summaryrefslogtreecommitdiff
path: root/fs/xfs/xfs_iwalk.c
blob: 7558486f49371c861e3d38a0d803ef2537fa4e06 (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
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2019 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_ialloc_btree.h"
#include "xfs_iwalk.h"
#include "xfs_error.h"
#include "xfs_trace.h"
#include "xfs_icache.h"
#include "xfs_health.h"
#include "xfs_trans.h"
#include "xfs_pwork.h"
#include "xfs_ag.h"

/*
 * Walking Inodes in the Filesystem
 * ================================
 *
 * This iterator function walks a subset of filesystem inodes in increasing
 * order from @startino until there are no more inodes.  For each allocated
 * inode it finds, it calls a walk function with the relevant inode number and
 * a pointer to caller-provided data.  The walk function can return the usual
 * negative error code to stop the iteration; 0 to continue the iteration; or
 * -ECANCELED to stop the iteration.  This return value is returned to the
 * caller.
 *
 * Internally, we allow the walk function to do anything, which means that we
 * cannot maintain the inobt cursor or our lock on the AGI buffer.  We
 * therefore cache the inobt records in kernel memory and only call the walk
 * function when our memory buffer is full.  @nr_recs is the number of records
 * that we've cached, and @sz_recs is the size of our cache.
 *
 * It is the responsibility of the walk function to ensure it accesses
 * allocated inodes, as the inobt records may be stale by the time they are
 * acted upon.
 */

struct xfs_iwalk_ag {
	/* parallel work control data; will be null if single threaded */
	struct xfs_pwork		pwork;

	struct xfs_mount		*mp;
	struct xfs_trans		*tp;
	struct xfs_perag		*pag;

	/* Where do we start the traversal? */
	xfs_ino_t			startino;

	/* What was the last inode number we saw when iterating the inobt? */
	xfs_ino_t			lastino;

	/* Array of inobt records we cache. */
	struct xfs_inobt_rec_incore	*recs;

	/* Number of entries allocated for the @recs array. */
	unsigned int			sz_recs;

	/* Number of entries in the @recs array that are in use. */
	unsigned int			nr_recs;

	/* Inode walk function and data pointer. */
	xfs_iwalk_fn			iwalk_fn;
	xfs_inobt_walk_fn		inobt_walk_fn;
	void				*data;

	/*
	 * Make it look like the inodes up to startino are free so that
	 * bulkstat can start its inode iteration at the correct place without
	 * needing to special case everywhere.
	 */
	unsigned int			trim_start:1;

	/* Skip empty inobt records? */
	unsigned int			skip_empty:1;

	/* Drop the (hopefully empty) transaction when calling iwalk_fn. */
	unsigned int			drop_trans:1;
};

/*
 * Loop over all clusters in a chunk for a given incore inode allocation btree
 * record.  Do a readahead if there are any allocated inodes in that cluster.
 */
STATIC void
xfs_iwalk_ichunk_ra(
	struct xfs_mount		*mp,
	struct xfs_perag		*pag,
	struct xfs_inobt_rec_incore	*irec)
{
	struct xfs_ino_geometry		*igeo = M_IGEO(mp);
	xfs_agblock_t			agbno;
	struct blk_plug			plug;
	int				i;	/* inode chunk index */

	agbno = XFS_AGINO_TO_AGBNO(mp, irec->ir_startino);

	blk_start_plug(&plug);
	for (i = 0; i < XFS_INODES_PER_CHUNK; i += igeo->inodes_per_cluster) {
		xfs_inofree_t	imask;

		imask = xfs_inobt_maskn(i, igeo->inodes_per_cluster);
		if (imask & ~irec->ir_free) {
			xfs_btree_reada_bufs(mp, pag->pag_agno, agbno,
					igeo->blocks_per_cluster,
					&xfs_inode_buf_ops);
		}
		agbno += igeo->blocks_per_cluster;
	}
	blk_finish_plug(&plug);
}

/*
 * Set the bits in @irec's free mask that correspond to the inodes before
 * @agino so that we skip them.  This is how we restart an inode walk that was
 * interrupted in the middle of an inode record.
 */
STATIC void
xfs_iwalk_adjust_start(
	xfs_agino_t			agino,	/* starting inode of chunk */
	struct xfs_inobt_rec_incore	*irec)	/* btree record */
{
	int				idx;	/* index into inode chunk */
	int				i;

	idx = agino - irec->ir_startino;

