summaryrefslogtreecommitdiff
path: root/mm/memory.c
blob: 7a089145cad4b2b2fd32b47390277760eb15cc18 (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
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
5007
5008
5009
5010
5011
5012
5013
5014
5015
5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064
5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
5076
5077
5078
5079
5080
5081
5082
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
5103
5104
5105
5106
5107
5108
5109
5110
5111
5112
5113
5114
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
5374
5375
5376
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
5413
5414
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434
5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466
5467
5468
5469
5470
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
5499
5500
5501
5502
5503
5504
5505
5506
5507
5508
5509
5510
5511
5512
5513
5514
5515
5516
5517
5518
5519
5520
5521
5522
5523
5524
5525
5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546
5547
5548
5549
5550
5551
5552
5553
5554
5555
5556
5557
5558
5559
5560
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
5583
5584
5585
5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
5599
5600
5601
5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626
5627
5628
5629
5630
5631
5632
5633
5634
5635
5636
5637
5638
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
5686
5687
5688
5689
5690
5691
5692
5693
5694
5695
5696
5697
5698
5699
5700
5701
5702
5703
5704
5705
5706
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
5721
5722
5723
5724
5725
5726
5727
5728
5729
5730
5731
5732
5733
5734
5735
5736
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
5756
5757
5758
5759
5760
5761
5762
5763
5764
5765
5766
5767
5768
5769
5770
5771
5772
5773
5774
// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/mm/memory.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 */

/*
 * demand-loading started 01.12.91 - seems it is high on the list of
 * things wanted, and it should be easy to implement. - Linus
 */

/*
 * Ok, demand-loading was easy, shared pages a little bit tricker. Shared
 * pages started 02.12.91, seems to work. - Linus.
 *
 * Tested sharing by executing about 30 /bin/sh: under the old kernel it
 * would have taken more than the 6M I have free, but it worked well as
 * far as I could see.
 *
 * Also corrected some "invalidate()"s - I wasn't doing enough of them.
 */

/*
 * Real VM (paging to/from disk) started 18.12.91. Much more work and
 * thought has to go into this. Oh, well..
 * 19.12.91  -  works, somewhat. Sometimes I get faults, don't know why.
 *		Found it. Everything seems to work now.
 * 20.12.91  -  Ok, making the swap-device changeable like the root.
 */

/*
 * 05.04.94  -  Multi-page memory management added for v1.1.
 *              Idea by Alex Bligh (alex@cconcepts.co.uk)
 *
 * 16.07.99  -  Support of BIGMEM added by Gerhard Wichert, Siemens AG
 *		(Gerhard.Wichert@pdb.siemens.de)
 *
 * Aug/Sep 2004 Changed to four level page tables (Andi Kleen)
 */

#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/mm_inline.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/sched/numa_balancing.h>
#include <linux/sched/task.h>
#include <linux/hugetlb.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/memremap.h>
#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/export.h>
#include <linux/delayacct.h>
#include <linux/init.h>
#include <linux/pfn_t.h>
#include <linux/writeback.h>
#include <linux/memcontrol.h>
#include <linux/mmu_notifier.h>
#include <linux/swapops.h>
#include <linux/elf.h>
#include <linux/gfp.h>
#include <linux/migrate.h>
#include <linux/string.h>
#include <linux/debugfs.h>
#include <linux/userfaultfd_k.h>
#include <linux/dax.h>
#include <linux/oom.h>
#include <linux/numa.h>
#include <linux/perf_event.h>
#include <linux/ptrace.h>
#include <linux/vmalloc.h>

#include <trace/events/kmem.h>

#include <asm/io.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>
#include <linux/uaccess.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>

#include "pgalloc-track.h"
#include "internal.h"
#include "swap.h"

#if defined(LAST_CPUPID_NOT_IN_PAGE_FLAGS) && !defined(CONFIG_COMPILE_TEST)
#warning Unfortunate NUMA and NUMA Balancing config, growing page-frame for last_cpupid.
#endif

#ifndef CONFIG_NUMA
unsigned long max_mapnr;
EXPORT_SYMBOL(max_mapnr);

struct page *mem_map;
EXPORT_SYMBOL(mem_map);
#endif

static vm_fault_t do_fault(struct vm_fault *vmf);

/*
 * A number of key systems in x86 including ioremap() rely on the assumption
 * that high_memory defines the upper bound on direct map memory, then end
 * of ZONE_NORMAL.  Under CONFIG_DISCONTIG this means that max_low_pfn and
 * highstart_pfn must be the same; there must be no gap between ZONE_NORMAL
 * and ZONE_HIGHMEM.
 */
void *high_memory;
EXPORT_SYMBOL(high_memory);

/*
 * Randomize the address space (stacks, mmaps, brk, etc.).
 *
 * ( When CONFIG_COMPAT_BRK=y we exclude brk from randomization,
 *   as ancient (libc5 based) binaries can segfault. )
 */
int randomize_va_space __read_mostly =
#ifdef CONFIG_COMPAT_BRK
					1;
#else
					2;
#endif

#ifndef arch_faults_on_old_pte
static inline bool arch_faults_on_old_pte(void)
{
	/*
	 * Those arches which don't have hw access flag feature need to
	 * implement their own helper. By default, "true" means pagefault
	 * will be hit on old pte.
	 */
	return true;
}
#endif

#ifndef arch_wants_old_prefaulted_pte
static inline bool arch_wants_old_prefaulted_pte(void)
{
	/*
	 * Transitioning a PTE from 'old' to 'young' can be expensive on
	 * some architectures, even if it's performed in hardware. By
	 * default, "false" means prefaulted entries will be 'young'.
	 */
	return false;
}
#endif

static int __init disable_randmaps(char *s)
{
	randomize_va_space = 0;
	return 1;
}
__setup("norandmaps", disable_randmaps);

unsigned long zero_pfn __read_mostly;
EXPORT_SYMBOL(zero_pfn);

unsigned long highest_memmap_pfn __read_mostly;

/*
 * CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
 */
static int __init init_zero_pfn(void)
{
	zero_pfn = page_to_pfn(ZERO_PAGE(0));
	return 0;
}
early_initcall(init_zero_pfn);

void mm_trace_rss_stat(struct mm_struct *mm, int member, long count)
{
	trace_rss_stat(mm, member, count);
}

#if defined(SPLIT_RSS_COUNTING)

void sync_mm_rss(struct mm_struct *mm)
{
	int i;

	for (i = 0; i < NR_MM_COUNTERS; i++) {
		if (current->rss_stat.count[i]) {
			add_mm_counter(mm, i, current->rss_stat.count[i]);
			current->rss_stat.count[i] = 0;
		}
	}
	current->rss_stat.events = 0;
}

static void add_mm_counter_fast(struct mm_struct *mm, int member, int val)
{
	struct task_struct *task = current;

	if (likely(task->mm == mm))
		task->rss_stat.count[member] += val;
	else
		add_mm_counter(mm, member, val);
}
#define inc_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, 1)
#define dec_mm_counter_fast(mm, member) add_mm_counter_fast(mm, member, -1)

/* sync counter once per 64 page faults */
#define TASK_RSS_EVENTS_THRESH	(64)
static void check_sync_rss_stat(struct task_struct *task)
{
	if (unlikely(task != current))
		return;
	if (unlikely(task->rss_stat.events++ > TASK_RSS_EVENTS_THRESH))
		sync_mm_rss(task->mm);
}
#else /* SPLIT_RSS_COUNTING */

#define inc_mm_counter_fast(mm, member) inc_mm_counter(mm, member)
#define dec_mm_counter_fast(mm, member) dec_mm_counter(mm, member)

static void check_sync_rss_stat(struct task_struct *task)
{
}

#endif /* SPLIT_RSS_COUNTING */

/*
 * Note: this doesn't free the actual pages themselves. That
 * has been handled earlier when unmapping all the memory regions.
 */
static void free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
			   unsigned long addr)
{
	pgtable_t token = pmd_pgtable(*pmd);
	pmd_clear(pmd);
	pte_free_tlb(tlb, token, addr);
	mm_dec_nr_ptes(tlb->mm);
}

static inline void free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
				unsigned long addr, unsigned long end,
				unsigned long floor, unsigned long ceiling)
{
	pmd_t *pmd;
	unsigned long next;
	unsigned long start;

	start = addr;
	pmd = pmd_offset(pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (pmd_none_or_clear_bad(pmd))
			continue;
		free_pte_range(tlb, pmd, addr);
	} while (pmd++, addr = next, addr != end);

	start &= PUD_MASK;
	if (start < floor)
		return;
	if (ceiling) {
		ceiling &= PUD_MASK;
		if (!ceiling)
			return;
	}
	if (end - 1 > ceiling - 1)
		return;

	pmd = pmd_offset(pud, start);
	pud_clear(pud);
	pmd_free_tlb(tlb, pmd, start);
	mm_dec_nr_pmds(tlb->mm);
}

static inline void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d,
				unsigned long addr, unsigned long end,
				unsigned long floor, unsigned long ceiling)
{
	pud_t *pud;
	unsigned long next;
	unsigned long start;

	start = addr;
	pud = pud_offset(p4d, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_none_or_clear_bad(pud))
			continue;
		free_pmd_range(tlb, pud, addr, next, floor, ceiling);
	} while (pud++, addr = next, addr != end);

	start &= P4D_MASK;
	if (start < floor)
		return;
	if (ceiling) {
		ceiling &= P4D_MASK;
		if (!ceiling)
			return;
	}
	if (end - 1 > ceiling - 1)
		return;

	pud = pud_offset(p4d, start);
	p4d_clear(p4d);
	pud_free_tlb(tlb, pud, start);
	mm_dec_nr_puds(tlb->mm);
}

static inline void free_p4d_range(struct mmu_gather *tlb, pgd_t *pgd,
				unsigned long addr, unsigned long end,
				unsigned long floor, unsigned long ceiling)
{
	p4d_t *p4d;
	unsigned long next;
	unsigned long start;

	start = addr;
	p4d = p4d_offset(pgd, addr);
	do {
		next = p4d_addr_end(addr, end);
		if (p4d_none_or_clear_bad(p4d))
			continue;
		free_pud_range(tlb, p4d, addr, next, floor, ceiling);
	} while (p4d++, addr = next, addr != end);

	start &= PGDIR_MASK;
	if (start < floor)
		return;
	if (ceiling) {
		ceiling &= PGDIR_MASK;
		if (!ceiling)
			return;
	}
	if (end - 1 > ceiling - 1)
		return;

	p4d = p4d_offset(pgd, start);
	pgd_clear(pgd);
	p4d_free_tlb(tlb, p4d, start);
}

/*
 * This function frees user-level page tables of a process.
 */
void free_pgd_range(struct mmu_gather *tlb,
			unsigned long addr, unsigned long end,
			unsigned long floor, unsigned long ceiling)
{
	pgd_t *pgd;
	unsigned long next;

	/*
	 * The next few lines have given us lots of grief...
	 *
	 * Why are we testing PMD* at this top level?  Because often
	 * there will be no work to do at all, and we'd prefer not to
	 * go all the way down to the bottom just to discover that.
	 *
	 * Why all these "- 1"s?  Because 0 represents both the bottom
	 * of the address space and the top of it (using -1 for the
	 * top wouldn't help much: the masks would do the wrong thing).
	 * The rule is that addr 0 and floor 0 refer to the bottom of
	 * the address space, but end 0 and ceiling 0 refer to the top
	 * Comparisons need to use "end - 1" and "ceiling - 1" (though
	 * that end 0 case should be mythical).
	 *
	 * Wherever addr is brought up or ceiling brought down, we must
	 * be careful to reject "the opposite 0" before it confuses the
	 * subsequent tests.  But what about where end is brought down
	 * by PMD_SIZE below? no, end can't go down to 0 there.
	 *
	 * Whereas we round start (addr) and ceiling down, by different
	 * masks at different levels, in order to test whether a table
	 * now has no other vmas using it, so can be freed, we don't
	 * bother to round floor or end up - the tests don't need that.
	 */

	addr &= PMD_MASK;
	if (addr < floor) {
		addr += PMD_SIZE;
		if (!addr)
			return;
	}
	if (ceiling) {
		ceiling &= PMD_MASK;
		if (!ceiling)
			return;
	}
	if (end - 1 > ceiling - 1)
		end -= PMD_SIZE;
	if (addr > end - 1)
		return;
	/*
	 * We add page table cache pages with PAGE_SIZE,
	 * (see pte_free_tlb()), flush the tlb if we need
	 */
	tlb_change_page_size(tlb, PAGE_SIZE);
	pgd = pgd_offset(tlb->mm, addr);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none_or_clear_bad(pgd))
			continue;
		free_p4d_range(tlb, pgd, addr, next, floor, ceiling);
	} while (pgd++, addr = next, addr != end);
}

void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
		unsigned long floor, unsigned long ceiling)
{
	while (vma) {
		struct vm_area_struct *next = vma->vm_next;
		unsigned long addr = vma->vm_start;

		/*
		 * Hide vma from rmap and truncate_pagecache before freeing
		 * pgtables
		 */
		unlink_anon_vmas(vma);
		unlink_file_vma(vma);

		if (is_vm_hugetlb_page(vma)) {
			hugetlb_free_pgd_range(tlb, addr, vma->vm_end,
				floor, next ? next->vm_start : ceiling);
		} else {
			/*
			 * Optimization: gather nearby vmas into one call down
			 */
			while (next && next->vm_start <= vma->vm_end + PMD_SIZE
			       && !is_vm_hugetlb_page(next)) {
				vma = next;
				next = vma->vm_next;
				unlink_anon_vmas(vma);
				unlink_file_vma(vma);
			}
			free_pgd_range(tlb, addr, vma->vm_end,
				floor, next ? next->vm_start : ceiling);
		}
		vma = next;
	}
}

void pmd_install(struct mm_struct *mm, pmd_t *pmd, pgtable_t *pte)
{
	spinlock_t *ptl = pmd_lock(mm, pmd);

	if (likely(pmd_none(*pmd))) {	/* Has another populated it ? */
		mm_inc_nr_ptes(mm);
		/*
		 * Ensure all pte setup (eg. pte page lock and page clearing) are
		 * visible before the pte is made visible to other CPUs by being
		 * put into page tables.
		 *
		 * The other side of the story is the pointer chasing in the page
		 * table walking code (when walking the page table without locking;
		 * ie. most of the time). Fortunately, these data accesses consist
		 * of a chain of data-dependent loads, meaning most CPUs (alpha
		 * being the notable exception) will already guarantee loads are
		 * seen in-order. See the alpha page table accessors for the
		 * smp_rmb() barriers in page table walking code.
		 */
		smp_wmb(); /* Could be smp_wmb__xxx(before|after)_spin_lock */
		pmd_populate(mm, pmd, *pte);
		*pte = NULL;
	}
	spin_unlock(ptl);
}

int __pte_alloc(struct mm_struct *mm, pmd_t *pmd)
{
	pgtable_t new = pte_alloc_one(mm);
	if (!new)
		return -ENOMEM;

	pmd_install(mm, pmd, &new);
	if (new)
		pte_free(mm, new);
	return 0;
}

int __pte_alloc_kernel(pmd_t *pmd)
{
	pte_t *new = pte_alloc_one_kernel(&init_mm);
	if (!new)
		return -ENOMEM;

	spin_lock(&init_mm.page_table_lock);
	if (likely(pmd_none(*pmd))) {	/* Has another populated it ? */
		smp_wmb(); /* See comment in pmd_install() */
		pmd_populate_kernel(&init_mm, pmd, new);
		new = NULL;
	}
	spin_unlock(&init_mm.page_table_lock);
	if (new)
		pte_free_kernel(&init_mm, new);
	return 0;
}

static inline void init_rss_vec(int *rss)
{
	memset(rss, 0, sizeof(int) * NR_MM_COUNTERS);
}

static inline void add_mm_rss_vec(struct mm_struct *mm, int *rss)
{
	int i;

	if (current->mm == mm)
		sync_mm_rss(mm);
	for (i = 0; i < NR_MM_COUNTERS; i++)
		if (rss[i])
			add_mm_counter(mm, i, rss[i]);
}

/*
 * This function is called to print an error when a bad pte
 * is found. For example, we might have a PFN-mapped pte in
 * a region that doesn't allow it.
 *
 * The calling function must still handle the error.
 */
static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
			  pte_t pte, struct page *page)
{
	pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
	p4d_t *p4d = p4d_offset(pgd, addr);
	pud_t *pud = pud_offset(p4d, addr);
	pmd_t *pmd = pmd_offset(pud, addr);
	struct address_space *mapping;
	pgoff_t index;
	static unsigned long resume;
	static unsigned long nr_shown;
	static unsigned long nr_unshown;

	/*
	 * Allow a burst of 60 reports, then keep quiet for that minute;
	 * or allow a steady drip of one report per second.
	 */
	if (nr_shown == 60) {
		if (time_before(jiffies, resume)) {
			nr_unshown++;
			return;
		}
		if (nr_unshown) {
			pr_alert("BUG: Bad page map: %lu messages suppressed\n",
				 nr_unshown);
			nr_unshown = 0;
		}
		nr_shown = 0;
	}
	if (nr_shown++ == 0)
		resume = jiffies + 60 * HZ;

	mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
	index = linear_page_index(vma, addr);

	pr_alert("BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
		 current->comm,
		 (long long)pte_val(pte), (long long)pmd_val(*pmd));
	if (page)
		dump_page(page, "bad pte");
	pr_alert("addr:%px vm_flags:%08lx anon_vma:%px mapping:%px index:%lx\n",
		 (void *)addr, vma->vm_flags, vma->anon_vma, mapping, index);
	pr_alert("file:%pD fault:%ps mmap:%ps read_folio:%ps\n",
		 vma->vm_file,
		 vma->vm_ops ? vma->vm_ops->fault : NULL,
		 vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
		 mapping ? mapping->a_ops->read_folio : NULL);
	dump_stack();
	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
}

/*
 * vm_normal_page -- This function gets the "struct page" associated with a pte.
 *
 * "Special" mappings do not wish to be associated with a "struct page" (either
 * it doesn't exist, or it exists but they don't want to touch it). In this
 * case, NULL is returned here. "Normal" mappings do have a struct page.
 *
 * There are 2 broad cases. Firstly, an architecture may define a pte_special()
 * pte bit, in which case this function is trivial. Secondly, an architecture
 * may not have a spare pte bit, which requires a more complicated scheme,
 * described below.
 *
 * A raw VM_PFNMAP mapping (ie. one that is not COWed) is always considered a
 * special mapping (even if there are underlying and valid "struct pages").
 * COWed pages of a VM_PFNMAP are always normal.
 *
 * The way we recognize COWed pages within VM_PFNMAP mappings is through the
 * rules set up by "remap_pfn_range()": the vma will have the VM_PFNMAP bit
 * set, and the vm_pgoff will point to the first PFN mapped: thus every special
 * mapping will always honor the rule
 *
 *	pfn_of_page == vma->vm_pgoff + ((addr - vma->vm_start) >> PAGE_SHIFT)
 *
 * And for normal mappings this is false.
 *
 * This restricts such mappings to be a linear translation from virtual address
 * to pfn. To get around this restriction, we allow arbitrary mappings so long
 * as the vma is not a COW mapping; in that case, we know that all ptes are
 * special (because none can have been COWed).
 *
 *
 * In order to support COW of arbitrary special mappings, we have VM_MIXEDMAP.
 *
 * VM_MIXEDMAP mappings can likewise contain memory with or without "struct
 * page" backing, however the difference is that _all_ pages with a struct
 * page (that is, those where pfn_valid is true) are refcounted and considered
 * normal pages by the VM. The disadvantage is that pages are refcounted
 * (which can be slower and simply not an option for some PFNMAP users). The
 * advantage is that we don't have to follow the strict linearity rule of
 * PFNMAP mappings in order to support COWable mappings.
 *
 */
struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
			    pte_t pte)
{
	unsigned long pfn = pte_pfn(pte);

	if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
		if (likely(!pte_special(pte)))
			goto check_pfn;
		if (vma->vm_ops && vma->vm_ops->find_special_page)
			return vma->vm_ops->find_special_page(vma, addr);
		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
			return NULL;
		if (is_zero_pfn(pfn))
			return NULL;
		if (pte_devmap(pte))
			return NULL;

		print_bad_pte(vma, addr, pte, NULL);
		return NULL;
	}

	/* !CONFIG_ARCH_HAS_PTE_SPECIAL case follows: */

	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
		if (vma->vm_flags & VM_MIXEDMAP) {
			if (!pfn_valid(pfn))
				return NULL;
			goto out;
		} else {
			unsigned long off;
			off = (addr - vma->vm_start) >> PAGE_SHIFT;
			if (pfn == vma->vm_pgoff + off)
				return NULL;
			if (!is_cow_mapping(vma->vm_flags))
				return NULL;
		}
	}

	if (is_zero_pfn(pfn))
		return NULL;

check_pfn:
	if (unlikely(pfn > highest_memmap_pfn)) {
		print_bad_pte(vma, addr, pte, NULL);
		return NULL;
	}

	/*
	 * NOTE! We still have PageReserved() pages in the page tables.
	 * eg. VDSO mappings can cause them to exist.
	 */
out:
	return pfn_to_page(pfn);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
				pmd_t pmd)
{
	unsigned long pfn = pmd_pfn(pmd);

	/*
	 * There is no pmd_special() but there may be special pmds, e.g.
	 * in a direct-access (dax) mapping, so let's just replicate the
	 * !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here.
	 */
	if (unlikely(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP))) {
		if (vma->vm_flags & VM_MIXEDMAP) {
			if (!pfn_valid(pfn))
				return NULL;
			goto out;
		} else {
			unsigned long off;
			off = (addr - vma->vm_start) >> PAGE_SHIFT;
			if (pfn == vma->vm_pgoff + off)
				return NULL;
			if (!is_cow_mapping(vma->vm_flags))
				return NULL;
		}
	}

	if (pmd_devmap(pmd))
		return NULL;
	if (is_huge_zero_pmd(pmd))
		return NULL;
	if (unlikely(pfn > highest_memmap_pfn))
		return NULL;

	/*
	 * NOTE! We still have PageReserved() pages in the page tables.
	 * eg. VDSO mappings can cause them to exist.
	 */
out:
	return pfn_to_page(pfn);
}
#endif

static void restore_exclusive_pte(struct vm_area_struct *vma,
				  struct page *page, unsigned long address,
				  pte_t *ptep)
{
	pte_t pte;
	swp_entry_t entry;

	pte = pte_mkold(mk_pte(page, READ_ONCE(vma->vm_page_prot)));
	if (pte_swp_soft_dirty(*ptep))
		pte = pte_mksoft_dirty(pte);

	entry = pte_to_swp_entry(*ptep);
	if (pte_swp_uffd_wp(*ptep))
		pte = pte_mkuffd_wp(pte);
	else if (is_writable_device_exclusive_entry(entry))
		pte = maybe_mkwrite(pte_mkdirty(pte), vma);

