TNC - tree node cache - the central UBIFS entity. It is basically
in-RAM cache of the on-flash indexing B-tree. But TNC also indexes
the journal, so that they are not always equivalent.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
---
 fs/ubifs/tnc.c | 3483 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 3483 insertions(+), 0 deletions(-)

diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
new file mode 100644
index 0000000..27e2b60
--- /dev/null
+++ b/fs/ubifs/tnc.c
@@ -0,0 +1,3483 @@
+/*
+ * 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 TNC (Tree Node Cache) which caches indexing nodes of
+ * the UBIFS B-tree.
+ *
+ * At the moment the locking rules of the TNC tree are quite simple and
+ * straightforward. We just have a mutex and lock it when we traverse the
+ * tree. If a znode is not in memory, we read it from flash while still having
+ * the mutex locked.
+ */
+
+#include <linux/crc32.h>
+#include "ubifs.h"
+
+/**
+ * insert_old_idx - record an index node obsoleted since the last commit start.
+ * @c: UBIFS file-system description object
+ * @lnum: LEB number of obsoleted index node
+ * @offs: offset of obsoleted index node
+ *
+ * Returns %0 on success, and a negative error code on failure.
+ */
+static int insert_old_idx(struct ubifs_info *c, int lnum, int offs)
+{
+	struct ubifs_old_idx *old_idx, *o;
+	struct rb_node **p, *parent = NULL;
+
+	ubifs_assert(lnum >= c->main_first && lnum < c->leb_cnt);
+	ubifs_assert(offs >= 0 && offs < c->leb_size);
+
+	old_idx = kmalloc(sizeof(struct ubifs_old_idx), GFP_NOFS);
+	if (!old_idx)
+		return -ENOMEM;
+	old_idx->lnum = lnum;
+	old_idx->offs = offs;
+
+	p = &c->old_idx.rb_node;
+	while (*p) {
+		parent = *p;
+		o = rb_entry(parent, struct ubifs_old_idx, rb);
+		if (lnum < o->lnum)
+			p = &(*p)->rb_left;
+		else if (lnum > o->lnum)
+			p = &(*p)->rb_right;
+		else if (offs < o->offs)
+			p = &(*p)->rb_left;
+		else if (offs > o->offs)
+			p = &(*p)->rb_right;
+		else {
+			ubifs_err("old idx added twice!");
+			kfree(old_idx);
+			return 0;
+		}
+	}
+	rb_link_node(&old_idx->rb, parent, p);
+	rb_insert_color(&old_idx->rb, &c->old_idx);
+	return 0;
+}
+
+/**
+ * insert_old_idx_znode - record a znode obsoleted since last commit start.
+ * @c: UBIFS file-system description object
+ * @znode: znode of obsoleted index node
+ *
+ * Returns %0 on success, and a negative error code on failure.
+ */
+int insert_old_idx_znode(struct ubifs_info *c, struct ubifs_znode *znode)
+{
+	if (znode->parent) {
+		struct ubifs_zbranch *zbr;
+
+		zbr = &znode->parent->zbranch[znode->iip];
+		if (zbr->len)
+			return insert_old_idx(c, zbr->lnum, zbr->offs);
+	} else
+		if (c->zroot.len)
+			return insert_old_idx(c, c->zroot.lnum,
+					      c->zroot.offs);
+	return 0;
+}
+
+/**
+ * ins_clr_old_idx_znode - record a znode obsoleted since last commit start.
+ * @c: UBIFS file-system description object
+ * @znode: znode of obsoleted index node
+ *
+ * Returns %0 on success, and a negative error code on failure.
+ */
+static int ins_clr_old_idx_znode(struct ubifs_info *c,
+				 struct ubifs_znode *znode)
+{
+	int err;
+
+	if (znode->parent) {
+		struct ubifs_zbranch *zbr;
+
+		zbr = &znode->parent->zbranch[znode->iip];
+		if (zbr->len) {
+			err = insert_old_idx(c, zbr->lnum, zbr->offs);
+			if (err)
+				return err;
+			zbr->lnum = 0;
+			zbr->offs = 0;
+			zbr->len = 0;
+		}
+	} else
+		if (c->zroot.len) {
+			err = insert_old_idx(c, c->zroot.lnum, c->zroot.offs);
+			if (err)
+				return err;
+			c->zroot.lnum = 0;
+			c->zroot.offs = 0;
+			c->zroot.len = 0;
+		}
+	return 0;
+}
+
+/**
+ * destroy_old_idx - destroy the old_idx RB-tree.
+ * @c: UBIFS file-system description object
+ *
+ * During start commit, the old_idx RB-tree is used to avoid overwriting index
+ * nodes that were in the index last commit but have since been deleted.  This
+ * is necessary for recovery i.e. the old index must be kept intact until the
+ * new index is successfully written.  The old-idx RB-tree is used for the
+ * in-the-gaps method of writing index nodes and is destroyed every commit.
+ */
+void destroy_old_idx(struct ubifs_info *c)
+{
+	struct rb_node *this = c->old_idx.rb_node;
+	struct ubifs_old_idx *old_idx;
+
+	while (this) {
+		if (this->rb_left) {
+			this = this->rb_left;
+			continue;
+		} else if (this->rb_right) {
+			this = this->rb_right;
+			continue;
+		}
+		old_idx = rb_entry(this, struct ubifs_old_idx, rb);
+		this = rb_parent(this);
+		if (this) {
+			if (this->rb_left == &old_idx->rb)
+				this->rb_left = NULL;
+			else
+				this->rb_right = NULL;
+		}
+		kfree(old_idx);
+	}
+	c->old_idx = RB_ROOT;
+}
+
+/**
+ * search_zbranch - search znode branch.
