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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2019 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
5 */
6#include "xfs.h"
7#include "xfs_fs.h"
8#include "xfs_shared.h"
9#include "xfs_format.h"
10#include "xfs_log_format.h"
11#include "xfs_trans_resv.h"
12#include "xfs_mount.h"
13#include "xfs_inode.h"
14#include "xfs_btree.h"
15#include "xfs_ialloc.h"
16#include "xfs_ialloc_btree.h"
17#include "xfs_iwalk.h"
18#include "xfs_error.h"
19#include "xfs_trace.h"
20#include "xfs_icache.h"
21#include "xfs_health.h"
22#include "xfs_trans.h"
23#include "xfs_pwork.h"
24#include "xfs_ag.h"
25#include "xfs_bit.h"
26
27/*
28 * Walking Inodes in the Filesystem
29 * ================================
30 *
31 * This iterator function walks a subset of filesystem inodes in increasing
32 * order from @startino until there are no more inodes. For each allocated
33 * inode it finds, it calls a walk function with the relevant inode number and
34 * a pointer to caller-provided data. The walk function can return the usual
35 * negative error code to stop the iteration; 0 to continue the iteration; or
36 * -ECANCELED to stop the iteration. This return value is returned to the
37 * caller.
38 *
39 * Internally, we allow the walk function to do anything, which means that we
40 * cannot maintain the inobt cursor or our lock on the AGI buffer. We
41 * therefore cache the inobt records in kernel memory and only call the walk
42 * function when our memory buffer is full. @nr_recs is the number of records
43 * that we've cached, and @sz_recs is the size of our cache.
44 *
45 * It is the responsibility of the walk function to ensure it accesses
46 * allocated inodes, as the inobt records may be stale by the time they are
47 * acted upon.
48 */
49
50struct xfs_iwalk_ag {
51 /* parallel work control data; will be null if single threaded */
52 struct xfs_pwork pwork;
53
54 struct xfs_mount *mp;
55 struct xfs_trans *tp;
56 struct xfs_perag *pag;
57
58 /* Where do we start the traversal? */
59 xfs_ino_t startino;
60
61 /* What was the last inode number we saw when iterating the inobt? */
62 xfs_ino_t lastino;
63
64 /* Array of inobt records we cache. */
65 struct xfs_inobt_rec_incore *recs;
66
67 /* Number of entries allocated for the @recs array. */
68 unsigned int sz_recs;
69
70 /* Number of entries in the @recs array that are in use. */
71 unsigned int nr_recs;
72
73 /* Inode walk function and data pointer. */
74 xfs_iwalk_fn iwalk_fn;
75 xfs_inobt_walk_fn inobt_walk_fn;
76 void *data;
77
78 /*
79 * Make it look like the inodes up to startino are free so that
80 * bulkstat can start its inode iteration at the correct place without
81 * needing to special case everywhere.
82 */
83 unsigned int trim_start:1;
84
85 /* Skip empty inobt records? */
86 unsigned int skip_empty:1;
87
88 /* Drop the (hopefully empty) transaction when calling iwalk_fn. */
89 unsigned int drop_trans:1;
90};
91
92/*
93 * Loop over all clusters in a chunk for a given incore inode allocation btree
94 * record. Do a readahead if there are any allocated inodes in that cluster.
