aboutsummaryrefslogtreecommitdiff
path: root/drivers/md/dm-thin.c
blob: 242ac2ea5f295c0bf2ad2db85fdd86812936851d (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
/*
 * Copyright (C) 2011-2012 Red Hat UK.
 *
 * This file is released under the GPL.
 */

#include "dm-thin-metadata.h"
#include "dm-bio-prison.h"
#include "dm.h"

#include <linux/device-mapper.h>
#include <linux/dm-io.h>
#include <linux/dm-kcopyd.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/rbtree.h>

#define	DM_MSG_PREFIX	"thin"

/*
 * Tunable constants
 */
#define ENDIO_HOOK_POOL_SIZE 1024
#define MAPPING_POOL_SIZE 1024
#define PRISON_CELLS 1024
#define COMMIT_PERIOD HZ
#define NO_SPACE_TIMEOUT_SECS 60

static unsigned no_space_timeout_secs = NO_SPACE_TIMEOUT_SECS;

DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(snapshot_copy_throttle,
		"A percentage of time allocated for copy on write");

/*
 * The block size of the device holding pool data must be
 * between 64KB and 1GB.
 */
#define DATA_DEV_BLOCK_SIZE_MIN_SECTORS (64 * 1024 >> SECTOR_SHIFT)
#define DATA_DEV_BLOCK_SIZE_MAX_SECTORS (1024 * 1024 * 1024 >> SECTOR_SHIFT)

/*
 * Device id is restricted to 24 bits.
 */
#define MAX_DEV_ID ((1 << 24) - 1)

/*
 * How do we handle breaking sharing of data blocks?
 * =================================================
 *
 * We use a standard copy-on-write btree to store the mappings for the
 * devices (note I'm talking about copy-on-write of the metadata here, not
 * the data).  When you take an internal snapshot you clone the root node
 * of the origin btree.  After this there is no concept of an origin or a
 * snapshot.  They are just two device trees that happen to point to the
 * same data blocks.
 *
 * When we get a write in we decide if it's to a shared data block using
 * some timestamp magic.  If it is, we have to break sharing.
 *
 * Let's say we write to a shared block in what was the origin.  The
 * steps are:
 *
 * i) plug io further to this physical block. (see bio_prison code).
 *
 * ii) quiesce any read io to that shared data block.  Obviously
 * including all devices that share this block.  (see dm_deferred_set code)
 *
 * iii) copy the data block to a newly allocate block.  This step can be
 * missed out if the io covers the block. (schedule_copy).
 *
 * iv) insert the new mapping into the origin's btree
 * (process_prepared_mapping).  This act of inserting breaks some
 * sharing of btree nodes between the two devices.  Breaking sharing only
 * effects the btree of that specific device.  Btrees for the other
 * devices that share the block never change.  The btree for the origin
 * device as it was after the last commit is untouched, ie. we're using
 * persistent data structures in the functional programming sense.
 *
 * v) unplug io to this physical block, including the io that triggered
 * the breaking of sharing.
 *
 * Steps (ii) and (iii) occur in parallel.
 *
 * The metadata _doesn't_ need to be committed before the io continues.  We
 * get away with this because the io is always written to a _new_ block.
 * If there's a crash, then:
 *
 * - The origin mapping will point to the old origin block (the shared
 * one).  This will contain the data as it was before the io that triggered
 * the breaking of sharing came in.
 *
 * - The snap mapping still points to the old block.  As it would after
 * the commit.
 *
 * The downside of this scheme is the timestamp magic isn't perfect, and
 * will continue to think that data block in the snapshot device is shared
 * even after the write to the origin has broken sharing.  I suspect data
 * blocks will typically be shared by many different devices, so we're
 * breaking sharing n + 1 times, rather than n, where n is the number of
 * devices that reference this data block.  At the moment I think the
 * benefits far, far outweigh the disadvantages.
 */

/*----------------------------------------------------------------*/

/*
 * Key building.
 */
static void build_data_key(struct dm_thin_device *td,
			   dm_block_t b, struct dm_cell_key *key)
{
	key->virtual = 0;
	key->dev = dm_thin_dev_id(td);
	key->block = b;
}

static void build_virtual_key(struct dm_thin_device *td, dm_block_t b,
			      struct dm_cell_key *key)
{
	key->virtual = 1;
	key->dev = dm_thin_dev_id(td);
	key->block = b;
}

/*----------------------------------------------------------------*/

/*
 * A pool device ties together a metadata device and a data device.  It
 * also provides the interface for creating and destroying internal
 * devices.
 */
struct dm_thin_new_mapping;

/*
 * The pool runs in 4 modes.  Ordered in degraded order for comparisons.
 */
enum pool_mode {
	PM_WRITE,		/* metadata may be changed */
	PM_OUT_OF_DATA_SPACE,	/* metadata may be changed, though data may not be allocated */
	PM_READ_ONLY,		/* metadata may not be changed */
	PM_FAIL,		/* all I/O fails */
};

struct pool_features {
	enum pool_mode mode;

	bool zero_new_blocks:1;
	bool discard_enabled:1;
	bool discard_passdown:1;
	bool error_if_no_space:1;
};

struct thin_c;
typedef void (*process_bio_fn)(struct thin_c *tc, struct bio *bio);
typedef void (*process_mapping_fn)(struct dm_thin_new_mapping *m);

struct pool {
	struct list_head list;
	struct dm_target *ti;	/* Only set if a pool target is bound */

	struct mapped_device *pool_md;
	struct block_device *md_dev;
	struct dm_pool_metadata *pmd;

	dm_block_t low_water_blocks;
	uint32_t sectors_per_block;
	int sectors_per_block_shift;

	struct pool_features pf;
	bool low_water_triggered:1;	/* A dm event has been sent */

	struct dm_bio_prison *prison;
	struct dm_kcopyd_client *copier;

	struct workqueue_struct *wq;
	struct work_struct worker;
	struct delayed_work waker;
	struct delayed_work no_space_timeout;

	unsigned long last_commit_jiffies;
	unsigned ref_count;

	spinlock_t lock;
	struct bio_list deferred_flush_bios;
	struct list_head prepared_mappings;
	struct list_head prepared_discards;
	struct list_head active_thins;

	struct dm_deferred_set *shared_read_ds;
	struct dm_deferred_set *all_io_ds;

	struct dm_thin_new_mapping *next_mapping;
	mempool_t *mapping_pool;

	process_bio_fn process_bio;
	process_bio_fn process_discard;

	process_mapping_fn process_prepared_mapping;
	process_mapping_fn process_prepared_discard;
};

static enum pool_mode get_pool_mode(struct pool *pool);
static void metadata_operation_failed(struct pool *pool, const char *op, int r);

/*
 * Target context for a pool.
 */
struct pool_c {
	struct dm_target *ti;
	struct pool *pool;
	struct dm_dev *data_dev;
	struct dm_dev *metadata_dev;
	struct dm_target_callbacks callbacks;

	dm_block_t low_water_blocks;
	struct pool_features requested_pf; /* Features requested during table load */
	struct pool_features adjusted_pf;  /* Features used after adjusting for constituent devices */
};

/*
 * Target context for a thin.
 */
struct thin_c {
	struct list_head list;
	struct dm_dev *pool_dev;
	struct dm_dev *origin_dev;
	dm_thin_id dev_id;

	struct pool *pool;
	struct dm_thin_device *td;
	bool requeue_mode:1;
	spinlock_t lock;
	struct bio_list deferred_bio_list;
	struct bio_list retry_on_resume_list;
	struct rb_root sort_bio_list; /* sorted list of deferred bios */

	/*
	 * Ensures the thin is not destroyed until the worker has finished
	 * iterating the active_thins list.
	 */
	atomic_t refcount;
	struct completion can_destroy;
};

/*----------------------------------------------------------------*/

/*
 * wake_worker() is used when new work is queued and when pool_resume is
 * ready to continue deferred IO processing.
 */
static void wake_worker(struct pool *pool)
{
	queue_work(pool->wq, &pool->worker);
}

/*----------------------------------------------------------------*/

static int bio_detain(struct pool *pool, struct dm_cell_key *key, struct bio *bio,
		      struct dm_bio_prison_cell **cell_result)
{
	int r;
	struct dm_bio_prison_cell *cell_prealloc;

	/*
	 * Allocate a cell from the prison's mempool.
	 * This might block but it can't fail.
	 */
	cell_prealloc = dm_bio_prison_alloc_cell(pool->prison, GFP_NOIO);

	r = dm_bio_detain(pool->prison, key, bio, cell_prealloc, cell_result);
	if (r)
		/*
		 * We reused an old cell; we can get rid of
		 * the new one.
		 */
		dm_bio_prison_free_cell(pool->prison, cell_prealloc);

	return r;
}

static void cell_release(struct pool *pool,
			 struct dm_bio_prison_cell *cell,
			 struct bio_list *bios)
{
	dm_cell_release(pool->prison, cell, bios);
	dm_bio_prison_free_cell(pool->prison, cell);
}

static void cell_release_no_holder(struct pool *pool,
				   struct dm_bio_prison_cell *cell,
				   struct bio_list *bios)
{
	dm_cell_release_no_holder(pool->prison, cell, bios);
	dm_bio_prison_free_cell(pool->prison, cell);
}

static void cell_defer_no_holder_no_free(struct thin_c *tc,
					 struct dm_bio_prison_cell *cell)
{
	struct pool *pool = tc->pool;
	unsigned long flags;

	spin_lock_irqsave(&tc->lock, flags);
	dm_cell_release_no_holder(pool->prison, cell, &tc->deferred_bio_list);
	spin_unlock_irqrestore(&tc->lock, flags);

	wake_worker(pool);
}

static void cell_error(struct pool *pool,
		       struct dm_bio_prison_cell *cell)
{
	dm_cell_error(pool->prison, cell);
	dm_bio_prison_free_cell(pool->prison, cell);
}

/*----------------------------------------------------------------*/

/*
 * A global list of pools that uses a struct mapped_device as a key.
 */
static struct dm_thin_pool_table {
	struct mutex mutex;
	struct list_head pools;
} dm_thin_pool_table;

static void pool_table_init(void)
{
	mutex_init(&dm_thin_pool_table.mutex);
	INIT_LIST_HEAD(&dm_thin_pool_table.pools);
}

static void __pool_table_insert(struct pool *pool)
{
	BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
	list_add(&pool->list, &dm_thin_pool_table.pools);
}

static void __pool_table_remove(struct pool *pool)
{
	BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
	list_del(&pool->list);
}

static struct pool *__pool_table_lookup(struct mapped_device *md)
{
	struct pool *pool = NULL, *tmp;

	BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));

	list_for_each_entry(tmp, &dm_thin_pool_table.pools, list) {
		if (tmp->pool_md == md) {
			pool = tmp;
			break;
		}
	}

	return pool;
}

static struct pool *__pool_table_lookup_metadata_dev(struct block_device *md_dev)
{
	struct pool *pool = NULL, *tmp;

	BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));

	list_for_each_entry(tmp, &dm_thin_pool_table.pools, list) {
		if (tmp->md_dev == md_dev) {
			pool = tmp;
			break;
		}
	}

	return pool;
}

/*----------------------------------------------------------------*/

struct dm_thin_endio_hook {
	struct thin_c *tc;
	struct dm_deferred_entry *shared_read_entry;
	struct dm_deferred_entry *all_io_entry;
	struct dm_thin_new_mapping *overwrite_mapping;
	struct rb_node rb_node;
};

static void requeue_bio_list(struct thin_c *tc, struct bio_list *master)
{
	struct bio *bio;
	struct bio_list bios;
	unsigned long flags;

	bio_list_init(&bios);

	spin_lock_irqsave(&tc->lock, flags);
	bio_list_merge(&bios, master);
	bio_list_init(master);
	spin_unlock_irqrestore(&tc->lock, flags);

	while ((bio = bio_list_pop(&bios)))
		bio_endio(bio, DM_ENDIO_REQUEUE);
}

static void requeue_io(struct thin_c *tc)
{
	requeue_bio_list(tc, &tc->deferred_bio_list);
	requeue_bio_list(tc, &tc->retry_on_resume_list);
}

static void error_thin_retry_list(struct thin_c *tc)
{
	struct bio *bio;
	unsigned long flags;
	struct bio_list bios;

	bio_list_init(&bios);

	spin_lock_irqsave(&tc->lock, flags);
	bio_list_merge(&bios, &tc->retry_on_resume_list);
	bio_list_init(&tc->retry_on_resume_list);
	spin_unlock_irqrestore(&tc->lock, flags);

	while ((bio = bio_list_pop(&bios)))
		bio_io_error(bio);
}

static void error_retry_list(struct pool *pool)
{
	struct thin_c *tc;

	rcu_read_lock();
	list_for_each_entry_rcu(tc, &pool->active_thins, list)
		error_thin_retry_list(tc);
	rcu_read_unlock();
}