+ * @c: UBIFS file-system description object
+ * @znode: znode to search in
+ * @key: key to search for
+ * @n: znode branch slot number is returned here
+ *
+ * This is a helper function which search branch with key @key in @znode using
+ * binary search. The result of the search may be:
+ *   o exact match, then %1 is returned, and the slot number of the branch is
+ *     stored in @n;
+ *   o no exact match, then %0 is returned and the slot number of the left
+ *   closest branch is returned in @n.
+ */
+static int search_zbranch(const struct ubifs_info *c,
+			  const struct ubifs_znode *znode,
+			  const union ubifs_key *key, int *n)
+{
+	int beg = 0, end = znode->child_cnt, uninitialized_var(mid);
+	int uninitialized_var(cmp);
+	const struct ubifs_zbranch *zbr = &znode->zbranch[0];
+
+	ubifs_assert(end > beg);
+
+	while (end > beg) {
+		mid = (beg + end) >> 1;
+		cmp = keys_cmp(c, key, &zbr[mid].key);
+		if (cmp > 0)
+			beg = mid + 1;
+		else if (cmp < 0)
+			end = mid;
+		else {
+			*n = mid;
+			return 1;
+		}
+	}
+
+	*n = end - 1;
+
+	/* The insert point is after *n */
+	ubifs_assert(*n >= -1 && *n < znode->child_cnt);
+	if (*n == -1)
+		ubifs_assert(keys_cmp(c, key, &zbr[0].key) < 0);
+	else
+		ubifs_assert(keys_cmp(c, key, &zbr[*n].key) > 0);
+	if (*n + 1 < znode->child_cnt)
+		ubifs_assert(keys_cmp(c, key, &zbr[*n + 1].key) < 0);
+
+	return 0;
+}
+
+/**
+ * read_znode - read an indexing node from flash and fill znode.
+ * @c: UBIFS file-system description object
+ * @lnum: LEB of the indexing node to read
+ * @offs: node offset
+ * @len: node length
+ * @znode: znode to read to
+ *
+ * This function reads an indexing node from the flash media and fills znode
+ * with the read data. Returns zero in case of success and a negative error
+ * code in case of failure. The read indexing node is validated and if anything
+ * is wrong with it, this function prints complaint messages and returns
+ * %-EINVAL.
+ */
+static int read_znode(struct ubifs_info *c, int lnum, int offs, int len,
+		      struct ubifs_znode *znode)
+{
+	int i, err, type, cmp;
+	struct ubifs_idx_node *idx;
+
+	idx = kmalloc(c->max_idx_node_sz, GFP_KERNEL);
+	if (!idx)
+		return -ENOMEM;
+
+	err = ubifs_read_node(c, idx, UBIFS_IDX_NODE, len, lnum, offs);
+	if (err < 0)
+		goto out;
+
+	znode->child_cnt = le16_to_cpu(idx->child_cnt);
+	znode->level = le16_to_cpu(idx->level);
+
+	dbg_tnc("LEB %d:%d, level %d, %d branch",
+		lnum, offs, znode->level, znode->child_cnt);
+
+	if (znode->child_cnt > c->fanout || znode->level > UBIFS_MAX_LEVELS) {
+		dbg_err("current fanout %d, branch count %d",
+			c->fanout, znode->child_cnt);
+		dbg_err("max levels %d, znode level %d",
+			UBIFS_MAX_LEVELS, znode->level);
+		goto out_dump;
+	}
+
+	for (i = 0; i < znode->child_cnt; i++) {
+		const struct ubifs_branch *br = ubifs_idx_branch(c, idx, i);
+		struct ubifs_zbranch *zbr = &znode->zbranch[i];
+
+		key_read(c, &br->key, &zbr->key);
+		zbr->lnum = le32_to_cpu(br->lnum);
+		zbr->offs = le32_to_cpu(br->offs);
+		zbr->len  = le32_to_cpu(br->len);
+		zbr->znode = NULL;
+
+		/* Validate branch */
+
+		if (unlikely(zbr->lnum < c->main_first ||
+			     zbr->lnum >= c->leb_cnt || zbr->offs < 0 ||
+			     zbr->offs + zbr->len > c->leb_size ||
+			     zbr->offs & 7)) {
+			dbg_err("bad branch %d", i);
+			goto out_dump;
+		}
+
+		switch (key_type(c, &zbr->key)) {
+		case UBIFS_INO_KEY:
+		case UBIFS_DATA_KEY:
+		case UBIFS_DENT_KEY:
+		case UBIFS_XENT_KEY:
+			break;
+		default:
+			dbg_key(c, &zbr->key, "bad key type at slot %d: ", i);
+			goto out_dump;
+		}
+
+		if (znode->level)
+			continue;
+
+		type = key_type(c, &zbr->key);
+		if (c->ranges[type].max_len == 0) {
+			if (unlikely(zbr->len != c->ranges[type].len)) {
+				dbg_err("bad target node (type %d) length (%d)",
+					type, zbr->len);
+				dbg_err("have to be %d", c->ranges[type].len);
+				goto out_dump;
+			}
+		} else if (unlikely(zbr->len < c->ranges[type].min_len ||
+				    zbr->len > c->ranges[type].max_len)) {
+			dbg_err("bad target node (type %d) length (%d)",
+				type, zbr->len);
+			dbg_err("have to be in range of %d-%d",
+				c->ranges[type].min_len,
+				c->ranges[type].max_len);
+			goto out_dump;
+		}
+	}
+
+	/*
+	 * Ensure that the next key is greater or equivalent to the
+	 * previous one.
