summaryrefslogtreecommitdiff
path: root/block/blk-iocost.c
blob: e01267f9918390f38424337140778c2c983bb7a4 (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
/* SPDX-License-Identifier: GPL-2.0
 *
 * IO cost model based controller.
 *
 * Copyright (C) 2019 Tejun Heo <tj@kernel.org>
 * Copyright (C) 2019 Andy Newell <newella@fb.com>
 * Copyright (C) 2019 Facebook
 *
 * One challenge of controlling IO resources is the lack of trivially
 * observable cost metric.  This is distinguished from CPU and memory where
 * wallclock time and the number of bytes can serve as accurate enough
 * approximations.
 *
 * Bandwidth and iops are the most commonly used metrics for IO devices but
 * depending on the type and specifics of the device, different IO patterns
 * easily lead to multiple orders of magnitude variations rendering them
 * useless for the purpose of IO capacity distribution.  While on-device
 * time, with a lot of clutches, could serve as a useful approximation for
 * non-queued rotational devices, this is no longer viable with modern
 * devices, even the rotational ones.
 *
 * While there is no cost metric we can trivially observe, it isn't a
 * complete mystery.  For example, on a rotational device, seek cost
 * dominates while a contiguous transfer contributes a smaller amount
 * proportional to the size.  If we can characterize at least the relative
 * costs of these different types of IOs, it should be possible to
 * implement a reasonable work-conserving proportional IO resource
 * distribution.
 *
 * 1. IO Cost Model
 *
 * IO cost model estimates the cost of an IO given its basic parameters and
 * history (e.g. the end sector of the last IO).  The cost is measured in
 * device time.  If a given IO is estimated to cost 10ms, the device should
 * be able to process ~100 of those IOs in a second.
 *
 * Currently, there's only one builtin cost model - linear.  Each IO is
 * classified as sequential or random and given a base cost accordingly.
 * On top of that, a size cost proportional to the length of the IO is
 * added.  While simple, this model captures the operational
 * characteristics of a wide varienty of devices well enough.  Default
 * paramters for several different classes of devices are provided and the
 * parameters can be configured from userspace via
 * /sys/fs/cgroup/io.cost.model.
 *
 * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate
 * device-specific coefficients.
 *
 * If needed, tools/cgroup/iocost_coef_gen.py can be used to generate
 * device-specific coefficients.
 *
 * 2. Control Strategy
 *
 * The device virtual time (vtime) is used as the primary control metric.
 * The control strategy is composed of the following three parts.
 *
 * 2-1. Vtime Distribution
 *
 * When a cgroup becomes active in terms of IOs, its hierarchical share is
 * calculated.  Please consider the following hierarchy where the numbers
 * inside parentheses denote the configured weights.
 *
 *           root
 *         /       \
 *      A (w:100)  B (w:300)
 *      /       \
 *  A0 (w:100)  A1 (w:100)
 *
 * If B is idle and only A0 and A1 are actively issuing IOs, as the two are
 * of equal weight, each gets 50% share.  If then B starts issuing IOs, B
 * gets 300/(100+300) or 75% share, and A0 and A1 equally splits the rest,
 * 12.5% each.  The distribution mechanism only cares about these flattened
 * shares.  They're called hweights (hierarchical weights) and always add
 * upto 1 (HWEIGHT_WHOLE).
 *
 * A given cgroup's vtime runs slower in inverse proportion to its hweight.
 * For example, with 12.5% weight, A0's time runs 8 times slower (100/12.5)
 * against the device vtime - an IO which takes 10ms on the underlying
 * device is considered to take 80ms on A0.
 *
 * This constitutes the basis of IO capacity distribution.  Each cgroup's
 * vtime is running at a rate determined by its hweight.  A cgroup tracks
 * the vtime consumed by past IOs and can issue a new IO iff doing so
 * wouldn't outrun the current device vtime.  Otherwise, the IO is
 * suspended until the vtime has progressed enough to cover it.
 *
 * 2-2. Vrate Adjustment
 *
 * It's unrealistic to expect the cost model to be perfect.  There are too
 * many devices and even on the same device the overall performance
 * fluctuates depending on numerous factors such as IO mixture and device
 * internal garbage collection.  The controller needs to adapt dynamically.
 *
 * This is achieved by adjusting the overall IO rate according to how busy
 * the device is.  If the device becomes overloaded, we're sending down too
 * many IOs and should generally slow down.  If there are waiting issuers
 * but the device isn't saturated, we're issuing too few and should
 * generally speed up.
 *
 * To slow down, we lower the vrate - the rate at which the device vtime
 * passes compared to the wall clock.  For example, if the vtime is running
 * at the vrate of 75%, all cgroups added up would only be able to issue
 * 750ms worth of IOs per second, and vice-versa for speeding up.
 *
 * Device business is determined using two criteria - rq wait and
 * completion latencies.
 *
 * When a device gets saturated, the on-device and then the request queues
 * fill up and a bio which is ready to be issued has to wait for a request
 * to become available.  When this delay becomes noticeable, it's a clear
 * indication that the device is saturated and we lower the vrate.  This
 * saturation signal is fairly conservative as it only triggers when both
 * hardware and software queues are filled up, and is used as the default
 * busy signal.
 *
 * As devices can have deep queues and be unfair in how the queued commands
 * are executed, soley depending on rq wait may not result in satisfactory
 * control quality.  For a better control quality, completion latency QoS
 * parameters can be configured so that the device is considered saturated
 * if N'th percentile completion latency rises above the set point.
 *
 * The completion latency requirements are a function of both the
 * underlying device characteristics and the desired IO latency quality of
 * service.  There is an inherent trade-off - the tighter the latency QoS,
 * the higher the bandwidth lossage.  Latency QoS is disabled by default
 * and can be set through /sys/fs/cgroup/io.cost.qos.
 *
 * 2-3. Work Conservation
 *
 * Imagine two cgroups A and B with equal weights.  A is issuing a small IO
 * periodically while B is sending out enough parallel IOs to saturate the
 * device on its own.  Let's say A's usage amounts to 100ms worth of IO
 * cost per second, i.e., 10% of the device capacity.  The naive
 * distribution of half and half would lead to 60% utilization of the
 * device, a significant reduction in the total amount of work done
 * compared to free-for-all competition.  This is too high a cost to pay
 * for IO control.
 *
 * To conserve the total amount of work done, we keep track of how much
 * each active cgroup is actually using and yield part of its weight if
 * there are other cgroups which can make use of it.  In the above case,
 * A's weight will be lowered so that it hovers above the actual usage and
 * B would be able to use the rest.
 *
 * As we don't want to penalize a cgroup for donating its weight, the
 * surplus weight adjustment factors in a margin and has an immediate
 * snapback mechanism in case the cgroup needs more IO vtime for itself.
 *
 * Note that adjusting down surplus weights has the same effects as
 * accelerating vtime for other cgroups and work conservation can also be
 * implemented by adjusting vrate dynamically.  However, squaring who can
 * donate and should take back how much requires hweight propagations
 * anyway making it easier to implement and understand as a separate
 * mechanism.
 *
 * 3. Monitoring
 *
 * Instead of debugfs or other clumsy monitoring mechanisms, this
 * controller uses a drgn based monitoring script -
 * tools/cgroup/iocost_monitor.py.  For details on drgn, please see
 * https://github.com/osandov/drgn.  The ouput looks like the following.
 *
 *  sdb RUN   per=300ms cur_per=234.218:v203.695 busy= +1 vrate= 62.12%
 *                 active      weight      hweight% inflt% dbt  delay usages%
 *  test/a              *    50/   50  33.33/ 33.33  27.65   2  0*041 033:033:033
 *  test/b              *   100/  100  66.67/ 66.67  17.56   0  0*000 066:079:077
 *
 * - per	: Timer period
 * - cur_per	: Internal wall and device vtime clock
 * - vrate	: Device virtual time rate against wall clock
 * - weight	: Surplus-adjusted and configured weights
 * - hweight	: Surplus-adjusted and configured hierarchical weights
 * - inflt	: The percentage of in-flight IO cost at the end of last period
 * - del_ms	: Deferred issuer delay induction level and duration
 * - usages	: Usage history
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/timer.h>
#include <linux/time64.h>
#include <linux/parser.h>
#include <linux/sched/signal.h>
#include <linux/blk-cgroup.h>
#include "blk-rq-qos.h"
#include "blk-stat.h"
#include "blk-wbt.h"

#ifdef CONFIG_TRACEPOINTS

/* copied from TRACE_CGROUP_PATH, see cgroup-internal.h */
#define TRACE_IOCG_PATH_LEN 1024
static DEFINE_SPINLOCK(trace_iocg_path_lock);
static char trace_iocg_path[TRACE_IOCG_PATH_LEN];

#define TRACE_IOCG_PATH(type, iocg, ...)					\
	do {									\
		unsigned long flags;						\
		if (trace_iocost_##type##_enabled()) {				\
			spin_lock_irqsave(&trace_iocg_path_lock, flags);	\
			cgroup_path(iocg_to_blkg(iocg)->blkcg->css.cgroup,	\
				    trace_iocg_path, TRACE_IOCG_PATH_LEN);	\
			trace_iocost_##type(iocg, trace_iocg_path,		\
					      ##__VA_ARGS__);			\
			spin_unlock_irqrestore(&trace_iocg_path_lock, flags);	\
		}								\
	} while (0)

#else	/* CONFIG_TRACE_POINTS */
#define TRACE_IOCG_PATH(type, iocg, ...)	do { } while (0)
#endif	/* CONFIG_TRACE_POINTS */

enum {
	MILLION			= 1000000,

	/* timer period is calculated from latency requirements, bound it */
	MIN_PERIOD		= USEC_PER_MSEC,
	MAX_PERIOD		= USEC_PER_SEC,

	/*
	 * A cgroup's vtime can run 50% behind the device vtime, which
	 * serves as its IO credit buffer.  Surplus weight adjustment is
	 * immediately canceled if the vtime margin runs below 10%.
	 */
	MARGIN_PCT		= 50,
	INUSE_MARGIN_PCT	= 10,

	/* Have some play in waitq timer operations */
	WAITQ_TIMER_MARGIN_PCT	= 5,

	/*
	 * vtime can wrap well within a reasonable uptime when vrate is
	 * consistently raised.  Don't trust recorded cgroup vtime if the
	 * period counter indicates that it's older than 5mins.
	 */
	VTIME_VALID_DUR		= 300 * USEC_PER_SEC,

	/*
	 * Remember the past three non-zero usages and use the max for
	 * surplus calculation.  Three slots guarantee that we remember one
	 * full period usage from the last active stretch even after
	 * partial deactivation and re-activation periods.  Don't start
	 * giving away weight before collecting two data points to prevent
	 * hweight adjustments based on one partial activation period.
	 */
	NR_USAGE_SLOTS		= 3,
	MIN_VALID_USAGES	= 2,

	/* 1/64k is granular enough and can easily be handled w/ u32 */
	HWEIGHT_WHOLE		= 1 << 16,

