aboutsummaryrefslogtreecommitdiff
path: root/net/rds/ib_recv.c
blob: d67de453c35aae7257bd29e9791adc2595f6a7d7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/pci.h>
#include <linux/dma-mapping.h>
#include <rdma/rdma_cm.h>

#include "rds.h"
#include "ib.h"

static struct kmem_cache *rds_ib_incoming_slab;
static struct kmem_cache *rds_ib_frag_slab;
static atomic_t	rds_ib_allocation = ATOMIC_INIT(0);

void rds_ib_recv_init_ring(struct rds_ib_connection *ic)
{
	struct rds_ib_recv_work *recv;
	u32 i;

	for (i = 0, recv = ic->i_recvs; i < ic->i_recv_ring.w_nr; i++, recv++) {
		struct ib_sge *sge;

		recv->r_ibinc = NULL;
		recv->r_frag = NULL;

		recv->r_wr.next = NULL;
		recv->r_wr.wr_id = i;
		recv->r_wr.sg_list = recv->r_sge;
		recv->r_wr.num_sge = RDS_IB_RECV_SGE;

		sge = &recv->r_sge[0];
		sge->addr = ic->i_recv_hdrs_dma + (i * sizeof(struct rds_header));
		sge->length = sizeof(struct rds_header);
		sge->lkey = ic->i_mr->lkey;

		sge = &recv->r_sge[1];
		sge->addr = 0;
		sge->length = RDS_FRAG_SIZE;
		sge->lkey = ic->i_mr->lkey;
	}
}

/*
 * The entire 'from' list, including the from element itself, is put on
 * to the tail of the 'to' list.
 */
static void list_splice_entire_tail(struct list_head *from,
				    struct list_head *to)
{
	struct list_head *from_last = from->prev;

	list_splice_tail(from_last, to);
	list_add_tail(from_last, to);
}

static void rds_ib_cache_xfer_to_ready(struct rds_ib_refill_cache *cache)
{
	struct list_head *tmp;

	tmp = xchg(&cache->xfer, NULL);
	if (tmp) {
		if (cache->ready)
			list_splice_entire_tail(tmp, cache->ready);
		else
			cache->ready = tmp;
	}
}

static int rds_ib_recv_alloc_cache(struct rds_ib_refill_cache *cache)
{
	struct rds_ib_cache_head *head;
	int cpu;

	cache->percpu = alloc_percpu(struct rds_ib_cache_head);
	if (!cache->percpu)
	       return -ENOMEM;

	for_each_possible_cpu(cpu) {
		head = per_cpu_ptr(cache->percpu, cpu);
		head->first = NULL;
		head->count = 0;
	}
	cache->xfer = NULL;
	cache->ready = NULL;

	return 0;
}

int rds_ib_recv_alloc_caches(struct rds_ib_connection *ic)
{
	int ret;

	ret = rds_ib_recv_alloc_cache(&ic->i_cache_incs);
	if (!ret) {
		ret = rds_ib_recv_alloc_cache(&ic->i_cache_frags);
		if (ret)
			free_percpu(ic->i_cache_incs.percpu);
	}

	return ret;
}

static void rds_ib_cache_splice_all_lists(struct rds_ib_refill_cache *cache,
					  struct list_head *caller_list)
{
	struct rds_ib_cache_head *head;
	int cpu;

	for_each_possible_cpu(cpu) {
		head = per_cpu_ptr(cache->percpu, cpu);
		if (head->first) {
			list_splice_entire_tail(head->first, caller_list);
			head->first = NULL;
		}
	}

	if (cache->ready) {
		list_splice_entire_tail(cache->ready, caller_list);
		cache->ready = NULL;
	}
}

void rds_ib_recv_free_caches(struct rds_ib_connection *ic)
{
	struct rds_ib_incoming *inc;
	struct rds_ib_incoming *inc_tmp;
	struct rds_page_frag *frag;
	struct rds_page_frag *frag_tmp;
	LIST_HEAD(list);

	rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
	rds_ib_cache_splice_all_lists(&ic->i_cache_incs, &list);
	free_percpu(ic->i_cache_incs.percpu);

	list_for_each_entry_safe(inc, inc_tmp, &list, ii_cache_entry) {
		list_del(&inc->ii_cache_entry);
		WARN_ON(!list_empty(&inc->ii_frags));
		kmem_cache_free(rds_ib_incoming_slab, inc);
	}

	rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);
	rds_ib_cache_splice_all_lists(&ic->i_cache_frags, &list);
	free_percpu(ic->i_cache_frags.percpu);

	list_for_each_entry_safe(frag, frag_tmp, &list, f_cache_entry) {
		list_del(&frag->f_cache_entry);
		WARN_ON(!list_empty(&frag->f_item));
		kmem_cache_free(rds_ib_frag_slab, frag);
	}
}