	/*
	 * We got a right chunk with some left inodes allocated at it.  Grab
	 * the chunk record.  Mark all the uninteresting inodes free because
	 * they're before our start point.
	 */
	for (i = 0; i < idx; i++) {
		if (XFS_INOBT_MASK(i) & ~irec->ir_free)
			irec->ir_freecount++;
	}

	irec->ir_free |= xfs_inobt_maskn(0, idx);
}

/* Allocate memory for a walk. */
STATIC int
xfs_iwalk_alloc(
	struct xfs_iwalk_ag	*iwag)
{
	size_t			size;

	ASSERT(iwag->recs == NULL);
	iwag->nr_recs = 0;

	/* Allocate a prefetch buffer for inobt records. */
	size = iwag->sz_recs * sizeof(struct xfs_inobt_rec_incore);
	iwag->recs = kmem_alloc(size, KM_MAYFAIL);
	if (iwag->recs == NULL)
		return -ENOMEM;

	return 0;
}

/* Free memory we allocated for a walk. */
STATIC void
xfs_iwalk_free(
	struct xfs_iwalk_ag	*iwag)
{
	kmem_free(iwag->recs);
	iwag->recs = NULL;
}

/* For each inuse inode in each cached inobt record, call our function. */
STATIC int
xfs_iwalk_ag_recs(
	struct xfs_iwalk_ag	*iwag)
{
	struct xfs_mount	*mp = iwag->mp;
	struct xfs_trans	*tp = iwag->tp;
	struct xfs_perag	*pag = iwag->pag;
	xfs_ino_t		ino;
	unsigned int		i, j;
	int			error;

	for (i = 0; i < iwag->nr_recs; i++) {
		struct xfs_inobt_rec_incore	*irec = &iwag->recs[i];

		trace_xfs_iwalk_ag_rec(mp, pag->pag_agno, irec);

		if (xfs_pwork_want_abort(&iwag->pwork))
			return 0;

		if (iwag->inobt_walk_fn) {
			error = iwag->inobt_walk_fn(mp, tp, pag->pag_agno, irec,
					iwag->data);
			if (error)
				return error;
		}

		if (!iwag->iwalk_fn)
			continue;

		for (j = 0; j < XFS_INODES_PER_CHUNK; j++) {
			if (xfs_pwork_want_abort(&iwag->pwork))
				return 0;

			/* Skip if this inode is free */
			if (XFS_INOBT_MASK(j) & irec->ir_free)
				continue;

			/* Otherwise call our function. */
			ino = XFS_AGINO_TO_INO(mp, pag->pag_agno,
						irec->ir_startino + j);
			error = iwag->iwalk_fn(mp, tp, ino, iwag->data);
			if (error)
				return error;
		}
	}

	return 0;
}

/* Delete cursor and let go of AGI. */
static inline void
xfs_iwalk_del_inobt(
	struct xfs_trans	*tp,
	struct xfs_btree_cur	**curpp,
	struct xfs_buf		**agi_bpp,
	int			error)
{
	if (*curpp) {
		xfs_btree_del_cursor(*curpp, error);
		*curpp = NULL;
	}
	if (*agi_bpp) {
		xfs_trans_brelse(tp, *agi_bpp);
		*agi_bpp = NULL;
	}
}

/*
 * Set ourselves up for walking inobt records starting from a given point in
 * the filesystem.
 *
 * If caller passed in a nonzero start inode number, load the record from the
 * inobt and make the record look like all the inodes before agino are free so
 * that we skip them, and then move the cursor to the next inobt record.  This
 * is how we support starting an iwalk in the middle of an inode chunk.
 *
 * If the caller passed in a start number of zero, move the cursor to the first
 * inobt record.
 *
 * The caller is responsible for cleaning up the cursor and buffer pointer
 * regardless of the error status.
 */
STATIC int
xfs_iwalk_ag_start(
	struct xfs_iwalk_ag	*iwag,
	xfs_agino_t		agino,
	struct xfs_btree_cur	**curpp,
	struct xfs_buf		**agi_bpp,
	int			*has_more)
{
	struct xfs_mount	*mp = iwag->mp;
	struct xfs_trans	*tp = iwag->tp;
	struct xfs_perag	*pag = iwag->pag;
	struct xfs_inobt_rec_incore *irec;
	int			error;

