aboutsummaryrefslogtreecommitdiff
path: root/fs/ocfs2/cluster/heartbeat.c
blob: 2461eb3272edfab9c6c4949cb435252181938b72 (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
/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * Copyright (C) 2004, 2005 Oracle.  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; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will 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 to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/file.h>
#include <linux/kthread.h>
#include <linux/configfs.h>
#include <linux/random.h>
#include <linux/crc32.h>
#include <linux/time.h>
#include <linux/debugfs.h>
#include <linux/slab.h>

#include "heartbeat.h"
#include "tcp.h"
#include "nodemanager.h"
#include "quorum.h"

#include "masklog.h"


/*
 * The first heartbeat pass had one global thread that would serialize all hb
 * callback calls.  This global serializing sem should only be removed once
 * we've made sure that all callees can deal with being called concurrently
 * from multiple hb region threads.
 */
static DECLARE_RWSEM(o2hb_callback_sem);

/*
 * multiple hb threads are watching multiple regions.  A node is live
 * whenever any of the threads sees activity from the node in its region.
 */
static DEFINE_SPINLOCK(o2hb_live_lock);
static struct list_head o2hb_live_slots[O2NM_MAX_NODES];
static unsigned long o2hb_live_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
static LIST_HEAD(o2hb_node_events);
static DECLARE_WAIT_QUEUE_HEAD(o2hb_steady_queue);

/*
 * In global heartbeat, we maintain a series of region bitmaps.
 * 	- o2hb_region_bitmap allows us to limit the region number to max region.
 * 	- o2hb_live_region_bitmap tracks live regions (seen steady iterations).
 * 	- o2hb_quorum_region_bitmap tracks live regions that have seen all nodes
 * 		heartbeat on it.
 * 	- o2hb_failed_region_bitmap tracks the regions that have seen io timeouts.
 */
static unsigned long o2hb_region_bitmap[BITS_TO_LONGS(O2NM_MAX_REGIONS)];
static unsigned long o2hb_live_region_bitmap[BITS_TO_LONGS(O2NM_MAX_REGIONS)];
static unsigned long o2hb_quorum_region_bitmap[BITS_TO_LONGS(O2NM_MAX_REGIONS)];
static unsigned long o2hb_failed_region_bitmap[BITS_TO_LONGS(O2NM_MAX_REGIONS)];

#define O2HB_DB_TYPE_LIVENODES		0
#define O2HB_DB_TYPE_LIVEREGIONS	1
#define O2HB_DB_TYPE_QUORUMREGIONS	2
#define O2HB_DB_TYPE_FAILEDREGIONS	3
#define O2HB_DB_TYPE_REGION_LIVENODES	4
#define O2HB_DB_TYPE_REGION_NUMBER	5
#define O2HB_DB_TYPE_REGION_ELAPSED_TIME	6
#define O2HB_DB_TYPE_REGION_PINNED	7
struct o2hb_debug_buf {
	int db_type;
	int db_size;
	int db_len;
	void *db_data;
};

static struct o2hb_debug_buf *o2hb_db_livenodes;
static struct o2hb_debug_buf *o2hb_db_liveregions;
static struct o2hb_debug_buf *o2hb_db_quorumregions;
static struct o2hb_debug_buf *o2hb_db_failedregions;

#define O2HB_DEBUG_DIR			"o2hb"
#define O2HB_DEBUG_LIVENODES		"livenodes"
#define O2HB_DEBUG_LIVEREGIONS		"live_regions"
#define O2HB_DEBUG_QUORUMREGIONS	"quorum_regions"
#define O2HB_DEBUG_FAILEDREGIONS	"failed_regions"
#define O2HB_DEBUG_REGION_NUMBER	"num"
#define O2HB_DEBUG_REGION_ELAPSED_TIME	"elapsed_time_in_ms"
#define O2HB_DEBUG_REGION_PINNED	"pinned"

static struct dentry *o2hb_debug_dir;
static struct dentry *o2hb_debug_livenodes;
static struct dentry *o2hb_debug_liveregions;
static struct dentry *o2hb_debug_quorumregions;
static struct dentry *o2hb_debug_failedregions;

static LIST_HEAD(o2hb_all_regions);

static struct o2hb_callback {
	struct list_head list;
} o2hb_callbacks[O2HB_NUM_CB];

static struct o2hb_callback *hbcall_from_type(enum o2hb_callback_type type);

#define O2HB_DEFAULT_BLOCK_BITS       9

enum o2hb_heartbeat_modes {
	O2HB_HEARTBEAT_LOCAL		= 0,
	O2HB_HEARTBEAT_GLOBAL,
	O2HB_HEARTBEAT_NUM_MODES,
};

char *o2hb_heartbeat_mode_desc[O2HB_HEARTBEAT_NUM_MODES] = {
		"local",	/* O2HB_HEARTBEAT_LOCAL */
		"global",	/* O2HB_HEARTBEAT_GLOBAL */
};

unsigned int o2hb_dead_threshold = O2HB_DEFAULT_DEAD_THRESHOLD;
unsigned int o2hb_heartbeat_mode = O2HB_HEARTBEAT_LOCAL;

/*
 * o2hb_dependent_users tracks the number of registered callbacks that depend
 * on heartbeat. o2net and o2dlm are two entities that register this callback.
 * However only o2dlm depends on the heartbeat. It does not want the heartbeat
 * to stop while a dlm domain is still active.
 */
unsigned int o2hb_dependent_users;

/*
 * In global heartbeat mode, all regions are pinned if there are one or more
 * dependent users and the quorum region count is <= O2HB_PIN_CUT_OFF. All
 * regions are unpinned if the region count exceeds the cut off or the number
 * of dependent users falls to zero.
 */
#define O2HB_PIN_CUT_OFF		3

/*
 * In local heartbeat mode, we assume the dlm domain name to be the same as
 * region uuid. This is true for domains created for the file system but not
 * necessarily true for userdlm domains. This is a known limitation.
 *
 * In global heartbeat mode, we pin/unpin all o2hb regions. This solution
 * works for both file system and userdlm domains.
 */
static int o2hb_region_pin(const char *region_uuid);
static void o2hb_region_unpin(const char *region_uuid);

/* Only sets a new threshold if there are no active regions.
 *
 * No locking or otherwise interesting code is required for reading
 * o2hb_dead_threshold as it can't change once regions are active and
 * it's not interesting to anyone until then anyway. */
static void o2hb_dead_threshold_set(unsigned int threshold)
{
	if (threshold > O2HB_MIN_DEAD_THRESHOLD) {
		spin_lock(&o2hb_live_lock);
		if (list_empty(&o2hb_all_regions))
			o2hb_dead_threshold = threshold;
		spin_unlock(&o2hb_live_lock);
	}
}

static int o2hb_global_hearbeat_mode_set(unsigned int hb_mode)
{
	int ret = -1;

	if (hb_mode < O2HB_HEARTBEAT_NUM_MODES) {
		spin_lock(&o2hb_live_lock);
		if (list_empty(&o2hb_all_regions)) {
			o2hb_heartbeat_mode = hb_mode;
			ret = 0;
		}
		spin_unlock(&o2hb_live_lock);
	}

	return ret;
}

struct o2hb_node_event {
	struct list_head        hn_item;
	enum o2hb_callback_type hn_event_type;
	struct o2nm_node        *hn_node;
	int                     hn_node_num;
};

struct o2hb_disk_slot {
	struct o2hb_disk_heartbeat_block *ds_raw_block;
	u8			ds_node_num;
	u64			ds_last_time;
	u64			ds_last_generation;
	u16			ds_equal_samples;
	u16			ds_changed_samples;
	struct list_head	ds_live_item;
};

/* each thread owns a region.. when we're asked to tear down the region
 * we ask the thread to stop, who cleans up the region */
struct o2hb_region {
	struct config_item	hr_item;

	struct list_head	hr_all_item;
	unsigned		hr_unclean_stop:1,
				hr_item_pinned:1,
				hr_item_dropped:1;

	/* protected by the hr_callback_sem */
	struct task_struct 	*hr_task;

	unsigned int		hr_blocks;
	unsigned long long	hr_start_block;

	unsigned int		hr_block_bits;
	unsigned int		hr_block_bytes;

	unsigned int		hr_slots_per_page;
	unsigned int		hr_num_pages;

	struct page             **hr_slot_data;
	struct block_device	*hr_bdev;
	struct o2hb_disk_slot	*hr_slots;

	/* live node map of this region */
	unsigned long		hr_live_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
	unsigned int		hr_region_num;

	struct dentry		*hr_debug_dir;
	struct dentry		*hr_debug_livenodes;
	struct dentry		*hr_debug_regnum;
	struct dentry		*hr_debug_elapsed_time;
	struct dentry		*hr_debug_pinned;
	struct o2hb_debug_buf	*hr_db_livenodes;
	struct o2hb_debug_buf	*hr_db_regnum;
	struct o2hb_debug_buf	*hr_db_elapsed_time;
	struct o2hb_debug_buf	*hr_db_pinned;

	/* let the person setting up hb wait for it to return until it
	 * has reached a 'steady' state.  This will be fixed when we have
	 * a more complete api that doesn't lead to this sort of fragility. */
	atomic_t		hr_steady_iterations;

	char			hr_dev_name[BDEVNAME_SIZE];

	unsigned int		hr_timeout_ms;

	/* randomized as the region goes up and down so that a node
	 * recognizes a node going up and down in one iteration */
	u64			hr_generation;

	struct delayed_work	hr_write_timeout_work;
	unsigned long		hr_last_timeout_start;

	/* Used during o2hb_check_slot to hold a copy of the block
	 * being checked because we temporarily have to zero out the
	 * crc field. */
	struct o2hb_disk_heartbeat_block *hr_tmp_block;
};

struct o2hb_bio_wait_ctxt {
	atomic_t          wc_num_reqs;
	struct completion wc_io_complete;
	int               wc_error;
};

static int o2hb_pop_count(void *map, int count)
{
	int i = -1, pop = 0;

	while ((i = find_next_bit(map, count, i + 1)) < count)
		pop++;
	return pop;
}

static void o2hb_write_timeout(struct work_struct *work)
{
	int failed, quorum;
	unsigned long flags;
	struct o2hb_region *reg =
		container_of(work, struct o2hb_region,
			     hr_write_timeout_work.work);

	mlog(ML_ERROR, "Heartbeat write timeout to device %s after %u "
	     "milliseconds\n", reg->hr_dev_name,
	     jiffies_to_msecs(jiffies - reg->hr_last_timeout_start));

	if (o2hb_global_heartbeat_active()) {
		spin_lock_irqsave(&o2hb_live_lock, flags);
		if (test_bit(reg->hr_region_num, o2hb_quorum_region_bitmap))
			set_bit(reg->hr_region_num, o2hb_failed_region_bitmap);
		failed = o2hb_pop_count(&o2hb_failed_region_bitmap,
					O2NM_MAX_REGIONS);
		quorum = o2hb_pop_count(&o2hb_quorum_region_bitmap,
					O2NM_MAX_REGIONS);
		spin_unlock_irqrestore(&o2hb_live_lock, flags);

		mlog(ML_HEARTBEAT, "Number of regions %d, failed regions %d\n",
		     quorum, failed);

