net/rds/ib_send.c

   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/in.h>
  35 #include <linux/device.h>
  36 #include <linux/dmapool.h>
  37
  38 #include "rds.h"
  39 #include "ib.h"
  40
  41 static void rds_ib_send_rdma_complete(struct rds_message *rm,
  42                                       int wc_status)
  43 {
  44         int notify_status;
  45
  46         switch (wc_status) {
  47         case IB_WC_WR_FLUSH_ERR:
  48                 return;
  49
  50         case IB_WC_SUCCESS:
  51                 notify_status = RDS_RDMA_SUCCESS;
  52                 break;
  53
  54         case IB_WC_REM_ACCESS_ERR:
  55                 notify_status = RDS_RDMA_REMOTE_ERROR;
  56                 break;
  57
  58         default:
  59                 notify_status = RDS_RDMA_OTHER_ERROR;
  60                 break;
  61         }
  62         rds_rdma_send_complete(rm, notify_status);
  63 }
  64
  65 static void rds_ib_send_unmap_rdma(struct rds_ib_connection *ic,
  66                                    struct rds_rdma_op *op)
  67 {
  68         if (op->r_mapped) {
  69                 ib_dma_unmap_sg(ic->i_cm_id->device,
  70                         op->r_sg, op->r_nents,
  71                         op->r_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
  72                 op->r_mapped = 0;
  73         }
  74 }
  75
  76 static void rds_ib_send_unmap_rm(struct rds_ib_connection *ic,
  77                           struct rds_ib_send_work *send,
  78                           int wc_status)
  79 {
  80         struct rds_message *rm = send->s_rm;
  81
  82         rdsdebug("ic %p send %p rm %p\n", ic, send, rm);
  83
  84         ib_dma_unmap_sg(ic->i_cm_id->device,
  85                         rm->data.m_sg, rm->data.m_nents,
  86                         DMA_TO_DEVICE);
  87
  88         if (rm->rdma.m_rdma_op.r_active) {
  89                 rds_ib_send_unmap_rdma(ic, &rm->rdma.m_rdma_op);
  90
  91                 /* If the user asked for a completion notification on this
  92                  * message, we can implement three different semantics:
  93                  *  1.  Notify when we received the ACK on the RDS message
  94                  *      that was queued with the RDMA. This provides reliable
  95                  *      notification of RDMA status at the expense of a one-way
  96                  *      packet delay.
  97                  *  2.  Notify when the IB stack gives us the completion event for
  98                  *      the RDMA operation.
  99                  *  3.  Notify when the IB stack gives us the completion event for
 100                  *      the accompanying RDS messages.
 101                  * Here, we implement approach #3. To implement approach #2,
 102                  * call rds_rdma_send_complete from the cq_handler. To implement #1,
 103                  * don't call rds_rdma_send_complete at all, and fall back to the notify
 104                  * handling in the ACK processing code.
 105                  *
 106                  * Note: There's no need to explicitly sync any RDMA buffers using
 107                  * ib_dma_sync_sg_for_cpu - the completion for the RDMA
 108                  * operation itself unmapped the RDMA buffers, which takes care
 109                  * of synching.