+	 */
+	for (i = 0; i < znode->child_cnt - 1; i++) {
+		const union ubifs_key *key1, *key2;
+
+		key1 = &znode->zbranch[i].key;
+		key2 = &znode->zbranch[i + 1].key;
+
+		cmp = keys_cmp(c, key1, key2);
+		if (cmp > 0) {
+			dbg_err("bad key order (keys %d and %d)", i, i + 1);
+			goto out_dump;
+		} else if (cmp == 0 && !is_hash_key(c, key1)) {
+			/* These can only be keys with colliding hash */
+			dbg_err("keys %d and %d are not hashed but equivalent",
+				i, i + 1);
+			goto out_dump;
+		}
+	}
+
+	kfree(idx);
+	return 0;
+
+out:
+	kfree(idx);
+	return err;
+
+out_dump:
+	ubifs_err("bad indexing node at LEB %d:%d", lnum, offs);
+	dbg_dump_node(c, idx);
+	kfree(idx);
+	return -EINVAL;
+}
+
+/**
+ * load_znode - load znode to TNC cache.
+ * @c: UBIFS file-system description object
+ * @zbr: znode branch
+ * @parent: znode's parent
+ * @iip: index in parent
+ *
+ * This function loads znode pointed to by @zbr into the TNC cache and
+ * returns pointer to it in case of success and a negative error code in case
+ * of failure.
+ */
+static struct ubifs_znode *load_znode(struct ubifs_info *c,
+				      struct ubifs_zbranch *zbr,
+				      struct ubifs_znode *parent, int iip)
+{
+	int err;
+	struct ubifs_znode *znode;
+
+	ubifs_assert(!zbr->znode);
+	/*
+	 * A slab cache is not presently used for znodes because the znode size
+	 * depends on the fanout which is stored in the superblock.
+	 */
+	znode = kzalloc(c->max_znode_sz, GFP_NOFS);
+	if (!znode)
+		return ERR_PTR(-ENOMEM);
+
+	err = read_znode(c, zbr->lnum, zbr->offs, zbr->len, znode);
+	if (err)
+		goto out;
+
+	atomic_long_inc(&c->clean_zn_cnt);
+
+	/*
+	 * Increment the global clean znode counter as well. It is OK that
+	 * global and per-FS clean znode counters may be inconsistent for some
+	 * short time (because we might be preempted at this point), the global
+	 * one is only used in shrinker.
+	 */
+	atomic_long_inc(&ubifs_clean_zn_cnt);
+
+	zbr->znode = znode;
+	znode->parent = parent;
+	znode->time = get_seconds();
+	znode->iip = iip;
+
+	return znode;
+
+out:
+	kfree(znode);
+	return ERR_PTR(err);
+}
+
+/**
+ * copy_znode - copy a dirty znode.
+ * @c: UBIFS file-system description object
+ * @znode: znode to copy
+ *
+ * A dirty znode being committed may not be changed, so it is copied.
+ */
+static struct ubifs_znode *copy_znode(struct ubifs_info *c,
+				      struct ubifs_znode *znode)
+{
+	struct ubifs_znode *zn;
+
+	zn = kzalloc(c->max_znode_sz, GFP_NOFS);
+	if (!zn)
+		return ERR_PTR(-ENOMEM);
+
+	memcpy(zn, znode, c->max_znode_sz);
+
+	ubifs_assert(!test_bit(OBSOLETE_ZNODE, &znode->flags));
+	set_bit(OBSOLETE_ZNODE, &znode->flags);
+
+	if (znode->level != 0) {
+		int i;
+		const int n = zn->child_cnt;
+
+		/* The children now have new parent */
+		for (i = 0; i < n; i++) {
+			struct ubifs_zbranch *zbr = &zn->zbranch[i];
+
+			if (zbr->znode)
+				zbr->znode->parent = zn;
+		}
+	}
+
+	zn->cnext = NULL;
+	set_bit(DIRTY_ZNODE, &zn->flags);
+	clear_bit(COW_ZNODE, &zn->flags);
+	atomic_long_inc(&c->dirty_zn_cnt);
+
+	return zn;
+}
+
+/**
+ * add_idx_dirt - add dirt due to a dirty znode.
+ * @c: UBIFS file-system description object
+ * @lnum: LEB number of index node
+ * @dirt: size of index node
+ *
+ * This function updates lprops dirty space and the new size of the index.
+ */
+static int add_idx_dirt(struct ubifs_info *c, int lnum, int dirt)
+{
+	c->calc_idx_sz -= ALIGN(dirt, 8);
+	return ubifs_add_dirt(c, lnum, dirt);
+}
+
+/**
+ * dirty_cow_znode - ensure a znode is not being committed.
+ * @c: UBIFS file-system description object
+ * @zbr: branch of znode to check
+ *
+ * Returns dirtied znode on success or negative error code on failure.
+ */
+static struct ubifs_znode *dirty_cow_znode(struct ubifs_info *c,
+					   struct ubifs_zbranch *zbr)
+{
+	struct ubifs_znode *znode = zbr->znode;
+	struct ubifs_znode *zn;
+	int err;
+
+	if (!test_bit(COW_ZNODE, &znode->flags)) {
+		/* znode is not being committed */
+		if (!test_and_set_bit(DIRTY_ZNODE, &znode->flags)) {
+			atomic_long_inc(&c->dirty_zn_cnt);
+			atomic_long_dec(&c->clean_zn_cnt);
+			atomic_long_dec(&ubifs_clean_zn_cnt);
+			err = add_idx_dirt(c, zbr->lnum, zbr->len);
+			if (err)
+				return ERR_PTR(err);
+		}
+		return znode;
+	}
+
+	zn = copy_znode(c, znode);
+	if (IS_ERR(zn))
+		return zn;
+
+	if (zbr->len) {
+		err = insert_old_idx(c, zbr->lnum, zbr->offs);
+		if (err)
+			return ERR_PTR(err);
+
+		err = add_idx_dirt(c, zbr->lnum, zbr->len);
+	} else
+		err = 0;
+
+	zbr->znode = zn;
+	zbr->lnum = 0;
+	zbr->offs = 0;
+	zbr->len = 0;
+
+	if (err)
+		return ERR_PTR(err);
+
+	return zn;
+}
+
+/**
+ * lookup_level0 - search for zero-level znode
+ * @c: UBIFS file-system description object
+ * @key:  key to lookup
+ * @zn: znode is returned here
+ * @n: znode branch slot number is returned here
+ *
+ * This function looks up the TNC tree and search for zero-level znode which
+ * refers key @key. The found zero-level znode is returned in @zn. There are 3
+ * cases:
+ *   o exact match, i.e. the found zero-level znode contains key @key, then %1
+ *     is returned and slot number of the matched branch is stored in @n;
+ *   o not exact match, which means that zero-level znode does not contain @key
+ *     then %0 is returned and slot number of the closed branch is stored in
+ *     @n;
+ *   o @key is so small that it is even less then the lowest key of the
+ *     leftmost zero-level node, then %0 is returned and %0 is stored in @n.
