summaryrefslogtreecommitdiff
path: root/mm/filemap.c
blob: 582f5317ff717d8d9fa017d0395a3bda3628a1f6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
// SPDX-License-Identifier: GPL-2.0-only
/*
 *	linux/mm/filemap.c
 *
 * Copyright (C) 1994-1999  Linus Torvalds
 */

/*
 * This file handles the generic file mmap semantics used by
 * most "normal" filesystems (but you don't /have/ to use this:
 * the NFS filesystem used to do this differently, for example)
 */
#include <linux/export.h>
#include <linux/compiler.h>
#include <linux/dax.h>
#include <linux/fs.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <linux/capability.h>
#include <linux/kernel_stat.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/syscalls.h>
#include <linux/mman.h>
#include <linux/pagemap.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/error-injection.h>
#include <linux/hash.h>
#include <linux/writeback.h>
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/security.h>
#include <linux/cpuset.h>
#include <linux/hugetlb.h>
#include <linux/memcontrol.h>
#include <linux/shmem_fs.h>
#include <linux/rmap.h>
#include <linux/delayacct.h>
#include <linux/psi.h>
#include <linux/ramfs.h>
#include <linux/page_idle.h>
#include <linux/migrate.h>
#include <linux/pipe_fs_i.h>
#include <linux/splice.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include "internal.h"

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

/*
 * FIXME: remove all knowledge of the buffer layer from the core VM
 */
#include <linux/buffer_head.h> /* for try_to_free_buffers */

#include <asm/mman.h>

#include "swap.h"

/*
 * Shared mappings implemented 30.11.1994. It's not fully working yet,
 * though.
 *
 * Shared mappings now work. 15.8.1995  Bruno.
 *
 * finished 'unifying' the page and buffer cache and SMP-threaded the
 * page-cache, 21.05.1999, Ingo Molnar <mingo@redhat.com>
 *
 * SMP-threaded pagemap-LRU 1999, Andrea Arcangeli <andrea@suse.de>
 */

/*
 * Lock ordering:
 *
 *  ->i_mmap_rwsem		(truncate_pagecache)
 *    ->private_lock		(__free_pte->block_dirty_folio)
 *      ->swap_lock		(exclusive_swap_page, others)
 *        ->i_pages lock
 *
 *  ->i_rwsem
 *    ->invalidate_lock		(acquired by fs in truncate path)
 *      ->i_mmap_rwsem		(truncate->unmap_mapping_range)
 *
 *  ->mmap_lock
 *    ->i_mmap_rwsem
 *      ->page_table_lock or pte_lock	(various, mainly in memory.c)
 *        ->i_pages lock	(arch-dependent flush_dcache_mmap_lock)
 *
 *  ->mmap_lock
 *    ->invalidate_lock		(filemap_fault)
 *      ->lock_page		(filemap_fault, access_process_vm)
 *
 *  ->i_rwsem			(generic_perform_write)
 *    ->mmap_lock		(fault_in_readable->do_page_fault)
 *
 *  bdi->wb.list_lock
 *    sb_lock			(fs/fs-writeback.c)
 *    ->i_pages lock		(__sync_single_inode)
 *
 *  ->i_mmap_rwsem
 *    ->anon_vma.lock		(vma_merge)
 *
 *  ->anon_vma.lock
 *    ->page_table_lock or pte_lock	(anon_vma_prepare and various)
 *
 *  ->page_table_lock or pte_lock
 *    ->swap_lock		(try_to_unmap_one)
 *    ->private_lock		(try_to_unmap_one)
 *    ->i_pages lock		(try_to_unmap_one)
 *    ->lruvec->lru_lock	(follow_page->mark_page_accessed)
 *    ->lruvec->lru_lock	(check_pte_range->isolate_lru_page)
 *    ->private_lock		(page_remove_rmap->set_page_dirty)
 *    ->i_pages lock		(page_remove_rmap->set_page_dirty)
 *    bdi.wb->list_lock		(page_remove_rmap->set_page_dirty)
 *    ->inode->i_lock		(page_remove_rmap->set_page_dirty)
 *    ->memcg->move_lock	(page_remove_rmap->folio_memcg_lock)
 *    bdi.wb->list_lock		(zap_pte_range->set_page_dirty)
 *    ->inode->i_lock		(zap_pte_range->set_page_dirty)
 *    ->private_lock		(zap_pte_range->block_dirty_folio)
 */

static void page_cache_delete(struct address_space *mapping,
				   struct folio *folio, void *shadow)
{
	XA_STATE(xas, &mapping->i_pages, folio->index);
	long nr = 1;

	mapping_set_update(&xas, mapping);

	/* hugetlb pages are represented by a single entry in the xarray */
	if (!folio_test_hugetlb(folio)) {
		xas_set_order(&xas, folio->index, folio_order(folio));
		nr = folio_nr_pages(folio);
	}

	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);

	xas_store(&xas, shadow);
	xas_init_marks(&xas);

	folio->mapping = NULL;
	/* Leave page->index set: truncation lookup relies upon it */
	mapping->nrpages -= nr;
}

static void filemap_unaccount_folio(struct address_space *mapping,
		struct folio *folio)
{
	long nr;

	VM_BUG_ON_FOLIO(folio_mapped(folio), folio);
	if (!IS_ENABLED(CONFIG_DEBUG_VM) && unlikely(folio_mapped(folio))) {
		pr_alert("BUG: Bad page cache in process %s  pfn:%05lx\n",
			 current->comm, folio_pfn(folio));
		dump_page(&folio->page, "still mapped when deleted");
		dump_stack();
		add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);

		if (mapping_exiting(mapping) && !folio_test_large(folio)) {
			int mapcount = page_mapcount(&folio->page);

			if (folio_ref_count(folio) >= mapcount + 2) {
				/*
				 * All vmas have already been torn down, so it's
				 * a good bet that actually the page is unmapped
				 * and we'd rather not leak it: if we're wrong,
				 * another bad page check should catch it later.
				 */
				page_mapcount_reset(&folio->page);
				folio_ref_sub(folio, mapcount);
			}
		}
	}

	/* hugetlb folios do not participate in page cache accounting. */
	if (folio_test_hugetlb(folio))
		return;

	nr = folio_nr_pages(folio);

	__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, -nr);
	if (folio_test_swapbacked(folio)) {
		__lruvec_stat_mod_folio(folio, NR_SHMEM, -nr);
		if (folio_test_pmd_mappable(folio))
			__lruvec_stat_mod_folio(folio, NR_SHMEM_THPS, -nr);
	} else if (folio_test_pmd_mappable(folio)) {
		__lruvec_stat_mod_folio(folio, NR_FILE_THPS, -nr);
		filemap_nr_thps_dec(mapping);
	}

	/*
	 * At this point folio must be either written or cleaned by
	 * truncate.  Dirty folio here signals a bug and loss of
	 * unwritten data - on ordinary filesystems.
	 *
	 * But it's harmless on in-memory filesystems like tmpfs; and can
	 * occur when a driver which did get_user_pages() sets page dirty
	 * before putting it, while the inode is being finally evicted.
	 *
	 * Below fixes dirty accounting after removing the folio entirely
	 * but leaves the dirty flag set: it has no effect for truncated
	 * folio and anyway will be cleared before returning folio to
	 * buddy allocator.
	 */
	if (WARN_ON_ONCE(folio_test_dirty(folio) &&
			 mapping_can_writeback(mapping)))
		folio_account_cleaned(folio, inode_to_wb(mapping->host));
}

/*
 * Delete a page from the page cache and free it. Caller has to make
 * sure the page is locked and that nobody else uses it - or that usage
 * is safe.  The caller must hold the i_pages lock.
 */
void __filemap_remove_folio(struct folio *folio, void *shadow)
{
	struct address_space *mapping = folio->mapping;

	trace_mm_filemap_delete_from_page_cache(folio);
	filemap_unaccount_folio(mapping, folio);
	page_cache_delete(mapping, folio, shadow);
}

void filemap_free_folio(struct address_space *mapping, struct folio *folio)
{
	void (*free_folio)(struct folio *);
	int refs = 1;

	free_folio = mapping->a_ops->free_folio;
	if (free_folio)
		free_folio(folio);

	if (folio_test_large(folio) && !folio_test_hugetlb(folio))
		refs = folio_nr_pages(folio);
	folio_put_refs(folio, refs);
}

/**
 * filemap_remove_folio - Remove folio from page cache.
 * @folio: The folio.
 *
 * This must be called only on folios that are locked and have been
 * verified to be in the page cache.  It will never put the folio into
 * the free list because the caller has a reference on the page.
 */
void filemap_remove_folio(struct folio *folio)
{
	struct address_space *mapping = folio->mapping;

	BUG_ON(!folio_test_locked(folio));
	spin_lock(&mapping->host->i_lock);
	xa_lock_irq(&mapping->i_pages);
	__filemap_remove_folio(folio, NULL);
	xa_unlock_irq(&mapping->i_pages);
	if (mapping_shrinkable(mapping))
		inode_add_lru(mapping->host);
	spin_unlock(&mapping->host->i_lock);

	filemap_free_folio(mapping, folio);
}

/*
 * page_cache_delete_batch - delete several folios from page cache
 * @mapping: the mapping to which folios belong
 * @fbatch: batch of folios to delete
 *
 * The function walks over mapping->i_pages and removes folios passed in
 * @fbatch from the mapping. The function expects @fbatch to be sorted
 * by page index and is optimised for it to be dense.
 * It tolerates holes in @fbatch (mapping entries at those indices are not
 * modified).
 *
 * The function expects the i_pages lock to be held.
 */
static void page_cache_delete_batch(struct address_space *mapping,
			     struct folio_batch *fbatch)
{
	XA_STATE(xas, &mapping->i_pages, fbatch->folios[0]->index);
	long total_pages = 0;
	int i = 0;
	struct folio *folio;

	mapping_set_update(&xas, mapping);
	xas_for_each(&xas, folio, ULONG_MAX) {
		if (i >= folio_batch_count(fbatch))
			break;

		/* A swap/dax/shadow entry got inserted? Skip it. */
		if (xa_is_value(folio))
			continue;
		/*
		 * A page got inserted in our range? Skip it. We have our
		 * pages locked so they are protected from being removed.
		 * If we see a page whose index is higher than ours, it
		 * means our page has been removed, which shouldn't be
		 * possible because we're holding the PageLock.
		 */
		if (folio != fbatch->folios[i]) {
			VM_BUG_ON_FOLIO(folio->index >
					fbatch->folios[i]->index, folio);
			continue;
		}

		WARN_ON_ONCE(!folio_test_locked(folio));

		folio->mapping = NULL;
		/* Leave folio->index set: truncation lookup relies on it */

		i++;
		xas_store(&xas, NULL);
		total_pages += folio_nr_pages(folio);
	}
	mapping->nrpages -= total_pages;
}

void delete_from_page_cache_batch(struct address_space *mapping,
				  struct folio_batch *fbatch)
{
	int i;

	if (!folio_batch_count(fbatch))
		return;

	spin_lock(&mapping->host->i_lock);
	xa_lock_irq(&mapping->i_pages);
	for (i = 0; i < folio_batch_count(fbatch); i++) {
		struct folio *folio = fbatch->folios[i];

		trace_mm_filemap_delete_from_page_cache(folio);
		filemap_unaccount_folio(mapping, folio);
	}
	page_cache_delete_batch(mapping, fbatch);
	xa_unlock_irq(&mapping->i_pages);
	if (mapping_shrinkable(mapping))
		inode_add_lru(mapping->host);
	spin_unlock(&mapping->host->i_lock);

	for (i = 0; i < folio_batch_count(fbatch); i++)
		filemap_free_folio(mapping, fbatch->folios[i]);
}

int filemap_check_errors(struct address_space *mapping)
{
	int ret = 0;
	/* Check for outstanding write errors */
	if (test_bit(AS_ENOSPC, &mapping->flags) &&
	    test_and_clear_bit(AS_ENOSPC, &mapping->flags))
		ret = -ENOSPC;
	if (test_bit(AS_EIO, &mapping->flags) &&
	    test_and_clear_bit(AS_EIO, &mapping->flags))
		ret = -EIO;
	return ret;
}
EXPORT_SYMBOL(filemap_check_errors);

static int filemap_check_and_keep_errors(struct address_space *mapping)
{
	/* Check for outstanding write errors */
	if (test_bit(AS_EIO, &mapping->flags))
		return -EIO;
	if (test_bit(AS_ENOSPC, &mapping->flags))
		return -ENOSPC;
	return 0;
}

/**
 * filemap_fdatawrite_wbc - start writeback on mapping dirty pages in range
 * @mapping:	address space structure to write
 * @wbc:	the writeback_control controlling the writeout
 *
 * Call writepages on the mapping using the provided wbc to control the
 * writeout.
 *
 * Return: %0 on success, negative error code otherwise.
 */
int filemap_fdatawrite_wbc(struct address_space *mapping,
			   struct writeback_control *wbc)
{
	int ret;

	if (!mapping_can_writeback(mapping) ||
	    !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
		return 0;

	wbc_attach_fdatawrite_inode(wbc, mapping->host);
	ret = do_writepages(mapping, wbc);
	wbc_detach_inode(wbc);
	return ret;
}
EXPORT_SYMBOL(filemap_fdatawrite_wbc);

/**
 * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
 * @mapping:	address space structure to write
 * @start:	offset in bytes where the range starts
 * @end:	offset in bytes where the range ends (inclusive)
 * @sync_mode:	enable synchronous operation
 *
 * Start writeback against all of a mapping's dirty pages that lie
 * within the byte offsets <start, end> inclusive.
 *
 * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
 * opposed to a regular memory cleansing writeback.  The difference between
 * these two operations is that if a dirty page/buffer is encountered, it must
 * be waited upon, and not just skipped over.
 *
 * Return: %0 on success, negative error code otherwise.
 */
int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
				loff_t end, int sync_mode)
{
	struct writeback_control wbc = {
		.sync_mode = sync_mode,
		.nr_to_write = LONG_MAX,
		.range_start = start,
		.range_end = end,
	};

	return filemap_fdatawrite_wbc(mapping, &wbc);
}

static inline int __filemap_fdatawrite(struct address_space *mapping,
	int sync_mode)
{
	return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
}

int filemap_fdatawrite(struct address_space *mapping)
{
	return __filemap_fdatawrite(mapping, WB_SYNC_ALL);
}
EXPORT_SYMBOL(filemap_fdatawrite);

int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
				loff_t end)
{
	return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
}
EXPORT_SYMBOL(filemap_fdatawrite_range);

/**
 * filemap_flush - mostly a non-blocking flush
 * @mapping:	target address_space
 *
 * This is a mostly non-blocking flush.  Not suitable for data-integrity
 * purposes - I/O may not be started against all dirty pages.
 *
 * Return: %0 on success, negative error code otherwise.
 */
int filemap_flush(struct address_space *mapping)
{
	return __filemap_fdatawrite(mapping, WB_SYNC_NONE);
}
EXPORT_SYMBOL(filemap_flush);

/**
 * filemap_range_has_page - check if a page exists in range.
 * @mapping:           address space within which to check
 * @start_byte:        offset in bytes where the range starts
 * @end_byte:          offset in bytes where the range ends (inclusive)
 *
 * Find at least one page in the range supplied, usually used to check if
 * direct writing in this range will trigger a writeback.
 *
 * Return: %true if at least one page exists in the specified range,
 * %false otherwise.
 */
bool filemap_range_has_page(struct address_space *mapping,
			   loff_t start_byte, loff_t end_byte)
{
	struct folio *folio;
	XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
	pgoff_t max = end_byte >> PAGE_SHIFT;

	if (end_byte < start_byte)
		return false;

	rcu_read_lock();
	for (;;) {
		folio = xas_find(&xas, max);
		if (xas_retry(&xas, folio))
			continue;
		/* Shadow entries don't count */
		if (xa_is_value(folio))
			continue;
		/*
		 * We don't need to try to pin this page; we're about to
		 * release the RCU lock anyway.  It is enough to know that
		 * there was a page here recently.
		 */
		break;
	}
	rcu_read_unlock();

	return folio != NULL;
}
EXPORT_SYMBOL(filemap_range_has_page);

static void __filemap_fdatawait_range(struct address_space *mapping,
				     loff_t start_byte, loff_t end_byte)
{
	pgoff_t index = start_byte >> PAGE_SHIFT;
	pgoff_t end = end_byte >> PAGE_SHIFT;
	struct folio_batch fbatch;
	unsigned nr_folios;

	folio_batch_init(&fbatch);

	while (index <= end) {
		unsigned i;

		nr_folios = filemap_get_folios_tag(mapping, &index, end,
				PAGECACHE_TAG_WRITEBACK, &fbatch);

		if (!nr_folios)
			break;

		for (i = 0; i < nr_folios; i++) {
			struct folio *folio = fbatch.folios[i];

			folio_wait_writeback(folio);
			folio_clear_error(folio);
		}
		folio_batch_release(&fbatch);
		cond_resched();
	}
}

