/*
   * This file is part of UBIFS.
   *
   * Copyright (C) 2006-2008 Nokia Corporation.
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 as published by
   * the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
   * more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc., 51
   * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
   *
   * Author: Adrian Hunter
   */
  
  #include "ubifs.h"
  
  /*
   * An orphan is an inode number whose inode node has been committed to the index
   * with a link count of zero. That happens when an open file is deleted
   * (unlinked) and then a commit is run. In the normal course of events the inode
   * would be deleted when the file is closed. However in the case of an unclean
   * unmount, orphans need to be accounted for. After an unclean unmount, the
   * orphans' inodes must be deleted which means either scanning the entire index
   * looking for them, or keeping a list on flash somewhere. This unit implements
   * the latter approach.
   *
   * The orphan area is a fixed number of LEBs situated between the LPT area and
   * the main area. The number of orphan area LEBs is specified when the file
   * system is created. The minimum number is 1. The size of the orphan area
   * should be so that it can hold the maximum number of orphans that are expected
   * to ever exist at one time.
   *
   * The number of orphans that can fit in a LEB is:
   *
   *         (c->leb_size - UBIFS_ORPH_NODE_SZ) / sizeof(__le64)
   *
   * For example: a 15872 byte LEB can fit 1980 orphans so 1 LEB may be enough.
   *
   * Orphans are accumulated in a rb-tree. When an inode's link count drops to
   * zero, the inode number is added to the rb-tree. It is removed from the tree
   * when the inode is deleted.  Any new orphans that are in the orphan tree when

   * the commit is run, are written to the orphan area in 1 or more orphan nodes.

   * If the orphan area is full, it is consolidated to make space.  There is
   * always enough space because validation prevents the user from creating more
   * than the maximum number of orphans allowed.
   */

  static int dbg_check_orphans(struct ubifs_info *c);

  
  /**
   * ubifs_add_orphan - add an orphan.
   * @c: UBIFS file-system description object
   * @inum: orphan inode number
   *
   * Add an orphan. This function is called when an inodes link count drops to
   * zero.
   */
  int ubifs_add_orphan(struct ubifs_info *c, ino_t inum)
  {
  	struct ubifs_orphan *orphan, *o;
  	struct rb_node **p, *parent = NULL;
  
  	orphan = kzalloc(sizeof(struct ubifs_orphan), GFP_NOFS);
  	if (!orphan)
  		return -ENOMEM;
  	orphan->inum = inum;
  	orphan->new = 1;
  
  	spin_lock(&c->orphan_lock);
  	if (c->tot_orphans >= c->max_orphans) {
  		spin_unlock(&c->orphan_lock);
  		kfree(orphan);
  		return -ENFILE;
  	}
  	p = &c->orph_tree.rb_node;
  	while (*p) {
  		parent = *p;
  		o = rb_entry(parent, struct ubifs_orphan, rb);
  		if (inum < o->inum)
  			p = &(*p)->rb_left;
  		else if (inum > o->inum)
  			p = &(*p)->rb_right;
  		else {

  			ubifs_err(c, "orphaned twice");

  			spin_unlock(&c->orphan_lock);
  			kfree(orphan);
  			return 0;
  		}
  	}
  	c->tot_orphans += 1;
  	c->new_orphans += 1;
  	rb_link_node(&orphan->rb, parent, p);
  	rb_insert_color(&orphan->rb, &c->orph_tree);
  	list_add_tail(&orphan->list, &c->orph_list);
  	list_add_tail(&orphan->new_list, &c->orph_new);
  	spin_unlock(&c->orphan_lock);

  	dbg_gen("ino %lu", (unsigned long)inum);

  	return 0;
  }
  
  /**
   * ubifs_delete_orphan - delete an orphan.
   * @c: UBIFS file-system description object
   * @inum: orphan inode number
   *
   * Delete an orphan. This function is called when an inode is deleted.
   */
  void ubifs_delete_orphan(struct ubifs_info *c, ino_t inum)
  {
  	struct ubifs_orphan *o;
  	struct rb_node *p;
  
