1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * This file is part of UBIFS.
4 *
5 * Copyright (C) 2006-2008 Nokia Corporation.
6 *
7 * Authors: Adrian Hunter
8 * Artem Bityutskiy (Битюцкий Артём)
9 */
10
11 /*
12 * This file implements garbage collection. The procedure for garbage collection
13 * is different depending on whether a LEB as an index LEB (contains index
14 * nodes) or not. For non-index LEBs, garbage collection finds a LEB which
15 * contains a lot of dirty space (obsolete nodes), and copies the non-obsolete
16 * nodes to the journal, at which point the garbage-collected LEB is free to be
17 * reused. For index LEBs, garbage collection marks the non-obsolete index nodes
18 * dirty in the TNC, and after the next commit, the garbage-collected LEB is
19 * to be reused. Garbage collection will cause the number of dirty index nodes
20 * to grow, however sufficient space is reserved for the index to ensure the
21 * commit will never run out of space.
22 *
23 * Notes about dead watermark. At current UBIFS implementation we assume that
24 * LEBs which have less than @c->dead_wm bytes of free + dirty space are full
25 * and not worth garbage-collecting. The dead watermark is one min. I/O unit
26 * size, or min. UBIFS node size, depending on what is greater. Indeed, UBIFS
27 * Garbage Collector has to synchronize the GC head's write buffer before
28 * returning, so this is about wasting one min. I/O unit. However, UBIFS GC can
29 * actually reclaim even very small pieces of dirty space by garbage collecting
30 * enough dirty LEBs, but we do not bother doing this at this implementation.
31 *
32 * Notes about dark watermark. The results of GC work depends on how big are
33 * the UBIFS nodes GC deals with. Large nodes make GC waste more space. Indeed,
34 * if GC move data from LEB A to LEB B and nodes in LEB A are large, GC would
35 * have to waste large pieces of free space at the end of LEB B, because nodes
36 * from LEB A would not fit. And the worst situation is when all nodes are of
37 * maximum size. So dark watermark is the amount of free + dirty space in LEB
38 * which are guaranteed to be reclaimable. If LEB has less space, the GC might
39 * be unable to reclaim it. So, LEBs with free + dirty greater than dark
40 * watermark are "good" LEBs from GC's point of view. The other LEBs are not so
41 * good, and GC takes extra care when moving them.
42 */
43
44 #include <linux/slab.h>
45 #include <linux/pagemap.h>
46 #include <linux/list_sort.h>
47 #include "ubifs.h"
48
49 /*
50 * GC may need to move more than one LEB to make progress. The below constants
51 * define "soft" and "hard" limits on the number of LEBs the garbage collector
52 * may move.
53 */
54 #define SOFT_LEBS_LIMIT 4
55 #define HARD_LEBS_LIMIT 32
56
57 /**
58 * switch_gc_head - switch the garbage collection journal head.
59 * @c: UBIFS file-system description object
60 *
61 * This function switch the GC head to the next LEB which is reserved in
62 * @c->gc_lnum. Returns %0 in case of success, %-EAGAIN if commit is required,
63 * and other negative error code in case of failures.
64 */
switch_gc_head(struct ubifs_info * c)65 static int switch_gc_head(struct ubifs_info *c)
66 {
67 int err, gc_lnum = c->gc_lnum;
68 struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
69
70 ubifs_assert(c, gc_lnum != -1);
71 dbg_gc("switch GC head from LEB %d:%d to LEB %d (waste %d bytes)",
72 wbuf->lnum, wbuf->offs + wbuf->used, gc_lnum,
73 c->leb_size - wbuf->offs - wbuf->used);
74
75 err = ubifs_wbuf_sync_nolock(wbuf);
76 if (err)
77 return err;
78
79 /*
80 * The GC write-buffer was synchronized, we may safely unmap
81 * 'c->gc_lnum'.
82 */
83 err = ubifs_leb_unmap(c, gc_lnum);
84 if (err)
85 return err;
86
87 err = ubifs_add_bud_to_log(c, GCHD, gc_lnum, 0);
88 if (err)
89 return err;
90
91 c->gc_lnum = -1;
92 err = ubifs_wbuf_seek_nolock(wbuf, gc_lnum, 0);
93 return err;
94 }
95
96 /**
97 * data_nodes_cmp - compare 2 data nodes.
98 * @priv: UBIFS file-system description object
99 * @a: first data node
100 * @b: second data node
101 *
102 * This function compares data nodes @a and @b. Returns %1 if @a has greater
103 * inode or block number, and %-1 otherwise.