	VM_BUG_ON(pte_write(pte) && !(PageAnon(page) && PageAnonExclusive(page)));

	/*
	 * No need to take a page reference as one was already
	 * created when the swap entry was made.
	 */
	if (PageAnon(page))
		page_add_anon_rmap(page, vma, address, RMAP_NONE);
	else
		/*
		 * Currently device exclusive access only supports anonymous
		 * memory so the entry shouldn't point to a filebacked page.
		 */
		WARN_ON_ONCE(!PageAnon(page));

	set_pte_at(vma->vm_mm, address, ptep, pte);

	/*
	 * No need to invalidate - it was non-present before. However
	 * secondary CPUs may have mappings that need invalidating.
	 */
	update_mmu_cache(vma, address, ptep);
}

/*
 * Tries to restore an exclusive pte if the page lock can be acquired without
 * sleeping.
 */
static int
try_restore_exclusive_pte(pte_t *src_pte, struct vm_area_struct *vma,
			unsigned long addr)
{
	swp_entry_t entry = pte_to_swp_entry(*src_pte);
	struct page *page = pfn_swap_entry_to_page(entry);

	if (trylock_page(page)) {
		restore_exclusive_pte(vma, page, addr, src_pte);
		unlock_page(page);
		return 0;
	}

	return -EBUSY;
}

/*
 * copy one vm_area from one task to the other. Assumes the page tables
 * already present in the new task to be cleared in the whole range
 * covered by this vma.
 */

static unsigned long
copy_nonpresent_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
		pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *dst_vma,
		struct vm_area_struct *src_vma, unsigned long addr, int *rss)
{
	unsigned long vm_flags = dst_vma->vm_flags;
	pte_t pte = *src_pte;
	struct page *page;
	swp_entry_t entry = pte_to_swp_entry(pte);

	if (likely(!non_swap_entry(entry))) {
		if (swap_duplicate(entry) < 0)
			return -EIO;

		/* make sure dst_mm is on swapoff's mmlist. */
		if (unlikely(list_empty(&dst_mm->mmlist))) {
			spin_lock(&mmlist_lock);
			if (list_empty(&dst_mm->mmlist))
				list_add(&dst_mm->mmlist,
						&src_mm->mmlist);
			spin_unlock(&mmlist_lock);
		}
		/* Mark the swap entry as shared. */
		if (pte_swp_exclusive(*src_pte)) {
			pte = pte_swp_clear_exclusive(*src_pte);
			set_pte_at(src_mm, addr, src_pte, pte);
		}
		rss[MM_SWAPENTS]++;
	} else if (is_migration_entry(entry)) {
		page = pfn_swap_entry_to_page(entry);

		rss[mm_counter(page)]++;

		if (!is_readable_migration_entry(entry) &&
				is_cow_mapping(vm_flags)) {
			/*
			 * COW mappings require pages in both parent and child
			 * to be set to read. A previously exclusive entry is
			 * now shared.
			 */
			entry = make_readable_migration_entry(
							swp_offset(entry));
			pte = swp_entry_to_pte(entry);
			if (pte_swp_soft_dirty(*src_pte))
				pte = pte_swp_mksoft_dirty(pte);
			if (pte_swp_uffd_wp(*src_pte))
				pte = pte_swp_mkuffd_wp(pte);
			set_pte_at(src_mm, addr, src_pte, pte);
		}
	} else if (is_device_private_entry(entry)) {
		page = pfn_swap_entry_to_page(entry);

		/*
		 * Update rss count even for unaddressable pages, as
		 * they should treated just like normal pages in this
		 * respect.
		 *
		 * We will likely want to have some new rss counters
		 * for unaddressable pages, at some point. But for now
		 * keep things as they are.
		 */
		get_page(page);
		rss[mm_counter(page)]++;
		/* Cannot fail as these pages cannot get pinned. */
		BUG_ON(page_try_dup_anon_rmap(page, false, src_vma));

		/*
		 * We do not preserve soft-dirty information, because so
		 * far, checkpoint/restore is the only feature that
		 * requires that. And checkpoint/restore does not work
		 * when a device driver is involved (you cannot easily
		 * save and restore device driver state).
		 */
		if (is_writable_device_private_entry(entry) &&
		    is_cow_mapping(vm_flags)) {
			entry = make_readable_device_private_entry(
							swp_offset(entry));
			pte = swp_entry_to_pte(entry);
			if (pte_swp_uffd_wp(*src_pte))
				pte = pte_swp_mkuffd_wp(pte);
			set_pte_at(src_mm, addr, src_pte, pte);
		}
	} else if (is_device_exclusive_entry(entry)) {
		/*
		 * Make device exclusive entries present by restoring the
		 * original entry then copying as for a present pte. Device
		 * exclusive entries currently only support private writable
		 * (ie. COW) mappings.
		 */
		VM_BUG_ON(!is_cow_mapping(src_vma->vm_flags));
		if (try_restore_exclusive_pte(src_pte, src_vma, addr))
			return -EBUSY;
		return -ENOENT;
	} else if (is_pte_marker_entry(entry)) {
		/*
		 * We're copying the pgtable should only because dst_vma has
		 * uffd-wp enabled, do sanity check.
		 */
		WARN_ON_ONCE(!userfaultfd_wp(dst_vma));
		set_pte_at(dst_mm, addr, dst_pte, pte);
		return 0;
	}
	if (!userfaultfd_wp(dst_vma))
		pte = pte_swp_clear_uffd_wp(pte);
	set_pte_at(dst_mm, addr, dst_pte, pte);
	return 0;
}

/*
 * Copy a present and normal page.
 *
 * NOTE! The usual case is that this isn't required;
 * instead, the caller can just increase the page refcount
 * and re-use the pte the traditional way.
 *
 * And if we need a pre-allocated page but don't yet have
 * one, return a negative error to let the preallocation
 * code know so that it can do so outside the page table
 * lock.
 */
static inline int
copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
		  pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss,
		  struct page **prealloc, struct page *page)
{
	struct page *new_page;
	pte_t pte;

	new_page = *prealloc;
	if (!new_page)
		return -EAGAIN;

	/*
	 * We have a prealloc page, all good!  Take it
	 * over and copy the page & arm it.
	 */
	*prealloc = NULL;
	copy_user_highpage(new_page, page, addr, src_vma);
	__SetPageUptodate(new_page);
	page_add_new_anon_rmap(new_page, dst_vma, addr);
	lru_cache_add_inactive_or_unevictable(new_page, dst_vma);
	rss[mm_counter(new_page)]++;

	/* All done, just insert the new page copy in the child */
	pte = mk_pte(new_page, dst_vma->vm_page_prot);
	pte = maybe_mkwrite(pte_mkdirty(pte), dst_vma);
	if (userfaultfd_pte_wp(dst_vma, *src_pte))
		/* Uffd-wp needs to be delivered to dest pte as well */
		pte = pte_wrprotect(pte_mkuffd_wp(pte));
	set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte);
	return 0;
}

/*
 * Copy one pte.  Returns 0 if succeeded, or -EAGAIN if one preallocated page
 * is required to copy this pte.
 */
static inline int
copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
		 pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss,
		 struct page **prealloc)
{
	struct mm_struct *src_mm = src_vma->vm_mm;
	unsigned long vm_flags = src_vma->vm_flags;
	pte_t pte = *src_pte;
	struct page *page;

	page = vm_normal_page(src_vma, addr, pte);
	if (page && PageAnon(page)) {
		/*
		 * If this page may have been pinned by the parent process,
		 * copy the page immediately for the child so that we'll always
		 * guarantee the pinned page won't be randomly replaced in the
		 * future.
		 */
		get_page(page);
		if (unlikely(page_try_dup_anon_rmap(page, false, src_vma))) {
			/* Page maybe pinned, we have to copy. */
			put_page(page);
			return copy_present_page(dst_vma, src_vma, dst_pte, src_pte,
						 addr, rss, prealloc, page);
		}
		rss[mm_counter(page)]++;
	} else if (page) {
		get_page(page);
		page_dup_file_rmap(page, false);
		rss[mm_counter(page)]++;
	}

	/*
	 * If it's a COW mapping, write protect it both
	 * in the parent and the child
	 */
	if (is_cow_mapping(vm_flags) && pte_write(pte)) {
		ptep_set_wrprotect(src_mm, addr, src_pte);
		pte = pte_wrprotect(pte);
	}
	VM_BUG_ON(page && PageAnon(page) && PageAnonExclusive(page));

	/*
	 * If it's a shared mapping, mark it clean in
	 * the child
	 */
	if (vm_flags & VM_SHARED)
		pte = pte_mkclean(pte);
	pte = pte_mkold(pte);

	if (!userfaultfd_wp(dst_vma))
		pte = pte_clear_uffd_wp(pte);

	set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte);
	return 0;
}

static inline struct page *
page_copy_prealloc(struct mm_struct *src_mm, struct vm_area_struct *vma,
		   unsigned long addr)
{
	struct page *new_page;

	new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, addr);
	if (!new_page)
		return NULL;

	if (mem_cgroup_charge(page_folio(new_page), src_mm, GFP_KERNEL)) {
		put_page(new_page);
		return NULL;
	}
	cgroup_throttle_swaprate(new_page, GFP_KERNEL);

	return new_page;
}

static int
copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
	       pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
	       unsigned long end)
{
	struct mm_struct *dst_mm = dst_vma->vm_mm;
	struct mm_struct *src_mm = src_vma->vm_mm;
	pte_t *orig_src_pte, *orig_dst_pte;
	pte_t *src_pte, *dst_pte;
	spinlock_t *src_ptl, *dst_ptl;
	int progress, ret = 0;
	int rss[NR_MM_COUNTERS];
	swp_entry_t entry = (swp_entry_t){0};
	struct page *prealloc = NULL;

again:
	progress = 0;
	init_rss_vec(rss);

	dst_pte = pte_alloc_map_lock(dst_mm, dst_pmd, addr, &dst_ptl);
	if (!dst_pte) {
		ret = -ENOMEM;
		goto out;
	}
	src_pte = pte_offset_map(src_pmd, addr);
	src_ptl = pte_lockptr(src_mm, src_pmd);
	spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);
	orig_src_pte = src_pte;
	orig_dst_pte = dst_pte;
	arch_enter_lazy_mmu_mode();

	do {
		/*
		 * We are holding two locks at this point - either of them
		 * could generate latencies in another task on another CPU.
		 */
		if (progress >= 32) {
			progress = 0;
			if (need_resched() ||
			    spin_needbreak(src_ptl) || spin_needbreak(dst_ptl))
				break;
		}
		if (pte_none(*src_pte)) {
			progress++;
			continue;
		}
		if (unlikely(!pte_present(*src_pte))) {
			ret = copy_nonpresent_pte(dst_mm, src_mm,
						  dst_pte, src_pte,
						  dst_vma, src_vma,
						  addr, rss);
			if (ret == -EIO) {
				entry = pte_to_swp_entry(*src_pte);
				break;
			} else if (ret == -EBUSY) {
				break;
			} else if (!ret) {
				progress += 8;
				continue;
			}

			/*
			 * Device exclusive entry restored, continue by copying
			 * the now present pte.
			 */
			WARN_ON_ONCE(ret != -ENOENT);
		}
		/* copy_present_pte() will clear `*prealloc' if consumed */
		ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte,
				       addr, rss, &prealloc);
		/*
		 * If we need a pre-allocated page for this pte, drop the
		 * locks, allocate, and try again.
		 */
		if (unlikely(ret == -EAGAIN))
			break;
		if (unlikely(prealloc)) {
			/*
			 * pre-alloc page cannot be reused by next time so as
			 * to strictly follow mempolicy (e.g., alloc_page_vma()
			 * will allocate page according to address).  This
			 * could only happen if one pinned pte changed.
			 */
			put_page(prealloc);
			prealloc = NULL;
		}
		progress += 8;
	} while (dst_pte++, src_pte++, addr += PAGE_SIZE, addr != end);

	arch_leave_lazy_mmu_mode();
	spin_unlock(src_ptl);
	pte_unmap(orig_src_pte);
	add_mm_rss_vec(dst_mm, rss);
	pte_unmap_unlock(orig_dst_pte, dst_ptl);
	cond_resched();

	if (ret == -EIO) {
		VM_WARN_ON_ONCE(!entry.val);
		if (add_swap_count_continuation(entry, GFP_KERNEL) < 0) {
			ret = -ENOMEM;
			goto out;
		}
		entry.val = 0;
	} else if (ret == -EBUSY) {
		goto out;
	} else if (ret ==  -EAGAIN) {
		prealloc = page_copy_prealloc(src_mm, src_vma, addr);
		if (!prealloc)
			return -ENOMEM;
	} else if (ret) {
		VM_WARN_ON_ONCE(1);
	}

	/* We've captured and resolved the error. Reset, try again. */
	ret = 0;

	if (addr != end)
		goto again;
out:
	if (unlikely(prealloc))
		put_page(prealloc);
	return ret;
}

static inline int
copy_pmd_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
	       pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
	       unsigned long end)
{
	struct mm_struct *dst_mm = dst_vma->vm_mm;
	struct mm_struct *src_mm = src_vma->vm_mm;
	pmd_t *src_pmd, *dst_pmd;
	unsigned long next;

	dst_pmd = pmd_alloc(dst_mm, dst_pud, addr);
	if (!dst_pmd)
		return -ENOMEM;
	src_pmd = pmd_offset(src_pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (is_swap_pmd(*src_pmd) || pmd_trans_huge(*src_pmd)
			|| pmd_devmap(*src_pmd)) {
			int err;
			VM_BUG_ON_VMA(next-addr != HPAGE_PMD_SIZE, src_vma);
			err = copy_huge_pmd(dst_mm, src_mm, dst_pmd, src_pmd,
					    addr, dst_vma, src_vma);
			if (err == -ENOMEM)
				return -ENOMEM;
			if (!err)
				continue;
			/* fall through */
		}
		if (pmd_none_or_clear_bad(src_pmd))
			continue;
		if (copy_pte_range(dst_vma, src_vma, dst_pmd, src_pmd,
				   addr, next))
			return -ENOMEM;
	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
	return 0;
}

static inline int
copy_pud_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
	       p4d_t *dst_p4d, p4d_t *src_p4d, unsigned long addr,
	       unsigned long end)
{
	struct mm_struct *dst_mm = dst_vma->vm_mm;
	struct mm_struct *src_mm = src_vma->vm_mm;
	pud_t *src_pud, *dst_pud;
	unsigned long next;

	dst_pud = pud_alloc(dst_mm, dst_p4d, addr);
	if (!dst_pud)
		return -ENOMEM;
	src_pud = pud_offset(src_p4d, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_trans_huge(*src_pud) || pud_devmap(*src_pud)) {
			int err;

			VM_BUG_ON_VMA(next-addr != HPAGE_PUD_SIZE, src_vma);
			err = copy_huge_pud(dst_mm, src_mm,
					    dst_pud, src_pud, addr, src_vma);
			if (err == -ENOMEM)
				return -ENOMEM;
			if (!err)
				continue;
			/* fall through */
		}
		if (pud_none_or_clear_bad(src_pud))
			continue;
		if (copy_pmd_range(dst_vma, src_vma, dst_pud, src_pud,
				   addr, next))
			return -ENOMEM;
	} while (dst_pud++, src_pud++, addr = next, addr != end);
	return 0;
}

static inline int
copy_p4d_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
	       pgd_t *dst_pgd, pgd_t *src_pgd, unsigned long addr,
	       unsigned long end)
{
	struct mm_struct *dst_mm = dst_vma->vm_mm;
	p4d_t *src_p4d, *dst_p4d;
	unsigned long next;

	dst_p4d = p4d_alloc(dst_mm, dst_pgd, addr);
	if (!dst_p4d)
		return -ENOMEM;
	src_p4d = p4d_offset(src_pgd, addr);
	do {
		next = p4d_addr_end(addr, end);
		if (p4d_none_or_clear_bad(src_p4d))
			continue;
		if (copy_pud_range(dst_vma, src_vma, dst_p4d, src_p4d,
				   addr, next))
			return -ENOMEM;
	} while (dst_p4d++, src_p4d++, addr = next, addr != end);
	return 0;
}

/*
 * Return true if the vma needs to copy the pgtable during this fork().  Return
 * false when we can speed up fork() by allowing lazy page faults later until
 * when the child accesses the memory range.
 */
static bool
vma_needs_copy(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
{
	/*
	 * Always copy pgtables when dst_vma has uffd-wp enabled even if it's
	 * file-backed (e.g. shmem). Because when uffd-wp is enabled, pgtable
	 * contains uffd-wp protection information, that's something we can't
	 * retrieve from page cache, and skip copying will lose those info.
	 */
	if (userfaultfd_wp(dst_vma))
		return true;

	if (src_vma->vm_flags & (VM_HUGETLB | VM_PFNMAP | VM_MIXEDMAP))
		return true;

	if (src_vma->anon_vma)
		return true;

	/*
	 * Don't copy ptes where a page fault will fill them correctly.  Fork
	 * becomes much lighter when there are big shared or private readonly
	 * mappings. The tradeoff is that copy_page_range is more efficient
	 * than faulting.
	 */
	return false;
}

int
copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
{
	pgd_t *src_pgd, *dst_pgd;
	unsigned long next;
	unsigned long addr = src_vma->vm_start;
	unsigned long end = src_vma->vm_end;
	struct mm_struct *dst_mm = dst_vma->vm_mm;
	struct mm_struct *src_mm = src_vma->vm_mm;
	struct mmu_notifier_range range;
	bool is_cow;
	int ret;

	if (!vma_needs_copy(dst_vma, src_vma))
		return 0;

	if (is_vm_hugetlb_page(src_vma))
		return copy_hugetlb_page_range(dst_mm, src_mm, dst_vma, src_vma);

	if (unlikely(src_vma->vm_flags & VM_PFNMAP)) {
		/*
		 * We do not free on error cases below as remove_vma
		 * gets called on error from higher level routine
		 */
		ret = track_pfn_copy(src_vma);
		if (ret)
			return ret;
	}

	/*
	 * We need to invalidate the secondary MMU mappings only when
	 * there could be a permission downgrade on the ptes of the
	 * parent mm. And a permission downgrade will only happen if
	 * is_cow_mapping() returns true.
	 */
	is_cow = is_cow_mapping(src_vma->vm_flags);

	if (is_cow) {
		mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE,
					0, src_vma, src_mm, addr, end);
		mmu_notifier_invalidate_range_start(&range);
		/*
		 * Disabling preemption is not needed for the write side, as
		 * the read side doesn't spin, but goes to the mmap_lock.
		 *
		 * Use the raw variant of the seqcount_t write API to avoid
		 * lockdep complaining about preemptibility.
		 */
		mmap_assert_write_locked(src_mm);
		raw_write_seqcount_begin(&src_mm->write_protect_seq);
	}

	ret = 0;
	dst_pgd = pgd_offset(dst_mm, addr);
	src_pgd = pgd_offset(src_mm, addr);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none_or_clear_bad(src_pgd))
			continue;
		if (unlikely(copy_p4d_range(dst_vma, src_vma, dst_pgd, src_pgd,
					    addr, next))) {
			ret = -ENOMEM;
			break;
		}
	} while (dst_pgd++, src_pgd++, addr = next, addr != end);

	if (is_cow) {
		raw_write_seqcount_end(&src_mm->write_protect_seq);
		mmu_notifier_invalidate_range_end(&range);
	}
	return ret;
}

/*
 * Parameter block passed down to zap_pte_range in exceptional cases.
 */
struct zap_details {
	struct folio *single_folio;	/* Locked folio to be unmapped */
	bool even_cows;			/* Zap COWed private pages too? */
	zap_flags_t zap_flags;		/* Extra flags for zapping */
};

/* Whether we should zap all COWed (private) pages too */
static inline bool should_zap_cows(struct zap_details *details)
{
	/* By default, zap all pages */
	if (!details)
		return true;

	/* Or, we zap COWed pages only if the caller wants to */
	return details->even_cows;
}

/* Decides whether we should zap this page with the page pointer specified */
static inline bool should_zap_page(struct zap_details *details, struct page *page)
{
	/* If we can make a decision without *page.. */
	if (should_zap_cows(details))
		return true;

	/* E.g. the caller passes NULL for the case of a zero page */
	if (!page)
		return true;

	/* Otherwise we should only zap non-anon pages */
	return !PageAnon(page);
}

static inline bool zap_drop_file_uffd_wp(struct zap_details *details)
{
	if (!details)
		return false;

	return details->zap_flags & ZAP_FLAG_DROP_MARKER;
}

/*
 * This function makes sure that we'll replace the none pte with an uffd-wp
 * swap special pte marker when necessary. Must be with the pgtable lock held.
 */
static inline void
zap_install_uffd_wp_if_needed(struct vm_area_struct *vma,
			      unsigned long addr, pte_t *pte,
			      struct zap_details *details, pte_t pteval)
{
	if (zap_drop_file_uffd_wp(details))
		return;

	pte_install_uffd_wp_if_needed(vma, addr, pte, pteval);
}

static unsigned long zap_pte_range(struct mmu_gather *tlb,
				struct vm_area_struct *vma, pmd_t *pmd,
				unsigned long addr, unsigned long end,
				struct zap_details *details)
{
	struct mm_struct *mm = tlb->mm;
	int force_flush = 0;
	int rss[NR_MM_COUNTERS];
	spinlock_t *ptl;
	pte_t *start_pte;
	pte_t *pte;
	swp_entry_t entry;

	tlb_change_page_size(tlb, PAGE_SIZE);
again:
	init_rss_vec(rss);
	start_pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
	pte = start_pte;
	flush_tlb_batched_pending(mm);
	arch_enter_lazy_mmu_mode();
	do {
		pte_t ptent = *pte;
		struct page *page;

		if (pte_none(ptent))
			continue;

		if (need_resched())
			break;

		if (pte_present(ptent)) {
			page = vm_normal_page(vma, addr, ptent);
			if (unlikely(!should_zap_page(details, page)))
				continue;
			ptent = ptep_get_and_clear_full(mm, addr, pte,
							tlb->fullmm);
			tlb_remove_tlb_entry(tlb, pte, addr);
			zap_install_uffd_wp_if_needed(vma, addr, pte, details,
						      ptent);
			if (unlikely(!page))
				continue;

			if (!PageAnon(page)) {
				if (pte_dirty(ptent)) {
					force_flush = 1;
					set_page_dirty(page);
				}
				if (pte_young(ptent) &&
				    likely(!(vma->vm_flags & VM_SEQ_READ)))
					mark_page_accessed(page);
			}
			rss[mm_counter(page)]--;
			page_remove_rmap(page, vma, false);
			if (unlikely(page_mapcount(page) < 0))
				print_bad_pte(vma, addr, ptent, page);
			if (unlikely(__tlb_remove_page(tlb, page))) {
				force_flush = 1;
				addr += PAGE_SIZE;
				break;
			}
			continue;
		}

		entry = pte_to_swp_entry(ptent);
		if (is_device_private_entry(entry) ||
		    is_device_exclusive_entry(entry)) {
			page = pfn_swap_entry_to_page(entry);
			if (unlikely(!should_zap_page(details, page)))
				continue;
			/*
			 * Both device private/exclusive mappings should only
			 * work with anonymous page so far, so we don't need to
			 * consider uffd-wp bit when zap. For more information,
			 * see zap_install_uffd_wp_if_needed().
			 */
			WARN_ON_ONCE(!vma_is_anonymous(vma));
			rss[mm_counter(page)]--;
			if (is_device_private_entry(entry))
				page_remove_rmap(page, vma, false);
			put_page(page);
		} else if (!non_swap_entry(entry)) {
			/* Genuine swap entry, hence a private anon page */
			if (!should_zap_cows(details))
				continue;
			rss[MM_SWAPENTS]--;
			if (unlikely(!free_swap_and_cache(entry)))
				print_bad_pte(vma, addr, ptent, NULL);
		} else if (is_migration_entry(entry)) {
			page = pfn_swap_entry_to_page(entry);
			if (!should_zap_page(details, page))
				continue;
			rss[mm_counter(page)]--;
		} else if (pte_marker_entry_uffd_wp(entry)) {
			/* Only drop the uffd-wp marker if explicitly requested */
			if (!zap_drop_file_uffd_wp(details))
				continue;
		} else if (is_hwpoison_entry(entry) ||
			   is_swapin_error_entry(entry)) {
			if (!should_zap_cows(details))
				continue;
		} else {
			/* We should have covered all the swap entry types */
			WARN_ON_ONCE(1);
		}
		pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
		zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);
	} while (pte++, addr += PAGE_SIZE, addr != end);

	add_mm_rss_vec(mm, rss);
	arch_leave_lazy_mmu_mode();

