summaryrefslogtreecommitdiff
path: root/drivers/infiniband/ulp/rtrs/rtrs-clt.c
blob: 0a08b4b742a3d080ddf363f2b85ed486824026b1 (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
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * RDMA Transport Layer
 *
 * Copyright (c) 2014 - 2018 ProfitBricks GmbH. All rights reserved.
 * Copyright (c) 2018 - 2019 1&1 IONOS Cloud GmbH. All rights reserved.
 * Copyright (c) 2019 - 2020 1&1 IONOS SE. All rights reserved.
 */

#undef pr_fmt
#define pr_fmt(fmt) KBUILD_MODNAME " L" __stringify(__LINE__) ": " fmt

#include <linux/module.h>
#include <linux/rculist.h>
#include <linux/random.h>

#include "rtrs-clt.h"
#include "rtrs-log.h"

#define RTRS_CONNECT_TIMEOUT_MS 30000
/*
 * Wait a bit before trying to reconnect after a failure
 * in order to give server time to finish clean up which
 * leads to "false positives" failed reconnect attempts
 */
#define RTRS_RECONNECT_BACKOFF 1000
/*
 * Wait for additional random time between 0 and 8 seconds
 * before starting to reconnect to avoid clients reconnecting
 * all at once in case of a major network outage
 */
#define RTRS_RECONNECT_SEED 8

#define FIRST_CONN 0x01

MODULE_DESCRIPTION("RDMA Transport Client");
MODULE_LICENSE("GPL");

static const struct rtrs_rdma_dev_pd_ops dev_pd_ops;
static struct rtrs_rdma_dev_pd dev_pd = {
	.ops = &dev_pd_ops
};

static struct workqueue_struct *rtrs_wq;
static struct class *rtrs_clt_dev_class;

static inline bool rtrs_clt_is_connected(const struct rtrs_clt *clt)
{
	struct rtrs_clt_sess *sess;
	bool connected = false;

	rcu_read_lock();
	list_for_each_entry_rcu(sess, &clt->paths_list, s.entry)
		connected |= READ_ONCE(sess->state) == RTRS_CLT_CONNECTED;
	rcu_read_unlock();

	return connected;
}

static struct rtrs_permit *
__rtrs_get_permit(struct rtrs_clt *clt, enum rtrs_clt_con_type con_type)
{
	size_t max_depth = clt->queue_depth;
	struct rtrs_permit *permit;
	int bit;

	/*
	 * Adapted from null_blk get_tag(). Callers from different cpus may
	 * grab the same bit, since find_first_zero_bit is not atomic.
	 * But then the test_and_set_bit_lock will fail for all the
	 * callers but one, so that they will loop again.
	 * This way an explicit spinlock is not required.
	 */
	do {
		bit = find_first_zero_bit(clt->permits_map, max_depth);
		if (unlikely(bit >= max_depth))
			return NULL;
	} while (unlikely(test_and_set_bit_lock(bit, clt->permits_map)));

	permit = get_permit(clt, bit);
	WARN_ON(permit->mem_id != bit);
	permit->cpu_id = raw_smp_processor_id();
	permit->con_type = con_type;

	return permit;
}

static inline void __rtrs_put_permit(struct rtrs_clt *clt,
				      struct rtrs_permit *permit)
{
	clear_bit_unlock(permit->mem_id, clt->permits_map);
}

/**
 * rtrs_clt_get_permit() - allocates permit for future RDMA operation
 * @clt:	Current session
 * @con_type:	Type of connection to use with the permit
 * @can_wait:	Wait type
 *
 * Description:
 *    Allocates permit for the following RDMA operation.  Permit is used
 *    to preallocate all resources and to propagate memory pressure
 *    up earlier.
 *
 * Context:
 *    Can sleep if @wait == RTRS_TAG_WAIT
 */
struct rtrs_permit *rtrs_clt_get_permit(struct rtrs_clt *clt,
					  enum rtrs_clt_con_type con_type,
					  int can_wait)
{
	struct rtrs_permit *permit;
	DEFINE_WAIT(wait);

	permit = __rtrs_get_permit(clt, con_type);
	if (likely(permit) || !can_wait)
		return permit;

	do {
		prepare_to_wait(&clt->permits_wait, &wait,
				TASK_UNINTERRUPTIBLE);
		permit = __rtrs_get_permit(clt, con_type);
		if (likely(permit))
			break;

		io_schedule();
	} while (1);

	finish_wait(&clt->permits_wait, &wait);

	return permit;
}
EXPORT_SYMBOL(rtrs_clt_get_permit);

/**
 * rtrs_clt_put_permit() - puts allocated permit
 * @clt:	Current session
 * @permit:	Permit to be freed
 *
 * Context:
 *    Does not matter
 */
void rtrs_clt_put_permit(struct rtrs_clt *clt, struct rtrs_permit *permit)
{
	if (WARN_ON(!test_bit(permit->mem_id, clt->permits_map)))
		return;

	__rtrs_put_permit(clt, permit);

	/*
	 * rtrs_clt_get_permit() adds itself to the &clt->permits_wait list
	 * before calling schedule(). So if rtrs_clt_get_permit() is sleeping
	 * it must have added itself to &clt->permits_wait before
	 * __rtrs_put_permit() finished.
	 * Hence it is safe to guard wake_up() with a waitqueue_active() test.
	 */
	if (waitqueue_active(&clt->permits_wait))
		wake_up(&clt->permits_wait);
}
EXPORT_SYMBOL(rtrs_clt_put_permit);

/**
 * rtrs_permit_to_clt_con() - returns RDMA connection pointer by the permit
 * @sess: client session pointer
 * @permit: permit for the allocation of the RDMA buffer
 * Note:
 *     IO connection starts from 1.
 *     0 connection is for user messages.
 */
static
struct rtrs_clt_con *rtrs_permit_to_clt_con(struct rtrs_clt_sess *sess,
					    struct rtrs_permit *permit)
{
	int id = 0;

	if (likely(permit->con_type == RTRS_IO_CON))
		id = (permit->cpu_id % (sess->s.con_num - 1)) + 1;

	return to_clt_con(sess->s.con[id]);
}

/**
 * rtrs_clt_change_state() - change the session state through session state
 * machine.
 *
 * @sess: client session to change the state of.
 * @new_state: state to change to.
 *
 * returns true if sess's state is changed to new state, otherwise return false.
 *
 * Locks:
 * state_wq lock must be hold.
 */
static bool rtrs_clt_change_state(struct rtrs_clt_sess *sess,
				     enum rtrs_clt_state new_state)
{
	enum rtrs_clt_state old_state;
	bool changed = false;

	lockdep_assert_held(&sess->state_wq.lock);

	old_state = sess->state;
	switch (new_state) {
	case RTRS_CLT_CONNECTING:
		switch (old_state) {
		case RTRS_CLT_RECONNECTING:
			changed = true;
			fallthrough;
		default:
			break;
		}
		break;
	case RTRS_CLT_RECONNECTING:
		switch (old_state) {
		case RTRS_CLT_CONNECTED:
		case RTRS_CLT_CONNECTING_ERR:
		case RTRS_CLT_CLOSED:
			changed = true;
			fallthrough;
		default:
			break;
		}
		break;
	case RTRS_CLT_CONNECTED:
		switch (old_state) {
		case RTRS_CLT_CONNECTING:
			changed = true;
			fallthrough;
		default:
			break;
		}
		break;
	case RTRS_CLT_CONNECTING_ERR:
		switch (old_state) {
		case RTRS_CLT_CONNECTING:
			changed = true;
			fallthrough;
		default:
			break;
		}
		break;
	case RTRS_CLT_CLOSING:
		switch (old_state) {
		case RTRS_CLT_CONNECTING:
		case RTRS_CLT_CONNECTING_ERR:
		case RTRS_CLT_RECONNECTING:
		case RTRS_CLT_CONNECTED:
			changed = true;
			fallthrough;
		default:
			break;
		}
		break;
	case RTRS_CLT_CLOSED:
		switch (old_state) {
		case RTRS_CLT_CLOSING:
			changed = true;
			fallthrough;
		default:
			break;
		}
		break;
	case RTRS_CLT_DEAD:
		switch (old_state) {
		case RTRS_CLT_CLOSED:
			changed = true;
			fallthrough;
		default:
			break;
		}
		break;
	default:
		break;
	}
	if (changed) {
		sess->state = new_state;
		wake_up_locked(&sess->state_wq);
	}

	return changed;
}

static bool rtrs_clt_change_state_from_to(struct rtrs_clt_sess *sess,
					   enum rtrs_clt_state old_state,
					   enum rtrs_clt_state new_state)
{
	bool changed = false;

	spin_lock_irq(&sess->state_wq.lock);
	if (sess->state == old_state)
		changed = rtrs_clt_change_state(sess, new_state);
	spin_unlock_irq(&sess->state_wq.lock);

	return changed;
}

static void rtrs_rdma_error_recovery(struct rtrs_clt_con *con)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);

	if (rtrs_clt_change_state_from_to(sess,
					   RTRS_CLT_CONNECTED,
					   RTRS_CLT_RECONNECTING)) {
		struct rtrs_clt *clt = sess->clt;
		unsigned int delay_ms;

		/*
		 * Normal scenario, reconnect if we were successfully connected
		 */
		delay_ms = clt->reconnect_delay_sec * 1000;
		queue_delayed_work(rtrs_wq, &sess->reconnect_dwork,
				   msecs_to_jiffies(delay_ms +
						    prandom_u32() % RTRS_RECONNECT_SEED));
	} else {
		/*
		 * Error can happen just on establishing new connection,
		 * so notify waiter with error state, waiter is responsible
		 * for cleaning the rest and reconnect if needed.
		 */
		rtrs_clt_change_state_from_to(sess,
					       RTRS_CLT_CONNECTING,
					       RTRS_CLT_CONNECTING_ERR);
	}
}

static void rtrs_clt_fast_reg_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct rtrs_clt_con *con = cq->cq_context;

	if (unlikely(wc->status != IB_WC_SUCCESS)) {
		rtrs_err(con->c.sess, "Failed IB_WR_REG_MR: %s\n",
			  ib_wc_status_msg(wc->status));
		rtrs_rdma_error_recovery(con);
	}
}

static struct ib_cqe fast_reg_cqe = {
	.done = rtrs_clt_fast_reg_done
};

static void complete_rdma_req(struct rtrs_clt_io_req *req, int errno,
			      bool notify, bool can_wait);

static void rtrs_clt_inv_rkey_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct rtrs_clt_io_req *req =
		container_of(wc->wr_cqe, typeof(*req), inv_cqe);
	struct rtrs_clt_con *con = cq->cq_context;

	if (unlikely(wc->status != IB_WC_SUCCESS)) {
		rtrs_err(con->c.sess, "Failed IB_WR_LOCAL_INV: %s\n",
			  ib_wc_status_msg(wc->status));
		rtrs_rdma_error_recovery(con);
	}
	req->need_inv = false;
	if (likely(req->need_inv_comp))
		complete(&req->inv_comp);
	else
		/* Complete request from INV callback */
		complete_rdma_req(req, req->inv_errno, true, false);
}

static int rtrs_inv_rkey(struct rtrs_clt_io_req *req)
{
	struct rtrs_clt_con *con = req->con;
	struct ib_send_wr wr = {
		.opcode		    = IB_WR_LOCAL_INV,
		.wr_cqe		    = &req->inv_cqe,
		.send_flags	    = IB_SEND_SIGNALED,
		.ex.invalidate_rkey = req->mr->rkey,
	};
	req->inv_cqe.done = rtrs_clt_inv_rkey_done;

	return ib_post_send(con->c.qp, &wr, NULL);
}

static void complete_rdma_req(struct rtrs_clt_io_req *req, int errno,
			      bool notify, bool can_wait)
{
	struct rtrs_clt_con *con = req->con;
	struct rtrs_clt_sess *sess;
	int err;

	if (WARN_ON(!req->in_use))
		return;
	if (WARN_ON(!req->con))
		return;
	sess = to_clt_sess(con->c.sess);

	if (req->sg_cnt) {
		if (unlikely(req->dir == DMA_FROM_DEVICE && req->need_inv)) {
			/*
			 * We are here to invalidate read requests
			 * ourselves.  In normal scenario server should
			 * send INV for all read requests, but
			 * we are here, thus two things could happen:
			 *
			 *    1.  this is failover, when errno != 0
			 *        and can_wait == 1,
			 *
			 *    2.  something totally bad happened and
			 *        server forgot to send INV, so we
			 *        should do that ourselves.
			 */

			if (likely(can_wait)) {
				req->need_inv_comp = true;
			} else {
				/* This should be IO path, so always notify */
				WARN_ON(!notify);
				/* Save errno for INV callback */
				req->inv_errno = errno;
			}

			err = rtrs_inv_rkey(req);
			if (unlikely(err)) {
				rtrs_err(con->c.sess, "Send INV WR key=%#x: %d\n",
					  req->mr->rkey, err);
			} else if (likely(can_wait)) {
				wait_for_completion(&req->inv_comp);
			} else {
				/*
				 * Something went wrong, so request will be
				 * completed from INV callback.
				 */
				WARN_ON_ONCE(1);

				return;
			}
		}
		ib_dma_unmap_sg(sess->s.dev->ib_dev, req->sglist,
				req->sg_cnt, req->dir);
	}
	if (sess->clt->mp_policy == MP_POLICY_MIN_INFLIGHT)
		atomic_dec(&sess->stats->inflight);

	req->in_use = false;
	req->con = NULL;

	if (notify)
		req->conf(req->priv, errno);
}

static int rtrs_post_send_rdma(struct rtrs_clt_con *con,
				struct rtrs_clt_io_req *req,
				struct rtrs_rbuf *rbuf, u32 off,
				u32 imm, struct ib_send_wr *wr)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	enum ib_send_flags flags;
	struct ib_sge sge;

	if (unlikely(!req->sg_size)) {
		rtrs_wrn(con->c.sess,
			 "Doing RDMA Write failed, no data supplied\n");
		return -EINVAL;
	}

