text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * This file is part of UBIFS.
   *
   * Copyright (C) 2006-2008 Nokia Corporation.
   *
   * Authors: Artem Bityutskiy (Битюцкий Артём)
   *          Adrian Hunter
   */
  
  /*
   * This file is a part of UBIFS journal implementation and contains various
   * functions which manipulate the log. The log is a fixed area on the flash
   * which does not contain any data but refers to buds. The log is a part of the
   * journal.
   */
  
  #include "ubifs.h"
  
  static int dbg_check_bud_bytes(struct ubifs_info *c);
  
  /**
   * ubifs_search_bud - search bud LEB.
   * @c: UBIFS file-system description object
   * @lnum: logical eraseblock number to search
   *
   * This function searches bud LEB @lnum. Returns bud description object in case
   * of success and %NULL if there is no bud with this LEB number.
   */
  struct ubifs_bud *ubifs_search_bud(struct ubifs_info *c, int lnum)
  {
  	struct rb_node *p;
  	struct ubifs_bud *bud;
  
  	spin_lock(&c->buds_lock);
  	p = c->buds.rb_node;
  	while (p) {
  		bud = rb_entry(p, struct ubifs_bud, rb);
  		if (lnum < bud->lnum)
  			p = p->rb_left;
  		else if (lnum > bud->lnum)
  			p = p->rb_right;
  		else {
  			spin_unlock(&c->buds_lock);
  			return bud;
  		}
  	}
  	spin_unlock(&c->buds_lock);
  	return NULL;
  }
  
  /**
   * ubifs_get_wbuf - get the wbuf associated with a LEB, if there is one.
   * @c: UBIFS file-system description object
   * @lnum: logical eraseblock number to search
   *
   * This functions returns the wbuf for @lnum or %NULL if there is not one.
   */
  struct ubifs_wbuf *ubifs_get_wbuf(struct ubifs_info *c, int lnum)
  {
  	struct rb_node *p;
  	struct ubifs_bud *bud;
  	int jhead;
  
  	if (!c->jheads)
  		return NULL;
  
  	spin_lock(&c->buds_lock);
  	p = c->buds.rb_node;
  	while (p) {
  		bud = rb_entry(p, struct ubifs_bud, rb);
  		if (lnum < bud->lnum)
  			p = p->rb_left;
  		else if (lnum > bud->lnum)
  			p = p->rb_right;
  		else {
  			jhead = bud->jhead;
  			spin_unlock(&c->buds_lock);
  			return &c->jheads[jhead].wbuf;
  		}
  	}
  	spin_unlock(&c->buds_lock);
  	return NULL;
  }
  
  /**
   * empty_log_bytes - calculate amount of empty space in the log.
   * @c: UBIFS file-system description object
   */
  static inline long long empty_log_bytes(const struct ubifs_info *c)
  {
  	long long h, t;
  
  	h = (long long)c->lhead_lnum * c->leb_size + c->lhead_offs;
  	t = (long long)c->ltail_lnum * c->leb_size;
  
  	if (h > t)
  		return c->log_bytes - h + t;
  	else if (h != t)
  		return t - h;
  	else if (c->lhead_lnum != c->ltail_lnum)
  		return 0;
  	else
  		return c->log_bytes;
  }
  
  /**
   * ubifs_add_bud - add bud LEB to the tree of buds and its journal head list.
   * @c: UBIFS file-system description object
   * @bud: the bud to add
   */
  void ubifs_add_bud(struct ubifs_info *c, struct ubifs_bud *bud)
  {
  	struct rb_node **p, *parent = NULL;
  	struct ubifs_bud *b;
  	struct ubifs_jhead *jhead;
  
  	spin_lock(&c->buds_lock);
  	p = &c->buds.rb_node;
  	while (*p) {
  		parent = *p;
  		b = rb_entry(parent, struct ubifs_bud, rb);
  		ubifs_assert(c, bud->lnum != b->lnum);
  		if (bud->lnum < b->lnum)
  			p = &(*p)->rb_left;
  		else
  			p = &(*p)->rb_right;
  	}
  
  	rb_link_node(&bud->rb, parent, p);
  	rb_insert_color(&bud->rb, &c->buds);
  	if (c->jheads) {
  		jhead = &c->jheads[bud->jhead];
  		list_add_tail(&bud->list, &jhead->buds_list);
  	} else
  		ubifs_assert(c, c->replaying && c->ro_mount);
  
