linux/net/rds/ib_recv.c
<<
>>
Prefs
   1/*
   2 * Copyright (c) 2006 Oracle.  All rights reserved.
   3 *
   4 * This software is available to you under a choice of one of two
   5 * licenses.  You may choose to be licensed under the terms of the GNU
   6 * General Public License (GPL) Version 2, available from the file
   7 * COPYING in the main directory of this source tree, or the
   8 * OpenIB.org BSD license below:
   9 *
  10 *     Redistribution and use in source and binary forms, with or
  11 *     without modification, are permitted provided that the following
  12 *     conditions are met:
  13 *
  14 *      - Redistributions of source code must retain the above
  15 *        copyright notice, this list of conditions and the following
  16 *        disclaimer.
  17 *
  18 *      - Redistributions in binary form must reproduce the above
  19 *        copyright notice, this list of conditions and the following
  20 *        disclaimer in the documentation and/or other materials
  21 *        provided with the distribution.
  22 *
  23 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  27 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  28 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  29 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  30 * SOFTWARE.
  31 *
  32 */
  33#include <linux/kernel.h>
  34#include <linux/slab.h>
  35#include <linux/pci.h>
  36#include <linux/dma-mapping.h>
  37#include <rdma/rdma_cm.h>
  38
  39#include "rds.h"
  40#include "ib.h"
  41
  42static struct kmem_cache *rds_ib_incoming_slab;
  43static struct kmem_cache *rds_ib_frag_slab;
  44static atomic_t rds_ib_allocation = ATOMIC_INIT(0);
  45
  46void rds_ib_recv_init_ring(struct rds_ib_connection *ic)
  47{
  48        struct rds_ib_recv_work *recv;
  49        u32 i;
  50
  51        for (i = 0, recv = ic->i_recvs; i < ic->i_recv_ring.w_nr; i++, recv++) {
  52                struct ib_sge *sge;
  53
  54                recv->r_ibinc = NULL;
  55                recv->r_frag = NULL;
  56
  57                recv->r_wr.next = NULL;
  58                recv->r_wr.wr_id = i;
  59                recv->r_wr.sg_list = recv->r_sge;
  60                recv->r_wr.num_sge = RDS_IB_RECV_SGE;
  61
  62                sge = &recv->r_sge[0];
  63                sge->addr = ic->i_recv_hdrs_dma + (i * sizeof(struct rds_header));
  64                sge->length = sizeof(struct rds_header);
  65                sge->lkey = ic->i_mr->lkey;
  66
  67                sge = &recv->r_sge[1];
  68                sge->addr = 0;
  69                sge->length = RDS_FRAG_SIZE;
  70                sge->lkey = ic->i_mr->lkey;
  71        }
  72}
  73
  74/*
  75 * The entire 'from' list, including the from element itself, is put on
  76 * to the tail of the 'to' list.
  77 */
  78static void list_splice_entire_tail(struct list_head *from,
  79                                    struct list_head *to)
  80{
  81        struct list_head *from_last = from->prev;
  82
  83        list_splice_tail(from_last, to);
  84        list_add_tail(from_last, to);
  85}
  86
  87static void rds_ib_cache_xfer_to_ready(struct rds_ib_refill_cache *cache)
  88{
  89        struct list_head *tmp;
  90
  91        tmp = xchg(&cache->xfer, NULL);
  92        if (tmp) {
  93                if (cache->ready)
  94                        list_splice_entire_tail(tmp, cache->ready);
  95                else
  96                        cache->ready = tmp;
  97        }
  98}
  99
 100static int rds_ib_recv_alloc_cache(struct rds_ib_refill_cache *cache)
 101{
 102        struct rds_ib_cache_head *head;
 103        int cpu;
 104
 105        cache->percpu = alloc_percpu(struct rds_ib_cache_head);
 106        if (!cache->percpu)
 107               return -ENOMEM;
 108
 109        for_each_possible_cpu(cpu) {
 110                head = per_cpu_ptr(cache->percpu, cpu);
 111                head->first = NULL;
 112                head->count = 0;
 113        }
 114        cache->xfer = NULL;
 115        cache->ready = NULL;
 116
 117        return 0;
 118}
 119
 120int rds_ib_recv_alloc_caches(struct rds_ib_connection *ic)
 121{
 122        int ret;
 123
 124        ret = rds_ib_recv_alloc_cache(&ic->i_cache_incs);
 125        if (!ret) {
 126                ret = rds_ib_recv_alloc_cache(&ic->i_cache_frags);
 127                if (ret)
 128                        free_percpu(ic->i_cache_incs.percpu);
 129        }
 130
 131        return ret;
 132}
 133
 134static void rds_ib_cache_splice_all_lists(struct rds_ib_refill_cache *cache,
 135                                          struct list_head *caller_list)
 136{
 137        struct rds_ib_cache_head *head;
 138        int cpu;
 139
 140        for_each_possible_cpu(cpu) {
 141                head = per_cpu_ptr(cache->percpu, cpu);
 142                if (head->first) {
 143                        list_splice_entire_tail(head->first, caller_list);
 144                        head->first = NULL;
 145                }
 146        }
 147
 148        if (cache->ready) {