95 */
96STATIC void
97xfs_iwalk_ichunk_ra(
98 struct xfs_mount *mp,
99 struct xfs_perag *pag,
100 struct xfs_inobt_rec_incore *irec)
101{
102 struct xfs_ino_geometry *igeo = M_IGEO(mp);
103 xfs_agblock_t agbno;
104 struct blk_plug plug;
105 int i; /* inode chunk index */
106
107 agbno = XFS_AGINO_TO_AGBNO(mp, irec->ir_startino);
108
109 blk_start_plug(&plug);
110 for (i = 0; i < XFS_INODES_PER_CHUNK; i += igeo->inodes_per_cluster) {
111 xfs_inofree_t imask;
112
113 imask = xfs_inobt_maskn(i, igeo->inodes_per_cluster);
114 if (imask & ~irec->ir_free) {
115 xfs_buf_readahead(mp->m_ddev_targp,
116 xfs_agbno_to_daddr(pag, agbno),
117 igeo->blocks_per_cluster * mp->m_bsize,
118 &xfs_inode_buf_ops);
119 }
120 agbno += igeo->blocks_per_cluster;
121 }
122 blk_finish_plug(&plug);
123}
124
125/*
126 * Set the bits in @irec's free mask that correspond to the inodes before
127 * @agino so that we skip them. This is how we restart an inode walk that was
128 * interrupted in the middle of an inode record.
129 */
130STATIC void
131xfs_iwalk_adjust_start(
132 xfs_agino_t agino, /* starting inode of chunk */
133 struct xfs_inobt_rec_incore *irec) /* btree record */
134{
135 int idx; /* index into inode chunk */
136
137 idx = agino - irec->ir_startino;
138
139 irec->ir_free |= xfs_inobt_maskn(0, idx);
140 irec->ir_freecount = hweight64(irec->ir_free);
141}
142
143/* Allocate memory for a walk. */
144STATIC int
145xfs_iwalk_alloc(
146 struct xfs_iwalk_ag *iwag)
147{
148 size_t size;
149
150 ASSERT(iwag->recs == NULL);
151 iwag->nr_recs = 0;
152
153 /* Allocate a prefetch buffer for inobt records. */
154 size = iwag->sz_recs * sizeof(struct xfs_inobt_rec_incore);
155 iwag->recs = kmalloc(size, GFP_KERNEL | __GFP_RETRY_MAYFAIL);
156 if (iwag->recs == NULL)
157 return -ENOMEM;
158
159 return 0;
160}
161
162/* Free memory we allocated for a walk. */
163STATIC void
164xfs_iwalk_free(
165 struct xfs_iwalk_ag *iwag)
166{
167 kfree(iwag->recs);
168 iwag->recs = NULL;
169}
170
171/* For each inuse inode in each cached inobt record, call our function. */
172STATIC int
173xfs_iwalk_ag_recs(
174 struct xfs_iwalk_ag *iwag)
175{
176 struct xfs_mount *mp = iwag->mp;
177 struct xfs_trans *tp = iwag->tp;
178 struct xfs_perag *pag = iwag->pag;
179 unsigned int i, j;
180 int error;
181
182 for (i = 0; i < iwag->nr_recs; i++) {
183 struct xfs_inobt_rec_incore *irec = &iwag->recs[i];
184
185 trace_xfs_iwalk_ag_rec(pag, irec);
186
187 if (xfs_pwork_want_abort(&iwag->pwork))
188 return 0;
189
190 if (iwag->inobt_walk_fn) {
191 error = iwag->inobt_walk_fn(mp, tp, pag_agno(pag), irec,
192 iwag->data);
193 if (error)
194 return error;
195 }
196
197 if (!iwag->iwalk_fn)
198 continue;
199
200 for (j = 0; j < XFS_INODES_PER_CHUNK; j++) {
201 if (xfs_pwork_want_abort(&iwag->pwork))
202 return 0;
203
204 /* Skip if this inode is free */
205 if (XFS_INOBT_MASK(j) & irec->ir_free)
206 continue;
207
208 /* Otherwise call our function. */
209 error = iwag->iwalk_fn(mp, tp,
210 xfs_agino_to_ino(pag,
211 irec->ir_startino + j),
212 iwag->data);
213 if (error)
214 return error;
215 }
216 }
217
218 return 0;
219}
220
221/* Delete cursor and let go of AGI. */
222static inline void
223xfs_iwalk_del_inobt(
224 struct xfs_trans *tp,
225 struct xfs_btree_cur **curpp,
226 struct xfs_buf **agi_bpp,
227 int error)
228{
229 if (*curpp) {
230 xfs_btree_del_cursor(*curpp, error);
231 *curpp = NULL;
232 }
233 if (*agi_bpp) {
234 xfs_trans_brelse(tp, *agi_bpp);
235 *agi_bpp = NULL;
236 }
237}
238
239/*
240 * Set ourselves up for walking inobt records starting from a given point in
241 * the filesystem.