  	/*
  	 * Note, although this is a new bud, we anyway account this space now,
  	 * before any data has been written to it, because this is about to
  	 * guarantee fixed mount time, and this bud will anyway be read and
  	 * scanned.
  	 */
  	c->bud_bytes += c->leb_size - bud->start;
  
  	dbg_log("LEB %d:%d, jhead %s, bud_bytes %lld", bud->lnum,
  		bud->start, dbg_jhead(bud->jhead), c->bud_bytes);
  	spin_unlock(&c->buds_lock);
  }
  
  /**
   * ubifs_add_bud_to_log - add a new bud to the log.
   * @c: UBIFS file-system description object
   * @jhead: journal head the bud belongs to
   * @lnum: LEB number of the bud
   * @offs: starting offset of the bud
   *
   * This function writes a reference node for the new bud LEB @lnum to the log,
   * and adds it to the buds trees. It also makes sure that log size does not
   * exceed the 'c->max_bud_bytes' limit. Returns zero in case of success,
   * %-EAGAIN if commit is required, and a negative error code in case of
   * failure.
   */
  int ubifs_add_bud_to_log(struct ubifs_info *c, int jhead, int lnum, int offs)
  {
  	int err;
  	struct ubifs_bud *bud;
  	struct ubifs_ref_node *ref;
  
  	bud = kmalloc(sizeof(struct ubifs_bud), GFP_NOFS);
  	if (!bud)
  		return -ENOMEM;
  	ref = kzalloc(c->ref_node_alsz, GFP_NOFS);
  	if (!ref) {
  		kfree(bud);
  		return -ENOMEM;
  	}
  
  	mutex_lock(&c->log_mutex);
  	ubifs_assert(c, !c->ro_media && !c->ro_mount);
  	if (c->ro_error) {
  		err = -EROFS;
  		goto out_unlock;
  	}
  
  	/* Make sure we have enough space in the log */
  	if (empty_log_bytes(c) - c->ref_node_alsz < c->min_log_bytes) {
  		dbg_log("not enough log space - %lld, required %d",
  			empty_log_bytes(c), c->min_log_bytes);
  		ubifs_commit_required(c);
  		err = -EAGAIN;
  		goto out_unlock;
  	}
  
  	/*
  	 * Make sure the amount of space in buds will not exceed the
  	 * 'c->max_bud_bytes' limit, because we want to guarantee mount time
  	 * limits.
  	 *
  	 * It is not necessary to hold @c->buds_lock when reading @c->bud_bytes
  	 * because we are holding @c->log_mutex. All @c->bud_bytes take place
  	 * when both @c->log_mutex and @c->bud_bytes are locked.
  	 */
  	if (c->bud_bytes + c->leb_size - offs > c->max_bud_bytes) {
  		dbg_log("bud bytes %lld (%lld max), require commit",
  			c->bud_bytes, c->max_bud_bytes);
  		ubifs_commit_required(c);
  		err = -EAGAIN;
  		goto out_unlock;
  	}
  
