RDS: cleanup: remove "== NULL"s and "!= NULL"s in ptr comparisons
[linux-2.6.git] / 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 "rdma.h"
40 #include "ib.h"
41
42 static void rds_ib_send_rdma_complete(struct rds_message *rm,
43                                       int wc_status)
44 {
45         int notify_status;
46
47         switch (wc_status) {
48         case IB_WC_WR_FLUSH_ERR:
49                 return;
50
51         case IB_WC_SUCCESS:
52                 notify_status = RDS_RDMA_SUCCESS;
53                 break;
54
55         case IB_WC_REM_ACCESS_ERR:
56                 notify_status = RDS_RDMA_REMOTE_ERROR;
57                 break;
58
59         default:
60                 notify_status = RDS_RDMA_OTHER_ERROR;
61                 break;
62         }
63         rds_rdma_send_complete(rm, notify_status);
64 }
65
66 static void rds_ib_send_unmap_rdma(struct rds_ib_connection *ic,
67                                    struct rds_rdma_op *op)
68 {
69         if (op->r_mapped) {
70                 ib_dma_unmap_sg(ic->i_cm_id->device,
71                         op->r_sg, op->r_nents,
72                         op->r_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
73                 op->r_mapped = 0;
74         }
75 }
76
77 static void rds_ib_send_unmap_rm(struct rds_ib_connection *ic,
78                           struct rds_ib_send_work *send,
79                           int wc_status)
80 {
81         struct rds_message *rm = send->s_rm;
82
83         rdsdebug("ic %p send %p rm %p\n", ic, send, rm);
84
85         ib_dma_unmap_sg(ic->i_cm_id->device,
86                      rm->m_sg, rm->m_nents,
87                      DMA_TO_DEVICE);
88
89         if (rm->m_rdma_op) {
90                 rds_ib_send_unmap_rdma(ic, rm->m_rdma_op);
91
92                 /* If the user asked for a completion notification on this
93                  * message, we can implement three different semantics:
94                  *  1.  Notify when we received the ACK on the RDS message
95                  *      that was queued with the RDMA. This provides reliable
96                  *      notification of RDMA status at the expense of a one-way
97                  *      packet delay.
98                  *  2.  Notify when the IB stack gives us the completion event for
99                  *      the RDMA operation.
100                  *  3.  Notify when the IB stack gives us the completion event for
101                  *      the accompanying RDS messages.
102                  * Here, we implement approach #3. To implement approach #2,
103                  * call rds_rdma_send_complete from the cq_handler. To implement #1,
104                  * don't call rds_rdma_send_complete at all, and fall back to the notify
105                  * handling in the ACK processing code.
106                  *
107                  * Note: There's no need to explicitly sync any RDMA buffers using
108                  * ib_dma_sync_sg_for_cpu - the completion for the RDMA
109                  * operation itself unmapped the RDMA buffers, which takes care
110                  * of synching.
111                  */
112                 rds_ib_send_rdma_complete(rm, wc_status);
113
114                 if (rm->m_rdma_op->r_write)
115                         rds_stats_add(s_send_rdma_bytes, rm->m_rdma_op->r_bytes);
116                 else
117                         rds_stats_add(s_recv_rdma_bytes, rm->m_rdma_op->r_bytes);
118         }
119
120         /* If anyone waited for this message to get flushed out, wake
121          * them up now */
122         rds_message_unmapped(rm);
123
124         rds_message_put(rm);
125         send->s_rm = NULL;
126 }
127
128 void rds_ib_send_init_ring(struct rds_ib_connection *ic)
129 {
130         struct rds_ib_send_work *send;
131         u32 i;
132
133         for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
134                 struct ib_sge *sge;
135
136                 send->s_rm = NULL;
137                 send->s_op = NULL;
138
139                 send->s_wr.wr_id = i;
140                 send->s_wr.sg_list = send->s_sge;
141                 send->s_wr.num_sge = 1;
142                 send->s_wr.opcode = IB_WR_SEND;
143                 send->s_wr.send_flags = 0;
144                 send->s_wr.ex.imm_data = 0;
145
146                 sge = rds_ib_data_sge(ic, send->s_sge);
147                 sge->lkey = ic->i_mr->lkey;
148
149                 sge = rds_ib_header_sge(ic, send->s_sge);
150                 sge->addr = ic->i_send_hdrs_dma + (i * sizeof(struct rds_header));
151                 sge->length = sizeof(struct rds_header);
152                 sge->lkey = ic->i_mr->lkey;
153         }
154 }
155
156 void rds_ib_send_clear_ring(struct rds_ib_connection *ic)
157 {
158         struct rds_ib_send_work *send;
159         u32 i;
160
161         for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
162                 if (send->s_wr.opcode == 0xdead)
163                         continue;
164                 if (send->s_rm)
165                         rds_ib_send_unmap_rm(ic, send, IB_WC_WR_FLUSH_ERR);
166                 if (send->s_op)
167                         rds_ib_send_unmap_rdma(ic, send->s_op);
168         }
169 }
170
171 /*
172  * The _oldest/_free ring operations here race cleanly with the alloc/unalloc
173  * operations performed in the send path.  As the sender allocs and potentially
174  * unallocs the next free entry in the ring it doesn't alter which is
175  * the next to be freed, which is what this is concerned with.
