aboutsummaryrefslogtreecommitdiffstats
path: root/fs/xfs/xfs_alloc.c
blob: e9c70249d2c5cb338aee050b1946fbc9cc736667 (plain) (blame)
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
/*
 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_alloc.h"
#include "xfs_error.h"


#define XFS_ABSDIFF(a,b)	(((a) <= (b)) ? ((b) - (a)) : ((a) - (b)))

#define	XFSA_FIXUP_BNO_OK	1
#define	XFSA_FIXUP_CNT_OK	2

STATIC void
xfs_alloc_search_busy(xfs_trans_t *tp,
		    xfs_agnumber_t agno,
		    xfs_agblock_t bno,
		    xfs_extlen_t len);

#if defined(XFS_ALLOC_TRACE)
ktrace_t *xfs_alloc_trace_buf;

#define	TRACE_ALLOC(s,a)	\
	xfs_alloc_trace_alloc(__func__, s, a, __LINE__)
#define	TRACE_FREE(s,a,b,x,f)	\
	xfs_alloc_trace_free(__func__, s, mp, a, b, x, f, __LINE__)
#define	TRACE_MODAGF(s,a,f)	\
	xfs_alloc_trace_modagf(__func__, s, mp, a, f, __LINE__)
#define	TRACE_BUSY(__func__,s,ag,agb,l,sl,tp)	\
	xfs_alloc_trace_busy(__func__, s, mp, ag, agb, l, sl, tp, XFS_ALLOC_KTRACE_BUSY, __LINE__)
#define	TRACE_UNBUSY(__func__,s,ag,sl,tp)	\
	xfs_alloc_trace_busy(__func__, s, mp, ag, -1, -1, sl, tp, XFS_ALLOC_KTRACE_UNBUSY, __LINE__)
#define	TRACE_BUSYSEARCH(__func__,s,ag,agb,l,tp)	\
	xfs_alloc_trace_busy(__func__, s, mp, ag, agb, l, 0, tp, XFS_ALLOC_KTRACE_BUSYSEARCH, __LINE__)
#else
#define	TRACE_ALLOC(s,a)
#define	TRACE_FREE(s,a,b,x,f)
#define	TRACE_MODAGF(s,a,f)
#define	TRACE_BUSY(s,a,ag,agb,l,sl,tp)
#define	TRACE_UNBUSY(fname,s,ag,sl,tp)
#define	TRACE_BUSYSEARCH(fname,s,ag,agb,l,tp)
#endif	/* XFS_ALLOC_TRACE */

/*
 * Prototypes for per-ag allocation routines
 */

STATIC int xfs_alloc_ag_vextent_exact(xfs_alloc_arg_t *);
STATIC int xfs_alloc_ag_vextent_near(xfs_alloc_arg_t *);
STATIC int xfs_alloc_ag_vextent_size(xfs_alloc_arg_t *);
STATIC int xfs_alloc_ag_vextent_small(xfs_alloc_arg_t *,
	xfs_btree_cur_t *, xfs_agblock_t *, xfs_extlen_t *, int *);

/*
 * Internal functions.
 */

/*
 * Lookup the record equal to [bno, len] in the btree given by cur.
 */
STATIC int				/* error */
xfs_alloc_lookup_eq(
	struct xfs_btree_cur	*cur,	/* btree cursor */
	xfs_agblock_t		bno,	/* starting block of extent */
	xfs_extlen_t		len,	/* length of extent */
	int			*stat)	/* success/failure */
{
	cur->bc_rec.a.ar_startblock = bno;
	cur->bc_rec.a.ar_blockcount = len;
	return xfs_btree_lookup(cur, XFS_LOOKUP_EQ, stat);
}

/*
 * Lookup the first record greater than or equal to [bno, len]
 * in the btree given by cur.
 */
STATIC int				/* error */
xfs_alloc_lookup_ge(
	struct xfs_btree_cur	*cur,	/* btree cursor */
	xfs_agblock_t		bno,	/* starting block of extent */
	xfs_extlen_t		len,	/* length of extent */
	int			*stat)	/* success/failure */
{
	cur->bc_rec.a.ar_startblock = bno;
	cur->bc_rec.a.ar_blockcount = len;
	return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
}

/*
 * Lookup the first record less than or equal to [bno, len]
 * in the btree given by cur.
 */
STATIC int				/* error */
xfs_alloc_lookup_le(
	struct xfs_btree_cur	*cur,	/* btree cursor */
	xfs_agblock_t		bno,	/* starting block of extent */
	xfs_extlen_t		len,	/* length of extent */
	int			*stat)	/* success/failure */
{
	cur->bc_rec.a.ar_startblock = bno;
	cur->bc_rec.a.ar_blockcount = len;
	return xfs_btree_lookup(cur, XFS_LOOKUP_LE, stat);
}

/*
 * Update the record referred to by cur to the value given
 * by [bno, len].
 * This either works (return 0) or gets an EFSCORRUPTED error.
 */
STATIC int				/* error */
xfs_alloc_update(
	struct xfs_btree_cur	*cur,	/* btree cursor */
	xfs_agblock_t		bno,	/* starting block of extent */
	xfs_extlen_t		len)	/* length of extent */
{
	union xfs_btree_rec	rec;

	rec.alloc.ar_startblock = cpu_to_be32(bno);
	rec.alloc.ar_blockcount = cpu_to_be32(len);
	return xfs_btree_update(cur, &rec);
}

/*
 * Compute aligned version of the found extent.
 * Takes alignment and min length into account.
 */
STATIC void
xfs_alloc_compute_aligned(
	xfs_agblock_t	foundbno,	/* starting block in found extent */
	xfs_extlen_t	foundlen,	/* length in found extent */
	xfs_extlen_t	alignment,	/* alignment for allocation */
	xfs_extlen_t	minlen,		/* minimum length for allocation */
	xfs_agblock_t	*resbno,	/* result block number */
	xfs_extlen_t	*reslen)	/* result length */
{
	xfs_agblock_t	bno;
	xfs_extlen_t	diff;
	xfs_extlen_t	len;

	if (alignment > 1 && foundlen >= minlen) {
		bno = roundup(foundbno, alignment);
		diff = bno - foundbno;
		len = diff >= foundlen ? 0 : foundlen - diff;
	} else {
		bno = foundbno;
		len = foundlen;
	}
	*resbno = bno;
	*reslen = len;
}

/*
 * Compute best start block and diff for "near" allocations.
 * freelen >= wantlen already checked by caller.
 */
STATIC xfs_extlen_t			/* difference value (absolute) */
xfs_alloc_compute_diff(
	xfs_agblock_t	wantbno,	/* target starting block */
	xfs_extlen_t	wantlen,	/* target length */
	xfs_extlen_t	alignment,	/* target alignment */
	xfs_agblock_t	freebno,	/* freespace's starting block */
	xfs_extlen_t	freelen,	/* freespace's length */
	xfs_agblock_t	*newbnop)	/* result: best start block from free */
{
	xfs_agblock_t	freeend;	/* end of freespace extent */
	xfs_agblock_t	newbno1;	/* return block number */
	xfs_agblock_t	newbno2;	/* other new block number */
	xfs_extlen_t	newlen1=0;	/* length with newbno1 */
	xfs_extlen_t	newlen2=0;	/* length with newbno2 */
	xfs_agblock_t	wantend;	/* end of target extent */

	ASSERT(freelen >= wantlen);
	freeend = freebno + freelen;
	wantend = wantbno + wantlen;
	if (freebno >= wantbno) {
		if ((newbno1 = roundup(freebno, alignment)) >= freeend)
			newbno1 = NULLAGBLOCK;
	} else if (freeend >= wantend && alignment > 1) {
		newbno1 = roundup(wantbno, alignment);
		newbno2 = newbno1 - alignment;
		if (newbno1 >= freeend)
			newbno1 = NULLAGBLOCK;
		else
			newlen1 = XFS_EXTLEN_MIN(wantlen, freeend - newbno1);
		if (newbno2 < freebno)
			newbno2 = NULLAGBLOCK;
		else
			newlen2 = XFS_EXTLEN_MIN(wantlen, freeend - newbno2);
		if (newbno1 != NULLAGBLOCK && newbno2 != NULLAGBLOCK) {
			if (newlen1 < newlen2 ||
			    (newlen1 == newlen2 &&
			     XFS_ABSDIFF(newbno1, wantbno) >
			     XFS_ABSDIFF(newbno2, wantbno)))
				newbno1 = newbno2;
		} else if (newbno2 != NULLAGBLOCK)
			newbno1 = newbno2;
	} else if (freeend >= wantend) {
		newbno1 = wantbno;
	} else if (alignment > 1) {
		newbno1 = roundup(freeend - wantlen, alignment);
		if (newbno1 > freeend - wantlen &&
		    newbno1 - alignment >= freebno)
			newbno1 -= alignment;
		else if (newbno1 >= freeend)
			newbno1 = NULLAGBLOCK;
	} else
		newbno1 = freeend - wantlen;
	*newbnop = newbno1;
	return newbno1 == NULLAGBLOCK ? 0 : XFS_ABSDIFF(newbno1, wantbno);
}

/*
 * Fix up the length, based on mod and prod.
 * len should be k * prod + mod for some k.
 * If len is too small it is returned unchanged.
 * If len hits maxlen it is left alone.
 */
STATIC void
xfs_alloc_fix_len(
	xfs_alloc_arg_t	*args)		/* allocation argument structure */
{
	xfs_extlen_t	k;
	xfs_extlen_t	rlen;

	ASSERT(args->mod < args->prod);
	rlen = args->len;
	ASSERT(rlen >= args->minlen);
	ASSERT(rlen <= args->maxlen);
	if (args->prod <= 1 || rlen < args->mod || rlen == args->maxlen ||
	    (args->mod == 0 && rlen < args->prod))
		return;
	k = rlen % args->prod;
	if (k == args->mod)
		return;
	if (k > args->mod) {
		if ((int)(rlen = rlen - k - args->mod) < (int)args->minlen)
			return;
	} else {
		if ((int)(rlen = rlen - args->prod - (args->mod - k)) <
		    (int)args->minlen)
			return;
	}
	ASSERT(rlen >= args->minlen);
	ASSERT(rlen <= args->maxlen);
	args->len = rlen;
}

/*
 * Fix up length if there is too little space left in the a.g.
 * Return 1 if ok, 0 if too little, should give up.
 */
STATIC int
xfs_alloc_fix_minleft(
	xfs_alloc_arg_t	*args)		/* allocation argument structure */
{
	xfs_agf_t	*agf;		/* a.g. freelist header */
	int		diff;		/* free space difference */

	if (args->minleft == 0)
		return 1;
	agf = XFS_BUF_TO_AGF(args->agbp);
	diff = be32_to_cpu(agf->agf_freeblks)
		+ be32_to_cpu(agf->agf_flcount)
		- args->len - args->minleft;
	if (diff >= 0)
		return 1;
	args->len += diff;		/* shrink the allocated space */
	if (args->len >= args->minlen)
		return 1;
	args->agbno = NULLAGBLOCK;
	return 0;
}

/*
 * Update the two btrees, logically removing from freespace the extent
 * starting at rbno, rlen blocks.  The extent is contained within the
 * actual (current) free extent fbno for flen blocks.
 * Flags are passed in indicating whether the cursors are set to the
 * relevant records.
 */
STATIC int				/* error code */
xfs_alloc_fixup_trees(
	xfs_btree_cur_t	*cnt_cur,	/* cursor for by-size btree */
	xfs_btree_cur_t	*bno_cur,	/* cursor for by-block btree */
	xfs_agblock_t	fbno,		/* starting block of free extent */
	xfs_extlen_t	flen,		/* length of free extent */
	xfs_agblock_t	rbno,		/* starting block of returned extent */
	xfs_extlen_t	rlen,		/* length of returned extent */
	int		flags)		/* flags, XFSA_FIXUP_... */
{
	int		error;		/* error code */
	int		i;		/* operation results */
	xfs_agblock_t	nfbno1;		/* first new free startblock */
	xfs_agblock_t	nfbno2;		/* second new free startblock */
	xfs_extlen_t	nflen1=0;	/* first new free length */
	xfs_extlen_t	nflen2=0;	/* second new free length */