	/* user data and user message in the first list element */
	sge.addr   = req->iu->dma_addr;
	sge.length = req->sg_size;
	sge.lkey   = sess->s.dev->ib_pd->local_dma_lkey;

	/*
	 * From time to time we have to post signalled sends,
	 * or send queue will fill up and only QP reset can help.
	 */
	flags = atomic_inc_return(&con->io_cnt) % sess->queue_depth ?
			0 : IB_SEND_SIGNALED;

	ib_dma_sync_single_for_device(sess->s.dev->ib_dev, req->iu->dma_addr,
				      req->sg_size, DMA_TO_DEVICE);

	return rtrs_iu_post_rdma_write_imm(&con->c, req->iu, &sge, 1,
					    rbuf->rkey, rbuf->addr + off,
					    imm, flags, wr);
}

static void process_io_rsp(struct rtrs_clt_sess *sess, u32 msg_id,
			   s16 errno, bool w_inval)
{
	struct rtrs_clt_io_req *req;

	if (WARN_ON(msg_id >= sess->queue_depth))
		return;

	req = &sess->reqs[msg_id];
	/* Drop need_inv if server responded with send with invalidation */
	req->need_inv &= !w_inval;
	complete_rdma_req(req, errno, true, false);
}

static void rtrs_clt_recv_done(struct rtrs_clt_con *con, struct ib_wc *wc)
{
	struct rtrs_iu *iu;
	int err;
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);

	WARN_ON((sess->flags & RTRS_MSG_NEW_RKEY_F) == 0);
	iu = container_of(wc->wr_cqe, struct rtrs_iu,
			  cqe);
	err = rtrs_iu_post_recv(&con->c, iu);
	if (unlikely(err)) {
		rtrs_err(con->c.sess, "post iu failed %d\n", err);
		rtrs_rdma_error_recovery(con);
	}
}

static void rtrs_clt_rkey_rsp_done(struct rtrs_clt_con *con, struct ib_wc *wc)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	struct rtrs_msg_rkey_rsp *msg;
	u32 imm_type, imm_payload;
	bool w_inval = false;
	struct rtrs_iu *iu;
	u32 buf_id;
	int err;

	WARN_ON((sess->flags & RTRS_MSG_NEW_RKEY_F) == 0);

	iu = container_of(wc->wr_cqe, struct rtrs_iu, cqe);

	if (unlikely(wc->byte_len < sizeof(*msg))) {
		rtrs_err(con->c.sess, "rkey response is malformed: size %d\n",
			  wc->byte_len);
		goto out;
	}
	ib_dma_sync_single_for_cpu(sess->s.dev->ib_dev, iu->dma_addr,
				   iu->size, DMA_FROM_DEVICE);
	msg = iu->buf;
	if (unlikely(le16_to_cpu(msg->type) != RTRS_MSG_RKEY_RSP)) {
		rtrs_err(sess->clt, "rkey response is malformed: type %d\n",
			  le16_to_cpu(msg->type));
		goto out;
	}
	buf_id = le16_to_cpu(msg->buf_id);
	if (WARN_ON(buf_id >= sess->queue_depth))
		goto out;

	rtrs_from_imm(be32_to_cpu(wc->ex.imm_data), &imm_type, &imm_payload);
	if (likely(imm_type == RTRS_IO_RSP_IMM ||
		   imm_type == RTRS_IO_RSP_W_INV_IMM)) {
		u32 msg_id;

		w_inval = (imm_type == RTRS_IO_RSP_W_INV_IMM);
		rtrs_from_io_rsp_imm(imm_payload, &msg_id, &err);

		if (WARN_ON(buf_id != msg_id))
			goto out;
		sess->rbufs[buf_id].rkey = le32_to_cpu(msg->rkey);
		process_io_rsp(sess, msg_id, err, w_inval);
	}
	ib_dma_sync_single_for_device(sess->s.dev->ib_dev, iu->dma_addr,
				      iu->size, DMA_FROM_DEVICE);
	return rtrs_clt_recv_done(con, wc);
out:
	rtrs_rdma_error_recovery(con);
}

static void rtrs_clt_rdma_done(struct ib_cq *cq, struct ib_wc *wc);

static struct ib_cqe io_comp_cqe = {
	.done = rtrs_clt_rdma_done
};

/*
 * Post x2 empty WRs: first is for this RDMA with IMM,
 * second is for RECV with INV, which happened earlier.
 */
static int rtrs_post_recv_empty_x2(struct rtrs_con *con, struct ib_cqe *cqe)
{
	struct ib_recv_wr wr_arr[2], *wr;
	int i;

	memset(wr_arr, 0, sizeof(wr_arr));
	for (i = 0; i < ARRAY_SIZE(wr_arr); i++) {
		wr = &wr_arr[i];
		wr->wr_cqe  = cqe;
		if (i)
			/* Chain backwards */
			wr->next = &wr_arr[i - 1];
	}

	return ib_post_recv(con->qp, wr, NULL);
}

static void rtrs_clt_rdma_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct rtrs_clt_con *con = cq->cq_context;
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	u32 imm_type, imm_payload;
	bool w_inval = false;
	int err;

	if (unlikely(wc->status != IB_WC_SUCCESS)) {
		if (wc->status != IB_WC_WR_FLUSH_ERR) {
			rtrs_err(sess->clt, "RDMA failed: %s\n",
				  ib_wc_status_msg(wc->status));
			rtrs_rdma_error_recovery(con);
		}
		return;
	}
	rtrs_clt_update_wc_stats(con);

	switch (wc->opcode) {
	case IB_WC_RECV_RDMA_WITH_IMM:
		/*
		 * post_recv() RDMA write completions of IO reqs (read/write)
		 * and hb
		 */
		if (WARN_ON(wc->wr_cqe->done != rtrs_clt_rdma_done))
			return;
		rtrs_from_imm(be32_to_cpu(wc->ex.imm_data),
			       &imm_type, &imm_payload);
		if (likely(imm_type == RTRS_IO_RSP_IMM ||
			   imm_type == RTRS_IO_RSP_W_INV_IMM)) {
			u32 msg_id;

			w_inval = (imm_type == RTRS_IO_RSP_W_INV_IMM);
			rtrs_from_io_rsp_imm(imm_payload, &msg_id, &err);

			process_io_rsp(sess, msg_id, err, w_inval);
		} else if (imm_type == RTRS_HB_MSG_IMM) {
			WARN_ON(con->c.cid);
			rtrs_send_hb_ack(&sess->s);
			if (sess->flags & RTRS_MSG_NEW_RKEY_F)
				return  rtrs_clt_recv_done(con, wc);
		} else if (imm_type == RTRS_HB_ACK_IMM) {
			WARN_ON(con->c.cid);
			sess->s.hb_missed_cnt = 0;
			if (sess->flags & RTRS_MSG_NEW_RKEY_F)
				return  rtrs_clt_recv_done(con, wc);
		} else {
			rtrs_wrn(con->c.sess, "Unknown IMM type %u\n",
				  imm_type);
		}
		if (w_inval)
			/*
			 * Post x2 empty WRs: first is for this RDMA with IMM,
			 * second is for RECV with INV, which happened earlier.
			 */
			err = rtrs_post_recv_empty_x2(&con->c, &io_comp_cqe);
		else
			err = rtrs_post_recv_empty(&con->c, &io_comp_cqe);
		if (unlikely(err)) {
			rtrs_err(con->c.sess, "rtrs_post_recv_empty(): %d\n",
				  err);
			rtrs_rdma_error_recovery(con);
			break;
		}
		break;
	case IB_WC_RECV:
		/*
		 * Key invalidations from server side
		 */
		WARN_ON(!(wc->wc_flags & IB_WC_WITH_INVALIDATE ||
			  wc->wc_flags & IB_WC_WITH_IMM));
		WARN_ON(wc->wr_cqe->done != rtrs_clt_rdma_done);
		if (sess->flags & RTRS_MSG_NEW_RKEY_F) {
			if (wc->wc_flags & IB_WC_WITH_INVALIDATE)
				return  rtrs_clt_recv_done(con, wc);

			return  rtrs_clt_rkey_rsp_done(con, wc);
		}
		break;
	case IB_WC_RDMA_WRITE:
		/*
		 * post_send() RDMA write completions of IO reqs (read/write)
		 */
		break;

	default:
		rtrs_wrn(sess->clt, "Unexpected WC type: %d\n", wc->opcode);
		return;
	}
}

static int post_recv_io(struct rtrs_clt_con *con, size_t q_size)
{
	int err, i;
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);

	for (i = 0; i < q_size; i++) {
		if (sess->flags & RTRS_MSG_NEW_RKEY_F) {
			struct rtrs_iu *iu = &con->rsp_ius[i];

			err = rtrs_iu_post_recv(&con->c, iu);
		} else {
			err = rtrs_post_recv_empty(&con->c, &io_comp_cqe);
		}
		if (unlikely(err))
			return err;
	}

	return 0;
}

static int post_recv_sess(struct rtrs_clt_sess *sess)
{
	size_t q_size = 0;
	int err, cid;

	for (cid = 0; cid < sess->s.con_num; cid++) {
		if (cid == 0)
			q_size = SERVICE_CON_QUEUE_DEPTH;
		else
			q_size = sess->queue_depth;

		/*
		 * x2 for RDMA read responses + FR key invalidations,
		 * RDMA writes do not require any FR registrations.
		 */
		q_size *= 2;

		err = post_recv_io(to_clt_con(sess->s.con[cid]), q_size);
		if (unlikely(err)) {
			rtrs_err(sess->clt, "post_recv_io(), err: %d\n", err);
			return err;
		}
	}

	return 0;
}

struct path_it {
	int i;
	struct list_head skip_list;
	struct rtrs_clt *clt;
	struct rtrs_clt_sess *(*next_path)(struct path_it *it);
};

/**
 * list_next_or_null_rr_rcu - get next list element in round-robin fashion.
 * @head:	the head for the list.
 * @ptr:        the list head to take the next element from.
 * @type:       the type of the struct this is embedded in.
 * @memb:       the name of the list_head within the struct.
 *
 * Next element returned in round-robin fashion, i.e. head will be skipped,
 * but if list is observed as empty, NULL will be returned.
 *
 * This primitive may safely run concurrently with the _rcu list-mutation
 * primitives such as list_add_rcu() as long as it's guarded by rcu_read_lock().
 */
#define list_next_or_null_rr_rcu(head, ptr, type, memb) \
({ \
	list_next_or_null_rcu(head, ptr, type, memb) ?: \
		list_next_or_null_rcu(head, READ_ONCE((ptr)->next), \
				      type, memb); \
})

/**
 * get_next_path_rr() - Returns path in round-robin fashion.
 * @it:	the path pointer
 *
 * Related to @MP_POLICY_RR
 *
 * Locks:
 *    rcu_read_lock() must be hold.
 */
static struct rtrs_clt_sess *get_next_path_rr(struct path_it *it)
{
	struct rtrs_clt_sess __rcu **ppcpu_path;
	struct rtrs_clt_sess *path;
	struct rtrs_clt *clt;

	clt = it->clt;