104 */
data_nodes_cmp(void * priv,struct list_head * a,struct list_head * b)105 static int data_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
106 {
107 ino_t inuma, inumb;
108 struct ubifs_info *c = priv;
109 struct ubifs_scan_node *sa, *sb;
110
111 cond_resched();
112 if (a == b)
113 return 0;
114
115 sa = list_entry(a, struct ubifs_scan_node, list);
116 sb = list_entry(b, struct ubifs_scan_node, list);
117
118 ubifs_assert(c, key_type(c, &sa->key) == UBIFS_DATA_KEY);
119 ubifs_assert(c, key_type(c, &sb->key) == UBIFS_DATA_KEY);
120 ubifs_assert(c, sa->type == UBIFS_DATA_NODE);
121 ubifs_assert(c, sb->type == UBIFS_DATA_NODE);
122
123 inuma = key_inum(c, &sa->key);
124 inumb = key_inum(c, &sb->key);
125
126 if (inuma == inumb) {
127 unsigned int blka = key_block(c, &sa->key);
128 unsigned int blkb = key_block(c, &sb->key);
129
130 if (blka <= blkb)
131 return -1;
132 } else if (inuma <= inumb)
133 return -1;
134
135 return 1;
136 }
137
138 /*
139 * nondata_nodes_cmp - compare 2 non-data nodes.
140 * @priv: UBIFS file-system description object
141 * @a: first node
142 * @a: second node
143 *
144 * This function compares nodes @a and @b. It makes sure that inode nodes go
145 * first and sorted by length in descending order. Directory entry nodes go
146 * after inode nodes and are sorted in ascending hash valuer order.
147 */
nondata_nodes_cmp(void * priv,struct list_head * a,struct list_head * b)148 static int nondata_nodes_cmp(void *priv, struct list_head *a,
149 struct list_head *b)
150 {
151 ino_t inuma, inumb;
152 struct ubifs_info *c = priv;
153 struct ubifs_scan_node *sa, *sb;
154
155 cond_resched();
156 if (a == b)
157 return 0;
158
159 sa = list_entry(a, struct ubifs_scan_node, list);
160 sb = list_entry(b, struct ubifs_scan_node, list);
161
162 ubifs_assert(c, key_type(c, &sa->key) != UBIFS_DATA_KEY &&
163 key_type(c, &sb->key) != UBIFS_DATA_KEY);
164 ubifs_assert(c, sa->type != UBIFS_DATA_NODE &&
165 sb->type != UBIFS_DATA_NODE);
166
167 /* Inodes go before directory entries */
168 if (sa->type == UBIFS_INO_NODE) {
169 if (sb->type == UBIFS_INO_NODE)
170 return sb->len - sa->len;
171 return -1;
172 }
173 if (sb->type == UBIFS_INO_NODE)
174 return 1;
175
176 ubifs_assert(c, key_type(c, &sa->key) == UBIFS_DENT_KEY ||
177 key_type(c, &sa->key) == UBIFS_XENT_KEY);
178 ubifs_assert(c, key_type(c, &sb->key) == UBIFS_DENT_KEY ||
179 key_type(c, &sb->key) == UBIFS_XENT_KEY);
180 ubifs_assert(c, sa->type == UBIFS_DENT_NODE ||
181 sa->type == UBIFS_XENT_NODE);
182 ubifs_assert(c, sb->type == UBIFS_DENT_NODE ||
183 sb->type == UBIFS_XENT_NODE);
184
185 inuma = key_inum(c, &sa->key);
186 inumb = key_inum(c, &sb->key);
187
188 if (inuma == inumb) {
189 uint32_t hasha = key_hash(c, &sa->key);
190 uint32_t hashb = key_hash(c, &sb->key);
191
192 if (hasha <= hashb)
193 return -1;
194 } else if (inuma <= inumb)
195 return -1;
196
197 return 1;
198 }
199
200 /**
201 * sort_nodes - sort nodes for GC.
202 * @c: UBIFS file-system description object
203 * @sleb: describes nodes to sort and contains the result on exit
204 * @nondata: contains non-data nodes on exit
205 * @min: minimum node size is returned here
206 *
207 * This function sorts the list of inodes to garbage collect. First of all, it
208 * kills obsolete nodes and separates data and non-data nodes to the
209 * @sleb->nodes and @nondata lists correspondingly.
210 *
211 * Data nodes are then sorted in block number order - this is important for
212 * bulk-read; data nodes with lower inode number go before data nodes with
213 * higher inode number, and data nodes with lower block number go before data
214 * nodes with higher block number;
215 *
216 * Non-data nodes are sorted as follows.