 149                list_splice_entire_tail(cache->ready, caller_list);
 150                cache->ready = NULL;
 151        }
 152}
 153
 154void rds_ib_recv_free_caches(struct rds_ib_connection *ic)
 155{
 156        struct rds_ib_incoming *inc;
 157        struct rds_ib_incoming *inc_tmp;
 158        struct rds_page_frag *frag;
 159        struct rds_page_frag *frag_tmp;
 160        LIST_HEAD(list);
 161
 162        rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
 163        rds_ib_cache_splice_all_lists(&ic->i_cache_incs, &list);
 164        free_percpu(ic->i_cache_incs.percpu);
 165
 166        list_for_each_entry_safe(inc, inc_tmp, &list, ii_cache_entry) {
 167                list_del(&inc->ii_cache_entry);
 168                WARN_ON(!list_empty(&inc->ii_frags));
 169                kmem_cache_free(rds_ib_incoming_slab, inc);
 170        }
 171
 172        rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
 173        rds_ib_cache_splice_all_lists(&ic->i_cache_frags, &list);
 174        free_percpu(ic->i_cache_frags.percpu);
 175
 176        list_for_each_entry_safe(frag, frag_tmp, &list, f_cache_entry) {
 177                list_del(&frag->f_cache_entry);
 178                WARN_ON(!list_empty(&frag->f_item));
 179                kmem_cache_free(rds_ib_frag_slab, frag);
 180        }
 181}
 182
 183/* fwd decl */
 184static void rds_ib_recv_cache_put(struct list_head *new_item,
 185                                  struct rds_ib_refill_cache *cache);
 186static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache);
 187
 188
 189/* Recycle frag and attached recv buffer f_sg */
 190static void rds_ib_frag_free(struct rds_ib_connection *ic,
 191                             struct rds_page_frag *frag)
 192{
 193        rdsdebug("frag %p page %p\n", frag, sg_page(&frag->f_sg));
 194
 195        rds_ib_recv_cache_put(&frag->f_cache_entry, &ic->i_cache_frags);
 196}
 197
 198/* Recycle inc after freeing attached frags */
 199void rds_ib_inc_free(struct rds_incoming *inc)
 200{
 201        struct rds_ib_incoming *ibinc;
 202        struct rds_page_frag *frag;
 203        struct rds_page_frag *pos;
 204        struct rds_ib_connection *ic = inc->i_conn->c_transport_data;
 205
 206        ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
 207
 208        /* Free attached frags */
 209        list_for_each_entry_safe(frag, pos, &ibinc->ii_frags, f_item) {
 210                list_del_init(&frag->f_item);
 211                rds_ib_frag_free(ic, frag);
 212        }
 213        BUG_ON(!list_empty(&ibinc->ii_frags));
 214
 215        rdsdebug("freeing ibinc %p inc %p\n", ibinc, inc);
 216        rds_ib_recv_cache_put(&ibinc->ii_cache_entry, &ic->i_cache_incs);
 217}
 218
 219static void rds_ib_recv_clear_one(struct rds_ib_connection *ic,
 220                                  struct rds_ib_recv_work *recv)
 221{
 222        if (recv->r_ibinc) {
 223                rds_inc_put(&recv->r_ibinc->ii_inc);
 224                recv->r_ibinc = NULL;
 225        }
 226        if (recv->r_frag) {
 227                ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
 228                rds_ib_frag_free(ic, recv->r_frag);
 229                recv->r_frag = NULL;
 230        }
 231}
 232
 233void rds_ib_recv_clear_ring(struct rds_ib_connection *ic)
 234{
 235        u32 i;
 236
 237        for (i = 0; i < ic->i_recv_ring.w_nr; i++)
 238                rds_ib_recv_clear_one(ic, &ic->i_recvs[i]);
 239}
 240
 241static struct rds_ib_incoming *rds_ib_refill_one_inc(struct rds_ib_connection *ic,
 242                                                     gfp_t slab_mask)
 243{
 244        struct rds_ib_incoming *ibinc;
 245        struct list_head *cache_item;
 246        int avail_allocs;
 247
 248        cache_item = rds_ib_recv_cache_get(&ic->i_cache_incs);
 249        if (cache_item) {
 250                ibinc = container_of(cache_item, struct rds_ib_incoming, ii_cache_entry);
 251        } else {
 252                avail_allocs = atomic_add_unless(&rds_ib_allocation,
 253                                                 1, rds_ib_sysctl_max_recv_allocation);
 254                if (!avail_allocs) {
 255                        rds_ib_stats_inc(s_ib_rx_alloc_limit);
 256                        return NULL;
 257                }
 258                ibinc = kmem_cache_alloc(rds_ib_incoming_slab, slab_mask);
 259                if (!ibinc) {
 260                        atomic_dec(&rds_ib_allocation);
 261                        return NULL;
 262                }
 263        }
 264        INIT_LIST_HEAD(&ibinc->ii_frags);
 265        rds_inc_init(&ibinc->ii_inc, ic->conn, ic->conn->c_faddr);
 266
 267        return ibinc;
 268}
 269
 270static struct rds_page_frag *rds_ib_refill_one_frag(struct rds_ib_connection *ic,
 271                                                    gfp_t slab_mask, gfp_t page_mask)
 272{
 273        struct rds_page_frag *frag;
 274        struct list_head *cache_item;
 275        int ret;
 276
 277        cache_item = rds_ib_recv_cache_get(&ic->i_cache_frags);
 278        if (cache_item) {