  	spin_lock(&c->orphan_lock);
  	p = c->orph_tree.rb_node;
  	while (p) {
  		o = rb_entry(p, struct ubifs_orphan, rb);
  		if (inum < o->inum)
  			p = p->rb_left;
  		else if (inum > o->inum)
  			p = p->rb_right;
  		else {

  			if (o->del) {

  				spin_unlock(&c->orphan_lock);

  				dbg_gen("deleted twice ino %lu",
  					(unsigned long)inum);

  				return;
  			}

  			if (o->cmt) {

  				o->del = 1;

  				o->dnext = c->orph_dnext;
  				c->orph_dnext = o;
  				spin_unlock(&c->orphan_lock);

  				dbg_gen("delete later ino %lu",
  					(unsigned long)inum);

  				return;
  			}
  			rb_erase(p, &c->orph_tree);
  			list_del(&o->list);
  			c->tot_orphans -= 1;
  			if (o->new) {
  				list_del(&o->new_list);
  				c->new_orphans -= 1;
  			}
  			spin_unlock(&c->orphan_lock);
  			kfree(o);

  			dbg_gen("inum %lu", (unsigned long)inum);

  			return;
  		}
  	}
  	spin_unlock(&c->orphan_lock);

  	ubifs_err(c, "missing orphan ino %lu", (unsigned long)inum);

  	dump_stack();

  }
  
  /**
   * ubifs_orphan_start_commit - start commit of orphans.
   * @c: UBIFS file-system description object
   *
   * Start commit of orphans.
   */
  int ubifs_orphan_start_commit(struct ubifs_info *c)
  {
  	struct ubifs_orphan *orphan, **last;
  
  	spin_lock(&c->orphan_lock);
  	last = &c->orph_cnext;
  	list_for_each_entry(orphan, &c->orph_new, new_list) {
  		ubifs_assert(orphan->new);

  		ubifs_assert(!orphan->cmt);

  		orphan->new = 0;

  		orphan->cmt = 1;

  		*last = orphan;
  		last = &orphan->cnext;
  	}

  	*last = NULL;

  	c->cmt_orphans = c->new_orphans;
  	c->new_orphans = 0;
  	dbg_cmt("%d orphans to commit", c->cmt_orphans);
  	INIT_LIST_HEAD(&c->orph_new);
  	if (c->tot_orphans == 0)
  		c->no_orphs = 1;
  	else
  		c->no_orphs = 0;
  	spin_unlock(&c->orphan_lock);
  	return 0;
  }
  
  /**
   * avail_orphs - calculate available space.
   * @c: UBIFS file-system description object
   *
   * This function returns the number of orphans that can be written in the
   * available space.
   */
  static int avail_orphs(struct ubifs_info *c)
  {
  	int avail_lebs, avail, gap;
  
  	avail_lebs = c->orph_lebs - (c->ohead_lnum - c->orph_first) - 1;
  	avail = avail_lebs *
  	       ((c->leb_size - UBIFS_ORPH_NODE_SZ) / sizeof(__le64));
  	gap = c->leb_size - c->ohead_offs;
  	if (gap >= UBIFS_ORPH_NODE_SZ + sizeof(__le64))
  		avail += (gap - UBIFS_ORPH_NODE_SZ) / sizeof(__le64);
  	return avail;
  }
  
  /**
   * tot_avail_orphs - calculate total space.
   * @c: UBIFS file-system description object
   *
   * This function returns the number of orphans that can be written in half
   * the total space. That leaves half the space for adding new orphans.
   */
  static int tot_avail_orphs(struct ubifs_info *c)
  {
  	int avail_lebs, avail;
  
  	avail_lebs = c->orph_lebs;
  	avail = avail_lebs *
  	       ((c->leb_size - UBIFS_ORPH_NODE_SZ) / sizeof(__le64));
  	return avail / 2;
  }
  
  /**

   * do_write_orph_node - write a node to the orphan head.