		/*
		 * Fence if the number of failed regions >= half the number
		 * of  quorum regions
		 */
		if ((failed << 1) < quorum)
			return;
	}

	o2quo_disk_timeout();
}

static void o2hb_arm_write_timeout(struct o2hb_region *reg)
{
	mlog(ML_HEARTBEAT, "Queue write timeout for %u ms\n",
	     O2HB_MAX_WRITE_TIMEOUT_MS);

	if (o2hb_global_heartbeat_active()) {
		spin_lock(&o2hb_live_lock);
		clear_bit(reg->hr_region_num, o2hb_failed_region_bitmap);
		spin_unlock(&o2hb_live_lock);
	}
	cancel_delayed_work(&reg->hr_write_timeout_work);
	reg->hr_last_timeout_start = jiffies;
	schedule_delayed_work(&reg->hr_write_timeout_work,
			      msecs_to_jiffies(O2HB_MAX_WRITE_TIMEOUT_MS));
}

static void o2hb_disarm_write_timeout(struct o2hb_region *reg)
{
	cancel_delayed_work_sync(&reg->hr_write_timeout_work);
}

static inline void o2hb_bio_wait_init(struct o2hb_bio_wait_ctxt *wc)
{
	atomic_set(&wc->wc_num_reqs, 1);
	init_completion(&wc->wc_io_complete);
	wc->wc_error = 0;
}

/* Used in error paths too */
static inline void o2hb_bio_wait_dec(struct o2hb_bio_wait_ctxt *wc,
				     unsigned int num)
{
	/* sadly atomic_sub_and_test() isn't available on all platforms.  The
	 * good news is that the fast path only completes one at a time */
	while(num--) {
		if (atomic_dec_and_test(&wc->wc_num_reqs)) {
			BUG_ON(num > 0);
			complete(&wc->wc_io_complete);
		}
	}
}

static void o2hb_wait_on_io(struct o2hb_region *reg,
			    struct o2hb_bio_wait_ctxt *wc)
{
	o2hb_bio_wait_dec(wc, 1);
	wait_for_completion(&wc->wc_io_complete);
}

static void o2hb_bio_end_io(struct bio *bio,
			   int error)
{
	struct o2hb_bio_wait_ctxt *wc = bio->bi_private;

	if (error) {
		mlog(ML_ERROR, "IO Error %d\n", error);
		wc->wc_error = error;
	}

	o2hb_bio_wait_dec(wc, 1);
	bio_put(bio);
}

/* Setup a Bio to cover I/O against num_slots slots starting at
 * start_slot. */
static struct bio *o2hb_setup_one_bio(struct o2hb_region *reg,
				      struct o2hb_bio_wait_ctxt *wc,
				      unsigned int *current_slot,
				      unsigned int max_slots)
{
	int len, current_page;
	unsigned int vec_len, vec_start;
	unsigned int bits = reg->hr_block_bits;
	unsigned int spp = reg->hr_slots_per_page;
	unsigned int cs = *current_slot;
	struct bio *bio;
	struct page *page;

	/* Testing has shown this allocation to take long enough under
	 * GFP_KERNEL that the local node can get fenced. It would be
	 * nicest if we could pre-allocate these bios and avoid this
	 * all together. */
	bio = bio_alloc(GFP_ATOMIC, 16);
	if (!bio) {
		mlog(ML_ERROR, "Could not alloc slots BIO!\n");
		bio = ERR_PTR(-ENOMEM);
		goto bail;
	}

	/* Must put everything in 512 byte sectors for the bio... */
	bio->bi_sector = (reg->hr_start_block + cs) << (bits - 9);
	bio->bi_bdev = reg->hr_bdev;
	bio->bi_private = wc;
	bio->bi_end_io = o2hb_bio_end_io;

	vec_start = (cs << bits) % PAGE_CACHE_SIZE;
	while(cs < max_slots) {
		current_page = cs / spp;
		page = reg->hr_slot_data[current_page];

		vec_len = min(PAGE_CACHE_SIZE - vec_start,
			      (max_slots-cs) * (PAGE_CACHE_SIZE/spp) );

		mlog(ML_HB_BIO, "page %d, vec_len = %u, vec_start = %u\n",
		     current_page, vec_len, vec_start);

		len = bio_add_page(bio, page, vec_len, vec_start);
		if (len != vec_len) break;

		cs += vec_len / (PAGE_CACHE_SIZE/spp);
		vec_start = 0;
	}

bail:
	*current_slot = cs;
	return bio;
}

static int o2hb_read_slots(struct o2hb_region *reg,
			   unsigned int max_slots)
{
	unsigned int current_slot=0;
	int status;
	struct o2hb_bio_wait_ctxt wc;
	struct bio *bio;

	o2hb_bio_wait_init(&wc);

	while(current_slot < max_slots) {
		bio = o2hb_setup_one_bio(reg, &wc, &current_slot, max_slots);
		if (IS_ERR(bio)) {
			status = PTR_ERR(bio);
			mlog_errno(status);
			goto bail_and_wait;
		}

		atomic_inc(&wc.wc_num_reqs);
		submit_bio(READ, bio);
	}

	status = 0;

bail_and_wait:
	o2hb_wait_on_io(reg, &wc);
	if (wc.wc_error && !status)
		status = wc.wc_error;

	return status;
}

static int o2hb_issue_node_write(struct o2hb_region *reg,
				 struct o2hb_bio_wait_ctxt *write_wc)
{
	int status;
	unsigned int slot;
	struct bio *bio;

	o2hb_bio_wait_init(write_wc);

	slot = o2nm_this_node();

	bio = o2hb_setup_one_bio(reg, write_wc, &slot, slot+1);
	if (IS_ERR(bio)) {
		status = PTR_ERR(bio);
		mlog_errno(status);
		goto bail;
	}

	atomic_inc(&write_wc->wc_num_reqs);
	submit_bio(WRITE, bio);

	status = 0;
bail:
	return status;
}

static u32 o2hb_compute_block_crc_le(struct o2hb_region *reg,
				     struct o2hb_disk_heartbeat_block *hb_block)
{
	__le32 old_cksum;
	u32 ret;

	/* We want to compute the block crc with a 0 value in the
	 * hb_cksum field. Save it off here and replace after the
	 * crc. */
	old_cksum = hb_block->hb_cksum;
	hb_block->hb_cksum = 0;

	ret = crc32_le(0, (unsigned char *) hb_block, reg->hr_block_bytes);

	hb_block->hb_cksum = old_cksum;

	return ret;
}

static void o2hb_dump_slot(struct o2hb_disk_heartbeat_block *hb_block)
{
	mlog(ML_ERROR, "Dump slot information: seq = 0x%llx, node = %u, "
	     "cksum = 0x%x, generation 0x%llx\n",
	     (long long)le64_to_cpu(hb_block->hb_seq),
	     hb_block->hb_node, le32_to_cpu(hb_block->hb_cksum),
	     (long long)le64_to_cpu(hb_block->hb_generation));
}

static int o2hb_verify_crc(struct o2hb_region *reg,
			   struct o2hb_disk_heartbeat_block *hb_block)
{
	u32 read, computed;

	read = le32_to_cpu(hb_block->hb_cksum);
	computed = o2hb_compute_block_crc_le(reg, hb_block);

	return read == computed;
}

/* We want to make sure that nobody is heartbeating on top of us --
 * this will help detect an invalid configuration. */
static int o2hb_check_last_timestamp(struct o2hb_region *reg)
{
	int node_num, ret;
	struct o2hb_disk_slot *slot;
	struct o2hb_disk_heartbeat_block *hb_block;

	node_num = o2nm_this_node();

	ret = 1;
	slot = &reg->hr_slots[node_num];
	/* Don't check on our 1st timestamp */
	if (slot->ds_last_time) {
		hb_block = slot->ds_raw_block;

		if (le64_to_cpu(hb_block->hb_seq) != slot->ds_last_time)
			ret = 0;
	}

	return ret;
}

static inline void o2hb_prepare_block(struct o2hb_region *reg,
				      u64 generation)
{
	int node_num;
	u64 cputime;
	struct o2hb_disk_slot *slot;
	struct o2hb_disk_heartbeat_block *hb_block;

	node_num = o2nm_this_node();
	slot = &reg->hr_slots[node_num];

	hb_block = (struct o2hb_disk_heartbeat_block *)slot->ds_raw_block;
	memset(hb_block, 0, reg->hr_block_bytes);
	/* TODO: time stuff */
	cputime = CURRENT_TIME.tv_sec;
	if (!cputime)
		cputime = 1;

	hb_block->hb_seq = cpu_to_le64(cputime);
	hb_block->hb_node = node_num;
	hb_block->hb_generation = cpu_to_le64(generation);
	hb_block->hb_dead_ms = cpu_to_le32(o2hb_dead_threshold * O2HB_REGION_TIMEOUT_MS);

	/* This step must always happen last! */
	hb_block->hb_cksum = cpu_to_le32(o2hb_compute_block_crc_le(reg,
								   hb_block));

	mlog(ML_HB_BIO, "our node generation = 0x%llx, cksum = 0x%x\n",
	     (long long)generation,
	     le32_to_cpu(hb_block->hb_cksum));
}

static void o2hb_fire_callbacks(struct o2hb_callback *hbcall,
				struct o2nm_node *node,
				int idx)
{
	struct list_head *iter;
	struct o2hb_callback_func *f;

	list_for_each(iter, &hbcall->list) {
		f = list_entry(iter, struct o2hb_callback_func, hc_item);
		mlog(ML_HEARTBEAT, "calling funcs %p\n", f);
		(f->hc_func)(node, idx, f->hc_data);
	}
}

/* Will run the list in order until we process the passed event */
static void o2hb_run_event_list(struct o2hb_node_event *queued_event)
{
	int empty;
	struct o2hb_callback *hbcall;
	struct o2hb_node_event *event;

	spin_lock(&o2hb_live_lock);
	empty = list_empty(&queued_event->hn_item);
	spin_unlock(&o2hb_live_lock);
	if (empty)
		return;

	/* Holding callback sem assures we don't alter the callback
	 * lists when doing this, and serializes ourselves with other
	 * processes wanting callbacks. */
	down_write(&o2hb_callback_sem);

	spin_lock(&o2hb_live_lock);
	while (!list_empty(&o2hb_node_events)
	       && !list_empty(&queued_event->hn_item)) {
		event = list_entry(o2hb_node_events.next,
				   struct o2hb_node_event,
				   hn_item);
		list_del_init(&event->hn_item);
		spin_unlock(&o2hb_live_lock);

		mlog(ML_HEARTBEAT, "Node %s event for %d\n",
		     event->hn_event_type == O2HB_NODE_UP_CB ? "UP" : "DOWN",
		     event->hn_node_num);

		hbcall = hbcall_from_type(event->hn_event_type);