	/* Set up a fresh cursor and empty the inobt cache. */
	iwag->nr_recs = 0;
	error = xfs_inobt_cur(mp, tp, pag, XFS_BTNUM_INO, curpp, agi_bpp);
	if (error)
		return error;

	/* Starting at the beginning of the AG?  That's easy! */
	if (agino == 0)
		return xfs_inobt_lookup(*curpp, 0, XFS_LOOKUP_GE, has_more);

	/*
	 * Otherwise, we have to grab the inobt record where we left off, stuff
	 * the record into our cache, and then see if there are more records.
	 * We require a lookup cache of at least two elements so that the
	 * caller doesn't have to deal with tearing down the cursor to walk the
	 * records.
	 */
	error = xfs_inobt_lookup(*curpp, agino, XFS_LOOKUP_LE, has_more);
	if (error)
		return error;

	/*
	 * If the LE lookup at @agino yields no records, jump ahead to the
	 * inobt cursor increment to see if there are more records to process.
	 */
	if (!*has_more)
		goto out_advance;

	/* Get the record, should always work */
	irec = &iwag->recs[iwag->nr_recs];
	error = xfs_inobt_get_rec(*curpp, irec, has_more);
	if (error)
		return error;
	if (XFS_IS_CORRUPT(mp, *has_more != 1))
		return -EFSCORRUPTED;

	iwag->lastino = XFS_AGINO_TO_INO(mp, pag->pag_agno,
				irec->ir_startino + XFS_INODES_PER_CHUNK - 1);

	/*
	 * If the LE lookup yielded an inobt record before the cursor position,
	 * skip it and see if there's another one after it.
	 */
	if (irec->ir_startino + XFS_INODES_PER_CHUNK <= agino)
		goto out_advance;

	/*
	 * If agino fell in the middle of the inode record, make it look like
	 * the inodes up to agino are free so that we don't return them again.
	 */
	if (iwag->trim_start)
		xfs_iwalk_adjust_start(agino, irec);

	/*
	 * The prefetch calculation is supposed to give us a large enough inobt
	 * record cache that grab_ichunk can stage a partial first record and
	 * the loop body can cache a record without having to check for cache
	 * space until after it reads an inobt record.
	 */
	iwag->nr_recs++;
	ASSERT(iwag->nr_recs < iwag->sz_recs);

out_advance:
	return xfs_btree_increment(*curpp, 0, has_more);
}

/*
 * The inobt record cache is full, so preserve the inobt cursor state and
 * run callbacks on the cached inobt records.  When we're done, restore the
 * cursor state to wherever the cursor would have been had the cache not been
 * full (and therefore we could've just incremented the cursor) if *@has_more
 * is true.  On exit, *@has_more will indicate whether or not the caller should
 * try for more inode records.
 */
STATIC int
xfs_iwalk_run_callbacks(
	struct xfs_iwalk_ag		*iwag,
	struct xfs_btree_cur		**curpp,
	struct xfs_buf			**agi_bpp,
	int				*has_more)
{
	struct xfs_mount		*mp = iwag->mp;
	struct xfs_inobt_rec_incore	*irec;
	xfs_agino_t			next_agino;
	int				error;

	next_agino = XFS_INO_TO_AGINO(mp, iwag->lastino) + 1;

	ASSERT(iwag->nr_recs > 0);

	/* Delete cursor but remember the last record we cached... */
	xfs_iwalk_del_inobt(iwag->tp, curpp, agi_bpp, 0);
	irec = &iwag->recs[iwag->nr_recs - 1];
	ASSERT(next_agino >= irec->ir_startino + XFS_INODES_PER_CHUNK);

	if (iwag->drop_trans) {
		xfs_trans_cancel(iwag->tp);
		iwag->tp = NULL;
	}

	error = xfs_iwalk_ag_recs(iwag);
	if (error)
		return error;

	/* ...empty the cache... */
	iwag->nr_recs = 0;

	if (!has_more)
		return 0;

	if (iwag->drop_trans) {
		error = xfs_trans_alloc_empty(mp, &iwag->tp);
		if (error)
			return error;
	}