 110                  */
 111                 rds_ib_send_rdma_complete(rm, wc_status);
 112
 113                 if (rm->rdma.m_rdma_op.r_write)
 114                         rds_stats_add(s_send_rdma_bytes, rm->rdma.m_rdma_op.r_bytes);
 115                 else
 116                         rds_stats_add(s_recv_rdma_bytes, rm->rdma.m_rdma_op.r_bytes);
 117         }
 118
 119         /* If anyone waited for this message to get flushed out, wake
 120          * them up now */
 121         rds_message_unmapped(rm);
 122
 123         rds_message_put(rm);
 124         send->s_rm = NULL;
 125 }
 126
 127 void rds_ib_send_init_ring(struct rds_ib_connection *ic)
 128 {
 129         struct rds_ib_send_work *send;
 130         u32 i;
 131
 132         for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
 133                 struct ib_sge *sge;
 134
 135                 send->s_rm = NULL;
 136                 send->s_op = NULL;
 137
 138                 send->s_wr.wr_id = i;
 139                 send->s_wr.sg_list = send->s_sge;
 140                 send->s_wr.num_sge = 1;
 141                 send->s_wr.opcode = IB_WR_SEND;
 142                 send->s_wr.send_flags = 0;
 143                 send->s_wr.ex.imm_data = 0;
 144
 145                 sge = rds_ib_data_sge(ic, send->s_sge);
 146                 sge->lkey = ic->i_mr->lkey;
 147
 148                 sge = rds_ib_header_sge(ic, send->s_sge);
 149                 sge->addr = ic->i_send_hdrs_dma + (i * sizeof(struct rds_header));
 150                 sge->length = sizeof(struct rds_header);
 151                 sge->lkey = ic->i_mr->lkey;
 152         }
 153 }
 154
 155 void rds_ib_send_clear_ring(struct rds_ib_connection *ic)
 156 {
 157         struct rds_ib_send_work *send;
 158         u32 i;
 159
 160         for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
 161                 if (send->s_wr.opcode == 0xdead)
 162                         continue;
 163                 if (send->s_rm)
 164                         rds_ib_send_unmap_rm(ic, send, IB_WC_WR_FLUSH_ERR);
 165                 if (send->s_op)
 166                         rds_ib_send_unmap_rdma(ic, send->s_op);
 167         }
 168 }
 169
 170 /*
 171  * The _oldest/_free ring operations here race cleanly with the alloc/unalloc
 172  * operations performed in the send path.  As the sender allocs and potentially
 173  * unallocs the next free entry in the ring it doesn't alter which is
 174  * the next to be freed, which is what this is concerned with.
 175  */
 176 void rds_ib_send_cq_comp_handler(struct ib_cq *cq, void *context)
 177 {
 178         struct rds_connection *conn = context;
 179         struct rds_ib_connection *ic = conn->c_transport_data;
 180         struct ib_wc wc;
 181         struct rds_ib_send_work *send;
 182         u32 completed;
 183         u32 oldest;
 184         u32 i = 0;
 185         int ret;
 186
 187         rdsdebug("cq %p conn %p\n", cq, conn);
 188         rds_ib_stats_inc(s_ib_tx_cq_call);
 189         ret = ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
 190         if (ret)
 191                 rdsdebug("ib_req_notify_cq send failed: %d\n", ret);
 192
 193         while (ib_poll_cq(cq, 1, &wc) > 0) {
 194                 rdsdebug("wc wr_id 0x%llx status %u byte_len %u imm_data %u\n",
 195                          (unsigned long long)wc.wr_id, wc.status, wc.byte_len,
 196                          be32_to_cpu(wc.ex.imm_data));
 197                 rds_ib_stats_inc(s_ib_tx_cq_event);
 198
 199                 if (wc.wr_id == RDS_IB_ACK_WR_ID) {
 200                         if (ic->i_ack_queued + HZ/2 < jiffies)
 201                                 rds_ib_stats_inc(s_ib_tx_stalled);
 202                         rds_ib_ack_send_complete(ic);
 203                         continue;
 204                 }
 205
 206                 oldest = rds_ib_ring_oldest(&ic->i_send_ring);
 207
 208                 completed = rds_ib_ring_completed(&ic->i_send_ring, wc.wr_id, oldest);
 209
 210                 for (i = 0; i < completed; i++) {
 211                         send = &ic->i_sends[oldest];
 212
 213                         /* In the error case, wc.opcode sometimes contains garbage */
 214                         switch (send->s_wr.opcode) {
 215                         case IB_WR_SEND:
 216                                 if (send->s_rm)
 217                                         rds_ib_send_unmap_rm(ic, send, wc.status);
 218                                 break;
 219                         case IB_WR_RDMA_WRITE:
 220                         case IB_WR_RDMA_READ:
 221                                 /* Nothing to be done - the SG list will be unmapped
 222                                  * when the SEND completes. */
 223                                 break;
 224                         default:
 225                                 if (printk_ratelimit())
 226                                         printk(KERN_NOTICE
 227                                                 "RDS/IB: %s: unexpected opcode 0x%x in WR!\n",
 228                                                 __func__, send->s_wr.opcode);
 229                                 break;
 230                         }
 231
 232                         send->s_wr.opcode = 0xdead;
 233                         send->s_wr.num_sge = 1;
 234                         if (send->s_queued + HZ/2 < jiffies)
 235                                 rds_ib_stats_inc(s_ib_tx_stalled);
 236
 237                         /* If a RDMA operation produced an error, signal this right
 238                          * away. If we don't, the subsequent SEND that goes with this