/* fwd decl */
static void rds_ib_recv_cache_put(struct list_head *new_item,
				  struct rds_ib_refill_cache *cache);
static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache);


/* Recycle frag and attached recv buffer f_sg */
static void rds_ib_frag_free(struct rds_ib_connection *ic,
			     struct rds_page_frag *frag)
{
	rdsdebug("frag %p page %p\n", frag, sg_page(&frag->f_sg));

	rds_ib_recv_cache_put(&frag->f_cache_entry, &ic->i_cache_frags);
}

/* Recycle inc after freeing attached frags */
void rds_ib_inc_free(struct rds_incoming *inc)
{
	struct rds_ib_incoming *ibinc;
	struct rds_page_frag *frag;
	struct rds_page_frag *pos;
	struct rds_ib_connection *ic = inc->i_conn->c_transport_data;

	ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);

	/* Free attached frags */
	list_for_each_entry_safe(frag, pos, &ibinc->ii_frags, f_item) {
		list_del_init(&frag->f_item);
		rds_ib_frag_free(ic, frag);
	}
	BUG_ON(!list_empty(&ibinc->ii_frags));

	rdsdebug("freeing ibinc %p inc %p\n", ibinc, inc);
	rds_ib_recv_cache_put(&ibinc->ii_cache_entry, &ic->i_cache_incs);
}

static void rds_ib_recv_clear_one(struct rds_ib_connection *ic,
				  struct rds_ib_recv_work *recv)
{
	if (recv->r_ibinc) {
		rds_inc_put(&recv->r_ibinc->ii_inc);
		recv->r_ibinc = NULL;
	}
	if (recv->r_frag) {
		ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);
		rds_ib_frag_free(ic, recv->r_frag);
		recv->r_frag = NULL;
	}
}

void rds_ib_recv_clear_ring(struct rds_ib_connection *ic)
{
	u32 i;

	for (i = 0; i < ic->i_recv_ring.w_nr; i++)
		rds_ib_recv_clear_one(ic, &ic->i_recvs[i]);
}

static struct rds_ib_incoming *rds_ib_refill_one_inc(struct rds_ib_connection *ic,
						     gfp_t slab_mask)
{
	struct rds_ib_incoming *ibinc;
	struct list_head *cache_item;
	int avail_allocs;

	cache_item = rds_ib_recv_cache_get(&ic->i_cache_incs);
	if (cache_item) {
		ibinc = container_of(cache_item, struct rds_ib_incoming, ii_cache_entry);
	} else {
		avail_allocs = atomic_add_unless(&rds_ib_allocation,
						 1, rds_ib_sysctl_max_recv_allocation);
		if (!avail_allocs) {
			rds_ib_stats_inc(s_ib_rx_alloc_limit);
			return NULL;
		}
		ibinc = kmem_cache_alloc(rds_ib_incoming_slab, slab_mask);
		if (!ibinc) {
			atomic_dec(&rds_ib_allocation);
			return NULL;
		}
	}
	INIT_LIST_HEAD(&ibinc->ii_frags);
	rds_inc_init(&ibinc->ii_inc, ic->conn, ic->conn->c_faddr);

	return ibinc;
}

static struct rds_page_frag *rds_ib_refill_one_frag(struct rds_ib_connection *ic,
						    gfp_t slab_mask, gfp_t page_mask)
{
	struct rds_page_frag *frag;
	struct list_head *cache_item;
	int ret;

	cache_item = rds_ib_recv_cache_get(&ic->i_cache_frags);
	if (cache_item) {
		frag = container_of(cache_item, struct rds_page_frag, f_cache_entry);
	} else {
		frag = kmem_cache_alloc(rds_ib_frag_slab, slab_mask);
		if (!frag)
			return NULL;

		sg_init_table(&frag->f_sg, 1);
		ret = rds_page_remainder_alloc(&frag->f_sg,
					       RDS_FRAG_SIZE, page_mask);
		if (ret) {
			kmem_cache_free(rds_ib_frag_slab, frag);
			return NULL;
		}
	}

