Root/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
42static 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
66static 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
77static 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 != NULL) {
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
128void 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
156void 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 */
177void 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                    rds_ib_send_rdma_complete(rm, wc.status);
248            }
249
250            oldest = (oldest + 1) % ic->i_send_ring.w_nr;
251        }
252
253        rds_ib_ring_free(&ic->i_send_ring, completed);
254
255        if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags) ||
256            test_bit(0, &conn->c_map_queued))
257            queue_delayed_work(rds_wq, &conn->c_send_w, 0);
258
259        /* We expect errors as the qp is drained during shutdown */
260        if (wc.status != IB_WC_SUCCESS && rds_conn_up(conn)) {
261            rds_ib_conn_error(conn,
262                "send completion on %pI4 "
263                "had status %u, disconnecting and reconnecting\n",
264                &conn->c_faddr, wc.status);
265        }
266    }
267}
268
269/*
270 * This is the main function for allocating credits when sending
271 * messages.
272 *
273 * Conceptually, we have two counters:
274 * - send credits: this tells us how many WRs we're allowed
275 * to submit without overruning the reciever's queue. For
276 * each SEND WR we post, we decrement this by one.
277 *
278 * - posted credits: this tells us how many WRs we recently
279 * posted to the receive queue. This value is transferred
280 * to the peer as a "credit update" in a RDS header field.
281 * Every time we transmit credits to the peer, we subtract
282 * the amount of transferred credits from this counter.
283 *
284 * It is essential that we avoid situations where both sides have
285 * exhausted their send credits, and are unable to send new credits
286 * to the peer. We achieve this by requiring that we send at least
287 * one credit update to the peer before exhausting our credits.
288 * When new credits arrive, we subtract one credit that is withheld
289 * until we've posted new buffers and are ready to transmit these
290 * credits (see rds_ib_send_add_credits below).
291 *
292 * The RDS send code is essentially single-threaded; rds_send_xmit
293 * grabs c_send_lock to ensure exclusive access to the send ring.
294 * However, the ACK sending code is independent and can race with
295 * message SENDs.
296 *
297 * In the send path, we need to update the counters for send credits
298 * and the counter of posted buffers atomically - when we use the
299 * last available credit, we cannot allow another thread to race us
300 * and grab the posted credits counter. Hence, we have to use a
301 * spinlock to protect the credit counter, or use atomics.
302 *
303 * Spinlocks shared between the send and the receive path are bad,
304 * because they create unnecessary delays. An early implementation
305 * using a spinlock showed a 5% degradation in throughput at some
306 * loads.
307 *
308 * This implementation avoids spinlocks completely, putting both
309 * counters into a single atomic, and updating that atomic using
310 * atomic_add (in the receive path, when receiving fresh credits),
311 * and using atomic_cmpxchg when updating the two counters.
312 */
313int rds_ib_send_grab_credits(struct rds_ib_connection *ic,
314                 u32 wanted, u32 *adv_credits, int need_posted, int max_posted)
315{
316    unsigned int avail, posted, got = 0, advertise;
317    long oldval, newval;
318
319    *adv_credits = 0;
320    if (!ic->i_flowctl)
321        return wanted;
322
323try_again:
324    advertise = 0;
325    oldval = newval = atomic_read(&ic->i_credits);
326    posted = IB_GET_POST_CREDITS(oldval);
327    avail = IB_GET_SEND_CREDITS(oldval);
328
329    rdsdebug("rds_ib_send_grab_credits(%u): credits=%u posted=%u\n",
330            wanted, avail, posted);
331
332    /* The last credit must be used to send a credit update. */
333    if (avail && !posted)
334        avail--;
335
336    if (avail < wanted) {
337        struct rds_connection *conn = ic->i_cm_id->context;
338
339        /* Oops, there aren't that many credits left! */
340        set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
341        got = avail;
342    } else {
343        /* Sometimes you get what you want, lalala. */
344        got = wanted;
345    }
346    newval -= IB_SET_SEND_CREDITS(got);
347
348    /*
349     * If need_posted is non-zero, then the caller wants
350     * the posted regardless of whether any send credits are
351     * available.