217 * o First go inode nodes - they are sorted in descending length order.
218 * o Then go directory entry nodes - they are sorted in hash order, which
219 * should supposedly optimize 'readdir()'. Direntry nodes with lower parent
220 * inode number go before direntry nodes with higher parent inode number,
221 * and direntry nodes with lower name hash values go before direntry nodes
222 * with higher name hash values.
223 *
224 * This function returns zero in case of success and a negative error code in
225 * case of failure.
226 */
sort_nodes(struct ubifs_info * c,struct ubifs_scan_leb * sleb,struct list_head * nondata,int * min)227 static int sort_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
228 struct list_head *nondata, int *min)
229 {
230 int err;
231 struct ubifs_scan_node *snod, *tmp;
232
233 *min = INT_MAX;
234
235 /* Separate data nodes and non-data nodes */
236 list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
237 ubifs_assert(c, snod->type == UBIFS_INO_NODE ||
238 snod->type == UBIFS_DATA_NODE ||
239 snod->type == UBIFS_DENT_NODE ||
240 snod->type == UBIFS_XENT_NODE ||
241 snod->type == UBIFS_TRUN_NODE ||
242 snod->type == UBIFS_AUTH_NODE);
243
244 if (snod->type != UBIFS_INO_NODE &&
245 snod->type != UBIFS_DATA_NODE &&
246 snod->type != UBIFS_DENT_NODE &&
247 snod->type != UBIFS_XENT_NODE) {
248 /* Probably truncation node, zap it */
249 list_del(&snod->list);
250 kfree(snod);
251 continue;
252 }
253
254 ubifs_assert(c, key_type(c, &snod->key) == UBIFS_DATA_KEY ||
255 key_type(c, &snod->key) == UBIFS_INO_KEY ||
256 key_type(c, &snod->key) == UBIFS_DENT_KEY ||
257 key_type(c, &snod->key) == UBIFS_XENT_KEY);
258
259 err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
260 snod->offs, 0);
261 if (err < 0)
262 return err;
263
264 if (!err) {
265 /* The node is obsolete, remove it from the list */
266 list_del(&snod->list);
267 kfree(snod);
268 continue;
269 }
270
271 if (snod->len < *min)
272 *min = snod->len;
273
274 if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
275 list_move_tail(&snod->list, nondata);
276 }
277
278 /* Sort data and non-data nodes */
279 list_sort(c, &sleb->nodes, &data_nodes_cmp);
280 list_sort(c, nondata, &nondata_nodes_cmp);
281
282 err = dbg_check_data_nodes_order(c, &sleb->nodes);
283 if (err)
284 return err;
285 err = dbg_check_nondata_nodes_order(c, nondata);
286 if (err)
287 return err;
288 return 0;
289 }
290
291 /**
292 * move_node - move a node.
293 * @c: UBIFS file-system description object
294 * @sleb: describes the LEB to move nodes from
295 * @snod: the mode to move
296 * @wbuf: write-buffer to move node to
297 *
298 * This function moves node @snod to @wbuf, changes TNC correspondingly, and
299 * destroys @snod. Returns zero in case of success and a negative error code in
300 * case of failure.
301 */
move_node(struct ubifs_info * c,struct ubifs_scan_leb * sleb,struct ubifs_scan_node * snod,struct ubifs_wbuf * wbuf)302 static int move_node(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
303 struct ubifs_scan_node *snod, struct ubifs_wbuf *wbuf)
304 {
305 int err, new_lnum = wbuf->lnum, new_offs = wbuf->offs + wbuf->used;
306
307 cond_resched();
308 err = ubifs_wbuf_write_nolock(wbuf, snod->node, snod->len);
309 if (err)
310 return err;
311
312 err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
313 snod->offs, new_lnum, new_offs,
314 snod->len);
315 list_del(&snod->list);
316 kfree(snod);
317 return err;
318 }
319
320 /**
321 * move_nodes - move nodes.
322 * @c: UBIFS file-system description object
323 * @sleb: describes the LEB to move nodes from
324 *
325 * This function moves valid nodes from data LEB described by @sleb to the GC
326 * journal head. This function returns zero in case of success, %-EAGAIN if
327 * commit is required, and other negative error codes in case of other
328 * failures.
329 */
move_nodes(struct ubifs_info * c,struct ubifs_scan_leb * sleb)330 static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
331 {
332 int err, min;
333 LIST_HEAD(nondata);
334 struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
335
336 if (wbuf->lnum == -1) {
337 /*
338 * The GC journal head is not set, because it is the first GC
339 * invocation since mount.