		/* We should *never* have gotten on to the list with a
		 * bad type... This isn't something that we should try
		 * to recover from. */
		BUG_ON(IS_ERR(hbcall));

		o2hb_fire_callbacks(hbcall, event->hn_node, event->hn_node_num);

		spin_lock(&o2hb_live_lock);
	}
	spin_unlock(&o2hb_live_lock);

	up_write(&o2hb_callback_sem);
}

static void o2hb_queue_node_event(struct o2hb_node_event *event,
				  enum o2hb_callback_type type,
				  struct o2nm_node *node,
				  int node_num)
{
	assert_spin_locked(&o2hb_live_lock);

	BUG_ON((!node) && (type != O2HB_NODE_DOWN_CB));

	event->hn_event_type = type;
	event->hn_node = node;
	event->hn_node_num = node_num;

	mlog(ML_HEARTBEAT, "Queue node %s event for node %d\n",
	     type == O2HB_NODE_UP_CB ? "UP" : "DOWN", node_num);

	list_add_tail(&event->hn_item, &o2hb_node_events);
}

static void o2hb_shutdown_slot(struct o2hb_disk_slot *slot)
{
	struct o2hb_node_event event =
		{ .hn_item = LIST_HEAD_INIT(event.hn_item), };
	struct o2nm_node *node;

	node = o2nm_get_node_by_num(slot->ds_node_num);
	if (!node)
		return;

	spin_lock(&o2hb_live_lock);
	if (!list_empty(&slot->ds_live_item)) {
		mlog(ML_HEARTBEAT, "Shutdown, node %d leaves region\n",
		     slot->ds_node_num);

		list_del_init(&slot->ds_live_item);

		if (list_empty(&o2hb_live_slots[slot->ds_node_num])) {
			clear_bit(slot->ds_node_num, o2hb_live_node_bitmap);

			o2hb_queue_node_event(&event, O2HB_NODE_DOWN_CB, node,
					      slot->ds_node_num);
		}
	}
	spin_unlock(&o2hb_live_lock);

	o2hb_run_event_list(&event);

	o2nm_node_put(node);
}

static void o2hb_set_quorum_device(struct o2hb_region *reg,
				   struct o2hb_disk_slot *slot)
{
	assert_spin_locked(&o2hb_live_lock);

	if (!o2hb_global_heartbeat_active())
		return;

	if (test_bit(reg->hr_region_num, o2hb_quorum_region_bitmap))
		return;

	/*
	 * A region can be added to the quorum only when it sees all
	 * live nodes heartbeat on it. In other words, the region has been
	 * added to all nodes.
	 */
	if (memcmp(reg->hr_live_node_bitmap, o2hb_live_node_bitmap,
		   sizeof(o2hb_live_node_bitmap)))
		return;

	if (slot->ds_changed_samples < O2HB_LIVE_THRESHOLD)
		return;

	printk(KERN_NOTICE "o2hb: Region %s is now a quorum device\n",
	       config_item_name(&reg->hr_item));

	set_bit(reg->hr_region_num, o2hb_quorum_region_bitmap);

	/*
	 * If global heartbeat active, unpin all regions if the
	 * region count > CUT_OFF
	 */
	if (o2hb_pop_count(&o2hb_quorum_region_bitmap,
			   O2NM_MAX_REGIONS) > O2HB_PIN_CUT_OFF)
		o2hb_region_unpin(NULL);
}

static int o2hb_check_slot(struct o2hb_region *reg,
			   struct o2hb_disk_slot *slot)
{
	int changed = 0, gen_changed = 0;
	struct o2hb_node_event event =
		{ .hn_item = LIST_HEAD_INIT(event.hn_item), };
	struct o2nm_node *node;
	struct o2hb_disk_heartbeat_block *hb_block = reg->hr_tmp_block;
	u64 cputime;
	unsigned int dead_ms = o2hb_dead_threshold * O2HB_REGION_TIMEOUT_MS;
	unsigned int slot_dead_ms;
	int tmp;

	memcpy(hb_block, slot->ds_raw_block, reg->hr_block_bytes);

	/*
	 * If a node is no longer configured but is still in the livemap, we
	 * may need to clear that bit from the livemap.
	 */
	node = o2nm_get_node_by_num(slot->ds_node_num);
	if (!node) {
		spin_lock(&o2hb_live_lock);
		tmp = test_bit(slot->ds_node_num, o2hb_live_node_bitmap);
		spin_unlock(&o2hb_live_lock);
		if (!tmp)
			return 0;
	}

	if (!o2hb_verify_crc(reg, hb_block)) {
		/* all paths from here will drop o2hb_live_lock for
		 * us. */
		spin_lock(&o2hb_live_lock);

		/* Don't print an error on the console in this case -
		 * a freshly formatted heartbeat area will not have a
		 * crc set on it. */
		if (list_empty(&slot->ds_live_item))
			goto out;

		/* The node is live but pushed out a bad crc. We
		 * consider it a transient miss but don't populate any
		 * other values as they may be junk. */
		mlog(ML_ERROR, "Node %d has written a bad crc to %s\n",
		     slot->ds_node_num, reg->hr_dev_name);
		o2hb_dump_slot(hb_block);

		slot->ds_equal_samples++;
		goto fire_callbacks;
	}

	/* we don't care if these wrap.. the state transitions below
	 * clear at the right places */
	cputime = le64_to_cpu(hb_block->hb_seq);
	if (slot->ds_last_time != cputime)
		slot->ds_changed_samples++;
	else
		slot->ds_equal_samples++;
	slot->ds_last_time = cputime;

	/* The node changed heartbeat generations. We assume this to
	 * mean it dropped off but came back before we timed out. We
	 * want to consider it down for the time being but don't want
	 * to lose any changed_samples state we might build up to
	 * considering it live again. */
	if (slot->ds_last_generation != le64_to_cpu(hb_block->hb_generation)) {
		gen_changed = 1;
		slot->ds_equal_samples = 0;
		mlog(ML_HEARTBEAT, "Node %d changed generation (0x%llx "
		     "to 0x%llx)\n", slot->ds_node_num,
		     (long long)slot->ds_last_generation,
		     (long long)le64_to_cpu(hb_block->hb_generation));
	}

	slot->ds_last_generation = le64_to_cpu(hb_block->hb_generation);

	mlog(ML_HEARTBEAT, "Slot %d gen 0x%llx cksum 0x%x "
	     "seq %llu last %llu changed %u equal %u\n",
	     slot->ds_node_num, (long long)slot->ds_last_generation,
	     le32_to_cpu(hb_block->hb_cksum),
	     (unsigned long long)le64_to_cpu(hb_block->hb_seq),
	     (unsigned long long)slot->ds_last_time, slot->ds_changed_samples,
	     slot->ds_equal_samples);

	spin_lock(&o2hb_live_lock);

fire_callbacks:
	/* dead nodes only come to life after some number of
	 * changes at any time during their dead time */
	if (list_empty(&slot->ds_live_item) &&
	    slot->ds_changed_samples >= O2HB_LIVE_THRESHOLD) {
		mlog(ML_HEARTBEAT, "Node %d (id 0x%llx) joined my region\n",
		     slot->ds_node_num, (long long)slot->ds_last_generation);

		set_bit(slot->ds_node_num, reg->hr_live_node_bitmap);

		/* first on the list generates a callback */
		if (list_empty(&o2hb_live_slots[slot->ds_node_num])) {
			mlog(ML_HEARTBEAT, "o2hb: Add node %d to live nodes "
			     "bitmap\n", slot->ds_node_num);
			set_bit(slot->ds_node_num, o2hb_live_node_bitmap);

			o2hb_queue_node_event(&event, O2HB_NODE_UP_CB, node,
					      slot->ds_node_num);

			changed = 1;
		}

		list_add_tail(&slot->ds_live_item,
			      &o2hb_live_slots[slot->ds_node_num]);

		slot->ds_equal_samples = 0;

		/* We want to be sure that all nodes agree on the
		 * number of milliseconds before a node will be
		 * considered dead. The self-fencing timeout is
		 * computed from this value, and a discrepancy might
		 * result in heartbeat calling a node dead when it
		 * hasn't self-fenced yet. */
		slot_dead_ms = le32_to_cpu(hb_block->hb_dead_ms);
		if (slot_dead_ms && slot_dead_ms != dead_ms) {
			/* TODO: Perhaps we can fail the region here. */
			mlog(ML_ERROR, "Node %d on device %s has a dead count "
			     "of %u ms, but our count is %u ms.\n"
			     "Please double check your configuration values "
			     "for 'O2CB_HEARTBEAT_THRESHOLD'\n",
			     slot->ds_node_num, reg->hr_dev_name, slot_dead_ms,
			     dead_ms);
		}
		goto out;
	}

	/* if the list is dead, we're done.. */
	if (list_empty(&slot->ds_live_item))
		goto out;

	/* live nodes only go dead after enough consequtive missed
	 * samples..  reset the missed counter whenever we see
	 * activity */
	if (slot->ds_equal_samples >= o2hb_dead_threshold || gen_changed) {
		mlog(ML_HEARTBEAT, "Node %d left my region\n",
		     slot->ds_node_num);

		clear_bit(slot->ds_node_num, reg->hr_live_node_bitmap);

		/* last off the live_slot generates a callback */
		list_del_init(&slot->ds_live_item);
		if (list_empty(&o2hb_live_slots[slot->ds_node_num])) {
			mlog(ML_HEARTBEAT, "o2hb: Remove node %d from live "
			     "nodes bitmap\n", slot->ds_node_num);
			clear_bit(slot->ds_node_num, o2hb_live_node_bitmap);

			/* node can be null */
			o2hb_queue_node_event(&event, O2HB_NODE_DOWN_CB,
					      node, slot->ds_node_num);

			changed = 1;
		}

		/* We don't clear this because the node is still
		 * actually writing new blocks. */
		if (!gen_changed)
			slot->ds_changed_samples = 0;
		goto out;
	}
	if (slot->ds_changed_samples) {
		slot->ds_changed_samples = 0;
		slot->ds_equal_samples = 0;
	}
out:
	o2hb_set_quorum_device(reg, slot);

	spin_unlock(&o2hb_live_lock);

	o2hb_run_event_list(&event);

	if (node)
		o2nm_node_put(node);
	return changed;
}

/* This could be faster if we just implmented a find_last_bit, but I
 * don't think the circumstances warrant it. */
static int o2hb_highest_node(unsigned long *nodes,
			     int numbits)
{
	int highest, node;

	highest = numbits;
	node = -1;
	while ((node = find_next_bit(nodes, numbits, node + 1)) != -1) {
		if (node >= numbits)
			break;

		highest = node;
	}

	return highest;
}

static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
{
	int i, ret, highest_node, change = 0;
	unsigned long configured_nodes[BITS_TO_LONGS(O2NM_MAX_NODES)];
	unsigned long live_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
	struct o2hb_bio_wait_ctxt write_wc;

	ret = o2nm_configured_node_map(configured_nodes,
				       sizeof(configured_nodes));
	if (ret) {
		mlog_errno(ret);
		return ret;
	}

