aboutsummaryrefslogtreecommitdiffstats
path: root/fs/gfs2/log.c
blob: 4752eadc7f6efda56c1e60bcea78900a895467f7 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#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/delay.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/bio.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"

#define PULL 1

/**
 * gfs2_struct2blk - compute stuff
 * @sdp: the filesystem
 * @nstruct: the number of structures
 * @ssize: the size of the 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 ssize)
{
	unsigned int blks;
	unsigned int first, second;

	blks = 1;
	first = (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_log_descriptor)) / ssize;

	if (nstruct > first) {
		second = (sdp->sd_sb.sb_bsize -
			  sizeof(struct gfs2_meta_header)) / ssize;
		blks += DIV_ROUND_UP(nstruct - first, second);
	}

	return blks;
}

/**
 * gfs2_remove_from_ail - Remove an entry from the ail lists, updating counters
 * @mapping: The associated mapping (maybe NULL)
 * @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_ail = 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 part of the AIL
 * @sdp: the filesystem
 * @wbc: The writeback control structure
 * @ai: The ail structure
 *
 */

static int gfs2_ail1_start_one(struct gfs2_sbd *sdp,
			       struct writeback_control *wbc,
			       struct gfs2_ail *ai)
__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;

	list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list, bd_ail_st_list) {
		bh = bd->bd_bh;

		gfs2_assert(sdp, bd->bd_ail == ai);

		if (!buffer_busy(bh)) {
			if (!buffer_uptodate(bh))
				gfs2_io_error_bh(sdp, bh);
			list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
			continue;
		}

		if (!buffer_dirty(bh))
			continue;
		if (gl == bd->bd_gl)
			continue;
		gl = bd->bd_gl;
		list_move(&bd->bd_ail_st_list, &ai->ai_ail1_list);
		mapping = bh->b_page->mapping;
		if (!mapping)
			continue;
		spin_unlock(&sdp->sd_ail_lock);
		generic_writepages(mapping, wbc);
		spin_lock(&sdp->sd_ail_lock);
		if (wbc->nr_to_write <= 0)
			break;
		return 1;
	}

	return 0;
}


/**
 * 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_ail *ai;

	trace_gfs2_ail_flush(sdp, wbc, 1);
	spin_lock(&sdp->sd_ail_lock);
restart:
	list_for_each_entry_reverse(ai, head, ai_list) {
		if (wbc->nr_to_write <= 0)
			break;
		if (gfs2_ail1_start_one(sdp, wbc, ai))
			goto restart;
	}
	spin_unlock(&sdp->sd_ail_lock);
	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);
}

/**
 * gfs2_ail1_empty_one - Check whether or not a trans in the AIL has been synced
 * @sdp: the filesystem
 * @ai: the AIL entry
 *
 */

static void gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
{
	struct gfs2_bufdata *bd, *s;
	struct buffer_head *bh;

	list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list,
					 bd_ail_st_list) {
		bh = bd->bd_bh;
		gfs2_assert(sdp, bd->bd_ail == ai);
		if (buffer_busy(bh))
			continue;
		if (!buffer_uptodate(bh))
			gfs2_io_error_bh(sdp, bh);
		list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
	}

}

/**
 * gfs2_ail1_empty - Try to empty the ail1 lists
 * @sdp: The superblock
 *
 * Tries to empty the ail1 lists, starting with the oldest first
 */

static int gfs2_ail1_empty(struct gfs2_sbd *sdp)
{
	struct gfs2_ail *ai, *s;
	int ret;

	spin_lock(&sdp->sd_ail_lock);
	list_for_each_entry_safe_reverse(ai, s, &sdp->sd_ail1_list, ai_list) {
		gfs2_ail1_empty_one(sdp, ai);
		if (list_empty(&ai->ai_ail1_list))
			list_move(&ai->ai_list, &sdp->sd_ail2_list);
		else
			break;
	}
	ret = list_empty(&sdp->sd_ail1_list);
	spin_unlock(&sdp->sd_ail_lock);

	return ret;
}

static void gfs2_ail1_wait(struct gfs2_sbd *sdp)
{
	struct gfs2_ail *ai;
	struct gfs2_bufdata *bd;
	struct buffer_head *bh;

	spin_lock(&sdp->sd_ail_lock);
	list_for_each_entry_reverse(ai, &sdp->sd_ail1_list, ai_list) {
		list_for_each_entry(bd, &ai->ai_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);
}