340 */
341 err = switch_gc_head(c);
342 if (err)
343 return err;
344 }
345
346 err = sort_nodes(c, sleb, &nondata, &min);
347 if (err)
348 goto out;
349
350 /* Write nodes to their new location. Use the first-fit strategy */
351 while (1) {
352 int avail, moved = 0;
353 struct ubifs_scan_node *snod, *tmp;
354
355 /* Move data nodes */
356 list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
357 avail = c->leb_size - wbuf->offs - wbuf->used -
358 ubifs_auth_node_sz(c);
359 if (snod->len > avail)
360 /*
361 * Do not skip data nodes in order to optimize
362 * bulk-read.
363 */
364 break;
365
366 err = ubifs_shash_update(c, c->jheads[GCHD].log_hash,
367 snod->node, snod->len);
368 if (err)
369 goto out;
370
371 err = move_node(c, sleb, snod, wbuf);
372 if (err)
373 goto out;
374 moved = 1;
375 }
376
377 /* Move non-data nodes */
378 list_for_each_entry_safe(snod, tmp, &nondata, list) {
379 avail = c->leb_size - wbuf->offs - wbuf->used -
380 ubifs_auth_node_sz(c);
381 if (avail < min)
382 break;
383
384 if (snod->len > avail) {
385 /*
386 * Keep going only if this is an inode with
387 * some data. Otherwise stop and switch the GC
388 * head. IOW, we assume that data-less inode
389 * nodes and direntry nodes are roughly of the
390 * same size.
391 */
392 if (key_type(c, &snod->key) == UBIFS_DENT_KEY ||
393 snod->len == UBIFS_INO_NODE_SZ)
394 break;
395 continue;
396 }
397
398 err = ubifs_shash_update(c, c->jheads[GCHD].log_hash,
399 snod->node, snod->len);
400 if (err)
401 goto out;
402
403 err = move_node(c, sleb, snod, wbuf);
404 if (err)
405 goto out;
406 moved = 1;
407 }
408
409 if (ubifs_authenticated(c) && moved) {
410 struct ubifs_auth_node *auth;
411
412 auth = kmalloc(ubifs_auth_node_sz(c), GFP_NOFS);
413 if (!auth) {
414 err = -ENOMEM;
415 goto out;
416 }
417
418 err = ubifs_prepare_auth_node(c, auth,
419 c->jheads[GCHD].log_hash);
420 if (err) {
421 kfree(auth);
422 goto out;
423 }
424
425 err = ubifs_wbuf_write_nolock(wbuf, auth,
426 ubifs_auth_node_sz(c));
427 if (err) {
428 kfree(auth);
429 goto out;
430 }
431
432 ubifs_add_dirt(c, wbuf->lnum, ubifs_auth_node_sz(c));
433 }
434
435 if (list_empty(&sleb->nodes) && list_empty(&nondata))
436 break;
437
438 /*
439 * Waste the rest of the space in the LEB and switch to the
440 * next LEB.
441 */
442 err = switch_gc_head(c);
443 if (err)
444 goto out;
445 }
446
447 return 0;
448
449 out:
450 list_splice_tail(&nondata, &sleb->nodes);
451 return err;
452 }
453
454 /**
455 * gc_sync_wbufs - sync write-buffers for GC.
456 * @c: UBIFS file-system description object
457 *
458 * We must guarantee that obsoleting nodes are on flash. Unfortunately they may
459 * be in a write-buffer instead. That is, a node could be written to a
460 * write-buffer, obsoleting another node in a LEB that is GC'd. If that LEB is
461 * erased before the write-buffer is sync'd and then there is an unclean
462 * unmount, then an existing node is lost. To avoid this, we sync all
463 * write-buffers.
464 *
465 * This function returns %0 on success or a negative error code on failure.
466 */
gc_sync_wbufs(struct ubifs_info * c)467 static int gc_sync_wbufs(struct ubifs_info *c)
468 {
469 int err, i;
470
471 for (i = 0; i < c->jhead_cnt; i++) {
472 if (i == GCHD)
473 continue;
474 err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
475 if (err)
476 return err;
477 }
478 return 0;
479 }
480
481 /**
482 * ubifs_garbage_collect_leb - garbage-collect a logical eraseblock.
483 * @c: UBIFS file-system description object
484 * @lp: describes the LEB to garbage collect
485 *
486 * This function garbage-collects an LEB and returns one of the @LEB_FREED,
487 * @LEB_RETAINED, etc positive codes in case of success, %-EAGAIN if commit is
488 * required, and other negative error codes in case of failures.