	/*
	 * As vtime is used to calculate the cost of each IO, it needs to
	 * be fairly high precision.  For example, it should be able to
	 * represent the cost of a single page worth of discard with
	 * suffificient accuracy.  At the same time, it should be able to
	 * represent reasonably long enough durations to be useful and
	 * convenient during operation.
	 *
	 * 1s worth of vtime is 2^37.  This gives us both sub-nanosecond
	 * granularity and days of wrap-around time even at extreme vrates.
	 */
	VTIME_PER_SEC_SHIFT	= 37,
	VTIME_PER_SEC		= 1LLU << VTIME_PER_SEC_SHIFT,
	VTIME_PER_USEC		= VTIME_PER_SEC / USEC_PER_SEC,

	/* bound vrate adjustments within two orders of magnitude */
	VRATE_MIN_PPM		= 10000,	/* 1% */
	VRATE_MAX_PPM		= 100000000,	/* 10000% */

	VRATE_MIN		= VTIME_PER_USEC * VRATE_MIN_PPM / MILLION,
	VRATE_CLAMP_ADJ_PCT	= 4,

	/* if IOs end up waiting for requests, issue less */
	RQ_WAIT_BUSY_PCT	= 5,

	/* unbusy hysterisis */
	UNBUSY_THR_PCT		= 75,

	/* don't let cmds which take a very long time pin lagging for too long */
	MAX_LAGGING_PERIODS	= 10,

	/*
	 * If usage% * 1.25 + 2% is lower than hweight% by more than 3%,
	 * donate the surplus.
	 */
	SURPLUS_SCALE_PCT	= 125,			/* * 125% */
	SURPLUS_SCALE_ABS	= HWEIGHT_WHOLE / 50,	/* + 2% */
	SURPLUS_MIN_ADJ_DELTA	= HWEIGHT_WHOLE / 33,	/* 3% */

	/* switch iff the conditions are met for longer than this */
	AUTOP_CYCLE_NSEC	= 10LLU * NSEC_PER_SEC,

	/*
	 * Count IO size in 4k pages.  The 12bit shift helps keeping
	 * size-proportional components of cost calculation in closer
	 * numbers of digits to per-IO cost components.
	 */
	IOC_PAGE_SHIFT		= 12,
	IOC_PAGE_SIZE		= 1 << IOC_PAGE_SHIFT,
	IOC_SECT_TO_PAGE_SHIFT	= IOC_PAGE_SHIFT - SECTOR_SHIFT,

	/* if apart further than 16M, consider randio for linear model */
	LCOEF_RANDIO_PAGES	= 4096,
};

enum ioc_running {
	IOC_IDLE,
	IOC_RUNNING,
	IOC_STOP,
};

/* io.cost.qos controls including per-dev enable of the whole controller */
enum {
	QOS_ENABLE,
	QOS_CTRL,
	NR_QOS_CTRL_PARAMS,
};

/* io.cost.qos params */
enum {
	QOS_RPPM,
	QOS_RLAT,
	QOS_WPPM,
	QOS_WLAT,
	QOS_MIN,
	QOS_MAX,
	NR_QOS_PARAMS,
};

/* io.cost.model controls */
enum {
	COST_CTRL,
	COST_MODEL,
	NR_COST_CTRL_PARAMS,
};

/* builtin linear cost model coefficients */
enum {
	I_LCOEF_RBPS,
	I_LCOEF_RSEQIOPS,
	I_LCOEF_RRANDIOPS,
	I_LCOEF_WBPS,
	I_LCOEF_WSEQIOPS,
	I_LCOEF_WRANDIOPS,
	NR_I_LCOEFS,
};

enum {
	LCOEF_RPAGE,
	LCOEF_RSEQIO,
	LCOEF_RRANDIO,
	LCOEF_WPAGE,
	LCOEF_WSEQIO,
	LCOEF_WRANDIO,
	NR_LCOEFS,
};

enum {
	AUTOP_INVALID,
	AUTOP_HDD,
	AUTOP_SSD_QD1,
	AUTOP_SSD_DFL,
	AUTOP_SSD_FAST,
};

struct ioc_gq;

struct ioc_params {
	u32				qos[NR_QOS_PARAMS];
	u64				i_lcoefs[NR_I_LCOEFS];
	u64				lcoefs[NR_LCOEFS];
	u32				too_fast_vrate_pct;
	u32				too_slow_vrate_pct;
};

struct ioc_missed {
	u32				nr_met;
	u32				nr_missed;
	u32				last_met;
	u32				last_missed;
};

struct ioc_pcpu_stat {
	struct ioc_missed		missed[2];

	u64				rq_wait_ns;
	u64				last_rq_wait_ns;
};

/* per device */
struct ioc {
	struct rq_qos			rqos;

	bool				enabled;

	struct ioc_params		params;
	u32				period_us;
	u32				margin_us;
	u64				vrate_min;
	u64				vrate_max;

	spinlock_t			lock;
	struct timer_list		timer;
	struct list_head		active_iocgs;	/* active cgroups */
	struct ioc_pcpu_stat __percpu	*pcpu_stat;

	enum ioc_running		running;
	atomic64_t			vtime_rate;

	seqcount_t			period_seqcount;
	u32				period_at;	/* wallclock starttime */
	u64				period_at_vtime; /* vtime starttime */

	atomic64_t			cur_period;	/* inc'd each period */
	int				busy_level;	/* saturation history */

	u64				inuse_margin_vtime;
	bool				weights_updated;
	atomic_t			hweight_gen;	/* for lazy hweights */

	u64				autop_too_fast_at;
	u64				autop_too_slow_at;
	int				autop_idx;
	bool				user_qos_params:1;
	bool				user_cost_model:1;
};

/* per device-cgroup pair */
struct ioc_gq {
	struct blkg_policy_data		pd;
	struct ioc			*ioc;

	/*
	 * A iocg can get its weight from two sources - an explicit
	 * per-device-cgroup configuration or the default weight of the
	 * cgroup.  `cfg_weight` is the explicit per-device-cgroup
	 * configuration.  `weight` is the effective considering both
	 * sources.
	 *
	 * When an idle cgroup becomes active its `active` goes from 0 to
	 * `weight`.  `inuse` is the surplus adjusted active weight.
	 * `active` and `inuse` are used to calculate `hweight_active` and
	 * `hweight_inuse`.
	 *
	 * `last_inuse` remembers `inuse` while an iocg is idle to persist
	 * surplus adjustments.
	 */
	u32				cfg_weight;
	u32				weight;
	u32				active;
	u32				inuse;
	u32				last_inuse;

	sector_t			cursor;		/* to detect randio */

	/*
	 * `vtime` is this iocg's vtime cursor which progresses as IOs are
	 * issued.  If lagging behind device vtime, the delta represents
	 * the currently available IO budget.  If runnning ahead, the
	 * overage.
	 *
	 * `vtime_done` is the same but progressed on completion rather
	 * than issue.  The delta behind `vtime` represents the cost of
	 * currently in-flight IOs.
	 *
	 * `last_vtime` is used to remember `vtime` at the end of the last
	 * period to calculate utilization.
	 */
	atomic64_t			vtime;
	atomic64_t			done_vtime;
	atomic64_t			abs_vdebt;
	u64				last_vtime;

	/*
	 * The period this iocg was last active in.  Used for deactivation
	 * and invalidating `vtime`.
	 */
	atomic64_t			active_period;
	struct list_head		active_list;

	/* see __propagate_active_weight() and current_hweight() for details */
	u64				child_active_sum;
	u64				child_inuse_sum;
	int				hweight_gen;
	u32				hweight_active;
	u32				hweight_inuse;
	bool				has_surplus;

	struct wait_queue_head		waitq;
	struct hrtimer			waitq_timer;
	struct hrtimer			delay_timer;

	/* usage is recorded as fractions of HWEIGHT_WHOLE */
	int				usage_idx;
	u32				usages[NR_USAGE_SLOTS];

	/* this iocg's depth in the hierarchy and ancestors including self */
	int				level;
	struct ioc_gq			*ancestors[];
};

/* per cgroup */
struct ioc_cgrp {
	struct blkcg_policy_data	cpd;
	unsigned int			dfl_weight;
};

struct ioc_now {
	u64				now_ns;
	u32				now;
	u64				vnow;
	u64				vrate;
};

struct iocg_wait {
	struct wait_queue_entry		wait;
	struct bio			*bio;
	u64				abs_cost;
	bool				committed;
};

struct iocg_wake_ctx {
	struct ioc_gq			*iocg;
	u32				hw_inuse;
	s64				vbudget;
};

static const struct ioc_params autop[] = {
	[AUTOP_HDD] = {
		.qos				= {
			[QOS_RLAT]		=        250000, /* 250ms */
			[QOS_WLAT]		=        250000,
			[QOS_MIN]		= VRATE_MIN_PPM,
			[QOS_MAX]		= VRATE_MAX_PPM,
		},
		.i_lcoefs			= {
			[I_LCOEF_RBPS]		=     174019176,
			[I_LCOEF_RSEQIOPS]	=         41708,
			[I_LCOEF_RRANDIOPS]	=           370,
			[I_LCOEF_WBPS]		=     178075866,
			[I_LCOEF_WSEQIOPS]	=         42705,
			[I_LCOEF_WRANDIOPS]	=           378,
		},
	},
	[AUTOP_SSD_QD1] = {
		.qos				= {
			[QOS_RLAT]		=         25000, /* 25ms */
			[QOS_WLAT]		=         25000,
			[QOS_MIN]		= VRATE_MIN_PPM,
			[QOS_MAX]		= VRATE_MAX_PPM,
		},
		.i_lcoefs			= {
			[I_LCOEF_RBPS]		=     245855193,
			[I_LCOEF_RSEQIOPS]	=         61575,
			[I_LCOEF_RRANDIOPS]	=          6946,
			[I_LCOEF_WBPS]		=     141365009,
			[I_LCOEF_WSEQIOPS]	=         33716,
			[I_LCOEF_WRANDIOPS]	=         26796,
		},
	},
	[AUTOP_SSD_DFL] = {
		.qos				= {
			[QOS_RLAT]		=         25000, /* 25ms */
			[QOS_WLAT]		=         25000,
			[QOS_MIN]		= VRATE_MIN_PPM,
			[QOS_MAX]		= VRATE_MAX_PPM,
		},
		.i_lcoefs			= {
			[I_LCOEF_RBPS]		=     488636629,
			[I_LCOEF_RSEQIOPS]	=          8932,
			[I_LCOEF_RRANDIOPS]	=          8518,
			[I_LCOEF_WBPS]		=     427891549,
			[I_LCOEF_WSEQIOPS]	=         28755,
			[I_LCOEF_WRANDIOPS]	=         21940,
		},
		.too_fast_vrate_pct		=           500,
	},
	[AUTOP_SSD_FAST] = {
		.qos				= {
			[QOS_RLAT]		=          5000, /* 5ms */
			[QOS_WLAT]		=          5000,
			[QOS_MIN]		= VRATE_MIN_PPM,
			[QOS_MAX]		= VRATE_MAX_PPM,
		},
		.i_lcoefs			= {
			[I_LCOEF_RBPS]		=    3102524156LLU,
			[I_LCOEF_RSEQIOPS]	=        724816,
			[I_LCOEF_RRANDIOPS]	=        778122,
			[I_LCOEF_WBPS]		=    1742780862LLU,
			[I_LCOEF_WSEQIOPS]	=        425702,
			[I_LCOEF_WRANDIOPS]	=	 443193,
		},
		.too_slow_vrate_pct		=            10,
	},
};

