summaryrefslogtreecommitdiff
path: root/fs/gfs2/log.c
blob: 42c15cfc08219f0a2f17d45f00aa2ed362a58901 (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
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/gfs2_ondisk.h>
#include <linux/crc32.h>
#include <linux/crc32c.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/writeback.h>
#include <linux/list_sort.h>

#include "gfs2.h"
#include "incore.h"
#include "bmap.h"
#include "glock.h"
#include "log.h"
#include "lops.h"
#include "meta_io.h"
#include "util.h"
#include "dir.h"
#include "trace_gfs2.h"
#include "trans.h"

static void gfs2_log_shutdown(struct gfs2_sbd *sdp);

/**
 * gfs2_struct2blk - compute stuff
 * @sdp: the filesystem
 * @nstruct: the number of structures
 *
 * Compute the number of log descriptor blocks needed to hold a certain number
 * of structures of a certain size.
 *
 * Returns: the number of blocks needed (minimum is always 1)
 */

unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct)
{
	unsigned int blks;
	unsigned int first, second;

	/* The initial struct gfs2_log_descriptor block */
	blks = 1;
	first = sdp->sd_ldptrs;

	if (nstruct > first) {
		/* Subsequent struct gfs2_meta_header blocks */
		second = sdp->sd_inptrs;
		blks += DIV_ROUND_UP(nstruct - first, second);
	}

	return blks;
}

/**
 * gfs2_remove_from_ail - Remove an entry from the ail lists, updating counters
 * @bd: The gfs2_bufdata to remove
 *
 * The ail lock _must_ be held when calling this function
 *
 */

void gfs2_remove_from_ail(struct gfs2_bufdata *bd)
{
	bd->bd_tr = NULL;
	list_del_init(&bd->bd_ail_st_list);
	list_del_init(&bd->bd_ail_gl_list);
	atomic_dec(&bd->bd_gl->gl_ail_count);
	brelse(bd->bd_bh);
}

/**
 * gfs2_ail1_start_one - Start I/O on a transaction
 * @sdp: The superblock
 * @wbc: The writeback control structure
 * @tr: The transaction to start I/O on
 * @plug: The block plug currently active
 */

static int gfs2_ail1_start_one(struct gfs2_sbd *sdp,
			       struct writeback_control *wbc,
			       struct gfs2_trans *tr, struct blk_plug *plug)
__releases(&sdp->sd_ail_lock)
__acquires(&sdp->sd_ail_lock)
{
	struct gfs2_glock *gl = NULL;
	struct address_space *mapping;
	struct gfs2_bufdata *bd, *s;
	struct buffer_head *bh;
	int ret = 0;

	list_for_each_entry_safe_reverse(bd, s, &tr->tr_ail1_list, bd_ail_st_list) {
		bh = bd->bd_bh;

		gfs2_assert(sdp, bd->bd_tr == tr);

		if (!buffer_busy(bh)) {
			if (buffer_uptodate(bh)) {
				list_move(&bd->bd_ail_st_list,
					  &tr->tr_ail2_list);
				continue;
			}
			if (!cmpxchg(&sdp->sd_log_error, 0, -EIO)) {
				gfs2_io_error_bh(sdp, bh);
				gfs2_withdraw_delayed(sdp);
			}
		}

		if (gfs2_withdrawn(sdp)) {
			gfs2_remove_from_ail(bd);
			continue;
		}
		if (!buffer_dirty(bh))
			continue;
		if (gl == bd->bd_gl)
			continue;
		gl = bd->bd_gl;
		list_move(&bd->bd_ail_st_list, &tr->tr_ail1_list);
		mapping = bh->b_page->mapping;
		if (!mapping)
			continue;
		spin_unlock(&sdp->sd_ail_lock);
		ret = generic_writepages(mapping, wbc);
		if (need_resched()) {
			blk_finish_plug(plug);
			cond_resched();
			blk_start_plug(plug);
		}
		spin_lock(&sdp->sd_ail_lock);
		if (ret == -ENODATA) /* if a jdata write into a new hole */
			ret = 0; /* ignore it */
		if (ret || wbc->nr_to_write <= 0)
			break;
		return -EBUSY;
	}

	return ret;
}

static void dump_ail_list(struct gfs2_sbd *sdp)
{
	struct gfs2_trans *tr;
	struct gfs2_bufdata *bd;
	struct buffer_head *bh;

	list_for_each_entry_reverse(tr, &sdp->sd_ail1_list, tr_list) {
		list_for_each_entry_reverse(bd, &tr->tr_ail1_list,
					    bd_ail_st_list) {
			bh = bd->bd_bh;
			fs_err(sdp, "bd %p: blk:0x%llx bh=%p ", bd,
			       (unsigned long long)bd->bd_blkno, bh);
			if (!bh) {
				fs_err(sdp, "\n");
				continue;
			}
			fs_err(sdp, "0x%llx up2:%d dirt:%d lkd:%d req:%d "
			       "map:%d new:%d ar:%d aw:%d delay:%d "
			       "io err:%d unwritten:%d dfr:%d pin:%d esc:%d\n",
			       (unsigned long long)bh->b_blocknr,
			       buffer_uptodate(bh), buffer_dirty(bh),
			       buffer_locked(bh), buffer_req(bh),
			       buffer_mapped(bh), buffer_new(bh),
			       buffer_async_read(bh), buffer_async_write(bh),
			       buffer_delay(bh), buffer_write_io_error(bh),
			       buffer_unwritten(bh),
			       buffer_defer_completion(bh),
			       buffer_pinned(bh), buffer_escaped(bh));
		}
	}
}

