aboutsummaryrefslogtreecommitdiffstats
path: root/block/blk-mq.c
blob: d4d7c1caa439666f212c63df86a2a61a81a68ca9 (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
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
// SPDX-License-Identifier: GPL-2.0
/*
 * Block multiqueue core code
 *
 * Copyright (C) 2013-2014 Jens Axboe
 * Copyright (C) 2013-2014 Christoph Hellwig
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/backing-dev.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/kmemleak.h>
#include <linux/mm.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/smp.h>
#include <linux/llist.h>
#include <linux/list_sort.h>
#include <linux/cpu.h>
#include <linux/cache.h>
#include <linux/sched/sysctl.h>
#include <linux/sched/topology.h>
#include <linux/sched/signal.h>
#include <linux/delay.h>
#include <linux/crash_dump.h>
#include <linux/prefetch.h>
#include <linux/blk-crypto.h>

#include <trace/events/block.h>

#include <linux/blk-mq.h>
#include <linux/t10-pi.h>
#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-debugfs.h"
#include "blk-mq-tag.h"
#include "blk-pm.h"
#include "blk-stat.h"
#include "blk-mq-sched.h"
#include "blk-rq-qos.h"

static DEFINE_PER_CPU(struct llist_head, blk_cpu_done);

static void blk_mq_poll_stats_start(struct request_queue *q);
static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);

static int blk_mq_poll_stats_bkt(const struct request *rq)
{
	int ddir, sectors, bucket;

	ddir = rq_data_dir(rq);
	sectors = blk_rq_stats_sectors(rq);

	bucket = ddir + 2 * ilog2(sectors);

	if (bucket < 0)
		return -1;
	else if (bucket >= BLK_MQ_POLL_STATS_BKTS)
		return ddir + BLK_MQ_POLL_STATS_BKTS - 2;

	return bucket;
}

/*
 * Check if any of the ctx, dispatch list or elevator
 * have pending work in this hardware queue.
 */
static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
{
	return !list_empty_careful(&hctx->dispatch) ||
		sbitmap_any_bit_set(&hctx->ctx_map) ||
			blk_mq_sched_has_work(hctx);
}

/*
 * Mark this ctx as having pending work in this hardware queue
 */
static void blk_mq_hctx_mark_pending(struct blk_mq_hw_ctx *hctx,
				     struct blk_mq_ctx *ctx)
{
	const int bit = ctx->index_hw[hctx->type];

	if (!sbitmap_test_bit(&hctx->ctx_map, bit))
		sbitmap_set_bit(&hctx->ctx_map, bit);
}

static void blk_mq_hctx_clear_pending(struct blk_mq_hw_ctx *hctx,
				      struct blk_mq_ctx *ctx)
{
	const int bit = ctx->index_hw[hctx->type];

	sbitmap_clear_bit(&hctx->ctx_map, bit);
}

struct mq_inflight {
	struct block_device *part;
	unsigned int inflight[2];
};

static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
				  struct request *rq, void *priv,
				  bool reserved)
{
	struct mq_inflight *mi = priv;

	if ((!mi->part->bd_partno || rq->part == mi->part) &&
	    blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)
		mi->inflight[rq_data_dir(rq)]++;

	return true;
}

unsigned int blk_mq_in_flight(struct request_queue *q,
		struct block_device *part)
{
	struct mq_inflight mi = { .part = part };

	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);

	return mi.inflight[0] + mi.inflight[1];
}

void blk_mq_in_flight_rw(struct request_queue *q, struct block_device *part,
		unsigned int inflight[2])
{
	struct mq_inflight mi = { .part = part };

	blk_mq_queue_tag_busy_iter(q, blk_mq_check_inflight, &mi);
	inflight[0] = mi.inflight[0];
	inflight[1] = mi.inflight[1];
}

void blk_freeze_queue_start(struct request_queue *q)
{
	mutex_lock(&q->mq_freeze_lock);
	if (++q->mq_freeze_depth == 1) {
		percpu_ref_kill(&q->q_usage_counter);
		mutex_unlock(&q->mq_freeze_lock);
		if (queue_is_mq(q))
			blk_mq_run_hw_queues(q, false);
	} else {
		mutex_unlock(&q->mq_freeze_lock);
	}
}
EXPORT_SYMBOL_GPL(blk_freeze_queue_start);

void blk_mq_freeze_queue_wait(struct request_queue *q)
{
	wait_event(q->mq_freeze_wq, percpu_ref_is_zero(&q->q_usage_counter));
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait);

int blk_mq_freeze_queue_wait_timeout(struct request_queue *q,
				     unsigned long timeout)
{
	return wait_event_timeout(q->mq_freeze_wq,
					percpu_ref_is_zero(&q->q_usage_counter),
					timeout);
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue_wait_timeout);

/*
 * Guarantee no request is in use, so we can change any data structure of
 * the queue afterward.
 */
void blk_freeze_queue(struct request_queue *q)
{
	/*
	 * In the !blk_mq case we are only calling this to kill the
	 * q_usage_counter, otherwise this increases the freeze depth
	 * and waits for it to return to zero.  For this reason there is
	 * no blk_unfreeze_queue(), and blk_freeze_queue() is not
	 * exported to drivers as the only user for unfreeze is blk_mq.
	 */
	blk_freeze_queue_start(q);
	blk_mq_freeze_queue_wait(q);
}

void blk_mq_freeze_queue(struct request_queue *q)
{
	/*
	 * ...just an alias to keep freeze and unfreeze actions balanced
	 * in the blk_mq_* namespace
	 */
	blk_freeze_queue(q);
}
EXPORT_SYMBOL_GPL(blk_mq_freeze_queue);

void blk_mq_unfreeze_queue(struct request_queue *q)
{
	mutex_lock(&q->mq_freeze_lock);
	q->mq_freeze_depth--;
	WARN_ON_ONCE(q->mq_freeze_depth < 0);
	if (!q->mq_freeze_depth) {
		percpu_ref_resurrect(&q->q_usage_counter);
		wake_up_all(&q->mq_freeze_wq);
	}
	mutex_unlock(&q->mq_freeze_lock);
}
EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);

/*
 * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
 * mpt3sas driver such that this function can be removed.
 */
void blk_mq_quiesce_queue_nowait(struct request_queue *q)
{
	blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
}
EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);

/**
 * blk_mq_quiesce_queue() - wait until all ongoing dispatches have finished
 * @q: request queue.
 *
 * Note: this function does not prevent that the struct request end_io()
 * callback function is invoked. Once this function is returned, we make
 * sure no dispatch can happen until the queue is unquiesced via
 * blk_mq_unquiesce_queue().
 */
void blk_mq_quiesce_queue(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx;
	unsigned int i;
	bool rcu = false;

	blk_mq_quiesce_queue_nowait(q);

	queue_for_each_hw_ctx(q, hctx, i) {
		if (hctx->flags & BLK_MQ_F_BLOCKING)
			synchronize_srcu(hctx->srcu);
		else
			rcu = true;
	}
	if (rcu)
		synchronize_rcu();
}
EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);

/*
 * blk_mq_unquiesce_queue() - counterpart of blk_mq_quiesce_queue()
 * @q: request queue.
 *
 * This function recovers queue into the state before quiescing
 * which is done by blk_mq_quiesce_queue.
 */
void blk_mq_unquiesce_queue(struct request_queue *q)
{
	blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);

	/* dispatch requests which are inserted during quiescing */
	blk_mq_run_hw_queues(q, true);
}
EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);

void blk_mq_wake_waiters(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx;
	unsigned int i;

	queue_for_each_hw_ctx(q, hctx, i)
		if (blk_mq_hw_queue_mapped(hctx))
			blk_mq_tag_wakeup_all(hctx->tags, true);
}

/*
 * Only need start/end time stamping if we have iostat or
 * blk stats enabled, or using an IO scheduler.
 */
static inline bool blk_mq_need_time_stamp(struct request *rq)
{
	return (rq->rq_flags & (RQF_IO_STAT | RQF_STATS)) || rq->q->elevator;
}

static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
		unsigned int tag, u64 alloc_time_ns)
{
	struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
	struct request *rq = tags->static_rqs[tag];

	if (data->q->elevator) {
		rq->tag = BLK_MQ_NO_TAG;
		rq->internal_tag = tag;
	} else {
		rq->tag = tag;
		rq->internal_tag = BLK_MQ_NO_TAG;
	}

	/* csd/requeue_work/fifo_time is initialized before use */
	rq->q = data->q;
	rq->mq_ctx = data->ctx;
	rq->mq_hctx = data->hctx;
	rq->rq_flags = 0;
	rq->cmd_flags = data->cmd_flags;
	if (data->flags & BLK_MQ_REQ_PM)
		rq->rq_flags |= RQF_PM;
	if (blk_queue_io_stat(data->q))
		rq->rq_flags |= RQF_IO_STAT;
	INIT_LIST_HEAD(&rq->queuelist);
	INIT_HLIST_NODE(&rq->hash);
	RB_CLEAR_NODE(&rq->rb_node);
	rq->rq_disk = NULL;
	rq->part = NULL;
#ifdef CONFIG_BLK_RQ_ALLOC_TIME
	rq->alloc_time_ns = alloc_time_ns;
#endif
	if (blk_mq_need_time_stamp(rq))
		rq->start_time_ns = ktime_get_ns();
	else
		rq->start_time_ns = 0;
	rq->io_start_time_ns = 0;
	rq->stats_sectors = 0;
	rq->nr_phys_segments = 0;
#if defined(CONFIG_BLK_DEV_INTEGRITY)
	rq->nr_integrity_segments = 0;
#endif
	blk_crypto_rq_set_defaults(rq);
	/* tag was already set */
	WRITE_ONCE(rq->deadline, 0);

	rq->timeout = 0;

	rq->end_io = NULL;
	rq->end_io_data = NULL;

	data->ctx->rq_dispatched[op_is_sync(data->cmd_flags)]++;
	refcount_set(&rq->ref, 1);

	if (!op_is_flush(data->cmd_flags)) {
		struct elevator_queue *e = data->q->elevator;

		rq->elv.icq = NULL;
		if (e && e->type->ops.prepare_request) {
			if (e->type->icq_cache)
				blk_mq_sched_assign_ioc(rq);

			e->type->ops.prepare_request(rq);
			rq->rq_flags |= RQF_ELVPRIV;
		}
	}

	data->hctx->queued++;
	return rq;
}

static struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data)
{
	struct request_queue *q = data->q;
	struct elevator_queue *e = q->elevator;
	u64 alloc_time_ns = 0;
	unsigned int tag;

	/* alloc_time includes depth and tag waits */
	if (blk_queue_rq_alloc_time(q))
		alloc_time_ns = ktime_get_ns();

	if (data->cmd_flags & REQ_NOWAIT)
		data->flags |= BLK_MQ_REQ_NOWAIT;

	if (e) {
		/*
		 * Flush requests are special and go directly to the
		 * dispatch list. Don't include reserved tags in the
		 * limiting, as it isn't useful.
		 */
		if (!op_is_flush(data->cmd_flags) &&
		    e->type->ops.limit_depth &&
		    !(data->flags & BLK_MQ_REQ_RESERVED))
			e->type->ops.limit_depth(data->cmd_flags, data);
	}

retry:
	data->ctx = blk_mq_get_ctx(q);
	data->hctx = blk_mq_map_queue(q, data->cmd_flags, data->ctx);
	if (!e)
		blk_mq_tag_busy(data->hctx);

	/*
	 * Waiting allocations only fail because of an inactive hctx.  In that
	 * case just retry the hctx assignment and tag allocation as CPU hotplug
	 * should have migrated us to an online CPU by now.
	 */
	tag = blk_mq_get_tag(data);
	if (tag == BLK_MQ_NO_TAG) {
		if (data->flags & BLK_MQ_REQ_NOWAIT)
			return NULL;

		/*
		 * Give up the CPU and sleep for a random short time to ensure
		 * that thread using a realtime scheduling class are migrated
		 * off the CPU, and thus off the hctx that is going away.
		 */
		msleep(3);
		goto retry;
	}
	return blk_mq_rq_ctx_init(data, tag, alloc_time_ns);
}

struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op,
		blk_mq_req_flags_t flags)
{
	struct blk_mq_alloc_data data = {
		.q		= q,
		.flags		= flags,
		.cmd_flags	= op,
	};
	struct request *rq;
	int ret;

	ret = blk_queue_enter(q, flags);
	if (ret)
		return ERR_PTR(ret);

	rq = __blk_mq_alloc_request(&data);
	if (!rq)
		goto out_queue_exit;
	rq->__data_len = 0;
	rq->__sector = (sector_t) -1;
	rq->bio = rq->biotail = NULL;
	return rq;
out_queue_exit:
	blk_queue_exit(q);
	return ERR_PTR(-EWOULDBLOCK);
}
EXPORT_SYMBOL(blk_mq_alloc_request);

struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
	unsigned int op, blk_mq_req_flags_t flags, unsigned int hctx_idx)
{
	struct blk_mq_alloc_data data = {
		.q		= q,
		.flags		= flags,
		.cmd_flags	= op,
	};
	u64 alloc_time_ns = 0;
	unsigned int cpu;
	unsigned int tag;
	int ret;

	/* alloc_time includes depth and tag waits */
	if (blk_queue_rq_alloc_time(q))
		alloc_time_ns = ktime_get_ns();

	/*
	 * If the tag allocator sleeps we could get an allocation for a
	 * different hardware context.  No need to complicate the low level
	 * allocator for this for the rare use case of a command tied to
	 * a specific queue.
	 */
	if (WARN_ON_ONCE(!(flags & (BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_RESERVED))))
		return ERR_PTR(-EINVAL);

	if (hctx_idx >= q->nr_hw_queues)
		return ERR_PTR(-EIO);

	ret = blk_queue_enter(q, flags);
	if (ret)
		return ERR_PTR(ret);

	/*
	 * Check if the hardware context is actually mapped to anything.
	 * If not tell the caller that it should skip this queue.
	 */
	ret = -EXDEV;
	data.hctx = q->queue_hw_ctx[hctx_idx];
	if (!blk_mq_hw_queue_mapped(data.hctx))
		goto out_queue_exit;
	cpu = cpumask_first_and(data.hctx->cpumask, cpu_online_mask);
	data.ctx = __blk_mq_get_ctx(q, cpu);

	if (!q->elevator)
		blk_mq_tag_busy(data.hctx);

	ret = -EWOULDBLOCK;
	tag = blk_mq_get_tag(&data);
	if (tag == BLK_MQ_NO_TAG)
		goto out_queue_exit;
	return blk_mq_rq_ctx_init(&data, tag, alloc_time_ns);

out_queue_exit:
	blk_queue_exit(q);
	return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);

static void __blk_mq_free_request(struct request *rq)
{
	struct request_queue *q = rq->q;
	struct blk_mq_ctx *ctx = rq->mq_ctx;
	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
	const int sched_tag = rq->internal_tag;

	blk_crypto_free_request(rq);
	blk_pm_mark_last_busy(rq);
	rq->mq_hctx = NULL;
	if (rq->tag != BLK_MQ_NO_TAG)
		blk_mq_put_tag(hctx->tags, ctx, rq->tag);
	if (sched_tag != BLK_MQ_NO_TAG)
		blk_mq_put_tag(hctx->sched_tags, ctx, sched_tag);
	blk_mq_sched_restart(hctx);
	blk_queue_exit(q);
}

void blk_mq_free_request(struct request *rq)
{
	struct request_queue *q = rq->q;
	struct elevator_queue *e = q->elevator;
	struct blk_mq_ctx *ctx = rq->mq_ctx;
	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

	if (rq->rq_flags & RQF_ELVPRIV) {
		if (e && e->type->ops.finish_request)
			e->type->ops.finish_request(rq);
		if (rq->elv.icq) {
			put_io_context(rq->elv.icq->ioc);
			rq->elv.icq = NULL;
		}
	}

	ctx->rq_completed[rq_is_sync(rq)]++;
	if (rq->rq_flags & RQF_MQ_INFLIGHT)
		__blk_mq_dec_active_requests(hctx);

	if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
		laptop_io_completion(q->backing_dev_info);

	rq_qos_done(q, rq);