/*
 * vrate adjust percentages indexed by ioc->busy_level.  We adjust up on
 * vtime credit shortage and down on device saturation.
 */
static u32 vrate_adj_pct[] =
	{ 0, 0, 0, 0,
	  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
	  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
	  4, 4, 4, 4, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16 };

static struct blkcg_policy blkcg_policy_iocost;

/* accessors and helpers */
static struct ioc *rqos_to_ioc(struct rq_qos *rqos)
{
	return container_of(rqos, struct ioc, rqos);
}

static struct ioc *q_to_ioc(struct request_queue *q)
{
	return rqos_to_ioc(rq_qos_id(q, RQ_QOS_COST));
}

static const char *q_name(struct request_queue *q)
{
	if (test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
		return kobject_name(q->kobj.parent);
	else
		return "<unknown>";
}

static const char __maybe_unused *ioc_name(struct ioc *ioc)
{
	return q_name(ioc->rqos.q);
}

static struct ioc_gq *pd_to_iocg(struct blkg_policy_data *pd)
{
	return pd ? container_of(pd, struct ioc_gq, pd) : NULL;
}

static struct ioc_gq *blkg_to_iocg(struct blkcg_gq *blkg)
{
	return pd_to_iocg(blkg_to_pd(blkg, &blkcg_policy_iocost));
}

static struct blkcg_gq *iocg_to_blkg(struct ioc_gq *iocg)
{
	return pd_to_blkg(&iocg->pd);
}

static struct ioc_cgrp *blkcg_to_iocc(struct blkcg *blkcg)
{
	return container_of(blkcg_to_cpd(blkcg, &blkcg_policy_iocost),
			    struct ioc_cgrp, cpd);
}

/*
 * Scale @abs_cost to the inverse of @hw_inuse.  The lower the hierarchical
 * weight, the more expensive each IO.  Must round up.
 */
static u64 abs_cost_to_cost(u64 abs_cost, u32 hw_inuse)
{
	return DIV64_U64_ROUND_UP(abs_cost * HWEIGHT_WHOLE, hw_inuse);
}

/*
 * The inverse of abs_cost_to_cost().  Must round up.
 */
static u64 cost_to_abs_cost(u64 cost, u32 hw_inuse)
{
	return DIV64_U64_ROUND_UP(cost * hw_inuse, HWEIGHT_WHOLE);
}

static void iocg_commit_bio(struct ioc_gq *iocg, struct bio *bio, u64 cost)
{
	bio->bi_iocost_cost = cost;
	atomic64_add(cost, &iocg->vtime);
}

#define CREATE_TRACE_POINTS
#include <trace/events/iocost.h>

/* latency Qos params changed, update period_us and all the dependent params */
static void ioc_refresh_period_us(struct ioc *ioc)
{
	u32 ppm, lat, multi, period_us;

	lockdep_assert_held(&ioc->lock);

	/* pick the higher latency target */
	if (ioc->params.qos[QOS_RLAT] >= ioc->params.qos[QOS_WLAT]) {
		ppm = ioc->params.qos[QOS_RPPM];
		lat = ioc->params.qos[QOS_RLAT];
	} else {
		ppm = ioc->params.qos[QOS_WPPM];
		lat = ioc->params.qos[QOS_WLAT];
	}

	/*
	 * We want the period to be long enough to contain a healthy number
	 * of IOs while short enough for granular control.  Define it as a
	 * multiple of the latency target.  Ideally, the multiplier should
	 * be scaled according to the percentile so that it would nominally
	 * contain a certain number of requests.  Let's be simpler and
	 * scale it linearly so that it's 2x >= pct(90) and 10x at pct(50).
	 */
	if (ppm)
		multi = max_t(u32, (MILLION - ppm) / 50000, 2);
	else
		multi = 2;
	period_us = multi * lat;
	period_us = clamp_t(u32, period_us, MIN_PERIOD, MAX_PERIOD);

	/* calculate dependent params */
	ioc->period_us = period_us;
	ioc->margin_us = period_us * MARGIN_PCT / 100;
	ioc->inuse_margin_vtime = DIV64_U64_ROUND_UP(
			period_us * VTIME_PER_USEC * INUSE_MARGIN_PCT, 100);
}

static int ioc_autop_idx(struct ioc *ioc)
{
	int idx = ioc->autop_idx;
	const struct ioc_params *p = &autop[idx];
	u32 vrate_pct;
	u64 now_ns;

	/* rotational? */
	if (!blk_queue_nonrot(ioc->rqos.q))
		return AUTOP_HDD;

	/* handle SATA SSDs w/ broken NCQ */
	if (blk_queue_depth(ioc->rqos.q) == 1)
		return AUTOP_SSD_QD1;

	/* use one of the normal ssd sets */
	if (idx < AUTOP_SSD_DFL)
		return AUTOP_SSD_DFL;

	/* if user is overriding anything, maintain what was there */
	if (ioc->user_qos_params || ioc->user_cost_model)
		return idx;

	/* step up/down based on the vrate */
	vrate_pct = div64_u64(atomic64_read(&ioc->vtime_rate) * 100,
			      VTIME_PER_USEC);
	now_ns = ktime_get_ns();

	if (p->too_fast_vrate_pct && p->too_fast_vrate_pct <= vrate_pct) {
		if (!ioc->autop_too_fast_at)
			ioc->autop_too_fast_at = now_ns;
		if (now_ns - ioc->autop_too_fast_at >= AUTOP_CYCLE_NSEC)
			return idx + 1;
	} else {
		ioc->autop_too_fast_at = 0;
	}

	if (p->too_slow_vrate_pct && p->too_slow_vrate_pct >= vrate_pct) {
		if (!ioc->autop_too_slow_at)
			ioc->autop_too_slow_at = now_ns;
		if (now_ns - ioc->autop_too_slow_at >= AUTOP_CYCLE_NSEC)
			return idx - 1;
	} else {
		ioc->autop_too_slow_at = 0;
	}

	return idx;
}

/*
 * Take the followings as input
 *
 *  @bps	maximum sequential throughput
 *  @seqiops	maximum sequential 4k iops
 *  @randiops	maximum random 4k iops
 *
 * and calculate the linear model cost coefficients.
 *
 *  *@page	per-page cost		1s / (@bps / 4096)
 *  *@seqio	base cost of a seq IO	max((1s / @seqiops) - *@page, 0)
 *  @randiops	base cost of a rand IO	max((1s / @randiops) - *@page, 0)
 */
static void calc_lcoefs(u64 bps, u64 seqiops, u64 randiops,
			u64 *page, u64 *seqio, u64 *randio)
{
	u64 v;

	*page = *seqio = *randio = 0;

	if (bps)
		*page = DIV64_U64_ROUND_UP(VTIME_PER_SEC,
					   DIV_ROUND_UP_ULL(bps, IOC_PAGE_SIZE));

	if (seqiops) {
		v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, seqiops);
		if (v > *page)
			*seqio = v - *page;
	}

	if (randiops) {
		v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, randiops);
		if (v > *page)
			*randio = v - *page;
	}
}

static void ioc_refresh_lcoefs(struct ioc *ioc)
{
	u64 *u = ioc->params.i_lcoefs;
	u64 *c = ioc->params.lcoefs;

	calc_lcoefs(u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
		    &c[LCOEF_RPAGE], &c[LCOEF_RSEQIO], &c[LCOEF_RRANDIO]);
	calc_lcoefs(u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS],
		    &c[LCOEF_WPAGE], &c[LCOEF_WSEQIO], &c[LCOEF_WRANDIO]);
}

static bool ioc_refresh_params(struct ioc *ioc, bool force)
{
	const struct ioc_params *p;
	int idx;

	lockdep_assert_held(&ioc->lock);

	idx = ioc_autop_idx(ioc);
	p = &autop[idx];

	if (idx == ioc->autop_idx && !force)
		return false;

	if (idx != ioc->autop_idx)
		atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC);

	ioc->autop_idx = idx;
	ioc->autop_too_fast_at = 0;
	ioc->autop_too_slow_at = 0;

	if (!ioc->user_qos_params)
		memcpy(ioc->params.qos, p->qos, sizeof(p->qos));
	if (!ioc->user_cost_model)
		memcpy(ioc->params.i_lcoefs, p->i_lcoefs, sizeof(p->i_lcoefs));

	ioc_refresh_period_us(ioc);
	ioc_refresh_lcoefs(ioc);

	ioc->vrate_min = DIV64_U64_ROUND_UP((u64)ioc->params.qos[QOS_MIN] *
					    VTIME_PER_USEC, MILLION);
	ioc->vrate_max = div64_u64((u64)ioc->params.qos[QOS_MAX] *
				   VTIME_PER_USEC, MILLION);

	return true;
}

/* take a snapshot of the current [v]time and vrate */
static void ioc_now(struct ioc *ioc, struct ioc_now *now)
{
	unsigned seq;

	now->now_ns = ktime_get();
	now->now = ktime_to_us(now->now_ns);
	now->vrate = atomic64_read(&ioc->vtime_rate);

	/*
	 * The current vtime is
	 *
	 *   vtime at period start + (wallclock time since the start) * vrate
	 *
	 * As a consistent snapshot of `period_at_vtime` and `period_at` is
	 * needed, they're seqcount protected.
	 */
	do {
		seq = read_seqcount_begin(&ioc->period_seqcount);
		now->vnow = ioc->period_at_vtime +
			(now->now - ioc->period_at) * now->vrate;
	} while (read_seqcount_retry(&ioc->period_seqcount, seq));
}

static void ioc_start_period(struct ioc *ioc, struct ioc_now *now)
{
	lockdep_assert_held(&ioc->lock);
	WARN_ON_ONCE(ioc->running != IOC_RUNNING);

	write_seqcount_begin(&ioc->period_seqcount);
	ioc->period_at = now->now;
	ioc->period_at_vtime = now->vnow;
	write_seqcount_end(&ioc->period_seqcount);

	ioc->timer.expires = jiffies + usecs_to_jiffies(ioc->period_us);
	add_timer(&ioc->timer);
}

/*
 * Update @iocg's `active` and `inuse` to @active and @inuse, update level
 * weight sums and propagate upwards accordingly.
 */
static void __propagate_active_weight(struct ioc_gq *iocg, u32 active, u32 inuse)
{
	struct ioc *ioc = iocg->ioc;
	int lvl;

	lockdep_assert_held(&ioc->lock);

	inuse = min(active, inuse);

	for (lvl = iocg->level - 1; lvl >= 0; lvl--) {
		struct ioc_gq *parent = iocg->ancestors[lvl];
		struct ioc_gq *child = iocg->ancestors[lvl + 1];
		u32 parent_active = 0, parent_inuse = 0;