/*
 * This section of code contains the logic for processing a thin device's IO.
 * Much of the code depends on pool object resources (lists, workqueues, etc)
 * but most is exclusively called from the thin target rather than the thin-pool
 * target.
 */

static bool block_size_is_power_of_two(struct pool *pool)
{
	return pool->sectors_per_block_shift >= 0;
}

static dm_block_t get_bio_block(struct thin_c *tc, struct bio *bio)
{
	struct pool *pool = tc->pool;
	sector_t block_nr = bio->bi_iter.bi_sector;

	if (block_size_is_power_of_two(pool))
		block_nr >>= pool->sectors_per_block_shift;
	else
		(void) sector_div(block_nr, pool->sectors_per_block);

	return block_nr;
}

static void remap(struct thin_c *tc, struct bio *bio, dm_block_t block)
{
	struct pool *pool = tc->pool;
	sector_t bi_sector = bio->bi_iter.bi_sector;

	bio->bi_bdev = tc->pool_dev->bdev;
	if (block_size_is_power_of_two(pool))
		bio->bi_iter.bi_sector =
			(block << pool->sectors_per_block_shift) |
			(bi_sector & (pool->sectors_per_block - 1));
	else
		bio->bi_iter.bi_sector = (block * pool->sectors_per_block) +
				 sector_div(bi_sector, pool->sectors_per_block);
}

static void remap_to_origin(struct thin_c *tc, struct bio *bio)
{
	bio->bi_bdev = tc->origin_dev->bdev;
}

static int bio_triggers_commit(struct thin_c *tc, struct bio *bio)
{
	return (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) &&
		dm_thin_changed_this_transaction(tc->td);
}

static void inc_all_io_entry(struct pool *pool, struct bio *bio)
{
	struct dm_thin_endio_hook *h;

	if (bio->bi_rw & REQ_DISCARD)
		return;

	h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
	h->all_io_entry = dm_deferred_entry_inc(pool->all_io_ds);
}

static void issue(struct thin_c *tc, struct bio *bio)
{
	struct pool *pool = tc->pool;
	unsigned long flags;

	if (!bio_triggers_commit(tc, bio)) {
		generic_make_request(bio);
		return;
	}

	/*
	 * Complete bio with an error if earlier I/O caused changes to
	 * the metadata that can't be committed e.g, due to I/O errors
	 * on the metadata device.
	 */
	if (dm_thin_aborted_changes(tc->td)) {
		bio_io_error(bio);
		return;
	}

	/*
	 * Batch together any bios that trigger commits and then issue a
	 * single commit for them in process_deferred_bios().
	 */
	spin_lock_irqsave(&pool->lock, flags);
	bio_list_add(&pool->deferred_flush_bios, bio);
	spin_unlock_irqrestore(&pool->lock, flags);
}

static void remap_to_origin_and_issue(struct thin_c *tc, struct bio *bio)
{
	remap_to_origin(tc, bio);
	issue(tc, bio);
}

static void remap_and_issue(struct thin_c *tc, struct bio *bio,
			    dm_block_t block)
{
	remap(tc, bio, block);
	issue(tc, bio);
}

/*----------------------------------------------------------------*/

/*
 * Bio endio functions.
 */
struct dm_thin_new_mapping {
	struct list_head list;

	bool quiesced:1;
	bool prepared:1;
	bool pass_discard:1;
	bool definitely_not_shared:1;

	int err;
	struct thin_c *tc;
	dm_block_t virt_block;
	dm_block_t data_block;
	struct dm_bio_prison_cell *cell, *cell2;

	/*
	 * If the bio covers the whole area of a block then we can avoid
	 * zeroing or copying.  Instead this bio is hooked.  The bio will
	 * still be in the cell, so care has to be taken to avoid issuing
	 * the bio twice.
	 */
	struct bio *bio;
	bio_end_io_t *saved_bi_end_io;
};

static void __maybe_add_mapping(struct dm_thin_new_mapping *m)
{
	struct pool *pool = m->tc->pool;

	if (m->quiesced && m->prepared) {
		list_add_tail(&m->list, &pool->prepared_mappings);
		wake_worker(pool);
	}
}

static void copy_complete(int read_err, unsigned long write_err, void *context)
{
	unsigned long flags;
	struct dm_thin_new_mapping *m = context;
	struct pool *pool = m->tc->pool;

	m->err = read_err || write_err ? -EIO : 0;

	spin_lock_irqsave(&pool->lock, flags);
	m->prepared = true;
	__maybe_add_mapping(m);
	spin_unlock_irqrestore(&pool->lock, flags);
}

static void overwrite_endio(struct bio *bio, int err)
{
	unsigned long flags;
	struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
	struct dm_thin_new_mapping *m = h->overwrite_mapping;
	struct pool *pool = m->tc->pool;

	m->err = err;

	spin_lock_irqsave(&pool->lock, flags);
	m->prepared = true;
	__maybe_add_mapping(m);
	spin_unlock_irqrestore(&pool->lock, flags);
}

/*----------------------------------------------------------------*/

/*
 * Workqueue.
 */

/*
 * Prepared mapping jobs.
 */

/*
 * This sends the bios in the cell back to the deferred_bios list.
 */
static void cell_defer(struct thin_c *tc, struct dm_bio_prison_cell *cell)
{
	struct pool *pool = tc->pool;
	unsigned long flags;

	spin_lock_irqsave(&tc->lock, flags);
	cell_release(pool, cell, &tc->deferred_bio_list);
	spin_unlock_irqrestore(&tc->lock, flags);

	wake_worker(pool);
}

/*
 * Same as cell_defer above, except it omits the original holder of the cell.
 */
static void cell_defer_no_holder(struct thin_c *tc, struct dm_bio_prison_cell *cell)
{
	struct pool *pool = tc->pool;
	unsigned long flags;

	spin_lock_irqsave(&tc->lock, flags);
	cell_release_no_holder(pool, cell, &tc->deferred_bio_list);
	spin_unlock_irqrestore(&tc->lock, flags);

	wake_worker(pool);
}

static void process_prepared_mapping_fail(struct dm_thin_new_mapping *m)
{
	if (m->bio) {
		m->bio->bi_end_io = m->saved_bi_end_io;
		atomic_inc(&m->bio->bi_remaining);
	}
	cell_error(m->tc->pool, m->cell);
	list_del(&m->list);
	mempool_free(m, m->tc->pool->mapping_pool);
}

static void process_prepared_mapping(struct dm_thin_new_mapping *m)
{
	struct thin_c *tc = m->tc;
	struct pool *pool = tc->pool;
	struct bio *bio;
	int r;

	bio = m->bio;
	if (bio) {
		bio->bi_end_io = m->saved_bi_end_io;
		atomic_inc(&bio->bi_remaining);
	}

	if (m->err) {
		cell_error(pool, m->cell);
		goto out;
	}

	/*
	 * Commit the prepared block into the mapping btree.
	 * Any I/O for this block arriving after this point will get
	 * remapped to it directly.
	 */
	r = dm_thin_insert_block(tc->td, m->virt_block, m->data_block);
	if (r) {
		metadata_operation_failed(pool, "dm_thin_insert_block", r);
		cell_error(pool, m->cell);
		goto out;
	}

	/*
	 * Release any bios held while the block was being provisioned.
	 * If we are processing a write bio that completely covers the block,
	 * we already processed it so can ignore it now when processing
	 * the bios in the cell.
	 */
	if (bio) {
		cell_defer_no_holder(tc, m->cell);
		bio_endio(bio, 0);
	} else
		cell_defer(tc, m->cell);

out:
	list_del(&m->list);
	mempool_free(m, pool->mapping_pool);
}

static void process_prepared_discard_fail(struct dm_thin_new_mapping *m)
{
	struct thin_c *tc = m->tc;

	bio_io_error(m->bio);
	cell_defer_no_holder(tc, m->cell);
	cell_defer_no_holder(tc, m->cell2);
	mempool_free(m, tc->pool->mapping_pool);
}

static void process_prepared_discard_passdown(struct dm_thin_new_mapping *m)
{
	struct thin_c *tc = m->tc;

	inc_all_io_entry(tc->pool, m->bio);
	cell_defer_no_holder(tc, m->cell);
	cell_defer_no_holder(tc, m->cell2);

	if (m->pass_discard)
		if (m->definitely_not_shared)
			remap_and_issue(tc, m->bio, m->data_block);
		else {
			bool used = false;
			if (dm_pool_block_is_used(tc->pool->pmd, m->data_block, &used) || used)
				bio_endio(m->bio, 0);
			else
				remap_and_issue(tc, m->bio, m->data_block);
		}
	else
		bio_endio(m->bio, 0);

	mempool_free(m, tc->pool->mapping_pool);
}

static void process_prepared_discard(struct dm_thin_new_mapping *m)
{
	int r;
	struct thin_c *tc = m->tc;

	r = dm_thin_remove_block(tc->td, m->virt_block);
	if (r)
		DMERR_LIMIT("dm_thin_remove_block() failed");

	process_prepared_discard_passdown(m);
}

static void process_prepared(struct pool *pool, struct list_head *head,
			     process_mapping_fn *fn)
{
	unsigned long flags;
	struct list_head maps;
	struct dm_thin_new_mapping *m, *tmp;

	INIT_LIST_HEAD(&maps);
	spin_lock_irqsave(&pool->lock, flags);
	list_splice_init(head, &maps);
	spin_unlock_irqrestore(&pool->lock, flags);

	list_for_each_entry_safe(m, tmp, &maps, list)
		(*fn)(m);
}

/*
 * Deferred bio jobs.
 */
static int io_overlaps_block(struct pool *pool, struct bio *bio)
{
	return bio->bi_iter.bi_size ==
		(pool->sectors_per_block << SECTOR_SHIFT);
}

static int io_overwrites_block(struct pool *pool, struct bio *bio)
{
	return (bio_data_dir(bio) == WRITE) &&
		io_overlaps_block(pool, bio);
}

static void save_and_set_endio(struct bio *bio, bio_end_io_t **save,
			       bio_end_io_t *fn)
{
	*save = bio->bi_end_io;
	bio->bi_end_io = fn;
}

static int ensure_next_mapping(struct pool *pool)
{
	if (pool->next_mapping)
		return 0;

	pool->next_mapping = mempool_alloc(pool->mapping_pool, GFP_ATOMIC);

	return pool->next_mapping ? 0 : -ENOMEM;
}

static struct dm_thin_new_mapping *get_next_mapping(struct pool *pool)
{
	struct dm_thin_new_mapping *m = pool->next_mapping;

	BUG_ON(!pool->next_mapping);

	memset(m, 0, sizeof(struct dm_thin_new_mapping));
	INIT_LIST_HEAD(&m->list);
	m->bio = NULL;

	pool->next_mapping = NULL;

	return m;
}

static void schedule_copy(struct thin_c *tc, dm_block_t virt_block,
			  struct dm_dev *origin, dm_block_t data_origin,
			  dm_block_t data_dest,
			  struct dm_bio_prison_cell *cell, struct bio *bio)
{
	int r;
	struct pool *pool = tc->pool;
	struct dm_thin_new_mapping *m = get_next_mapping(pool);

	m->tc = tc;
	m->virt_block = virt_block;
	m->data_block = data_dest;
	m->cell = cell;

	if (!dm_deferred_set_add_work(pool->shared_read_ds, &m->list))
		m->quiesced = true;

	/*
	 * IO to pool_dev remaps to the pool target's data_dev.
	 *
	 * If the whole block of data is being overwritten, we can issue the
	 * bio immediately. Otherwise we use kcopyd to clone the data first.
	 */
	if (io_overwrites_block(pool, bio)) {
		struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));

		h->overwrite_mapping = m;
		m->bio = bio;
		save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
		inc_all_io_entry(pool, bio);
		remap_and_issue(tc, bio, data_dest);
	} else {
		struct dm_io_region from, to;

		from.bdev = origin->bdev;
		from.sector = data_origin * pool->sectors_per_block;
		from.count = pool->sectors_per_block;

		to.bdev = tc->pool_dev->bdev;
		to.sector = data_dest * pool->sectors_per_block;
		to.count = pool->sectors_per_block;

		r = dm_kcopyd_copy(pool->copier, &from, 1, &to,
				   0, copy_complete, m);
		if (r < 0) {
			mempool_free(m, pool->mapping_pool);
			DMERR_LIMIT("dm_kcopyd_copy() failed");
			cell_error(pool, cell);
		}
	}
}

static void schedule_internal_copy(struct thin_c *tc, dm_block_t virt_block,
				   dm_block_t data_origin, dm_block_t data_dest,
				   struct dm_bio_prison_cell *cell, struct bio *bio)
{
	schedule_copy(tc, virt_block, tc->pool_dev,
		      data_origin, data_dest, cell, bio);
}

static void schedule_external_copy(struct thin_c *tc, dm_block_t virt_block,
				   dm_block_t data_dest,
				   struct dm_bio_prison_cell *cell, struct bio *bio)
{
	schedule_copy(tc, virt_block, tc->origin_dev,
		      virt_block, data_dest, cell, bio);
}

static void schedule_zero(struct thin_c *tc, dm_block_t virt_block,
			  dm_block_t data_block, struct dm_bio_prison_cell *cell,
			  struct bio *bio)
{
	struct pool *pool = tc->pool;
	struct dm_thin_new_mapping *m = get_next_mapping(pool);

	m->quiesced = true;
	m->prepared = false;
	m->tc = tc;
	m->virt_block = virt_block;
	m->data_block = data_block;
	m->cell = cell;