	WRITE_ONCE(rq->state, MQ_RQ_IDLE);
	if (refcount_dec_and_test(&rq->ref))
		__blk_mq_free_request(rq);
}
EXPORT_SYMBOL_GPL(blk_mq_free_request);

inline void __blk_mq_end_request(struct request *rq, blk_status_t error)
{
	u64 now = 0;

	if (blk_mq_need_time_stamp(rq))
		now = ktime_get_ns();

	if (rq->rq_flags & RQF_STATS) {
		blk_mq_poll_stats_start(rq->q);
		blk_stat_add(rq, now);
	}

	blk_mq_sched_completed_request(rq, now);

	blk_account_io_done(rq, now);

	if (rq->end_io) {
		rq_qos_done(rq->q, rq);
		rq->end_io(rq, error);
	} else {
		blk_mq_free_request(rq);
	}
}
EXPORT_SYMBOL(__blk_mq_end_request);

void blk_mq_end_request(struct request *rq, blk_status_t error)
{
	if (blk_update_request(rq, error, blk_rq_bytes(rq)))
		BUG();
	__blk_mq_end_request(rq, error);
}
EXPORT_SYMBOL(blk_mq_end_request);

static void blk_complete_reqs(struct llist_head *list)
{
	struct llist_node *entry = llist_reverse_order(llist_del_all(list));
	struct request *rq, *next;

	llist_for_each_entry_safe(rq, next, entry, ipi_list)
		rq->q->mq_ops->complete(rq);
}

static __latent_entropy void blk_done_softirq(struct softirq_action *h)
{
	blk_complete_reqs(this_cpu_ptr(&blk_cpu_done));
}

static int blk_softirq_cpu_dead(unsigned int cpu)
{
	blk_complete_reqs(&per_cpu(blk_cpu_done, cpu));
	return 0;
}

static void __blk_mq_complete_request_remote(void *data)
{
	__raise_softirq_irqoff(BLOCK_SOFTIRQ);
}

static inline bool blk_mq_complete_need_ipi(struct request *rq)
{
	int cpu = raw_smp_processor_id();

	if (!IS_ENABLED(CONFIG_SMP) ||
	    !test_bit(QUEUE_FLAG_SAME_COMP, &rq->q->queue_flags))
		return false;
	/*
	 * With force threaded interrupts enabled, raising softirq from an SMP
	 * function call will always result in waking the ksoftirqd thread.
	 * This is probably worse than completing the request on a different
	 * cache domain.
	 */
	if (force_irqthreads)
		return false;

	/* same CPU or cache domain?  Complete locally */
	if (cpu == rq->mq_ctx->cpu ||
	    (!test_bit(QUEUE_FLAG_SAME_FORCE, &rq->q->queue_flags) &&
	     cpus_share_cache(cpu, rq->mq_ctx->cpu)))
		return false;

	/* don't try to IPI to an offline CPU */
	return cpu_online(rq->mq_ctx->cpu);
}

static void blk_mq_complete_send_ipi(struct request *rq)
{
	struct llist_head *list;
	unsigned int cpu;

	cpu = rq->mq_ctx->cpu;
	list = &per_cpu(blk_cpu_done, cpu);
	if (llist_add(&rq->ipi_list, list)) {
		INIT_CSD(&rq->csd, __blk_mq_complete_request_remote, rq);
		smp_call_function_single_async(cpu, &rq->csd);
	}
}

static void blk_mq_raise_softirq(struct request *rq)
{
	struct llist_head *list;

	preempt_disable();
	list = this_cpu_ptr(&blk_cpu_done);
	if (llist_add(&rq->ipi_list, list))
		raise_softirq(BLOCK_SOFTIRQ);
	preempt_enable();
}

bool blk_mq_complete_request_remote(struct request *rq)
{
	WRITE_ONCE(rq->state, MQ_RQ_COMPLETE);

	/*
	 * For a polled request, always complete locallly, it's pointless
	 * to redirect the completion.
	 */
	if (rq->cmd_flags & REQ_HIPRI)
		return false;

	if (blk_mq_complete_need_ipi(rq)) {
		blk_mq_complete_send_ipi(rq);
		return true;
	}

	if (rq->q->nr_hw_queues == 1) {
		blk_mq_raise_softirq(rq);
		return true;
	}
	return false;
}
EXPORT_SYMBOL_GPL(blk_mq_complete_request_remote);

/**
 * blk_mq_complete_request - end I/O on a request
 * @rq:		the request being processed
 *
 * Description:
 *	Complete a request by scheduling the ->complete_rq operation.
 **/
void blk_mq_complete_request(struct request *rq)
{
	if (!blk_mq_complete_request_remote(rq))
		rq->q->mq_ops->complete(rq);
}
EXPORT_SYMBOL(blk_mq_complete_request);

static void hctx_unlock(struct blk_mq_hw_ctx *hctx, int srcu_idx)
	__releases(hctx->srcu)
{
	if (!(hctx->flags & BLK_MQ_F_BLOCKING))
		rcu_read_unlock();
	else
		srcu_read_unlock(hctx->srcu, srcu_idx);
}

static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
	__acquires(hctx->srcu)
{
	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
		/* shut up gcc false positive */
		*srcu_idx = 0;
		rcu_read_lock();
	} else
		*srcu_idx = srcu_read_lock(hctx->srcu);
}

/**
 * blk_mq_start_request - Start processing a request
 * @rq: Pointer to request to be started
 *
 * Function used by device drivers to notify the block layer that a request
 * is going to be processed now, so blk layer can do proper initializations
 * such as starting the timeout timer.
 */
void blk_mq_start_request(struct request *rq)
{
	struct request_queue *q = rq->q;

	trace_block_rq_issue(rq);

	if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
		rq->io_start_time_ns = ktime_get_ns();
		rq->stats_sectors = blk_rq_sectors(rq);
		rq->rq_flags |= RQF_STATS;
		rq_qos_issue(q, rq);
	}

	WARN_ON_ONCE(blk_mq_rq_state(rq) != MQ_RQ_IDLE);

	blk_add_timer(rq);
	WRITE_ONCE(rq->state, MQ_RQ_IN_FLIGHT);

#ifdef CONFIG_BLK_DEV_INTEGRITY
	if (blk_integrity_rq(rq) && req_op(rq) == REQ_OP_WRITE)
		q->integrity.profile->prepare_fn(rq);
#endif
}
EXPORT_SYMBOL(blk_mq_start_request);

static void __blk_mq_requeue_request(struct request *rq)
{
	struct request_queue *q = rq->q;

	blk_mq_put_driver_tag(rq);

	trace_block_rq_requeue(rq);
	rq_qos_requeue(q, rq);

	if (blk_mq_request_started(rq)) {
		WRITE_ONCE(rq->state, MQ_RQ_IDLE);
		rq->rq_flags &= ~RQF_TIMED_OUT;
	}
}

void blk_mq_requeue_request(struct request *rq, bool kick_requeue_list)
{
	__blk_mq_requeue_request(rq);

	/* this request will be re-inserted to io scheduler queue */
	blk_mq_sched_requeue_request(rq);

	BUG_ON(!list_empty(&rq->queuelist));
	blk_mq_add_to_requeue_list(rq, true, kick_requeue_list);
}
EXPORT_SYMBOL(blk_mq_requeue_request);

static void blk_mq_requeue_work(struct work_struct *work)
{
	struct request_queue *q =
		container_of(work, struct request_queue, requeue_work.work);
	LIST_HEAD(rq_list);
	struct request *rq, *next;

	spin_lock_irq(&q->requeue_lock);
	list_splice_init(&q->requeue_list, &rq_list);
	spin_unlock_irq(&q->requeue_lock);

	list_for_each_entry_safe(rq, next, &rq_list, queuelist) {
		if (!(rq->rq_flags & (RQF_SOFTBARRIER | RQF_DONTPREP)))
			continue;

		rq->rq_flags &= ~RQF_SOFTBARRIER;
		list_del_init(&rq->queuelist);
		/*
		 * If RQF_DONTPREP, rq has contained some driver specific
		 * data, so insert it to hctx dispatch list to avoid any
		 * merge.
		 */
		if (rq->rq_flags & RQF_DONTPREP)
			blk_mq_request_bypass_insert(rq, false, false);
		else
			blk_mq_sched_insert_request(rq, true, false, false);
	}

	while (!list_empty(&rq_list)) {
		rq = list_entry(rq_list.next, struct request, queuelist);
		list_del_init(&rq->queuelist);
		blk_mq_sched_insert_request(rq, false, false, false);
	}

	blk_mq_run_hw_queues(q, false);
}

void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
				bool kick_requeue_list)
{
	struct request_queue *q = rq->q;
	unsigned long flags;

	/*
	 * We abuse this flag that is otherwise used by the I/O scheduler to
	 * request head insertion from the workqueue.
	 */
	BUG_ON(rq->rq_flags & RQF_SOFTBARRIER);

	spin_lock_irqsave(&q->requeue_lock, flags);
	if (at_head) {
		rq->rq_flags |= RQF_SOFTBARRIER;
		list_add(&rq->queuelist, &q->requeue_list);
	} else {
		list_add_tail(&rq->queuelist, &q->requeue_list);
	}
	spin_unlock_irqrestore(&q->requeue_lock, flags);

	if (kick_requeue_list)
		blk_mq_kick_requeue_list(q);
}

void blk_mq_kick_requeue_list(struct request_queue *q)
{
	kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work, 0);
}
EXPORT_SYMBOL(blk_mq_kick_requeue_list);

void blk_mq_delay_kick_requeue_list(struct request_queue *q,
				    unsigned long msecs)
{
	kblockd_mod_delayed_work_on(WORK_CPU_UNBOUND, &q->requeue_work,
				    msecs_to_jiffies(msecs));
}
EXPORT_SYMBOL(blk_mq_delay_kick_requeue_list);

struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
{
	if (tag < tags->nr_tags) {
		prefetch(tags->rqs[tag]);
		return tags->rqs[tag];
	}

	return NULL;
}
EXPORT_SYMBOL(blk_mq_tag_to_rq);

static bool blk_mq_rq_inflight(struct blk_mq_hw_ctx *hctx, struct request *rq,
			       void *priv, bool reserved)
{
	/*
	 * If we find a request that isn't idle and the queue matches,
	 * we know the queue is busy. Return false to stop the iteration.
	 */
	if (blk_mq_request_started(rq) && rq->q == hctx->queue) {
		bool *busy = priv;

		*busy = true;
		return false;
	}

	return true;
}

bool blk_mq_queue_inflight(struct request_queue *q)
{
	bool busy = false;

	blk_mq_queue_tag_busy_iter(q, blk_mq_rq_inflight, &busy);
	return busy;
}
EXPORT_SYMBOL_GPL(blk_mq_queue_inflight);

static void blk_mq_rq_timed_out(struct request *req, bool reserved)
{
	req->rq_flags |= RQF_TIMED_OUT;
	if (req->q->mq_ops->timeout) {
		enum blk_eh_timer_return ret;

		ret = req->q->mq_ops->timeout(req, reserved);
		if (ret == BLK_EH_DONE)
			return;
		WARN_ON_ONCE(ret != BLK_EH_RESET_TIMER);
	}

	blk_add_timer(req);
}

static bool blk_mq_req_expired(struct request *rq, unsigned long *next)
{
	unsigned long deadline;

	if (blk_mq_rq_state(rq) != MQ_RQ_IN_FLIGHT)
		return false;
	if (rq->rq_flags & RQF_TIMED_OUT)
		return false;

	deadline = READ_ONCE(rq->deadline);
	if (time_after_eq(jiffies, deadline))
		return true;

	if (*next == 0)
		*next = deadline;
	else if (time_after(*next, deadline))
		*next = deadline;
	return false;
}

static bool blk_mq_check_expired(struct blk_mq_hw_ctx *hctx,
		struct request *rq, void *priv, bool reserved)
{
	unsigned long *next = priv;

	/*
	 * Just do a quick check if it is expired before locking the request in
	 * so we're not unnecessarilly synchronizing across CPUs.
	 */
	if (!blk_mq_req_expired(rq, next))
		return true;

	/*
	 * We have reason to believe the request may be expired. Take a
	 * reference on the request to lock this request lifetime into its
	 * currently allocated context to prevent it from being reallocated in
	 * the event the completion by-passes this timeout handler.
	 *
	 * If the reference was already released, then the driver beat the
	 * timeout handler to posting a natural completion.
	 */
	if (!refcount_inc_not_zero(&rq->ref))
		return true;

	/*
	 * The request is now locked and cannot be reallocated underneath the
	 * timeout handler's processing. Re-verify this exact request is truly
	 * expired; if it is not expired, then the request was completed and
	 * reallocated as a new request.
	 */
	if (blk_mq_req_expired(rq, next))
		blk_mq_rq_timed_out(rq, reserved);

	if (is_flush_rq(rq, hctx))
		rq->end_io(rq, 0);
	else if (refcount_dec_and_test(&rq->ref))
		__blk_mq_free_request(rq);

	return true;
}

static void blk_mq_timeout_work(struct work_struct *work)
{
	struct request_queue *q =
		container_of(work, struct request_queue, timeout_work);
	unsigned long next = 0;
	struct blk_mq_hw_ctx *hctx;
	int i;