 239                          * RDMA will be canceled with ERR_WFLUSH, and the application
 240                          * never learn that the RDMA failed. */
 241                         if (unlikely(wc.status == IB_WC_REM_ACCESS_ERR && send->s_op)) {
 242                                 struct rds_message *rm;
 243
 244                                 rm = rds_send_get_message(conn, send->s_op);
 245                                 if (rm) {
 246                                         if (rm->rdma.m_rdma_op.r_active)
 247                                                 rds_ib_send_unmap_rdma(ic, &rm->rdma.m_rdma_op);
 248                                         rds_ib_send_rdma_complete(rm, wc.status);
 249                                         rds_message_put(rm);
 250                                 }
 251                         }
 252
 253                         oldest = (oldest + 1) % ic->i_send_ring.w_nr;
 254                 }
 255
 256                 rds_ib_ring_free(&ic->i_send_ring, completed);
 257
 258                 if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags) ||
 259                     test_bit(0, &conn->c_map_queued))
 260                         queue_delayed_work(rds_wq, &conn->c_send_w, 0);
 261
 262                 /* We expect errors as the qp is drained during shutdown */
 263                 if (wc.status != IB_WC_SUCCESS && rds_conn_up(conn)) {
 264                         rds_ib_conn_error(conn,
 265                                 "send completion on %pI4 "
 266                                 "had status %u, disconnecting and reconnecting\n",
 267                                 &conn->c_faddr, wc.status);
 268                 }
 269         }
 270 }
 271
 272 /*
 273  * This is the main function for allocating credits when sending
 274  * messages.
 275  *
 276  * Conceptually, we have two counters:
 277  *  -   send credits: this tells us how many WRs we're allowed
 278  *      to submit without overruning the reciever's queue. For
 279  *      each SEND WR we post, we decrement this by one.
 280  *
 281  *  -   posted credits: this tells us how many WRs we recently
 282  *      posted to the receive queue. This value is transferred
 283  *      to the peer as a "credit update" in a RDS header field.
 284  *      Every time we transmit credits to the peer, we subtract
 285  *      the amount of transferred credits from this counter.
 286  *
 287  * It is essential that we avoid situations where both sides have
 288  * exhausted their send credits, and are unable to send new credits
 289  * to the peer. We achieve this by requiring that we send at least
 290  * one credit update to the peer before exhausting our credits.
 291  * When new credits arrive, we subtract one credit that is withheld
 292  * until we've posted new buffers and are ready to transmit these
 293  * credits (see rds_ib_send_add_credits below).
 294  *
 295  * The RDS send code is essentially single-threaded; rds_send_xmit
 296  * grabs c_send_lock to ensure exclusive access to the send ring.
 297  * However, the ACK sending code is independent and can race with
 298  * message SENDs.
 299  *
 300  * In the send path, we need to update the counters for send credits
 301  * and the counter of posted buffers atomically - when we use the
 302  * last available credit, we cannot allow another thread to race us
 303  * and grab the posted credits counter.  Hence, we have to use a
 304  * spinlock to protect the credit counter, or use atomics.
 305  *
 306  * Spinlocks shared between the send and the receive path are bad,
 307  * because they create unnecessary delays. An early implementation
 308  * using a spinlock showed a 5% degradation in throughput at some
 309  * loads.
 310  *
 311  * This implementation avoids spinlocks completely, putting both
 312  * counters into a single atomic, and updating that atomic using
 313  * atomic_add (in the receive path, when receiving fresh credits),
 314  * and using atomic_cmpxchg when updating the two counters.
 315  */
 316 int rds_ib_send_grab_credits(struct rds_ib_connection *ic,
 317                              u32 wanted, u32 *adv_credits, int need_posted, int max_posted)
 318 {
 319         unsigned int avail, posted, got = 0, advertise;
 320         long oldval, newval;
 321
 322         *adv_credits = 0;
 323         if (!ic->i_flowctl)
 324                 return wanted;
 325
 326 try_again:
 327         advertise = 0;
 328         oldval = newval = atomic_read(&ic->i_credits);
 329         posted = IB_GET_POST_CREDITS(oldval);
 330         avail = IB_GET_SEND_CREDITS(oldval);
 331
 332         rdsdebug("rds_ib_send_grab_credits(%u): credits=%u posted=%u\n",
 333                         wanted, avail, posted);
 334
 335         /* The last credit must be used to send a credit update. */
 336         if (avail && !posted)
 337                 avail--;
 338
 339         if (avail < wanted) {
 340                 struct rds_connection *conn = ic->i_cm_id->context;
 341
 342                 /* Oops, there aren't that many credits left! */
 343                 set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
 344                 got = avail;
 345         } else {
 346                 /* Sometimes you get what you want, lalala. */
 347                 got = wanted;
 348         }
 349         newval -= IB_SET_SEND_CREDITS(got);
 350
 351         /*
 352          * If need_posted is non-zero, then the caller wants
 353          * the posted regardless of whether any send credits are
 354          * available.
