1 /*
2  * This file is part of UBIFS.
3  *
4  * Copyright (C) 2006-2008 Nokia Corporation.
5  *
6  * This program is free software; you can redistribute it and/or modify it
7  * under the terms of the GNU General Public License version 2 as published by
8  * the Free Software Foundation.
9  *
10  * This program is distributed in the hope that it will be useful, but WITHOUT
11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
13  * more details.
14  *
15  * You should have received a copy of the GNU General Public License along with
16  * this program; if not, write to the Free Software Foundation, Inc., 51
17  * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
18  *
19  * Authors: Adrian Hunter
20  *          Artem Bityutskiy (Битюцкий Артём)
21  */
22 
23 /*
24  * This file implements garbage collection. The procedure for garbage collection
25  * is different depending on whether a LEB as an index LEB (contains index
26  * nodes) or not. For non-index LEBs, garbage collection finds a LEB which
27  * contains a lot of dirty space (obsolete nodes), and copies the non-obsolete
28  * nodes to the journal, at which point the garbage-collected LEB is free to be
29  * reused. For index LEBs, garbage collection marks the non-obsolete index nodes
30  * dirty in the TNC, and after the next commit, the garbage-collected LEB is
31  * to be reused. Garbage collection will cause the number of dirty index nodes
32  * to grow, however sufficient space is reserved for the index to ensure the
33  * commit will never run out of space.
34  *
35  * Notes about dead watermark. At current UBIFS implementation we assume that
36  * LEBs which have less than @c->dead_wm bytes of free + dirty space are full
37  * and not worth garbage-collecting. The dead watermark is one min. I/O unit
38  * size, or min. UBIFS node size, depending on what is greater. Indeed, UBIFS
39  * Garbage Collector has to synchronize the GC head's write buffer before
40  * returning, so this is about wasting one min. I/O unit. However, UBIFS GC can
41  * actually reclaim even very small pieces of dirty space by garbage collecting
42  * enough dirty LEBs, but we do not bother doing this at this implementation.
43  *
44  * Notes about dark watermark. The results of GC work depends on how big are
45  * the UBIFS nodes GC deals with. Large nodes make GC waste more space. Indeed,
46  * if GC move data from LEB A to LEB B and nodes in LEB A are large, GC would
47  * have to waste large pieces of free space at the end of LEB B, because nodes
48  * from LEB A would not fit. And the worst situation is when all nodes are of
49  * maximum size. So dark watermark is the amount of free + dirty space in LEB
50  * which are guaranteed to be reclaimable. If LEB has less space, the GC might
51  * be unable to reclaim it. So, LEBs with free + dirty greater than dark
52  * watermark are "good" LEBs from GC's point of view. The other LEBs are not so
53  * good, and GC takes extra care when moving them.
54  */
55 
56 #include <linux/slab.h>
57 #include <linux/pagemap.h>
58 #include <linux/list_sort.h>
59 #include "ubifs.h"
60 
61 /*
62  * GC may need to move more than one LEB to make progress. The below constants
63  * define "soft" and "hard" limits on the number of LEBs the garbage collector
64  * may move.
65  */
66 #define SOFT_LEBS_LIMIT 4
67 #define HARD_LEBS_LIMIT 32
68 
69 /**
70  * switch_gc_head - switch the garbage collection journal head.
71  * @c: UBIFS file-system description object
72  * @buf: buffer to write
73  * @len: length of the buffer to write
74  * @lnum: LEB number written is returned here
75  * @offs: offset written is returned here
76  *
77  * This function switch the GC head to the next LEB which is reserved in
78  * @c->gc_lnum. Returns %0 in case of success, %-EAGAIN if commit is required,
79  * and other negative error code in case of failures.
80  */
switch_gc_head(struct ubifs_info * c)81 static int switch_gc_head(struct ubifs_info *c)
82 {
83 	int err, gc_lnum = c->gc_lnum;
84 	struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
85 
86 	ubifs_assert(c, gc_lnum != -1);
87 	dbg_gc("switch GC head from LEB %d:%d to LEB %d (waste %d bytes)",
88 	       wbuf->lnum, wbuf->offs + wbuf->used, gc_lnum,
89 	       c->leb_size - wbuf->offs - wbuf->used);
90 
91 	err = ubifs_wbuf_sync_nolock(wbuf);
92 	if (err)
93 		return err;
94 
95 	/*
96 	 * The GC write-buffer was synchronized, we may safely unmap
97 	 * 'c->gc_lnum'.
98 	 */
99 	err = ubifs_leb_unmap(c, gc_lnum);
100 	if (err)
101 		return err;
102 
103 	err = ubifs_add_bud_to_log(c, GCHD, gc_lnum, 0);
104 	if (err)
105 		return err;
106 
107 	c->gc_lnum = -1;
108 	err = ubifs_wbuf_seek_nolock(wbuf, gc_lnum, 0);
109 	return err;
110 }
111 
112 /**
113  * data_nodes_cmp - compare 2 data nodes.