	/* A deadlock might occur if a request is stuck requiring a
	 * timeout at the same time a queue freeze is waiting
	 * completion, since the timeout code would not be able to
	 * acquire the queue reference here.
	 *
	 * That's why we don't use blk_queue_enter here; instead, we use
	 * percpu_ref_tryget directly, because we need to be able to
	 * obtain a reference even in the short window between the queue
	 * starting to freeze, by dropping the first reference in
	 * blk_freeze_queue_start, and the moment the last request is
	 * consumed, marked by the instant q_usage_counter reaches
	 * zero.
	 */
	if (!percpu_ref_tryget(&q->q_usage_counter))
		return;

	blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next);

	if (next != 0) {
		mod_timer(&q->timeout, next);
	} else {
		/*
		 * Request timeouts are handled as a forward rolling timer. If
		 * we end up here it means that no requests are pending and
		 * also that no request has been pending for a while. Mark
		 * each hctx as idle.
		 */
		queue_for_each_hw_ctx(q, hctx, i) {
			/* the hctx may be unmapped, so check it here */
			if (blk_mq_hw_queue_mapped(hctx))
				blk_mq_tag_idle(hctx);
		}
	}
	blk_queue_exit(q);
}

struct flush_busy_ctx_data {
	struct blk_mq_hw_ctx *hctx;
	struct list_head *list;
};

static bool flush_busy_ctx(struct sbitmap *sb, unsigned int bitnr, void *data)
{
	struct flush_busy_ctx_data *flush_data = data;
	struct blk_mq_hw_ctx *hctx = flush_data->hctx;
	struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
	enum hctx_type type = hctx->type;

	spin_lock(&ctx->lock);
	list_splice_tail_init(&ctx->rq_lists[type], flush_data->list);
	sbitmap_clear_bit(sb, bitnr);
	spin_unlock(&ctx->lock);
	return true;
}

/*
 * Process software queues that have been marked busy, splicing them
 * to the for-dispatch
 */
void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
{
	struct flush_busy_ctx_data data = {
		.hctx = hctx,
		.list = list,
	};

	sbitmap_for_each_set(&hctx->ctx_map, flush_busy_ctx, &data);
}
EXPORT_SYMBOL_GPL(blk_mq_flush_busy_ctxs);

struct dispatch_rq_data {
	struct blk_mq_hw_ctx *hctx;
	struct request *rq;
};

static bool dispatch_rq_from_ctx(struct sbitmap *sb, unsigned int bitnr,
		void *data)
{
	struct dispatch_rq_data *dispatch_data = data;
	struct blk_mq_hw_ctx *hctx = dispatch_data->hctx;
	struct blk_mq_ctx *ctx = hctx->ctxs[bitnr];
	enum hctx_type type = hctx->type;

	spin_lock(&ctx->lock);
	if (!list_empty(&ctx->rq_lists[type])) {
		dispatch_data->rq = list_entry_rq(ctx->rq_lists[type].next);
		list_del_init(&dispatch_data->rq->queuelist);
		if (list_empty(&ctx->rq_lists[type]))
			sbitmap_clear_bit(sb, bitnr);
	}
	spin_unlock(&ctx->lock);

	return !dispatch_data->rq;
}

struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
					struct blk_mq_ctx *start)
{
	unsigned off = start ? start->index_hw[hctx->type] : 0;
	struct dispatch_rq_data data = {
		.hctx = hctx,
		.rq   = NULL,
	};

	__sbitmap_for_each_set(&hctx->ctx_map, off,
			       dispatch_rq_from_ctx, &data);

	return data.rq;
}

static inline unsigned int queued_to_index(unsigned int queued)
{
	if (!queued)
		return 0;

	return min(BLK_MQ_MAX_DISPATCH_ORDER - 1, ilog2(queued) + 1);
}

static bool __blk_mq_get_driver_tag(struct request *rq)
{
	struct sbitmap_queue *bt = rq->mq_hctx->tags->bitmap_tags;
	unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
	int tag;

	blk_mq_tag_busy(rq->mq_hctx);

	if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) {
		bt = rq->mq_hctx->tags->breserved_tags;
		tag_offset = 0;
	} else {
		if (!hctx_may_queue(rq->mq_hctx, bt))
			return false;
	}

	tag = __sbitmap_queue_get(bt);
	if (tag == BLK_MQ_NO_TAG)
		return false;

	rq->tag = tag + tag_offset;
	return true;
}

static bool blk_mq_get_driver_tag(struct request *rq)
{
	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

	if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_get_driver_tag(rq))
		return false;

	if ((hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) &&
			!(rq->rq_flags & RQF_MQ_INFLIGHT)) {
		rq->rq_flags |= RQF_MQ_INFLIGHT;
		__blk_mq_inc_active_requests(hctx);
	}
	hctx->tags->rqs[rq->tag] = rq;
	return true;
}

static int blk_mq_dispatch_wake(wait_queue_entry_t *wait, unsigned mode,
				int flags, void *key)
{
	struct blk_mq_hw_ctx *hctx;

	hctx = container_of(wait, struct blk_mq_hw_ctx, dispatch_wait);

	spin_lock(&hctx->dispatch_wait_lock);
	if (!list_empty(&wait->entry)) {
		struct sbitmap_queue *sbq;

		list_del_init(&wait->entry);
		sbq = hctx->tags->bitmap_tags;
		atomic_dec(&sbq->ws_active);
	}
	spin_unlock(&hctx->dispatch_wait_lock);

	blk_mq_run_hw_queue(hctx, true);
	return 1;
}

/*
 * Mark us waiting for a tag. For shared tags, this involves hooking us into
 * the tag wakeups. For non-shared tags, we can simply mark us needing a
 * restart. For both cases, take care to check the condition again after
 * marking us as waiting.
 */
static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx,
				 struct request *rq)
{
	struct sbitmap_queue *sbq = hctx->tags->bitmap_tags;
	struct wait_queue_head *wq;
	wait_queue_entry_t *wait;
	bool ret;

	if (!(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
		blk_mq_sched_mark_restart_hctx(hctx);

		/*
		 * It's possible that a tag was freed in the window between the
		 * allocation failure and adding the hardware queue to the wait
		 * queue.
		 *
		 * Don't clear RESTART here, someone else could have set it.
		 * At most this will cost an extra queue run.
		 */
		return blk_mq_get_driver_tag(rq);
	}

	wait = &hctx->dispatch_wait;
	if (!list_empty_careful(&wait->entry))
		return false;

	wq = &bt_wait_ptr(sbq, hctx)->wait;

	spin_lock_irq(&wq->lock);
	spin_lock(&hctx->dispatch_wait_lock);
	if (!list_empty(&wait->entry)) {
		spin_unlock(&hctx->dispatch_wait_lock);
		spin_unlock_irq(&wq->lock);
		return false;
	}

	atomic_inc(&sbq->ws_active);
	wait->flags &= ~WQ_FLAG_EXCLUSIVE;
	__add_wait_queue(wq, wait);

	/*
	 * It's possible that a tag was freed in the window between the
	 * allocation failure and adding the hardware queue to the wait
	 * queue.
	 */
	ret = blk_mq_get_driver_tag(rq);
	if (!ret) {
		spin_unlock(&hctx->dispatch_wait_lock);
		spin_unlock_irq(&wq->lock);
		return false;
	}

	/*
	 * We got a tag, remove ourselves from the wait queue to ensure
	 * someone else gets the wakeup.
	 */
	list_del_init(&wait->entry);
	atomic_dec(&sbq->ws_active);
	spin_unlock(&hctx->dispatch_wait_lock);
	spin_unlock_irq(&wq->lock);

	return true;
}

#define BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT  8
#define BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR  4
/*
 * Update dispatch busy with the Exponential Weighted Moving Average(EWMA):
 * - EWMA is one simple way to compute running average value
 * - weight(7/8 and 1/8) is applied so that it can decrease exponentially
 * - take 4 as factor for avoiding to get too small(0) result, and this
 *   factor doesn't matter because EWMA decreases exponentially
 */
static void blk_mq_update_dispatch_busy(struct blk_mq_hw_ctx *hctx, bool busy)
{
	unsigned int ewma;

	if (hctx->queue->elevator)
		return;

	ewma = hctx->dispatch_busy;

	if (!ewma && !busy)
		return;

	ewma *= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT - 1;
	if (busy)
		ewma += 1 << BLK_MQ_DISPATCH_BUSY_EWMA_FACTOR;
	ewma /= BLK_MQ_DISPATCH_BUSY_EWMA_WEIGHT;

	hctx->dispatch_busy = ewma;
}

#define BLK_MQ_RESOURCE_DELAY	3		/* ms units */

static void blk_mq_handle_dev_resource(struct request *rq,
				       struct list_head *list)
{
	struct request *next =
		list_first_entry_or_null(list, struct request, queuelist);

	/*
	 * If an I/O scheduler has been configured and we got a driver tag for
	 * the next request already, free it.
	 */
	if (next)
		blk_mq_put_driver_tag(next);

	list_add(&rq->queuelist, list);
	__blk_mq_requeue_request(rq);
}

static void blk_mq_handle_zone_resource(struct request *rq,
					struct list_head *zone_list)
{
	/*
	 * If we end up here it is because we cannot dispatch a request to a
	 * specific zone due to LLD level zone-write locking or other zone
	 * related resource not being available. In this case, set the request
	 * aside in zone_list for retrying it later.
	 */
	list_add(&rq->queuelist, zone_list);
	__blk_mq_requeue_request(rq);
}

enum prep_dispatch {
	PREP_DISPATCH_OK,
	PREP_DISPATCH_NO_TAG,
	PREP_DISPATCH_NO_BUDGET,
};

static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
						  bool need_budget)
{
	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

	if (need_budget && !blk_mq_get_dispatch_budget(rq->q)) {
		blk_mq_put_driver_tag(rq);
		return PREP_DISPATCH_NO_BUDGET;
	}

	if (!blk_mq_get_driver_tag(rq)) {
		/*
		 * The initial allocation attempt failed, so we need to
		 * rerun the hardware queue when a tag is freed. The
		 * waitqueue takes care of that. If the queue is run
		 * before we add this entry back on the dispatch list,
		 * we'll re-run it below.
		 */
		if (!blk_mq_mark_tag_wait(hctx, rq)) {
			/*
			 * All budgets not got from this function will be put
			 * together during handling partial dispatch
			 */
			if (need_budget)
				blk_mq_put_dispatch_budget(rq->q);
			return PREP_DISPATCH_NO_TAG;
		}
	}

	return PREP_DISPATCH_OK;
}

/* release all allocated budgets before calling to blk_mq_dispatch_rq_list */
static void blk_mq_release_budgets(struct request_queue *q,
		unsigned int nr_budgets)
{
	int i;

	for (i = 0; i < nr_budgets; i++)
		blk_mq_put_dispatch_budget(q);
}

/*
 * Returns true if we did some work AND can potentially do more.
 */
bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
			     unsigned int nr_budgets)
{
	enum prep_dispatch prep;
	struct request_queue *q = hctx->queue;
	struct request *rq, *nxt;
	int errors, queued;
	blk_status_t ret = BLK_STS_OK;
	LIST_HEAD(zone_list);

	if (list_empty(list))
		return false;

	/*
	 * Now process all the entries, sending them to the driver.
	 */
	errors = queued = 0;
	do {
		struct blk_mq_queue_data bd;

		rq = list_first_entry(list, struct request, queuelist);

		WARN_ON_ONCE(hctx != rq->mq_hctx);
		prep = blk_mq_prep_dispatch_rq(rq, !nr_budgets);
		if (prep != PREP_DISPATCH_OK)
			break;

		list_del_init(&rq->queuelist);

		bd.rq = rq;

		/*
		 * Flag last if we have no more requests, or if we have more
		 * but can't assign a driver tag to it.
		 */
		if (list_empty(list))
			bd.last = true;
		else {
			nxt = list_first_entry(list, struct request, queuelist);
			bd.last = !blk_mq_get_driver_tag(nxt);
		}

		/*
		 * once the request is queued to lld, no need to cover the
		 * budget any more
		 */
		if (nr_budgets)
			nr_budgets--;
		ret = q->mq_ops->queue_rq(hctx, &bd);
		switch (ret) {
		case BLK_STS_OK:
			queued++;
			break;
		case BLK_STS_RESOURCE:
		case BLK_STS_DEV_RESOURCE:
			blk_mq_handle_dev_resource(rq, list);
			goto out;
		case BLK_STS_ZONE_RESOURCE:
			/*
			 * Move the request to zone_list and keep going through
			 * the dispatch list to find more requests the drive can
			 * accept.
			 */
			blk_mq_handle_zone_resource(rq, &zone_list);
			break;
		default:
			errors++;
			blk_mq_end_request(rq, ret);
		}
	} while (!list_empty(list));
out:
	if (!list_empty(&zone_list))
		list_splice_tail_init(&zone_list, list);

	hctx->dispatched[queued_to_index(queued)]++;

	/* If we didn't flush the entire list, we could have told the driver
	 * there was more coming, but that turned out to be a lie.
	 */
	if ((!list_empty(list) || errors) && q->mq_ops->commit_rqs && queued)
		q->mq_ops->commit_rqs(hctx);
	/*
	 * Any items that need requeuing? Stuff them into hctx->dispatch,
	 * that is where we will continue on next queue run.
	 */
	if (!list_empty(list)) {
		bool needs_restart;
		/* For non-shared tags, the RESTART check will suffice */
		bool no_tag = prep == PREP_DISPATCH_NO_TAG &&
			(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED);
		bool no_budget_avail = prep == PREP_DISPATCH_NO_BUDGET;

		blk_mq_release_budgets(q, nr_budgets);

		spin_lock(&hctx->lock);
		list_splice_tail_init(list, &hctx->dispatch);
		spin_unlock(&hctx->lock);

		/*
		 * Order adding requests to hctx->dispatch and checking
		 * SCHED_RESTART flag. The pair of this smp_mb() is the one
		 * in blk_mq_sched_restart(). Avoid restart code path to
		 * miss the new added requests to hctx->dispatch, meantime
		 * SCHED_RESTART is observed here.
		 */
		smp_mb();

		/*
		 * If SCHED_RESTART was set by the caller of this function and
		 * it is no longer set that means that it was cleared by another
		 * thread and hence that a queue rerun is needed.
		 *
		 * If 'no_tag' is set, that means that we failed getting
		 * a driver tag with an I/O scheduler attached. If our dispatch
		 * waitqueue is no longer active, ensure that we run the queue
		 * AFTER adding our entries back to the list.
		 *
		 * If no I/O scheduler has been configured it is possible that
		 * the hardware queue got stopped and restarted before requests
		 * were pushed back onto the dispatch list. Rerun the queue to
		 * avoid starvation. Notes:
		 * - blk_mq_run_hw_queue() checks whether or not a queue has
		 *   been stopped before rerunning a queue.
		 * - Some but not all block drivers stop a queue before
		 *   returning BLK_STS_RESOURCE. Two exceptions are scsi-mq
		 *   and dm-rq.
		 *
		 * If driver returns BLK_STS_RESOURCE and SCHED_RESTART
		 * bit is set, run queue after a delay to avoid IO stalls
		 * that could otherwise occur if the queue is idle.  We'll do
		 * similar if we couldn't get budget and SCHED_RESTART is set.
		 */
		needs_restart = blk_mq_sched_needs_restart(hctx);
		if (!needs_restart ||
		    (no_tag && list_empty_careful(&hctx->dispatch_wait.entry)))
			blk_mq_run_hw_queue(hctx, true);
		else if (needs_restart && (ret == BLK_STS_RESOURCE ||
					   no_budget_avail))
			blk_mq_delay_run_hw_queue(hctx, BLK_MQ_RESOURCE_DELAY);

		blk_mq_update_dispatch_busy(hctx, true);
		return false;
	} else
		blk_mq_update_dispatch_busy(hctx, false);

	return (queued + errors) != 0;
}

/**
 * __blk_mq_run_hw_queue - Run a hardware queue.
 * @hctx: Pointer to the hardware queue to run.
 *
 * Send pending requests to the hardware.
 */
static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx)
{
	int srcu_idx;