 355          */
 356         if (posted && (got || need_posted)) {
 357                 advertise = min_t(unsigned int, posted, max_posted);
 358                 newval -= IB_SET_POST_CREDITS(advertise);
 359         }
 360
 361         /* Finally bill everything */
 362         if (atomic_cmpxchg(&ic->i_credits, oldval, newval) != oldval)
 363                 goto try_again;
 364
 365         *adv_credits = advertise;
 366         return got;
 367 }
 368
 369 void rds_ib_send_add_credits(struct rds_connection *conn, unsigned int credits)
 370 {
 371         struct rds_ib_connection *ic = conn->c_transport_data;
 372
 373         if (credits == 0)
 374                 return;
 375
 376         rdsdebug("rds_ib_send_add_credits(%u): current=%u%s\n",
 377                         credits,
 378                         IB_GET_SEND_CREDITS(atomic_read(&ic->i_credits)),
 379                         test_bit(RDS_LL_SEND_FULL, &conn->c_flags) ? ", ll_send_full" : "");
 380
 381         atomic_add(IB_SET_SEND_CREDITS(credits), &ic->i_credits);
 382         if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags))
 383                 queue_delayed_work(rds_wq, &conn->c_send_w, 0);
 384
 385         WARN_ON(IB_GET_SEND_CREDITS(credits) >= 16384);
 386
 387         rds_ib_stats_inc(s_ib_rx_credit_updates);
 388 }
 389
 390 void rds_ib_advertise_credits(struct rds_connection *conn, unsigned int posted)
 391 {
 392         struct rds_ib_connection *ic = conn->c_transport_data;
 393
 394         if (posted == 0)
 395                 return;
 396
 397         atomic_add(IB_SET_POST_CREDITS(posted), &ic->i_credits);
 398
 399         /* Decide whether to send an update to the peer now.
 400          * If we would send a credit update for every single buffer we
 401          * post, we would end up with an ACK storm (ACK arrives,
 402          * consumes buffer, we refill the ring, send ACK to remote
 403          * advertising the newly posted buffer... ad inf)
 404          *
 405          * Performance pretty much depends on how often we send
 406          * credit updates - too frequent updates mean lots of ACKs.
 407          * Too infrequent updates, and the peer will run out of
 408          * credits and has to throttle.
 409          * For the time being, 16 seems to be a good compromise.
 410          */
 411         if (IB_GET_POST_CREDITS(atomic_read(&ic->i_credits)) >= 16)
 412                 set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
 413 }
 414
 415 static inline void
 416 rds_ib_xmit_populate_wr(struct rds_ib_connection *ic,
 417                 struct rds_ib_send_work *send, unsigned int pos,
 418                 unsigned long buffer, unsigned int length,
 419                 int send_flags)
 420 {
 421         struct ib_sge *sge;
 422
 423         WARN_ON(pos != send - ic->i_sends);
 424
 425         send->s_wr.send_flags = send_flags;
 426         send->s_wr.opcode = IB_WR_SEND;
 427         send->s_wr.num_sge = 2;
 428         send->s_wr.next = NULL;
 429         send->s_queued = jiffies;
 430         send->s_op = NULL;
 431
 432         if (length != 0) {
 433                 sge = rds_ib_data_sge(ic, send->s_sge);
 434                 sge->addr = buffer;
 435                 sge->length = length;
 436                 sge->lkey = ic->i_mr->lkey;
 437
 438                 sge = rds_ib_header_sge(ic, send->s_sge);
 439         } else {
 440                 /* We're sending a packet with no payload. There is only
 441                  * one SGE */
 442                 send->s_wr.num_sge = 1;
 443                 sge = &send->s_sge[0];
 444         }
 445
 446         sge->addr = ic->i_send_hdrs_dma + (pos * sizeof(struct rds_header));
 447         sge->length = sizeof(struct rds_header);
 448         sge->lkey = ic->i_mr->lkey;
 449 }
 450
 451 /*
 452  * This can be called multiple times for a given message.  The first time
 453  * we see a message we map its scatterlist into the IB device so that
 454  * we can provide that mapped address to the IB scatter gather entries
 455  * in the IB work requests.  We translate the scatterlist into a series
 456  * of work requests that fragment the message.  These work requests complete
 457  * in order so we pass ownership of the message to the completion handler
 458  * once we send the final fragment.