 279                frag = container_of(cache_item, struct rds_page_frag, f_cache_entry);
 280        } else {
 281                frag = kmem_cache_alloc(rds_ib_frag_slab, slab_mask);
 282                if (!frag)
 283                        return NULL;
 284
 285                sg_init_table(&frag->f_sg, 1);
 286                ret = rds_page_remainder_alloc(&frag->f_sg,
 287                                               RDS_FRAG_SIZE, page_mask);
 288                if (ret) {
 289                        kmem_cache_free(rds_ib_frag_slab, frag);
 290                        return NULL;
 291                }
 292        }
 293
 294        INIT_LIST_HEAD(&frag->f_item);
 295
 296        return frag;
 297}
 298
 299static int rds_ib_recv_refill_one(struct rds_connection *conn,
 300                                  struct rds_ib_recv_work *recv, int prefill)
 301{
 302        struct rds_ib_connection *ic = conn->c_transport_data;
 303        struct ib_sge *sge;
 304        int ret = -ENOMEM;
 305        gfp_t slab_mask = GFP_NOWAIT;
 306        gfp_t page_mask = GFP_NOWAIT;
 307
 308        if (prefill) {
 309                slab_mask = GFP_KERNEL;
 310                page_mask = GFP_HIGHUSER;
 311        }
 312
 313        if (!ic->i_cache_incs.ready)
 314                rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
 315        if (!ic->i_cache_frags.ready)
 316                rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
 317
 318        /*
 319         * ibinc was taken from recv if recv contained the start of a message.
 320         * recvs that were continuations will still have this allocated.
 321         */
 322        if (!recv->r_ibinc) {
 323                recv->r_ibinc = rds_ib_refill_one_inc(ic, slab_mask);
 324                if (!recv->r_ibinc)
 325                        goto out;
 326        }
 327
 328        WARN_ON(recv->r_frag); /* leak! */
 329        recv->r_frag = rds_ib_refill_one_frag(ic, slab_mask, page_mask);
 330        if (!recv->r_frag)
 331                goto out;
 332
 333        ret = ib_dma_map_sg(ic->i_cm_id->device, &recv->r_frag->f_sg,
 334                            1, DMA_FROM_DEVICE);
 335        WARN_ON(ret != 1);
 336
 337        sge = &recv->r_sge[0];
 338        sge->addr = ic->i_recv_hdrs_dma + (recv - ic->i_recvs) * sizeof(struct rds_header);
 339        sge->length = sizeof(struct rds_header);
 340
 341        sge = &recv->r_sge[1];
 342        sge->addr = sg_dma_address(&recv->r_frag->f_sg);
 343        sge->length = sg_dma_len(&recv->r_frag->f_sg);
 344
 345        ret = 0;
 346out:
 347        return ret;
 348}
 349
 350/*
 351 * This tries to allocate and post unused work requests after making sure that
 352 * they have all the allocations they need to queue received fragments into
 353 * sockets.
 354 *
 355 * -1 is returned if posting fails due to temporary resource exhaustion.
 356 */
 357void rds_ib_recv_refill(struct rds_connection *conn, int prefill)
 358{
 359        struct rds_ib_connection *ic = conn->c_transport_data;
 360        struct rds_ib_recv_work *recv;
 361        struct ib_recv_wr *failed_wr;
 362        unsigned int posted = 0;
 363        int ret = 0;
 364        u32 pos;
 365
 366        while ((prefill || rds_conn_up(conn)) &&
 367               rds_ib_ring_alloc(&ic->i_recv_ring, 1, &pos)) {
 368                if (pos >= ic->i_recv_ring.w_nr) {
 369                        printk(KERN_NOTICE "Argh - ring alloc returned pos=%u\n",
 370                                        pos);
 371                        break;
 372                }
 373
 374                recv = &ic->i_recvs[pos];
 375                ret = rds_ib_recv_refill_one(conn, recv, prefill);
 376                if (ret) {
 377                        break;
 378                }
 379
 380                /* XXX when can this fail? */
 381                ret = ib_post_recv(ic->i_cm_id->qp, &recv->r_wr, &failed_wr);
 382                rdsdebug("recv %p ibinc %p page %p addr %lu ret %d\n", recv,
 383                         recv->r_ibinc, sg_page(&recv->r_frag->f_sg),
 384                         (long) sg_dma_address(&recv->r_frag->f_sg), ret);
 385                if (ret) {
 386                        rds_ib_conn_error(conn, "recv post on "
 387                               "%pI4 returned %d, disconnecting and "
 388                               "reconnecting\n", &conn->c_faddr,
 389                               ret);
 390                        break;
 391                }
 392
 393                posted++;
 394        }
 395
 396        /* We're doing flow control - update the window. */
 397        if (ic->i_flowctl && posted)
 398                rds_ib_advertise_credits(conn, posted);
 399
 400        if (ret)
 401                rds_ib_ring_unalloc(&ic->i_recv_ring, 1);
 402}
 403
 404/*
 405 * We want to recycle several types of recv allocations, like incs and frags.
 406 * To use this, the *_free() function passes in the ptr to a list_head within
 407 * the recyclee, as well as the cache to put it on.
