/*
   * 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
   *
   * Authors: Adrian Hunter
   *          Artem Bityutskiy (Битюцкий Артём)
   */
  
  /*
   * This file implements functions that manage the running of the commit process.
   * Each affected module has its own functions to accomplish their part in the
   * commit and those functions are called here.
   *
   * The commit is the process whereby all updates to the index and LEB properties
   * are written out together and the journal becomes empty. This keeps the
   * file system consistent - at all times the state can be recreated by reading
   * the index and LEB properties and then replaying the journal.
   *
   * The commit is split into two parts named "commit start" and "commit end".
   * During commit start, the commit process has exclusive access to the journal
   * by holding the commit semaphore down for writing. As few I/O operations as
   * possible are performed during commit start, instead the nodes that are to be
   * written are merely identified. During commit end, the commit semaphore is no
   * longer held and the journal is again in operation, allowing users to continue
   * to use the file system while the bulk of the commit I/O is performed. The
   * purpose of this two-step approach is to prevent the commit from causing any
   * latency blips. Note that in any case, the commit does not prevent lookups
   * (as permitted by the TNC mutex), or access to VFS data structures e.g. page
   * cache.
   */
  
  #include <linux/freezer.h>
  #include <linux/kthread.h>

  #include <linux/slab.h>

  #include "ubifs.h"

  /*
   * nothing_to_commit - check if there is nothing to commit.
   * @c: UBIFS file-system description object
   *
   * This is a helper function which checks if there is anything to commit. It is
   * used as an optimization to avoid starting the commit if it is not really
   * necessary. Indeed, the commit operation always assumes flash I/O (e.g.,
   * writing the commit start node to the log), and it is better to avoid doing
   * this unnecessarily. E.g., 'ubifs_sync_fs()' runs the commit, but if there is
   * nothing to commit, it is more optimal to avoid any flash I/O.
   *
   * This function has to be called with @c->commit_sem locked for writing -
   * this function does not take LPT/TNC locks because the @c->commit_sem
   * guarantees that we have exclusive access to the TNC and LPT data structures.
   *
   * This function returns %1 if there is nothing to commit and %0 otherwise.
   */
  static int nothing_to_commit(struct ubifs_info *c)
  {
  	/*
  	 * During mounting or remounting from R/O mode to R/W mode we may
  	 * commit for various recovery-related reasons.
  	 */
  	if (c->mounting || c->remounting_rw)
  		return 0;
  
  	/*
  	 * If the root TNC node is dirty, we definitely have something to
  	 * commit.
  	 */

  	if (c->zroot.znode && ubifs_zn_dirty(c->zroot.znode))

  		return 0;
  
  	/*
  	 * Even though the TNC is clean, the LPT tree may have dirty nodes. For
  	 * example, this may happen if the budgeting subsystem invoked GC to
  	 * make some free space, and the GC found an LEB with only dirty and
  	 * free space. In this case GC would just change the lprops of this
  	 * LEB (by turning all space into free space) and unmap it.
  	 */
  	if (c->nroot && test_bit(DIRTY_CNODE, &c->nroot->flags))
  		return 0;
  
  	ubifs_assert(atomic_long_read(&c->dirty_zn_cnt) == 0);
  	ubifs_assert(c->dirty_pn_cnt == 0);
  	ubifs_assert(c->dirty_nn_cnt == 0);
  
  	return 1;
  }

  /**
   * do_commit - commit the journal.
   * @c: UBIFS file-system description object
   *
   * This function implements UBIFS commit. It has to be called with commit lock
   * locked. Returns zero in case of success and a negative error code in case of
   * failure.
   */
  static int do_commit(struct ubifs_info *c)
  {
  	int err, new_ltail_lnum, old_ltail_lnum, i;
  	struct ubifs_zbranch zroot;
  	struct ubifs_lp_stats lst;
  
  	dbg_cmt("start");

  	ubifs_assert(!c->ro_media && !c->ro_mount);

  
  	if (c->ro_error) {

  		err = -EROFS;
  		goto out_up;
  	}

  	if (nothing_to_commit(c)) {
  		up_write(&c->commit_sem);
  		err = 0;
  		goto out_cancel;
  	}