176  */
177 void rds_ib_send_cq_comp_handler(struct ib_cq *cq, void *context)
178 {
179         struct rds_connection *conn = context;
180         struct rds_ib_connection *ic = conn->c_transport_data;
181         struct ib_wc wc;
182         struct rds_ib_send_work *send;
183         u32 completed;
184         u32 oldest;
185         u32 i = 0;
186         int ret;
187
188         rdsdebug("cq %p conn %p\n", cq, conn);
189         rds_ib_stats_inc(s_ib_tx_cq_call);
190         ret = ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
191         if (ret)
192                 rdsdebug("ib_req_notify_cq send failed: %d\n", ret);
193
194         while (ib_poll_cq(cq, 1, &wc) > 0) {
195                 rdsdebug("wc wr_id 0x%llx status %u byte_len %u imm_data %u\n",
196                          (unsigned long long)wc.wr_id, wc.status, wc.byte_len,
197                          be32_to_cpu(wc.ex.imm_data));
198                 rds_ib_stats_inc(s_ib_tx_cq_event);
199
200                 if (wc.wr_id == RDS_IB_ACK_WR_ID) {
201                         if (ic->i_ack_queued + HZ/2 < jiffies)
202                                 rds_ib_stats_inc(s_ib_tx_stalled);
203                         rds_ib_ack_send_complete(ic);
204                         continue;
205                 }
206
207                 oldest = rds_ib_ring_oldest(&ic->i_send_ring);
208
209                 completed = rds_ib_ring_completed(&ic->i_send_ring, wc.wr_id, oldest);
210
211                 for (i = 0; i < completed; i++) {
212                         send = &ic->i_sends[oldest];
213
214                         /* In the error case, wc.opcode sometimes contains garbage */
215                         switch (send->s_wr.opcode) {
216                         case IB_WR_SEND:
217                                 if (send->s_rm)
218                                         rds_ib_send_unmap_rm(ic, send, wc.status);
219                                 break;
220                         case IB_WR_RDMA_WRITE:
221                         case IB_WR_RDMA_READ:
222                                 /* Nothing to be done - the SG list will be unmapped
223                                  * when the SEND completes. */
224                                 break;
225                         default:
226                                 if (printk_ratelimit())
227                                         printk(KERN_NOTICE
228                                                 "RDS/IB: %s: unexpected opcode 0x%x in WR!\n",
229                                                 __func__, send->s_wr.opcode);
230                                 break;
231                         }
232
233                         send->s_wr.opcode = 0xdead;
234                         send->s_wr.num_sge = 1;
235                         if (send->s_queued + HZ/2 < jiffies)
236                                 rds_ib_stats_inc(s_ib_tx_stalled);
237
238                         /* If a RDMA operation produced an error, signal this right
239                          * away. If we don't, the subsequent SEND that goes with this
240                          * RDMA will be canceled with ERR_WFLUSH, and the application
241                          * never learn that the RDMA failed. */
242                         if (unlikely(wc.status == IB_WC_REM_ACCESS_ERR && send->s_op)) {
243                                 struct rds_message *rm;
244
245                                 rm = rds_send_get_message(conn, send->s_op);
246                                 if (rm) {
247                                         if (rm->m_rdma_op)
248                                                 rds_ib_send_unmap_rdma(ic, rm->m_rdma_op);
249                                         rds_ib_send_rdma_complete(rm, wc.status);
250                                         rds_message_put(rm);
251                                 }
252                         }
253
254                         oldest = (oldest + 1) % ic->i_send_ring.w_nr;
255                 }
256
257                 rds_ib_ring_free(&ic->i_send_ring, completed);
258
259                 if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags) ||
260                     test_bit(0, &conn->c_map_queued))
261                         queue_delayed_work(rds_wq, &conn->c_send_w, 0);