/**
 * gfs2_ail1_flush - start writeback of some ail1 entries 
 * @sdp: The super block
 * @wbc: The writeback control structure
 *
 * Writes back some ail1 entries, according to the limits in the
 * writeback control structure
 */

void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
{
	struct list_head *head = &sdp->sd_ail1_list;
	struct gfs2_trans *tr;
	struct blk_plug plug;
	int ret;
	unsigned long flush_start = jiffies;

	trace_gfs2_ail_flush(sdp, wbc, 1);
	blk_start_plug(&plug);
	spin_lock(&sdp->sd_ail_lock);
restart:
	ret = 0;
	if (time_after(jiffies, flush_start + (HZ * 600))) {
		fs_err(sdp, "Error: In %s for ten minutes! t=%d\n",
		       __func__, current->journal_info ? 1 : 0);
		dump_ail_list(sdp);
		goto out;
	}
	list_for_each_entry_reverse(tr, head, tr_list) {
		if (wbc->nr_to_write <= 0)
			break;
		ret = gfs2_ail1_start_one(sdp, wbc, tr, &plug);
		if (ret) {
			if (ret == -EBUSY)
				goto restart;
			break;
		}
	}
out:
	spin_unlock(&sdp->sd_ail_lock);
	blk_finish_plug(&plug);
	if (ret) {
		gfs2_lm(sdp, "gfs2_ail1_start_one (generic_writepages) "
			"returned: %d\n", ret);
		gfs2_withdraw(sdp);
	}
	trace_gfs2_ail_flush(sdp, wbc, 0);
}

/**
 * gfs2_ail1_start - start writeback of all ail1 entries
 * @sdp: The superblock
 */

static void gfs2_ail1_start(struct gfs2_sbd *sdp)
{
	struct writeback_control wbc = {
		.sync_mode = WB_SYNC_NONE,
		.nr_to_write = LONG_MAX,
		.range_start = 0,
		.range_end = LLONG_MAX,
	};

	return gfs2_ail1_flush(sdp, &wbc);
}

static void gfs2_log_update_flush_tail(struct gfs2_sbd *sdp)
{
	unsigned int new_flush_tail = sdp->sd_log_head;
	struct gfs2_trans *tr;

	if (!list_empty(&sdp->sd_ail1_list)) {
		tr = list_last_entry(&sdp->sd_ail1_list,
				     struct gfs2_trans, tr_list);
		new_flush_tail = tr->tr_first;
	}
	sdp->sd_log_flush_tail = new_flush_tail;
}

static void gfs2_log_update_head(struct gfs2_sbd *sdp)
{
	unsigned int new_head = sdp->sd_log_flush_head;

	if (sdp->sd_log_flush_tail == sdp->sd_log_head)
		sdp->sd_log_flush_tail = new_head;
	sdp->sd_log_head = new_head;
}

/*
 * gfs2_ail_empty_tr - empty one of the ail lists of a transaction
 */

static void gfs2_ail_empty_tr(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
			      struct list_head *head)
{
	struct gfs2_bufdata *bd;

	while (!list_empty(head)) {
		bd = list_first_entry(head, struct gfs2_bufdata,
				      bd_ail_st_list);
		gfs2_assert(sdp, bd->bd_tr == tr);
		gfs2_remove_from_ail(bd);
	}
}

/**
 * gfs2_ail1_empty_one - Check whether or not a trans in the AIL has been synced
 * @sdp: the filesystem
 * @tr: the transaction
 * @max_revokes: If nonzero, issue revokes for the bd items for written buffers
 *
 * returns: the transaction's count of remaining active items
 */

static int gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
				int *max_revokes)
{
	struct gfs2_bufdata *bd, *s;
	struct buffer_head *bh;
	int active_count = 0;

	list_for_each_entry_safe_reverse(bd, s, &tr->tr_ail1_list,
					 bd_ail_st_list) {
		bh = bd->bd_bh;
		gfs2_assert(sdp, bd->bd_tr == tr);
		/*
		 * If another process flagged an io error, e.g. writing to the
		 * journal, error all other bhs and move them off the ail1 to
		 * prevent a tight loop when unmount tries to flush ail1,
		 * regardless of whether they're still busy. If no outside
		 * errors were found and the buffer is busy, move to the next.
		 * If the ail buffer is not busy and caught an error, flag it
		 * for others.
		 */
		if (!sdp->sd_log_error && buffer_busy(bh)) {
			active_count++;
			continue;
		}
		if (!buffer_uptodate(bh) &&
		    !cmpxchg(&sdp->sd_log_error, 0, -EIO)) {
			gfs2_io_error_bh(sdp, bh);
			gfs2_withdraw_delayed(sdp);
		}
		/*
		 * If we have space for revokes and the bd is no longer on any
		 * buf list, we can just add a revoke for it immediately and
		 * avoid having to put it on the ail2 list, where it would need
		 * to be revoked later.
		 */
		if (*max_revokes && list_empty(&bd->bd_list)) {
			gfs2_add_revoke(sdp, bd);
			(*max_revokes)--;
			continue;
		}
		list_move(&bd->bd_ail_st_list, &tr->tr_ail2_list);
	}
	return active_count;
}

/**
 * gfs2_ail1_empty - Try to empty the ail1 lists
 * @sdp: The superblock
 * @max_revokes: If non-zero, add revokes where appropriate
 *
 * Tries to empty the ail1 lists, starting with the oldest first
 */

static int gfs2_ail1_empty(struct gfs2_sbd *sdp, int max_revokes)
{
	struct gfs2_trans *tr, *s;
	int oldest_tr = 1;
	int ret;

	spin_lock(&sdp->sd_ail_lock);
	list_for_each_entry_safe_reverse(tr, s, &sdp->sd_ail1_list, tr_list) {
		if (!gfs2_ail1_empty_one(sdp, tr, &max_revokes) && oldest_tr)
			list_move(&tr->tr_list, &sdp->sd_ail2_list);
		else
			oldest_tr = 0;
	}
	gfs2_log_update_flush_tail(sdp);
	ret = list_empty(&sdp->sd_ail1_list);
	spin_unlock(&sdp->sd_ail_lock);

	if (test_bit(SDF_WITHDRAWING, &sdp->sd_flags)) {
		gfs2_lm(sdp, "fatal: I/O error(s)\n");
		gfs2_withdraw(sdp);
	}

	return ret;
}

static void gfs2_ail1_wait(struct gfs2_sbd *sdp)
{
	struct gfs2_trans *tr;
	struct gfs2_bufdata *bd;
	struct buffer_head *bh;