+ *
+ * Note, when the TNC tree is traversed, some znodes may be absent, then this
+ * function reads corresponding indexing nodes and inserts them to TNC.. In
+ * case of failure, a negative error code is returned.
+ */
+static int lookup_level0(struct ubifs_info *c, const union ubifs_key *key,
+			 struct ubifs_znode **zn, int *n)
+{
+	int exact;
+	struct ubifs_znode *znode;
+	unsigned long time = get_seconds();
+
+	dbg_tnc_key(c, key, "search key");
+
+	znode = c->zroot.znode;
+	if (unlikely(!znode)) {
+		znode = load_znode(c, &c->zroot, NULL, 0);
+		if (IS_ERR(znode))
+			return PTR_ERR(znode);
+	}
+
+	znode->time = time;
+
+	while (1) {
+		struct ubifs_zbranch *zbr;
+
+		/*
+		 * The below is a debugging hack to make UBIFS eat RAM and
+		 * cause fake memory pressure. It is compiled out if it is not
+		 * enabled in kernel configuration.
+		 */
+		dbg_eat_memory();
+
+		exact = search_zbranch(c, znode, key, n);
+
+		if (znode->level == 0)
+			break;
+
+		if (*n < 0)
+			*n = 0;
+		zbr = &znode->zbranch[*n];
+
+		dbg_tnc_key(c, &zbr->key, "at lvl %d, next zbr %d, key",
+			    znode->level, *n);
+
+		if (zbr->znode) {
+			znode->time = time;
+			znode = zbr->znode;
+			continue;
+		}
+
+		/* znode is not in TNC cache, load it from the media */
+		znode = load_znode(c, zbr, znode, *n);
+		if (IS_ERR(znode))
+			return PTR_ERR(znode);
+	}
+
+	*zn = znode;
+	ubifs_assert(exact >= 0 && exact < c->fanout);
+	return exact;
+}
+
+/**
+ * lookup_level0_dirty - search for zero-level znode dirtying
+ * @c: UBIFS file-system description object
+ * @key:  key to lookup
+ * @zn: znode is returned here
+ * @n: znode branch slot number is returned here
+ *
+ * This function looks up the TNC tree and search for zero-level znode which
+ * refers key @key. The found zero-level znode is returned in @zn. There are 3
+ * cases:
+ *   o exact match, i.e. the found zero-level znode contains key @key, then %1
+ *     is returned and slot number of the matched branch is stored in @n;
+ *   o not exact match, which means that zero-level znode does not contain @key
+ *     then %0 is returned and slot number of the closed branch is stored in
+ *     @n;
+ *   o @key is so small that it is even less then the lowest key of the
+ *     leftmost zero-level node, then %0 is returned and %0 is stored in @n.
+ *
+ * Additionally all znodes in the path from the root to the located zero-level
+ * znode are marked as dirty.
+ *
+ * Note, when the TNC tree is traversed, some znodes may be absent, then this
+ * function reads corresponding indexing nodes and inserts them to TNC.. In
+ * case of failure, a negative error code is returned.
+ */
+static int lookup_level0_dirty(struct ubifs_info *c, const union ubifs_key *key,
+			       struct ubifs_znode **zn, int *n)
+{
+	int exact;
+	struct ubifs_znode *znode;
+	unsigned long time = get_seconds();
+
+	dbg_tnc_key(c, key, "search and dirty key");
+
+	znode = c->zroot.znode;
+	if (unlikely(!znode)) {
+		znode = load_znode(c, &c->zroot, NULL, 0);
+		if (IS_ERR(znode))
+			return PTR_ERR(znode);
+	}
+
+	znode = dirty_cow_znode(c, &c->zroot);
+	if (IS_ERR(znode))
+		return PTR_ERR(znode);
+
+	znode->time = time;
+
+	while (1) {
+		struct ubifs_zbranch *zbr;
+
+		/*
+		 * The below is a debugging hack to make UBIFS eat RAM and
+		 * cause fake memory pressure. It is compiled out if it is not
+		 * enabled in kernel configuration.
+		 */
+		dbg_eat_memory();
+
+		exact = search_zbranch(c, znode, key, n);
+
+		if (znode->level == 0)
+			break;
+
+		if (*n < 0)
+			*n = 0;
+		zbr = &znode->zbranch[*n];
+
+		dbg_tnc_key(c, &zbr->key, "at lvl %d, next zbr %d, key",
+			    znode->level, *n);
+
+		if (zbr->znode) {
+			znode->time = time;
+			znode = dirty_cow_znode(c, zbr);
+			if (IS_ERR(znode))
+				return PTR_ERR(znode);
+			continue;
+		}
+
+		/* znode is not in TNC cache, load it from the media */
+		znode = load_znode(c, zbr, znode, *n);
+		if (IS_ERR(znode))
+			return PTR_ERR(znode);
+		znode = dirty_cow_znode(c, zbr);
+		if (IS_ERR(znode))
+			return PTR_ERR(znode);
+	}
+
+	*zn = znode;
+	ubifs_assert(exact >= 0 && exact < c->fanout);
+	return exact;
+}
+
+/**
+ * lnc_lookup - lookup the leaf-node-cache.
