_len, chunk_off, chunk_len_sum;
 124        struct smc_connection *conn = &smc->conn;
 125        union smc_host_cursor prep;
 126        struct sock *sk = &smc->sk;
 127        char *sndbuf_base;
 128        int tx_cnt_prep;
 129        int writespace;
 130        int rc, chunk;
 131
 132        /* This should be in poll */
 133        sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk);
 134
 135        if (sk->sk_err || (sk->sk_shutdown & SEND_SHUTDOWN)) {
 136                rc = -EPIPE;
 137                goto out_err;
 138        }
 139
 140        while (msg_data_left(msg)) {
 141                if (sk->sk_state == SMC_INIT)
 142                        return -ENOTCONN;
 143                if (smc->sk.sk_shutdown & SEND_SHUTDOWN ||
 144                    (smc->sk.sk_err == ECONNABORTED) ||
 145                    conn->local_tx_ctrl.conn_state_flags.peer_conn_abort)
 146                        return -EPIPE;
 147                if (smc_cdc_rxed_any_close(conn))
 148                        return send_done ?: -ECONNRESET;
 149
 150                if (!atomic_read(&conn->sndbuf_space)) {
 151                        rc = smc_tx_wait_memory(smc, msg->msg_flags);
 152                        if (rc) {
 153                                if (send_done)
 154                                        return send_done;
 155                                goto out_err;
 156                        }
 157                        continue;
 158                }
 159
 160                /* initialize variables for 1st iteration of subsequent loop */
 161                /* could be just 1 byte, even after smc_tx_wait_memory above */
 162                writespace = atomic_read(&conn->sndbuf_space);
 163                /* not more than what user space asked for */
 164                copylen = min_t(size_t, send_remaining, writespace);
 165                /* determine start of sndbuf */
 166                sndbuf_base = conn->sndbuf_desc->cpu_addr;
 167                smc_curs_write(&prep,
 168                               smc_curs_read(&conn->tx_curs_prep, conn),
 169                               conn);
 170                tx_cnt_prep = prep.count;
 171                /* determine chunks where to write into sndbuf */
 172                /* either unwrapped case, or 1st chunk of wrapped case */
 173                chunk_len = min_t(size_t,
 174                                  copylen, conn->sndbuf_size - tx_cnt_prep);
 175                chunk_len_sum = chunk_len;
 176                chunk_off = tx_cnt_prep;
 177                for (chunk = 0; chunk < 2; chunk++) {
 178                        rc = memcpy_from_msg(sndbuf_base + chunk_off,
 179                                             msg, chunk_len);
 180                        if (rc) {
 181                                if (send_done)
 182                                        return send_done;
 183                                goto out_err;
 184                        }
 185                        send_done += chunk_len;
 186                        send_remaining -= chunk_len;
 187
 188                        if (chunk_len_sum == copylen)
 189                                break; /* either on 1st or 2nd iteration */
 190                        /* prepare next (== 2nd) iteration */
 191                        chunk_len = copylen - chunk_len; /* remainder */
 192                        chunk_len_sum += chunk_len;
 193                        chunk_off = 0; /* modulo offset in send ring buffer */
 194                }
 195                /* update cursors */
 196                smc_curs_add(conn->sndbuf_size, &prep, copylen);
 197                smc_curs_write(&conn->tx_curs_prep,
 198                               smc_curs_read(&prep, conn),
 199                               conn);
 200                /* increased in send tasklet smc_cdc_tx_handler() */
 201                smp_mb__before_atomic();
 202                atomic_sub(copylen, &conn->sndbuf_space);
 203                /* guarantee 0 <= sndbuf_space <= sndbuf_size */
 204                smp_mb__after_atomic();
 205                /* since we just produced more new data into sndbuf,
 206                 * trigger sndbuf consumer: RDMA write into peer RMBE and CDC