	spin_lock(&sdp->sd_ail_lock);
	list_for_each_entry_reverse(tr, &sdp->sd_ail1_list, tr_list) {
		list_for_each_entry(bd, &tr->tr_ail1_list, bd_ail_st_list) {
			bh = bd->bd_bh;
			if (!buffer_locked(bh))
				continue;
			get_bh(bh);
			spin_unlock(&sdp->sd_ail_lock);
			wait_on_buffer(bh);
			brelse(bh);
			return;
		}
	}
	spin_unlock(&sdp->sd_ail_lock);
}

static void __ail2_empty(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
	gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
	list_del(&tr->tr_list);
	gfs2_assert_warn(sdp, list_empty(&tr->tr_ail1_list));
	gfs2_assert_warn(sdp, list_empty(&tr->tr_ail2_list));
	gfs2_trans_free(sdp, tr);
}

static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
{
	struct list_head *ail2_list = &sdp->sd_ail2_list;
	unsigned int old_tail = sdp->sd_log_tail;
	struct gfs2_trans *tr, *safe;

	spin_lock(&sdp->sd_ail_lock);
	if (old_tail <= new_tail) {
		list_for_each_entry_safe(tr, safe, ail2_list, tr_list) {
			if (old_tail <= tr->tr_first && tr->tr_first < new_tail)
				__ail2_empty(sdp, tr);
		}
	} else {
		list_for_each_entry_safe(tr, safe, ail2_list, tr_list) {
			if (old_tail <= tr->tr_first || tr->tr_first < new_tail)
				__ail2_empty(sdp, tr);
		}
	}
	spin_unlock(&sdp->sd_ail_lock);
}

/**
 * gfs2_log_is_empty - Check if the log is empty
 * @sdp: The GFS2 superblock
 */

bool gfs2_log_is_empty(struct gfs2_sbd *sdp) {
	return atomic_read(&sdp->sd_log_blks_free) == sdp->sd_jdesc->jd_blocks;
}

static bool __gfs2_log_try_reserve_revokes(struct gfs2_sbd *sdp, unsigned int revokes)
{
	unsigned int available;

	available = atomic_read(&sdp->sd_log_revokes_available);
	while (available >= revokes) {
		if (atomic_try_cmpxchg(&sdp->sd_log_revokes_available,
				       &available, available - revokes))
			return true;
	}
	return false;
}

/**
 * gfs2_log_release_revokes - Release a given number of revokes
 * @sdp: The GFS2 superblock
 * @revokes: The number of revokes to release
 *
 * sdp->sd_log_flush_lock must be held.
 */
void gfs2_log_release_revokes(struct gfs2_sbd *sdp, unsigned int revokes)
{
	if (revokes)
		atomic_add(revokes, &sdp->sd_log_revokes_available);
}

/**
 * gfs2_log_release - Release a given number of log blocks
 * @sdp: The GFS2 superblock
 * @blks: The number of blocks
 *
 */

void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks)
{
	atomic_add(blks, &sdp->sd_log_blks_free);
	trace_gfs2_log_blocks(sdp, blks);
	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
				  sdp->sd_jdesc->jd_blocks);
	if (atomic_read(&sdp->sd_log_blks_needed))
		wake_up(&sdp->sd_log_waitq);
}

/**
 * __gfs2_log_try_reserve - Try to make a log reservation
 * @sdp: The GFS2 superblock
 * @blks: The number of blocks to reserve
 * @taboo_blks: The number of blocks to leave free
 *
 * Try to do the same as __gfs2_log_reserve(), but fail if no more log
 * space is immediately available.
 */
static bool __gfs2_log_try_reserve(struct gfs2_sbd *sdp, unsigned int blks,
				   unsigned int taboo_blks)
{
	unsigned wanted = blks + taboo_blks;
	unsigned int free_blocks;

	free_blocks = atomic_read(&sdp->sd_log_blks_free);
	while (free_blocks >= wanted) {
		if (atomic_try_cmpxchg(&sdp->sd_log_blks_free, &free_blocks,
				       free_blocks - blks)) {
			trace_gfs2_log_blocks(sdp, -blks);
			return true;
		}
	}
	return false;
}

/**
 * __gfs2_log_reserve - Make a log reservation
 * @sdp: The GFS2 superblock
 * @blks: The number of blocks to reserve
 * @taboo_blks: The number of blocks to leave free
 *
 * @taboo_blks is set to 0 for logd, and to GFS2_LOG_FLUSH_MIN_BLOCKS
 * for all other processes.  This ensures that when the log is almost full,
 * logd will still be able to call gfs2_log_flush one more time  without
 * blocking, which will advance the tail and make some more log space
 * available.
 *
 * We no longer flush the log here, instead we wake up logd to do that
 * for us. To avoid the thundering herd and to ensure that we deal fairly
 * with queued waiters, we use an exclusive wait. This means that when we
 * get woken with enough journal space to get our reservation, we need to
 * wake the next waiter on the list.
 */

static void __gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks,
			       unsigned int taboo_blks)
{
	unsigned wanted = blks + taboo_blks;
	unsigned int free_blocks;

	atomic_add(blks, &sdp->sd_log_blks_needed);
	for (;;) {
		if (current != sdp->sd_logd_process)
			wake_up(&sdp->sd_logd_waitq);
		io_wait_event(sdp->sd_log_waitq,
			(free_blocks = atomic_read(&sdp->sd_log_blks_free),
			 free_blocks >= wanted));
		do {
			if (atomic_try_cmpxchg(&sdp->sd_log_blks_free,
					       &free_blocks,
					       free_blocks - blks))
				goto reserved;
		} while (free_blocks >= wanted);
	}

reserved:
	trace_gfs2_log_blocks(sdp, -blks);
	if (atomic_sub_return(blks, &sdp->sd_log_blks_needed))
		wake_up(&sdp->sd_log_waitq);
}

/**
 * gfs2_log_try_reserve - Try to make a log reservation
 * @sdp: The GFS2 superblock
 * @tr: The transaction
 * @extra_revokes: The number of additional revokes reserved (output)
 *
 * This is similar to gfs2_log_reserve, but sdp->sd_log_flush_lock must be
 * held for correct revoke accounting.
 */

bool gfs2_log_try_reserve(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
			  unsigned int *extra_revokes)
{
	unsigned int blks = tr->tr_reserved;
	unsigned int revokes = tr->tr_revokes;
	unsigned int revoke_blks = 0;