	/*
	 * If the whole block of data is being overwritten or we are not
	 * zeroing pre-existing data, we can issue the bio immediately.
	 * Otherwise we use kcopyd to zero the data first.
	 */
	if (!pool->pf.zero_new_blocks)
		process_prepared_mapping(m);

	else if (io_overwrites_block(pool, bio)) {
		struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));

		h->overwrite_mapping = m;
		m->bio = bio;
		save_and_set_endio(bio, &m->saved_bi_end_io, overwrite_endio);
		inc_all_io_entry(pool, bio);
		remap_and_issue(tc, bio, data_block);
	} else {
		int r;
		struct dm_io_region to;

		to.bdev = tc->pool_dev->bdev;
		to.sector = data_block * pool->sectors_per_block;
		to.count = pool->sectors_per_block;

		r = dm_kcopyd_zero(pool->copier, 1, &to, 0, copy_complete, m);
		if (r < 0) {
			mempool_free(m, pool->mapping_pool);
			DMERR_LIMIT("dm_kcopyd_zero() failed");
			cell_error(pool, cell);
		}
	}
}

/*
 * A non-zero return indicates read_only or fail_io mode.
 * Many callers don't care about the return value.
 */
static int commit(struct pool *pool)
{
	int r;

	if (get_pool_mode(pool) >= PM_READ_ONLY)
		return -EINVAL;

	r = dm_pool_commit_metadata(pool->pmd);
	if (r)
		metadata_operation_failed(pool, "dm_pool_commit_metadata", r);

	return r;
}

static void check_low_water_mark(struct pool *pool, dm_block_t free_blocks)
{
	unsigned long flags;

	if (free_blocks <= pool->low_water_blocks && !pool->low_water_triggered) {
		DMWARN("%s: reached low water mark for data device: sending event.",
		       dm_device_name(pool->pool_md));
		spin_lock_irqsave(&pool->lock, flags);
		pool->low_water_triggered = true;
		spin_unlock_irqrestore(&pool->lock, flags);
		dm_table_event(pool->ti->table);
	}
}

static void set_pool_mode(struct pool *pool, enum pool_mode new_mode);

static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
{
	int r;
	dm_block_t free_blocks;
	struct pool *pool = tc->pool;

	if (WARN_ON(get_pool_mode(pool) != PM_WRITE))
		return -EINVAL;

	r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
	if (r) {
		metadata_operation_failed(pool, "dm_pool_get_free_block_count", r);
		return r;
	}

	check_low_water_mark(pool, free_blocks);

	if (!free_blocks) {
		/*
		 * Try to commit to see if that will free up some
		 * more space.
		 */
		r = commit(pool);
		if (r)
			return r;

		r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
		if (r) {
			metadata_operation_failed(pool, "dm_pool_get_free_block_count", r);
			return r;
		}

		if (!free_blocks) {
			set_pool_mode(pool, PM_OUT_OF_DATA_SPACE);
			return -ENOSPC;
		}
	}

	r = dm_pool_alloc_data_block(pool->pmd, result);
	if (r) {
		metadata_operation_failed(pool, "dm_pool_alloc_data_block", r);
		return r;
	}

	return 0;
}

/*
 * If we have run out of space, queue bios until the device is
 * resumed, presumably after having been reloaded with more space.
 */
static void retry_on_resume(struct bio *bio)
{
	struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
	struct thin_c *tc = h->tc;
	unsigned long flags;

	spin_lock_irqsave(&tc->lock, flags);
	bio_list_add(&tc->retry_on_resume_list, bio);
	spin_unlock_irqrestore(&tc->lock, flags);
}

static bool should_error_unserviceable_bio(struct pool *pool)
{
	enum pool_mode m = get_pool_mode(pool);

	switch (m) {
	case PM_WRITE:
		/* Shouldn't get here */
		DMERR_LIMIT("bio unserviceable, yet pool is in PM_WRITE mode");
		return true;

	case PM_OUT_OF_DATA_SPACE:
		return pool->pf.error_if_no_space;

	case PM_READ_ONLY:
	case PM_FAIL:
		return true;
	default:
		/* Shouldn't get here */
		DMERR_LIMIT("bio unserviceable, yet pool has an unknown mode");
		return true;
	}
}

static void handle_unserviceable_bio(struct pool *pool, struct bio *bio)
{
	if (should_error_unserviceable_bio(pool))
		bio_io_error(bio);
	else
		retry_on_resume(bio);
}

static void retry_bios_on_resume(struct pool *pool, struct dm_bio_prison_cell *cell)
{
	struct bio *bio;
	struct bio_list bios;

	if (should_error_unserviceable_bio(pool)) {
		cell_error(pool, cell);
		return;
	}

	bio_list_init(&bios);
	cell_release(pool, cell, &bios);

	if (should_error_unserviceable_bio(pool))
		while ((bio = bio_list_pop(&bios)))
			bio_io_error(bio);
	else
		while ((bio = bio_list_pop(&bios)))
			retry_on_resume(bio);
}

static void process_discard(struct thin_c *tc, struct bio *bio)
{
	int r;
	unsigned long flags;
	struct pool *pool = tc->pool;
	struct dm_bio_prison_cell *cell, *cell2;
	struct dm_cell_key key, key2;
	dm_block_t block = get_bio_block(tc, bio);
	struct dm_thin_lookup_result lookup_result;
	struct dm_thin_new_mapping *m;

	build_virtual_key(tc->td, block, &key);
	if (bio_detain(tc->pool, &key, bio, &cell))
		return;

	r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
	switch (r) {
	case 0:
		/*
		 * Check nobody is fiddling with this pool block.  This can
		 * happen if someone's in the process of breaking sharing
		 * on this block.
		 */
		build_data_key(tc->td, lookup_result.block, &key2);
		if (bio_detain(tc->pool, &key2, bio, &cell2)) {
			cell_defer_no_holder(tc, cell);
			break;
		}

		if (io_overlaps_block(pool, bio)) {
			/*
			 * IO may still be going to the destination block.  We must
			 * quiesce before we can do the removal.
			 */
			m = get_next_mapping(pool);
			m->tc = tc;
			m->pass_discard = pool->pf.discard_passdown;
			m->definitely_not_shared = !lookup_result.shared;
			m->virt_block = block;
			m->data_block = lookup_result.block;
			m->cell = cell;
			m->cell2 = cell2;
			m->bio = bio;

			if (!dm_deferred_set_add_work(pool->all_io_ds, &m->list)) {
				spin_lock_irqsave(&pool->lock, flags);
				list_add_tail(&m->list, &pool->prepared_discards);
				spin_unlock_irqrestore(&pool->lock, flags);
				wake_worker(pool);
			}
		} else {
			inc_all_io_entry(pool, bio);
			cell_defer_no_holder(tc, cell);
			cell_defer_no_holder(tc, cell2);

			/*
			 * The DM core makes sure that the discard doesn't span
			 * a block boundary.  So we submit the discard of a
			 * partial block appropriately.
			 */
			if ((!lookup_result.shared) && pool->pf.discard_passdown)
				remap_and_issue(tc, bio, lookup_result.block);
			else
				bio_endio(bio, 0);
		}
		break;

	case -ENODATA:
		/*
		 * It isn't provisioned, just forget it.
		 */
		cell_defer_no_holder(tc, cell);
		bio_endio(bio, 0);
		break;

	default:
		DMERR_LIMIT("%s: dm_thin_find_block() failed: error = %d",
			    __func__, r);
		cell_defer_no_holder(tc, cell);
		bio_io_error(bio);
		break;
	}
}

static void break_sharing(struct thin_c *tc, struct bio *bio, dm_block_t block,
			  struct dm_cell_key *key,
			  struct dm_thin_lookup_result *lookup_result,
			  struct dm_bio_prison_cell *cell)
{
	int r;
	dm_block_t data_block;
	struct pool *pool = tc->pool;

	r = alloc_data_block(tc, &data_block);
	switch (r) {
	case 0:
		schedule_internal_copy(tc, block, lookup_result->block,
				       data_block, cell, bio);
		break;

	case -ENOSPC:
		retry_bios_on_resume(pool, cell);
		break;

	default:
		DMERR_LIMIT("%s: alloc_data_block() failed: error = %d",
			    __func__, r);
		cell_error(pool, cell);
		break;
	}
}

static void process_shared_bio(struct thin_c *tc, struct bio *bio,
			       dm_block_t block,
			       struct dm_thin_lookup_result *lookup_result)
{
	struct dm_bio_prison_cell *cell;
	struct pool *pool = tc->pool;
	struct dm_cell_key key;

	/*
	 * If cell is already occupied, then sharing is already in the process
	 * of being broken so we have nothing further to do here.
	 */
	build_data_key(tc->td, lookup_result->block, &key);
	if (bio_detain(pool, &key, bio, &cell))
		return;

	if (bio_data_dir(bio) == WRITE && bio->bi_iter.bi_size)
		break_sharing(tc, bio, block, &key, lookup_result, cell);
	else {
		struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));

		h->shared_read_entry = dm_deferred_entry_inc(pool->shared_read_ds);
		inc_all_io_entry(pool, bio);
		cell_defer_no_holder(tc, cell);

		remap_and_issue(tc, bio, lookup_result->block);
	}
}

static void provision_block(struct thin_c *tc, struct bio *bio, dm_block_t block,
			    struct dm_bio_prison_cell *cell)
{
	int r;
	dm_block_t data_block;
	struct pool *pool = tc->pool;

	/*
	 * Remap empty bios (flushes) immediately, without provisioning.
	 */
	if (!bio->bi_iter.bi_size) {
		inc_all_io_entry(pool, bio);
		cell_defer_no_holder(tc, cell);

		remap_and_issue(tc, bio, 0);
		return;
	}

	/*
	 * Fill read bios with zeroes and complete them immediately.
	 */
	if (bio_data_dir(bio) == READ) {
		zero_fill_bio(bio);
		cell_defer_no_holder(tc, cell);
		bio_endio(bio, 0);
		return;
	}

	r = alloc_data_block(tc, &data_block);
	switch (r) {
	case 0:
		if (tc->origin_dev)
			schedule_external_copy(tc, block, data_block, cell, bio);
		else
			schedule_zero(tc, block, data_block, cell, bio);
		break;

	case -ENOSPC:
		retry_bios_on_resume(pool, cell);
		break;

	default:
		DMERR_LIMIT("%s: alloc_data_block() failed: error = %d",
			    __func__, r);
		cell_error(pool, cell);
		break;
	}
}

static void process_bio(struct thin_c *tc, struct bio *bio)
{
	int r;
	struct pool *pool = tc->pool;
	dm_block_t block = get_bio_block(tc, bio);
	struct dm_bio_prison_cell *cell;
	struct dm_cell_key key;
	struct dm_thin_lookup_result lookup_result;

	/*
	 * If cell is already occupied, then the block is already
	 * being provisioned so we have nothing further to do here.
	 */
	build_virtual_key(tc->td, block, &key);
	if (bio_detain(pool, &key, bio, &cell))
		return;

	r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
	switch (r) {
	case 0:
		if (lookup_result.shared) {
			process_shared_bio(tc, bio, block, &lookup_result);
			cell_defer_no_holder(tc, cell); /* FIXME: pass this cell into process_shared? */
		} else {
			inc_all_io_entry(pool, bio);
			cell_defer_no_holder(tc, cell);

			remap_and_issue(tc, bio, lookup_result.block);
		}
		break;

	case -ENODATA:
		if (bio_data_dir(bio) == READ && tc->origin_dev) {
			inc_all_io_entry(pool, bio);
			cell_defer_no_holder(tc, cell);

			remap_to_origin_and_issue(tc, bio);
		} else
			provision_block(tc, bio, block, cell);
		break;

	default:
		DMERR_LIMIT("%s: dm_thin_find_block() failed: error = %d",
			    __func__, r);
		cell_defer_no_holder(tc, cell);
		bio_io_error(bio);
		break;
	}
}

static void process_bio_read_only(struct thin_c *tc, struct bio *bio)
{
	int r;
	int rw = bio_data_dir(bio);
	dm_block_t block = get_bio_block(tc, bio);
	struct dm_thin_lookup_result lookup_result;

	r = dm_thin_find_block(tc->td, block, 1, &lookup_result);
	switch (r) {
	case 0:
		if (lookup_result.shared && (rw == WRITE) && bio->bi_iter.bi_size)
			handle_unserviceable_bio(tc->pool, bio);
		else {
			inc_all_io_entry(tc->pool, bio);
			remap_and_issue(tc, bio, lookup_result.block);
		}
		break;

	case -ENODATA:
		if (rw != READ) {
			handle_unserviceable_bio(tc->pool, bio);
			break;
		}

		if (tc->origin_dev) {
			inc_all_io_entry(tc->pool, bio);
			remap_to_origin_and_issue(tc, bio);
			break;
		}

		zero_fill_bio(bio);
		bio_endio(bio, 0);
		break;

	default:
		DMERR_LIMIT("%s: dm_thin_find_block() failed: error = %d",
			    __func__, r);
		bio_io_error(bio);
		break;
	}
}

static void process_bio_success(struct thin_c *tc, struct bio *bio)
{
	bio_endio(bio, 0);
}

static void process_bio_fail(struct thin_c *tc, struct bio *bio)
{
	bio_io_error(bio);
}