		/* update the level sums */
		parent->child_active_sum += (s32)(active - child->active);
		parent->child_inuse_sum += (s32)(inuse - child->inuse);
		/* apply the udpates */
		child->active = active;
		child->inuse = inuse;

		/*
		 * The delta between inuse and active sums indicates that
		 * that much of weight is being given away.  Parent's inuse
		 * and active should reflect the ratio.
		 */
		if (parent->child_active_sum) {
			parent_active = parent->weight;
			parent_inuse = DIV64_U64_ROUND_UP(
				parent_active * parent->child_inuse_sum,
				parent->child_active_sum);
		}

		/* do we need to keep walking up? */
		if (parent_active == parent->active &&
		    parent_inuse == parent->inuse)
			break;

		active = parent_active;
		inuse = parent_inuse;
	}

	ioc->weights_updated = true;
}

static void commit_active_weights(struct ioc *ioc)
{
	lockdep_assert_held(&ioc->lock);

	if (ioc->weights_updated) {
		/* paired with rmb in current_hweight(), see there */
		smp_wmb();
		atomic_inc(&ioc->hweight_gen);
		ioc->weights_updated = false;
	}
}

static void propagate_active_weight(struct ioc_gq *iocg, u32 active, u32 inuse)
{
	__propagate_active_weight(iocg, active, inuse);
	commit_active_weights(iocg->ioc);
}

static void current_hweight(struct ioc_gq *iocg, u32 *hw_activep, u32 *hw_inusep)
{
	struct ioc *ioc = iocg->ioc;
	int lvl;
	u32 hwa, hwi;
	int ioc_gen;

	/* hot path - if uptodate, use cached */
	ioc_gen = atomic_read(&ioc->hweight_gen);
	if (ioc_gen == iocg->hweight_gen)
		goto out;

	/*
	 * Paired with wmb in commit_active_weights().  If we saw the
	 * updated hweight_gen, all the weight updates from
	 * __propagate_active_weight() are visible too.
	 *
	 * We can race with weight updates during calculation and get it
	 * wrong.  However, hweight_gen would have changed and a future
	 * reader will recalculate and we're guaranteed to discard the
	 * wrong result soon.
	 */
	smp_rmb();

	hwa = hwi = HWEIGHT_WHOLE;
	for (lvl = 0; lvl <= iocg->level - 1; lvl++) {
		struct ioc_gq *parent = iocg->ancestors[lvl];
		struct ioc_gq *child = iocg->ancestors[lvl + 1];
		u32 active_sum = READ_ONCE(parent->child_active_sum);
		u32 inuse_sum = READ_ONCE(parent->child_inuse_sum);
		u32 active = READ_ONCE(child->active);
		u32 inuse = READ_ONCE(child->inuse);

		/* we can race with deactivations and either may read as zero */
		if (!active_sum || !inuse_sum)
			continue;

		active_sum = max(active, active_sum);
		hwa = hwa * active / active_sum;	/* max 16bits * 10000 */

		inuse_sum = max(inuse, inuse_sum);
		hwi = hwi * inuse / inuse_sum;		/* max 16bits * 10000 */
	}

	iocg->hweight_active = max_t(u32, hwa, 1);
	iocg->hweight_inuse = max_t(u32, hwi, 1);
	iocg->hweight_gen = ioc_gen;
out:
	if (hw_activep)
		*hw_activep = iocg->hweight_active;
	if (hw_inusep)
		*hw_inusep = iocg->hweight_inuse;
}

static void weight_updated(struct ioc_gq *iocg)
{
	struct ioc *ioc = iocg->ioc;
	struct blkcg_gq *blkg = iocg_to_blkg(iocg);
	struct ioc_cgrp *iocc = blkcg_to_iocc(blkg->blkcg);
	u32 weight;

	lockdep_assert_held(&ioc->lock);

	weight = iocg->cfg_weight ?: iocc->dfl_weight;
	if (weight != iocg->weight && iocg->active)
		propagate_active_weight(iocg, weight,
			DIV64_U64_ROUND_UP(iocg->inuse * weight, iocg->weight));
	iocg->weight = weight;
}

static bool iocg_activate(struct ioc_gq *iocg, struct ioc_now *now)
{
	struct ioc *ioc = iocg->ioc;
	u64 last_period, cur_period, max_period_delta;
	u64 vtime, vmargin, vmin;
	int i;

	/*
	 * If seem to be already active, just update the stamp to tell the
	 * timer that we're still active.  We don't mind occassional races.
	 */
	if (!list_empty(&iocg->active_list)) {
		ioc_now(ioc, now);
		cur_period = atomic64_read(&ioc->cur_period);
		if (atomic64_read(&iocg->active_period) != cur_period)
			atomic64_set(&iocg->active_period, cur_period);
		return true;
	}

	/* racy check on internal node IOs, treat as root level IOs */
	if (iocg->child_active_sum)
		return false;

	spin_lock_irq(&ioc->lock);

	ioc_now(ioc, now);

	/* update period */
	cur_period = atomic64_read(&ioc->cur_period);
	last_period = atomic64_read(&iocg->active_period);
	atomic64_set(&iocg->active_period, cur_period);

	/* already activated or breaking leaf-only constraint? */
	if (!list_empty(&iocg->active_list))
		goto succeed_unlock;
	for (i = iocg->level - 1; i > 0; i--)
		if (!list_empty(&iocg->ancestors[i]->active_list))
			goto fail_unlock;

	if (iocg->child_active_sum)
		goto fail_unlock;

	/*
	 * vtime may wrap when vrate is raised substantially due to
	 * underestimated IO costs.  Look at the period and ignore its
	 * vtime if the iocg has been idle for too long.  Also, cap the
	 * budget it can start with to the margin.
	 */
	max_period_delta = DIV64_U64_ROUND_UP(VTIME_VALID_DUR, ioc->period_us);
	vtime = atomic64_read(&iocg->vtime);
	vmargin = ioc->margin_us * now->vrate;
	vmin = now->vnow - vmargin;

	if (last_period + max_period_delta < cur_period ||
	    time_before64(vtime, vmin)) {
		atomic64_add(vmin - vtime, &iocg->vtime);
		atomic64_add(vmin - vtime, &iocg->done_vtime);
		vtime = vmin;
	}

	/*
	 * Activate, propagate weight and start period timer if not
	 * running.  Reset hweight_gen to avoid accidental match from
	 * wrapping.
	 */
	iocg->hweight_gen = atomic_read(&ioc->hweight_gen) - 1;
	list_add(&iocg->active_list, &ioc->active_iocgs);
	propagate_active_weight(iocg, iocg->weight,
				iocg->last_inuse ?: iocg->weight);

	TRACE_IOCG_PATH(iocg_activate, iocg, now,
			last_period, cur_period, vtime);

	iocg->last_vtime = vtime;

	if (ioc->running == IOC_IDLE) {
		ioc->running = IOC_RUNNING;
		ioc_start_period(ioc, now);
	}

succeed_unlock:
	spin_unlock_irq(&ioc->lock);
	return true;

fail_unlock:
	spin_unlock_irq(&ioc->lock);
	return false;
}

static int iocg_wake_fn(struct wait_queue_entry *wq_entry, unsigned mode,
			int flags, void *key)
{
	struct iocg_wait *wait = container_of(wq_entry, struct iocg_wait, wait);
	struct iocg_wake_ctx *ctx = (struct iocg_wake_ctx *)key;
	u64 cost = abs_cost_to_cost(wait->abs_cost, ctx->hw_inuse);

	ctx->vbudget -= cost;

	if (ctx->vbudget < 0)
		return -1;

	iocg_commit_bio(ctx->iocg, wait->bio, cost);

	/*
	 * autoremove_wake_function() removes the wait entry only when it
	 * actually changed the task state.  We want the wait always
	 * removed.  Remove explicitly and use default_wake_function().
	 */
	list_del_init(&wq_entry->entry);
	wait->committed = true;

	default_wake_function(wq_entry, mode, flags, key);
	return 0;
}

static void iocg_kick_waitq(struct ioc_gq *iocg, struct ioc_now *now)
{
	struct ioc *ioc = iocg->ioc;
	struct iocg_wake_ctx ctx = { .iocg = iocg };
	u64 margin_ns = (u64)(ioc->period_us *
			      WAITQ_TIMER_MARGIN_PCT / 100) * NSEC_PER_USEC;
	u64 abs_vdebt, vdebt, vshortage, expires, oexpires;
	s64 vbudget;
	u32 hw_inuse;

	lockdep_assert_held(&iocg->waitq.lock);

	current_hweight(iocg, NULL, &hw_inuse);
	vbudget = now->vnow - atomic64_read(&iocg->vtime);

	/* pay off debt */
	abs_vdebt = atomic64_read(&iocg->abs_vdebt);
	vdebt = abs_cost_to_cost(abs_vdebt, hw_inuse);
	if (vdebt && vbudget > 0) {
		u64 delta = min_t(u64, vbudget, vdebt);
		u64 abs_delta = min(cost_to_abs_cost(delta, hw_inuse),
				    abs_vdebt);

		atomic64_add(delta, &iocg->vtime);
		atomic64_add(delta, &iocg->done_vtime);
		atomic64_sub(abs_delta, &iocg->abs_vdebt);
		if (WARN_ON_ONCE(atomic64_read(&iocg->abs_vdebt) < 0))
			atomic64_set(&iocg->abs_vdebt, 0);
	}

	/*
	 * Wake up the ones which are due and see how much vtime we'll need
	 * for the next one.
	 */
	ctx.hw_inuse = hw_inuse;
	ctx.vbudget = vbudget - vdebt;
	__wake_up_locked_key(&iocg->waitq, TASK_NORMAL, &ctx);
	if (!waitqueue_active(&iocg->waitq))
		return;
	if (WARN_ON_ONCE(ctx.vbudget >= 0))
		return;

	/* determine next wakeup, add a quarter margin to guarantee chunking */
	vshortage = -ctx.vbudget;
	expires = now->now_ns +
		DIV64_U64_ROUND_UP(vshortage, now->vrate) * NSEC_PER_USEC;
	expires += margin_ns / 4;

	/* if already active and close enough, don't bother */
	oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->waitq_timer));
	if (hrtimer_is_queued(&iocg->waitq_timer) &&
	    abs(oexpires - expires) <= margin_ns / 4)
		return;

	hrtimer_start_range_ns(&iocg->waitq_timer, ns_to_ktime(expires),
			       margin_ns / 4, HRTIMER_MODE_ABS);
}

static enum hrtimer_restart iocg_waitq_timer_fn(struct hrtimer *timer)
{
	struct ioc_gq *iocg = container_of(timer, struct ioc_gq, waitq_timer);
	struct ioc_now now;
	unsigned long flags;

	ioc_now(iocg->ioc, &now);

	spin_lock_irqsave(&iocg->waitq.lock, flags);
	iocg_kick_waitq(iocg, &now);
	spin_unlock_irqrestore(&iocg->waitq.lock, flags);

	return HRTIMER_NORESTART;
}

static void iocg_kick_delay(struct ioc_gq *iocg, struct ioc_now *now, u64 cost)
{
	struct ioc *ioc = iocg->ioc;
	struct blkcg_gq *blkg = iocg_to_blkg(iocg);
	u64 vtime = atomic64_read(&iocg->vtime);
	u64 vmargin = ioc->margin_us * now->vrate;
	u64 margin_ns = ioc->margin_us * NSEC_PER_USEC;
	u64 expires, oexpires;
	u32 hw_inuse;