114  * @priv: UBIFS file-system description object
115  * @a: first data node
116  * @b: second data node
117  *
118  * This function compares data nodes @a and @b. Returns %1 if @a has greater
119  * inode or block number, and %-1 otherwise.
120  */
data_nodes_cmp(void * priv,struct list_head * a,struct list_head * b)121 static int data_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
122 {
123 	ino_t inuma, inumb;
124 	struct ubifs_info *c = priv;
125 	struct ubifs_scan_node *sa, *sb;
126 
127 	cond_resched();
128 	if (a == b)
129 		return 0;
130 
131 	sa = list_entry(a, struct ubifs_scan_node, list);
132 	sb = list_entry(b, struct ubifs_scan_node, list);
133 
134 	ubifs_assert(c, key_type(c, &sa->key) == UBIFS_DATA_KEY);
135 	ubifs_assert(c, key_type(c, &sb->key) == UBIFS_DATA_KEY);
136 	ubifs_assert(c, sa->type == UBIFS_DATA_NODE);
137 	ubifs_assert(c, sb->type == UBIFS_DATA_NODE);
138 
139 	inuma = key_inum(c, &sa->key);
140 	inumb = key_inum(c, &sb->key);
141 
142 	if (inuma == inumb) {
143 		unsigned int blka = key_block(c, &sa->key);
144 		unsigned int blkb = key_block(c, &sb->key);
145 
146 		if (blka <= blkb)
147 			return -1;
148 	} else if (inuma <= inumb)
149 		return -1;
150 
151 	return 1;
152 }
153 
154 /*
155  * nondata_nodes_cmp - compare 2 non-data nodes.
156  * @priv: UBIFS file-system description object
157  * @a: first node
158  * @a: second node
159  *
160  * This function compares nodes @a and @b. It makes sure that inode nodes go
161  * first and sorted by length in descending order. Directory entry nodes go
162  * after inode nodes and are sorted in ascending hash valuer order.
163  */
nondata_nodes_cmp(void * priv,struct list_head * a,struct list_head * b)164 static int nondata_nodes_cmp(void *priv, struct list_head *a,
165 			     struct list_head *b)
166 {
167 	ino_t inuma, inumb;
168 	struct ubifs_info *c = priv;
169 	struct ubifs_scan_node *sa, *sb;
170 
171 	cond_resched();
172 	if (a == b)
173 		return 0;
174 
175 	sa = list_entry(a, struct ubifs_scan_node, list);
176 	sb = list_entry(b, struct ubifs_scan_node, list);
177 
178 	ubifs_assert(c, key_type(c, &sa->key) != UBIFS_DATA_KEY &&
179 		     key_type(c, &sb->key) != UBIFS_DATA_KEY);
180 	ubifs_assert(c, sa->type != UBIFS_DATA_NODE &&
181 		     sb->type != UBIFS_DATA_NODE);
182 
183 	/* Inodes go before directory entries */
184 	if (sa->type == UBIFS_INO_NODE) {
185 		if (sb->type == UBIFS_INO_NODE)
186 			return sb->len - sa->len;
187 		return -1;
188 	}
189 	if (sb->type == UBIFS_INO_NODE)
190 		return 1;
191 
192 	ubifs_assert(c, key_type(c, &sa->key) == UBIFS_DENT_KEY ||
193 		     key_type(c, &sa->key) == UBIFS_XENT_KEY);
194 	ubifs_assert(c, key_type(c, &sb->key) == UBIFS_DENT_KEY ||
195 		     key_type(c, &sb->key) == UBIFS_XENT_KEY);
196 	ubifs_assert(c, sa->type == UBIFS_DENT_NODE ||
197 		     sa->type == UBIFS_XENT_NODE);
198 	ubifs_assert(c, sb->type == UBIFS_DENT_NODE ||
199 		     sb->type == UBIFS_XENT_NODE);
200 
201 	inuma = key_inum(c, &sa->key);
202 	inumb = key_inum(c, &sb->key);
203 
204 	if (inuma == inumb) {
205 		uint32_t hasha = key_hash(c, &sa->key);
206 		uint32_t hashb = key_hash(c, &sb->key);
207 
208 		if (hasha <= hashb)
209 			return -1;
210 	} else if (inuma <= inumb)
211 		return -1;
212 
213 	return 1;
214 }
215 
216 /**
217  * sort_nodes - sort nodes for GC.