  	/* Sync all write buffers (necessary for recovery) */
  	for (i = 0; i < c->jhead_cnt; i++) {
  		err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
  		if (err)
  			goto out_up;
  	}

  	c->cmt_no += 1;

  	err = ubifs_gc_start_commit(c);
  	if (err)
  		goto out_up;
  	err = dbg_check_lprops(c);
  	if (err)
  		goto out_up;
  	err = ubifs_log_start_commit(c, &new_ltail_lnum);
  	if (err)
  		goto out_up;
  	err = ubifs_tnc_start_commit(c, &zroot);
  	if (err)
  		goto out_up;
  	err = ubifs_lpt_start_commit(c);
  	if (err)
  		goto out_up;
  	err = ubifs_orphan_start_commit(c);
  	if (err)
  		goto out_up;
  
  	ubifs_get_lp_stats(c, &lst);
  
  	up_write(&c->commit_sem);
  
  	err = ubifs_tnc_end_commit(c);
  	if (err)
  		goto out;
  	err = ubifs_lpt_end_commit(c);
  	if (err)
  		goto out;
  	err = ubifs_orphan_end_commit(c);
  	if (err)
  		goto out;
  	old_ltail_lnum = c->ltail_lnum;
  	err = ubifs_log_end_commit(c, new_ltail_lnum);
  	if (err)
  		goto out;
  	err = dbg_check_old_index(c, &zroot);
  	if (err)
  		goto out;
  
  	mutex_lock(&c->mst_mutex);

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

  	c->mst_node->log_lnum    = cpu_to_le32(new_ltail_lnum);
  	c->mst_node->root_lnum   = cpu_to_le32(zroot.lnum);
  	c->mst_node->root_offs   = cpu_to_le32(zroot.offs);
  	c->mst_node->root_len    = cpu_to_le32(zroot.len);
  	c->mst_node->ihead_lnum  = cpu_to_le32(c->ihead_lnum);
  	c->mst_node->ihead_offs  = cpu_to_le32(c->ihead_offs);

  	c->mst_node->index_size  = cpu_to_le64(c->bi.old_idx_sz);

  	c->mst_node->lpt_lnum    = cpu_to_le32(c->lpt_lnum);
  	c->mst_node->lpt_offs    = cpu_to_le32(c->lpt_offs);
  	c->mst_node->nhead_lnum  = cpu_to_le32(c->nhead_lnum);
  	c->mst_node->nhead_offs  = cpu_to_le32(c->nhead_offs);
  	c->mst_node->ltab_lnum   = cpu_to_le32(c->ltab_lnum);
  	c->mst_node->ltab_offs   = cpu_to_le32(c->ltab_offs);
  	c->mst_node->lsave_lnum  = cpu_to_le32(c->lsave_lnum);
  	c->mst_node->lsave_offs  = cpu_to_le32(c->lsave_offs);
  	c->mst_node->lscan_lnum  = cpu_to_le32(c->lscan_lnum);
  	c->mst_node->empty_lebs  = cpu_to_le32(lst.empty_lebs);
  	c->mst_node->idx_lebs    = cpu_to_le32(lst.idx_lebs);
  	c->mst_node->total_free  = cpu_to_le64(lst.total_free);
  	c->mst_node->total_dirty = cpu_to_le64(lst.total_dirty);
  	c->mst_node->total_used  = cpu_to_le64(lst.total_used);
  	c->mst_node->total_dead  = cpu_to_le64(lst.total_dead);
  	c->mst_node->total_dark  = cpu_to_le64(lst.total_dark);
  	if (c->no_orphs)
  		c->mst_node->flags |= cpu_to_le32(UBIFS_MST_NO_ORPHS);
  	else
  		c->mst_node->flags &= ~cpu_to_le32(UBIFS_MST_NO_ORPHS);
  	err = ubifs_write_master(c);
  	mutex_unlock(&c->mst_mutex);
  	if (err)
  		goto out;
  
  	err = ubifs_log_post_commit(c, old_ltail_lnum);
  	if (err)
  		goto out;
  	err = ubifs_gc_end_commit(c);
  	if (err)
  		goto out;
  	err = ubifs_lpt_post_commit(c);
  	if (err)
  		goto out;

  out_cancel:

  	spin_lock(&c->cs_lock);
  	c->cmt_state = COMMIT_RESTING;
  	wake_up(&c->cmt_wq);
  	dbg_cmt("commit end");
  	spin_unlock(&c->cs_lock);

  	return 0;
  
  out_up:
  	up_write(&c->commit_sem);
  out:
  	ubifs_err("commit failed, error %d", err);
  	spin_lock(&c->cs_lock);
  	c->cmt_state = COMMIT_BROKEN;
  	wake_up(&c->cmt_wq);
  	spin_unlock(&c->cs_lock);
  	ubifs_ro_mode(c, err);
  	return err;
  }
  