   * @c: UBIFS file-system description object
   * @len: length of node
   * @atomic: write atomically
   *
   * This function writes a node to the orphan head from the orphan buffer. If
   * %atomic is not zero, then the write is done atomically. On success, %0 is
   * returned, otherwise a negative error code is returned.
   */
  static int do_write_orph_node(struct ubifs_info *c, int len, int atomic)
  {
  	int err = 0;
  
  	if (atomic) {
  		ubifs_assert(c->ohead_offs == 0);
  		ubifs_prepare_node(c, c->orph_buf, len, 1);
  		len = ALIGN(len, c->min_io_size);

  		err = ubifs_leb_change(c, c->ohead_lnum, c->orph_buf, len);

  	} else {
  		if (c->ohead_offs == 0) {
  			/* Ensure LEB has been unmapped */
  			err = ubifs_leb_unmap(c, c->ohead_lnum);
  			if (err)
  				return err;
  		}
  		err = ubifs_write_node(c, c->orph_buf, len, c->ohead_lnum,

  				       c->ohead_offs);

  	}
  	return err;
  }
  
  /**

   * write_orph_node - write an orphan node.

   * @c: UBIFS file-system description object
   * @atomic: write atomically
   *

   * This function builds an orphan node from the cnext list and writes it to the

   * orphan head. On success, %0 is returned, otherwise a negative error code
   * is returned.
   */
  static int write_orph_node(struct ubifs_info *c, int atomic)
  {
  	struct ubifs_orphan *orphan, *cnext;
  	struct ubifs_orph_node *orph;
  	int gap, err, len, cnt, i;
  
  	ubifs_assert(c->cmt_orphans > 0);
  	gap = c->leb_size - c->ohead_offs;
  	if (gap < UBIFS_ORPH_NODE_SZ + sizeof(__le64)) {
  		c->ohead_lnum += 1;
  		c->ohead_offs = 0;
  		gap = c->leb_size;
  		if (c->ohead_lnum > c->orph_last) {
  			/*
  			 * We limit the number of orphans so that this should
  			 * never happen.
  			 */

  			ubifs_err(c, "out of space in orphan area");

  			return -EINVAL;
  		}
  	}
  	cnt = (gap - UBIFS_ORPH_NODE_SZ) / sizeof(__le64);
  	if (cnt > c->cmt_orphans)
  		cnt = c->cmt_orphans;
  	len = UBIFS_ORPH_NODE_SZ + cnt * sizeof(__le64);
  	ubifs_assert(c->orph_buf);
  	orph = c->orph_buf;
  	orph->ch.node_type = UBIFS_ORPH_NODE;
  	spin_lock(&c->orphan_lock);
  	cnext = c->orph_cnext;
  	for (i = 0; i < cnt; i++) {
  		orphan = cnext;

  		ubifs_assert(orphan->cmt);

  		orph->inos[i] = cpu_to_le64(orphan->inum);

  		orphan->cmt = 0;

  		cnext = orphan->cnext;
  		orphan->cnext = NULL;
  	}
  	c->orph_cnext = cnext;
  	c->cmt_orphans -= cnt;
  	spin_unlock(&c->orphan_lock);
  	if (c->cmt_orphans)

  		orph->cmt_no = cpu_to_le64(c->cmt_no);

  	else
  		/* Mark the last node of the commit */

  		orph->cmt_no = cpu_to_le64((c->cmt_no) | (1ULL << 63));

  	ubifs_assert(c->ohead_offs + len <= c->leb_size);
  	ubifs_assert(c->ohead_lnum >= c->orph_first);
  	ubifs_assert(c->ohead_lnum <= c->orph_last);
  	err = do_write_orph_node(c, len, atomic);
  	c->ohead_offs += ALIGN(len, c->min_io_size);
  	c->ohead_offs = ALIGN(c->ohead_offs, 8);
  	return err;
  }
  
  /**

   * write_orph_nodes - write orphan nodes until there are no more to commit.