352     */
353    if (posted && (got || need_posted)) {
354        advertise = min_t(unsigned int, posted, max_posted);
355        newval -= IB_SET_POST_CREDITS(advertise);
356    }
357
358    /* Finally bill everything */
359    if (atomic_cmpxchg(&ic->i_credits, oldval, newval) != oldval)
360        goto try_again;
361
362    *adv_credits = advertise;
363    return got;
364}
365
366void rds_ib_send_add_credits(struct rds_connection *conn, unsigned int credits)
367{
368    struct rds_ib_connection *ic = conn->c_transport_data;
369
370    if (credits == 0)
371        return;
372
373    rdsdebug("rds_ib_send_add_credits(%u): current=%u%s\n",
374            credits,
375            IB_GET_SEND_CREDITS(atomic_read(&ic->i_credits)),
376            test_bit(RDS_LL_SEND_FULL, &conn->c_flags) ? ", ll_send_full" : "");
377
378    atomic_add(IB_SET_SEND_CREDITS(credits), &ic->i_credits);
379    if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags))
380        queue_delayed_work(rds_wq, &conn->c_send_w, 0);
381
382    WARN_ON(IB_GET_SEND_CREDITS(credits) >= 16384);
383
384    rds_ib_stats_inc(s_ib_rx_credit_updates);
385}
386
387void rds_ib_advertise_credits(struct rds_connection *conn, unsigned int posted)
388{
389    struct rds_ib_connection *ic = conn->c_transport_data;
390
391    if (posted == 0)
392        return;
393
394    atomic_add(IB_SET_POST_CREDITS(posted), &ic->i_credits);
395
396    /* Decide whether to send an update to the peer now.
397     * If we would send a credit update for every single buffer we
398     * post, we would end up with an ACK storm (ACK arrives,
399     * consumes buffer, we refill the ring, send ACK to remote
400     * advertising the newly posted buffer... ad inf)
401     *
402     * Performance pretty much depends on how often we send
403     * credit updates - too frequent updates mean lots of ACKs.
404     * Too infrequent updates, and the peer will run out of
405     * credits and has to throttle.
406     * For the time being, 16 seems to be a good compromise.
407     */
408    if (IB_GET_POST_CREDITS(atomic_read(&ic->i_credits)) >= 16)
409        set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
410}
411
412static inline void
413rds_ib_xmit_populate_wr(struct rds_ib_connection *ic,
414        struct rds_ib_send_work *send, unsigned int pos,
415        unsigned long buffer, unsigned int length,
416        int send_flags)
417{
418    struct ib_sge *sge;
419
420    WARN_ON(pos != send - ic->i_sends);
421
422    send->s_wr.send_flags = send_flags;
423    send->s_wr.opcode = IB_WR_SEND;
424    send->s_wr.num_sge = 2;
425    send->s_wr.next = NULL;
426    send->s_queued = jiffies;
427    send->s_op = NULL;
428
429    if (length != 0) {
430        sge = rds_ib_data_sge(ic, send->s_sge);
431        sge->addr = buffer;
432        sge->length = length;
433        sge->lkey = ic->i_mr->lkey;
434
435        sge = rds_ib_header_sge(ic, send->s_sge);
436    } else {
437        /* We're sending a packet with no payload. There is only
438         * one SGE */
439        send->s_wr.num_sge = 1;
440        sge = &send->s_sge[0];
441    }
442
443    sge->addr = ic->i_send_hdrs_dma + (pos * sizeof(struct rds_header));
444    sge->length = sizeof(struct rds_header);
445    sge->lkey = ic->i_mr->lkey;
446}
447
448/*
449 * This can be called multiple times for a given message. The first time
450 * we see a message we map its scatterlist into the IB device so that
451 * we can provide that mapped address to the IB scatter gather entries
452 * in the IB work requests. We translate the scatterlist into a series
453 * of work requests that fragment the message. These work requests complete
454 * in order so we pass ownership of the message to the completion handler
455 * once we send the final fragment.