	/* Do the actual TLB flush before dropping ptl */
	if (force_flush)
		tlb_flush_mmu_tlbonly(tlb);
	pte_unmap_unlock(start_pte, ptl);

	/*
	 * If we forced a TLB flush (either due to running out of
	 * batch buffers or because we needed to flush dirty TLB
	 * entries before releasing the ptl), free the batched
	 * memory too. Restart if we didn't do everything.
	 */
	if (force_flush) {
		force_flush = 0;
		tlb_flush_mmu(tlb);
	}

	if (addr != end) {
		cond_resched();
		goto again;
	}

	return addr;
}

static inline unsigned long zap_pmd_range(struct mmu_gather *tlb,
				struct vm_area_struct *vma, pud_t *pud,
				unsigned long addr, unsigned long end,
				struct zap_details *details)
{
	pmd_t *pmd;
	unsigned long next;

	pmd = pmd_offset(pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (is_swap_pmd(*pmd) || pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
			if (next - addr != HPAGE_PMD_SIZE)
				__split_huge_pmd(vma, pmd, addr, false, NULL);
			else if (zap_huge_pmd(tlb, vma, pmd, addr))
				goto next;
			/* fall through */
		} else if (details && details->single_folio &&
			   folio_test_pmd_mappable(details->single_folio) &&
			   next - addr == HPAGE_PMD_SIZE && pmd_none(*pmd)) {
			spinlock_t *ptl = pmd_lock(tlb->mm, pmd);
			/*
			 * Take and drop THP pmd lock so that we cannot return
			 * prematurely, while zap_huge_pmd() has cleared *pmd,
			 * but not yet decremented compound_mapcount().
			 */
			spin_unlock(ptl);
		}

		/*
		 * Here there can be other concurrent MADV_DONTNEED or
		 * trans huge page faults running, and if the pmd is
		 * none or trans huge it can change under us. This is
		 * because MADV_DONTNEED holds the mmap_lock in read
		 * mode.
		 */
		if (pmd_none_or_trans_huge_or_clear_bad(pmd))
			goto next;
		next = zap_pte_range(tlb, vma, pmd, addr, next, details);
next:
		cond_resched();
	} while (pmd++, addr = next, addr != end);

	return addr;
}

static inline unsigned long zap_pud_range(struct mmu_gather *tlb,
				struct vm_area_struct *vma, p4d_t *p4d,
				unsigned long addr, unsigned long end,
				struct zap_details *details)
{
	pud_t *pud;
	unsigned long next;

	pud = pud_offset(p4d, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_trans_huge(*pud) || pud_devmap(*pud)) {
			if (next - addr != HPAGE_PUD_SIZE) {
				mmap_assert_locked(tlb->mm);
				split_huge_pud(vma, pud, addr);
			} else if (zap_huge_pud(tlb, vma, pud, addr))
				goto next;
			/* fall through */
		}
		if (pud_none_or_clear_bad(pud))
			continue;
		next = zap_pmd_range(tlb, vma, pud, addr, next, details);
next:
		cond_resched();
	} while (pud++, addr = next, addr != end);

	return addr;
}

static inline unsigned long zap_p4d_range(struct mmu_gather *tlb,
				struct vm_area_struct *vma, pgd_t *pgd,
				unsigned long addr, unsigned long end,
				struct zap_details *details)
{
	p4d_t *p4d;
	unsigned long next;

	p4d = p4d_offset(pgd, addr);
	do {
		next = p4d_addr_end(addr, end);
		if (p4d_none_or_clear_bad(p4d))
			continue;
		next = zap_pud_range(tlb, vma, p4d, addr, next, details);
	} while (p4d++, addr = next, addr != end);

	return addr;
}

void unmap_page_range(struct mmu_gather *tlb,
			     struct vm_area_struct *vma,
			     unsigned long addr, unsigned long end,
			     struct zap_details *details)
{
	pgd_t *pgd;
	unsigned long next;

	BUG_ON(addr >= end);
	tlb_start_vma(tlb, vma);
	pgd = pgd_offset(vma->vm_mm, addr);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none_or_clear_bad(pgd))
			continue;
		next = zap_p4d_range(tlb, vma, pgd, addr, next, details);
	} while (pgd++, addr = next, addr != end);
	tlb_end_vma(tlb, vma);
}


static void unmap_single_vma(struct mmu_gather *tlb,
		struct vm_area_struct *vma, unsigned long start_addr,
		unsigned long end_addr,
		struct zap_details *details)
{
	unsigned long start = max(vma->vm_start, start_addr);
	unsigned long end;

	if (start >= vma->vm_end)
		return;
	end = min(vma->vm_end, end_addr);
	if (end <= vma->vm_start)
		return;

	if (vma->vm_file)
		uprobe_munmap(vma, start, end);

	if (unlikely(vma->vm_flags & VM_PFNMAP))
		untrack_pfn(vma, 0, 0);

	if (start != end) {
		if (unlikely(is_vm_hugetlb_page(vma))) {
			/*
			 * It is undesirable to test vma->vm_file as it
			 * should be non-null for valid hugetlb area.
			 * However, vm_file will be NULL in the error
			 * cleanup path of mmap_region. When
			 * hugetlbfs ->mmap method fails,
			 * mmap_region() nullifies vma->vm_file
			 * before calling this function to clean up.
			 * Since no pte has actually been setup, it is
			 * safe to do nothing in this case.
			 */
			if (vma->vm_file) {
				zap_flags_t zap_flags = details ?
				    details->zap_flags : 0;
				i_mmap_lock_write(vma->vm_file->f_mapping);
				__unmap_hugepage_range_final(tlb, vma, start, end,
							     NULL, zap_flags);
				i_mmap_unlock_write(vma->vm_file->f_mapping);
			}
		} else
			unmap_page_range(tlb, vma, start, end, details);
	}
}

/**
 * unmap_vmas - unmap a range of memory covered by a list of vma's
 * @tlb: address of the caller's struct mmu_gather
 * @vma: the starting vma
 * @start_addr: virtual address at which to start unmapping
 * @end_addr: virtual address at which to end unmapping
 *
 * Unmap all pages in the vma list.
 *
 * Only addresses between `start' and `end' will be unmapped.
 *
 * The VMA list must be sorted in ascending virtual address order.
 *
 * unmap_vmas() assumes that the caller will flush the whole unmapped address
 * range after unmap_vmas() returns.  So the only responsibility here is to
 * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
 * drops the lock and schedules.
 */
void unmap_vmas(struct mmu_gather *tlb,
		struct vm_area_struct *vma, unsigned long start_addr,
		unsigned long end_addr)
{
	struct mmu_notifier_range range;
	struct zap_details details = {
		.zap_flags = ZAP_FLAG_DROP_MARKER,
		/* Careful - we need to zap private pages too! */
		.even_cows = true,
	};

	mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma, vma->vm_mm,
				start_addr, end_addr);
	mmu_notifier_invalidate_range_start(&range);
	for ( ; vma && vma->vm_start < end_addr; vma = vma->vm_next)
		unmap_single_vma(tlb, vma, start_addr, end_addr, &details);
	mmu_notifier_invalidate_range_end(&range);
}

/**
 * zap_page_range - remove user pages in a given range
 * @vma: vm_area_struct holding the applicable pages
 * @start: starting address of pages to zap
 * @size: number of bytes to zap
 *
 * Caller must protect the VMA list
 */
void zap_page_range(struct vm_area_struct *vma, unsigned long start,
		unsigned long size)
{
	struct mmu_notifier_range range;
	struct mmu_gather tlb;

	lru_add_drain();
	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
				start, start + size);
	tlb_gather_mmu(&tlb, vma->vm_mm);
	update_hiwater_rss(vma->vm_mm);
	mmu_notifier_invalidate_range_start(&range);
	for ( ; vma && vma->vm_start < range.end; vma = vma->vm_next)
		unmap_single_vma(&tlb, vma, start, range.end, NULL);
	mmu_notifier_invalidate_range_end(&range);
	tlb_finish_mmu(&tlb);
}

/**
 * zap_page_range_single - remove user pages in a given range
 * @vma: vm_area_struct holding the applicable pages
 * @address: starting address of pages to zap
 * @size: number of bytes to zap
 * @details: details of shared cache invalidation
 *
 * The range must fit into one VMA.
 */
static void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
		unsigned long size, struct zap_details *details)
{
	struct mmu_notifier_range range;
	struct mmu_gather tlb;

	lru_add_drain();
	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm,
				address, address + size);
	tlb_gather_mmu(&tlb, vma->vm_mm);
	update_hiwater_rss(vma->vm_mm);
	mmu_notifier_invalidate_range_start(&range);
	unmap_single_vma(&tlb, vma, address, range.end, details);
	mmu_notifier_invalidate_range_end(&range);
	tlb_finish_mmu(&tlb);
}

/**
 * zap_vma_ptes - remove ptes mapping the vma
 * @vma: vm_area_struct holding ptes to be zapped
 * @address: starting address of pages to zap
 * @size: number of bytes to zap
 *
 * This function only unmaps ptes assigned to VM_PFNMAP vmas.
 *
 * The entire address range must be fully contained within the vma.
 *
 */
void zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
		unsigned long size)
{
	if (!range_in_vma(vma, address, address + size) ||
	    		!(vma->vm_flags & VM_PFNMAP))
		return;

	zap_page_range_single(vma, address, size, NULL);
}
EXPORT_SYMBOL_GPL(zap_vma_ptes);

static pmd_t *walk_to_pmd(struct mm_struct *mm, unsigned long addr)
{
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;

	pgd = pgd_offset(mm, addr);
	p4d = p4d_alloc(mm, pgd, addr);
	if (!p4d)
		return NULL;
	pud = pud_alloc(mm, p4d, addr);
	if (!pud)
		return NULL;
	pmd = pmd_alloc(mm, pud, addr);
	if (!pmd)
		return NULL;

	VM_BUG_ON(pmd_trans_huge(*pmd));
	return pmd;
}

pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
			spinlock_t **ptl)
{
	pmd_t *pmd = walk_to_pmd(mm, addr);

	if (!pmd)
		return NULL;
	return pte_alloc_map_lock(mm, pmd, addr, ptl);
}

static int validate_page_before_insert(struct page *page)
{
	if (PageAnon(page) || PageSlab(page) || page_has_type(page))
		return -EINVAL;
	flush_dcache_page(page);
	return 0;
}

static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte,
			unsigned long addr, struct page *page, pgprot_t prot)
{
	if (!pte_none(*pte))
		return -EBUSY;
	/* Ok, finally just insert the thing.. */
	get_page(page);
	inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
	page_add_file_rmap(page, vma, false);
	set_pte_at(vma->vm_mm, addr, pte, mk_pte(page, prot));
	return 0;
}

/*
 * This is the old fallback for page remapping.
 *
 * For historical reasons, it only allows reserved pages. Only
 * old drivers should use this, and they needed to mark their
 * pages reserved for the old functions anyway.
 */
static int insert_page(struct vm_area_struct *vma, unsigned long addr,
			struct page *page, pgprot_t prot)
{
	int retval;
	pte_t *pte;
	spinlock_t *ptl;

	retval = validate_page_before_insert(page);
	if (retval)
		goto out;
	retval = -ENOMEM;
	pte = get_locked_pte(vma->vm_mm, addr, &ptl);
	if (!pte)
		goto out;
	retval = insert_page_into_pte_locked(vma, pte, addr, page, prot);
	pte_unmap_unlock(pte, ptl);
out:
	return retval;
}

#ifdef pte_index
static int insert_page_in_batch_locked(struct vm_area_struct *vma, pte_t *pte,
			unsigned long addr, struct page *page, pgprot_t prot)
{
	int err;

	if (!page_count(page))
		return -EINVAL;
	err = validate_page_before_insert(page);
	if (err)
		return err;
	return insert_page_into_pte_locked(vma, pte, addr, page, prot);
}

/* insert_pages() amortizes the cost of spinlock operations
 * when inserting pages in a loop. Arch *must* define pte_index.
 */
static int insert_pages(struct vm_area_struct *vma, unsigned long addr,
			struct page **pages, unsigned long *num, pgprot_t prot)
{
	pmd_t *pmd = NULL;
	pte_t *start_pte, *pte;
	spinlock_t *pte_lock;
	struct mm_struct *const mm = vma->vm_mm;
	unsigned long curr_page_idx = 0;
	unsigned long remaining_pages_total = *num;
	unsigned long pages_to_write_in_pmd;
	int ret;
more:
	ret = -EFAULT;
	pmd = walk_to_pmd(mm, addr);
	if (!pmd)
		goto out;

	pages_to_write_in_pmd = min_t(unsigned long,
		remaining_pages_total, PTRS_PER_PTE - pte_index(addr));

	/* Allocate the PTE if necessary; takes PMD lock once only. */
	ret = -ENOMEM;
	if (pte_alloc(mm, pmd))
		goto out;

	while (pages_to_write_in_pmd) {
		int pte_idx = 0;
		const int batch_size = min_t(int, pages_to_write_in_pmd, 8);

		start_pte = pte_offset_map_lock(mm, pmd, addr, &pte_lock);
		for (pte = start_pte; pte_idx < batch_size; ++pte, ++pte_idx) {
			int err = insert_page_in_batch_locked(vma, pte,
				addr, pages[curr_page_idx], prot);
			if (unlikely(err)) {
				pte_unmap_unlock(start_pte, pte_lock);
				ret = err;
				remaining_pages_total -= pte_idx;
				goto out;
			}
			addr += PAGE_SIZE;
			++curr_page_idx;
		}
		pte_unmap_unlock(start_pte, pte_lock);
		pages_to_write_in_pmd -= batch_size;
		remaining_pages_total -= batch_size;
	}
	if (remaining_pages_total)
		goto more;
	ret = 0;
out:
	*num = remaining_pages_total;
	return ret;
}
#endif  /* ifdef pte_index */

/**
 * vm_insert_pages - insert multiple pages into user vma, batching the pmd lock.
 * @vma: user vma to map to
 * @addr: target start user address of these pages
 * @pages: source kernel pages
 * @num: in: number of pages to map. out: number of pages that were *not*
 * mapped. (0 means all pages were successfully mapped).
 *
 * Preferred over vm_insert_page() when inserting multiple pages.
 *
 * In case of error, we may have mapped a subset of the provided
 * pages. It is the caller's responsibility to account for this case.
 *
 * The same restrictions apply as in vm_insert_page().
 */
int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
			struct page **pages, unsigned long *num)
{
#ifdef pte_index
	const unsigned long end_addr = addr + (*num * PAGE_SIZE) - 1;

	if (addr < vma->vm_start || end_addr >= vma->vm_end)
		return -EFAULT;
	if (!(vma->vm_flags & VM_MIXEDMAP)) {
		BUG_ON(mmap_read_trylock(vma->vm_mm));
		BUG_ON(vma->vm_flags & VM_PFNMAP);
		vma->vm_flags |= VM_MIXEDMAP;
	}
	/* Defer page refcount checking till we're about to map that page. */
	return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
#else
	unsigned long idx = 0, pgcount = *num;
	int err = -EINVAL;

	for (; idx < pgcount; ++idx) {
		err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]);
		if (err)
			break;
	}
	*num = pgcount - idx;
	return err;
#endif  /* ifdef pte_index */
}
EXPORT_SYMBOL(vm_insert_pages);

/**
 * vm_insert_page - insert single page into user vma
 * @vma: user vma to map to
 * @addr: target user address of this page
 * @page: source kernel page
 *
 * This allows drivers to insert individual pages they've allocated
 * into a user vma.
 *
 * The page has to be a nice clean _individual_ kernel allocation.
 * If you allocate a compound page, you need to have marked it as
 * such (__GFP_COMP), or manually just split the page up yourself
 * (see split_page()).
 *
 * NOTE! Traditionally this was done with "remap_pfn_range()" which
 * took an arbitrary page protection parameter. This doesn't allow
 * that. Your vma protection will have to be set up correctly, which
 * means that if you want a shared writable mapping, you'd better
 * ask for a shared writable mapping!
 *
 * The page does not need to be reserved.
 *
 * Usually this function is called from f_op->mmap() handler
 * under mm->mmap_lock write-lock, so it can change vma->vm_flags.
 * Caller must set VM_MIXEDMAP on vma if it wants to call this
 * function from other places, for example from page-fault handler.
 *
 * Return: %0 on success, negative error code otherwise.
 */
int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
			struct page *page)
{
	if (addr < vma->vm_start || addr >= vma->vm_end)
		return -EFAULT;
	if (!page_count(page))
		return -EINVAL;
	if (!(vma->vm_flags & VM_MIXEDMAP)) {
		BUG_ON(mmap_read_trylock(vma->vm_mm));
		BUG_ON(vma->vm_flags & VM_PFNMAP);
		vma->vm_flags |= VM_MIXEDMAP;
	}
	return insert_page(vma, addr, page, vma->vm_page_prot);
}
EXPORT_SYMBOL(vm_insert_page);

/*
 * __vm_map_pages - maps range of kernel pages into user vma
 * @vma: user vma to map to
 * @pages: pointer to array of source kernel pages
 * @num: number of pages in page array
 * @offset: user's requested vm_pgoff
 *
 * This allows drivers to map range of kernel pages into a user vma.
 *
 * Return: 0 on success and error code otherwise.
 */
static int __vm_map_pages(struct vm_area_struct *vma, struct page **pages,
				unsigned long num, unsigned long offset)
{
	unsigned long count = vma_pages(vma);
	unsigned long uaddr = vma->vm_start;
	int ret, i;

	/* Fail if the user requested offset is beyond the end of the object */
	if (offset >= num)
		return -ENXIO;

	/* Fail if the user requested size exceeds available object size */
	if (count > num - offset)
		return -ENXIO;

	for (i = 0; i < count; i++) {
		ret = vm_insert_page(vma, uaddr, pages[offset + i]);
		if (ret < 0)
			return ret;
		uaddr += PAGE_SIZE;
	}

	return 0;
}

/**
 * vm_map_pages - maps range of kernel pages starts with non zero offset
 * @vma: user vma to map to
 * @pages: pointer to array of source kernel pages
 * @num: number of pages in page array
 *
 * Maps an object consisting of @num pages, catering for the user's
 * requested vm_pgoff
 *
 * If we fail to insert any page into the vma, the function will return
 * immediately leaving any previously inserted pages present.  Callers
 * from the mmap handler may immediately return the error as their caller
 * will destroy the vma, removing any successfully inserted pages. Other
 * callers should make their own arrangements for calling unmap_region().
 *
 * Context: Process context. Called by mmap handlers.
 * Return: 0 on success and error code otherwise.
 */
int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
				unsigned long num)
{
	return __vm_map_pages(vma, pages, num, vma->vm_pgoff);
}
EXPORT_SYMBOL(vm_map_pages);

/**
 * vm_map_pages_zero - map range of kernel pages starts with zero offset
 * @vma: user vma to map to
 * @pages: pointer to array of source kernel pages
 * @num: number of pages in page array
 *
 * Similar to vm_map_pages(), except that it explicitly sets the offset
 * to 0. This function is intended for the drivers that did not consider
 * vm_pgoff.
 *
 * Context: Process context. Called by mmap handlers.
 * Return: 0 on success and error code otherwise.
 */
int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
				unsigned long num)
{
	return __vm_map_pages(vma, pages, num, 0);
}
EXPORT_SYMBOL(vm_map_pages_zero);

static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
			pfn_t pfn, pgprot_t prot, bool mkwrite)
{
	struct mm_struct *mm = vma->vm_mm;
	pte_t *pte, entry;
	spinlock_t *ptl;

	pte = get_locked_pte(mm, addr, &ptl);
	if (!pte)
		return VM_FAULT_OOM;
	if (!pte_none(*pte)) {
		if (mkwrite) {
			/*
			 * For read faults on private mappings the PFN passed
			 * in may not match the PFN we have mapped if the
			 * mapped PFN is a writeable COW page.  In the mkwrite
			 * case we are creating a writable PTE for a shared
			 * mapping and we expect the PFNs to match. If they
			 * don't match, we are likely racing with block
			 * allocation and mapping invalidation so just skip the
			 * update.
			 */
			if (pte_pfn(*pte) != pfn_t_to_pfn(pfn)) {
				WARN_ON_ONCE(!is_zero_pfn(pte_pfn(*pte)));
				goto out_unlock;
			}
			entry = pte_mkyoung(*pte);
			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
			if (ptep_set_access_flags(vma, addr, pte, entry, 1))
				update_mmu_cache(vma, addr, pte);
		}
		goto out_unlock;
	}