+ * @c: UBIFS file-system description object
+ * @zbr: zbranch of leaf node
+ * @node: leaf node
+ *
+ * Leaf nodes are non-index nodes like dent (directory entry) nodes or data
+ * nodes.  The purpose of the leaf-node-cache is to save re-reading the same
+ * leaf node over and over again.  Most things are cached by VFS, however the
+ * file system must cache directory entries for readdir and for resolving hash
+ * collisions.  The present implementation of the leaf-node-cache is extremely
+ * simple, and allows for error returns that are not used but that may be needed
+ * if a more complex implementation is created.
+ *
+ * This function returns %1 if the leaf node is in the cache, %0 if it is not,
+ * and a negative error code otherwise.
+ */
+static int lnc_lookup(struct ubifs_info *c, struct ubifs_zbranch *zbr,
+		      void *node)
+{
+	if (zbr->leaf == NULL)
+		return 0;
+	ubifs_assert(zbr->len != 0);
+	memcpy(node, zbr->leaf, zbr->len);
+	return 1;
+}
+
+/**
+ * ubifs_validate_entry - validate directory or extended attribute entry node.
+ * @c: UBIFS file-system description object
+ * @dent: the node to validate
+ *
+ * This function validates directory or extended attribute entry node @dent.
+ * Returns zero if the node is all right and a %-EINVAL if not.
+ */
+int ubifs_validate_entry(struct ubifs_info *c,
+			 const struct ubifs_dent_node *dent)
+{
+	int key_type, nlen = le16_to_cpu(dent->nlen);
+
+	if (le32_to_cpu(dent->ch.len) != nlen + UBIFS_DENT_NODE_SZ + 1 ||
+	    dent->type >= UBIFS_ITYPES_CNT ||
+	    nlen > UBIFS_MAX_NLEN || dent->name[nlen] != 0 ||
+	    strnlen(dent->name, nlen) != nlen ||
+	    le64_to_cpu(dent->inum) > MAX_INUM) {
+		const char *node_type;
+
+		if (key_type_flash(c, dent->key) == UBIFS_DENT_KEY)
+			node_type = "directory entry";
+		else
+			node_type = "extended attribute entry";
+
+		ubifs_err("bad %s node", node_type);
+		return -EINVAL;
+	}
+
+	key_type = key_type_flash(c, dent->key);
+	if (key_type_flash(c, dent->key) != UBIFS_DENT_KEY &&
+	    key_type_flash(c, dent->key) != UBIFS_XENT_KEY) {
+		ubifs_err("bad key type %d", key_type);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * lnc_add - add a leaf node to the leaf-node-cache.
+ * @c: UBIFS file-system description object
+ * @zbr: zbranch of leaf node
+ * @node: leaf node
+ *
+ * This function returns %0 to indicate success and a negative error code
+ * otherwise.
+ */
+static int lnc_add(struct ubifs_info *c, struct ubifs_zbranch *zbr,
+		   const void *node)
+{
+	int err;
+	void *lnc_node;
+	const struct ubifs_dent_node *dent = node;
+
+	ubifs_assert(zbr->leaf == NULL);
+	ubifs_assert(zbr->len != 0);
+
+	/* Add all dents, but nothing else */
+	if (key_type(c, &zbr->key) != UBIFS_DENT_KEY)
+		return 0;
+
+	err = ubifs_validate_entry(c, dent);
+	if (err) {
+		dbg_dump_node(c, dent);
+		return err;
+	}
+
+	lnc_node = kmalloc(zbr->len, GFP_NOFS);
+	if (!lnc_node)
+		return 0; /* We don't have to have the cache, so no error */
+
+	memcpy(lnc_node, node, zbr->len);
+	zbr->leaf = lnc_node;
+	return 0;
+}
+
+/**
+ * lnc_free - remove a leaf node from the leaf-node-cache.
+ * @zbr: zbranch of leaf node
+ * @node: leaf node
+ *
+ * This function returns %0 to indicate success and a negative error code
+ * otherwise.
+ */
+static void lnc_free(struct ubifs_zbranch *zbr)
+{
+	if (zbr->leaf == NULL)
+		return;
+	kfree(zbr->leaf);
+	zbr->leaf = NULL;
+}
+
+/**
+ * tnc_read_node - read a leaf node.
+ * @c: UBIFS file-system description object
+ * @zbr:  key and position of node
+ * @node: node returned
+ *
+ * This function reads a node or returns a negative error code.
+ */
+static int tnc_read_node(struct ubifs_info *c, struct ubifs_zbranch *zbr,
+			 void *node)
+{
+	union ubifs_key key1, *key = &zbr->key;
+	int err, type = key_type(c, key);
+	const struct ubifs_bud *bud;
+
+	dbg_tnc_key(c, key, "LEB %d:%d, len %d, key",
+		    zbr->lnum, zbr->offs, zbr->len);
+
+	if (lnc_lookup(c, zbr, node))
+		return 0; /* Read from the leaf-node-cache */
+	/*
+	 * 'zbr' has to point to on-flash node. The node may sit in a bud and
+	 * may even be in a write buffer, so we have to take care about this.