  /**
   * run_bg_commit - run background commit if it is needed.
   * @c: UBIFS file-system description object
   *
   * This function runs background commit if it is needed. Returns zero in case
   * of success and a negative error code in case of failure.
   */
  static int run_bg_commit(struct ubifs_info *c)
  {
  	spin_lock(&c->cs_lock);
  	/*
  	 * Run background commit only if background commit was requested or if
  	 * commit is required.
  	 */
  	if (c->cmt_state != COMMIT_BACKGROUND &&
  	    c->cmt_state != COMMIT_REQUIRED)
  		goto out;
  	spin_unlock(&c->cs_lock);
  
  	down_write(&c->commit_sem);
  	spin_lock(&c->cs_lock);
  	if (c->cmt_state == COMMIT_REQUIRED)
  		c->cmt_state = COMMIT_RUNNING_REQUIRED;
  	else if (c->cmt_state == COMMIT_BACKGROUND)
  		c->cmt_state = COMMIT_RUNNING_BACKGROUND;
  	else
  		goto out_cmt_unlock;
  	spin_unlock(&c->cs_lock);
  
  	return do_commit(c);
  
  out_cmt_unlock:
  	up_write(&c->commit_sem);
  out:
  	spin_unlock(&c->cs_lock);
  	return 0;
  }
  
  /**
   * ubifs_bg_thread - UBIFS background thread function.
   * @info: points to the file-system description object
   *
   * This function implements various file-system background activities:
   * o when a write-buffer timer expires it synchronizes the appropriate
   *   write-buffer;
   * o when the journal is about to be full, it starts in-advance commit.
   *
   * Note, other stuff like background garbage collection may be added here in
   * future.
   */
  int ubifs_bg_thread(void *info)
  {
  	int err;
  	struct ubifs_info *c = info;

  	ubifs_msg("background thread \"%s\" started, PID %d",
  		  c->bgt_name, current->pid);

  	set_freezable();
  
  	while (1) {
  		if (kthread_should_stop())
  			break;
  
  		if (try_to_freeze())
  			continue;
  
  		set_current_state(TASK_INTERRUPTIBLE);
  		/* Check if there is something to do */
  		if (!c->need_bgt) {
  			/*
  			 * Nothing prevents us from going sleep now and
  			 * be never woken up and block the task which
  			 * could wait in 'kthread_stop()' forever.
  			 */
  			if (kthread_should_stop())
  				break;
  			schedule();
  			continue;
  		} else
  			__set_current_state(TASK_RUNNING);
  
  		c->need_bgt = 0;
  		err = ubifs_bg_wbufs_sync(c);
  		if (err)
  			ubifs_ro_mode(c, err);
  
  		run_bg_commit(c);
  		cond_resched();
  	}

  	ubifs_msg("background thread \"%s\" stops", c->bgt_name);

  	return 0;
  }
  
  /**
   * ubifs_commit_required - set commit state to "required".
   * @c: UBIFS file-system description object
   *
   * This function is called if a commit is required but cannot be done from the
   * calling function, so it is just flagged instead.
   */
  void ubifs_commit_required(struct ubifs_info *c)
  {
  	spin_lock(&c->cs_lock);
  	switch (c->cmt_state) {
  	case COMMIT_RESTING:
  	case COMMIT_BACKGROUND:
  		dbg_cmt("old: %s, new: %s", dbg_cstate(c->cmt_state),
  			dbg_cstate(COMMIT_REQUIRED));
  		c->cmt_state = COMMIT_REQUIRED;
  		break;
  	case COMMIT_RUNNING_BACKGROUND:
  		dbg_cmt("old: %s, new: %s", dbg_cstate(c->cmt_state),
  			dbg_cstate(COMMIT_RUNNING_REQUIRED));
  		c->cmt_state = COMMIT_RUNNING_REQUIRED;
  		break;
  	case COMMIT_REQUIRED:
  	case COMMIT_RUNNING_REQUIRED:
  	case COMMIT_BROKEN:
  		break;
  	}
  	spin_unlock(&c->cs_lock);
  }
  