   * @c: UBIFS file-system description object
   * @atomic: write atomically
   *

   * This function writes orphan nodes for all the orphans to commit. On success,

   * %0 is returned, otherwise a negative error code is returned.
   */
  static int write_orph_nodes(struct ubifs_info *c, int atomic)
  {
  	int err;
  
  	while (c->cmt_orphans > 0) {
  		err = write_orph_node(c, atomic);
  		if (err)
  			return err;
  	}
  	if (atomic) {
  		int lnum;
  
  		/* Unmap any unused LEBs after consolidation */

  		for (lnum = c->ohead_lnum + 1; lnum <= c->orph_last; lnum++) {
  			err = ubifs_leb_unmap(c, lnum);
  			if (err)
  				return err;
  		}
  	}
  	return 0;
  }
  
  /**
   * consolidate - consolidate the orphan area.
   * @c: UBIFS file-system description object
   *
   * This function enables consolidation by putting all the orphans into the list
   * to commit. The list is in the order that the orphans were added, and the
   * LEBs are written atomically in order, so at no time can orphans be lost by
   * an unclean unmount.
   *
   * This function returns %0 on success and a negative error code on failure.
   */
  static int consolidate(struct ubifs_info *c)
  {
  	int tot_avail = tot_avail_orphs(c), err = 0;
  
  	spin_lock(&c->orphan_lock);
  	dbg_cmt("there is space for %d orphans and there are %d",
  		tot_avail, c->tot_orphans);
  	if (c->tot_orphans - c->new_orphans <= tot_avail) {
  		struct ubifs_orphan *orphan, **last;
  		int cnt = 0;
  
  		/* Change the cnext list to include all non-new orphans */
  		last = &c->orph_cnext;
  		list_for_each_entry(orphan, &c->orph_list, list) {
  			if (orphan->new)
  				continue;

  			orphan->cmt = 1;

  			*last = orphan;
  			last = &orphan->cnext;
  			cnt += 1;
  		}

  		*last = NULL;

  		ubifs_assert(cnt == c->tot_orphans - c->new_orphans);
  		c->cmt_orphans = cnt;
  		c->ohead_lnum = c->orph_first;
  		c->ohead_offs = 0;
  	} else {
  		/*
  		 * We limit the number of orphans so that this should
  		 * never happen.
  		 */

  		ubifs_err(c, "out of space in orphan area");

  		err = -EINVAL;
  	}
  	spin_unlock(&c->orphan_lock);
  	return err;
  }
  
  /**
   * commit_orphans - commit orphans.
   * @c: UBIFS file-system description object
   *
   * This function commits orphans to flash. On success, %0 is returned,
   * otherwise a negative error code is returned.
   */
  static int commit_orphans(struct ubifs_info *c)
  {
  	int avail, atomic = 0, err;
  
  	ubifs_assert(c->cmt_orphans > 0);
  	avail = avail_orphs(c);
  	if (avail < c->cmt_orphans) {
  		/* Not enough space to write new orphans, so consolidate */
  		err = consolidate(c);
  		if (err)
  			return err;
  		atomic = 1;
  	}
  	err = write_orph_nodes(c, atomic);
  	return err;
  }
  
  /**
   * erase_deleted - erase the orphans marked for deletion.
   * @c: UBIFS file-system description object
   *
   * During commit, the orphans being committed cannot be deleted, so they are
   * marked for deletion and deleted by this function. Also, the recovery
   * adds killed orphans to the deletion list, and therefore they are deleted
   * here too.
   */
  static void erase_deleted(struct ubifs_info *c)
  {
  	struct ubifs_orphan *orphan, *dnext;
  
  	spin_lock(&c->orphan_lock);
  	dnext = c->orph_dnext;
  	while (dnext) {
  		orphan = dnext;
  		dnext = orphan->dnext;
  		ubifs_assert(!orphan->new);

  		ubifs_assert(orphan->del);

  		rb_erase(&orphan->rb, &c->orph_tree);
  		list_del(&orphan->list);
  		c->tot_orphans -= 1;

  		dbg_gen("deleting orphan ino %lu", (unsigned long)orphan->inum);

  		kfree(orphan);
  	}
  	c->orph_dnext = NULL;
  	spin_unlock(&c->orphan_lock);
  }
  
  /**
   * ubifs_orphan_end_commit - end commit of orphans.
   * @c: UBIFS file-system description object
   *
   * End commit of orphans.
   */
  int ubifs_orphan_end_commit(struct ubifs_info *c)
  {
  	int err;
  
  	if (c->cmt_orphans != 0) {
  		err = commit_orphans(c);
  		if (err)
  			return err;
  	}
  	erase_deleted(c);
  	err = dbg_check_orphans(c);
  	return err;
  }
  
  /**

   * ubifs_clear_orphans - erase all LEBs used for orphans.