489 */
ubifs_garbage_collect_leb(struct ubifs_info * c,struct ubifs_lprops * lp)490 int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
491 {
492 struct ubifs_scan_leb *sleb;
493 struct ubifs_scan_node *snod;
494 struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
495 int err = 0, lnum = lp->lnum;
496
497 ubifs_assert(c, c->gc_lnum != -1 || wbuf->offs + wbuf->used == 0 ||
498 c->need_recovery);
499 ubifs_assert(c, c->gc_lnum != lnum);
500 ubifs_assert(c, wbuf->lnum != lnum);
501
502 if (lp->free + lp->dirty == c->leb_size) {
503 /* Special case - a free LEB */
504 dbg_gc("LEB %d is free, return it", lp->lnum);
505 ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
506
507 if (lp->free != c->leb_size) {
508 /*
509 * Write buffers must be sync'd before unmapping
510 * freeable LEBs, because one of them may contain data
511 * which obsoletes something in 'lp->lnum'.
512 */
513 err = gc_sync_wbufs(c);
514 if (err)
515 return err;
516 err = ubifs_change_one_lp(c, lp->lnum, c->leb_size,
517 0, 0, 0, 0);
518 if (err)
519 return err;
520 }
521 err = ubifs_leb_unmap(c, lp->lnum);
522 if (err)
523 return err;
524
525 if (c->gc_lnum == -1) {
526 c->gc_lnum = lnum;
527 return LEB_RETAINED;
528 }
529
530 return LEB_FREED;
531 }
532
533 /*
534 * We scan the entire LEB even though we only really need to scan up to
535 * (c->leb_size - lp->free).
536 */
537 sleb = ubifs_scan(c, lnum, 0, c->sbuf, 0);
538 if (IS_ERR(sleb))
539 return PTR_ERR(sleb);
540
541 ubifs_assert(c, !list_empty(&sleb->nodes));
542 snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
543
544 if (snod->type == UBIFS_IDX_NODE) {
545 struct ubifs_gced_idx_leb *idx_gc;
546
547 dbg_gc("indexing LEB %d (free %d, dirty %d)",
548 lnum, lp->free, lp->dirty);
549 list_for_each_entry(snod, &sleb->nodes, list) {
550 struct ubifs_idx_node *idx = snod->node;
551 int level = le16_to_cpu(idx->level);
552
553 ubifs_assert(c, snod->type == UBIFS_IDX_NODE);
554 key_read(c, ubifs_idx_key(c, idx), &snod->key);
555 err = ubifs_dirty_idx_node(c, &snod->key, level, lnum,
556 snod->offs);
557 if (err)
558 goto out;
559 }
560
561 idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
562 if (!idx_gc) {
563 err = -ENOMEM;
564 goto out;
565 }
566
567 idx_gc->lnum = lnum;
568 idx_gc->unmap = 0;
569 list_add(&idx_gc->list, &c->idx_gc);
570
571 /*
572 * Don't release the LEB until after the next commit, because
573 * it may contain data which is needed for recovery. So
574 * although we freed this LEB, it will become usable only after
575 * the commit.
576 */
577 err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0,
578 LPROPS_INDEX, 1);
579 if (err)
580 goto out;
581 err = LEB_FREED_IDX;
582 } else {
583 dbg_gc("data LEB %d (free %d, dirty %d)",
584 lnum, lp->free, lp->dirty);
585
586 err = move_nodes(c, sleb);
587 if (err)
588 goto out_inc_seq;
589
590 err = gc_sync_wbufs(c);
591 if (err)
592 goto out_inc_seq;
593
594 err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0, 0, 0);
595 if (err)
596 goto out_inc_seq;
597
598 /* Allow for races with TNC */
599 c->gced_lnum = lnum;
600 smp_wmb();
601 c->gc_seq += 1;
602 smp_wmb();
603
604 if (c->gc_lnum == -1) {
605 c->gc_lnum = lnum;
606 err = LEB_RETAINED;
607 } else {
608 err = ubifs_wbuf_sync_nolock(wbuf);
609 if (err)
610 goto out;
611
612 err = ubifs_leb_unmap(c, lnum);
613 if (err)
614 goto out;
615
616 err = LEB_FREED;
617 }
618 }
619
620 out:
621 ubifs_scan_destroy(sleb);
622 return err;
623
624 out_inc_seq:
625 /* We may have moved at least some nodes so allow for races with TNC */
626 c->gced_lnum = lnum;
627 smp_wmb();
628 c->gc_seq += 1;
629 smp_wmb();
630 goto out;
631 }
632
633 /**
634 * ubifs_garbage_collect - UBIFS garbage collector.