/**
 * filemap_fdatawait_range - wait for writeback to complete
 * @mapping:		address space structure to wait for
 * @start_byte:		offset in bytes where the range starts
 * @end_byte:		offset in bytes where the range ends (inclusive)
 *
 * Walk the list of under-writeback pages of the given address space
 * in the given range and wait for all of them.  Check error status of
 * the address space and return it.
 *
 * Since the error status of the address space is cleared by this function,
 * callers are responsible for checking the return value and handling and/or
 * reporting the error.
 *
 * Return: error status of the address space.
 */
int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
			    loff_t end_byte)
{
	__filemap_fdatawait_range(mapping, start_byte, end_byte);
	return filemap_check_errors(mapping);
}
EXPORT_SYMBOL(filemap_fdatawait_range);

/**
 * filemap_fdatawait_range_keep_errors - wait for writeback to complete
 * @mapping:		address space structure to wait for
 * @start_byte:		offset in bytes where the range starts
 * @end_byte:		offset in bytes where the range ends (inclusive)
 *
 * Walk the list of under-writeback pages of the given address space in the
 * given range and wait for all of them.  Unlike filemap_fdatawait_range(),
 * this function does not clear error status of the address space.
 *
 * Use this function if callers don't handle errors themselves.  Expected
 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
 * fsfreeze(8)
 */
int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
		loff_t start_byte, loff_t end_byte)
{
	__filemap_fdatawait_range(mapping, start_byte, end_byte);
	return filemap_check_and_keep_errors(mapping);
}
EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);

/**
 * file_fdatawait_range - wait for writeback to complete
 * @file:		file pointing to address space structure to wait for
 * @start_byte:		offset in bytes where the range starts
 * @end_byte:		offset in bytes where the range ends (inclusive)
 *
 * Walk the list of under-writeback pages of the address space that file
 * refers to, in the given range and wait for all of them.  Check error
 * status of the address space vs. the file->f_wb_err cursor and return it.
 *
 * Since the error status of the file is advanced by this function,
 * callers are responsible for checking the return value and handling and/or
 * reporting the error.
 *
 * Return: error status of the address space vs. the file->f_wb_err cursor.
 */
int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
{
	struct address_space *mapping = file->f_mapping;

	__filemap_fdatawait_range(mapping, start_byte, end_byte);
	return file_check_and_advance_wb_err(file);
}
EXPORT_SYMBOL(file_fdatawait_range);

/**
 * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
 * @mapping: address space structure to wait for
 *
 * Walk the list of under-writeback pages of the given address space
 * and wait for all of them.  Unlike filemap_fdatawait(), this function
 * does not clear error status of the address space.
 *
 * Use this function if callers don't handle errors themselves.  Expected
 * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
 * fsfreeze(8)
 *
 * Return: error status of the address space.
 */
int filemap_fdatawait_keep_errors(struct address_space *mapping)
{
	__filemap_fdatawait_range(mapping, 0, LLONG_MAX);
	return filemap_check_and_keep_errors(mapping);
}
EXPORT_SYMBOL(filemap_fdatawait_keep_errors);

/* Returns true if writeback might be needed or already in progress. */
static bool mapping_needs_writeback(struct address_space *mapping)
{
	return mapping->nrpages;
}

bool filemap_range_has_writeback(struct address_space *mapping,
				 loff_t start_byte, loff_t end_byte)
{
	XA_STATE(xas, &mapping->i_pages, start_byte >> PAGE_SHIFT);
	pgoff_t max = end_byte >> PAGE_SHIFT;
	struct folio *folio;

	if (end_byte < start_byte)
		return false;

	rcu_read_lock();
	xas_for_each(&xas, folio, max) {
		if (xas_retry(&xas, folio))
			continue;
		if (xa_is_value(folio))
			continue;
		if (folio_test_dirty(folio) || folio_test_locked(folio) ||
				folio_test_writeback(folio))
			break;
	}
	rcu_read_unlock();
	return folio != NULL;
}
EXPORT_SYMBOL_GPL(filemap_range_has_writeback);

/**
 * filemap_write_and_wait_range - write out & wait on a file range
 * @mapping:	the address_space for the pages
 * @lstart:	offset in bytes where the range starts
 * @lend:	offset in bytes where the range ends (inclusive)
 *
 * Write out and wait upon file offsets lstart->lend, inclusive.
 *
 * Note that @lend is inclusive (describes the last byte to be written) so
 * that this function can be used to write to the very end-of-file (end = -1).
 *
 * Return: error status of the address space.
 */
int filemap_write_and_wait_range(struct address_space *mapping,
				 loff_t lstart, loff_t lend)
{
	int err = 0, err2;

	if (lend < lstart)
		return 0;

	if (mapping_needs_writeback(mapping)) {
		err = __filemap_fdatawrite_range(mapping, lstart, lend,
						 WB_SYNC_ALL);
		/*
		 * Even if the above returned error, the pages may be
		 * written partially (e.g. -ENOSPC), so we wait for it.
		 * But the -EIO is special case, it may indicate the worst
		 * thing (e.g. bug) happened, so we avoid waiting for it.
		 */
		if (err != -EIO)
			__filemap_fdatawait_range(mapping, lstart, lend);
	}
	err2 = filemap_check_errors(mapping);
	if (!err)
		err = err2;
	return err;
}
EXPORT_SYMBOL(filemap_write_and_wait_range);

void __filemap_set_wb_err(struct address_space *mapping, int err)
{
	errseq_t eseq = errseq_set(&mapping->wb_err, err);

	trace_filemap_set_wb_err(mapping, eseq);
}
EXPORT_SYMBOL(__filemap_set_wb_err);

/**
 * file_check_and_advance_wb_err - report wb error (if any) that was previously
 * 				   and advance wb_err to current one
 * @file: struct file on which the error is being reported
 *
 * When userland calls fsync (or something like nfsd does the equivalent), we
 * want to report any writeback errors that occurred since the last fsync (or
 * since the file was opened if there haven't been any).
 *
 * Grab the wb_err from the mapping. If it matches what we have in the file,
 * then just quickly return 0. The file is all caught up.
 *
 * If it doesn't match, then take the mapping value, set the "seen" flag in
 * it and try to swap it into place. If it works, or another task beat us
 * to it with the new value, then update the f_wb_err and return the error
 * portion. The error at this point must be reported via proper channels
 * (a'la fsync, or NFS COMMIT operation, etc.).
 *
 * While we handle mapping->wb_err with atomic operations, the f_wb_err
 * value is protected by the f_lock since we must ensure that it reflects
 * the latest value swapped in for this file descriptor.
 *
 * Return: %0 on success, negative error code otherwise.
 */
int file_check_and_advance_wb_err(struct file *file)
{
	int err = 0;
	errseq_t old = READ_ONCE(file->f_wb_err);
	struct address_space *mapping = file->f_mapping;

	/* Locklessly handle the common case where nothing has changed */
	if (errseq_check(&mapping->wb_err, old)) {
		/* Something changed, must use slow path */
		spin_lock(&file->f_lock);
		old = file->f_wb_err;
		err = errseq_check_and_advance(&mapping->wb_err,
						&file->f_wb_err);
		trace_file_check_and_advance_wb_err(file, old);
		spin_unlock(&file->f_lock);
	}

	/*
	 * We're mostly using this function as a drop in replacement for
	 * filemap_check_errors. Clear AS_EIO/AS_ENOSPC to emulate the effect
	 * that the legacy code would have had on these flags.
	 */
	clear_bit(AS_EIO, &mapping->flags);
	clear_bit(AS_ENOSPC, &mapping->flags);
	return err;
}
EXPORT_SYMBOL(file_check_and_advance_wb_err);

/**
 * file_write_and_wait_range - write out & wait on a file range
 * @file:	file pointing to address_space with pages
 * @lstart:	offset in bytes where the range starts
 * @lend:	offset in bytes where the range ends (inclusive)
 *
 * Write out and wait upon file offsets lstart->lend, inclusive.
 *
 * Note that @lend is inclusive (describes the last byte to be written) so
 * that this function can be used to write to the very end-of-file (end = -1).
 *
 * After writing out and waiting on the data, we check and advance the
 * f_wb_err cursor to the latest value, and return any errors detected there.
 *
 * Return: %0 on success, negative error code otherwise.
 */
int file_write_and_wait_range(struct file *file, loff_t lstart, loff_t lend)
{
	int err = 0, err2;
	struct address_space *mapping = file->f_mapping;

	if (lend < lstart)
		return 0;

	if (mapping_needs_writeback(mapping)) {
		err = __filemap_fdatawrite_range(mapping, lstart, lend,
						 WB_SYNC_ALL);
		/* See comment of filemap_write_and_wait() */
		if (err != -EIO)
			__filemap_fdatawait_range(mapping, lstart, lend);
	}
	err2 = file_check_and_advance_wb_err(file);
	if (!err)
		err = err2;
	return err;
}
EXPORT_SYMBOL(file_write_and_wait_range);

/**
 * replace_page_cache_folio - replace a pagecache folio with a new one
 * @old:	folio to be replaced
 * @new:	folio to replace with
 *
 * This function replaces a folio in the pagecache with a new one.  On
 * success it acquires the pagecache reference for the new folio and
 * drops it for the old folio.  Both the old and new folios must be
 * locked.  This function does not add the new folio to the LRU, the
 * caller must do that.
 *
 * The remove + add is atomic.  This function cannot fail.
 */
void replace_page_cache_folio(struct folio *old, struct folio *new)
{
	struct address_space *mapping = old->mapping;
	void (*free_folio)(struct folio *) = mapping->a_ops->free_folio;
	pgoff_t offset = old->index;
	XA_STATE(xas, &mapping->i_pages, offset);

	VM_BUG_ON_FOLIO(!folio_test_locked(old), old);
	VM_BUG_ON_FOLIO(!folio_test_locked(new), new);
	VM_BUG_ON_FOLIO(new->mapping, new);

	folio_get(new);
	new->mapping = mapping;
	new->index = offset;

	mem_cgroup_migrate(old, new);

	xas_lock_irq(&xas);
	xas_store(&xas, new);

	old->mapping = NULL;
	/* hugetlb pages do not participate in page cache accounting. */
	if (!folio_test_hugetlb(old))
		__lruvec_stat_sub_folio(old, NR_FILE_PAGES);
	if (!folio_test_hugetlb(new))
		__lruvec_stat_add_folio(new, NR_FILE_PAGES);
	if (folio_test_swapbacked(old))
		__lruvec_stat_sub_folio(old, NR_SHMEM);
	if (folio_test_swapbacked(new))
		__lruvec_stat_add_folio(new, NR_SHMEM);
	xas_unlock_irq(&xas);
	if (free_folio)
		free_folio(old);
	folio_put(old);
}
EXPORT_SYMBOL_GPL(replace_page_cache_folio);

noinline int __filemap_add_folio(struct address_space *mapping,
		struct folio *folio, pgoff_t index, gfp_t gfp, void **shadowp)
{
	XA_STATE(xas, &mapping->i_pages, index);
	int huge = folio_test_hugetlb(folio);
	bool charged = false;
	long nr = 1;

	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
	VM_BUG_ON_FOLIO(folio_test_swapbacked(folio), folio);
	mapping_set_update(&xas, mapping);

	if (!huge) {
		int error = mem_cgroup_charge(folio, NULL, gfp);
		VM_BUG_ON_FOLIO(index & (folio_nr_pages(folio) - 1), folio);
		if (error)
			return error;
		charged = true;
		xas_set_order(&xas, index, folio_order(folio));
		nr = folio_nr_pages(folio);
	}

	gfp &= GFP_RECLAIM_MASK;
	folio_ref_add(folio, nr);
	folio->mapping = mapping;
	folio->index = xas.xa_index;

	do {
		unsigned int order = xa_get_order(xas.xa, xas.xa_index);
		void *entry, *old = NULL;

		if (order > folio_order(folio))
			xas_split_alloc(&xas, xa_load(xas.xa, xas.xa_index),
					order, gfp);
		xas_lock_irq(&xas);
		xas_for_each_conflict(&xas, entry) {
			old = entry;
			if (!xa_is_value(entry)) {
				xas_set_err(&xas, -EEXIST);
				goto unlock;
			}
		}

		if (old) {
			if (shadowp)
				*shadowp = old;
			/* entry may have been split before we acquired lock */
			order = xa_get_order(xas.xa, xas.xa_index);
			if (order > folio_order(folio)) {
				/* How to handle large swap entries? */
				BUG_ON(shmem_mapping(mapping));
				xas_split(&xas, old, order);
				xas_reset(&xas);
			}
		}

		xas_store(&xas, folio);
		if (xas_error(&xas))
			goto unlock;

		mapping->nrpages += nr;

		/* hugetlb pages do not participate in page cache accounting */
		if (!huge) {
			__lruvec_stat_mod_folio(folio, NR_FILE_PAGES, nr);
			if (folio_test_pmd_mappable(folio))
				__lruvec_stat_mod_folio(folio,
						NR_FILE_THPS, nr);
		}
unlock:
		xas_unlock_irq(&xas);
	} while (xas_nomem(&xas, gfp));

	if (xas_error(&xas))
		goto error;

	trace_mm_filemap_add_to_page_cache(folio);
	return 0;
error:
	if (charged)
		mem_cgroup_uncharge(folio);
	folio->mapping = NULL;
	/* Leave page->index set: truncation relies upon it */
	folio_put_refs(folio, nr);
	return xas_error(&xas);
}
ALLOW_ERROR_INJECTION(__filemap_add_folio, ERRNO);

int filemap_add_folio(struct address_space *mapping, struct folio *folio,
				pgoff_t index, gfp_t gfp)
{
	void *shadow = NULL;
	int ret;

	__folio_set_locked(folio);
	ret = __filemap_add_folio(mapping, folio, index, gfp, &shadow);
	if (unlikely(ret))
		__folio_clear_locked(folio);
	else {
		/*
		 * The folio might have been evicted from cache only
		 * recently, in which case it should be activated like
		 * any other repeatedly accessed folio.
		 * The exception is folios getting rewritten; evicting other
		 * data from the working set, only to cache data that will
		 * get overwritten with something else, is a waste of memory.
		 */
		WARN_ON_ONCE(folio_test_active(folio));
		if (!(gfp & __GFP_WRITE) && shadow)
			workingset_refault(folio, shadow);
		folio_add_lru(folio);
	}
	return ret;
}
EXPORT_SYMBOL_GPL(filemap_add_folio);

#ifdef CONFIG_NUMA
struct folio *filemap_alloc_folio(gfp_t gfp, unsigned int order)
{
	int n;
	struct folio *folio;

	if (cpuset_do_page_mem_spread()) {
		unsigned int cpuset_mems_cookie;
		do {
			cpuset_mems_cookie = read_mems_allowed_begin();
			n = cpuset_mem_spread_node();
			folio = __folio_alloc_node(gfp, order, n);
		} while (!folio && read_mems_allowed_retry(cpuset_mems_cookie));

		return folio;
	}
	return folio_alloc(gfp, order);
}
EXPORT_SYMBOL(filemap_alloc_folio);
#endif

/*
 * filemap_invalidate_lock_two - lock invalidate_lock for two mappings
 *
 * Lock exclusively invalidate_lock of any passed mapping that is not NULL.
 *
 * @mapping1: the first mapping to lock
 * @mapping2: the second mapping to lock
 */
void filemap_invalidate_lock_two(struct address_space *mapping1,
				 struct address_space *mapping2)
{
	if (mapping1 > mapping2)
		swap(mapping1, mapping2);
	if (mapping1)
		down_write(&mapping1->invalidate_lock);
	if (mapping2 && mapping1 != mapping2)
		down_write_nested(&mapping2->invalidate_lock, 1);
}
EXPORT_SYMBOL(filemap_invalidate_lock_two);

/*
 * filemap_invalidate_unlock_two - unlock invalidate_lock for two mappings
 *
 * Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
 *
 * @mapping1: the first mapping to unlock
 * @mapping2: the second mapping to unlock
 */
void filemap_invalidate_unlock_two(struct address_space *mapping1,
				   struct address_space *mapping2)
{
	if (mapping1)
		up_write(&mapping1->invalidate_lock);
	if (mapping2 && mapping1 != mapping2)
		up_write(&mapping2->invalidate_lock);
}
EXPORT_SYMBOL(filemap_invalidate_unlock_two);