	INIT_LIST_HEAD(&frag->f_item);

	return frag;
}

static int rds_ib_recv_refill_one(struct rds_connection *conn,
				  struct rds_ib_recv_work *recv, int prefill)
{
	struct rds_ib_connection *ic = conn->c_transport_data;
	struct ib_sge *sge;
	int ret = -ENOMEM;
	gfp_t slab_mask = GFP_NOWAIT;
	gfp_t page_mask = GFP_NOWAIT;

	if (prefill) {
		slab_mask = GFP_KERNEL;
		page_mask = GFP_HIGHUSER;
	}

	if (!ic->i_cache_incs.ready)
		rds_ib_cache_xfer_to_ready(&ic->i_cache_incs);
	if (!ic->i_cache_frags.ready)
		rds_ib_cache_xfer_to_ready(&ic->i_cache_frags);

	/*
	 * ibinc was taken from recv if recv contained the start of a message.
	 * recvs that were continuations will still have this allocated.
	 */
	if (!recv->r_ibinc) {
		recv->r_ibinc = rds_ib_refill_one_inc(ic, slab_mask);
		if (!recv->r_ibinc)
			goto out;
	}

	WARN_ON(recv->r_frag); /* leak! */
	recv->r_frag = rds_ib_refill_one_frag(ic, slab_mask, page_mask);
	if (!recv->r_frag)
		goto out;

	ret = ib_dma_map_sg(ic->i_cm_id->device, &recv->r_frag->f_sg,
			    1, DMA_FROM_DEVICE);
	WARN_ON(ret != 1);

	sge = &recv->r_sge[0];
	sge->addr = ic->i_recv_hdrs_dma + (recv - ic->i_recvs) * sizeof(struct rds_header);
	sge->length = sizeof(struct rds_header);

	sge = &recv->r_sge[1];
	sge->addr = ib_sg_dma_address(ic->i_cm_id->device, &recv->r_frag->f_sg);
	sge->length = ib_sg_dma_len(ic->i_cm_id->device, &recv->r_frag->f_sg);

	ret = 0;
out:
	return ret;
}

/*
 * This tries to allocate and post unused work requests after making sure that
 * they have all the allocations they need to queue received fragments into
 * sockets.
 *
 * -1 is returned if posting fails due to temporary resource exhaustion.
 */
void rds_ib_recv_refill(struct rds_connection *conn, int prefill)
{
	struct rds_ib_connection *ic = conn->c_transport_data;
	struct rds_ib_recv_work *recv;
	struct ib_recv_wr *failed_wr;
	unsigned int posted = 0;
	int ret = 0;
	u32 pos;

	while ((prefill || rds_conn_up(conn)) &&
	       rds_ib_ring_alloc(&ic->i_recv_ring, 1, &pos)) {
		if (pos >= ic->i_recv_ring.w_nr) {
			printk(KERN_NOTICE "Argh - ring alloc returned pos=%u\n",
					pos);
			break;
		}

		recv = &ic->i_recvs[pos];
		ret = rds_ib_recv_refill_one(conn, recv, prefill);
		if (ret) {
			break;
		}

		/* XXX when can this fail? */
		ret = ib_post_recv(ic->i_cm_id->qp, &recv->r_wr, &failed_wr);
		rdsdebug("recv %p ibinc %p page %p addr %lu ret %d\n", recv,
			 recv->r_ibinc, sg_page(&recv->r_frag->f_sg),
			 (long) ib_sg_dma_address(
				ic->i_cm_id->device,
				&recv->r_frag->f_sg),
			ret);
		if (ret) {
			rds_ib_conn_error(conn, "recv post on "
			       "%pI4 returned %d, disconnecting and "
			       "reconnecting\n", &conn->c_faddr,
			       ret);
			break;
		}

		posted++;
	}

	/* We're doing flow control - update the window. */
	if (ic->i_flowctl && posted)
		rds_ib_advertise_credits(conn, posted);

	if (ret)
		rds_ib_ring_unalloc(&ic->i_recv_ring, 1);
}

/*
 * We want to recycle several types of recv allocations, like incs and frags.
 * To use this, the *_free() function passes in the ptr to a list_head within
 * the recyclee, as well as the cache to put it on.
 *
 * First, we put the memory on a percpu list. When this reaches a certain size,
 * We move it to an intermediate non-percpu list in a lockless manner, with some
 * xchg/compxchg wizardry.
 *
 * N.B. Instead of a list_head as the anchor, we use a single pointer, which can
 * be NULL and xchg'd. The list is actually empty when the pointer is NULL, and
 * list_empty() will return true with one element is actually present.
 */
static void rds_ib_recv_cache_put(struct list_head *new_item,
				 struct rds_ib_refill_cache *cache)
{
	unsigned long flags;
	struct list_head *old, *chpfirst;

	local_irq_save(flags);

	chpfirst = __this_cpu_read(cache->percpu->first);
	if (!chpfirst)
		INIT_LIST_HEAD(new_item);
	else /* put on front */
		list_add_tail(new_item, chpfirst);