	/*
	 * Look up the record in the by-size tree if necessary.
	 */
	if (flags & XFSA_FIXUP_CNT_OK) {
#ifdef DEBUG
		if ((error = xfs_alloc_get_rec(cnt_cur, &nfbno1, &nflen1, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(
			i == 1 && nfbno1 == fbno && nflen1 == flen);
#endif
	} else {
		if ((error = xfs_alloc_lookup_eq(cnt_cur, fbno, flen, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 1);
	}
	/*
	 * Look up the record in the by-block tree if necessary.
	 */
	if (flags & XFSA_FIXUP_BNO_OK) {
#ifdef DEBUG
		if ((error = xfs_alloc_get_rec(bno_cur, &nfbno1, &nflen1, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(
			i == 1 && nfbno1 == fbno && nflen1 == flen);
#endif
	} else {
		if ((error = xfs_alloc_lookup_eq(bno_cur, fbno, flen, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 1);
	}
#ifdef DEBUG
	{
		xfs_alloc_block_t	*bnoblock;
		xfs_alloc_block_t	*cntblock;

		if (bno_cur->bc_nlevels == 1 &&
		    cnt_cur->bc_nlevels == 1) {
			bnoblock = XFS_BUF_TO_ALLOC_BLOCK(bno_cur->bc_bufs[0]);
			cntblock = XFS_BUF_TO_ALLOC_BLOCK(cnt_cur->bc_bufs[0]);
			XFS_WANT_CORRUPTED_RETURN(
				be16_to_cpu(bnoblock->bb_numrecs) ==
				be16_to_cpu(cntblock->bb_numrecs));
		}
	}
#endif
	/*
	 * Deal with all four cases: the allocated record is contained
	 * within the freespace record, so we can have new freespace
	 * at either (or both) end, or no freespace remaining.
	 */
	if (rbno == fbno && rlen == flen)
		nfbno1 = nfbno2 = NULLAGBLOCK;
	else if (rbno == fbno) {
		nfbno1 = rbno + rlen;
		nflen1 = flen - rlen;
		nfbno2 = NULLAGBLOCK;
	} else if (rbno + rlen == fbno + flen) {
		nfbno1 = fbno;
		nflen1 = flen - rlen;
		nfbno2 = NULLAGBLOCK;
	} else {
		nfbno1 = fbno;
		nflen1 = rbno - fbno;
		nfbno2 = rbno + rlen;
		nflen2 = (fbno + flen) - nfbno2;
	}
	/*
	 * Delete the entry from the by-size btree.
	 */
	if ((error = xfs_btree_delete(cnt_cur, &i)))
		return error;
	XFS_WANT_CORRUPTED_RETURN(i == 1);
	/*
	 * Add new by-size btree entry(s).
	 */
	if (nfbno1 != NULLAGBLOCK) {
		if ((error = xfs_alloc_lookup_eq(cnt_cur, nfbno1, nflen1, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 0);
		if ((error = xfs_btree_insert(cnt_cur, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 1);
	}
	if (nfbno2 != NULLAGBLOCK) {
		if ((error = xfs_alloc_lookup_eq(cnt_cur, nfbno2, nflen2, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 0);
		if ((error = xfs_btree_insert(cnt_cur, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 1);
	}
	/*
	 * Fix up the by-block btree entry(s).
	 */
	if (nfbno1 == NULLAGBLOCK) {
		/*
		 * No remaining freespace, just delete the by-block tree entry.
		 */
		if ((error = xfs_btree_delete(bno_cur, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 1);
	} else {
		/*
		 * Update the by-block entry to start later|be shorter.
		 */
		if ((error = xfs_alloc_update(bno_cur, nfbno1, nflen1)))
			return error;
	}
	if (nfbno2 != NULLAGBLOCK) {
		/*
		 * 2 resulting free entries, need to add one.
		 */
		if ((error = xfs_alloc_lookup_eq(bno_cur, nfbno2, nflen2, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 0);
		if ((error = xfs_btree_insert(bno_cur, &i)))
			return error;
		XFS_WANT_CORRUPTED_RETURN(i == 1);
	}
	return 0;
}

/*
 * Read in the allocation group free block array.
 */
STATIC int				/* error */
xfs_alloc_read_agfl(
	xfs_mount_t	*mp,		/* mount point structure */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_agnumber_t	agno,		/* allocation group number */
	xfs_buf_t	**bpp)		/* buffer for the ag free block array */
{
	xfs_buf_t	*bp;		/* return value */
	int		error;

	ASSERT(agno != NULLAGNUMBER);
	error = xfs_trans_read_buf(
			mp, tp, mp->m_ddev_targp,
			XFS_AG_DADDR(mp, agno, XFS_AGFL_DADDR(mp)),
			XFS_FSS_TO_BB(mp, 1), 0, &bp);
	if (error)
		return error;
	ASSERT(bp);
	ASSERT(!XFS_BUF_GETERROR(bp));
	XFS_BUF_SET_VTYPE_REF(bp, B_FS_AGFL, XFS_AGFL_REF);
	*bpp = bp;
	return 0;
}

#if defined(XFS_ALLOC_TRACE)
/*
 * Add an allocation trace entry for an alloc call.
 */
STATIC void
xfs_alloc_trace_alloc(
	const char	*name,		/* function tag string */
	char		*str,		/* additional string */
	xfs_alloc_arg_t	*args,		/* allocation argument structure */
	int		line)		/* source line number */
{
	ktrace_enter(xfs_alloc_trace_buf,
		(void *)(__psint_t)(XFS_ALLOC_KTRACE_ALLOC | (line << 16)),
		(void *)name,
		(void *)str,
		(void *)args->mp,
		(void *)(__psunsigned_t)args->agno,
		(void *)(__psunsigned_t)args->agbno,
		(void *)(__psunsigned_t)args->minlen,
		(void *)(__psunsigned_t)args->maxlen,
		(void *)(__psunsigned_t)args->mod,
		(void *)(__psunsigned_t)args->prod,
		(void *)(__psunsigned_t)args->minleft,
		(void *)(__psunsigned_t)args->total,
		(void *)(__psunsigned_t)args->alignment,
		(void *)(__psunsigned_t)args->len,
		(void *)((((__psint_t)args->type) << 16) |
			 (__psint_t)args->otype),
		(void *)(__psint_t)((args->wasdel << 3) |
				    (args->wasfromfl << 2) |
				    (args->isfl << 1) |
				    (args->userdata << 0)));
}

/*
 * Add an allocation trace entry for a free call.
 */
STATIC void
xfs_alloc_trace_free(
	const char	*name,		/* function tag string */
	char		*str,		/* additional string */
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_agnumber_t	agno,		/* allocation group number */
	xfs_agblock_t	agbno,		/* a.g. relative block number */
	xfs_extlen_t	len,		/* length of extent */
	int		isfl,		/* set if is freelist allocation/free */
	int		line)		/* source line number */
{
	ktrace_enter(xfs_alloc_trace_buf,
		(void *)(__psint_t)(XFS_ALLOC_KTRACE_FREE | (line << 16)),
		(void *)name,
		(void *)str,
		(void *)mp,
		(void *)(__psunsigned_t)agno,
		(void *)(__psunsigned_t)agbno,
		(void *)(__psunsigned_t)len,
		(void *)(__psint_t)isfl,
		NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/*
 * Add an allocation trace entry for modifying an agf.
 */
STATIC void
xfs_alloc_trace_modagf(
	const char	*name,		/* function tag string */
	char		*str,		/* additional string */
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_agf_t	*agf,		/* new agf value */
	int		flags,		/* logging flags for agf */
	int		line)		/* source line number */
{
	ktrace_enter(xfs_alloc_trace_buf,
		(void *)(__psint_t)(XFS_ALLOC_KTRACE_MODAGF | (line << 16)),
		(void *)name,
		(void *)str,
		(void *)mp,
		(void *)(__psint_t)flags,
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_seqno),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_length),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_roots[XFS_BTNUM_BNO]),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_roots[XFS_BTNUM_CNT]),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_flfirst),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_fllast),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_flcount),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_freeblks),
		(void *)(__psunsigned_t)be32_to_cpu(agf->agf_longest));
}

STATIC void
xfs_alloc_trace_busy(
	const char	*name,		/* function tag string */
	char		*str,		/* additional string */
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_agnumber_t	agno,		/* allocation group number */
	xfs_agblock_t	agbno,		/* a.g. relative block number */
	xfs_extlen_t	len,		/* length of extent */
	int		slot,		/* perag Busy slot */
	xfs_trans_t	*tp,
	int		trtype,		/* type: add, delete, search */
	int		line)		/* source line number */
{
	ktrace_enter(xfs_alloc_trace_buf,
		(void *)(__psint_t)(trtype | (line << 16)),
		(void *)name,
		(void *)str,
		(void *)mp,
		(void *)(__psunsigned_t)agno,
		(void *)(__psunsigned_t)agbno,
		(void *)(__psunsigned_t)len,
		(void *)(__psint_t)slot,
		(void *)tp,
		NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}
#endif	/* XFS_ALLOC_TRACE */

/*
 * Allocation group level functions.
 */

/*
 * Allocate a variable extent in the allocation group agno.
 * Type and bno are used to determine where in the allocation group the
 * extent will start.
 * Extent's length (returned in *len) will be between minlen and maxlen,
 * and of the form k * prod + mod unless there's nothing that large.
 * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
 */
STATIC int			/* error */
xfs_alloc_ag_vextent(
	xfs_alloc_arg_t	*args)	/* argument structure for allocation */
{
	int		error=0;

	ASSERT(args->minlen > 0);
	ASSERT(args->maxlen > 0);
	ASSERT(args->minlen <= args->maxlen);
	ASSERT(args->mod < args->prod);
	ASSERT(args->alignment > 0);
	/*
	 * Branch to correct routine based on the type.
	 */
	args->wasfromfl = 0;
	switch (args->type) {
	case XFS_ALLOCTYPE_THIS_AG:
		error = xfs_alloc_ag_vextent_size(args);
		break;
	case XFS_ALLOCTYPE_NEAR_BNO:
		error = xfs_alloc_ag_vextent_near(args);
		break;
	case XFS_ALLOCTYPE_THIS_BNO:
		error = xfs_alloc_ag_vextent_exact(args);
		break;
	default:
		ASSERT(0);
		/* NOTREACHED */
	}
	if (error)
		return error;
	/*
	 * If the allocation worked, need to change the agf structure
	 * (and log it), and the superblock.
	 */
	if (args->agbno != NULLAGBLOCK) {
		xfs_agf_t	*agf;	/* allocation group freelist header */
#ifdef XFS_ALLOC_TRACE
		xfs_mount_t	*mp = args->mp;
#endif
		long		slen = (long)args->len;