/*
 * In order to wait for pages to become available there must be
 * waitqueues associated with pages. By using a hash table of
 * waitqueues where the bucket discipline is to maintain all
 * waiters on the same queue and wake all when any of the pages
 * become available, and for the woken contexts to check to be
 * sure the appropriate page became available, this saves space
 * at a cost of "thundering herd" phenomena during rare hash
 * collisions.
 */
#define PAGE_WAIT_TABLE_BITS 8
#define PAGE_WAIT_TABLE_SIZE (1 << PAGE_WAIT_TABLE_BITS)
static wait_queue_head_t folio_wait_table[PAGE_WAIT_TABLE_SIZE] __cacheline_aligned;

static wait_queue_head_t *folio_waitqueue(struct folio *folio)
{
	return &folio_wait_table[hash_ptr(folio, PAGE_WAIT_TABLE_BITS)];
}

void __init pagecache_init(void)
{
	int i;

	for (i = 0; i < PAGE_WAIT_TABLE_SIZE; i++)
		init_waitqueue_head(&folio_wait_table[i]);

	page_writeback_init();
}

/*
 * The page wait code treats the "wait->flags" somewhat unusually, because
 * we have multiple different kinds of waits, not just the usual "exclusive"
 * one.
 *
 * We have:
 *
 *  (a) no special bits set:
 *
 *	We're just waiting for the bit to be released, and when a waker
 *	calls the wakeup function, we set WQ_FLAG_WOKEN and wake it up,
 *	and remove it from the wait queue.
 *
 *	Simple and straightforward.
 *
 *  (b) WQ_FLAG_EXCLUSIVE:
 *
 *	The waiter is waiting to get the lock, and only one waiter should
 *	be woken up to avoid any thundering herd behavior. We'll set the
 *	WQ_FLAG_WOKEN bit, wake it up, and remove it from the wait queue.
 *
 *	This is the traditional exclusive wait.
 *
 *  (c) WQ_FLAG_EXCLUSIVE | WQ_FLAG_CUSTOM:
 *
 *	The waiter is waiting to get the bit, and additionally wants the
 *	lock to be transferred to it for fair lock behavior. If the lock
 *	cannot be taken, we stop walking the wait queue without waking
 *	the waiter.
 *
 *	This is the "fair lock handoff" case, and in addition to setting
 *	WQ_FLAG_WOKEN, we set WQ_FLAG_DONE to let the waiter easily see
 *	that it now has the lock.
 */
static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync, void *arg)
{
	unsigned int flags;
	struct wait_page_key *key = arg;
	struct wait_page_queue *wait_page
		= container_of(wait, struct wait_page_queue, wait);

	if (!wake_page_match(wait_page, key))
		return 0;

	/*
	 * If it's a lock handoff wait, we get the bit for it, and
	 * stop walking (and do not wake it up) if we can't.
	 */
	flags = wait->flags;
	if (flags & WQ_FLAG_EXCLUSIVE) {
		if (test_bit(key->bit_nr, &key->folio->flags))
			return -1;
		if (flags & WQ_FLAG_CUSTOM) {
			if (test_and_set_bit(key->bit_nr, &key->folio->flags))
				return -1;
			flags |= WQ_FLAG_DONE;
		}
	}

	/*
	 * We are holding the wait-queue lock, but the waiter that
	 * is waiting for this will be checking the flags without
	 * any locking.
	 *
	 * So update the flags atomically, and wake up the waiter
	 * afterwards to avoid any races. This store-release pairs
	 * with the load-acquire in folio_wait_bit_common().
	 */
	smp_store_release(&wait->flags, flags | WQ_FLAG_WOKEN);
	wake_up_state(wait->private, mode);

	/*
	 * Ok, we have successfully done what we're waiting for,
	 * and we can unconditionally remove the wait entry.
	 *
	 * Note that this pairs with the "finish_wait()" in the
	 * waiter, and has to be the absolute last thing we do.
	 * After this list_del_init(&wait->entry) the wait entry
	 * might be de-allocated and the process might even have
	 * exited.
	 */
	list_del_init_careful(&wait->entry);
	return (flags & WQ_FLAG_EXCLUSIVE) != 0;
}

static void folio_wake_bit(struct folio *folio, int bit_nr)
{
	wait_queue_head_t *q = folio_waitqueue(folio);
	struct wait_page_key key;
	unsigned long flags;
	wait_queue_entry_t bookmark;

	key.folio = folio;
	key.bit_nr = bit_nr;
	key.page_match = 0;

	bookmark.flags = 0;
	bookmark.private = NULL;
	bookmark.func = NULL;
	INIT_LIST_HEAD(&bookmark.entry);

	spin_lock_irqsave(&q->lock, flags);
	__wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);

	while (bookmark.flags & WQ_FLAG_BOOKMARK) {
		/*
		 * Take a breather from holding the lock,
		 * allow pages that finish wake up asynchronously
		 * to acquire the lock and remove themselves
		 * from wait queue
		 */
		spin_unlock_irqrestore(&q->lock, flags);
		cpu_relax();
		spin_lock_irqsave(&q->lock, flags);
		__wake_up_locked_key_bookmark(q, TASK_NORMAL, &key, &bookmark);
	}

	/*
	 * It's possible to miss clearing waiters here, when we woke our page
	 * waiters, but the hashed waitqueue has waiters for other pages on it.
	 * That's okay, it's a rare case. The next waker will clear it.
	 *
	 * Note that, depending on the page pool (buddy, hugetlb, ZONE_DEVICE,
	 * other), the flag may be cleared in the course of freeing the page;
	 * but that is not required for correctness.
	 */
	if (!waitqueue_active(q) || !key.page_match)
		folio_clear_waiters(folio);

	spin_unlock_irqrestore(&q->lock, flags);
}

static void folio_wake(struct folio *folio, int bit)
{
	if (!folio_test_waiters(folio))
		return;
	folio_wake_bit(folio, bit);
}

/*
 * A choice of three behaviors for folio_wait_bit_common():
 */
enum behavior {
	EXCLUSIVE,	/* Hold ref to page and take the bit when woken, like
			 * __folio_lock() waiting on then setting PG_locked.
			 */
	SHARED,		/* Hold ref to page and check the bit when woken, like
			 * folio_wait_writeback() waiting on PG_writeback.
			 */
	DROP,		/* Drop ref to page before wait, no check when woken,
			 * like folio_put_wait_locked() on PG_locked.
			 */
};

/*
 * Attempt to check (or get) the folio flag, and mark us done
 * if successful.
 */
static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
					struct wait_queue_entry *wait)
{
	if (wait->flags & WQ_FLAG_EXCLUSIVE) {
		if (test_and_set_bit(bit_nr, &folio->flags))
			return false;
	} else if (test_bit(bit_nr, &folio->flags))
		return false;

	wait->flags |= WQ_FLAG_WOKEN | WQ_FLAG_DONE;
	return true;
}

/* How many times do we accept lock stealing from under a waiter? */
int sysctl_page_lock_unfairness = 5;

static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
		int state, enum behavior behavior)
{
	wait_queue_head_t *q = folio_waitqueue(folio);
	int unfairness = sysctl_page_lock_unfairness;
	struct wait_page_queue wait_page;
	wait_queue_entry_t *wait = &wait_page.wait;
	bool thrashing = false;
	unsigned long pflags;
	bool in_thrashing;

	if (bit_nr == PG_locked &&
	    !folio_test_uptodate(folio) && folio_test_workingset(folio)) {
		delayacct_thrashing_start(&in_thrashing);
		psi_memstall_enter(&pflags);
		thrashing = true;
	}

	init_wait(wait);
	wait->func = wake_page_function;
	wait_page.folio = folio;
	wait_page.bit_nr = bit_nr;

repeat:
	wait->flags = 0;
	if (behavior == EXCLUSIVE) {
		wait->flags = WQ_FLAG_EXCLUSIVE;
		if (--unfairness < 0)
			wait->flags |= WQ_FLAG_CUSTOM;
	}

	/*
	 * Do one last check whether we can get the
	 * page bit synchronously.
	 *
	 * Do the folio_set_waiters() marking before that
	 * to let any waker we _just_ missed know they
	 * need to wake us up (otherwise they'll never
	 * even go to the slow case that looks at the
	 * page queue), and add ourselves to the wait
	 * queue if we need to sleep.
	 *
	 * This part needs to be done under the queue
	 * lock to avoid races.
	 */
	spin_lock_irq(&q->lock);
	folio_set_waiters(folio);
	if (!folio_trylock_flag(folio, bit_nr, wait))
		__add_wait_queue_entry_tail(q, wait);
	spin_unlock_irq(&q->lock);

	/*
	 * From now on, all the logic will be based on
	 * the WQ_FLAG_WOKEN and WQ_FLAG_DONE flag, to
	 * see whether the page bit testing has already
	 * been done by the wake function.
	 *
	 * We can drop our reference to the folio.
	 */
	if (behavior == DROP)
		folio_put(folio);

	/*
	 * Note that until the "finish_wait()", or until
	 * we see the WQ_FLAG_WOKEN flag, we need to
	 * be very careful with the 'wait->flags', because
	 * we may race with a waker that sets them.
	 */
	for (;;) {
		unsigned int flags;

		set_current_state(state);

		/* Loop until we've been woken or interrupted */
		flags = smp_load_acquire(&wait->flags);
		if (!(flags & WQ_FLAG_WOKEN)) {
			if (signal_pending_state(state, current))
				break;

			io_schedule();
			continue;
		}

		/* If we were non-exclusive, we're done */
		if (behavior != EXCLUSIVE)
			break;

		/* If the waker got the lock for us, we're done */
		if (flags & WQ_FLAG_DONE)
			break;

		/*
		 * Otherwise, if we're getting the lock, we need to
		 * try to get it ourselves.
		 *
		 * And if that fails, we'll have to retry this all.
		 */
		if (unlikely(test_and_set_bit(bit_nr, folio_flags(folio, 0))))
			goto repeat;

		wait->flags |= WQ_FLAG_DONE;
		break;
	}

	/*
	 * If a signal happened, this 'finish_wait()' may remove the last
	 * waiter from the wait-queues, but the folio waiters bit will remain
	 * set. That's ok. The next wakeup will take care of it, and trying
	 * to do it here would be difficult and prone to races.
	 */
	finish_wait(q, wait);

	if (thrashing) {
		delayacct_thrashing_end(&in_thrashing);
		psi_memstall_leave(&pflags);
	}

	/*
	 * NOTE! The wait->flags weren't stable until we've done the
	 * 'finish_wait()', and we could have exited the loop above due
	 * to a signal, and had a wakeup event happen after the signal
	 * test but before the 'finish_wait()'.
	 *
	 * So only after the finish_wait() can we reliably determine
	 * if we got woken up or not, so we can now figure out the final
	 * return value based on that state without races.
	 *
	 * Also note that WQ_FLAG_WOKEN is sufficient for a non-exclusive
	 * waiter, but an exclusive one requires WQ_FLAG_DONE.
	 */
	if (behavior == EXCLUSIVE)
		return wait->flags & WQ_FLAG_DONE ? 0 : -EINTR;

	return wait->flags & WQ_FLAG_WOKEN ? 0 : -EINTR;
}

#ifdef CONFIG_MIGRATION
/**
 * migration_entry_wait_on_locked - Wait for a migration entry to be removed
 * @entry: migration swap entry.
 * @ptl: already locked ptl. This function will drop the lock.
 *
 * Wait for a migration entry referencing the given page to be removed. This is
 * equivalent to put_and_wait_on_page_locked(page, TASK_UNINTERRUPTIBLE) except
 * this can be called without taking a reference on the page. Instead this
 * should be called while holding the ptl for the migration entry referencing
 * the page.
 *
 * Returns after unlocking the ptl.
 *
 * This follows the same logic as folio_wait_bit_common() so see the comments
 * there.
 */
void migration_entry_wait_on_locked(swp_entry_t entry, spinlock_t *ptl)
	__releases(ptl)
{
	struct wait_page_queue wait_page;
	wait_queue_entry_t *wait = &wait_page.wait;
	bool thrashing = false;
	unsigned long pflags;
	bool in_thrashing;
	wait_queue_head_t *q;
	struct folio *folio = page_folio(pfn_swap_entry_to_page(entry));

	q = folio_waitqueue(folio);
	if (!folio_test_uptodate(folio) && folio_test_workingset(folio)) {
		delayacct_thrashing_start(&in_thrashing);
		psi_memstall_enter(&pflags);
		thrashing = true;
	}

	init_wait(wait);
	wait->func = wake_page_function;
	wait_page.folio = folio;
	wait_page.bit_nr = PG_locked;
	wait->flags = 0;

	spin_lock_irq(&q->lock);
	folio_set_waiters(folio);
	if (!folio_trylock_flag(folio, PG_locked, wait))
		__add_wait_queue_entry_tail(q, wait);
	spin_unlock_irq(&q->lock);

	/*
	 * If a migration entry exists for the page the migration path must hold
	 * a valid reference to the page, and it must take the ptl to remove the
	 * migration entry. So the page is valid until the ptl is dropped.
	 */
	spin_unlock(ptl);

	for (;;) {
		unsigned int flags;

		set_current_state(TASK_UNINTERRUPTIBLE);

		/* Loop until we've been woken or interrupted */
		flags = smp_load_acquire(&wait->flags);
		if (!(flags & WQ_FLAG_WOKEN)) {
			if (signal_pending_state(TASK_UNINTERRUPTIBLE, current))
				break;

			io_schedule();
			continue;
		}
		break;
	}

	finish_wait(q, wait);

	if (thrashing) {
		delayacct_thrashing_end(&in_thrashing);
		psi_memstall_leave(&pflags);
	}
}
#endif

void folio_wait_bit(struct folio *folio, int bit_nr)
{
	folio_wait_bit_common(folio, bit_nr, TASK_UNINTERRUPTIBLE, SHARED);
}
EXPORT_SYMBOL(folio_wait_bit);

int folio_wait_bit_killable(struct folio *folio, int bit_nr)
{
	return folio_wait_bit_common(folio, bit_nr, TASK_KILLABLE, SHARED);
}
EXPORT_SYMBOL(folio_wait_bit_killable);

/**
 * folio_put_wait_locked - Drop a reference and wait for it to be unlocked
 * @folio: The folio to wait for.
 * @state: The sleep state (TASK_KILLABLE, TASK_UNINTERRUPTIBLE, etc).
 *
 * The caller should hold a reference on @folio.  They expect the page to
 * become unlocked relatively soon, but do not wish to hold up migration
 * (for example) by holding the reference while waiting for the folio to
 * come unlocked.  After this function returns, the caller should not
 * dereference @folio.
 *
 * Return: 0 if the folio was unlocked or -EINTR if interrupted by a signal.
 */
static int folio_put_wait_locked(struct folio *folio, int state)
{
	return folio_wait_bit_common(folio, PG_locked, state, DROP);
}

/**
 * folio_add_wait_queue - Add an arbitrary waiter to a folio's wait queue
 * @folio: Folio defining the wait queue of interest
 * @waiter: Waiter to add to the queue
 *
 * Add an arbitrary @waiter to the wait queue for the nominated @folio.
 */
void folio_add_wait_queue(struct folio *folio, wait_queue_entry_t *waiter)
{
	wait_queue_head_t *q = folio_waitqueue(folio);
	unsigned long flags;

	spin_lock_irqsave(&q->lock, flags);
	__add_wait_queue_entry_tail(q, waiter);
	folio_set_waiters(folio);
	spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(folio_add_wait_queue);

#ifndef clear_bit_unlock_is_negative_byte

/*
 * PG_waiters is the high bit in the same byte as PG_lock.
 *
 * On x86 (and on many other architectures), we can clear PG_lock and
 * test the sign bit at the same time. But if the architecture does
 * not support that special operation, we just do this all by hand
 * instead.
 *
 * The read of PG_waiters has to be after (or concurrently with) PG_locked
 * being cleared, but a memory barrier should be unnecessary since it is
 * in the same byte as PG_locked.
 */
static inline bool clear_bit_unlock_is_negative_byte(long nr, volatile void *mem)
{
	clear_bit_unlock(nr, mem);
	/* smp_mb__after_atomic(); */
	return test_bit(PG_waiters, mem);
}

#endif

/**
 * folio_unlock - Unlock a locked folio.
 * @folio: The folio.
 *
 * Unlocks the folio and wakes up any thread sleeping on the page lock.
 *
 * Context: May be called from interrupt or process context.  May not be
 * called from NMI context.
 */
void folio_unlock(struct folio *folio)
{
	/* Bit 7 allows x86 to check the byte's sign bit */
	BUILD_BUG_ON(PG_waiters != 7);
	BUILD_BUG_ON(PG_locked > 7);
	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
	if (clear_bit_unlock_is_negative_byte(PG_locked, folio_flags(folio, 0)))
		folio_wake_bit(folio, PG_locked);
}
EXPORT_SYMBOL(folio_unlock);

/**
 * folio_end_private_2 - Clear PG_private_2 and wake any waiters.
 * @folio: The folio.
 *
 * Clear the PG_private_2 bit on a folio and wake up any sleepers waiting for
 * it.  The folio reference held for PG_private_2 being set is released.
 *
 * This is, for example, used when a netfs folio is being written to a local
 * disk cache, thereby allowing writes to the cache for the same folio to be
 * serialised.
 */
void folio_end_private_2(struct folio *folio)
{
	VM_BUG_ON_FOLIO(!folio_test_private_2(folio), folio);
	clear_bit_unlock(PG_private_2, folio_flags(folio, 0));
	folio_wake_bit(folio, PG_private_2);
	folio_put(folio);
}
EXPORT_SYMBOL(folio_end_private_2);