  	/*
  	 * If the journal is full enough - start background commit. Note, it is
  	 * OK to read 'c->cmt_state' without spinlock because integer reads
  	 * are atomic in the kernel.
  	 */
  	if (c->bud_bytes >= c->bg_bud_bytes &&
  	    c->cmt_state == COMMIT_RESTING) {
  		dbg_log("bud bytes %lld (%lld max), initiate BG commit",
  			c->bud_bytes, c->max_bud_bytes);
  		ubifs_request_bg_commit(c);
  	}
  
  	bud->lnum = lnum;
  	bud->start = offs;
  	bud->jhead = jhead;
  	bud->log_hash = NULL;
  
  	ref->ch.node_type = UBIFS_REF_NODE;
  	ref->lnum = cpu_to_le32(bud->lnum);
  	ref->offs = cpu_to_le32(bud->start);
  	ref->jhead = cpu_to_le32(jhead);
  
  	if (c->lhead_offs > c->leb_size - c->ref_node_alsz) {
  		c->lhead_lnum = ubifs_next_log_lnum(c, c->lhead_lnum);
  		ubifs_assert(c, c->lhead_lnum != c->ltail_lnum);
  		c->lhead_offs = 0;
  	}
  
  	if (c->lhead_offs == 0) {
  		/* Must ensure next log LEB has been unmapped */
  		err = ubifs_leb_unmap(c, c->lhead_lnum);
  		if (err)
  			goto out_unlock;
  	}
  
  	if (bud->start == 0) {
  		/*
  		 * Before writing the LEB reference which refers an empty LEB
  		 * to the log, we have to make sure it is mapped, because
  		 * otherwise we'd risk to refer an LEB with garbage in case of
  		 * an unclean reboot, because the target LEB might have been
  		 * unmapped, but not yet physically erased.
  		 */
  		err = ubifs_leb_map(c, bud->lnum);
  		if (err)
  			goto out_unlock;
  	}
  
  	dbg_log("write ref LEB %d:%d",
  		c->lhead_lnum, c->lhead_offs);
  	err = ubifs_write_node(c, ref, UBIFS_REF_NODE_SZ, c->lhead_lnum,
  			       c->lhead_offs);
  	if (err)
  		goto out_unlock;
  
  	err = ubifs_shash_update(c, c->log_hash, ref, UBIFS_REF_NODE_SZ);
  	if (err)
  		goto out_unlock;
  
  	err = ubifs_shash_copy_state(c, c->log_hash, c->jheads[jhead].log_hash);
  	if (err)
  		goto out_unlock;
  
  	c->lhead_offs += c->ref_node_alsz;
  
  	ubifs_add_bud(c, bud);
  
  	mutex_unlock(&c->log_mutex);
  	kfree(ref);
  	return 0;
  
  out_unlock:
  	mutex_unlock(&c->log_mutex);
  	kfree(ref);
  	kfree(bud);
  	return err;
  }
  
  /**
   * remove_buds - remove used buds.
   * @c: UBIFS file-system description object
   *
   * This function removes use buds from the buds tree. It does not remove the
   * buds which are pointed to by journal heads.
   */
  static void remove_buds(struct ubifs_info *c)
  {
  	struct rb_node *p;
  
  	ubifs_assert(c, list_empty(&c->old_buds));
  	c->cmt_bud_bytes = 0;
  	spin_lock(&c->buds_lock);
  	p = rb_first(&c->buds);
  	while (p) {
  		struct rb_node *p1 = p;
  		struct ubifs_bud *bud;
  		struct ubifs_wbuf *wbuf;
  
  		p = rb_next(p);
  		bud = rb_entry(p1, struct ubifs_bud, rb);
  		wbuf = &c->jheads[bud->jhead].wbuf;
  