/*
 * FIXME: should we also commit due to size of transaction, measured in
 * metadata blocks?
 */
static int need_commit_due_to_time(struct pool *pool)
{
	return jiffies < pool->last_commit_jiffies ||
	       jiffies > pool->last_commit_jiffies + COMMIT_PERIOD;
}

#define thin_pbd(node) rb_entry((node), struct dm_thin_endio_hook, rb_node)
#define thin_bio(pbd) dm_bio_from_per_bio_data((pbd), sizeof(struct dm_thin_endio_hook))

static void __thin_bio_rb_add(struct thin_c *tc, struct bio *bio)
{
	struct rb_node **rbp, *parent;
	struct dm_thin_endio_hook *pbd;
	sector_t bi_sector = bio->bi_iter.bi_sector;

	rbp = &tc->sort_bio_list.rb_node;
	parent = NULL;
	while (*rbp) {
		parent = *rbp;
		pbd = thin_pbd(parent);

		if (bi_sector < thin_bio(pbd)->bi_iter.bi_sector)
			rbp = &(*rbp)->rb_left;
		else
			rbp = &(*rbp)->rb_right;
	}

	pbd = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
	rb_link_node(&pbd->rb_node, parent, rbp);
	rb_insert_color(&pbd->rb_node, &tc->sort_bio_list);
}

static void __extract_sorted_bios(struct thin_c *tc)
{
	struct rb_node *node;
	struct dm_thin_endio_hook *pbd;
	struct bio *bio;

	for (node = rb_first(&tc->sort_bio_list); node; node = rb_next(node)) {
		pbd = thin_pbd(node);
		bio = thin_bio(pbd);

		bio_list_add(&tc->deferred_bio_list, bio);
		rb_erase(&pbd->rb_node, &tc->sort_bio_list);
	}

	WARN_ON(!RB_EMPTY_ROOT(&tc->sort_bio_list));
}

static void __sort_thin_deferred_bios(struct thin_c *tc)
{
	struct bio *bio;
	struct bio_list bios;

	bio_list_init(&bios);
	bio_list_merge(&bios, &tc->deferred_bio_list);
	bio_list_init(&tc->deferred_bio_list);

	/* Sort deferred_bio_list using rb-tree */
	while ((bio = bio_list_pop(&bios)))
		__thin_bio_rb_add(tc, bio);

	/*
	 * Transfer the sorted bios in sort_bio_list back to
	 * deferred_bio_list to allow lockless submission of
	 * all bios.
	 */
	__extract_sorted_bios(tc);
}

static void process_thin_deferred_bios(struct thin_c *tc)
{
	struct pool *pool = tc->pool;
	unsigned long flags;
	struct bio *bio;
	struct bio_list bios;
	struct blk_plug plug;

	if (tc->requeue_mode) {
		requeue_bio_list(tc, &tc->deferred_bio_list);
		return;
	}

	bio_list_init(&bios);

	spin_lock_irqsave(&tc->lock, flags);

	if (bio_list_empty(&tc->deferred_bio_list)) {
		spin_unlock_irqrestore(&tc->lock, flags);
		return;
	}

	__sort_thin_deferred_bios(tc);

	bio_list_merge(&bios, &tc->deferred_bio_list);
	bio_list_init(&tc->deferred_bio_list);

	spin_unlock_irqrestore(&tc->lock, flags);

	blk_start_plug(&plug);
	while ((bio = bio_list_pop(&bios))) {
		/*
		 * If we've got no free new_mapping structs, and processing
		 * this bio might require one, we pause until there are some
		 * prepared mappings to process.
		 */
		if (ensure_next_mapping(pool)) {
			spin_lock_irqsave(&tc->lock, flags);
			bio_list_add(&tc->deferred_bio_list, bio);
			bio_list_merge(&tc->deferred_bio_list, &bios);
			spin_unlock_irqrestore(&tc->lock, flags);
			break;
		}

		if (bio->bi_rw & REQ_DISCARD)
			pool->process_discard(tc, bio);
		else
			pool->process_bio(tc, bio);
	}
	blk_finish_plug(&plug);
}

static void thin_get(struct thin_c *tc);
static void thin_put(struct thin_c *tc);

/*
 * We can't hold rcu_read_lock() around code that can block.  So we
 * find a thin with the rcu lock held; bump a refcount; then drop
 * the lock.
 */
static struct thin_c *get_first_thin(struct pool *pool)
{
	struct thin_c *tc = NULL;

	rcu_read_lock();
	if (!list_empty(&pool->active_thins)) {
		tc = list_entry_rcu(pool->active_thins.next, struct thin_c, list);
		thin_get(tc);
	}
	rcu_read_unlock();

	return tc;
}

static struct thin_c *get_next_thin(struct pool *pool, struct thin_c *tc)
{
	struct thin_c *old_tc = tc;

	rcu_read_lock();
	list_for_each_entry_continue_rcu(tc, &pool->active_thins, list) {
		thin_get(tc);
		thin_put(old_tc);
		rcu_read_unlock();
		return tc;
	}
	thin_put(old_tc);
	rcu_read_unlock();

	return NULL;
}

static void process_deferred_bios(struct pool *pool)
{
	unsigned long flags;
	struct bio *bio;
	struct bio_list bios;
	struct thin_c *tc;

	tc = get_first_thin(pool);
	while (tc) {
		process_thin_deferred_bios(tc);
		tc = get_next_thin(pool, tc);
	}

	/*
	 * If there are any deferred flush bios, we must commit
	 * the metadata before issuing them.
	 */
	bio_list_init(&bios);
	spin_lock_irqsave(&pool->lock, flags);
	bio_list_merge(&bios, &pool->deferred_flush_bios);
	bio_list_init(&pool->deferred_flush_bios);
	spin_unlock_irqrestore(&pool->lock, flags);

	if (bio_list_empty(&bios) &&
	    !(dm_pool_changed_this_transaction(pool->pmd) && need_commit_due_to_time(pool)))
		return;

	if (commit(pool)) {
		while ((bio = bio_list_pop(&bios)))
			bio_io_error(bio);
		return;
	}
	pool->last_commit_jiffies = jiffies;

	while ((bio = bio_list_pop(&bios)))
		generic_make_request(bio);
}

static void do_worker(struct work_struct *ws)
{
	struct pool *pool = container_of(ws, struct pool, worker);

	process_prepared(pool, &pool->prepared_mappings, &pool->process_prepared_mapping);
	process_prepared(pool, &pool->prepared_discards, &pool->process_prepared_discard);
	process_deferred_bios(pool);
}

/*
 * We want to commit periodically so that not too much
 * unwritten data builds up.
 */
static void do_waker(struct work_struct *ws)
{
	struct pool *pool = container_of(to_delayed_work(ws), struct pool, waker);
	wake_worker(pool);
	queue_delayed_work(pool->wq, &pool->waker, COMMIT_PERIOD);
}

/*
 * We're holding onto IO to allow userland time to react.  After the
 * timeout either the pool will have been resized (and thus back in
 * PM_WRITE mode), or we degrade to PM_READ_ONLY and start erroring IO.
 */
static void do_no_space_timeout(struct work_struct *ws)
{
	struct pool *pool = container_of(to_delayed_work(ws), struct pool,
					 no_space_timeout);

	if (get_pool_mode(pool) == PM_OUT_OF_DATA_SPACE && !pool->pf.error_if_no_space)
		set_pool_mode(pool, PM_READ_ONLY);
}

/*----------------------------------------------------------------*/

struct noflush_work {
	struct work_struct worker;
	struct thin_c *tc;

	atomic_t complete;
	wait_queue_head_t wait;
};

static void complete_noflush_work(struct noflush_work *w)
{
	atomic_set(&w->complete, 1);
	wake_up(&w->wait);
}

static void do_noflush_start(struct work_struct *ws)
{
	struct noflush_work *w = container_of(ws, struct noflush_work, worker);
	w->tc->requeue_mode = true;
	requeue_io(w->tc);
	complete_noflush_work(w);
}

static void do_noflush_stop(struct work_struct *ws)
{
	struct noflush_work *w = container_of(ws, struct noflush_work, worker);
	w->tc->requeue_mode = false;
	complete_noflush_work(w);
}

static void noflush_work(struct thin_c *tc, void (*fn)(struct work_struct *))
{
	struct noflush_work w;

	INIT_WORK_ONSTACK(&w.worker, fn);
	w.tc = tc;
	atomic_set(&w.complete, 0);
	init_waitqueue_head(&w.wait);

	queue_work(tc->pool->wq, &w.worker);

	wait_event(w.wait, atomic_read(&w.complete));
}

/*----------------------------------------------------------------*/

static enum pool_mode get_pool_mode(struct pool *pool)
{
	return pool->pf.mode;
}

static void notify_of_pool_mode_change(struct pool *pool, const char *new_mode)
{
	dm_table_event(pool->ti->table);
	DMINFO("%s: switching pool to %s mode",
	       dm_device_name(pool->pool_md), new_mode);
}

static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
{
	struct pool_c *pt = pool->ti->private;
	bool needs_check = dm_pool_metadata_needs_check(pool->pmd);
	enum pool_mode old_mode = get_pool_mode(pool);
	unsigned long no_space_timeout = ACCESS_ONCE(no_space_timeout_secs) * HZ;

	/*
	 * Never allow the pool to transition to PM_WRITE mode if user
	 * intervention is required to verify metadata and data consistency.
	 */
	if (new_mode == PM_WRITE && needs_check) {
		DMERR("%s: unable to switch pool to write mode until repaired.",
		      dm_device_name(pool->pool_md));
		if (old_mode != new_mode)
			new_mode = old_mode;
		else
			new_mode = PM_READ_ONLY;
	}
	/*
	 * If we were in PM_FAIL mode, rollback of metadata failed.  We're
	 * not going to recover without a thin_repair.	So we never let the
	 * pool move out of the old mode.
	 */
	if (old_mode == PM_FAIL)
		new_mode = old_mode;

	switch (new_mode) {
	case PM_FAIL:
		if (old_mode != new_mode)
			notify_of_pool_mode_change(pool, "failure");
		dm_pool_metadata_read_only(pool->pmd);
		pool->process_bio = process_bio_fail;
		pool->process_discard = process_bio_fail;
		pool->process_prepared_mapping = process_prepared_mapping_fail;
		pool->process_prepared_discard = process_prepared_discard_fail;

		error_retry_list(pool);
		break;

	case PM_READ_ONLY:
		if (old_mode != new_mode)
			notify_of_pool_mode_change(pool, "read-only");
		dm_pool_metadata_read_only(pool->pmd);
		pool->process_bio = process_bio_read_only;
		pool->process_discard = process_bio_success;
		pool->process_prepared_mapping = process_prepared_mapping_fail;
		pool->process_prepared_discard = process_prepared_discard_passdown;

		error_retry_list(pool);
		break;

	case PM_OUT_OF_DATA_SPACE:
		/*
		 * Ideally we'd never hit this state; the low water mark
		 * would trigger userland to extend the pool before we
		 * completely run out of data space.  However, many small
		 * IOs to unprovisioned space can consume data space at an
		 * alarming rate.  Adjust your low water mark if you're
		 * frequently seeing this mode.
		 */
		if (old_mode != new_mode)
			notify_of_pool_mode_change(pool, "out-of-data-space");
		pool->process_bio = process_bio_read_only;
		pool->process_discard = process_discard;
		pool->process_prepared_mapping = process_prepared_mapping;
		pool->process_prepared_discard = process_prepared_discard_passdown;

		if (!pool->pf.error_if_no_space && no_space_timeout)
			queue_delayed_work(pool->wq, &pool->no_space_timeout, no_space_timeout);
		break;

	case PM_WRITE:
		if (old_mode != new_mode)
			notify_of_pool_mode_change(pool, "write");
		dm_pool_metadata_read_write(pool->pmd);
		pool->process_bio = process_bio;
		pool->process_discard = process_discard;
		pool->process_prepared_mapping = process_prepared_mapping;
		pool->process_prepared_discard = process_prepared_discard;
		break;
	}

	pool->pf.mode = new_mode;
	/*
	 * The pool mode may have changed, sync it so bind_control_target()
	 * doesn't cause an unexpected mode transition on resume.
	 */
	pt->adjusted_pf.mode = new_mode;
}

static void abort_transaction(struct pool *pool)
{
	const char *dev_name = dm_device_name(pool->pool_md);