	/*
	 * We can't run the queue inline with ints disabled. Ensure that
	 * we catch bad users of this early.
	 */
	WARN_ON_ONCE(in_interrupt());

	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);

	hctx_lock(hctx, &srcu_idx);
	blk_mq_sched_dispatch_requests(hctx);
	hctx_unlock(hctx, srcu_idx);
}

static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx)
{
	int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask);

	if (cpu >= nr_cpu_ids)
		cpu = cpumask_first(hctx->cpumask);
	return cpu;
}

/*
 * It'd be great if the workqueue API had a way to pass
 * in a mask and had some smarts for more clever placement.
 * For now we just round-robin here, switching for every
 * BLK_MQ_CPU_WORK_BATCH queued items.
 */
static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx)
{
	bool tried = false;
	int next_cpu = hctx->next_cpu;

	if (hctx->queue->nr_hw_queues == 1)
		return WORK_CPU_UNBOUND;

	if (--hctx->next_cpu_batch <= 0) {
select_cpu:
		next_cpu = cpumask_next_and(next_cpu, hctx->cpumask,
				cpu_online_mask);
		if (next_cpu >= nr_cpu_ids)
			next_cpu = blk_mq_first_mapped_cpu(hctx);
		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
	}

	/*
	 * Do unbound schedule if we can't find a online CPU for this hctx,
	 * and it should only happen in the path of handling CPU DEAD.
	 */
	if (!cpu_online(next_cpu)) {
		if (!tried) {
			tried = true;
			goto select_cpu;
		}

		/*
		 * Make sure to re-select CPU next time once after CPUs
		 * in hctx->cpumask become online again.
		 */
		hctx->next_cpu = next_cpu;
		hctx->next_cpu_batch = 1;
		return WORK_CPU_UNBOUND;
	}

	hctx->next_cpu = next_cpu;
	return next_cpu;
}

/**
 * __blk_mq_delay_run_hw_queue - Run (or schedule to run) a hardware queue.
 * @hctx: Pointer to the hardware queue to run.
 * @async: If we want to run the queue asynchronously.
 * @msecs: Milliseconds of delay to wait before running the queue.
 *
 * If !@async, try to run the queue now. Else, run the queue asynchronously and
 * with a delay of @msecs.
 */
static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async,
					unsigned long msecs)
{
	if (unlikely(blk_mq_hctx_stopped(hctx)))
		return;

	if (!async && !(hctx->flags & BLK_MQ_F_BLOCKING)) {
		int cpu = get_cpu();
		if (cpumask_test_cpu(cpu, hctx->cpumask)) {
			__blk_mq_run_hw_queue(hctx);
			put_cpu();
			return;
		}

		put_cpu();
	}

	kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work,
				    msecs_to_jiffies(msecs));
}

/**
 * blk_mq_delay_run_hw_queue - Run a hardware queue asynchronously.
 * @hctx: Pointer to the hardware queue to run.
 * @msecs: Milliseconds of delay to wait before running the queue.
 *
 * Run a hardware queue asynchronously with a delay of @msecs.
 */
void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
{
	__blk_mq_delay_run_hw_queue(hctx, true, msecs);
}
EXPORT_SYMBOL(blk_mq_delay_run_hw_queue);

/**
 * blk_mq_run_hw_queue - Start to run a hardware queue.
 * @hctx: Pointer to the hardware queue to run.
 * @async: If we want to run the queue asynchronously.
 *
 * Check if the request queue is not in a quiesced state and if there are
 * pending requests to be sent. If this is true, run the queue to send requests
 * to hardware.
 */
void blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
{
	int srcu_idx;
	bool need_run;

	/*
	 * When queue is quiesced, we may be switching io scheduler, or
	 * updating nr_hw_queues, or other things, and we can't run queue
	 * any more, even __blk_mq_hctx_has_pending() can't be called safely.
	 *
	 * And queue will be rerun in blk_mq_unquiesce_queue() if it is
	 * quiesced.
	 */
	hctx_lock(hctx, &srcu_idx);
	need_run = !blk_queue_quiesced(hctx->queue) &&
		blk_mq_hctx_has_pending(hctx);
	hctx_unlock(hctx, srcu_idx);

	if (need_run)
		__blk_mq_delay_run_hw_queue(hctx, async, 0);
}
EXPORT_SYMBOL(blk_mq_run_hw_queue);

/*
 * Is the request queue handled by an IO scheduler that does not respect
 * hardware queues when dispatching?
 */
static bool blk_mq_has_sqsched(struct request_queue *q)
{
	struct elevator_queue *e = q->elevator;

	if (e && e->type->ops.dispatch_request &&
	    !(e->type->elevator_features & ELEVATOR_F_MQ_AWARE))
		return true;
	return false;
}

/*
 * Return prefered queue to dispatch from (if any) for non-mq aware IO
 * scheduler.
 */
static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx;

	/*
	 * If the IO scheduler does not respect hardware queues when
	 * dispatching, we just don't bother with multiple HW queues and
	 * dispatch from hctx for the current CPU since running multiple queues
	 * just causes lock contention inside the scheduler and pointless cache
	 * bouncing.
	 */
	hctx = blk_mq_map_queue_type(q, HCTX_TYPE_DEFAULT,
				     raw_smp_processor_id());
	if (!blk_mq_hctx_stopped(hctx))
		return hctx;
	return NULL;
}

/**
 * blk_mq_run_hw_queues - Run all hardware queues in a request queue.
 * @q: Pointer to the request queue to run.
 * @async: If we want to run the queue asynchronously.
 */
void blk_mq_run_hw_queues(struct request_queue *q, bool async)
{
	struct blk_mq_hw_ctx *hctx, *sq_hctx;
	int i;

	sq_hctx = NULL;
	if (blk_mq_has_sqsched(q))
		sq_hctx = blk_mq_get_sq_hctx(q);
	queue_for_each_hw_ctx(q, hctx, i) {
		if (blk_mq_hctx_stopped(hctx))
			continue;
		/*
		 * Dispatch from this hctx either if there's no hctx preferred
		 * by IO scheduler or if it has requests that bypass the
		 * scheduler.
		 */
		if (!sq_hctx || sq_hctx == hctx ||
		    !list_empty_careful(&hctx->dispatch))
			blk_mq_run_hw_queue(hctx, async);
	}
}
EXPORT_SYMBOL(blk_mq_run_hw_queues);

/**
 * blk_mq_delay_run_hw_queues - Run all hardware queues asynchronously.
 * @q: Pointer to the request queue to run.
 * @msecs: Milliseconds of delay to wait before running the queues.
 */
void blk_mq_delay_run_hw_queues(struct request_queue *q, unsigned long msecs)
{
	struct blk_mq_hw_ctx *hctx, *sq_hctx;
	int i;

	sq_hctx = NULL;
	if (blk_mq_has_sqsched(q))
		sq_hctx = blk_mq_get_sq_hctx(q);
	queue_for_each_hw_ctx(q, hctx, i) {
		if (blk_mq_hctx_stopped(hctx))
			continue;
		/*
		 * Dispatch from this hctx either if there's no hctx preferred
		 * by IO scheduler or if it has requests that bypass the
		 * scheduler.
		 */
		if (!sq_hctx || sq_hctx == hctx ||
		    !list_empty_careful(&hctx->dispatch))
			blk_mq_delay_run_hw_queue(hctx, msecs);
	}
}
EXPORT_SYMBOL(blk_mq_delay_run_hw_queues);

/**
 * blk_mq_queue_stopped() - check whether one or more hctxs have been stopped
 * @q: request queue.
 *
 * The caller is responsible for serializing this function against
 * blk_mq_{start,stop}_hw_queue().
 */
bool blk_mq_queue_stopped(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx;
	int i;

	queue_for_each_hw_ctx(q, hctx, i)
		if (blk_mq_hctx_stopped(hctx))
			return true;

	return false;
}
EXPORT_SYMBOL(blk_mq_queue_stopped);

/*
 * This function is often used for pausing .queue_rq() by driver when
 * there isn't enough resource or some conditions aren't satisfied, and
 * BLK_STS_RESOURCE is usually returned.
 *
 * We do not guarantee that dispatch can be drained or blocked
 * after blk_mq_stop_hw_queue() returns. Please use
 * blk_mq_quiesce_queue() for that requirement.
 */
void blk_mq_stop_hw_queue(struct blk_mq_hw_ctx *hctx)
{
	cancel_delayed_work(&hctx->run_work);

	set_bit(BLK_MQ_S_STOPPED, &hctx->state);
}
EXPORT_SYMBOL(blk_mq_stop_hw_queue);

/*
 * This function is often used for pausing .queue_rq() by driver when
 * there isn't enough resource or some conditions aren't satisfied, and
 * BLK_STS_RESOURCE is usually returned.
 *
 * We do not guarantee that dispatch can be drained or blocked
 * after blk_mq_stop_hw_queues() returns. Please use
 * blk_mq_quiesce_queue() for that requirement.
 */
void blk_mq_stop_hw_queues(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx;
	int i;

	queue_for_each_hw_ctx(q, hctx, i)
		blk_mq_stop_hw_queue(hctx);
}
EXPORT_SYMBOL(blk_mq_stop_hw_queues);

void blk_mq_start_hw_queue(struct blk_mq_hw_ctx *hctx)
{
	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);

	blk_mq_run_hw_queue(hctx, false);
}
EXPORT_SYMBOL(blk_mq_start_hw_queue);

void blk_mq_start_hw_queues(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx;
	int i;

	queue_for_each_hw_ctx(q, hctx, i)
		blk_mq_start_hw_queue(hctx);
}
EXPORT_SYMBOL(blk_mq_start_hw_queues);

void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async)
{
	if (!blk_mq_hctx_stopped(hctx))
		return;

	clear_bit(BLK_MQ_S_STOPPED, &hctx->state);
	blk_mq_run_hw_queue(hctx, async);
}
EXPORT_SYMBOL_GPL(blk_mq_start_stopped_hw_queue);

void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async)
{
	struct blk_mq_hw_ctx *hctx;
	int i;

	queue_for_each_hw_ctx(q, hctx, i)
		blk_mq_start_stopped_hw_queue(hctx, async);
}
EXPORT_SYMBOL(blk_mq_start_stopped_hw_queues);

static void blk_mq_run_work_fn(struct work_struct *work)
{
	struct blk_mq_hw_ctx *hctx;

	hctx = container_of(work, struct blk_mq_hw_ctx, run_work.work);

	/*
	 * If we are stopped, don't run the queue.
	 */
	if (blk_mq_hctx_stopped(hctx))
		return;

	__blk_mq_run_hw_queue(hctx);
}

static inline void __blk_mq_insert_req_list(struct blk_mq_hw_ctx *hctx,
					    struct request *rq,
					    bool at_head)
{
	struct blk_mq_ctx *ctx = rq->mq_ctx;
	enum hctx_type type = hctx->type;

	lockdep_assert_held(&ctx->lock);

	trace_block_rq_insert(rq);

	if (at_head)
		list_add(&rq->queuelist, &ctx->rq_lists[type]);
	else
		list_add_tail(&rq->queuelist, &ctx->rq_lists[type]);
}

void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
			     bool at_head)
{
	struct blk_mq_ctx *ctx = rq->mq_ctx;

	lockdep_assert_held(&ctx->lock);

	__blk_mq_insert_req_list(hctx, rq, at_head);
	blk_mq_hctx_mark_pending(hctx, ctx);
}

/**
 * blk_mq_request_bypass_insert - Insert a request at dispatch list.
 * @rq: Pointer to request to be inserted.
 * @at_head: true if the request should be inserted at the head of the list.
 * @run_queue: If we should run the hardware queue after inserting the request.
 *
 * Should only be used carefully, when the caller knows we want to
 * bypass a potential IO scheduler on the target device.
 */
void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
				  bool run_queue)
{
	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

	spin_lock(&hctx->lock);
	if (at_head)
		list_add(&rq->queuelist, &hctx->dispatch);
	else
		list_add_tail(&rq->queuelist, &hctx->dispatch);
	spin_unlock(&hctx->lock);

	if (run_queue)
		blk_mq_run_hw_queue(hctx, false);
}

void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
			    struct list_head *list)

{
	struct request *rq;
	enum hctx_type type = hctx->type;

	/*
	 * preemption doesn't flush plug list, so it's possible ctx->cpu is
	 * offline now
	 */
	list_for_each_entry(rq, list, queuelist) {
		BUG_ON(rq->mq_ctx != ctx);
		trace_block_rq_insert(rq);
	}

	spin_lock(&ctx->lock);
	list_splice_tail_init(list, &ctx->rq_lists[type]);
	blk_mq_hctx_mark_pending(hctx, ctx);
	spin_unlock(&ctx->lock);
}

static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
{
	struct request *rqa = container_of(a, struct request, queuelist);
	struct request *rqb = container_of(b, struct request, queuelist);

	if (rqa->mq_ctx != rqb->mq_ctx)
		return rqa->mq_ctx > rqb->mq_ctx;
	if (rqa->mq_hctx != rqb->mq_hctx)
		return rqa->mq_hctx > rqb->mq_hctx;

	return blk_rq_pos(rqa) > blk_rq_pos(rqb);
}

void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
{
	LIST_HEAD(list);

	if (list_empty(&plug->mq_list))
		return;
	list_splice_init(&plug->mq_list, &list);

	if (plug->rq_count > 2 && plug->multiple_queues)
		list_sort(NULL, &list, plug_rq_cmp);

	plug->rq_count = 0;

	do {
		struct list_head rq_list;
		struct request *rq, *head_rq = list_entry_rq(list.next);
		struct list_head *pos = &head_rq->queuelist; /* skip first */
		struct blk_mq_hw_ctx *this_hctx = head_rq->mq_hctx;
		struct blk_mq_ctx *this_ctx = head_rq->mq_ctx;
		unsigned int depth = 1;

		list_for_each_continue(pos, &list) {
			rq = list_entry_rq(pos);
			BUG_ON(!rq->q);
			if (rq->mq_hctx != this_hctx || rq->mq_ctx != this_ctx)
				break;
			depth++;
		}

		list_cut_before(&rq_list, &list, pos);
		trace_block_unplug(head_rq->q, depth, !from_schedule);
		blk_mq_sched_insert_requests(this_hctx, this_ctx, &rq_list,
						from_schedule);
	} while(!list_empty(&list));
}

static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
		unsigned int nr_segs)
{
	int err;

	if (bio->bi_opf & REQ_RAHEAD)
		rq->cmd_flags |= REQ_FAILFAST_MASK;

	rq->__sector = bio->bi_iter.bi_sector;
	rq->write_hint = bio->bi_write_hint;
	blk_rq_bio_prep(rq, bio, nr_segs);

