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