456 *
457 * The RDS core uses the c_send_lock to only enter this function once
458 * per connection. This makes sure that the tx ring alloc/unalloc pairs
459 * don't get out of sync and confuse the ring.
460 */
461int rds_ib_xmit(struct rds_connection *conn, struct rds_message *rm,
462        unsigned int hdr_off, unsigned int sg, unsigned int off)
463{
464    struct rds_ib_connection *ic = conn->c_transport_data;
465    struct ib_device *dev = ic->i_cm_id->device;
466    struct rds_ib_send_work *send = NULL;
467    struct rds_ib_send_work *first;
468    struct rds_ib_send_work *prev;
469    struct ib_send_wr *failed_wr;
470    struct scatterlist *scat;
471    u32 pos;
472    u32 i;
473    u32 work_alloc;
474    u32 credit_alloc;
475    u32 posted;
476    u32 adv_credits = 0;
477    int send_flags = 0;
478    int sent;
479    int ret;
480    int flow_controlled = 0;
481
482    BUG_ON(off % RDS_FRAG_SIZE);
483    BUG_ON(hdr_off != 0 && hdr_off != sizeof(struct rds_header));
484
485    /* FIXME we may overallocate here */
486    if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0)
487        i = 1;
488    else
489        i = ceil(be32_to_cpu(rm->m_inc.i_hdr.h_len), RDS_FRAG_SIZE);
490
491    work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
492    if (work_alloc == 0) {
493        set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
494        rds_ib_stats_inc(s_ib_tx_ring_full);
495        ret = -ENOMEM;
496        goto out;
497    }
498
499    credit_alloc = work_alloc;
500    if (ic->i_flowctl) {
501        credit_alloc = rds_ib_send_grab_credits(ic, work_alloc, &posted, 0, RDS_MAX_ADV_CREDIT);
502        adv_credits += posted;
503        if (credit_alloc < work_alloc) {
504            rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - credit_alloc);
505            work_alloc = credit_alloc;
506            flow_controlled++;
507        }
508        if (work_alloc == 0) {
509            set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
510            rds_ib_stats_inc(s_ib_tx_throttle);
511            ret = -ENOMEM;
512            goto out;
513        }
514    }
515
516    /* map the message the first time we see it */
517    if (ic->i_rm == NULL) {
518        /*
519        printk(KERN_NOTICE "rds_ib_xmit prep msg dport=%u flags=0x%x len=%d\n",
520                be16_to_cpu(rm->m_inc.i_hdr.h_dport),
521                rm->m_inc.i_hdr.h_flags,
522                be32_to_cpu(rm->m_inc.i_hdr.h_len));
523           */
524        if (rm->m_nents) {
525            rm->m_count = ib_dma_map_sg(dev,
526                     rm->m_sg, rm->m_nents, DMA_TO_DEVICE);
527            rdsdebug("ic %p mapping rm %p: %d\n", ic, rm, rm->m_count);
528            if (rm->m_count == 0) {
529                rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
530                rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
531                ret = -ENOMEM; /* XXX ? */
532                goto out;
533            }
534        } else {
535            rm->m_count = 0;
536        }
537
538        ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
539        ic->i_unsignaled_bytes = rds_ib_sysctl_max_unsig_bytes;
540        rds_message_addref(rm);
541        ic->i_rm = rm;
542
543        /* Finalize the header */
544        if (test_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags))
545            rm->m_inc.i_hdr.h_flags |= RDS_FLAG_ACK_REQUIRED;
546        if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
547            rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;
548
549        /* If it has a RDMA op, tell the peer we did it. This is
550         * used by the peer to release use-once RDMA MRs. */
551        if (rm->m_rdma_op) {
552            struct rds_ext_header_rdma ext_hdr;
553
554            ext_hdr.h_rdma_rkey = cpu_to_be32(rm->m_rdma_op->r_key);
555            rds_message_add_extension(&rm->m_inc.i_hdr,
556                    RDS_EXTHDR_RDMA, &ext_hdr, sizeof(ext_hdr));
557        }
558        if (rm->m_rdma_cookie) {
559            rds_message_add_rdma_dest_extension(&rm->m_inc.i_hdr,
560                    rds_rdma_cookie_key(rm->m_rdma_cookie),
561                    rds_rdma_cookie_offset(rm->m_rdma_cookie));
562        }
563
564        /* Note - rds_ib_piggyb_ack clears the ACK_REQUIRED bit, so
565         * we should not do this unless we have a chance of at least
566         * sticking the header into the send ring. Which is why we
567         * should call rds_ib_ring_alloc first. */
568        rm->m_inc.i_hdr.h_ack = cpu_to_be64(rds_ib_piggyb_ack(ic));
569        rds_message_make_checksum(&rm->m_inc.i_hdr);
570
571        /*
572         * Update adv_credits since we reset the ACK_REQUIRED bit.