218  * @c: UBIFS file-system description object
219  * @sleb: describes nodes to sort and contains the result on exit
220  * @nondata: contains non-data nodes on exit
221  * @min: minimum node size is returned here
222  *
223  * This function sorts the list of inodes to garbage collect. First of all, it
224  * kills obsolete nodes and separates data and non-data nodes to the
225  * @sleb->nodes and @nondata lists correspondingly.
226  *
227  * Data nodes are then sorted in block number order - this is important for
228  * bulk-read; data nodes with lower inode number go before data nodes with
229  * higher inode number, and data nodes with lower block number go before data
230  * nodes with higher block number;
231  *
232  * Non-data nodes are sorted as follows.
233  *   o First go inode nodes - they are sorted in descending length order.
234  *   o Then go directory entry nodes - they are sorted in hash order, which
235  *     should supposedly optimize 'readdir()'. Direntry nodes with lower parent
236  *     inode number go before direntry nodes with higher parent inode number,
237  *     and direntry nodes with lower name hash values go before direntry nodes
238  *     with higher name hash values.
239  *
240  * This function returns zero in case of success and a negative error code in
241  * case of failure.
242  */
sort_nodes(struct ubifs_info * c,struct ubifs_scan_leb * sleb,struct list_head * nondata,int * min)243 static int sort_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
244 		      struct list_head *nondata, int *min)
245 {
246 	int err;
247 	struct ubifs_scan_node *snod, *tmp;
248 
249 	*min = INT_MAX;
250 
251 	/* Separate data nodes and non-data nodes */
252 	list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
253 		ubifs_assert(c, snod->type == UBIFS_INO_NODE  ||
254 			     snod->type == UBIFS_DATA_NODE ||
255 			     snod->type == UBIFS_DENT_NODE ||
256 			     snod->type == UBIFS_XENT_NODE ||
257 			     snod->type == UBIFS_TRUN_NODE);
258 
259 		if (snod->type != UBIFS_INO_NODE  &&
260 		    snod->type != UBIFS_DATA_NODE &&
261 		    snod->type != UBIFS_DENT_NODE &&
262 		    snod->type != UBIFS_XENT_NODE) {
263 			/* Probably truncation node, zap it */
264 			list_del(&snod->list);
265 			kfree(snod);
266 			continue;
267 		}
268 
269 		ubifs_assert(c, key_type(c, &snod->key) == UBIFS_DATA_KEY ||
270 			     key_type(c, &snod->key) == UBIFS_INO_KEY  ||
271 			     key_type(c, &snod->key) == UBIFS_DENT_KEY ||
272 			     key_type(c, &snod->key) == UBIFS_XENT_KEY);
273 
274 		err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
275 					 snod->offs, 0);
276 		if (err < 0)
277 			return err;
278 
279 		if (!err) {
280 			/* The node is obsolete, remove it from the list */
281 			list_del(&snod->list);
282 			kfree(snod);
283 			continue;
284 		}
285 
286 		if (snod->len < *min)
287 			*min = snod->len;
288 
289 		if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
290 			list_move_tail(&snod->list, nondata);
291 	}
292 
293 	/* Sort data and non-data nodes */
294 	list_sort(c, &sleb->nodes, &data_nodes_cmp);
295 	list_sort(c, nondata, &nondata_nodes_cmp);
296 
297 	err = dbg_check_data_nodes_order(c, &sleb->nodes);
298 	if (err)
299 		return err;
300 	err = dbg_check_nondata_nodes_order(c, nondata);
301 	if (err)
302 		return err;
303 	return 0;
304 }
305 
306 /**
307  * move_node - move a node.
308  * @c: UBIFS file-system description object
309  * @sleb: describes the LEB to move nodes from
310  * @snod: the mode to move
311  * @wbuf: write-buffer to move node to
312  *
313  * This function moves node @snod to @wbuf, changes TNC correspondingly, and
314  * destroys @snod. Returns zero in case of success and a negative error code in
315  * case of failure.
316  */
move_node(struct ubifs_info * c,struct ubifs_scan_leb * sleb,struct ubifs_scan_node * snod,struct ubifs_wbuf * wbuf)317 static int move_node(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
318 		     struct ubifs_scan_node *snod, struct ubifs_wbuf *wbuf)
319 {
320 	int err, new_lnum = wbuf->lnum, new_offs = wbuf->offs + wbuf->used;
321 
322 	cond_resched();
323 	err = ubifs_wbuf_write_nolock(wbuf, snod->node, snod->len);
324 	if (err)
325 		return err;
326 
327 	err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
328 				snod->offs, new_lnum, new_offs,
329 				snod->len);
330 	list_del(&snod->list);
331 	kfree(snod);
332 	return err;
333 }
334 
335 /**
336  * move_nodes - move nodes.
