summaryrefslogtreecommitdiff
path: root/fs/ocfs2/reservations.c
blob: 87fa35791f184700b01ef0f18a8bd0e1b7ed5917 (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
/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * reservations.c
 *
 * Allocation reservations implementation
 *
 * Some code borrowed from fs/ext3/balloc.c and is:
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 * The rest is copyright (C) 2010 Novell.  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 version 2 as published by the Free Software Foundation.
 *
 * 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.
 */

#include <linux/fs.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/bitops.h>
#include <linux/list.h>

#define MLOG_MASK_PREFIX ML_RESERVATIONS
#include <cluster/masklog.h>

#include "ocfs2.h"

#ifdef CONFIG_OCFS2_DEBUG_FS
#define OCFS2_CHECK_RESERVATIONS
#endif

DEFINE_SPINLOCK(resv_lock);

#define	OCFS2_MIN_RESV_WINDOW_BITS	8
#define	OCFS2_MAX_RESV_WINDOW_BITS	1024
#define	OCFS2_RESV_DIR_WINDOW_BITS	OCFS2_MIN_RESV_WINDOW_BITS

static unsigned int ocfs2_resv_window_bits(struct ocfs2_reservation_map *resmap,
					   struct ocfs2_alloc_reservation *resv)
{
	struct ocfs2_super *osb = resmap->m_osb;
	unsigned int bits;

	if (!(resv->r_flags & OCFS2_RESV_FLAG_DIR)) {
		/* 8, 16, 32, 64, 128, 256, 512, 1024 */
		bits = 4 << osb->osb_resv_level;
	} else {
		/* For now, treat directories the same as files. */
		bits = 4 << osb->osb_resv_level;
	}
	return bits;
}

static inline unsigned int ocfs2_resv_end(struct ocfs2_alloc_reservation *resv)
{
	if (resv->r_len)
		return resv->r_start + resv->r_len - 1;
	return resv->r_start;
}

static inline int ocfs2_resv_empty(struct ocfs2_alloc_reservation *resv)
{
	return !!(resv->r_len == 0);
}

static inline int ocfs2_resmap_disabled(struct ocfs2_reservation_map *resmap)
{
	if (resmap->m_osb->osb_resv_level == 0)
		return 1;
	return 0;
}

static void ocfs2_dump_resv(struct ocfs2_reservation_map *resmap)
{
	struct ocfs2_super *osb = resmap->m_osb;
	struct rb_node *node;
	struct ocfs2_alloc_reservation *resv;
	int i = 0;

	mlog(ML_NOTICE, "Dumping resmap for device %s. Bitmap length: %u\n",
	     osb->dev_str, resmap->m_bitmap_len);

	node = rb_first(&resmap->m_reservations);
	while (node) {
		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);

		mlog(ML_NOTICE, "start: %u\tend: %u\tlen: %u\tlast_start: %u"
		     "\tlast_len: %u\n", resv->r_start,
		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
		     resv->r_last_len);

		node = rb_next(node);
		i++;
	}

	mlog(ML_NOTICE, "%d reservations found. LRU follows\n", i);

	i = 0;
	list_for_each_entry(resv, &resmap->m_lru, r_lru) {
		mlog(ML_NOTICE, "LRU(%d) start: %u\tend: %u\tlen: %u\t"
		     "last_start: %u\tlast_len: %u\n", i, resv->r_start,
		     ocfs2_resv_end(resv), resv->r_len, resv->r_last_start,
		     resv->r_last_len);

		i++;
	}
}

#ifdef OCFS2_CHECK_RESERVATIONS
static int ocfs2_validate_resmap_bits(struct ocfs2_reservation_map *resmap,
				      int i,
				      struct ocfs2_alloc_reservation *resv)
{
	char *disk_bitmap = resmap->m_disk_bitmap;
	unsigned int start = resv->r_start;
	unsigned int end = ocfs2_resv_end(resv);

	while (start <= end) {
		if (ocfs2_test_bit(start, disk_bitmap)) {
			mlog(ML_ERROR,
			     "reservation %d covers an allocated area "
			     "starting at bit %u!\n", i, start);
			return 1;
		}

		start++;
	}
	return 0;
}

static void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
{
	unsigned int off = 0;
	int i = 0;
	struct rb_node *node;
	struct ocfs2_alloc_reservation *resv;