/**
 * folio_wait_private_2 - Wait for PG_private_2 to be cleared on a folio.
 * @folio: The folio to wait on.
 *
 * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio.
 */
void folio_wait_private_2(struct folio *folio)
{
	while (folio_test_private_2(folio))
		folio_wait_bit(folio, PG_private_2);
}
EXPORT_SYMBOL(folio_wait_private_2);

/**
 * folio_wait_private_2_killable - Wait for PG_private_2 to be cleared on a folio.
 * @folio: The folio to wait on.
 *
 * Wait for PG_private_2 (aka PG_fscache) to be cleared on a folio or until a
 * fatal signal is received by the calling task.
 *
 * Return:
 * - 0 if successful.
 * - -EINTR if a fatal signal was encountered.
 */
int folio_wait_private_2_killable(struct folio *folio)
{
	int ret = 0;

	while (folio_test_private_2(folio)) {
		ret = folio_wait_bit_killable(folio, PG_private_2);
		if (ret < 0)
			break;
	}

	return ret;
}
EXPORT_SYMBOL(folio_wait_private_2_killable);

/**
 * folio_end_writeback - End writeback against a folio.
 * @folio: The folio.
 */
void folio_end_writeback(struct folio *folio)
{
	/*
	 * folio_test_clear_reclaim() could be used here but it is an
	 * atomic operation and overkill in this particular case. Failing
	 * to shuffle a folio marked for immediate reclaim is too mild
	 * a gain to justify taking an atomic operation penalty at the
	 * end of every folio writeback.
	 */
	if (folio_test_reclaim(folio)) {
		folio_clear_reclaim(folio);
		folio_rotate_reclaimable(folio);
	}

	/*
	 * Writeback does not hold a folio reference of its own, relying
	 * on truncation to wait for the clearing of PG_writeback.
	 * But here we must make sure that the folio is not freed and
	 * reused before the folio_wake().
	 */
	folio_get(folio);
	if (!__folio_end_writeback(folio))
		BUG();

	smp_mb__after_atomic();
	folio_wake(folio, PG_writeback);
	acct_reclaim_writeback(folio);
	folio_put(folio);
}
EXPORT_SYMBOL(folio_end_writeback);

/**
 * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.
 * @folio: The folio to lock
 */
void __folio_lock(struct folio *folio)
{
	folio_wait_bit_common(folio, PG_locked, TASK_UNINTERRUPTIBLE,
				EXCLUSIVE);
}
EXPORT_SYMBOL(__folio_lock);

int __folio_lock_killable(struct folio *folio)
{
	return folio_wait_bit_common(folio, PG_locked, TASK_KILLABLE,
					EXCLUSIVE);
}
EXPORT_SYMBOL_GPL(__folio_lock_killable);

static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait)
{
	struct wait_queue_head *q = folio_waitqueue(folio);
	int ret = 0;

	wait->folio = folio;
	wait->bit_nr = PG_locked;

	spin_lock_irq(&q->lock);
	__add_wait_queue_entry_tail(q, &wait->wait);
	folio_set_waiters(folio);
	ret = !folio_trylock(folio);
	/*
	 * If we were successful now, we know we're still on the
	 * waitqueue as we're still under the lock. This means it's
	 * safe to remove and return success, we know the callback
	 * isn't going to trigger.
	 */
	if (!ret)
		__remove_wait_queue(q, &wait->wait);
	else
		ret = -EIOCBQUEUED;
	spin_unlock_irq(&q->lock);
	return ret;
}

/*
 * Return values:
 * 0 - folio is locked.
 * non-zero - folio is not locked.
 *     mmap_lock or per-VMA lock has been released (mmap_read_unlock() or
 *     vma_end_read()), unless flags had both FAULT_FLAG_ALLOW_RETRY and
 *     FAULT_FLAG_RETRY_NOWAIT set, in which case the lock is still held.
 *
 * If neither ALLOW_RETRY nor KILLABLE are set, will always return 0
 * with the folio locked and the mmap_lock/per-VMA lock is left unperturbed.
 */
vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf)
{
	unsigned int flags = vmf->flags;

	if (fault_flag_allow_retry_first(flags)) {
		/*
		 * CAUTION! In this case, mmap_lock/per-VMA lock is not
		 * released even though returning VM_FAULT_RETRY.
		 */
		if (flags & FAULT_FLAG_RETRY_NOWAIT)
			return VM_FAULT_RETRY;

		release_fault_lock(vmf);
		if (flags & FAULT_FLAG_KILLABLE)
			folio_wait_locked_killable(folio);
		else
			folio_wait_locked(folio);
		return VM_FAULT_RETRY;
	}
	if (flags & FAULT_FLAG_KILLABLE) {
		bool ret;

		ret = __folio_lock_killable(folio);
		if (ret) {
			release_fault_lock(vmf);
			return VM_FAULT_RETRY;
		}
	} else {
		__folio_lock(folio);
	}

	return 0;
}

/**
 * page_cache_next_miss() - Find the next gap in the page cache.
 * @mapping: Mapping.
 * @index: Index.
 * @max_scan: Maximum range to search.
 *
 * Search the range [index, min(index + max_scan - 1, ULONG_MAX)] for the
 * gap with the lowest index.
 *
 * This function may be called under the rcu_read_lock.  However, this will
 * not atomically search a snapshot of the cache at a single point in time.
 * For example, if a gap is created at index 5, then subsequently a gap is
 * created at index 10, page_cache_next_miss covering both indices may
 * return 10 if called under the rcu_read_lock.
 *
 * Return: The index of the gap if found, otherwise an index outside the
 * range specified (in which case 'return - index >= max_scan' will be true).
 * In the rare case of index wrap-around, 0 will be returned.
 */
pgoff_t page_cache_next_miss(struct address_space *mapping,
			     pgoff_t index, unsigned long max_scan)
{
	XA_STATE(xas, &mapping->i_pages, index);

	while (max_scan--) {
		void *entry = xas_next(&xas);
		if (!entry || xa_is_value(entry))
			break;
		if (xas.xa_index == 0)
			break;
	}

	return xas.xa_index;
}
EXPORT_SYMBOL(page_cache_next_miss);

/**
 * page_cache_prev_miss() - Find the previous gap in the page cache.
 * @mapping: Mapping.
 * @index: Index.
 * @max_scan: Maximum range to search.
 *
 * Search the range [max(index - max_scan + 1, 0), index] for the
 * gap with the highest index.
 *
 * This function may be called under the rcu_read_lock.  However, this will
 * not atomically search a snapshot of the cache at a single point in time.
 * For example, if a gap is created at index 10, then subsequently a gap is
 * created at index 5, page_cache_prev_miss() covering both indices may
 * return 5 if called under the rcu_read_lock.
 *
 * Return: The index of the gap if found, otherwise an index outside the
 * range specified (in which case 'index - return >= max_scan' will be true).
 * In the rare case of wrap-around, ULONG_MAX will be returned.
 */
pgoff_t page_cache_prev_miss(struct address_space *mapping,
			     pgoff_t index, unsigned long max_scan)
{
	XA_STATE(xas, &mapping->i_pages, index);

	while (max_scan--) {
		void *entry = xas_prev(&xas);
		if (!entry || xa_is_value(entry))
			break;
		if (xas.xa_index == ULONG_MAX)
			break;
	}

	return xas.xa_index;
}
EXPORT_SYMBOL(page_cache_prev_miss);

/*
 * Lockless page cache protocol:
 * On the lookup side:
 * 1. Load the folio from i_pages
 * 2. Increment the refcount if it's not zero
 * 3. If the folio is not found by xas_reload(), put the refcount and retry
 *
 * On the removal side:
 * A. Freeze the page (by zeroing the refcount if nobody else has a reference)
 * B. Remove the page from i_pages
 * C. Return the page to the page allocator
 *
 * This means that any page may have its reference count temporarily
 * increased by a speculative page cache (or fast GUP) lookup as it can
 * be allocated by another user before the RCU grace period expires.
 * Because the refcount temporarily acquired here may end up being the
 * last refcount on the page, any page allocation must be freeable by
 * folio_put().
 */

/*
 * filemap_get_entry - Get a page cache entry.
 * @mapping: the address_space to search
 * @index: The page cache index.
 *
 * Looks up the page cache entry at @mapping & @index.  If it is a folio,
 * it is returned with an increased refcount.  If it is a shadow entry
 * of a previously evicted folio, or a swap entry from shmem/tmpfs,
 * it is returned without further action.
 *
 * Return: The folio, swap or shadow entry, %NULL if nothing is found.
 */
void *filemap_get_entry(struct address_space *mapping, pgoff_t index)
{
	XA_STATE(xas, &mapping->i_pages, index);
	struct folio *folio;

	rcu_read_lock();
repeat:
	xas_reset(&xas);
	folio = xas_load(&xas);
	if (xas_retry(&xas, folio))
		goto repeat;
	/*
	 * A shadow entry of a recently evicted page, or a swap entry from
	 * shmem/tmpfs.  Return it without attempting to raise page count.
	 */
	if (!folio || xa_is_value(folio))
		goto out;

	if (!folio_try_get_rcu(folio))
		goto repeat;

	if (unlikely(folio != xas_reload(&xas))) {
		folio_put(folio);
		goto repeat;
	}
out:
	rcu_read_unlock();

	return folio;
}

/**
 * __filemap_get_folio - Find and get a reference to a folio.
 * @mapping: The address_space to search.
 * @index: The page index.
 * @fgp_flags: %FGP flags modify how the folio is returned.
 * @gfp: Memory allocation flags to use if %FGP_CREAT is specified.
 *
 * Looks up the page cache entry at @mapping & @index.
 *
 * If %FGP_LOCK or %FGP_CREAT are specified then the function may sleep even
 * if the %GFP flags specified for %FGP_CREAT are atomic.
 *
 * If this function returns a folio, it is returned with an increased refcount.
 *
 * Return: The found folio or an ERR_PTR() otherwise.
 */
struct folio *__filemap_get_folio(struct address_space *mapping, pgoff_t index,
		fgf_t fgp_flags, gfp_t gfp)
{
	struct folio *folio;

repeat:
	folio = filemap_get_entry(mapping, index);
	if (xa_is_value(folio))
		folio = NULL;
	if (!folio)
		goto no_page;

	if (fgp_flags & FGP_LOCK) {
		if (fgp_flags & FGP_NOWAIT) {
			if (!folio_trylock(folio)) {
				folio_put(folio);
				return ERR_PTR(-EAGAIN);
			}
		} else {
			folio_lock(folio);
		}

		/* Has the page been truncated? */
		if (unlikely(folio->mapping != mapping)) {
			folio_unlock(folio);
			folio_put(folio);
			goto repeat;
		}
		VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);
	}

	if (fgp_flags & FGP_ACCESSED)
		folio_mark_accessed(folio);
	else if (fgp_flags & FGP_WRITE) {
		/* Clear idle flag for buffer write */
		if (folio_test_idle(folio))
			folio_clear_idle(folio);
	}

	if (fgp_flags & FGP_STABLE)
		folio_wait_stable(folio);
no_page:
	if (!folio && (fgp_flags & FGP_CREAT)) {
		unsigned order = FGF_GET_ORDER(fgp_flags);
		int err;

		if ((fgp_flags & FGP_WRITE) && mapping_can_writeback(mapping))
			gfp |= __GFP_WRITE;
		if (fgp_flags & FGP_NOFS)
			gfp &= ~__GFP_FS;
		if (fgp_flags & FGP_NOWAIT) {
			gfp &= ~GFP_KERNEL;
			gfp |= GFP_NOWAIT | __GFP_NOWARN;
		}
		if (WARN_ON_ONCE(!(fgp_flags & (FGP_LOCK | FGP_FOR_MMAP))))
			fgp_flags |= FGP_LOCK;

		if (!mapping_large_folio_support(mapping))
			order = 0;
		if (order > MAX_PAGECACHE_ORDER)
			order = MAX_PAGECACHE_ORDER;
		/* If we're not aligned, allocate a smaller folio */
		if (index & ((1UL << order) - 1))
			order = __ffs(index);

		do {
			gfp_t alloc_gfp = gfp;

			err = -ENOMEM;
			if (order == 1)
				order = 0;
			if (order > 0)
				alloc_gfp |= __GFP_NORETRY | __GFP_NOWARN;
			folio = filemap_alloc_folio(alloc_gfp, order);
			if (!folio)
				continue;

			/* Init accessed so avoid atomic mark_page_accessed later */
			if (fgp_flags & FGP_ACCESSED)
				__folio_set_referenced(folio);

			err = filemap_add_folio(mapping, folio, index, gfp);
			if (!err)
				break;
			folio_put(folio);
			folio = NULL;
		} while (order-- > 0);

		if (err == -EEXIST)
			goto repeat;
		if (err)
			return ERR_PTR(err);
		/*
		 * filemap_add_folio locks the page, and for mmap
		 * we expect an unlocked page.
		 */
		if (folio && (fgp_flags & FGP_FOR_MMAP))
			folio_unlock(folio);
	}

	if (!folio)
		return ERR_PTR(-ENOENT);
	return folio;
}
EXPORT_SYMBOL(__filemap_get_folio);

static inline struct folio *find_get_entry(struct xa_state *xas, pgoff_t max,
		xa_mark_t mark)
{
	struct folio *folio;

retry:
	if (mark == XA_PRESENT)
		folio = xas_find(xas, max);
	else
		folio = xas_find_marked(xas, max, mark);

	if (xas_retry(xas, folio))
		goto retry;
	/*
	 * A shadow entry of a recently evicted page, a swap
	 * entry from shmem/tmpfs or a DAX entry.  Return it
	 * without attempting to raise page count.
	 */
	if (!folio || xa_is_value(folio))
		return folio;

	if (!folio_try_get_rcu(folio))
		goto reset;

	if (unlikely(folio != xas_reload(xas))) {
		folio_put(folio);
		goto reset;
	}

	return folio;
reset:
	xas_reset(xas);
	goto retry;
}

/**
 * find_get_entries - gang pagecache lookup
 * @mapping:	The address_space to search
 * @start:	The starting page cache index
 * @end:	The final page index (inclusive).
 * @fbatch:	Where the resulting entries are placed.
 * @indices:	The cache indices corresponding to the entries in @entries
 *
 * find_get_entries() will search for and return a batch of entries in
 * the mapping.  The entries are placed in @fbatch.  find_get_entries()
 * takes a reference on any actual folios it returns.
 *
 * The entries have ascending indexes.  The indices may not be consecutive
 * due to not-present entries or large folios.
 *
 * Any shadow entries of evicted folios, or swap entries from
 * shmem/tmpfs, are included in the returned array.
 *
 * Return: The number of entries which were found.
 */
unsigned find_get_entries(struct address_space *mapping, pgoff_t *start,
		pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
{
	XA_STATE(xas, &mapping->i_pages, *start);
	struct folio *folio;

	rcu_read_lock();
	while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
		indices[fbatch->nr] = xas.xa_index;
		if (!folio_batch_add(fbatch, folio))
			break;
	}
	rcu_read_unlock();

	if (folio_batch_count(fbatch)) {
		unsigned long nr = 1;
		int idx = folio_batch_count(fbatch) - 1;

		folio = fbatch->folios[idx];
		if (!xa_is_value(folio) && !folio_test_hugetlb(folio))
			nr = folio_nr_pages(folio);
		*start = indices[idx] + nr;
	}
	return folio_batch_count(fbatch);
}

/**
 * find_lock_entries - Find a batch of pagecache entries.
 * @mapping:	The address_space to search.
 * @start:	The starting page cache index.
 * @end:	The final page index (inclusive).
 * @fbatch:	Where the resulting entries are placed.
 * @indices:	The cache indices of the entries in @fbatch.
 *
 * find_lock_entries() will return a batch of entries from @mapping.
 * Swap, shadow and DAX entries are included.  Folios are returned
 * locked and with an incremented refcount.  Folios which are locked
 * by somebody else or under writeback are skipped.  Folios which are
 * partially outside the range are not returned.
 *
 * The entries have ascending indexes.  The indices may not be consecutive
 * due to not-present entries, large folios, folios which could not be
 * locked or folios under writeback.
 *
 * Return: The number of entries which were found.
 */
unsigned find_lock_entries(struct address_space *mapping, pgoff_t *start,
		pgoff_t end, struct folio_batch *fbatch, pgoff_t *indices)
{
	XA_STATE(xas, &mapping->i_pages, *start);
	struct folio *folio;

	rcu_read_lock();
	while ((folio = find_get_entry(&xas, end, XA_PRESENT))) {
		if (!xa_is_value(folio)) {
			if (folio->index < *start)
				goto put;
			if (folio_next_index(folio) - 1 > end)
				goto put;
			if (!folio_trylock(folio))
				goto put;
			if (folio->mapping != mapping ||
			    folio_test_writeback(folio))
				goto unlock;
			VM_BUG_ON_FOLIO(!folio_contains(folio, xas.xa_index),
					folio);
		}
		indices[fbatch->nr] = xas.xa_index;
		if (!folio_batch_add(fbatch, folio))
			break;
		continue;
unlock:
		folio_unlock(folio);
put:
		folio_put(folio);
	}
	rcu_read_unlock();

	if (folio_batch_count(fbatch)) {
		unsigned long nr = 1;
		int idx = folio_batch_count(fbatch) - 1;

		folio = fbatch->folios[idx];
		if (!xa_is_value(folio) && !folio_test_hugetlb(folio))
			nr = folio_nr_pages(folio);
		*start = indices[idx] + nr;
	}
	return folio_batch_count(fbatch);
}