337  * @c: UBIFS file-system description object
338  * @sleb: describes the LEB to move nodes from
339  *
340  * This function moves valid nodes from data LEB described by @sleb to the GC
341  * journal head. This function returns zero in case of success, %-EAGAIN if
342  * commit is required, and other negative error codes in case of other
343  * failures.
344  */
move_nodes(struct ubifs_info * c,struct ubifs_scan_leb * sleb)345 static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
346 {
347 	int err, min;
348 	LIST_HEAD(nondata);
349 	struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
350 
351 	if (wbuf->lnum == -1) {
352 		/*
353 		 * The GC journal head is not set, because it is the first GC
354 		 * invocation since mount.
355 		 */
356 		err = switch_gc_head(c);
357 		if (err)
358 			return err;
359 	}
360 
361 	err = sort_nodes(c, sleb, &nondata, &min);
362 	if (err)
363 		goto out;
364 
365 	/* Write nodes to their new location. Use the first-fit strategy */
366 	while (1) {
367 		int avail;
368 		struct ubifs_scan_node *snod, *tmp;
369 
370 		/* Move data nodes */
371 		list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
372 			avail = c->leb_size - wbuf->offs - wbuf->used;
373 			if  (snod->len > avail)
374 				/*
375 				 * Do not skip data nodes in order to optimize
376 				 * bulk-read.
377 				 */
378 				break;
379 
380 			err = move_node(c, sleb, snod, wbuf);
381 			if (err)
382 				goto out;
383 		}
384 
385 		/* Move non-data nodes */
386 		list_for_each_entry_safe(snod, tmp, &nondata, list) {
387 			avail = c->leb_size - wbuf->offs - wbuf->used;
388 			if (avail < min)
389 				break;
390 
391 			if  (snod->len > avail) {
392 				/*
393 				 * Keep going only if this is an inode with
394 				 * some data. Otherwise stop and switch the GC
395 				 * head. IOW, we assume that data-less inode
396 				 * nodes and direntry nodes are roughly of the
397 				 * same size.
398 				 */
399 				if (key_type(c, &snod->key) == UBIFS_DENT_KEY ||
400 				    snod->len == UBIFS_INO_NODE_SZ)
401 					break;
402 				continue;
403 			}
404 
405 			err = move_node(c, sleb, snod, wbuf);
406 			if (err)
407 				goto out;
408 		}
409 
410 		if (list_empty(&sleb->nodes) && list_empty(&nondata))
411 			break;
412 
413 		/*
414 		 * Waste the rest of the space in the LEB and switch to the
415 		 * next LEB.
416 		 */
417 		err = switch_gc_head(c);
418 		if (err)
419 			goto out;
420 	}
421 
422 	return 0;
423 
424 out:
425 	list_splice_tail(&nondata, &sleb->nodes);
426 	return err;
427 }
428 
429 /**
430  * gc_sync_wbufs - sync write-buffers for GC.
431  * @c: UBIFS file-system description object
432  *
433  * We must guarantee that obsoleting nodes are on flash. Unfortunately they may
434  * be in a write-buffer instead. That is, a node could be written to a
435  * write-buffer, obsoleting another node in a LEB that is GC'd. If that LEB is
436  * erased before the write-buffer is sync'd and then there is an unclean
437  * unmount, then an existing node is lost. To avoid this, we sync all
438  * write-buffers.
439  *
440  * This function returns %0 on success or a negative error code on failure.
441  */
gc_sync_wbufs(struct ubifs_info * c)442 static int gc_sync_wbufs(struct ubifs_info *c)
443 {
444 	int err, i;
445 
446 	for (i = 0; i < c->jhead_cnt; i++) {
447 		if (i == GCHD)
448 			continue;
449 		err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
450 		if (err)
451 			return err;
452 	}
453 	return 0;
454 }
455 
456 /**
457  * ubifs_garbage_collect_leb - garbage-collect a logical eraseblock.
458  * @c: UBIFS file-system description object
459  * @lp: describes the LEB to garbage collect
460  *
461  * This function garbage-collects an LEB and returns one of the @LEB_FREED,
462  * @LEB_RETAINED, etc positive codes in case of success, %-EAGAIN if commit is
463  * required, and other negative error codes in case of failures.
464  */
ubifs_garbage_collect_leb(struct ubifs_info * c,struct ubifs_lprops * lp)465 int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
466 {
467 	struct ubifs_scan_leb *sleb;
468 	struct ubifs_scan_node *snod;
469 	struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
470 	int err = 0, lnum = lp->lnum;
471 
472 	ubifs_assert(c, c->gc_lnum != -1 || wbuf->offs + wbuf->used == 0 ||
473 		     c->need_recovery);
474 	ubifs_assert(c, c->gc_lnum != lnum);
475 	ubifs_assert(c, wbuf->lnum != lnum);
476 
477 	if (lp->free + lp->dirty == c->leb_size) {
478 		/* Special case - a free LEB  */
479 		dbg_gc("LEB %d is free, return it", lp->lnum);
480 		ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
481 
482 		if (lp->free != c->leb_size) {
483 			/*
484 			 * Write buffers must be sync'd before unmapping
485 			 * freeable LEBs, because one of them may contain data
486 			 * which obsoletes something in 'lp->lnum'.