 459  *
 460  * The RDS core uses the c_send_lock to only enter this function once
 461  * per connection.  This makes sure that the tx ring alloc/unalloc pairs
 462  * don't get out of sync and confuse the ring.
 463  */
 464 int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
 465                 unsigned int hdr_off, unsigned int sg, unsigned int off)
 466 {
 467         struct rds_ib_connection *ic = conn->c_transport_data;
 468         struct ib_device *dev = ic->i_cm_id->device;
 469         struct rds_ib_send_work *send = NULL;
 470         struct rds_ib_send_work *first;
 471         struct rds_ib_send_work *prev;
 472         struct ib_send_wr *failed_wr;
 473         struct scatterlist *scat;
 474         u32 pos;
 475         u32 i;
 476         u32 work_alloc;
 477         u32 credit_alloc;
 478         u32 posted;
 479         u32 adv_credits = 0;
 480         int send_flags = 0;
 481         int sent;
 482         int ret;
 483         int flow_controlled = 0;
 484
 485         BUG_ON(off % RDS_FRAG_SIZE);
 486         BUG_ON(hdr_off != 0 && hdr_off != sizeof(struct rds_header));
 487
 488         /* Do not send cong updates to IB loopback */
 489         if (conn->c_loopback
 490             && rm->m_inc.i_hdr.h_flags & RDS_FLAG_CONG_BITMAP) {
 491                 rds_cong_map_updated(conn->c_fcong, ~(u64) 0);
 492                 return sizeof(struct rds_header) + RDS_CONG_MAP_BYTES;
 493         }
 494
 495         /* FIXME we may overallocate here */
 496         if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0)
 497                 i = 1;
 498         else
 499                 i = ceil(be32_to_cpu(rm->m_inc.i_hdr.h_len), RDS_FRAG_SIZE);
 500
 501         work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
 502         if (work_alloc == 0) {
 503                 set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
 504                 rds_ib_stats_inc(s_ib_tx_ring_full);
 505                 ret = -ENOMEM;
 506                 goto out;
 507         }
 508
 509         credit_alloc = work_alloc;
 510         if (ic->i_flowctl) {
 511                 credit_alloc = rds_ib_send_grab_credits(ic, work_alloc, &posted, 0, RDS_MAX_ADV_CREDIT);
 512                 adv_credits += posted;
 513                 if (credit_alloc < work_alloc) {
 514                         rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - credit_alloc);
 515                         work_alloc = credit_alloc;
 516                         flow_controlled++;
 517                 }
 518                 if (work_alloc == 0) {
 519                         set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
 520                         rds_ib_stats_inc(s_ib_tx_throttle);
 521                         ret = -ENOMEM;
 522                         goto out;
 523                 }
 524         }
 525
 526         /* map the message the first time we see it */
 527         if (!ic->i_rm) {
 528                 /*
 529                 printk(KERN_NOTICE "rds_ib_xmit prep msg dport=%u flags=0x%x len=%d\n",
 530                                 be16_to_cpu(rm->m_inc.i_hdr.h_dport),
 531                                 rm->m_inc.i_hdr.h_flags,
 532                                 be32_to_cpu(rm->m_inc.i_hdr.h_len));
 533                    */
 534                 if (rm->data.m_nents) {
 535                         rm->data.m_count = ib_dma_map_sg(dev,
 536                                                             rm->data.m_sg,
 537                                                             rm->data.m_nents,
 538                                                             DMA_TO_DEVICE);
 539                         rdsdebug("ic %p mapping rm %p: %d\n", ic, rm, rm->data.m_count);
 540                         if (rm->data.m_count == 0) {
 541                                 rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
 542                                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
 543                                 ret = -ENOMEM; /* XXX ? */
 544                                 goto out;
 545                         }
 546                 } else {
 547                         rm->data.m_count = 0;
 548                 }
 549
 550                 ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
 551                 ic->i_unsignaled_bytes = rds_ib_sysctl_max_unsig_bytes;
 552                 rds_message_addref(rm);
 553                 ic->i_rm = rm;
 554
 555                 /* Finalize the header */
 556                 if (test_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags))