 207                 */
 208                smc_tx_sndbuf_nonempty(conn);
 209        } /* while (msg_data_left(msg)) */
 210
 211        return send_done;
 212
 213out_err:
 214        rc = sk_stream_error(sk, msg->msg_flags, rc);
 215        /* make sure we wake any epoll edge trigger waiter */
 216        if (unlikely(rc == -EAGAIN))
 217                sk->sk_write_space(sk);
 218        return rc;
 219}
 220
 221/***************************** sndbuf consumer *******************************/
 222
 223/* sndbuf consumer: actual data transfer of one target chunk with RDMA write */
 224static int smc_tx_rdma_write(struct smc_connection *conn, int peer_rmbe_offset,
 225                             int num_sges, struct ib_sge sges[])
 226{
 227        struct smc_link_group *lgr = conn->lgr;
 228        struct ib_send_wr *failed_wr = NULL;
 229        struct ib_rdma_wr rdma_wr;
 230        struct smc_link *link;
 231        int rc;
 232
 233        memset(&rdma_wr, 0, sizeof(rdma_wr));
 234        link = &lgr->lnk[SMC_SINGLE_LINK];
 235        rdma_wr.wr.wr_id = smc_wr_tx_get_next_wr_id(link);
 236        rdma_wr.wr.sg_list = sges;
 237        rdma_wr.wr.num_sge = num_sges;
 238        rdma_wr.wr.opcode = IB_WR_RDMA_WRITE;
 239        rdma_wr.remote_addr =
 240                lgr->rtokens[conn->rtoken_idx][SMC_SINGLE_LINK].dma_addr +
 241                /* RMBE within RMB */
 242                ((conn->peer_conn_idx - 1) * conn->peer_rmbe_size) +
 243                /* offset within RMBE */
 244                peer_rmbe_offset;
 245        rdma_wr.rkey = lgr->rtokens[conn->rtoken_idx][SMC_SINGLE_LINK].rkey;
 246        rc = ib_post_send(link->roce_qp, &rdma_wr.wr, &failed_wr);
 247        if (rc)
 248                conn->local_tx_ctrl.conn_state_flags.peer_conn_abort = 1;
 249        return rc;
 250}
 251
 252/* sndbuf consumer */
 253static inline void smc_tx_advance_cursors(struct smc_connection *conn,
 254                                          union smc_host_cursor *prod,
 255                                          union smc_host_cursor *sent,
 256                                          size_t len)
 257{
 258        smc_curs_add(conn->peer_rmbe_size, prod, len);
 259        /* increased in recv tasklet smc_cdc_msg_rcv() */
 260        smp_mb__before_atomic();
 261        /* data in flight reduces usable snd_wnd */
 262        atomic_sub(len, &conn->peer_rmbe_space);
 263        /* guarantee 0 <= peer_rmbe_space <= peer_rmbe_size */
 264        smp_mb__after_atomic();
 265        smc_curs_add(conn->sndbuf_size, sent, len);
 266}
 267
 268/* sndbuf consumer: prepare all necessary (src&dst) chunks of data transmit;
 269 * usable snd_wnd as max transmit
 270 */
 271static int smc_tx_rdma_writes(struct smc_connection *conn)
 272{
 273        size_t src_off, src_len, dst_off, dst_len; /* current chunk values */
 274        size_t len, dst_len_sum, src_len_sum, dstchunk, srcchunk;
 275        union smc_host_cursor sent, prep, prod, cons;
 276        struct ib_sge sges[SMC_IB_MAX_SEND_SGE];
 277        struct smc_link_group *lgr = conn->lgr;
 278        int to_send, rmbespace;
 279        struct smc_link *link;
 280        int num_sges;
 281        int rc;
 282
 283        /* source: sndbuf */
 284        smc_curs_write(&sent, smc_curs_read(&conn->tx_curs_sent, conn), conn);
 285        smc_curs_write(&prep, smc_curs_read(&conn->tx_curs_prep, conn), conn);
 286        /* cf. wmem_alloc - (snd_max - snd_una) */
 287        to_send = smc_curs_diff(conn->sndbuf_size, &sent, &prep);
 288        if (to_send <= 0)
 289                return 0;
 290
 291        /* destination: RMBE */
 292        /* cf. snd_wnd */
 293        rmbespace = atomic_read(&conn->peer_rmbe_space);
 294        if (rmbespace <= 0)
 295                return 0;
 296        smc_curs_write(&prod,
 297                       smc_curs_read(&conn->local_tx_ctrl.prod, conn),
 298                       conn);
 299        smc_curs_write(&cons,
 300                       smc_curs_read(&conn->local_rx_ctrl.cons, conn),
 301                       conn);
 302
 303        /* if usable snd_wnd closes ask peer to advertise once it opens again */