 408 *
 409 * First, we put the memory on a percpu list. When this reaches a certain size,
 410 * We move it to an intermediate non-percpu list in a lockless manner, with some
 411 * xchg/compxchg wizardry.
 412 *
 413 * N.B. Instead of a list_head as the anchor, we use a single pointer, which can
 414 * be NULL and xchg'd. The list is actually empty when the pointer is NULL, and
 415 * list_empty() will return true with one element is actually present.
 416 */
 417static void rds_ib_recv_cache_put(struct list_head *new_item,
 418                                 struct rds_ib_refill_cache *cache)
 419{
 420        unsigned long flags;
 421        struct rds_ib_cache_head *chp;
 422        struct list_head *old;
 423
 424        local_irq_save(flags);
 425
 426        chp = per_cpu_ptr(cache->percpu, smp_processor_id());
 427        if (!chp->first)
 428                INIT_LIST_HEAD(new_item);
 429        else /* put on front */
 430                list_add_tail(new_item, chp->first);
 431        chp->first = new_item;
 432        chp->count++;
 433
 434        if (chp->count < RDS_IB_RECYCLE_BATCH_COUNT)
 435                goto end;
 436
 437        /*
 438         * Return our per-cpu first list to the cache's xfer by atomically
 439         * grabbing the current xfer list, appending it to our per-cpu list,
 440         * and then atomically returning that entire list back to the
 441         * cache's xfer list as long as it's still empty.
 442         */
 443        do {
 444                old = xchg(&cache->xfer, NULL);
 445                if (old)
 446                        list_splice_entire_tail(old, chp->first);
 447                old = cmpxchg(&cache->xfer, NULL, chp->first);
 448        } while (old);
 449
 450        chp->first = NULL;
 451        chp->count = 0;
 452end:
 453        local_irq_restore(flags);
 454}
 455
 456static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache)
 457{
 458        struct list_head *head = cache->ready;
 459
 460        if (head) {
 461                if (!list_empty(head)) {
 462                        cache->ready = head->next;
 463                        list_del_init(head);
 464                } else
 465                        cache->ready = NULL;
 466        }
 467
 468        return head;
 469}
 470
 471int rds_ib_inc_copy_to_user(struct rds_incoming *inc, struct iovec *first_iov,
 472                            size_t size)
 473{
 474        struct rds_ib_incoming *ibinc;
 475        struct rds_page_frag *frag;
 476        struct iovec *iov = first_iov;
 477        unsigned long to_copy;
 478        unsigned long frag_off = 0;
 479        unsigned long iov_off = 0;
 480        int copied = 0;
 481        int ret;
 482        u32 len;
 483
 484        ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
 485        frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
 486        len = be32_to_cpu(inc->i_hdr.h_len);
 487
 488        while (copied < size && copied < len) {
 489                if (frag_off == RDS_FRAG_SIZE) {
 490                        frag = list_entry(frag->f_item.next,
 491                                          struct rds_page_frag, f_item);
 492                        frag_off = 0;
 493                }
 494                while (iov_off == iov->iov_len) {
 495                        iov_off = 0;
 496                        iov++;
 497                }
 498
 499                to_copy = min(iov->iov_len - iov_off, RDS_FRAG_SIZE - frag_off);
 500                to_copy = min_t(size_t, to_copy, size - copied);
 501                to_copy = min_t(unsigned long, to_copy, len - copied);
 502
 503                rdsdebug("%lu bytes to user [%p, %zu] + %lu from frag "
 504                         "[%p, %u] + %lu\n",
 505                         to_copy, iov->iov_base, iov->iov_len, iov_off,
 506                         sg_page(&frag->f_sg), frag->f_sg.offset, frag_off);
 507
 508                /* XXX needs + offset for multiple recvs per page */
 509                ret = rds_page_copy_to_user(sg_page(&frag->f_sg),
 510                                            frag->f_sg.offset + frag_off,
 511                                            iov->iov_base + iov_off,
 512                                            to_copy);
 513                if (ret) {
 514                        copied = ret;
 515                        break;
 516                }
 517
 518                iov_off += to_copy;
 519                frag_off += to_copy;
 520                copied += to_copy;
 521        }
 522
 523        return copied;
 524}
 525
 526/* ic starts out kzalloc()ed */
 527void rds_ib_recv_init_ack(struct rds_ib_connection *ic)
 528{
 529        struct ib_send_wr *wr = &ic->i_ack_wr;
 530        struct ib_sge *sge = &ic->i_ack_sge;
 531
 532        sge->addr = ic->i_ack_dma;
 533        sge->length = sizeof(struct rds_header);
 534        sge->lkey = ic->i_mr->lkey;
 535
 536        wr->sg_list = sge;
 537        wr->num_sge = 1;
 538        wr->opcode = IB_WR_SEND;
 539        wr->wr_id = RDS_IB_ACK_WR_ID;
 540        wr->send_flags = IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 541}
 542
 543/*
 544 * You'd think that with reliable IB connections you wouldn't need to ack
 545 * messages that have been received.  The problem is that IB hardware generates
 546 * an ack message before it has DMAed the message into memory.  This creates a
 547 * potential message loss if the HCA is disabled for any reason between when it
 548 * sends the ack and before the message is DMAed and processed.  This is only a
 549 * potential issue if another HCA is available for fail-over.