	/* Ok, finally just insert the thing.. */
	if (pfn_t_devmap(pfn))
		entry = pte_mkdevmap(pfn_t_pte(pfn, prot));
	else
		entry = pte_mkspecial(pfn_t_pte(pfn, prot));

	if (mkwrite) {
		entry = pte_mkyoung(entry);
		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
	}

	set_pte_at(mm, addr, pte, entry);
	update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */

out_unlock:
	pte_unmap_unlock(pte, ptl);
	return VM_FAULT_NOPAGE;
}

/**
 * vmf_insert_pfn_prot - insert single pfn into user vma with specified pgprot
 * @vma: user vma to map to
 * @addr: target user address of this page
 * @pfn: source kernel pfn
 * @pgprot: pgprot flags for the inserted page
 *
 * This is exactly like vmf_insert_pfn(), except that it allows drivers
 * to override pgprot on a per-page basis.
 *
 * This only makes sense for IO mappings, and it makes no sense for
 * COW mappings.  In general, using multiple vmas is preferable;
 * vmf_insert_pfn_prot should only be used if using multiple VMAs is
 * impractical.
 *
 * See vmf_insert_mixed_prot() for a discussion of the implication of using
 * a value of @pgprot different from that of @vma->vm_page_prot.
 *
 * Context: Process context.  May allocate using %GFP_KERNEL.
 * Return: vm_fault_t value.
 */
vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
			unsigned long pfn, pgprot_t pgprot)
{
	/*
	 * Technically, architectures with pte_special can avoid all these
	 * restrictions (same for remap_pfn_range).  However we would like
	 * consistency in testing and feature parity among all, so we should
	 * try to keep these invariants in place for everybody.
	 */
	BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
	BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
						(VM_PFNMAP|VM_MIXEDMAP));
	BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
	BUG_ON((vma->vm_flags & VM_MIXEDMAP) && pfn_valid(pfn));

	if (addr < vma->vm_start || addr >= vma->vm_end)
		return VM_FAULT_SIGBUS;

	if (!pfn_modify_allowed(pfn, pgprot))
		return VM_FAULT_SIGBUS;

	track_pfn_insert(vma, &pgprot, __pfn_to_pfn_t(pfn, PFN_DEV));

	return insert_pfn(vma, addr, __pfn_to_pfn_t(pfn, PFN_DEV), pgprot,
			false);
}
EXPORT_SYMBOL(vmf_insert_pfn_prot);

/**
 * vmf_insert_pfn - insert single pfn into user vma
 * @vma: user vma to map to
 * @addr: target user address of this page
 * @pfn: source kernel pfn
 *
 * Similar to vm_insert_page, this allows drivers to insert individual pages
 * they've allocated into a user vma. Same comments apply.
 *
 * This function should only be called from a vm_ops->fault handler, and
 * in that case the handler should return the result of this function.
 *
 * vma cannot be a COW mapping.
 *
 * As this is called only for pages that do not currently exist, we
 * do not need to flush old virtual caches or the TLB.
 *
 * Context: Process context.  May allocate using %GFP_KERNEL.
 * Return: vm_fault_t value.
 */
vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
			unsigned long pfn)
{
	return vmf_insert_pfn_prot(vma, addr, pfn, vma->vm_page_prot);
}
EXPORT_SYMBOL(vmf_insert_pfn);

static bool vm_mixed_ok(struct vm_area_struct *vma, pfn_t pfn)
{
	/* these checks mirror the abort conditions in vm_normal_page */
	if (vma->vm_flags & VM_MIXEDMAP)
		return true;
	if (pfn_t_devmap(pfn))
		return true;
	if (pfn_t_special(pfn))
		return true;
	if (is_zero_pfn(pfn_t_to_pfn(pfn)))
		return true;
	return false;
}

static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma,
		unsigned long addr, pfn_t pfn, pgprot_t pgprot,
		bool mkwrite)
{
	int err;

	BUG_ON(!vm_mixed_ok(vma, pfn));

	if (addr < vma->vm_start || addr >= vma->vm_end)
		return VM_FAULT_SIGBUS;

	track_pfn_insert(vma, &pgprot, pfn);

	if (!pfn_modify_allowed(pfn_t_to_pfn(pfn), pgprot))
		return VM_FAULT_SIGBUS;

	/*
	 * If we don't have pte special, then we have to use the pfn_valid()
	 * based VM_MIXEDMAP scheme (see vm_normal_page), and thus we *must*
	 * refcount the page if pfn_valid is true (hence insert_page rather
	 * than insert_pfn).  If a zero_pfn were inserted into a VM_MIXEDMAP
	 * without pte special, it would there be refcounted as a normal page.
	 */
	if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) &&
	    !pfn_t_devmap(pfn) && pfn_t_valid(pfn)) {
		struct page *page;

		/*
		 * At this point we are committed to insert_page()
		 * regardless of whether the caller specified flags that
		 * result in pfn_t_has_page() == false.
		 */
		page = pfn_to_page(pfn_t_to_pfn(pfn));
		err = insert_page(vma, addr, page, pgprot);
	} else {
		return insert_pfn(vma, addr, pfn, pgprot, mkwrite);
	}

	if (err == -ENOMEM)
		return VM_FAULT_OOM;
	if (err < 0 && err != -EBUSY)
		return VM_FAULT_SIGBUS;

	return VM_FAULT_NOPAGE;
}

/**
 * vmf_insert_mixed_prot - insert single pfn into user vma with specified pgprot
 * @vma: user vma to map to
 * @addr: target user address of this page
 * @pfn: source kernel pfn
 * @pgprot: pgprot flags for the inserted page
 *
 * This is exactly like vmf_insert_mixed(), except that it allows drivers
 * to override pgprot on a per-page basis.
 *
 * Typically this function should be used by drivers to set caching- and
 * encryption bits different than those of @vma->vm_page_prot, because
 * the caching- or encryption mode may not be known at mmap() time.
 * This is ok as long as @vma->vm_page_prot is not used by the core vm
 * to set caching and encryption bits for those vmas (except for COW pages).
 * This is ensured by core vm only modifying these page table entries using
 * functions that don't touch caching- or encryption bits, using pte_modify()
 * if needed. (See for example mprotect()).
 * Also when new page-table entries are created, this is only done using the
 * fault() callback, and never using the value of vma->vm_page_prot,
 * except for page-table entries that point to anonymous pages as the result
 * of COW.
 *
 * Context: Process context.  May allocate using %GFP_KERNEL.
 * Return: vm_fault_t value.
 */
vm_fault_t vmf_insert_mixed_prot(struct vm_area_struct *vma, unsigned long addr,
				 pfn_t pfn, pgprot_t pgprot)
{
	return __vm_insert_mixed(vma, addr, pfn, pgprot, false);
}
EXPORT_SYMBOL(vmf_insert_mixed_prot);

vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
		pfn_t pfn)
{
	return __vm_insert_mixed(vma, addr, pfn, vma->vm_page_prot, false);
}
EXPORT_SYMBOL(vmf_insert_mixed);

/*
 *  If the insertion of PTE failed because someone else already added a
 *  different entry in the mean time, we treat that as success as we assume
 *  the same entry was actually inserted.
 */
vm_fault_t vmf_insert_mixed_mkwrite(struct vm_area_struct *vma,
		unsigned long addr, pfn_t pfn)
{
	return __vm_insert_mixed(vma, addr, pfn, vma->vm_page_prot, true);
}
EXPORT_SYMBOL(vmf_insert_mixed_mkwrite);

/*
 * maps a range of physical memory into the requested pages. the old
 * mappings are removed. any references to nonexistent pages results
 * in null mappings (currently treated as "copy-on-access")
 */
static int remap_pte_range(struct mm_struct *mm, pmd_t *pmd,
			unsigned long addr, unsigned long end,
			unsigned long pfn, pgprot_t prot)
{
	pte_t *pte, *mapped_pte;
	spinlock_t *ptl;
	int err = 0;

	mapped_pte = pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
	if (!pte)
		return -ENOMEM;
	arch_enter_lazy_mmu_mode();
	do {
		BUG_ON(!pte_none(*pte));
		if (!pfn_modify_allowed(pfn, prot)) {
			err = -EACCES;
			break;
		}
		set_pte_at(mm, addr, pte, pte_mkspecial(pfn_pte(pfn, prot)));
		pfn++;
	} while (pte++, addr += PAGE_SIZE, addr != end);
	arch_leave_lazy_mmu_mode();
	pte_unmap_unlock(mapped_pte, ptl);
	return err;
}

static inline int remap_pmd_range(struct mm_struct *mm, pud_t *pud,
			unsigned long addr, unsigned long end,
			unsigned long pfn, pgprot_t prot)
{
	pmd_t *pmd;
	unsigned long next;
	int err;

	pfn -= addr >> PAGE_SHIFT;
	pmd = pmd_alloc(mm, pud, addr);
	if (!pmd)
		return -ENOMEM;
	VM_BUG_ON(pmd_trans_huge(*pmd));
	do {
		next = pmd_addr_end(addr, end);
		err = remap_pte_range(mm, pmd, addr, next,
				pfn + (addr >> PAGE_SHIFT), prot);
		if (err)
			return err;
	} while (pmd++, addr = next, addr != end);
	return 0;
}

static inline int remap_pud_range(struct mm_struct *mm, p4d_t *p4d,
			unsigned long addr, unsigned long end,
			unsigned long pfn, pgprot_t prot)
{
	pud_t *pud;
	unsigned long next;
	int err;

	pfn -= addr >> PAGE_SHIFT;
	pud = pud_alloc(mm, p4d, addr);
	if (!pud)
		return -ENOMEM;
	do {
		next = pud_addr_end(addr, end);
		err = remap_pmd_range(mm, pud, addr, next,
				pfn + (addr >> PAGE_SHIFT), prot);
		if (err)
			return err;
	} while (pud++, addr = next, addr != end);
	return 0;
}

static inline int remap_p4d_range(struct mm_struct *mm, pgd_t *pgd,
			unsigned long addr, unsigned long end,
			unsigned long pfn, pgprot_t prot)
{
	p4d_t *p4d;
	unsigned long next;
	int err;

	pfn -= addr >> PAGE_SHIFT;
	p4d = p4d_alloc(mm, pgd, addr);
	if (!p4d)
		return -ENOMEM;
	do {
		next = p4d_addr_end(addr, end);
		err = remap_pud_range(mm, p4d, addr, next,
				pfn + (addr >> PAGE_SHIFT), prot);
		if (err)
			return err;
	} while (p4d++, addr = next, addr != end);
	return 0;
}

/*
 * Variant of remap_pfn_range that does not call track_pfn_remap.  The caller
 * must have pre-validated the caching bits of the pgprot_t.
 */
int remap_pfn_range_notrack(struct vm_area_struct *vma, unsigned long addr,
		unsigned long pfn, unsigned long size, pgprot_t prot)
{
	pgd_t *pgd;
	unsigned long next;
	unsigned long end = addr + PAGE_ALIGN(size);
	struct mm_struct *mm = vma->vm_mm;
	int err;

	if (WARN_ON_ONCE(!PAGE_ALIGNED(addr)))
		return -EINVAL;

	/*
	 * Physically remapped pages are special. Tell the
	 * rest of the world about it:
	 *   VM_IO tells people not to look at these pages
	 *	(accesses can have side effects).
	 *   VM_PFNMAP tells the core MM that the base pages are just
	 *	raw PFN mappings, and do not have a "struct page" associated
	 *	with them.
	 *   VM_DONTEXPAND
	 *      Disable vma merging and expanding with mremap().
	 *   VM_DONTDUMP
	 *      Omit vma from core dump, even when VM_IO turned off.
	 *
	 * There's a horrible special case to handle copy-on-write
	 * behaviour that some programs depend on. We mark the "original"
	 * un-COW'ed pages by matching them up with "vma->vm_pgoff".
	 * See vm_normal_page() for details.
	 */
	if (is_cow_mapping(vma->vm_flags)) {
		if (addr != vma->vm_start || end != vma->vm_end)
			return -EINVAL;
		vma->vm_pgoff = pfn;
	}

	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;

	BUG_ON(addr >= end);
	pfn -= addr >> PAGE_SHIFT;
	pgd = pgd_offset(mm, addr);
	flush_cache_range(vma, addr, end);
	do {
		next = pgd_addr_end(addr, end);
		err = remap_p4d_range(mm, pgd, addr, next,
				pfn + (addr >> PAGE_SHIFT), prot);
		if (err)
			return err;
	} while (pgd++, addr = next, addr != end);

	return 0;
}

/**
 * remap_pfn_range - remap kernel memory to userspace
 * @vma: user vma to map to
 * @addr: target page aligned user address to start at
 * @pfn: page frame number of kernel physical memory address
 * @size: size of mapping area
 * @prot: page protection flags for this mapping
 *
 * Note: this is only safe if the mm semaphore is held when called.
 *
 * Return: %0 on success, negative error code otherwise.
 */
int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
		    unsigned long pfn, unsigned long size, pgprot_t prot)
{
	int err;

	err = track_pfn_remap(vma, &prot, pfn, addr, PAGE_ALIGN(size));
	if (err)
		return -EINVAL;

	err = remap_pfn_range_notrack(vma, addr, pfn, size, prot);
	if (err)
		untrack_pfn(vma, pfn, PAGE_ALIGN(size));
	return err;
}
EXPORT_SYMBOL(remap_pfn_range);

/**
 * vm_iomap_memory - remap memory to userspace
 * @vma: user vma to map to
 * @start: start of the physical memory to be mapped
 * @len: size of area
 *
 * This is a simplified io_remap_pfn_range() for common driver use. The
 * driver just needs to give us the physical memory range to be mapped,
 * we'll figure out the rest from the vma information.
 *
 * NOTE! Some drivers might want to tweak vma->vm_page_prot first to get
 * whatever write-combining details or similar.
 *
 * Return: %0 on success, negative error code otherwise.
 */
int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
{
	unsigned long vm_len, pfn, pages;

	/* Check that the physical memory area passed in looks valid */
	if (start + len < start)
		return -EINVAL;
	/*
	 * You *really* shouldn't map things that aren't page-aligned,
	 * but we've historically allowed it because IO memory might
	 * just have smaller alignment.
	 */
	len += start & ~PAGE_MASK;
	pfn = start >> PAGE_SHIFT;
	pages = (len + ~PAGE_MASK) >> PAGE_SHIFT;
	if (pfn + pages < pfn)
		return -EINVAL;

	/* We start the mapping 'vm_pgoff' pages into the area */
	if (vma->vm_pgoff > pages)
		return -EINVAL;
	pfn += vma->vm_pgoff;
	pages -= vma->vm_pgoff;

	/* Can we fit all of the mapping? */
	vm_len = vma->vm_end - vma->vm_start;
	if (vm_len >> PAGE_SHIFT > pages)
		return -EINVAL;

	/* Ok, let it rip */
	return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
}
EXPORT_SYMBOL(vm_iomap_memory);

static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
				     unsigned long addr, unsigned long end,
				     pte_fn_t fn, void *data, bool create,
				     pgtbl_mod_mask *mask)
{
	pte_t *pte, *mapped_pte;
	int err = 0;
	spinlock_t *ptl;

	if (create) {
		mapped_pte = pte = (mm == &init_mm) ?
			pte_alloc_kernel_track(pmd, addr, mask) :
			pte_alloc_map_lock(mm, pmd, addr, &ptl);
		if (!pte)
			return -ENOMEM;
	} else {
		mapped_pte = pte = (mm == &init_mm) ?
			pte_offset_kernel(pmd, addr) :
			pte_offset_map_lock(mm, pmd, addr, &ptl);
	}

	BUG_ON(pmd_huge(*pmd));

	arch_enter_lazy_mmu_mode();

	if (fn) {
		do {
			if (create || !pte_none(*pte)) {
				err = fn(pte++, addr, data);
				if (err)
					break;
			}
		} while (addr += PAGE_SIZE, addr != end);
	}
	*mask |= PGTBL_PTE_MODIFIED;

	arch_leave_lazy_mmu_mode();

	if (mm != &init_mm)
		pte_unmap_unlock(mapped_pte, ptl);
	return err;
}

static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
				     unsigned long addr, unsigned long end,
				     pte_fn_t fn, void *data, bool create,
				     pgtbl_mod_mask *mask)
{
	pmd_t *pmd;
	unsigned long next;
	int err = 0;

	BUG_ON(pud_huge(*pud));

	if (create) {
		pmd = pmd_alloc_track(mm, pud, addr, mask);
		if (!pmd)
			return -ENOMEM;
	} else {
		pmd = pmd_offset(pud, addr);
	}
	do {
		next = pmd_addr_end(addr, end);
		if (pmd_none(*pmd) && !create)
			continue;
		if (WARN_ON_ONCE(pmd_leaf(*pmd)))
			return -EINVAL;
		if (!pmd_none(*pmd) && WARN_ON_ONCE(pmd_bad(*pmd))) {
			if (!create)
				continue;
			pmd_clear_bad(pmd);
		}
		err = apply_to_pte_range(mm, pmd, addr, next,
					 fn, data, create, mask);
		if (err)
			break;
	} while (pmd++, addr = next, addr != end);

	return err;
}

static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d,
				     unsigned long addr, unsigned long end,
				     pte_fn_t fn, void *data, bool create,
				     pgtbl_mod_mask *mask)
{
	pud_t *pud;
	unsigned long next;
	int err = 0;

	if (create) {
		pud = pud_alloc_track(mm, p4d, addr, mask);
		if (!pud)
			return -ENOMEM;
	} else {
		pud = pud_offset(p4d, addr);
	}
	do {
		next = pud_addr_end(addr, end);
		if (pud_none(*pud) && !create)
			continue;
		if (WARN_ON_ONCE(pud_leaf(*pud)))
			return -EINVAL;
		if (!pud_none(*pud) && WARN_ON_ONCE(pud_bad(*pud))) {
			if (!create)
				continue;
			pud_clear_bad(pud);
		}
		err = apply_to_pmd_range(mm, pud, addr, next,
					 fn, data, create, mask);
		if (err)
			break;
	} while (pud++, addr = next, addr != end);

	return err;
}

static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd,
				     unsigned long addr, unsigned long end,
				     pte_fn_t fn, void *data, bool create,
				     pgtbl_mod_mask *mask)
{
	p4d_t *p4d;
	unsigned long next;
	int err = 0;

	if (create) {
		p4d = p4d_alloc_track(mm, pgd, addr, mask);
		if (!p4d)
			return -ENOMEM;
	} else {
		p4d = p4d_offset(pgd, addr);
	}
	do {
		next = p4d_addr_end(addr, end);
		if (p4d_none(*p4d) && !create)
			continue;
		if (WARN_ON_ONCE(p4d_leaf(*p4d)))
			return -EINVAL;
		if (!p4d_none(*p4d) && WARN_ON_ONCE(p4d_bad(*p4d))) {
			if (!create)
				continue;
			p4d_clear_bad(p4d);
		}
		err = apply_to_pud_range(mm, p4d, addr, next,
					 fn, data, create, mask);
		if (err)
			break;
	} while (p4d++, addr = next, addr != end);

	return err;
}

static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr,
				 unsigned long size, pte_fn_t fn,
				 void *data, bool create)
{
	pgd_t *pgd;
	unsigned long start = addr, next;
	unsigned long end = addr + size;
	pgtbl_mod_mask mask = 0;
	int err = 0;

	if (WARN_ON(addr >= end))
		return -EINVAL;

	pgd = pgd_offset(mm, addr);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none(*pgd) && !create)
			continue;
		if (WARN_ON_ONCE(pgd_leaf(*pgd)))
			return -EINVAL;
		if (!pgd_none(*pgd) && WARN_ON_ONCE(pgd_bad(*pgd))) {
			if (!create)
				continue;
			pgd_clear_bad(pgd);
		}
		err = apply_to_p4d_range(mm, pgd, addr, next,
					 fn, data, create, &mask);
		if (err)
			break;
	} while (pgd++, addr = next, addr != end);

	if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
		arch_sync_kernel_mappings(start, start + size);

	return err;
}

/*
 * Scan a region of virtual memory, filling in page tables as necessary
 * and calling a provided function on each leaf page table.
 */
int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
			unsigned long size, pte_fn_t fn, void *data)
{
	return __apply_to_page_range(mm, addr, size, fn, data, true);
}
EXPORT_SYMBOL_GPL(apply_to_page_range);

/*
 * Scan a region of virtual memory, calling a provided function on
 * each leaf page table where it exists.
 *
 * Unlike apply_to_page_range, this does _not_ fill in page tables
 * where they are absent.
 */
int apply_to_existing_page_range(struct mm_struct *mm, unsigned long addr,
				 unsigned long size, pte_fn_t fn, void *data)
{
	return __apply_to_page_range(mm, addr, size, fn, data, false);
}
EXPORT_SYMBOL_GPL(apply_to_existing_page_range);

/*
 * handle_pte_fault chooses page fault handler according to an entry which was
 * read non-atomically.  Before making any commitment, on those architectures
 * or configurations (e.g. i386 with PAE) which might give a mix of unmatched
 * parts, do_swap_page must check under lock before unmapping the pte and
 * proceeding (but do_wp_page is only called after already making such a check;
 * and do_anonymous_page can safely check later on).
 */
static inline int pte_unmap_same(struct vm_fault *vmf)
{
	int same = 1;
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPTION)
	if (sizeof(pte_t) > sizeof(unsigned long)) {
		spinlock_t *ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
		spin_lock(ptl);
		same = pte_same(*vmf->pte, vmf->orig_pte);
		spin_unlock(ptl);
	}
#endif
	pte_unmap(vmf->pte);
	vmf->pte = NULL;
	return same;
}

static inline bool __wp_page_copy_user(struct page *dst, struct page *src,
				       struct vm_fault *vmf)
{
	bool ret;
	void *kaddr;
	void __user *uaddr;
	bool locked = false;
	struct vm_area_struct *vma = vmf->vma;
	struct mm_struct *mm = vma->vm_mm;
	unsigned long addr = vmf->address;

	if (likely(src)) {
		copy_user_highpage(dst, src, addr, vma);
		return true;
	}

	/*
	 * If the source page was a PFN mapping, we don't have
	 * a "struct page" for it. We do a best-effort copy by
	 * just copying from the original user address. If that
	 * fails, we just zero-fill it. Live with it.
	 */
	kaddr = kmap_atomic(dst);
	uaddr = (void __user *)(addr & PAGE_MASK);

	/*
	 * On architectures with software "accessed" bits, we would
	 * take a double page fault, so mark it accessed here.
	 */
	if (arch_faults_on_old_pte() && !pte_young(vmf->orig_pte)) {
		pte_t entry;

		vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl);
		locked = true;
		if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) {
			/*
			 * Other thread has already handled the fault
			 * and update local tlb only
			 */
			update_mmu_tlb(vma, addr, vmf->pte);
			ret = false;
			goto pte_unlock;
		}

		entry = pte_mkyoung(vmf->orig_pte);
		if (ptep_set_access_flags(vma, addr, vmf->pte, entry, 0))
			update_mmu_cache(vma, addr, vmf->pte);
	}