573         */
574        rds_ib_send_grab_credits(ic, 0, &posted, 1, RDS_MAX_ADV_CREDIT - adv_credits);
575        adv_credits += posted;
576        BUG_ON(adv_credits > 255);
577    } else if (ic->i_rm != rm)
578        BUG();
579
580    send = &ic->i_sends[pos];
581    first = send;
582    prev = NULL;
583    scat = &rm->m_sg[sg];
584    sent = 0;
585    i = 0;
586
587    /* Sometimes you want to put a fence between an RDMA
588     * READ and the following SEND.
589     * We could either do this all the time
590     * or when requested by the user. Right now, we let
591     * the application choose.
592     */
593    if (rm->m_rdma_op && rm->m_rdma_op->r_fence)
594        send_flags = IB_SEND_FENCE;
595
596    /*
597     * We could be copying the header into the unused tail of the page.
598     * That would need to be changed in the future when those pages might
599     * be mapped userspace pages or page cache pages. So instead we always
600     * use a second sge and our long-lived ring of mapped headers. We send
601     * the header after the data so that the data payload can be aligned on
602     * the receiver.
603     */
604
605    /* handle a 0-len message */
606    if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0) {
607        rds_ib_xmit_populate_wr(ic, send, pos, 0, 0, send_flags);
608        goto add_header;
609    }
610
611    /* if there's data reference it with a chain of work reqs */
612    for (; i < work_alloc && scat != &rm->m_sg[rm->m_count]; i++) {
613        unsigned int len;
614
615        send = &ic->i_sends[pos];
616
617        len = min(RDS_FRAG_SIZE, ib_sg_dma_len(dev, scat) - off);
618        rds_ib_xmit_populate_wr(ic, send, pos,
619                ib_sg_dma_address(dev, scat) + off, len,
620                send_flags);
621
622        /*
623         * We want to delay signaling completions just enough to get
624         * the batching benefits but not so much that we create dead time
625         * on the wire.
626         */
627        if (ic->i_unsignaled_wrs-- == 0) {
628            ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
629            send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
630        }
631
632        ic->i_unsignaled_bytes -= len;
633        if (ic->i_unsignaled_bytes <= 0) {
634            ic->i_unsignaled_bytes = rds_ib_sysctl_max_unsig_bytes;
635            send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
636        }
637
638        /*
639         * Always signal the last one if we're stopping due to flow control.