+	 */
+	if (c->jheads)
+		bud = ubifs_search_bud(c, zbr->lnum);
+	else
+		bud = NULL;
+	if (bud)
+		/* The bud can't go because we are under @c->commit_sem */
+		err = ubifs_read_node_wbuf(&c->jheads[bud->jhead].wbuf,
+					   node, type, zbr->len, zbr->lnum,
+					   zbr->offs);
+	else
+		err = ubifs_read_node(c, node, type, zbr->len, zbr->lnum,
+				      zbr->offs);
+
+	if (err) {
+		dbg_tnc_key(c, key, "key");
+		return err;
+	}
+
+	/* Make sure the key of the read node is correct */
+	key_read(c, key, &key1);
+	if (memcmp(node + UBIFS_CH_SZ, &key1, c->key_len)) {
+		ubifs_err("bad key in node at LEB %d:%d",
+			  zbr->lnum, zbr->offs);
+		dbg_tnc_key(c, key, "looked for key");
+		dbg_tnc_key(c, &key1, "found node's key");
+		dbg_dump_node(c, node);
+		return err;
+	}
+
+	/* Consider adding the node to the leaf node cache */
+	err = lnc_add(c, zbr, node);
+	return err;
+}
+
+/**
+ * ubifs_try_read_node - read a node if it is a node.
+ * @c: UBIFS file-system description object
+ * @buf: buffer to read to
+ * @type: node type
+ * @len: node length (not aligned)
+ * @lnum: LEB number of node to read
+ * @offs: offset of node to read
+ *
+ * This function tries to read a node of known type and length, checks it and
+ * stores it in @buf. This function returns %1 if a node is present and %0 if
+ * a node is not present.  A negative error code is returned for I/O errors.
+ * This function performs that same function as ubifs_read_node except that
+ * it does not require that there is actually a node present and instead
+ * the return code indicates if a node was read.
+ */
+static int try_read_node(const struct ubifs_info *c, void *buf, int type,
+			 int len, int lnum, int offs)
+{
+	int err, node_len;
+	struct ubifs_ch *ch = buf;
+	uint32_t crc, node_crc;
+
+	dbg_io("LEB %d:%d, %s, length %d", lnum, offs, dbg_ntype(type), len);
+	ubifs_assert(lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
+	ubifs_assert(len >= UBIFS_CH_SZ && offs + len <= c->leb_size);
+	ubifs_assert(!(offs & 7) && offs < c->leb_size);
+	ubifs_assert(type >= 0 && type < UBIFS_NODE_TYPES_CNT);
+
+	err = ubi_read(c->ubi, lnum, buf, offs, len);
+	if (err) {
+		ubifs_err("cannot read node type %d from LEB %d:%d, error %d",
+			  type, lnum, offs, err);
+		return err;
+	}
+
+	if (le32_to_cpu(ch->magic) != UBIFS_NODE_MAGIC)
+		return 0;
+
+	if (ch->node_type != type)
+		return 0;
+
+	node_len = le32_to_cpu(ch->len);
+	if (node_len != len)
+		return 0;
+
+	crc = crc32(UBIFS_CRC32_INIT, buf + 8, node_len - 8);
+	node_crc = le32_to_cpu(ch->crc);
+	if (crc != node_crc)
+		return 0;
+
+	return 1;
+}
+
+/**
+ * fallible_read_node - try to read a leaf node.
+ * @c: UBIFS file-system description object
+ * @key:  key of node to read
+ * @zbr:  position of node
+ * @node: node returned
+ *
+ * This function tries to read a node and returns %1 if the node is read, %0
+ * if the node is not present, and a negative error code in the case of error.
+ */
+static int fallible_read_node(struct ubifs_info *c, const union ubifs_key *key,
+			      struct ubifs_zbranch *zbr, void *node)
+{
+	int ret;
+
+	dbg_tnc_key(c, key, "key");
+
+	if (lnc_lookup(c, zbr, node))
+		return 0; /* Read from the leaf-node-cache */
+
+	ret = try_read_node(c, node, key_type(c, key), zbr->len, zbr->lnum,
+			    zbr->offs);
+	if (ret == 1) {
+		union ubifs_key node_key;
+
+		/* All nodes have key in the same place */
+		key_read(c, &((struct ubifs_dent_node *)node)->key, &node_key);
+		if (keys_cmp(c, key, &node_key) == 0) {
+			/* Consider adding the node to the leaf node cache */
+			int err = lnc_add(c, zbr, node);
+
+			if (err)
+				return err;
+		} else
+			ret = 0;
+	} else if (ret == 0)
+		dbg_gc_key(c, key, "dangling branch LEB %d:%d len %d, key",
+			   zbr->lnum, zbr->offs, zbr->len);
+	return ret;
+}
+
+/**
+ * matches_name - determine if a directory or extended attribute entry matches
+ *                a given name.
+ * @c: UBIFS file-system description object
+ * @zt: zbranch of dent
+ * @nm: name to match
+ *
+ * This function returns %1 if the name matches, %0 if the name does not match
+ * and a negative error code otherwise.
+ */
+static int matches_name(struct ubifs_info *c, struct ubifs_zbranch *zt,
+			const struct qstr *nm)
+{
+	struct ubifs_dent_node *dent;
+	int nlen, err;
+
+	/* If possible, match against the dent in the leaf-node-cache */
+	dent = zt->leaf;
+	if (dent) {
+		nlen = le16_to_cpu(dent->nlen);
+
+		if (nlen == nm->len && !memcmp(dent->name, nm->name, nlen))
+			return 1;
+		return 0;
+	}
+
+	dent = kmalloc(zt->len, GFP_NOFS);
+	if (!dent)
+		return -ENOMEM;
+	/*
+	 * In this case we end up allocating another dent object in lnc_add(),
+	 * although it could have just inserted this dent.
+	 */
+	err = tnc_read_node(c, zt, dent);
+	if (!err) {
+		err = ubifs_validate_entry(c, dent);
+		if (err) {
+			dbg_dump_node(c, dent);
+			goto out;
+		}
+
+		nlen = le16_to_cpu(dent->nlen);
+		if (nlen == nm->len && !memcmp(dent->name, nm->name, nlen))
+			err = 1;
+	}
+
+out:
+	kfree(dent);
+	return err;
+}
+
+/**
+ * get_znode - get a TNC znode that may not be loaded yet.