242 *
243 * If caller passed in a nonzero start inode number, load the record from the
244 * inobt and make the record look like all the inodes before agino are free so
245 * that we skip them, and then move the cursor to the next inobt record. This
246 * is how we support starting an iwalk in the middle of an inode chunk.
247 *
248 * If the caller passed in a start number of zero, move the cursor to the first
249 * inobt record.
250 *
251 * The caller is responsible for cleaning up the cursor and buffer pointer
252 * regardless of the error status.
253 */
254STATIC int
255xfs_iwalk_ag_start(
256 struct xfs_iwalk_ag *iwag,
257 xfs_agino_t agino,
258 struct xfs_btree_cur **curpp,
259 struct xfs_buf **agi_bpp,
260 int *has_more)
261{
262 struct xfs_mount *mp = iwag->mp;
263 struct xfs_trans *tp = iwag->tp;
264 struct xfs_perag *pag = iwag->pag;
265 struct xfs_inobt_rec_incore *irec;
266 int error;
267
268 /* Set up a fresh cursor and empty the inobt cache. */
269 iwag->nr_recs = 0;
270 error = xfs_ialloc_read_agi(pag, tp, 0, agi_bpp);
271 if (error)
272 return error;
273 *curpp = xfs_inobt_init_cursor(pag, tp, *agi_bpp);
274
275 /* Starting at the beginning of the AG? That's easy! */
276 if (agino == 0)
277 return xfs_inobt_lookup(*curpp, 0, XFS_LOOKUP_GE, has_more);
278
279 /*
280 * Otherwise, we have to grab the inobt record where we left off, stuff
281 * the record into our cache, and then see if there are more records.
282 * We require a lookup cache of at least two elements so that the
283 * caller doesn't have to deal with tearing down the cursor to walk the
284 * records.
285 */
286 error = xfs_inobt_lookup(*curpp, agino, XFS_LOOKUP_LE, has_more);
287 if (error)
288 return error;
289
290 /*
291 * If the LE lookup at @agino yields no records, jump ahead to the
292 * inobt cursor increment to see if there are more records to process.
293 */
294 if (!*has_more)
295 goto out_advance;
296
297 /* Get the record, should always work */
298 irec = &iwag->recs[iwag->nr_recs];
299 error = xfs_inobt_get_rec(*curpp, irec, has_more);
300 if (error)
301 return error;
302 if (XFS_IS_CORRUPT(mp, *has_more != 1)) {
303 xfs_btree_mark_sick(*curpp);
304 return -EFSCORRUPTED;
305 }
306
307 iwag->lastino = xfs_agino_to_ino(pag,
308 irec->ir_startino + XFS_INODES_PER_CHUNK - 1);
309
310 /*
311 * If the LE lookup yielded an inobt record before the cursor position,
312 * skip it and see if there's another one after it.
313 */
314 if (irec->ir_startino + XFS_INODES_PER_CHUNK <= agino)
315 goto out_advance;
316
317 /*
318 * If agino fell in the middle of the inode record, make it look like
319 * the inodes up to agino are free so that we don't return them again.
320 */
321 if (iwag->trim_start)
322 xfs_iwalk_adjust_start(agino, irec);
323
324 /*
325 * The prefetch calculation is supposed to give us a large enough inobt
326 * record cache that grab_ichunk can stage a partial first record and
327 * the loop body can cache a record without having to check for cache
328 * space until after it reads an inobt record.