		ASSERT(args->len >= args->minlen && args->len <= args->maxlen);
		ASSERT(!(args->wasfromfl) || !args->isfl);
		ASSERT(args->agbno % args->alignment == 0);
		if (!(args->wasfromfl)) {

			agf = XFS_BUF_TO_AGF(args->agbp);
			be32_add_cpu(&agf->agf_freeblks, -(args->len));
			xfs_trans_agblocks_delta(args->tp,
						 -((long)(args->len)));
			args->pag->pagf_freeblks -= args->len;
			ASSERT(be32_to_cpu(agf->agf_freeblks) <=
				be32_to_cpu(agf->agf_length));
			TRACE_MODAGF(NULL, agf, XFS_AGF_FREEBLKS);
			xfs_alloc_log_agf(args->tp, args->agbp,
						XFS_AGF_FREEBLKS);
			/* search the busylist for these blocks */
			xfs_alloc_search_busy(args->tp, args->agno,
					args->agbno, args->len);
		}
		if (!args->isfl)
			xfs_trans_mod_sb(args->tp,
				args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS :
					XFS_TRANS_SB_FDBLOCKS, -slen);
		XFS_STATS_INC(xs_allocx);
		XFS_STATS_ADD(xs_allocb, args->len);
	}
	return 0;
}

/*
 * Allocate a variable extent at exactly agno/bno.
 * Extent's length (returned in *len) will be between minlen and maxlen,
 * and of the form k * prod + mod unless there's nothing that large.
 * Return the starting a.g. block (bno), or NULLAGBLOCK if we can't do it.
 */
STATIC int			/* error */
xfs_alloc_ag_vextent_exact(
	xfs_alloc_arg_t	*args)	/* allocation argument structure */
{
	xfs_btree_cur_t	*bno_cur;/* by block-number btree cursor */
	xfs_btree_cur_t	*cnt_cur;/* by count btree cursor */
	xfs_agblock_t	end;	/* end of allocated extent */
	int		error;
	xfs_agblock_t	fbno;	/* start block of found extent */
	xfs_agblock_t	fend;	/* end block of found extent */
	xfs_extlen_t	flen;	/* length of found extent */
	int		i;	/* success/failure of operation */
	xfs_agblock_t	maxend;	/* end of maximal extent */
	xfs_agblock_t	minend;	/* end of minimal extent */
	xfs_extlen_t	rlen;	/* length of returned extent */

	ASSERT(args->alignment == 1);
	/*
	 * Allocate/initialize a cursor for the by-number freespace btree.
	 */
	bno_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
		args->agno, XFS_BTNUM_BNO);
	/*
	 * Lookup bno and minlen in the btree (minlen is irrelevant, really).
	 * Look for the closest free block <= bno, it must contain bno
	 * if any free block does.
	 */
	if ((error = xfs_alloc_lookup_le(bno_cur, args->agbno, args->minlen, &i)))
		goto error0;
	if (!i) {
		/*
		 * Didn't find it, return null.
		 */
		xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
		args->agbno = NULLAGBLOCK;
		return 0;
	}
	/*
	 * Grab the freespace record.
	 */
	if ((error = xfs_alloc_get_rec(bno_cur, &fbno, &flen, &i)))
		goto error0;
	XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
	ASSERT(fbno <= args->agbno);
	minend = args->agbno + args->minlen;
	maxend = args->agbno + args->maxlen;
	fend = fbno + flen;
	/*
	 * Give up if the freespace isn't long enough for the minimum request.
	 */
	if (fend < minend) {
		xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
		args->agbno = NULLAGBLOCK;
		return 0;
	}
	/*
	 * End of extent will be smaller of the freespace end and the
	 * maximal requested end.
	 */
	end = XFS_AGBLOCK_MIN(fend, maxend);
	/*
	 * Fix the length according to mod and prod if given.
	 */
	args->len = end - args->agbno;
	xfs_alloc_fix_len(args);
	if (!xfs_alloc_fix_minleft(args)) {
		xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
		return 0;
	}
	rlen = args->len;
	ASSERT(args->agbno + rlen <= fend);
	end = args->agbno + rlen;
	/*
	 * We are allocating agbno for rlen [agbno .. end]
	 * Allocate/initialize a cursor for the by-size btree.
	 */
	cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
		args->agno, XFS_BTNUM_CNT);
	ASSERT(args->agbno + args->len <=
		be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
	if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur, fbno, flen,
			args->agbno, args->len, XFSA_FIXUP_BNO_OK))) {
		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
		goto error0;
	}
	xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
	xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
	TRACE_ALLOC("normal", args);
	args->wasfromfl = 0;
	return 0;

error0:
	xfs_btree_del_cursor(bno_cur, XFS_BTREE_ERROR);
	TRACE_ALLOC("error", args);
	return error;
}

/*
 * Allocate a variable extent near bno in the allocation group agno.
 * Extent's length (returned in len) will be between minlen and maxlen,
 * and of the form k * prod + mod unless there's nothing that large.
 * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
 */
STATIC int				/* error */
xfs_alloc_ag_vextent_near(
	xfs_alloc_arg_t	*args)		/* allocation argument structure */
{
	xfs_btree_cur_t	*bno_cur_gt;	/* cursor for bno btree, right side */
	xfs_btree_cur_t	*bno_cur_lt;	/* cursor for bno btree, left side */
	xfs_btree_cur_t	*cnt_cur;	/* cursor for count btree */
	xfs_agblock_t	gtbno;		/* start bno of right side entry */
	xfs_agblock_t	gtbnoa;		/* aligned ... */
	xfs_extlen_t	gtdiff;		/* difference to right side entry */
	xfs_extlen_t	gtlen;		/* length of right side entry */
	xfs_extlen_t	gtlena;		/* aligned ... */
	xfs_agblock_t	gtnew;		/* useful start bno of right side */
	int		error;		/* error code */
	int		i;		/* result code, temporary */
	int		j;		/* result code, temporary */
	xfs_agblock_t	ltbno;		/* start bno of left side entry */
	xfs_agblock_t	ltbnoa;		/* aligned ... */
	xfs_extlen_t	ltdiff;		/* difference to left side entry */
	/*REFERENCED*/
	xfs_agblock_t	ltend;		/* end bno of left side entry */
	xfs_extlen_t	ltlen;		/* length of left side entry */
	xfs_extlen_t	ltlena;		/* aligned ... */
	xfs_agblock_t	ltnew;		/* useful start bno of left side */
	xfs_extlen_t	rlen;		/* length of returned extent */
#if defined(DEBUG) && defined(__KERNEL__)
	/*
	 * Randomly don't execute the first algorithm.
	 */
	int		dofirst;	/* set to do first algorithm */

	dofirst = random32() & 1;
#endif
	/*
	 * Get a cursor for the by-size btree.
	 */
	cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
		args->agno, XFS_BTNUM_CNT);
	ltlen = 0;
	bno_cur_lt = bno_cur_gt = NULL;
	/*
	 * See if there are any free extents as big as maxlen.
	 */
	if ((error = xfs_alloc_lookup_ge(cnt_cur, 0, args->maxlen, &i)))
		goto error0;
	/*
	 * If none, then pick up the last entry in the tree unless the
	 * tree is empty.
	 */
	if (!i) {
		if ((error = xfs_alloc_ag_vextent_small(args, cnt_cur, &ltbno,
				&ltlen, &i)))
			goto error0;
		if (i == 0 || ltlen == 0) {
			xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
			return 0;
		}
		ASSERT(i == 1);
	}
	args->wasfromfl = 0;
	/*
	 * First algorithm.
	 * If the requested extent is large wrt the freespaces available
	 * in this a.g., then the cursor will be pointing to a btree entry
	 * near the right edge of the tree.  If it's in the last btree leaf
	 * block, then we just examine all the entries in that block
	 * that are big enough, and pick the best one.
	 * This is written as a while loop so we can break out of it,
	 * but we never loop back to the top.
	 */
	while (xfs_btree_islastblock(cnt_cur, 0)) {
		xfs_extlen_t	bdiff;
		int		besti=0;
		xfs_extlen_t	blen=0;
		xfs_agblock_t	bnew=0;