	/* This can't fail, since GFP_NOIO includes __GFP_DIRECT_RECLAIM. */
	err = blk_crypto_rq_bio_prep(rq, bio, GFP_NOIO);
	WARN_ON_ONCE(err);

	blk_account_io_start(rq);
}

static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
					    struct request *rq,
					    blk_qc_t *cookie, bool last)
{
	struct request_queue *q = rq->q;
	struct blk_mq_queue_data bd = {
		.rq = rq,
		.last = last,
	};
	blk_qc_t new_cookie;
	blk_status_t ret;

	new_cookie = request_to_qc_t(hctx, rq);

	/*
	 * For OK queue, we are done. For error, caller may kill it.
	 * Any other error (busy), just add it to our list as we
	 * previously would have done.
	 */
	ret = q->mq_ops->queue_rq(hctx, &bd);
	switch (ret) {
	case BLK_STS_OK:
		blk_mq_update_dispatch_busy(hctx, false);
		*cookie = new_cookie;
		break;
	case BLK_STS_RESOURCE:
	case BLK_STS_DEV_RESOURCE:
		blk_mq_update_dispatch_busy(hctx, true);
		__blk_mq_requeue_request(rq);
		break;
	default:
		blk_mq_update_dispatch_busy(hctx, false);
		*cookie = BLK_QC_T_NONE;
		break;
	}

	return ret;
}

static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
						struct request *rq,
						blk_qc_t *cookie,
						bool bypass_insert, bool last)
{
	struct request_queue *q = rq->q;
	bool run_queue = true;

	/*
	 * RCU or SRCU read lock is needed before checking quiesced flag.
	 *
	 * When queue is stopped or quiesced, ignore 'bypass_insert' from
	 * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
	 * and avoid driver to try to dispatch again.
	 */
	if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
		run_queue = false;
		bypass_insert = false;
		goto insert;
	}

	if (q->elevator && !bypass_insert)
		goto insert;

	if (!blk_mq_get_dispatch_budget(q))
		goto insert;

	if (!blk_mq_get_driver_tag(rq)) {
		blk_mq_put_dispatch_budget(q);
		goto insert;
	}

	return __blk_mq_issue_directly(hctx, rq, cookie, last);
insert:
	if (bypass_insert)
		return BLK_STS_RESOURCE;

	blk_mq_sched_insert_request(rq, false, run_queue, false);

	return BLK_STS_OK;
}

/**
 * blk_mq_try_issue_directly - Try to send a request directly to device driver.
 * @hctx: Pointer of the associated hardware queue.
 * @rq: Pointer to request to be sent.
 * @cookie: Request queue cookie.
 *
 * If the device has enough resources to accept a new request now, send the
 * request directly to device driver. Else, insert at hctx->dispatch queue, so
 * we can try send it another time in the future. Requests inserted at this
 * queue have higher priority.
 */
static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
		struct request *rq, blk_qc_t *cookie)
{
	blk_status_t ret;
	int srcu_idx;

	might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);

	hctx_lock(hctx, &srcu_idx);

	ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false, true);
	if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE)
		blk_mq_request_bypass_insert(rq, false, true);
	else if (ret != BLK_STS_OK)
		blk_mq_end_request(rq, ret);

	hctx_unlock(hctx, srcu_idx);
}

blk_status_t blk_mq_request_issue_directly(struct request *rq, bool last)
{
	blk_status_t ret;
	int srcu_idx;
	blk_qc_t unused_cookie;
	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

	hctx_lock(hctx, &srcu_idx);
	ret = __blk_mq_try_issue_directly(hctx, rq, &unused_cookie, true, last);
	hctx_unlock(hctx, srcu_idx);

	return ret;
}

void blk_mq_try_issue_list_directly(struct blk_mq_hw_ctx *hctx,
		struct list_head *list)
{
	int queued = 0;
	int errors = 0;

	while (!list_empty(list)) {
		blk_status_t ret;
		struct request *rq = list_first_entry(list, struct request,
				queuelist);

		list_del_init(&rq->queuelist);
		ret = blk_mq_request_issue_directly(rq, list_empty(list));
		if (ret != BLK_STS_OK) {
			if (ret == BLK_STS_RESOURCE ||
					ret == BLK_STS_DEV_RESOURCE) {
				blk_mq_request_bypass_insert(rq, false,
							list_empty(list));
				break;
			}
			blk_mq_end_request(rq, ret);
			errors++;
		} else
			queued++;
	}

	/*
	 * If we didn't flush the entire list, we could have told
	 * the driver there was more coming, but that turned out to
	 * be a lie.
	 */
	if ((!list_empty(list) || errors) &&
	     hctx->queue->mq_ops->commit_rqs && queued)
		hctx->queue->mq_ops->commit_rqs(hctx);
}

static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
{
	list_add_tail(&rq->queuelist, &plug->mq_list);
	plug->rq_count++;
	if (!plug->multiple_queues && !list_is_singular(&plug->mq_list)) {
		struct request *tmp;

		tmp = list_first_entry(&plug->mq_list, struct request,
						queuelist);
		if (tmp->q != rq->q)
			plug->multiple_queues = true;
	}
}

/**
 * blk_mq_submit_bio - Create and send a request to block device.
 * @bio: Bio pointer.
 *
 * Builds up a request structure from @q and @bio and send to the device. The
 * request may not be queued directly to hardware if:
 * * This request can be merged with another one
 * * We want to place request at plug queue for possible future merging
 * * There is an IO scheduler active at this queue
 *
 * It will not queue the request if there is an error with the bio, or at the
 * request creation.
 *
 * Returns: Request queue cookie.
 */
blk_qc_t blk_mq_submit_bio(struct bio *bio)
{
	struct request_queue *q = bio->bi_bdev->bd_disk->queue;
	const int is_sync = op_is_sync(bio->bi_opf);
	const int is_flush_fua = op_is_flush(bio->bi_opf);
	struct blk_mq_alloc_data data = {
		.q		= q,
	};
	struct request *rq;
	struct blk_plug *plug;
	struct request *same_queue_rq = NULL;
	unsigned int nr_segs;
	blk_qc_t cookie;
	blk_status_t ret;
	bool hipri;

	blk_queue_bounce(q, &bio);
	__blk_queue_split(&bio, &nr_segs);

	if (!bio_integrity_prep(bio))
		goto queue_exit;

	if (!is_flush_fua && !blk_queue_nomerges(q) &&
	    blk_attempt_plug_merge(q, bio, nr_segs, &same_queue_rq))
		goto queue_exit;

	if (blk_mq_sched_bio_merge(q, bio, nr_segs))
		goto queue_exit;

	rq_qos_throttle(q, bio);

	hipri = bio->bi_opf & REQ_HIPRI;

	data.cmd_flags = bio->bi_opf;
	rq = __blk_mq_alloc_request(&data);
	if (unlikely(!rq)) {
		rq_qos_cleanup(q, bio);
		if (bio->bi_opf & REQ_NOWAIT)
			bio_wouldblock_error(bio);
		goto queue_exit;
	}

	trace_block_getrq(bio);

	rq_qos_track(q, rq, bio);

	cookie = request_to_qc_t(data.hctx, rq);

	blk_mq_bio_to_request(rq, bio, nr_segs);

	ret = blk_crypto_init_request(rq);
	if (ret != BLK_STS_OK) {
		bio->bi_status = ret;
		bio_endio(bio);
		blk_mq_free_request(rq);
		return BLK_QC_T_NONE;
	}

	plug = blk_mq_plug(q, bio);
	if (unlikely(is_flush_fua)) {
		/* Bypass scheduler for flush requests */
		blk_insert_flush(rq);
		blk_mq_run_hw_queue(data.hctx, true);
	} else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs ||
				!blk_queue_nonrot(q))) {
		/*
		 * Use plugging if we have a ->commit_rqs() hook as well, as
		 * we know the driver uses bd->last in a smart fashion.
		 *
		 * Use normal plugging if this disk is slow HDD, as sequential
		 * IO may benefit a lot from plug merging.
		 */
		unsigned int request_count = plug->rq_count;
		struct request *last = NULL;

		if (!request_count)
			trace_block_plug(q);
		else
			last = list_entry_rq(plug->mq_list.prev);

		if (request_count >= BLK_MAX_REQUEST_COUNT || (last &&
		    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
			blk_flush_plug_list(plug, false);
			trace_block_plug(q);
		}

		blk_add_rq_to_plug(plug, rq);
	} else if (q->elevator) {
		/* Insert the request at the IO scheduler queue */
		blk_mq_sched_insert_request(rq, false, true, true);
	} else if (plug && !blk_queue_nomerges(q)) {
		/*
		 * We do limited plugging. If the bio can be merged, do that.
		 * Otherwise the existing request in the plug list will be
		 * issued. So the plug list will have one request at most
		 * The plug list might get flushed before this. If that happens,
		 * the plug list is empty, and same_queue_rq is invalid.
		 */
		if (list_empty(&plug->mq_list))
			same_queue_rq = NULL;
		if (same_queue_rq) {
			list_del_init(&same_queue_rq->queuelist);
			plug->rq_count--;
		}
		blk_add_rq_to_plug(plug, rq);
		trace_block_plug(q);

		if (same_queue_rq) {
			data.hctx = same_queue_rq->mq_hctx;
			trace_block_unplug(q, 1, true);
			blk_mq_try_issue_directly(data.hctx, same_queue_rq,
					&cookie);
		}
	} else if ((q->nr_hw_queues > 1 && is_sync) ||
			!data.hctx->dispatch_busy) {
		/*
		 * There is no scheduler and we can try to send directly
		 * to the hardware.
		 */
		blk_mq_try_issue_directly(data.hctx, rq, &cookie);
	} else {
		/* Default case. */
		blk_mq_sched_insert_request(rq, false, true, true);
	}

	if (!hipri)
		return BLK_QC_T_NONE;
	return cookie;
queue_exit:
	blk_queue_exit(q);
	return BLK_QC_T_NONE;
}

void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
		     unsigned int hctx_idx)
{
	struct page *page;

	if (tags->rqs && set->ops->exit_request) {
		int i;

		for (i = 0; i < tags->nr_tags; i++) {
			struct request *rq = tags->static_rqs[i];

			if (!rq)
				continue;
			set->ops->exit_request(set, rq, hctx_idx);
			tags->static_rqs[i] = NULL;
		}
	}

	while (!list_empty(&tags->page_list)) {
		page = list_first_entry(&tags->page_list, struct page, lru);
		list_del_init(&page->lru);
		/*
		 * Remove kmemleak object previously allocated in
		 * blk_mq_alloc_rqs().
		 */
		kmemleak_free(page_address(page));
		__free_pages(page, page->private);
	}
}

void blk_mq_free_rq_map(struct blk_mq_tags *tags, unsigned int flags)
{
	kfree(tags->rqs);
	tags->rqs = NULL;
	kfree(tags->static_rqs);
	tags->static_rqs = NULL;

	blk_mq_free_tags(tags, flags);
}

struct blk_mq_tags *blk_mq_alloc_rq_map(struct blk_mq_tag_set *set,
					unsigned int hctx_idx,
					unsigned int nr_tags,
					unsigned int reserved_tags,
					unsigned int flags)
{
	struct blk_mq_tags *tags;
	int node;

	node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], hctx_idx);
	if (node == NUMA_NO_NODE)
		node = set->numa_node;

	tags = blk_mq_init_tags(nr_tags, reserved_tags, node, flags);
	if (!tags)
		return NULL;

	tags->rqs = kcalloc_node(nr_tags, sizeof(struct request *),
				 GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
				 node);
	if (!tags->rqs) {
		blk_mq_free_tags(tags, flags);
		return NULL;
	}

	tags->static_rqs = kcalloc_node(nr_tags, sizeof(struct request *),
					GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY,
					node);
	if (!tags->static_rqs) {
		kfree(tags->rqs);
		blk_mq_free_tags(tags, flags);
		return NULL;
	}

	return tags;
}

static size_t order_to_size(unsigned int order)
{
	return (size_t)PAGE_SIZE << order;
}

static int blk_mq_init_request(struct blk_mq_tag_set *set, struct request *rq,
			       unsigned int hctx_idx, int node)
{
	int ret;

	if (set->ops->init_request) {
		ret = set->ops->init_request(set, rq, hctx_idx, node);
		if (ret)
			return ret;
	}

	WRITE_ONCE(rq->state, MQ_RQ_IDLE);
	return 0;
}

int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
		     unsigned int hctx_idx, unsigned int depth)
{
	unsigned int i, j, entries_per_page, max_order = 4;
	size_t rq_size, left;
	int node;

	node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], hctx_idx);
	if (node == NUMA_NO_NODE)
		node = set->numa_node;

	INIT_LIST_HEAD(&tags->page_list);

	/*
	 * rq_size is the size of the request plus driver payload, rounded
	 * to the cacheline size
	 */
	rq_size = round_up(sizeof(struct request) + set->cmd_size,
				cache_line_size());
	left = rq_size * depth;

	for (i = 0; i < depth; ) {
		int this_order = max_order;
		struct page *page;
		int to_do;
		void *p;

		while (this_order && left < order_to_size(this_order - 1))
			this_order--;

		do {
			page = alloc_pages_node(node,
				GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY | __GFP_ZERO,
				this_order);
			if (page)
				break;
			if (!this_order--)
				break;
			if (order_to_size(this_order) < rq_size)
				break;
		} while (1);

		if (!page)
			goto fail;

		page->private = this_order;
		list_add_tail(&page->lru, &tags->page_list);

		p = page_address(page);
		/*
		 * Allow kmemleak to scan these pages as they contain pointers
		 * to additional allocations like via ops->init_request().
		 */
		kmemleak_alloc(p, order_to_size(this_order), 1, GFP_NOIO);
		entries_per_page = order_to_size(this_order) / rq_size;
		to_do = min(entries_per_page, depth - i);
		left -= to_do * rq_size;
		for (j = 0; j < to_do; j++) {
			struct request *rq = p;

			tags->static_rqs[i] = rq;
			if (blk_mq_init_request(set, rq, hctx_idx, node)) {
				tags->static_rqs[i] = NULL;
				goto fail;
			}

			p += rq_size;
			i++;
		}
	}
	return 0;

fail:
	blk_mq_free_rqs(set, tags, hctx_idx);
	return -ENOMEM;
}

struct rq_iter_data {
	struct blk_mq_hw_ctx *hctx;
	bool has_rq;
};

static bool blk_mq_has_request(struct request *rq, void *data, bool reserved)
{
	struct rq_iter_data *iter_data = data;

	if (rq->mq_hctx != iter_data->hctx)
		return true;
	iter_data->has_rq = true;
	return false;
}

static bool blk_mq_hctx_has_requests(struct blk_mq_hw_ctx *hctx)
{
	struct blk_mq_tags *tags = hctx->sched_tags ?
			hctx->sched_tags : hctx->tags;
	struct rq_iter_data data = {
		.hctx	= hctx,
	};

	blk_mq_all_tag_iter(tags, blk_mq_has_request, &data);
	return data.has_rq;
}

static inline bool blk_mq_last_cpu_in_hctx(unsigned int cpu,
		struct blk_mq_hw_ctx *hctx)
{
	if (cpumask_next_and(-1, hctx->cpumask, cpu_online_mask) != cpu)
		return false;
	if (cpumask_next_and(cpu, hctx->cpumask, cpu_online_mask) < nr_cpu_ids)
		return false;
	return true;
}

static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node)
{
	struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
			struct blk_mq_hw_ctx, cpuhp_online);

	if (!cpumask_test_cpu(cpu, hctx->cpumask) ||
	    !blk_mq_last_cpu_in_hctx(cpu, hctx))
		return 0;