+ * @c: UBIFS file-system description object
+ * @znode: parent znode
+ * @n: znode branch slot number
+ *
+ * This function returns the znode or a negative error code.
+ */
+static struct ubifs_znode *get_znode(struct ubifs_info *c,
+				     struct ubifs_znode *znode, int n)
+{
+	struct ubifs_zbranch *zbr;
+
+	zbr = &znode->zbranch[n];
+	if (zbr->znode)
+		znode = zbr->znode;
+	else
+		znode = load_znode(c, zbr, znode, n);
+	return znode;
+}
+
+/**
+ * tnc_next - find next TNC entry.
+ * @c: UBIFS file-system description object
+ * @zn: znode is passed and returned here
+ * @nn: znode branch slot number is passed and returned here
+ *
+ * This function returns %0 if the next TNC entry is found, %-ENOENT if there is
+ * no next entry, or a negative error code otherwise.
+ */
+static int tnc_next(struct ubifs_info *c, struct ubifs_znode **zn, int *nn)
+{
+	struct ubifs_znode *znode = *zn;
+	int n = *nn;
+
+	n += 1;
+	if (n < znode->child_cnt) {
+		*nn = n;
+		return 0;
+	}
+	while (1) {
+		struct ubifs_znode *zp;
+
+		zp = znode->parent;
+		if (!zp)
+			return -ENOENT;
+		n = znode->iip + 1;
+		znode = zp;
+		if (n < znode->child_cnt) {
+			znode = get_znode(c, znode, n);
+			if (IS_ERR(znode))
+				return PTR_ERR(znode);
+			while (znode->level != 0) {
+				znode = get_znode(c, znode, 0);
+				if (IS_ERR(znode))
+					return PTR_ERR(znode);
+			}
+			n = 0;
+			break;
+		}
+	}
+	*zn = znode;
+	*nn = n;
+	return 0;
+}
+
+/**
+ * tnc_prev - find previous TNC entry.
+ * @c: UBIFS file-system description object
+ * @zn: znode is returned here
+ * @nn: znode branch slot number is passed and returned here
+ *
+ * This function returns %0 if the previous TNC entry is found, %-ENOENT if
+ * there is no next entry, or a negative error code otherwise.
+ */
+static int tnc_prev(struct ubifs_info *c, struct ubifs_znode **zn, int *nn)
+{
+	struct ubifs_znode *znode = *zn;
+	int n = *nn;
+
+	if (n > 0) {
+		*nn = n - 1;
+		return 0;
+	}
+	while (1) {
+		struct ubifs_znode *zp;
+
+		zp = znode->parent;
+		if (!zp)
+			return -ENOENT;
+		n = znode->iip - 1;
+		znode = zp;
+		if (n >= 0) {
+			znode = get_znode(c, znode, n);
+			if (IS_ERR(znode))
+				return PTR_ERR(znode);
+			while (znode->level != 0) {
+				n = znode->child_cnt - 1;
+				znode = get_znode(c, znode, n);
+				if (IS_ERR(znode))
+					return PTR_ERR(znode);
+			}
+			n = znode->child_cnt - 1;
+			break;
+		}
+	}
+	*zn = znode;
+	*nn = n;
+	return 0;
+}
+
+/**
+ * resolve_collision - resolve a collision.
+ * @c: UBIFS file-system description object
+ * @key: key of a directory or extended attribute entry
+ * @zn: znode is returned here
+ * @nn: znode branch slot number is passed and returned here
+ * @nm: name of the entry
+ *
+ * This function returns %1 and sets @zn and @nn if the collision is resolved.
+ * %0 is returned if @nm is not found and @zn and @nn are set to the next
+ * entry. %-ENOENT is returned if there are no following entries for the same
+ * inode. Otherwise a negative error code is returned.
+ */
+static int resolve_collision(struct ubifs_info *c, const union ubifs_key *key,
+			     struct ubifs_znode **zn, int *nn,
+			     const struct qstr *nm)
+{
+	struct ubifs_znode *znode;
+	union ubifs_key *okey;
+	int n, err;
+
+	dbg_tnc_key(c, key, "key");
+
+	znode = *zn;
+	n = *nn;
+	err = matches_name(c, &znode->zbranch[n], nm);
+	if (err < 0)
+		return err;
+	if (err == 1)
+		return 1;
+
+	/* Look left */
+	while (1) {
+		err = tnc_prev(c, &znode, &n);
+		if (err == -ENOENT)
+			break;
+		if (err)
+			return err;
+		if (keys_cmp(c, &znode->zbranch[n].key, key))
+			break;
+		err = matches_name(c, &znode->zbranch[n], nm);
+		if (err < 0)
+			return err;
+		if (err == 1) {
+			dbg_tnc_key(c, key, "collision resolved");
+			*zn = znode;
+			*nn = n;
+			return 1;
+		}
+	}
+
+	/* Look right */
+	znode = *zn;
+	n = *nn;
+	while (1) {
+		err = tnc_next(c, &znode, &n);
+		if (err)
+			return err;
+		okey = &znode->zbranch[n].key;
+		if (keys_cmp(c, okey, key))
+			return -ENOENT;
+		err = matches_name(c, &znode->zbranch[n], nm);
+		if (err < 0)
+			return err;
+		if (err == 1) {
+			dbg_tnc_key(c, key, "collision resolved");
+			*zn = znode;
+			*nn = n;
+			return 1;
+		}
+	}
+
+	return -EINVAL;
+}
+
+/**
+ * fallible_matches_name - determine if a dent matches a given name.
+ * @c: UBIFS file-system description object
+ * @zt: zbranch of dent
+ * @nm: name to match
+ *
+ * This function returns %1 if the name matches, %0 if the name does not match,
+ * %2 if the node was not present, and a negative error code otherwise.