487 			 */
488 			err = gc_sync_wbufs(c);
489 			if (err)
490 				return err;
491 			err = ubifs_change_one_lp(c, lp->lnum, c->leb_size,
492 						  0, 0, 0, 0);
493 			if (err)
494 				return err;
495 		}
496 		err = ubifs_leb_unmap(c, lp->lnum);
497 		if (err)
498 			return err;
499 
500 		if (c->gc_lnum == -1) {
501 			c->gc_lnum = lnum;
502 			return LEB_RETAINED;
503 		}
504 
505 		return LEB_FREED;
506 	}
507 
508 	/*
509 	 * We scan the entire LEB even though we only really need to scan up to
510 	 * (c->leb_size - lp->free).
511 	 */
512 	sleb = ubifs_scan(c, lnum, 0, c->sbuf, 0);
513 	if (IS_ERR(sleb))
514 		return PTR_ERR(sleb);
515 
516 	ubifs_assert(c, !list_empty(&sleb->nodes));
517 	snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
518 
519 	if (snod->type == UBIFS_IDX_NODE) {
520 		struct ubifs_gced_idx_leb *idx_gc;
521 
522 		dbg_gc("indexing LEB %d (free %d, dirty %d)",
523 		       lnum, lp->free, lp->dirty);
524 		list_for_each_entry(snod, &sleb->nodes, list) {
525 			struct ubifs_idx_node *idx = snod->node;
526 			int level = le16_to_cpu(idx->level);
527 
528 			ubifs_assert(c, snod->type == UBIFS_IDX_NODE);
529 			key_read(c, ubifs_idx_key(c, idx), &snod->key);
530 			err = ubifs_dirty_idx_node(c, &snod->key, level, lnum,
531 						   snod->offs);
532 			if (err)
533 				goto out;
534 		}
535 
536 		idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
537 		if (!idx_gc) {
538 			err = -ENOMEM;
539 			goto out;
540 		}
541 
542 		idx_gc->lnum = lnum;
543 		idx_gc->unmap = 0;
544 		list_add(&idx_gc->list, &c->idx_gc);
545 
546 		/*
547 		 * Don't release the LEB until after the next commit, because
548 		 * it may contain data which is needed for recovery. So
549 		 * although we freed this LEB, it will become usable only after
550 		 * the commit.
551 		 */
552 		err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0,
553 					  LPROPS_INDEX, 1);
554 		if (err)
555 			goto out;
556 		err = LEB_FREED_IDX;
557 	} else {
558 		dbg_gc("data LEB %d (free %d, dirty %d)",
559 		       lnum, lp->free, lp->dirty);
560 
561 		err = move_nodes(c, sleb);
562 		if (err)
563 			goto out_inc_seq;
564 
565 		err = gc_sync_wbufs(c);
566 		if (err)
567 			goto out_inc_seq;
568 
569 		err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0, 0, 0);
570 		if (err)
571 			goto out_inc_seq;
572 
573 		/* Allow for races with TNC */
574 		c->gced_lnum = lnum;
575 		smp_wmb();
576 		c->gc_seq += 1;
577 		smp_wmb();
578 
579 		if (c->gc_lnum == -1) {
580 			c->gc_lnum = lnum;
581 			err = LEB_RETAINED;
582 		} else {
583 			err = ubifs_wbuf_sync_nolock(wbuf);
584 			if (err)
585 				goto out;
586 
587 			err = ubifs_leb_unmap(c, lnum);
588 			if (err)
589 				goto out;
590 
591 			err = LEB_FREED;
592 		}
593 	}
594 
595 out:
596 	ubifs_scan_destroy(sleb);
597 	return err;
598 
599 out_inc_seq:
600 	/* We may have moved at least some nodes so allow for races with TNC */
601 	c->gced_lnum = lnum;
602 	smp_wmb();
603 	c->gc_seq += 1;
604 	smp_wmb();
605 	goto out;
606 }
607 
608 /**
609  * ubifs_garbage_collect - UBIFS garbage collector.
610  * @c: UBIFS file-system description object
611  * @anyway: do GC even if there are free LEBs
612  *
613  * This function does out-of-place garbage collection. The return codes are:
614  *   o positive LEB number if the LEB has been freed and may be used;
615  *   o %-EAGAIN if the caller has to run commit;
616  *   o %-ENOSPC if GC failed to make any progress;
617  *   o other negative error codes in case of other errors.