	/*
	 * Prevent new request from being allocated on the current hctx.
	 *
	 * The smp_mb__after_atomic() Pairs with the implied barrier in
	 * test_and_set_bit_lock in sbitmap_get().  Ensures the inactive flag is
	 * seen once we return from the tag allocator.
	 */
	set_bit(BLK_MQ_S_INACTIVE, &hctx->state);
	smp_mb__after_atomic();

	/*
	 * Try to grab a reference to the queue and wait for any outstanding
	 * requests.  If we could not grab a reference the queue has been
	 * frozen and there are no requests.
	 */
	if (percpu_ref_tryget(&hctx->queue->q_usage_counter)) {
		while (blk_mq_hctx_has_requests(hctx))
			msleep(5);
		percpu_ref_put(&hctx->queue->q_usage_counter);
	}

	return 0;
}

static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node)
{
	struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node,
			struct blk_mq_hw_ctx, cpuhp_online);

	if (cpumask_test_cpu(cpu, hctx->cpumask))
		clear_bit(BLK_MQ_S_INACTIVE, &hctx->state);
	return 0;
}

/*
 * 'cpu' is going away. splice any existing rq_list entries from this
 * software queue to the hw queue dispatch list, and ensure that it
 * gets run.
 */
static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node)
{
	struct blk_mq_hw_ctx *hctx;
	struct blk_mq_ctx *ctx;
	LIST_HEAD(tmp);
	enum hctx_type type;

	hctx = hlist_entry_safe(node, struct blk_mq_hw_ctx, cpuhp_dead);
	if (!cpumask_test_cpu(cpu, hctx->cpumask))
		return 0;

	ctx = __blk_mq_get_ctx(hctx->queue, cpu);
	type = hctx->type;

	spin_lock(&ctx->lock);
	if (!list_empty(&ctx->rq_lists[type])) {
		list_splice_init(&ctx->rq_lists[type], &tmp);
		blk_mq_hctx_clear_pending(hctx, ctx);
	}
	spin_unlock(&ctx->lock);

	if (list_empty(&tmp))
		return 0;

	spin_lock(&hctx->lock);
	list_splice_tail_init(&tmp, &hctx->dispatch);
	spin_unlock(&hctx->lock);

	blk_mq_run_hw_queue(hctx, true);
	return 0;
}

static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx)
{
	if (!(hctx->flags & BLK_MQ_F_STACKING))
		cpuhp_state_remove_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
						    &hctx->cpuhp_online);
	cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD,
					    &hctx->cpuhp_dead);
}

/* hctx->ctxs will be freed in queue's release handler */
static void blk_mq_exit_hctx(struct request_queue *q,
		struct blk_mq_tag_set *set,
		struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
{
	if (blk_mq_hw_queue_mapped(hctx))
		blk_mq_tag_idle(hctx);

	if (set->ops->exit_request)
		set->ops->exit_request(set, hctx->fq->flush_rq, hctx_idx);

	if (set->ops->exit_hctx)
		set->ops->exit_hctx(hctx, hctx_idx);

	blk_mq_remove_cpuhp(hctx);

	spin_lock(&q->unused_hctx_lock);
	list_add(&hctx->hctx_list, &q->unused_hctx_list);
	spin_unlock(&q->unused_hctx_lock);
}

static void blk_mq_exit_hw_queues(struct request_queue *q,
		struct blk_mq_tag_set *set, int nr_queue)
{
	struct blk_mq_hw_ctx *hctx;
	unsigned int i;

	queue_for_each_hw_ctx(q, hctx, i) {
		if (i == nr_queue)
			break;
		blk_mq_debugfs_unregister_hctx(hctx);
		blk_mq_exit_hctx(q, set, hctx, i);
	}
}

static int blk_mq_hw_ctx_size(struct blk_mq_tag_set *tag_set)
{
	int hw_ctx_size = sizeof(struct blk_mq_hw_ctx);

	BUILD_BUG_ON(ALIGN(offsetof(struct blk_mq_hw_ctx, srcu),
			   __alignof__(struct blk_mq_hw_ctx)) !=
		     sizeof(struct blk_mq_hw_ctx));

	if (tag_set->flags & BLK_MQ_F_BLOCKING)
		hw_ctx_size += sizeof(struct srcu_struct);

	return hw_ctx_size;
}

static int blk_mq_init_hctx(struct request_queue *q,
		struct blk_mq_tag_set *set,
		struct blk_mq_hw_ctx *hctx, unsigned hctx_idx)
{
	hctx->queue_num = hctx_idx;

	if (!(hctx->flags & BLK_MQ_F_STACKING))
		cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE,
				&hctx->cpuhp_online);
	cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead);

	hctx->tags = set->tags[hctx_idx];

	if (set->ops->init_hctx &&
	    set->ops->init_hctx(hctx, set->driver_data, hctx_idx))
		goto unregister_cpu_notifier;

	if (blk_mq_init_request(set, hctx->fq->flush_rq, hctx_idx,
				hctx->numa_node))
		goto exit_hctx;
	return 0;

 exit_hctx:
	if (set->ops->exit_hctx)
		set->ops->exit_hctx(hctx, hctx_idx);
 unregister_cpu_notifier:
	blk_mq_remove_cpuhp(hctx);
	return -1;
}

static struct blk_mq_hw_ctx *
blk_mq_alloc_hctx(struct request_queue *q, struct blk_mq_tag_set *set,
		int node)
{
	struct blk_mq_hw_ctx *hctx;
	gfp_t gfp = GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY;

	hctx = kzalloc_node(blk_mq_hw_ctx_size(set), gfp, node);
	if (!hctx)
		goto fail_alloc_hctx;

	if (!zalloc_cpumask_var_node(&hctx->cpumask, gfp, node))
		goto free_hctx;

	atomic_set(&hctx->nr_active, 0);
	if (node == NUMA_NO_NODE)
		node = set->numa_node;
	hctx->numa_node = node;

	INIT_DELAYED_WORK(&hctx->run_work, blk_mq_run_work_fn);
	spin_lock_init(&hctx->lock);
	INIT_LIST_HEAD(&hctx->dispatch);
	hctx->queue = q;
	hctx->flags = set->flags & ~BLK_MQ_F_TAG_QUEUE_SHARED;

	INIT_LIST_HEAD(&hctx->hctx_list);

	/*
	 * Allocate space for all possible cpus to avoid allocation at
	 * runtime
	 */
	hctx->ctxs = kmalloc_array_node(nr_cpu_ids, sizeof(void *),
			gfp, node);
	if (!hctx->ctxs)
		goto free_cpumask;

	if (sbitmap_init_node(&hctx->ctx_map, nr_cpu_ids, ilog2(8),
				gfp, node))
		goto free_ctxs;
	hctx->nr_ctx = 0;

	spin_lock_init(&hctx->dispatch_wait_lock);
	init_waitqueue_func_entry(&hctx->dispatch_wait, blk_mq_dispatch_wake);
	INIT_LIST_HEAD(&hctx->dispatch_wait.entry);

	hctx->fq = blk_alloc_flush_queue(hctx->numa_node, set->cmd_size, gfp);
	if (!hctx->fq)
		goto free_bitmap;

	if (hctx->flags & BLK_MQ_F_BLOCKING)
		init_srcu_struct(hctx->srcu);
	blk_mq_hctx_kobj_init(hctx);

	return hctx;

 free_bitmap:
	sbitmap_free(&hctx->ctx_map);
 free_ctxs:
	kfree(hctx->ctxs);
 free_cpumask:
	free_cpumask_var(hctx->cpumask);
 free_hctx:
	kfree(hctx);
 fail_alloc_hctx:
	return NULL;
}

static void blk_mq_init_cpu_queues(struct request_queue *q,
				   unsigned int nr_hw_queues)
{
	struct blk_mq_tag_set *set = q->tag_set;
	unsigned int i, j;

	for_each_possible_cpu(i) {
		struct blk_mq_ctx *__ctx = per_cpu_ptr(q->queue_ctx, i);
		struct blk_mq_hw_ctx *hctx;
		int k;

		__ctx->cpu = i;
		spin_lock_init(&__ctx->lock);
		for (k = HCTX_TYPE_DEFAULT; k < HCTX_MAX_TYPES; k++)
			INIT_LIST_HEAD(&__ctx->rq_lists[k]);

		__ctx->queue = q;

		/*
		 * Set local node, IFF we have more than one hw queue. If
		 * not, we remain on the home node of the device
		 */
		for (j = 0; j < set->nr_maps; j++) {
			hctx = blk_mq_map_queue_type(q, j, i);
			if (nr_hw_queues > 1 && hctx->numa_node == NUMA_NO_NODE)
				hctx->numa_node = cpu_to_node(i);
		}
	}
}

static bool __blk_mq_alloc_map_and_request(struct blk_mq_tag_set *set,
					int hctx_idx)
{
	unsigned int flags = set->flags;
	int ret = 0;

	set->tags[hctx_idx] = blk_mq_alloc_rq_map(set, hctx_idx,
					set->queue_depth, set->reserved_tags, flags);
	if (!set->tags[hctx_idx])
		return false;

	ret = blk_mq_alloc_rqs(set, set->tags[hctx_idx], hctx_idx,
				set->queue_depth);
	if (!ret)
		return true;

	blk_mq_free_rq_map(set->tags[hctx_idx], flags);
	set->tags[hctx_idx] = NULL;
	return false;
}

static void blk_mq_free_map_and_requests(struct blk_mq_tag_set *set,
					 unsigned int hctx_idx)
{
	unsigned int flags = set->flags;

	if (set->tags && set->tags[hctx_idx]) {
		blk_mq_free_rqs(set, set->tags[hctx_idx], hctx_idx);
		blk_mq_free_rq_map(set->tags[hctx_idx], flags);
		set->tags[hctx_idx] = NULL;
	}
}

static void blk_mq_map_swqueue(struct request_queue *q)
{
	unsigned int i, j, hctx_idx;
	struct blk_mq_hw_ctx *hctx;
	struct blk_mq_ctx *ctx;
	struct blk_mq_tag_set *set = q->tag_set;

	queue_for_each_hw_ctx(q, hctx, i) {
		cpumask_clear(hctx->cpumask);
		hctx->nr_ctx = 0;
		hctx->dispatch_from = NULL;
	}

	/*
	 * Map software to hardware queues.
	 *
	 * If the cpu isn't present, the cpu is mapped to first hctx.
	 */
	for_each_possible_cpu(i) {

		ctx = per_cpu_ptr(q->queue_ctx, i);
		for (j = 0; j < set->nr_maps; j++) {
			if (!set->map[j].nr_queues) {
				ctx->hctxs[j] = blk_mq_map_queue_type(q,
						HCTX_TYPE_DEFAULT, i);
				continue;
			}
			hctx_idx = set->map[j].mq_map[i];
			/* unmapped hw queue can be remapped after CPU topo changed */
			if (!set->tags[hctx_idx] &&
			    !__blk_mq_alloc_map_and_request(set, hctx_idx)) {
				/*
				 * If tags initialization fail for some hctx,
				 * that hctx won't be brought online.  In this
				 * case, remap the current ctx to hctx[0] which
				 * is guaranteed to always have tags allocated
				 */
				set->map[j].mq_map[i] = 0;
			}

			hctx = blk_mq_map_queue_type(q, j, i);
			ctx->hctxs[j] = hctx;
			/*
			 * If the CPU is already set in the mask, then we've
			 * mapped this one already. This can happen if
			 * devices share queues across queue maps.
			 */
			if (cpumask_test_cpu(i, hctx->cpumask))
				continue;

			cpumask_set_cpu(i, hctx->cpumask);
			hctx->type = j;
			ctx->index_hw[hctx->type] = hctx->nr_ctx;
			hctx->ctxs[hctx->nr_ctx++] = ctx;

			/*
			 * If the nr_ctx type overflows, we have exceeded the
			 * amount of sw queues we can support.
			 */
			BUG_ON(!hctx->nr_ctx);
		}

		for (; j < HCTX_MAX_TYPES; j++)
			ctx->hctxs[j] = blk_mq_map_queue_type(q,
					HCTX_TYPE_DEFAULT, i);
	}

	queue_for_each_hw_ctx(q, hctx, i) {
		/*
		 * If no software queues are mapped to this hardware queue,
		 * disable it and free the request entries.
		 */
		if (!hctx->nr_ctx) {
			/* Never unmap queue 0.  We need it as a
			 * fallback in case of a new remap fails
			 * allocation
			 */
			if (i && set->tags[i])
				blk_mq_free_map_and_requests(set, i);

			hctx->tags = NULL;
			continue;
		}

		hctx->tags = set->tags[i];
		WARN_ON(!hctx->tags);

		/*
		 * Set the map size to the number of mapped software queues.
		 * This is more accurate and more efficient than looping
		 * over all possibly mapped software queues.
		 */
		sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx);

		/*
		 * Initialize batch roundrobin counts
		 */
		hctx->next_cpu = blk_mq_first_mapped_cpu(hctx);
		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
	}
}

/*
 * Caller needs to ensure that we're either frozen/quiesced, or that
 * the queue isn't live yet.
 */
static void queue_set_hctx_shared(struct request_queue *q, bool shared)
{
	struct blk_mq_hw_ctx *hctx;
	int i;

	queue_for_each_hw_ctx(q, hctx, i) {
		if (shared)
			hctx->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
		else
			hctx->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
	}
}

static void blk_mq_update_tag_set_shared(struct blk_mq_tag_set *set,
					 bool shared)
{
	struct request_queue *q;

	lockdep_assert_held(&set->tag_list_lock);

	list_for_each_entry(q, &set->tag_list, tag_set_list) {
		blk_mq_freeze_queue(q);
		queue_set_hctx_shared(q, shared);
		blk_mq_unfreeze_queue(q);
	}
}

static void blk_mq_del_queue_tag_set(struct request_queue *q)
{
	struct blk_mq_tag_set *set = q->tag_set;

	mutex_lock(&set->tag_list_lock);
	list_del(&q->tag_set_list);
	if (list_is_singular(&set->tag_list)) {
		/* just transitioned to unshared */
		set->flags &= ~BLK_MQ_F_TAG_QUEUE_SHARED;
		/* update existing queue */
		blk_mq_update_tag_set_shared(set, false);
	}
	mutex_unlock(&set->tag_list_lock);
	INIT_LIST_HEAD(&q->tag_set_list);
}

static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
				     struct request_queue *q)
{
	mutex_lock(&set->tag_list_lock);