	/* debt-adjust vtime */
	current_hweight(iocg, NULL, &hw_inuse);
	vtime += abs_cost_to_cost(atomic64_read(&iocg->abs_vdebt), hw_inuse);

	/* clear or maintain depending on the overage */
	if (time_before_eq64(vtime, now->vnow)) {
		blkcg_clear_delay(blkg);
		return;
	}
	if (!atomic_read(&blkg->use_delay) &&
	    time_before_eq64(vtime, now->vnow + vmargin))
		return;

	/* use delay */
	if (cost) {
		u64 cost_ns = DIV64_U64_ROUND_UP(cost * NSEC_PER_USEC,
						 now->vrate);
		blkcg_add_delay(blkg, now->now_ns, cost_ns);
	}
	blkcg_use_delay(blkg);

	expires = now->now_ns + DIV64_U64_ROUND_UP(vtime - now->vnow,
						   now->vrate) * NSEC_PER_USEC;

	/* if already active and close enough, don't bother */
	oexpires = ktime_to_ns(hrtimer_get_softexpires(&iocg->delay_timer));
	if (hrtimer_is_queued(&iocg->delay_timer) &&
	    abs(oexpires - expires) <= margin_ns / 4)
		return;

	hrtimer_start_range_ns(&iocg->delay_timer, ns_to_ktime(expires),
			       margin_ns / 4, HRTIMER_MODE_ABS);
}

static enum hrtimer_restart iocg_delay_timer_fn(struct hrtimer *timer)
{
	struct ioc_gq *iocg = container_of(timer, struct ioc_gq, delay_timer);
	struct ioc_now now;

	ioc_now(iocg->ioc, &now);
	iocg_kick_delay(iocg, &now, 0);

	return HRTIMER_NORESTART;
}

static void ioc_lat_stat(struct ioc *ioc, u32 *missed_ppm_ar, u32 *rq_wait_pct_p)
{
	u32 nr_met[2] = { };
	u32 nr_missed[2] = { };
	u64 rq_wait_ns = 0;
	int cpu, rw;

	for_each_online_cpu(cpu) {
		struct ioc_pcpu_stat *stat = per_cpu_ptr(ioc->pcpu_stat, cpu);
		u64 this_rq_wait_ns;

		for (rw = READ; rw <= WRITE; rw++) {
			u32 this_met = READ_ONCE(stat->missed[rw].nr_met);
			u32 this_missed = READ_ONCE(stat->missed[rw].nr_missed);

			nr_met[rw] += this_met - stat->missed[rw].last_met;
			nr_missed[rw] += this_missed - stat->missed[rw].last_missed;
			stat->missed[rw].last_met = this_met;
			stat->missed[rw].last_missed = this_missed;
		}

		this_rq_wait_ns = READ_ONCE(stat->rq_wait_ns);
		rq_wait_ns += this_rq_wait_ns - stat->last_rq_wait_ns;
		stat->last_rq_wait_ns = this_rq_wait_ns;
	}

	for (rw = READ; rw <= WRITE; rw++) {
		if (nr_met[rw] + nr_missed[rw])
			missed_ppm_ar[rw] =
				DIV64_U64_ROUND_UP((u64)nr_missed[rw] * MILLION,
						   nr_met[rw] + nr_missed[rw]);
		else
			missed_ppm_ar[rw] = 0;
	}

	*rq_wait_pct_p = div64_u64(rq_wait_ns * 100,
				   ioc->period_us * NSEC_PER_USEC);
}

/* was iocg idle this period? */
static bool iocg_is_idle(struct ioc_gq *iocg)
{
	struct ioc *ioc = iocg->ioc;

	/* did something get issued this period? */
	if (atomic64_read(&iocg->active_period) ==
	    atomic64_read(&ioc->cur_period))
		return false;

	/* is something in flight? */
	if (atomic64_read(&iocg->done_vtime) < atomic64_read(&iocg->vtime))
		return false;

	return true;
}

/* returns usage with margin added if surplus is large enough */
static u32 surplus_adjusted_hweight_inuse(u32 usage, u32 hw_inuse)
{
	/* add margin */
	usage = DIV_ROUND_UP(usage * SURPLUS_SCALE_PCT, 100);
	usage += SURPLUS_SCALE_ABS;

	/* don't bother if the surplus is too small */
	if (usage + SURPLUS_MIN_ADJ_DELTA > hw_inuse)
		return 0;

	return usage;
}

static void ioc_timer_fn(struct timer_list *timer)
{
	struct ioc *ioc = container_of(timer, struct ioc, timer);
	struct ioc_gq *iocg, *tiocg;
	struct ioc_now now;
	int nr_surpluses = 0, nr_shortages = 0, nr_lagging = 0;
	u32 ppm_rthr = MILLION - ioc->params.qos[QOS_RPPM];
	u32 ppm_wthr = MILLION - ioc->params.qos[QOS_WPPM];
	u32 missed_ppm[2], rq_wait_pct;
	u64 period_vtime;
	int prev_busy_level, i;

	/* how were the latencies during the period? */
	ioc_lat_stat(ioc, missed_ppm, &rq_wait_pct);

	/* take care of active iocgs */
	spin_lock_irq(&ioc->lock);

	ioc_now(ioc, &now);

	period_vtime = now.vnow - ioc->period_at_vtime;
	if (WARN_ON_ONCE(!period_vtime)) {
		spin_unlock_irq(&ioc->lock);
		return;
	}

	/*
	 * Waiters determine the sleep durations based on the vrate they
	 * saw at the time of sleep.  If vrate has increased, some waiters
	 * could be sleeping for too long.  Wake up tardy waiters which
	 * should have woken up in the last period and expire idle iocgs.
	 */
	list_for_each_entry_safe(iocg, tiocg, &ioc->active_iocgs, active_list) {
		if (!waitqueue_active(&iocg->waitq) &&
		    !atomic64_read(&iocg->abs_vdebt) && !iocg_is_idle(iocg))
			continue;

		spin_lock(&iocg->waitq.lock);

		if (waitqueue_active(&iocg->waitq) ||
		    atomic64_read(&iocg->abs_vdebt)) {
			/* might be oversleeping vtime / hweight changes, kick */
			iocg_kick_waitq(iocg, &now);
			iocg_kick_delay(iocg, &now, 0);
		} else if (iocg_is_idle(iocg)) {
			/* no waiter and idle, deactivate */
			iocg->last_inuse = iocg->inuse;
			__propagate_active_weight(iocg, 0, 0);
			list_del_init(&iocg->active_list);
		}

		spin_unlock(&iocg->waitq.lock);
	}
	commit_active_weights(ioc);

	/* calc usages and see whether some weights need to be moved around */
	list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
		u64 vdone, vtime, vusage, vmargin, vmin;
		u32 hw_active, hw_inuse, usage;

		/*
		 * Collect unused and wind vtime closer to vnow to prevent
		 * iocgs from accumulating a large amount of budget.
		 */
		vdone = atomic64_read(&iocg->done_vtime);
		vtime = atomic64_read(&iocg->vtime);
		current_hweight(iocg, &hw_active, &hw_inuse);

		/*
		 * Latency QoS detection doesn't account for IOs which are
		 * in-flight for longer than a period.  Detect them by
		 * comparing vdone against period start.  If lagging behind
		 * IOs from past periods, don't increase vrate.
		 */
		if ((ppm_rthr != MILLION || ppm_wthr != MILLION) &&
		    !atomic_read(&iocg_to_blkg(iocg)->use_delay) &&
		    time_after64(vtime, vdone) &&
		    time_after64(vtime, now.vnow -
				 MAX_LAGGING_PERIODS * period_vtime) &&
		    time_before64(vdone, now.vnow - period_vtime))
			nr_lagging++;

		if (waitqueue_active(&iocg->waitq))
			vusage = now.vnow - iocg->last_vtime;
		else if (time_before64(iocg->last_vtime, vtime))
			vusage = vtime - iocg->last_vtime;
		else
			vusage = 0;

		iocg->last_vtime += vusage;
		/*
		 * Factor in in-flight vtime into vusage to avoid
		 * high-latency completions appearing as idle.  This should
		 * be done after the above ->last_time adjustment.
		 */
		vusage = max(vusage, vtime - vdone);

		/* calculate hweight based usage ratio and record */
		if (vusage) {
			usage = DIV64_U64_ROUND_UP(vusage * hw_inuse,
						   period_vtime);
			iocg->usage_idx = (iocg->usage_idx + 1) % NR_USAGE_SLOTS;
			iocg->usages[iocg->usage_idx] = usage;
		} else {
			usage = 0;
		}

		/* see whether there's surplus vtime */
		vmargin = ioc->margin_us * now.vrate;
		vmin = now.vnow - vmargin;

		iocg->has_surplus = false;

		if (!waitqueue_active(&iocg->waitq) &&
		    time_before64(vtime, vmin)) {
			u64 delta = vmin - vtime;

			/* throw away surplus vtime */
			atomic64_add(delta, &iocg->vtime);
			atomic64_add(delta, &iocg->done_vtime);
			iocg->last_vtime += delta;
			/* if usage is sufficiently low, maybe it can donate */
			if (surplus_adjusted_hweight_inuse(usage, hw_inuse)) {
				iocg->has_surplus = true;
				nr_surpluses++;
			}
		} else if (hw_inuse < hw_active) {
			u32 new_hwi, new_inuse;

			/* was donating but might need to take back some */
			if (waitqueue_active(&iocg->waitq)) {
				new_hwi = hw_active;
			} else {
				new_hwi = max(hw_inuse,
					      usage * SURPLUS_SCALE_PCT / 100 +
					      SURPLUS_SCALE_ABS);
			}

			new_inuse = div64_u64((u64)iocg->inuse * new_hwi,
					      hw_inuse);
			new_inuse = clamp_t(u32, new_inuse, 1, iocg->active);

			if (new_inuse > iocg->inuse) {
				TRACE_IOCG_PATH(inuse_takeback, iocg, &now,
						iocg->inuse, new_inuse,
						hw_inuse, new_hwi);
				__propagate_active_weight(iocg, iocg->weight,
							  new_inuse);
			}
		} else {
			/* genuninely out of vtime */
			nr_shortages++;
		}
	}

	if (!nr_shortages || !nr_surpluses)
		goto skip_surplus_transfers;

	/* there are both shortages and surpluses, transfer surpluses */
	list_for_each_entry(iocg, &ioc->active_iocgs, active_list) {
		u32 usage, hw_active, hw_inuse, new_hwi, new_inuse;
		int nr_valid = 0;

		if (!iocg->has_surplus)
			continue;