262
263                 /* We expect errors as the qp is drained during shutdown */
264                 if (wc.status != IB_WC_SUCCESS && rds_conn_up(conn)) {
265                         rds_ib_conn_error(conn,
266                                 "send completion on %pI4 "
267                                 "had status %u, disconnecting and reconnecting\n",
268                                 &conn->c_faddr, wc.status);
269                 }
270         }
271 }
272
273 /*
274  * This is the main function for allocating credits when sending
275  * messages.
276  *
277  * Conceptually, we have two counters:
278  *  -   send credits: this tells us how many WRs we're allowed
279  *      to submit without overruning the reciever's queue. For
280  *      each SEND WR we post, we decrement this by one.
281  *
282  *  -   posted credits: this tells us how many WRs we recently
283  *      posted to the receive queue. This value is transferred
284  *      to the peer as a "credit update" in a RDS header field.
285  *      Every time we transmit credits to the peer, we subtract
286  *      the amount of transferred credits from this counter.
287  *
288  * It is essential that we avoid situations where both sides have
289  * exhausted their send credits, and are unable to send new credits
290  * to the peer. We achieve this by requiring that we send at least
291  * one credit update to the peer before exhausting our credits.
292  * When new credits arrive, we subtract one credit that is withheld
293  * until we've posted new buffers and are ready to transmit these
294  * credits (see rds_ib_send_add_credits below).
295  *
296  * The RDS send code is essentially single-threaded; rds_send_xmit
297  * grabs c_send_lock to ensure exclusive access to the send ring.
298  * However, the ACK sending code is independent and can race with
299  * message SENDs.
300  *
301  * In the send path, we need to update the counters for send credits
302  * and the counter of posted buffers atomically - when we use the
303  * last available credit, we cannot allow another thread to race us
304  * and grab the posted credits counter.  Hence, we have to use a
305  * spinlock to protect the credit counter, or use atomics.
306  *
307  * Spinlocks shared between the send and the receive path are bad,
308  * because they create unnecessary delays. An early implementation
309  * using a spinlock showed a 5% degradation in throughput at some
310  * loads.
311  *
312  * This implementation avoids spinlocks completely, putting both
313  * counters into a single atomic, and updating that atomic using
314  * atomic_add (in the receive path, when receiving fresh credits),
315  * and using atomic_cmpxchg when updating the two counters.
316  */
317 int rds_ib_send_grab_credits(struct rds_ib_connection *ic,
318                              u32 wanted, u32 *adv_credits, int need_posted, int max_posted)
319 {
320         unsigned int avail, posted, got = 0, advertise;
321         long oldval, newval;
322
323         *adv_credits = 0;
324         if (!ic->i_flowctl)
325                 return wanted;
326
327 try_again:
328         advertise = 0;
329         oldval = newval = atomic_read(&ic->i_credits);
330         posted = IB_GET_POST_CREDITS(oldval);
331         avail = IB_GET_SEND_CREDITS(oldval);
332
333         rdsdebug("rds_ib_send_grab_credits(%u): credits=%u posted=%u\n",
334                         wanted, avail, posted);
335
336         /* The last credit must be used to send a credit update. */
337         if (avail && !posted)
338                 avail--;
339
340         if (avail < wanted) {
341                 struct rds_connection *conn = ic->i_cm_id->context;
342
343                 /* Oops, there aren't that many credits left! */
344                 set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
345                 got = avail;
346         } else {
347                 /* Sometimes you get what you want, lalala. */
348                 got = wanted;
349         }
350         newval -= IB_SET_SEND_CREDITS(got);
351
352         /*
353          * If need_posted is non-zero, then the caller wants
354          * the posted regardless of whether any send credits are
355          * available.