	__this_cpu_write(cache->percpu->first, new_item);
	__this_cpu_inc(cache->percpu->count);

	if (__this_cpu_read(cache->percpu->count) < RDS_IB_RECYCLE_BATCH_COUNT)
		goto end;

	/*
	 * Return our per-cpu first list to the cache's xfer by atomically
	 * grabbing the current xfer list, appending it to our per-cpu list,
	 * and then atomically returning that entire list back to the
	 * cache's xfer list as long as it's still empty.
	 */
	do {
		old = xchg(&cache->xfer, NULL);
		if (old)
			list_splice_entire_tail(old, chpfirst);
		old = cmpxchg(&cache->xfer, NULL, chpfirst);
	} while (old);


	__this_cpu_write(cache->percpu->first, NULL);
	__this_cpu_write(cache->percpu->count, 0);
end:
	local_irq_restore(flags);
}

static struct list_head *rds_ib_recv_cache_get(struct rds_ib_refill_cache *cache)
{
	struct list_head *head = cache->ready;

	if (head) {
		if (!list_empty(head)) {
			cache->ready = head->next;
			list_del_init(head);
		} else
			cache->ready = NULL;
	}

	return head;
}

int rds_ib_inc_copy_to_user(struct rds_incoming *inc, struct iovec *first_iov,
			    size_t size)
{
	struct rds_ib_incoming *ibinc;
	struct rds_page_frag *frag;
	struct iovec *iov = first_iov;
	unsigned long to_copy;
	unsigned long frag_off = 0;
	unsigned long iov_off = 0;
	int copied = 0;
	int ret;
	u32 len;

	ibinc = container_of(inc, struct rds_ib_incoming, ii_inc);
	frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
	len = be32_to_cpu(inc->i_hdr.h_len);

	while (copied < size && copied < len) {
		if (frag_off == RDS_FRAG_SIZE) {
			frag = list_entry(frag->f_item.next,
					  struct rds_page_frag, f_item);
			frag_off = 0;
		}
		while (iov_off == iov->iov_len) {
			iov_off = 0;
			iov++;
		}

		to_copy = min(iov->iov_len - iov_off, RDS_FRAG_SIZE - frag_off);
		to_copy = min_t(size_t, to_copy, size - copied);
		to_copy = min_t(unsigned long, to_copy, len - copied);

		rdsdebug("%lu bytes to user [%p, %zu] + %lu from frag "
			 "[%p, %u] + %lu\n",
			 to_copy, iov->iov_base, iov->iov_len, iov_off,
			 sg_page(&frag->f_sg), frag->f_sg.offset, frag_off);

		/* XXX needs + offset for multiple recvs per page */
		ret = rds_page_copy_to_user(sg_page(&frag->f_sg),
					    frag->f_sg.offset + frag_off,
					    iov->iov_base + iov_off,
					    to_copy);
		if (ret) {
			copied = ret;
			break;
		}

		iov_off += to_copy;
		frag_off += to_copy;
		copied += to_copy;
	}

	return copied;
}

/* ic starts out kzalloc()ed */
void rds_ib_recv_init_ack(struct rds_ib_connection *ic)
{
	struct ib_send_wr *wr = &ic->i_ack_wr;
	struct ib_sge *sge = &ic->i_ack_sge;

	sge->addr = ic->i_ack_dma;
	sge->length = sizeof(struct rds_header);
	sge->lkey = ic->i_mr->lkey;

	wr->sg_list = sge;
	wr->num_sge = 1;
	wr->opcode = IB_WR_SEND;
	wr->wr_id = RDS_IB_ACK_WR_ID;
	wr->send_flags = IB_SEND_SIGNALED | IB_SEND_SOLICITED;
}

/*
 * You'd think that with reliable IB connections you wouldn't need to ack
 * messages that have been received.  The problem is that IB hardware generates
 * an ack message before it has DMAed the message into memory.  This creates a
 * potential message loss if the HCA is disabled for any reason between when it
 * sends the ack and before the message is DMAed and processed.  This is only a
 * potential issue if another HCA is available for fail-over.
 *
 * When the remote host receives our ack they'll free the sent message from
 * their send queue.  To decrease the latency of this we always send an ack
 * immediately after we've received messages.
 *
 * For simplicity, we only have one ack in flight at a time.  This puts
 * pressure on senders to have deep enough send queues to absorb the latency of
 * a single ack frame being in flight.  This might not be good enough.
 *
 * This is implemented by have a long-lived send_wr and sge which point to a
 * statically allocated ack frame.  This ack wr does not fall under the ring
 * accounting that the tx and rx wrs do.  The QP attribute specifically makes
 * room for it beyond the ring size.  Send completion notices its special
 * wr_id and avoids working with the ring in that case.
 */
#ifndef KERNEL_HAS_ATOMIC64
static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
				int ack_required)
{
	unsigned long flags;

	spin_lock_irqsave(&ic->i_ack_lock, flags);
	ic->i_ack_next = seq;
	if (ack_required)
		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
	spin_unlock_irqrestore(&ic->i_ack_lock, flags);
}

static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
{
	unsigned long flags;
	u64 seq;