	/*
	 * Here we use two RCU objects: @paths_list and @pcpu_path
	 * pointer.  See rtrs_clt_remove_path_from_arr() for details
	 * how that is handled.
	 */

	ppcpu_path = this_cpu_ptr(clt->pcpu_path);
	path = rcu_dereference(*ppcpu_path);
	if (unlikely(!path))
		path = list_first_or_null_rcu(&clt->paths_list,
					      typeof(*path), s.entry);
	else
		path = list_next_or_null_rr_rcu(&clt->paths_list,
						&path->s.entry,
						typeof(*path),
						s.entry);
	rcu_assign_pointer(*ppcpu_path, path);

	return path;
}

/**
 * get_next_path_min_inflight() - Returns path with minimal inflight count.
 * @it:	the path pointer
 *
 * Related to @MP_POLICY_MIN_INFLIGHT
 *
 * Locks:
 *    rcu_read_lock() must be hold.
 */
static struct rtrs_clt_sess *get_next_path_min_inflight(struct path_it *it)
{
	struct rtrs_clt_sess *min_path = NULL;
	struct rtrs_clt *clt = it->clt;
	struct rtrs_clt_sess *sess;
	int min_inflight = INT_MAX;
	int inflight;

	list_for_each_entry_rcu(sess, &clt->paths_list, s.entry) {
		if (unlikely(!list_empty(raw_cpu_ptr(sess->mp_skip_entry))))
			continue;

		inflight = atomic_read(&sess->stats->inflight);

		if (inflight < min_inflight) {
			min_inflight = inflight;
			min_path = sess;
		}
	}

	/*
	 * add the path to the skip list, so that next time we can get
	 * a different one
	 */
	if (min_path)
		list_add(raw_cpu_ptr(min_path->mp_skip_entry), &it->skip_list);

	return min_path;
}

static inline void path_it_init(struct path_it *it, struct rtrs_clt *clt)
{
	INIT_LIST_HEAD(&it->skip_list);
	it->clt = clt;
	it->i = 0;

	if (clt->mp_policy == MP_POLICY_RR)
		it->next_path = get_next_path_rr;
	else
		it->next_path = get_next_path_min_inflight;
}

static inline void path_it_deinit(struct path_it *it)
{
	struct list_head *skip, *tmp;
	/*
	 * The skip_list is used only for the MIN_INFLIGHT policy.
	 * We need to remove paths from it, so that next IO can insert
	 * paths (->mp_skip_entry) into a skip_list again.
	 */
	list_for_each_safe(skip, tmp, &it->skip_list)
		list_del_init(skip);
}

/**
 * rtrs_clt_init_req() Initialize an rtrs_clt_io_req holding information
 * about an inflight IO.
 * The user buffer holding user control message (not data) is copied into
 * the corresponding buffer of rtrs_iu (req->iu->buf), which later on will
 * also hold the control message of rtrs.
 * @req: an io request holding information about IO.
 * @sess: client session
 * @conf: conformation callback function to notify upper layer.
 * @permit: permit for allocation of RDMA remote buffer
 * @priv: private pointer
 * @vec: kernel vector containing control message
 * @usr_len: length of the user message
 * @sg: scater list for IO data
 * @sg_cnt: number of scater list entries
 * @data_len: length of the IO data
 * @dir: direction of the IO.
 */
static void rtrs_clt_init_req(struct rtrs_clt_io_req *req,
			      struct rtrs_clt_sess *sess,
			      void (*conf)(void *priv, int errno),
			      struct rtrs_permit *permit, void *priv,
			      const struct kvec *vec, size_t usr_len,
			      struct scatterlist *sg, size_t sg_cnt,
			      size_t data_len, int dir)
{
	struct iov_iter iter;
	size_t len;

	req->permit = permit;
	req->in_use = true;
	req->usr_len = usr_len;
	req->data_len = data_len;
	req->sglist = sg;
	req->sg_cnt = sg_cnt;
	req->priv = priv;
	req->dir = dir;
	req->con = rtrs_permit_to_clt_con(sess, permit);
	req->conf = conf;
	req->need_inv = false;
	req->need_inv_comp = false;
	req->inv_errno = 0;

	iov_iter_kvec(&iter, READ, vec, 1, usr_len);
	len = _copy_from_iter(req->iu->buf, usr_len, &iter);
	WARN_ON(len != usr_len);

	reinit_completion(&req->inv_comp);
}

static struct rtrs_clt_io_req *
rtrs_clt_get_req(struct rtrs_clt_sess *sess,
		 void (*conf)(void *priv, int errno),
		 struct rtrs_permit *permit, void *priv,
		 const struct kvec *vec, size_t usr_len,
		 struct scatterlist *sg, size_t sg_cnt,
		 size_t data_len, int dir)
{
	struct rtrs_clt_io_req *req;

	req = &sess->reqs[permit->mem_id];
	rtrs_clt_init_req(req, sess, conf, permit, priv, vec, usr_len,
			   sg, sg_cnt, data_len, dir);
	return req;
}

static struct rtrs_clt_io_req *
rtrs_clt_get_copy_req(struct rtrs_clt_sess *alive_sess,
		       struct rtrs_clt_io_req *fail_req)
{
	struct rtrs_clt_io_req *req;
	struct kvec vec = {
		.iov_base = fail_req->iu->buf,
		.iov_len  = fail_req->usr_len
	};

	req = &alive_sess->reqs[fail_req->permit->mem_id];
	rtrs_clt_init_req(req, alive_sess, fail_req->conf, fail_req->permit,
			   fail_req->priv, &vec, fail_req->usr_len,
			   fail_req->sglist, fail_req->sg_cnt,
			   fail_req->data_len, fail_req->dir);
	return req;
}

static int rtrs_post_rdma_write_sg(struct rtrs_clt_con *con,
				    struct rtrs_clt_io_req *req,
				    struct rtrs_rbuf *rbuf,
				    u32 size, u32 imm)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	struct ib_sge *sge = req->sge;
	enum ib_send_flags flags;
	struct scatterlist *sg;
	size_t num_sge;
	int i;

	for_each_sg(req->sglist, sg, req->sg_cnt, i) {
		sge[i].addr   = sg_dma_address(sg);
		sge[i].length = sg_dma_len(sg);
		sge[i].lkey   = sess->s.dev->ib_pd->local_dma_lkey;
	}
	sge[i].addr   = req->iu->dma_addr;
	sge[i].length = size;
	sge[i].lkey   = sess->s.dev->ib_pd->local_dma_lkey;

	num_sge = 1 + req->sg_cnt;

	/*
	 * From time to time we have to post signalled sends,
	 * or send queue will fill up and only QP reset can help.
	 */
	flags = atomic_inc_return(&con->io_cnt) % sess->queue_depth ?
			0 : IB_SEND_SIGNALED;

	ib_dma_sync_single_for_device(sess->s.dev->ib_dev, req->iu->dma_addr,
				      size, DMA_TO_DEVICE);

	return rtrs_iu_post_rdma_write_imm(&con->c, req->iu, sge, num_sge,
					    rbuf->rkey, rbuf->addr, imm,
					    flags, NULL);
}

static int rtrs_clt_write_req(struct rtrs_clt_io_req *req)
{
	struct rtrs_clt_con *con = req->con;
	struct rtrs_sess *s = con->c.sess;
	struct rtrs_clt_sess *sess = to_clt_sess(s);
	struct rtrs_msg_rdma_write *msg;

	struct rtrs_rbuf *rbuf;
	int ret, count = 0;
	u32 imm, buf_id;

	const size_t tsize = sizeof(*msg) + req->data_len + req->usr_len;

	if (unlikely(tsize > sess->chunk_size)) {
		rtrs_wrn(s, "Write request failed, size too big %zu > %d\n",
			  tsize, sess->chunk_size);
		return -EMSGSIZE;
	}
	if (req->sg_cnt) {
		count = ib_dma_map_sg(sess->s.dev->ib_dev, req->sglist,
				      req->sg_cnt, req->dir);
		if (unlikely(!count)) {
			rtrs_wrn(s, "Write request failed, map failed\n");
			return -EINVAL;
		}
	}
	/* put rtrs msg after sg and user message */
	msg = req->iu->buf + req->usr_len;
	msg->type = cpu_to_le16(RTRS_MSG_WRITE);
	msg->usr_len = cpu_to_le16(req->usr_len);

	/* rtrs message on server side will be after user data and message */
	imm = req->permit->mem_off + req->data_len + req->usr_len;
	imm = rtrs_to_io_req_imm(imm);
	buf_id = req->permit->mem_id;
	req->sg_size = tsize;
	rbuf = &sess->rbufs[buf_id];

	/*
	 * Update stats now, after request is successfully sent it is not
	 * safe anymore to touch it.
	 */
	rtrs_clt_update_all_stats(req, WRITE);

	ret = rtrs_post_rdma_write_sg(req->con, req, rbuf,
				       req->usr_len + sizeof(*msg),
				       imm);
	if (unlikely(ret)) {
		rtrs_err(s, "Write request failed: %d\n", ret);
		if (sess->clt->mp_policy == MP_POLICY_MIN_INFLIGHT)
			atomic_dec(&sess->stats->inflight);
		if (req->sg_cnt)
			ib_dma_unmap_sg(sess->s.dev->ib_dev, req->sglist,
					req->sg_cnt, req->dir);
	}

	return ret;
}

static int rtrs_map_sg_fr(struct rtrs_clt_io_req *req, size_t count)
{
	int nr;

	/* Align the MR to a 4K page size to match the block virt boundary */
	nr = ib_map_mr_sg(req->mr, req->sglist, count, NULL, SZ_4K);
	if (nr < 0)
		return nr;
	if (unlikely(nr < req->sg_cnt))
		return -EINVAL;
	ib_update_fast_reg_key(req->mr, ib_inc_rkey(req->mr->rkey));

	return nr;
}

static int rtrs_clt_read_req(struct rtrs_clt_io_req *req)
{
	struct rtrs_clt_con *con = req->con;
	struct rtrs_sess *s = con->c.sess;
	struct rtrs_clt_sess *sess = to_clt_sess(s);
	struct rtrs_msg_rdma_read *msg;
	struct rtrs_ib_dev *dev;

	struct ib_reg_wr rwr;
	struct ib_send_wr *wr = NULL;

	int ret, count = 0;
	u32 imm, buf_id;

	const size_t tsize = sizeof(*msg) + req->data_len + req->usr_len;

	s = &sess->s;
	dev = sess->s.dev;

	if (unlikely(tsize > sess->chunk_size)) {
		rtrs_wrn(s,
			  "Read request failed, message size is %zu, bigger than CHUNK_SIZE %d\n",
			  tsize, sess->chunk_size);
		return -EMSGSIZE;
	}

	if (req->sg_cnt) {
		count = ib_dma_map_sg(dev->ib_dev, req->sglist, req->sg_cnt,
				      req->dir);
		if (unlikely(!count)) {
			rtrs_wrn(s,
				  "Read request failed, dma map failed\n");
			return -EINVAL;
		}
	}
	/* put our message into req->buf after user message*/
	msg = req->iu->buf + req->usr_len;
	msg->type = cpu_to_le16(RTRS_MSG_READ);
	msg->usr_len = cpu_to_le16(req->usr_len);

	if (count) {
		ret = rtrs_map_sg_fr(req, count);
		if (ret < 0) {
			rtrs_err_rl(s,
				     "Read request failed, failed to map  fast reg. data, err: %d\n",
				     ret);
			ib_dma_unmap_sg(dev->ib_dev, req->sglist, req->sg_cnt,
					req->dir);
			return ret;
		}
		rwr = (struct ib_reg_wr) {
			.wr.opcode = IB_WR_REG_MR,
			.wr.wr_cqe = &fast_reg_cqe,
			.mr = req->mr,
			.key = req->mr->rkey,
			.access = (IB_ACCESS_LOCAL_WRITE |
				   IB_ACCESS_REMOTE_WRITE),
		};
		wr = &rwr.wr;

		msg->sg_cnt = cpu_to_le16(1);
		msg->flags = cpu_to_le16(RTRS_MSG_NEED_INVAL_F);

		msg->desc[0].addr = cpu_to_le64(req->mr->iova);
		msg->desc[0].key = cpu_to_le32(req->mr->rkey);
		msg->desc[0].len = cpu_to_le32(req->mr->length);

		/* Further invalidation is required */
		req->need_inv = !!RTRS_MSG_NEED_INVAL_F;

	} else {
		msg->sg_cnt = 0;
		msg->flags = 0;
	}
	/*
	 * rtrs message will be after the space reserved for disk data and
	 * user message
	 */
	imm = req->permit->mem_off + req->data_len + req->usr_len;
	imm = rtrs_to_io_req_imm(imm);
	buf_id = req->permit->mem_id;

	req->sg_size  = sizeof(*msg);
	req->sg_size += le16_to_cpu(msg->sg_cnt) * sizeof(struct rtrs_sg_desc);
	req->sg_size += req->usr_len;