329 */
330 iwag->nr_recs++;
331 ASSERT(iwag->nr_recs < iwag->sz_recs);
332
333out_advance:
334 return xfs_btree_increment(*curpp, 0, has_more);
335}
336
337/*
338 * The inobt record cache is full, so preserve the inobt cursor state and
339 * run callbacks on the cached inobt records. When we're done, restore the
340 * cursor state to wherever the cursor would have been had the cache not been
341 * full (and therefore we could've just incremented the cursor) if *@has_more
342 * is true. On exit, *@has_more will indicate whether or not the caller should
343 * try for more inode records.
344 */
345STATIC int
346xfs_iwalk_run_callbacks(
347 struct xfs_iwalk_ag *iwag,
348 struct xfs_btree_cur **curpp,
349 struct xfs_buf **agi_bpp,
350 int *has_more)
351{
352 struct xfs_mount *mp = iwag->mp;
353 xfs_agino_t next_agino;
354 int error;
355
356 next_agino = XFS_INO_TO_AGINO(mp, iwag->lastino) + 1;
357
358 ASSERT(iwag->nr_recs > 0);
359
360 /* Delete cursor but remember the last record we cached... */
361 xfs_iwalk_del_inobt(iwag->tp, curpp, agi_bpp, 0);
362 ASSERT(next_agino >= iwag->recs[iwag->nr_recs - 1].ir_startino +
363 XFS_INODES_PER_CHUNK);
364
365 if (iwag->drop_trans) {
366 xfs_trans_cancel(iwag->tp);
367 iwag->tp = NULL;
368 }
369
370 error = xfs_iwalk_ag_recs(iwag);
371 if (error)
372 return error;
373
374 /* ...empty the cache... */
375 iwag->nr_recs = 0;
376
377 if (!has_more)
378 return 0;
379
380 if (iwag->drop_trans) {
381 error = xfs_trans_alloc_empty(mp, &iwag->tp);
382 if (error)
383 return error;
384 }
385
386 /* ...and recreate the cursor just past where we left off. */
387 error = xfs_ialloc_read_agi(iwag->pag, iwag->tp, 0, agi_bpp);
388 if (error)
389 return error;
390 *curpp = xfs_inobt_init_cursor(iwag->pag, iwag->tp, *agi_bpp);
391 return xfs_inobt_lookup(*curpp, next_agino, XFS_LOOKUP_GE, has_more);
392}
393
394/* Walk all inodes in a single AG, from @iwag->startino to the end of the AG. */
395STATIC int
396xfs_iwalk_ag(
397 struct xfs_iwalk_ag *iwag)
398{
399 struct xfs_mount *mp = iwag->mp;
400 struct xfs_perag *pag = iwag->pag;
401 struct xfs_buf *agi_bp = NULL;
402 struct xfs_btree_cur *cur = NULL;
403 xfs_agino_t agino;
404 int has_more;
405 int error = 0;
406
407 /* Set up our cursor at the right place in the inode btree. */
408 ASSERT(pag_agno(pag) == XFS_INO_TO_AGNO(mp, iwag->startino));
409 agino = XFS_INO_TO_AGINO(mp, iwag->startino);
410 error = xfs_iwalk_ag_start(iwag, agino, &cur, &agi_bp, &has_more);
411
412 while (!error && has_more) {
413 struct xfs_inobt_rec_incore *irec;
414 xfs_ino_t rec_fsino;
415
416 cond_resched();
417 if (xfs_pwork_want_abort(&iwag->pwork))
418 goto out;
419
420 /* Fetch the inobt record. */
421 irec = &iwag->recs[iwag->nr_recs];
422 error = xfs_inobt_get_rec(cur, irec, &has_more);
423 if (error || !has_more)
424 break;
425
426 /* Make sure that we always move forward. */
427 rec_fsino = xfs_agino_to_ino(pag, irec->ir_startino);
428 if (iwag->lastino != NULLFSINO &&
429 XFS_IS_CORRUPT(mp, iwag->lastino >= rec_fsino)) {
430 xfs_btree_mark_sick(cur);
431 error = -EFSCORRUPTED;
432 goto out;
433 }
434 iwag->lastino = rec_fsino + XFS_INODES_PER_CHUNK - 1;
435
436 /* No allocated inodes in this chunk; skip it. */
437 if (iwag->skip_empty && irec->ir_freecount == irec->ir_count) {
438 error = xfs_btree_increment(cur, 0, &has_more);
439 if (error)
440 break;
441 continue;
442 }
443
444 /*
445 * Start readahead for this inode chunk in anticipation of
446 * walking the inodes.