	node = rb_first(&resmap->m_reservations);
	while (node) {
		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);

		if (i > 0 && resv->r_start <= off) {
			mlog(ML_ERROR, "reservation %d has bad start off!\n",
			     i);
			goto bad;
		}

		if (resv->r_len == 0) {
			mlog(ML_ERROR, "reservation %d has no length!\n",
			     i);
			goto bad;
		}

		if (resv->r_start > ocfs2_resv_end(resv)) {
			mlog(ML_ERROR, "reservation %d has invalid range!\n",
			     i);
			goto bad;
		}

		if (ocfs2_resv_end(resv) >= resmap->m_bitmap_len) {
			mlog(ML_ERROR, "reservation %d extends past bitmap!\n",
			     i);
			goto bad;
		}

		if (ocfs2_validate_resmap_bits(resmap, i, resv))
			goto bad;

		off = ocfs2_resv_end(resv);
		node = rb_next(node);

		i++;
	}
	return;

bad:
	ocfs2_dump_resv(resmap);
	BUG();
}
#else
static inline void ocfs2_check_resmap(struct ocfs2_reservation_map *resmap)
{

}
#endif

void ocfs2_resv_init_once(struct ocfs2_alloc_reservation *resv)
{
	memset(resv, 0, sizeof(*resv));
	INIT_LIST_HEAD(&resv->r_lru);
}

void ocfs2_resv_set_type(struct ocfs2_alloc_reservation *resv,
			 unsigned int flags)
{
	BUG_ON(flags & ~OCFS2_RESV_TYPES);

	resv->r_flags |= flags;
}

int ocfs2_resmap_init(struct ocfs2_super *osb,
		      struct ocfs2_reservation_map *resmap)
{
	memset(resmap, 0, sizeof(*resmap));

	resmap->m_osb = osb;
	resmap->m_reservations = RB_ROOT;
	/* m_bitmap_len is initialized to zero by the above memset. */
	INIT_LIST_HEAD(&resmap->m_lru);

	return 0;
}

static void ocfs2_resv_mark_lru(struct ocfs2_reservation_map *resmap,
				struct ocfs2_alloc_reservation *resv)
{
	assert_spin_locked(&resv_lock);

	if (!list_empty(&resv->r_lru))
		list_del_init(&resv->r_lru);

	list_add_tail(&resv->r_lru, &resmap->m_lru);
}

static void __ocfs2_resv_trunc(struct ocfs2_alloc_reservation *resv)
{
	resv->r_len = 0;
	resv->r_start = 0;
}

static void ocfs2_resv_remove(struct ocfs2_reservation_map *resmap,
			      struct ocfs2_alloc_reservation *resv)
{
	if (resv->r_flags & OCFS2_RESV_FLAG_INUSE) {
		list_del_init(&resv->r_lru);
		rb_erase(&resv->r_node, &resmap->m_reservations);
		resv->r_flags &= ~OCFS2_RESV_FLAG_INUSE;
	}
}

static void __ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
				 struct ocfs2_alloc_reservation *resv)
{
	assert_spin_locked(&resv_lock);

	__ocfs2_resv_trunc(resv);
	/*
	 * last_len and last_start no longer make sense if
	 * we're changing the range of our allocations.
	 */
	resv->r_last_len = resv->r_last_start = 0;

	ocfs2_resv_remove(resmap, resv);
}

/* does nothing if 'resv' is null */
void ocfs2_resv_discard(struct ocfs2_reservation_map *resmap,
			struct ocfs2_alloc_reservation *resv)
{
	if (resv) {
		spin_lock(&resv_lock);
		__ocfs2_resv_discard(resmap, resv);
		spin_unlock(&resv_lock);
	}
}

static void ocfs2_resmap_clear_all_resv(struct ocfs2_reservation_map *resmap)
{
	struct rb_node *node;
	struct ocfs2_alloc_reservation *resv;

	assert_spin_locked(&resv_lock);

	while ((node = rb_last(&resmap->m_reservations)) != NULL) {
		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);