	/*
	 * Update stats now, after request is successfully sent it is not
	 * safe anymore to touch it.
	 */
	rtrs_clt_update_all_stats(req, READ);

	ret = rtrs_post_send_rdma(req->con, req, &sess->rbufs[buf_id],
				   req->data_len, imm, wr);
	if (unlikely(ret)) {
		rtrs_err(s, "Read request failed: %d\n", ret);
		if (sess->clt->mp_policy == MP_POLICY_MIN_INFLIGHT)
			atomic_dec(&sess->stats->inflight);
		req->need_inv = false;
		if (req->sg_cnt)
			ib_dma_unmap_sg(dev->ib_dev, req->sglist,
					req->sg_cnt, req->dir);
	}

	return ret;
}

/**
 * rtrs_clt_failover_req() Try to find an active path for a failed request
 * @clt: clt context
 * @fail_req: a failed io request.
 */
static int rtrs_clt_failover_req(struct rtrs_clt *clt,
				 struct rtrs_clt_io_req *fail_req)
{
	struct rtrs_clt_sess *alive_sess;
	struct rtrs_clt_io_req *req;
	int err = -ECONNABORTED;
	struct path_it it;

	rcu_read_lock();
	for (path_it_init(&it, clt);
	     (alive_sess = it.next_path(&it)) && it.i < it.clt->paths_num;
	     it.i++) {
		if (unlikely(READ_ONCE(alive_sess->state) !=
			     RTRS_CLT_CONNECTED))
			continue;
		req = rtrs_clt_get_copy_req(alive_sess, fail_req);
		if (req->dir == DMA_TO_DEVICE)
			err = rtrs_clt_write_req(req);
		else
			err = rtrs_clt_read_req(req);
		if (unlikely(err)) {
			req->in_use = false;
			continue;
		}
		/* Success path */
		rtrs_clt_inc_failover_cnt(alive_sess->stats);
		break;
	}
	path_it_deinit(&it);
	rcu_read_unlock();

	return err;
}

static void fail_all_outstanding_reqs(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt *clt = sess->clt;
	struct rtrs_clt_io_req *req;
	int i, err;

	if (!sess->reqs)
		return;
	for (i = 0; i < sess->queue_depth; ++i) {
		req = &sess->reqs[i];
		if (!req->in_use)
			continue;

		/*
		 * Safely (without notification) complete failed request.
		 * After completion this request is still useble and can
		 * be failovered to another path.
		 */
		complete_rdma_req(req, -ECONNABORTED, false, true);

		err = rtrs_clt_failover_req(clt, req);
		if (unlikely(err))
			/* Failover failed, notify anyway */
			req->conf(req->priv, err);
	}
}

static void free_sess_reqs(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt_io_req *req;
	int i;

	if (!sess->reqs)
		return;
	for (i = 0; i < sess->queue_depth; ++i) {
		req = &sess->reqs[i];
		if (req->mr)
			ib_dereg_mr(req->mr);
		kfree(req->sge);
		rtrs_iu_free(req->iu, sess->s.dev->ib_dev, 1);
	}
	kfree(sess->reqs);
	sess->reqs = NULL;
}

static int alloc_sess_reqs(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt_io_req *req;
	struct rtrs_clt *clt = sess->clt;
	int i, err = -ENOMEM;

	sess->reqs = kcalloc(sess->queue_depth, sizeof(*sess->reqs),
			     GFP_KERNEL);
	if (!sess->reqs)
		return -ENOMEM;

	for (i = 0; i < sess->queue_depth; ++i) {
		req = &sess->reqs[i];
		req->iu = rtrs_iu_alloc(1, sess->max_hdr_size, GFP_KERNEL,
					 sess->s.dev->ib_dev,
					 DMA_TO_DEVICE,
					 rtrs_clt_rdma_done);
		if (!req->iu)
			goto out;

		req->sge = kmalloc_array(clt->max_segments + 1,
					 sizeof(*req->sge), GFP_KERNEL);
		if (!req->sge)
			goto out;

		req->mr = ib_alloc_mr(sess->s.dev->ib_pd, IB_MR_TYPE_MEM_REG,
				      sess->max_pages_per_mr);
		if (IS_ERR(req->mr)) {
			err = PTR_ERR(req->mr);
			req->mr = NULL;
			pr_err("Failed to alloc sess->max_pages_per_mr %d\n",
			       sess->max_pages_per_mr);
			goto out;
		}

		init_completion(&req->inv_comp);
	}

	return 0;

out:
	free_sess_reqs(sess);

	return err;
}

static int alloc_permits(struct rtrs_clt *clt)
{
	unsigned int chunk_bits;
	int err, i;

	clt->permits_map = kcalloc(BITS_TO_LONGS(clt->queue_depth),
				   sizeof(long), GFP_KERNEL);
	if (!clt->permits_map) {
		err = -ENOMEM;
		goto out_err;
	}
	clt->permits = kcalloc(clt->queue_depth, permit_size(clt), GFP_KERNEL);
	if (!clt->permits) {
		err = -ENOMEM;
		goto err_map;
	}
	chunk_bits = ilog2(clt->queue_depth - 1) + 1;
	for (i = 0; i < clt->queue_depth; i++) {
		struct rtrs_permit *permit;

		permit = get_permit(clt, i);
		permit->mem_id = i;
		permit->mem_off = i << (MAX_IMM_PAYL_BITS - chunk_bits);
	}

	return 0;

err_map:
	kfree(clt->permits_map);
	clt->permits_map = NULL;
out_err:
	return err;
}

static void free_permits(struct rtrs_clt *clt)
{
	if (clt->permits_map) {
		size_t sz = clt->queue_depth;

		wait_event(clt->permits_wait,
			   find_first_bit(clt->permits_map, sz) >= sz);
	}
	kfree(clt->permits_map);
	clt->permits_map = NULL;
	kfree(clt->permits);
	clt->permits = NULL;
}

static void query_fast_reg_mode(struct rtrs_clt_sess *sess)
{
	struct ib_device *ib_dev;
	u64 max_pages_per_mr;
	int mr_page_shift;

	ib_dev = sess->s.dev->ib_dev;

	/*
	 * Use the smallest page size supported by the HCA, down to a
	 * minimum of 4096 bytes. We're unlikely to build large sglists
	 * out of smaller entries.
	 */
	mr_page_shift      = max(12, ffs(ib_dev->attrs.page_size_cap) - 1);
	max_pages_per_mr   = ib_dev->attrs.max_mr_size;
	do_div(max_pages_per_mr, (1ull << mr_page_shift));
	sess->max_pages_per_mr =
		min3(sess->max_pages_per_mr, (u32)max_pages_per_mr,
		     ib_dev->attrs.max_fast_reg_page_list_len);
	sess->max_send_sge = ib_dev->attrs.max_send_sge;
}

static bool rtrs_clt_change_state_get_old(struct rtrs_clt_sess *sess,
					   enum rtrs_clt_state new_state,
					   enum rtrs_clt_state *old_state)
{
	bool changed;

	spin_lock_irq(&sess->state_wq.lock);
	if (old_state)
		*old_state = sess->state;
	changed = rtrs_clt_change_state(sess, new_state);
	spin_unlock_irq(&sess->state_wq.lock);

	return changed;
}

static void rtrs_clt_hb_err_handler(struct rtrs_con *c)
{
	struct rtrs_clt_con *con = container_of(c, typeof(*con), c);

	rtrs_rdma_error_recovery(con);
}

static void rtrs_clt_init_hb(struct rtrs_clt_sess *sess)
{
	rtrs_init_hb(&sess->s, &io_comp_cqe,
		      RTRS_HB_INTERVAL_MS,
		      RTRS_HB_MISSED_MAX,
		      rtrs_clt_hb_err_handler,
		      rtrs_wq);
}

static void rtrs_clt_start_hb(struct rtrs_clt_sess *sess)
{
	rtrs_start_hb(&sess->s);
}

static void rtrs_clt_stop_hb(struct rtrs_clt_sess *sess)
{
	rtrs_stop_hb(&sess->s);
}

static void rtrs_clt_reconnect_work(struct work_struct *work);
static void rtrs_clt_close_work(struct work_struct *work);

static struct rtrs_clt_sess *alloc_sess(struct rtrs_clt *clt,
					 const struct rtrs_addr *path,
					 size_t con_num, u16 max_segments,
					 size_t max_segment_size)
{
	struct rtrs_clt_sess *sess;
	int err = -ENOMEM;
	int cpu;

	sess = kzalloc(sizeof(*sess), GFP_KERNEL);
	if (!sess)
		goto err;

	/* Extra connection for user messages */
	con_num += 1;

	sess->s.con = kcalloc(con_num, sizeof(*sess->s.con), GFP_KERNEL);
	if (!sess->s.con)
		goto err_free_sess;

	sess->stats = kzalloc(sizeof(*sess->stats), GFP_KERNEL);
	if (!sess->stats)
		goto err_free_con;

	mutex_init(&sess->init_mutex);
	uuid_gen(&sess->s.uuid);
	memcpy(&sess->s.dst_addr, path->dst,
	       rdma_addr_size((struct sockaddr *)path->dst));

	/*
	 * rdma_resolve_addr() passes src_addr to cma_bind_addr, which
	 * checks the sa_family to be non-zero. If user passed src_addr=NULL
	 * the sess->src_addr will contain only zeros, which is then fine.
	 */
	if (path->src)
		memcpy(&sess->s.src_addr, path->src,
		       rdma_addr_size((struct sockaddr *)path->src));
	strlcpy(sess->s.sessname, clt->sessname, sizeof(sess->s.sessname));
	sess->s.con_num = con_num;
	sess->clt = clt;
	sess->max_pages_per_mr = max_segments * max_segment_size >> 12;
	init_waitqueue_head(&sess->state_wq);
	sess->state = RTRS_CLT_CONNECTING;
	atomic_set(&sess->connected_cnt, 0);
	INIT_WORK(&sess->close_work, rtrs_clt_close_work);
	INIT_DELAYED_WORK(&sess->reconnect_dwork, rtrs_clt_reconnect_work);
	rtrs_clt_init_hb(sess);

	sess->mp_skip_entry = alloc_percpu(typeof(*sess->mp_skip_entry));
	if (!sess->mp_skip_entry)
		goto err_free_stats;

	for_each_possible_cpu(cpu)
		INIT_LIST_HEAD(per_cpu_ptr(sess->mp_skip_entry, cpu));

	err = rtrs_clt_init_stats(sess->stats);
	if (err)
		goto err_free_percpu;

	return sess;

err_free_percpu:
	free_percpu(sess->mp_skip_entry);
err_free_stats:
	kfree(sess->stats);
err_free_con:
	kfree(sess->s.con);
err_free_sess:
	kfree(sess);
err:
	return ERR_PTR(err);
}

void free_sess(struct rtrs_clt_sess *sess)
{
	free_percpu(sess->mp_skip_entry);
	mutex_destroy(&sess->init_mutex);
	kfree(sess->s.con);
	kfree(sess->rbufs);
	kfree(sess);
}

static int create_con(struct rtrs_clt_sess *sess, unsigned int cid)
{
	struct rtrs_clt_con *con;

	con = kzalloc(sizeof(*con), GFP_KERNEL);
	if (!con)
		return -ENOMEM;

	/* Map first two connections to the first CPU */
	con->cpu  = (cid ? cid - 1 : 0) % nr_cpu_ids;
	con->c.cid = cid;
	con->c.sess = &sess->s;
	atomic_set(&con->io_cnt, 0);
	mutex_init(&con->con_mutex);

	sess->s.con[cid] = &con->c;

	return 0;
}

static void destroy_con(struct rtrs_clt_con *con)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);

	sess->s.con[con->c.cid] = NULL;
	mutex_destroy(&con->con_mutex);
	kfree(con);
}

static int create_con_cq_qp(struct rtrs_clt_con *con)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	u32 max_send_wr, max_recv_wr, cq_size;
	int err, cq_vector;
	struct rtrs_msg_rkey_rsp *rsp;

	lockdep_assert_held(&con->con_mutex);
	if (con->c.cid == 0) {
		/*
		 * One completion for each receive and two for each send
		 * (send request + registration)
		 * + 2 for drain and heartbeat
		 * in case qp gets into error state
		 */
		max_send_wr = SERVICE_CON_QUEUE_DEPTH * 2 + 2;
		max_recv_wr = SERVICE_CON_QUEUE_DEPTH * 2 + 2;
		/* We must be the first here */
		if (WARN_ON(sess->s.dev))
			return -EINVAL;