  /**
   * ubifs_request_bg_commit - notify the background thread to do a commit.
   * @c: UBIFS file-system description object
   *
   * This function is called if the journal is full enough to make a commit
   * worthwhile, so background thread is kicked to start it.
   */
  void ubifs_request_bg_commit(struct ubifs_info *c)
  {
  	spin_lock(&c->cs_lock);
  	if (c->cmt_state == COMMIT_RESTING) {
  		dbg_cmt("old: %s, new: %s", dbg_cstate(c->cmt_state),
  			dbg_cstate(COMMIT_BACKGROUND));
  		c->cmt_state = COMMIT_BACKGROUND;
  		spin_unlock(&c->cs_lock);
  		ubifs_wake_up_bgt(c);
  	} else
  		spin_unlock(&c->cs_lock);
  }
  
  /**
   * wait_for_commit - wait for commit.
   * @c: UBIFS file-system description object
   *
   * This function sleeps until the commit operation is no longer running.
   */
  static int wait_for_commit(struct ubifs_info *c)
  {
  	dbg_cmt("pid %d goes sleep", current->pid);
  
  	/*
  	 * The following sleeps if the condition is false, and will be woken
  	 * when the commit ends. It is possible, although very unlikely, that we
  	 * will wake up and see the subsequent commit running, rather than the
  	 * one we were waiting for, and go back to sleep.  However, we will be
  	 * woken again, so there is no danger of sleeping forever.
  	 */
  	wait_event(c->cmt_wq, c->cmt_state != COMMIT_RUNNING_BACKGROUND &&
  			      c->cmt_state != COMMIT_RUNNING_REQUIRED);
  	dbg_cmt("commit finished, pid %d woke up", current->pid);
  	return 0;
  }
  
  /**
   * ubifs_run_commit - run or wait for commit.
   * @c: UBIFS file-system description object
   *
   * This function runs commit and returns zero in case of success and a negative
   * error code in case of failure.
   */
  int ubifs_run_commit(struct ubifs_info *c)
  {
  	int err = 0;
  
  	spin_lock(&c->cs_lock);
  	if (c->cmt_state == COMMIT_BROKEN) {

  		err = -EROFS;

  		goto out;
  	}
  
  	if (c->cmt_state == COMMIT_RUNNING_BACKGROUND)
  		/*
  		 * We set the commit state to 'running required' to indicate
  		 * that we want it to complete as quickly as possible.
  		 */
  		c->cmt_state = COMMIT_RUNNING_REQUIRED;
  
  	if (c->cmt_state == COMMIT_RUNNING_REQUIRED) {
  		spin_unlock(&c->cs_lock);
  		return wait_for_commit(c);
  	}
  	spin_unlock(&c->cs_lock);
  
  	/* Ok, the commit is indeed needed */
  
  	down_write(&c->commit_sem);
  	spin_lock(&c->cs_lock);
  	/*
  	 * Since we unlocked 'c->cs_lock', the state may have changed, so
  	 * re-check it.
  	 */
  	if (c->cmt_state == COMMIT_BROKEN) {

  		err = -EROFS;

  		goto out_cmt_unlock;
  	}
  
  	if (c->cmt_state == COMMIT_RUNNING_BACKGROUND)
  		c->cmt_state = COMMIT_RUNNING_REQUIRED;
  
  	if (c->cmt_state == COMMIT_RUNNING_REQUIRED) {
  		up_write(&c->commit_sem);
  		spin_unlock(&c->cs_lock);
  		return wait_for_commit(c);
  	}
  	c->cmt_state = COMMIT_RUNNING_REQUIRED;
  	spin_unlock(&c->cs_lock);
  
  	err = do_commit(c);
  	return err;
  
  out_cmt_unlock:
  	up_write(&c->commit_sem);
  out:
  	spin_unlock(&c->cs_lock);
  	return err;
  }
  
  /**
   * ubifs_gc_should_commit - determine if it is time for GC to run commit.
   * @c: UBIFS file-system description object
   *
   * This function is called by garbage collection to determine if commit should
   * be run. If commit state is @COMMIT_BACKGROUND, which means that the journal
   * is full enough to start commit, this function returns true. It is not
   * absolutely necessary to commit yet, but it feels like this should be better
   * then to keep doing GC. This function returns %1 if GC has to initiate commit
   * and %0 if not.
   */
  int ubifs_gc_should_commit(struct ubifs_info *c)
  {
  	int ret = 0;
  
  	spin_lock(&c->cs_lock);
  	if (c->cmt_state == COMMIT_BACKGROUND) {
  		dbg_cmt("commit required now");
  		c->cmt_state = COMMIT_REQUIRED;
  	} else
  		dbg_cmt("commit not requested");
  	if (c->cmt_state == COMMIT_REQUIRED)
  		ret = 1;
  	spin_unlock(&c->cs_lock);
  	return ret;
  }