618  *
619  * Garbage collector writes data to the journal when GC'ing data LEBs, and just
620  * marking indexing nodes dirty when GC'ing indexing LEBs. Thus, at some point
621  * commit may be required. But commit cannot be run from inside GC, because the
622  * caller might be holding the commit lock, so %-EAGAIN is returned instead;
623  * And this error code means that the caller has to run commit, and re-run GC
624  * if there is still no free space.
625  *
626  * There are many reasons why this function may return %-EAGAIN:
627  * o the log is full and there is no space to write an LEB reference for
628  *   @c->gc_lnum;
629  * o the journal is too large and exceeds size limitations;
630  * o GC moved indexing LEBs, but they can be used only after the commit;
631  * o the shrinker fails to find clean znodes to free and requests the commit;
632  * o etc.
633  *
634  * Note, if the file-system is close to be full, this function may return
635  * %-EAGAIN infinitely, so the caller has to limit amount of re-invocations of
636  * the function. E.g., this happens if the limits on the journal size are too
637  * tough and GC writes too much to the journal before an LEB is freed. This
638  * might also mean that the journal is too large, and the TNC becomes to big,
639  * so that the shrinker is constantly called, finds not clean znodes to free,
640  * and requests commit. Well, this may also happen if the journal is all right,
641  * but another kernel process consumes too much memory. Anyway, infinite
642  * %-EAGAIN may happen, but in some extreme/misconfiguration cases.
643  */
ubifs_garbage_collect(struct ubifs_info * c,int anyway)644 int ubifs_garbage_collect(struct ubifs_info *c, int anyway)
645 {
646 	int i, err, ret, min_space = c->dead_wm;
647 	struct ubifs_lprops lp;
648 	struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
649 
650 	ubifs_assert_cmt_locked(c);
651 	ubifs_assert(c, !c->ro_media && !c->ro_mount);
652 
653 	if (ubifs_gc_should_commit(c))
654 		return -EAGAIN;
655 
656 	mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
657 
658 	if (c->ro_error) {
659 		ret = -EROFS;
660 		goto out_unlock;
661 	}
662 
663 	/* We expect the write-buffer to be empty on entry */
664 	ubifs_assert(c, !wbuf->used);
665 
666 	for (i = 0; ; i++) {
667 		int space_before, space_after;
668 
669 		cond_resched();
670 
671 		/* Give the commit an opportunity to run */
672 		if (ubifs_gc_should_commit(c)) {
673 			ret = -EAGAIN;
674 			break;
675 		}
676 
677 		if (i > SOFT_LEBS_LIMIT && !list_empty(&c->idx_gc)) {
678 			/*
679 			 * We've done enough iterations. Indexing LEBs were
680 			 * moved and will be available after the commit.
681 			 */
682 			dbg_gc("soft limit, some index LEBs GC'ed, -EAGAIN");
683 			ubifs_commit_required(c);
684 			ret = -EAGAIN;
685 			break;
686 		}
687 
688 		if (i > HARD_LEBS_LIMIT) {
689 			/*
690 			 * We've moved too many LEBs and have not made
691 			 * progress, give up.
692 			 */
693 			dbg_gc("hard limit, -ENOSPC");
694 			ret = -ENOSPC;
695 			break;
696 		}
697 
698 		/*
699 		 * Empty and freeable LEBs can turn up while we waited for
700 		 * the wbuf lock, or while we have been running GC. In that
701 		 * case, we should just return one of those instead of
702 		 * continuing to GC dirty LEBs. Hence we request
703 		 * 'ubifs_find_dirty_leb()' to return an empty LEB if it can.
704 		 */
705 		ret = ubifs_find_dirty_leb(c, &lp, min_space, anyway ? 0 : 1);
706 		if (ret) {
707 			if (ret == -ENOSPC)
708 				dbg_gc("no more dirty LEBs");
709 			break;
710 		}
711 
712 		dbg_gc("found LEB %d: free %d, dirty %d, sum %d (min. space %d)",
713 		       lp.lnum, lp.free, lp.dirty, lp.free + lp.dirty,
714 		       min_space);
715 
716 		space_before = c->leb_size - wbuf->offs - wbuf->used;
717 		if (wbuf->lnum == -1)
718 			space_before = 0;
719 
720 		ret = ubifs_garbage_collect_leb(c, &lp);
721 		if (ret < 0) {
722 			if (ret == -EAGAIN) {
723 				/*
724 				 * This is not error, so we have to return the
725 				 * LEB to lprops. But if 'ubifs_return_leb()'
726 				 * fails, its failure code is propagated to the
727 				 * caller instead of the original '-EAGAIN'.