 304        conn->local_tx_ctrl.prod_flags.write_blocked = (to_send >= rmbespace);
 305        /* cf. usable snd_wnd */
 306        len = min(to_send, rmbespace);
 307
 308        /* initialize variables for first iteration of subsequent nested loop */
 309        link = &lgr->lnk[SMC_SINGLE_LINK];
 310        dst_off = prod.count;
 311        if (prod.wrap == cons.wrap) {
 312                /* the filled destination area is unwrapped,
 313                 * hence the available free destination space is wrapped
 314                 * and we need 2 destination chunks of sum len; start with 1st
 315                 * which is limited by what's available in sndbuf
 316                 */
 317                dst_len = min_t(size_t,
 318                                conn->peer_rmbe_size - prod.count, len);
 319        } else {
 320                /* the filled destination area is wrapped,
 321                 * hence the available free destination space is unwrapped
 322                 * and we need a single destination chunk of entire len
 323                 */
 324                dst_len = len;
 325        }
 326        dst_len_sum = dst_len;
 327        src_off = sent.count;
 328        /* dst_len determines the maximum src_len */
 329        if (sent.count + dst_len <= conn->sndbuf_size) {
 330                /* unwrapped src case: single chunk of entire dst_len */
 331                src_len = dst_len;
 332        } else {
 333                /* wrapped src case: 2 chunks of sum dst_len; start with 1st: */
 334                src_len = conn->sndbuf_size - sent.count;
 335        }
 336        src_len_sum = src_len;
 337        for (dstchunk = 0; dstchunk < 2; dstchunk++) {
 338                num_sges = 0;
 339                for (srcchunk = 0; srcchunk < 2; srcchunk++) {
 340                        sges[srcchunk].addr =
 341                                conn->sndbuf_desc->dma_addr[SMC_SINGLE_LINK] +
 342                                src_off;
 343                        sges[srcchunk].length = src_len;
 344                        sges[srcchunk].lkey = link->roce_pd->local_dma_lkey;
 345                        num_sges++;
 346                        src_off += src_len;
 347                        if (src_off >= conn->sndbuf_size)
 348                                src_off -= conn->sndbuf_size;
 349                                                /* modulo in send ring */
 350                        if (src_len_sum == dst_len)
 351                                break; /* either on 1st or 2nd iteration */
 352                        /* prepare next (== 2nd) iteration */
 353                        src_len = dst_len - src_len; /* remainder */
 354                        src_len_sum += src_len;
 355                }
 356                rc = smc_tx_rdma_write(conn, dst_off, num_sges, sges);
 357                if (rc)
 358                        return rc;
 359                if (dst_len_sum == len)
 360                        break; /* either on 1st or 2nd iteration */
 361                /* prepare next (== 2nd) iteration */
 362                dst_off = 0; /* modulo offset in RMBE ring buffer */
 363                dst_len = len - dst_len; /* remainder */
 364                dst_len_sum += dst_len;
 365                src_len = min_t(int,
 366                                dst_len, conn->sndbuf_size - sent.count);
 367                src_len_sum = src_len;
 368        }
 369
 370        smc_tx_advance_cursors(conn, &prod, &sent, len);
 371        /* update connection's cursors with advanced local cursors */
 372        smc_curs_write(&conn->local_tx_ctrl.prod,
 373                       smc_curs_read(&prod, conn),
 374                       conn);
 375                                                        /* dst: peer RMBE */
 376        smc_curs_write(&conn->tx_curs_sent,
 377                       smc_curs_read(&sent, conn),
 378                       conn);
 379                                                        /* src: local sndbuf */
 380
 381        return 0;
 382}
 383
 384/* Wakeup sndbuf consumers from any context (IRQ or process)
 385 * since there is more data to transmit; usable snd_wnd as max transmit
 386 */