	*extra_revokes = 0;
	if (revokes && !__gfs2_log_try_reserve_revokes(sdp, revokes)) {
		revoke_blks = DIV_ROUND_UP(revokes, sdp->sd_inptrs);
		*extra_revokes = revoke_blks * sdp->sd_inptrs - revokes;
		blks += revoke_blks;
	}
	if (!blks)
		return true;
	if (__gfs2_log_try_reserve(sdp, blks, GFS2_LOG_FLUSH_MIN_BLOCKS))
		return true;
	if (!revoke_blks)
		gfs2_log_release_revokes(sdp, revokes);
	return false;
}

/**
 * gfs2_log_reserve - Make a log reservation
 * @sdp: The GFS2 superblock
 * @tr: The transaction
 * @extra_revokes: The number of additional revokes reserved (output)
 *
 * sdp->sd_log_flush_lock must not be held.
 */

void gfs2_log_reserve(struct gfs2_sbd *sdp, struct gfs2_trans *tr,
		      unsigned int *extra_revokes)
{
	unsigned int blks = tr->tr_reserved;
	unsigned int revokes = tr->tr_revokes;
	unsigned int revoke_blks = 0;

	*extra_revokes = 0;
	if (revokes) {
		revoke_blks = DIV_ROUND_UP(revokes, sdp->sd_inptrs);
		*extra_revokes = revoke_blks * sdp->sd_inptrs - revokes;
		blks += revoke_blks;
	}
	__gfs2_log_reserve(sdp, blks, GFS2_LOG_FLUSH_MIN_BLOCKS);
}

/**
 * log_distance - Compute distance between two journal blocks
 * @sdp: The GFS2 superblock
 * @newer: The most recent journal block of the pair
 * @older: The older journal block of the pair
 *
 *   Compute the distance (in the journal direction) between two
 *   blocks in the journal
 *
 * Returns: the distance in blocks
 */

static inline unsigned int log_distance(struct gfs2_sbd *sdp, unsigned int newer,
					unsigned int older)
{
	int dist;

	dist = newer - older;
	if (dist < 0)
		dist += sdp->sd_jdesc->jd_blocks;

	return dist;
}

/**
 * calc_reserved - Calculate the number of blocks to keep reserved
 * @sdp: The GFS2 superblock
 *
 * This is complex.  We need to reserve room for all our currently used
 * metadata blocks (e.g. normal file I/O rewriting file time stamps) and
 * all our journaled data blocks for journaled files (e.g. files in the
 * meta_fs like rindex, or files for which chattr +j was done.)
 * If we don't reserve enough space, corruption will follow.
 *
 * We can have metadata blocks and jdata blocks in the same journal.  Each
 * type gets its own log descriptor, for which we need to reserve a block.
 * In fact, each type has the potential for needing more than one log descriptor
 * in cases where we have more blocks than will fit in a log descriptor.
 * Metadata journal entries take up half the space of journaled buffer entries.
 *
 * Also, we need to reserve blocks for revoke journal entries and one for an
 * overall header for the lot.
 *
 * Returns: the number of blocks reserved
 */
static unsigned int calc_reserved(struct gfs2_sbd *sdp)
{
	unsigned int reserved = GFS2_LOG_FLUSH_MIN_BLOCKS;
	unsigned int blocks;
	struct gfs2_trans *tr = sdp->sd_log_tr;

	if (tr) {
		blocks = tr->tr_num_buf_new - tr->tr_num_buf_rm;
		reserved += blocks + DIV_ROUND_UP(blocks, buf_limit(sdp));
		blocks = tr->tr_num_databuf_new - tr->tr_num_databuf_rm;
		reserved += blocks + DIV_ROUND_UP(blocks, databuf_limit(sdp));
	}
	return reserved;
}

static void log_pull_tail(struct gfs2_sbd *sdp)
{
	unsigned int new_tail = sdp->sd_log_flush_tail;
	unsigned int dist;

	if (new_tail == sdp->sd_log_tail)
		return;
	dist = log_distance(sdp, new_tail, sdp->sd_log_tail);
	ail2_empty(sdp, new_tail);
	gfs2_log_release(sdp, dist);
	sdp->sd_log_tail = new_tail;
}


void log_flush_wait(struct gfs2_sbd *sdp)
{
	DEFINE_WAIT(wait);

	if (atomic_read(&sdp->sd_log_in_flight)) {
		do {
			prepare_to_wait(&sdp->sd_log_flush_wait, &wait,
					TASK_UNINTERRUPTIBLE);
			if (atomic_read(&sdp->sd_log_in_flight))
				io_schedule();
		} while(atomic_read(&sdp->sd_log_in_flight));
		finish_wait(&sdp->sd_log_flush_wait, &wait);
	}
}

static int ip_cmp(void *priv, const struct list_head *a, const struct list_head *b)
{
	struct gfs2_inode *ipa, *ipb;

	ipa = list_entry(a, struct gfs2_inode, i_ordered);
	ipb = list_entry(b, struct gfs2_inode, i_ordered);

	if (ipa->i_no_addr < ipb->i_no_addr)
		return -1;
	if (ipa->i_no_addr > ipb->i_no_addr)
		return 1;
	return 0;
}

static void __ordered_del_inode(struct gfs2_inode *ip)
{
	if (!list_empty(&ip->i_ordered))
		list_del_init(&ip->i_ordered);
}

static void gfs2_ordered_write(struct gfs2_sbd *sdp)
{
	struct gfs2_inode *ip;
	LIST_HEAD(written);