356          */
357         if (posted && (got || need_posted)) {
358                 advertise = min_t(unsigned int, posted, max_posted);
359                 newval -= IB_SET_POST_CREDITS(advertise);
360         }
361
362         /* Finally bill everything */
363         if (atomic_cmpxchg(&ic->i_credits, oldval, newval) != oldval)
364                 goto try_again;
365
366         *adv_credits = advertise;
367         return got;
368 }
369
370 void rds_ib_send_add_credits(struct rds_connection *conn, unsigned int credits)
371 {
372         struct rds_ib_connection *ic = conn->c_transport_data;
373
374         if (credits == 0)
375                 return;
376
377         rdsdebug("rds_ib_send_add_credits(%u): current=%u%s\n",
378                         credits,
379                         IB_GET_SEND_CREDITS(atomic_read(&ic->i_credits)),
380                         test_bit(RDS_LL_SEND_FULL, &conn->c_flags) ? ", ll_send_full" : "");
381
382         atomic_add(IB_SET_SEND_CREDITS(credits), &ic->i_credits);
383         if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags))
384                 queue_delayed_work(rds_wq, &conn->c_send_w, 0);
385
386         WARN_ON(IB_GET_SEND_CREDITS(credits) >= 16384);
387
388         rds_ib_stats_inc(s_ib_rx_credit_updates);
389 }
390
391 void rds_ib_advertise_credits(struct rds_connection *conn, unsigned int posted)
392 {
393         struct rds_ib_connection *ic = conn->c_transport_data;
394
395         if (posted == 0)
396                 return;
397
398         atomic_add(IB_SET_POST_CREDITS(posted), &ic->i_credits);
399
400         /* Decide whether to send an update to the peer now.
401          * If we would send a credit update for every single buffer we
402          * post, we would end up with an ACK storm (ACK arrives,
403          * consumes buffer, we refill the ring, send ACK to remote
404          * advertising the newly posted buffer... ad inf)
405          *
406          * Performance pretty much depends on how often we send
407          * credit updates - too frequent updates mean lots of ACKs.
408          * Too infrequent updates, and the peer will run out of
409          * credits and has to throttle.
410          * For the time being, 16 seems to be a good compromise.
411          */
412         if (IB_GET_POST_CREDITS(atomic_read(&ic->i_credits)) >= 16)
413                 set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
414 }
415
416 static inline void
417 rds_ib_xmit_populate_wr(struct rds_ib_connection *ic,
418                 struct rds_ib_send_work *send, unsigned int pos,
419                 unsigned long buffer, unsigned int length,
420                 int send_flags)
421 {
422         struct ib_sge *sge;
423
424         WARN_ON(pos != send - ic->i_sends);
425
426         send->s_wr.send_flags = send_flags;
427         send->s_wr.opcode = IB_WR_SEND;
428         send->s_wr.num_sge = 2;
429         send->s_wr.next = NULL;
430         send->s_queued = jiffies;
431         send->s_op = NULL;
432
433         if (length != 0) {
434                 sge = rds_ib_data_sge(ic, send->s_sge);
435                 sge->addr = buffer;
436                 sge->length = length;
437                 sge->lkey = ic->i_mr->lkey;
438
439                 sge = rds_ib_header_sge(ic, send->s_sge);
440         } else {
441                 /* We're sending a packet with no payload. There is only
442                  * one SGE */
443                 send->s_wr.num_sge = 1;
444                 sge = &send->s_sge[0];
445         }
446
447         sge->addr = ic->i_send_hdrs_dma + (pos * sizeof(struct rds_header));
448         sge->length = sizeof(struct rds_header);
449         sge->lkey = ic->i_mr->lkey;
450 }
451
452 /*
453  * This can be called multiple times for a given message.  The first time
454  * we see a message we map its scatterlist into the IB device so that
455  * we can provide that mapped address to the IB scatter gather entries
456  * in the IB work requests.  We translate the scatterlist into a series
457  * of work requests that fragment the message.  These work requests complete
458  * in order so we pass ownership of the message to the completion handler
459  * once we send the final fragment.