 557                         rm->m_inc.i_hdr.h_flags |= RDS_FLAG_ACK_REQUIRED;
 558                 if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
 559                         rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;
 560
 561                 /* If it has a RDMA op, tell the peer we did it. This is
 562                  * used by the peer to release use-once RDMA MRs. */
 563                 if (rm->rdma.m_rdma_op.r_active) {
 564                         struct rds_ext_header_rdma ext_hdr;
 565
 566                         ext_hdr.h_rdma_rkey = cpu_to_be32(rm->rdma.m_rdma_op.r_key);
 567                         rds_message_add_extension(&rm->m_inc.i_hdr,
 568                                         RDS_EXTHDR_RDMA, &ext_hdr, sizeof(ext_hdr));
 569                 }
 570                 if (rm->m_rdma_cookie) {
 571                         rds_message_add_rdma_dest_extension(&rm->m_inc.i_hdr,
 572                                         rds_rdma_cookie_key(rm->m_rdma_cookie),
 573                                         rds_rdma_cookie_offset(rm->m_rdma_cookie));
 574                 }
 575
 576                 /* Note - rds_ib_piggyb_ack clears the ACK_REQUIRED bit, so
 577                  * we should not do this unless we have a chance of at least
 578                  * sticking the header into the send ring. Which is why we
 579                  * should call rds_ib_ring_alloc first. */
 580                 rm->m_inc.i_hdr.h_ack = cpu_to_be64(rds_ib_piggyb_ack(ic));
 581                 rds_message_make_checksum(&rm->m_inc.i_hdr);
 582
 583                 /*
 584                  * Update adv_credits since we reset the ACK_REQUIRED bit.
 585                  */
 586                 rds_ib_send_grab_credits(ic, 0, &posted, 1, RDS_MAX_ADV_CREDIT - adv_credits);
 587                 adv_credits += posted;
 588                 BUG_ON(adv_credits > 255);
 589         }
 590
 591         send = &ic->i_sends[pos];
 592         first = send;
 593         prev = NULL;
 594         scat = &rm->data.m_sg[sg];
 595         sent = 0;
 596         i = 0;
 597
 598         /* Sometimes you want to put a fence between an RDMA
 599          * READ and the following SEND.
 600          * We could either do this all the time
 601          * or when requested by the user. Right now, we let
 602          * the application choose.
 603          */
 604         if (rm->rdma.m_rdma_op.r_active && rm->rdma.m_rdma_op.r_fence)
 605                 send_flags = IB_SEND_FENCE;
 606
 607         /*
 608          * We could be copying the header into the unused tail of the page.
 609          * That would need to be changed in the future when those pages might
 610          * be mapped userspace pages or page cache pages.  So instead we always
 611          * use a second sge and our long-lived ring of mapped headers.  We send
 612          * the header after the data so that the data payload can be aligned on
 613          * the receiver.
 614          */
 615
 616         /* handle a 0-len message */
 617         if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0) {
 618                 rds_ib_xmit_populate_wr(ic, send, pos, 0, 0, send_flags);
 619                 goto add_header;
 620         }
 621
 622         /* if there's data reference it with a chain of work reqs */
 623         for (; i < work_alloc && scat != &rm->data.m_sg[rm->data.m_count]; i++) {
 624                 unsigned int len;
 625
 626                 send = &ic->i_sends[pos];
 627
 628                 len = min(RDS_FRAG_SIZE, ib_sg_dma_len(dev, scat) - off);
 629                 rds_ib_xmit_populate_wr(ic, send, pos,
 630                                 ib_sg_dma_address(dev, scat) + off, len,
 631                                 send_flags);
 632
 633                 /*
 634                  * We want to delay signaling completions just enough to get
 635                  * the batching benefits but not so much that we create dead time
 636                  * on the wire.
 637                  */
 638                 if (ic->i_unsignaled_wrs-- == 0) {
 639                         ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
 640                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 641                 }
 642
 643                 ic->i_unsignaled_bytes -= len;
 644                 if (ic->i_unsignaled_bytes <= 0) {
 645                         ic->i_unsignaled_bytes = rds_ib_sysctl_max_unsig_bytes;
 646                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 647                 }
 648
 649                 /*
 650                  * Always signal the last one if we're stopping due to flow control.