#if defined(DEBUG) && defined(__KERNEL__)
		if (!dofirst)
			break;
#endif
		/*
		 * Start from the entry that lookup found, sequence through
		 * all larger free blocks.  If we're actually pointing at a
		 * record smaller than maxlen, go to the start of this block,
		 * and skip all those smaller than minlen.
		 */
		if (ltlen || args->alignment > 1) {
			cnt_cur->bc_ptrs[0] = 1;
			do {
				if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno,
						&ltlen, &i)))
					goto error0;
				XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
				if (ltlen >= args->minlen)
					break;
				if ((error = xfs_btree_increment(cnt_cur, 0, &i)))
					goto error0;
			} while (i);
			ASSERT(ltlen >= args->minlen);
			if (!i)
				break;
		}
		i = cnt_cur->bc_ptrs[0];
		for (j = 1, blen = 0, bdiff = 0;
		     !error && j && (blen < args->maxlen || bdiff > 0);
		     error = xfs_btree_increment(cnt_cur, 0, &j)) {
			/*
			 * For each entry, decide if it's better than
			 * the previous best entry.
			 */
			if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno, &ltlen, &i)))
				goto error0;
			XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
			xfs_alloc_compute_aligned(ltbno, ltlen, args->alignment,
					args->minlen, &ltbnoa, &ltlena);
			if (ltlena < args->minlen)
				continue;
			args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
			xfs_alloc_fix_len(args);
			ASSERT(args->len >= args->minlen);
			if (args->len < blen)
				continue;
			ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
				args->alignment, ltbno, ltlen, &ltnew);
			if (ltnew != NULLAGBLOCK &&
			    (args->len > blen || ltdiff < bdiff)) {
				bdiff = ltdiff;
				bnew = ltnew;
				blen = args->len;
				besti = cnt_cur->bc_ptrs[0];
			}
		}
		/*
		 * It didn't work.  We COULD be in a case where
		 * there's a good record somewhere, so try again.
		 */
		if (blen == 0)
			break;
		/*
		 * Point at the best entry, and retrieve it again.
		 */
		cnt_cur->bc_ptrs[0] = besti;
		if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno, &ltlen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		ltend = ltbno + ltlen;
		ASSERT(ltend <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
		args->len = blen;
		if (!xfs_alloc_fix_minleft(args)) {
			xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
			TRACE_ALLOC("nominleft", args);
			return 0;
		}
		blen = args->len;
		/*
		 * We are allocating starting at bnew for blen blocks.
		 */
		args->agbno = bnew;
		ASSERT(bnew >= ltbno);
		ASSERT(bnew + blen <= ltend);
		/*
		 * Set up a cursor for the by-bno tree.
		 */
		bno_cur_lt = xfs_allocbt_init_cursor(args->mp, args->tp,
			args->agbp, args->agno, XFS_BTNUM_BNO);
		/*
		 * Fix up the btree entries.
		 */
		if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur_lt, ltbno,
				ltlen, bnew, blen, XFSA_FIXUP_CNT_OK)))
			goto error0;
		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
		xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
		TRACE_ALLOC("first", args);
		return 0;
	}
	/*
	 * Second algorithm.
	 * Search in the by-bno tree to the left and to the right
	 * simultaneously, until in each case we find a space big enough,
	 * or run into the edge of the tree.  When we run into the edge,
	 * we deallocate that cursor.
	 * If both searches succeed, we compare the two spaces and pick
	 * the better one.
	 * With alignment, it's possible for both to fail; the upper
	 * level algorithm that picks allocation groups for allocations
	 * is not supposed to do this.
	 */
	/*
	 * Allocate and initialize the cursor for the leftward search.
	 */
	bno_cur_lt = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
		args->agno, XFS_BTNUM_BNO);
	/*
	 * Lookup <= bno to find the leftward search's starting point.
	 */
	if ((error = xfs_alloc_lookup_le(bno_cur_lt, args->agbno, args->maxlen, &i)))
		goto error0;
	if (!i) {
		/*
		 * Didn't find anything; use this cursor for the rightward
		 * search.
		 */
		bno_cur_gt = bno_cur_lt;
		bno_cur_lt = NULL;
	}
	/*
	 * Found something.  Duplicate the cursor for the rightward search.
	 */
	else if ((error = xfs_btree_dup_cursor(bno_cur_lt, &bno_cur_gt)))
		goto error0;
	/*
	 * Increment the cursor, so we will point at the entry just right
	 * of the leftward entry if any, or to the leftmost entry.
	 */
	if ((error = xfs_btree_increment(bno_cur_gt, 0, &i)))
		goto error0;
	if (!i) {
		/*
		 * It failed, there are no rightward entries.
		 */
		xfs_btree_del_cursor(bno_cur_gt, XFS_BTREE_NOERROR);
		bno_cur_gt = NULL;
	}
	/*
	 * Loop going left with the leftward cursor, right with the
	 * rightward cursor, until either both directions give up or
	 * we find an entry at least as big as minlen.
	 */
	do {
		if (bno_cur_lt) {
			if ((error = xfs_alloc_get_rec(bno_cur_lt, &ltbno, &ltlen, &i)))
				goto error0;
			XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
			xfs_alloc_compute_aligned(ltbno, ltlen, args->alignment,
					args->minlen, &ltbnoa, &ltlena);
			if (ltlena >= args->minlen)
				break;
			if ((error = xfs_btree_decrement(bno_cur_lt, 0, &i)))
				goto error0;
			if (!i) {
				xfs_btree_del_cursor(bno_cur_lt,
						     XFS_BTREE_NOERROR);
				bno_cur_lt = NULL;
			}
		}
		if (bno_cur_gt) {
			if ((error = xfs_alloc_get_rec(bno_cur_gt, &gtbno, &gtlen, &i)))
				goto error0;
			XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
			xfs_alloc_compute_aligned(gtbno, gtlen, args->alignment,
					args->minlen, &gtbnoa, &gtlena);
			if (gtlena >= args->minlen)
				break;
			if ((error = xfs_btree_increment(bno_cur_gt, 0, &i)))
				goto error0;
			if (!i) {
				xfs_btree_del_cursor(bno_cur_gt,
						     XFS_BTREE_NOERROR);
				bno_cur_gt = NULL;
			}
		}
	} while (bno_cur_lt || bno_cur_gt);
	/*
	 * Got both cursors still active, need to find better entry.
	 */
	if (bno_cur_lt && bno_cur_gt) {
		/*
		 * Left side is long enough, look for a right side entry.
		 */
		if (ltlena >= args->minlen) {
			/*
			 * Fix up the length.
			 */
			args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
			xfs_alloc_fix_len(args);
			rlen = args->len;
			ltdiff = xfs_alloc_compute_diff(args->agbno, rlen,
				args->alignment, ltbno, ltlen, &ltnew);
			/*
			 * Not perfect.
			 */
			if (ltdiff) {
				/*
				 * Look until we find a better one, run out of
				 * space, or run off the end.
				 */
				while (bno_cur_lt && bno_cur_gt) {
					if ((error = xfs_alloc_get_rec(
							bno_cur_gt, &gtbno,
							&gtlen, &i)))
						goto error0;
					XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
					xfs_alloc_compute_aligned(gtbno, gtlen,
						args->alignment, args->minlen,
						&gtbnoa, &gtlena);
					/*
					 * The left one is clearly better.
					 */
					if (gtbnoa >= args->agbno + ltdiff) {
						xfs_btree_del_cursor(
							bno_cur_gt,
							XFS_BTREE_NOERROR);
						bno_cur_gt = NULL;
						break;
					}
					/*
					 * If we reach a big enough entry,
					 * compare the two and pick the best.
					 */
					if (gtlena >= args->minlen) {
						args->len =
							XFS_EXTLEN_MIN(gtlena,
								args->maxlen);
						xfs_alloc_fix_len(args);
						rlen = args->len;
						gtdiff = xfs_alloc_compute_diff(
							args->agbno, rlen,
							args->alignment,
							gtbno, gtlen, &gtnew);
						/*
						 * Right side is better.
						 */
						if (gtdiff < ltdiff) {
							xfs_btree_del_cursor(
								bno_cur_lt,
								XFS_BTREE_NOERROR);
							bno_cur_lt = NULL;
						}
						/*
						 * Left side is better.
						 */
						else {
							xfs_btree_del_cursor(
								bno_cur_gt,
								XFS_BTREE_NOERROR);
							bno_cur_gt = NULL;
						}
						break;
					}
					/*
					 * Fell off the right end.
					 */
					if ((error = xfs_btree_increment(
							bno_cur_gt, 0, &i)))
						goto error0;
					if (!i) {
						xfs_btree_del_cursor(
							bno_cur_gt,
							XFS_BTREE_NOERROR);
						bno_cur_gt = NULL;
						break;
					}
				}
			}
			/*
			 * The left side is perfect, trash the right side.
			 */
			else {
				xfs_btree_del_cursor(bno_cur_gt,
						     XFS_BTREE_NOERROR);
				bno_cur_gt = NULL;
			}
		}
		/*
		 * It's the right side that was found first, look left.
		 */
		else {
			/*
			 * Fix up the length.
			 */
			args->len = XFS_EXTLEN_MIN(gtlena, args->maxlen);
			xfs_alloc_fix_len(args);
			rlen = args->len;
			gtdiff = xfs_alloc_compute_diff(args->agbno, rlen,
				args->alignment, gtbno, gtlen, &gtnew);
			/*
			 * Right side entry isn't perfect.
			 */
			if (gtdiff) {
				/*
				 * Look until we find a better one, run out of
				 * space, or run off the end.
				 */
				while (bno_cur_lt && bno_cur_gt) {
					if ((error = xfs_alloc_get_rec(
							bno_cur_lt, &ltbno,
							&ltlen, &i)))
						goto error0;
					XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
					xfs_alloc_compute_aligned(ltbno, ltlen,
						args->alignment, args->minlen,
						&ltbnoa, &ltlena);
					/*
					 * The right one is clearly better.
					 */
					if (ltbnoa <= args->agbno - gtdiff) {
						xfs_btree_del_cursor(
							bno_cur_lt,
							XFS_BTREE_NOERROR);
						bno_cur_lt = NULL;
						break;
					}
					/*
					 * If we reach a big enough entry,
					 * compare the two and pick the best.
					 */
					if (ltlena >= args->minlen) {
						args->len = XFS_EXTLEN_MIN(
							ltlena, args->maxlen);
						xfs_alloc_fix_len(args);
						rlen = args->len;
						ltdiff = xfs_alloc_compute_diff(
							args->agbno, rlen,
							args->alignment,
							ltbno, ltlen, &ltnew);
						/*
						 * Left side is better.
						 */
						if (ltdiff < gtdiff) {
							xfs_btree_del_cursor(
								bno_cur_gt,
								XFS_BTREE_NOERROR);
							bno_cur_gt = NULL;
						}
						/*
						 * Right side is better.
						 */
						else {
							xfs_btree_del_cursor(
								bno_cur_lt,
								XFS_BTREE_NOERROR);
							bno_cur_lt = NULL;
						}
						break;
					}
					/*
					 * Fell off the left end.
					 */
					if ((error = xfs_btree_decrement(
							bno_cur_lt, 0, &i)))
						goto error0;
					if (!i) {
						xfs_btree_del_cursor(bno_cur_lt,
							XFS_BTREE_NOERROR);
						bno_cur_lt = NULL;
						break;
					}
				}
			}
			/*
			 * The right side is perfect, trash the left side.
			 */
			else {
				xfs_btree_del_cursor(bno_cur_lt,
					XFS_BTREE_NOERROR);
				bno_cur_lt = NULL;
			}
		}
	}
	/*
	 * If we couldn't get anything, give up.
	 */
	if (bno_cur_lt == NULL && bno_cur_gt == NULL) {
		TRACE_ALLOC("neither", args);
		args->agbno = NULLAGBLOCK;
		return 0;
	}
	/*
	 * At this point we have selected a freespace entry, either to the
	 * left or to the right.  If it's on the right, copy all the
	 * useful variables to the "left" set so we only have one
	 * copy of this code.
	 */
	if (bno_cur_gt) {
		bno_cur_lt = bno_cur_gt;
		bno_cur_gt = NULL;
		ltbno = gtbno;
		ltbnoa = gtbnoa;
		ltlen = gtlen;
		ltlena = gtlena;
		j = 1;
	} else
		j = 0;
	/*
	 * Fix up the length and compute the useful address.
	 */
	ltend = ltbno + ltlen;
	args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
	xfs_alloc_fix_len(args);
	if (!xfs_alloc_fix_minleft(args)) {
		TRACE_ALLOC("nominleft", args);
		xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
		return 0;
	}
	rlen = args->len;
	(void)xfs_alloc_compute_diff(args->agbno, rlen, args->alignment, ltbno,
		ltlen, &ltnew);
	ASSERT(ltnew >= ltbno);
	ASSERT(ltnew + rlen <= ltend);
	ASSERT(ltnew + rlen <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
	args->agbno = ltnew;
	if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur_lt, ltbno, ltlen,
			ltnew, rlen, XFSA_FIXUP_BNO_OK)))
		goto error0;
	TRACE_ALLOC(j ? "gt" : "lt", args);
	xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
	xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
	return 0;

 error0:
	TRACE_ALLOC("error", args);
	if (cnt_cur != NULL)
		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
	if (bno_cur_lt != NULL)
		xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_ERROR);
	if (bno_cur_gt != NULL)
		xfs_btree_del_cursor(bno_cur_gt, XFS_BTREE_ERROR);
	return error;
}

/*
 * Allocate a variable extent anywhere in the allocation group agno.
 * Extent's length (returned in len) will be between minlen and maxlen,
 * and of the form k * prod + mod unless there's nothing that large.
 * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
 */
STATIC int				/* error */
xfs_alloc_ag_vextent_size(
	xfs_alloc_arg_t	*args)		/* allocation argument structure */
{
	xfs_btree_cur_t	*bno_cur;	/* cursor for bno btree */
	xfs_btree_cur_t	*cnt_cur;	/* cursor for cnt btree */
	int		error;		/* error result */
	xfs_agblock_t	fbno;		/* start of found freespace */
	xfs_extlen_t	flen;		/* length of found freespace */
	int		i;		/* temp status variable */
	xfs_agblock_t	rbno;		/* returned block number */
	xfs_extlen_t	rlen;		/* length of returned extent */