		__ocfs2_resv_discard(resmap, resv);
	}
}

void ocfs2_resmap_restart(struct ocfs2_reservation_map *resmap,
			  unsigned int clen, char *disk_bitmap)
{
	if (ocfs2_resmap_disabled(resmap))
		return;

	spin_lock(&resv_lock);

	ocfs2_resmap_clear_all_resv(resmap);
	resmap->m_bitmap_len = clen;
	resmap->m_disk_bitmap = disk_bitmap;

	spin_unlock(&resv_lock);
}

void ocfs2_resmap_uninit(struct ocfs2_reservation_map *resmap)
{
	/* Does nothing for now. Keep this around for API symmetry */
}

static void ocfs2_resv_insert(struct ocfs2_reservation_map *resmap,
			      struct ocfs2_alloc_reservation *new)
{
	struct rb_root *root = &resmap->m_reservations;
	struct rb_node *parent = NULL;
	struct rb_node **p = &root->rb_node;
	struct ocfs2_alloc_reservation *tmp;

	assert_spin_locked(&resv_lock);

	mlog(0, "Insert reservation start: %u len: %u\n", new->r_start,
	     new->r_len);

	while (*p) {
		parent = *p;

		tmp = rb_entry(parent, struct ocfs2_alloc_reservation, r_node);

		if (new->r_start < tmp->r_start) {
			p = &(*p)->rb_left;

			/*
			 * This is a good place to check for
			 * overlapping reservations.
			 */
			BUG_ON(ocfs2_resv_end(new) >= tmp->r_start);
		} else if (new->r_start > ocfs2_resv_end(tmp)) {
			p = &(*p)->rb_right;
		} else {
			/* This should never happen! */
			mlog(ML_ERROR, "Duplicate reservation window!\n");
			BUG();
		}
	}

	rb_link_node(&new->r_node, parent, p);
	rb_insert_color(&new->r_node, root);
	new->r_flags |= OCFS2_RESV_FLAG_INUSE;

	ocfs2_resv_mark_lru(resmap, new);

	ocfs2_check_resmap(resmap);
}

/**
 * ocfs2_find_resv_lhs() - find the window which contains goal
 * @resmap: reservation map to search
 * @goal: which bit to search for
 *
 * If a window containing that goal is not found, we return the window
 * which comes before goal. Returns NULL on empty rbtree or no window
 * before goal.
 */
static struct ocfs2_alloc_reservation *
ocfs2_find_resv_lhs(struct ocfs2_reservation_map *resmap, unsigned int goal)
{
	struct ocfs2_alloc_reservation *resv = NULL;
	struct ocfs2_alloc_reservation *prev_resv = NULL;
	struct rb_node *node = resmap->m_reservations.rb_node;
	struct rb_node *prev = NULL;

	assert_spin_locked(&resv_lock);

	if (!node)
		return NULL;

	node = rb_first(&resmap->m_reservations);
	while (node) {
		resv = rb_entry(node, struct ocfs2_alloc_reservation, r_node);

		if (resv->r_start <= goal && ocfs2_resv_end(resv) >= goal)
			break;

		/* Check if we overshot the reservation just before goal? */
		if (resv->r_start > goal) {
			resv = prev_resv;
			break;
		}

		prev_resv = resv;
		prev = node;
		node = rb_next(node);
	}

	return resv;
}

/*
 * We are given a range within the bitmap, which corresponds to a gap
 * inside the reservations tree (search_start, search_len). The range
 * can be anything from the whole bitmap, to a gap between
 * reservations.
 *
 * The start value of *rstart is insignificant.
 *
 * This function searches the bitmap range starting at search_start
 * with length csearch_len for a set of contiguous free bits. We try
 * to find up to 'wanted' bits, but can sometimes return less.
 *
 * Returns the length of allocation, 0 if no free bits are found.
 *
 * *cstart and *clen will also be populated with the result.
 */
static int ocfs2_resmap_find_free_bits(struct ocfs2_reservation_map *resmap,
				       unsigned int wanted,
				       unsigned int search_start,
				       unsigned int search_len,
				       unsigned int *rstart,
				       unsigned int *rlen)
{
	void *bitmap = resmap->m_disk_bitmap;
	unsigned int best_start, best_len = 0;
	int offset, start, found;

	mlog(0, "Find %u bits within range (%u, len %u) resmap len: %u\n",
	     wanted, search_start, search_len, resmap->m_bitmap_len);

	found = best_start = best_len = 0;

	start = search_start;
	while ((offset = ocfs2_find_next_zero_bit(bitmap, resmap->m_bitmap_len,
						 start)) != -1) {
		/* Search reached end of the region */
		if (offset >= (search_start + search_len))
			break;

		if (offset == start) {
			/* we found a zero */
			found++;
			/* move start to the next bit to test */
			start++;
		} else {
			/* got a zero after some ones */
			found = 1;
			start = offset + 1;
		}
		if (found > best_len) {
			best_len = found;
			best_start = start - found;
		}

		if (found >= wanted)
			break;
	}

	if (best_len == 0)
		return 0;

	if (best_len >= wanted)
		best_len = wanted;