/**
 * filemap_get_folios - Get a batch of folios
 * @mapping:	The address_space to search
 * @start:	The starting page index
 * @end:	The final page index (inclusive)
 * @fbatch:	The batch to fill.
 *
 * Search for and return a batch of folios in the mapping starting at
 * index @start and up to index @end (inclusive).  The folios are returned
 * in @fbatch with an elevated reference count.
 *
 * The first folio may start before @start; if it does, it will contain
 * @start.  The final folio may extend beyond @end; if it does, it will
 * contain @end.  The folios have ascending indices.  There may be gaps
 * between the folios if there are indices which have no folio in the
 * page cache.  If folios are added to or removed from the page cache
 * while this is running, they may or may not be found by this call.
 *
 * Return: The number of folios which were found.
 * We also update @start to index the next folio for the traversal.
 */
unsigned filemap_get_folios(struct address_space *mapping, pgoff_t *start,
		pgoff_t end, struct folio_batch *fbatch)
{
	XA_STATE(xas, &mapping->i_pages, *start);
	struct folio *folio;

	rcu_read_lock();
	while ((folio = find_get_entry(&xas, end, XA_PRESENT)) != NULL) {
		/* Skip over shadow, swap and DAX entries */
		if (xa_is_value(folio))
			continue;
		if (!folio_batch_add(fbatch, folio)) {
			unsigned long nr = folio_nr_pages(folio);

			if (folio_test_hugetlb(folio))
				nr = 1;
			*start = folio->index + nr;
			goto out;
		}
	}

	/*
	 * We come here when there is no page beyond @end. We take care to not
	 * overflow the index @start as it confuses some of the callers. This
	 * breaks the iteration when there is a page at index -1 but that is
	 * already broken anyway.
	 */
	if (end == (pgoff_t)-1)
		*start = (pgoff_t)-1;
	else
		*start = end + 1;
out:
	rcu_read_unlock();

	return folio_batch_count(fbatch);
}
EXPORT_SYMBOL(filemap_get_folios);

/**
 * filemap_get_folios_contig - Get a batch of contiguous folios
 * @mapping:	The address_space to search
 * @start:	The starting page index
 * @end:	The final page index (inclusive)
 * @fbatch:	The batch to fill
 *
 * filemap_get_folios_contig() works exactly like filemap_get_folios(),
 * except the returned folios are guaranteed to be contiguous. This may
 * not return all contiguous folios if the batch gets filled up.
 *
 * Return: The number of folios found.
 * Also update @start to be positioned for traversal of the next folio.
 */

unsigned filemap_get_folios_contig(struct address_space *mapping,
		pgoff_t *start, pgoff_t end, struct folio_batch *fbatch)
{
	XA_STATE(xas, &mapping->i_pages, *start);
	unsigned long nr;
	struct folio *folio;

	rcu_read_lock();

	for (folio = xas_load(&xas); folio && xas.xa_index <= end;
			folio = xas_next(&xas)) {
		if (xas_retry(&xas, folio))
			continue;
		/*
		 * If the entry has been swapped out, we can stop looking.
		 * No current caller is looking for DAX entries.
		 */
		if (xa_is_value(folio))
			goto update_start;

		if (!folio_try_get_rcu(folio))
			goto retry;

		if (unlikely(folio != xas_reload(&xas)))
			goto put_folio;

		if (!folio_batch_add(fbatch, folio)) {
			nr = folio_nr_pages(folio);

			if (folio_test_hugetlb(folio))
				nr = 1;
			*start = folio->index + nr;
			goto out;
		}
		continue;
put_folio:
		folio_put(folio);

retry:
		xas_reset(&xas);
	}

update_start:
	nr = folio_batch_count(fbatch);

	if (nr) {
		folio = fbatch->folios[nr - 1];
		if (folio_test_hugetlb(folio))
			*start = folio->index + 1;
		else
			*start = folio_next_index(folio);
	}
out:
	rcu_read_unlock();
	return folio_batch_count(fbatch);
}
EXPORT_SYMBOL(filemap_get_folios_contig);

/**
 * filemap_get_folios_tag - Get a batch of folios matching @tag
 * @mapping:    The address_space to search
 * @start:      The starting page index
 * @end:        The final page index (inclusive)
 * @tag:        The tag index
 * @fbatch:     The batch to fill
 *
 * Same as filemap_get_folios(), but only returning folios tagged with @tag.
 *
 * Return: The number of folios found.
 * Also update @start to index the next folio for traversal.
 */
unsigned filemap_get_folios_tag(struct address_space *mapping, pgoff_t *start,
			pgoff_t end, xa_mark_t tag, struct folio_batch *fbatch)
{
	XA_STATE(xas, &mapping->i_pages, *start);
	struct folio *folio;

	rcu_read_lock();
	while ((folio = find_get_entry(&xas, end, tag)) != NULL) {
		/*
		 * Shadow entries should never be tagged, but this iteration
		 * is lockless so there is a window for page reclaim to evict
		 * a page we saw tagged. Skip over it.
		 */
		if (xa_is_value(folio))
			continue;
		if (!folio_batch_add(fbatch, folio)) {
			unsigned long nr = folio_nr_pages(folio);

			if (folio_test_hugetlb(folio))
				nr = 1;
			*start = folio->index + nr;
			goto out;
		}
	}
	/*
	 * We come here when there is no page beyond @end. We take care to not
	 * overflow the index @start as it confuses some of the callers. This
	 * breaks the iteration when there is a page at index -1 but that is
	 * already broke anyway.
	 */
	if (end == (pgoff_t)-1)
		*start = (pgoff_t)-1;
	else
		*start = end + 1;
out:
	rcu_read_unlock();

	return folio_batch_count(fbatch);
}
EXPORT_SYMBOL(filemap_get_folios_tag);

/*
 * CD/DVDs are error prone. When a medium error occurs, the driver may fail
 * a _large_ part of the i/o request. Imagine the worst scenario:
 *
 *      ---R__________________________________________B__________
 *         ^ reading here                             ^ bad block(assume 4k)
 *
 * read(R) => miss => readahead(R...B) => media error => frustrating retries
 * => failing the whole request => read(R) => read(R+1) =>
 * readahead(R+1...B+1) => bang => read(R+2) => read(R+3) =>
 * readahead(R+3...B+2) => bang => read(R+3) => read(R+4) =>
 * readahead(R+4...B+3) => bang => read(R+4) => read(R+5) => ......
 *
 * It is going insane. Fix it by quickly scaling down the readahead size.
 */
static void shrink_readahead_size_eio(struct file_ra_state *ra)
{
	ra->ra_pages /= 4;
}

/*
 * filemap_get_read_batch - Get a batch of folios for read
 *
 * Get a batch of folios which represent a contiguous range of bytes in
 * the file.  No exceptional entries will be returned.  If @index is in
 * the middle of a folio, the entire folio will be returned.  The last
 * folio in the batch may have the readahead flag set or the uptodate flag
 * clear so that the caller can take the appropriate action.
 */
static void filemap_get_read_batch(struct address_space *mapping,
		pgoff_t index, pgoff_t max, struct folio_batch *fbatch)
{
	XA_STATE(xas, &mapping->i_pages, index);
	struct folio *folio;

	rcu_read_lock();
	for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
		if (xas_retry(&xas, folio))
			continue;
		if (xas.xa_index > max || xa_is_value(folio))
			break;
		if (xa_is_sibling(folio))
			break;
		if (!folio_try_get_rcu(folio))
			goto retry;

		if (unlikely(folio != xas_reload(&xas)))
			goto put_folio;

		if (!folio_batch_add(fbatch, folio))
			break;
		if (!folio_test_uptodate(folio))
			break;
		if (folio_test_readahead(folio))
			break;
		xas_advance(&xas, folio_next_index(folio) - 1);
		continue;
put_folio:
		folio_put(folio);
retry:
		xas_reset(&xas);
	}
	rcu_read_unlock();
}

static int filemap_read_folio(struct file *file, filler_t filler,
		struct folio *folio)
{
	bool workingset = folio_test_workingset(folio);
	unsigned long pflags;
	int error;

	/*
	 * A previous I/O error may have been due to temporary failures,
	 * eg. multipath errors.  PG_error will be set again if read_folio
	 * fails.
	 */
	folio_clear_error(folio);

	/* Start the actual read. The read will unlock the page. */
	if (unlikely(workingset))
		psi_memstall_enter(&pflags);
	error = filler(file, folio);
	if (unlikely(workingset))
		psi_memstall_leave(&pflags);
	if (error)
		return error;

	error = folio_wait_locked_killable(folio);
	if (error)
		return error;
	if (folio_test_uptodate(folio))
		return 0;
	if (file)
		shrink_readahead_size_eio(&file->f_ra);
	return -EIO;
}

static bool filemap_range_uptodate(struct address_space *mapping,
		loff_t pos, size_t count, struct folio *folio,
		bool need_uptodate)
{
	if (folio_test_uptodate(folio))
		return true;
	/* pipes can't handle partially uptodate pages */
	if (need_uptodate)
		return false;
	if (!mapping->a_ops->is_partially_uptodate)
		return false;
	if (mapping->host->i_blkbits >= folio_shift(folio))
		return false;

	if (folio_pos(folio) > pos) {
		count -= folio_pos(folio) - pos;
		pos = 0;
	} else {
		pos -= folio_pos(folio);
	}

	return mapping->a_ops->is_partially_uptodate(folio, pos, count);
}

static int filemap_update_page(struct kiocb *iocb,
		struct address_space *mapping, size_t count,
		struct folio *folio, bool need_uptodate)
{
	int error;

	if (iocb->ki_flags & IOCB_NOWAIT) {
		if (!filemap_invalidate_trylock_shared(mapping))
			return -EAGAIN;
	} else {
		filemap_invalidate_lock_shared(mapping);
	}

	if (!folio_trylock(folio)) {
		error = -EAGAIN;
		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO))
			goto unlock_mapping;
		if (!(iocb->ki_flags & IOCB_WAITQ)) {
			filemap_invalidate_unlock_shared(mapping);
			/*
			 * This is where we usually end up waiting for a
			 * previously submitted readahead to finish.
			 */
			folio_put_wait_locked(folio, TASK_KILLABLE);
			return AOP_TRUNCATED_PAGE;
		}
		error = __folio_lock_async(folio, iocb->ki_waitq);
		if (error)
			goto unlock_mapping;
	}

	error = AOP_TRUNCATED_PAGE;
	if (!folio->mapping)
		goto unlock;

	error = 0;
	if (filemap_range_uptodate(mapping, iocb->ki_pos, count, folio,
				   need_uptodate))
		goto unlock;

	error = -EAGAIN;
	if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ))
		goto unlock;

	error = filemap_read_folio(iocb->ki_filp, mapping->a_ops->read_folio,
			folio);
	goto unlock_mapping;
unlock:
	folio_unlock(folio);
unlock_mapping:
	filemap_invalidate_unlock_shared(mapping);
	if (error == AOP_TRUNCATED_PAGE)
		folio_put(folio);
	return error;
}

static int filemap_create_folio(struct file *file,
		struct address_space *mapping, pgoff_t index,
		struct folio_batch *fbatch)
{
	struct folio *folio;
	int error;

	folio = filemap_alloc_folio(mapping_gfp_mask(mapping), 0);
	if (!folio)
		return -ENOMEM;

	/*
	 * Protect against truncate / hole punch. Grabbing invalidate_lock
	 * here assures we cannot instantiate and bring uptodate new
	 * pagecache folios after evicting page cache during truncate
	 * and before actually freeing blocks.	Note that we could
	 * release invalidate_lock after inserting the folio into
	 * the page cache as the locked folio would then be enough to
	 * synchronize with hole punching. But there are code paths
	 * such as filemap_update_page() filling in partially uptodate
	 * pages or ->readahead() that need to hold invalidate_lock
	 * while mapping blocks for IO so let's hold the lock here as
	 * well to keep locking rules simple.
	 */
	filemap_invalidate_lock_shared(mapping);
	error = filemap_add_folio(mapping, folio, index,
			mapping_gfp_constraint(mapping, GFP_KERNEL));
	if (error == -EEXIST)
		error = AOP_TRUNCATED_PAGE;
	if (error)
		goto error;

	error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
	if (error)
		goto error;

	filemap_invalidate_unlock_shared(mapping);
	folio_batch_add(fbatch, folio);
	return 0;
error:
	filemap_invalidate_unlock_shared(mapping);
	folio_put(folio);
	return error;
}

static int filemap_readahead(struct kiocb *iocb, struct file *file,
		struct address_space *mapping, struct folio *folio,
		pgoff_t last_index)
{
	DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, folio->index);

	if (iocb->ki_flags & IOCB_NOIO)
		return -EAGAIN;
	page_cache_async_ra(&ractl, folio, last_index - folio->index);
	return 0;
}

static int filemap_get_pages(struct kiocb *iocb, size_t count,
		struct folio_batch *fbatch, bool need_uptodate)
{
	struct file *filp = iocb->ki_filp;
	struct address_space *mapping = filp->f_mapping;
	struct file_ra_state *ra = &filp->f_ra;
	pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
	pgoff_t last_index;
	struct folio *folio;
	int err = 0;

	/* "last_index" is the index of the page beyond the end of the read */
	last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE);
retry:
	if (fatal_signal_pending(current))
		return -EINTR;

	filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
	if (!folio_batch_count(fbatch)) {
		if (iocb->ki_flags & IOCB_NOIO)
			return -EAGAIN;
		page_cache_sync_readahead(mapping, ra, filp, index,
				last_index - index);
		filemap_get_read_batch(mapping, index, last_index - 1, fbatch);
	}
	if (!folio_batch_count(fbatch)) {
		if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ))
			return -EAGAIN;
		err = filemap_create_folio(filp, mapping,
				iocb->ki_pos >> PAGE_SHIFT, fbatch);
		if (err == AOP_TRUNCATED_PAGE)
			goto retry;
		return err;
	}

	folio = fbatch->folios[folio_batch_count(fbatch) - 1];
	if (folio_test_readahead(folio)) {
		err = filemap_readahead(iocb, filp, mapping, folio, last_index);
		if (err)
			goto err;
	}
	if (!folio_test_uptodate(folio)) {
		if ((iocb->ki_flags & IOCB_WAITQ) &&
		    folio_batch_count(fbatch) > 1)
			iocb->ki_flags |= IOCB_NOWAIT;
		err = filemap_update_page(iocb, mapping, count, folio,
					  need_uptodate);
		if (err)
			goto err;
	}

	return 0;
err:
	if (err < 0)
		folio_put(folio);
	if (likely(--fbatch->nr))
		return 0;
	if (err == AOP_TRUNCATED_PAGE)
		goto retry;
	return err;
}

static inline bool pos_same_folio(loff_t pos1, loff_t pos2, struct folio *folio)
{
	unsigned int shift = folio_shift(folio);

	return (pos1 >> shift == pos2 >> shift);
}

/**
 * filemap_read - Read data from the page cache.
 * @iocb: The iocb to read.
 * @iter: Destination for the data.
 * @already_read: Number of bytes already read by the caller.
 *
 * Copies data from the page cache.  If the data is not currently present,
 * uses the readahead and read_folio address_space operations to fetch it.
 *
 * Return: Total number of bytes copied, including those already read by
 * the caller.  If an error happens before any bytes are copied, returns
 * a negative error number.
 */
ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
		ssize_t already_read)
{
	struct file *filp = iocb->ki_filp;
	struct file_ra_state *ra = &filp->f_ra;
	struct address_space *mapping = filp->f_mapping;
	struct inode *inode = mapping->host;
	struct folio_batch fbatch;
	int i, error = 0;
	bool writably_mapped;
	loff_t isize, end_offset;
	loff_t last_pos = ra->prev_pos;

	if (unlikely(iocb->ki_pos >= inode->i_sb->s_maxbytes))
		return 0;
	if (unlikely(!iov_iter_count(iter)))
		return 0;

	iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
	folio_batch_init(&fbatch);

	do {
		cond_resched();

		/*
		 * If we've already successfully copied some data, then we
		 * can no longer safely return -EIOCBQUEUED. Hence mark
		 * an async read NOWAIT at that point.
		 */
		if ((iocb->ki_flags & IOCB_WAITQ) && already_read)
			iocb->ki_flags |= IOCB_NOWAIT;

		if (unlikely(iocb->ki_pos >= i_size_read(inode)))
			break;

		error = filemap_get_pages(iocb, iter->count, &fbatch, false);
		if (error < 0)
			break;