 550 *
 551 * When the remote host receives our ack they'll free the sent message from
 552 * their send queue.  To decrease the latency of this we always send an ack
 553 * immediately after we've received messages.
 554 *
 555 * For simplicity, we only have one ack in flight at a time.  This puts
 556 * pressure on senders to have deep enough send queues to absorb the latency of
 557 * a single ack frame being in flight.  This might not be good enough.
 558 *
 559 * This is implemented by have a long-lived send_wr and sge which point to a
 560 * statically allocated ack frame.  This ack wr does not fall under the ring
 561 * accounting that the tx and rx wrs do.  The QP attribute specifically makes
 562 * room for it beyond the ring size.  Send completion notices its special
 563 * wr_id and avoids working with the ring in that case.
 564 */
 565#ifndef KERNEL_HAS_ATOMIC64
 566static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
 567                                int ack_required)
 568{
 569        unsigned long flags;
 570
 571        spin_lock_irqsave(&ic->i_ack_lock, flags);
 572        ic->i_ack_next = seq;
 573        if (ack_required)
 574                set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
 575        spin_unlock_irqrestore(&ic->i_ack_lock, flags);
 576}
 577
 578static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
 579{
 580        unsigned long flags;
 581        u64 seq;
 582
 583        clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
 584
 585        spin_lock_irqsave(&ic->i_ack_lock, flags);
 586        seq = ic->i_ack_next;
 587        spin_unlock_irqrestore(&ic->i_ack_lock, flags);
 588
 589        return seq;
 590}
 591#else
 592static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
 593                                int ack_required)
 594{
 595        atomic64_set(&ic->i_ack_next, seq);
 596        if (ack_required) {
 597                smp_mb__before_clear_bit();
 598                set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
 599        }
 600}
 601
 602static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
 603{
 604        clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
 605        smp_mb__after_clear_bit();
 606
 607        return atomic64_read(&ic->i_ack_next);
 608}
 609#endif
 610
 611
 612static void rds_ib_send_ack(struct rds_ib_connection *ic, unsigned int adv_credits)
 613{
 614        struct rds_header *hdr = ic->i_ack;
 615        struct ib_send_wr *failed_wr;
 616        u64 seq;
 617        int ret;
 618
 619        seq = rds_ib_get_ack(ic);
 620
 621        rdsdebug("send_ack: ic %p ack %llu\n", ic, (unsigned long long) seq);
 622        rds_message_populate_header(hdr, 0, 0, 0);
 623        hdr->h_ack = cpu_to_be64(seq);
 624        hdr->h_credit = adv_credits;
 625        rds_message_make_checksum(hdr);
 626        ic->i_ack_queued = jiffies;
 627
 628        ret = ib_post_send(ic->i_cm_id->qp, &ic->i_ack_wr, &failed_wr);
 629        if (unlikely(ret)) {
 630                /* Failed to send. Release the WR, and
 631                 * force another ACK.
 632                 */
 633                clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
 634                set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
 635
 636                rds_ib_stats_inc(s_ib_ack_send_failure);
 637
 638                rds_ib_conn_error(ic->conn, "sending ack failed\n");
 639        } else
 640                rds_ib_stats_inc(s_ib_ack_sent);
 641}
 642
 643/*
 644 * There are 3 ways of getting acknowledgements to the peer:
 645 *  1.  We call rds_ib_attempt_ack from the recv completion handler
 646 *      to send an ACK-only frame.
 647 *      However, there can be only one such frame in the send queue
 648 *      at any time, so we may have to postpone it.
 649 *  2.  When another (data) packet is transmitted while there's
 650 *      an ACK in the queue, we piggyback the ACK sequence number
 651 *      on the data packet.
 652 *  3.  If the ACK WR is done sending, we get called from the
 653 *      send queue completion handler, and check whether there's
 654 *      another ACK pending (postponed because the WR was on the
 655 *      queue). If so, we transmit it.
 656 *
 657 * We maintain 2 variables:
 658 *  -   i_ack_flags, which keeps track of whether the ACK WR
 659 *      is currently in the send queue or not (IB_ACK_IN_FLIGHT)
 660 *  -   i_ack_next, which is the last sequence number we received
 661 *
 662 * Potentially, send queue and receive queue handlers can run concurrently.
 663 * It would be nice to not have to use a spinlock to synchronize things,
 664 * but the one problem that rules this out is that 64bit updates are
 665 * not atomic on all platforms. Things would be a lot simpler if
 666 * we had atomic64 or maybe cmpxchg64 everywhere.
 667 *
 668 * Reconnecting complicates this picture just slightly. When we
 669 * reconnect, we may be seeing duplicate packets. The peer
 670 * is retransmitting them, because it hasn't seen an ACK for
 671 * them. It is important that we ACK these.
 672 *
 673 * ACK mitigation adds a header flag "ACK_REQUIRED"; any packet with
 674 * this flag set *MUST* be acknowledged immediately.
 675 */
 676
 677/*
 678 * When we get here, we're called from the recv queue handler.
 679 * Check whether we ought to transmit an ACK.