460  *
461  * The RDS core uses the c_send_lock to only enter this function once
462  * per connection.  This makes sure that the tx ring alloc/unalloc pairs
463  * don't get out of sync and confuse the ring.
464  */
465 int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
466                 unsigned int hdr_off, unsigned int sg, unsigned int off)
467 {
468         struct rds_ib_connection *ic = conn->c_transport_data;
469         struct ib_device *dev = ic->i_cm_id->device;
470         struct rds_ib_send_work *send = NULL;
471         struct rds_ib_send_work *first;
472         struct rds_ib_send_work *prev;
473         struct ib_send_wr *failed_wr;
474         struct scatterlist *scat;
475         u32 pos;
476         u32 i;
477         u32 work_alloc;
478         u32 credit_alloc;
479         u32 posted;
480         u32 adv_credits = 0;
481         int send_flags = 0;
482         int sent;
483         int ret;
484         int flow_controlled = 0;
485
486         BUG_ON(off % RDS_FRAG_SIZE);
487         BUG_ON(hdr_off != 0 && hdr_off != sizeof(struct rds_header));
488
489         /* Do not send cong updates to IB loopback */
490         if (conn->c_loopback
491             && rm->m_inc.i_hdr.h_flags & RDS_FLAG_CONG_BITMAP) {
492                 rds_cong_map_updated(conn->c_fcong, ~(u64) 0);
493                 return sizeof(struct rds_header) + RDS_CONG_MAP_BYTES;
494         }
495
496         /* FIXME we may overallocate here */
497         if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0)
498                 i = 1;
499         else
500                 i = ceil(be32_to_cpu(rm->m_inc.i_hdr.h_len), RDS_FRAG_SIZE);
501
502         work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
503         if (work_alloc == 0) {
504                 set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
505                 rds_ib_stats_inc(s_ib_tx_ring_full);
506                 ret = -ENOMEM;
507                 goto out;
508         }
509
510         credit_alloc = work_alloc;
511         if (ic->i_flowctl) {
512                 credit_alloc = rds_ib_send_grab_credits(ic, work_alloc, &posted, 0, RDS_MAX_ADV_CREDIT);
513                 adv_credits += posted;
514                 if (credit_alloc < work_alloc) {
515                         rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - credit_alloc);
516                         work_alloc = credit_alloc;
517                         flow_controlled++;
518                 }
519                 if (work_alloc == 0) {
520                         set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
521                         rds_ib_stats_inc(s_ib_tx_throttle);
522                         ret = -ENOMEM;
523                         goto out;
524                 }
525         }
526
527         /* map the message the first time we see it */
528         if (!ic->i_rm) {
529                 /*
530                 printk(KERN_NOTICE "rds_ib_xmit prep msg dport=%u flags=0x%x len=%d\n",
531                                 be16_to_cpu(rm->m_inc.i_hdr.h_dport),
532                                 rm->m_inc.i_hdr.h_flags,
533                                 be32_to_cpu(rm->m_inc.i_hdr.h_len));
534                    */
535                 if (rm->m_nents) {
536                         rm->m_count = ib_dma_map_sg(dev,
537                                          rm->m_sg, rm->m_nents, DMA_TO_DEVICE);
538                         rdsdebug("ic %p mapping rm %p: %d\n", ic, rm, rm->m_count);
539                         if (rm->m_count == 0) {
540                                 rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
541                                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
542                                 ret = -ENOMEM; /* XXX ? */
543                                 goto out;
544                         }
545                 } else {
546                         rm->m_count = 0;
547                 }
548
549                 ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
550                 ic->i_unsignaled_bytes = rds_ib_sysctl_max_unsig_bytes;
551                 rds_message_addref(rm);
552                 ic->i_rm = rm;
553
554                 /* Finalize the header */
555                 if (test_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags))
556                         rm->m_inc.i_hdr.h_flags |= RDS_FLAG_ACK_REQUIRED;