447 */
448 if (iwag->iwalk_fn)
449 xfs_iwalk_ichunk_ra(mp, pag, irec);
450
451 /*
452 * If there's space in the buffer for more records, increment
453 * the btree cursor and grab more.
454 */
455 if (++iwag->nr_recs < iwag->sz_recs) {
456 error = xfs_btree_increment(cur, 0, &has_more);
457 if (error || !has_more)
458 break;
459 continue;
460 }
461
462 /*
463 * Otherwise, we need to save cursor state and run the callback
464 * function on the cached records. The run_callbacks function
465 * is supposed to return a cursor pointing to the record where
466 * we would be if we had been able to increment like above.
467 */
468 ASSERT(has_more);
469 error = xfs_iwalk_run_callbacks(iwag, &cur, &agi_bp, &has_more);
470 }
471
472 if (iwag->nr_recs == 0 || error)
473 goto out;
474
475 /* Walk the unprocessed records in the cache. */
476 error = xfs_iwalk_run_callbacks(iwag, &cur, &agi_bp, &has_more);
477
478out:
479 xfs_iwalk_del_inobt(iwag->tp, &cur, &agi_bp, error);
480 return error;
481}
482
483/*
484 * We experimentally determined that the reduction in ioctl call overhead
485 * diminishes when userspace asks for more than 2048 inodes, so we'll cap
486 * prefetch at this point.
487 */
488#define IWALK_MAX_INODE_PREFETCH (2048U)
489
490/*
491 * Given the number of inodes to prefetch, set the number of inobt records that
492 * we cache in memory, which controls the number of inodes we try to read
493 * ahead. Set the maximum if @inodes == 0.
494 */
495static inline unsigned int
496xfs_iwalk_prefetch(
497 unsigned int inodes)
498{
499 unsigned int inobt_records;
500
501 /*
502 * If the caller didn't tell us the number of inodes they wanted,
503 * assume the maximum prefetch possible for best performance.
504 * Otherwise, cap prefetch at that maximum so that we don't start an
505 * absurd amount of prefetch.
506 */
507 if (inodes == 0)
508 inodes = IWALK_MAX_INODE_PREFETCH;
509 inodes = min(inodes, IWALK_MAX_INODE_PREFETCH);
510
511 /* Round the inode count up to a full chunk. */
512 inodes = round_up(inodes, XFS_INODES_PER_CHUNK);
513
514 /*
515 * In order to convert the number of inodes to prefetch into an
516 * estimate of the number of inobt records to cache, we require a
517 * conversion factor that reflects our expectations of the average
518 * loading factor of an inode chunk. Based on data gathered, most
519 * (but not all) filesystems manage to keep the inode chunks totally
520 * full, so we'll underestimate slightly so that our readahead will
521 * still deliver the performance we want on aging filesystems:
522 *
523 * inobt = inodes / (INODES_PER_CHUNK * (4 / 5));
524 *
525 * The funny math is to avoid integer division.
526 */
527 inobt_records = (inodes * 5) / (4 * XFS_INODES_PER_CHUNK);
528
529 /*
530 * Allocate enough space to prefetch at least two inobt records so that
531 * we can cache both the record where the iwalk started and the next
532 * record. This simplifies the AG inode walk loop setup code.