  		if (wbuf->lnum == bud->lnum) {
  			/*
  			 * Do not remove buds which are pointed to by journal
  			 * heads (non-closed buds).
  			 */
  			c->cmt_bud_bytes += wbuf->offs - bud->start;
  			dbg_log("preserve %d:%d, jhead %s, bud bytes %d, cmt_bud_bytes %lld",
  				bud->lnum, bud->start, dbg_jhead(bud->jhead),
  				wbuf->offs - bud->start, c->cmt_bud_bytes);
  			bud->start = wbuf->offs;
  		} else {
  			c->cmt_bud_bytes += c->leb_size - bud->start;
  			dbg_log("remove %d:%d, jhead %s, bud bytes %d, cmt_bud_bytes %lld",
  				bud->lnum, bud->start, dbg_jhead(bud->jhead),
  				c->leb_size - bud->start, c->cmt_bud_bytes);
  			rb_erase(p1, &c->buds);
  			/*
  			 * If the commit does not finish, the recovery will need
  			 * to replay the journal, in which case the old buds
  			 * must be unchanged. Do not release them until post
  			 * commit i.e. do not allow them to be garbage
  			 * collected.
  			 */
  			list_move(&bud->list, &c->old_buds);
  		}
  	}
  	spin_unlock(&c->buds_lock);
  }
  
  /**
   * ubifs_log_start_commit - start commit.
   * @c: UBIFS file-system description object
   * @ltail_lnum: return new log tail LEB number
   *
   * The commit operation starts with writing "commit start" node to the log and
   * reference nodes for all journal heads which will define new journal after
   * the commit has been finished. The commit start and reference nodes are
   * written in one go to the nearest empty log LEB (hence, when commit is
   * finished UBIFS may safely unmap all the previous log LEBs). This function
   * returns zero in case of success and a negative error code in case of
   * failure.
   */
  int ubifs_log_start_commit(struct ubifs_info *c, int *ltail_lnum)
  {
  	void *buf;
  	struct ubifs_cs_node *cs;
  	struct ubifs_ref_node *ref;
  	int err, i, max_len, len;
  
  	err = dbg_check_bud_bytes(c);
  	if (err)
  		return err;
  
  	max_len = UBIFS_CS_NODE_SZ + c->jhead_cnt * UBIFS_REF_NODE_SZ;
  	max_len = ALIGN(max_len, c->min_io_size);
  	buf = cs = kmalloc(max_len, GFP_NOFS);
  	if (!buf)
  		return -ENOMEM;
  
  	cs->ch.node_type = UBIFS_CS_NODE;
  	cs->cmt_no = cpu_to_le64(c->cmt_no);
  	ubifs_prepare_node(c, cs, UBIFS_CS_NODE_SZ, 0);
  
  	err = ubifs_shash_init(c, c->log_hash);
  	if (err)
  		goto out;
  
  	err = ubifs_shash_update(c, c->log_hash, cs, UBIFS_CS_NODE_SZ);
  	if (err < 0)
  		goto out;
  
  	/*
  	 * Note, we do not lock 'c->log_mutex' because this is the commit start
  	 * phase and we are exclusively using the log. And we do not lock
  	 * write-buffer because nobody can write to the file-system at this
  	 * phase.
  	 */
  
  	len = UBIFS_CS_NODE_SZ;
  	for (i = 0; i < c->jhead_cnt; i++) {
  		int lnum = c->jheads[i].wbuf.lnum;
  		int offs = c->jheads[i].wbuf.offs;
  
  		if (lnum == -1 || offs == c->leb_size)
  			continue;
  
  		dbg_log("add ref to LEB %d:%d for jhead %s",
  			lnum, offs, dbg_jhead(i));
  		ref = buf + len;
  		ref->ch.node_type = UBIFS_REF_NODE;
  		ref->lnum = cpu_to_le32(lnum);
  		ref->offs = cpu_to_le32(offs);
  		ref->jhead = cpu_to_le32(i);
  
  		ubifs_prepare_node(c, ref, UBIFS_REF_NODE_SZ, 0);
  		len += UBIFS_REF_NODE_SZ;
  
  		err = ubifs_shash_update(c, c->log_hash, ref,
  					 UBIFS_REF_NODE_SZ);
  		if (err)
  			goto out;
  		ubifs_shash_copy_state(c, c->log_hash, c->jheads[i].log_hash);
  	}
  
  	ubifs_pad(c, buf + len, ALIGN(len, c->min_io_size) - len);
  