	/*
	 * If a node is not configured but is in the livemap, we still need
	 * to read the slot so as to be able to remove it from the livemap.
	 */
	o2hb_fill_node_map(live_node_bitmap, sizeof(live_node_bitmap));
	i = -1;
	while ((i = find_next_bit(live_node_bitmap,
				  O2NM_MAX_NODES, i + 1)) < O2NM_MAX_NODES) {
		set_bit(i, configured_nodes);
	}

	highest_node = o2hb_highest_node(configured_nodes, O2NM_MAX_NODES);
	if (highest_node >= O2NM_MAX_NODES) {
		mlog(ML_NOTICE, "ocfs2_heartbeat: no configured nodes found!\n");
		return -EINVAL;
	}

	/* No sense in reading the slots of nodes that don't exist
	 * yet. Of course, if the node definitions have holes in them
	 * then we're reading an empty slot anyway... Consider this
	 * best-effort. */
	ret = o2hb_read_slots(reg, highest_node + 1);
	if (ret < 0) {
		mlog_errno(ret);
		return ret;
	}

	/* With an up to date view of the slots, we can check that no
	 * other node has been improperly configured to heartbeat in
	 * our slot. */
	if (!o2hb_check_last_timestamp(reg))
		mlog(ML_ERROR, "Device \"%s\": another node is heartbeating "
		     "in our slot!\n", reg->hr_dev_name);

	/* fill in the proper info for our next heartbeat */
	o2hb_prepare_block(reg, reg->hr_generation);

	/* And fire off the write. Note that we don't wait on this I/O
	 * until later. */
	ret = o2hb_issue_node_write(reg, &write_wc);
	if (ret < 0) {
		mlog_errno(ret);
		return ret;
	}

	i = -1;
	while((i = find_next_bit(configured_nodes, O2NM_MAX_NODES, i + 1)) < O2NM_MAX_NODES) {

		change |= o2hb_check_slot(reg, &reg->hr_slots[i]);
	}

	/*
	 * We have to be sure we've advertised ourselves on disk
	 * before we can go to steady state.  This ensures that
	 * people we find in our steady state have seen us.
	 */
	o2hb_wait_on_io(reg, &write_wc);
	if (write_wc.wc_error) {
		/* Do not re-arm the write timeout on I/O error - we
		 * can't be sure that the new block ever made it to
		 * disk */
		mlog(ML_ERROR, "Write error %d on device \"%s\"\n",
		     write_wc.wc_error, reg->hr_dev_name);
		return write_wc.wc_error;
	}

	o2hb_arm_write_timeout(reg);

	/* let the person who launched us know when things are steady */
	if (!change && (atomic_read(&reg->hr_steady_iterations) != 0)) {
		if (atomic_dec_and_test(&reg->hr_steady_iterations))
			wake_up(&o2hb_steady_queue);
	}

	return 0;
}

/* Subtract b from a, storing the result in a. a *must* have a larger
 * value than b. */
static void o2hb_tv_subtract(struct timeval *a,
			     struct timeval *b)
{
	/* just return 0 when a is after b */
	if (a->tv_sec < b->tv_sec ||
	    (a->tv_sec == b->tv_sec && a->tv_usec < b->tv_usec)) {
		a->tv_sec = 0;
		a->tv_usec = 0;
		return;
	}

	a->tv_sec -= b->tv_sec;
	a->tv_usec -= b->tv_usec;
	while ( a->tv_usec < 0 ) {
		a->tv_sec--;
		a->tv_usec += 1000000;
	}
}

static unsigned int o2hb_elapsed_msecs(struct timeval *start,
				       struct timeval *end)
{
	struct timeval res = *end;

	o2hb_tv_subtract(&res, start);

	return res.tv_sec * 1000 + res.tv_usec / 1000;
}

/*
 * we ride the region ref that the region dir holds.  before the region
 * dir is removed and drops it ref it will wait to tear down this
 * thread.
 */
static int o2hb_thread(void *data)
{
	int i, ret;
	struct o2hb_region *reg = data;
	struct o2hb_bio_wait_ctxt write_wc;
	struct timeval before_hb, after_hb;
	unsigned int elapsed_msec;

	mlog(ML_HEARTBEAT|ML_KTHREAD, "hb thread running\n");

	set_user_nice(current, -20);

	/* Pin node */
	o2nm_depend_this_node();

	while (!kthread_should_stop() && !reg->hr_unclean_stop) {
		/* We track the time spent inside
		 * o2hb_do_disk_heartbeat so that we avoid more than
		 * hr_timeout_ms between disk writes. On busy systems
		 * this should result in a heartbeat which is less
		 * likely to time itself out. */
		do_gettimeofday(&before_hb);

		i = 0;
		do {
			ret = o2hb_do_disk_heartbeat(reg);
		} while (ret && ++i < 2);

		do_gettimeofday(&after_hb);
		elapsed_msec = o2hb_elapsed_msecs(&before_hb, &after_hb);

		mlog(ML_HEARTBEAT,
		     "start = %lu.%lu, end = %lu.%lu, msec = %u\n",
		     before_hb.tv_sec, (unsigned long) before_hb.tv_usec,
		     after_hb.tv_sec, (unsigned long) after_hb.tv_usec,
		     elapsed_msec);

		if (elapsed_msec < reg->hr_timeout_ms) {
			/* the kthread api has blocked signals for us so no
			 * need to record the return value. */
			msleep_interruptible(reg->hr_timeout_ms - elapsed_msec);
		}
	}

	o2hb_disarm_write_timeout(reg);

	/* unclean stop is only used in very bad situation */
	for(i = 0; !reg->hr_unclean_stop && i < reg->hr_blocks; i++)
		o2hb_shutdown_slot(&reg->hr_slots[i]);

	/* Explicit down notification - avoid forcing the other nodes
	 * to timeout on this region when we could just as easily
	 * write a clear generation - thus indicating to them that
	 * this node has left this region.
	 *
	 * XXX: Should we skip this on unclean_stop? */
	o2hb_prepare_block(reg, 0);
	ret = o2hb_issue_node_write(reg, &write_wc);
	if (ret == 0) {
		o2hb_wait_on_io(reg, &write_wc);
	} else {
		mlog_errno(ret);
	}

	/* Unpin node */
	o2nm_undepend_this_node();

	mlog(ML_HEARTBEAT|ML_KTHREAD, "hb thread exiting\n");

	return 0;
}

#ifdef CONFIG_DEBUG_FS
static int o2hb_debug_open(struct inode *inode, struct file *file)
{
	struct o2hb_debug_buf *db = inode->i_private;
	struct o2hb_region *reg;
	unsigned long map[BITS_TO_LONGS(O2NM_MAX_NODES)];
	char *buf = NULL;
	int i = -1;
	int out = 0;

	/* max_nodes should be the largest bitmap we pass here */
	BUG_ON(sizeof(map) < db->db_size);

	buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!buf)
		goto bail;

	switch (db->db_type) {
	case O2HB_DB_TYPE_LIVENODES:
	case O2HB_DB_TYPE_LIVEREGIONS:
	case O2HB_DB_TYPE_QUORUMREGIONS:
	case O2HB_DB_TYPE_FAILEDREGIONS:
		spin_lock(&o2hb_live_lock);
		memcpy(map, db->db_data, db->db_size);
		spin_unlock(&o2hb_live_lock);
		break;

	case O2HB_DB_TYPE_REGION_LIVENODES:
		spin_lock(&o2hb_live_lock);
		reg = (struct o2hb_region *)db->db_data;
		memcpy(map, reg->hr_live_node_bitmap, db->db_size);
		spin_unlock(&o2hb_live_lock);
		break;

	case O2HB_DB_TYPE_REGION_NUMBER:
		reg = (struct o2hb_region *)db->db_data;
		out += snprintf(buf + out, PAGE_SIZE - out, "%d\n",
				reg->hr_region_num);
		goto done;

	case O2HB_DB_TYPE_REGION_ELAPSED_TIME:
		reg = (struct o2hb_region *)db->db_data;
		out += snprintf(buf + out, PAGE_SIZE - out, "%u\n",
				jiffies_to_msecs(jiffies -
						 reg->hr_last_timeout_start));
		goto done;

	case O2HB_DB_TYPE_REGION_PINNED:
		reg = (struct o2hb_region *)db->db_data;
		out += snprintf(buf + out, PAGE_SIZE - out, "%u\n",
				!!reg->hr_item_pinned);
		goto done;

	default:
		goto done;
	}

	while ((i = find_next_bit(map, db->db_len, i + 1)) < db->db_len)
		out += snprintf(buf + out, PAGE_SIZE - out, "%d ", i);
	out += snprintf(buf + out, PAGE_SIZE - out, "\n");

done:
	i_size_write(inode, out);

	file->private_data = buf;

	return 0;
bail:
	return -ENOMEM;
}

static int o2hb_debug_release(struct inode *inode, struct file *file)
{
	kfree(file->private_data);
	return 0;
}

static ssize_t o2hb_debug_read(struct file *file, char __user *buf,
				 size_t nbytes, loff_t *ppos)
{
	return simple_read_from_buffer(buf, nbytes, ppos, file->private_data,
				       i_size_read(file->f_mapping->host));
}
#else
static int o2hb_debug_open(struct inode *inode, struct file *file)
{
	return 0;
}
static int o2hb_debug_release(struct inode *inode, struct file *file)
{
	return 0;
}
static ssize_t o2hb_debug_read(struct file *file, char __user *buf,
			       size_t nbytes, loff_t *ppos)
{
	return 0;
}
#endif  /* CONFIG_DEBUG_FS */

static const struct file_operations o2hb_debug_fops = {
	.open =		o2hb_debug_open,
	.release =	o2hb_debug_release,
	.read =		o2hb_debug_read,
	.llseek =	generic_file_llseek,
};

void o2hb_exit(void)
{
	kfree(o2hb_db_livenodes);
	kfree(o2hb_db_liveregions);
	kfree(o2hb_db_quorumregions);
	kfree(o2hb_db_failedregions);
	debugfs_remove(o2hb_debug_failedregions);
	debugfs_remove(o2hb_debug_quorumregions);
	debugfs_remove(o2hb_debug_liveregions);
	debugfs_remove(o2hb_debug_livenodes);
	debugfs_remove(o2hb_debug_dir);
}

static struct dentry *o2hb_debug_create(const char *name, struct dentry *dir,
					struct o2hb_debug_buf **db, int db_len,
					int type, int size, int len, void *data)
{
	*db = kmalloc(db_len, GFP_KERNEL);
	if (!*db)
		return NULL;