/**
 * gfs2_ail2_empty_one - Check whether or not a trans in the AIL has been synced
 * @sdp: the filesystem
 * @ai: the AIL entry
 *
 */

static void gfs2_ail2_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
{
	struct list_head *head = &ai->ai_ail2_list;
	struct gfs2_bufdata *bd;

	while (!list_empty(head)) {
		bd = list_entry(head->prev, struct gfs2_bufdata,
				bd_ail_st_list);
		gfs2_assert(sdp, bd->bd_ail == ai);
		gfs2_remove_from_ail(bd);
	}
}

static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
{
	struct gfs2_ail *ai, *safe;
	unsigned int old_tail = sdp->sd_log_tail;
	int wrap = (new_tail < old_tail);
	int a, b, rm;

	spin_lock(&sdp->sd_ail_lock);

	list_for_each_entry_safe(ai, safe, &sdp->sd_ail2_list, ai_list) {
		a = (old_tail <= ai->ai_first);
		b = (ai->ai_first < new_tail);
		rm = (wrap) ? (a || b) : (a && b);
		if (!rm)
			continue;

		gfs2_ail2_empty_one(sdp, ai);
		list_del(&ai->ai_list);
		gfs2_assert_warn(sdp, list_empty(&ai->ai_ail1_list));
		gfs2_assert_warn(sdp, list_empty(&ai->ai_ail2_list));
		kfree(ai);
	}

	spin_unlock(&sdp->sd_ail_lock);
}

/**
 * gfs2_log_reserve - Make a log reservation
 * @sdp: The GFS2 superblock
 * @blks: The number of blocks to reserve
 *
 * Note that we never give out the last few blocks of the journal. Thats
 * due to the fact that there is a small number of header blocks
 * associated with each log flush. The exact number can't be known until
 * flush time, so we ensure that we have just enough free blocks at all
 * times to avoid running out during a log flush.
 *
 * 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.
 *
 * Returns: errno
 */

int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
{
	unsigned reserved_blks = 6 * (4096 / sdp->sd_vfs->s_blocksize);
	unsigned wanted = blks + reserved_blks;
	DEFINE_WAIT(wait);
	int did_wait = 0;
	unsigned int free_blocks;

	if (gfs2_assert_warn(sdp, blks) ||
	    gfs2_assert_warn(sdp, blks <= sdp->sd_jdesc->jd_blocks))
		return -EINVAL;
retry:
	free_blocks = atomic_read(&sdp->sd_log_blks_free);
	if (unlikely(free_blocks <= wanted)) {
		do {
			prepare_to_wait_exclusive(&sdp->sd_log_waitq, &wait,
					TASK_UNINTERRUPTIBLE);
			wake_up(&sdp->sd_logd_waitq);
			did_wait = 1;
			if (atomic_read(&sdp->sd_log_blks_free) <= wanted)
				io_schedule();
			free_blocks = atomic_read(&sdp->sd_log_blks_free);
		} while(free_blocks <= wanted);
		finish_wait(&sdp->sd_log_waitq, &wait);
	}
	if (atomic_cmpxchg(&sdp->sd_log_blks_free, free_blocks,
				free_blocks - blks) != free_blocks)
		goto retry;
	trace_gfs2_log_blocks(sdp, -blks);

	/*
	 * If we waited, then so might others, wake them up _after_ we get
	 * our share of the log.
	 */
	if (unlikely(did_wait))
		wake_up(&sdp->sd_log_waitq);

	down_read(&sdp->sd_log_flush_lock);

	return 0;
}

u64 gfs2_log_bmap(struct gfs2_sbd *sdp, unsigned int lbn)
{
	struct gfs2_journal_extent *je;

	list_for_each_entry(je, &sdp->sd_jdesc->extent_list, extent_list) {
		if (lbn >= je->lblock && lbn < je->lblock + je->blocks)
			return je->dblock + lbn - je->lblock;
	}

	return -1;
}

/**
 * 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 reserve when
 *                 refunding a transaction's unused buffers.
 * @sdp: The GFS2 superblock
 *
 * This is complex.  We need to reserve room for all our currently used
 * metadata buffers (e.g. normal file I/O rewriting file time stamps) and 
 * all our journaled data buffers 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, gfs2_log_refund and gfs2_log_flush
 * will count it as free space (sd_log_blks_free) and corruption will follow.
 *
 * We can have metadata bufs and jdata bufs in the same journal.  So each
 * type gets its own log header, for which we need to reserve a block.
 * In fact, each type has the potential for needing more than one header 
 * in cases where we have more buffers than will fit on a journal page.
 * Metadata journal entries take up half the space of journaled buffer entries.
 * Thus, metadata entries have buf_limit (502) and journaled buffers have
 * databuf_limit (251) before they cause a wrap around.
 *
 * 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 = 0;
	unsigned int mbuf_limit, metabufhdrs_needed;
	unsigned int dbuf_limit, databufhdrs_needed;
	unsigned int revokes = 0;