	spin_lock(&sdp->sd_ordered_lock);
	list_sort(NULL, &sdp->sd_log_ordered, &ip_cmp);
	while (!list_empty(&sdp->sd_log_ordered)) {
		ip = list_first_entry(&sdp->sd_log_ordered, struct gfs2_inode, i_ordered);
		if (ip->i_inode.i_mapping->nrpages == 0) {
			__ordered_del_inode(ip);
			continue;
		}
		list_move(&ip->i_ordered, &written);
		spin_unlock(&sdp->sd_ordered_lock);
		filemap_fdatawrite(ip->i_inode.i_mapping);
		spin_lock(&sdp->sd_ordered_lock);
	}
	list_splice(&written, &sdp->sd_log_ordered);
	spin_unlock(&sdp->sd_ordered_lock);
}

static void gfs2_ordered_wait(struct gfs2_sbd *sdp)
{
	struct gfs2_inode *ip;

	spin_lock(&sdp->sd_ordered_lock);
	while (!list_empty(&sdp->sd_log_ordered)) {
		ip = list_first_entry(&sdp->sd_log_ordered, struct gfs2_inode, i_ordered);
		__ordered_del_inode(ip);
		if (ip->i_inode.i_mapping->nrpages == 0)
			continue;
		spin_unlock(&sdp->sd_ordered_lock);
		filemap_fdatawait(ip->i_inode.i_mapping);
		spin_lock(&sdp->sd_ordered_lock);
	}
	spin_unlock(&sdp->sd_ordered_lock);
}

void gfs2_ordered_del_inode(struct gfs2_inode *ip)
{
	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);

	spin_lock(&sdp->sd_ordered_lock);
	__ordered_del_inode(ip);
	spin_unlock(&sdp->sd_ordered_lock);
}

void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
{
	struct buffer_head *bh = bd->bd_bh;
	struct gfs2_glock *gl = bd->bd_gl;

	sdp->sd_log_num_revoke++;
	if (atomic_inc_return(&gl->gl_revokes) == 1)
		gfs2_glock_hold(gl);
	bh->b_private = NULL;
	bd->bd_blkno = bh->b_blocknr;
	gfs2_remove_from_ail(bd); /* drops ref on bh */
	bd->bd_bh = NULL;
	set_bit(GLF_LFLUSH, &gl->gl_flags);
	list_add(&bd->bd_list, &sdp->sd_log_revokes);
}

void gfs2_glock_remove_revoke(struct gfs2_glock *gl)
{
	if (atomic_dec_return(&gl->gl_revokes) == 0) {
		clear_bit(GLF_LFLUSH, &gl->gl_flags);
		gfs2_glock_queue_put(gl);
	}
}

/**
 * gfs2_flush_revokes - Add as many revokes to the system transaction as we can
 * @sdp: The GFS2 superblock
 *
 * Our usual strategy is to defer writing revokes as much as we can in the hope
 * that we'll eventually overwrite the journal, which will make those revokes
 * go away.  This changes when we flush the log: at that point, there will
 * likely be some left-over space in the last revoke block of that transaction.
 * We can fill that space with additional revokes for blocks that have already
 * been written back.  This will basically come at no cost now, and will save
 * us from having to keep track of those blocks on the AIL2 list later.
 */
void gfs2_flush_revokes(struct gfs2_sbd *sdp)
{
	/* number of revokes we still have room for */
	unsigned int max_revokes = atomic_read(&sdp->sd_log_revokes_available);

	gfs2_log_lock(sdp);
	gfs2_ail1_empty(sdp, max_revokes);
	gfs2_log_unlock(sdp);
}

/**
 * gfs2_write_log_header - Write a journal log header buffer at lblock
 * @sdp: The GFS2 superblock
 * @jd: journal descriptor of the journal to which we are writing
 * @seq: sequence number
 * @tail: tail of the log
 * @lblock: value for lh_blkno (block number relative to start of journal)
 * @flags: log header flags GFS2_LOG_HEAD_*
 * @op_flags: flags to pass to the bio
 *
 * Returns: the initialized log buffer descriptor
 */

void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
			   u64 seq, u32 tail, u32 lblock, u32 flags,
			   int op_flags)
{
	struct gfs2_log_header *lh;
	u32 hash, crc;
	struct page *page;
	struct gfs2_statfs_change_host *l_sc = &sdp->sd_statfs_local;
	struct timespec64 tv;
	struct super_block *sb = sdp->sd_vfs;
	u64 dblock;

	if (gfs2_withdrawn(sdp))
		return;

	page = mempool_alloc(gfs2_page_pool, GFP_NOIO);
	lh = page_address(page);
	clear_page(lh);

	lh->lh_header.mh_magic = cpu_to_be32(GFS2_MAGIC);
	lh->lh_header.mh_type = cpu_to_be32(GFS2_METATYPE_LH);
	lh->lh_header.__pad0 = cpu_to_be64(0);
	lh->lh_header.mh_format = cpu_to_be32(GFS2_FORMAT_LH);
	lh->lh_header.mh_jid = cpu_to_be32(sdp->sd_jdesc->jd_jid);
	lh->lh_sequence = cpu_to_be64(seq);
	lh->lh_flags = cpu_to_be32(flags);
	lh->lh_tail = cpu_to_be32(tail);
	lh->lh_blkno = cpu_to_be32(lblock);
	hash = ~crc32(~0, lh, LH_V1_SIZE);
	lh->lh_hash = cpu_to_be32(hash);

	ktime_get_coarse_real_ts64(&tv);
	lh->lh_nsec = cpu_to_be32(tv.tv_nsec);
	lh->lh_sec = cpu_to_be64(tv.tv_sec);
	if (!list_empty(&jd->extent_list))
		dblock = gfs2_log_bmap(jd, lblock);
	else {
		unsigned int extlen;
		int ret;

		extlen = 1;
		ret = gfs2_get_extent(jd->jd_inode, lblock, &dblock, &extlen);
		if (gfs2_assert_withdraw(sdp, ret == 0))
			return;
	}
	lh->lh_addr = cpu_to_be64(dblock);
	lh->lh_jinode = cpu_to_be64(GFS2_I(jd->jd_inode)->i_no_addr);