		/*
		 * i_size must be checked after we know the pages are Uptodate.
		 *
		 * Checking i_size after the check allows us to calculate
		 * the correct value for "nr", which means the zero-filled
		 * part of the page is not copied back to userspace (unless
		 * another truncate extends the file - this is desired though).
		 */
		isize = i_size_read(inode);
		if (unlikely(iocb->ki_pos >= isize))
			goto put_folios;
		end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);

		/*
		 * Once we start copying data, we don't want to be touching any
		 * cachelines that might be contended:
		 */
		writably_mapped = mapping_writably_mapped(mapping);

		/*
		 * When a read accesses the same folio several times, only
		 * mark it as accessed the first time.
		 */
		if (!pos_same_folio(iocb->ki_pos, last_pos - 1,
				    fbatch.folios[0]))
			folio_mark_accessed(fbatch.folios[0]);

		for (i = 0; i < folio_batch_count(&fbatch); i++) {
			struct folio *folio = fbatch.folios[i];
			size_t fsize = folio_size(folio);
			size_t offset = iocb->ki_pos & (fsize - 1);
			size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
					     fsize - offset);
			size_t copied;

			if (end_offset < folio_pos(folio))
				break;
			if (i > 0)
				folio_mark_accessed(folio);
			/*
			 * If users can be writing to this folio using arbitrary
			 * virtual addresses, take care of potential aliasing
			 * before reading the folio on the kernel side.
			 */
			if (writably_mapped)
				flush_dcache_folio(folio);

			copied = copy_folio_to_iter(folio, offset, bytes, iter);

			already_read += copied;
			iocb->ki_pos += copied;
			last_pos = iocb->ki_pos;

			if (copied < bytes) {
				error = -EFAULT;
				break;
			}
		}
put_folios:
		for (i = 0; i < folio_batch_count(&fbatch); i++)
			folio_put(fbatch.folios[i]);
		folio_batch_init(&fbatch);
	} while (iov_iter_count(iter) && iocb->ki_pos < isize && !error);

	file_accessed(filp);
	ra->prev_pos = last_pos;
	return already_read ? already_read : error;
}
EXPORT_SYMBOL_GPL(filemap_read);

int kiocb_write_and_wait(struct kiocb *iocb, size_t count)
{
	struct address_space *mapping = iocb->ki_filp->f_mapping;
	loff_t pos = iocb->ki_pos;
	loff_t end = pos + count - 1;

	if (iocb->ki_flags & IOCB_NOWAIT) {
		if (filemap_range_needs_writeback(mapping, pos, end))
			return -EAGAIN;
		return 0;
	}

	return filemap_write_and_wait_range(mapping, pos, end);
}

int kiocb_invalidate_pages(struct kiocb *iocb, size_t count)
{
	struct address_space *mapping = iocb->ki_filp->f_mapping;
	loff_t pos = iocb->ki_pos;
	loff_t end = pos + count - 1;
	int ret;

	if (iocb->ki_flags & IOCB_NOWAIT) {
		/* we could block if there are any pages in the range */
		if (filemap_range_has_page(mapping, pos, end))
			return -EAGAIN;
	} else {
		ret = filemap_write_and_wait_range(mapping, pos, end);
		if (ret)
			return ret;
	}

	/*
	 * After a write we want buffered reads to be sure to go to disk to get
	 * the new data.  We invalidate clean cached page from the region we're
	 * about to write.  We do this *before* the write so that we can return
	 * without clobbering -EIOCBQUEUED from ->direct_IO().
	 */
	return invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT,
					     end >> PAGE_SHIFT);
}

/**
 * generic_file_read_iter - generic filesystem read routine
 * @iocb:	kernel I/O control block
 * @iter:	destination for the data read
 *
 * This is the "read_iter()" routine for all filesystems
 * that can use the page cache directly.
 *
 * The IOCB_NOWAIT flag in iocb->ki_flags indicates that -EAGAIN shall
 * be returned when no data can be read without waiting for I/O requests
 * to complete; it doesn't prevent readahead.
 *
 * The IOCB_NOIO flag in iocb->ki_flags indicates that no new I/O
 * requests shall be made for the read or for readahead.  When no data
 * can be read, -EAGAIN shall be returned.  When readahead would be
 * triggered, a partial, possibly empty read shall be returned.
 *
 * Return:
 * * number of bytes copied, even for partial reads
 * * negative error code (or 0 if IOCB_NOIO) if nothing was read
 */
ssize_t
generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
	size_t count = iov_iter_count(iter);
	ssize_t retval = 0;

	if (!count)
		return 0; /* skip atime */

	if (iocb->ki_flags & IOCB_DIRECT) {
		struct file *file = iocb->ki_filp;
		struct address_space *mapping = file->f_mapping;
		struct inode *inode = mapping->host;

		retval = kiocb_write_and_wait(iocb, count);
		if (retval < 0)
			return retval;
		file_accessed(file);

		retval = mapping->a_ops->direct_IO(iocb, iter);
		if (retval >= 0) {
			iocb->ki_pos += retval;
			count -= retval;
		}
		if (retval != -EIOCBQUEUED)
			iov_iter_revert(iter, count - iov_iter_count(iter));

		/*
		 * Btrfs can have a short DIO read if we encounter
		 * compressed extents, so if there was an error, or if
		 * we've already read everything we wanted to, or if
		 * there was a short read because we hit EOF, go ahead
		 * and return.  Otherwise fallthrough to buffered io for
		 * the rest of the read.  Buffered reads will not work for
		 * DAX files, so don't bother trying.
		 */
		if (retval < 0 || !count || IS_DAX(inode))
			return retval;
		if (iocb->ki_pos >= i_size_read(inode))
			return retval;
	}

	return filemap_read(iocb, iter, retval);
}
EXPORT_SYMBOL(generic_file_read_iter);

/*
 * Splice subpages from a folio into a pipe.
 */
size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
			      struct folio *folio, loff_t fpos, size_t size)
{
	struct page *page;
	size_t spliced = 0, offset = offset_in_folio(folio, fpos);

	page = folio_page(folio, offset / PAGE_SIZE);
	size = min(size, folio_size(folio) - offset);
	offset %= PAGE_SIZE;

	while (spliced < size &&
	       !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
		struct pipe_buffer *buf = pipe_head_buf(pipe);
		size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);

		*buf = (struct pipe_buffer) {
			.ops	= &page_cache_pipe_buf_ops,
			.page	= page,
			.offset	= offset,
			.len	= part,
		};
		folio_get(folio);
		pipe->head++;
		page++;
		spliced += part;
		offset = 0;
	}

	return spliced;
}

/**
 * filemap_splice_read -  Splice data from a file's pagecache into a pipe
 * @in: The file to read from
 * @ppos: Pointer to the file position to read from
 * @pipe: The pipe to splice into
 * @len: The amount to splice
 * @flags: The SPLICE_F_* flags
 *
 * This function gets folios from a file's pagecache and splices them into the
 * pipe.  Readahead will be called as necessary to fill more folios.  This may
 * be used for blockdevs also.
 *
 * Return: On success, the number of bytes read will be returned and *@ppos
 * will be updated if appropriate; 0 will be returned if there is no more data
 * to be read; -EAGAIN will be returned if the pipe had no space, and some
 * other negative error code will be returned on error.  A short read may occur
 * if the pipe has insufficient space, we reach the end of the data or we hit a
 * hole.
 */
ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
			    struct pipe_inode_info *pipe,
			    size_t len, unsigned int flags)
{
	struct folio_batch fbatch;
	struct kiocb iocb;
	size_t total_spliced = 0, used, npages;
	loff_t isize, end_offset;
	bool writably_mapped;
	int i, error = 0;

	if (unlikely(*ppos >= in->f_mapping->host->i_sb->s_maxbytes))
		return 0;

	init_sync_kiocb(&iocb, in);
	iocb.ki_pos = *ppos;

	/* Work out how much data we can actually add into the pipe */
	used = pipe_occupancy(pipe->head, pipe->tail);
	npages = max_t(ssize_t, pipe->max_usage - used, 0);
	len = min_t(size_t, len, npages * PAGE_SIZE);

	folio_batch_init(&fbatch);

	do {
		cond_resched();

		if (*ppos >= i_size_read(in->f_mapping->host))
			break;

		iocb.ki_pos = *ppos;
		error = filemap_get_pages(&iocb, len, &fbatch, true);
		if (error < 0)
			break;

		/*
		 * i_size must be checked after we know the pages are Uptodate.
		 *
		 * Checking i_size after the check allows us to calculate
		 * the correct value for "nr", which means the zero-filled
		 * part of the page is not copied back to userspace (unless
		 * another truncate extends the file - this is desired though).
		 */
		isize = i_size_read(in->f_mapping->host);
		if (unlikely(*ppos >= isize))
			break;
		end_offset = min_t(loff_t, isize, *ppos + len);

		/*
		 * Once we start copying data, we don't want to be touching any
		 * cachelines that might be contended:
		 */
		writably_mapped = mapping_writably_mapped(in->f_mapping);

		for (i = 0; i < folio_batch_count(&fbatch); i++) {
			struct folio *folio = fbatch.folios[i];
			size_t n;

			if (folio_pos(folio) >= end_offset)
				goto out;
			folio_mark_accessed(folio);

			/*
			 * If users can be writing to this folio using arbitrary
			 * virtual addresses, take care of potential aliasing
			 * before reading the folio on the kernel side.
			 */
			if (writably_mapped)
				flush_dcache_folio(folio);

			n = min_t(loff_t, len, isize - *ppos);
			n = splice_folio_into_pipe(pipe, folio, *ppos, n);
			if (!n)
				goto out;
			len -= n;
			total_spliced += n;
			*ppos += n;
			in->f_ra.prev_pos = *ppos;
			if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
				goto out;
		}

		folio_batch_release(&fbatch);
	} while (len);

out:
	folio_batch_release(&fbatch);
	file_accessed(in);

	return total_spliced ? total_spliced : error;
}
EXPORT_SYMBOL(filemap_splice_read);

static inline loff_t folio_seek_hole_data(struct xa_state *xas,
		struct address_space *mapping, struct folio *folio,
		loff_t start, loff_t end, bool seek_data)
{
	const struct address_space_operations *ops = mapping->a_ops;
	size_t offset, bsz = i_blocksize(mapping->host);

	if (xa_is_value(folio) || folio_test_uptodate(folio))
		return seek_data ? start : end;
	if (!ops->is_partially_uptodate)
		return seek_data ? end : start;

	xas_pause(xas);
	rcu_read_unlock();
	folio_lock(folio);
	if (unlikely(folio->mapping != mapping))
		goto unlock;

	offset = offset_in_folio(folio, start) & ~(bsz - 1);

	do {
		if (ops->is_partially_uptodate(folio, offset, bsz) ==
							seek_data)
			break;
		start = (start + bsz) & ~(bsz - 1);
		offset += bsz;
	} while (offset < folio_size(folio));
unlock:
	folio_unlock(folio);
	rcu_read_lock();
	return start;
}

static inline size_t seek_folio_size(struct xa_state *xas, struct folio *folio)
{
	if (xa_is_value(folio))
		return PAGE_SIZE << xa_get_order(xas->xa, xas->xa_index);
	return folio_size(folio);
}

/**
 * mapping_seek_hole_data - Seek for SEEK_DATA / SEEK_HOLE in the page cache.
 * @mapping: Address space to search.
 * @start: First byte to consider.
 * @end: Limit of search (exclusive).
 * @whence: Either SEEK_HOLE or SEEK_DATA.
 *
 * If the page cache knows which blocks contain holes and which blocks
 * contain data, your filesystem can use this function to implement
 * SEEK_HOLE and SEEK_DATA.  This is useful for filesystems which are
 * entirely memory-based such as tmpfs, and filesystems which support
 * unwritten extents.
 *
 * Return: The requested offset on success, or -ENXIO if @whence specifies
 * SEEK_DATA and there is no data after @start.  There is an implicit hole
 * after @end - 1, so SEEK_HOLE returns @end if all the bytes between @start
 * and @end contain data.
 */
loff_t mapping_seek_hole_data(struct address_space *mapping, loff_t start,
		loff_t end, int whence)
{
	XA_STATE(xas, &mapping->i_pages, start >> PAGE_SHIFT);
	pgoff_t max = (end - 1) >> PAGE_SHIFT;
	bool seek_data = (whence == SEEK_DATA);
	struct folio *folio;

	if (end <= start)
		return -ENXIO;

	rcu_read_lock();
	while ((folio = find_get_entry(&xas, max, XA_PRESENT))) {
		loff_t pos = (u64)xas.xa_index << PAGE_SHIFT;
		size_t seek_size;

		if (start < pos) {
			if (!seek_data)
				goto unlock;
			start = pos;
		}

		seek_size = seek_folio_size(&xas, folio);
		pos = round_up((u64)pos + 1, seek_size);
		start = folio_seek_hole_data(&xas, mapping, folio, start, pos,
				seek_data);
		if (start < pos)
			goto unlock;
		if (start >= end)
			break;
		if (seek_size > PAGE_SIZE)
			xas_set(&xas, pos >> PAGE_SHIFT);
		if (!xa_is_value(folio))
			folio_put(folio);
	}
	if (seek_data)
		start = -ENXIO;
unlock:
	rcu_read_unlock();
	if (folio && !xa_is_value(folio))
		folio_put(folio);
	if (start > end)
		return end;
	return start;
}

#ifdef CONFIG_MMU
#define MMAP_LOTSAMISS  (100)
/*
 * lock_folio_maybe_drop_mmap - lock the page, possibly dropping the mmap_lock
 * @vmf - the vm_fault for this fault.
 * @folio - the folio to lock.
 * @fpin - the pointer to the file we may pin (or is already pinned).
 *
 * This works similar to lock_folio_or_retry in that it can drop the
 * mmap_lock.  It differs in that it actually returns the folio locked
 * if it returns 1 and 0 if it couldn't lock the folio.  If we did have
 * to drop the mmap_lock then fpin will point to the pinned file and
 * needs to be fput()'ed at a later point.
 */
static int lock_folio_maybe_drop_mmap(struct vm_fault *vmf, struct folio *folio,
				     struct file **fpin)
{
	if (folio_trylock(folio))
		return 1;

	/*
	 * NOTE! This will make us return with VM_FAULT_RETRY, but with
	 * the mmap_lock still held. That's how FAULT_FLAG_RETRY_NOWAIT
	 * is supposed to work. We have way too many special cases..
	 */
	if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
		return 0;

	*fpin = maybe_unlock_mmap_for_io(vmf, *fpin);
	if (vmf->flags & FAULT_FLAG_KILLABLE) {
		if (__folio_lock_killable(folio)) {
			/*
			 * We didn't have the right flags to drop the mmap_lock,
			 * but all fault_handlers only check for fatal signals
			 * if we return VM_FAULT_RETRY, so we need to drop the
			 * mmap_lock here and return 0 if we don't have a fpin.
			 */
			if (*fpin == NULL)
				mmap_read_unlock(vmf->vma->vm_mm);
			return 0;
		}
	} else
		__folio_lock(folio);

	return 1;
}

/*
 * Synchronous readahead happens when we don't even find a page in the page
 * cache at all.  We don't want to perform IO under the mmap sem, so if we have
 * to drop the mmap sem we return the file that was pinned in order for us to do
 * that.  If we didn't pin a file then we return NULL.  The file that is
 * returned needs to be fput()'ed when we're done with it.
 */
static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
{
	struct file *file = vmf->vma->vm_file;
	struct file_ra_state *ra = &file->f_ra;
	struct address_space *mapping = file->f_mapping;
	DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
	struct file *fpin = NULL;
	unsigned long vm_flags = vmf->vma->vm_flags;
	unsigned int mmap_miss;

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	/* Use the readahead code, even if readahead is disabled */
	if (vm_flags & VM_HUGEPAGE) {
		fpin = maybe_unlock_mmap_for_io(vmf, fpin);
		ractl._index &= ~((unsigned long)HPAGE_PMD_NR - 1);
		ra->size = HPAGE_PMD_NR;
		/*
		 * Fetch two PMD folios, so we get the chance to actually
		 * readahead, unless we've been told not to.
		 */
		if (!(vm_flags & VM_RAND_READ))
			ra->size *= 2;
		ra->async_size = HPAGE_PMD_NR;
		page_cache_ra_order(&ractl, ra, HPAGE_PMD_ORDER);
		return fpin;
	}
#endif

	/* If we don't want any read-ahead, don't bother */
	if (vm_flags & VM_RAND_READ)
		return fpin;
	if (!ra->ra_pages)
		return fpin;

	if (vm_flags & VM_SEQ_READ) {
		fpin = maybe_unlock_mmap_for_io(vmf, fpin);
		page_cache_sync_ra(&ractl, ra->ra_pages);
		return fpin;
	}