	DMERR_LIMIT("%s: aborting current metadata transaction", dev_name);
	if (dm_pool_abort_metadata(pool->pmd)) {
		DMERR("%s: failed to abort metadata transaction", dev_name);
		set_pool_mode(pool, PM_FAIL);
	}

	if (dm_pool_metadata_set_needs_check(pool->pmd)) {
		DMERR("%s: failed to set 'needs_check' flag in metadata", dev_name);
		set_pool_mode(pool, PM_FAIL);
	}
}

static void metadata_operation_failed(struct pool *pool, const char *op, int r)
{
	DMERR_LIMIT("%s: metadata operation '%s' failed: error = %d",
		    dm_device_name(pool->pool_md), op, r);

	abort_transaction(pool);
	set_pool_mode(pool, PM_READ_ONLY);
}

/*----------------------------------------------------------------*/

/*
 * Mapping functions.
 */

/*
 * Called only while mapping a thin bio to hand it over to the workqueue.
 */
static void thin_defer_bio(struct thin_c *tc, struct bio *bio)
{
	unsigned long flags;
	struct pool *pool = tc->pool;

	spin_lock_irqsave(&tc->lock, flags);
	bio_list_add(&tc->deferred_bio_list, bio);
	spin_unlock_irqrestore(&tc->lock, flags);

	wake_worker(pool);
}

static void thin_hook_bio(struct thin_c *tc, struct bio *bio)
{
	struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));

	h->tc = tc;
	h->shared_read_entry = NULL;
	h->all_io_entry = NULL;
	h->overwrite_mapping = NULL;
}

/*
 * Non-blocking function called from the thin target's map function.
 */
static int thin_bio_map(struct dm_target *ti, struct bio *bio)
{
	int r;
	struct thin_c *tc = ti->private;
	dm_block_t block = get_bio_block(tc, bio);
	struct dm_thin_device *td = tc->td;
	struct dm_thin_lookup_result result;
	struct dm_bio_prison_cell cell1, cell2;
	struct dm_bio_prison_cell *cell_result;
	struct dm_cell_key key;

	thin_hook_bio(tc, bio);

	if (tc->requeue_mode) {
		bio_endio(bio, DM_ENDIO_REQUEUE);
		return DM_MAPIO_SUBMITTED;
	}

	if (get_pool_mode(tc->pool) == PM_FAIL) {
		bio_io_error(bio);
		return DM_MAPIO_SUBMITTED;
	}

	if (bio->bi_rw & (REQ_DISCARD | REQ_FLUSH | REQ_FUA)) {
		thin_defer_bio(tc, bio);
		return DM_MAPIO_SUBMITTED;
	}

	r = dm_thin_find_block(td, block, 0, &result);

	/*
	 * Note that we defer readahead too.
	 */
	switch (r) {
	case 0:
		if (unlikely(result.shared)) {
			/*
			 * We have a race condition here between the
			 * result.shared value returned by the lookup and
			 * snapshot creation, which may cause new
			 * sharing.
			 *
			 * To avoid this always quiesce the origin before
			 * taking the snap.  You want to do this anyway to
			 * ensure a consistent application view
			 * (i.e. lockfs).
			 *
			 * More distant ancestors are irrelevant. The
			 * shared flag will be set in their case.
			 */
			thin_defer_bio(tc, bio);
			return DM_MAPIO_SUBMITTED;
		}

		build_virtual_key(tc->td, block, &key);
		if (dm_bio_detain(tc->pool->prison, &key, bio, &cell1, &cell_result))
			return DM_MAPIO_SUBMITTED;

		build_data_key(tc->td, result.block, &key);
		if (dm_bio_detain(tc->pool->prison, &key, bio, &cell2, &cell_result)) {
			cell_defer_no_holder_no_free(tc, &cell1);
			return DM_MAPIO_SUBMITTED;
		}

		inc_all_io_entry(tc->pool, bio);
		cell_defer_no_holder_no_free(tc, &cell2);
		cell_defer_no_holder_no_free(tc, &cell1);

		remap(tc, bio, result.block);
		return DM_MAPIO_REMAPPED;

	case -ENODATA:
		if (get_pool_mode(tc->pool) == PM_READ_ONLY) {
			/*
			 * This block isn't provisioned, and we have no way
			 * of doing so.
			 */
			handle_unserviceable_bio(tc->pool, bio);
			return DM_MAPIO_SUBMITTED;
		}
		/* fall through */

	case -EWOULDBLOCK:
		/*
		 * In future, the failed dm_thin_find_block above could
		 * provide the hint to load the metadata into cache.
		 */
		thin_defer_bio(tc, bio);
		return DM_MAPIO_SUBMITTED;

	default:
		/*
		 * Must always call bio_io_error on failure.
		 * dm_thin_find_block can fail with -EINVAL if the
		 * pool is switched to fail-io mode.
		 */
		bio_io_error(bio);
		return DM_MAPIO_SUBMITTED;
	}
}

static int pool_is_congested(struct dm_target_callbacks *cb, int bdi_bits)
{
	struct pool_c *pt = container_of(cb, struct pool_c, callbacks);
	struct request_queue *q;

	if (get_pool_mode(pt->pool) == PM_OUT_OF_DATA_SPACE)
		return 1;

	q = bdev_get_queue(pt->data_dev->bdev);
	return bdi_congested(&q->backing_dev_info, bdi_bits);
}

static void requeue_bios(struct pool *pool)
{
	unsigned long flags;
	struct thin_c *tc;

	rcu_read_lock();
	list_for_each_entry_rcu(tc, &pool->active_thins, list) {
		spin_lock_irqsave(&tc->lock, flags);
		bio_list_merge(&tc->deferred_bio_list, &tc->retry_on_resume_list);
		bio_list_init(&tc->retry_on_resume_list);
		spin_unlock_irqrestore(&tc->lock, flags);
	}
	rcu_read_unlock();
}

/*----------------------------------------------------------------
 * Binding of control targets to a pool object
 *--------------------------------------------------------------*/
static bool data_dev_supports_discard(struct pool_c *pt)
{
	struct request_queue *q = bdev_get_queue(pt->data_dev->bdev);

	return q && blk_queue_discard(q);
}

static bool is_factor(sector_t block_size, uint32_t n)
{
	return !sector_div(block_size, n);
}

/*
 * If discard_passdown was enabled verify that the data device
 * supports discards.  Disable discard_passdown if not.
 */
static void disable_passdown_if_not_supported(struct pool_c *pt)
{
	struct pool *pool = pt->pool;
	struct block_device *data_bdev = pt->data_dev->bdev;
	struct queue_limits *data_limits = &bdev_get_queue(data_bdev)->limits;
	sector_t block_size = pool->sectors_per_block << SECTOR_SHIFT;
	const char *reason = NULL;
	char buf[BDEVNAME_SIZE];

	if (!pt->adjusted_pf.discard_passdown)
		return;

	if (!data_dev_supports_discard(pt))
		reason = "discard unsupported";

	else if (data_limits->max_discard_sectors < pool->sectors_per_block)
		reason = "max discard sectors smaller than a block";

	else if (data_limits->discard_granularity > block_size)
		reason = "discard granularity larger than a block";

	else if (!is_factor(block_size, data_limits->discard_granularity))
		reason = "discard granularity not a factor of block size";

	if (reason) {
		DMWARN("Data device (%s) %s: Disabling discard passdown.", bdevname(data_bdev, buf), reason);
		pt->adjusted_pf.discard_passdown = false;
	}
}

static int bind_control_target(struct pool *pool, struct dm_target *ti)
{
	struct pool_c *pt = ti->private;

	/*
	 * We want to make sure that a pool in PM_FAIL mode is never upgraded.
	 */
	enum pool_mode old_mode = get_pool_mode(pool);
	enum pool_mode new_mode = pt->adjusted_pf.mode;

	/*
	 * Don't change the pool's mode until set_pool_mode() below.
	 * Otherwise the pool's process_* function pointers may
	 * not match the desired pool mode.
	 */
	pt->adjusted_pf.mode = old_mode;

	pool->ti = ti;
	pool->pf = pt->adjusted_pf;
	pool->low_water_blocks = pt->low_water_blocks;

	set_pool_mode(pool, new_mode);

	return 0;
}

static void unbind_control_target(struct pool *pool, struct dm_target *ti)
{
	if (pool->ti == ti)
		pool->ti = NULL;
}

/*----------------------------------------------------------------
 * Pool creation
 *--------------------------------------------------------------*/
/* Initialize pool features. */
static void pool_features_init(struct pool_features *pf)
{
	pf->mode = PM_WRITE;
	pf->zero_new_blocks = true;
	pf->discard_enabled = true;
	pf->discard_passdown = true;
	pf->error_if_no_space = false;
}

static void __pool_destroy(struct pool *pool)
{
	__pool_table_remove(pool);

	if (dm_pool_metadata_close(pool->pmd) < 0)
		DMWARN("%s: dm_pool_metadata_close() failed.", __func__);

	dm_bio_prison_destroy(pool->prison);
	dm_kcopyd_client_destroy(pool->copier);

	if (pool->wq)
		destroy_workqueue(pool->wq);

	if (pool->next_mapping)
		mempool_free(pool->next_mapping, pool->mapping_pool);
	mempool_destroy(pool->mapping_pool);
	dm_deferred_set_destroy(pool->shared_read_ds);
	dm_deferred_set_destroy(pool->all_io_ds);
	kfree(pool);
}

static struct kmem_cache *_new_mapping_cache;

static struct pool *pool_create(struct mapped_device *pool_md,
				struct block_device *metadata_dev,
				unsigned long block_size,
				int read_only, char **error)
{
	int r;
	void *err_p;
	struct pool *pool;
	struct dm_pool_metadata *pmd;
	bool format_device = read_only ? false : true;

	pmd = dm_pool_metadata_open(metadata_dev, block_size, format_device);
	if (IS_ERR(pmd)) {
		*error = "Error creating metadata object";
		return (struct pool *)pmd;
	}

	pool = kmalloc(sizeof(*pool), GFP_KERNEL);
	if (!pool) {
		*error = "Error allocating memory for pool";
		err_p = ERR_PTR(-ENOMEM);
		goto bad_pool;
	}

	pool->pmd = pmd;
	pool->sectors_per_block = block_size;
	if (block_size & (block_size - 1))
		pool->sectors_per_block_shift = -1;
	else
		pool->sectors_per_block_shift = __ffs(block_size);
	pool->low_water_blocks = 0;
	pool_features_init(&pool->pf);
	pool->prison = dm_bio_prison_create(PRISON_CELLS);
	if (!pool->prison) {
		*error = "Error creating pool's bio prison";
		err_p = ERR_PTR(-ENOMEM);
		goto bad_prison;
	}

	pool->copier = dm_kcopyd_client_create(&dm_kcopyd_throttle);
	if (IS_ERR(pool->copier)) {
		r = PTR_ERR(pool->copier);
		*error = "Error creating pool's kcopyd client";
		err_p = ERR_PTR(r);
		goto bad_kcopyd_client;
	}

	/*
	 * Create singlethreaded workqueue that will service all devices
	 * that use this metadata.
	 */
	pool->wq = alloc_ordered_workqueue("dm-" DM_MSG_PREFIX, WQ_MEM_RECLAIM);
	if (!pool->wq) {
		*error = "Error creating pool's workqueue";
		err_p = ERR_PTR(-ENOMEM);
		goto bad_wq;
	}

	INIT_WORK(&pool->worker, do_worker);
	INIT_DELAYED_WORK(&pool->waker, do_waker);
	INIT_DELAYED_WORK(&pool->no_space_timeout, do_no_space_timeout);
	spin_lock_init(&pool->lock);
	bio_list_init(&pool->deferred_flush_bios);
	INIT_LIST_HEAD(&pool->prepared_mappings);
	INIT_LIST_HEAD(&pool->prepared_discards);
	INIT_LIST_HEAD(&pool->active_thins);
	pool->low_water_triggered = false;

	pool->shared_read_ds = dm_deferred_set_create();
	if (!pool->shared_read_ds) {
		*error = "Error creating pool's shared read deferred set";
		err_p = ERR_PTR(-ENOMEM);
		goto bad_shared_read_ds;
	}

	pool->all_io_ds = dm_deferred_set_create();
	if (!pool->all_io_ds) {
		*error = "Error creating pool's all io deferred set";
		err_p = ERR_PTR(-ENOMEM);
		goto bad_all_io_ds;
	}

	pool->next_mapping = NULL;
	pool->mapping_pool = mempool_create_slab_pool(MAPPING_POOL_SIZE,
						      _new_mapping_cache);
	if (!pool->mapping_pool) {
		*error = "Error creating pool's mapping mempool";
		err_p = ERR_PTR(-ENOMEM);
		goto bad_mapping_pool;
	}

	pool->ref_count = 1;
	pool->last_commit_jiffies = jiffies;
	pool->pool_md = pool_md;
	pool->md_dev = metadata_dev;
	__pool_table_insert(pool);

	return pool;

bad_mapping_pool:
	dm_deferred_set_destroy(pool->all_io_ds);
bad_all_io_ds:
	dm_deferred_set_destroy(pool->shared_read_ds);
bad_shared_read_ds:
	destroy_workqueue(pool->wq);
bad_wq:
	dm_kcopyd_client_destroy(pool->copier);
bad_kcopyd_client:
	dm_bio_prison_destroy(pool->prison);
bad_prison:
	kfree(pool);
bad_pool:
	if (dm_pool_metadata_close(pmd))
		DMWARN("%s: dm_pool_metadata_close() failed.", __func__);

	return err_p;
}

static void __pool_inc(struct pool *pool)
{
	BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
	pool->ref_count++;
}

static void __pool_dec(struct pool *pool)
{
	BUG_ON(!mutex_is_locked(&dm_thin_pool_table.mutex));
	BUG_ON(!pool->ref_count);
	if (!--pool->ref_count)
		__pool_destroy(pool);
}

static struct pool *__pool_find(struct mapped_device *pool_md,
				struct block_device *metadata_dev,
				unsigned long block_size, int read_only,
				char **error, int *created)
{
	struct pool *pool = __pool_table_lookup_metadata_dev(metadata_dev);

	if (pool) {
		if (pool->pool_md != pool_md) {
			*error = "metadata device already in use by a pool";
			return ERR_PTR(-EBUSY);
		}
		__pool_inc(pool);