		/* base the decision on max historical usage */
		for (i = 0, usage = 0; i < NR_USAGE_SLOTS; i++) {
			if (iocg->usages[i]) {
				usage = max(usage, iocg->usages[i]);
				nr_valid++;
			}
		}
		if (nr_valid < MIN_VALID_USAGES)
			continue;

		current_hweight(iocg, &hw_active, &hw_inuse);
		new_hwi = surplus_adjusted_hweight_inuse(usage, hw_inuse);
		if (!new_hwi)
			continue;

		new_inuse = DIV64_U64_ROUND_UP((u64)iocg->inuse * new_hwi,
					       hw_inuse);
		if (new_inuse < iocg->inuse) {
			TRACE_IOCG_PATH(inuse_giveaway, iocg, &now,
					iocg->inuse, new_inuse,
					hw_inuse, new_hwi);
			__propagate_active_weight(iocg, iocg->weight, new_inuse);
		}
	}
skip_surplus_transfers:
	commit_active_weights(ioc);

	/*
	 * If q is getting clogged or we're missing too much, we're issuing
	 * too much IO and should lower vtime rate.  If we're not missing
	 * and experiencing shortages but not surpluses, we're too stingy
	 * and should increase vtime rate.
	 */
	prev_busy_level = ioc->busy_level;
	if (rq_wait_pct > RQ_WAIT_BUSY_PCT ||
	    missed_ppm[READ] > ppm_rthr ||
	    missed_ppm[WRITE] > ppm_wthr) {
		ioc->busy_level = max(ioc->busy_level, 0);
		ioc->busy_level++;
	} else if (rq_wait_pct <= RQ_WAIT_BUSY_PCT * UNBUSY_THR_PCT / 100 &&
		   missed_ppm[READ] <= ppm_rthr * UNBUSY_THR_PCT / 100 &&
		   missed_ppm[WRITE] <= ppm_wthr * UNBUSY_THR_PCT / 100) {
		/* take action iff there is contention */
		if (nr_shortages && !nr_lagging) {
			ioc->busy_level = min(ioc->busy_level, 0);
			/* redistribute surpluses first */
			if (!nr_surpluses)
				ioc->busy_level--;
		}
	} else {
		ioc->busy_level = 0;
	}

	ioc->busy_level = clamp(ioc->busy_level, -1000, 1000);

	if (ioc->busy_level > 0 || (ioc->busy_level < 0 && !nr_lagging)) {
		u64 vrate = atomic64_read(&ioc->vtime_rate);
		u64 vrate_min = ioc->vrate_min, vrate_max = ioc->vrate_max;

		/* rq_wait signal is always reliable, ignore user vrate_min */
		if (rq_wait_pct > RQ_WAIT_BUSY_PCT)
			vrate_min = VRATE_MIN;

		/*
		 * If vrate is out of bounds, apply clamp gradually as the
		 * bounds can change abruptly.  Otherwise, apply busy_level
		 * based adjustment.
		 */
		if (vrate < vrate_min) {
			vrate = div64_u64(vrate * (100 + VRATE_CLAMP_ADJ_PCT),
					  100);
			vrate = min(vrate, vrate_min);
		} else if (vrate > vrate_max) {
			vrate = div64_u64(vrate * (100 - VRATE_CLAMP_ADJ_PCT),
					  100);
			vrate = max(vrate, vrate_max);
		} else {
			int idx = min_t(int, abs(ioc->busy_level),
					ARRAY_SIZE(vrate_adj_pct) - 1);
			u32 adj_pct = vrate_adj_pct[idx];

			if (ioc->busy_level > 0)
				adj_pct = 100 - adj_pct;
			else
				adj_pct = 100 + adj_pct;

			vrate = clamp(DIV64_U64_ROUND_UP(vrate * adj_pct, 100),
				      vrate_min, vrate_max);
		}

		trace_iocost_ioc_vrate_adj(ioc, vrate, &missed_ppm, rq_wait_pct,
					   nr_lagging, nr_shortages,
					   nr_surpluses);

		atomic64_set(&ioc->vtime_rate, vrate);
		ioc->inuse_margin_vtime = DIV64_U64_ROUND_UP(
			ioc->period_us * vrate * INUSE_MARGIN_PCT, 100);
	} else if (ioc->busy_level != prev_busy_level || nr_lagging) {
		trace_iocost_ioc_vrate_adj(ioc, atomic64_read(&ioc->vtime_rate),
					   &missed_ppm, rq_wait_pct, nr_lagging,
					   nr_shortages, nr_surpluses);
	}

	ioc_refresh_params(ioc, false);

	/*
	 * This period is done.  Move onto the next one.  If nothing's
	 * going on with the device, stop the timer.
	 */
	atomic64_inc(&ioc->cur_period);

	if (ioc->running != IOC_STOP) {
		if (!list_empty(&ioc->active_iocgs)) {
			ioc_start_period(ioc, &now);
		} else {
			ioc->busy_level = 0;
			ioc->running = IOC_IDLE;
		}
	}

	spin_unlock_irq(&ioc->lock);
}

static void calc_vtime_cost_builtin(struct bio *bio, struct ioc_gq *iocg,
				    bool is_merge, u64 *costp)
{
	struct ioc *ioc = iocg->ioc;
	u64 coef_seqio, coef_randio, coef_page;
	u64 pages = max_t(u64, bio_sectors(bio) >> IOC_SECT_TO_PAGE_SHIFT, 1);
	u64 seek_pages = 0;
	u64 cost = 0;

	switch (bio_op(bio)) {
	case REQ_OP_READ:
		coef_seqio	= ioc->params.lcoefs[LCOEF_RSEQIO];
		coef_randio	= ioc->params.lcoefs[LCOEF_RRANDIO];
		coef_page	= ioc->params.lcoefs[LCOEF_RPAGE];
		break;
	case REQ_OP_WRITE:
		coef_seqio	= ioc->params.lcoefs[LCOEF_WSEQIO];
		coef_randio	= ioc->params.lcoefs[LCOEF_WRANDIO];
		coef_page	= ioc->params.lcoefs[LCOEF_WPAGE];
		break;
	default:
		goto out;
	}

	if (iocg->cursor) {
		seek_pages = abs(bio->bi_iter.bi_sector - iocg->cursor);
		seek_pages >>= IOC_SECT_TO_PAGE_SHIFT;
	}

	if (!is_merge) {
		if (seek_pages > LCOEF_RANDIO_PAGES) {
			cost += coef_randio;
		} else {
			cost += coef_seqio;
		}
	}
	cost += pages * coef_page;
out:
	*costp = cost;
}

static u64 calc_vtime_cost(struct bio *bio, struct ioc_gq *iocg, bool is_merge)
{
	u64 cost;

	calc_vtime_cost_builtin(bio, iocg, is_merge, &cost);
	return cost;
}

static void ioc_rqos_throttle(struct rq_qos *rqos, struct bio *bio)
{
	struct blkcg_gq *blkg = bio->bi_blkg;
	struct ioc *ioc = rqos_to_ioc(rqos);
	struct ioc_gq *iocg = blkg_to_iocg(blkg);
	struct ioc_now now;
	struct iocg_wait wait;
	u32 hw_active, hw_inuse;
	u64 abs_cost, cost, vtime;

	/* bypass IOs if disabled or for root cgroup */
	if (!ioc->enabled || !iocg->level)
		return;

	/* always activate so that even 0 cost IOs get protected to some level */
	if (!iocg_activate(iocg, &now))
		return;

	/* calculate the absolute vtime cost */
	abs_cost = calc_vtime_cost(bio, iocg, false);
	if (!abs_cost)
		return;

	iocg->cursor = bio_end_sector(bio);

	vtime = atomic64_read(&iocg->vtime);
	current_hweight(iocg, &hw_active, &hw_inuse);

	if (hw_inuse < hw_active &&
	    time_after_eq64(vtime + ioc->inuse_margin_vtime, now.vnow)) {
		TRACE_IOCG_PATH(inuse_reset, iocg, &now,
				iocg->inuse, iocg->weight, hw_inuse, hw_active);
		spin_lock_irq(&ioc->lock);
		propagate_active_weight(iocg, iocg->weight, iocg->weight);
		spin_unlock_irq(&ioc->lock);
		current_hweight(iocg, &hw_active, &hw_inuse);
	}

	cost = abs_cost_to_cost(abs_cost, hw_inuse);

	/*
	 * If no one's waiting and within budget, issue right away.  The
	 * tests are racy but the races aren't systemic - we only miss once
	 * in a while which is fine.
	 */
	if (!waitqueue_active(&iocg->waitq) &&
	    !atomic64_read(&iocg->abs_vdebt) &&
	    time_before_eq64(vtime + cost, now.vnow)) {
		iocg_commit_bio(iocg, bio, cost);
		return;
	}

	/*
	 * We're over budget.  If @bio has to be issued regardless,
	 * remember the abs_cost instead of advancing vtime.
	 * iocg_kick_waitq() will pay off the debt before waking more IOs.
	 * This way, the debt is continuously paid off each period with the
	 * actual budget available to the cgroup.  If we just wound vtime,
	 * we would incorrectly use the current hw_inuse for the entire
	 * amount which, for example, can lead to the cgroup staying
	 * blocked for a long time even with substantially raised hw_inuse.
	 */
	if (bio_issue_as_root_blkg(bio) || fatal_signal_pending(current)) {
		atomic64_add(abs_cost, &iocg->abs_vdebt);
		iocg_kick_delay(iocg, &now, cost);
		return;
	}

	/*
	 * Append self to the waitq and schedule the wakeup timer if we're
	 * the first waiter.  The timer duration is calculated based on the
	 * current vrate.  vtime and hweight changes can make it too short
	 * or too long.  Each wait entry records the absolute cost it's
	 * waiting for to allow re-evaluation using a custom wait entry.
	 *
	 * If too short, the timer simply reschedules itself.  If too long,
	 * the period timer will notice and trigger wakeups.
	 *
	 * All waiters are on iocg->waitq and the wait states are
	 * synchronized using waitq.lock.
	 */
	spin_lock_irq(&iocg->waitq.lock);

	/*
	 * We activated above but w/o any synchronization.  Deactivation is
	 * synchronized with waitq.lock and we won't get deactivated as
	 * long as we're waiting, so we're good if we're activated here.
	 * In the unlikely case that we are deactivated, just issue the IO.
	 */
	if (unlikely(list_empty(&iocg->active_list))) {
		spin_unlock_irq(&iocg->waitq.lock);
		iocg_commit_bio(iocg, bio, cost);
		return;
	}

	init_waitqueue_func_entry(&wait.wait, iocg_wake_fn);
	wait.wait.private = current;
	wait.bio = bio;
	wait.abs_cost = abs_cost;
	wait.committed = false;	/* will be set true by waker */

	__add_wait_queue_entry_tail(&iocg->waitq, &wait.wait);
	iocg_kick_waitq(iocg, &now);

	spin_unlock_irq(&iocg->waitq.lock);

	while (true) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		if (wait.committed)
			break;
		io_schedule();
	}