640         */
641        if (flow_controlled && i == (work_alloc-1))
642            send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
643
644        rdsdebug("send %p wr %p num_sge %u next %p\n", send,
645             &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
646
647        sent += len;
648        off += len;
649        if (off == ib_sg_dma_len(dev, scat)) {
650            scat++;
651            off = 0;
652        }
653
654add_header:
655        /* Tack on the header after the data. The header SGE should already
656         * have been set up to point to the right header buffer. */
657        memcpy(&ic->i_send_hdrs[pos], &rm->m_inc.i_hdr, sizeof(struct rds_header));
658
659        if (0) {
660            struct rds_header *hdr = &ic->i_send_hdrs[pos];
661
662            printk(KERN_NOTICE "send WR dport=%u flags=0x%x len=%d\n",
663                be16_to_cpu(hdr->h_dport),
664                hdr->h_flags,
665                be32_to_cpu(hdr->h_len));
666        }
667        if (adv_credits) {
668            struct rds_header *hdr = &ic->i_send_hdrs[pos];
669
670            /* add credit and redo the header checksum */
671            hdr->h_credit = adv_credits;
672            rds_message_make_checksum(hdr);
673            adv_credits = 0;
674            rds_ib_stats_inc(s_ib_tx_credit_updates);
675        }
676
677        if (prev)
678            prev->s_wr.next = &send->s_wr;
679        prev = send;
680
681        pos = (pos + 1) % ic->i_send_ring.w_nr;
682    }
683
684    /* Account the RDS header in the number of bytes we sent, but just once.
685     * The caller has no concept of fragmentation. */
686    if (hdr_off == 0)
687        sent += sizeof(struct rds_header);
688
689    /* if we finished the message then send completion owns it */
690    if (scat == &rm->m_sg[rm->m_count]) {
691        prev->s_rm = ic->i_rm;
692        prev->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
693        ic->i_rm = NULL;
694    }
695
696    if (i < work_alloc) {
697        rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
698        work_alloc = i;
699    }
700    if (ic->i_flowctl && i < credit_alloc)
701        rds_ib_send_add_credits(conn, credit_alloc - i);
702
703    /* XXX need to worry about failed_wr and partial sends. */
704    failed_wr = &first->s_wr;
705    ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
706    rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
707         first, &first->s_wr, ret, failed_wr);
708    BUG_ON(failed_wr != &first->s_wr);
709    if (ret) {
710        printk(KERN_WARNING "RDS/IB: ib_post_send to %pI4 "
711               "returned %d\n", &conn->c_faddr, ret);
712        rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
713        if (prev->s_rm) {
714            ic->i_rm = prev->s_rm;
715            prev->s_rm = NULL;
716        }
717        /* Finesse this later */
718        BUG();
719        goto out;
720    }
721
722    ret = sent;
723out:
724    BUG_ON(adv_credits);
725    return ret;
726}
727
728int rds_ib_xmit_rdma(struct rds_connection *conn, struct rds_rdma_op *op)
729{
730    struct rds_ib_connection *ic = conn->c_transport_data;
731    struct rds_ib_send_work *send = NULL;
732    struct rds_ib_send_work *first;
733    struct rds_ib_send_work *prev;
734    struct ib_send_wr *failed_wr;
735    struct rds_ib_device *rds_ibdev;
736    struct scatterlist *scat;
737    unsigned long len;
738    u64 remote_addr = op->r_remote_addr;
739    u32 pos;
740    u32 work_alloc;
741    u32 i;
742    u32 j;
743    int sent;
744    int ret;
745    int num_sge;
746
747    rds_ibdev = ib_get_client_data(ic->i_cm_id->device, &rds_ib_client);
748
749    /* map the message the first time we see it */
750    if (!op->r_mapped) {
751        op->r_count = ib_dma_map_sg(ic->i_cm_id->device,
752                    op->r_sg, op->r_nents, (op->r_write) ?
753                    DMA_TO_DEVICE : DMA_FROM_DEVICE);
754        rdsdebug("ic %p mapping op %p: %d\n", ic, op, op->r_count);
755        if (op->r_count == 0) {
756            rds_ib_stats_inc(s_ib_tx_sg_mapping_failure);
757            ret = -ENOMEM; /* XXX ? */
758            goto out;
759        }
760
761        op->r_mapped = 1;
762    }
763
764    /*
765     * Instead of knowing how to return a partial rdma read/write we insist that there
766     * be enough work requests to send the entire message.