	} else {
		pool = __pool_table_lookup(pool_md);
		if (pool) {
			if (pool->md_dev != metadata_dev) {
				*error = "different pool cannot replace a pool";
				return ERR_PTR(-EINVAL);
			}
			__pool_inc(pool);

		} else {
			pool = pool_create(pool_md, metadata_dev, block_size, read_only, error);
			*created = 1;
		}
	}

	return pool;
}

/*----------------------------------------------------------------
 * Pool target methods
 *--------------------------------------------------------------*/
static void pool_dtr(struct dm_target *ti)
{
	struct pool_c *pt = ti->private;

	mutex_lock(&dm_thin_pool_table.mutex);

	unbind_control_target(pt->pool, ti);
	__pool_dec(pt->pool);
	dm_put_device(ti, pt->metadata_dev);
	dm_put_device(ti, pt->data_dev);
	kfree(pt);

	mutex_unlock(&dm_thin_pool_table.mutex);
}

static int parse_pool_features(struct dm_arg_set *as, struct pool_features *pf,
			       struct dm_target *ti)
{
	int r;
	unsigned argc;
	const char *arg_name;

	static struct dm_arg _args[] = {
		{0, 4, "Invalid number of pool feature arguments"},
	};

	/*
	 * No feature arguments supplied.
	 */
	if (!as->argc)
		return 0;

	r = dm_read_arg_group(_args, as, &argc, &ti->error);
	if (r)
		return -EINVAL;

	while (argc && !r) {
		arg_name = dm_shift_arg(as);
		argc--;

		if (!strcasecmp(arg_name, "skip_block_zeroing"))
			pf->zero_new_blocks = false;

		else if (!strcasecmp(arg_name, "ignore_discard"))
			pf->discard_enabled = false;

		else if (!strcasecmp(arg_name, "no_discard_passdown"))
			pf->discard_passdown = false;

		else if (!strcasecmp(arg_name, "read_only"))
			pf->mode = PM_READ_ONLY;

		else if (!strcasecmp(arg_name, "error_if_no_space"))
			pf->error_if_no_space = true;

		else {
			ti->error = "Unrecognised pool feature requested";
			r = -EINVAL;
			break;
		}
	}

	return r;
}

static void metadata_low_callback(void *context)
{
	struct pool *pool = context;

	DMWARN("%s: reached low water mark for metadata device: sending event.",
	       dm_device_name(pool->pool_md));

	dm_table_event(pool->ti->table);
}

static sector_t get_dev_size(struct block_device *bdev)
{
	return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT;
}

static void warn_if_metadata_device_too_big(struct block_device *bdev)
{
	sector_t metadata_dev_size = get_dev_size(bdev);
	char buffer[BDEVNAME_SIZE];

	if (metadata_dev_size > THIN_METADATA_MAX_SECTORS_WARNING)
		DMWARN("Metadata device %s is larger than %u sectors: excess space will not be used.",
		       bdevname(bdev, buffer), THIN_METADATA_MAX_SECTORS);
}

static sector_t get_metadata_dev_size(struct block_device *bdev)
{
	sector_t metadata_dev_size = get_dev_size(bdev);

	if (metadata_dev_size > THIN_METADATA_MAX_SECTORS)
		metadata_dev_size = THIN_METADATA_MAX_SECTORS;

	return metadata_dev_size;
}

static dm_block_t get_metadata_dev_size_in_blocks(struct block_device *bdev)
{
	sector_t metadata_dev_size = get_metadata_dev_size(bdev);

	sector_div(metadata_dev_size, THIN_METADATA_BLOCK_SIZE);

	return metadata_dev_size;
}

/*
 * When a metadata threshold is crossed a dm event is triggered, and
 * userland should respond by growing the metadata device.  We could let
 * userland set the threshold, like we do with the data threshold, but I'm
 * not sure they know enough to do this well.
 */
static dm_block_t calc_metadata_threshold(struct pool_c *pt)
{
	/*
	 * 4M is ample for all ops with the possible exception of thin
	 * device deletion which is harmless if it fails (just retry the
	 * delete after you've grown the device).
	 */
	dm_block_t quarter = get_metadata_dev_size_in_blocks(pt->metadata_dev->bdev) / 4;
	return min((dm_block_t)1024ULL /* 4M */, quarter);
}

/*
 * thin-pool <metadata dev> <data dev>
 *	     <data block size (sectors)>
 *	     <low water mark (blocks)>
 *	     [<#feature args> [<arg>]*]
 *
 * Optional feature arguments are:
 *	     skip_block_zeroing: skips the zeroing of newly-provisioned blocks.
 *	     ignore_discard: disable discard
 *	     no_discard_passdown: don't pass discards down to the data device
 *	     read_only: Don't allow any changes to be made to the pool metadata.
 *	     error_if_no_space: error IOs, instead of queueing, if no space.
 */
static int pool_ctr(struct dm_target *ti, unsigned argc, char **argv)
{
	int r, pool_created = 0;
	struct pool_c *pt;
	struct pool *pool;
	struct pool_features pf;
	struct dm_arg_set as;
	struct dm_dev *data_dev;
	unsigned long block_size;
	dm_block_t low_water_blocks;
	struct dm_dev *metadata_dev;
	fmode_t metadata_mode;

	/*
	 * FIXME Remove validation from scope of lock.
	 */
	mutex_lock(&dm_thin_pool_table.mutex);

	if (argc < 4) {
		ti->error = "Invalid argument count";
		r = -EINVAL;
		goto out_unlock;
	}

	as.argc = argc;
	as.argv = argv;

	/*
	 * Set default pool features.
	 */
	pool_features_init(&pf);

	dm_consume_args(&as, 4);
	r = parse_pool_features(&as, &pf, ti);
	if (r)
		goto out_unlock;

	metadata_mode = FMODE_READ | ((pf.mode == PM_READ_ONLY) ? 0 : FMODE_WRITE);
	r = dm_get_device(ti, argv[0], metadata_mode, &metadata_dev);
	if (r) {
		ti->error = "Error opening metadata block device";
		goto out_unlock;
	}
	warn_if_metadata_device_too_big(metadata_dev->bdev);

	r = dm_get_device(ti, argv[1], FMODE_READ | FMODE_WRITE, &data_dev);
	if (r) {
		ti->error = "Error getting data device";
		goto out_metadata;
	}

	if (kstrtoul(argv[2], 10, &block_size) || !block_size ||
	    block_size < DATA_DEV_BLOCK_SIZE_MIN_SECTORS ||
	    block_size > DATA_DEV_BLOCK_SIZE_MAX_SECTORS ||
	    block_size & (DATA_DEV_BLOCK_SIZE_MIN_SECTORS - 1)) {
		ti->error = "Invalid block size";
		r = -EINVAL;
		goto out;
	}

	if (kstrtoull(argv[3], 10, (unsigned long long *)&low_water_blocks)) {
		ti->error = "Invalid low water mark";
		r = -EINVAL;
		goto out;
	}

	pt = kzalloc(sizeof(*pt), GFP_KERNEL);
	if (!pt) {
		r = -ENOMEM;
		goto out;
	}

	pool = __pool_find(dm_table_get_md(ti->table), metadata_dev->bdev,
			   block_size, pf.mode == PM_READ_ONLY, &ti->error, &pool_created);
	if (IS_ERR(pool)) {
		r = PTR_ERR(pool);
		goto out_free_pt;
	}

	/*
	 * 'pool_created' reflects whether this is the first table load.
	 * Top level discard support is not allowed to be changed after
	 * initial load.  This would require a pool reload to trigger thin
	 * device changes.
	 */
	if (!pool_created && pf.discard_enabled != pool->pf.discard_enabled) {
		ti->error = "Discard support cannot be disabled once enabled";
		r = -EINVAL;
		goto out_flags_changed;
	}

	pt->pool = pool;
	pt->ti = ti;
	pt->metadata_dev = metadata_dev;
	pt->data_dev = data_dev;
	pt->low_water_blocks = low_water_blocks;
	pt->adjusted_pf = pt->requested_pf = pf;
	ti->num_flush_bios = 1;

	/*
	 * Only need to enable discards if the pool should pass
	 * them down to the data device.  The thin device's discard
	 * processing will cause mappings to be removed from the btree.
	 */
	ti->discard_zeroes_data_unsupported = true;
	if (pf.discard_enabled && pf.discard_passdown) {
		ti->num_discard_bios = 1;

		/*
		 * Setting 'discards_supported' circumvents the normal
		 * stacking of discard limits (this keeps the pool and
		 * thin devices' discard limits consistent).
		 */
		ti->discards_supported = true;
	}
	ti->private = pt;

	r = dm_pool_register_metadata_threshold(pt->pool->pmd,
						calc_metadata_threshold(pt),
						metadata_low_callback,
						pool);
	if (r)
		goto out_free_pt;

	pt->callbacks.congested_fn = pool_is_congested;
	dm_table_add_target_callbacks(ti->table, &pt->callbacks);

	mutex_unlock(&dm_thin_pool_table.mutex);

	return 0;

out_flags_changed:
	__pool_dec(pool);
out_free_pt:
	kfree(pt);
out:
	dm_put_device(ti, data_dev);
out_metadata:
	dm_put_device(ti, metadata_dev);
out_unlock:
	mutex_unlock(&dm_thin_pool_table.mutex);

	return r;
}

static int pool_map(struct dm_target *ti, struct bio *bio)
{
	int r;
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;
	unsigned long flags;

	/*
	 * As this is a singleton target, ti->begin is always zero.
	 */
	spin_lock_irqsave(&pool->lock, flags);
	bio->bi_bdev = pt->data_dev->bdev;
	r = DM_MAPIO_REMAPPED;
	spin_unlock_irqrestore(&pool->lock, flags);

	return r;
}

static int maybe_resize_data_dev(struct dm_target *ti, bool *need_commit)
{
	int r;
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;
	sector_t data_size = ti->len;
	dm_block_t sb_data_size;

	*need_commit = false;

	(void) sector_div(data_size, pool->sectors_per_block);

	r = dm_pool_get_data_dev_size(pool->pmd, &sb_data_size);
	if (r) {
		DMERR("%s: failed to retrieve data device size",
		      dm_device_name(pool->pool_md));
		return r;
	}

	if (data_size < sb_data_size) {
		DMERR("%s: pool target (%llu blocks) too small: expected %llu",
		      dm_device_name(pool->pool_md),
		      (unsigned long long)data_size, sb_data_size);
		return -EINVAL;

	} else if (data_size > sb_data_size) {
		if (dm_pool_metadata_needs_check(pool->pmd)) {
			DMERR("%s: unable to grow the data device until repaired.",
			      dm_device_name(pool->pool_md));
			return 0;
		}

		if (sb_data_size)
			DMINFO("%s: growing the data device from %llu to %llu blocks",
			       dm_device_name(pool->pool_md),
			       sb_data_size, (unsigned long long)data_size);
		r = dm_pool_resize_data_dev(pool->pmd, data_size);
		if (r) {
			metadata_operation_failed(pool, "dm_pool_resize_data_dev", r);
			return r;
		}

		*need_commit = true;
	}

	return 0;
}

static int maybe_resize_metadata_dev(struct dm_target *ti, bool *need_commit)
{
	int r;
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;
	dm_block_t metadata_dev_size, sb_metadata_dev_size;

	*need_commit = false;

	metadata_dev_size = get_metadata_dev_size_in_blocks(pool->md_dev);

	r = dm_pool_get_metadata_dev_size(pool->pmd, &sb_metadata_dev_size);
	if (r) {
		DMERR("%s: failed to retrieve metadata device size",
		      dm_device_name(pool->pool_md));
		return r;
	}

	if (metadata_dev_size < sb_metadata_dev_size) {
		DMERR("%s: metadata device (%llu blocks) too small: expected %llu",
		      dm_device_name(pool->pool_md),
		      metadata_dev_size, sb_metadata_dev_size);
		return -EINVAL;

	} else if (metadata_dev_size > sb_metadata_dev_size) {
		if (dm_pool_metadata_needs_check(pool->pmd)) {
			DMERR("%s: unable to grow the metadata device until repaired.",
			      dm_device_name(pool->pool_md));
			return 0;
		}

		warn_if_metadata_device_too_big(pool->md_dev);
		DMINFO("%s: growing the metadata device from %llu to %llu blocks",
		       dm_device_name(pool->pool_md),
		       sb_metadata_dev_size, metadata_dev_size);
		r = dm_pool_resize_metadata_dev(pool->pmd, metadata_dev_size);
		if (r) {
			metadata_operation_failed(pool, "dm_pool_resize_metadata_dev", r);
			return r;
		}