	/* waker already committed us, proceed */
	finish_wait(&iocg->waitq, &wait.wait);
}

static void ioc_rqos_merge(struct rq_qos *rqos, struct request *rq,
			   struct bio *bio)
{
	struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);
	struct ioc *ioc = iocg->ioc;
	sector_t bio_end = bio_end_sector(bio);
	struct ioc_now now;
	u32 hw_inuse;
	u64 abs_cost, cost;

	/* bypass if disabled or for root cgroup */
	if (!ioc->enabled || !iocg->level)
		return;

	abs_cost = calc_vtime_cost(bio, iocg, true);
	if (!abs_cost)
		return;

	ioc_now(ioc, &now);
	current_hweight(iocg, NULL, &hw_inuse);
	cost = abs_cost_to_cost(abs_cost, hw_inuse);

	/* update cursor if backmerging into the request at the cursor */
	if (blk_rq_pos(rq) < bio_end &&
	    blk_rq_pos(rq) + blk_rq_sectors(rq) == iocg->cursor)
		iocg->cursor = bio_end;

	/*
	 * Charge if there's enough vtime budget and the existing request
	 * has cost assigned.  Otherwise, account it as debt.  See debt
	 * handling in ioc_rqos_throttle() for details.
	 */
	if (rq->bio && rq->bio->bi_iocost_cost &&
	    time_before_eq64(atomic64_read(&iocg->vtime) + cost, now.vnow))
		iocg_commit_bio(iocg, bio, cost);
	else
		atomic64_add(abs_cost, &iocg->abs_vdebt);
}

static void ioc_rqos_done_bio(struct rq_qos *rqos, struct bio *bio)
{
	struct ioc_gq *iocg = blkg_to_iocg(bio->bi_blkg);

	if (iocg && bio->bi_iocost_cost)
		atomic64_add(bio->bi_iocost_cost, &iocg->done_vtime);
}

static void ioc_rqos_done(struct rq_qos *rqos, struct request *rq)
{
	struct ioc *ioc = rqos_to_ioc(rqos);
	u64 on_q_ns, rq_wait_ns;
	int pidx, rw;

	if (!ioc->enabled || !rq->alloc_time_ns || !rq->start_time_ns)
		return;

	switch (req_op(rq) & REQ_OP_MASK) {
	case REQ_OP_READ:
		pidx = QOS_RLAT;
		rw = READ;
		break;
	case REQ_OP_WRITE:
		pidx = QOS_WLAT;
		rw = WRITE;
		break;
	default:
		return;
	}

	on_q_ns = ktime_get_ns() - rq->alloc_time_ns;
	rq_wait_ns = rq->start_time_ns - rq->alloc_time_ns;

	if (on_q_ns <= ioc->params.qos[pidx] * NSEC_PER_USEC)
		this_cpu_inc(ioc->pcpu_stat->missed[rw].nr_met);
	else
		this_cpu_inc(ioc->pcpu_stat->missed[rw].nr_missed);

	this_cpu_add(ioc->pcpu_stat->rq_wait_ns, rq_wait_ns);
}

static void ioc_rqos_queue_depth_changed(struct rq_qos *rqos)
{
	struct ioc *ioc = rqos_to_ioc(rqos);

	spin_lock_irq(&ioc->lock);
	ioc_refresh_params(ioc, false);
	spin_unlock_irq(&ioc->lock);
}

static void ioc_rqos_exit(struct rq_qos *rqos)
{
	struct ioc *ioc = rqos_to_ioc(rqos);

	blkcg_deactivate_policy(rqos->q, &blkcg_policy_iocost);

	spin_lock_irq(&ioc->lock);
	ioc->running = IOC_STOP;
	spin_unlock_irq(&ioc->lock);

	del_timer_sync(&ioc->timer);
	free_percpu(ioc->pcpu_stat);
	kfree(ioc);
}

static struct rq_qos_ops ioc_rqos_ops = {
	.throttle = ioc_rqos_throttle,
	.merge = ioc_rqos_merge,
	.done_bio = ioc_rqos_done_bio,
	.done = ioc_rqos_done,
	.queue_depth_changed = ioc_rqos_queue_depth_changed,
	.exit = ioc_rqos_exit,
};

static int blk_iocost_init(struct request_queue *q)
{
	struct ioc *ioc;
	struct rq_qos *rqos;
	int ret;

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

	ioc->pcpu_stat = alloc_percpu(struct ioc_pcpu_stat);
	if (!ioc->pcpu_stat) {
		kfree(ioc);
		return -ENOMEM;
	}

	rqos = &ioc->rqos;
	rqos->id = RQ_QOS_COST;
	rqos->ops = &ioc_rqos_ops;
	rqos->q = q;

	spin_lock_init(&ioc->lock);
	timer_setup(&ioc->timer, ioc_timer_fn, 0);
	INIT_LIST_HEAD(&ioc->active_iocgs);

	ioc->running = IOC_IDLE;
	atomic64_set(&ioc->vtime_rate, VTIME_PER_USEC);
	seqcount_init(&ioc->period_seqcount);
	ioc->period_at = ktime_to_us(ktime_get());
	atomic64_set(&ioc->cur_period, 0);
	atomic_set(&ioc->hweight_gen, 0);

	spin_lock_irq(&ioc->lock);
	ioc->autop_idx = AUTOP_INVALID;
	ioc_refresh_params(ioc, true);
	spin_unlock_irq(&ioc->lock);

	rq_qos_add(q, rqos);
	ret = blkcg_activate_policy(q, &blkcg_policy_iocost);
	if (ret) {
		rq_qos_del(q, rqos);
		free_percpu(ioc->pcpu_stat);
		kfree(ioc);
		return ret;
	}
	return 0;
}

static struct blkcg_policy_data *ioc_cpd_alloc(gfp_t gfp)
{
	struct ioc_cgrp *iocc;

	iocc = kzalloc(sizeof(struct ioc_cgrp), gfp);
	if (!iocc)
		return NULL;

	iocc->dfl_weight = CGROUP_WEIGHT_DFL;
	return &iocc->cpd;
}

static void ioc_cpd_free(struct blkcg_policy_data *cpd)
{
	kfree(container_of(cpd, struct ioc_cgrp, cpd));
}

static struct blkg_policy_data *ioc_pd_alloc(gfp_t gfp, struct request_queue *q,
					     struct blkcg *blkcg)
{
	int levels = blkcg->css.cgroup->level + 1;
	struct ioc_gq *iocg;

	iocg = kzalloc_node(sizeof(*iocg) + levels * sizeof(iocg->ancestors[0]),
			    gfp, q->node);
	if (!iocg)
		return NULL;

	return &iocg->pd;
}

static void ioc_pd_init(struct blkg_policy_data *pd)
{
	struct ioc_gq *iocg = pd_to_iocg(pd);
	struct blkcg_gq *blkg = pd_to_blkg(&iocg->pd);
	struct ioc *ioc = q_to_ioc(blkg->q);
	struct ioc_now now;
	struct blkcg_gq *tblkg;
	unsigned long flags;

	ioc_now(ioc, &now);

	iocg->ioc = ioc;
	atomic64_set(&iocg->vtime, now.vnow);
	atomic64_set(&iocg->done_vtime, now.vnow);
	atomic64_set(&iocg->abs_vdebt, 0);
	atomic64_set(&iocg->active_period, atomic64_read(&ioc->cur_period));
	INIT_LIST_HEAD(&iocg->active_list);
	iocg->hweight_active = HWEIGHT_WHOLE;
	iocg->hweight_inuse = HWEIGHT_WHOLE;

	init_waitqueue_head(&iocg->waitq);
	hrtimer_init(&iocg->waitq_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
	iocg->waitq_timer.function = iocg_waitq_timer_fn;
	hrtimer_init(&iocg->delay_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
	iocg->delay_timer.function = iocg_delay_timer_fn;

	iocg->level = blkg->blkcg->css.cgroup->level;

	for (tblkg = blkg; tblkg; tblkg = tblkg->parent) {
		struct ioc_gq *tiocg = blkg_to_iocg(tblkg);
		iocg->ancestors[tiocg->level] = tiocg;
	}

	spin_lock_irqsave(&ioc->lock, flags);
	weight_updated(iocg);
	spin_unlock_irqrestore(&ioc->lock, flags);
}

static void ioc_pd_free(struct blkg_policy_data *pd)
{
	struct ioc_gq *iocg = pd_to_iocg(pd);
	struct ioc *ioc = iocg->ioc;

	if (ioc) {
		spin_lock(&ioc->lock);
		if (!list_empty(&iocg->active_list)) {
			propagate_active_weight(iocg, 0, 0);
			list_del_init(&iocg->active_list);
		}
		spin_unlock(&ioc->lock);

		hrtimer_cancel(&iocg->waitq_timer);
		hrtimer_cancel(&iocg->delay_timer);
	}
	kfree(iocg);
}

static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
			     int off)
{
	const char *dname = blkg_dev_name(pd->blkg);
	struct ioc_gq *iocg = pd_to_iocg(pd);

	if (dname && iocg->cfg_weight)
		seq_printf(sf, "%s %u\n", dname, iocg->cfg_weight);
	return 0;
}


static int ioc_weight_show(struct seq_file *sf, void *v)
{
	struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
	struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);

	seq_printf(sf, "default %u\n", iocc->dfl_weight);
	blkcg_print_blkgs(sf, blkcg, ioc_weight_prfill,
			  &blkcg_policy_iocost, seq_cft(sf)->private, false);
	return 0;
}

static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
				size_t nbytes, loff_t off)
{
	struct blkcg *blkcg = css_to_blkcg(of_css(of));
	struct ioc_cgrp *iocc = blkcg_to_iocc(blkcg);
	struct blkg_conf_ctx ctx;
	struct ioc_gq *iocg;
	u32 v;
	int ret;

	if (!strchr(buf, ':')) {
		struct blkcg_gq *blkg;

		if (!sscanf(buf, "default %u", &v) && !sscanf(buf, "%u", &v))
			return -EINVAL;

		if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
			return -EINVAL;

		spin_lock(&blkcg->lock);
		iocc->dfl_weight = v;
		hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
			struct ioc_gq *iocg = blkg_to_iocg(blkg);

			if (iocg) {
				spin_lock_irq(&iocg->ioc->lock);
				weight_updated(iocg);
				spin_unlock_irq(&iocg->ioc->lock);
			}
		}
		spin_unlock(&blkcg->lock);

		return nbytes;
	}

	ret = blkg_conf_prep(blkcg, &blkcg_policy_iocost, buf, &ctx);
	if (ret)
		return ret;

	iocg = blkg_to_iocg(ctx.blkg);

	if (!strncmp(ctx.body, "default", 7)) {
		v = 0;
	} else {
		if (!sscanf(ctx.body, "%u", &v))
			goto einval;
		if (v < CGROUP_WEIGHT_MIN || v > CGROUP_WEIGHT_MAX)
			goto einval;
	}

	spin_lock(&iocg->ioc->lock);
	iocg->cfg_weight = v;
	weight_updated(iocg);
	spin_unlock(&iocg->ioc->lock);

	blkg_conf_finish(&ctx);
	return nbytes;