	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);

	spin_lock_irqsave(&ic->i_ack_lock, flags);
	seq = ic->i_ack_next;
	spin_unlock_irqrestore(&ic->i_ack_lock, flags);

	return seq;
}
#else
static void rds_ib_set_ack(struct rds_ib_connection *ic, u64 seq,
				int ack_required)
{
	atomic64_set(&ic->i_ack_next, seq);
	if (ack_required) {
		smp_mb__before_atomic();
		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
	}
}

static u64 rds_ib_get_ack(struct rds_ib_connection *ic)
{
	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
	smp_mb__after_atomic();

	return atomic64_read(&ic->i_ack_next);
}
#endif


static void rds_ib_send_ack(struct rds_ib_connection *ic, unsigned int adv_credits)
{
	struct rds_header *hdr = ic->i_ack;
	struct ib_send_wr *failed_wr;
	u64 seq;
	int ret;

	seq = rds_ib_get_ack(ic);

	rdsdebug("send_ack: ic %p ack %llu\n", ic, (unsigned long long) seq);
	rds_message_populate_header(hdr, 0, 0, 0);
	hdr->h_ack = cpu_to_be64(seq);
	hdr->h_credit = adv_credits;
	rds_message_make_checksum(hdr);
	ic->i_ack_queued = jiffies;

	ret = ib_post_send(ic->i_cm_id->qp, &ic->i_ack_wr, &failed_wr);
	if (unlikely(ret)) {
		/* Failed to send. Release the WR, and
		 * force another ACK.
		 */
		clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);

		rds_ib_stats_inc(s_ib_ack_send_failure);

		rds_ib_conn_error(ic->conn, "sending ack failed\n");
	} else
		rds_ib_stats_inc(s_ib_ack_sent);
}

/*
 * There are 3 ways of getting acknowledgements to the peer:
 *  1.	We call rds_ib_attempt_ack from the recv completion handler
 *	to send an ACK-only frame.
 *	However, there can be only one such frame in the send queue
 *	at any time, so we may have to postpone it.
 *  2.	When another (data) packet is transmitted while there's
 *	an ACK in the queue, we piggyback the ACK sequence number
 *	on the data packet.
 *  3.	If the ACK WR is done sending, we get called from the
 *	send queue completion handler, and check whether there's
 *	another ACK pending (postponed because the WR was on the
 *	queue). If so, we transmit it.
 *
 * We maintain 2 variables:
 *  -	i_ack_flags, which keeps track of whether the ACK WR
 *	is currently in the send queue or not (IB_ACK_IN_FLIGHT)
 *  -	i_ack_next, which is the last sequence number we received
 *
 * Potentially, send queue and receive queue handlers can run concurrently.
 * It would be nice to not have to use a spinlock to synchronize things,
 * but the one problem that rules this out is that 64bit updates are
 * not atomic on all platforms. Things would be a lot simpler if
 * we had atomic64 or maybe cmpxchg64 everywhere.
 *
 * Reconnecting complicates this picture just slightly. When we
 * reconnect, we may be seeing duplicate packets. The peer
 * is retransmitting them, because it hasn't seen an ACK for
 * them. It is important that we ACK these.
 *
 * ACK mitigation adds a header flag "ACK_REQUIRED"; any packet with
 * this flag set *MUST* be acknowledged immediately.
 */

/*
 * When we get here, we're called from the recv queue handler.
 * Check whether we ought to transmit an ACK.
 */
void rds_ib_attempt_ack(struct rds_ib_connection *ic)
{
	unsigned int adv_credits;

	if (!test_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
		return;

	if (test_and_set_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags)) {
		rds_ib_stats_inc(s_ib_ack_send_delayed);
		return;
	}

	/* Can we get a send credit? */
	if (!rds_ib_send_grab_credits(ic, 1, &adv_credits, 0, RDS_MAX_ADV_CREDIT)) {
		rds_ib_stats_inc(s_ib_tx_throttle);
		clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
		return;
	}

	clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
	rds_ib_send_ack(ic, adv_credits);
}