 680 */
 681void rds_ib_attempt_ack(struct rds_ib_connection *ic)
 682{
 683        unsigned int adv_credits;
 684
 685        if (!test_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
 686                return;
 687
 688        if (test_and_set_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags)) {
 689                rds_ib_stats_inc(s_ib_ack_send_delayed);
 690                return;
 691        }
 692
 693        /* Can we get a send credit? */
 694        if (!rds_ib_send_grab_credits(ic, 1, &adv_credits, 0, RDS_MAX_ADV_CREDIT)) {
 695                rds_ib_stats_inc(s_ib_tx_throttle);
 696                clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
 697                return;
 698        }
 699
 700        clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
 701        rds_ib_send_ack(ic, adv_credits);
 702}
 703
 704/*
 705 * We get here from the send completion handler, when the
 706 * adapter tells us the ACK frame was sent.
 707 */
 708void rds_ib_ack_send_complete(struct rds_ib_connection *ic)
 709{
 710        clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
 711        rds_ib_attempt_ack(ic);
 712}
 713
 714/*
 715 * This is called by the regular xmit code when it wants to piggyback
 716 * an ACK on an outgoing frame.
 717 */
 718u64 rds_ib_piggyb_ack(struct rds_ib_connection *ic)
 719{
 720        if (test_and_clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
 721                rds_ib_stats_inc(s_ib_ack_send_piggybacked);
 722        return rds_ib_get_ack(ic);
 723}
 724
 725/*
 726 * It's kind of lame that we're copying from the posted receive pages into
 727 * long-lived bitmaps.  We could have posted the bitmaps and rdma written into
 728 * them.  But receiving new congestion bitmaps should be a *rare* event, so
 729 * hopefully we won't need to invest that complexity in making it more
 730 * efficient.  By copying we can share a simpler core with TCP which has to
 731 * copy.
 732 */
 733static void rds_ib_cong_recv(struct rds_connection *conn,
 734                              struct rds_ib_incoming *ibinc)
 735{
 736        struct rds_cong_map *map;
 737        unsigned int map_off;
 738        unsigned int map_page;
 739        struct rds_page_frag *frag;
 740        unsigned long frag_off;
 741        unsigned long to_copy;
 742        unsigned long copied;
 743        uint64_t uncongested = 0;
 744        void *addr;
 745
 746        /* catch completely corrupt packets */
 747        if (be32_to_cpu(ibinc->ii_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
 748                return;
 749
 750        map = conn->c_fcong;
 751        map_page = 0;
 752        map_off = 0;
 753
 754        frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
 755        frag_off = 0;
 756
 757        copied = 0;
 758
 759        while (copied < RDS_CONG_MAP_BYTES) {
 760                uint64_t *src, *dst;
 761                unsigned int k;
 762
 763                to_copy = min(RDS_FRAG_SIZE - frag_off, PAGE_SIZE - map_off);
 764                BUG_ON(to_copy & 7); /* Must be 64bit aligned. */
 765
 766                addr = kmap_atomic(sg_page(&frag->f_sg));
 767
 768                src = addr + frag_off;
 769                dst = (void *)map->m_page_addrs[map_page] + map_off;
 770                for (k = 0; k < to_copy; k += 8) {
 771                        /* Record ports that became uncongested, ie
 772                         * bits that changed from 0 to 1. */
 773                        uncongested |= ~(*src) & *dst;
 774                        *dst++ = *src++;
 775                }
 776                kunmap_atomic(addr);
 777
 778                copied += to_copy;
 779
 780                map_off += to_copy;
 781                if (map_off == PAGE_SIZE) {
 782                        map_off = 0;
 783                        map_page++;
 784                }
 785
 786                frag_off += to_copy;
 787                if (frag_off == RDS_FRAG_SIZE) {
 788                        frag = list_entry(frag->f_item.next,
 789                                          struct rds_page_frag, f_item);
 790                        frag_off = 0;
 791                }
 792        }
 793
 794        /* the congestion map is in little endian order */
 795        uncongested = le64_to_cpu(uncongested);
 796
 797        rds_cong_map_updated(map, uncongested);
 798}
 799
 800/*
 801 * Rings are posted with all the allocations they'll need to queue the
 802 * incoming message to the receiving socket so this can't fail.
 803 * All fragments start with a header, so we can make sure we're not receiving
 804 * garbage, and we can tell a small 8 byte fragment from an ACK frame.