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

  
  /**
   * struct idx_node - hold index nodes during index tree traversal.
   * @list: list
   * @iip: index in parent (slot number of this indexing node in the parent
   *       indexing node)
   * @upper_key: all keys in this indexing node have to be less or equivalent to
   *             this key
   * @idx: index node (8-byte aligned because all node structures must be 8-byte
   *       aligned)
   */
  struct idx_node {
  	struct list_head list;
  	int iip;
  	union ubifs_key upper_key;

  	struct ubifs_idx_node idx __aligned(8);

  };
  
  /**
   * dbg_old_index_check_init - get information for the next old index check.
   * @c: UBIFS file-system description object
   * @zroot: root of the index
   *
   * This function records information about the index that will be needed for the
   * next old index check i.e. 'dbg_check_old_index()'.
   *
   * This function returns %0 on success and a negative error code on failure.
   */
  int dbg_old_index_check_init(struct ubifs_info *c, struct ubifs_zbranch *zroot)
  {
  	struct ubifs_idx_node *idx;
  	int lnum, offs, len, err = 0;

  	struct ubifs_debug_info *d = c->dbg;

  	d->old_zroot = *zroot;
  	lnum = d->old_zroot.lnum;
  	offs = d->old_zroot.offs;
  	len = d->old_zroot.len;

  
  	idx = kmalloc(c->max_idx_node_sz, GFP_NOFS);
  	if (!idx)
  		return -ENOMEM;
  
  	err = ubifs_read_node(c, idx, UBIFS_IDX_NODE, len, lnum, offs);
  	if (err)
  		goto out;

  	d->old_zroot_level = le16_to_cpu(idx->level);
  	d->old_zroot_sqnum = le64_to_cpu(idx->ch.sqnum);

  out:
  	kfree(idx);
  	return err;
  }
  
  /**
   * dbg_check_old_index - check the old copy of the index.
   * @c: UBIFS file-system description object
   * @zroot: root of the new index
   *
   * In order to be able to recover from an unclean unmount, a complete copy of
   * the index must exist on flash. This is the "old" index. The commit process
   * must write the "new" index to flash without overwriting or destroying any
   * part of the old index. This function is run at commit end in order to check
   * that the old index does indeed exist completely intact.
   *
   * This function returns %0 on success and a negative error code on failure.
   */
  int dbg_check_old_index(struct ubifs_info *c, struct ubifs_zbranch *zroot)
  {
  	int lnum, offs, len, err = 0, uninitialized_var(last_level), child_cnt;
  	int first = 1, iip;

  	struct ubifs_debug_info *d = c->dbg;

  	union ubifs_key uninitialized_var(lower_key), upper_key, l_key, u_key;

  	unsigned long long uninitialized_var(last_sqnum);
  	struct ubifs_idx_node *idx;
  	struct list_head list;
  	struct idx_node *i;
  	size_t sz;

  	if (!dbg_is_chk_index(c))

  		return 0;

  
  	INIT_LIST_HEAD(&list);
  
  	sz = sizeof(struct idx_node) + ubifs_idx_node_sz(c, c->fanout) -
  	     UBIFS_IDX_NODE_SZ;
  
  	/* Start at the old zroot */

  	lnum = d->old_zroot.lnum;
  	offs = d->old_zroot.offs;
  	len = d->old_zroot.len;

  	iip = 0;
  
  	/*
  	 * Traverse the index tree preorder depth-first i.e. do a node and then
  	 * its subtrees from left to right.
  	 */
  	while (1) {
  		struct ubifs_branch *br;
  