		/*
		 * The whole session uses device from user connection.
		 * Be careful not to close user connection before ib dev
		 * is gracefully put.
		 */
		sess->s.dev = rtrs_ib_dev_find_or_add(con->c.cm_id->device,
						       &dev_pd);
		if (!sess->s.dev) {
			rtrs_wrn(sess->clt,
				  "rtrs_ib_dev_find_get_or_add(): no memory\n");
			return -ENOMEM;
		}
		sess->s.dev_ref = 1;
		query_fast_reg_mode(sess);
	} else {
		/*
		 * Here we assume that session members are correctly set.
		 * This is always true if user connection (cid == 0) is
		 * established first.
		 */
		if (WARN_ON(!sess->s.dev))
			return -EINVAL;
		if (WARN_ON(!sess->queue_depth))
			return -EINVAL;

		/* Shared between connections */
		sess->s.dev_ref++;
		max_send_wr =
			min_t(int, sess->s.dev->ib_dev->attrs.max_qp_wr,
			      /* QD * (REQ + RSP + FR REGS or INVS) + drain */
			      sess->queue_depth * 3 + 1);
		max_recv_wr =
			min_t(int, sess->s.dev->ib_dev->attrs.max_qp_wr,
			      sess->queue_depth * 3 + 1);
	}
	/* alloc iu to recv new rkey reply when server reports flags set */
	if (sess->flags & RTRS_MSG_NEW_RKEY_F || con->c.cid == 0) {
		con->rsp_ius = rtrs_iu_alloc(max_recv_wr, sizeof(*rsp),
					      GFP_KERNEL, sess->s.dev->ib_dev,
					      DMA_FROM_DEVICE,
					      rtrs_clt_rdma_done);
		if (!con->rsp_ius)
			return -ENOMEM;
		con->queue_size = max_recv_wr;
	}
	cq_size = max_send_wr + max_recv_wr;
	cq_vector = con->cpu % sess->s.dev->ib_dev->num_comp_vectors;
	err = rtrs_cq_qp_create(&sess->s, &con->c, sess->max_send_sge,
				 cq_vector, cq_size, max_send_wr,
				 max_recv_wr, IB_POLL_SOFTIRQ);
	/*
	 * In case of error we do not bother to clean previous allocations,
	 * since destroy_con_cq_qp() must be called.
	 */
	return err;
}

static void destroy_con_cq_qp(struct rtrs_clt_con *con)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);

	/*
	 * Be careful here: destroy_con_cq_qp() can be called even
	 * create_con_cq_qp() failed, see comments there.
	 */
	lockdep_assert_held(&con->con_mutex);
	rtrs_cq_qp_destroy(&con->c);
	if (con->rsp_ius) {
		rtrs_iu_free(con->rsp_ius, sess->s.dev->ib_dev, con->queue_size);
		con->rsp_ius = NULL;
		con->queue_size = 0;
	}
	if (sess->s.dev_ref && !--sess->s.dev_ref) {
		rtrs_ib_dev_put(sess->s.dev);
		sess->s.dev = NULL;
	}
}

static void stop_cm(struct rtrs_clt_con *con)
{
	rdma_disconnect(con->c.cm_id);
	if (con->c.qp)
		ib_drain_qp(con->c.qp);
}

static void destroy_cm(struct rtrs_clt_con *con)
{
	rdma_destroy_id(con->c.cm_id);
	con->c.cm_id = NULL;
}

static int rtrs_rdma_addr_resolved(struct rtrs_clt_con *con)
{
	struct rtrs_sess *s = con->c.sess;
	int err;

	mutex_lock(&con->con_mutex);
	err = create_con_cq_qp(con);
	mutex_unlock(&con->con_mutex);
	if (err) {
		rtrs_err(s, "create_con_cq_qp(), err: %d\n", err);
		return err;
	}
	err = rdma_resolve_route(con->c.cm_id, RTRS_CONNECT_TIMEOUT_MS);
	if (err)
		rtrs_err(s, "Resolving route failed, err: %d\n", err);

	return err;
}

static int rtrs_rdma_route_resolved(struct rtrs_clt_con *con)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	struct rtrs_clt *clt = sess->clt;
	struct rtrs_msg_conn_req msg;
	struct rdma_conn_param param;

	int err;

	param = (struct rdma_conn_param) {
		.retry_count = 7,
		.rnr_retry_count = 7,
		.private_data = &msg,
		.private_data_len = sizeof(msg),
	};

	msg = (struct rtrs_msg_conn_req) {
		.magic = cpu_to_le16(RTRS_MAGIC),
		.version = cpu_to_le16(RTRS_PROTO_VER),
		.cid = cpu_to_le16(con->c.cid),
		.cid_num = cpu_to_le16(sess->s.con_num),
		.recon_cnt = cpu_to_le16(sess->s.recon_cnt),
	};
	msg.first_conn = sess->for_new_clt ? FIRST_CONN : 0;
	uuid_copy(&msg.sess_uuid, &sess->s.uuid);
	uuid_copy(&msg.paths_uuid, &clt->paths_uuid);

	err = rdma_connect_locked(con->c.cm_id, &param);
	if (err)
		rtrs_err(clt, "rdma_connect_locked(): %d\n", err);

	return err;
}

static int rtrs_rdma_conn_established(struct rtrs_clt_con *con,
				       struct rdma_cm_event *ev)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	struct rtrs_clt *clt = sess->clt;
	const struct rtrs_msg_conn_rsp *msg;
	u16 version, queue_depth;
	int errno;
	u8 len;

	msg = ev->param.conn.private_data;
	len = ev->param.conn.private_data_len;
	if (len < sizeof(*msg)) {
		rtrs_err(clt, "Invalid RTRS connection response\n");
		return -ECONNRESET;
	}
	if (le16_to_cpu(msg->magic) != RTRS_MAGIC) {
		rtrs_err(clt, "Invalid RTRS magic\n");
		return -ECONNRESET;
	}
	version = le16_to_cpu(msg->version);
	if (version >> 8 != RTRS_PROTO_VER_MAJOR) {
		rtrs_err(clt, "Unsupported major RTRS version: %d, expected %d\n",
			  version >> 8, RTRS_PROTO_VER_MAJOR);
		return -ECONNRESET;
	}
	errno = le16_to_cpu(msg->errno);
	if (errno) {
		rtrs_err(clt, "Invalid RTRS message: errno %d\n",
			  errno);
		return -ECONNRESET;
	}
	if (con->c.cid == 0) {
		queue_depth = le16_to_cpu(msg->queue_depth);

		if (queue_depth > MAX_SESS_QUEUE_DEPTH) {
			rtrs_err(clt, "Invalid RTRS message: queue=%d\n",
				  queue_depth);
			return -ECONNRESET;
		}
		if (!sess->rbufs || sess->queue_depth < queue_depth) {
			kfree(sess->rbufs);
			sess->rbufs = kcalloc(queue_depth, sizeof(*sess->rbufs),
					      GFP_KERNEL);
			if (!sess->rbufs)
				return -ENOMEM;
		}
		sess->queue_depth = queue_depth;
		sess->max_hdr_size = le32_to_cpu(msg->max_hdr_size);
		sess->max_io_size = le32_to_cpu(msg->max_io_size);
		sess->flags = le32_to_cpu(msg->flags);
		sess->chunk_size = sess->max_io_size + sess->max_hdr_size;

		/*
		 * Global queue depth and IO size is always a minimum.
		 * If while a reconnection server sends us a value a bit
		 * higher - client does not care and uses cached minimum.
		 *
		 * Since we can have several sessions (paths) restablishing
		 * connections in parallel, use lock.
		 */
		mutex_lock(&clt->paths_mutex);
		clt->queue_depth = min_not_zero(sess->queue_depth,
						clt->queue_depth);
		clt->max_io_size = min_not_zero(sess->max_io_size,
						clt->max_io_size);
		mutex_unlock(&clt->paths_mutex);

		/*
		 * Cache the hca_port and hca_name for sysfs
		 */
		sess->hca_port = con->c.cm_id->port_num;
		scnprintf(sess->hca_name, sizeof(sess->hca_name),
			  sess->s.dev->ib_dev->name);
		sess->s.src_addr = con->c.cm_id->route.addr.src_addr;
		/* set for_new_clt, to allow future reconnect on any path */
		sess->for_new_clt = 1;
	}

	return 0;
}

static inline void flag_success_on_conn(struct rtrs_clt_con *con)
{
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);

	atomic_inc(&sess->connected_cnt);
	con->cm_err = 1;
}

static int rtrs_rdma_conn_rejected(struct rtrs_clt_con *con,
				    struct rdma_cm_event *ev)
{
	struct rtrs_sess *s = con->c.sess;
	const struct rtrs_msg_conn_rsp *msg;
	const char *rej_msg;
	int status, errno;
	u8 data_len;

	status = ev->status;
	rej_msg = rdma_reject_msg(con->c.cm_id, status);
	msg = rdma_consumer_reject_data(con->c.cm_id, ev, &data_len);

	if (msg && data_len >= sizeof(*msg)) {
		errno = (int16_t)le16_to_cpu(msg->errno);
		if (errno == -EBUSY)
			rtrs_err(s,
				  "Previous session is still exists on the server, please reconnect later\n");
		else
			rtrs_err(s,
				  "Connect rejected: status %d (%s), rtrs errno %d\n",
				  status, rej_msg, errno);
	} else {
		rtrs_err(s,
			  "Connect rejected but with malformed message: status %d (%s)\n",
			  status, rej_msg);
	}

	return -ECONNRESET;
}

static void rtrs_clt_close_conns(struct rtrs_clt_sess *sess, bool wait)
{
	if (rtrs_clt_change_state_get_old(sess, RTRS_CLT_CLOSING, NULL))
		queue_work(rtrs_wq, &sess->close_work);
	if (wait)
		flush_work(&sess->close_work);
}

static inline void flag_error_on_conn(struct rtrs_clt_con *con, int cm_err)
{
	if (con->cm_err == 1) {
		struct rtrs_clt_sess *sess;

		sess = to_clt_sess(con->c.sess);
		if (atomic_dec_and_test(&sess->connected_cnt))

			wake_up(&sess->state_wq);
	}
	con->cm_err = cm_err;
}

static int rtrs_clt_rdma_cm_handler(struct rdma_cm_id *cm_id,
				     struct rdma_cm_event *ev)
{
	struct rtrs_clt_con *con = cm_id->context;
	struct rtrs_sess *s = con->c.sess;
	struct rtrs_clt_sess *sess = to_clt_sess(s);
	int cm_err = 0;

	switch (ev->event) {
	case RDMA_CM_EVENT_ADDR_RESOLVED:
		cm_err = rtrs_rdma_addr_resolved(con);
		break;
	case RDMA_CM_EVENT_ROUTE_RESOLVED:
		cm_err = rtrs_rdma_route_resolved(con);
		break;
	case RDMA_CM_EVENT_ESTABLISHED:
		cm_err = rtrs_rdma_conn_established(con, ev);
		if (likely(!cm_err)) {
			/*
			 * Report success and wake up. Here we abuse state_wq,
			 * i.e. wake up without state change, but we set cm_err.
			 */
			flag_success_on_conn(con);
			wake_up(&sess->state_wq);
			return 0;
		}
		break;
	case RDMA_CM_EVENT_REJECTED:
		cm_err = rtrs_rdma_conn_rejected(con, ev);
		break;
	case RDMA_CM_EVENT_DISCONNECTED:
		/* No message for disconnecting */
		cm_err = -ECONNRESET;
		break;
	case RDMA_CM_EVENT_CONNECT_ERROR:
	case RDMA_CM_EVENT_UNREACHABLE:
	case RDMA_CM_EVENT_ADDR_CHANGE:
	case RDMA_CM_EVENT_TIMEWAIT_EXIT:
		rtrs_wrn(s, "CM error event %d\n", ev->event);
		cm_err = -ECONNRESET;
		break;
	case RDMA_CM_EVENT_ADDR_ERROR:
	case RDMA_CM_EVENT_ROUTE_ERROR:
		rtrs_wrn(s, "CM error event %d\n", ev->event);
		cm_err = -EHOSTUNREACH;
		break;
	case RDMA_CM_EVENT_DEVICE_REMOVAL:
		/*
		 * Device removal is a special case.  Queue close and return 0.
		 */
		rtrs_clt_close_conns(sess, false);
		return 0;
	default:
		rtrs_err(s, "Unexpected RDMA CM event (%d)\n", ev->event);
		cm_err = -ECONNRESET;
		break;
	}

	if (cm_err) {
		/*
		 * cm error makes sense only on connection establishing,
		 * in other cases we rely on normal procedure of reconnecting.
		 */
		flag_error_on_conn(con, cm_err);
		rtrs_rdma_error_recovery(con);
	}