	/* Avoid banging the cache line if not needed */
	mmap_miss = READ_ONCE(ra->mmap_miss);
	if (mmap_miss < MMAP_LOTSAMISS * 10)
		WRITE_ONCE(ra->mmap_miss, ++mmap_miss);

	/*
	 * Do we miss much more than hit in this file? If so,
	 * stop bothering with read-ahead. It will only hurt.
	 */
	if (mmap_miss > MMAP_LOTSAMISS)
		return fpin;

	/*
	 * mmap read-around
	 */
	fpin = maybe_unlock_mmap_for_io(vmf, fpin);
	ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2);
	ra->size = ra->ra_pages;
	ra->async_size = ra->ra_pages / 4;
	ractl._index = ra->start;
	page_cache_ra_order(&ractl, ra, 0);
	return fpin;
}

/*
 * Asynchronous readahead happens when we find the page and PG_readahead,
 * so we want to possibly extend the readahead further.  We return the file that
 * was pinned if we have to drop the mmap_lock in order to do IO.
 */
static struct file *do_async_mmap_readahead(struct vm_fault *vmf,
					    struct folio *folio)
{
	struct file *file = vmf->vma->vm_file;
	struct file_ra_state *ra = &file->f_ra;
	DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff);
	struct file *fpin = NULL;
	unsigned int mmap_miss;

	/* If we don't want any read-ahead, don't bother */
	if (vmf->vma->vm_flags & VM_RAND_READ || !ra->ra_pages)
		return fpin;

	mmap_miss = READ_ONCE(ra->mmap_miss);
	if (mmap_miss)
		WRITE_ONCE(ra->mmap_miss, --mmap_miss);

	if (folio_test_readahead(folio)) {
		fpin = maybe_unlock_mmap_for_io(vmf, fpin);
		page_cache_async_ra(&ractl, folio, ra->ra_pages);
	}
	return fpin;
}

/**
 * filemap_fault - read in file data for page fault handling
 * @vmf:	struct vm_fault containing details of the fault
 *
 * filemap_fault() is invoked via the vma operations vector for a
 * mapped memory region to read in file data during a page fault.
 *
 * The goto's are kind of ugly, but this streamlines the normal case of having
 * it in the page cache, and handles the special cases reasonably without
 * having a lot of duplicated code.
 *
 * vma->vm_mm->mmap_lock must be held on entry.
 *
 * If our return value has VM_FAULT_RETRY set, it's because the mmap_lock
 * may be dropped before doing I/O or by lock_folio_maybe_drop_mmap().
 *
 * If our return value does not have VM_FAULT_RETRY set, the mmap_lock
 * has not been released.
 *
 * We never return with VM_FAULT_RETRY and a bit from VM_FAULT_ERROR set.
 *
 * Return: bitwise-OR of %VM_FAULT_ codes.
 */
vm_fault_t filemap_fault(struct vm_fault *vmf)
{
	int error;
	struct file *file = vmf->vma->vm_file;
	struct file *fpin = NULL;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	pgoff_t max_idx, index = vmf->pgoff;
	struct folio *folio;
	vm_fault_t ret = 0;
	bool mapping_locked = false;

	max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
	if (unlikely(index >= max_idx))
		return VM_FAULT_SIGBUS;

	/*
	 * Do we have something in the page cache already?
	 */
	folio = filemap_get_folio(mapping, index);
	if (likely(!IS_ERR(folio))) {
		/*
		 * We found the page, so try async readahead before waiting for
		 * the lock.
		 */
		if (!(vmf->flags & FAULT_FLAG_TRIED))
			fpin = do_async_mmap_readahead(vmf, folio);
		if (unlikely(!folio_test_uptodate(folio))) {
			filemap_invalidate_lock_shared(mapping);
			mapping_locked = true;
		}
	} else {
		/* No page in the page cache at all */
		count_vm_event(PGMAJFAULT);
		count_memcg_event_mm(vmf->vma->vm_mm, PGMAJFAULT);
		ret = VM_FAULT_MAJOR;
		fpin = do_sync_mmap_readahead(vmf);
retry_find:
		/*
		 * See comment in filemap_create_folio() why we need
		 * invalidate_lock
		 */
		if (!mapping_locked) {
			filemap_invalidate_lock_shared(mapping);
			mapping_locked = true;
		}
		folio = __filemap_get_folio(mapping, index,
					  FGP_CREAT|FGP_FOR_MMAP,
					  vmf->gfp_mask);
		if (IS_ERR(folio)) {
			if (fpin)
				goto out_retry;
			filemap_invalidate_unlock_shared(mapping);
			return VM_FAULT_OOM;
		}
	}

	if (!lock_folio_maybe_drop_mmap(vmf, folio, &fpin))
		goto out_retry;

	/* Did it get truncated? */
	if (unlikely(folio->mapping != mapping)) {
		folio_unlock(folio);
		folio_put(folio);
		goto retry_find;
	}
	VM_BUG_ON_FOLIO(!folio_contains(folio, index), folio);

	/*
	 * We have a locked page in the page cache, now we need to check
	 * that it's up-to-date. If not, it is going to be due to an error.
	 */
	if (unlikely(!folio_test_uptodate(folio))) {
		/*
		 * The page was in cache and uptodate and now it is not.
		 * Strange but possible since we didn't hold the page lock all
		 * the time. Let's drop everything get the invalidate lock and
		 * try again.
		 */
		if (!mapping_locked) {
			folio_unlock(folio);
			folio_put(folio);
			goto retry_find;
		}
		goto page_not_uptodate;
	}

	/*
	 * We've made it this far and we had to drop our mmap_lock, now is the
	 * time to return to the upper layer and have it re-find the vma and
	 * redo the fault.
	 */
	if (fpin) {
		folio_unlock(folio);
		goto out_retry;
	}
	if (mapping_locked)
		filemap_invalidate_unlock_shared(mapping);

	/*
	 * Found the page and have a reference on it.
	 * We must recheck i_size under page lock.
	 */
	max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE);
	if (unlikely(index >= max_idx)) {
		folio_unlock(folio);
		folio_put(folio);
		return VM_FAULT_SIGBUS;
	}

	vmf->page = folio_file_page(folio, index);
	return ret | VM_FAULT_LOCKED;

page_not_uptodate:
	/*
	 * Umm, take care of errors if the page isn't up-to-date.
	 * Try to re-read it _once_. We do this synchronously,
	 * because there really aren't any performance issues here
	 * and we need to check for errors.
	 */
	fpin = maybe_unlock_mmap_for_io(vmf, fpin);
	error = filemap_read_folio(file, mapping->a_ops->read_folio, folio);
	if (fpin)
		goto out_retry;
	folio_put(folio);

	if (!error || error == AOP_TRUNCATED_PAGE)
		goto retry_find;
	filemap_invalidate_unlock_shared(mapping);

	return VM_FAULT_SIGBUS;

out_retry:
	/*
	 * We dropped the mmap_lock, we need to return to the fault handler to
	 * re-find the vma and come back and find our hopefully still populated
	 * page.
	 */
	if (!IS_ERR(folio))
		folio_put(folio);
	if (mapping_locked)
		filemap_invalidate_unlock_shared(mapping);
	if (fpin)
		fput(fpin);
	return ret | VM_FAULT_RETRY;
}
EXPORT_SYMBOL(filemap_fault);

static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
		pgoff_t start)
{
	struct mm_struct *mm = vmf->vma->vm_mm;

	/* Huge page is mapped? No need to proceed. */
	if (pmd_trans_huge(*vmf->pmd)) {
		folio_unlock(folio);
		folio_put(folio);
		return true;
	}

	if (pmd_none(*vmf->pmd) && folio_test_pmd_mappable(folio)) {
		struct page *page = folio_file_page(folio, start);
		vm_fault_t ret = do_set_pmd(vmf, page);
		if (!ret) {
			/* The page is mapped successfully, reference consumed. */
			folio_unlock(folio);
			return true;
		}
	}

	if (pmd_none(*vmf->pmd))
		pmd_install(mm, vmf->pmd, &vmf->prealloc_pte);

	return false;
}

static struct folio *next_uptodate_folio(struct xa_state *xas,
		struct address_space *mapping, pgoff_t end_pgoff)
{
	struct folio *folio = xas_next_entry(xas, end_pgoff);
	unsigned long max_idx;

	do {
		if (!folio)
			return NULL;
		if (xas_retry(xas, folio))
			continue;
		if (xa_is_value(folio))
			continue;
		if (folio_test_locked(folio))
			continue;
		if (!folio_try_get_rcu(folio))
			continue;
		/* Has the page moved or been split? */
		if (unlikely(folio != xas_reload(xas)))
			goto skip;
		if (!folio_test_uptodate(folio) || folio_test_readahead(folio))
			goto skip;
		if (!folio_trylock(folio))
			goto skip;
		if (folio->mapping != mapping)
			goto unlock;
		if (!folio_test_uptodate(folio))
			goto unlock;
		max_idx = DIV_ROUND_UP(i_size_read(mapping->host), PAGE_SIZE);
		if (xas->xa_index >= max_idx)
			goto unlock;
		return folio;
unlock:
		folio_unlock(folio);
skip:
		folio_put(folio);
	} while ((folio = xas_next_entry(xas, end_pgoff)) != NULL);

	return NULL;
}

/*
 * Map page range [start_page, start_page + nr_pages) of folio.
 * start_page is gotten from start by folio_page(folio, start)
 */
static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
			struct folio *folio, unsigned long start,
			unsigned long addr, unsigned int nr_pages)
{
	vm_fault_t ret = 0;
	struct vm_area_struct *vma = vmf->vma;
	struct file *file = vma->vm_file;
	struct page *page = folio_page(folio, start);
	unsigned int mmap_miss = READ_ONCE(file->f_ra.mmap_miss);
	unsigned int count = 0;
	pte_t *old_ptep = vmf->pte;

	do {
		if (PageHWPoison(page + count))
			goto skip;

		if (mmap_miss > 0)
			mmap_miss--;

		/*
		 * NOTE: If there're PTE markers, we'll leave them to be
		 * handled in the specific fault path, and it'll prohibit the
		 * fault-around logic.
		 */
		if (!pte_none(vmf->pte[count]))
			goto skip;

		count++;
		continue;
skip:
		if (count) {
			set_pte_range(vmf, folio, page, count, addr);
			folio_ref_add(folio, count);
			if (in_range(vmf->address, addr, count))
				ret = VM_FAULT_NOPAGE;
		}

		count++;
		page += count;
		vmf->pte += count;
		addr += count * PAGE_SIZE;
		count = 0;
	} while (--nr_pages > 0);

	if (count) {
		set_pte_range(vmf, folio, page, count, addr);
		folio_ref_add(folio, count);
		if (in_range(vmf->address, addr, count))
			ret = VM_FAULT_NOPAGE;
	}

	vmf->pte = old_ptep;
	WRITE_ONCE(file->f_ra.mmap_miss, mmap_miss);

	return ret;
}

vm_fault_t filemap_map_pages(struct vm_fault *vmf,
			     pgoff_t start_pgoff, pgoff_t end_pgoff)
{
	struct vm_area_struct *vma = vmf->vma;
	struct file *file = vma->vm_file;
	struct address_space *mapping = file->f_mapping;
	pgoff_t last_pgoff = start_pgoff;
	unsigned long addr;
	XA_STATE(xas, &mapping->i_pages, start_pgoff);
	struct folio *folio;
	vm_fault_t ret = 0;
	int nr_pages = 0;

	rcu_read_lock();
	folio = next_uptodate_folio(&xas, mapping, end_pgoff);
	if (!folio)
		goto out;

	if (filemap_map_pmd(vmf, folio, start_pgoff)) {
		ret = VM_FAULT_NOPAGE;
		goto out;
	}

	addr = vma->vm_start + ((start_pgoff - vma->vm_pgoff) << PAGE_SHIFT);
	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, addr, &vmf->ptl);
	if (!vmf->pte) {
		folio_unlock(folio);
		folio_put(folio);
		goto out;
	}
	do {
		unsigned long end;

		addr += (xas.xa_index - last_pgoff) << PAGE_SHIFT;
		vmf->pte += xas.xa_index - last_pgoff;
		last_pgoff = xas.xa_index;
		end = folio->index + folio_nr_pages(folio) - 1;
		nr_pages = min(end, end_pgoff) - xas.xa_index + 1;

		/*
		 * NOTE: If there're PTE markers, we'll leave them to be
		 * handled in the specific fault path, and it'll prohibit the
		 * fault-around logic.
		 */
		if (!pte_none(ptep_get(vmf->pte)))
			goto unlock;

		ret |= filemap_map_folio_range(vmf, folio,
				xas.xa_index - folio->index, addr, nr_pages);

unlock:
		folio_unlock(folio);
		folio_put(folio);
		folio = next_uptodate_folio(&xas, mapping, end_pgoff);
	} while (folio);
	pte_unmap_unlock(vmf->pte, vmf->ptl);
out:
	rcu_read_unlock();
	return ret;
}
EXPORT_SYMBOL(filemap_map_pages);

vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
{
	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
	struct folio *folio = page_folio(vmf->page);
	vm_fault_t ret = VM_FAULT_LOCKED;

	sb_start_pagefault(mapping->host->i_sb);
	file_update_time(vmf->vma->vm_file);
	folio_lock(folio);
	if (folio->mapping != mapping) {
		folio_unlock(folio);
		ret = VM_FAULT_NOPAGE;
		goto out;
	}
	/*
	 * We mark the folio dirty already here so that when freeze is in
	 * progress, we are guaranteed that writeback during freezing will
	 * see the dirty folio and writeprotect it again.
	 */
	folio_mark_dirty(folio);
	folio_wait_stable(folio);
out:
	sb_end_pagefault(mapping->host->i_sb);
	return ret;
}

const struct vm_operations_struct generic_file_vm_ops = {
	.fault		= filemap_fault,
	.map_pages	= filemap_map_pages,
	.page_mkwrite	= filemap_page_mkwrite,
};

/* This is used for a general mmap of a disk file */

int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
{
	struct address_space *mapping = file->f_mapping;

	if (!mapping->a_ops->read_folio)
		return -ENOEXEC;
	file_accessed(file);
	vma->vm_ops = &generic_file_vm_ops;
	return 0;
}

/*
 * This is for filesystems which do not implement ->writepage.
 */
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
{
	if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE))
		return -EINVAL;
	return generic_file_mmap(file, vma);
}
#else
vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf)
{
	return VM_FAULT_SIGBUS;
}
int generic_file_mmap(struct file *file, struct vm_area_struct *vma)
{
	return -ENOSYS;
}
int generic_file_readonly_mmap(struct file *file, struct vm_area_struct *vma)
{
	return -ENOSYS;
}
#endif /* CONFIG_MMU */

EXPORT_SYMBOL(filemap_page_mkwrite);
EXPORT_SYMBOL(generic_file_mmap);
EXPORT_SYMBOL(generic_file_readonly_mmap);

static struct folio *do_read_cache_folio(struct address_space *mapping,
		pgoff_t index, filler_t filler, struct file *file, gfp_t gfp)
{
	struct folio *folio;
	int err;

	if (!filler)
		filler = mapping->a_ops->read_folio;
repeat:
	folio = filemap_get_folio(mapping, index);
	if (IS_ERR(folio)) {
		folio = filemap_alloc_folio(gfp, 0);
		if (!folio)
			return ERR_PTR(-ENOMEM);
		err = filemap_add_folio(mapping, folio, index, gfp);
		if (unlikely(err)) {
			folio_put(folio);
			if (err == -EEXIST)
				goto repeat;
			/* Presumably ENOMEM for xarray node */
			return ERR_PTR(err);
		}

		goto filler;
	}
	if (folio_test_uptodate(folio))
		goto out;

	if (!folio_trylock(folio)) {
		folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE);
		goto repeat;
	}

	/* Folio was truncated from mapping */
	if (!folio->mapping) {
		folio_unlock(folio);
		folio_put(folio);
		goto repeat;
	}

	/* Someone else locked and filled the page in a very small window */
	if (folio_test_uptodate(folio)) {
		folio_unlock(folio);
		goto out;
	}

filler:
	err = filemap_read_folio(file, filler, folio);
	if (err) {
		folio_put(folio);
		if (err == AOP_TRUNCATED_PAGE)
			goto repeat;
		return ERR_PTR(err);
	}

out:
	folio_mark_accessed(folio);
	return folio;
}

/**
 * read_cache_folio - Read into page cache, fill it if needed.
 * @mapping: The address_space to read from.
 * @index: The index to read.
 * @filler: Function to perform the read, or NULL to use aops->read_folio().
 * @file: Passed to filler function, may be NULL if not required.
 *
 * Read one page into the page cache.  If it succeeds, the folio returned
 * will contain @index, but it may not be the first page of the folio.
 *
 * If the filler function returns an error, it will be returned to the
 * caller.
 *
 * Context: May sleep.  Expects mapping->invalidate_lock to be held.
 * Return: An uptodate folio on success, ERR_PTR() on failure.
 */
struct folio *read_cache_folio(struct address_space *mapping, pgoff_t index,
		filler_t filler, struct file *file)
{
	return do_read_cache_folio(mapping, index, filler, file,
			mapping_gfp_mask(mapping));
}
EXPORT_SYMBOL(read_cache_folio);