	/*
	 * Check to see if we're transitioning to shared (from 1 to 2 queues).
	 */
	if (!list_empty(&set->tag_list) &&
	    !(set->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
		set->flags |= BLK_MQ_F_TAG_QUEUE_SHARED;
		/* update existing queue */
		blk_mq_update_tag_set_shared(set, true);
	}
	if (set->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
		queue_set_hctx_shared(q, true);
	list_add_tail(&q->tag_set_list, &set->tag_list);

	mutex_unlock(&set->tag_list_lock);
}

/* All allocations will be freed in release handler of q->mq_kobj */
static int blk_mq_alloc_ctxs(struct request_queue *q)
{
	struct blk_mq_ctxs *ctxs;
	int cpu;

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

	ctxs->queue_ctx = alloc_percpu(struct blk_mq_ctx);
	if (!ctxs->queue_ctx)
		goto fail;

	for_each_possible_cpu(cpu) {
		struct blk_mq_ctx *ctx = per_cpu_ptr(ctxs->queue_ctx, cpu);
		ctx->ctxs = ctxs;
	}

	q->mq_kobj = &ctxs->kobj;
	q->queue_ctx = ctxs->queue_ctx;

	return 0;
 fail:
	kfree(ctxs);
	return -ENOMEM;
}

/*
 * It is the actual release handler for mq, but we do it from
 * request queue's release handler for avoiding use-after-free
 * and headache because q->mq_kobj shouldn't have been introduced,
 * but we can't group ctx/kctx kobj without it.
 */
void blk_mq_release(struct request_queue *q)
{
	struct blk_mq_hw_ctx *hctx, *next;
	int i;

	queue_for_each_hw_ctx(q, hctx, i)
		WARN_ON_ONCE(hctx && list_empty(&hctx->hctx_list));

	/* all hctx are in .unused_hctx_list now */
	list_for_each_entry_safe(hctx, next, &q->unused_hctx_list, hctx_list) {
		list_del_init(&hctx->hctx_list);
		kobject_put(&hctx->kobj);
	}

	kfree(q->queue_hw_ctx);

	/*
	 * release .mq_kobj and sw queue's kobject now because
	 * both share lifetime with request queue.
	 */
	blk_mq_sysfs_deinit(q);
}

struct request_queue *blk_mq_init_queue_data(struct blk_mq_tag_set *set,
		void *queuedata)
{
	struct request_queue *uninit_q, *q;

	uninit_q = blk_alloc_queue(set->numa_node);
	if (!uninit_q)
		return ERR_PTR(-ENOMEM);
	uninit_q->queuedata = queuedata;

	/*
	 * Initialize the queue without an elevator. device_add_disk() will do
	 * the initialization.
	 */
	q = blk_mq_init_allocated_queue(set, uninit_q, false);
	if (IS_ERR(q))
		blk_cleanup_queue(uninit_q);

	return q;
}
EXPORT_SYMBOL_GPL(blk_mq_init_queue_data);

struct request_queue *blk_mq_init_queue(struct blk_mq_tag_set *set)
{
	return blk_mq_init_queue_data(set, NULL);
}
EXPORT_SYMBOL(blk_mq_init_queue);

/*
 * Helper for setting up a queue with mq ops, given queue depth, and
 * the passed in mq ops flags.
 */
struct request_queue *blk_mq_init_sq_queue(struct blk_mq_tag_set *set,
					   const struct blk_mq_ops *ops,
					   unsigned int queue_depth,
					   unsigned int set_flags)
{
	struct request_queue *q;
	int ret;

	memset(set, 0, sizeof(*set));
	set->ops = ops;
	set->nr_hw_queues = 1;
	set->nr_maps = 1;
	set->queue_depth = queue_depth;
	set->numa_node = NUMA_NO_NODE;
	set->flags = set_flags;

	ret = blk_mq_alloc_tag_set(set);
	if (ret)
		return ERR_PTR(ret);

	q = blk_mq_init_queue(set);
	if (IS_ERR(q)) {
		blk_mq_free_tag_set(set);
		return q;
	}

	return q;
}
EXPORT_SYMBOL(blk_mq_init_sq_queue);

static struct blk_mq_hw_ctx *blk_mq_alloc_and_init_hctx(
		struct blk_mq_tag_set *set, struct request_queue *q,
		int hctx_idx, int node)
{
	struct blk_mq_hw_ctx *hctx = NULL, *tmp;

	/* reuse dead hctx first */
	spin_lock(&q->unused_hctx_lock);
	list_for_each_entry(tmp, &q->unused_hctx_list, hctx_list) {
		if (tmp->numa_node == node) {
			hctx = tmp;
			break;
		}
	}
	if (hctx)
		list_del_init(&hctx->hctx_list);
	spin_unlock(&q->unused_hctx_lock);

	if (!hctx)
		hctx = blk_mq_alloc_hctx(q, set, node);
	if (!hctx)
		goto fail;

	if (blk_mq_init_hctx(q, set, hctx, hctx_idx))
		goto free_hctx;

	return hctx;

 free_hctx:
	kobject_put(&hctx->kobj);
 fail:
	return NULL;
}

static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
						struct request_queue *q)
{
	int i, j, end;
	struct blk_mq_hw_ctx **hctxs = q->queue_hw_ctx;

	if (q->nr_hw_queues < set->nr_hw_queues) {
		struct blk_mq_hw_ctx **new_hctxs;

		new_hctxs = kcalloc_node(set->nr_hw_queues,
				       sizeof(*new_hctxs), GFP_KERNEL,
				       set->numa_node);
		if (!new_hctxs)
			return;
		if (hctxs)
			memcpy(new_hctxs, hctxs, q->nr_hw_queues *
			       sizeof(*hctxs));
		q->queue_hw_ctx = new_hctxs;
		kfree(hctxs);
		hctxs = new_hctxs;
	}

	/* protect against switching io scheduler  */
	mutex_lock(&q->sysfs_lock);
	for (i = 0; i < set->nr_hw_queues; i++) {
		int node;
		struct blk_mq_hw_ctx *hctx;

		node = blk_mq_hw_queue_to_node(&set->map[HCTX_TYPE_DEFAULT], i);
		/*
		 * If the hw queue has been mapped to another numa node,
		 * we need to realloc the hctx. If allocation fails, fallback
		 * to use the previous one.
		 */
		if (hctxs[i] && (hctxs[i]->numa_node == node))
			continue;

		hctx = blk_mq_alloc_and_init_hctx(set, q, i, node);
		if (hctx) {
			if (hctxs[i])
				blk_mq_exit_hctx(q, set, hctxs[i], i);
			hctxs[i] = hctx;
		} else {
			if (hctxs[i])
				pr_warn("Allocate new hctx on node %d fails,\
						fallback to previous one on node %d\n",
						node, hctxs[i]->numa_node);
			else
				break;
		}
	}
	/*
	 * Increasing nr_hw_queues fails. Free the newly allocated
	 * hctxs and keep the previous q->nr_hw_queues.
	 */
	if (i != set->nr_hw_queues) {
		j = q->nr_hw_queues;
		end = i;
	} else {
		j = i;
		end = q->nr_hw_queues;
		q->nr_hw_queues = set->nr_hw_queues;
	}

	for (; j < end; j++) {
		struct blk_mq_hw_ctx *hctx = hctxs[j];

		if (hctx) {
			if (hctx->tags)
				blk_mq_free_map_and_requests(set, j);
			blk_mq_exit_hctx(q, set, hctx, j);
			hctxs[j] = NULL;
		}
	}
	mutex_unlock(&q->sysfs_lock);
}

struct request_queue *blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
						  struct request_queue *q,
						  bool elevator_init)
{
	/* mark the queue as mq asap */
	q->mq_ops = set->ops;

	q->poll_cb = blk_stat_alloc_callback(blk_mq_poll_stats_fn,
					     blk_mq_poll_stats_bkt,
					     BLK_MQ_POLL_STATS_BKTS, q);
	if (!q->poll_cb)
		goto err_exit;

	if (blk_mq_alloc_ctxs(q))
		goto err_poll;

	/* init q->mq_kobj and sw queues' kobjects */
	blk_mq_sysfs_init(q);

	INIT_LIST_HEAD(&q->unused_hctx_list);
	spin_lock_init(&q->unused_hctx_lock);

	blk_mq_realloc_hw_ctxs(set, q);
	if (!q->nr_hw_queues)
		goto err_hctxs;

	INIT_WORK(&q->timeout_work, blk_mq_timeout_work);
	blk_queue_rq_timeout(q, set->timeout ? set->timeout : 30 * HZ);

	q->tag_set = set;

	q->queue_flags |= QUEUE_FLAG_MQ_DEFAULT;
	if (set->nr_maps > HCTX_TYPE_POLL &&
	    set->map[HCTX_TYPE_POLL].nr_queues)
		blk_queue_flag_set(QUEUE_FLAG_POLL, q);

	q->sg_reserved_size = INT_MAX;

	INIT_DELAYED_WORK(&q->requeue_work, blk_mq_requeue_work);
	INIT_LIST_HEAD(&q->requeue_list);
	spin_lock_init(&q->requeue_lock);

	q->nr_requests = set->queue_depth;

	/*
	 * Default to classic polling
	 */
	q->poll_nsec = BLK_MQ_POLL_CLASSIC;

	blk_mq_init_cpu_queues(q, set->nr_hw_queues);
	blk_mq_add_queue_tag_set(set, q);
	blk_mq_map_swqueue(q);

	if (elevator_init)
		elevator_init_mq(q);

	return q;

err_hctxs:
	kfree(q->queue_hw_ctx);
	q->nr_hw_queues = 0;
	blk_mq_sysfs_deinit(q);
err_poll:
	blk_stat_free_callback(q->poll_cb);
	q->poll_cb = NULL;
err_exit:
	q->mq_ops = NULL;
	return ERR_PTR(-ENOMEM);
}
EXPORT_SYMBOL(blk_mq_init_allocated_queue);

/* tags can _not_ be used after returning from blk_mq_exit_queue */
void blk_mq_exit_queue(struct request_queue *q)
{
	struct blk_mq_tag_set	*set = q->tag_set;

	blk_mq_del_queue_tag_set(q);
	blk_mq_exit_hw_queues(q, set, set->nr_hw_queues);
}

static int __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
{
	int i;

	for (i = 0; i < set->nr_hw_queues; i++) {
		if (!__blk_mq_alloc_map_and_request(set, i))
			goto out_unwind;
		cond_resched();
	}

	return 0;

out_unwind:
	while (--i >= 0)
		blk_mq_free_map_and_requests(set, i);

	return -ENOMEM;
}

/*
 * Allocate the request maps associated with this tag_set. Note that this
 * may reduce the depth asked for, if memory is tight. set->queue_depth
 * will be updated to reflect the allocated depth.
 */
static int blk_mq_alloc_map_and_requests(struct blk_mq_tag_set *set)
{
	unsigned int depth;
	int err;

	depth = set->queue_depth;
	do {
		err = __blk_mq_alloc_rq_maps(set);
		if (!err)
			break;

		set->queue_depth >>= 1;
		if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN) {
			err = -ENOMEM;
			break;
		}
	} while (set->queue_depth);

	if (!set->queue_depth || err) {
		pr_err("blk-mq: failed to allocate request map\n");
		return -ENOMEM;
	}

	if (depth != set->queue_depth)
		pr_info("blk-mq: reduced tag depth (%u -> %u)\n",
						depth, set->queue_depth);

	return 0;
}

static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
{
	/*
	 * blk_mq_map_queues() and multiple .map_queues() implementations
	 * expect that set->map[HCTX_TYPE_DEFAULT].nr_queues is set to the
	 * number of hardware queues.
	 */
	if (set->nr_maps == 1)
		set->map[HCTX_TYPE_DEFAULT].nr_queues = set->nr_hw_queues;

	if (set->ops->map_queues && !is_kdump_kernel()) {
		int i;

		/*
		 * transport .map_queues is usually done in the following
		 * way:
		 *
		 * for (queue = 0; queue < set->nr_hw_queues; queue++) {
		 * 	mask = get_cpu_mask(queue)
		 * 	for_each_cpu(cpu, mask)
		 * 		set->map[x].mq_map[cpu] = queue;
		 * }
		 *
		 * When we need to remap, the table has to be cleared for
		 * killing stale mapping since one CPU may not be mapped
		 * to any hw queue.
		 */
		for (i = 0; i < set->nr_maps; i++)
			blk_mq_clear_mq_map(&set->map[i]);

		return set->ops->map_queues(set);
	} else {
		BUG_ON(set->nr_maps > 1);
		return blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
	}
}

static int blk_mq_realloc_tag_set_tags(struct blk_mq_tag_set *set,
				  int cur_nr_hw_queues, int new_nr_hw_queues)
{
	struct blk_mq_tags **new_tags;

	if (cur_nr_hw_queues >= new_nr_hw_queues)
		return 0;

	new_tags = kcalloc_node(new_nr_hw_queues, sizeof(struct blk_mq_tags *),
				GFP_KERNEL, set->numa_node);
	if (!new_tags)
		return -ENOMEM;

	if (set->tags)
		memcpy(new_tags, set->tags, cur_nr_hw_queues *
		       sizeof(*set->tags));
	kfree(set->tags);
	set->tags = new_tags;
	set->nr_hw_queues = new_nr_hw_queues;

	return 0;
}

static int blk_mq_alloc_tag_set_tags(struct blk_mq_tag_set *set,
				int new_nr_hw_queues)
{
	return blk_mq_realloc_tag_set_tags(set, 0, new_nr_hw_queues);
}

/*
 * Alloc a tag set to be associated with one or more request queues.
 * May fail with EINVAL for various error conditions. May adjust the
 * requested depth down, if it's too large. In that case, the set
 * value will be stored in set->queue_depth.
 */
int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
{
	int i, ret;

	BUILD_BUG_ON(BLK_MQ_MAX_DEPTH > 1 << BLK_MQ_UNIQUE_TAG_BITS);

	if (!set->nr_hw_queues)
		return -EINVAL;
	if (!set->queue_depth)
		return -EINVAL;
	if (set->queue_depth < set->reserved_tags + BLK_MQ_TAG_MIN)
		return -EINVAL;

	if (!set->ops->queue_rq)
		return -EINVAL;

	if (!set->ops->get_budget ^ !set->ops->put_budget)
		return -EINVAL;

	if (set->queue_depth > BLK_MQ_MAX_DEPTH) {
		pr_info("blk-mq: reduced tag depth to %u\n",
			BLK_MQ_MAX_DEPTH);
		set->queue_depth = BLK_MQ_MAX_DEPTH;
	}

	if (!set->nr_maps)
		set->nr_maps = 1;
	else if (set->nr_maps > HCTX_MAX_TYPES)
		return -EINVAL;