	/*
	 * This really shouldn't fail, because the page is there
	 * in the page tables. But it might just be unreadable,
	 * in which case we just give up and fill the result with
	 * zeroes.
	 */
	if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) {
		if (locked)
			goto warn;

		/* Re-validate under PTL if the page is still mapped */
		vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl);
		locked = true;
		if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) {
			/* The PTE changed under us, update local tlb */
			update_mmu_tlb(vma, addr, vmf->pte);
			ret = false;
			goto pte_unlock;
		}

		/*
		 * The same page can be mapped back since last copy attempt.
		 * Try to copy again under PTL.
		 */
		if (__copy_from_user_inatomic(kaddr, uaddr, PAGE_SIZE)) {
			/*
			 * Give a warn in case there can be some obscure
			 * use-case
			 */
warn:
			WARN_ON_ONCE(1);
			clear_page(kaddr);
		}
	}

	ret = true;

pte_unlock:
	if (locked)
		pte_unmap_unlock(vmf->pte, vmf->ptl);
	kunmap_atomic(kaddr);
	flush_dcache_page(dst);

	return ret;
}

static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma)
{
	struct file *vm_file = vma->vm_file;

	if (vm_file)
		return mapping_gfp_mask(vm_file->f_mapping) | __GFP_FS | __GFP_IO;

	/*
	 * Special mappings (e.g. VDSO) do not have any file so fake
	 * a default GFP_KERNEL for them.
	 */
	return GFP_KERNEL;
}

/*
 * Notify the address space that the page is about to become writable so that
 * it can prohibit this or wait for the page to get into an appropriate state.
 *
 * We do this without the lock held, so that it can sleep if it needs to.
 */
static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
{
	vm_fault_t ret;
	struct page *page = vmf->page;
	unsigned int old_flags = vmf->flags;

	vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;

	if (vmf->vma->vm_file &&
	    IS_SWAPFILE(vmf->vma->vm_file->f_mapping->host))
		return VM_FAULT_SIGBUS;

	ret = vmf->vma->vm_ops->page_mkwrite(vmf);
	/* Restore original flags so that caller is not surprised */
	vmf->flags = old_flags;
	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
		return ret;
	if (unlikely(!(ret & VM_FAULT_LOCKED))) {
		lock_page(page);
		if (!page->mapping) {
			unlock_page(page);
			return 0; /* retry */
		}
		ret |= VM_FAULT_LOCKED;
	} else
		VM_BUG_ON_PAGE(!PageLocked(page), page);
	return ret;
}

/*
 * Handle dirtying of a page in shared file mapping on a write fault.
 *
 * The function expects the page to be locked and unlocks it.
 */
static vm_fault_t fault_dirty_shared_page(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct address_space *mapping;
	struct page *page = vmf->page;
	bool dirtied;
	bool page_mkwrite = vma->vm_ops && vma->vm_ops->page_mkwrite;

	dirtied = set_page_dirty(page);
	VM_BUG_ON_PAGE(PageAnon(page), page);
	/*
	 * Take a local copy of the address_space - page.mapping may be zeroed
	 * by truncate after unlock_page().   The address_space itself remains
	 * pinned by vma->vm_file's reference.  We rely on unlock_page()'s
	 * release semantics to prevent the compiler from undoing this copying.
	 */
	mapping = page_rmapping(page);
	unlock_page(page);

	if (!page_mkwrite)
		file_update_time(vma->vm_file);

	/*
	 * Throttle page dirtying rate down to writeback speed.
	 *
	 * mapping may be NULL here because some device drivers do not
	 * set page.mapping but still dirty their pages
	 *
	 * Drop the mmap_lock before waiting on IO, if we can. The file
	 * is pinning the mapping, as per above.
	 */
	if ((dirtied || page_mkwrite) && mapping) {
		struct file *fpin;

		fpin = maybe_unlock_mmap_for_io(vmf, NULL);
		balance_dirty_pages_ratelimited(mapping);
		if (fpin) {
			fput(fpin);
			return VM_FAULT_RETRY;
		}
	}

	return 0;
}

/*
 * Handle write page faults for pages that can be reused in the current vma
 *
 * This can happen either due to the mapping being with the VM_SHARED flag,
 * or due to us being the last reference standing to the page. In either
 * case, all we need to do here is to mark the page as writable and update
 * any related book-keeping.
 */
static inline void wp_page_reuse(struct vm_fault *vmf)
	__releases(vmf->ptl)
{
	struct vm_area_struct *vma = vmf->vma;
	struct page *page = vmf->page;
	pte_t entry;

	VM_BUG_ON(!(vmf->flags & FAULT_FLAG_WRITE));
	VM_BUG_ON(PageAnon(page) && !PageAnonExclusive(page));

	/*
	 * Clear the pages cpupid information as the existing
	 * information potentially belongs to a now completely
	 * unrelated process.
	 */
	if (page)
		page_cpupid_xchg_last(page, (1 << LAST_CPUPID_SHIFT) - 1);

	flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
	entry = pte_mkyoung(vmf->orig_pte);
	entry = maybe_mkwrite(pte_mkdirty(entry), vma);
	if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
		update_mmu_cache(vma, vmf->address, vmf->pte);
	pte_unmap_unlock(vmf->pte, vmf->ptl);
	count_vm_event(PGREUSE);
}

/*
 * Handle the case of a page which we actually need to copy to a new page,
 * either due to COW or unsharing.
 *
 * Called with mmap_lock locked and the old page referenced, but
 * without the ptl held.
 *
 * High level logic flow:
 *
 * - Allocate a page, copy the content of the old page to the new one.
 * - Handle book keeping and accounting - cgroups, mmu-notifiers, etc.
 * - Take the PTL. If the pte changed, bail out and release the allocated page
 * - If the pte is still the way we remember it, update the page table and all
 *   relevant references. This includes dropping the reference the page-table
 *   held to the old page, as well as updating the rmap.
 * - In any case, unlock the PTL and drop the reference we took to the old page.
 */
static vm_fault_t wp_page_copy(struct vm_fault *vmf)
{
	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
	struct vm_area_struct *vma = vmf->vma;
	struct mm_struct *mm = vma->vm_mm;
	struct page *old_page = vmf->page;
	struct page *new_page = NULL;
	pte_t entry;
	int page_copied = 0;
	struct mmu_notifier_range range;

	delayacct_wpcopy_start();

	if (unlikely(anon_vma_prepare(vma)))
		goto oom;

	if (is_zero_pfn(pte_pfn(vmf->orig_pte))) {
		new_page = alloc_zeroed_user_highpage_movable(vma,
							      vmf->address);
		if (!new_page)
			goto oom;
	} else {
		new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma,
				vmf->address);
		if (!new_page)
			goto oom;

		if (!__wp_page_copy_user(new_page, old_page, vmf)) {
			/*
			 * COW failed, if the fault was solved by other,
			 * it's fine. If not, userspace would re-fault on
			 * the same address and we will handle the fault
			 * from the second attempt.
			 */
			put_page(new_page);
			if (old_page)
				put_page(old_page);

			delayacct_wpcopy_end();
			return 0;
		}
	}

	if (mem_cgroup_charge(page_folio(new_page), mm, GFP_KERNEL))
		goto oom_free_new;
	cgroup_throttle_swaprate(new_page, GFP_KERNEL);

	__SetPageUptodate(new_page);

	mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, mm,
				vmf->address & PAGE_MASK,
				(vmf->address & PAGE_MASK) + PAGE_SIZE);
	mmu_notifier_invalidate_range_start(&range);

	/*
	 * Re-check the pte - we dropped the lock
	 */
	vmf->pte = pte_offset_map_lock(mm, vmf->pmd, vmf->address, &vmf->ptl);
	if (likely(pte_same(*vmf->pte, vmf->orig_pte))) {
		if (old_page) {
			if (!PageAnon(old_page)) {
				dec_mm_counter_fast(mm,
						mm_counter_file(old_page));
				inc_mm_counter_fast(mm, MM_ANONPAGES);
			}
		} else {
			inc_mm_counter_fast(mm, MM_ANONPAGES);
		}
		flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
		entry = mk_pte(new_page, vma->vm_page_prot);
		entry = pte_sw_mkyoung(entry);
		if (unlikely(unshare)) {
			if (pte_soft_dirty(vmf->orig_pte))
				entry = pte_mksoft_dirty(entry);
			if (pte_uffd_wp(vmf->orig_pte))
				entry = pte_mkuffd_wp(entry);
		} else {
			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
		}

		/*
		 * Clear the pte entry and flush it first, before updating the
		 * pte with the new entry, to keep TLBs on different CPUs in
		 * sync. This code used to set the new PTE then flush TLBs, but
		 * that left a window where the new PTE could be loaded into
		 * some TLBs while the old PTE remains in others.
		 */
		ptep_clear_flush_notify(vma, vmf->address, vmf->pte);
		page_add_new_anon_rmap(new_page, vma, vmf->address);
		lru_cache_add_inactive_or_unevictable(new_page, vma);
		/*
		 * We call the notify macro here because, when using secondary
		 * mmu page tables (such as kvm shadow page tables), we want the
		 * new page to be mapped directly into the secondary page table.
		 */
		BUG_ON(unshare && pte_write(entry));
		set_pte_at_notify(mm, vmf->address, vmf->pte, entry);
		update_mmu_cache(vma, vmf->address, vmf->pte);
		if (old_page) {
			/*
			 * Only after switching the pte to the new page may
			 * we remove the mapcount here. Otherwise another
			 * process may come and find the rmap count decremented
			 * before the pte is switched to the new page, and
			 * "reuse" the old page writing into it while our pte
			 * here still points into it and can be read by other
			 * threads.
			 *
			 * The critical issue is to order this
			 * page_remove_rmap with the ptp_clear_flush above.
			 * Those stores are ordered by (if nothing else,)
			 * the barrier present in the atomic_add_negative
			 * in page_remove_rmap.
			 *
			 * Then the TLB flush in ptep_clear_flush ensures that
			 * no process can access the old page before the
			 * decremented mapcount is visible. And the old page
			 * cannot be reused until after the decremented
			 * mapcount is visible. So transitively, TLBs to
			 * old page will be flushed before it can be reused.
			 */
			page_remove_rmap(old_page, vma, false);
		}

		/* Free the old page.. */
		new_page = old_page;
		page_copied = 1;
	} else {
		update_mmu_tlb(vma, vmf->address, vmf->pte);
	}

	if (new_page)
		put_page(new_page);

	pte_unmap_unlock(vmf->pte, vmf->ptl);
	/*
	 * No need to double call mmu_notifier->invalidate_range() callback as
	 * the above ptep_clear_flush_notify() did already call it.
	 */
	mmu_notifier_invalidate_range_only_end(&range);
	if (old_page) {
		if (page_copied)
			free_swap_cache(old_page);
		put_page(old_page);
	}

	delayacct_wpcopy_end();
	return (page_copied && !unshare) ? VM_FAULT_WRITE : 0;
oom_free_new:
	put_page(new_page);
oom:
	if (old_page)
		put_page(old_page);

	delayacct_wpcopy_end();
	return VM_FAULT_OOM;
}

/**
 * finish_mkwrite_fault - finish page fault for a shared mapping, making PTE
 *			  writeable once the page is prepared
 *
 * @vmf: structure describing the fault
 *
 * This function handles all that is needed to finish a write page fault in a
 * shared mapping due to PTE being read-only once the mapped page is prepared.
 * It handles locking of PTE and modifying it.
 *
 * The function expects the page to be locked or other protection against
 * concurrent faults / writeback (such as DAX radix tree locks).
 *
 * Return: %0 on success, %VM_FAULT_NOPAGE when PTE got changed before
 * we acquired PTE lock.
 */
vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf)
{
	WARN_ON_ONCE(!(vmf->vma->vm_flags & VM_SHARED));
	vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, vmf->address,
				       &vmf->ptl);
	/*
	 * We might have raced with another page fault while we released the
	 * pte_offset_map_lock.
	 */
	if (!pte_same(*vmf->pte, vmf->orig_pte)) {
		update_mmu_tlb(vmf->vma, vmf->address, vmf->pte);
		pte_unmap_unlock(vmf->pte, vmf->ptl);
		return VM_FAULT_NOPAGE;
	}
	wp_page_reuse(vmf);
	return 0;
}

/*
 * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED
 * mapping
 */
static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;

	if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
		vm_fault_t ret;

		pte_unmap_unlock(vmf->pte, vmf->ptl);
		vmf->flags |= FAULT_FLAG_MKWRITE;
		ret = vma->vm_ops->pfn_mkwrite(vmf);
		if (ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))
			return ret;
		return finish_mkwrite_fault(vmf);
	}
	wp_page_reuse(vmf);
	return VM_FAULT_WRITE;
}

static vm_fault_t wp_page_shared(struct vm_fault *vmf)
	__releases(vmf->ptl)
{
	struct vm_area_struct *vma = vmf->vma;
	vm_fault_t ret = VM_FAULT_WRITE;

	get_page(vmf->page);

	if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
		vm_fault_t tmp;

		pte_unmap_unlock(vmf->pte, vmf->ptl);
		tmp = do_page_mkwrite(vmf);
		if (unlikely(!tmp || (tmp &
				      (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
			put_page(vmf->page);
			return tmp;
		}
		tmp = finish_mkwrite_fault(vmf);
		if (unlikely(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
			unlock_page(vmf->page);
			put_page(vmf->page);
			return tmp;
		}
	} else {
		wp_page_reuse(vmf);
		lock_page(vmf->page);
	}
	ret |= fault_dirty_shared_page(vmf);
	put_page(vmf->page);

	return ret;
}

/*
 * This routine handles present pages, when
 * * users try to write to a shared page (FAULT_FLAG_WRITE)
 * * GUP wants to take a R/O pin on a possibly shared anonymous page
 *   (FAULT_FLAG_UNSHARE)
 *
 * It is done by copying the page to a new address and decrementing the
 * shared-page counter for the old page.
 *
 * Note that this routine assumes that the protection checks have been
 * done by the caller (the low-level page fault routine in most cases).
 * Thus, with FAULT_FLAG_WRITE, we can safely just mark it writable once we've
 * done any necessary COW.
 *
 * In case of FAULT_FLAG_WRITE, we also mark the page dirty at this point even
 * though the page will change only once the write actually happens. This
 * avoids a few races, and potentially makes it more efficient.
 *
 * We enter with non-exclusive mmap_lock (to exclude vma changes,
 * but allow concurrent faults), with pte both mapped and locked.
 * We return with mmap_lock still held, but pte unmapped and unlocked.
 */
static vm_fault_t do_wp_page(struct vm_fault *vmf)
	__releases(vmf->ptl)
{
	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;
	struct vm_area_struct *vma = vmf->vma;

	VM_BUG_ON(unshare && (vmf->flags & FAULT_FLAG_WRITE));
	VM_BUG_ON(!unshare && !(vmf->flags & FAULT_FLAG_WRITE));

	if (likely(!unshare)) {
		if (userfaultfd_pte_wp(vma, *vmf->pte)) {
			pte_unmap_unlock(vmf->pte, vmf->ptl);
			return handle_userfault(vmf, VM_UFFD_WP);
		}

		/*
		 * Userfaultfd write-protect can defer flushes. Ensure the TLB
		 * is flushed in this case before copying.
		 */
		if (unlikely(userfaultfd_wp(vmf->vma) &&
			     mm_tlb_flush_pending(vmf->vma->vm_mm)))
			flush_tlb_page(vmf->vma, vmf->address);
	}

	vmf->page = vm_normal_page(vma, vmf->address, vmf->orig_pte);
	if (!vmf->page) {
		if (unlikely(unshare)) {
			/* No anonymous page -> nothing to do. */
			pte_unmap_unlock(vmf->pte, vmf->ptl);
			return 0;
		}

		/*
		 * VM_MIXEDMAP !pfn_valid() case, or VM_SOFTDIRTY clear on a
		 * VM_PFNMAP VMA.
		 *
		 * We should not cow pages in a shared writeable mapping.
		 * Just mark the pages writable and/or call ops->pfn_mkwrite.
		 */
		if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
				     (VM_WRITE|VM_SHARED))
			return wp_pfn_shared(vmf);

		pte_unmap_unlock(vmf->pte, vmf->ptl);
		return wp_page_copy(vmf);
	}

	/*
	 * Take out anonymous pages first, anonymous shared vmas are
	 * not dirty accountable.
	 */
	if (PageAnon(vmf->page)) {
		struct page *page = vmf->page;

		/*
		 * If the page is exclusive to this process we must reuse the
		 * page without further checks.
		 */
		if (PageAnonExclusive(page))
			goto reuse;

		/*
		 * We have to verify under page lock: these early checks are
		 * just an optimization to avoid locking the page and freeing
		 * the swapcache if there is little hope that we can reuse.
		 *
		 * PageKsm() doesn't necessarily raise the page refcount.
		 */
		if (PageKsm(page) || page_count(page) > 3)
			goto copy;
		if (!PageLRU(page))
			/*
			 * Note: We cannot easily detect+handle references from
			 * remote LRU pagevecs or references to PageLRU() pages.
			 */
			lru_add_drain();
		if (page_count(page) > 1 + PageSwapCache(page))
			goto copy;
		if (!trylock_page(page))
			goto copy;
		if (PageSwapCache(page))
			try_to_free_swap(page);
		if (PageKsm(page) || page_count(page) != 1) {
			unlock_page(page);
			goto copy;
		}
		/*
		 * Ok, we've got the only page reference from our mapping
		 * and the page is locked, it's dark out, and we're wearing
		 * sunglasses. Hit it.
		 */
		page_move_anon_rmap(page, vma);
		unlock_page(page);
reuse:
		if (unlikely(unshare)) {
			pte_unmap_unlock(vmf->pte, vmf->ptl);
			return 0;
		}
		wp_page_reuse(vmf);
		return VM_FAULT_WRITE;
	} else if (unshare) {
		/* No anonymous page -> nothing to do. */
		pte_unmap_unlock(vmf->pte, vmf->ptl);
		return 0;
	} else if (unlikely((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
					(VM_WRITE|VM_SHARED))) {
		return wp_page_shared(vmf);
	}
copy:
	/*
	 * Ok, we need to copy. Oh, well..
	 */
	get_page(vmf->page);

	pte_unmap_unlock(vmf->pte, vmf->ptl);
#ifdef CONFIG_KSM
	if (PageKsm(vmf->page))
		count_vm_event(COW_KSM);
#endif
	return wp_page_copy(vmf);
}

static void unmap_mapping_range_vma(struct vm_area_struct *vma,
		unsigned long start_addr, unsigned long end_addr,
		struct zap_details *details)
{
	zap_page_range_single(vma, start_addr, end_addr - start_addr, details);
}

static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
					    pgoff_t first_index,
					    pgoff_t last_index,
					    struct zap_details *details)
{
	struct vm_area_struct *vma;
	pgoff_t vba, vea, zba, zea;

	vma_interval_tree_foreach(vma, root, first_index, last_index) {
		vba = vma->vm_pgoff;
		vea = vba + vma_pages(vma) - 1;
		zba = max(first_index, vba);
		zea = min(last_index, vea);

		unmap_mapping_range_vma(vma,
			((zba - vba) << PAGE_SHIFT) + vma->vm_start,
			((zea - vba + 1) << PAGE_SHIFT) + vma->vm_start,
				details);
	}
}

/**
 * unmap_mapping_folio() - Unmap single folio from processes.
 * @folio: The locked folio to be unmapped.
 *
 * Unmap this folio from any userspace process which still has it mmaped.
 * Typically, for efficiency, the range of nearby pages has already been
 * unmapped by unmap_mapping_pages() or unmap_mapping_range().  But once
 * truncation or invalidation holds the lock on a folio, it may find that
 * the page has been remapped again: and then uses unmap_mapping_folio()
 * to unmap it finally.
 */
void unmap_mapping_folio(struct folio *folio)
{
	struct address_space *mapping = folio->mapping;
	struct zap_details details = { };
	pgoff_t	first_index;
	pgoff_t	last_index;

	VM_BUG_ON(!folio_test_locked(folio));

	first_index = folio->index;
	last_index = folio->index + folio_nr_pages(folio) - 1;

	details.even_cows = false;
	details.single_folio = folio;
	details.zap_flags = ZAP_FLAG_DROP_MARKER;

	i_mmap_lock_read(mapping);
	if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
		unmap_mapping_range_tree(&mapping->i_mmap, first_index,
					 last_index, &details);
	i_mmap_unlock_read(mapping);
}

/**
 * unmap_mapping_pages() - Unmap pages from processes.
 * @mapping: The address space containing pages to be unmapped.
 * @start: Index of first page to be unmapped.
 * @nr: Number of pages to be unmapped.  0 to unmap to end of file.
 * @even_cows: Whether to unmap even private COWed pages.
 *
 * Unmap the pages in this address space from any userspace process which
 * has them mmaped.  Generally, you want to remove COWed pages as well when
 * a file is being truncated, but not when invalidating pages from the page
 * cache.
 */
void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
		pgoff_t nr, bool even_cows)
{
	struct zap_details details = { };
	pgoff_t	first_index = start;
	pgoff_t	last_index = start + nr - 1;

	details.even_cows = even_cows;
	if (last_index < first_index)
		last_index = ULONG_MAX;

	i_mmap_lock_read(mapping);
	if (unlikely(!RB_EMPTY_ROOT(&mapping->i_mmap.rb_root)))
		unmap_mapping_range_tree(&mapping->i_mmap, first_index,
					 last_index, &details);
	i_mmap_unlock_read(mapping);
}
EXPORT_SYMBOL_GPL(unmap_mapping_pages);

/**
 * unmap_mapping_range - unmap the portion of all mmaps in the specified
 * address_space corresponding to the specified byte range in the underlying
 * file.
 *
 * @mapping: the address space containing mmaps to be unmapped.
 * @holebegin: byte in first page to unmap, relative to the start of
 * the underlying file.  This will be rounded down to a PAGE_SIZE
 * boundary.  Note that this is different from truncate_pagecache(), which
 * must keep the partial page.  In contrast, we must get rid of
 * partial pages.
 * @holelen: size of prospective hole in bytes.  This will be rounded
 * up to a PAGE_SIZE boundary.  A holelen of zero truncates to the
 * end of the file.
 * @even_cows: 1 when truncating a file, unmap even private COWed pages;
 * but 0 when invalidating pagecache, don't throw away private data.
 */
void unmap_mapping_range(struct address_space *mapping,
		loff_t const holebegin, loff_t const holelen, int even_cows)
{
	pgoff_t hba = holebegin >> PAGE_SHIFT;
	pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;