635 * @c: UBIFS file-system description object
636 * @anyway: do GC even if there are free LEBs
637 *
638 * This function does out-of-place garbage collection. The return codes are:
639 * o positive LEB number if the LEB has been freed and may be used;
640 * o %-EAGAIN if the caller has to run commit;
641 * o %-ENOSPC if GC failed to make any progress;
642 * o other negative error codes in case of other errors.
643 *
644 * Garbage collector writes data to the journal when GC'ing data LEBs, and just
645 * marking indexing nodes dirty when GC'ing indexing LEBs. Thus, at some point
646 * commit may be required. But commit cannot be run from inside GC, because the
647 * caller might be holding the commit lock, so %-EAGAIN is returned instead;
648 * And this error code means that the caller has to run commit, and re-run GC
649 * if there is still no free space.
650 *
651 * There are many reasons why this function may return %-EAGAIN:
652 * o the log is full and there is no space to write an LEB reference for
653 * @c->gc_lnum;
654 * o the journal is too large and exceeds size limitations;
655 * o GC moved indexing LEBs, but they can be used only after the commit;
656 * o the shrinker fails to find clean znodes to free and requests the commit;
657 * o etc.
658 *
659 * Note, if the file-system is close to be full, this function may return
660 * %-EAGAIN infinitely, so the caller has to limit amount of re-invocations of
661 * the function. E.g., this happens if the limits on the journal size are too
662 * tough and GC writes too much to the journal before an LEB is freed. This
663 * might also mean that the journal is too large, and the TNC becomes to big,
664 * so that the shrinker is constantly called, finds not clean znodes to free,
665 * and requests commit. Well, this may also happen if the journal is all right,
666 * but another kernel process consumes too much memory. Anyway, infinite
667 * %-EAGAIN may happen, but in some extreme/misconfiguration cases.
668 */
ubifs_garbage_collect(struct ubifs_info * c,int anyway)669 int ubifs_garbage_collect(struct ubifs_info *c, int anyway)
670 {
671 int i, err, ret, min_space = c->dead_wm;
672 struct ubifs_lprops lp;
673 struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
674
675 ubifs_assert_cmt_locked(c);
676 ubifs_assert(c, !c->ro_media && !c->ro_mount);
677
678 if (ubifs_gc_should_commit(c))
679 return -EAGAIN;
680
681 mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
682
683 if (c->ro_error) {
684 ret = -EROFS;
685 goto out_unlock;
686 }
687
688 /* We expect the write-buffer to be empty on entry */
689 ubifs_assert(c, !wbuf->used);
690
691 for (i = 0; ; i++) {
692 int space_before, space_after;
693
694 cond_resched();
695
696 /* Give the commit an opportunity to run */
697 if (ubifs_gc_should_commit(c)) {
698 ret = -EAGAIN;
699 break;
700 }
701
702 if (i > SOFT_LEBS_LIMIT && !list_empty(&c->idx_gc)) {
703 /*
704 * We've done enough iterations. Indexing LEBs were
705 * moved and will be available after the commit.
706 */
707 dbg_gc("soft limit, some index LEBs GC'ed, -EAGAIN");
708 ubifs_commit_required(c);
709 ret = -EAGAIN;
710 break;
711 }
712
713 if (i > HARD_LEBS_LIMIT) {
714 /*
715 * We've moved too many LEBs and have not made
716 * progress, give up.
717 */
718 dbg_gc("hard limit, -ENOSPC");
719 ret = -ENOSPC;
720 break;
721 }
722
723 /*
724 * Empty and freeable LEBs can turn up while we waited for
725 * the wbuf lock, or while we have been running GC. In that
726 * case, we should just return one of those instead of
727 * continuing to GC dirty LEBs. Hence we request
728 * 'ubifs_find_dirty_leb()' to return an empty LEB if it can.
729 */
730 ret = ubifs_find_dirty_leb(c, &lp, min_space, anyway ? 0 : 1);
731 if (ret) {
732 if (ret == -ENOSPC)
733 dbg_gc("no more dirty LEBs");
734 break;
735 }
736
737 dbg_gc("found LEB %d: free %d, dirty %d, sum %d (min. space %d)",
738 lp.lnum, lp.free, lp.dirty, lp.free + lp.dirty,
739 min_space);
740
741 space_before = c->leb_size - wbuf->offs - wbuf->used;
742 if (wbuf->lnum == -1)
743 space_before = 0;
744
745 ret = ubifs_garbage_collect_leb(c, &lp);
746 if (ret < 0) {
747 if (ret == -EAGAIN) {
748 /*
749 * This is not error, so we have to return the
750 * LEB to lprops. But if 'ubifs_return_leb()'
751 * fails, its failure code is propagated to the
752 * caller instead of the original '-EAGAIN'.