557                 if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
558                         rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;
559
560                 /* If it has a RDMA op, tell the peer we did it. This is
561                  * used by the peer to release use-once RDMA MRs. */
562                 if (rm->m_rdma_op) {
563                         struct rds_ext_header_rdma ext_hdr;
564
565                         ext_hdr.h_rdma_rkey = cpu_to_be32(rm->m_rdma_op->r_key);
566                         rds_message_add_extension(&rm->m_inc.i_hdr,
567                                         RDS_EXTHDR_RDMA, &ext_hdr, sizeof(ext_hdr));
568                 }
569                 if (rm->m_rdma_cookie) {
570                         rds_message_add_rdma_dest_extension(&rm->m_inc.i_hdr,
571                                         rds_rdma_cookie_key(rm->m_rdma_cookie),
572                                         rds_rdma_cookie_offset(rm->m_rdma_cookie));
573                 }
574
575                 /* Note - rds_ib_piggyb_ack clears the ACK_REQUIRED bit, so
576                  * we should not do this unless we have a chance of at least
577                  * sticking the header into the send ring. Which is why we
578                  * should call rds_ib_ring_alloc first. */
579                 rm->m_inc.i_hdr.h_ack = cpu_to_be64(rds_ib_piggyb_ack(ic));
580                 rds_message_make_checksum(&rm->m_inc.i_hdr);
581
582                 /*
583                  * Update adv_credits since we reset the ACK_REQUIRED bit.
584                  */
585                 rds_ib_send_grab_credits(ic, 0, &posted, 1, RDS_MAX_ADV_CREDIT - adv_credits);
586                 adv_credits += posted;
587                 BUG_ON(adv_credits > 255);
588         }
589
590         send = &ic->i_sends[pos];
591         first = send;
592         prev = NULL;
593         scat = &rm->m_sg[sg];
594         sent = 0;
595         i = 0;
596
597         /* Sometimes you want to put a fence between an RDMA
598          * READ and the following SEND.
599          * We could either do this all the time
600          * or when requested by the user. Right now, we let
601          * the application choose.
602          */
603         if (rm->m_rdma_op && rm->m_rdma_op->r_fence)
604                 send_flags = IB_SEND_FENCE;
605
606         /*
607          * We could be copying the header into the unused tail of the page.
608          * That would need to be changed in the future when those pages might
609          * be mapped userspace pages or page cache pages.  So instead we always
610          * use a second sge and our long-lived ring of mapped headers.  We send
611          * the header after the data so that the data payload can be aligned on
612          * the receiver.
613          */
614
615         /* handle a 0-len message */
616         if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0) {
617                 rds_ib_xmit_populate_wr(ic, send, pos, 0, 0, send_flags);
618                 goto add_header;
619         }
620
621         /* if there's data reference it with a chain of work reqs */
622         for (; i < work_alloc && scat != &rm->m_sg[rm->m_count]; i++) {
623                 unsigned int len;
624
625                 send = &ic->i_sends[pos];
626
627                 len = min(RDS_FRAG_SIZE, ib_sg_dma_len(dev, scat) - off);
628                 rds_ib_xmit_populate_wr(ic, send, pos,
629                                 ib_sg_dma_address(dev, scat) + off, len,
630                                 send_flags);
631
632                 /*
633                  * We want to delay signaling completions just enough to get
634                  * the batching benefits but not so much that we create dead time
635                  * on the wire.
636                  */
637                 if (ic->i_unsignaled_wrs-- == 0) {
638                         ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
639                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
640                 }
641
642                 ic->i_unsignaled_bytes -= len;
643                 if (ic->i_unsignaled_bytes <= 0) {
644                         ic->i_unsignaled_bytes = rds_ib_sysctl_max_unsig_bytes;
645                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
646                 }
647
648                 /*
649                  * Always signal the last one if we're stopping due to flow control.