/*
 * We get here from the send completion handler, when the
 * adapter tells us the ACK frame was sent.
 */
void rds_ib_ack_send_complete(struct rds_ib_connection *ic)
{
	clear_bit(IB_ACK_IN_FLIGHT, &ic->i_ack_flags);
	rds_ib_attempt_ack(ic);
}

/*
 * This is called by the regular xmit code when it wants to piggyback
 * an ACK on an outgoing frame.
 */
u64 rds_ib_piggyb_ack(struct rds_ib_connection *ic)
{
	if (test_and_clear_bit(IB_ACK_REQUESTED, &ic->i_ack_flags))
		rds_ib_stats_inc(s_ib_ack_send_piggybacked);
	return rds_ib_get_ack(ic);
}

/*
 * It's kind of lame that we're copying from the posted receive pages into
 * long-lived bitmaps.  We could have posted the bitmaps and rdma written into
 * them.  But receiving new congestion bitmaps should be a *rare* event, so
 * hopefully we won't need to invest that complexity in making it more
 * efficient.  By copying we can share a simpler core with TCP which has to
 * copy.
 */
static void rds_ib_cong_recv(struct rds_connection *conn,
			      struct rds_ib_incoming *ibinc)
{
	struct rds_cong_map *map;
	unsigned int map_off;
	unsigned int map_page;
	struct rds_page_frag *frag;
	unsigned long frag_off;
	unsigned long to_copy;
	unsigned long copied;
	uint64_t uncongested = 0;
	void *addr;

	/* catch completely corrupt packets */
	if (be32_to_cpu(ibinc->ii_inc.i_hdr.h_len) != RDS_CONG_MAP_BYTES)
		return;

	map = conn->c_fcong;
	map_page = 0;
	map_off = 0;

	frag = list_entry(ibinc->ii_frags.next, struct rds_page_frag, f_item);
	frag_off = 0;

	copied = 0;

	while (copied < RDS_CONG_MAP_BYTES) {
		uint64_t *src, *dst;
		unsigned int k;

		to_copy = min(RDS_FRAG_SIZE - frag_off, PAGE_SIZE - map_off);
		BUG_ON(to_copy & 7); /* Must be 64bit aligned. */

		addr = kmap_atomic(sg_page(&frag->f_sg));

		src = addr + frag_off;
		dst = (void *)map->m_page_addrs[map_page] + map_off;
		for (k = 0; k < to_copy; k += 8) {
			/* Record ports that became uncongested, ie
			 * bits that changed from 0 to 1. */
			uncongested |= ~(*src) & *dst;
			*dst++ = *src++;
		}
		kunmap_atomic(addr);

		copied += to_copy;

		map_off += to_copy;
		if (map_off == PAGE_SIZE) {
			map_off = 0;
			map_page++;
		}

		frag_off += to_copy;
		if (frag_off == RDS_FRAG_SIZE) {
			frag = list_entry(frag->f_item.next,
					  struct rds_page_frag, f_item);
			frag_off = 0;
		}
	}

	/* the congestion map is in little endian order */
	uncongested = le64_to_cpu(uncongested);

	rds_cong_map_updated(map, uncongested);
}

/*
 * Rings are posted with all the allocations they'll need to queue the
 * incoming message to the receiving socket so this can't fail.
 * All fragments start with a header, so we can make sure we're not receiving
 * garbage, and we can tell a small 8 byte fragment from an ACK frame.
 */
struct rds_ib_ack_state {
	u64		ack_next;
	u64		ack_recv;
	unsigned int	ack_required:1;
	unsigned int	ack_next_valid:1;
	unsigned int	ack_recv_valid:1;
};

static void rds_ib_process_recv(struct rds_connection *conn,
				struct rds_ib_recv_work *recv, u32 data_len,
				struct rds_ib_ack_state *state)
{
	struct rds_ib_connection *ic = conn->c_transport_data;
	struct rds_ib_incoming *ibinc = ic->i_ibinc;
	struct rds_header *ihdr, *hdr;

	/* XXX shut down the connection if port 0,0 are seen? */

	rdsdebug("ic %p ibinc %p recv %p byte len %u\n", ic, ibinc, recv,
		 data_len);

	if (data_len < sizeof(struct rds_header)) {
		rds_ib_conn_error(conn, "incoming message "
		       "from %pI4 didn't include a "
		       "header, disconnecting and "
		       "reconnecting\n",
		       &conn->c_faddr);
		return;
	}
	data_len -= sizeof(struct rds_header);

	ihdr = &ic->i_recv_hdrs[recv - ic->i_recvs];