 651                  */
 652                 if (flow_controlled && i == (work_alloc-1))
 653                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 654
 655                 rdsdebug("send %p wr %p num_sge %u next %p\n", send,
 656                          &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
 657
 658                 sent += len;
 659                 off += len;
 660                 if (off == ib_sg_dma_len(dev, scat)) {
 661                         scat++;
 662                         off = 0;
 663                 }
 664
 665 add_header:
 666                 /* Tack on the header after the data. The header SGE should already
 667                  * have been set up to point to the right header buffer. */
 668                 memcpy(&ic->i_send_hdrs[pos], &rm->m_inc.i_hdr, sizeof(struct rds_header));
 669
 670                 if (0) {
 671                         struct rds_header *hdr = &ic->i_send_hdrs[pos];
 672
 673                         printk(KERN_NOTICE "send WR dport=%u flags=0x%x len=%d\n",
 674                                 be16_to_cpu(hdr->h_dport),
 675                                 hdr->h_flags,
 676                                 be32_to_cpu(hdr->h_len));
 677                 }
 678                 if (adv_credits) {
 679                         struct rds_header *hdr = &ic->i_send_hdrs[pos];
 680
 681                         /* add credit and redo the header checksum */
 682                         hdr->h_credit = adv_credits;
 683                         rds_message_make_checksum(hdr);
 684                         adv_credits = 0;
 685                         rds_ib_stats_inc(s_ib_tx_credit_updates);
 686                 }
 687
 688                 if (prev)
 689                         prev->s_wr.next = &send->s_wr;
 690                 prev = send;
 691
 692                 pos = (pos + 1) % ic->i_send_ring.w_nr;
 693         }
 694
 695         /* Account the RDS header in the number of bytes we sent, but just once.
 696          * The caller has no concept of fragmentation. */
 697         if (hdr_off == 0)
 698                 sent += sizeof(struct rds_header);
 699
 700         /* if we finished the message then send completion owns it */
 701         if (scat == &rm->data.m_sg[rm->data.m_count]) {
 702                 prev->s_rm = ic->i_rm;
 703                 prev->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
 704                 ic->i_rm = NULL;
 705         }
 706
 707         if (i < work_alloc) {
 708                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
 709                 work_alloc = i;
 710         }
 711         if (ic->i_flowctl && i < credit_alloc)
 712                 rds_ib_send_add_credits(conn, credit_alloc - i);
 713
 714         /* XXX need to worry about failed_wr and partial sends. */
 715         failed_wr = &first->s_wr;
 716         ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
 717         rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
 718                  first, &first->s_wr, ret, failed_wr);
 719         BUG_ON(failed_wr != &first->s_wr);
 720         if (ret) {
 721                 printk(KERN_WARNING "RDS/IB: ib_post_send to %pI4 "
 722                        "returned %d\n", &conn->c_faddr, ret);
 723                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
 724                 if (prev->s_rm) {
 725                         ic->i_rm = prev->s_rm;
 726                         prev->s_rm = NULL;
 727                 }
 728
 729                 rds_ib_conn_error(ic->conn, "ib_post_send failed\n");
 730                 goto out;
 731         }
 732
 733         ret = sent;
 734 out:
 735         BUG_ON(adv_credits);
 736         return ret;
 737 }
 738
 739 int rds_ib_xmit_rdma(struct rds_connection *conn, struct rds_rdma_op *op)
 740 {
 741         struct rds_ib_connection *ic = conn->c_transport_data;
 742         struct rds_ib_send_work *send = NULL;
 743         struct rds_ib_send_work *first;
 744         struct rds_ib_send_work *prev;
 745         struct ib_send_wr *failed_wr;
 746         struct rds_ib_device *rds_ibdev;
 747         struct scatterlist *scat;
 748         unsigned long len;
 749         u64 remote_addr = op->r_remote_addr;
 750         u32 pos;
 751         u32 work_alloc;
 752         u32 i;
 753         u32 j;
 754         int sent;
 755         int ret;
 756         int num_sge;
 757
 758         rds_ibdev = ib_get_client_data(ic->i_cm_id->device, &rds_ib_client);
 759
 760         /* map the message the first time we see it */
 761         if (!op->r_mapped) {
 762                 op->r_count = ib_dma_map_sg(ic->i_cm_id->device,
 763                                         op->r_sg, op->r_nents, (op->r_write) ?
 764                                         DMA_TO_DEVICE : DMA_FROM_DEVICE);
 765                 rdsdebug("ic %p mapping op %p: %d\n", ic, op, op->r_count);
 766                 if (op->r_count == 0) {
 767                         rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
 768                         ret = -ENOMEM; /* XXX ? */
 769                         goto out;
 770                 }
 771
 772                 op->r_mapped = 1;
 773         }
 774
 775         /*
 776          * Instead of knowing how to return a partial rdma read/write we insist that there
 777          * be enough work requests to send the entire message.