	/* We may only write local statfs, quota, etc., when writing to our
	   own journal. The values are left 0 when recovering a journal
	   different from our own. */
	if (!(flags & GFS2_LOG_HEAD_RECOVERY)) {
		lh->lh_statfs_addr =
			cpu_to_be64(GFS2_I(sdp->sd_sc_inode)->i_no_addr);
		lh->lh_quota_addr =
			cpu_to_be64(GFS2_I(sdp->sd_qc_inode)->i_no_addr);

		spin_lock(&sdp->sd_statfs_spin);
		lh->lh_local_total = cpu_to_be64(l_sc->sc_total);
		lh->lh_local_free = cpu_to_be64(l_sc->sc_free);
		lh->lh_local_dinodes = cpu_to_be64(l_sc->sc_dinodes);
		spin_unlock(&sdp->sd_statfs_spin);
	}

	BUILD_BUG_ON(offsetof(struct gfs2_log_header, lh_crc) != LH_V1_SIZE);

	crc = crc32c(~0, (void *)lh + LH_V1_SIZE + 4,
		     sb->s_blocksize - LH_V1_SIZE - 4);
	lh->lh_crc = cpu_to_be32(crc);

	gfs2_log_write(sdp, jd, page, sb->s_blocksize, 0, dblock);
	gfs2_log_submit_bio(&jd->jd_log_bio, REQ_OP_WRITE | op_flags);
}

/**
 * log_write_header - Get and initialize a journal header buffer
 * @sdp: The GFS2 superblock
 * @flags: The log header flags, including log header origin
 *
 * Returns: the initialized log buffer descriptor
 */

static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
{
	int op_flags = REQ_PREFLUSH | REQ_FUA | REQ_META | REQ_SYNC;
	enum gfs2_freeze_state state = atomic_read(&sdp->sd_freeze_state);

	gfs2_assert_withdraw(sdp, (state != SFS_FROZEN));

	if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags)) {
		gfs2_ordered_wait(sdp);
		log_flush_wait(sdp);
		op_flags = REQ_SYNC | REQ_META | REQ_PRIO;
	}
	sdp->sd_log_idle = (sdp->sd_log_flush_tail == sdp->sd_log_flush_head);
	gfs2_write_log_header(sdp, sdp->sd_jdesc, sdp->sd_log_sequence++,
			      sdp->sd_log_flush_tail, sdp->sd_log_flush_head,
			      flags, op_flags);
	gfs2_log_incr_head(sdp);
	log_flush_wait(sdp);
	log_pull_tail(sdp);
	gfs2_log_update_head(sdp);
}

/**
 * gfs2_ail_drain - drain the ail lists after a withdraw
 * @sdp: Pointer to GFS2 superblock
 */
void gfs2_ail_drain(struct gfs2_sbd *sdp)
{
	struct gfs2_trans *tr;

	spin_lock(&sdp->sd_ail_lock);
	/*
	 * For transactions on the sd_ail1_list we need to drain both the
	 * ail1 and ail2 lists. That's because function gfs2_ail1_start_one
	 * (temporarily) moves items from its tr_ail1 list to tr_ail2 list
	 * before revokes are sent for that block. Items on the sd_ail2_list
	 * should have already gotten beyond that point, so no need.
	 */
	while (!list_empty(&sdp->sd_ail1_list)) {
		tr = list_first_entry(&sdp->sd_ail1_list, struct gfs2_trans,
				      tr_list);
		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail1_list);
		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
		list_del(&tr->tr_list);
		gfs2_trans_free(sdp, tr);
	}
	while (!list_empty(&sdp->sd_ail2_list)) {
		tr = list_first_entry(&sdp->sd_ail2_list, struct gfs2_trans,
				      tr_list);
		gfs2_ail_empty_tr(sdp, tr, &tr->tr_ail2_list);
		list_del(&tr->tr_list);
		gfs2_trans_free(sdp, tr);
	}
	gfs2_drain_revokes(sdp);
	spin_unlock(&sdp->sd_ail_lock);
}

/**
 * empty_ail1_list - try to start IO and empty the ail1 list
 * @sdp: Pointer to GFS2 superblock
 */
static void empty_ail1_list(struct gfs2_sbd *sdp)
{
	unsigned long start = jiffies;

	for (;;) {
		if (time_after(jiffies, start + (HZ * 600))) {
			fs_err(sdp, "Error: In %s for 10 minutes! t=%d\n",
			       __func__, current->journal_info ? 1 : 0);
			dump_ail_list(sdp);
			return;
		}
		gfs2_ail1_start(sdp);
		gfs2_ail1_wait(sdp);
		if (gfs2_ail1_empty(sdp, 0))
			return;
	}
}

/**
 * trans_drain - drain the buf and databuf queue for a failed transaction
 * @tr: the transaction to drain
 *
 * When this is called, we're taking an error exit for a log write that failed
 * but since we bypassed the after_commit functions, we need to remove the
 * items from the buf and databuf queue.
 */
static void trans_drain(struct gfs2_trans *tr)
{
	struct gfs2_bufdata *bd;
	struct list_head *head;

	if (!tr)
		return;

	head = &tr->tr_buf;
	while (!list_empty(head)) {
		bd = list_first_entry(head, struct gfs2_bufdata, bd_list);
		list_del_init(&bd->bd_list);
		if (!list_empty(&bd->bd_ail_st_list))
			gfs2_remove_from_ail(bd);
		kmem_cache_free(gfs2_bufdata_cachep, bd);
	}
	head = &tr->tr_databuf;
	while (!list_empty(head)) {
		bd = list_first_entry(head, struct gfs2_bufdata, bd_list);
		list_del_init(&bd->bd_list);
		if (!list_empty(&bd->bd_ail_st_list))
			gfs2_remove_from_ail(bd);
		kmem_cache_free(gfs2_bufdata_cachep, bd);
	}
}

/**
 * gfs2_log_flush - flush incore transaction(s)
 * @sdp: The filesystem
 * @gl: The glock structure to flush.  If NULL, flush the whole incore log
 * @flags: The log header flags: GFS2_LOG_HEAD_FLUSH_* and debug flags
 *
 */

void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl, u32 flags)
{
	struct gfs2_trans *tr = NULL;
	unsigned int reserved_blocks = 0, used_blocks = 0;
	enum gfs2_freeze_state state = atomic_read(&sdp->sd_freeze_state);
	unsigned int first_log_head;
	unsigned int reserved_revokes = 0;

	down_write(&sdp->sd_log_flush_lock);
	trace_gfs2_log_flush(sdp, 1, flags);

repeat:
	/*
	 * Do this check while holding the log_flush_lock to prevent new
	 * buffers from being added to the ail via gfs2_pin()
	 */
	if (gfs2_withdrawn(sdp) || !test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))
		goto out;