	*rlen = best_len;
	*rstart = best_start;

	mlog(0, "Found start: %u len: %u\n", best_start, best_len);

	return *rlen;
}

static void __ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
				     struct ocfs2_alloc_reservation *resv,
				     unsigned int goal, unsigned int wanted)
{
	struct rb_root *root = &resmap->m_reservations;
	unsigned int gap_start, gap_end, gap_len;
	struct ocfs2_alloc_reservation *prev_resv, *next_resv;
	struct rb_node *prev, *next;
	unsigned int cstart, clen;
	unsigned int best_start = 0, best_len = 0;

	/*
	 * Nasty cases to consider:
	 *
	 * - rbtree is empty
	 * - our window should be first in all reservations
	 * - our window should be last in all reservations
	 * - need to make sure we don't go past end of bitmap
	 */

	mlog(0, "resv start: %u resv end: %u goal: %u wanted: %u\n",
	     resv->r_start, ocfs2_resv_end(resv), goal, wanted);

	assert_spin_locked(&resv_lock);

	if (RB_EMPTY_ROOT(root)) {
		/*
		 * Easiest case - empty tree. We can just take
		 * whatever window of free bits we want.
		 */

		mlog(0, "Empty root\n");

		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
						   resmap->m_bitmap_len - goal,
						   &cstart, &clen);

		/*
		 * This should never happen - the local alloc window
		 * will always have free bits when we're called.
		 */
		BUG_ON(goal == 0 && clen == 0);

		if (clen == 0)
			return;

		resv->r_start = cstart;
		resv->r_len = clen;

		ocfs2_resv_insert(resmap, resv);
		return;
	}

	prev_resv = ocfs2_find_resv_lhs(resmap, goal);

	if (prev_resv == NULL) {
		mlog(0, "Goal on LHS of leftmost window\n");

		/*
		 * A NULL here means that the search code couldn't
		 * find a window that starts before goal.
		 *
		 * However, we can take the first window after goal,
		 * which is also by definition, the leftmost window in
		 * the entire tree. If we can find free bits in the
		 * gap between goal and the LHS window, then the
		 * reservation can safely be placed there.
		 *
		 * Otherwise we fall back to a linear search, checking
		 * the gaps in between windows for a place to
		 * allocate.
		 */

		next = rb_first(root);
		next_resv = rb_entry(next, struct ocfs2_alloc_reservation,
				     r_node);

		/*
		 * The search should never return such a window. (see
		 * comment above
		 */
		if (next_resv->r_start <= goal) {
			mlog(ML_ERROR, "goal: %u next_resv: start %u len %u\n",
			     goal, next_resv->r_start, next_resv->r_len);
			ocfs2_dump_resv(resmap);
			BUG();
		}

		clen = ocfs2_resmap_find_free_bits(resmap, wanted, goal,
						   next_resv->r_start - goal,
						   &cstart, &clen);
		if (clen) {
			best_len = clen;
			best_start = cstart;
			if (best_len == wanted)
				goto out_insert;
		}

		prev_resv = next_resv;
		next_resv = NULL;
	}

	prev = &prev_resv->r_node;

	/* Now we do a linear search for a window, starting at 'prev_rsv' */
	while (1) {
		next = rb_next(prev);
		if (next) {
			mlog(0, "One more resv found in linear search\n");
			next_resv = rb_entry(next,
					     struct ocfs2_alloc_reservation,
					     r_node);

			gap_start = ocfs2_resv_end(prev_resv) + 1;
			gap_end = next_resv->r_start - 1;
			gap_len = gap_end - gap_start + 1;
		} else {
			mlog(0, "No next node\n");
			/*
			 * We're at the rightmost edge of the
			 * tree. See if a reservation between this
			 * window and the end of the bitmap will work.
			 */
			gap_start = ocfs2_resv_end(prev_resv) + 1;
			gap_len = resmap->m_bitmap_len - gap_start;
			gap_end = resmap->m_bitmap_len - 1;
		}