	/*
	 * Allocate and initialize a cursor for the by-size btree.
	 */
	cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
		args->agno, XFS_BTNUM_CNT);
	bno_cur = NULL;
	/*
	 * Look for an entry >= maxlen+alignment-1 blocks.
	 */
	if ((error = xfs_alloc_lookup_ge(cnt_cur, 0,
			args->maxlen + args->alignment - 1, &i)))
		goto error0;
	/*
	 * If none, then pick up the last entry in the tree unless the
	 * tree is empty.
	 */
	if (!i) {
		if ((error = xfs_alloc_ag_vextent_small(args, cnt_cur, &fbno,
				&flen, &i)))
			goto error0;
		if (i == 0 || flen == 0) {
			xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
			TRACE_ALLOC("noentry", args);
			return 0;
		}
		ASSERT(i == 1);
	}
	/*
	 * There's a freespace as big as maxlen+alignment-1, get it.
	 */
	else {
		if ((error = xfs_alloc_get_rec(cnt_cur, &fbno, &flen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
	}
	/*
	 * In the first case above, we got the last entry in the
	 * by-size btree.  Now we check to see if the space hits maxlen
	 * once aligned; if not, we search left for something better.
	 * This can't happen in the second case above.
	 */
	xfs_alloc_compute_aligned(fbno, flen, args->alignment, args->minlen,
		&rbno, &rlen);
	rlen = XFS_EXTLEN_MIN(args->maxlen, rlen);
	XFS_WANT_CORRUPTED_GOTO(rlen == 0 ||
			(rlen <= flen && rbno + rlen <= fbno + flen), error0);
	if (rlen < args->maxlen) {
		xfs_agblock_t	bestfbno;
		xfs_extlen_t	bestflen;
		xfs_agblock_t	bestrbno;
		xfs_extlen_t	bestrlen;

		bestrlen = rlen;
		bestrbno = rbno;
		bestflen = flen;
		bestfbno = fbno;
		for (;;) {
			if ((error = xfs_btree_decrement(cnt_cur, 0, &i)))
				goto error0;
			if (i == 0)
				break;
			if ((error = xfs_alloc_get_rec(cnt_cur, &fbno, &flen,
					&i)))
				goto error0;
			XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
			if (flen < bestrlen)
				break;
			xfs_alloc_compute_aligned(fbno, flen, args->alignment,
				args->minlen, &rbno, &rlen);
			rlen = XFS_EXTLEN_MIN(args->maxlen, rlen);
			XFS_WANT_CORRUPTED_GOTO(rlen == 0 ||
				(rlen <= flen && rbno + rlen <= fbno + flen),
				error0);
			if (rlen > bestrlen) {
				bestrlen = rlen;
				bestrbno = rbno;
				bestflen = flen;
				bestfbno = fbno;
				if (rlen == args->maxlen)
					break;
			}
		}
		if ((error = xfs_alloc_lookup_eq(cnt_cur, bestfbno, bestflen,
				&i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		rlen = bestrlen;
		rbno = bestrbno;
		flen = bestflen;
		fbno = bestfbno;
	}
	args->wasfromfl = 0;
	/*
	 * Fix up the length.
	 */
	args->len = rlen;
	xfs_alloc_fix_len(args);
	if (rlen < args->minlen || !xfs_alloc_fix_minleft(args)) {
		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
		TRACE_ALLOC("nominleft", args);
		args->agbno = NULLAGBLOCK;
		return 0;
	}
	rlen = args->len;
	XFS_WANT_CORRUPTED_GOTO(rlen <= flen, error0);
	/*
	 * Allocate and initialize a cursor for the by-block tree.
	 */
	bno_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
		args->agno, XFS_BTNUM_BNO);
	if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur, fbno, flen,
			rbno, rlen, XFSA_FIXUP_CNT_OK)))
		goto error0;
	xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
	xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
	cnt_cur = bno_cur = NULL;
	args->len = rlen;
	args->agbno = rbno;
	XFS_WANT_CORRUPTED_GOTO(
		args->agbno + args->len <=
			be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length),
		error0);
	TRACE_ALLOC("normal", args);
	return 0;

error0:
	TRACE_ALLOC("error", args);
	if (cnt_cur)
		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
	if (bno_cur)
		xfs_btree_del_cursor(bno_cur, XFS_BTREE_ERROR);
	return error;
}

/*
 * Deal with the case where only small freespaces remain.
 * Either return the contents of the last freespace record,
 * or allocate space from the freelist if there is nothing in the tree.
 */
STATIC int			/* error */
xfs_alloc_ag_vextent_small(
	xfs_alloc_arg_t	*args,	/* allocation argument structure */
	xfs_btree_cur_t	*ccur,	/* by-size cursor */
	xfs_agblock_t	*fbnop,	/* result block number */
	xfs_extlen_t	*flenp,	/* result length */
	int		*stat)	/* status: 0-freelist, 1-normal/none */
{
	int		error;
	xfs_agblock_t	fbno;
	xfs_extlen_t	flen;
	int		i;

	if ((error = xfs_btree_decrement(ccur, 0, &i)))
		goto error0;
	if (i) {
		if ((error = xfs_alloc_get_rec(ccur, &fbno, &flen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
	}
	/*
	 * Nothing in the btree, try the freelist.  Make sure
	 * to respect minleft even when pulling from the
	 * freelist.
	 */
	else if (args->minlen == 1 && args->alignment == 1 && !args->isfl &&
		 (be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_flcount)
		  > args->minleft)) {
		error = xfs_alloc_get_freelist(args->tp, args->agbp, &fbno, 0);
		if (error)
			goto error0;
		if (fbno != NULLAGBLOCK) {
			if (args->userdata) {
				xfs_buf_t	*bp;

				bp = xfs_btree_get_bufs(args->mp, args->tp,
					args->agno, fbno, 0);
				xfs_trans_binval(args->tp, bp);
			}
			args->len = 1;
			args->agbno = fbno;
			XFS_WANT_CORRUPTED_GOTO(
				args->agbno + args->len <=
				be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length),
				error0);
			args->wasfromfl = 1;
			TRACE_ALLOC("freelist", args);
			*stat = 0;
			return 0;
		}
		/*
		 * Nothing in the freelist.
		 */
		else
			flen = 0;
	}
	/*
	 * Can't allocate from the freelist for some reason.
	 */
	else {
		fbno = NULLAGBLOCK;
		flen = 0;
	}
	/*
	 * Can't do the allocation, give up.
	 */
	if (flen < args->minlen) {
		args->agbno = NULLAGBLOCK;
		TRACE_ALLOC("notenough", args);
		flen = 0;
	}
	*fbnop = fbno;
	*flenp = flen;
	*stat = 1;
	TRACE_ALLOC("normal", args);
	return 0;

error0:
	TRACE_ALLOC("error", args);
	return error;
}

/*
 * Free the extent starting at agno/bno for length.
 */
STATIC int			/* error */
xfs_free_ag_extent(
	xfs_trans_t	*tp,	/* transaction pointer */
	xfs_buf_t	*agbp,	/* buffer for a.g. freelist header */
	xfs_agnumber_t	agno,	/* allocation group number */
	xfs_agblock_t	bno,	/* starting block number */
	xfs_extlen_t	len,	/* length of extent */
	int		isfl)	/* set if is freelist blocks - no sb acctg */
{
	xfs_btree_cur_t	*bno_cur;	/* cursor for by-block btree */
	xfs_btree_cur_t	*cnt_cur;	/* cursor for by-size btree */
	int		error;		/* error return value */
	xfs_agblock_t	gtbno;		/* start of right neighbor block */
	xfs_extlen_t	gtlen;		/* length of right neighbor block */
	int		haveleft;	/* have a left neighbor block */
	int		haveright;	/* have a right neighbor block */
	int		i;		/* temp, result code */
	xfs_agblock_t	ltbno;		/* start of left neighbor block */
	xfs_extlen_t	ltlen;		/* length of left neighbor block */
	xfs_mount_t	*mp;		/* mount point struct for filesystem */
	xfs_agblock_t	nbno;		/* new starting block of freespace */
	xfs_extlen_t	nlen;		/* new length of freespace */

	mp = tp->t_mountp;
	/*
	 * Allocate and initialize a cursor for the by-block btree.
	 */
	bno_cur = xfs_allocbt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_BNO);
	cnt_cur = NULL;
	/*
	 * Look for a neighboring block on the left (lower block numbers)
	 * that is contiguous with this space.
	 */
	if ((error = xfs_alloc_lookup_le(bno_cur, bno, len, &haveleft)))
		goto error0;
	if (haveleft) {
		/*
		 * There is a block to our left.
		 */
		if ((error = xfs_alloc_get_rec(bno_cur, &ltbno, &ltlen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		/*
		 * It's not contiguous, though.
		 */
		if (ltbno + ltlen < bno)
			haveleft = 0;
		else {
			/*
			 * If this failure happens the request to free this
			 * space was invalid, it's (partly) already free.
			 * Very bad.
			 */
			XFS_WANT_CORRUPTED_GOTO(ltbno + ltlen <= bno, error0);
		}
	}
	/*
	 * Look for a neighboring block on the right (higher block numbers)
	 * that is contiguous with this space.
	 */
	if ((error = xfs_btree_increment(bno_cur, 0, &haveright)))
		goto error0;
	if (haveright) {
		/*
		 * There is a block to our right.
		 */
		if ((error = xfs_alloc_get_rec(bno_cur, &gtbno, &gtlen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		/*
		 * It's not contiguous, though.
		 */
		if (bno + len < gtbno)
			haveright = 0;
		else {
			/*
			 * If this failure happens the request to free this
			 * space was invalid, it's (partly) already free.
			 * Very bad.
			 */
			XFS_WANT_CORRUPTED_GOTO(gtbno >= bno + len, error0);
		}
	}
	/*
	 * Now allocate and initialize a cursor for the by-size tree.
	 */
	cnt_cur = xfs_allocbt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_CNT);
	/*
	 * Have both left and right contiguous neighbors.
	 * Merge all three into a single free block.
	 */
	if (haveleft && haveright) {
		/*
		 * Delete the old by-size entry on the left.
		 */
		if ((error = xfs_alloc_lookup_eq(cnt_cur, ltbno, ltlen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		if ((error = xfs_btree_delete(cnt_cur, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		/*
		 * Delete the old by-size entry on the right.
		 */
		if ((error = xfs_alloc_lookup_eq(cnt_cur, gtbno, gtlen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		if ((error = xfs_btree_delete(cnt_cur, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		/*
		 * Delete the old by-block entry for the right block.
		 */
		if ((error = xfs_btree_delete(bno_cur, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		/*
		 * Move the by-block cursor back to the left neighbor.
		 */
		if ((error = xfs_btree_decrement(bno_cur, 0, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
#ifdef DEBUG
		/*
		 * Check that this is the right record: delete didn't
		 * mangle the cursor.
		 */
		{
			xfs_agblock_t	xxbno;
			xfs_extlen_t	xxlen;

			if ((error = xfs_alloc_get_rec(bno_cur, &xxbno, &xxlen,
					&i)))
				goto error0;
			XFS_WANT_CORRUPTED_GOTO(
				i == 1 && xxbno == ltbno && xxlen == ltlen,
				error0);
		}
#endif
		/*
		 * Update remaining by-block entry to the new, joined block.
		 */
		nbno = ltbno;
		nlen = len + ltlen + gtlen;
		if ((error = xfs_alloc_update(bno_cur, nbno, nlen)))
			goto error0;
	}
	/*
	 * Have only a left contiguous neighbor.
	 * Merge it together with the new freespace.
	 */
	else if (haveleft) {
		/*
		 * Delete the old by-size entry on the left.
		 */
		if ((error = xfs_alloc_lookup_eq(cnt_cur, ltbno, ltlen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		if ((error = xfs_btree_delete(cnt_cur, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		/*
		 * Back up the by-block cursor to the left neighbor, and
		 * update its length.
		 */
		if ((error = xfs_btree_decrement(bno_cur, 0, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		nbno = ltbno;
		nlen = len + ltlen;
		if ((error = xfs_alloc_update(bno_cur, nbno, nlen)))
			goto error0;
	}
	/*
	 * Have only a right contiguous neighbor.
	 * Merge it together with the new freespace.
	 */
	else if (haveright) {
		/*
		 * Delete the old by-size entry on the right.
		 */
		if ((error = xfs_alloc_lookup_eq(cnt_cur, gtbno, gtlen, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		if ((error = xfs_btree_delete(cnt_cur, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
		/*
		 * Update the starting block and length of the right
		 * neighbor in the by-block tree.
		 */
		nbno = bno;
		nlen = len + gtlen;
		if ((error = xfs_alloc_update(bno_cur, nbno, nlen)))
			goto error0;
	}
	/*
	 * No contiguous neighbors.
	 * Insert the new freespace into the by-block tree.
	 */
	else {
		nbno = bno;
		nlen = len;
		if ((error = xfs_btree_insert(bno_cur, &i)))
			goto error0;
		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
	}
	xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
	bno_cur = NULL;
	/*
	 * In all cases we need to insert the new freespace in the by-size tree.
	 */
	if ((error = xfs_alloc_lookup_eq(cnt_cur, nbno, nlen, &i)))
		goto error0;
	XFS_WANT_CORRUPTED_GOTO(i == 0, error0);
	if ((error = xfs_btree_insert(cnt_cur, &i)))
		goto error0;
	XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
	xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
	cnt_cur = NULL;
	/*
	 * Update the freespace totals in the ag and superblock.
	 */
	{
		xfs_agf_t	*agf;
		xfs_perag_t	*pag;		/* per allocation group data */

		agf = XFS_BUF_TO_AGF(agbp);
		pag = &mp->m_perag[agno];
		be32_add_cpu(&agf->agf_freeblks, len);
		xfs_trans_agblocks_delta(tp, len);
		pag->pagf_freeblks += len;
		XFS_WANT_CORRUPTED_GOTO(
			be32_to_cpu(agf->agf_freeblks) <=
			be32_to_cpu(agf->agf_length),
			error0);
		TRACE_MODAGF(NULL, agf, XFS_AGF_FREEBLKS);
		xfs_alloc_log_agf(tp, agbp, XFS_AGF_FREEBLKS);
		if (!isfl)
			xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (long)len);
		XFS_STATS_INC(xs_freex);
		XFS_STATS_ADD(xs_freeb, len);
	}
	TRACE_FREE(haveleft ?
			(haveright ? "both" : "left") :
			(haveright ? "right" : "none"),
		agno, bno, len, isfl);