 805 */
 806struct rds_ib_ack_state {
 807        u64             ack_next;
 808        u64             ack_recv;
 809        unsigned int    ack_required:1;
 810        unsigned int    ack_next_valid:1;
 811        unsigned int    ack_recv_valid:1;
 812};
 813
 814static void rds_ib_process_recv(struct rds_connection *conn,
 815                                struct rds_ib_recv_work *recv, u32 data_len,
 816                                struct rds_ib_ack_state *state)
 817{
 818        struct rds_ib_connection *ic = conn->c_transport_data;
 819        struct rds_ib_incoming *ibinc = ic->i_ibinc;
 820        struct rds_header *ihdr, *hdr;
 821
 822        /* XXX shut down the connection if port 0,0 are seen? */
 823
 824        rdsdebug("ic %p ibinc %p recv %p byte len %u\n", ic, ibinc, recv,
 825                 data_len);
 826
 827        if (data_len < sizeof(struct rds_header)) {
 828                rds_ib_conn_error(conn, "incoming message "
 829                       "from %pI4 didn't include a "
 830                       "header, disconnecting and "
 831                       "reconnecting\n",
 832                       &conn->c_faddr);
 833                return;
 834        }
 835        data_len -= sizeof(struct rds_header);
 836
 837        ihdr = &ic->i_recv_hdrs[recv - ic->i_recvs];
 838
 839        /* Validate the checksum. */
 840        if (!rds_message_verify_checksum(ihdr)) {
 841                rds_ib_conn_error(conn, "incoming message "
 842                       "from %pI4 has corrupted header - "
 843                       "forcing a reconnect\n",
 844                       &conn->c_faddr);
 845                rds_stats_inc(s_recv_drop_bad_checksum);
 846                return;
 847        }
 848
 849        /* Process the ACK sequence which comes with every packet */
 850        state->ack_recv = be64_to_cpu(ihdr->h_ack);
 851        state->ack_recv_valid = 1;
 852
 853        /* Process the credits update if there was one */
 854        if (ihdr->h_credit)
 855                rds_ib_send_add_credits(conn, ihdr->h_credit);
 856
 857        if (ihdr->h_sport == 0 && ihdr->h_dport == 0 && data_len == 0) {
 858                /* This is an ACK-only packet. The fact that it gets
 859                 * special treatment here is that historically, ACKs
 860                 * were rather special beasts.
 861                 */
 862                rds_ib_stats_inc(s_ib_ack_received);
 863
 864                /*
 865                 * Usually the frags make their way on to incs and are then freed as
 866                 * the inc is freed.  We don't go that route, so we have to drop the
 867                 * page ref ourselves.  We can't just leave the page on the recv
 868                 * because that confuses the dma mapping of pages and each recv's use
 869                 * of a partial page.
 870                 *
 871                 * FIXME: Fold this into the code path below.
 872                 */
 873                rds_ib_frag_free(ic, recv->r_frag);
 874                recv->r_frag = NULL;
 875                return;
 876        }
 877
 878        /*
 879         * If we don't already have an inc on the connection then this
 880         * fragment has a header and starts a message.. copy its header
 881         * into the inc and save the inc so we can hang upcoming fragments
 882         * off its list.
 883         */
 884        if (!ibinc) {
 885                ibinc = recv->r_ibinc;
 886                recv->r_ibinc = NULL;
 887                ic->i_ibinc = ibinc;
 888
 889                hdr = &ibinc->ii_inc.i_hdr;
 890                memcpy(hdr, ihdr, sizeof(*hdr));
 891                ic->i_recv_data_rem = be32_to_cpu(hdr->h_len);
 892
 893                rdsdebug("ic %p ibinc %p rem %u flag 0x%x\n", ic, ibinc,
 894                         ic->i_recv_data_rem, hdr->h_flags);
 895        } else {
 896                hdr = &ibinc->ii_inc.i_hdr;
 897                /* We can't just use memcmp here; fragments of a
 898                 * single message may carry different ACKs */
 899                if (hdr->h_sequence != ihdr->h_sequence ||
 900                    hdr->h_len != ihdr->h_len ||
 901                    hdr->h_sport != ihdr->h_sport ||
 902                    hdr->h_dport != ihdr->h_dport) {
 903                        rds_ib_conn_error(conn,
 904                                "fragment header mismatch; forcing reconnect\n");
 905                        return;
 906                }
 907        }
 908
 909        list_add_tail(&recv->r_frag->f_item, &ibinc->ii_frags);
 910        recv->r_frag = NULL;
 911
 912        if (ic->i_recv_data_rem > RDS_FRAG_SIZE)
 913                ic->i_recv_data_rem -= RDS_FRAG_SIZE;
 914        else {
 915                ic->i_recv_data_rem = 0;
 916                ic->i_ibinc = NULL;
 917
 918                if (ibinc->ii_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP)
 919                        rds_ib_cong_recv(conn, ibinc);
 920                else {
 921                        rds_recv_incoming(conn, conn->c_faddr, conn->c_laddr,
 922                                          &ibinc->ii_inc, GFP_ATOMIC);
 923                        state->ack_next = be64_to_cpu(hdr->h_sequence);
 924                        state->ack_next_valid = 1;
 925                }
 926
 927                /* Evaluate the ACK_REQUIRED flag *after* we received
 928                 * the complete frame, and after bumping the next_rx
 929                 * sequence. */
 930                if (hdr->h_flags & RDS_FLAG_ACK_REQUIRED) {
 931                        rds_stats_inc(s_recv_ack_required);
 932                        state->ack_required = 1;
 933                }
 934
 935                rds_inc_put(&ibinc->ii_inc);
 936        }
 937}
 938
 939/*
 940 * Plucking the oldest entry from the ring can be done concurrently with
 941 * the thread refilling the ring.  Each ring operation is protected by
 942 * spinlocks and the transient state of refilling doesn't change the
 943 * recording of which entry is oldest.
 944 *
 945 * This relies on IB only calling one cq comp_handler for each cq so that
 946 * there will only be one caller of rds_recv_incoming() per RDS connection.