		/*
		 * No need to check this gap if we have already found
		 * a larger region of free bits.
		 */
		if (gap_len <= best_len)
			goto next_resv;

		clen = ocfs2_resmap_find_free_bits(resmap, wanted, gap_start,
						   gap_len, &cstart, &clen);
		if (clen == wanted) {
			best_len = clen;
			best_start = cstart;
			goto out_insert;
		} else if (clen > best_len) {
			best_len = clen;
			best_start = cstart;
		}

next_resv:
		if (!next)
			break;

		prev = next;
		prev_resv = rb_entry(prev, struct ocfs2_alloc_reservation,
				     r_node);
	}

out_insert:
	if (best_len) {
		resv->r_start = best_start;
		resv->r_len = best_len;
		ocfs2_resv_insert(resmap, resv);
	}
}

static void ocfs2_cannibalize_resv(struct ocfs2_reservation_map *resmap,
				   struct ocfs2_alloc_reservation *resv,
				   unsigned int wanted)
{
	struct ocfs2_alloc_reservation *lru_resv;
	int tmpwindow = !!(resv->r_flags & OCFS2_RESV_FLAG_TMP);
	unsigned int min_bits;

	if (!tmpwindow)
		min_bits = ocfs2_resv_window_bits(resmap, resv) >> 1;
	else
		min_bits = wanted; /* We at know the temp window will use all
				    * of these bits */

	/*
	 * Take the first reservation off the LRU as our 'target'. We
	 * don't try to be smart about it. There might be a case for
	 * searching based on size but I don't have enough data to be
	 * sure. --Mark (3/16/2010)
	 */
	lru_resv = list_first_entry(&resmap->m_lru,
				    struct ocfs2_alloc_reservation, r_lru);

	mlog(0, "lru resv: start: %u len: %u end: %u\n", lru_resv->r_start,
	     lru_resv->r_len, ocfs2_resv_end(lru_resv));

	/*
	 * Cannibalize (some or all) of the target reservation and
	 * feed it to the current window.
	 */
	if (lru_resv->r_len <= min_bits) {
		/*
		 * Discard completely if size is less than or equal to a
		 * reasonable threshold - 50% of window bits for non temporary
		 * windows.
		 */
		resv->r_start = lru_resv->r_start;
		resv->r_len = lru_resv->r_len;

		__ocfs2_resv_discard(resmap, lru_resv);
	} else {
		unsigned int shrink;
		if (tmpwindow)
			shrink = min_bits;
		else
			shrink = lru_resv->r_len / 2;

		lru_resv->r_len -= shrink;

		resv->r_start = ocfs2_resv_end(lru_resv) + 1;
		resv->r_len = shrink;
	}

	mlog(0, "Reservation now looks like: r_start: %u r_end: %u "
	     "r_len: %u r_last_start: %u r_last_len: %u\n",
	     resv->r_start, ocfs2_resv_end(resv), resv->r_len,
	     resv->r_last_start, resv->r_last_len);

	ocfs2_resv_insert(resmap, resv);
}

static void ocfs2_resv_find_window(struct ocfs2_reservation_map *resmap,
				   struct ocfs2_alloc_reservation *resv,
				   unsigned int wanted)
{
	unsigned int goal = 0;

	BUG_ON(!ocfs2_resv_empty(resv));

	/*
	 * Begin by trying to get a window as close to the previous
	 * one as possible. Using the most recent allocation as a
	 * start goal makes sense.
	 */
	if (resv->r_last_len) {
		goal = resv->r_last_start + resv->r_last_len;
		if (goal >= resmap->m_bitmap_len)
			goal = 0;
	}

	__ocfs2_resv_find_window(resmap, resv, goal, wanted);

	/* Search from last alloc didn't work, try once more from beginning. */
	if (ocfs2_resv_empty(resv) && goal != 0)
		__ocfs2_resv_find_window(resmap, resv, 0, wanted);

	if (ocfs2_resv_empty(resv)) {
		/*
		 * Still empty? Pull oldest one off the LRU, remove it from
		 * tree, put this one in it's place.
		 */
		ocfs2_cannibalize_resv(resmap, resv, wanted);
	}