	mbuf_limit = buf_limit(sdp);
	metabufhdrs_needed = (sdp->sd_log_commited_buf +
			      (mbuf_limit - 1)) / mbuf_limit;
	dbuf_limit = databuf_limit(sdp);
	databufhdrs_needed = (sdp->sd_log_commited_databuf +
			      (dbuf_limit - 1)) / dbuf_limit;

	if (sdp->sd_log_commited_revoke > 0)
		revokes = gfs2_struct2blk(sdp, sdp->sd_log_commited_revoke,
					  sizeof(u64));

	reserved = sdp->sd_log_commited_buf + metabufhdrs_needed +
		sdp->sd_log_commited_databuf + databufhdrs_needed +
		revokes;
	/* One for the overall header */
	if (reserved)
		reserved++;
	return reserved;
}

static unsigned int current_tail(struct gfs2_sbd *sdp)
{
	struct gfs2_ail *ai;
	unsigned int tail;

	spin_lock(&sdp->sd_ail_lock);

	if (list_empty(&sdp->sd_ail1_list)) {
		tail = sdp->sd_log_head;
	} else {
		ai = list_entry(sdp->sd_ail1_list.prev, struct gfs2_ail, ai_list);
		tail = ai->ai_first;
	}

	spin_unlock(&sdp->sd_ail_lock);

	return tail;
}

void gfs2_log_incr_head(struct gfs2_sbd *sdp)
{
	BUG_ON((sdp->sd_log_flush_head == sdp->sd_log_tail) &&
	       (sdp->sd_log_flush_head != sdp->sd_log_head));

	if (++sdp->sd_log_flush_head == sdp->sd_jdesc->jd_blocks) {
		sdp->sd_log_flush_head = 0;
		sdp->sd_log_flush_wrapped = 1;
	}
}

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

	ail2_empty(sdp, new_tail);

	atomic_add(dist, &sdp->sd_log_blks_free);
	trace_gfs2_log_blocks(sdp, dist);
	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
			     sdp->sd_jdesc->jd_blocks);

	sdp->sd_log_tail = new_tail;
}


static 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 bd_cmp(void *priv, struct list_head *a, struct list_head *b)
{
	struct gfs2_bufdata *bda, *bdb;

	bda = list_entry(a, struct gfs2_bufdata, bd_le.le_list);
	bdb = list_entry(b, struct gfs2_bufdata, bd_le.le_list);

	if (bda->bd_bh->b_blocknr < bdb->bd_bh->b_blocknr)
		return -1;
	if (bda->bd_bh->b_blocknr > bdb->bd_bh->b_blocknr)
		return 1;
	return 0;
}

static void gfs2_ordered_write(struct gfs2_sbd *sdp)
{
	struct gfs2_bufdata *bd;
	struct buffer_head *bh;
	LIST_HEAD(written);

	gfs2_log_lock(sdp);
	list_sort(NULL, &sdp->sd_log_le_ordered, &bd_cmp);
	while (!list_empty(&sdp->sd_log_le_ordered)) {
		bd = list_entry(sdp->sd_log_le_ordered.next, struct gfs2_bufdata, bd_le.le_list);
		list_move(&bd->bd_le.le_list, &written);
		bh = bd->bd_bh;
		if (!buffer_dirty(bh))
			continue;
		get_bh(bh);
		gfs2_log_unlock(sdp);
		lock_buffer(bh);
		if (buffer_mapped(bh) && test_clear_buffer_dirty(bh)) {
			bh->b_end_io = end_buffer_write_sync;
			submit_bh(WRITE_SYNC, bh);
		} else {
			unlock_buffer(bh);
			brelse(bh);
		}
		gfs2_log_lock(sdp);
	}
	list_splice(&written, &sdp->sd_log_le_ordered);
	gfs2_log_unlock(sdp);
}

static void gfs2_ordered_wait(struct gfs2_sbd *sdp)
{
	struct gfs2_bufdata *bd;
	struct buffer_head *bh;

	gfs2_log_lock(sdp);
	while (!list_empty(&sdp->sd_log_le_ordered)) {
		bd = list_entry(sdp->sd_log_le_ordered.prev, struct gfs2_bufdata, bd_le.le_list);
		bh = bd->bd_bh;
		if (buffer_locked(bh)) {
			get_bh(bh);
			gfs2_log_unlock(sdp);
			wait_on_buffer(bh);
			brelse(bh);
			gfs2_log_lock(sdp);
			continue;
		}
		list_del_init(&bd->bd_le.le_list);
	}
	gfs2_log_unlock(sdp);
}