	(*db)->db_type = type;
	(*db)->db_size = size;
	(*db)->db_len = len;
	(*db)->db_data = data;

	return debugfs_create_file(name, S_IFREG|S_IRUSR, dir, *db,
				   &o2hb_debug_fops);
}

static int o2hb_debug_init(void)
{
	int ret = -ENOMEM;

	o2hb_debug_dir = debugfs_create_dir(O2HB_DEBUG_DIR, NULL);
	if (!o2hb_debug_dir) {
		mlog_errno(ret);
		goto bail;
	}

	o2hb_debug_livenodes = o2hb_debug_create(O2HB_DEBUG_LIVENODES,
						 o2hb_debug_dir,
						 &o2hb_db_livenodes,
						 sizeof(*o2hb_db_livenodes),
						 O2HB_DB_TYPE_LIVENODES,
						 sizeof(o2hb_live_node_bitmap),
						 O2NM_MAX_NODES,
						 o2hb_live_node_bitmap);
	if (!o2hb_debug_livenodes) {
		mlog_errno(ret);
		goto bail;
	}

	o2hb_debug_liveregions = o2hb_debug_create(O2HB_DEBUG_LIVEREGIONS,
						   o2hb_debug_dir,
						   &o2hb_db_liveregions,
						   sizeof(*o2hb_db_liveregions),
						   O2HB_DB_TYPE_LIVEREGIONS,
						   sizeof(o2hb_live_region_bitmap),
						   O2NM_MAX_REGIONS,
						   o2hb_live_region_bitmap);
	if (!o2hb_debug_liveregions) {
		mlog_errno(ret);
		goto bail;
	}

	o2hb_debug_quorumregions =
			o2hb_debug_create(O2HB_DEBUG_QUORUMREGIONS,
					  o2hb_debug_dir,
					  &o2hb_db_quorumregions,
					  sizeof(*o2hb_db_quorumregions),
					  O2HB_DB_TYPE_QUORUMREGIONS,
					  sizeof(o2hb_quorum_region_bitmap),
					  O2NM_MAX_REGIONS,
					  o2hb_quorum_region_bitmap);
	if (!o2hb_debug_quorumregions) {
		mlog_errno(ret);
		goto bail;
	}

	o2hb_debug_failedregions =
			o2hb_debug_create(O2HB_DEBUG_FAILEDREGIONS,
					  o2hb_debug_dir,
					  &o2hb_db_failedregions,
					  sizeof(*o2hb_db_failedregions),
					  O2HB_DB_TYPE_FAILEDREGIONS,
					  sizeof(o2hb_failed_region_bitmap),
					  O2NM_MAX_REGIONS,
					  o2hb_failed_region_bitmap);
	if (!o2hb_debug_failedregions) {
		mlog_errno(ret);
		goto bail;
	}

	ret = 0;
bail:
	if (ret)
		o2hb_exit();

	return ret;
}

int o2hb_init(void)
{
	int i;

	for (i = 0; i < ARRAY_SIZE(o2hb_callbacks); i++)
		INIT_LIST_HEAD(&o2hb_callbacks[i].list);

	for (i = 0; i < ARRAY_SIZE(o2hb_live_slots); i++)
		INIT_LIST_HEAD(&o2hb_live_slots[i]);

	INIT_LIST_HEAD(&o2hb_node_events);

	memset(o2hb_live_node_bitmap, 0, sizeof(o2hb_live_node_bitmap));
	memset(o2hb_region_bitmap, 0, sizeof(o2hb_region_bitmap));
	memset(o2hb_live_region_bitmap, 0, sizeof(o2hb_live_region_bitmap));
	memset(o2hb_quorum_region_bitmap, 0, sizeof(o2hb_quorum_region_bitmap));
	memset(o2hb_failed_region_bitmap, 0, sizeof(o2hb_failed_region_bitmap));

	o2hb_dependent_users = 0;

	return o2hb_debug_init();
}

/* if we're already in a callback then we're already serialized by the sem */
static void o2hb_fill_node_map_from_callback(unsigned long *map,
					     unsigned bytes)
{
	BUG_ON(bytes < (BITS_TO_LONGS(O2NM_MAX_NODES) * sizeof(unsigned long)));

	memcpy(map, &o2hb_live_node_bitmap, bytes);
}

/*
 * get a map of all nodes that are heartbeating in any regions
 */
void o2hb_fill_node_map(unsigned long *map, unsigned bytes)
{
	/* callers want to serialize this map and callbacks so that they
	 * can trust that they don't miss nodes coming to the party */
	down_read(&o2hb_callback_sem);
	spin_lock(&o2hb_live_lock);
	o2hb_fill_node_map_from_callback(map, bytes);
	spin_unlock(&o2hb_live_lock);
	up_read(&o2hb_callback_sem);
}
EXPORT_SYMBOL_GPL(o2hb_fill_node_map);

/*
 * heartbeat configfs bits.  The heartbeat set is a default set under
 * the cluster set in nodemanager.c.
 */

static struct o2hb_region *to_o2hb_region(struct config_item *item)
{
	return item ? container_of(item, struct o2hb_region, hr_item) : NULL;
}

/* drop_item only drops its ref after killing the thread, nothing should
 * be using the region anymore.  this has to clean up any state that
 * attributes might have built up. */
static void o2hb_region_release(struct config_item *item)
{
	int i;
	struct page *page;
	struct o2hb_region *reg = to_o2hb_region(item);

	if (reg->hr_tmp_block)
		kfree(reg->hr_tmp_block);

	if (reg->hr_slot_data) {
		for (i = 0; i < reg->hr_num_pages; i++) {
			page = reg->hr_slot_data[i];
			if (page)
				__free_page(page);
		}
		kfree(reg->hr_slot_data);
	}

	if (reg->hr_bdev)
		blkdev_put(reg->hr_bdev, FMODE_READ|FMODE_WRITE);

	if (reg->hr_slots)
		kfree(reg->hr_slots);

	kfree(reg->hr_db_regnum);
	kfree(reg->hr_db_livenodes);
	debugfs_remove(reg->hr_debug_livenodes);
	debugfs_remove(reg->hr_debug_regnum);
	debugfs_remove(reg->hr_debug_elapsed_time);
	debugfs_remove(reg->hr_debug_pinned);
	debugfs_remove(reg->hr_debug_dir);

	spin_lock(&o2hb_live_lock);
	list_del(&reg->hr_all_item);
	spin_unlock(&o2hb_live_lock);

	kfree(reg);
}

static int o2hb_read_block_input(struct o2hb_region *reg,
				 const char *page,
				 size_t count,
				 unsigned long *ret_bytes,
				 unsigned int *ret_bits)
{
	unsigned long bytes;
	char *p = (char *)page;

	bytes = simple_strtoul(p, &p, 0);
	if (!p || (*p && (*p != '\n')))
		return -EINVAL;

	/* Heartbeat and fs min / max block sizes are the same. */
	if (bytes > 4096 || bytes < 512)
		return -ERANGE;
	if (hweight16(bytes) != 1)
		return -EINVAL;

	if (ret_bytes)
		*ret_bytes = bytes;
	if (ret_bits)
		*ret_bits = ffs(bytes) - 1;

	return 0;
}

static ssize_t o2hb_region_block_bytes_read(struct o2hb_region *reg,
					    char *page)
{
	return sprintf(page, "%u\n", reg->hr_block_bytes);
}

static ssize_t o2hb_region_block_bytes_write(struct o2hb_region *reg,
					     const char *page,
					     size_t count)
{
	int status;
	unsigned long block_bytes;
	unsigned int block_bits;

	if (reg->hr_bdev)
		return -EINVAL;

	status = o2hb_read_block_input(reg, page, count,
				       &block_bytes, &block_bits);
	if (status)
		return status;

	reg->hr_block_bytes = (unsigned int)block_bytes;
	reg->hr_block_bits = block_bits;

	return count;
}

static ssize_t o2hb_region_start_block_read(struct o2hb_region *reg,
					    char *page)
{
	return sprintf(page, "%llu\n", reg->hr_start_block);
}

static ssize_t o2hb_region_start_block_write(struct o2hb_region *reg,
					     const char *page,
					     size_t count)
{
	unsigned long long tmp;
	char *p = (char *)page;

	if (reg->hr_bdev)
		return -EINVAL;

	tmp = simple_strtoull(p, &p, 0);
	if (!p || (*p && (*p != '\n')))
		return -EINVAL;

	reg->hr_start_block = tmp;

	return count;
}

static ssize_t o2hb_region_blocks_read(struct o2hb_region *reg,
				       char *page)
{
	return sprintf(page, "%d\n", reg->hr_blocks);
}

static ssize_t o2hb_region_blocks_write(struct o2hb_region *reg,
					const char *page,
					size_t count)
{
	unsigned long tmp;
	char *p = (char *)page;

	if (reg->hr_bdev)
		return -EINVAL;

	tmp = simple_strtoul(p, &p, 0);
	if (!p || (*p && (*p != '\n')))
		return -EINVAL;

	if (tmp > O2NM_MAX_NODES || tmp == 0)
		return -ERANGE;

	reg->hr_blocks = (unsigned int)tmp;

	return count;
}

static ssize_t o2hb_region_dev_read(struct o2hb_region *reg,
				    char *page)
{
	unsigned int ret = 0;

	if (reg->hr_bdev)
		ret = sprintf(page, "%s\n", reg->hr_dev_name);

	return ret;
}

static void o2hb_init_region_params(struct o2hb_region *reg)
{
	reg->hr_slots_per_page = PAGE_CACHE_SIZE >> reg->hr_block_bits;
	reg->hr_timeout_ms = O2HB_REGION_TIMEOUT_MS;

	mlog(ML_HEARTBEAT, "hr_start_block = %llu, hr_blocks = %u\n",
	     reg->hr_start_block, reg->hr_blocks);
	mlog(ML_HEARTBEAT, "hr_block_bytes = %u, hr_block_bits = %u\n",
	     reg->hr_block_bytes, reg->hr_block_bits);
	mlog(ML_HEARTBEAT, "hr_timeout_ms = %u\n", reg->hr_timeout_ms);
	mlog(ML_HEARTBEAT, "dead threshold = %u\n", o2hb_dead_threshold);
}

static int o2hb_map_slot_data(struct o2hb_region *reg)
{
	int i, j;
	unsigned int last_slot;
	unsigned int spp = reg->hr_slots_per_page;
	struct page *page;
	char *raw;
	struct o2hb_disk_slot *slot;

	reg->hr_tmp_block = kmalloc(reg->hr_block_bytes, GFP_KERNEL);
	if (reg->hr_tmp_block == NULL) {
		mlog_errno(-ENOMEM);
		return -ENOMEM;
	}