	/* Validate the checksum. */
	if (!rds_message_verify_checksum(ihdr)) {
		rds_ib_conn_error(conn, "incoming message "
		       "from %pI4 has corrupted header - "
		       "forcing a reconnect\n",
		       &conn->c_faddr);
		rds_stats_inc(s_recv_drop_bad_checksum);
		return;
	}

	/* Process the ACK sequence which comes with every packet */
	state->ack_recv = be64_to_cpu(ihdr->h_ack);
	state->ack_recv_valid = 1;

	/* Process the credits update if there was one */
	if (ihdr->h_credit)
		rds_ib_send_add_credits(conn, ihdr->h_credit);

	if (ihdr->h_sport == 0 && ihdr->h_dport == 0 && data_len == 0) {
		/* This is an ACK-only packet. The fact that it gets
		 * special treatment here is that historically, ACKs
		 * were rather special beasts.
		 */
		rds_ib_stats_inc(s_ib_ack_received);

		/*
		 * Usually the frags make their way on to incs and are then freed as
		 * the inc is freed.  We don't go that route, so we have to drop the
		 * page ref ourselves.  We can't just leave the page on the recv
		 * because that confuses the dma mapping of pages and each recv's use
		 * of a partial page.
		 *
		 * FIXME: Fold this into the code path below.
		 */
		rds_ib_frag_free(ic, recv->r_frag);
		recv->r_frag = NULL;
		return;
	}

	/*
	 * If we don't already have an inc on the connection then this
	 * fragment has a header and starts a message.. copy its header
	 * into the inc and save the inc so we can hang upcoming fragments
	 * off its list.
	 */
	if (!ibinc) {
		ibinc = recv->r_ibinc;
		recv->r_ibinc = NULL;
		ic->i_ibinc = ibinc;

		hdr = &ibinc->ii_inc.i_hdr;
		memcpy(hdr, ihdr, sizeof(*hdr));
		ic->i_recv_data_rem = be32_to_cpu(hdr->h_len);

		rdsdebug("ic %p ibinc %p rem %u flag 0x%x\n", ic, ibinc,
			 ic->i_recv_data_rem, hdr->h_flags);
	} else {
		hdr = &ibinc->ii_inc.i_hdr;
		/* We can't just use memcmp here; fragments of a
		 * single message may carry different ACKs */
		if (hdr->h_sequence != ihdr->h_sequence ||
		    hdr->h_len != ihdr->h_len ||
		    hdr->h_sport != ihdr->h_sport ||
		    hdr->h_dport != ihdr->h_dport) {
			rds_ib_conn_error(conn,
				"fragment header mismatch; forcing reconnect\n");
			return;
		}
	}

	list_add_tail(&recv->r_frag->f_item, &ibinc->ii_frags);
	recv->r_frag = NULL;

	if (ic->i_recv_data_rem > RDS_FRAG_SIZE)
		ic->i_recv_data_rem -= RDS_FRAG_SIZE;
	else {
		ic->i_recv_data_rem = 0;
		ic->i_ibinc = NULL;

		if (ibinc->ii_inc.i_hdr.h_flags == RDS_FLAG_CONG_BITMAP)
			rds_ib_cong_recv(conn, ibinc);
		else {
			rds_recv_incoming(conn, conn->c_faddr, conn->c_laddr,
					  &ibinc->ii_inc, GFP_ATOMIC);
			state->ack_next = be64_to_cpu(hdr->h_sequence);
			state->ack_next_valid = 1;
		}

		/* Evaluate the ACK_REQUIRED flag *after* we received
		 * the complete frame, and after bumping the next_rx
		 * sequence. */
		if (hdr->h_flags & RDS_FLAG_ACK_REQUIRED) {
			rds_stats_inc(s_recv_ack_required);
			state->ack_required = 1;
		}

		rds_inc_put(&ibinc->ii_inc);
	}
}

/*
 * Plucking the oldest entry from the ring can be done concurrently with
 * the thread refilling the ring.  Each ring operation is protected by
 * spinlocks and the transient state of refilling doesn't change the
 * recording of which entry is oldest.
 *
 * This relies on IB only calling one cq comp_handler for each cq so that
 * there will only be one caller of rds_recv_incoming() per RDS connection.
 */
void rds_ib_recv_cq_comp_handler(struct ib_cq *cq, void *context)
{
	struct rds_connection *conn = context;
	struct rds_ib_connection *ic = conn->c_transport_data;

	rdsdebug("conn %p cq %p\n", conn, cq);

	rds_ib_stats_inc(s_ib_rx_cq_call);