   * @c: UBIFS file-system description object
   *
   * If recovery is not required, then the orphans from the previous session
   * are not needed. This function locates the LEBs used to record
   * orphans, and un-maps them.
   */

  int ubifs_clear_orphans(struct ubifs_info *c)

  {
  	int lnum, err;
  
  	for (lnum = c->orph_first; lnum <= c->orph_last; lnum++) {
  		err = ubifs_leb_unmap(c, lnum);
  		if (err)
  			return err;
  	}
  	c->ohead_lnum = c->orph_first;
  	c->ohead_offs = 0;
  	return 0;
  }
  
  /**
   * insert_dead_orphan - insert an orphan.
   * @c: UBIFS file-system description object
   * @inum: orphan inode number
   *
   * This function is a helper to the 'do_kill_orphans()' function. The orphan
   * must be kept until the next commit, so it is added to the rb-tree and the
   * deletion list.
   */
  static int insert_dead_orphan(struct ubifs_info *c, ino_t inum)
  {
  	struct ubifs_orphan *orphan, *o;
  	struct rb_node **p, *parent = NULL;
  
  	orphan = kzalloc(sizeof(struct ubifs_orphan), GFP_KERNEL);
  	if (!orphan)
  		return -ENOMEM;
  	orphan->inum = inum;
  
  	p = &c->orph_tree.rb_node;
  	while (*p) {
  		parent = *p;
  		o = rb_entry(parent, struct ubifs_orphan, rb);
  		if (inum < o->inum)
  			p = &(*p)->rb_left;
  		else if (inum > o->inum)
  			p = &(*p)->rb_right;
  		else {
  			/* Already added - no problem */
  			kfree(orphan);
  			return 0;
  		}
  	}
  	c->tot_orphans += 1;
  	rb_link_node(&orphan->rb, parent, p);
  	rb_insert_color(&orphan->rb, &c->orph_tree);
  	list_add_tail(&orphan->list, &c->orph_list);

  	orphan->del = 1;

  	orphan->dnext = c->orph_dnext;
  	c->orph_dnext = orphan;

  	dbg_mnt("ino %lu, new %d, tot %d", (unsigned long)inum,
  		c->new_orphans, c->tot_orphans);

  	return 0;
  }
  
  /**
   * do_kill_orphans - remove orphan inodes from the index.
   * @c: UBIFS file-system description object
   * @sleb: scanned LEB

   * @last_cmt_no: cmt_no of last orphan node read is passed and returned here

   * @outofdate: whether the LEB is out of date is returned here

   * @last_flagged: whether the end orphan node is encountered

   *
   * This function is a helper to the 'kill_orphans()' function. It goes through
   * every orphan node in a LEB and for every inode number recorded, removes
   * all keys for that inode from the TNC.
   */
  static int do_kill_orphans(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
  			   unsigned long long *last_cmt_no, int *outofdate,
  			   int *last_flagged)
  {
  	struct ubifs_scan_node *snod;
  	struct ubifs_orph_node *orph;
  	unsigned long long cmt_no;
  	ino_t inum;
  	int i, n, err, first = 1;
  
  	list_for_each_entry(snod, &sleb->nodes, list) {
  		if (snod->type != UBIFS_ORPH_NODE) {

  			ubifs_err(c, "invalid node type %d in orphan area at %d:%d",

  				  snod->type, sleb->lnum, snod->offs);

  			ubifs_dump_node(c, snod->node);

  			return -EINVAL;
  		}
  
  		orph = snod->node;
  
  		/* Check commit number */
  		cmt_no = le64_to_cpu(orph->cmt_no) & LLONG_MAX;
  		/*
  		 * The commit number on the master node may be less, because
  		 * of a failed commit. If there are several failed commits in a

  		 * row, the commit number written on orphan nodes will continue
  		 * to increase (because the commit number is adjusted here) even

  		 * though the commit number on the master node stays the same
  		 * because the master node has not been re-written.
  		 */
  		if (cmt_no > c->cmt_no)
  			c->cmt_no = cmt_no;
  		if (cmt_no < *last_cmt_no && *last_flagged) {
  			/*

  			 * The last orphan node had a higher commit number and
  			 * was flagged as the last written for that commit
  			 * number. That makes this orphan node, out of date.