767     */
768    i = ceil(op->r_count, rds_ibdev->max_sge);
769
770    work_alloc = rds_ib_ring_alloc(&ic->i_send_ring, i, &pos);
771    if (work_alloc != i) {
772        rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
773        rds_ib_stats_inc(s_ib_tx_ring_full);
774        ret = -ENOMEM;
775        goto out;
776    }
777
778    send = &ic->i_sends[pos];
779    first = send;
780    prev = NULL;
781    scat = &op->r_sg[0];
782    sent = 0;
783    num_sge = op->r_count;
784
785    for (i = 0; i < work_alloc && scat != &op->r_sg[op->r_count]; i++) {
786        send->s_wr.send_flags = 0;
787        send->s_queued = jiffies;
788        /*
789         * We want to delay signaling completions just enough to get
790         * the batching benefits but not so much that we create dead time on the wire.
791         */
792        if (ic->i_unsignaled_wrs-- == 0) {
793            ic->i_unsignaled_wrs = rds_ib_sysctl_max_unsig_wrs;
794            send->s_wr.send_flags = IB_SEND_SIGNALED;
795        }
796
797        send->s_wr.opcode = op->r_write ? IB_WR_RDMA_WRITE : IB_WR_RDMA_READ;
798        send->s_wr.wr.rdma.remote_addr = remote_addr;
799        send->s_wr.wr.rdma.rkey = op->r_key;
800        send->s_op = op;
801
802        if (num_sge > rds_ibdev->max_sge) {
803            send->s_wr.num_sge = rds_ibdev->max_sge;
804            num_sge -= rds_ibdev->max_sge;
805        } else {
806            send->s_wr.num_sge = num_sge;
807        }
808
809        send->s_wr.next = NULL;
810
811        if (prev)
812            prev->s_wr.next = &send->s_wr;
813
814        for (j = 0; j < send->s_wr.num_sge && scat != &op->r_sg[op->r_count]; j++) {
815            len = ib_sg_dma_len(ic->i_cm_id->device, scat);
816            send->s_sge[j].addr =
817                 ib_sg_dma_address(ic->i_cm_id->device, scat);
818            send->s_sge[j].length = len;
819            send->s_sge[j].lkey = ic->i_mr->lkey;
820
821            sent += len;
822            rdsdebug("ic %p sent %d remote_addr %llu\n", ic, sent, remote_addr);
823
824            remote_addr += len;
825            scat++;
826        }
827
828        rdsdebug("send %p wr %p num_sge %u next %p\n", send,
829            &send->s_wr, send->s_wr.num_sge, send->s_wr.next);
830
831        prev = send;
832        if (++send == &ic->i_sends[ic->i_send_ring.w_nr])
833            send = ic->i_sends;
834    }
835
836    /* if we finished the message then send completion owns it */
837    if (scat == &op->r_sg[op->r_count])
838        prev->s_wr.send_flags = IB_SEND_SIGNALED;
839
840    if (i < work_alloc) {
841        rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc - i);
842        work_alloc = i;
843    }
844
845    failed_wr = &first->s_wr;
846    ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
847    rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
848         first, &first->s_wr, ret, failed_wr);
849    BUG_ON(failed_wr != &first->s_wr);
850    if (ret) {
851        printk(KERN_WARNING "RDS/IB: rdma ib_post_send to %pI4 "
852               "returned %d\n", &conn->c_faddr, ret);
853        rds_ib_ring_unalloc(&ic->i_send_ring, work_alloc);
854        goto out;
855    }
856
857    if (unlikely(failed_wr != &first->s_wr)) {
858        printk(KERN_WARNING "RDS/IB: ib_post_send() rc=%d, but failed_wqe updated!\n", ret);
859        BUG_ON(failed_wr != &first->s_wr);
860    }
861
862
863out:
864    return ret;
865}
866
867void rds_ib_xmit_complete(struct rds_connection *conn)
868{
869    struct rds_ib_connection *ic = conn->c_transport_data;
870
871    /* We may have a pending ACK or window update we were unable
872     * to send previously (due to flow control). Try again. */
873    rds_ib_attempt_ack(ic);
874}
875

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