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

static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull)
{
	u64 blkno = gfs2_log_bmap(sdp, sdp->sd_log_flush_head);
	struct buffer_head *bh;
	struct gfs2_log_header *lh;
	unsigned int tail;
	u32 hash;

	bh = sb_getblk(sdp->sd_vfs, blkno);
	lock_buffer(bh);
	memset(bh->b_data, 0, bh->b_size);
	set_buffer_uptodate(bh);
	clear_buffer_dirty(bh);

	gfs2_ail1_empty(sdp);
	tail = current_tail(sdp);

	lh = (struct gfs2_log_header *)bh->b_data;
	memset(lh, 0, sizeof(struct gfs2_log_header));
	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(sdp->sd_log_sequence++);
	lh->lh_flags = cpu_to_be32(flags);
	lh->lh_tail = cpu_to_be32(tail);
	lh->lh_blkno = cpu_to_be32(sdp->sd_log_flush_head);
	hash = gfs2_disk_hash(bh->b_data, sizeof(struct gfs2_log_header));
	lh->lh_hash = cpu_to_be32(hash);

	bh->b_end_io = end_buffer_write_sync;
	get_bh(bh);
	if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags)) {
		gfs2_ordered_wait(sdp);
		log_flush_wait(sdp);
		submit_bh(WRITE_SYNC | REQ_META | REQ_PRIO, bh);
	} else {
		submit_bh(WRITE_FLUSH_FUA | REQ_META, bh);
	}
	wait_on_buffer(bh);

	if (!buffer_uptodate(bh))
		gfs2_io_error_bh(sdp, bh);
	brelse(bh);

	if (sdp->sd_log_tail != tail)
		log_pull_tail(sdp, tail);
	else
		gfs2_assert_withdraw(sdp, !pull);

	sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
	gfs2_log_incr_head(sdp);
}

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

void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl)
{
	struct gfs2_ail *ai;

	down_write(&sdp->sd_log_flush_lock);

	/* Log might have been flushed while we waited for the flush lock */
	if (gl && !test_bit(GLF_LFLUSH, &gl->gl_flags)) {
		up_write(&sdp->sd_log_flush_lock);
		return;
	}
	trace_gfs2_log_flush(sdp, 1);

	ai = kzalloc(sizeof(struct gfs2_ail), GFP_NOFS | __GFP_NOFAIL);
	INIT_LIST_HEAD(&ai->ai_ail1_list);
	INIT_LIST_HEAD(&ai->ai_ail2_list);

	if (sdp->sd_log_num_buf != sdp->sd_log_commited_buf) {
		printk(KERN_INFO "GFS2: log buf %u %u\n", sdp->sd_log_num_buf,
		       sdp->sd_log_commited_buf);
		gfs2_assert_withdraw(sdp, 0);
	}
	if (sdp->sd_log_num_databuf != sdp->sd_log_commited_databuf) {
		printk(KERN_INFO "GFS2: log databuf %u %u\n",
		       sdp->sd_log_num_databuf, sdp->sd_log_commited_databuf);
		gfs2_assert_withdraw(sdp, 0);
	}
	gfs2_assert_withdraw(sdp,
			sdp->sd_log_num_revoke == sdp->sd_log_commited_revoke);

	sdp->sd_log_flush_head = sdp->sd_log_head;
	sdp->sd_log_flush_wrapped = 0;
	ai->ai_first = sdp->sd_log_flush_head;

	gfs2_ordered_write(sdp);
	lops_before_commit(sdp);

	if (sdp->sd_log_head != sdp->sd_log_flush_head) {
		log_write_header(sdp, 0, 0);
	} else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle){
		gfs2_log_lock(sdp);
		atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
		trace_gfs2_log_blocks(sdp, -1);
		gfs2_log_unlock(sdp);
		log_write_header(sdp, 0, PULL);
	}
	lops_after_commit(sdp, ai);

	gfs2_log_lock(sdp);
	sdp->sd_log_head = sdp->sd_log_flush_head;
	sdp->sd_log_blks_reserved = 0;
	sdp->sd_log_commited_buf = 0;
	sdp->sd_log_commited_databuf = 0;
	sdp->sd_log_commited_revoke = 0;

	spin_lock(&sdp->sd_ail_lock);
	if (!list_empty(&ai->ai_ail1_list)) {
		list_add(&ai->ai_list, &sdp->sd_ail1_list);
		ai = NULL;
	}
	spin_unlock(&sdp->sd_ail_lock);
	gfs2_log_unlock(sdp);
	trace_gfs2_log_flush(sdp, 0);
	up_write(&sdp->sd_log_flush_lock);