	reg->hr_slots = kcalloc(reg->hr_blocks,
				sizeof(struct o2hb_disk_slot), GFP_KERNEL);
	if (reg->hr_slots == NULL) {
		mlog_errno(-ENOMEM);
		return -ENOMEM;
	}

	for(i = 0; i < reg->hr_blocks; i++) {
		slot = &reg->hr_slots[i];
		slot->ds_node_num = i;
		INIT_LIST_HEAD(&slot->ds_live_item);
		slot->ds_raw_block = NULL;
	}

	reg->hr_num_pages = (reg->hr_blocks + spp - 1) / spp;
	mlog(ML_HEARTBEAT, "Going to require %u pages to cover %u blocks "
			   "at %u blocks per page\n",
	     reg->hr_num_pages, reg->hr_blocks, spp);

	reg->hr_slot_data = kcalloc(reg->hr_num_pages, sizeof(struct page *),
				    GFP_KERNEL);
	if (!reg->hr_slot_data) {
		mlog_errno(-ENOMEM);
		return -ENOMEM;
	}

	for(i = 0; i < reg->hr_num_pages; i++) {
		page = alloc_page(GFP_KERNEL);
		if (!page) {
			mlog_errno(-ENOMEM);
			return -ENOMEM;
		}

		reg->hr_slot_data[i] = page;

		last_slot = i * spp;
		raw = page_address(page);
		for (j = 0;
		     (j < spp) && ((j + last_slot) < reg->hr_blocks);
		     j++) {
			BUG_ON((j + last_slot) >= reg->hr_blocks);

			slot = &reg->hr_slots[j + last_slot];
			slot->ds_raw_block =
				(struct o2hb_disk_heartbeat_block *) raw;

			raw += reg->hr_block_bytes;
		}
	}

	return 0;
}

/* Read in all the slots available and populate the tracking
 * structures so that we can start with a baseline idea of what's
 * there. */
static int o2hb_populate_slot_data(struct o2hb_region *reg)
{
	int ret, i;
	struct o2hb_disk_slot *slot;
	struct o2hb_disk_heartbeat_block *hb_block;

	ret = o2hb_read_slots(reg, reg->hr_blocks);
	if (ret) {
		mlog_errno(ret);
		goto out;
	}

	/* We only want to get an idea of the values initially in each
	 * slot, so we do no verification - o2hb_check_slot will
	 * actually determine if each configured slot is valid and
	 * whether any values have changed. */
	for(i = 0; i < reg->hr_blocks; i++) {
		slot = &reg->hr_slots[i];
		hb_block = (struct o2hb_disk_heartbeat_block *) slot->ds_raw_block;

		/* Only fill the values that o2hb_check_slot uses to
		 * determine changing slots */
		slot->ds_last_time = le64_to_cpu(hb_block->hb_seq);
		slot->ds_last_generation = le64_to_cpu(hb_block->hb_generation);
	}

out:
	return ret;
}

/* this is acting as commit; we set up all of hr_bdev and hr_task or nothing */
static ssize_t o2hb_region_dev_write(struct o2hb_region *reg,
				     const char *page,
				     size_t count)
{
	struct task_struct *hb_task;
	long fd;
	int sectsize;
	char *p = (char *)page;
	struct file *filp = NULL;
	struct inode *inode = NULL;
	ssize_t ret = -EINVAL;

	if (reg->hr_bdev)
		goto out;

	/* We can't heartbeat without having had our node number
	 * configured yet. */
	if (o2nm_this_node() == O2NM_MAX_NODES)
		goto out;

	fd = simple_strtol(p, &p, 0);
	if (!p || (*p && (*p != '\n')))
		goto out;

	if (fd < 0 || fd >= INT_MAX)
		goto out;

	filp = fget(fd);
	if (filp == NULL)
		goto out;

	if (reg->hr_blocks == 0 || reg->hr_start_block == 0 ||
	    reg->hr_block_bytes == 0)
		goto out;

	inode = igrab(filp->f_mapping->host);
	if (inode == NULL)
		goto out;

	if (!S_ISBLK(inode->i_mode))
		goto out;

	reg->hr_bdev = I_BDEV(filp->f_mapping->host);
	ret = blkdev_get(reg->hr_bdev, FMODE_WRITE | FMODE_READ, NULL);
	if (ret) {
		reg->hr_bdev = NULL;
		goto out;
	}
	inode = NULL;

	bdevname(reg->hr_bdev, reg->hr_dev_name);

	sectsize = bdev_logical_block_size(reg->hr_bdev);
	if (sectsize != reg->hr_block_bytes) {
		mlog(ML_ERROR,
		     "blocksize %u incorrect for device, expected %d",
		     reg->hr_block_bytes, sectsize);
		ret = -EINVAL;
		goto out;
	}

	o2hb_init_region_params(reg);

	/* Generation of zero is invalid */
	do {
		get_random_bytes(&reg->hr_generation,
				 sizeof(reg->hr_generation));
	} while (reg->hr_generation == 0);

	ret = o2hb_map_slot_data(reg);
	if (ret) {
		mlog_errno(ret);
		goto out;
	}

	ret = o2hb_populate_slot_data(reg);
	if (ret) {
		mlog_errno(ret);
		goto out;
	}

	INIT_DELAYED_WORK(&reg->hr_write_timeout_work, o2hb_write_timeout);

	/*
	 * A node is considered live after it has beat LIVE_THRESHOLD
	 * times.  We're not steady until we've given them a chance
	 * _after_ our first read.
	 */
	atomic_set(&reg->hr_steady_iterations, O2HB_LIVE_THRESHOLD + 1);

	hb_task = kthread_run(o2hb_thread, reg, "o2hb-%s",
			      reg->hr_item.ci_name);
	if (IS_ERR(hb_task)) {
		ret = PTR_ERR(hb_task);
		mlog_errno(ret);
		goto out;
	}

	spin_lock(&o2hb_live_lock);
	reg->hr_task = hb_task;
	spin_unlock(&o2hb_live_lock);

	ret = wait_event_interruptible(o2hb_steady_queue,
				atomic_read(&reg->hr_steady_iterations) == 0);
	if (ret) {
		/* We got interrupted (hello ptrace!).  Clean up */
		spin_lock(&o2hb_live_lock);
		hb_task = reg->hr_task;
		reg->hr_task = NULL;
		spin_unlock(&o2hb_live_lock);

		if (hb_task)
			kthread_stop(hb_task);
		goto out;
	}

	/* Ok, we were woken.  Make sure it wasn't by drop_item() */
	spin_lock(&o2hb_live_lock);
	hb_task = reg->hr_task;
	if (o2hb_global_heartbeat_active())
		set_bit(reg->hr_region_num, o2hb_live_region_bitmap);
	spin_unlock(&o2hb_live_lock);

	if (hb_task)
		ret = count;
	else
		ret = -EIO;

	if (hb_task && o2hb_global_heartbeat_active())
		printk(KERN_NOTICE "o2hb: Heartbeat started on region %s\n",
		       config_item_name(&reg->hr_item));

out:
	if (filp)
		fput(filp);
	if (inode)
		iput(inode);
	if (ret < 0) {
		if (reg->hr_bdev) {
			blkdev_put(reg->hr_bdev, FMODE_READ|FMODE_WRITE);
			reg->hr_bdev = NULL;
		}
	}
	return ret;
}

static ssize_t o2hb_region_pid_read(struct o2hb_region *reg,
                                      char *page)
{
	pid_t pid = 0;

	spin_lock(&o2hb_live_lock);
	if (reg->hr_task)
		pid = task_pid_nr(reg->hr_task);
	spin_unlock(&o2hb_live_lock);

	if (!pid)
		return 0;

	return sprintf(page, "%u\n", pid);
}

struct o2hb_region_attribute {
	struct configfs_attribute attr;
	ssize_t (*show)(struct o2hb_region *, char *);
	ssize_t (*store)(struct o2hb_region *, const char *, size_t);
};

static struct o2hb_region_attribute o2hb_region_attr_block_bytes = {
	.attr	= { .ca_owner = THIS_MODULE,
		    .ca_name = "block_bytes",
		    .ca_mode = S_IRUGO | S_IWUSR },
	.show	= o2hb_region_block_bytes_read,
	.store	= o2hb_region_block_bytes_write,
};

static struct o2hb_region_attribute o2hb_region_attr_start_block = {
	.attr	= { .ca_owner = THIS_MODULE,
		    .ca_name = "start_block",
		    .ca_mode = S_IRUGO | S_IWUSR },
	.show	= o2hb_region_start_block_read,
	.store	= o2hb_region_start_block_write,
};

static struct o2hb_region_attribute o2hb_region_attr_blocks = {
	.attr	= { .ca_owner = THIS_MODULE,
		    .ca_name = "blocks",
		    .ca_mode = S_IRUGO | S_IWUSR },
	.show	= o2hb_region_blocks_read,
	.store	= o2hb_region_blocks_write,
};

static struct o2hb_region_attribute o2hb_region_attr_dev = {
	.attr	= { .ca_owner = THIS_MODULE,
		    .ca_name = "dev",
		    .ca_mode = S_IRUGO | S_IWUSR },
	.show	= o2hb_region_dev_read,
	.store	= o2hb_region_dev_write,
};

static struct o2hb_region_attribute o2hb_region_attr_pid = {
       .attr   = { .ca_owner = THIS_MODULE,
                   .ca_name = "pid",
                   .ca_mode = S_IRUGO | S_IRUSR },
       .show   = o2hb_region_pid_read,
};

static struct configfs_attribute *o2hb_region_attrs[] = {
	&o2hb_region_attr_block_bytes.attr,
	&o2hb_region_attr_start_block.attr,
	&o2hb_region_attr_blocks.attr,
	&o2hb_region_attr_dev.attr,
	&o2hb_region_attr_pid.attr,
	NULL,
};

static ssize_t o2hb_region_show(struct config_item *item,
				struct configfs_attribute *attr,
				char *page)
{
	struct o2hb_region *reg = to_o2hb_region(item);
	struct o2hb_region_attribute *o2hb_region_attr =
		container_of(attr, struct o2hb_region_attribute, attr);
	ssize_t ret = 0;

	if (o2hb_region_attr->show)
		ret = o2hb_region_attr->show(reg, page);
	return ret;
}

static ssize_t o2hb_region_store(struct config_item *item,
				 struct configfs_attribute *attr,
				 const char *page, size_t count)
{
	struct o2hb_region *reg = to_o2hb_region(item);
	struct o2hb_region_attribute *o2hb_region_attr =
		container_of(attr, struct o2hb_region_attribute, attr);
	ssize_t ret = -EINVAL;

	if (o2hb_region_attr->store)
		ret = o2hb_region_attr->store(reg, page, count);
	return ret;
}

static struct configfs_item_operations o2hb_region_item_ops = {
	.release		= o2hb_region_release,
	.show_attribute		= o2hb_region_show,
	.store_attribute	= o2hb_region_store,
};

static struct config_item_type o2hb_region_type = {
	.ct_item_ops	= &o2hb_region_item_ops,
	.ct_attrs	= o2hb_region_attrs,
	.ct_owner	= THIS_MODULE,
};