einval:
	blkg_conf_finish(&ctx);
	return -EINVAL;
}

static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
			  int off)
{
	const char *dname = blkg_dev_name(pd->blkg);
	struct ioc *ioc = pd_to_iocg(pd)->ioc;

	if (!dname)
		return 0;

	seq_printf(sf, "%s enable=%d ctrl=%s rpct=%u.%02u rlat=%u wpct=%u.%02u wlat=%u min=%u.%02u max=%u.%02u\n",
		   dname, ioc->enabled, ioc->user_qos_params ? "user" : "auto",
		   ioc->params.qos[QOS_RPPM] / 10000,
		   ioc->params.qos[QOS_RPPM] % 10000 / 100,
		   ioc->params.qos[QOS_RLAT],
		   ioc->params.qos[QOS_WPPM] / 10000,
		   ioc->params.qos[QOS_WPPM] % 10000 / 100,
		   ioc->params.qos[QOS_WLAT],
		   ioc->params.qos[QOS_MIN] / 10000,
		   ioc->params.qos[QOS_MIN] % 10000 / 100,
		   ioc->params.qos[QOS_MAX] / 10000,
		   ioc->params.qos[QOS_MAX] % 10000 / 100);
	return 0;
}

static int ioc_qos_show(struct seq_file *sf, void *v)
{
	struct blkcg *blkcg = css_to_blkcg(seq_css(sf));

	blkcg_print_blkgs(sf, blkcg, ioc_qos_prfill,
			  &blkcg_policy_iocost, seq_cft(sf)->private, false);
	return 0;
}

static const match_table_t qos_ctrl_tokens = {
	{ QOS_ENABLE,		"enable=%u"	},
	{ QOS_CTRL,		"ctrl=%s"	},
	{ NR_QOS_CTRL_PARAMS,	NULL		},
};

static const match_table_t qos_tokens = {
	{ QOS_RPPM,		"rpct=%s"	},
	{ QOS_RLAT,		"rlat=%u"	},
	{ QOS_WPPM,		"wpct=%s"	},
	{ QOS_WLAT,		"wlat=%u"	},
	{ QOS_MIN,		"min=%s"	},
	{ QOS_MAX,		"max=%s"	},
	{ NR_QOS_PARAMS,	NULL		},
};

static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
			     size_t nbytes, loff_t off)
{
	struct gendisk *disk;
	struct ioc *ioc;
	u32 qos[NR_QOS_PARAMS];
	bool enable, user;
	char *p;
	int ret;

	disk = blkcg_conf_get_disk(&input);
	if (IS_ERR(disk))
		return PTR_ERR(disk);

	ioc = q_to_ioc(disk->queue);
	if (!ioc) {
		ret = blk_iocost_init(disk->queue);
		if (ret)
			goto err;
		ioc = q_to_ioc(disk->queue);
	}

	spin_lock_irq(&ioc->lock);
	memcpy(qos, ioc->params.qos, sizeof(qos));
	enable = ioc->enabled;
	user = ioc->user_qos_params;
	spin_unlock_irq(&ioc->lock);

	while ((p = strsep(&input, " \t\n"))) {
		substring_t args[MAX_OPT_ARGS];
		char buf[32];
		int tok;
		s64 v;

		if (!*p)
			continue;

		switch (match_token(p, qos_ctrl_tokens, args)) {
		case QOS_ENABLE:
			match_u64(&args[0], &v);
			enable = v;
			continue;
		case QOS_CTRL:
			match_strlcpy(buf, &args[0], sizeof(buf));
			if (!strcmp(buf, "auto"))
				user = false;
			else if (!strcmp(buf, "user"))
				user = true;
			else
				goto einval;
			continue;
		}

		tok = match_token(p, qos_tokens, args);
		switch (tok) {
		case QOS_RPPM:
		case QOS_WPPM:
			if (match_strlcpy(buf, &args[0], sizeof(buf)) >=
			    sizeof(buf))
				goto einval;
			if (cgroup_parse_float(buf, 2, &v))
				goto einval;
			if (v < 0 || v > 10000)
				goto einval;
			qos[tok] = v * 100;
			break;
		case QOS_RLAT:
		case QOS_WLAT:
			if (match_u64(&args[0], &v))
				goto einval;
			qos[tok] = v;
			break;
		case QOS_MIN:
		case QOS_MAX:
			if (match_strlcpy(buf, &args[0], sizeof(buf)) >=
			    sizeof(buf))
				goto einval;
			if (cgroup_parse_float(buf, 2, &v))
				goto einval;
			if (v < 0)
				goto einval;
			qos[tok] = clamp_t(s64, v * 100,
					   VRATE_MIN_PPM, VRATE_MAX_PPM);
			break;
		default:
			goto einval;
		}
		user = true;
	}

	if (qos[QOS_MIN] > qos[QOS_MAX])
		goto einval;

	spin_lock_irq(&ioc->lock);

	if (enable) {
		blk_queue_flag_set(QUEUE_FLAG_RQ_ALLOC_TIME, ioc->rqos.q);
		ioc->enabled = true;
	} else {
		blk_queue_flag_clear(QUEUE_FLAG_RQ_ALLOC_TIME, ioc->rqos.q);
		ioc->enabled = false;
	}

	if (user) {
		memcpy(ioc->params.qos, qos, sizeof(qos));
		ioc->user_qos_params = true;
	} else {
		ioc->user_qos_params = false;
	}

	ioc_refresh_params(ioc, true);
	spin_unlock_irq(&ioc->lock);

	put_disk_and_module(disk);
	return nbytes;
einval:
	ret = -EINVAL;
err:
	put_disk_and_module(disk);
	return ret;
}

static u64 ioc_cost_model_prfill(struct seq_file *sf,
				 struct blkg_policy_data *pd, int off)
{
	const char *dname = blkg_dev_name(pd->blkg);
	struct ioc *ioc = pd_to_iocg(pd)->ioc;
	u64 *u = ioc->params.i_lcoefs;

	if (!dname)
		return 0;

	seq_printf(sf, "%s ctrl=%s model=linear "
		   "rbps=%llu rseqiops=%llu rrandiops=%llu "
		   "wbps=%llu wseqiops=%llu wrandiops=%llu\n",
		   dname, ioc->user_cost_model ? "user" : "auto",
		   u[I_LCOEF_RBPS], u[I_LCOEF_RSEQIOPS], u[I_LCOEF_RRANDIOPS],
		   u[I_LCOEF_WBPS], u[I_LCOEF_WSEQIOPS], u[I_LCOEF_WRANDIOPS]);
	return 0;
}

static int ioc_cost_model_show(struct seq_file *sf, void *v)
{
	struct blkcg *blkcg = css_to_blkcg(seq_css(sf));

	blkcg_print_blkgs(sf, blkcg, ioc_cost_model_prfill,
			  &blkcg_policy_iocost, seq_cft(sf)->private, false);
	return 0;
}

static const match_table_t cost_ctrl_tokens = {
	{ COST_CTRL,		"ctrl=%s"	},
	{ COST_MODEL,		"model=%s"	},
	{ NR_COST_CTRL_PARAMS,	NULL		},
};

static const match_table_t i_lcoef_tokens = {
	{ I_LCOEF_RBPS,		"rbps=%u"	},
	{ I_LCOEF_RSEQIOPS,	"rseqiops=%u"	},
	{ I_LCOEF_RRANDIOPS,	"rrandiops=%u"	},
	{ I_LCOEF_WBPS,		"wbps=%u"	},
	{ I_LCOEF_WSEQIOPS,	"wseqiops=%u"	},
	{ I_LCOEF_WRANDIOPS,	"wrandiops=%u"	},
	{ NR_I_LCOEFS,		NULL		},
};

static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
				    size_t nbytes, loff_t off)
{
	struct gendisk *disk;
	struct ioc *ioc;
	u64 u[NR_I_LCOEFS];
	bool user;
	char *p;
	int ret;

	disk = blkcg_conf_get_disk(&input);
	if (IS_ERR(disk))
		return PTR_ERR(disk);

	ioc = q_to_ioc(disk->queue);
	if (!ioc) {
		ret = blk_iocost_init(disk->queue);
		if (ret)
			goto err;
		ioc = q_to_ioc(disk->queue);
	}

	spin_lock_irq(&ioc->lock);
	memcpy(u, ioc->params.i_lcoefs, sizeof(u));
	user = ioc->user_cost_model;
	spin_unlock_irq(&ioc->lock);

	while ((p = strsep(&input, " \t\n"))) {
		substring_t args[MAX_OPT_ARGS];
		char buf[32];
		int tok;
		u64 v;

		if (!*p)
			continue;

		switch (match_token(p, cost_ctrl_tokens, args)) {
		case COST_CTRL:
			match_strlcpy(buf, &args[0], sizeof(buf));
			if (!strcmp(buf, "auto"))
				user = false;
			else if (!strcmp(buf, "user"))
				user = true;
			else
				goto einval;
			continue;
		case COST_MODEL:
			match_strlcpy(buf, &args[0], sizeof(buf));
			if (strcmp(buf, "linear"))
				goto einval;
			continue;
		}

		tok = match_token(p, i_lcoef_tokens, args);
		if (tok == NR_I_LCOEFS)
			goto einval;
		if (match_u64(&args[0], &v))
			goto einval;
		u[tok] = v;
		user = true;
	}

	spin_lock_irq(&ioc->lock);
	if (user) {
		memcpy(ioc->params.i_lcoefs, u, sizeof(u));
		ioc->user_cost_model = true;
	} else {
		ioc->user_cost_model = false;
	}
	ioc_refresh_params(ioc, true);
	spin_unlock_irq(&ioc->lock);

	put_disk_and_module(disk);
	return nbytes;

einval:
	ret = -EINVAL;
err:
	put_disk_and_module(disk);
	return ret;
}

static struct cftype ioc_files[] = {
	{
		.name = "weight",
		.flags = CFTYPE_NOT_ON_ROOT,
		.seq_show = ioc_weight_show,
		.write = ioc_weight_write,
	},
	{
		.name = "cost.qos",
		.flags = CFTYPE_ONLY_ON_ROOT,
		.seq_show = ioc_qos_show,
		.write = ioc_qos_write,
	},
	{
		.name = "cost.model",
		.flags = CFTYPE_ONLY_ON_ROOT,
		.seq_show = ioc_cost_model_show,
		.write = ioc_cost_model_write,
	},
	{}
};

static struct blkcg_policy blkcg_policy_iocost = {
	.dfl_cftypes	= ioc_files,
	.cpd_alloc_fn	= ioc_cpd_alloc,
	.cpd_free_fn	= ioc_cpd_free,
	.pd_alloc_fn	= ioc_pd_alloc,
	.pd_init_fn	= ioc_pd_init,
	.pd_free_fn	= ioc_pd_free,
};

static int __init ioc_init(void)
{
	return blkcg_policy_register(&blkcg_policy_iocost);
}

static void __exit ioc_exit(void)
{
	return blkcg_policy_unregister(&blkcg_policy_iocost);
}

module_init(ioc_init);
module_exit(ioc_exit);