	/* Log might have been flushed while we waited for the flush lock */
	if (gl && !test_bit(GLF_LFLUSH, &gl->gl_flags))
		goto out;

	first_log_head = sdp->sd_log_head;
	sdp->sd_log_flush_head = first_log_head;

	tr = sdp->sd_log_tr;
	if (tr || sdp->sd_log_num_revoke) {
		if (reserved_blocks)
			gfs2_log_release(sdp, reserved_blocks);
		reserved_blocks = sdp->sd_log_blks_reserved;
		reserved_revokes = sdp->sd_log_num_revoke;
		if (tr) {
			sdp->sd_log_tr = NULL;
			tr->tr_first = first_log_head;
			if (unlikely (state == SFS_FROZEN)) {
				if (gfs2_assert_withdraw_delayed(sdp,
				       !tr->tr_num_buf_new && !tr->tr_num_databuf_new))
					goto out_withdraw;
			}
		}
	} else if (!reserved_blocks) {
		unsigned int taboo_blocks = GFS2_LOG_FLUSH_MIN_BLOCKS;

		reserved_blocks = GFS2_LOG_FLUSH_MIN_BLOCKS;
		if (current == sdp->sd_logd_process)
			taboo_blocks = 0;

		if (!__gfs2_log_try_reserve(sdp, reserved_blocks, taboo_blocks)) {
			up_write(&sdp->sd_log_flush_lock);
			__gfs2_log_reserve(sdp, reserved_blocks, taboo_blocks);
			down_write(&sdp->sd_log_flush_lock);
			goto repeat;
		}
		BUG_ON(sdp->sd_log_num_revoke);
	}

	if (flags & GFS2_LOG_HEAD_FLUSH_SHUTDOWN)
		clear_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);

	if (unlikely(state == SFS_FROZEN))
		if (gfs2_assert_withdraw_delayed(sdp, !reserved_revokes))
			goto out_withdraw;

	gfs2_ordered_write(sdp);
	if (gfs2_withdrawn(sdp))
		goto out_withdraw;
	lops_before_commit(sdp, tr);
	if (gfs2_withdrawn(sdp))
		goto out_withdraw;
	gfs2_log_submit_bio(&sdp->sd_jdesc->jd_log_bio, REQ_OP_WRITE);
	if (gfs2_withdrawn(sdp))
		goto out_withdraw;

	if (sdp->sd_log_head != sdp->sd_log_flush_head) {
		log_write_header(sdp, flags);
	} else if (sdp->sd_log_tail != sdp->sd_log_flush_tail && !sdp->sd_log_idle) {
		log_write_header(sdp, flags);
	}
	if (gfs2_withdrawn(sdp))
		goto out_withdraw;
	lops_after_commit(sdp, tr);

	gfs2_log_lock(sdp);
	sdp->sd_log_blks_reserved = 0;

	spin_lock(&sdp->sd_ail_lock);
	if (tr && !list_empty(&tr->tr_ail1_list)) {
		list_add(&tr->tr_list, &sdp->sd_ail1_list);
		tr = NULL;
	}
	spin_unlock(&sdp->sd_ail_lock);
	gfs2_log_unlock(sdp);

	if (!(flags & GFS2_LOG_HEAD_FLUSH_NORMAL)) {
		if (!sdp->sd_log_idle) {
			empty_ail1_list(sdp);
			if (gfs2_withdrawn(sdp))
				goto out_withdraw;
			log_write_header(sdp, flags);
		}
		if (flags & (GFS2_LOG_HEAD_FLUSH_SHUTDOWN |
			     GFS2_LOG_HEAD_FLUSH_FREEZE))
			gfs2_log_shutdown(sdp);
		if (flags & GFS2_LOG_HEAD_FLUSH_FREEZE)
			atomic_set(&sdp->sd_freeze_state, SFS_FROZEN);
	}

out_end:
	used_blocks = log_distance(sdp, sdp->sd_log_flush_head, first_log_head);
	reserved_revokes += atomic_read(&sdp->sd_log_revokes_available);
	atomic_set(&sdp->sd_log_revokes_available, sdp->sd_ldptrs);
	gfs2_assert_withdraw(sdp, reserved_revokes % sdp->sd_inptrs == sdp->sd_ldptrs);
	if (reserved_revokes > sdp->sd_ldptrs)
		reserved_blocks += (reserved_revokes - sdp->sd_ldptrs) / sdp->sd_inptrs;
out:
	if (used_blocks != reserved_blocks) {
		gfs2_assert_withdraw_delayed(sdp, used_blocks < reserved_blocks);
		gfs2_log_release(sdp, reserved_blocks - used_blocks);
	}
	up_write(&sdp->sd_log_flush_lock);
	gfs2_trans_free(sdp, tr);
	if (gfs2_withdrawing(sdp))
		gfs2_withdraw(sdp);
	trace_gfs2_log_flush(sdp, 0, flags);
	return;

out_withdraw:
	trans_drain(tr);
	/**
	 * If the tr_list is empty, we're withdrawing during a log
	 * flush that targets a transaction, but the transaction was
	 * never queued onto any of the ail lists. Here we add it to
	 * ail1 just so that ail_drain() will find and free it.
	 */
	spin_lock(&sdp->sd_ail_lock);
	if (tr && list_empty(&tr->tr_list))
		list_add(&tr->tr_list, &sdp->sd_ail1_list);
	spin_unlock(&sdp->sd_ail_lock);
	tr = NULL;
	goto out_end;
}

/**
 * gfs2_merge_trans - Merge a new transaction into a cached transaction
 * @sdp: the filesystem
 * @new: New transaction to be merged
 */

static void gfs2_merge_trans(struct gfs2_sbd *sdp, struct gfs2_trans *new)
{
	struct gfs2_trans *old = sdp->sd_log_tr;