  			 */
  			if (!first) {

  				ubifs_err(c, "out of order commit number %llu in orphan node at %d:%d",

  					  cmt_no, sleb->lnum, snod->offs);

  				ubifs_dump_node(c, snod->node);

  				return -EINVAL;
  			}
  			dbg_rcvry("out of date LEB %d", sleb->lnum);
  			*outofdate = 1;
  			return 0;
  		}
  
  		if (first)
  			first = 0;
  
  		n = (le32_to_cpu(orph->ch.len) - UBIFS_ORPH_NODE_SZ) >> 3;
  		for (i = 0; i < n; i++) {
  			inum = le64_to_cpu(orph->inos[i]);

  			dbg_rcvry("deleting orphaned inode %lu",
  				  (unsigned long)inum);

  			err = ubifs_tnc_remove_ino(c, inum);
  			if (err)
  				return err;
  			err = insert_dead_orphan(c, inum);
  			if (err)
  				return err;
  		}
  
  		*last_cmt_no = cmt_no;
  		if (le64_to_cpu(orph->cmt_no) & (1ULL << 63)) {
  			dbg_rcvry("last orph node for commit %llu at %d:%d",
  				  cmt_no, sleb->lnum, snod->offs);
  			*last_flagged = 1;
  		} else
  			*last_flagged = 0;
  	}
  
  	return 0;
  }
  
  /**
   * kill_orphans - remove all orphan inodes from the index.
   * @c: UBIFS file-system description object
   *
   * If recovery is required, then orphan inodes recorded during the previous
   * session (which ended with an unclean unmount) must be deleted from the index.
   * This is done by updating the TNC, but since the index is not updated until
   * the next commit, the LEBs where the orphan information is recorded are not
   * erased until the next commit.
   */
  static int kill_orphans(struct ubifs_info *c)
  {
  	unsigned long long last_cmt_no = 0;
  	int lnum, err = 0, outofdate = 0, last_flagged = 0;
  
  	c->ohead_lnum = c->orph_first;
  	c->ohead_offs = 0;
  	/* Check no-orphans flag and skip this if no orphans */
  	if (c->no_orphs) {
  		dbg_rcvry("no orphans");
  		return 0;
  	}
  	/*
  	 * Orph nodes always start at c->orph_first and are written to each
  	 * successive LEB in turn. Generally unused LEBs will have been unmapped

  	 * but may contain out of date orphan nodes if the unmap didn't go
  	 * through. In addition, the last orphan node written for each commit is

  	 * marked (top bit of orph->cmt_no is set to 1). It is possible that

  	 * there are orphan nodes from the next commit (i.e. the commit did not

  	 * complete successfully). In that case, no orphans will have been lost
  	 * due to the way that orphans are written, and any orphans added will
  	 * be valid orphans anyway and so can be deleted.
  	 */
  	for (lnum = c->orph_first; lnum <= c->orph_last; lnum++) {
  		struct ubifs_scan_leb *sleb;
  
  		dbg_rcvry("LEB %d", lnum);

  		sleb = ubifs_scan(c, lnum, 0, c->sbuf, 1);

  		if (IS_ERR(sleb)) {

  			if (PTR_ERR(sleb) == -EUCLEAN)

  				sleb = ubifs_recover_leb(c, lnum, 0,

  							 c->sbuf, -1);

  			if (IS_ERR(sleb)) {
  				err = PTR_ERR(sleb);
  				break;
  			}
  		}
  		err = do_kill_orphans(c, sleb, &last_cmt_no, &outofdate,
  				      &last_flagged);
  		if (err || outofdate) {
  			ubifs_scan_destroy(sleb);
  			break;
  		}
  		if (sleb->endpt) {
  			c->ohead_lnum = lnum;
  			c->ohead_offs = sleb->endpt;
  		}
  		ubifs_scan_destroy(sleb);
  	}
  	return err;
  }
  