 778          */
 779         i = ceil(op->r_count, rds_ibdev->max_sge);
 780
 781         work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
 782         if (work_alloc != i) {
 783                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
 784                 rds_ib_stats_inc(s_ib_tx_ring_full);
 785                 ret = -ENOMEM;
 786                 goto out;
 787         }
 788
 789         send = &ic->i_sends[pos];
 790         first = send;
 791         prev = NULL;
 792         scat = &op->r_sg[0];
 793         sent = 0;
 794         num_sge = op->r_count;
 795
 796         for (i = 0; i < work_alloc && scat != &op->r_sg[op->r_count]; i++) {
 797                 send->s_wr.send_flags = 0;
 798                 send->s_queued = jiffies;
 799                 /*
 800                  * We want to delay signaling completions just enough to get
 801                  * the batching benefits but not so much that we create dead time on the wire.
 802                  */
 803                 if (ic->i_unsignaled_wrs-- == 0) {
 804                         ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
 805                         send->s_wr.send_flags = IB_SEND_SIGNALED;
 806                 }
 807
 808                 send->s_wr.opcode = op->r_write ? IB_WR_RDMA_WRITE : IB_WR_RDMA_READ;
 809                 send->s_wr.wr.rdma.remote_addr = remote_addr;
 810                 send->s_wr.wr.rdma.rkey = op->r_key;
 811                 send->s_op = op;
 812
 813                 if (num_sge > rds_ibdev->max_sge) {
 814                         send->s_wr.num_sge = rds_ibdev->max_sge;
 815                         num_sge -= rds_ibdev->max_sge;
 816                 } else {
 817                         send->s_wr.num_sge = num_sge;
 818                 }
 819
 820                 send->s_wr.next = NULL;
 821
 822                 if (prev)
 823                         prev->s_wr.next = &send->s_wr;
 824
 825                 for (j = 0; j < send->s_wr.num_sge && scat != &op->r_sg[op->r_count]; j++) {
 826                         len = ib_sg_dma_len(ic->i_cm_id->device, scat);
 827                         send->s_sge[j].addr =
 828                                  ib_sg_dma_address(ic->i_cm_id->device, scat);
 829                         send->s_sge[j].length = len;
 830                         send->s_sge[j].lkey = ic->i_mr->lkey;
 831
 832                         sent += len;
 833                         rdsdebug("ic %p sent %d remote_addr %llu\n", ic, sent, remote_addr);
 834
 835                         remote_addr += len;
 836                         scat++;
 837                 }
 838
 839                 rdsdebug("send %p wr %p num_sge %u next %p\n", send,
 840                         &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
 841
 842                 prev = send;
 843                 if (++send == &ic->i_sends[ic->i_send_ring.w_nr])
 844                         send = ic->i_sends;
 845         }
 846
 847         /* if we finished the message then send completion owns it */
 848         if (scat == &op->r_sg[op->r_count])
 849                 prev->s_wr.send_flags = IB_SEND_SIGNALED;
 850
 851         if (i < work_alloc) {
 852                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
 853                 work_alloc = i;
 854         }
 855
 856         failed_wr = &first->s_wr;
 857         ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
 858         rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
 859                  first, &first->s_wr, ret, failed_wr);
 860         BUG_ON(failed_wr != &first->s_wr);
 861         if (ret) {
 862                 printk(KERN_WARNING "RDS/IB: rdma ib_post_send to %pI4 "
 863                        "returned %d\n", &conn->c_faddr, ret);
 864                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
 865                 goto out;
 866         }
 867
 868         if (unlikely(failed_wr != &first->s_wr)) {
 869                 printk(KERN_WARNING "RDS/IB: ib_post_send() rc=%d, but failed_wqe updated!\n", ret);
 870                 BUG_ON(failed_wr != &first->s_wr);
 871         }
 872
 873
 874 out:
 875         return ret;
 876 }
 877
 878 void rds_ib_xmit_complete(struct rds_connection *conn)
 879 {
 880         struct rds_ib_connection *ic = conn->c_transport_data;
 881
 882         /* We may have a pending ACK or window update we were unable
 883          * to send previously (due to flow control). Try again. */
 884         rds_ib_attempt_ack(ic);
 885 }