	tasklet_schedule(&ic->i_recv_tasklet);
}

static inline void rds_poll_cq(struct rds_ib_connection *ic,
			       struct rds_ib_ack_state *state)
{
	struct rds_connection *conn = ic->conn;
	struct ib_wc wc;
	struct rds_ib_recv_work *recv;

	while (ib_poll_cq(ic->i_recv_cq, 1, &wc) > 0) {
		rdsdebug("wc wr_id 0x%llx status %u (%s) byte_len %u imm_data %u\n",
			 (unsigned long long)wc.wr_id, wc.status,
			 rds_ib_wc_status_str(wc.status), wc.byte_len,
			 be32_to_cpu(wc.ex.imm_data));
		rds_ib_stats_inc(s_ib_rx_cq_event);

		recv = &ic->i_recvs[rds_ib_ring_oldest(&ic->i_recv_ring)];

		ib_dma_unmap_sg(ic->i_cm_id->device, &recv->r_frag->f_sg, 1, DMA_FROM_DEVICE);

		/*
		 * Also process recvs in connecting state because it is possible
		 * to get a recv completion _before_ the rdmacm ESTABLISHED
		 * event is processed.
		 */
		if (wc.status == IB_WC_SUCCESS) {
			rds_ib_process_recv(conn, recv, wc.byte_len, state);
		} else {
			/* We expect errors as the qp is drained during shutdown */
			if (rds_conn_up(conn) || rds_conn_connecting(conn))
				rds_ib_conn_error(conn, "recv completion on %pI4 had "
						  "status %u (%s), disconnecting and "
						  "reconnecting\n", &conn->c_faddr,
						  wc.status,
						  rds_ib_wc_status_str(wc.status));
		}

		/*
		 * It's very important that we only free this ring entry if we've truly
		 * freed the resources allocated to the entry.  The refilling path can
		 * leak if we don't.
		 */
		rds_ib_ring_free(&ic->i_recv_ring, 1);
	}
}

void rds_ib_recv_tasklet_fn(unsigned long data)
{
	struct rds_ib_connection *ic = (struct rds_ib_connection *) data;
	struct rds_connection *conn = ic->conn;
	struct rds_ib_ack_state state = { 0, };

	rds_poll_cq(ic, &state);
	ib_req_notify_cq(ic->i_recv_cq, IB_CQ_SOLICITED);
	rds_poll_cq(ic, &state);

	if (state.ack_next_valid)
		rds_ib_set_ack(ic, state.ack_next, state.ack_required);
	if (state.ack_recv_valid && state.ack_recv > ic->i_ack_recv) {
		rds_send_drop_acked(conn, state.ack_recv, NULL);
		ic->i_ack_recv = state.ack_recv;
	}
	if (rds_conn_up(conn))
		rds_ib_attempt_ack(ic);

	/* If we ever end up with a really empty receive ring, we're
	 * in deep trouble, as the sender will definitely see RNR
	 * timeouts. */
	if (rds_ib_ring_empty(&ic->i_recv_ring))
		rds_ib_stats_inc(s_ib_rx_ring_empty);

	if (rds_ib_ring_low(&ic->i_recv_ring))
		rds_ib_recv_refill(conn, 0);
}

int rds_ib_recv(struct rds_connection *conn)
{
	struct rds_ib_connection *ic = conn->c_transport_data;
	int ret = 0;

	rdsdebug("conn %p\n", conn);
	if (rds_conn_up(conn))
		rds_ib_attempt_ack(ic);

	return ret;
}

int rds_ib_recv_init(void)
{
	struct sysinfo si;
	int ret = -ENOMEM;

	/* Default to 30% of all available RAM for recv memory */
	si_meminfo(&si);
	rds_ib_sysctl_max_recv_allocation = si.totalram / 3 * PAGE_SIZE / RDS_FRAG_SIZE;

	rds_ib_incoming_slab = kmem_cache_create("rds_ib_incoming",
					sizeof(struct rds_ib_incoming),
					0, SLAB_HWCACHE_ALIGN, NULL);
	if (!rds_ib_incoming_slab)
		goto out;

	rds_ib_frag_slab = kmem_cache_create("rds_ib_frag",
					sizeof(struct rds_page_frag),
					0, SLAB_HWCACHE_ALIGN, NULL);
	if (!rds_ib_frag_slab)
		kmem_cache_destroy(rds_ib_incoming_slab);
	else
		ret = 0;
out:
	return ret;
}

void rds_ib_recv_exit(void)
{
	kmem_cache_destroy(rds_ib_incoming_slab);
	kmem_cache_destroy(rds_ib_frag_slab);
}