  /**
   * ubifs_mount_orphans - delete orphan inodes and erase LEBs that recorded them.
   * @c: UBIFS file-system description object
   * @unclean: indicates recovery from unclean unmount
   * @read_only: indicates read only mount
   *
   * This function is called when mounting to erase orphans from the previous
   * session. If UBIFS was not unmounted cleanly, then the inodes recorded as
   * orphans are deleted.
   */
  int ubifs_mount_orphans(struct ubifs_info *c, int unclean, int read_only)
  {
  	int err = 0;
  
  	c->max_orphans = tot_avail_orphs(c);
  
  	if (!read_only) {
  		c->orph_buf = vmalloc(c->leb_size);
  		if (!c->orph_buf)
  			return -ENOMEM;
  	}
  
  	if (unclean)
  		err = kill_orphans(c);
  	else if (!read_only)

  		err = ubifs_clear_orphans(c);

  
  	return err;
  }

  /*
   * Everything below is related to debugging.
   */

  
  struct check_orphan {
  	struct rb_node rb;
  	ino_t inum;
  };
  
  struct check_info {
  	unsigned long last_ino;
  	unsigned long tot_inos;
  	unsigned long missing;
  	unsigned long long leaf_cnt;
  	struct ubifs_ino_node *node;
  	struct rb_root root;
  };
  
  static int dbg_find_orphan(struct ubifs_info *c, ino_t inum)
  {
  	struct ubifs_orphan *o;
  	struct rb_node *p;
  
  	spin_lock(&c->orphan_lock);
  	p = c->orph_tree.rb_node;
  	while (p) {
  		o = rb_entry(p, struct ubifs_orphan, rb);
  		if (inum < o->inum)
  			p = p->rb_left;
  		else if (inum > o->inum)
  			p = p->rb_right;
  		else {
  			spin_unlock(&c->orphan_lock);
  			return 1;
  		}
  	}
  	spin_unlock(&c->orphan_lock);
  	return 0;
  }
  
  static int dbg_ins_check_orphan(struct rb_root *root, ino_t inum)
  {
  	struct check_orphan *orphan, *o;
  	struct rb_node **p, *parent = NULL;
  
  	orphan = kzalloc(sizeof(struct check_orphan), GFP_NOFS);
  	if (!orphan)
  		return -ENOMEM;
  	orphan->inum = inum;
  
  	p = &root->rb_node;
  	while (*p) {
  		parent = *p;
  		o = rb_entry(parent, struct check_orphan, rb);
  		if (inum < o->inum)
  			p = &(*p)->rb_left;
  		else if (inum > o->inum)
  			p = &(*p)->rb_right;
  		else {
  			kfree(orphan);
  			return 0;
  		}
  	}
  	rb_link_node(&orphan->rb, parent, p);
  	rb_insert_color(&orphan->rb, root);
  	return 0;
  }
  
  static int dbg_find_check_orphan(struct rb_root *root, ino_t inum)
  {
  	struct check_orphan *o;
  	struct rb_node *p;
  
  	p = root->rb_node;
  	while (p) {
  		o = rb_entry(p, struct check_orphan, rb);
  		if (inum < o->inum)
  			p = p->rb_left;
  		else if (inum > o->inum)
  			p = p->rb_right;
  		else
  			return 1;
  	}
  	return 0;
  }
  
  static void dbg_free_check_tree(struct rb_root *root)
  {

  	struct check_orphan *o, *n;

  	rbtree_postorder_for_each_entry_safe(o, n, root, rb)

  		kfree(o);