650                  */
651                 if (flow_controlled && i == (work_alloc-1))
652                         send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
653
654                 rdsdebug("send %p wr %p num_sge %u next %p\n", send,
655                          &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
656
657                 sent += len;
658                 off += len;
659                 if (off == ib_sg_dma_len(dev, scat)) {
660                         scat++;
661                         off = 0;
662                 }
663
664 add_header:
665                 /* Tack on the header after the data. The header SGE should already
666                  * have been set up to point to the right header buffer. */
667                 memcpy(&ic->i_send_hdrs[pos], &rm->m_inc.i_hdr, sizeof(struct rds_header));
668
669                 if (0) {
670                         struct rds_header *hdr = &ic->i_send_hdrs[pos];
671
672                         printk(KERN_NOTICE "send WR dport=%u flags=0x%x len=%d\n",
673                                 be16_to_cpu(hdr->h_dport),
674                                 hdr->h_flags,
675                                 be32_to_cpu(hdr->h_len));
676                 }
677                 if (adv_credits) {
678                         struct rds_header *hdr = &ic->i_send_hdrs[pos];
679
680                         /* add credit and redo the header checksum */
681                         hdr->h_credit = adv_credits;
682                         rds_message_make_checksum(hdr);
683                         adv_credits = 0;
684                         rds_ib_stats_inc(s_ib_tx_credit_updates);
685                 }
686
687                 if (prev)
688                         prev->s_wr.next = &send->s_wr;
689                 prev = send;
690
691                 pos = (pos + 1) % ic->i_send_ring.w_nr;
692         }
693
694         /* Account the RDS header in the number of bytes we sent, but just once.
695          * The caller has no concept of fragmentation. */
696         if (hdr_off == 0)
697                 sent += sizeof(struct rds_header);
698
699         /* if we finished the message then send completion owns it */
700         if (scat == &rm->m_sg[rm->m_count]) {
701                 prev->s_rm = ic->i_rm;
702                 prev->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
703                 ic->i_rm = NULL;
704         }
705
706         if (i < work_alloc) {
707                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
708                 work_alloc = i;
709         }
710         if (ic->i_flowctl && i < credit_alloc)
711                 rds_ib_send_add_credits(conn, credit_alloc - i);
712
713         /* XXX need to worry about failed_wr and partial sends. */
714         failed_wr = &first->s_wr;
715         ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
716         rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
717                  first, &first->s_wr, ret, failed_wr);
718         BUG_ON(failed_wr != &first->s_wr);
719         if (ret) {
720                 printk(KERN_WARNING "RDS/IB: ib_post_send to %pI4 "
721                        "returned %d\n", &conn->c_faddr, ret);
722                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
723                 if (prev->s_rm) {
724                         ic->i_rm = prev->s_rm;
725                         prev->s_rm = NULL;
726                 }
727
728                 rds_ib_conn_error(ic->conn, "ib_post_send failed\n");
729                 goto out;
730         }
731
732         ret = sent;
733 out:
734         BUG_ON(adv_credits);
735         return ret;
736 }
737
738 int rds_ib_xmit_rdma(struct rds_connection *conn, struct rds_rdma_op *op)
739 {
740         struct rds_ib_connection *ic = conn->c_transport_data;
741         struct rds_ib_send_work *send = NULL;
742         struct rds_ib_send_work *first;
743         struct rds_ib_send_work *prev;
744         struct ib_send_wr *failed_wr;
745         struct rds_ib_device *rds_ibdev;
746         struct scatterlist *scat;
747         unsigned long len;
748         u64 remote_addr = op->r_remote_addr;
749         u32 pos;
750         u32 work_alloc;
751         u32 i;
752         u32 j;
753         int sent;
754         int ret;
755         int num_sge;
756
757         rds_ibdev = ib_get_client_data(ic->i_cm_id->device, &rds_ib_client);
758
759         /* map the message the first time we see it */
760         if (!op->r_mapped) {
761                 op->r_count = ib_dma_map_sg(ic->i_cm_id->device,
762                                         op->r_sg, op->r_nents, (op->r_write) ?
763                                         DMA_TO_DEVICE : DMA_FROM_DEVICE);
764                 rdsdebug("ic %p mapping op %p: %d\n", ic, op, op->r_count);
765                 if (op->r_count == 0) {
766                         rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
767                         ret = -ENOMEM; /* XXX ? */
768                         goto out;
769                 }
770
771                 op->r_mapped = 1;
772         }
773
774         /*
775          * Instead of knowing how to return a partial rdma read/write we insist that there
776          * be enough work requests to send the entire message.