533 */
534 return max(inobt_records, 2U);
535}
536
537static int
538xfs_iwalk_args(
539 struct xfs_iwalk_ag *iwag,
540 unsigned int flags)
541{
542 struct xfs_mount *mp = iwag->mp;
543 xfs_agnumber_t start_agno;
544 int error;
545
546 start_agno = XFS_INO_TO_AGNO(iwag->mp, iwag->startino);
547 ASSERT(start_agno < iwag->mp->m_sb.sb_agcount);
548 ASSERT(!(flags & ~XFS_IWALK_FLAGS_ALL));
549
550 error = xfs_iwalk_alloc(iwag);
551 if (error)
552 return error;
553
554 while ((iwag->pag = xfs_perag_next_from(mp, iwag->pag, start_agno))) {
555 error = xfs_iwalk_ag(iwag);
556 if (error || (flags & XFS_IWALK_SAME_AG)) {
557 xfs_perag_rele(iwag->pag);
558 break;
559 }
560 iwag->startino =
561 XFS_AGINO_TO_INO(mp, pag_agno(iwag->pag) + 1, 0);
562 }
563
564 xfs_iwalk_free(iwag);
565 return error;
566}
567
568/*
569 * Walk all inodes in the filesystem starting from @startino. The @iwalk_fn
570 * will be called for each allocated inode, being passed the inode's number and
571 * @data. @max_prefetch controls how many inobt records' worth of inodes we
572 * try to readahead.
573 */
574int
575xfs_iwalk(
576 struct xfs_mount *mp,
577 struct xfs_trans *tp,
578 xfs_ino_t startino,
579 unsigned int flags,
580 xfs_iwalk_fn iwalk_fn,
581 unsigned int inode_records,
582 void *data)
583{
584 struct xfs_iwalk_ag iwag = {
585 .mp = mp,
586 .tp = tp,
587 .iwalk_fn = iwalk_fn,
588 .data = data,
589 .startino = startino,
590 .sz_recs = xfs_iwalk_prefetch(inode_records),
591 .trim_start = 1,
592 .skip_empty = 1,
593 .pwork = XFS_PWORK_SINGLE_THREADED,
594 .lastino = NULLFSINO,
595 };
596
597 return xfs_iwalk_args(&iwag, flags);
598}
599
600/* Run per-thread iwalk work. */
601static int
602xfs_iwalk_ag_work(
603 struct xfs_mount *mp,
604 struct xfs_pwork *pwork)
605{
606 struct xfs_iwalk_ag *iwag;
607 int error = 0;
608
609 iwag = container_of(pwork, struct xfs_iwalk_ag, pwork);
610 if (xfs_pwork_want_abort(pwork))
611 goto out;
612
613 error = xfs_iwalk_alloc(iwag);
614 if (error)
615 goto out;
616 /*
617 * Grab an empty transaction so that we can use its recursive buffer
618 * locking abilities to detect cycles in the inobt without deadlocking.
619 */
620 error = xfs_trans_alloc_empty(mp, &iwag->tp);
621 if (error)
622 goto out;
623 iwag->drop_trans = 1;
624
625 error = xfs_iwalk_ag(iwag);
626 if (iwag->tp)
627 xfs_trans_cancel(iwag->tp);
628 xfs_iwalk_free(iwag);
629out:
630 xfs_perag_put(iwag->pag);
631 kfree(iwag);
632 return error;
633}
634
635/*
636 * Walk all the inodes in the filesystem using multiple threads to process each
637 * AG.