	/*
	 * If a crashdump is active, then we are potentially in a very
	 * memory constrained environment. Limit us to 1 queue and
	 * 64 tags to prevent using too much memory.
	 */
	if (is_kdump_kernel()) {
		set->nr_hw_queues = 1;
		set->nr_maps = 1;
		set->queue_depth = min(64U, set->queue_depth);
	}
	/*
	 * There is no use for more h/w queues than cpus if we just have
	 * a single map
	 */
	if (set->nr_maps == 1 && set->nr_hw_queues > nr_cpu_ids)
		set->nr_hw_queues = nr_cpu_ids;

	if (blk_mq_alloc_tag_set_tags(set, set->nr_hw_queues) < 0)
		return -ENOMEM;

	ret = -ENOMEM;
	for (i = 0; i < set->nr_maps; i++) {
		set->map[i].mq_map = kcalloc_node(nr_cpu_ids,
						  sizeof(set->map[i].mq_map[0]),
						  GFP_KERNEL, set->numa_node);
		if (!set->map[i].mq_map)
			goto out_free_mq_map;
		set->map[i].nr_queues = is_kdump_kernel() ? 1 : set->nr_hw_queues;
	}

	ret = blk_mq_update_queue_map(set);
	if (ret)
		goto out_free_mq_map;

	ret = blk_mq_alloc_map_and_requests(set);
	if (ret)
		goto out_free_mq_map;

	if (blk_mq_is_sbitmap_shared(set->flags)) {
		atomic_set(&set->active_queues_shared_sbitmap, 0);

		if (blk_mq_init_shared_sbitmap(set, set->flags)) {
			ret = -ENOMEM;
			goto out_free_mq_rq_maps;
		}
	}

	mutex_init(&set->tag_list_lock);
	INIT_LIST_HEAD(&set->tag_list);

	return 0;

out_free_mq_rq_maps:
	for (i = 0; i < set->nr_hw_queues; i++)
		blk_mq_free_map_and_requests(set, i);
out_free_mq_map:
	for (i = 0; i < set->nr_maps; i++) {
		kfree(set->map[i].mq_map);
		set->map[i].mq_map = NULL;
	}
	kfree(set->tags);
	set->tags = NULL;
	return ret;
}
EXPORT_SYMBOL(blk_mq_alloc_tag_set);

void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
{
	int i, j;

	for (i = 0; i < set->nr_hw_queues; i++)
		blk_mq_free_map_and_requests(set, i);

	if (blk_mq_is_sbitmap_shared(set->flags))
		blk_mq_exit_shared_sbitmap(set);

	for (j = 0; j < set->nr_maps; j++) {
		kfree(set->map[j].mq_map);
		set->map[j].mq_map = NULL;
	}

	kfree(set->tags);
	set->tags = NULL;
}
EXPORT_SYMBOL(blk_mq_free_tag_set);

int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr)
{
	struct blk_mq_tag_set *set = q->tag_set;
	struct blk_mq_hw_ctx *hctx;
	int i, ret;

	if (!set)
		return -EINVAL;

	if (q->nr_requests == nr)
		return 0;

	blk_mq_freeze_queue(q);
	blk_mq_quiesce_queue(q);

	ret = 0;
	queue_for_each_hw_ctx(q, hctx, i) {
		if (!hctx->tags)
			continue;
		/*
		 * If we're using an MQ scheduler, just update the scheduler
		 * queue depth. This is similar to what the old code would do.
		 */
		if (!hctx->sched_tags) {
			ret = blk_mq_tag_update_depth(hctx, &hctx->tags, nr,
							false);
			if (!ret && blk_mq_is_sbitmap_shared(set->flags))
				blk_mq_tag_resize_shared_sbitmap(set, nr);
		} else {
			ret = blk_mq_tag_update_depth(hctx, &hctx->sched_tags,
							nr, true);
		}
		if (ret)
			break;
		if (q->elevator && q->elevator->type->ops.depth_updated)
			q->elevator->type->ops.depth_updated(hctx);
	}

	if (!ret)
		q->nr_requests = nr;

	blk_mq_unquiesce_queue(q);
	blk_mq_unfreeze_queue(q);

	return ret;
}

/*
 * request_queue and elevator_type pair.
 * It is just used by __blk_mq_update_nr_hw_queues to cache
 * the elevator_type associated with a request_queue.
 */
struct blk_mq_qe_pair {
	struct list_head node;
	struct request_queue *q;
	struct elevator_type *type;
};

/*
 * Cache the elevator_type in qe pair list and switch the
 * io scheduler to 'none'
 */
static bool blk_mq_elv_switch_none(struct list_head *head,
		struct request_queue *q)
{
	struct blk_mq_qe_pair *qe;

	if (!q->elevator)
		return true;

	qe = kmalloc(sizeof(*qe), GFP_NOIO | __GFP_NOWARN | __GFP_NORETRY);
	if (!qe)
		return false;

	INIT_LIST_HEAD(&qe->node);
	qe->q = q;
	qe->type = q->elevator->type;
	list_add(&qe->node, head);

	mutex_lock(&q->sysfs_lock);
	/*
	 * After elevator_switch_mq, the previous elevator_queue will be
	 * released by elevator_release. The reference of the io scheduler
	 * module get by elevator_get will also be put. So we need to get
	 * a reference of the io scheduler module here to prevent it to be
	 * removed.
	 */
	__module_get(qe->type->elevator_owner);
	elevator_switch_mq(q, NULL);
	mutex_unlock(&q->sysfs_lock);

	return true;
}

static void blk_mq_elv_switch_back(struct list_head *head,
		struct request_queue *q)
{
	struct blk_mq_qe_pair *qe;
	struct elevator_type *t = NULL;

	list_for_each_entry(qe, head, node)
		if (qe->q == q) {
			t = qe->type;
			break;
		}

	if (!t)
		return;

	list_del(&qe->node);
	kfree(qe);

	mutex_lock(&q->sysfs_lock);
	elevator_switch_mq(q, t);
	mutex_unlock(&q->sysfs_lock);
}

static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
							int nr_hw_queues)
{
	struct request_queue *q;
	LIST_HEAD(head);
	int prev_nr_hw_queues;

	lockdep_assert_held(&set->tag_list_lock);

	if (set->nr_maps == 1 && nr_hw_queues > nr_cpu_ids)
		nr_hw_queues = nr_cpu_ids;
	if (nr_hw_queues < 1)
		return;
	if (set->nr_maps == 1 && nr_hw_queues == set->nr_hw_queues)
		return;

	list_for_each_entry(q, &set->tag_list, tag_set_list)
		blk_mq_freeze_queue(q);
	/*
	 * Switch IO scheduler to 'none', cleaning up the data associated
	 * with the previous scheduler. We will switch back once we are done
	 * updating the new sw to hw queue mappings.
	 */
	list_for_each_entry(q, &set->tag_list, tag_set_list)
		if (!blk_mq_elv_switch_none(&head, q))
			goto switch_back;

	list_for_each_entry(q, &set->tag_list, tag_set_list) {
		blk_mq_debugfs_unregister_hctxs(q);
		blk_mq_sysfs_unregister(q);
	}

	prev_nr_hw_queues = set->nr_hw_queues;
	if (blk_mq_realloc_tag_set_tags(set, set->nr_hw_queues, nr_hw_queues) <
	    0)
		goto reregister;

	set->nr_hw_queues = nr_hw_queues;
fallback:
	blk_mq_update_queue_map(set);
	list_for_each_entry(q, &set->tag_list, tag_set_list) {
		blk_mq_realloc_hw_ctxs(set, q);
		if (q->nr_hw_queues != set->nr_hw_queues) {
			pr_warn("Increasing nr_hw_queues to %d fails, fallback to %d\n",
					nr_hw_queues, prev_nr_hw_queues);
			set->nr_hw_queues = prev_nr_hw_queues;
			blk_mq_map_queues(&set->map[HCTX_TYPE_DEFAULT]);
			goto fallback;
		}
		blk_mq_map_swqueue(q);
	}

reregister:
	list_for_each_entry(q, &set->tag_list, tag_set_list) {
		blk_mq_sysfs_register(q);
		blk_mq_debugfs_register_hctxs(q);
	}

switch_back:
	list_for_each_entry(q, &set->tag_list, tag_set_list)
		blk_mq_elv_switch_back(&head, q);

	list_for_each_entry(q, &set->tag_list, tag_set_list)
		blk_mq_unfreeze_queue(q);
}

void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
{
	mutex_lock(&set->tag_list_lock);
	__blk_mq_update_nr_hw_queues(set, nr_hw_queues);
	mutex_unlock(&set->tag_list_lock);
}
EXPORT_SYMBOL_GPL(blk_mq_update_nr_hw_queues);

/* Enable polling stats and return whether they were already enabled. */
static bool blk_poll_stats_enable(struct request_queue *q)
{
	if (test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
	    blk_queue_flag_test_and_set(QUEUE_FLAG_POLL_STATS, q))
		return true;
	blk_stat_add_callback(q, q->poll_cb);
	return false;
}

static void blk_mq_poll_stats_start(struct request_queue *q)
{
	/*
	 * We don't arm the callback if polling stats are not enabled or the
	 * callback is already active.
	 */
	if (!test_bit(QUEUE_FLAG_POLL_STATS, &q->queue_flags) ||
	    blk_stat_is_active(q->poll_cb))
		return;

	blk_stat_activate_msecs(q->poll_cb, 100);
}

static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb)
{
	struct request_queue *q = cb->data;
	int bucket;

	for (bucket = 0; bucket < BLK_MQ_POLL_STATS_BKTS; bucket++) {
		if (cb->stat[bucket].nr_samples)
			q->poll_stat[bucket] = cb->stat[bucket];
	}
}

static unsigned long blk_mq_poll_nsecs(struct request_queue *q,
				       struct request *rq)
{
	unsigned long ret = 0;
	int bucket;

	/*
	 * If stats collection isn't on, don't sleep but turn it on for
	 * future users
	 */
	if (!blk_poll_stats_enable(q))
		return 0;

	/*
	 * As an optimistic guess, use half of the mean service time
	 * for this type of request. We can (and should) make this smarter.
	 * For instance, if the completion latencies are tight, we can
	 * get closer than just half the mean. This is especially
	 * important on devices where the completion latencies are longer
	 * than ~10 usec. We do use the stats for the relevant IO size
	 * if available which does lead to better estimates.
	 */
	bucket = blk_mq_poll_stats_bkt(rq);
	if (bucket < 0)
		return ret;

	if (q->poll_stat[bucket].nr_samples)
		ret = (q->poll_stat[bucket].mean + 1) / 2;

	return ret;
}

static bool blk_mq_poll_hybrid_sleep(struct request_queue *q,
				     struct request *rq)
{
	struct hrtimer_sleeper hs;
	enum hrtimer_mode mode;
	unsigned int nsecs;
	ktime_t kt;

	if (rq->rq_flags & RQF_MQ_POLL_SLEPT)
		return false;

	/*
	 * If we get here, hybrid polling is enabled. Hence poll_nsec can be:
	 *
	 *  0:	use half of prev avg
	 * >0:	use this specific value
	 */
	if (q->poll_nsec > 0)
		nsecs = q->poll_nsec;
	else
		nsecs = blk_mq_poll_nsecs(q, rq);

	if (!nsecs)
		return false;

	rq->rq_flags |= RQF_MQ_POLL_SLEPT;

	/*
	 * This will be replaced with the stats tracking code, using
	 * 'avg_completion_time / 2' as the pre-sleep target.
	 */
	kt = nsecs;

	mode = HRTIMER_MODE_REL;
	hrtimer_init_sleeper_on_stack(&hs, CLOCK_MONOTONIC, mode);
	hrtimer_set_expires(&hs.timer, kt);

	do {
		if (blk_mq_rq_state(rq) == MQ_RQ_COMPLETE)
			break;
		set_current_state(TASK_UNINTERRUPTIBLE);
		hrtimer_sleeper_start_expires(&hs, mode);
		if (hs.task)
			io_schedule();
		hrtimer_cancel(&hs.timer);
		mode = HRTIMER_MODE_ABS;
	} while (hs.task && !signal_pending(current));

	__set_current_state(TASK_RUNNING);
	destroy_hrtimer_on_stack(&hs.timer);
	return true;
}

static bool blk_mq_poll_hybrid(struct request_queue *q,
			       struct blk_mq_hw_ctx *hctx, blk_qc_t cookie)
{
	struct request *rq;

	if (q->poll_nsec == BLK_MQ_POLL_CLASSIC)
		return false;

	if (!blk_qc_t_is_internal(cookie))
		rq = blk_mq_tag_to_rq(hctx->tags, blk_qc_t_to_tag(cookie));
	else {
		rq = blk_mq_tag_to_rq(hctx->sched_tags, blk_qc_t_to_tag(cookie));
		/*
		 * With scheduling, if the request has completed, we'll
		 * get a NULL return here, as we clear the sched tag when
		 * that happens. The request still remains valid, like always,
		 * so we should be safe with just the NULL check.
		 */
		if (!rq)
			return false;
	}

	return blk_mq_poll_hybrid_sleep(q, rq);
}

/**
 * blk_poll - poll for IO completions
 * @q:  the queue
 * @cookie: cookie passed back at IO submission time
 * @spin: whether to spin for completions
 *
 * Description:
 *    Poll for completions on the passed in queue. Returns number of
 *    completed entries found. If @spin is true, then blk_poll will continue
 *    looping until at least one completion is found, unless the task is
 *    otherwise marked running (or we need to reschedule).
 */
int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
{
	struct blk_mq_hw_ctx *hctx;
	long state;

	if (!blk_qc_t_valid(cookie) ||
	    !test_bit(QUEUE_FLAG_POLL, &q->queue_flags))
		return 0;

	if (current->plug)
		blk_flush_plug_list(current->plug, false);

	hctx = q->queue_hw_ctx[blk_qc_t_to_queue_num(cookie)];

	/*
	 * If we sleep, have the caller restart the poll loop to reset
	 * the state. Like for the other success return cases, the
	 * caller is responsible for checking if the IO completed. If
	 * the IO isn't complete, we'll get called again and will go
	 * straight to the busy poll loop. If specified not to spin,
	 * we also should not sleep.
	 */
	if (spin && blk_mq_poll_hybrid(q, hctx, cookie))
		return 1;

	hctx->poll_considered++;

	state = current->state;
	do {
		int ret;

		hctx->poll_invoked++;

		ret = q->mq_ops->poll(hctx);
		if (ret > 0) {
			hctx->poll_success++;
			__set_current_state(TASK_RUNNING);
			return ret;
		}

		if (signal_pending_state(state, current))
			__set_current_state(TASK_RUNNING);

		if (current->state == TASK_RUNNING)
			return 1;
		if (ret < 0 || !spin)
			break;
		cpu_relax();
	} while (!need_resched());

	__set_current_state(TASK_RUNNING);
	return 0;
}
EXPORT_SYMBOL_GPL(blk_poll);

unsigned int blk_mq_rq_cpu(struct request *rq)
{
	return rq->mq_ctx->cpu;
}
EXPORT_SYMBOL(blk_mq_rq_cpu);

static int __init blk_mq_init(void)
{
	int i;

	for_each_possible_cpu(i)
		init_llist_head(&per_cpu(blk_cpu_done, i));
	open_softirq(BLOCK_SOFTIRQ, blk_done_softirq);

	cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD,
				  "block/softirq:dead", NULL,
				  blk_softirq_cpu_dead);
	cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL,
				blk_mq_hctx_notify_dead);
	cpuhp_setup_state_multi(CPUHP_AP_BLK_MQ_ONLINE, "block/mq:online",
				blk_mq_hctx_notify_online,
				blk_mq_hctx_notify_offline);
	return 0;
}
subsys_initcall(blk_mq_init);

Privacy Policy