		*need_commit = true;
	}

	return 0;
}

/*
 * Retrieves the number of blocks of the data device from
 * the superblock and compares it to the actual device size,
 * thus resizing the data device in case it has grown.
 *
 * This both copes with opening preallocated data devices in the ctr
 * being followed by a resume
 * -and-
 * calling the resume method individually after userspace has
 * grown the data device in reaction to a table event.
 */
static int pool_preresume(struct dm_target *ti)
{
	int r;
	bool need_commit1, need_commit2;
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;

	/*
	 * Take control of the pool object.
	 */
	r = bind_control_target(pool, ti);
	if (r)
		return r;

	r = maybe_resize_data_dev(ti, &need_commit1);
	if (r)
		return r;

	r = maybe_resize_metadata_dev(ti, &need_commit2);
	if (r)
		return r;

	if (need_commit1 || need_commit2)
		(void) commit(pool);

	return 0;
}

static void pool_resume(struct dm_target *ti)
{
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;
	unsigned long flags;

	spin_lock_irqsave(&pool->lock, flags);
	pool->low_water_triggered = false;
	spin_unlock_irqrestore(&pool->lock, flags);
	requeue_bios(pool);

	do_waker(&pool->waker.work);
}

static void pool_postsuspend(struct dm_target *ti)
{
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;

	cancel_delayed_work(&pool->waker);
	cancel_delayed_work(&pool->no_space_timeout);
	flush_workqueue(pool->wq);
	(void) commit(pool);
}

static int check_arg_count(unsigned argc, unsigned args_required)
{
	if (argc != args_required) {
		DMWARN("Message received with %u arguments instead of %u.",
		       argc, args_required);
		return -EINVAL;
	}

	return 0;
}

static int read_dev_id(char *arg, dm_thin_id *dev_id, int warning)
{
	if (!kstrtoull(arg, 10, (unsigned long long *)dev_id) &&
	    *dev_id <= MAX_DEV_ID)
		return 0;

	if (warning)
		DMWARN("Message received with invalid device id: %s", arg);

	return -EINVAL;
}

static int process_create_thin_mesg(unsigned argc, char **argv, struct pool *pool)
{
	dm_thin_id dev_id;
	int r;

	r = check_arg_count(argc, 2);
	if (r)
		return r;

	r = read_dev_id(argv[1], &dev_id, 1);
	if (r)
		return r;

	r = dm_pool_create_thin(pool->pmd, dev_id);
	if (r) {
		DMWARN("Creation of new thinly-provisioned device with id %s failed.",
		       argv[1]);
		return r;
	}

	return 0;
}

static int process_create_snap_mesg(unsigned argc, char **argv, struct pool *pool)
{
	dm_thin_id dev_id;
	dm_thin_id origin_dev_id;
	int r;

	r = check_arg_count(argc, 3);
	if (r)
		return r;

	r = read_dev_id(argv[1], &dev_id, 1);
	if (r)
		return r;

	r = read_dev_id(argv[2], &origin_dev_id, 1);
	if (r)
		return r;

	r = dm_pool_create_snap(pool->pmd, dev_id, origin_dev_id);
	if (r) {
		DMWARN("Creation of new snapshot %s of device %s failed.",
		       argv[1], argv[2]);
		return r;
	}

	return 0;
}

static int process_delete_mesg(unsigned argc, char **argv, struct pool *pool)
{
	dm_thin_id dev_id;
	int r;

	r = check_arg_count(argc, 2);
	if (r)
		return r;

	r = read_dev_id(argv[1], &dev_id, 1);
	if (r)
		return r;

	r = dm_pool_delete_thin_device(pool->pmd, dev_id);
	if (r)
		DMWARN("Deletion of thin device %s failed.", argv[1]);

	return r;
}

static int process_set_transaction_id_mesg(unsigned argc, char **argv, struct pool *pool)
{
	dm_thin_id old_id, new_id;
	int r;

	r = check_arg_count(argc, 3);
	if (r)
		return r;

	if (kstrtoull(argv[1], 10, (unsigned long long *)&old_id)) {
		DMWARN("set_transaction_id message: Unrecognised id %s.", argv[1]);
		return -EINVAL;
	}

	if (kstrtoull(argv[2], 10, (unsigned long long *)&new_id)) {
		DMWARN("set_transaction_id message: Unrecognised new id %s.", argv[2]);
		return -EINVAL;
	}

	r = dm_pool_set_metadata_transaction_id(pool->pmd, old_id, new_id);
	if (r) {
		DMWARN("Failed to change transaction id from %s to %s.",
		       argv[1], argv[2]);
		return r;
	}

	return 0;
}

static int process_reserve_metadata_snap_mesg(unsigned argc, char **argv, struct pool *pool)
{
	int r;

	r = check_arg_count(argc, 1);
	if (r)
		return r;

	(void) commit(pool);

	r = dm_pool_reserve_metadata_snap(pool->pmd);
	if (r)
		DMWARN("reserve_metadata_snap message failed.");

	return r;
}

static int process_release_metadata_snap_mesg(unsigned argc, char **argv, struct pool *pool)
{
	int r;

	r = check_arg_count(argc, 1);
	if (r)
		return r;

	r = dm_pool_release_metadata_snap(pool->pmd);
	if (r)
		DMWARN("release_metadata_snap message failed.");

	return r;
}

/*
 * Messages supported:
 *   create_thin	<dev_id>
 *   create_snap	<dev_id> <origin_id>
 *   delete		<dev_id>
 *   trim		<dev_id> <new_size_in_sectors>
 *   set_transaction_id <current_trans_id> <new_trans_id>
 *   reserve_metadata_snap
 *   release_metadata_snap
 */
static int pool_message(struct dm_target *ti, unsigned argc, char **argv)
{
	int r = -EINVAL;
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;

	if (!strcasecmp(argv[0], "create_thin"))
		r = process_create_thin_mesg(argc, argv, pool);

	else if (!strcasecmp(argv[0], "create_snap"))
		r = process_create_snap_mesg(argc, argv, pool);

	else if (!strcasecmp(argv[0], "delete"))
		r = process_delete_mesg(argc, argv, pool);

	else if (!strcasecmp(argv[0], "set_transaction_id"))
		r = process_set_transaction_id_mesg(argc, argv, pool);

	else if (!strcasecmp(argv[0], "reserve_metadata_snap"))
		r = process_reserve_metadata_snap_mesg(argc, argv, pool);

	else if (!strcasecmp(argv[0], "release_metadata_snap"))
		r = process_release_metadata_snap_mesg(argc, argv, pool);

	else
		DMWARN("Unrecognised thin pool target message received: %s", argv[0]);

	if (!r)
		(void) commit(pool);

	return r;
}

static void emit_flags(struct pool_features *pf, char *result,
		       unsigned sz, unsigned maxlen)
{
	unsigned count = !pf->zero_new_blocks + !pf->discard_enabled +
		!pf->discard_passdown + (pf->mode == PM_READ_ONLY) +
		pf->error_if_no_space;
	DMEMIT("%u ", count);

	if (!pf->zero_new_blocks)
		DMEMIT("skip_block_zeroing ");

	if (!pf->discard_enabled)
		DMEMIT("ignore_discard ");

	if (!pf->discard_passdown)
		DMEMIT("no_discard_passdown ");

	if (pf->mode == PM_READ_ONLY)
		DMEMIT("read_only ");

	if (pf->error_if_no_space)
		DMEMIT("error_if_no_space ");
}

/*
 * Status line is:
 *    <transaction id> <used metadata sectors>/<total metadata sectors>
 *    <used data sectors>/<total data sectors> <held metadata root>
 */
static void pool_status(struct dm_target *ti, status_type_t type,
			unsigned status_flags, char *result, unsigned maxlen)
{
	int r;
	unsigned sz = 0;
	uint64_t transaction_id;
	dm_block_t nr_free_blocks_data;
	dm_block_t nr_free_blocks_metadata;
	dm_block_t nr_blocks_data;
	dm_block_t nr_blocks_metadata;
	dm_block_t held_root;
	char buf[BDEVNAME_SIZE];
	char buf2[BDEVNAME_SIZE];
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;

	switch (type) {
	case STATUSTYPE_INFO:
		if (get_pool_mode(pool) == PM_FAIL) {
			DMEMIT("Fail");
			break;
		}

		/* Commit to ensure statistics aren't out-of-date */
		if (!(status_flags & DM_STATUS_NOFLUSH_FLAG) && !dm_suspended(ti))
			(void) commit(pool);

		r = dm_pool_get_metadata_transaction_id(pool->pmd, &transaction_id);
		if (r) {
			DMERR("%s: dm_pool_get_metadata_transaction_id returned %d",
			      dm_device_name(pool->pool_md), r);
			goto err;
		}

		r = dm_pool_get_free_metadata_block_count(pool->pmd, &nr_free_blocks_metadata);
		if (r) {
			DMERR("%s: dm_pool_get_free_metadata_block_count returned %d",
			      dm_device_name(pool->pool_md), r);
			goto err;
		}

		r = dm_pool_get_metadata_dev_size(pool->pmd, &nr_blocks_metadata);
		if (r) {
			DMERR("%s: dm_pool_get_metadata_dev_size returned %d",
			      dm_device_name(pool->pool_md), r);
			goto err;
		}

		r = dm_pool_get_free_block_count(pool->pmd, &nr_free_blocks_data);
		if (r) {
			DMERR("%s: dm_pool_get_free_block_count returned %d",
			      dm_device_name(pool->pool_md), r);
			goto err;
		}

		r = dm_pool_get_data_dev_size(pool->pmd, &nr_blocks_data);
		if (r) {
			DMERR("%s: dm_pool_get_data_dev_size returned %d",
			      dm_device_name(pool->pool_md), r);
			goto err;
		}

		r = dm_pool_get_metadata_snap(pool->pmd, &held_root);
		if (r) {
			DMERR("%s: dm_pool_get_metadata_snap returned %d",
			      dm_device_name(pool->pool_md), r);
			goto err;
		}

		DMEMIT("%llu %llu/%llu %llu/%llu ",
		       (unsigned long long)transaction_id,
		       (unsigned long long)(nr_blocks_metadata - nr_free_blocks_metadata),
		       (unsigned long long)nr_blocks_metadata,
		       (unsigned long long)(nr_blocks_data - nr_free_blocks_data),
		       (unsigned long long)nr_blocks_data);

		if (held_root)
			DMEMIT("%llu ", held_root);
		else
			DMEMIT("- ");

		if (pool->pf.mode == PM_OUT_OF_DATA_SPACE)
			DMEMIT("out_of_data_space ");
		else if (pool->pf.mode == PM_READ_ONLY)
			DMEMIT("ro ");
		else
			DMEMIT("rw ");

		if (!pool->pf.discard_enabled)
			DMEMIT("ignore_discard ");
		else if (pool->pf.discard_passdown)
			DMEMIT("discard_passdown ");
		else
			DMEMIT("no_discard_passdown ");

		if (pool->pf.error_if_no_space)
			DMEMIT("error_if_no_space ");
		else
			DMEMIT("queue_if_no_space ");

		break;

	case STATUSTYPE_TABLE:
		DMEMIT("%s %s %lu %llu ",
		       format_dev_t(buf, pt->metadata_dev->bdev->bd_dev),
		       format_dev_t(buf2, pt->data_dev->bdev->bd_dev),
		       (unsigned long)pool->sectors_per_block,
		       (unsigned long long)pt->low_water_blocks);
		emit_flags(&pt->requested_pf, result, sz, maxlen);
		break;
	}
	return;

err:
	DMEMIT("Error");
}

static int pool_iterate_devices(struct dm_target *ti,
				iterate_devices_callout_fn fn, void *data)
{
	struct pool_c *pt = ti->private;

	return fn(ti, pt->data_dev, 0, ti->len, data);
}

static int pool_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
		      struct bio_vec *biovec, int max_size)
{
	struct pool_c *pt = ti->private;
	struct request_queue *q = bdev_get_queue(pt->data_dev->bdev);

	if (!q->merge_bvec_fn)
		return max_size;

	bvm->bi_bdev = pt->data_dev->bdev;

	return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}

static void set_discard_limits(struct pool_c *pt, struct queue_limits *limits)
{
	struct pool *pool = pt->pool;
	struct queue_limits *data_limits;

	limits->max_discard_sectors = pool->sectors_per_block;

	/*
	 * discard_granularity is just a hint, and not enforced.
	 */
	if (pt->adjusted_pf.discard_passdown) {
		data_limits = &bdev_get_queue(pt->data_dev->bdev)->limits;
		limits->discard_granularity = data_limits->discard_granularity;
	} else
		limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT;
}

static void pool_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
	struct pool_c *pt = ti->private;
	struct pool *pool = pt->pool;
	uint64_t io_opt_sectors = limits->io_opt >> SECTOR_SHIFT;