 947 */
 948void rds_ib_recv_cq_comp_handler(struct ib_cq *cq, void *context)
 949{
 950        struct rds_connection *conn = context;
 951        struct rds_ib_connection *ic = conn->c_transport_data;
 952
 953        rdsdebug("conn %p cq %p\n", conn, cq);
 954
 955        rds_ib_stats_inc(s_ib_rx_cq_call);
 956
 957        tasklet_schedule(&ic->i_recv_tasklet);
 958}
 959
 960static inline void rds_poll_cq(struct rds_ib_connection *ic,
 961                               struct rds_ib_ack_state *state)
 962{
 963        struct rds_connection *conn = ic->conn;
 964        struct ib_wc wc;
 965        struct rds_ib_recv_work *recv;
 966
 967        while (ib_poll_cq(ic->i_recv_cq, 1, &wc) > 0) {
 968                rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
 969                         (unsigned long long)wc.wr_id, wc.status,
 970                         rds_ib_wc_status_str(wc.status), wc.byte_len,
 971                         be32_to_cpu(wc.ex.imm_data));
 972                rds_ib_stats_inc(s_ib_rx_cq_event);
 973
 974                recv = &ic->i_recvs[rds_ib_ring_oldest(&ic->i_recv_ring)];
 975
 976                ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
 977
 978                /*
 979                 * Also process recvs in connecting state because it is possible
 980                 * to get a recv completion _before_ the rdmacm ESTABLISHED
 981                 * event is processed.
 982                 */
 983                if (wc.status == IB_WC_SUCCESS) {
 984                        rds_ib_process_recv(conn, recv, wc.byte_len, state);
 985                } else {
 986                        /* We expect errors as the qp is drained during shutdown */
 987                        if (rds_conn_up(conn) || rds_conn_connecting(conn))
 988                                rds_ib_conn_error(conn, "recv completion on %pI4 had "
 989                                                  "status %u (%s), disconnecting and "
 990                                                  "reconnecting\n", &conn->c_faddr,
 991                                                  wc.status,
 992                                                  rds_ib_wc_status_str(wc.status));
 993                }
 994
 995                /*
 996                 * It's very important that we only free this ring entry if we've truly
 997                 * freed the resources allocated to the entry.  The refilling path can
 998                 * leak if we don't.
 999                 */
1000                rds_ib_ring_free(&ic->i_recv_ring, 1);
1001        }
1002}
1003
1004void rds_ib_recv_tasklet_fn(unsigned long data)
1005{
1006        struct rds_ib_connection *ic = (struct rds_ib_connection *) data;
1007        struct rds_connection *conn = ic->conn;
1008        struct rds_ib_ack_state state = { 0, };
1009
1010        rds_poll_cq(ic, &state);
1011        ib_req_notify_cq(ic->i_recv_cq, IB_CQ_SOLICITED);
1012        rds_poll_cq(ic, &state);
1013
1014        if (state.ack_next_valid)
1015                rds_ib_set_ack(ic, state.ack_next, state.ack_required);
1016        if (state.ack_recv_valid && state.ack_recv > ic->i_ack_recv) {
1017                rds_send_drop_acked(conn, state.ack_recv, NULL);
1018                ic->i_ack_recv = state.ack_recv;
1019        }
1020        if (rds_conn_up(conn))
1021                rds_ib_attempt_ack(ic);
1022
1023        /* If we ever end up with a really empty receive ring, we're
1024         * in deep trouble, as the sender will definitely see RNR
1025         * timeouts. */
1026        if (rds_ib_ring_empty(&ic->i_recv_ring))
1027                rds_ib_stats_inc(s_ib_rx_ring_empty);
1028
1029        if (rds_ib_ring_low(&ic->i_recv_ring))
1030                rds_ib_recv_refill(conn, 0);
1031}
1032
1033int rds_ib_recv(struct rds_connection *conn)
1034{
1035        struct rds_ib_connection *ic = conn->c_transport_data;
1036        int ret = 0;
1037
1038        rdsdebug("conn %p\n", conn);
1039        if (rds_conn_up(conn))
1040                rds_ib_attempt_ack(ic);
1041
1042        return ret;
1043}
1044
1045int rds_ib_recv_init(void)
1046{
1047        struct sysinfo si;
1048        int ret = -ENOMEM;
1049
1050        /* Default to 30% of all available RAM for recv memory */
1051        si_meminfo(&si);
1052        rds_ib_sysctl_max_recv_allocation = si.totalram / 3 * PAGE_SIZE / RDS_FRAG_SIZE;
1053
1054        rds_ib_incoming_slab = kmem_cache_create("rds_ib_incoming",
1055                                        sizeof(struct rds_ib_incoming),
1056                                        0, SLAB_HWCACHE_ALIGN, NULL);
1057        if (!rds_ib_incoming_slab)
1058                goto out;
1059
1060        rds_ib_frag_slab = kmem_cache_create("rds_ib_frag",
1061                                        sizeof(struct rds_page_frag),
1062                                        0, SLAB_HWCACHE_ALIGN, NULL);
1063        if (!rds_ib_frag_slab)
1064                kmem_cache_destroy(rds_ib_incoming_slab);
1065        else
1066                ret = 0;
1067out:
1068        return ret;
1069}
1070
1071void rds_ib_recv_exit(void)
1072{
1073        kmem_cache_destroy(rds_ib_incoming_slab);
1074        kmem_cache_destroy(rds_ib_frag_slab);
1075}
1076
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.