753 */
754 err = ubifs_return_leb(c, lp.lnum);
755 if (err)
756 ret = err;
757 break;
758 }
759 goto out;
760 }
761
762 if (ret == LEB_FREED) {
763 /* An LEB has been freed and is ready for use */
764 dbg_gc("LEB %d freed, return", lp.lnum);
765 ret = lp.lnum;
766 break;
767 }
768
769 if (ret == LEB_FREED_IDX) {
770 /*
771 * This was an indexing LEB and it cannot be
772 * immediately used. And instead of requesting the
773 * commit straight away, we try to garbage collect some
774 * more.
775 */
776 dbg_gc("indexing LEB %d freed, continue", lp.lnum);
777 continue;
778 }
779
780 ubifs_assert(c, ret == LEB_RETAINED);
781 space_after = c->leb_size - wbuf->offs - wbuf->used;
782 dbg_gc("LEB %d retained, freed %d bytes", lp.lnum,
783 space_after - space_before);
784
785 if (space_after > space_before) {
786 /* GC makes progress, keep working */
787 min_space >>= 1;
788 if (min_space < c->dead_wm)
789 min_space = c->dead_wm;
790 continue;
791 }
792
793 dbg_gc("did not make progress");
794
795 /*
796 * GC moved an LEB bud have not done any progress. This means
797 * that the previous GC head LEB contained too few free space
798 * and the LEB which was GC'ed contained only large nodes which
799 * did not fit that space.
800 *
801 * We can do 2 things:
802 * 1. pick another LEB in a hope it'll contain a small node
803 * which will fit the space we have at the end of current GC
804 * head LEB, but there is no guarantee, so we try this out
805 * unless we have already been working for too long;
806 * 2. request an LEB with more dirty space, which will force
807 * 'ubifs_find_dirty_leb()' to start scanning the lprops
808 * table, instead of just picking one from the heap
809 * (previously it already picked the dirtiest LEB).
810 */
811 if (i < SOFT_LEBS_LIMIT) {
812 dbg_gc("try again");
813 continue;
814 }
815
816 min_space <<= 1;
817 if (min_space > c->dark_wm)
818 min_space = c->dark_wm;
819 dbg_gc("set min. space to %d", min_space);
820 }
821
822 if (ret == -ENOSPC && !list_empty(&c->idx_gc)) {
823 dbg_gc("no space, some index LEBs GC'ed, -EAGAIN");
824 ubifs_commit_required(c);
825 ret = -EAGAIN;
826 }
827
828 err = ubifs_wbuf_sync_nolock(wbuf);
829 if (!err)
830 err = ubifs_leb_unmap(c, c->gc_lnum);
831 if (err) {
832 ret = err;
833 goto out;
834 }
835 out_unlock:
836 mutex_unlock(&wbuf->io_mutex);
837 return ret;
838
839 out:
840 ubifs_assert(c, ret < 0);
841 ubifs_assert(c, ret != -ENOSPC && ret != -EAGAIN);
842 ubifs_wbuf_sync_nolock(wbuf);
843 ubifs_ro_mode(c, ret);
844 mutex_unlock(&wbuf->io_mutex);
845 ubifs_return_leb(c, lp.lnum);
846 return ret;
847 }
848
849 /**
850 * ubifs_gc_start_commit - garbage collection at start of commit.
851 * @c: UBIFS file-system description object
852 *
853 * If a LEB has only dirty and free space, then we may safely unmap it and make
854 * it free. Note, we cannot do this with indexing LEBs because dirty space may
855 * correspond index nodes that are required for recovery. In that case, the
856 * LEB cannot be unmapped until after the next commit.
857 *
858 * This function returns %0 upon success and a negative error code upon failure.
859 */
ubifs_gc_start_commit(struct ubifs_info * c)860 int ubifs_gc_start_commit(struct ubifs_info *c)
861 {
862 struct ubifs_gced_idx_leb *idx_gc;
863 const struct ubifs_lprops *lp;
864 int err = 0, flags;
865
866 ubifs_get_lprops(c);
867
868 /*
869 * Unmap (non-index) freeable LEBs. Note that recovery requires that all
870 * wbufs are sync'd before this, which is done in 'do_commit()'.