	WARN_ON_ONCE(!test_bit(TR_ATTACHED, &old->tr_flags));

	old->tr_num_buf_new	+= new->tr_num_buf_new;
	old->tr_num_databuf_new	+= new->tr_num_databuf_new;
	old->tr_num_buf_rm	+= new->tr_num_buf_rm;
	old->tr_num_databuf_rm	+= new->tr_num_databuf_rm;
	old->tr_revokes		+= new->tr_revokes;
	old->tr_num_revoke	+= new->tr_num_revoke;

	list_splice_tail_init(&new->tr_databuf, &old->tr_databuf);
	list_splice_tail_init(&new->tr_buf, &old->tr_buf);

	spin_lock(&sdp->sd_ail_lock);
	list_splice_tail_init(&new->tr_ail1_list, &old->tr_ail1_list);
	list_splice_tail_init(&new->tr_ail2_list, &old->tr_ail2_list);
	spin_unlock(&sdp->sd_ail_lock);
}

static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
	unsigned int reserved;
	unsigned int unused;
	unsigned int maxres;

	gfs2_log_lock(sdp);

	if (sdp->sd_log_tr) {
		gfs2_merge_trans(sdp, tr);
	} else if (tr->tr_num_buf_new || tr->tr_num_databuf_new) {
		gfs2_assert_withdraw(sdp, !test_bit(TR_ONSTACK, &tr->tr_flags));
		sdp->sd_log_tr = tr;
		set_bit(TR_ATTACHED, &tr->tr_flags);
	}

	reserved = calc_reserved(sdp);
	maxres = sdp->sd_log_blks_reserved + tr->tr_reserved;
	gfs2_assert_withdraw(sdp, maxres >= reserved);
	unused = maxres - reserved;
	if (unused)
		gfs2_log_release(sdp, unused);
	sdp->sd_log_blks_reserved = reserved;

	gfs2_log_unlock(sdp);
}

/**
 * gfs2_log_commit - Commit a transaction to the log
 * @sdp: the filesystem
 * @tr: the transaction
 *
 * We wake up gfs2_logd if the number of pinned blocks exceed thresh1
 * or the total number of used blocks (pinned blocks plus AIL blocks)
 * is greater than thresh2.
 *
 * At mount time thresh1 is 2/5ths of journal size, thresh2 is 4/5ths of
 * journal size.
 *
 * Returns: errno
 */

void gfs2_log_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
	log_refund(sdp, tr);

	if (atomic_read(&sdp->sd_log_pinned) > atomic_read(&sdp->sd_log_thresh1) ||
	    ((sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free)) >
	    atomic_read(&sdp->sd_log_thresh2)))
		wake_up(&sdp->sd_logd_waitq);
}

/**
 * gfs2_log_shutdown - write a shutdown header into a journal
 * @sdp: the filesystem
 *
 */

static void gfs2_log_shutdown(struct gfs2_sbd *sdp)
{
	gfs2_assert_withdraw(sdp, !sdp->sd_log_blks_reserved);
	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
	gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail1_list));

	log_write_header(sdp, GFS2_LOG_HEAD_UNMOUNT | GFS2_LFC_SHUTDOWN);
	log_pull_tail(sdp);

	gfs2_assert_warn(sdp, sdp->sd_log_head == sdp->sd_log_tail);
	gfs2_assert_warn(sdp, list_empty(&sdp->sd_ail2_list));
}

static inline int gfs2_jrnl_flush_reqd(struct gfs2_sbd *sdp)
{
	return (atomic_read(&sdp->sd_log_pinned) +
		atomic_read(&sdp->sd_log_blks_needed) >=
		atomic_read(&sdp->sd_log_thresh1));
}

static inline int gfs2_ail_flush_reqd(struct gfs2_sbd *sdp)
{
	unsigned int used_blocks = sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free);

	if (test_and_clear_bit(SDF_FORCE_AIL_FLUSH, &sdp->sd_flags))
		return 1;

	return used_blocks + atomic_read(&sdp->sd_log_blks_needed) >=
		atomic_read(&sdp->sd_log_thresh2);
}

/**
 * gfs2_logd - Update log tail as Active Items get flushed to in-place blocks
 * @data: Pointer to GFS2 superblock
 *
 * Also, periodically check to make sure that we're using the most recent
 * journal index.
 */

int gfs2_logd(void *data)
{
	struct gfs2_sbd *sdp = data;
	unsigned long t = 1;
	DEFINE_WAIT(wait);

	while (!kthread_should_stop()) {

		if (gfs2_withdrawn(sdp)) {
			msleep_interruptible(HZ);
			continue;
		}
		/* Check for errors writing to the journal */
		if (sdp->sd_log_error) {
			gfs2_lm(sdp,
				"GFS2: fsid=%s: error %d: "
				"withdrawing the file system to "
				"prevent further damage.\n",
				sdp->sd_fsname, sdp->sd_log_error);
			gfs2_withdraw(sdp);
			continue;
		}

		if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {
			gfs2_ail1_empty(sdp, 0);
			gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
						  GFS2_LFC_LOGD_JFLUSH_REQD);
		}

		if (gfs2_ail_flush_reqd(sdp)) {
			gfs2_ail1_start(sdp);
			gfs2_ail1_wait(sdp);
			gfs2_ail1_empty(sdp, 0);
			gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_NORMAL |
						  GFS2_LFC_LOGD_AIL_FLUSH_REQD);
		}

		t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;

		try_to_freeze();

		do {
			prepare_to_wait(&sdp->sd_logd_waitq, &wait,
					TASK_INTERRUPTIBLE);
			if (!gfs2_ail_flush_reqd(sdp) &&
			    !gfs2_jrnl_flush_reqd(sdp) &&
			    !kthread_should_stop())
				t = schedule_timeout(t);
		} while(t && !gfs2_ail_flush_reqd(sdp) &&
			!gfs2_jrnl_flush_reqd(sdp) &&
			!kthread_should_stop());
		finish_wait(&sdp->sd_logd_waitq, &wait);
	}

	return 0;
}