	return 0;
}

static int create_cm(struct rtrs_clt_con *con)
{
	struct rtrs_sess *s = con->c.sess;
	struct rtrs_clt_sess *sess = to_clt_sess(s);
	struct rdma_cm_id *cm_id;
	int err;

	cm_id = rdma_create_id(&init_net, rtrs_clt_rdma_cm_handler, con,
			       sess->s.dst_addr.ss_family == AF_IB ?
			       RDMA_PS_IB : RDMA_PS_TCP, IB_QPT_RC);
	if (IS_ERR(cm_id)) {
		err = PTR_ERR(cm_id);
		rtrs_err(s, "Failed to create CM ID, err: %d\n", err);

		return err;
	}
	con->c.cm_id = cm_id;
	con->cm_err = 0;
	/* allow the port to be reused */
	err = rdma_set_reuseaddr(cm_id, 1);
	if (err != 0) {
		rtrs_err(s, "Set address reuse failed, err: %d\n", err);
		goto destroy_cm;
	}
	err = rdma_resolve_addr(cm_id, (struct sockaddr *)&sess->s.src_addr,
				(struct sockaddr *)&sess->s.dst_addr,
				RTRS_CONNECT_TIMEOUT_MS);
	if (err) {
		rtrs_err(s, "Failed to resolve address, err: %d\n", err);
		goto destroy_cm;
	}
	/*
	 * Combine connection status and session events. This is needed
	 * for waiting two possible cases: cm_err has something meaningful
	 * or session state was really changed to error by device removal.
	 */
	err = wait_event_interruptible_timeout(
			sess->state_wq,
			con->cm_err || sess->state != RTRS_CLT_CONNECTING,
			msecs_to_jiffies(RTRS_CONNECT_TIMEOUT_MS));
	if (err == 0 || err == -ERESTARTSYS) {
		if (err == 0)
			err = -ETIMEDOUT;
		/* Timedout or interrupted */
		goto errr;
	}
	if (con->cm_err < 0) {
		err = con->cm_err;
		goto errr;
	}
	if (READ_ONCE(sess->state) != RTRS_CLT_CONNECTING) {
		/* Device removal */
		err = -ECONNABORTED;
		goto errr;
	}

	return 0;

errr:
	stop_cm(con);
	mutex_lock(&con->con_mutex);
	destroy_con_cq_qp(con);
	mutex_unlock(&con->con_mutex);
destroy_cm:
	destroy_cm(con);

	return err;
}

static void rtrs_clt_sess_up(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt *clt = sess->clt;
	int up;

	/*
	 * We can fire RECONNECTED event only when all paths were
	 * connected on rtrs_clt_open(), then each was disconnected
	 * and the first one connected again.  That's why this nasty
	 * game with counter value.
	 */

	mutex_lock(&clt->paths_ev_mutex);
	up = ++clt->paths_up;
	/*
	 * Here it is safe to access paths num directly since up counter
	 * is greater than MAX_PATHS_NUM only while rtrs_clt_open() is
	 * in progress, thus paths removals are impossible.
	 */
	if (up > MAX_PATHS_NUM && up == MAX_PATHS_NUM + clt->paths_num)
		clt->paths_up = clt->paths_num;
	else if (up == 1)
		clt->link_ev(clt->priv, RTRS_CLT_LINK_EV_RECONNECTED);
	mutex_unlock(&clt->paths_ev_mutex);

	/* Mark session as established */
	sess->established = true;
	sess->reconnect_attempts = 0;
	sess->stats->reconnects.successful_cnt++;
}

static void rtrs_clt_sess_down(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt *clt = sess->clt;

	if (!sess->established)
		return;

	sess->established = false;
	mutex_lock(&clt->paths_ev_mutex);
	WARN_ON(!clt->paths_up);
	if (--clt->paths_up == 0)
		clt->link_ev(clt->priv, RTRS_CLT_LINK_EV_DISCONNECTED);
	mutex_unlock(&clt->paths_ev_mutex);
}

static void rtrs_clt_stop_and_destroy_conns(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt_con *con;
	unsigned int cid;

	WARN_ON(READ_ONCE(sess->state) == RTRS_CLT_CONNECTED);

	/*
	 * Possible race with rtrs_clt_open(), when DEVICE_REMOVAL comes
	 * exactly in between.  Start destroying after it finishes.
	 */
	mutex_lock(&sess->init_mutex);
	mutex_unlock(&sess->init_mutex);

	/*
	 * All IO paths must observe !CONNECTED state before we
	 * free everything.
	 */
	synchronize_rcu();

	rtrs_clt_stop_hb(sess);

	/*
	 * The order it utterly crucial: firstly disconnect and complete all
	 * rdma requests with error (thus set in_use=false for requests),
	 * then fail outstanding requests checking in_use for each, and
	 * eventually notify upper layer about session disconnection.
	 */

	for (cid = 0; cid < sess->s.con_num; cid++) {
		if (!sess->s.con[cid])
			break;
		con = to_clt_con(sess->s.con[cid]);
		stop_cm(con);
	}
	fail_all_outstanding_reqs(sess);
	free_sess_reqs(sess);
	rtrs_clt_sess_down(sess);

	/*
	 * Wait for graceful shutdown, namely when peer side invokes
	 * rdma_disconnect(). 'connected_cnt' is decremented only on
	 * CM events, thus if other side had crashed and hb has detected
	 * something is wrong, here we will stuck for exactly timeout ms,
	 * since CM does not fire anything.  That is fine, we are not in
	 * hurry.
	 */
	wait_event_timeout(sess->state_wq, !atomic_read(&sess->connected_cnt),
			   msecs_to_jiffies(RTRS_CONNECT_TIMEOUT_MS));

	for (cid = 0; cid < sess->s.con_num; cid++) {
		if (!sess->s.con[cid])
			break;
		con = to_clt_con(sess->s.con[cid]);
		mutex_lock(&con->con_mutex);
		destroy_con_cq_qp(con);
		mutex_unlock(&con->con_mutex);
		destroy_cm(con);
		destroy_con(con);
	}
}

static inline bool xchg_sessions(struct rtrs_clt_sess __rcu **rcu_ppcpu_path,
				 struct rtrs_clt_sess *sess,
				 struct rtrs_clt_sess *next)
{
	struct rtrs_clt_sess **ppcpu_path;

	/* Call cmpxchg() without sparse warnings */
	ppcpu_path = (typeof(ppcpu_path))rcu_ppcpu_path;
	return sess == cmpxchg(ppcpu_path, sess, next);
}

static void rtrs_clt_remove_path_from_arr(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt *clt = sess->clt;
	struct rtrs_clt_sess *next;
	bool wait_for_grace = false;
	int cpu;

	mutex_lock(&clt->paths_mutex);
	list_del_rcu(&sess->s.entry);

	/* Make sure everybody observes path removal. */
	synchronize_rcu();

	/*
	 * At this point nobody sees @sess in the list, but still we have
	 * dangling pointer @pcpu_path which _can_ point to @sess.  Since
	 * nobody can observe @sess in the list, we guarantee that IO path
	 * will not assign @sess to @pcpu_path, i.e. @pcpu_path can be equal
	 * to @sess, but can never again become @sess.
	 */

	/*
	 * Decrement paths number only after grace period, because
	 * caller of do_each_path() must firstly observe list without
	 * path and only then decremented paths number.
	 *
	 * Otherwise there can be the following situation:
	 *    o Two paths exist and IO is coming.
	 *    o One path is removed:
	 *      CPU#0                          CPU#1
	 *      do_each_path():                rtrs_clt_remove_path_from_arr():
	 *          path = get_next_path()
	 *          ^^^                            list_del_rcu(path)
	 *          [!CONNECTED path]              clt->paths_num--
	 *                                              ^^^^^^^^^
	 *          load clt->paths_num                 from 2 to 1
	 *                    ^^^^^^^^^
	 *                    sees 1
	 *
	 *      path is observed as !CONNECTED, but do_each_path() loop
	 *      ends, because expression i < clt->paths_num is false.
	 */
	clt->paths_num--;

	/*
	 * Get @next connection from current @sess which is going to be
	 * removed.  If @sess is the last element, then @next is NULL.
	 */
	rcu_read_lock();
	next = list_next_or_null_rr_rcu(&clt->paths_list, &sess->s.entry,
					typeof(*next), s.entry);
	rcu_read_unlock();

	/*
	 * @pcpu paths can still point to the path which is going to be
	 * removed, so change the pointer manually.
	 */
	for_each_possible_cpu(cpu) {
		struct rtrs_clt_sess __rcu **ppcpu_path;

		ppcpu_path = per_cpu_ptr(clt->pcpu_path, cpu);
		if (rcu_dereference_protected(*ppcpu_path,
			lockdep_is_held(&clt->paths_mutex)) != sess)
			/*
			 * synchronize_rcu() was called just after deleting
			 * entry from the list, thus IO code path cannot
			 * change pointer back to the pointer which is going
			 * to be removed, we are safe here.
			 */
			continue;

		/*
		 * We race with IO code path, which also changes pointer,
		 * thus we have to be careful not to overwrite it.
		 */
		if (xchg_sessions(ppcpu_path, sess, next))
			/*
			 * @ppcpu_path was successfully replaced with @next,
			 * that means that someone could also pick up the
			 * @sess and dereferencing it right now, so wait for
			 * a grace period is required.
			 */
			wait_for_grace = true;
	}
	if (wait_for_grace)
		synchronize_rcu();

	mutex_unlock(&clt->paths_mutex);
}

static void rtrs_clt_add_path_to_arr(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt *clt = sess->clt;

	mutex_lock(&clt->paths_mutex);
	clt->paths_num++;

	list_add_tail_rcu(&sess->s.entry, &clt->paths_list);
	mutex_unlock(&clt->paths_mutex);
}

static void rtrs_clt_close_work(struct work_struct *work)
{
	struct rtrs_clt_sess *sess;

	sess = container_of(work, struct rtrs_clt_sess, close_work);

	cancel_delayed_work_sync(&sess->reconnect_dwork);
	rtrs_clt_stop_and_destroy_conns(sess);
	rtrs_clt_change_state_get_old(sess, RTRS_CLT_CLOSED, NULL);
}

static int init_conns(struct rtrs_clt_sess *sess)
{
	unsigned int cid;
	int err;

	/*
	 * On every new session connections increase reconnect counter
	 * to avoid clashes with previous sessions not yet closed
	 * sessions on a server side.
	 */
	sess->s.recon_cnt++;

	/* Establish all RDMA connections  */
	for (cid = 0; cid < sess->s.con_num; cid++) {
		err = create_con(sess, cid);
		if (err)
			goto destroy;

		err = create_cm(to_clt_con(sess->s.con[cid]));
		if (err) {
			destroy_con(to_clt_con(sess->s.con[cid]));
			goto destroy;
		}
	}
	err = alloc_sess_reqs(sess);
	if (err)
		goto destroy;

	rtrs_clt_start_hb(sess);

	return 0;

destroy:
	while (cid--) {
		struct rtrs_clt_con *con = to_clt_con(sess->s.con[cid]);

		stop_cm(con);

		mutex_lock(&con->con_mutex);
		destroy_con_cq_qp(con);
		mutex_unlock(&con->con_mutex);
		destroy_cm(con);
		destroy_con(con);
	}
	/*
	 * If we've never taken async path and got an error, say,
	 * doing rdma_resolve_addr(), switch to CONNECTION_ERR state
	 * manually to keep reconnecting.
	 */
	rtrs_clt_change_state_get_old(sess, RTRS_CLT_CONNECTING_ERR, NULL);

	return err;
}

static void rtrs_clt_info_req_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct rtrs_clt_con *con = cq->cq_context;
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	struct rtrs_iu *iu;

	iu = container_of(wc->wr_cqe, struct rtrs_iu, cqe);
	rtrs_iu_free(iu, sess->s.dev->ib_dev, 1);

	if (unlikely(wc->status != IB_WC_SUCCESS)) {
		rtrs_err(sess->clt, "Sess info request send failed: %s\n",
			  ib_wc_status_msg(wc->status));
		rtrs_clt_change_state_get_old(sess, RTRS_CLT_CONNECTING_ERR, NULL);
		return;
	}

	rtrs_clt_update_wc_stats(con);
}

static int process_info_rsp(struct rtrs_clt_sess *sess,
			    const struct rtrs_msg_info_rsp *msg)
{
	unsigned int sg_cnt, total_len;
	int i, sgi;

	sg_cnt = le16_to_cpu(msg->sg_cnt);
	if (unlikely(!sg_cnt || (sess->queue_depth % sg_cnt))) {
		rtrs_err(sess->clt, "Incorrect sg_cnt %d, is not multiple\n",
			  sg_cnt);
		return -EINVAL;
	}