	/*
	 * Since blocks move to the free list without the coordination
	 * used in xfs_bmap_finish, we can't allow block to be available
	 * for reallocation and non-transaction writing (user data)
	 * until we know that the transaction that moved it to the free
	 * list is permanently on disk.  We track the blocks by declaring
	 * these blocks as "busy"; the busy list is maintained on a per-ag
	 * basis and each transaction records which entries should be removed
	 * when the iclog commits to disk.  If a busy block is allocated,
	 * the iclog is pushed up to the LSN that freed the block.
	 */
	xfs_alloc_mark_busy(tp, agno, bno, len);
	return 0;

 error0:
	TRACE_FREE("error", agno, bno, len, isfl);
	if (bno_cur)
		xfs_btree_del_cursor(bno_cur, XFS_BTREE_ERROR);
	if (cnt_cur)
		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
	return error;
}

/*
 * Visible (exported) allocation/free functions.
 * Some of these are used just by xfs_alloc_btree.c and this file.
 */

/*
 * Compute and fill in value of m_ag_maxlevels.
 */
void
xfs_alloc_compute_maxlevels(
	xfs_mount_t	*mp)	/* file system mount structure */
{
	int		level;
	uint		maxblocks;
	uint		maxleafents;
	int		minleafrecs;
	int		minnoderecs;

	maxleafents = (mp->m_sb.sb_agblocks + 1) / 2;
	minleafrecs = mp->m_alloc_mnr[0];
	minnoderecs = mp->m_alloc_mnr[1];
	maxblocks = (maxleafents + minleafrecs - 1) / minleafrecs;
	for (level = 1; maxblocks > 1; level++)
		maxblocks = (maxblocks + minnoderecs - 1) / minnoderecs;
	mp->m_ag_maxlevels = level;
}

/*
 * Decide whether to use this allocation group for this allocation.
 * If so, fix up the btree freelist's size.
 */
STATIC int			/* error */
xfs_alloc_fix_freelist(
	xfs_alloc_arg_t	*args,	/* allocation argument structure */
	int		flags)	/* XFS_ALLOC_FLAG_... */
{
	xfs_buf_t	*agbp;	/* agf buffer pointer */
	xfs_agf_t	*agf;	/* a.g. freespace structure pointer */
	xfs_buf_t	*agflbp;/* agfl buffer pointer */
	xfs_agblock_t	bno;	/* freelist block */
	xfs_extlen_t	delta;	/* new blocks needed in freelist */
	int		error;	/* error result code */
	xfs_extlen_t	longest;/* longest extent in allocation group */
	xfs_mount_t	*mp;	/* file system mount point structure */
	xfs_extlen_t	need;	/* total blocks needed in freelist */
	xfs_perag_t	*pag;	/* per-ag information structure */
	xfs_alloc_arg_t	targs;	/* local allocation arguments */
	xfs_trans_t	*tp;	/* transaction pointer */

	mp = args->mp;

	pag = args->pag;
	tp = args->tp;
	if (!pag->pagf_init) {
		if ((error = xfs_alloc_read_agf(mp, tp, args->agno, flags,
				&agbp)))
			return error;
		if (!pag->pagf_init) {
			ASSERT(flags & XFS_ALLOC_FLAG_TRYLOCK);
			ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
			args->agbp = NULL;
			return 0;
		}
	} else
		agbp = NULL;

	/*
	 * If this is a metadata preferred pag and we are user data
	 * then try somewhere else if we are not being asked to
	 * try harder at this point
	 */
	if (pag->pagf_metadata && args->userdata &&
	    (flags & XFS_ALLOC_FLAG_TRYLOCK)) {
		ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
		args->agbp = NULL;
		return 0;
	}

	if (!(flags & XFS_ALLOC_FLAG_FREEING)) {
		need = XFS_MIN_FREELIST_PAG(pag, mp);
		delta = need > pag->pagf_flcount ? need - pag->pagf_flcount : 0;
		/*
		 * If it looks like there isn't a long enough extent, or enough
		 * total blocks, reject it.
		 */
		longest = (pag->pagf_longest > delta) ?
			(pag->pagf_longest - delta) :
			(pag->pagf_flcount > 0 || pag->pagf_longest > 0);
		if ((args->minlen + args->alignment + args->minalignslop - 1) >
				longest ||
		    ((int)(pag->pagf_freeblks + pag->pagf_flcount -
			   need - args->total) < (int)args->minleft)) {
			if (agbp)
				xfs_trans_brelse(tp, agbp);
			args->agbp = NULL;
			return 0;
		}
	}

	/*
	 * Get the a.g. freespace buffer.
	 * Can fail if we're not blocking on locks, and it's held.
	 */
	if (agbp == NULL) {
		if ((error = xfs_alloc_read_agf(mp, tp, args->agno, flags,
				&agbp)))
			return error;
		if (agbp == NULL) {
			ASSERT(flags & XFS_ALLOC_FLAG_TRYLOCK);
			ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
			args->agbp = NULL;
			return 0;
		}
	}
	/*
	 * Figure out how many blocks we should have in the freelist.
	 */
	agf = XFS_BUF_TO_AGF(agbp);
	need = XFS_MIN_FREELIST(agf, mp);
	/*
	 * If there isn't enough total or single-extent, reject it.
	 */
	if (!(flags & XFS_ALLOC_FLAG_FREEING)) {
		delta = need > be32_to_cpu(agf->agf_flcount) ?
			(need - be32_to_cpu(agf->agf_flcount)) : 0;
		longest = be32_to_cpu(agf->agf_longest);
		longest = (longest > delta) ? (longest - delta) :
			(be32_to_cpu(agf->agf_flcount) > 0 || longest > 0);
		if ((args->minlen + args->alignment + args->minalignslop - 1) >
				longest ||
		    ((int)(be32_to_cpu(agf->agf_freeblks) +
		     be32_to_cpu(agf->agf_flcount) - need - args->total) <
				(int)args->minleft)) {
			xfs_trans_brelse(tp, agbp);
			args->agbp = NULL;
			return 0;
		}
	}
	/*
	 * Make the freelist shorter if it's too long.
	 */
	while (be32_to_cpu(agf->agf_flcount) > need) {
		xfs_buf_t	*bp;

		error = xfs_alloc_get_freelist(tp, agbp, &bno, 0);
		if (error)
			return error;
		if ((error = xfs_free_ag_extent(tp, agbp, args->agno, bno, 1, 1)))
			return error;
		bp = xfs_btree_get_bufs(mp, tp, args->agno, bno, 0);
		xfs_trans_binval(tp, bp);
	}
	/*
	 * Initialize the args structure.
	 */
	targs.tp = tp;
	targs.mp = mp;
	targs.agbp = agbp;
	targs.agno = args->agno;
	targs.mod = targs.minleft = targs.wasdel = targs.userdata =
		targs.minalignslop = 0;
	targs.alignment = targs.minlen = targs.prod = targs.isfl = 1;
	targs.type = XFS_ALLOCTYPE_THIS_AG;
	targs.pag = pag;
	if ((error = xfs_alloc_read_agfl(mp, tp, targs.agno, &agflbp)))
		return error;
	/*
	 * Make the freelist longer if it's too short.
	 */
	while (be32_to_cpu(agf->agf_flcount) < need) {
		targs.agbno = 0;
		targs.maxlen = need - be32_to_cpu(agf->agf_flcount);
		/*
		 * Allocate as many blocks as possible at once.
		 */
		if ((error = xfs_alloc_ag_vextent(&targs))) {
			xfs_trans_brelse(tp, agflbp);
			return error;
		}
		/*
		 * Stop if we run out.  Won't happen if callers are obeying
		 * the restrictions correctly.  Can happen for free calls
		 * on a completely full ag.
		 */
		if (targs.agbno == NULLAGBLOCK) {
			if (flags & XFS_ALLOC_FLAG_FREEING)
				break;
			xfs_trans_brelse(tp, agflbp);
			args->agbp = NULL;
			return 0;
		}
		/*
		 * Put each allocated block on the list.
		 */
		for (bno = targs.agbno; bno < targs.agbno + targs.len; bno++) {
			error = xfs_alloc_put_freelist(tp, agbp,
							agflbp, bno, 0);
			if (error)
				return error;
		}
	}
	xfs_trans_brelse(tp, agflbp);
	args->agbp = agbp;
	return 0;
}

/*
 * Get a block from the freelist.
 * Returns with the buffer for the block gotten.
 */
int				/* error */
xfs_alloc_get_freelist(
	xfs_trans_t	*tp,	/* transaction pointer */
	xfs_buf_t	*agbp,	/* buffer containing the agf structure */
	xfs_agblock_t	*bnop,	/* block address retrieved from freelist */
	int		btreeblk) /* destination is a AGF btree */
{
	xfs_agf_t	*agf;	/* a.g. freespace structure */
	xfs_agfl_t	*agfl;	/* a.g. freelist structure */
	xfs_buf_t	*agflbp;/* buffer for a.g. freelist structure */
	xfs_agblock_t	bno;	/* block number returned */
	int		error;
	int		logflags;
	xfs_mount_t	*mp;	/* mount structure */
	xfs_perag_t	*pag;	/* per allocation group data */

	agf = XFS_BUF_TO_AGF(agbp);
	/*
	 * Freelist is empty, give up.
	 */
	if (!agf->agf_flcount) {
		*bnop = NULLAGBLOCK;
		return 0;
	}
	/*
	 * Read the array of free blocks.
	 */
	mp = tp->t_mountp;
	if ((error = xfs_alloc_read_agfl(mp, tp,
			be32_to_cpu(agf->agf_seqno), &agflbp)))
		return error;
	agfl = XFS_BUF_TO_AGFL(agflbp);
	/*
	 * Get the block number and update the data structures.
	 */
	bno = be32_to_cpu(agfl->agfl_bno[be32_to_cpu(agf->agf_flfirst)]);
	be32_add_cpu(&agf->agf_flfirst, 1);
	xfs_trans_brelse(tp, agflbp);
	if (be32_to_cpu(agf->agf_flfirst) == XFS_AGFL_SIZE(mp))
		agf->agf_flfirst = 0;
	pag = &mp->m_perag[be32_to_cpu(agf->agf_seqno)];
	be32_add_cpu(&agf->agf_flcount, -1);
	xfs_trans_agflist_delta(tp, -1);
	pag->pagf_flcount--;

	logflags = XFS_AGF_FLFIRST | XFS_AGF_FLCOUNT;
	if (btreeblk) {
		be32_add_cpu(&agf->agf_btreeblks, 1);
		pag->pagf_btreeblks++;
		logflags |= XFS_AGF_BTREEBLKS;
	}