  }
  
  static int dbg_orphan_check(struct ubifs_info *c, struct ubifs_zbranch *zbr,
  			    void *priv)
  {
  	struct check_info *ci = priv;
  	ino_t inum;
  	int err;
  
  	inum = key_inum(c, &zbr->key);
  	if (inum != ci->last_ino) {
  		/* Lowest node type is the inode node, so it comes first */
  		if (key_type(c, &zbr->key) != UBIFS_INO_KEY)

  			ubifs_err(c, "found orphan node ino %lu, type %d",

  				  (unsigned long)inum, key_type(c, &zbr->key));

  		ci->last_ino = inum;
  		ci->tot_inos += 1;
  		err = ubifs_tnc_read_node(c, zbr, ci->node);
  		if (err) {

  			ubifs_err(c, "node read failed, error %d", err);

  			return err;
  		}
  		if (ci->node->nlink == 0)
  			/* Must be recorded as an orphan */
  			if (!dbg_find_check_orphan(&ci->root, inum) &&
  			    !dbg_find_orphan(c, inum)) {

  				ubifs_err(c, "missing orphan, ino %lu",

  					  (unsigned long)inum);

  				ci->missing += 1;
  			}
  	}
  	ci->leaf_cnt += 1;
  	return 0;
  }
  
  static int dbg_read_orphans(struct check_info *ci, struct ubifs_scan_leb *sleb)
  {
  	struct ubifs_scan_node *snod;
  	struct ubifs_orph_node *orph;
  	ino_t inum;
  	int i, n, err;
  
  	list_for_each_entry(snod, &sleb->nodes, list) {
  		cond_resched();
  		if (snod->type != UBIFS_ORPH_NODE)
  			continue;
  		orph = snod->node;
  		n = (le32_to_cpu(orph->ch.len) - UBIFS_ORPH_NODE_SZ) >> 3;
  		for (i = 0; i < n; i++) {
  			inum = le64_to_cpu(orph->inos[i]);
  			err = dbg_ins_check_orphan(&ci->root, inum);
  			if (err)
  				return err;
  		}
  	}
  	return 0;
  }
  
  static int dbg_scan_orphans(struct ubifs_info *c, struct check_info *ci)
  {
  	int lnum, err = 0;

  	void *buf;

  
  	/* Check no-orphans flag and skip this if no orphans */
  	if (c->no_orphs)
  		return 0;

  	buf = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);

  	if (!buf) {

  		ubifs_err(c, "cannot allocate memory to check orphans");

  		return 0;
  	}

  	for (lnum = c->orph_first; lnum <= c->orph_last; lnum++) {
  		struct ubifs_scan_leb *sleb;

  		sleb = ubifs_scan(c, lnum, 0, buf, 0);

  		if (IS_ERR(sleb)) {
  			err = PTR_ERR(sleb);
  			break;
  		}
  
  		err = dbg_read_orphans(ci, sleb);
  		ubifs_scan_destroy(sleb);
  		if (err)
  			break;
  	}

  	vfree(buf);

  	return err;
  }
  
  static int dbg_check_orphans(struct ubifs_info *c)
  {
  	struct check_info ci;
  	int err;

  	if (!dbg_is_chk_orph(c))

  		return 0;
  
  	ci.last_ino = 0;
  	ci.tot_inos = 0;
  	ci.missing  = 0;
  	ci.leaf_cnt = 0;
  	ci.root = RB_ROOT;
  	ci.node = kmalloc(UBIFS_MAX_INO_NODE_SZ, GFP_NOFS);
  	if (!ci.node) {

  		ubifs_err(c, "out of memory");

  		return -ENOMEM;
  	}
  
  	err = dbg_scan_orphans(c, &ci);
  	if (err)
  		goto out;
  
  	err = dbg_walk_index(c, &dbg_orphan_check, NULL, &ci);
  	if (err) {

  		ubifs_err(c, "cannot scan TNC, error %d", err);

  		goto out;
  	}
  
  	if (ci.missing) {

  		ubifs_err(c, "%lu missing orphan(s)", ci.missing);

  		err = -EINVAL;
  		goto out;
  	}
  
  	dbg_cmt("last inode number is %lu", ci.last_ino);
  	dbg_cmt("total number of inodes is %lu", ci.tot_inos);
  	dbg_cmt("total number of leaf nodes is %llu", ci.leaf_cnt);
  
  out:
  	dbg_free_check_tree(&ci.root);
  	kfree(ci.node);
  	return err;
  }