	/* Check for overflow. */
	if (sizeof(holelen) > sizeof(hlen)) {
		long long holeend =
			(holebegin + holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
		if (holeend & ~(long long)ULONG_MAX)
			hlen = ULONG_MAX - hba + 1;
	}

	unmap_mapping_pages(mapping, hba, hlen, even_cows);
}
EXPORT_SYMBOL(unmap_mapping_range);

/*
 * Restore a potential device exclusive pte to a working pte entry
 */
static vm_fault_t remove_device_exclusive_entry(struct vm_fault *vmf)
{
	struct page *page = vmf->page;
	struct vm_area_struct *vma = vmf->vma;
	struct mmu_notifier_range range;

	if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags))
		return VM_FAULT_RETRY;
	mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, vma,
				vma->vm_mm, vmf->address & PAGE_MASK,
				(vmf->address & PAGE_MASK) + PAGE_SIZE, NULL);
	mmu_notifier_invalidate_range_start(&range);

	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
				&vmf->ptl);
	if (likely(pte_same(*vmf->pte, vmf->orig_pte)))
		restore_exclusive_pte(vma, page, vmf->address, vmf->pte);

	pte_unmap_unlock(vmf->pte, vmf->ptl);
	unlock_page(page);

	mmu_notifier_invalidate_range_end(&range);
	return 0;
}

static inline bool should_try_to_free_swap(struct page *page,
					   struct vm_area_struct *vma,
					   unsigned int fault_flags)
{
	if (!PageSwapCache(page))
		return false;
	if (mem_cgroup_swap_full(page) || (vma->vm_flags & VM_LOCKED) ||
	    PageMlocked(page))
		return true;
	/*
	 * If we want to map a page that's in the swapcache writable, we
	 * have to detect via the refcount if we're really the exclusive
	 * user. Try freeing the swapcache to get rid of the swapcache
	 * reference only in case it's likely that we'll be the exlusive user.
	 */
	return (fault_flags & FAULT_FLAG_WRITE) && !PageKsm(page) &&
		page_count(page) == 2;
}

static vm_fault_t pte_marker_clear(struct vm_fault *vmf)
{
	vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd,
				       vmf->address, &vmf->ptl);
	/*
	 * Be careful so that we will only recover a special uffd-wp pte into a
	 * none pte.  Otherwise it means the pte could have changed, so retry.
	 */
	if (is_pte_marker(*vmf->pte))
		pte_clear(vmf->vma->vm_mm, vmf->address, vmf->pte);
	pte_unmap_unlock(vmf->pte, vmf->ptl);
	return 0;
}

/*
 * This is actually a page-missing access, but with uffd-wp special pte
 * installed.  It means this pte was wr-protected before being unmapped.
 */
static vm_fault_t pte_marker_handle_uffd_wp(struct vm_fault *vmf)
{
	/*
	 * Just in case there're leftover special ptes even after the region
	 * got unregistered - we can simply clear them.  We can also do that
	 * proactively when e.g. when we do UFFDIO_UNREGISTER upon some uffd-wp
	 * ranges, but it should be more efficient to be done lazily here.
	 */
	if (unlikely(!userfaultfd_wp(vmf->vma) || vma_is_anonymous(vmf->vma)))
		return pte_marker_clear(vmf);

	/* do_fault() can handle pte markers too like none pte */
	return do_fault(vmf);
}

static vm_fault_t handle_pte_marker(struct vm_fault *vmf)
{
	swp_entry_t entry = pte_to_swp_entry(vmf->orig_pte);
	unsigned long marker = pte_marker_get(entry);

	/*
	 * PTE markers should always be with file-backed memories, and the
	 * marker should never be empty.  If anything weird happened, the best
	 * thing to do is to kill the process along with its mm.
	 */
	if (WARN_ON_ONCE(vma_is_anonymous(vmf->vma) || !marker))
		return VM_FAULT_SIGBUS;

	if (pte_marker_entry_uffd_wp(entry))
		return pte_marker_handle_uffd_wp(vmf);

	/* This is an unknown pte marker */
	return VM_FAULT_SIGBUS;
}

/*
 * We enter with non-exclusive mmap_lock (to exclude vma changes,
 * but allow concurrent faults), and pte mapped but not yet locked.
 * We return with pte unmapped and unlocked.
 *
 * We return with the mmap_lock locked or unlocked in the same cases
 * as does filemap_fault().
 */
vm_fault_t do_swap_page(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct page *page = NULL, *swapcache;
	struct swap_info_struct *si = NULL;
	rmap_t rmap_flags = RMAP_NONE;
	bool exclusive = false;
	swp_entry_t entry;
	pte_t pte;
	int locked;
	vm_fault_t ret = 0;
	void *shadow = NULL;

	if (!pte_unmap_same(vmf))
		goto out;

	entry = pte_to_swp_entry(vmf->orig_pte);
	if (unlikely(non_swap_entry(entry))) {
		if (is_migration_entry(entry)) {
			migration_entry_wait(vma->vm_mm, vmf->pmd,
					     vmf->address);
		} else if (is_device_exclusive_entry(entry)) {
			vmf->page = pfn_swap_entry_to_page(entry);
			ret = remove_device_exclusive_entry(vmf);
		} else if (is_device_private_entry(entry)) {
			vmf->page = pfn_swap_entry_to_page(entry);
			ret = vmf->page->pgmap->ops->migrate_to_ram(vmf);
		} else if (is_hwpoison_entry(entry)) {
			ret = VM_FAULT_HWPOISON;
		} else if (is_swapin_error_entry(entry)) {
			ret = VM_FAULT_SIGBUS;
		} else if (is_pte_marker_entry(entry)) {
			ret = handle_pte_marker(vmf);
		} else {
			print_bad_pte(vma, vmf->address, vmf->orig_pte, NULL);
			ret = VM_FAULT_SIGBUS;
		}
		goto out;
	}

	/* Prevent swapoff from happening to us. */
	si = get_swap_device(entry);
	if (unlikely(!si))
		goto out;

	page = lookup_swap_cache(entry, vma, vmf->address);
	swapcache = page;

	if (!page) {
		if (data_race(si->flags & SWP_SYNCHRONOUS_IO) &&
		    __swap_count(entry) == 1) {
			/* skip swapcache */
			page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma,
							vmf->address);
			if (page) {
				__SetPageLocked(page);
				__SetPageSwapBacked(page);

				if (mem_cgroup_swapin_charge_page(page,
					vma->vm_mm, GFP_KERNEL, entry)) {
					ret = VM_FAULT_OOM;
					goto out_page;
				}
				mem_cgroup_swapin_uncharge_swap(entry);

				shadow = get_shadow_from_swap_cache(entry);
				if (shadow)
					workingset_refault(page_folio(page),
								shadow);

				lru_cache_add(page);

				/* To provide entry to swap_readpage() */
				set_page_private(page, entry.val);
				swap_readpage(page, true, NULL);
				set_page_private(page, 0);
			}
		} else {
			page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
						vmf);
			swapcache = page;
		}

		if (!page) {
			/*
			 * Back out if somebody else faulted in this pte
			 * while we released the pte lock.
			 */
			vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
					vmf->address, &vmf->ptl);
			if (likely(pte_same(*vmf->pte, vmf->orig_pte)))
				ret = VM_FAULT_OOM;
			goto unlock;
		}

		/* Had to read the page from swap area: Major fault */
		ret = VM_FAULT_MAJOR;
		count_vm_event(PGMAJFAULT);
		count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
	} else if (PageHWPoison(page)) {
		/*
		 * hwpoisoned dirty swapcache pages are kept for killing
		 * owner processes (which may be unknown at hwpoison time)
		 */
		ret = VM_FAULT_HWPOISON;
		goto out_release;
	}

	locked = lock_page_or_retry(page, vma->vm_mm, vmf->flags);

	if (!locked) {
		ret |= VM_FAULT_RETRY;
		goto out_release;
	}

	if (swapcache) {
		/*
		 * Make sure try_to_free_swap or swapoff did not release the
		 * swapcache from under us.  The page pin, and pte_same test
		 * below, are not enough to exclude that.  Even if it is still
		 * swapcache, we need to check that the page's swap has not
		 * changed.
		 */
		if (unlikely(!PageSwapCache(page) ||
			     page_private(page) != entry.val))
			goto out_page;

		/*
		 * KSM sometimes has to copy on read faults, for example, if
		 * page->index of !PageKSM() pages would be nonlinear inside the
		 * anon VMA -- PageKSM() is lost on actual swapout.
		 */
		page = ksm_might_need_to_copy(page, vma, vmf->address);
		if (unlikely(!page)) {
			ret = VM_FAULT_OOM;
			page = swapcache;
			goto out_page;
		}

		/*
		 * If we want to map a page that's in the swapcache writable, we
		 * have to detect via the refcount if we're really the exclusive
		 * owner. Try removing the extra reference from the local LRU
		 * pagevecs if required.
		 */
		if ((vmf->flags & FAULT_FLAG_WRITE) && page == swapcache &&
		    !PageKsm(page) && !PageLRU(page))
			lru_add_drain();
	}

	cgroup_throttle_swaprate(page, GFP_KERNEL);

	/*
	 * Back out if somebody else already faulted in this pte.
	 */
	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
			&vmf->ptl);
	if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte)))
		goto out_nomap;

	if (unlikely(!PageUptodate(page))) {
		ret = VM_FAULT_SIGBUS;
		goto out_nomap;
	}

	/*
	 * PG_anon_exclusive reuses PG_mappedtodisk for anon pages. A swap pte
	 * must never point at an anonymous page in the swapcache that is
	 * PG_anon_exclusive. Sanity check that this holds and especially, that
	 * no filesystem set PG_mappedtodisk on a page in the swapcache. Sanity
	 * check after taking the PT lock and making sure that nobody
	 * concurrently faulted in this page and set PG_anon_exclusive.
	 */
	BUG_ON(!PageAnon(page) && PageMappedToDisk(page));
	BUG_ON(PageAnon(page) && PageAnonExclusive(page));

	/*
	 * Check under PT lock (to protect against concurrent fork() sharing
	 * the swap entry concurrently) for certainly exclusive pages.
	 */
	if (!PageKsm(page)) {
		/*
		 * Note that pte_swp_exclusive() == false for architectures
		 * without __HAVE_ARCH_PTE_SWP_EXCLUSIVE.
		 */
		exclusive = pte_swp_exclusive(vmf->orig_pte);
		if (page != swapcache) {
			/*
			 * We have a fresh page that is not exposed to the
			 * swapcache -> certainly exclusive.
			 */
			exclusive = true;
		} else if (exclusive && PageWriteback(page) &&
			  data_race(si->flags & SWP_STABLE_WRITES)) {
			/*
			 * This is tricky: not all swap backends support
			 * concurrent page modifications while under writeback.
			 *
			 * So if we stumble over such a page in the swapcache
			 * we must not set the page exclusive, otherwise we can
			 * map it writable without further checks and modify it
			 * while still under writeback.
			 *
			 * For these problematic swap backends, simply drop the
			 * exclusive marker: this is perfectly fine as we start
			 * writeback only if we fully unmapped the page and
			 * there are no unexpected references on the page after
			 * unmapping succeeded. After fully unmapped, no
			 * further GUP references (FOLL_GET and FOLL_PIN) can
			 * appear, so dropping the exclusive marker and mapping
			 * it only R/O is fine.
			 */
			exclusive = false;
		}
	}

	/*
	 * Remove the swap entry and conditionally try to free up the swapcache.
	 * We're already holding a reference on the page but haven't mapped it
	 * yet.
	 */
	swap_free(entry);
	if (should_try_to_free_swap(page, vma, vmf->flags))
		try_to_free_swap(page);

	inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
	dec_mm_counter_fast(vma->vm_mm, MM_SWAPENTS);
	pte = mk_pte(page, vma->vm_page_prot);

	/*
	 * Same logic as in do_wp_page(); however, optimize for pages that are
	 * certainly not shared either because we just allocated them without
	 * exposing them to the swapcache or because the swap entry indicates
	 * exclusivity.
	 */
	if (!PageKsm(page) && (exclusive || page_count(page) == 1)) {
		if (vmf->flags & FAULT_FLAG_WRITE) {
			pte = maybe_mkwrite(pte_mkdirty(pte), vma);
			vmf->flags &= ~FAULT_FLAG_WRITE;
			ret |= VM_FAULT_WRITE;
		}
		rmap_flags |= RMAP_EXCLUSIVE;
	}
	flush_icache_page(vma, page);
	if (pte_swp_soft_dirty(vmf->orig_pte))
		pte = pte_mksoft_dirty(pte);
	if (pte_swp_uffd_wp(vmf->orig_pte)) {
		pte = pte_mkuffd_wp(pte);
		pte = pte_wrprotect(pte);
	}
	vmf->orig_pte = pte;

	/* ksm created a completely new copy */
	if (unlikely(page != swapcache && swapcache)) {
		page_add_new_anon_rmap(page, vma, vmf->address);
		lru_cache_add_inactive_or_unevictable(page, vma);
	} else {
		page_add_anon_rmap(page, vma, vmf->address, rmap_flags);
	}

	VM_BUG_ON(!PageAnon(page) || (pte_write(pte) && !PageAnonExclusive(page)));
	set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte);
	arch_do_swap_page(vma->vm_mm, vma, vmf->address, pte, vmf->orig_pte);

	unlock_page(page);
	if (page != swapcache && swapcache) {
		/*
		 * Hold the lock to avoid the swap entry to be reused
		 * until we take the PT lock for the pte_same() check
		 * (to avoid false positives from pte_same). For
		 * further safety release the lock after the swap_free
		 * so that the swap count won't change under a
		 * parallel locked swapcache.
		 */
		unlock_page(swapcache);
		put_page(swapcache);
	}

	if (vmf->flags & FAULT_FLAG_WRITE) {
		ret |= do_wp_page(vmf);
		if (ret & VM_FAULT_ERROR)
			ret &= VM_FAULT_ERROR;
		goto out;
	}

	/* No need to invalidate - it was non-present before */
	update_mmu_cache(vma, vmf->address, vmf->pte);
unlock:
	pte_unmap_unlock(vmf->pte, vmf->ptl);
out:
	if (si)
		put_swap_device(si);
	return ret;
out_nomap:
	pte_unmap_unlock(vmf->pte, vmf->ptl);
out_page:
	unlock_page(page);
out_release:
	put_page(page);
	if (page != swapcache && swapcache) {
		unlock_page(swapcache);
		put_page(swapcache);
	}
	if (si)
		put_swap_device(si);
	return ret;
}

/*
 * We enter with non-exclusive mmap_lock (to exclude vma changes,
 * but allow concurrent faults), and pte mapped but not yet locked.
 * We return with mmap_lock still held, but pte unmapped and unlocked.
 */
static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct page *page;
	vm_fault_t ret = 0;
	pte_t entry;

	/* File mapping without ->vm_ops ? */
	if (vma->vm_flags & VM_SHARED)
		return VM_FAULT_SIGBUS;

	/*
	 * Use pte_alloc() instead of pte_alloc_map().  We can't run
	 * pte_offset_map() on pmds where a huge pmd might be created
	 * from a different thread.
	 *
	 * pte_alloc_map() is safe to use under mmap_write_lock(mm) or when
	 * parallel threads are excluded by other means.
	 *
	 * Here we only have mmap_read_lock(mm).
	 */
	if (pte_alloc(vma->vm_mm, vmf->pmd))
		return VM_FAULT_OOM;

	/* See comment in handle_pte_fault() */
	if (unlikely(pmd_trans_unstable(vmf->pmd)))
		return 0;

	/* Use the zero-page for reads */
	if (!(vmf->flags & FAULT_FLAG_WRITE) &&
			!mm_forbids_zeropage(vma->vm_mm)) {
		entry = pte_mkspecial(pfn_pte(my_zero_pfn(vmf->address),
						vma->vm_page_prot));
		vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
				vmf->address, &vmf->ptl);
		if (!pte_none(*vmf->pte)) {
			update_mmu_tlb(vma, vmf->address, vmf->pte);
			goto unlock;
		}
		ret = check_stable_address_space(vma->vm_mm);
		if (ret)
			goto unlock;
		/* Deliver the page fault to userland, check inside PT lock */
		if (userfaultfd_missing(vma)) {
			pte_unmap_unlock(vmf->pte, vmf->ptl);
			return handle_userfault(vmf, VM_UFFD_MISSING);
		}
		goto setpte;
	}

	/* Allocate our own private page. */
	if (unlikely(anon_vma_prepare(vma)))
		goto oom;
	page = alloc_zeroed_user_highpage_movable(vma, vmf->address);
	if (!page)
		goto oom;

	if (mem_cgroup_charge(page_folio(page), vma->vm_mm, GFP_KERNEL))
		goto oom_free_page;
	cgroup_throttle_swaprate(page, GFP_KERNEL);

	/*
	 * The memory barrier inside __SetPageUptodate makes sure that
	 * preceding stores to the page contents become visible before
	 * the set_pte_at() write.
	 */
	__SetPageUptodate(page);

	entry = mk_pte(page, vma->vm_page_prot);
	entry = pte_sw_mkyoung(entry);
	if (vma->vm_flags & VM_WRITE)
		entry = pte_mkwrite(pte_mkdirty(entry));

	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address,
			&vmf->ptl);
	if (!pte_none(*vmf->pte)) {
		update_mmu_cache(vma, vmf->address, vmf->pte);
		goto release;
	}

	ret = check_stable_address_space(vma->vm_mm);
	if (ret)
		goto release;

	/* Deliver the page fault to userland, check inside PT lock */
	if (userfaultfd_missing(vma)) {
		pte_unmap_unlock(vmf->pte, vmf->ptl);
		put_page(page);
		return handle_userfault(vmf, VM_UFFD_MISSING);
	}

	inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
	page_add_new_anon_rmap(page, vma, vmf->address);
	lru_cache_add_inactive_or_unevictable(page, vma);
setpte:
	set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);

	/* No need to invalidate - it was non-present before */
	update_mmu_cache(vma, vmf->address, vmf->pte);
unlock:
	pte_unmap_unlock(vmf->pte, vmf->ptl);
	return ret;
release:
	put_page(page);
	goto unlock;
oom_free_page:
	put_page(page);
oom:
	return VM_FAULT_OOM;
}

/*
 * The mmap_lock must have been held on entry, and may have been
 * released depending on flags and vma->vm_ops->fault() return value.
 * See filemap_fault() and __lock_page_retry().
 */
static vm_fault_t __do_fault(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	vm_fault_t ret;

	/*
	 * Preallocate pte before we take page_lock because this might lead to
	 * deadlocks for memcg reclaim which waits for pages under writeback:
	 *				lock_page(A)
	 *				SetPageWriteback(A)
	 *				unlock_page(A)
	 * lock_page(B)
	 *				lock_page(B)
	 * pte_alloc_one
	 *   shrink_page_list
	 *     wait_on_page_writeback(A)
	 *				SetPageWriteback(B)
	 *				unlock_page(B)
	 *				# flush A, B to clear the writeback
	 */
	if (pmd_none(*vmf->pmd) && !vmf->prealloc_pte) {
		vmf->prealloc_pte = pte_alloc_one(vma->vm_mm);
		if (!vmf->prealloc_pte)
			return VM_FAULT_OOM;
	}

	ret = vma->vm_ops->fault(vmf);
	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY |
			    VM_FAULT_DONE_COW)))
		return ret;

	if (unlikely(PageHWPoison(vmf->page))) {
		struct page *page = vmf->page;
		vm_fault_t poisonret = VM_FAULT_HWPOISON;
		if (ret & VM_FAULT_LOCKED) {
			if (page_mapped(page))
				unmap_mapping_pages(page_mapping(page),
						    page->index, 1, false);
			/* Retry if a clean page was removed from the cache. */
			if (invalidate_inode_page(page))
				poisonret = VM_FAULT_NOPAGE;
			unlock_page(page);
		}
		put_page(page);
		vmf->page = NULL;
		return poisonret;
	}

	if (unlikely(!(ret & VM_FAULT_LOCKED)))
		lock_page(vmf->page);
	else
		VM_BUG_ON_PAGE(!PageLocked(vmf->page), vmf->page);

	return ret;
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void deposit_prealloc_pte(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;

	pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, vmf->prealloc_pte);
	/*
	 * We are going to consume the prealloc table,
	 * count that as nr_ptes.
	 */
	mm_inc_nr_ptes(vma->vm_mm);
	vmf->prealloc_pte = NULL;
}

vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
{
	struct vm_area_struct *vma = vmf->vma;
	bool write = vmf->flags & FAULT_FLAG_WRITE;
	unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
	pmd_t entry;
	int i;
	vm_fault_t ret = VM_FAULT_FALLBACK;

	if (!transhuge_vma_suitable(vma, haddr))
		return ret;

	page = compound_head(page);
	if (compound_order(page) != HPAGE_PMD_ORDER)
		return ret;

	/*
	 * Just backoff if any subpage of a THP is corrupted otherwise
	 * the corrupted page may mapped by PMD silently to escape the
	 * check.  This kind of THP just can be PTE mapped.  Access to
	 * the corrupted subpage should trigger SIGBUS as expected.
	 */
	if (unlikely(PageHasHWPoisoned(page)))
		return ret;

	/*
	 * Archs like ppc64 need additional space to store information
	 * related to pte entry. Use the preallocated table for that.
	 */
	if (arch_needs_pgtable_deposit() && !vmf->prealloc_pte) {
		vmf->prealloc_pte = pte_alloc_one(vma->vm_mm);
		if (!vmf->prealloc_pte)
			return VM_FAULT_OOM;
	}

	vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
	if (unlikely(!pmd_none(*vmf->pmd)))
		goto out;

	for (i = 0; i < HPAGE_PMD_NR; i++)
		flush_icache_page(vma, page + i);

	entry = mk_huge_pmd(page, vma->vm_page_prot);
	if (write)
		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);

	add_mm_counter(vma->vm_mm, mm_counter_file(page), HPAGE_PMD_NR);
	page_add_file_rmap(page, vma, true);

	/*
	 * deposit and withdraw with pmd lock held
	 */
	if (arch_needs_pgtable_deposit())
		deposit_prealloc_pte(vmf);

	set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);

	update_mmu_cache_pmd(vma, haddr, vmf->pmd);