	/* ...and recreate the cursor just past where we left off. */
	error = xfs_inobt_cur(mp, iwag->tp, iwag->pag, XFS_BTNUM_INO, curpp,
			agi_bpp);
	if (error)
		return error;

	return xfs_inobt_lookup(*curpp, next_agino, XFS_LOOKUP_GE, has_more);
}

/* Walk all inodes in a single AG, from @iwag->startino to the end of the AG. */
STATIC int
xfs_iwalk_ag(
	struct xfs_iwalk_ag		*iwag)
{
	struct xfs_mount		*mp = iwag->mp;
	struct xfs_perag		*pag = iwag->pag;
	struct xfs_buf			*agi_bp = NULL;
	struct xfs_btree_cur		*cur = NULL;
	xfs_agino_t			agino;
	int				has_more;
	int				error = 0;

	/* Set up our cursor at the right place in the inode btree. */
	ASSERT(pag->pag_agno == XFS_INO_TO_AGNO(mp, iwag->startino));
	agino = XFS_INO_TO_AGINO(mp, iwag->startino);
	error = xfs_iwalk_ag_start(iwag, agino, &cur, &agi_bp, &has_more);

	while (!error && has_more) {
		struct xfs_inobt_rec_incore	*irec;
		xfs_ino_t			rec_fsino;

		cond_resched();
		if (xfs_pwork_want_abort(&iwag->pwork))
			goto out;

		/* Fetch the inobt record. */
		irec = &iwag->recs[iwag->nr_recs];
		error = xfs_inobt_get_rec(cur, irec, &has_more);
		if (error || !has_more)
			break;

		/* Make sure that we always move forward. */
		rec_fsino = XFS_AGINO_TO_INO(mp, pag->pag_agno, irec->ir_startino);
		if (iwag->lastino != NULLFSINO &&
		    XFS_IS_CORRUPT(mp, iwag->lastino >= rec_fsino)) {
			error = -EFSCORRUPTED;
			goto out;
		}
		iwag->lastino = rec_fsino + XFS_INODES_PER_CHUNK - 1;

		/* No allocated inodes in this chunk; skip it. */
		if (iwag->skip_empty && irec->ir_freecount == irec->ir_count) {
			error = xfs_btree_increment(cur, 0, &has_more);
			if (error)
				break;
			continue;
		}

		/*
		 * Start readahead for this inode chunk in anticipation of
		 * walking the inodes.
		 */
		if (iwag->iwalk_fn)
			xfs_iwalk_ichunk_ra(mp, pag, irec);

		/*
		 * If there's space in the buffer for more records, increment
		 * the btree cursor and grab more.
		 */
		if (++iwag->nr_recs < iwag->sz_recs) {
			error = xfs_btree_increment(cur, 0, &has_more);
			if (error || !has_more)
				break;
			continue;
		}

		/*
		 * Otherwise, we need to save cursor state and run the callback
		 * function on the cached records.  The run_callbacks function
		 * is supposed to return a cursor pointing to the record where
		 * we would be if we had been able to increment like above.
		 */
		ASSERT(has_more);
		error = xfs_iwalk_run_callbacks(iwag, &cur, &agi_bp, &has_more);
	}

	if (iwag->nr_recs == 0 || error)
		goto out;

	/* Walk the unprocessed records in the cache. */
	error = xfs_iwalk_run_callbacks(iwag, &cur, &agi_bp, &has_more);

out:
	xfs_iwalk_del_inobt(iwag->tp, &cur, &agi_bp, error);
	return error;
}

/*
 * We experimentally determined that the reduction in ioctl call overhead
 * diminishes when userspace asks for more than 2048 inodes, so we'll cap
 * prefetch at this point.
 */
#define IWALK_MAX_INODE_PREFETCH	(2048U)

/*
 * Given the number of inodes to prefetch, set the number of inobt records that
 * we cache in memory, which controls the number of inodes we try to read
 * ahead.  Set the maximum if @inodes == 0.
 */
static inline unsigned int
xfs_iwalk_prefetch(
	unsigned int		inodes)
{
	unsigned int		inobt_records;

	/*
	 * If the caller didn't tell us the number of inodes they wanted,
	 * assume the maximum prefetch possible for best performance.
	 * Otherwise, cap prefetch at that maximum so that we don't start an
	 * absurd amount of prefetch.
	 */
	if (inodes == 0)
		inodes = IWALK_MAX_INODE_PREFETCH;
	inodes = min(inodes, IWALK_MAX_INODE_PREFETCH);

	/* Round the inode count up to a full chunk. */
	inodes = round_up(inodes, XFS_INODES_PER_CHUNK);