  	/* Switch to the next log LEB */
  	if (c->lhead_offs) {
  		c->lhead_lnum = ubifs_next_log_lnum(c, c->lhead_lnum);
  		ubifs_assert(c, c->lhead_lnum != c->ltail_lnum);
  		c->lhead_offs = 0;
  	}
  
  	/* Must ensure next LEB has been unmapped */
  	err = ubifs_leb_unmap(c, c->lhead_lnum);
  	if (err)
  		goto out;
  
  	len = ALIGN(len, c->min_io_size);
  	dbg_log("writing commit start at LEB %d:0, len %d", c->lhead_lnum, len);
  	err = ubifs_leb_write(c, c->lhead_lnum, cs, 0, len);
  	if (err)
  		goto out;
  
  	*ltail_lnum = c->lhead_lnum;
  
  	c->lhead_offs += len;
  	if (c->lhead_offs == c->leb_size) {
  		c->lhead_lnum = ubifs_next_log_lnum(c, c->lhead_lnum);
  		c->lhead_offs = 0;
  	}
  
  	remove_buds(c);
  
  	/*
  	 * We have started the commit and now users may use the rest of the log
  	 * for new writes.
  	 */
  	c->min_log_bytes = 0;
  
  out:
  	kfree(buf);
  	return err;
  }
  
  /**
   * ubifs_log_end_commit - end commit.
   * @c: UBIFS file-system description object
   * @ltail_lnum: new log tail LEB number
   *
   * This function is called on when the commit operation was finished. It
   * moves log tail to new position and updates the master node so that it stores
   * the new log tail LEB number. Returns zero in case of success and a negative
   * error code in case of failure.
   */
  int ubifs_log_end_commit(struct ubifs_info *c, int ltail_lnum)
  {
  	int err;
  
  	/*
  	 * At this phase we have to lock 'c->log_mutex' because UBIFS allows FS
  	 * writes during commit. Its only short "commit" start phase when
  	 * writers are blocked.
  	 */
  	mutex_lock(&c->log_mutex);
  
  	dbg_log("old tail was LEB %d:0, new tail is LEB %d:0",
  		c->ltail_lnum, ltail_lnum);
  
  	c->ltail_lnum = ltail_lnum;
  	/*
  	 * The commit is finished and from now on it must be guaranteed that
  	 * there is always enough space for the next commit.
  	 */
  	c->min_log_bytes = c->leb_size;
  
  	spin_lock(&c->buds_lock);
  	c->bud_bytes -= c->cmt_bud_bytes;
  	spin_unlock(&c->buds_lock);
  
  	err = dbg_check_bud_bytes(c);
  	if (err)
  		goto out;
  
  	err = ubifs_write_master(c);
  
  out:
  	mutex_unlock(&c->log_mutex);
  	return err;
  }
  
  /**
   * ubifs_log_post_commit - things to do after commit is completed.
   * @c: UBIFS file-system description object
   * @old_ltail_lnum: old log tail LEB number
   *
   * Release buds only after commit is completed, because they must be unchanged
   * if recovery is needed.
   *
   * Unmap log LEBs only after commit is completed, because they may be needed for
   * recovery.
   *
   * This function returns %0 on success and a negative error code on failure.
   */
  int ubifs_log_post_commit(struct ubifs_info *c, int old_ltail_lnum)
  {
  	int lnum, err = 0;
  
  	while (!list_empty(&c->old_buds)) {
  		struct ubifs_bud *bud;
  
  		bud = list_entry(c->old_buds.next, struct ubifs_bud, list);
  		err = ubifs_return_leb(c, bud->lnum);
  		if (err)
  			return err;
  		list_del(&bud->list);
  		kfree(bud->log_hash);
  		kfree(bud);
  	}
  	mutex_lock(&c->log_mutex);
  	for (lnum = old_ltail_lnum; lnum != c->ltail_lnum;
  	     lnum = ubifs_next_log_lnum(c, lnum)) {
  		dbg_log("unmap log LEB %d", lnum);
  		err = ubifs_leb_unmap(c, lnum);
  		if (err)
  			goto out;
  	}
  out:
  	mutex_unlock(&c->log_mutex);
  	return err;
  }
  