  		/* Get the next index node */
  		i = kmalloc(sz, GFP_NOFS);
  		if (!i) {
  			err = -ENOMEM;
  			goto out_free;
  		}
  		i->iip = iip;
  		/* Keep the index nodes on our path in a linked list */
  		list_add_tail(&i->list, &list);
  		/* Read the index node */
  		idx = &i->idx;
  		err = ubifs_read_node(c, idx, UBIFS_IDX_NODE, len, lnum, offs);
  		if (err)
  			goto out_free;
  		/* Validate index node */
  		child_cnt = le16_to_cpu(idx->child_cnt);
  		if (child_cnt < 1 || child_cnt > c->fanout) {
  			err = 1;
  			goto out_dump;
  		}
  		if (first) {
  			first = 0;
  			/* Check root level and sqnum */

  			if (le16_to_cpu(idx->level) != d->old_zroot_level) {

  				err = 2;
  				goto out_dump;
  			}

  			if (le64_to_cpu(idx->ch.sqnum) != d->old_zroot_sqnum) {

  				err = 3;
  				goto out_dump;
  			}
  			/* Set last values as though root had a parent */
  			last_level = le16_to_cpu(idx->level) + 1;
  			last_sqnum = le64_to_cpu(idx->ch.sqnum) + 1;
  			key_read(c, ubifs_idx_key(c, idx), &lower_key);
  			highest_ino_key(c, &upper_key, INUM_WATERMARK);
  		}
  		key_copy(c, &upper_key, &i->upper_key);
  		if (le16_to_cpu(idx->level) != last_level - 1) {
  			err = 3;
  			goto out_dump;
  		}
  		/*
  		 * The index is always written bottom up hence a child's sqnum
  		 * is always less than the parents.
  		 */
  		if (le64_to_cpu(idx->ch.sqnum) >= last_sqnum) {
  			err = 4;
  			goto out_dump;
  		}
  		/* Check key range */
  		key_read(c, ubifs_idx_key(c, idx), &l_key);
  		br = ubifs_idx_branch(c, idx, child_cnt - 1);
  		key_read(c, &br->key, &u_key);
  		if (keys_cmp(c, &lower_key, &l_key) > 0) {
  			err = 5;
  			goto out_dump;
  		}
  		if (keys_cmp(c, &upper_key, &u_key) < 0) {
  			err = 6;
  			goto out_dump;
  		}
  		if (keys_cmp(c, &upper_key, &u_key) == 0)
  			if (!is_hash_key(c, &u_key)) {
  				err = 7;
  				goto out_dump;
  			}
  		/* Go to next index node */
  		if (le16_to_cpu(idx->level) == 0) {
  			/* At the bottom, so go up until can go right */
  			while (1) {
  				/* Drop the bottom of the list */
  				list_del(&i->list);
  				kfree(i);
  				/* No more list means we are done */
  				if (list_empty(&list))
  					goto out;
  				/* Look at the new bottom */
  				i = list_entry(list.prev, struct idx_node,
  					       list);
  				idx = &i->idx;
  				/* Can we go right */
  				if (iip + 1 < le16_to_cpu(idx->child_cnt)) {
  					iip = iip + 1;
  					break;
  				} else
  					/* Nope, so go up again */
  					iip = i->iip;
  			}
  		} else
  			/* Go down left */
  			iip = 0;
  		/*
  		 * We have the parent in 'idx' and now we set up for reading the
  		 * child pointed to by slot 'iip'.
  		 */
  		last_level = le16_to_cpu(idx->level);
  		last_sqnum = le64_to_cpu(idx->ch.sqnum);
  		br = ubifs_idx_branch(c, idx, iip);
  		lnum = le32_to_cpu(br->lnum);
  		offs = le32_to_cpu(br->offs);
  		len = le32_to_cpu(br->len);
  		key_read(c, &br->key, &lower_key);
  		if (iip + 1 < le16_to_cpu(idx->child_cnt)) {
  			br = ubifs_idx_branch(c, idx, iip + 1);
  			key_read(c, &br->key, &upper_key);
  		} else
  			key_copy(c, &i->upper_key, &upper_key);
  	}
  out:
  	err = dbg_old_index_check_init(c, zroot);
  	if (err)
  		goto out_free;
  
  	return 0;
  
  out_dump:

  	ubifs_err("dumping index node (iip=%d)", i->iip);

  	ubifs_dump_node(c, idx);

  	list_del(&i->list);
  	kfree(i);
  	if (!list_empty(&list)) {
  		i = list_entry(list.prev, struct idx_node, list);

  		ubifs_err("dumping parent index node");

  		ubifs_dump_node(c, &i->idx);

  	}
  out_free:
  	while (!list_empty(&list)) {
  		i = list_entry(list.next, struct idx_node, list);
  		list_del(&i->list);
  		kfree(i);
  	}
  	ubifs_err("failed, error %d", err);
  	if (err > 0)
  		err = -EINVAL;
  	return err;
  }