	TRACE_MODAGF(NULL, agf, logflags);
	xfs_alloc_log_agf(tp, agbp, logflags);
	*bnop = bno;

	/*
	 * As blocks are freed, they are added to the per-ag busy list
	 * and remain there until the freeing transaction is committed to
	 * disk.  Now that we have allocated blocks, this list must be
	 * searched to see if a block is being reused.  If one is, then
	 * the freeing transaction must be pushed to disk NOW by forcing
	 * to disk all iclogs up that transaction's LSN.
	 */
	xfs_alloc_search_busy(tp, be32_to_cpu(agf->agf_seqno), bno, 1);
	return 0;
}

/*
 * Log the given fields from the agf structure.
 */
void
xfs_alloc_log_agf(
	xfs_trans_t	*tp,	/* transaction pointer */
	xfs_buf_t	*bp,	/* buffer for a.g. freelist header */
	int		fields)	/* mask of fields to be logged (XFS_AGF_...) */
{
	int	first;		/* first byte offset */
	int	last;		/* last byte offset */
	static const short	offsets[] = {
		offsetof(xfs_agf_t, agf_magicnum),
		offsetof(xfs_agf_t, agf_versionnum),
		offsetof(xfs_agf_t, agf_seqno),
		offsetof(xfs_agf_t, agf_length),
		offsetof(xfs_agf_t, agf_roots[0]),
		offsetof(xfs_agf_t, agf_levels[0]),
		offsetof(xfs_agf_t, agf_flfirst),
		offsetof(xfs_agf_t, agf_fllast),
		offsetof(xfs_agf_t, agf_flcount),
		offsetof(xfs_agf_t, agf_freeblks),
		offsetof(xfs_agf_t, agf_longest),
		offsetof(xfs_agf_t, agf_btreeblks),
		sizeof(xfs_agf_t)
	};

	xfs_btree_offsets(fields, offsets, XFS_AGF_NUM_BITS, &first, &last);
	xfs_trans_log_buf(tp, bp, (uint)first, (uint)last);
}

/*
 * Interface for inode allocation to force the pag data to be initialized.
 */
int					/* error */
xfs_alloc_pagf_init(
	xfs_mount_t		*mp,	/* file system mount structure */
	xfs_trans_t		*tp,	/* transaction pointer */
	xfs_agnumber_t		agno,	/* allocation group number */
	int			flags)	/* XFS_ALLOC_FLAGS_... */
{
	xfs_buf_t		*bp;
	int			error;

	if ((error = xfs_alloc_read_agf(mp, tp, agno, flags, &bp)))
		return error;
	if (bp)
		xfs_trans_brelse(tp, bp);
	return 0;
}

/*
 * Put the block on the freelist for the allocation group.
 */
int					/* error */
xfs_alloc_put_freelist(
	xfs_trans_t		*tp,	/* transaction pointer */
	xfs_buf_t		*agbp,	/* buffer for a.g. freelist header */
	xfs_buf_t		*agflbp,/* buffer for a.g. free block array */
	xfs_agblock_t		bno,	/* block being freed */
	int			btreeblk) /* block came from a AGF btree */
{
	xfs_agf_t		*agf;	/* a.g. freespace structure */
	xfs_agfl_t		*agfl;	/* a.g. free block array */
	__be32			*blockp;/* pointer to array entry */
	int			error;
	int			logflags;
	xfs_mount_t		*mp;	/* mount structure */
	xfs_perag_t		*pag;	/* per allocation group data */

	agf = XFS_BUF_TO_AGF(agbp);
	mp = tp->t_mountp;

	if (!agflbp && (error = xfs_alloc_read_agfl(mp, tp,
			be32_to_cpu(agf->agf_seqno), &agflbp)))
		return error;
	agfl = XFS_BUF_TO_AGFL(agflbp);
	be32_add_cpu(&agf->agf_fllast, 1);
	if (be32_to_cpu(agf->agf_fllast) == XFS_AGFL_SIZE(mp))
		agf->agf_fllast = 0;
	pag = &mp->m_perag[be32_to_cpu(agf->agf_seqno)];
	be32_add_cpu(&agf->agf_flcount, 1);
	xfs_trans_agflist_delta(tp, 1);
	pag->pagf_flcount++;

	logflags = XFS_AGF_FLLAST | XFS_AGF_FLCOUNT;
	if (btreeblk) {
		be32_add_cpu(&agf->agf_btreeblks, -1);
		pag->pagf_btreeblks--;
		logflags |= XFS_AGF_BTREEBLKS;
	}

	TRACE_MODAGF(NULL, agf, logflags);
	xfs_alloc_log_agf(tp, agbp, logflags);

	ASSERT(be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp));
	blockp = &agfl->agfl_bno[be32_to_cpu(agf->agf_fllast)];
	*blockp = cpu_to_be32(bno);
	TRACE_MODAGF(NULL, agf, logflags);
	xfs_alloc_log_agf(tp, agbp, logflags);
	xfs_trans_log_buf(tp, agflbp,
		(int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl),
		(int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl +
			sizeof(xfs_agblock_t) - 1));
	return 0;
}

/*
 * Read in the allocation group header (free/alloc section).
 */
int					/* error */
xfs_alloc_read_agf(
	xfs_mount_t	*mp,		/* mount point structure */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_agnumber_t	agno,		/* allocation group number */
	int		flags,		/* XFS_ALLOC_FLAG_... */
	xfs_buf_t	**bpp)		/* buffer for the ag freelist header */
{
	xfs_agf_t	*agf;		/* ag freelist header */
	int		agf_ok;		/* set if agf is consistent */
	xfs_buf_t	*bp;		/* return value */
	xfs_perag_t	*pag;		/* per allocation group data */
	int		error;

	ASSERT(agno != NULLAGNUMBER);
	error = xfs_trans_read_buf(
			mp, tp, mp->m_ddev_targp,
			XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
			XFS_FSS_TO_BB(mp, 1),
			(flags & XFS_ALLOC_FLAG_TRYLOCK) ? XFS_BUF_TRYLOCK : 0U,
			&bp);
	if (error)
		return error;
	ASSERT(!bp || !XFS_BUF_GETERROR(bp));
	if (!bp) {
		*bpp = NULL;
		return 0;
	}
	/*
	 * Validate the magic number of the agf block.
	 */
	agf = XFS_BUF_TO_AGF(bp);
	agf_ok =
		be32_to_cpu(agf->agf_magicnum) == XFS_AGF_MAGIC &&
		XFS_AGF_GOOD_VERSION(be32_to_cpu(agf->agf_versionnum)) &&
		be32_to_cpu(agf->agf_freeblks) <= be32_to_cpu(agf->agf_length) &&
		be32_to_cpu(agf->agf_flfirst) < XFS_AGFL_SIZE(mp) &&
		be32_to_cpu(agf->agf_fllast) < XFS_AGFL_SIZE(mp) &&
		be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp);
	if (unlikely(XFS_TEST_ERROR(!agf_ok, mp, XFS_ERRTAG_ALLOC_READ_AGF,
			XFS_RANDOM_ALLOC_READ_AGF))) {
		XFS_CORRUPTION_ERROR("xfs_alloc_read_agf",
				     XFS_ERRLEVEL_LOW, mp, agf);
		xfs_trans_brelse(tp, bp);
		return XFS_ERROR(EFSCORRUPTED);
	}
	pag = &mp->m_perag[agno];
	if (!pag->pagf_init) {
		pag->pagf_freeblks = be32_to_cpu(agf->agf_freeblks);
		pag->pagf_btreeblks = be32_to_cpu(agf->agf_btreeblks);
		pag->pagf_flcount = be32_to_cpu(agf->agf_flcount);
		pag->pagf_longest = be32_to_cpu(agf->agf_longest);
		pag->pagf_levels[XFS_BTNUM_BNOi] =
			be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNOi]);
		pag->pagf_levels[XFS_BTNUM_CNTi] =
			be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]);
		spin_lock_init(&pag->pagb_lock);
		pag->pagb_list = kmem_zalloc(XFS_PAGB_NUM_SLOTS *
					sizeof(xfs_perag_busy_t), KM_SLEEP);
		pag->pagf_init = 1;
	}
#ifdef DEBUG
	else if (!XFS_FORCED_SHUTDOWN(mp)) {
		ASSERT(pag->pagf_freeblks == be32_to_cpu(agf->agf_freeblks));
		ASSERT(pag->pagf_flcount == be32_to_cpu(agf->agf_flcount));
		ASSERT(pag->pagf_longest == be32_to_cpu(agf->agf_longest));
		ASSERT(pag->pagf_levels[XFS_BTNUM_BNOi] ==
		       be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNOi]));
		ASSERT(pag->pagf_levels[XFS_BTNUM_CNTi] ==
		       be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]));
	}
#endif
	XFS_BUF_SET_VTYPE_REF(bp, B_FS_AGF, XFS_AGF_REF);
	*bpp = bp;
	return 0;
}

/*
 * Allocate an extent (variable-size).
 * Depending on the allocation type, we either look in a single allocation
 * group or loop over the allocation groups to find the result.
 */
int				/* error */
xfs_alloc_vextent(
	xfs_alloc_arg_t	*args)	/* allocation argument structure */
{
	xfs_agblock_t	agsize;	/* allocation group size */
	int		error;
	int		flags;	/* XFS_ALLOC_FLAG_... locking flags */
	xfs_extlen_t	minleft;/* minimum left value, temp copy */
	xfs_mount_t	*mp;	/* mount structure pointer */
	xfs_agnumber_t	sagno;	/* starting allocation group number */
	xfs_alloctype_t	type;	/* input allocation type */
	int		bump_rotor = 0;
	int		no_min = 0;
	xfs_agnumber_t	rotorstep = xfs_rotorstep; /* inode32 agf stepper */

	mp = args->mp;
	type = args->otype = args->type;
	args->agbno = NULLAGBLOCK;
	/*
	 * Just fix this up, for the case where the last a.g. is shorter
	 * (or there's only one a.g.) and the caller couldn't easily figure
	 * that out (xfs_bmap_alloc).
	 */
	agsize = mp->m_sb.sb_agblocks;
	if (args->maxlen > agsize)
		args->maxlen = agsize;
	if (args->alignment == 0)
		args->alignment = 1;
	ASSERT(XFS_FSB_TO_AGNO(mp, args->fsbno) < mp->m_sb.sb_agcount);
	ASSERT(XFS_FSB_TO_AGBNO(mp, args->fsbno) < agsize);
	ASSERT(args->minlen <= args->maxlen);
	ASSERT(args->minlen <= agsize);
	ASSERT(args->mod < args->prod);
	if (XFS_FSB_TO_AGNO(mp, args->fsbno) >= mp->m_sb.sb_agcount ||
	    XFS_FSB_TO_AGBNO(mp, args->fsbno) >= agsize ||
	    args->minlen > args->maxlen || args->minlen > agsize ||
	    args->mod >= args->prod) {
		args->fsbno = NULLFSBLOCK;
		TRACE_ALLOC("badargs", args);
		return 0;
	}
	minleft = args->minleft;