  /**
   * struct done_ref - references that have been done.
   * @rb: rb-tree node
   * @lnum: LEB number
   */
  struct done_ref {
  	struct rb_node rb;
  	int lnum;
  };
  
  /**
   * done_already - determine if a reference has been done already.
   * @done_tree: rb-tree to store references that have been done
   * @lnum: LEB number of reference
   *
   * This function returns %1 if the reference has been done, %0 if not, otherwise
   * a negative error code is returned.
   */
  static int done_already(struct rb_root *done_tree, int lnum)
  {
  	struct rb_node **p = &done_tree->rb_node, *parent = NULL;
  	struct done_ref *dr;
  
  	while (*p) {
  		parent = *p;
  		dr = rb_entry(parent, struct done_ref, rb);
  		if (lnum < dr->lnum)
  			p = &(*p)->rb_left;
  		else if (lnum > dr->lnum)
  			p = &(*p)->rb_right;
  		else
  			return 1;
  	}
  
  	dr = kzalloc(sizeof(struct done_ref), GFP_NOFS);
  	if (!dr)
  		return -ENOMEM;
  
  	dr->lnum = lnum;
  
  	rb_link_node(&dr->rb, parent, p);
  	rb_insert_color(&dr->rb, done_tree);
  
  	return 0;
  }
  
  /**
   * destroy_done_tree - destroy the done tree.
   * @done_tree: done tree to destroy
   */
  static void destroy_done_tree(struct rb_root *done_tree)
  {
  	struct done_ref *dr, *n;
  
  	rbtree_postorder_for_each_entry_safe(dr, n, done_tree, rb)
  		kfree(dr);
  }
  
  /**
   * add_node - add a node to the consolidated log.
   * @c: UBIFS file-system description object
   * @buf: buffer to which to add
   * @lnum: LEB number to which to write is passed and returned here
   * @offs: offset to where to write is passed and returned here
   * @node: node to add
   *
   * This function returns %0 on success and a negative error code on failure.
   */
  static int add_node(struct ubifs_info *c, void *buf, int *lnum, int *offs,
  		    void *node)
  {
  	struct ubifs_ch *ch = node;
  	int len = le32_to_cpu(ch->len), remains = c->leb_size - *offs;
  
  	if (len > remains) {
  		int sz = ALIGN(*offs, c->min_io_size), err;
  
  		ubifs_pad(c, buf + *offs, sz - *offs);
  		err = ubifs_leb_change(c, *lnum, buf, sz);
  		if (err)
  			return err;
  		*lnum = ubifs_next_log_lnum(c, *lnum);
  		*offs = 0;
  	}
  	memcpy(buf + *offs, node, len);
  	*offs += ALIGN(len, 8);
  	return 0;
  }
  
  /**
   * ubifs_consolidate_log - consolidate the log.
   * @c: UBIFS file-system description object
   *
   * Repeated failed commits could cause the log to be full, but at least 1 LEB is
   * needed for commit. This function rewrites the reference nodes in the log
   * omitting duplicates, and failed CS nodes, and leaving no gaps.
   *
   * This function returns %0 on success and a negative error code on failure.
   */
  int ubifs_consolidate_log(struct ubifs_info *c)
  {
  	struct ubifs_scan_leb *sleb;
  	struct ubifs_scan_node *snod;
  	struct rb_root done_tree = RB_ROOT;
  	int lnum, err, first = 1, write_lnum, offs = 0;
  	void *buf;
  