	/*
	 * Check if IB immediate data size is enough to hold the mem_id and
	 * the offset inside the memory chunk.
	 */
	if (unlikely((ilog2(sg_cnt - 1) + 1) +
		     (ilog2(sess->chunk_size - 1) + 1) >
		     MAX_IMM_PAYL_BITS)) {
		rtrs_err(sess->clt,
			  "RDMA immediate size (%db) not enough to encode %d buffers of size %dB\n",
			  MAX_IMM_PAYL_BITS, sg_cnt, sess->chunk_size);
		return -EINVAL;
	}
	total_len = 0;
	for (sgi = 0, i = 0; sgi < sg_cnt && i < sess->queue_depth; sgi++) {
		const struct rtrs_sg_desc *desc = &msg->desc[sgi];
		u32 len, rkey;
		u64 addr;

		addr = le64_to_cpu(desc->addr);
		rkey = le32_to_cpu(desc->key);
		len  = le32_to_cpu(desc->len);

		total_len += len;

		if (unlikely(!len || (len % sess->chunk_size))) {
			rtrs_err(sess->clt, "Incorrect [%d].len %d\n", sgi,
				  len);
			return -EINVAL;
		}
		for ( ; len && i < sess->queue_depth; i++) {
			sess->rbufs[i].addr = addr;
			sess->rbufs[i].rkey = rkey;

			len  -= sess->chunk_size;
			addr += sess->chunk_size;
		}
	}
	/* Sanity check */
	if (unlikely(sgi != sg_cnt || i != sess->queue_depth)) {
		rtrs_err(sess->clt, "Incorrect sg vector, not fully mapped\n");
		return -EINVAL;
	}
	if (unlikely(total_len != sess->chunk_size * sess->queue_depth)) {
		rtrs_err(sess->clt, "Incorrect total_len %d\n", total_len);
		return -EINVAL;
	}

	return 0;
}

static void rtrs_clt_info_rsp_done(struct ib_cq *cq, struct ib_wc *wc)
{
	struct rtrs_clt_con *con = cq->cq_context;
	struct rtrs_clt_sess *sess = to_clt_sess(con->c.sess);
	struct rtrs_msg_info_rsp *msg;
	enum rtrs_clt_state state;
	struct rtrs_iu *iu;
	size_t rx_sz;
	int err;

	state = RTRS_CLT_CONNECTING_ERR;

	WARN_ON(con->c.cid);
	iu = container_of(wc->wr_cqe, struct rtrs_iu, cqe);
	if (unlikely(wc->status != IB_WC_SUCCESS)) {
		rtrs_err(sess->clt, "Sess info response recv failed: %s\n",
			  ib_wc_status_msg(wc->status));
		goto out;
	}
	WARN_ON(wc->opcode != IB_WC_RECV);

	if (unlikely(wc->byte_len < sizeof(*msg))) {
		rtrs_err(sess->clt, "Sess info response is malformed: size %d\n",
			  wc->byte_len);
		goto out;
	}
	ib_dma_sync_single_for_cpu(sess->s.dev->ib_dev, iu->dma_addr,
				   iu->size, DMA_FROM_DEVICE);
	msg = iu->buf;
	if (unlikely(le16_to_cpu(msg->type) != RTRS_MSG_INFO_RSP)) {
		rtrs_err(sess->clt, "Sess info response is malformed: type %d\n",
			  le16_to_cpu(msg->type));
		goto out;
	}
	rx_sz  = sizeof(*msg);
	rx_sz += sizeof(msg->desc[0]) * le16_to_cpu(msg->sg_cnt);
	if (unlikely(wc->byte_len < rx_sz)) {
		rtrs_err(sess->clt, "Sess info response is malformed: size %d\n",
			  wc->byte_len);
		goto out;
	}
	err = process_info_rsp(sess, msg);
	if (unlikely(err))
		goto out;

	err = post_recv_sess(sess);
	if (unlikely(err))
		goto out;

	state = RTRS_CLT_CONNECTED;

out:
	rtrs_clt_update_wc_stats(con);
	rtrs_iu_free(iu, sess->s.dev->ib_dev, 1);
	rtrs_clt_change_state_get_old(sess, state, NULL);
}

static int rtrs_send_sess_info(struct rtrs_clt_sess *sess)
{
	struct rtrs_clt_con *usr_con = to_clt_con(sess->s.con[0]);
	struct rtrs_msg_info_req *msg;
	struct rtrs_iu *tx_iu, *rx_iu;
	size_t rx_sz;
	int err;

	rx_sz  = sizeof(struct rtrs_msg_info_rsp);
	rx_sz += sizeof(u64) * MAX_SESS_QUEUE_DEPTH;

	tx_iu = rtrs_iu_alloc(1, sizeof(struct rtrs_msg_info_req), GFP_KERNEL,
			       sess->s.dev->ib_dev, DMA_TO_DEVICE,
			       rtrs_clt_info_req_done);
	rx_iu = rtrs_iu_alloc(1, rx_sz, GFP_KERNEL, sess->s.dev->ib_dev,
			       DMA_FROM_DEVICE, rtrs_clt_info_rsp_done);
	if (unlikely(!tx_iu || !rx_iu)) {
		err = -ENOMEM;
		goto out;
	}
	/* Prepare for getting info response */
	err = rtrs_iu_post_recv(&usr_con->c, rx_iu);
	if (unlikely(err)) {
		rtrs_err(sess->clt, "rtrs_iu_post_recv(), err: %d\n", err);
		goto out;
	}
	rx_iu = NULL;

	msg = tx_iu->buf;
	msg->type = cpu_to_le16(RTRS_MSG_INFO_REQ);
	memcpy(msg->sessname, sess->s.sessname, sizeof(msg->sessname));

	ib_dma_sync_single_for_device(sess->s.dev->ib_dev, tx_iu->dma_addr,
				      tx_iu->size, DMA_TO_DEVICE);

	/* Send info request */
	err = rtrs_iu_post_send(&usr_con->c, tx_iu, sizeof(*msg), NULL);
	if (unlikely(err)) {
		rtrs_err(sess->clt, "rtrs_iu_post_send(), err: %d\n", err);
		goto out;
	}
	tx_iu = NULL;

	/* Wait for state change */
	wait_event_interruptible_timeout(sess->state_wq,
					 sess->state != RTRS_CLT_CONNECTING,
					 msecs_to_jiffies(
						 RTRS_CONNECT_TIMEOUT_MS));
	if (unlikely(READ_ONCE(sess->state) != RTRS_CLT_CONNECTED)) {
		if (READ_ONCE(sess->state) == RTRS_CLT_CONNECTING_ERR)
			err = -ECONNRESET;
		else
			err = -ETIMEDOUT;
	}

out:
	if (tx_iu)
		rtrs_iu_free(tx_iu, sess->s.dev->ib_dev, 1);
	if (rx_iu)
		rtrs_iu_free(rx_iu, sess->s.dev->ib_dev, 1);
	if (unlikely(err))
		/* If we've never taken async path because of malloc problems */
		rtrs_clt_change_state_get_old(sess, RTRS_CLT_CONNECTING_ERR, NULL);

	return err;
}

/**
 * init_sess() - establishes all session connections and does handshake
 * @sess: client session.
 * In case of error full close or reconnect procedure should be taken,
 * because reconnect or close async works can be started.
 */
static int init_sess(struct rtrs_clt_sess *sess)
{
	int err;

	mutex_lock(&sess->init_mutex);
	err = init_conns(sess);
	if (err) {
		rtrs_err(sess->clt, "init_conns(), err: %d\n", err);
		goto out;
	}
	err = rtrs_send_sess_info(sess);
	if (err) {
		rtrs_err(sess->clt, "rtrs_send_sess_info(), err: %d\n", err);
		goto out;
	}
	rtrs_clt_sess_up(sess);
out:
	mutex_unlock(&sess->init_mutex);

	return err;
}

static void rtrs_clt_reconnect_work(struct work_struct *work)
{
	struct rtrs_clt_sess *sess;
	struct rtrs_clt *clt;
	unsigned int delay_ms;
	int err;

	sess = container_of(to_delayed_work(work), struct rtrs_clt_sess,
			    reconnect_dwork);
	clt = sess->clt;

	if (READ_ONCE(sess->state) != RTRS_CLT_RECONNECTING)
		return;

	if (sess->reconnect_attempts >= clt->max_reconnect_attempts) {
		/* Close a session completely if max attempts is reached */
		rtrs_clt_close_conns(sess, false);
		return;
	}
	sess->reconnect_attempts++;

	/* Stop everything */
	rtrs_clt_stop_and_destroy_conns(sess);
	msleep(RTRS_RECONNECT_BACKOFF);
	if (rtrs_clt_change_state_get_old(sess, RTRS_CLT_CONNECTING, NULL)) {
		err = init_sess(sess);
		if (err)
			goto reconnect_again;
	}

	return;

reconnect_again:
	if (rtrs_clt_change_state_get_old(sess, RTRS_CLT_RECONNECTING, NULL)) {
		sess->stats->reconnects.fail_cnt++;
		delay_ms = clt->reconnect_delay_sec * 1000;
		queue_delayed_work(rtrs_wq, &sess->reconnect_dwork,
				   msecs_to_jiffies(delay_ms +
						    prandom_u32() %
						    RTRS_RECONNECT_SEED));
	}
}

static void rtrs_clt_dev_release(struct device *dev)
{
	struct rtrs_clt *clt = container_of(dev, struct rtrs_clt, dev);

	kfree(clt);
}

static struct rtrs_clt *alloc_clt(const char *sessname, size_t paths_num,
				  u16 port, size_t pdu_sz, void *priv,
				  void	(*link_ev)(void *priv,
						   enum rtrs_clt_link_ev ev),
				  unsigned int max_segments,
				  size_t max_segment_size,
				  unsigned int reconnect_delay_sec,
				  unsigned int max_reconnect_attempts)
{
	struct rtrs_clt *clt;
	int err;

	if (!paths_num || paths_num > MAX_PATHS_NUM)
		return ERR_PTR(-EINVAL);

	if (strlen(sessname) >= sizeof(clt->sessname))
		return ERR_PTR(-EINVAL);

	clt = kzalloc(sizeof(*clt), GFP_KERNEL);
	if (!clt)
		return ERR_PTR(-ENOMEM);

	clt->pcpu_path = alloc_percpu(typeof(*clt->pcpu_path));
	if (!clt->pcpu_path) {
		kfree(clt);
		return ERR_PTR(-ENOMEM);
	}

	uuid_gen(&clt->paths_uuid);
	INIT_LIST_HEAD_RCU(&clt->paths_list);
	clt->paths_num = paths_num;
	clt->paths_up = MAX_PATHS_NUM;
	clt->port = port;
	clt->pdu_sz = pdu_sz;
	clt->max_segments = max_segments;
	clt->max_segment_size = max_segment_size;
	clt->reconnect_delay_sec = reconnect_delay_sec;
	clt->max_reconnect_attempts = max_reconnect_attempts;
	clt->priv = priv;
	clt->link_ev = link_ev;
	clt->mp_policy = MP_POLICY_MIN_INFLIGHT;
	strlcpy(clt->sessname, sessname, sizeof(clt->sessname));
	init_waitqueue_head(&clt->permits_wait);
	mutex_init(&clt->paths_ev_mutex);
	mutex_init(&clt->paths_mutex);

	clt->dev.class = rtrs_clt_dev_class;
	clt->dev.release = rtrs_clt_dev_release;
	err = dev_set_name(&clt->dev, "%s", sessname);
	if (err)
		goto err;
	/*
	 * Suppress user space notification until
	 * sysfs files are created
	 */
	dev_set_uevent_suppress(&clt->dev, true);
	err = device_register(&clt->dev);
	if (err) {
		put_device(&clt->dev);
		goto err;
	}

	clt->kobj_paths = kobject_create_and_add("paths", &clt->dev.kobj);
	if (!clt->kobj_paths) {
		err = -ENOMEM;
		goto err_dev;
	}
	err = rtrs_clt_create_sysfs_root_files(clt);
	if (err) {
		kobject_del(clt->kobj_paths);
		kobject_put(clt->kobj_paths);
		goto err_dev;
	}
	dev_set_uevent_suppress(&clt->dev, false);
	kobject_uevent(&clt->dev.kobj, KOBJ_ADD);

	return clt;
err_dev:
	device_unregister(&clt->dev);
err:
	free_percpu(clt->pcpu_path);
	kfree(clt);
	return ERR_PTR(err);
}

static void free_clt(struct rtrs_clt *clt)
{
	free_permits(clt);
	free_percpu(clt->pcpu_path);
	mutex_destroy(&clt->paths_ev_mutex);
	mutex_destroy(&clt->paths_mutex);
	/* release callback will free clt in last put */
	device_unregister(&clt->dev);
}