728 				 */
729 				err = ubifs_return_leb(c, lp.lnum);
730 				if (err)
731 					ret = err;
732 				break;
733 			}
734 			goto out;
735 		}
736 
737 		if (ret == LEB_FREED) {
738 			/* An LEB has been freed and is ready for use */
739 			dbg_gc("LEB %d freed, return", lp.lnum);
740 			ret = lp.lnum;
741 			break;
742 		}
743 
744 		if (ret == LEB_FREED_IDX) {
745 			/*
746 			 * This was an indexing LEB and it cannot be
747 			 * immediately used. And instead of requesting the
748 			 * commit straight away, we try to garbage collect some
749 			 * more.
750 			 */
751 			dbg_gc("indexing LEB %d freed, continue", lp.lnum);
752 			continue;
753 		}
754 
755 		ubifs_assert(c, ret == LEB_RETAINED);
756 		space_after = c->leb_size - wbuf->offs - wbuf->used;
757 		dbg_gc("LEB %d retained, freed %d bytes", lp.lnum,
758 		       space_after - space_before);
759 
760 		if (space_after > space_before) {
761 			/* GC makes progress, keep working */
762 			min_space >>= 1;
763 			if (min_space < c->dead_wm)
764 				min_space = c->dead_wm;
765 			continue;
766 		}
767 
768 		dbg_gc("did not make progress");
769 
770 		/*
771 		 * GC moved an LEB bud have not done any progress. This means
772 		 * that the previous GC head LEB contained too few free space
773 		 * and the LEB which was GC'ed contained only large nodes which
774 		 * did not fit that space.
775 		 *
776 		 * We can do 2 things:
777 		 * 1. pick another LEB in a hope it'll contain a small node
778 		 *    which will fit the space we have at the end of current GC
779 		 *    head LEB, but there is no guarantee, so we try this out
780 		 *    unless we have already been working for too long;
781 		 * 2. request an LEB with more dirty space, which will force
782 		 *    'ubifs_find_dirty_leb()' to start scanning the lprops
783 		 *    table, instead of just picking one from the heap
784 		 *    (previously it already picked the dirtiest LEB).
785 		 */
786 		if (i < SOFT_LEBS_LIMIT) {
787 			dbg_gc("try again");
788 			continue;
789 		}
790 
791 		min_space <<= 1;
792 		if (min_space > c->dark_wm)
793 			min_space = c->dark_wm;
794 		dbg_gc("set min. space to %d", min_space);
795 	}
796 
797 	if (ret == -ENOSPC && !list_empty(&c->idx_gc)) {
798 		dbg_gc("no space, some index LEBs GC'ed, -EAGAIN");
799 		ubifs_commit_required(c);
800 		ret = -EAGAIN;
801 	}
802 
803 	err = ubifs_wbuf_sync_nolock(wbuf);
804 	if (!err)
805 		err = ubifs_leb_unmap(c, c->gc_lnum);
806 	if (err) {
807 		ret = err;
808 		goto out;
809 	}
810 out_unlock:
811 	mutex_unlock(&wbuf->io_mutex);
812 	return ret;
813 
814 out:
815 	ubifs_assert(c, ret < 0);
816 	ubifs_assert(c, ret != -ENOSPC && ret != -EAGAIN);
817 	ubifs_wbuf_sync_nolock(wbuf);
818 	ubifs_ro_mode(c, ret);
819 	mutex_unlock(&wbuf->io_mutex);
820 	ubifs_return_leb(c, lp.lnum);
821 	return ret;
822 }
823 
824 /**
825  * ubifs_gc_start_commit - garbage collection at start of commit.
826  * @c: UBIFS file-system description object
827  *
828  * If a LEB has only dirty and free space, then we may safely unmap it and make
829  * it free.  Note, we cannot do this with indexing LEBs because dirty space may
830  * correspond index nodes that are required for recovery.  In that case, the
831  * LEB cannot be unmapped until after the next commit.
832  *
833  * This function returns %0 upon success and a negative error code upon failure.
834  */
ubifs_gc_start_commit(struct ubifs_info * c)835 int ubifs_gc_start_commit(struct ubifs_info *c)
836 {
837 	struct ubifs_gced_idx_leb *idx_gc;
838 	const struct ubifs_lprops *lp;
839 	int err = 0, flags;
840 
841 	ubifs_get_lprops(c);
842 
843 	/*
844 	 * Unmap (non-index) freeable LEBs. Note that recovery requires that all
845 	 * wbufs are sync'd before this, which is done in 'do_commit()'.