/* heartbeat set */

struct o2hb_heartbeat_group {
	struct config_group hs_group;
	/* some stuff? */
};

static struct o2hb_heartbeat_group *to_o2hb_heartbeat_group(struct config_group *group)
{
	return group ?
		container_of(group, struct o2hb_heartbeat_group, hs_group)
		: NULL;
}

static int o2hb_debug_region_init(struct o2hb_region *reg, struct dentry *dir)
{
	int ret = -ENOMEM;

	reg->hr_debug_dir =
		debugfs_create_dir(config_item_name(&reg->hr_item), dir);
	if (!reg->hr_debug_dir) {
		mlog_errno(ret);
		goto bail;
	}

	reg->hr_debug_livenodes =
			o2hb_debug_create(O2HB_DEBUG_LIVENODES,
					  reg->hr_debug_dir,
					  &(reg->hr_db_livenodes),
					  sizeof(*(reg->hr_db_livenodes)),
					  O2HB_DB_TYPE_REGION_LIVENODES,
					  sizeof(reg->hr_live_node_bitmap),
					  O2NM_MAX_NODES, reg);
	if (!reg->hr_debug_livenodes) {
		mlog_errno(ret);
		goto bail;
	}

	reg->hr_debug_regnum =
			o2hb_debug_create(O2HB_DEBUG_REGION_NUMBER,
					  reg->hr_debug_dir,
					  &(reg->hr_db_regnum),
					  sizeof(*(reg->hr_db_regnum)),
					  O2HB_DB_TYPE_REGION_NUMBER,
					  0, O2NM_MAX_NODES, reg);
	if (!reg->hr_debug_regnum) {
		mlog_errno(ret);
		goto bail;
	}

	reg->hr_debug_elapsed_time =
			o2hb_debug_create(O2HB_DEBUG_REGION_ELAPSED_TIME,
					  reg->hr_debug_dir,
					  &(reg->hr_db_elapsed_time),
					  sizeof(*(reg->hr_db_elapsed_time)),
					  O2HB_DB_TYPE_REGION_ELAPSED_TIME,
					  0, 0, reg);
	if (!reg->hr_debug_elapsed_time) {
		mlog_errno(ret);
		goto bail;
	}

	reg->hr_debug_pinned =
			o2hb_debug_create(O2HB_DEBUG_REGION_PINNED,
					  reg->hr_debug_dir,
					  &(reg->hr_db_pinned),
					  sizeof(*(reg->hr_db_pinned)),
					  O2HB_DB_TYPE_REGION_PINNED,
					  0, 0, reg);
	if (!reg->hr_debug_pinned) {
		mlog_errno(ret);
		goto bail;
	}

	ret = 0;
bail:
	return ret;
}

static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *group,
							  const char *name)
{
	struct o2hb_region *reg = NULL;
	int ret;

	reg = kzalloc(sizeof(struct o2hb_region), GFP_KERNEL);
	if (reg == NULL)
		return ERR_PTR(-ENOMEM);

	if (strlen(name) > O2HB_MAX_REGION_NAME_LEN) {
		ret = -ENAMETOOLONG;
		goto free;
	}

	spin_lock(&o2hb_live_lock);
	reg->hr_region_num = 0;
	if (o2hb_global_heartbeat_active()) {
		reg->hr_region_num = find_first_zero_bit(o2hb_region_bitmap,
							 O2NM_MAX_REGIONS);
		if (reg->hr_region_num >= O2NM_MAX_REGIONS) {
			spin_unlock(&o2hb_live_lock);
			ret = -EFBIG;
			goto free;
		}
		set_bit(reg->hr_region_num, o2hb_region_bitmap);
	}
	list_add_tail(&reg->hr_all_item, &o2hb_all_regions);
	spin_unlock(&o2hb_live_lock);

	config_item_init_type_name(&reg->hr_item, name, &o2hb_region_type);

	ret = o2hb_debug_region_init(reg, o2hb_debug_dir);
	if (ret) {
		config_item_put(&reg->hr_item);
		goto free;
	}

	return &reg->hr_item;
free:
	kfree(reg);
	return ERR_PTR(ret);
}

static void o2hb_heartbeat_group_drop_item(struct config_group *group,
					   struct config_item *item)
{
	struct task_struct *hb_task;
	struct o2hb_region *reg = to_o2hb_region(item);
	int quorum_region = 0;

	/* stop the thread when the user removes the region dir */
	spin_lock(&o2hb_live_lock);
	if (o2hb_global_heartbeat_active()) {
		clear_bit(reg->hr_region_num, o2hb_region_bitmap);
		clear_bit(reg->hr_region_num, o2hb_live_region_bitmap);
		if (test_bit(reg->hr_region_num, o2hb_quorum_region_bitmap))
			quorum_region = 1;
		clear_bit(reg->hr_region_num, o2hb_quorum_region_bitmap);
	}
	hb_task = reg->hr_task;
	reg->hr_task = NULL;
	reg->hr_item_dropped = 1;
	spin_unlock(&o2hb_live_lock);

	if (hb_task)
		kthread_stop(hb_task);

	/*
	 * If we're racing a dev_write(), we need to wake them.  They will
	 * check reg->hr_task
	 */
	if (atomic_read(&reg->hr_steady_iterations) != 0) {
		atomic_set(&reg->hr_steady_iterations, 0);
		wake_up(&o2hb_steady_queue);
	}

	if (o2hb_global_heartbeat_active())
		printk(KERN_NOTICE "o2hb: Heartbeat stopped on region %s\n",
		       config_item_name(&reg->hr_item));

	config_item_put(item);

	if (!o2hb_global_heartbeat_active() || !quorum_region)
		return;

	/*
	 * If global heartbeat active and there are dependent users,
	 * pin all regions if quorum region count <= CUT_OFF
	 */
	spin_lock(&o2hb_live_lock);

	if (!o2hb_dependent_users)
		goto unlock;

	if (o2hb_pop_count(&o2hb_quorum_region_bitmap,
			   O2NM_MAX_REGIONS) <= O2HB_PIN_CUT_OFF)
		o2hb_region_pin(NULL);

unlock:
	spin_unlock(&o2hb_live_lock);
}

struct o2hb_heartbeat_group_attribute {
	struct configfs_attribute attr;
	ssize_t (*show)(struct o2hb_heartbeat_group *, char *);
	ssize_t (*store)(struct o2hb_heartbeat_group *, const char *, size_t);
};

static ssize_t o2hb_heartbeat_group_show(struct config_item *item,
					 struct configfs_attribute *attr,
					 char *page)
{
	struct o2hb_heartbeat_group *reg = to_o2hb_heartbeat_group(to_config_group(item));
	struct o2hb_heartbeat_group_attribute *o2hb_heartbeat_group_attr =
		container_of(attr, struct o2hb_heartbeat_group_attribute, attr);
	ssize_t ret = 0;

	if (o2hb_heartbeat_group_attr->show)
		ret = o2hb_heartbeat_group_attr->show(reg, page);
	return ret;
}

static ssize_t o2hb_heartbeat_group_store(struct config_item *item,
					  struct configfs_attribute *attr,
					  const char *page, size_t count)
{
	struct o2hb_heartbeat_group *reg = to_o2hb_heartbeat_group(to_config_group(item));
	struct o2hb_heartbeat_group_attribute *o2hb_heartbeat_group_attr =
		container_of(attr, struct o2hb_heartbeat_group_attribute, attr);
	ssize_t ret = -EINVAL;

	if (o2hb_heartbeat_group_attr->store)
		ret = o2hb_heartbeat_group_attr->store(reg, page, count);
	return ret;
}

static ssize_t o2hb_heartbeat_group_threshold_show(struct o2hb_heartbeat_group *group,
						     char *page)
{
	return sprintf(page, "%u\n", o2hb_dead_threshold);
}

static ssize_t o2hb_heartbeat_group_threshold_store(struct o2hb_heartbeat_group *group,
						    const char *page,
						    size_t count)
{
	unsigned long tmp;
	char *p = (char *)page;

	tmp = simple_strtoul(p, &p, 10);
	if (!p || (*p && (*p != '\n')))
                return -EINVAL;

	/* this will validate ranges for us. */
	o2hb_dead_threshold_set((unsigned int) tmp);

	return count;
}

static
ssize_t o2hb_heartbeat_group_mode_show(struct o2hb_heartbeat_group *group,
				       char *page)
{
	return sprintf(page, "%s\n",
		       o2hb_heartbeat_mode_desc[o2hb_heartbeat_mode]);
}

static
ssize_t o2hb_heartbeat_group_mode_store(struct o2hb_heartbeat_group *group,
					const char *page, size_t count)
{
	unsigned int i;
	int ret;
	size_t len;

	len = (page[count - 1] == '\n') ? count - 1 : count;
	if (!len)
		return -EINVAL;

	for (i = 0; i < O2HB_HEARTBEAT_NUM_MODES; ++i) {
		if (strnicmp(page, o2hb_heartbeat_mode_desc[i], len))
			continue;

		ret = o2hb_global_hearbeat_mode_set(i);
		if (!ret)
			printk(KERN_NOTICE "o2hb: Heartbeat mode set to %s\n",
			       o2hb_heartbeat_mode_desc[i]);
		return count;
	}

	return -EINVAL;

}

static struct o2hb_heartbeat_group_attribute o2hb_heartbeat_group_attr_threshold = {
	.attr	= { .ca_owner = THIS_MODULE,
		    .ca_name = "dead_threshold",
		    .ca_mode = S_IRUGO | S_IWUSR },
	.show	= o2hb_heartbeat_group_threshold_show,
	.store	= o2hb_heartbeat_group_threshold_store,
};

static struct o2hb_heartbeat_group_attribute o2hb_heartbeat_group_attr_mode = {
	.attr   = { .ca_owner = THIS_MODULE,
		.ca_name = "mode",
		.ca_mode = S_IRUGO | S_IWUSR },
	.show   = o2hb_heartbeat_group_mode_show,
	.store  = o2hb_heartbeat_group_mode_store,
};

static struct configfs_attribute *o2hb_heartbeat_group_attrs[] = {
	&o2hb_heartbeat_group_attr_threshold.attr,
	&o2hb_heartbeat_group_attr_mode.attr,
	NULL,
};

static struct configfs_item_operations o2hb_hearbeat_group_item_ops = {
	.show_attribute		= o2hb_heartbeat_group_show,
	.store_attribute	= o2hb_heartbeat_group_store,
};

static struct configfs_group_operations o2hb_heartbeat_group_group_ops = {
	.make_item	= o2hb_heartbeat_group_make_item,
	.drop_item	= o2hb_heartbeat_group_drop_item,
};

static struct config_item_type o2hb_heartbeat_group_type = {
	.ct_group_ops	= &o2hb_heartbeat_group_group_ops,
	.ct_item_ops	= &o2hb_hearbeat_group_item_ops,
	.ct_attrs	= o2hb_heartbeat_group_attrs,
	.ct_owner	= THIS_MODULE,
};