/**
 * rtrs_clt_open() - Open a session to an RTRS server
 * @ops: holds the link event callback and the private pointer.
 * @sessname: name of the session
 * @paths: Paths to be established defined by their src and dst addresses
 * @paths_num: Number of elements in the @paths array
 * @port: port to be used by the RTRS session
 * @pdu_sz: Size of extra payload which can be accessed after permit allocation.
 * @reconnect_delay_sec: time between reconnect tries
 * @max_segments: Max. number of segments per IO request
 * @max_segment_size: Max. size of one segment
 * @max_reconnect_attempts: Number of times to reconnect on error before giving
 *			    up, 0 for * disabled, -1 for forever
 *
 * Starts session establishment with the rtrs_server. The function can block
 * up to ~2000ms before it returns.
 *
 * Return a valid pointer on success otherwise PTR_ERR.
 */
struct rtrs_clt *rtrs_clt_open(struct rtrs_clt_ops *ops,
				 const char *sessname,
				 const struct rtrs_addr *paths,
				 size_t paths_num, u16 port,
				 size_t pdu_sz, u8 reconnect_delay_sec,
				 u16 max_segments,
				 size_t max_segment_size,
				 s16 max_reconnect_attempts)
{
	struct rtrs_clt_sess *sess, *tmp;
	struct rtrs_clt *clt;
	int err, i;

	clt = alloc_clt(sessname, paths_num, port, pdu_sz, ops->priv,
			ops->link_ev,
			max_segments, max_segment_size, reconnect_delay_sec,
			max_reconnect_attempts);
	if (IS_ERR(clt)) {
		err = PTR_ERR(clt);
		goto out;
	}
	for (i = 0; i < paths_num; i++) {
		struct rtrs_clt_sess *sess;

		sess = alloc_sess(clt, &paths[i], nr_cpu_ids,
				  max_segments, max_segment_size);
		if (IS_ERR(sess)) {
			err = PTR_ERR(sess);
			goto close_all_sess;
		}
		if (!i)
			sess->for_new_clt = 1;
		list_add_tail_rcu(&sess->s.entry, &clt->paths_list);

		err = init_sess(sess);
		if (err) {
			list_del_rcu(&sess->s.entry);
			rtrs_clt_close_conns(sess, true);
			free_sess(sess);
			goto close_all_sess;
		}

		err = rtrs_clt_create_sess_files(sess);
		if (err) {
			list_del_rcu(&sess->s.entry);
			rtrs_clt_close_conns(sess, true);
			free_sess(sess);
			goto close_all_sess;
		}
	}
	err = alloc_permits(clt);
	if (err)
		goto close_all_sess;

	return clt;

close_all_sess:
	list_for_each_entry_safe(sess, tmp, &clt->paths_list, s.entry) {
		rtrs_clt_destroy_sess_files(sess, NULL);
		rtrs_clt_close_conns(sess, true);
		kobject_put(&sess->kobj);
	}
	rtrs_clt_destroy_sysfs_root(clt);
	free_clt(clt);

out:
	return ERR_PTR(err);
}
EXPORT_SYMBOL(rtrs_clt_open);

/**
 * rtrs_clt_close() - Close a session
 * @clt: Session handle. Session is freed upon return.
 */
void rtrs_clt_close(struct rtrs_clt *clt)
{
	struct rtrs_clt_sess *sess, *tmp;

	/* Firstly forbid sysfs access */
	rtrs_clt_destroy_sysfs_root(clt);

	/* Now it is safe to iterate over all paths without locks */
	list_for_each_entry_safe(sess, tmp, &clt->paths_list, s.entry) {
		rtrs_clt_destroy_sess_files(sess, NULL);
		rtrs_clt_close_conns(sess, true);
		kobject_put(&sess->kobj);
	}
	free_clt(clt);
}
EXPORT_SYMBOL(rtrs_clt_close);

int rtrs_clt_reconnect_from_sysfs(struct rtrs_clt_sess *sess)
{
	enum rtrs_clt_state old_state;
	int err = -EBUSY;
	bool changed;

	changed = rtrs_clt_change_state_get_old(sess, RTRS_CLT_RECONNECTING,
						 &old_state);
	if (changed) {
		sess->reconnect_attempts = 0;
		queue_delayed_work(rtrs_wq, &sess->reconnect_dwork, 0);
	}
	if (changed || old_state == RTRS_CLT_RECONNECTING) {
		/*
		 * flush_delayed_work() queues pending work for immediate
		 * execution, so do the flush if we have queued something
		 * right now or work is pending.
		 */
		flush_delayed_work(&sess->reconnect_dwork);
		err = (READ_ONCE(sess->state) ==
		       RTRS_CLT_CONNECTED ? 0 : -ENOTCONN);
	}

	return err;
}

int rtrs_clt_disconnect_from_sysfs(struct rtrs_clt_sess *sess)
{
	rtrs_clt_close_conns(sess, true);

	return 0;
}

int rtrs_clt_remove_path_from_sysfs(struct rtrs_clt_sess *sess,
				     const struct attribute *sysfs_self)
{
	enum rtrs_clt_state old_state;
	bool changed;

	/*
	 * Continue stopping path till state was changed to DEAD or
	 * state was observed as DEAD:
	 * 1. State was changed to DEAD - we were fast and nobody
	 *    invoked rtrs_clt_reconnect(), which can again start
	 *    reconnecting.
	 * 2. State was observed as DEAD - we have someone in parallel
	 *    removing the path.
	 */
	do {
		rtrs_clt_close_conns(sess, true);
		changed = rtrs_clt_change_state_get_old(sess,
							RTRS_CLT_DEAD,
							&old_state);
	} while (!changed && old_state != RTRS_CLT_DEAD);

	if (likely(changed)) {
		rtrs_clt_destroy_sess_files(sess, sysfs_self);
		rtrs_clt_remove_path_from_arr(sess);
		kobject_put(&sess->kobj);
	}

	return 0;
}

void rtrs_clt_set_max_reconnect_attempts(struct rtrs_clt *clt, int value)
{
	clt->max_reconnect_attempts = (unsigned int)value;
}

int rtrs_clt_get_max_reconnect_attempts(const struct rtrs_clt *clt)
{
	return (int)clt->max_reconnect_attempts;
}

/**
 * rtrs_clt_request() - Request data transfer to/from server via RDMA.
 *
 * @dir:	READ/WRITE
 * @ops:	callback function to be called as confirmation, and the pointer.
 * @clt:	Session
 * @permit:	Preallocated permit
 * @vec:	Message that is sent to server together with the request.
 *		Sum of len of all @vec elements limited to <= IO_MSG_SIZE.
 *		Since the msg is copied internally it can be allocated on stack.
 * @nr:		Number of elements in @vec.
 * @data_len:	length of data sent to/from server
 * @sg:		Pages to be sent/received to/from server.
 * @sg_cnt:	Number of elements in the @sg
 *
 * Return:
 * 0:		Success
 * <0:		Error
 *
 * On dir=READ rtrs client will request a data transfer from Server to client.
 * The data that the server will respond with will be stored in @sg when
 * the user receives an %RTRS_CLT_RDMA_EV_RDMA_REQUEST_WRITE_COMPL event.
 * On dir=WRITE rtrs client will rdma write data in sg to server side.
 */
int rtrs_clt_request(int dir, struct rtrs_clt_req_ops *ops,
		     struct rtrs_clt *clt, struct rtrs_permit *permit,
		      const struct kvec *vec, size_t nr, size_t data_len,
		      struct scatterlist *sg, unsigned int sg_cnt)
{
	struct rtrs_clt_io_req *req;
	struct rtrs_clt_sess *sess;

	enum dma_data_direction dma_dir;
	int err = -ECONNABORTED, i;
	size_t usr_len, hdr_len;
	struct path_it it;

	/* Get kvec length */
	for (i = 0, usr_len = 0; i < nr; i++)
		usr_len += vec[i].iov_len;

	if (dir == READ) {
		hdr_len = sizeof(struct rtrs_msg_rdma_read) +
			  sg_cnt * sizeof(struct rtrs_sg_desc);
		dma_dir = DMA_FROM_DEVICE;
	} else {
		hdr_len = sizeof(struct rtrs_msg_rdma_write);
		dma_dir = DMA_TO_DEVICE;
	}

	rcu_read_lock();
	for (path_it_init(&it, clt);
	     (sess = it.next_path(&it)) && it.i < it.clt->paths_num; it.i++) {
		if (unlikely(READ_ONCE(sess->state) != RTRS_CLT_CONNECTED))
			continue;

		if (unlikely(usr_len + hdr_len > sess->max_hdr_size)) {
			rtrs_wrn_rl(sess->clt,
				     "%s request failed, user message size is %zu and header length %zu, but max size is %u\n",
				     dir == READ ? "Read" : "Write",
				     usr_len, hdr_len, sess->max_hdr_size);
			err = -EMSGSIZE;
			break;
		}
		req = rtrs_clt_get_req(sess, ops->conf_fn, permit, ops->priv,
				       vec, usr_len, sg, sg_cnt, data_len,
				       dma_dir);
		if (dir == READ)
			err = rtrs_clt_read_req(req);
		else
			err = rtrs_clt_write_req(req);
		if (unlikely(err)) {
			req->in_use = false;
			continue;
		}
		/* Success path */
		break;
	}
	path_it_deinit(&it);
	rcu_read_unlock();

	return err;
}
EXPORT_SYMBOL(rtrs_clt_request);

/**
 * rtrs_clt_query() - queries RTRS session attributes
 *@clt: session pointer
 *@attr: query results for session attributes.
 * Returns:
 *    0 on success
 *    -ECOMM		no connection to the server
 */
int rtrs_clt_query(struct rtrs_clt *clt, struct rtrs_attrs *attr)
{
	if (!rtrs_clt_is_connected(clt))
		return -ECOMM;

	attr->queue_depth      = clt->queue_depth;
	attr->max_io_size      = clt->max_io_size;
	attr->sess_kobj	       = &clt->dev.kobj;
	strlcpy(attr->sessname, clt->sessname, sizeof(attr->sessname));

	return 0;
}
EXPORT_SYMBOL(rtrs_clt_query);

int rtrs_clt_create_path_from_sysfs(struct rtrs_clt *clt,
				     struct rtrs_addr *addr)
{
	struct rtrs_clt_sess *sess;
	int err;

	sess = alloc_sess(clt, addr, nr_cpu_ids, clt->max_segments,
			  clt->max_segment_size);
	if (IS_ERR(sess))
		return PTR_ERR(sess);

	/*
	 * It is totally safe to add path in CONNECTING state: coming
	 * IO will never grab it.  Also it is very important to add
	 * path before init, since init fires LINK_CONNECTED event.
	 */
	rtrs_clt_add_path_to_arr(sess);

	err = init_sess(sess);
	if (err)
		goto close_sess;

	err = rtrs_clt_create_sess_files(sess);
	if (err)
		goto close_sess;

	return 0;

close_sess:
	rtrs_clt_remove_path_from_arr(sess);
	rtrs_clt_close_conns(sess, true);
	free_sess(sess);

	return err;
}

static int rtrs_clt_ib_dev_init(struct rtrs_ib_dev *dev)
{
	if (!(dev->ib_dev->attrs.device_cap_flags &
	      IB_DEVICE_MEM_MGT_EXTENSIONS)) {
		pr_err("Memory registrations not supported.\n");
		return -ENOTSUPP;
	}

	return 0;
}

static const struct rtrs_rdma_dev_pd_ops dev_pd_ops = {
	.init = rtrs_clt_ib_dev_init
};

static int __init rtrs_client_init(void)
{
	rtrs_rdma_dev_pd_init(0, &dev_pd);

	rtrs_clt_dev_class = class_create(THIS_MODULE, "rtrs-client");
	if (IS_ERR(rtrs_clt_dev_class)) {
		pr_err("Failed to create rtrs-client dev class\n");
		return PTR_ERR(rtrs_clt_dev_class);
	}
	rtrs_wq = alloc_workqueue("rtrs_client_wq", 0, 0);
	if (!rtrs_wq) {
		class_destroy(rtrs_clt_dev_class);
		return -ENOMEM;
	}

	return 0;
}

static void __exit rtrs_client_exit(void)
{
	destroy_workqueue(rtrs_wq);
	class_destroy(rtrs_clt_dev_class);
	rtrs_rdma_dev_pd_deinit(&dev_pd);
}

module_init(rtrs_client_init);
module_exit(rtrs_client_exit);