 387int smc_tx_sndbuf_nonempty(struct smc_connection *conn)
 388{
 389        struct smc_cdc_tx_pend *pend;
 390        struct smc_wr_buf *wr_buf;
 391        int rc;
 392
 393        spin_lock_bh(&conn->send_lock);
 394        rc = smc_cdc_get_free_slot(&conn->lgr->lnk[SMC_SINGLE_LINK], &wr_buf,
 395                                   &pend);
 396        if (rc < 0) {
 397                if (rc == -EBUSY) {
 398                        struct smc_sock *smc =
 399                                container_of(conn, struct smc_sock, conn);
 400
 401                        if (smc->sk.sk_err == ECONNABORTED) {
 402                                rc = sock_error(&smc->sk);
 403                                goto out_unlock;
 404                        }
 405                        rc = 0;
 406                        schedule_work(&conn->tx_work);
 407                }
 408                goto out_unlock;
 409        }
 410
 411        rc = smc_tx_rdma_writes(conn);
 412        if (rc) {
 413                smc_wr_tx_put_slot(&conn->lgr->lnk[SMC_SINGLE_LINK],
 414                                   (struct smc_wr_tx_pend_priv *)pend);
 415                goto out_unlock;
 416        }
 417
 418        rc = smc_cdc_msg_send(conn, wr_buf, pend);
 419
 420out_unlock:
 421        spin_unlock_bh(&conn->send_lock);
 422        return rc;
 423}
 424
 425/* Wakeup sndbuf consumers from process context
 426 * since there is more data to transmit
 427 */
 428static void smc_tx_work(struct work_struct *work)
 429{
 430        struct smc_connection *conn = container_of(work,
 431                                                   struct smc_connection,
 432                                                   tx_work);
 433        struct smc_sock *smc = container_of(conn, struct smc_sock, conn);
 434        int rc;
 435
 436        lock_sock(&smc->sk);
 437        rc = smc_tx_sndbuf_nonempty(conn);
 438        if (!rc && conn->local_rx_ctrl.prod_flags.write_blocked &&
 439            !atomic_read(&conn->bytes_to_rcv))
 440                conn->local_rx_ctrl.prod_flags.write_blocked = 0;
 441        release_sock(&smc->sk);
 442}
 443
 444void smc_tx_consumer_update(struct smc_connection *conn)
 445{
 446        union smc_host_cursor cfed, cons;
 447        struct smc_cdc_tx_pend *pend;
 448        struct smc_wr_buf *wr_buf;
 449        int to_confirm, rc;
 450
 451        smc_curs_write(&cons,
 452                       smc_curs_read(&conn->local_tx_ctrl.cons, conn),
 453                       conn);
 454        smc_curs_write(&cfed,
 455                       smc_curs_read(&conn->rx_curs_confirmed, conn),
 456                       conn);
 457        to_confirm = smc_curs_diff(conn->rmbe_size, &cfed, &cons);
 458
 459        if (conn->local_rx_ctrl.prod_flags.cons_curs_upd_req ||
 460            ((to_confirm > conn->rmbe_update_limit) &&
 461             ((to_confirm > (conn->rmbe_size / 2)) ||
 462              conn->local_rx_ctrl.prod_flags.write_blocked))) {
 463                rc = smc_cdc_get_free_slot(&conn->lgr->lnk[SMC_SINGLE_LINK],
 464                                           &wr_buf, &pend);
 465                if (!rc)
 466                        rc = smc_cdc_msg_send(conn, wr_buf, pend);
 467                if (rc < 0) {
 468                        schedule_work(&conn->tx_work);
 469                        return;
 470                }
 471                smc_curs_write(&conn->rx_curs_confirmed,
 472                               smc_curs_read(&conn->local_tx_ctrl.cons, conn),
 473                               conn);
 474                conn->local_rx_ctrl.prod_flags.cons_curs_upd_req = 0;
 475        }
 476        if (conn->local_rx_ctrl.prod_flags.write_blocked &&
 477            !atomic_read(&conn->bytes_to_rcv))
 478                conn->local_rx_ctrl.prod_flags.write_blocked = 0;
 479}
 480
 481/***************************** send initialize *******************************/
 482
 483/* Initialize send properties on connection establishment. NB: not __init! */
 484void smc_tx_init(struct smc_sock *smc)
 485{
 486        smc->sk.sk_write_space = smc_tx_write_space;
 487        INIT_WORK(&smc->conn.tx_work, smc_tx_work);
 488        spin_lock_init(&smc->conn.send_lock);
 489}
 490