	BUG_ON(ocfs2_resv_empty(resv));
}

int ocfs2_resmap_resv_bits(struct ocfs2_reservation_map *resmap,
			   struct ocfs2_alloc_reservation *resv,
			   int *cstart, int *clen)
{
	unsigned int wanted = *clen;

	if (resv == NULL || ocfs2_resmap_disabled(resmap))
		return -ENOSPC;

	spin_lock(&resv_lock);

	/*
	 * We don't want to over-allocate for temporary
	 * windows. Otherwise, we run the risk of fragmenting the
	 * allocation space.
	 */
	wanted = ocfs2_resv_window_bits(resmap, resv);
	if ((resv->r_flags & OCFS2_RESV_FLAG_TMP) || wanted < *clen)
		wanted = *clen;

	if (ocfs2_resv_empty(resv)) {
		mlog(0, "empty reservation, find new window\n");

		/*
		 * Try to get a window here. If it works, we must fall
		 * through and test the bitmap . This avoids some
		 * ping-ponging of windows due to non-reserved space
		 * being allocation before we initialize a window for
		 * that inode.
		 */
		ocfs2_resv_find_window(resmap, resv, wanted);
	}

	BUG_ON(ocfs2_resv_empty(resv));

	*cstart = resv->r_start;
	*clen = resv->r_len;

	spin_unlock(&resv_lock);
	return 0;
}

static void
	ocfs2_adjust_resv_from_alloc(struct ocfs2_reservation_map *resmap,
				     struct ocfs2_alloc_reservation *resv,
				     unsigned int start, unsigned int end)
{
	unsigned int lhs = 0, rhs = 0;

	BUG_ON(start < resv->r_start);

	/*
	 * Completely used? We can remove it then.
	 */
	if (ocfs2_resv_end(resv) <= end && resv->r_start >= start) {
		__ocfs2_resv_discard(resmap, resv);
		return;
	}

	if (end < ocfs2_resv_end(resv))
		rhs = end - ocfs2_resv_end(resv);

	if (start > resv->r_start)
		lhs = start - resv->r_start;

	/*
	 * This should have been trapped above. At the very least, rhs
	 * should be non zero.
	 */
	BUG_ON(rhs == 0 && lhs == 0);

	if (rhs >= lhs) {
		unsigned int old_end = ocfs2_resv_end(resv);

		resv->r_start = end + 1;
		resv->r_len = old_end - resv->r_start + 1;
	} else {
		resv->r_len = start - resv->r_start;
	}
}

void ocfs2_resmap_claimed_bits(struct ocfs2_reservation_map *resmap,
			       struct ocfs2_alloc_reservation *resv,
			       u32 cstart, u32 clen)
{
	unsigned int cend = cstart + clen - 1;

	if (resmap == NULL || ocfs2_resmap_disabled(resmap))
		return;

	if (resv == NULL)
		return;

	spin_lock(&resv_lock);

	mlog(0, "claim bits: cstart: %u cend: %u clen: %u r_start: %u "
	     "r_end: %u r_len: %u, r_last_start: %u r_last_len: %u\n",
	     cstart, cend, clen, resv->r_start, ocfs2_resv_end(resv),
	     resv->r_len, resv->r_last_start, resv->r_last_len);

	BUG_ON(cstart < resv->r_start);
	BUG_ON(cstart > ocfs2_resv_end(resv));
	BUG_ON(cend > ocfs2_resv_end(resv));

	ocfs2_adjust_resv_from_alloc(resmap, resv, cstart, cend);
	resv->r_last_start = cstart;
	resv->r_last_len = clen;

	/*
	 * May have been discarded above from
	 * ocfs2_adjust_resv_from_alloc().
	 */
	if (!ocfs2_resv_empty(resv))
		ocfs2_resv_mark_lru(resmap, resv);

	mlog(0, "Reservation now looks like: r_start: %u r_end: %u "
	     "r_len: %u r_last_start: %u r_last_len: %u\n",
	     resv->r_start, ocfs2_resv_end(resv), resv->r_len,
	     resv->r_last_start, resv->r_last_len);

	ocfs2_check_resmap(resmap);

	spin_unlock(&resv_lock);
}