777          */
778         i = ceil(op->r_count, rds_ibdev->max_sge);
779
780         work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
781         if (work_alloc != i) {
782                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
783                 rds_ib_stats_inc(s_ib_tx_ring_full);
784                 ret = -ENOMEM;
785                 goto out;
786         }
787
788         send = &ic->i_sends[pos];
789         first = send;
790         prev = NULL;
791         scat = &op->r_sg[0];
792         sent = 0;
793         num_sge = op->r_count;
794
795         for (i = 0; i < work_alloc && scat != &op->r_sg[op->r_count]; i++) {
796                 send->s_wr.send_flags = 0;
797                 send->s_queued = jiffies;
798                 /*
799                  * We want to delay signaling completions just enough to get
800                  * the batching benefits but not so much that we create dead time on the wire.
801                  */
802                 if (ic->i_unsignaled_wrs-- == 0) {
803                         ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
804                         send->s_wr.send_flags = IB_SEND_SIGNALED;
805                 }
806
807                 send->s_wr.opcode = op->r_write ? IB_WR_RDMA_WRITE : IB_WR_RDMA_READ;
808                 send->s_wr.wr.rdma.remote_addr = remote_addr;
809                 send->s_wr.wr.rdma.rkey = op->r_key;
810                 send->s_op = op;
811
812                 if (num_sge > rds_ibdev->max_sge) {
813                         send->s_wr.num_sge = rds_ibdev->max_sge;
814                         num_sge -= rds_ibdev->max_sge;
815                 } else {
816                         send->s_wr.num_sge = num_sge;
817                 }
818
819                 send->s_wr.next = NULL;
820
821                 if (prev)
822                         prev->s_wr.next = &send->s_wr;
823
824                 for (j = 0; j < send->s_wr.num_sge && scat != &op->r_sg[op->r_count]; j++) {
825                         len = ib_sg_dma_len(ic->i_cm_id->device, scat);
826                         send->s_sge[j].addr =
827                                  ib_sg_dma_address(ic->i_cm_id->device, scat);
828                         send->s_sge[j].length = len;
829                         send->s_sge[j].lkey = ic->i_mr->lkey;
830
831                         sent += len;
832                         rdsdebug("ic %p sent %d remote_addr %llu\n", ic, sent, remote_addr);
833
834                         remote_addr += len;
835                         scat++;
836                 }
837
838                 rdsdebug("send %p wr %p num_sge %u next %p\n", send,
839                         &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
840
841                 prev = send;
842                 if (++send == &ic->i_sends[ic->i_send_ring.w_nr])
843                         send = ic->i_sends;
844         }
845
846         /* if we finished the message then send completion owns it */
847         if (scat == &op->r_sg[op->r_count])
848                 prev->s_wr.send_flags = IB_SEND_SIGNALED;
849
850         if (i < work_alloc) {
851                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
852                 work_alloc = i;
853         }
854
855         failed_wr = &first->s_wr;
856         ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
857         rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
858                  first, &first->s_wr, ret, failed_wr);
859         BUG_ON(failed_wr != &first->s_wr);
860         if (ret) {
861                 printk(KERN_WARNING "RDS/IB: rdma ib_post_send to %pI4 "
862                        "returned %d\n", &conn->c_faddr, ret);
863                 rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
864                 goto out;
865         }
866
867         if (unlikely(failed_wr != &first->s_wr)) {
868                 printk(KERN_WARNING "RDS/IB: ib_post_send() rc=%d, but failed_wqe updated!\n", ret);
869                 BUG_ON(failed_wr != &first->s_wr);
870         }
871
872
873 out:
874         return ret;
875 }
876
877 void rds_ib_xmit_complete(struct rds_connection *conn)
878 {
879         struct rds_ib_connection *ic = conn->c_transport_data;
880
881         /* We may have a pending ACK or window update we were unable
882          * to send previously (due to flow control). Try again. */
883         rds_ib_attempt_ack(ic);
884 }