	/*
	 * In order to convert the number of inodes to prefetch into an
	 * estimate of the number of inobt records to cache, we require a
	 * conversion factor that reflects our expectations of the average
	 * loading factor of an inode chunk.  Based on data gathered, most
	 * (but not all) filesystems manage to keep the inode chunks totally
	 * full, so we'll underestimate slightly so that our readahead will
	 * still deliver the performance we want on aging filesystems:
	 *
	 * inobt = inodes / (INODES_PER_CHUNK * (4 / 5));
	 *
	 * The funny math is to avoid integer division.
	 */
	inobt_records = (inodes * 5) / (4 * XFS_INODES_PER_CHUNK);

	/*
	 * Allocate enough space to prefetch at least two inobt records so that
	 * we can cache both the record where the iwalk started and the next
	 * record.  This simplifies the AG inode walk loop setup code.
	 */
	return max(inobt_records, 2U);
}

/*
 * Walk all inodes in the filesystem starting from @startino.  The @iwalk_fn
 * will be called for each allocated inode, being passed the inode's number and
 * @data.  @max_prefetch controls how many inobt records' worth of inodes we
 * try to readahead.
 */
int
xfs_iwalk(
	struct xfs_mount	*mp,
	struct xfs_trans	*tp,
	xfs_ino_t		startino,
	unsigned int		flags,
	xfs_iwalk_fn		iwalk_fn,
	unsigned int		inode_records,
	void			*data)
{
	struct xfs_iwalk_ag	iwag = {
		.mp		= mp,
		.tp		= tp,
		.iwalk_fn	= iwalk_fn,
		.data		= data,
		.startino	= startino,
		.sz_recs	= xfs_iwalk_prefetch(inode_records),
		.trim_start	= 1,
		.skip_empty	= 1,
		.pwork		= XFS_PWORK_SINGLE_THREADED,
		.lastino	= NULLFSINO,
	};
	struct xfs_perag	*pag;
	xfs_agnumber_t		agno = XFS_INO_TO_AGNO(mp, startino);
	int			error;

	ASSERT(agno < mp->m_sb.sb_agcount);
	ASSERT(!(flags & ~XFS_IWALK_FLAGS_ALL));

	error = xfs_iwalk_alloc(&iwag);
	if (error)
		return error;

	for_each_perag_from(mp, agno, pag) {
		iwag.pag = pag;
		error = xfs_iwalk_ag(&iwag);
		if (error)
			break;
		iwag.startino = XFS_AGINO_TO_INO(mp, agno + 1, 0);
		if (flags & XFS_INOBT_WALK_SAME_AG)
			break;
		iwag.pag = NULL;
	}

	if (iwag.pag)
		xfs_perag_put(pag);
	xfs_iwalk_free(&iwag);
	return error;
}

/* Run per-thread iwalk work. */
static int
xfs_iwalk_ag_work(
	struct xfs_mount	*mp,
	struct xfs_pwork	*pwork)
{
	struct xfs_iwalk_ag	*iwag;
	int			error = 0;

	iwag = container_of(pwork, struct xfs_iwalk_ag, pwork);
	if (xfs_pwork_want_abort(pwork))
		goto out;

	error = xfs_iwalk_alloc(iwag);
	if (error)
		goto out;
	/*
	 * Grab an empty transaction so that we can use its recursive buffer
	 * locking abilities to detect cycles in the inobt without deadlocking.
	 */
	error = xfs_trans_alloc_empty(mp, &iwag->tp);
	if (error)
		goto out;
	iwag->drop_trans = 1;

	error = xfs_iwalk_ag(iwag);
	if (iwag->tp)
		xfs_trans_cancel(iwag->tp);
	xfs_iwalk_free(iwag);
out:
	xfs_perag_put(iwag->pag);
	kmem_free(iwag);
	return error;
}

/*
 * Walk all the inodes in the filesystem using multiple threads to process each
 * AG.
 */
int
xfs_iwalk_threaded(
	struct xfs_mount	*mp,
	xfs_ino_t		startino,
	unsigned int		flags,
	xfs_iwalk_fn		iwalk_fn,
	unsigned int		inode_records,
	bool			polled,
	void			*data)
{
	struct xfs_pwork_ctl	pctl;
	struct xfs_perag	*pag;
	xfs_agnumber_t		agno = XFS_INO_TO_AGNO(mp, startino);
	int			error;