/**
 * mapping_read_folio_gfp - Read into page cache, using specified allocation flags.
 * @mapping:	The address_space for the folio.
 * @index:	The index that the allocated folio will contain.
 * @gfp:	The page allocator flags to use if allocating.
 *
 * This is the same as "read_cache_folio(mapping, index, NULL, NULL)", but with
 * any new memory allocations done using the specified allocation flags.
 *
 * The most likely error from this function is EIO, but ENOMEM is
 * possible and so is EINTR.  If ->read_folio returns another error,
 * that will be returned to the caller.
 *
 * The function expects mapping->invalidate_lock to be already held.
 *
 * Return: Uptodate folio on success, ERR_PTR() on failure.
 */
struct folio *mapping_read_folio_gfp(struct address_space *mapping,
		pgoff_t index, gfp_t gfp)
{
	return do_read_cache_folio(mapping, index, NULL, NULL, gfp);
}
EXPORT_SYMBOL(mapping_read_folio_gfp);

static struct page *do_read_cache_page(struct address_space *mapping,
		pgoff_t index, filler_t *filler, struct file *file, gfp_t gfp)
{
	struct folio *folio;

	folio = do_read_cache_folio(mapping, index, filler, file, gfp);
	if (IS_ERR(folio))
		return &folio->page;
	return folio_file_page(folio, index);
}

struct page *read_cache_page(struct address_space *mapping,
			pgoff_t index, filler_t *filler, struct file *file)
{
	return do_read_cache_page(mapping, index, filler, file,
			mapping_gfp_mask(mapping));
}
EXPORT_SYMBOL(read_cache_page);

/**
 * read_cache_page_gfp - read into page cache, using specified page allocation flags.
 * @mapping:	the page's address_space
 * @index:	the page index
 * @gfp:	the page allocator flags to use if allocating
 *
 * This is the same as "read_mapping_page(mapping, index, NULL)", but with
 * any new page allocations done using the specified allocation flags.
 *
 * If the page does not get brought uptodate, return -EIO.
 *
 * The function expects mapping->invalidate_lock to be already held.
 *
 * Return: up to date page on success, ERR_PTR() on failure.
 */
struct page *read_cache_page_gfp(struct address_space *mapping,
				pgoff_t index,
				gfp_t gfp)
{
	return do_read_cache_page(mapping, index, NULL, NULL, gfp);
}
EXPORT_SYMBOL(read_cache_page_gfp);

/*
 * Warn about a page cache invalidation failure during a direct I/O write.
 */
static void dio_warn_stale_pagecache(struct file *filp)
{
	static DEFINE_RATELIMIT_STATE(_rs, 86400 * HZ, DEFAULT_RATELIMIT_BURST);
	char pathname[128];
	char *path;

	errseq_set(&filp->f_mapping->wb_err, -EIO);
	if (__ratelimit(&_rs)) {
		path = file_path(filp, pathname, sizeof(pathname));
		if (IS_ERR(path))
			path = "(unknown)";
		pr_crit("Page cache invalidation failure on direct I/O.  Possible data corruption due to collision with buffered I/O!\n");
		pr_crit("File: %s PID: %d Comm: %.20s\n", path, current->pid,
			current->comm);
	}
}

void kiocb_invalidate_post_direct_write(struct kiocb *iocb, size_t count)
{
	struct address_space *mapping = iocb->ki_filp->f_mapping;

	if (mapping->nrpages &&
	    invalidate_inode_pages2_range(mapping,
			iocb->ki_pos >> PAGE_SHIFT,
			(iocb->ki_pos + count - 1) >> PAGE_SHIFT))
		dio_warn_stale_pagecache(iocb->ki_filp);
}

ssize_t
generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
{
	struct address_space *mapping = iocb->ki_filp->f_mapping;
	size_t write_len = iov_iter_count(from);
	ssize_t written;

	/*
	 * If a page can not be invalidated, return 0 to fall back
	 * to buffered write.
	 */
	written = kiocb_invalidate_pages(iocb, write_len);
	if (written) {
		if (written == -EBUSY)
			return 0;
		return written;
	}

	written = mapping->a_ops->direct_IO(iocb, from);

	/*
	 * Finally, try again to invalidate clean pages which might have been
	 * cached by non-direct readahead, or faulted in by get_user_pages()
	 * if the source of the write was an mmap'ed region of the file
	 * we're writing.  Either one is a pretty crazy thing to do,
	 * so we don't support it 100%.  If this invalidation
	 * fails, tough, the write still worked...
	 *
	 * Most of the time we do not need this since dio_complete() will do
	 * the invalidation for us. However there are some file systems that
	 * do not end up with dio_complete() being called, so let's not break
	 * them by removing it completely.
	 *
	 * Noticeable example is a blkdev_direct_IO().
	 *
	 * Skip invalidation for async writes or if mapping has no pages.
	 */
	if (written > 0) {
		struct inode *inode = mapping->host;
		loff_t pos = iocb->ki_pos;

		kiocb_invalidate_post_direct_write(iocb, written);
		pos += written;
		write_len -= written;
		if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
			i_size_write(inode, pos);
			mark_inode_dirty(inode);
		}
		iocb->ki_pos = pos;
	}
	if (written != -EIOCBQUEUED)
		iov_iter_revert(from, write_len - iov_iter_count(from));
	return written;
}
EXPORT_SYMBOL(generic_file_direct_write);

ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
{
	struct file *file = iocb->ki_filp;
	loff_t pos = iocb->ki_pos;
	struct address_space *mapping = file->f_mapping;
	const struct address_space_operations *a_ops = mapping->a_ops;
	long status = 0;
	ssize_t written = 0;

	do {
		struct page *page;
		unsigned long offset;	/* Offset into pagecache page */
		unsigned long bytes;	/* Bytes to write to page */
		size_t copied;		/* Bytes copied from user */
		void *fsdata = NULL;

		offset = (pos & (PAGE_SIZE - 1));
		bytes = min_t(unsigned long, PAGE_SIZE - offset,
						iov_iter_count(i));

again:
		/*
		 * Bring in the user page that we will copy from _first_.
		 * Otherwise there's a nasty deadlock on copying from the
		 * same page as we're writing to, without it being marked
		 * up-to-date.
		 */
		if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
			status = -EFAULT;
			break;
		}

		if (fatal_signal_pending(current)) {
			status = -EINTR;
			break;
		}

		status = a_ops->write_begin(file, mapping, pos, bytes,
						&page, &fsdata);
		if (unlikely(status < 0))
			break;

		if (mapping_writably_mapped(mapping))
			flush_dcache_page(page);

		copied = copy_page_from_iter_atomic(page, offset, bytes, i);
		flush_dcache_page(page);

		status = a_ops->write_end(file, mapping, pos, bytes, copied,
						page, fsdata);
		if (unlikely(status != copied)) {
			iov_iter_revert(i, copied - max(status, 0L));
			if (unlikely(status < 0))
				break;
		}
		cond_resched();

		if (unlikely(status == 0)) {
			/*
			 * A short copy made ->write_end() reject the
			 * thing entirely.  Might be memory poisoning
			 * halfway through, might be a race with munmap,
			 * might be severe memory pressure.
			 */
			if (copied)
				bytes = copied;
			goto again;
		}
		pos += status;
		written += status;

		balance_dirty_pages_ratelimited(mapping);
	} while (iov_iter_count(i));

	if (!written)
		return status;
	iocb->ki_pos += written;
	return written;
}
EXPORT_SYMBOL(generic_perform_write);

/**
 * __generic_file_write_iter - write data to a file
 * @iocb:	IO state structure (file, offset, etc.)
 * @from:	iov_iter with data to write
 *
 * This function does all the work needed for actually writing data to a
 * file. It does all basic checks, removes SUID from the file, updates
 * modification times and calls proper subroutines depending on whether we
 * do direct IO or a standard buffered write.
 *
 * It expects i_rwsem to be grabbed unless we work on a block device or similar
 * object which does not need locking at all.
 *
 * This function does *not* take care of syncing data in case of O_SYNC write.
 * A caller has to handle it. This is mainly due to the fact that we want to
 * avoid syncing under i_rwsem.
 *
 * Return:
 * * number of bytes written, even for truncated writes
 * * negative error code if no data has been written at all
 */
ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
	struct file *file = iocb->ki_filp;
	struct address_space *mapping = file->f_mapping;
	struct inode *inode = mapping->host;
	ssize_t ret;

	ret = file_remove_privs(file);
	if (ret)
		return ret;

	ret = file_update_time(file);
	if (ret)
		return ret;

	if (iocb->ki_flags & IOCB_DIRECT) {
		ret = generic_file_direct_write(iocb, from);
		/*
		 * If the write stopped short of completing, fall back to
		 * buffered writes.  Some filesystems do this for writes to
		 * holes, for example.  For DAX files, a buffered write will
		 * not succeed (even if it did, DAX does not handle dirty
		 * page-cache pages correctly).
		 */
		if (ret < 0 || !iov_iter_count(from) || IS_DAX(inode))
			return ret;
		return direct_write_fallback(iocb, from, ret,
				generic_perform_write(iocb, from));
	}

	return generic_perform_write(iocb, from);
}
EXPORT_SYMBOL(__generic_file_write_iter);

/**
 * generic_file_write_iter - write data to a file
 * @iocb:	IO state structure
 * @from:	iov_iter with data to write
 *
 * This is a wrapper around __generic_file_write_iter() to be used by most
 * filesystems. It takes care of syncing the file in case of O_SYNC file
 * and acquires i_rwsem as needed.
 * Return:
 * * negative error code if no data has been written at all of
 *   vfs_fsync_range() failed for a synchronous write
 * * number of bytes written, even for truncated writes
 */
ssize_t generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
	struct file *file = iocb->ki_filp;
	struct inode *inode = file->f_mapping->host;
	ssize_t ret;

	inode_lock(inode);
	ret = generic_write_checks(iocb, from);
	if (ret > 0)
		ret = __generic_file_write_iter(iocb, from);
	inode_unlock(inode);

	if (ret > 0)
		ret = generic_write_sync(iocb, ret);
	return ret;
}
EXPORT_SYMBOL(generic_file_write_iter);

/**
 * filemap_release_folio() - Release fs-specific metadata on a folio.
 * @folio: The folio which the kernel is trying to free.
 * @gfp: Memory allocation flags (and I/O mode).
 *
 * The address_space is trying to release any data attached to a folio
 * (presumably at folio->private).
 *
 * This will also be called if the private_2 flag is set on a page,
 * indicating that the folio has other metadata associated with it.
 *
 * The @gfp argument specifies whether I/O may be performed to release
 * this page (__GFP_IO), and whether the call may block
 * (__GFP_RECLAIM & __GFP_FS).
 *
 * Return: %true if the release was successful, otherwise %false.
 */
bool filemap_release_folio(struct folio *folio, gfp_t gfp)
{
	struct address_space * const mapping = folio->mapping;

	BUG_ON(!folio_test_locked(folio));
	if (!folio_needs_release(folio))
		return true;
	if (folio_test_writeback(folio))
		return false;

	if (mapping && mapping->a_ops->release_folio)
		return mapping->a_ops->release_folio(folio, gfp);
	return try_to_free_buffers(folio);
}
EXPORT_SYMBOL(filemap_release_folio);

#ifdef CONFIG_CACHESTAT_SYSCALL
/**
 * filemap_cachestat() - compute the page cache statistics of a mapping
 * @mapping:	The mapping to compute the statistics for.
 * @first_index:	The starting page cache index.
 * @last_index:	The final page index (inclusive).
 * @cs:	the cachestat struct to write the result to.
 *
 * This will query the page cache statistics of a mapping in the
 * page range of [first_index, last_index] (inclusive). The statistics
 * queried include: number of dirty pages, number of pages marked for
 * writeback, and the number of (recently) evicted pages.
 */
static void filemap_cachestat(struct address_space *mapping,
		pgoff_t first_index, pgoff_t last_index, struct cachestat *cs)
{
	XA_STATE(xas, &mapping->i_pages, first_index);
	struct folio *folio;

	rcu_read_lock();
	xas_for_each(&xas, folio, last_index) {
		unsigned long nr_pages;
		pgoff_t folio_first_index, folio_last_index;

		if (xas_retry(&xas, folio))
			continue;

		if (xa_is_value(folio)) {
			/* page is evicted */
			void *shadow = (void *)folio;
			bool workingset; /* not used */
			int order = xa_get_order(xas.xa, xas.xa_index);

			nr_pages = 1 << order;
			folio_first_index = round_down(xas.xa_index, 1 << order);
			folio_last_index = folio_first_index + nr_pages - 1;

			/* Folios might straddle the range boundaries, only count covered pages */
			if (folio_first_index < first_index)
				nr_pages -= first_index - folio_first_index;

			if (folio_last_index > last_index)
				nr_pages -= folio_last_index - last_index;

			cs->nr_evicted += nr_pages;

#ifdef CONFIG_SWAP /* implies CONFIG_MMU */
			if (shmem_mapping(mapping)) {
				/* shmem file - in swap cache */
				swp_entry_t swp = radix_to_swp_entry(folio);

				shadow = get_shadow_from_swap_cache(swp);
			}
#endif
			if (workingset_test_recent(shadow, true, &workingset))
				cs->nr_recently_evicted += nr_pages;

			goto resched;
		}

		nr_pages = folio_nr_pages(folio);
		folio_first_index = folio_pgoff(folio);
		folio_last_index = folio_first_index + nr_pages - 1;

		/* Folios might straddle the range boundaries, only count covered pages */
		if (folio_first_index < first_index)
			nr_pages -= first_index - folio_first_index;

		if (folio_last_index > last_index)
			nr_pages -= folio_last_index - last_index;

		/* page is in cache */
		cs->nr_cache += nr_pages;

		if (folio_test_dirty(folio))
			cs->nr_dirty += nr_pages;

		if (folio_test_writeback(folio))
			cs->nr_writeback += nr_pages;

resched:
		if (need_resched()) {
			xas_pause(&xas);
			cond_resched_rcu();
		}
	}
	rcu_read_unlock();
}

/*
 * The cachestat(2) system call.
 *
 * cachestat() returns the page cache statistics of a file in the
 * bytes range specified by `off` and `len`: number of cached pages,
 * number of dirty pages, number of pages marked for writeback,
 * number of evicted pages, and number of recently evicted pages.
 *
 * An evicted page is a page that is previously in the page cache
 * but has been evicted since. A page is recently evicted if its last
 * eviction was recent enough that its reentry to the cache would
 * indicate that it is actively being used by the system, and that
 * there is memory pressure on the system.
 *
 * `off` and `len` must be non-negative integers. If `len` > 0,
 * the queried range is [`off`, `off` + `len`]. If `len` == 0,
 * we will query in the range from `off` to the end of the file.
 *
 * The `flags` argument is unused for now, but is included for future
 * extensibility. User should pass 0 (i.e no flag specified).
 *
 * Currently, hugetlbfs is not supported.
 *
 * Because the status of a page can change after cachestat() checks it
 * but before it returns to the application, the returned values may
 * contain stale information.
 *
 * return values:
 *  zero        - success
 *  -EFAULT     - cstat or cstat_range points to an illegal address
 *  -EINVAL     - invalid flags
 *  -EBADF      - invalid file descriptor
 *  -EOPNOTSUPP - file descriptor is of a hugetlbfs file
 */
SYSCALL_DEFINE4(cachestat, unsigned int, fd,
		struct cachestat_range __user *, cstat_range,
		struct cachestat __user *, cstat, unsigned int, flags)
{
	struct fd f = fdget(fd);
	struct address_space *mapping;
	struct cachestat_range csr;
	struct cachestat cs;
	pgoff_t first_index, last_index;

	if (!f.file)
		return -EBADF;

	if (copy_from_user(&csr, cstat_range,
			sizeof(struct cachestat_range))) {
		fdput(f);
		return -EFAULT;
	}

	/* hugetlbfs is not supported */
	if (is_file_hugepages(f.file)) {
		fdput(f);
		return -EOPNOTSUPP;
	}

	if (flags != 0) {
		fdput(f);
		return -EINVAL;
	}

	first_index = csr.off >> PAGE_SHIFT;
	last_index =
		csr.len == 0 ? ULONG_MAX : (csr.off + csr.len - 1) >> PAGE_SHIFT;
	memset(&cs, 0, sizeof(struct cachestat));
	mapping = f.file->f_mapping;
	filemap_cachestat(mapping, first_index, last_index, &cs);
	fdput(f);

	if (copy_to_user(cstat, &cs, sizeof(struct cachestat)))
		return -EFAULT;

	return 0;
}
#endif /* CONFIG_CACHESTAT_SYSCALL */