846 	 */
847 	while (1) {
848 		lp = ubifs_fast_find_freeable(c);
849 		if (!lp)
850 			break;
851 		ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
852 		ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
853 		err = ubifs_leb_unmap(c, lp->lnum);
854 		if (err)
855 			goto out;
856 		lp = ubifs_change_lp(c, lp, c->leb_size, 0, lp->flags, 0);
857 		if (IS_ERR(lp)) {
858 			err = PTR_ERR(lp);
859 			goto out;
860 		}
861 		ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
862 		ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
863 	}
864 
865 	/* Mark GC'd index LEBs OK to unmap after this commit finishes */
866 	list_for_each_entry(idx_gc, &c->idx_gc, list)
867 		idx_gc->unmap = 1;
868 
869 	/* Record index freeable LEBs for unmapping after commit */
870 	while (1) {
871 		lp = ubifs_fast_find_frdi_idx(c);
872 		if (IS_ERR(lp)) {
873 			err = PTR_ERR(lp);
874 			goto out;
875 		}
876 		if (!lp)
877 			break;
878 		idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
879 		if (!idx_gc) {
880 			err = -ENOMEM;
881 			goto out;
882 		}
883 		ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
884 		ubifs_assert(c, lp->flags & LPROPS_INDEX);
885 		/* Don't release the LEB until after the next commit */
886 		flags = (lp->flags | LPROPS_TAKEN) ^ LPROPS_INDEX;
887 		lp = ubifs_change_lp(c, lp, c->leb_size, 0, flags, 1);
888 		if (IS_ERR(lp)) {
889 			err = PTR_ERR(lp);
890 			kfree(idx_gc);
891 			goto out;
892 		}
893 		ubifs_assert(c, lp->flags & LPROPS_TAKEN);
894 		ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
895 		idx_gc->lnum = lp->lnum;
896 		idx_gc->unmap = 1;
897 		list_add(&idx_gc->list, &c->idx_gc);
898 	}
899 out:
900 	ubifs_release_lprops(c);
901 	return err;
902 }
903 
904 /**
905  * ubifs_gc_end_commit - garbage collection at end of commit.
906  * @c: UBIFS file-system description object
907  *
908  * This function completes out-of-place garbage collection of index LEBs.
909  */
ubifs_gc_end_commit(struct ubifs_info * c)910 int ubifs_gc_end_commit(struct ubifs_info *c)
911 {
912 	struct ubifs_gced_idx_leb *idx_gc, *tmp;
913 	struct ubifs_wbuf *wbuf;
914 	int err = 0;
915 
916 	wbuf = &c->jheads[GCHD].wbuf;
917 	mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
918 	list_for_each_entry_safe(idx_gc, tmp, &c->idx_gc, list)
919 		if (idx_gc->unmap) {
920 			dbg_gc("LEB %d", idx_gc->lnum);
921 			err = ubifs_leb_unmap(c, idx_gc->lnum);
922 			if (err)
923 				goto out;
924 			err = ubifs_change_one_lp(c, idx_gc->lnum, LPROPS_NC,
925 					  LPROPS_NC, 0, LPROPS_TAKEN, -1);
926 			if (err)
927 				goto out;
928 			list_del(&idx_gc->list);
929 			kfree(idx_gc);
930 		}
931 out:
932 	mutex_unlock(&wbuf->io_mutex);
933 	return err;
934 }
935 
936 /**
937  * ubifs_destroy_idx_gc - destroy idx_gc list.
938  * @c: UBIFS file-system description object
939  *
940  * This function destroys the @c->idx_gc list. It is called when unmounting
941  * so locks are not needed. Returns zero in case of success and a negative
942  * error code in case of failure.
943  */
ubifs_destroy_idx_gc(struct ubifs_info * c)944 void ubifs_destroy_idx_gc(struct ubifs_info *c)
945 {
946 	while (!list_empty(&c->idx_gc)) {
947 		struct ubifs_gced_idx_leb *idx_gc;
948 
949 		idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb,
950 				    list);
951 		c->idx_gc_cnt -= 1;
952 		list_del(&idx_gc->list);
953 		kfree(idx_gc);
954 	}
955 }
956 
957 /**
958  * ubifs_get_idx_gc_leb - get a LEB from GC'd index LEB list.
959  * @c: UBIFS file-system description object
960  *
961  * Called during start commit so locks are not needed.
962  */
ubifs_get_idx_gc_leb(struct ubifs_info * c)963 int ubifs_get_idx_gc_leb(struct ubifs_info *c)
964 {
965 	struct ubifs_gced_idx_leb *idx_gc;
966 	int lnum;
967 
968 	if (list_empty(&c->idx_gc))
969 		return -ENOSPC;
970 	idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb, list);
971 	lnum = idx_gc->lnum;
972 	/* c->idx_gc_cnt is updated by the caller when lprops are updated */
973 	list_del(&idx_gc->list);
974 	kfree(idx_gc);
975 	return lnum;
976 }
977