	/* fault is handled */
	ret = 0;
	count_vm_event(THP_FILE_MAPPED);
out:
	spin_unlock(vmf->ptl);
	return ret;
}
#else
vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
{
	return VM_FAULT_FALLBACK;
}
#endif

void do_set_pte(struct vm_fault *vmf, struct page *page, unsigned long addr)
{
	struct vm_area_struct *vma = vmf->vma;
	bool uffd_wp = pte_marker_uffd_wp(vmf->orig_pte);
	bool write = vmf->flags & FAULT_FLAG_WRITE;
	bool prefault = vmf->address != addr;
	pte_t entry;

	flush_icache_page(vma, page);
	entry = mk_pte(page, vma->vm_page_prot);

	if (prefault && arch_wants_old_prefaulted_pte())
		entry = pte_mkold(entry);
	else
		entry = pte_sw_mkyoung(entry);

	if (write)
		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
	if (unlikely(uffd_wp))
		entry = pte_mkuffd_wp(pte_wrprotect(entry));
	/* copy-on-write page */
	if (write && !(vma->vm_flags & VM_SHARED)) {
		inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
		page_add_new_anon_rmap(page, vma, addr);
		lru_cache_add_inactive_or_unevictable(page, vma);
	} else {
		inc_mm_counter_fast(vma->vm_mm, mm_counter_file(page));
		page_add_file_rmap(page, vma, false);
	}
	set_pte_at(vma->vm_mm, addr, vmf->pte, entry);
}

static bool vmf_pte_changed(struct vm_fault *vmf)
{
	if (vmf->flags & FAULT_FLAG_ORIG_PTE_VALID)
		return !pte_same(*vmf->pte, vmf->orig_pte);

	return !pte_none(*vmf->pte);
}

/**
 * finish_fault - finish page fault once we have prepared the page to fault
 *
 * @vmf: structure describing the fault
 *
 * This function handles all that is needed to finish a page fault once the
 * page to fault in is prepared. It handles locking of PTEs, inserts PTE for
 * given page, adds reverse page mapping, handles memcg charges and LRU
 * addition.
 *
 * The function expects the page to be locked and on success it consumes a
 * reference of a page being mapped (for the PTE which maps it).
 *
 * Return: %0 on success, %VM_FAULT_ code in case of error.
 */
vm_fault_t finish_fault(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct page *page;
	vm_fault_t ret;

	/* Did we COW the page? */
	if ((vmf->flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED))
		page = vmf->cow_page;
	else
		page = vmf->page;

	/*
	 * check even for read faults because we might have lost our CoWed
	 * page
	 */
	if (!(vma->vm_flags & VM_SHARED)) {
		ret = check_stable_address_space(vma->vm_mm);
		if (ret)
			return ret;
	}

	if (pmd_none(*vmf->pmd)) {
		if (PageTransCompound(page)) {
			ret = do_set_pmd(vmf, page);
			if (ret != VM_FAULT_FALLBACK)
				return ret;
		}

		if (vmf->prealloc_pte)
			pmd_install(vma->vm_mm, vmf->pmd, &vmf->prealloc_pte);
		else if (unlikely(pte_alloc(vma->vm_mm, vmf->pmd)))
			return VM_FAULT_OOM;
	}

	/* See comment in handle_pte_fault() */
	if (pmd_devmap_trans_unstable(vmf->pmd))
		return 0;

	vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd,
				      vmf->address, &vmf->ptl);
	ret = 0;
	/* Re-check under ptl */
	if (likely(!vmf_pte_changed(vmf)))
		do_set_pte(vmf, page, vmf->address);
	else
		ret = VM_FAULT_NOPAGE;

	update_mmu_tlb(vma, vmf->address, vmf->pte);
	pte_unmap_unlock(vmf->pte, vmf->ptl);
	return ret;
}

static unsigned long fault_around_bytes __read_mostly =
	rounddown_pow_of_two(65536);

#ifdef CONFIG_DEBUG_FS
static int fault_around_bytes_get(void *data, u64 *val)
{
	*val = fault_around_bytes;
	return 0;
}

/*
 * fault_around_bytes must be rounded down to the nearest page order as it's
 * what do_fault_around() expects to see.
 */
static int fault_around_bytes_set(void *data, u64 val)
{
	if (val / PAGE_SIZE > PTRS_PER_PTE)
		return -EINVAL;
	if (val > PAGE_SIZE)
		fault_around_bytes = rounddown_pow_of_two(val);
	else
		fault_around_bytes = PAGE_SIZE; /* rounddown_pow_of_two(0) is undefined */
	return 0;
}
DEFINE_DEBUGFS_ATTRIBUTE(fault_around_bytes_fops,
		fault_around_bytes_get, fault_around_bytes_set, "%llu\n");

static int __init fault_around_debugfs(void)
{
	debugfs_create_file_unsafe("fault_around_bytes", 0644, NULL, NULL,
				   &fault_around_bytes_fops);
	return 0;
}
late_initcall(fault_around_debugfs);
#endif

/*
 * do_fault_around() tries to map few pages around the fault address. The hope
 * is that the pages will be needed soon and this will lower the number of
 * faults to handle.
 *
 * It uses vm_ops->map_pages() to map the pages, which skips the page if it's
 * not ready to be mapped: not up-to-date, locked, etc.
 *
 * This function is called with the page table lock taken. In the split ptlock
 * case the page table lock only protects only those entries which belong to
 * the page table corresponding to the fault address.
 *
 * This function doesn't cross the VMA boundaries, in order to call map_pages()
 * only once.
 *
 * fault_around_bytes defines how many bytes we'll try to map.
 * do_fault_around() expects it to be set to a power of two less than or equal
 * to PTRS_PER_PTE.
 *
 * The virtual address of the area that we map is naturally aligned to
 * fault_around_bytes rounded down to the machine page size
 * (and therefore to page order).  This way it's easier to guarantee
 * that we don't cross page table boundaries.
 */
static vm_fault_t do_fault_around(struct vm_fault *vmf)
{
	unsigned long address = vmf->address, nr_pages, mask;
	pgoff_t start_pgoff = vmf->pgoff;
	pgoff_t end_pgoff;
	int off;

	nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT;
	mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK;

	address = max(address & mask, vmf->vma->vm_start);
	off = ((vmf->address - address) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
	start_pgoff -= off;

	/*
	 *  end_pgoff is either the end of the page table, the end of
	 *  the vma or nr_pages from start_pgoff, depending what is nearest.
	 */
	end_pgoff = start_pgoff -
		((address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)) +
		PTRS_PER_PTE - 1;
	end_pgoff = min3(end_pgoff, vma_pages(vmf->vma) + vmf->vma->vm_pgoff - 1,
			start_pgoff + nr_pages - 1);

	if (pmd_none(*vmf->pmd)) {
		vmf->prealloc_pte = pte_alloc_one(vmf->vma->vm_mm);
		if (!vmf->prealloc_pte)
			return VM_FAULT_OOM;
	}

	return vmf->vma->vm_ops->map_pages(vmf, start_pgoff, end_pgoff);
}

/* Return true if we should do read fault-around, false otherwise */
static inline bool should_fault_around(struct vm_fault *vmf)
{
	/* No ->map_pages?  No way to fault around... */
	if (!vmf->vma->vm_ops->map_pages)
		return false;

	if (uffd_disable_fault_around(vmf->vma))
		return false;

	return fault_around_bytes >> PAGE_SHIFT > 1;
}

static vm_fault_t do_read_fault(struct vm_fault *vmf)
{
	vm_fault_t ret = 0;

	/*
	 * Let's call ->map_pages() first and use ->fault() as fallback
	 * if page by the offset is not ready to be mapped (cold cache or
	 * something).
	 */
	if (should_fault_around(vmf)) {
		ret = do_fault_around(vmf);
		if (ret)
			return ret;
	}

	ret = __do_fault(vmf);
	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
		return ret;

	ret |= finish_fault(vmf);
	unlock_page(vmf->page);
	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
		put_page(vmf->page);
	return ret;
}

static vm_fault_t do_cow_fault(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	vm_fault_t ret;

	if (unlikely(anon_vma_prepare(vma)))
		return VM_FAULT_OOM;

	vmf->cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address);
	if (!vmf->cow_page)
		return VM_FAULT_OOM;

	if (mem_cgroup_charge(page_folio(vmf->cow_page), vma->vm_mm,
				GFP_KERNEL)) {
		put_page(vmf->cow_page);
		return VM_FAULT_OOM;
	}
	cgroup_throttle_swaprate(vmf->cow_page, GFP_KERNEL);

	ret = __do_fault(vmf);
	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
		goto uncharge_out;
	if (ret & VM_FAULT_DONE_COW)
		return ret;

	copy_user_highpage(vmf->cow_page, vmf->page, vmf->address, vma);
	__SetPageUptodate(vmf->cow_page);

	ret |= finish_fault(vmf);
	unlock_page(vmf->page);
	put_page(vmf->page);
	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
		goto uncharge_out;
	return ret;
uncharge_out:
	put_page(vmf->cow_page);
	return ret;
}

static vm_fault_t do_shared_fault(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	vm_fault_t ret, tmp;

	ret = __do_fault(vmf);
	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
		return ret;

	/*
	 * Check if the backing address space wants to know that the page is
	 * about to become writable
	 */
	if (vma->vm_ops->page_mkwrite) {
		unlock_page(vmf->page);
		tmp = do_page_mkwrite(vmf);
		if (unlikely(!tmp ||
				(tmp & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))) {
			put_page(vmf->page);
			return tmp;
		}
	}

	ret |= finish_fault(vmf);
	if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE |
					VM_FAULT_RETRY))) {
		unlock_page(vmf->page);
		put_page(vmf->page);
		return ret;
	}

	ret |= fault_dirty_shared_page(vmf);
	return ret;
}

/*
 * We enter with non-exclusive mmap_lock (to exclude vma changes,
 * but allow concurrent faults).
 * The mmap_lock may have been released depending on flags and our
 * return value.  See filemap_fault() and __folio_lock_or_retry().
 * If mmap_lock is released, vma may become invalid (for example
 * by other thread calling munmap()).
 */
static vm_fault_t do_fault(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct mm_struct *vm_mm = vma->vm_mm;
	vm_fault_t ret;

	/*
	 * The VMA was not fully populated on mmap() or missing VM_DONTEXPAND
	 */
	if (!vma->vm_ops->fault) {
		/*
		 * If we find a migration pmd entry or a none pmd entry, which
		 * should never happen, return SIGBUS
		 */
		if (unlikely(!pmd_present(*vmf->pmd)))
			ret = VM_FAULT_SIGBUS;
		else {
			vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm,
						       vmf->pmd,
						       vmf->address,
						       &vmf->ptl);
			/*
			 * Make sure this is not a temporary clearing of pte
			 * by holding ptl and checking again. A R/M/W update
			 * of pte involves: take ptl, clearing the pte so that
			 * we don't have concurrent modification by hardware
			 * followed by an update.
			 */
			if (unlikely(pte_none(*vmf->pte)))
				ret = VM_FAULT_SIGBUS;
			else
				ret = VM_FAULT_NOPAGE;

			pte_unmap_unlock(vmf->pte, vmf->ptl);
		}
	} else if (!(vmf->flags & FAULT_FLAG_WRITE))
		ret = do_read_fault(vmf);
	else if (!(vma->vm_flags & VM_SHARED))
		ret = do_cow_fault(vmf);
	else
		ret = do_shared_fault(vmf);

	/* preallocated pagetable is unused: free it */
	if (vmf->prealloc_pte) {
		pte_free(vm_mm, vmf->prealloc_pte);
		vmf->prealloc_pte = NULL;
	}
	return ret;
}

int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
		      unsigned long addr, int page_nid, int *flags)
{
	get_page(page);

	count_vm_numa_event(NUMA_HINT_FAULTS);
	if (page_nid == numa_node_id()) {
		count_vm_numa_event(NUMA_HINT_FAULTS_LOCAL);
		*flags |= TNF_FAULT_LOCAL;
	}

	return mpol_misplaced(page, vma, addr);
}

static vm_fault_t do_numa_page(struct vm_fault *vmf)
{
	struct vm_area_struct *vma = vmf->vma;
	struct page *page = NULL;
	int page_nid = NUMA_NO_NODE;
	int last_cpupid;
	int target_nid;
	pte_t pte, old_pte;
	bool was_writable = pte_savedwrite(vmf->orig_pte);
	int flags = 0;

	/*
	 * The "pte" at this point cannot be used safely without
	 * validation through pte_unmap_same(). It's of NUMA type but
	 * the pfn may be screwed if the read is non atomic.
	 */
	vmf->ptl = pte_lockptr(vma->vm_mm, vmf->pmd);
	spin_lock(vmf->ptl);
	if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
		pte_unmap_unlock(vmf->pte, vmf->ptl);
		goto out;
	}

	/* Get the normal PTE  */
	old_pte = ptep_get(vmf->pte);
	pte = pte_modify(old_pte, vma->vm_page_prot);

	page = vm_normal_page(vma, vmf->address, pte);
	if (!page)
		goto out_map;

	/* TODO: handle PTE-mapped THP */
	if (PageCompound(page))
		goto out_map;

	/*
	 * Avoid grouping on RO pages in general. RO pages shouldn't hurt as
	 * much anyway since they can be in shared cache state. This misses
	 * the case where a mapping is writable but the process never writes
	 * to it but pte_write gets cleared during protection updates and
	 * pte_dirty has unpredictable behaviour between PTE scan updates,
	 * background writeback, dirty balancing and application behaviour.
	 */
	if (!was_writable)
		flags |= TNF_NO_GROUP;

	/*
	 * Flag if the page is shared between multiple address spaces. This
	 * is later used when determining whether to group tasks together
	 */
	if (page_mapcount(page) > 1 && (vma->vm_flags & VM_SHARED))
		flags |= TNF_SHARED;

	last_cpupid = page_cpupid_last(page);
	page_nid = page_to_nid(page);
	target_nid = numa_migrate_prep(page, vma, vmf->address, page_nid,
			&flags);
	if (target_nid == NUMA_NO_NODE) {
		put_page(page);
		goto out_map;
	}
	pte_unmap_unlock(vmf->pte, vmf->ptl);

	/* Migrate to the requested node */
	if (migrate_misplaced_page(page, vma, target_nid)) {
		page_nid = target_nid;
		flags |= TNF_MIGRATED;
	} else {
		flags |= TNF_MIGRATE_FAIL;
		vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
		spin_lock(vmf->ptl);
		if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) {
			pte_unmap_unlock(vmf->pte, vmf->ptl);
			goto out;
		}
		goto out_map;
	}

out:
	if (page_nid != NUMA_NO_NODE)
		task_numa_fault(last_cpupid, page_nid, 1, flags);
	return 0;
out_map:
	/*
	 * Make it present again, depending on how arch implements
	 * non-accessible ptes, some can allow access by kernel mode.
	 */
	old_pte = ptep_modify_prot_start(vma, vmf->address, vmf->pte);
	pte = pte_modify(old_pte, vma->vm_page_prot);
	pte = pte_mkyoung(pte);
	if (was_writable)
		pte = pte_mkwrite(pte);
	ptep_modify_prot_commit(vma, vmf->address, vmf->pte, old_pte, pte);
	update_mmu_cache(vma, vmf->address, vmf->pte);
	pte_unmap_unlock(vmf->pte, vmf->ptl);
	goto out;
}

static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)
{
	if (vma_is_anonymous(vmf->vma))
		return do_huge_pmd_anonymous_page(vmf);
	if (vmf->vma->vm_ops->huge_fault)
		return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);
	return VM_FAULT_FALLBACK;
}

/* `inline' is required to avoid gcc 4.1.2 build error */
static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf)
{
	const bool unshare = vmf->flags & FAULT_FLAG_UNSHARE;

	if (vma_is_anonymous(vmf->vma)) {
		if (likely(!unshare) &&
		    userfaultfd_huge_pmd_wp(vmf->vma, vmf->orig_pmd))
			return handle_userfault(vmf, VM_UFFD_WP);
		return do_huge_pmd_wp_page(vmf);
	}
	if (vmf->vma->vm_ops->huge_fault) {
		vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PMD);

		if (!(ret & VM_FAULT_FALLBACK))
			return ret;
	}

	/* COW or write-notify handled on pte level: split pmd. */
	__split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL);

	return VM_FAULT_FALLBACK;
}

static vm_fault_t create_huge_pud(struct vm_fault *vmf)
{
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) &&			\
	defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD)
	/* No support for anonymous transparent PUD pages yet */
	if (vma_is_anonymous(vmf->vma))
		goto split;
	if (vmf->vma->vm_ops->huge_fault) {
		vm_fault_t ret = vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);

		if (!(ret & VM_FAULT_FALLBACK))
			return ret;
	}
split:
	/* COW or write-notify not handled on PUD level: split pud.*/
	__split_huge_pud(vmf->vma, vmf->pud, vmf->address);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
	return VM_FAULT_FALLBACK;
}

static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	/* No support for anonymous transparent PUD pages yet */
	if (vma_is_anonymous(vmf->vma))
		return VM_FAULT_FALLBACK;
	if (vmf->vma->vm_ops->huge_fault)
		return vmf->vma->vm_ops->huge_fault(vmf, PE_SIZE_PUD);
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
	return VM_FAULT_FALLBACK;
}

/*
 * These routines also need to handle stuff like marking pages dirty
 * and/or accessed for architectures that don't do it in hardware (most
 * RISC architectures).  The early dirtying is also good on the i386.
 *
 * There is also a hook called "update_mmu_cache()" that architectures
 * with external mmu caches can use to update those (ie the Sparc or
 * PowerPC hashed page tables that act as extended TLBs).
 *
 * We enter with non-exclusive mmap_lock (to exclude vma changes, but allow
 * concurrent faults).
 *
 * The mmap_lock may have been released depending on flags and our return value.
 * See filemap_fault() and __folio_lock_or_retry().
 */
static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
{
	pte_t entry;

	if (unlikely(pmd_none(*vmf->pmd))) {
		/*
		 * Leave __pte_alloc() until later: because vm_ops->fault may
		 * want to allocate huge page, and if we expose page table
		 * for an instant, it will be difficult to retract from
		 * concurrent faults and from rmap lookups.
		 */
		vmf->pte = NULL;
		vmf->flags &= ~FAULT_FLAG_ORIG_PTE_VALID;
	} else {
		/*
		 * If a huge pmd materialized under us just retry later.  Use
		 * pmd_trans_unstable() via pmd_devmap_trans_unstable() instead
		 * of pmd_trans_huge() to ensure the pmd didn't become
		 * pmd_trans_huge under us and then back to pmd_none, as a
		 * result of MADV_DONTNEED running immediately after a huge pmd
		 * fault in a different thread of this mm, in turn leading to a
		 * misleading pmd_trans_huge() retval. All we have to ensure is
		 * that it is a regular pmd that we can walk with
		 * pte_offset_map() and we can do that through an atomic read
		 * in C, which is what pmd_trans_unstable() provides.
		 */
		if (pmd_devmap_trans_unstable(vmf->pmd))
			return 0;
		/*
		 * A regular pmd is established and it can't morph into a huge
		 * pmd from under us anymore at this point because we hold the
		 * mmap_lock read mode and khugepaged takes it in write mode.
		 * So now it's safe to run pte_offset_map().
		 */
		vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
		vmf->orig_pte = *vmf->pte;
		vmf->flags |= FAULT_FLAG_ORIG_PTE_VALID;

		/*
		 * some architectures can have larger ptes than wordsize,
		 * e.g.ppc44x-defconfig has CONFIG_PTE_64BIT=y and
		 * CONFIG_32BIT=y, so READ_ONCE cannot guarantee atomic
		 * accesses.  The code below just needs a consistent view
		 * for the ifs and we later double check anyway with the
		 * ptl lock held. So here a barrier will do.
		 */
		barrier();
		if (pte_none(vmf->orig_pte)) {
			pte_unmap(vmf->pte);
			vmf->pte = NULL;
		}
	}

	if (!vmf->pte) {
		if (vma_is_anonymous(vmf->vma))
			return do_anonymous_page(vmf);
		else
			return do_fault(vmf);
	}

	if (!pte_present(vmf->orig_pte))
		return do_swap_page(vmf);

	if (pte_protnone(vmf->orig_pte) && vma_is_accessible(vmf->vma))
		return do_numa_page(vmf);

	vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
	spin_lock(vmf->ptl);
	entry = vmf->orig_pte;
	if (unlikely(!pte_same(*vmf->pte, entry))) {
		update_mmu_tlb(vmf->vma, vmf->address, vmf->pte);
		goto unlock;
	}
	if (vmf->flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) {
		if (!pte_write(entry))
			return do_wp_page(vmf);
		else if (likely(vmf->flags & FAULT_FLAG_WRITE))
			entry = pte_mkdirty(entry);
	}
	entry = pte_mkyoung(entry);
	if (ptep_set_access_flags(vmf->vma, vmf->address, vmf->pte, entry,
				vmf->flags & FAULT_FLAG_WRITE)) {
		update_mmu_cache(vmf->vma, vmf->address, vmf->pte);
	} else {
		/* Skip spurious TLB flush for retried page fault */
		if (vmf->flags & FAULT_FLAG_TRIED)
			goto unlock;
		/*
		 * This is needed only for protection faults but the arch code
		 * is not yet telling us if this is a protection fault or not.
		 * This still avoids useless tlb flushes for .text page faults
		 * with threads.
		 */
		if (vmf->flags & FAULT_FLAG_WRITE)
			flush_tlb_fix_spurious_fault(vmf->vma, vmf->address);
	}
unlock:
	pte_unmap_unlock(vmf->pte, vmf->ptl);
	return 0;
}

/*
 * By the time we get here, we already hold the mm semaphore
 *
 * The mmap_lock may have been released depending on flags and our
 * return value.  See filemap_fault() and __folio_lock_or_retry().
 */
static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
		unsigned long address, unsigned int flags)
{
	struct vm_fault vmf = {
		.vma = vma,
		.address = address & PAGE_MASK,
		.real_address = address,
		.flags = flags,
		.pgoff = linear_page_index(vma, address),
		.gfp_mask = __get_fault_gfp_mask(vma),
	};
	struct mm_struct *mm = vma->vm_mm;
	pgd_t *pgd;
	p4d_t *p4d;
	vm_fault_t ret;

	pgd = pgd_offset(mm, address);
	p4d = p4d_alloc(mm, pgd, address);
	if (!p4d)
		return VM_FAULT_OOM;

	vmf.pud = pud_alloc(mm, p4d, address);
	if (!vmf.pud)
		return VM_FAULT_OOM;
retry_pud:
	if (pud_none(*vmf.pud) && __transparent_hugepage_enabled(vma)) {
		ret = create_huge_pud(&vmf);
		if (!(ret & VM_FAULT_FALLBACK))
			return ret;
	} else {
		pud_t orig_pud = *vmf.pud;

		barrier();
		if (pud_trans_huge(orig_pud) || pud_devmap(orig_pud)) {

			/*
			 * TODO once we support anonymous PUDs: NUMA case and
			 * FAULT_FLAG_UNSHARE handling.
			 */
			if ((flags & FAULT_FLAG_WRITE) && !pud_write(orig_pud)) {
				ret = wp_huge_pud(&vmf, orig_pud);
				if (!(ret & VM_FAULT_FALLBACK))
					return ret;
			} else {
				huge_pud_set_accessed(&vmf, orig_pud);
				return 0;
			}
		}
	}

	vmf.pmd = pmd_alloc(mm, vmf.pud, address);
	if (!vmf.pmd)
		return VM_FAULT_OOM;