  	dbg_rcvry("log tail LEB %d, log head LEB %d", c->ltail_lnum,
  		  c->lhead_lnum);
  	buf = vmalloc(c->leb_size);
  	if (!buf)
  		return -ENOMEM;
  	lnum = c->ltail_lnum;
  	write_lnum = lnum;
  	while (1) {
  		sleb = ubifs_scan(c, lnum, 0, c->sbuf, 0);
  		if (IS_ERR(sleb)) {
  			err = PTR_ERR(sleb);
  			goto out_free;
  		}
  		list_for_each_entry(snod, &sleb->nodes, list) {
  			switch (snod->type) {
  			case UBIFS_REF_NODE: {
  				struct ubifs_ref_node *ref = snod->node;
  				int ref_lnum = le32_to_cpu(ref->lnum);
  
  				err = done_already(&done_tree, ref_lnum);
  				if (err < 0)
  					goto out_scan;
  				if (err != 1) {
  					err = add_node(c, buf, &write_lnum,
  						       &offs, snod->node);
  					if (err)
  						goto out_scan;
  				}
  				break;
  			}
  			case UBIFS_CS_NODE:
  				if (!first)
  					break;
  				err = add_node(c, buf, &write_lnum, &offs,
  					       snod->node);
  				if (err)
  					goto out_scan;
  				first = 0;
  				break;
  			}
  		}
  		ubifs_scan_destroy(sleb);
  		if (lnum == c->lhead_lnum)
  			break;
  		lnum = ubifs_next_log_lnum(c, lnum);
  	}
  	if (offs) {
  		int sz = ALIGN(offs, c->min_io_size);
  
  		ubifs_pad(c, buf + offs, sz - offs);
  		err = ubifs_leb_change(c, write_lnum, buf, sz);
  		if (err)
  			goto out_free;
  		offs = ALIGN(offs, c->min_io_size);
  	}
  	destroy_done_tree(&done_tree);
  	vfree(buf);
  	if (write_lnum == c->lhead_lnum) {
  		ubifs_err(c, "log is too full");
  		return -EINVAL;
  	}
  	/* Unmap remaining LEBs */
  	lnum = write_lnum;
  	do {
  		lnum = ubifs_next_log_lnum(c, lnum);
  		err = ubifs_leb_unmap(c, lnum);
  		if (err)
  			return err;
  	} while (lnum != c->lhead_lnum);
  	c->lhead_lnum = write_lnum;
  	c->lhead_offs = offs;
  	dbg_rcvry("new log head at %d:%d", c->lhead_lnum, c->lhead_offs);
  	return 0;
  
  out_scan:
  	ubifs_scan_destroy(sleb);
  out_free:
  	destroy_done_tree(&done_tree);
  	vfree(buf);
  	return err;
  }
  
  /**
   * dbg_check_bud_bytes - make sure bud bytes calculation are all right.
   * @c: UBIFS file-system description object
   *
   * This function makes sure the amount of flash space used by closed buds
   * ('c->bud_bytes' is correct). Returns zero in case of success and %-EINVAL in
   * case of failure.
   */
  static int dbg_check_bud_bytes(struct ubifs_info *c)
  {
  	int i, err = 0;
  	struct ubifs_bud *bud;
  	long long bud_bytes = 0;
  
  	if (!dbg_is_chk_gen(c))
  		return 0;
  
  	spin_lock(&c->buds_lock);
  	for (i = 0; i < c->jhead_cnt; i++)
  		list_for_each_entry(bud, &c->jheads[i].buds_list, list)
  			bud_bytes += c->leb_size - bud->start;
  
  	if (c->bud_bytes != bud_bytes) {
  		ubifs_err(c, "bad bud_bytes %lld, calculated %lld",
  			  c->bud_bytes, bud_bytes);
  		err = -EINVAL;
  	}
  	spin_unlock(&c->buds_lock);
  
  	return err;
  }
  