	ASSERT(agno < mp->m_sb.sb_agcount);
	ASSERT(!(flags & ~XFS_IWALK_FLAGS_ALL));

	error = xfs_pwork_init(mp, &pctl, xfs_iwalk_ag_work, "xfs_iwalk");
	if (error)
		return error;

	for_each_perag_from(mp, agno, pag) {
		struct xfs_iwalk_ag	*iwag;

		if (xfs_pwork_ctl_want_abort(&pctl))
			break;

		iwag = kmem_zalloc(sizeof(struct xfs_iwalk_ag), 0);
		iwag->mp = mp;

		/*
		 * perag is being handed off to async work, so take another
		 * reference for the async work to release.
		 */
		atomic_inc(&pag->pag_ref);
		iwag->pag = pag;
		iwag->iwalk_fn = iwalk_fn;
		iwag->data = data;
		iwag->startino = startino;
		iwag->sz_recs = xfs_iwalk_prefetch(inode_records);
		iwag->lastino = NULLFSINO;
		xfs_pwork_queue(&pctl, &iwag->pwork);
		startino = XFS_AGINO_TO_INO(mp, pag->pag_agno + 1, 0);
		if (flags & XFS_INOBT_WALK_SAME_AG)
			break;
	}
	if (pag)
		xfs_perag_put(pag);
	if (polled)
		xfs_pwork_poll(&pctl);
	return xfs_pwork_destroy(&pctl);
}

/*
 * Allow callers to cache up to a page's worth of inobt records.  This reflects
 * the existing inumbers prefetching behavior.  Since the inobt walk does not
 * itself do anything with the inobt records, we can set a fairly high limit
 * here.
 */
#define MAX_INOBT_WALK_PREFETCH	\
	(PAGE_SIZE / sizeof(struct xfs_inobt_rec_incore))

/*
 * Given the number of records that the user wanted, set the number of inobt
 * records that we buffer in memory.  Set the maximum if @inobt_records == 0.
 */
static inline unsigned int
xfs_inobt_walk_prefetch(
	unsigned int		inobt_records)
{
	/*
	 * If the caller didn't tell us the number of inobt records they
	 * wanted, assume the maximum prefetch possible for best performance.
	 */
	if (inobt_records == 0)
		inobt_records = MAX_INOBT_WALK_PREFETCH;

	/*
	 * Allocate enough space to prefetch at least two inobt records so that
	 * we can cache both the record where the iwalk started and the next
	 * record.  This simplifies the AG inode walk loop setup code.
	 */
	inobt_records = max(inobt_records, 2U);

	/*
	 * Cap prefetch at that maximum so that we don't use an absurd amount
	 * of memory.
	 */
	return min_t(unsigned int, inobt_records, MAX_INOBT_WALK_PREFETCH);
}

/*
 * Walk all inode btree records in the filesystem starting from @startino.  The
 * @inobt_walk_fn will be called for each btree record, being passed the incore
 * record and @data.  @max_prefetch controls how many inobt records we try to
 * cache ahead of time.
 */
int
xfs_inobt_walk(
	struct xfs_mount	*mp,
	struct xfs_trans	*tp,
	xfs_ino_t		startino,
	unsigned int		flags,
	xfs_inobt_walk_fn	inobt_walk_fn,
	unsigned int		inobt_records,
	void			*data)
{
	struct xfs_iwalk_ag	iwag = {
		.mp		= mp,
		.tp		= tp,
		.inobt_walk_fn	= inobt_walk_fn,
		.data		= data,
		.startino	= startino,
		.sz_recs	= xfs_inobt_walk_prefetch(inobt_records),
		.pwork		= XFS_PWORK_SINGLE_THREADED,
		.lastino	= NULLFSINO,
	};
	struct xfs_perag	*pag;
	xfs_agnumber_t		agno = XFS_INO_TO_AGNO(mp, startino);
	int			error;

	ASSERT(agno < mp->m_sb.sb_agcount);
	ASSERT(!(flags & ~XFS_INOBT_WALK_FLAGS_ALL));

	error = xfs_iwalk_alloc(&iwag);
	if (error)
		return error;

	for_each_perag_from(mp, agno, pag) {
		iwag.pag = pag;
		error = xfs_iwalk_ag(&iwag);
		if (error)
			break;
		iwag.startino = XFS_AGINO_TO_INO(mp, pag->pag_agno + 1, 0);
		if (flags & XFS_INOBT_WALK_SAME_AG)
			break;
		iwag.pag = NULL;
	}

	if (iwag.pag)
		xfs_perag_put(pag);
	xfs_iwalk_free(&iwag);
	return error;
}