	/* Huge pud page fault raced with pmd_alloc? */
	if (pud_trans_unstable(vmf.pud))
		goto retry_pud;

	if (pmd_none(*vmf.pmd) && __transparent_hugepage_enabled(vma)) {
		ret = create_huge_pmd(&vmf);
		if (!(ret & VM_FAULT_FALLBACK))
			return ret;
	} else {
		vmf.orig_pmd = *vmf.pmd;

		barrier();
		if (unlikely(is_swap_pmd(vmf.orig_pmd))) {
			VM_BUG_ON(thp_migration_supported() &&
					  !is_pmd_migration_entry(vmf.orig_pmd));
			if (is_pmd_migration_entry(vmf.orig_pmd))
				pmd_migration_entry_wait(mm, vmf.pmd);
			return 0;
		}
		if (pmd_trans_huge(vmf.orig_pmd) || pmd_devmap(vmf.orig_pmd)) {
			if (pmd_protnone(vmf.orig_pmd) && vma_is_accessible(vma))
				return do_huge_pmd_numa_page(&vmf);

			if ((flags & (FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE)) &&
			    !pmd_write(vmf.orig_pmd)) {
				ret = wp_huge_pmd(&vmf);
				if (!(ret & VM_FAULT_FALLBACK))
					return ret;
			} else {
				huge_pmd_set_accessed(&vmf);
				return 0;
			}
		}
	}

	return handle_pte_fault(&vmf);
}

/**
 * mm_account_fault - Do page fault accounting
 *
 * @regs: the pt_regs struct pointer.  When set to NULL, will skip accounting
 *        of perf event counters, but we'll still do the per-task accounting to
 *        the task who triggered this page fault.
 * @address: the faulted address.
 * @flags: the fault flags.
 * @ret: the fault retcode.
 *
 * This will take care of most of the page fault accounting.  Meanwhile, it
 * will also include the PERF_COUNT_SW_PAGE_FAULTS_[MAJ|MIN] perf counter
 * updates.  However, note that the handling of PERF_COUNT_SW_PAGE_FAULTS should
 * still be in per-arch page fault handlers at the entry of page fault.
 */
static inline void mm_account_fault(struct pt_regs *regs,
				    unsigned long address, unsigned int flags,
				    vm_fault_t ret)
{
	bool major;

	/*
	 * We don't do accounting for some specific faults:
	 *
	 * - Unsuccessful faults (e.g. when the address wasn't valid).  That
	 *   includes arch_vma_access_permitted() failing before reaching here.
	 *   So this is not a "this many hardware page faults" counter.  We
	 *   should use the hw profiling for that.
	 *
	 * - Incomplete faults (VM_FAULT_RETRY).  They will only be counted
	 *   once they're completed.
	 */
	if (ret & (VM_FAULT_ERROR | VM_FAULT_RETRY))
		return;

	/*
	 * We define the fault as a major fault when the final successful fault
	 * is VM_FAULT_MAJOR, or if it retried (which implies that we couldn't
	 * handle it immediately previously).
	 */
	major = (ret & VM_FAULT_MAJOR) || (flags & FAULT_FLAG_TRIED);

	if (major)
		current->maj_flt++;
	else
		current->min_flt++;

	/*
	 * If the fault is done for GUP, regs will be NULL.  We only do the
	 * accounting for the per thread fault counters who triggered the
	 * fault, and we skip the perf event updates.
	 */
	if (!regs)
		return;

	if (major)
		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
	else
		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
}

/*
 * By the time we get here, we already hold the mm semaphore
 *
 * The mmap_lock may have been released depending on flags and our
 * return value.  See filemap_fault() and __folio_lock_or_retry().
 */
vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
			   unsigned int flags, struct pt_regs *regs)
{
	vm_fault_t ret;

	__set_current_state(TASK_RUNNING);

	count_vm_event(PGFAULT);
	count_memcg_event_mm(vma->vm_mm, PGFAULT);

	/* do counter updates before entering really critical section. */
	check_sync_rss_stat(current);

	if (!arch_vma_access_permitted(vma, flags & FAULT_FLAG_WRITE,
					    flags & FAULT_FLAG_INSTRUCTION,
					    flags & FAULT_FLAG_REMOTE))
		return VM_FAULT_SIGSEGV;

	/*
	 * Enable the memcg OOM handling for faults triggered in user
	 * space.  Kernel faults are handled more gracefully.
	 */
	if (flags & FAULT_FLAG_USER)
		mem_cgroup_enter_user_fault();

	if (unlikely(is_vm_hugetlb_page(vma)))
		ret = hugetlb_fault(vma->vm_mm, vma, address, flags);
	else
		ret = __handle_mm_fault(vma, address, flags);

	if (flags & FAULT_FLAG_USER) {
		mem_cgroup_exit_user_fault();
		/*
		 * The task may have entered a memcg OOM situation but
		 * if the allocation error was handled gracefully (no
		 * VM_FAULT_OOM), there is no need to kill anything.
		 * Just clean up the OOM state peacefully.
		 */
		if (task_in_memcg_oom(current) && !(ret & VM_FAULT_OOM))
			mem_cgroup_oom_synchronize(false);
	}

	mm_account_fault(regs, address, flags, ret);

	return ret;
}
EXPORT_SYMBOL_GPL(handle_mm_fault);

#ifndef __PAGETABLE_P4D_FOLDED
/*
 * Allocate p4d page table.
 * We've already handled the fast-path in-line.
 */
int __p4d_alloc(struct mm_struct *mm, pgd_t *pgd, unsigned long address)
{
	p4d_t *new = p4d_alloc_one(mm, address);
	if (!new)
		return -ENOMEM;

	spin_lock(&mm->page_table_lock);
	if (pgd_present(*pgd)) {	/* Another has populated it */
		p4d_free(mm, new);
	} else {
		smp_wmb(); /* See comment in pmd_install() */
		pgd_populate(mm, pgd, new);
	}
	spin_unlock(&mm->page_table_lock);
	return 0;
}
#endif /* __PAGETABLE_P4D_FOLDED */

#ifndef __PAGETABLE_PUD_FOLDED
/*
 * Allocate page upper directory.
 * We've already handled the fast-path in-line.
 */
int __pud_alloc(struct mm_struct *mm, p4d_t *p4d, unsigned long address)
{
	pud_t *new = pud_alloc_one(mm, address);
	if (!new)
		return -ENOMEM;

	spin_lock(&mm->page_table_lock);
	if (!p4d_present(*p4d)) {
		mm_inc_nr_puds(mm);
		smp_wmb(); /* See comment in pmd_install() */
		p4d_populate(mm, p4d, new);
	} else	/* Another has populated it */
		pud_free(mm, new);
	spin_unlock(&mm->page_table_lock);
	return 0;
}
#endif /* __PAGETABLE_PUD_FOLDED */

#ifndef __PAGETABLE_PMD_FOLDED
/*
 * Allocate page middle directory.
 * We've already handled the fast-path in-line.
 */
int __pmd_alloc(struct mm_struct *mm, pud_t *pud, unsigned long address)
{
	spinlock_t *ptl;
	pmd_t *new = pmd_alloc_one(mm, address);
	if (!new)
		return -ENOMEM;

	ptl = pud_lock(mm, pud);
	if (!pud_present(*pud)) {
		mm_inc_nr_pmds(mm);
		smp_wmb(); /* See comment in pmd_install() */
		pud_populate(mm, pud, new);
	} else {	/* Another has populated it */
		pmd_free(mm, new);
	}
	spin_unlock(ptl);
	return 0;
}
#endif /* __PAGETABLE_PMD_FOLDED */

/**
 * follow_pte - look up PTE at a user virtual address
 * @mm: the mm_struct of the target address space
 * @address: user virtual address
 * @ptepp: location to store found PTE
 * @ptlp: location to store the lock for the PTE
 *
 * On a successful return, the pointer to the PTE is stored in @ptepp;
 * the corresponding lock is taken and its location is stored in @ptlp.
 * The contents of the PTE are only stable until @ptlp is released;
 * any further use, if any, must be protected against invalidation
 * with MMU notifiers.
 *
 * Only IO mappings and raw PFN mappings are allowed.  The mmap semaphore
 * should be taken for read.
 *
 * KVM uses this function.  While it is arguably less bad than ``follow_pfn``,
 * it is not a good general-purpose API.
 *
 * Return: zero on success, -ve otherwise.
 */
int follow_pte(struct mm_struct *mm, unsigned long address,
	       pte_t **ptepp, spinlock_t **ptlp)
{
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *ptep;

	pgd = pgd_offset(mm, address);
	if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
		goto out;

	p4d = p4d_offset(pgd, address);
	if (p4d_none(*p4d) || unlikely(p4d_bad(*p4d)))
		goto out;

	pud = pud_offset(p4d, address);
	if (pud_none(*pud) || unlikely(pud_bad(*pud)))
		goto out;

	pmd = pmd_offset(pud, address);
	VM_BUG_ON(pmd_trans_huge(*pmd));

	if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
		goto out;

	ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
	if (!pte_present(*ptep))
		goto unlock;
	*ptepp = ptep;
	return 0;
unlock:
	pte_unmap_unlock(ptep, *ptlp);
out:
	return -EINVAL;
}
EXPORT_SYMBOL_GPL(follow_pte);

/**
 * follow_pfn - look up PFN at a user virtual address
 * @vma: memory mapping
 * @address: user virtual address
 * @pfn: location to store found PFN
 *
 * Only IO mappings and raw PFN mappings are allowed.
 *
 * This function does not allow the caller to read the permissions
 * of the PTE.  Do not use it.
 *
 * Return: zero and the pfn at @pfn on success, -ve otherwise.
 */
int follow_pfn(struct vm_area_struct *vma, unsigned long address,
	unsigned long *pfn)
{
	int ret = -EINVAL;
	spinlock_t *ptl;
	pte_t *ptep;

	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
		return ret;

	ret = follow_pte(vma->vm_mm, address, &ptep, &ptl);
	if (ret)
		return ret;
	*pfn = pte_pfn(*ptep);
	pte_unmap_unlock(ptep, ptl);
	return 0;
}
EXPORT_SYMBOL(follow_pfn);

#ifdef CONFIG_HAVE_IOREMAP_PROT
int follow_phys(struct vm_area_struct *vma,
		unsigned long address, unsigned int flags,
		unsigned long *prot, resource_size_t *phys)
{
	int ret = -EINVAL;
	pte_t *ptep, pte;
	spinlock_t *ptl;

	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
		goto out;

	if (follow_pte(vma->vm_mm, address, &ptep, &ptl))
		goto out;
	pte = *ptep;

	if ((flags & FOLL_WRITE) && !pte_write(pte))
		goto unlock;

	*prot = pgprot_val(pte_pgprot(pte));
	*phys = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;

	ret = 0;
unlock:
	pte_unmap_unlock(ptep, ptl);
out:
	return ret;
}

/**
 * generic_access_phys - generic implementation for iomem mmap access
 * @vma: the vma to access
 * @addr: userspace address, not relative offset within @vma
 * @buf: buffer to read/write
 * @len: length of transfer
 * @write: set to FOLL_WRITE when writing, otherwise reading
 *
 * This is a generic implementation for &vm_operations_struct.access for an
 * iomem mapping. This callback is used by access_process_vm() when the @vma is
 * not page based.
 */
int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
			void *buf, int len, int write)
{
	resource_size_t phys_addr;
	unsigned long prot = 0;
	void __iomem *maddr;
	pte_t *ptep, pte;
	spinlock_t *ptl;
	int offset = offset_in_page(addr);
	int ret = -EINVAL;

	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
		return -EINVAL;

retry:
	if (follow_pte(vma->vm_mm, addr, &ptep, &ptl))
		return -EINVAL;
	pte = *ptep;
	pte_unmap_unlock(ptep, ptl);

	prot = pgprot_val(pte_pgprot(pte));
	phys_addr = (resource_size_t)pte_pfn(pte) << PAGE_SHIFT;

	if ((write & FOLL_WRITE) && !pte_write(pte))
		return -EINVAL;

	maddr = ioremap_prot(phys_addr, PAGE_ALIGN(len + offset), prot);
	if (!maddr)
		return -ENOMEM;

	if (follow_pte(vma->vm_mm, addr, &ptep, &ptl))
		goto out_unmap;

	if (!pte_same(pte, *ptep)) {
		pte_unmap_unlock(ptep, ptl);
		iounmap(maddr);

		goto retry;
	}

	if (write)
		memcpy_toio(maddr + offset, buf, len);
	else
		memcpy_fromio(buf, maddr + offset, len);
	ret = len;
	pte_unmap_unlock(ptep, ptl);
out_unmap:
	iounmap(maddr);

	return ret;
}
EXPORT_SYMBOL_GPL(generic_access_phys);
#endif

/*
 * Access another process' address space as given in mm.
 */
int __access_remote_vm(struct mm_struct *mm, unsigned long addr, void *buf,
		       int len, unsigned int gup_flags)
{
	struct vm_area_struct *vma;
	void *old_buf = buf;
	int write = gup_flags & FOLL_WRITE;

	if (mmap_read_lock_killable(mm))
		return 0;

	/* ignore errors, just check how much was successfully transferred */
	while (len) {
		int bytes, ret, offset;
		void *maddr;
		struct page *page = NULL;

		ret = get_user_pages_remote(mm, addr, 1,
				gup_flags, &page, &vma, NULL);
		if (ret <= 0) {
#ifndef CONFIG_HAVE_IOREMAP_PROT
			break;
#else
			/*
			 * Check if this is a VM_IO | VM_PFNMAP VMA, which
			 * we can access using slightly different code.
			 */
			vma = vma_lookup(mm, addr);
			if (!vma)
				break;
			if (vma->vm_ops && vma->vm_ops->access)
				ret = vma->vm_ops->access(vma, addr, buf,
							  len, write);
			if (ret <= 0)
				break;
			bytes = ret;
#endif
		} else {
			bytes = len;
			offset = addr & (PAGE_SIZE-1);
			if (bytes > PAGE_SIZE-offset)
				bytes = PAGE_SIZE-offset;

			maddr = kmap(page);
			if (write) {
				copy_to_user_page(vma, page, addr,
						  maddr + offset, buf, bytes);
				set_page_dirty_lock(page);
			} else {
				copy_from_user_page(vma, page, addr,
						    buf, maddr + offset, bytes);
			}
			kunmap(page);
			put_page(page);
		}
		len -= bytes;
		buf += bytes;
		addr += bytes;
	}
	mmap_read_unlock(mm);

	return buf - old_buf;
}

/**
 * access_remote_vm - access another process' address space
 * @mm:		the mm_struct of the target address space
 * @addr:	start address to access
 * @buf:	source or destination buffer
 * @len:	number of bytes to transfer
 * @gup_flags:	flags modifying lookup behaviour
 *
 * The caller must hold a reference on @mm.
 *
 * Return: number of bytes copied from source to destination.
 */
int access_remote_vm(struct mm_struct *mm, unsigned long addr,
		void *buf, int len, unsigned int gup_flags)
{
	return __access_remote_vm(mm, addr, buf, len, gup_flags);
}

/*
 * Access another process' address space.
 * Source/target buffer must be kernel space,
 * Do not walk the page table directly, use get_user_pages
 */
int access_process_vm(struct task_struct *tsk, unsigned long addr,
		void *buf, int len, unsigned int gup_flags)
{
	struct mm_struct *mm;
	int ret;

	mm = get_task_mm(tsk);
	if (!mm)
		return 0;

	ret = __access_remote_vm(mm, addr, buf, len, gup_flags);

	mmput(mm);

	return ret;
}
EXPORT_SYMBOL_GPL(access_process_vm);

/*
 * Print the name of a VMA.
 */
void print_vma_addr(char *prefix, unsigned long ip)
{
	struct mm_struct *mm = current->mm;
	struct vm_area_struct *vma;

	/*
	 * we might be running from an atomic context so we cannot sleep
	 */
	if (!mmap_read_trylock(mm))
		return;

	vma = find_vma(mm, ip);
	if (vma && vma->vm_file) {
		struct file *f = vma->vm_file;
		char *buf = (char *)__get_free_page(GFP_NOWAIT);
		if (buf) {
			char *p;

			p = file_path(f, buf, PAGE_SIZE);
			if (IS_ERR(p))
				p = "?";
			printk("%s%s[%lx+%lx]", prefix, kbasename(p),
					vma->vm_start,
					vma->vm_end - vma->vm_start);
			free_page((unsigned long)buf);
		}
	}
	mmap_read_unlock(mm);
}

#if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
void __might_fault(const char *file, int line)
{
	if (pagefault_disabled())
		return;
	__might_sleep(file, line);
#if defined(CONFIG_DEBUG_ATOMIC_SLEEP)
	if (current->mm)
		might_lock_read(&current->mm->mmap_lock);
#endif
}
EXPORT_SYMBOL(__might_fault);
#endif

#if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
/*
 * Process all subpages of the specified huge page with the specified
 * operation.  The target subpage will be processed last to keep its
 * cache lines hot.
 */
static inline void process_huge_page(
	unsigned long addr_hint, unsigned int pages_per_huge_page,
	void (*process_subpage)(unsigned long addr, int idx, void *arg),
	void *arg)
{
	int i, n, base, l;
	unsigned long addr = addr_hint &
		~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1);

	/* Process target subpage last to keep its cache lines hot */
	might_sleep();
	n = (addr_hint - addr) / PAGE_SIZE;
	if (2 * n <= pages_per_huge_page) {
		/* If target subpage in first half of huge page */
		base = 0;
		l = n;
		/* Process subpages at the end of huge page */
		for (i = pages_per_huge_page - 1; i >= 2 * n; i--) {
			cond_resched();
			process_subpage(addr + i * PAGE_SIZE, i, arg);
		}
	} else {
		/* If target subpage in second half of huge page */
		base = pages_per_huge_page - 2 * (pages_per_huge_page - n);
		l = pages_per_huge_page - n;
		/* Process subpages at the begin of huge page */
		for (i = 0; i < base; i++) {
			cond_resched();
			process_subpage(addr + i * PAGE_SIZE, i, arg);
		}
	}
	/*
	 * Process remaining subpages in left-right-left-right pattern
	 * towards the target subpage
	 */
	for (i = 0; i < l; i++) {
		int left_idx = base + i;
		int right_idx = base + 2 * l - 1 - i;

		cond_resched();
		process_subpage(addr + left_idx * PAGE_SIZE, left_idx, arg);
		cond_resched();
		process_subpage(addr + right_idx * PAGE_SIZE, right_idx, arg);
	}
}

static void clear_gigantic_page(struct page *page,
				unsigned long addr,
				unsigned int pages_per_huge_page)
{
	int i;
	struct page *p = page;

	might_sleep();
	for (i = 0; i < pages_per_huge_page;
	     i++, p = mem_map_next(p, page, i)) {
		cond_resched();
		clear_user_highpage(p, addr + i * PAGE_SIZE);
	}
}

static void clear_subpage(unsigned long addr, int idx, void *arg)
{
	struct page *page = arg;

	clear_user_highpage(page + idx, addr);
}

void clear_huge_page(struct page *page,
		     unsigned long addr_hint, unsigned int pages_per_huge_page)
{
	unsigned long addr = addr_hint &
		~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1);

	if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
		clear_gigantic_page(page, addr, pages_per_huge_page);
		return;
	}

	process_huge_page(addr_hint, pages_per_huge_page, clear_subpage, page);
}

static void copy_user_gigantic_page(struct page *dst, struct page *src,
				    unsigned long addr,
				    struct vm_area_struct *vma,
				    unsigned int pages_per_huge_page)
{
	int i;
	struct page *dst_base = dst;
	struct page *src_base = src;

	for (i = 0; i < pages_per_huge_page; ) {
		cond_resched();
		copy_user_highpage(dst, src, addr + i*PAGE_SIZE, vma);

		i++;
		dst = mem_map_next(dst, dst_base, i);
		src = mem_map_next(src, src_base, i);
	}
}

struct copy_subpage_arg {
	struct page *dst;
	struct page *src;
	struct vm_area_struct *vma;
};

static void copy_subpage(unsigned long addr, int idx, void *arg)
{
	struct copy_subpage_arg *copy_arg = arg;

	copy_user_highpage(copy_arg->dst + idx, copy_arg->src + idx,
			   addr, copy_arg->vma);
}

void copy_user_huge_page(struct page *dst, struct page *src,
			 unsigned long addr_hint, struct vm_area_struct *vma,
			 unsigned int pages_per_huge_page)
{
	unsigned long addr = addr_hint &
		~(((unsigned long)pages_per_huge_page << PAGE_SHIFT) - 1);
	struct copy_subpage_arg arg = {
		.dst = dst,
		.src = src,
		.vma = vma,
	};

	if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
		copy_user_gigantic_page(dst, src, addr, vma,
					pages_per_huge_page);
		return;
	}

	process_huge_page(addr_hint, pages_per_huge_page, copy_subpage, &arg);
}

long copy_huge_page_from_user(struct page *dst_page,
				const void __user *usr_src,
				unsigned int pages_per_huge_page,
				bool allow_pagefault)
{
	void *page_kaddr;
	unsigned long i, rc = 0;
	unsigned long ret_val = pages_per_huge_page * PAGE_SIZE;
	struct page *subpage = dst_page;

	for (i = 0; i < pages_per_huge_page;
	     i++, subpage = mem_map_next(subpage, dst_page, i)) {
		if (allow_pagefault)
			page_kaddr = kmap(subpage);
		else
			page_kaddr = kmap_atomic(subpage);
		rc = copy_from_user(page_kaddr,
				usr_src + i * PAGE_SIZE, PAGE_SIZE);
		if (allow_pagefault)
			kunmap(subpage);
		else
			kunmap_atomic(page_kaddr);

		ret_val -= (PAGE_SIZE - rc);
		if (rc)
			break;

		flush_dcache_page(subpage);

		cond_resched();
	}
	return ret_val;
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */

#if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS

static struct kmem_cache *page_ptl_cachep;

void __init ptlock_cache_init(void)
{
	page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
			SLAB_PANIC, NULL);
}

bool ptlock_alloc(struct page *page)
{
	spinlock_t *ptl;

	ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
	if (!ptl)
		return false;
	page->ptl = ptl;
	return true;
}

void ptlock_free(struct page *page)
{
	kmem_cache_free(page_ptl_cachep, page->ptl);
}
#endif