/* this is just here to avoid touching group in heartbeat.h which the
 * entire damn world #includes */
struct config_group *o2hb_alloc_hb_set(void)
{
	struct o2hb_heartbeat_group *hs = NULL;
	struct config_group *ret = NULL;

	hs = kzalloc(sizeof(struct o2hb_heartbeat_group), GFP_KERNEL);
	if (hs == NULL)
		goto out;

	config_group_init_type_name(&hs->hs_group, "heartbeat",
				    &o2hb_heartbeat_group_type);

	ret = &hs->hs_group;
out:
	if (ret == NULL)
		kfree(hs);
	return ret;
}

void o2hb_free_hb_set(struct config_group *group)
{
	struct o2hb_heartbeat_group *hs = to_o2hb_heartbeat_group(group);
	kfree(hs);
}

/* hb callback registration and issueing */

static struct o2hb_callback *hbcall_from_type(enum o2hb_callback_type type)
{
	if (type == O2HB_NUM_CB)
		return ERR_PTR(-EINVAL);

	return &o2hb_callbacks[type];
}

void o2hb_setup_callback(struct o2hb_callback_func *hc,
			 enum o2hb_callback_type type,
			 o2hb_cb_func *func,
			 void *data,
			 int priority)
{
	INIT_LIST_HEAD(&hc->hc_item);
	hc->hc_func = func;
	hc->hc_data = data;
	hc->hc_priority = priority;
	hc->hc_type = type;
	hc->hc_magic = O2HB_CB_MAGIC;
}
EXPORT_SYMBOL_GPL(o2hb_setup_callback);

/*
 * In local heartbeat mode, region_uuid passed matches the dlm domain name.
 * In global heartbeat mode, region_uuid passed is NULL.
 *
 * In local, we only pin the matching region. In global we pin all the active
 * regions.
 */
static int o2hb_region_pin(const char *region_uuid)
{
	int ret = 0, found = 0;
	struct o2hb_region *reg;
	char *uuid;

	assert_spin_locked(&o2hb_live_lock);

	list_for_each_entry(reg, &o2hb_all_regions, hr_all_item) {
		uuid = config_item_name(&reg->hr_item);

		/* local heartbeat */
		if (region_uuid) {
			if (strcmp(region_uuid, uuid))
				continue;
			found = 1;
		}

		if (reg->hr_item_pinned || reg->hr_item_dropped)
			goto skip_pin;

		/* Ignore ENOENT only for local hb (userdlm domain) */
		ret = o2nm_depend_item(&reg->hr_item);
		if (!ret) {
			mlog(ML_CLUSTER, "Pin region %s\n", uuid);
			reg->hr_item_pinned = 1;
		} else {
			if (ret == -ENOENT && found)
				ret = 0;
			else {
				mlog(ML_ERROR, "Pin region %s fails with %d\n",
				     uuid, ret);
				break;
			}
		}
skip_pin:
		if (found)
			break;
	}

	return ret;
}

/*
 * In local heartbeat mode, region_uuid passed matches the dlm domain name.
 * In global heartbeat mode, region_uuid passed is NULL.
 *
 * In local, we only unpin the matching region. In global we unpin all the
 * active regions.
 */
static void o2hb_region_unpin(const char *region_uuid)
{
	struct o2hb_region *reg;
	char *uuid;
	int found = 0;

	assert_spin_locked(&o2hb_live_lock);

	list_for_each_entry(reg, &o2hb_all_regions, hr_all_item) {
		uuid = config_item_name(&reg->hr_item);
		if (region_uuid) {
			if (strcmp(region_uuid, uuid))
				continue;
			found = 1;
		}

		if (reg->hr_item_pinned) {
			mlog(ML_CLUSTER, "Unpin region %s\n", uuid);
			o2nm_undepend_item(&reg->hr_item);
			reg->hr_item_pinned = 0;
		}
		if (found)
			break;
	}
}

static int o2hb_region_inc_user(const char *region_uuid)
{
	int ret = 0;

	spin_lock(&o2hb_live_lock);

	/* local heartbeat */
	if (!o2hb_global_heartbeat_active()) {
	    ret = o2hb_region_pin(region_uuid);
	    goto unlock;
	}

	/*
	 * if global heartbeat active and this is the first dependent user,
	 * pin all regions if quorum region count <= CUT_OFF
	 */
	o2hb_dependent_users++;
	if (o2hb_dependent_users > 1)
		goto unlock;

	if (o2hb_pop_count(&o2hb_quorum_region_bitmap,
			   O2NM_MAX_REGIONS) <= O2HB_PIN_CUT_OFF)
		ret = o2hb_region_pin(NULL);

unlock:
	spin_unlock(&o2hb_live_lock);
	return ret;
}

void o2hb_region_dec_user(const char *region_uuid)
{
	spin_lock(&o2hb_live_lock);

	/* local heartbeat */
	if (!o2hb_global_heartbeat_active()) {
	    o2hb_region_unpin(region_uuid);
	    goto unlock;
	}

	/*
	 * if global heartbeat active and there are no dependent users,
	 * unpin all quorum regions
	 */
	o2hb_dependent_users--;
	if (!o2hb_dependent_users)
		o2hb_region_unpin(NULL);

unlock:
	spin_unlock(&o2hb_live_lock);
}

int o2hb_register_callback(const char *region_uuid,
			   struct o2hb_callback_func *hc)
{
	struct o2hb_callback_func *tmp;
	struct list_head *iter;
	struct o2hb_callback *hbcall;
	int ret;

	BUG_ON(hc->hc_magic != O2HB_CB_MAGIC);
	BUG_ON(!list_empty(&hc->hc_item));

	hbcall = hbcall_from_type(hc->hc_type);
	if (IS_ERR(hbcall)) {
		ret = PTR_ERR(hbcall);
		goto out;
	}

	if (region_uuid) {
		ret = o2hb_region_inc_user(region_uuid);
		if (ret) {
			mlog_errno(ret);
			goto out;
		}
	}

	down_write(&o2hb_callback_sem);

	list_for_each(iter, &hbcall->list) {
		tmp = list_entry(iter, struct o2hb_callback_func, hc_item);
		if (hc->hc_priority < tmp->hc_priority) {
			list_add_tail(&hc->hc_item, iter);
			break;
		}
	}
	if (list_empty(&hc->hc_item))
		list_add_tail(&hc->hc_item, &hbcall->list);

	up_write(&o2hb_callback_sem);
	ret = 0;
out:
	mlog(ML_CLUSTER, "returning %d on behalf of %p for funcs %p\n",
	     ret, __builtin_return_address(0), hc);
	return ret;
}
EXPORT_SYMBOL_GPL(o2hb_register_callback);

void o2hb_unregister_callback(const char *region_uuid,
			      struct o2hb_callback_func *hc)
{
	BUG_ON(hc->hc_magic != O2HB_CB_MAGIC);

	mlog(ML_CLUSTER, "on behalf of %p for funcs %p\n",
	     __builtin_return_address(0), hc);

	/* XXX Can this happen _with_ a region reference? */
	if (list_empty(&hc->hc_item))
		return;

	if (region_uuid)
		o2hb_region_dec_user(region_uuid);

	down_write(&o2hb_callback_sem);

	list_del_init(&hc->hc_item);

	up_write(&o2hb_callback_sem);
}
EXPORT_SYMBOL_GPL(o2hb_unregister_callback);

int o2hb_check_node_heartbeating(u8 node_num)
{
	unsigned long testing_map[BITS_TO_LONGS(O2NM_MAX_NODES)];

	o2hb_fill_node_map(testing_map, sizeof(testing_map));
	if (!test_bit(node_num, testing_map)) {
		mlog(ML_HEARTBEAT,
		     "node (%u) does not have heartbeating enabled.\n",
		     node_num);
		return 0;
	}

	return 1;
}
EXPORT_SYMBOL_GPL(o2hb_check_node_heartbeating);

int o2hb_check_node_heartbeating_from_callback(u8 node_num)
{
	unsigned long testing_map[BITS_TO_LONGS(O2NM_MAX_NODES)];

	o2hb_fill_node_map_from_callback(testing_map, sizeof(testing_map));
	if (!test_bit(node_num, testing_map)) {
		mlog(ML_HEARTBEAT,
		     "node (%u) does not have heartbeating enabled.\n",
		     node_num);
		return 0;
	}

	return 1;
}
EXPORT_SYMBOL_GPL(o2hb_check_node_heartbeating_from_callback);

/* Makes sure our local node is configured with a node number, and is
 * heartbeating. */
int o2hb_check_local_node_heartbeating(void)
{
	u8 node_num;

	/* if this node was set then we have networking */
	node_num = o2nm_this_node();
	if (node_num == O2NM_MAX_NODES) {
		mlog(ML_HEARTBEAT, "this node has not been configured.\n");
		return 0;
	}

	return o2hb_check_node_heartbeating(node_num);
}
EXPORT_SYMBOL_GPL(o2hb_check_local_node_heartbeating);

/*
 * this is just a hack until we get the plumbing which flips file systems
 * read only and drops the hb ref instead of killing the node dead.
 */
void o2hb_stop_all_regions(void)
{
	struct o2hb_region *reg;

	mlog(ML_ERROR, "stopping heartbeat on all active regions.\n");

	spin_lock(&o2hb_live_lock);

	list_for_each_entry(reg, &o2hb_all_regions, hr_all_item)
		reg->hr_unclean_stop = 1;

	spin_unlock(&o2hb_live_lock);
}
EXPORT_SYMBOL_GPL(o2hb_stop_all_regions);

int o2hb_get_all_regions(char *region_uuids, u8 max_regions)
{
	struct o2hb_region *reg;
	int numregs = 0;
	char *p;

	spin_lock(&o2hb_live_lock);

	p = region_uuids;
	list_for_each_entry(reg, &o2hb_all_regions, hr_all_item) {
		mlog(0, "Region: %s\n", config_item_name(&reg->hr_item));
		if (numregs < max_regions) {
			memcpy(p, config_item_name(&reg->hr_item),
			       O2HB_MAX_REGION_NAME_LEN);
			p += O2HB_MAX_REGION_NAME_LEN;
		}
		numregs++;
	}

	spin_unlock(&o2hb_live_lock);

	return numregs;
}
EXPORT_SYMBOL_GPL(o2hb_get_all_regions);

int o2hb_global_heartbeat_active(void)
{
	return (o2hb_heartbeat_mode == O2HB_HEARTBEAT_GLOBAL);
}
EXPORT_SYMBOL(o2hb_global_heartbeat_active);