	switch (type) {
	case XFS_ALLOCTYPE_THIS_AG:
	case XFS_ALLOCTYPE_NEAR_BNO:
	case XFS_ALLOCTYPE_THIS_BNO:
		/*
		 * These three force us into a single a.g.
		 */
		args->agno = XFS_FSB_TO_AGNO(mp, args->fsbno);
		down_read(&mp->m_peraglock);
		args->pag = &mp->m_perag[args->agno];
		args->minleft = 0;
		error = xfs_alloc_fix_freelist(args, 0);
		args->minleft = minleft;
		if (error) {
			TRACE_ALLOC("nofix", args);
			goto error0;
		}
		if (!args->agbp) {
			up_read(&mp->m_peraglock);
			TRACE_ALLOC("noagbp", args);
			break;
		}
		args->agbno = XFS_FSB_TO_AGBNO(mp, args->fsbno);
		if ((error = xfs_alloc_ag_vextent(args)))
			goto error0;
		up_read(&mp->m_peraglock);
		break;
	case XFS_ALLOCTYPE_START_BNO:
		/*
		 * Try near allocation first, then anywhere-in-ag after
		 * the first a.g. fails.
		 */
		if ((args->userdata  == XFS_ALLOC_INITIAL_USER_DATA) &&
		    (mp->m_flags & XFS_MOUNT_32BITINODES)) {
			args->fsbno = XFS_AGB_TO_FSB(mp,
					((mp->m_agfrotor / rotorstep) %
					mp->m_sb.sb_agcount), 0);
			bump_rotor = 1;
		}
		args->agbno = XFS_FSB_TO_AGBNO(mp, args->fsbno);
		args->type = XFS_ALLOCTYPE_NEAR_BNO;
		/* FALLTHROUGH */
	case XFS_ALLOCTYPE_ANY_AG:
	case XFS_ALLOCTYPE_START_AG:
	case XFS_ALLOCTYPE_FIRST_AG:
		/*
		 * Rotate through the allocation groups looking for a winner.
		 */
		if (type == XFS_ALLOCTYPE_ANY_AG) {
			/*
			 * Start with the last place we left off.
			 */
			args->agno = sagno = (mp->m_agfrotor / rotorstep) %
					mp->m_sb.sb_agcount;
			args->type = XFS_ALLOCTYPE_THIS_AG;
			flags = XFS_ALLOC_FLAG_TRYLOCK;
		} else if (type == XFS_ALLOCTYPE_FIRST_AG) {
			/*
			 * Start with allocation group given by bno.
			 */
			args->agno = XFS_FSB_TO_AGNO(mp, args->fsbno);
			args->type = XFS_ALLOCTYPE_THIS_AG;
			sagno = 0;
			flags = 0;
		} else {
			if (type == XFS_ALLOCTYPE_START_AG)
				args->type = XFS_ALLOCTYPE_THIS_AG;
			/*
			 * Start with the given allocation group.
			 */
			args->agno = sagno = XFS_FSB_TO_AGNO(mp, args->fsbno);
			flags = XFS_ALLOC_FLAG_TRYLOCK;
		}
		/*
		 * Loop over allocation groups twice; first time with
		 * trylock set, second time without.
		 */
		down_read(&mp->m_peraglock);
		for (;;) {
			args->pag = &mp->m_perag[args->agno];
			if (no_min) args->minleft = 0;
			error = xfs_alloc_fix_freelist(args, flags);
			args->minleft = minleft;
			if (error) {
				TRACE_ALLOC("nofix", args);
				goto error0;
			}
			/*
			 * If we get a buffer back then the allocation will fly.
			 */
			if (args->agbp) {
				if ((error = xfs_alloc_ag_vextent(args)))
					goto error0;
				break;
			}
			TRACE_ALLOC("loopfailed", args);
			/*
			 * Didn't work, figure out the next iteration.
			 */
			if (args->agno == sagno &&
			    type == XFS_ALLOCTYPE_START_BNO)
				args->type = XFS_ALLOCTYPE_THIS_AG;
			/*
			* For the first allocation, we can try any AG to get
			* space.  However, if we already have allocated a
			* block, we don't want to try AGs whose number is below
			* sagno. Otherwise, we may end up with out-of-order
			* locking of AGF, which might cause deadlock.
			*/
			if (++(args->agno) == mp->m_sb.sb_agcount) {
				if (args->firstblock != NULLFSBLOCK)
					args->agno = sagno;
				else
					args->agno = 0;
			}
			/*
			 * Reached the starting a.g., must either be done
			 * or switch to non-trylock mode.
			 */
			if (args->agno == sagno) {
				if (no_min == 1) {
					args->agbno = NULLAGBLOCK;
					TRACE_ALLOC("allfailed", args);
					break;
				}
				if (flags == 0) {
					no_min = 1;
				} else {
					flags = 0;
					if (type == XFS_ALLOCTYPE_START_BNO) {
						args->agbno = XFS_FSB_TO_AGBNO(mp,
							args->fsbno);
						args->type = XFS_ALLOCTYPE_NEAR_BNO;
					}
				}
			}
		}
		up_read(&mp->m_peraglock);
		if (bump_rotor || (type == XFS_ALLOCTYPE_ANY_AG)) {
			if (args->agno == sagno)
				mp->m_agfrotor = (mp->m_agfrotor + 1) %
					(mp->m_sb.sb_agcount * rotorstep);
			else
				mp->m_agfrotor = (args->agno * rotorstep + 1) %
					(mp->m_sb.sb_agcount * rotorstep);
		}
		break;
	default:
		ASSERT(0);
		/* NOTREACHED */
	}
	if (args->agbno == NULLAGBLOCK)
		args->fsbno = NULLFSBLOCK;
	else {
		args->fsbno = XFS_AGB_TO_FSB(mp, args->agno, args->agbno);
#ifdef DEBUG
		ASSERT(args->len >= args->minlen);
		ASSERT(args->len <= args->maxlen);
		ASSERT(args->agbno % args->alignment == 0);
		XFS_AG_CHECK_DADDR(mp, XFS_FSB_TO_DADDR(mp, args->fsbno),
			args->len);
#endif
	}
	return 0;
error0:
	up_read(&mp->m_peraglock);
	return error;
}

/*
 * Free an extent.
 * Just break up the extent address and hand off to xfs_free_ag_extent
 * after fixing up the freelist.
 */
int				/* error */
xfs_free_extent(
	xfs_trans_t	*tp,	/* transaction pointer */
	xfs_fsblock_t	bno,	/* starting block number of extent */
	xfs_extlen_t	len)	/* length of extent */
{
	xfs_alloc_arg_t	args;
	int		error;

	ASSERT(len != 0);
	memset(&args, 0, sizeof(xfs_alloc_arg_t));
	args.tp = tp;
	args.mp = tp->t_mountp;
	args.agno = XFS_FSB_TO_AGNO(args.mp, bno);
	ASSERT(args.agno < args.mp->m_sb.sb_agcount);
	args.agbno = XFS_FSB_TO_AGBNO(args.mp, bno);
	down_read(&args.mp->m_peraglock);
	args.pag = &args.mp->m_perag[args.agno];
	if ((error = xfs_alloc_fix_freelist(&args, XFS_ALLOC_FLAG_FREEING)))
		goto error0;
#ifdef DEBUG
	ASSERT(args.agbp != NULL);
	ASSERT((args.agbno + len) <=
		be32_to_cpu(XFS_BUF_TO_AGF(args.agbp)->agf_length));
#endif
	error = xfs_free_ag_extent(tp, args.agbp, args.agno, args.agbno, len, 0);
error0:
	up_read(&args.mp->m_peraglock);
	return error;
}


/*
 * AG Busy list management
 * The busy list contains block ranges that have been freed but whose
 * transactions have not yet hit disk.  If any block listed in a busy
 * list is reused, the transaction that freed it must be forced to disk
 * before continuing to use the block.
 *
 * xfs_alloc_mark_busy - add to the per-ag busy list
 * xfs_alloc_clear_busy - remove an item from the per-ag busy list
 */
void
xfs_alloc_mark_busy(xfs_trans_t *tp,
		    xfs_agnumber_t agno,
		    xfs_agblock_t bno,
		    xfs_extlen_t len)
{
	xfs_mount_t		*mp;
	xfs_perag_busy_t	*bsy;
	int			n;

	mp = tp->t_mountp;
	spin_lock(&mp->m_perag[agno].pagb_lock);

	/* search pagb_list for an open slot */
	for (bsy = mp->m_perag[agno].pagb_list, n = 0;
	     n < XFS_PAGB_NUM_SLOTS;
	     bsy++, n++) {
		if (bsy->busy_tp == NULL) {
			break;
		}
	}

	if (n < XFS_PAGB_NUM_SLOTS) {
		bsy = &mp->m_perag[agno].pagb_list[n];
		mp->m_perag[agno].pagb_count++;
		TRACE_BUSY("xfs_alloc_mark_busy", "got", agno, bno, len, n, tp);
		bsy->busy_start = bno;
		bsy->busy_length = len;
		bsy->busy_tp = tp;
		xfs_trans_add_busy(tp, agno, n);
	} else {
		TRACE_BUSY("xfs_alloc_mark_busy", "FULL", agno, bno, len, -1, tp);
		/*
		 * The busy list is full!  Since it is now not possible to
		 * track the free block, make this a synchronous transaction
		 * to insure that the block is not reused before this
		 * transaction commits.
		 */
		xfs_trans_set_sync(tp);
	}

	spin_unlock(&mp->m_perag[agno].pagb_lock);
}

void
xfs_alloc_clear_busy(xfs_trans_t *tp,
		     xfs_agnumber_t agno,
		     int idx)
{
	xfs_mount_t		*mp;
	xfs_perag_busy_t	*list;

	mp = tp->t_mountp;

	spin_lock(&mp->m_perag[agno].pagb_lock);
	list = mp->m_perag[agno].pagb_list;

	ASSERT(idx < XFS_PAGB_NUM_SLOTS);
	if (list[idx].busy_tp == tp) {
		TRACE_UNBUSY("xfs_alloc_clear_busy", "found", agno, idx, tp);
		list[idx].busy_tp = NULL;
		mp->m_perag[agno].pagb_count--;
	} else {
		TRACE_UNBUSY("xfs_alloc_clear_busy", "missing", agno, idx, tp);
	}

	spin_unlock(&mp->m_perag[agno].pagb_lock);
}


/*
 * If we find the extent in the busy list, force the log out to get the
 * extent out of the busy list so the caller can use it straight away.
 */
STATIC void
xfs_alloc_search_busy(xfs_trans_t *tp,
		    xfs_agnumber_t agno,
		    xfs_agblock_t bno,
		    xfs_extlen_t len)
{
	xfs_mount_t		*mp;
	xfs_perag_busy_t	*bsy;
	xfs_agblock_t		uend, bend;
	xfs_lsn_t		lsn;
	int			cnt;

	mp = tp->t_mountp;

	spin_lock(&mp->m_perag[agno].pagb_lock);
	cnt = mp->m_perag[agno].pagb_count;

	uend = bno + len - 1;

	/* search pagb_list for this slot, skipping open slots */
	for (bsy = mp->m_perag[agno].pagb_list; cnt; bsy++) {

		/*
		 * (start1,length1) within (start2, length2)
		 */
		if (bsy->busy_tp != NULL) {
			bend = bsy->busy_start + bsy->busy_length - 1;
			if ((bno > bend) || (uend < bsy->busy_start)) {
				cnt--;
			} else {
				TRACE_BUSYSEARCH("xfs_alloc_search_busy",
					 "found1", agno, bno, len, tp);
				break;
			}
		}
	}

	/*
	 * If a block was found, force the log through the LSN of the
	 * transaction that freed the block
	 */
	if (cnt) {
		TRACE_BUSYSEARCH("xfs_alloc_search_busy", "found", agno, bno, len, tp);
		lsn = bsy->busy_tp->t_commit_lsn;
		spin_unlock(&mp->m_perag[agno].pagb_lock);
		xfs_log_force(mp, lsn, XFS_LOG_FORCE|XFS_LOG_SYNC);
	} else {
		TRACE_BUSYSEARCH("xfs_alloc_search_busy", "not-found", agno, bno, len, tp);
		spin_unlock(&mp->m_perag[agno].pagb_lock);
	}
}