638 */
639int
640xfs_iwalk_threaded(
641 struct xfs_mount *mp,
642 xfs_ino_t startino,
643 unsigned int flags,
644 xfs_iwalk_fn iwalk_fn,
645 unsigned int inode_records,
646 bool polled,
647 void *data)
648{
649 xfs_agnumber_t start_agno = XFS_INO_TO_AGNO(mp, startino);
650 struct xfs_pwork_ctl pctl;
651 struct xfs_perag *pag = NULL;
652 int error;
653
654 ASSERT(start_agno < mp->m_sb.sb_agcount);
655 ASSERT(!(flags & ~XFS_IWALK_FLAGS_ALL));
656
657 error = xfs_pwork_init(mp, &pctl, xfs_iwalk_ag_work, "xfs_iwalk");
658 if (error)
659 return error;
660
661 while ((pag = xfs_perag_next_from(mp, pag, start_agno))) {
662 struct xfs_iwalk_ag *iwag;
663
664 if (xfs_pwork_ctl_want_abort(&pctl))
665 break;
666
667 iwag = kzalloc(sizeof(struct xfs_iwalk_ag),
668 GFP_KERNEL | __GFP_NOFAIL);
669 iwag->mp = mp;
670
671 /*
672 * perag is being handed off to async work, so take a passive
673 * reference for the async work to release.
674 */
675 iwag->pag = xfs_perag_hold(pag);
676 iwag->iwalk_fn = iwalk_fn;
677 iwag->data = data;
678 iwag->startino = startino;
679 iwag->sz_recs = xfs_iwalk_prefetch(inode_records);
680 iwag->lastino = NULLFSINO;
681 xfs_pwork_queue(&pctl, &iwag->pwork);
682 startino = XFS_AGINO_TO_INO(mp, pag_agno(pag) + 1, 0);
683 if (flags & XFS_IWALK_SAME_AG)
684 break;
685 }
686 if (pag)
687 xfs_perag_rele(pag);
688 if (polled)
689 xfs_pwork_poll(&pctl);
690 return xfs_pwork_destroy(&pctl);
691}
692
693/*
694 * Allow callers to cache up to a page's worth of inobt records. This reflects
695 * the existing inumbers prefetching behavior. Since the inobt walk does not
696 * itself do anything with the inobt records, we can set a fairly high limit
697 * here.
698 */
699#define MAX_INOBT_WALK_PREFETCH \
700 (PAGE_SIZE / sizeof(struct xfs_inobt_rec_incore))
701
702/*
703 * Given the number of records that the user wanted, set the number of inobt
704 * records that we buffer in memory. Set the maximum if @inobt_records == 0.
705 */
706static inline unsigned int
707xfs_inobt_walk_prefetch(
708 unsigned int inobt_records)
709{
710 /*
711 * If the caller didn't tell us the number of inobt records they
712 * wanted, assume the maximum prefetch possible for best performance.
713 */
714 if (inobt_records == 0)
715 inobt_records = MAX_INOBT_WALK_PREFETCH;
716
717 /*
718 * Allocate enough space to prefetch at least two inobt records so that
719 * we can cache both the record where the iwalk started and the next
720 * record. This simplifies the AG inode walk loop setup code.
721 */
722 inobt_records = max(inobt_records, 2U);
723
724 /*
725 * Cap prefetch at that maximum so that we don't use an absurd amount
726 * of memory.
727 */
728 return min_t(unsigned int, inobt_records, MAX_INOBT_WALK_PREFETCH);
729}
730
731/*
732 * Walk all inode btree records in the filesystem starting from @startino. The
733 * @inobt_walk_fn will be called for each btree record, being passed the incore
734 * record and @data. @max_prefetch controls how many inobt records we try to
735 * cache ahead of time.
736 */
737int
738xfs_inobt_walk(
739 struct xfs_mount *mp,
740 struct xfs_trans *tp,
741 xfs_ino_t startino,
742 unsigned int flags,
743 xfs_inobt_walk_fn inobt_walk_fn,
744 unsigned int inobt_records,
745 void *data)
746{
747 struct xfs_iwalk_ag iwag = {
748 .mp = mp,
749 .tp = tp,
750 .inobt_walk_fn = inobt_walk_fn,
751 .data = data,
752 .startino = startino,
753 .sz_recs = xfs_inobt_walk_prefetch(inobt_records),
754 .pwork = XFS_PWORK_SINGLE_THREADED,
755 .lastino = NULLFSINO,
756 };
757
758 return xfs_iwalk_args(&iwag, flags);
759}