	/*
	 * If the system-determined stacked limits are compatible with the
	 * pool's blocksize (io_opt is a factor) do not override them.
	 */
	if (io_opt_sectors < pool->sectors_per_block ||
	    do_div(io_opt_sectors, pool->sectors_per_block)) {
		blk_limits_io_min(limits, 0);
		blk_limits_io_opt(limits, pool->sectors_per_block << SECTOR_SHIFT);
	}

	/*
	 * pt->adjusted_pf is a staging area for the actual features to use.
	 * They get transferred to the live pool in bind_control_target()
	 * called from pool_preresume().
	 */
	if (!pt->adjusted_pf.discard_enabled) {
		/*
		 * Must explicitly disallow stacking discard limits otherwise the
		 * block layer will stack them if pool's data device has support.
		 * QUEUE_FLAG_DISCARD wouldn't be set but there is no way for the
		 * user to see that, so make sure to set all discard limits to 0.
		 */
		limits->discard_granularity = 0;
		return;
	}

	disable_passdown_if_not_supported(pt);

	set_discard_limits(pt, limits);
}

static struct target_type pool_target = {
	.name = "thin-pool",
	.features = DM_TARGET_SINGLETON | DM_TARGET_ALWAYS_WRITEABLE |
		    DM_TARGET_IMMUTABLE,
	.version = {1, 12, 0},
	.module = THIS_MODULE,
	.ctr = pool_ctr,
	.dtr = pool_dtr,
	.map = pool_map,
	.postsuspend = pool_postsuspend,
	.preresume = pool_preresume,
	.resume = pool_resume,
	.message = pool_message,
	.status = pool_status,
	.merge = pool_merge,
	.iterate_devices = pool_iterate_devices,
	.io_hints = pool_io_hints,
};

/*----------------------------------------------------------------
 * Thin target methods
 *--------------------------------------------------------------*/
static void thin_get(struct thin_c *tc)
{
	atomic_inc(&tc->refcount);
}

static void thin_put(struct thin_c *tc)
{
	if (atomic_dec_and_test(&tc->refcount))
		complete(&tc->can_destroy);
}

static void thin_dtr(struct dm_target *ti)
{
	struct thin_c *tc = ti->private;
	unsigned long flags;

	thin_put(tc);
	wait_for_completion(&tc->can_destroy);

	spin_lock_irqsave(&tc->pool->lock, flags);
	list_del_rcu(&tc->list);
	spin_unlock_irqrestore(&tc->pool->lock, flags);
	synchronize_rcu();

	mutex_lock(&dm_thin_pool_table.mutex);

	__pool_dec(tc->pool);
	dm_pool_close_thin_device(tc->td);
	dm_put_device(ti, tc->pool_dev);
	if (tc->origin_dev)
		dm_put_device(ti, tc->origin_dev);
	kfree(tc);

	mutex_unlock(&dm_thin_pool_table.mutex);
}

/*
 * Thin target parameters:
 *
 * <pool_dev> <dev_id> [origin_dev]
 *
 * pool_dev: the path to the pool (eg, /dev/mapper/my_pool)
 * dev_id: the internal device identifier
 * origin_dev: a device external to the pool that should act as the origin
 *
 * If the pool device has discards disabled, they get disabled for the thin
 * device as well.
 */
static int thin_ctr(struct dm_target *ti, unsigned argc, char **argv)
{
	int r;
	struct thin_c *tc;
	struct dm_dev *pool_dev, *origin_dev;
	struct mapped_device *pool_md;
	unsigned long flags;

	mutex_lock(&dm_thin_pool_table.mutex);

	if (argc != 2 && argc != 3) {
		ti->error = "Invalid argument count";
		r = -EINVAL;
		goto out_unlock;
	}

	tc = ti->private = kzalloc(sizeof(*tc), GFP_KERNEL);
	if (!tc) {
		ti->error = "Out of memory";
		r = -ENOMEM;
		goto out_unlock;
	}
	spin_lock_init(&tc->lock);
	bio_list_init(&tc->deferred_bio_list);
	bio_list_init(&tc->retry_on_resume_list);
	tc->sort_bio_list = RB_ROOT;

	if (argc == 3) {
		r = dm_get_device(ti, argv[2], FMODE_READ, &origin_dev);
		if (r) {
			ti->error = "Error opening origin device";
			goto bad_origin_dev;
		}
		tc->origin_dev = origin_dev;
	}

	r = dm_get_device(ti, argv[0], dm_table_get_mode(ti->table), &pool_dev);
	if (r) {
		ti->error = "Error opening pool device";
		goto bad_pool_dev;
	}
	tc->pool_dev = pool_dev;

	if (read_dev_id(argv[1], (unsigned long long *)&tc->dev_id, 0)) {
		ti->error = "Invalid device id";
		r = -EINVAL;
		goto bad_common;
	}

	pool_md = dm_get_md(tc->pool_dev->bdev->bd_dev);
	if (!pool_md) {
		ti->error = "Couldn't get pool mapped device";
		r = -EINVAL;
		goto bad_common;
	}

	tc->pool = __pool_table_lookup(pool_md);
	if (!tc->pool) {
		ti->error = "Couldn't find pool object";
		r = -EINVAL;
		goto bad_pool_lookup;
	}
	__pool_inc(tc->pool);

	if (get_pool_mode(tc->pool) == PM_FAIL) {
		ti->error = "Couldn't open thin device, Pool is in fail mode";
		r = -EINVAL;
		goto bad_thin_open;
	}

	r = dm_pool_open_thin_device(tc->pool->pmd, tc->dev_id, &tc->td);
	if (r) {
		ti->error = "Couldn't open thin internal device";
		goto bad_thin_open;
	}

	r = dm_set_target_max_io_len(ti, tc->pool->sectors_per_block);
	if (r)
		goto bad_target_max_io_len;

	ti->num_flush_bios = 1;
	ti->flush_supported = true;
	ti->per_bio_data_size = sizeof(struct dm_thin_endio_hook);

	/* In case the pool supports discards, pass them on. */
	ti->discard_zeroes_data_unsupported = true;
	if (tc->pool->pf.discard_enabled) {
		ti->discards_supported = true;
		ti->num_discard_bios = 1;
		/* Discard bios must be split on a block boundary */
		ti->split_discard_bios = true;
	}

	dm_put(pool_md);

	mutex_unlock(&dm_thin_pool_table.mutex);

	atomic_set(&tc->refcount, 1);
	init_completion(&tc->can_destroy);

	spin_lock_irqsave(&tc->pool->lock, flags);
	list_add_tail_rcu(&tc->list, &tc->pool->active_thins);
	spin_unlock_irqrestore(&tc->pool->lock, flags);
	/*
	 * This synchronize_rcu() call is needed here otherwise we risk a
	 * wake_worker() call finding no bios to process (because the newly
	 * added tc isn't yet visible).  So this reduces latency since we
	 * aren't then dependent on the periodic commit to wake_worker().
	 */
	synchronize_rcu();

	return 0;

bad_target_max_io_len:
	dm_pool_close_thin_device(tc->td);
bad_thin_open:
	__pool_dec(tc->pool);
bad_pool_lookup:
	dm_put(pool_md);
bad_common:
	dm_put_device(ti, tc->pool_dev);
bad_pool_dev:
	if (tc->origin_dev)
		dm_put_device(ti, tc->origin_dev);
bad_origin_dev:
	kfree(tc);
out_unlock:
	mutex_unlock(&dm_thin_pool_table.mutex);

	return r;
}

static int thin_map(struct dm_target *ti, struct bio *bio)
{
	bio->bi_iter.bi_sector = dm_target_offset(ti, bio->bi_iter.bi_sector);

	return thin_bio_map(ti, bio);
}

static int thin_endio(struct dm_target *ti, struct bio *bio, int err)
{
	unsigned long flags;
	struct dm_thin_endio_hook *h = dm_per_bio_data(bio, sizeof(struct dm_thin_endio_hook));
	struct list_head work;
	struct dm_thin_new_mapping *m, *tmp;
	struct pool *pool = h->tc->pool;

	if (h->shared_read_entry) {
		INIT_LIST_HEAD(&work);
		dm_deferred_entry_dec(h->shared_read_entry, &work);

		spin_lock_irqsave(&pool->lock, flags);
		list_for_each_entry_safe(m, tmp, &work, list) {
			list_del(&m->list);
			m->quiesced = true;
			__maybe_add_mapping(m);
		}
		spin_unlock_irqrestore(&pool->lock, flags);
	}

	if (h->all_io_entry) {
		INIT_LIST_HEAD(&work);
		dm_deferred_entry_dec(h->all_io_entry, &work);
		if (!list_empty(&work)) {
			spin_lock_irqsave(&pool->lock, flags);
			list_for_each_entry_safe(m, tmp, &work, list)
				list_add_tail(&m->list, &pool->prepared_discards);
			spin_unlock_irqrestore(&pool->lock, flags);
			wake_worker(pool);
		}
	}

	return 0;
}

static void thin_presuspend(struct dm_target *ti)
{
	struct thin_c *tc = ti->private;

	if (dm_noflush_suspending(ti))
		noflush_work(tc, do_noflush_start);
}

static void thin_postsuspend(struct dm_target *ti)
{
	struct thin_c *tc = ti->private;

	/*
	 * The dm_noflush_suspending flag has been cleared by now, so
	 * unfortunately we must always run this.
	 */
	noflush_work(tc, do_noflush_stop);
}

/*
 * <nr mapped sectors> <highest mapped sector>
 */
static void thin_status(struct dm_target *ti, status_type_t type,
			unsigned status_flags, char *result, unsigned maxlen)
{
	int r;
	ssize_t sz = 0;
	dm_block_t mapped, highest;
	char buf[BDEVNAME_SIZE];
	struct thin_c *tc = ti->private;

	if (get_pool_mode(tc->pool) == PM_FAIL) {
		DMEMIT("Fail");
		return;
	}

	if (!tc->td)
		DMEMIT("-");
	else {
		switch (type) {
		case STATUSTYPE_INFO:
			r = dm_thin_get_mapped_count(tc->td, &mapped);
			if (r) {
				DMERR("dm_thin_get_mapped_count returned %d", r);
				goto err;
			}

			r = dm_thin_get_highest_mapped_block(tc->td, &highest);
			if (r < 0) {
				DMERR("dm_thin_get_highest_mapped_block returned %d", r);
				goto err;
			}

			DMEMIT("%llu ", mapped * tc->pool->sectors_per_block);
			if (r)
				DMEMIT("%llu", ((highest + 1) *
						tc->pool->sectors_per_block) - 1);
			else
				DMEMIT("-");
			break;

		case STATUSTYPE_TABLE:
			DMEMIT("%s %lu",
			       format_dev_t(buf, tc->pool_dev->bdev->bd_dev),
			       (unsigned long) tc->dev_id);
			if (tc->origin_dev)
				DMEMIT(" %s", format_dev_t(buf, tc->origin_dev->bdev->bd_dev));
			break;
		}
	}

	return;

err:
	DMEMIT("Error");
}

static int thin_iterate_devices(struct dm_target *ti,
				iterate_devices_callout_fn fn, void *data)
{
	sector_t blocks;
	struct thin_c *tc = ti->private;
	struct pool *pool = tc->pool;

	/*
	 * We can't call dm_pool_get_data_dev_size() since that blocks.  So
	 * we follow a more convoluted path through to the pool's target.
	 */
	if (!pool->ti)
		return 0;	/* nothing is bound */

	blocks = pool->ti->len;
	(void) sector_div(blocks, pool->sectors_per_block);
	if (blocks)
		return fn(ti, tc->pool_dev, 0, pool->sectors_per_block * blocks, data);

	return 0;
}

static struct target_type thin_target = {
	.name = "thin",
	.version = {1, 12, 0},
	.module	= THIS_MODULE,
	.ctr = thin_ctr,
	.dtr = thin_dtr,
	.map = thin_map,
	.end_io = thin_endio,
	.presuspend = thin_presuspend,
	.postsuspend = thin_postsuspend,
	.status = thin_status,
	.iterate_devices = thin_iterate_devices,
};

/*----------------------------------------------------------------*/

static int __init dm_thin_init(void)
{
	int r;

	pool_table_init();

	r = dm_register_target(&thin_target);
	if (r)
		return r;

	r = dm_register_target(&pool_target);
	if (r)
		goto bad_pool_target;

	r = -ENOMEM;

	_new_mapping_cache = KMEM_CACHE(dm_thin_new_mapping, 0);
	if (!_new_mapping_cache)
		goto bad_new_mapping_cache;

	return 0;

bad_new_mapping_cache:
	dm_unregister_target(&pool_target);
bad_pool_target:
	dm_unregister_target(&thin_target);

	return r;
}

static void dm_thin_exit(void)
{
	dm_unregister_target(&thin_target);
	dm_unregister_target(&pool_target);

	kmem_cache_destroy(_new_mapping_cache);
}

module_init(dm_thin_init);
module_exit(dm_thin_exit);

module_param_named(no_space_timeout, no_space_timeout_secs, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(no_space_timeout, "Out of data space queue IO timeout in seconds");

MODULE_DESCRIPTION(DM_NAME " thin provisioning target");
MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
MODULE_LICENSE("GPL");