	kfree(ai);
}

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

	gfs2_log_lock(sdp);

	sdp->sd_log_commited_buf += tr->tr_num_buf_new - tr->tr_num_buf_rm;
	sdp->sd_log_commited_databuf += tr->tr_num_databuf_new -
		tr->tr_num_databuf_rm;
	gfs2_assert_withdraw(sdp, (((int)sdp->sd_log_commited_buf) >= 0) ||
			     (((int)sdp->sd_log_commited_databuf) >= 0));
	sdp->sd_log_commited_revoke += tr->tr_num_revoke - tr->tr_num_revoke_rm;
	reserved = calc_reserved(sdp);
	gfs2_assert_withdraw(sdp, sdp->sd_log_blks_reserved + tr->tr_reserved >= reserved);
	unused = sdp->sd_log_blks_reserved - reserved + tr->tr_reserved;
	atomic_add(unused, &sdp->sd_log_blks_free);
	trace_gfs2_log_blocks(sdp, unused);
	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
			     sdp->sd_jdesc->jd_blocks);
	sdp->sd_log_blks_reserved = reserved;

	gfs2_log_unlock(sdp);
}

static void buf_lo_incore_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
	struct list_head *head = &tr->tr_list_buf;
	struct gfs2_bufdata *bd;

	gfs2_log_lock(sdp);
	while (!list_empty(head)) {
		bd = list_entry(head->next, struct gfs2_bufdata, bd_list_tr);
		list_del_init(&bd->bd_list_tr);
		tr->tr_num_buf--;
	}
	gfs2_log_unlock(sdp);
	gfs2_assert_warn(sdp, !tr->tr_num_buf);
}

/**
 * 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 1/3rd of journal size, thresh2 is 2/3rd of
 * journal size.
 *
 * Returns: errno
 */

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

	up_read(&sdp->sd_log_flush_lock);

	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
 *
 */

void gfs2_log_shutdown(struct gfs2_sbd *sdp)
{
	down_write(&sdp->sd_log_flush_lock);

	gfs2_assert_withdraw(sdp, !sdp->sd_log_blks_reserved);
	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_buf);
	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_rg);
	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_databuf);
	gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail1_list));

	sdp->sd_log_flush_head = sdp->sd_log_head;
	sdp->sd_log_flush_wrapped = 0;

	log_write_header(sdp, GFS2_LOG_HEAD_UNMOUNT,
			 (sdp->sd_log_tail == current_tail(sdp)) ? 0 : PULL);

	gfs2_assert_warn(sdp, atomic_read(&sdp->sd_log_blks_free) == sdp->sd_jdesc->jd_blocks);
	gfs2_assert_warn(sdp, sdp->sd_log_head == sdp->sd_log_tail);
	gfs2_assert_warn(sdp, list_empty(&sdp->sd_ail2_list));

	sdp->sd_log_head = sdp->sd_log_flush_head;
	sdp->sd_log_tail = sdp->sd_log_head;

	up_write(&sdp->sd_log_flush_lock);
}


/**
 * gfs2_meta_syncfs - sync all the buffers in a filesystem
 * @sdp: the filesystem
 *
 */

void gfs2_meta_syncfs(struct gfs2_sbd *sdp)
{
	gfs2_log_flush(sdp, NULL);
	for (;;) {
		gfs2_ail1_start(sdp);
		gfs2_ail1_wait(sdp);
		if (gfs2_ail1_empty(sdp))
			break;
	}
	gfs2_log_flush(sdp, NULL);
}

static inline int gfs2_jrnl_flush_reqd(struct gfs2_sbd *sdp)
{
	return (atomic_read(&sdp->sd_log_pinned) >= 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);
	return used_blocks >= atomic_read(&sdp->sd_log_thresh2);
}

/**
 * gfs2_logd - Update log tail as Active Items get flushed to in-place blocks
 * @sdp: 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);
	unsigned preflush;

	while (!kthread_should_stop()) {

		preflush = atomic_read(&sdp->sd_log_pinned);
		if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {
			gfs2_ail1_empty(sdp);
			gfs2_log_flush(sdp, NULL);
		}

		if (gfs2_ail_flush_reqd(sdp)) {
			gfs2_ail1_start(sdp);
			gfs2_ail1_wait(sdp);
			gfs2_ail1_empty(sdp);
			gfs2_log_flush(sdp, NULL);
		}

		if (!gfs2_ail_flush_reqd(sdp))
			wake_up(&sdp->sd_log_waitq);

		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;
}