871 */
872 while (1) {
873 lp = ubifs_fast_find_freeable(c);
874 if (!lp)
875 break;
876 ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
877 ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
878 err = ubifs_leb_unmap(c, lp->lnum);
879 if (err)
880 goto out;
881 lp = ubifs_change_lp(c, lp, c->leb_size, 0, lp->flags, 0);
882 if (IS_ERR(lp)) {
883 err = PTR_ERR(lp);
884 goto out;
885 }
886 ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
887 ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
888 }
889
890 /* Mark GC'd index LEBs OK to unmap after this commit finishes */
891 list_for_each_entry(idx_gc, &c->idx_gc, list)
892 idx_gc->unmap = 1;
893
894 /* Record index freeable LEBs for unmapping after commit */
895 while (1) {
896 lp = ubifs_fast_find_frdi_idx(c);
897 if (IS_ERR(lp)) {
898 err = PTR_ERR(lp);
899 goto out;
900 }
901 if (!lp)
902 break;
903 idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
904 if (!idx_gc) {
905 err = -ENOMEM;
906 goto out;
907 }
908 ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
909 ubifs_assert(c, lp->flags & LPROPS_INDEX);
910 /* Don't release the LEB until after the next commit */
911 flags = (lp->flags | LPROPS_TAKEN) ^ LPROPS_INDEX;
912 lp = ubifs_change_lp(c, lp, c->leb_size, 0, flags, 1);
913 if (IS_ERR(lp)) {
914 err = PTR_ERR(lp);
915 kfree(idx_gc);
916 goto out;
917 }
918 ubifs_assert(c, lp->flags & LPROPS_TAKEN);
919 ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
920 idx_gc->lnum = lp->lnum;
921 idx_gc->unmap = 1;
922 list_add(&idx_gc->list, &c->idx_gc);
923 }
924 out:
925 ubifs_release_lprops(c);
926 return err;
927 }
928
929 /**
930 * ubifs_gc_end_commit - garbage collection at end of commit.
931 * @c: UBIFS file-system description object
932 *
933 * This function completes out-of-place garbage collection of index LEBs.
934 */
ubifs_gc_end_commit(struct ubifs_info * c)935 int ubifs_gc_end_commit(struct ubifs_info *c)
936 {
937 struct ubifs_gced_idx_leb *idx_gc, *tmp;
938 struct ubifs_wbuf *wbuf;
939 int err = 0;
940
941 wbuf = &c->jheads[GCHD].wbuf;
942 mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
943 list_for_each_entry_safe(idx_gc, tmp, &c->idx_gc, list)
944 if (idx_gc->unmap) {
945 dbg_gc("LEB %d", idx_gc->lnum);
946 err = ubifs_leb_unmap(c, idx_gc->lnum);
947 if (err)
948 goto out;
949 err = ubifs_change_one_lp(c, idx_gc->lnum, LPROPS_NC,
950 LPROPS_NC, 0, LPROPS_TAKEN, -1);
951 if (err)
952 goto out;
953 list_del(&idx_gc->list);
954 kfree(idx_gc);
955 }
956 out:
957 mutex_unlock(&wbuf->io_mutex);
958 return err;
959 }
960
961 /**
962 * ubifs_destroy_idx_gc - destroy idx_gc list.
963 * @c: UBIFS file-system description object
964 *
965 * This function destroys the @c->idx_gc list. It is called when unmounting
966 * so locks are not needed. Returns zero in case of success and a negative
967 * error code in case of failure.
968 */
ubifs_destroy_idx_gc(struct ubifs_info * c)969 void ubifs_destroy_idx_gc(struct ubifs_info *c)
970 {
971 while (!list_empty(&c->idx_gc)) {
972 struct ubifs_gced_idx_leb *idx_gc;
973
974 idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb,
975 list);
976 c->idx_gc_cnt -= 1;
977 list_del(&idx_gc->list);
978 kfree(idx_gc);
979 }
980 }
981
982 /**
983 * ubifs_get_idx_gc_leb - get a LEB from GC'd index LEB list.
984 * @c: UBIFS file-system description object
985 *
986 * Called during start commit so locks are not needed.
987 */
ubifs_get_idx_gc_leb(struct ubifs_info * c)988 int ubifs_get_idx_gc_leb(struct ubifs_info *c)
989 {
990 struct ubifs_gced_idx_leb *idx_gc;
991 int lnum;
992
993 if (list_empty(&c->idx_gc))
994 return -ENOSPC;
995 idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb, list);
996 lnum = idx_gc->lnum;
997 /* c->idx_gc_cnt is updated by the caller when lprops are updated */
998 list_del(&idx_gc->list);
999 kfree(idx_gc);
1000 return lnum;
1001 }
1002