+ */
+static int fallible_matches_name(struct ubifs_info *c, struct ubifs_zbranch *zt,
+				 const struct qstr *nm)
+{
+	struct ubifs_dent_node *dent;
+	int nlen, err;
+
+	/* If possible, match against the dent in the leaf-node-cache */
+	dent = zt->leaf;
+	if (dent) {
+		nlen = le16_to_cpu(dent->nlen);
+
+		if (nlen == nm->len && !memcmp(dent->name, nm->name, nlen))
+			return 1;
+		return 0;
+	}
+
+	dent = kmalloc(zt->len, GFP_NOFS);
+	if (!dent)
+		return -ENOMEM;
+	/*
+	 * In this case we end up allocating another dent object in lnc_add(),
+	 * although it could have just inserted this dent.
+	 */
+	err = fallible_read_node(c, &zt->key, zt, dent);
+	if (err < 0)
+		goto out;
+	if (err == 0) {
+		err = 2; /* The node was not present */
+		goto out;
+	}
+	if (err == 1) {
+		err = ubifs_validate_entry(c, dent);
+		if (err) {
+			dbg_dump_node(c, dent);
+			goto out;
+		}
+
+		nlen = le16_to_cpu(dent->nlen);
+		if (nlen == nm->len && !memcmp(dent->name, nm->name, nlen))
+			err = 1;
+		else
+			err = 0;
+	}
+out:
+	kfree(dent);
+	return err;
+}
+
+/**
+ * fallible_resolve_collision - resolve a collision even if nodes are missing.
+ * @c: UBIFS file-system description object
+ * @key: key of directory entry
+ * @zn: znode is returned here
+ * @nn: znode branch slot number is passed and returned here
+ * @nm: name of directory entry
+ *
+ * This function returns %1 and sets @zn and @nn if the collision is resolved.
+ * %0 is returned if @nm is not found and @zn and @nn are set to the
+ * next directory entry.  %-ENOENT is returned if there are no
+ * following directory entries for the same inode.  Otherwise a negative error
+ * code is returned.
+ */
+static int fallible_resolve_collision(struct ubifs_info *c,
+				      const union ubifs_key *key,
+				      struct ubifs_znode **zn, int *nn,
+				      const struct qstr *nm)
+{
+	struct ubifs_znode *znode, *o_znode = NULL;
+	union ubifs_key *okey;
+	int n, o_n = 0, err;
+
+	dbg_tnc_key(c, key, "key");
+	znode = *zn;
+	n = *nn;
+	err = fallible_matches_name(c, &znode->zbranch[n], nm);
+	if (err < 0)
+		return err;
+	if (err == 1)
+		return 1;
+	if (err == 2) {
+		o_znode = znode;
+		o_n = n;
+	}
+
+	/* Look left */
+	while (1) {
+		err = tnc_prev(c, &znode, &n);
+		if (err == -ENOENT)
+			break;
+		if (err)
+			return err;
+		if (keys_cmp(c, &znode->zbranch[n].key, key))
+			break;
+		err = fallible_matches_name(c, &znode->zbranch[n], nm);
+		if (err < 0)
+			return err;
+		if (err == 1) {
+			dbg_tnc_key(c, key, "collision resolved");
+			*zn = znode;
+			*nn = n;
+			return 1;
+		}
+		if (err == 2) {
+			o_znode = znode;
+			o_n = n;
+		}
+	}
+	/* Look right */
+	znode = *zn;
+	n = *nn;
+	while (1) {
+		err = tnc_next(c, &znode, &n);
+		if (err == -ENOENT && o_znode) {
+			dbg_tnc_key(c, key, "collision resolved by default");
+			dbg_gc_key(c, key, "dangling match LEB %d:%d len %d ",
+				   o_znode->zbranch[o_n].lnum,
+				   o_znode->zbranch[o_n].offs,
+				   o_znode->zbranch[o_n].len);
+			*zn = o_znode;
+			*nn = o_n;
+			return 1;
+		}
+		if (err)
+			return err;
+		okey = &znode->zbranch[n].key;
+		if (keys_cmp(c, okey, key)) {
+			if (!o_znode)
+				return -ENOENT;
+			dbg_tnc_key(c, key, "collision resolved by default");
+			dbg_gc_key(c, key, "dangling match LEB %d:%d len %d ",
+				   o_znode->zbranch[o_n].lnum,
+				   o_znode->zbranch[o_n].offs,
+				   o_znode->zbranch[o_n].len);
+			*zn = o_znode;
+			*nn = o_n;
+			return 1;
+		}
+		err = fallible_matches_name(c, &znode->zbranch[n], nm);
+		if (err < 0)
+			return err;
+		if (err == 1) {
+			dbg_tnc_key(c, key, "collision resolved");
+			*zn = znode;
+			*nn = n;
+			return 1;
+		}
+		if (err == 2) {
+			o_znode = znode;
+			o_n = n;
+		}
+	}
+	return -EINVAL;
+}
+
+/**
+ * matches_position - determine if a zbranch matches a given position.
+ * @zt: zbranch of dent
+ * @lnum: LEB number of dent to match
+ * @offs: offset of dent to match
+ *
+ * This function returns %1 if @lnum:@offs matches, and %0 otherwise.
+ */
+static int matches_position(struct ubifs_zbranch *zt, int lnum, int offs)
+{
+	if (zt->lnum == lnum && zt->offs == offs)
+		return 1;
+	else
+		return 0;
+}
+
+/**
+ * resolve_collision_directly - resolve a collision directly.
+ * @c: UBIFS file-system description object
+ * @key: key of directory entry
+ * @zn: znode is passed and returned here
+ * @nn: znode branch slot number is passed and returned here
+ * @lnum: LEB number of dent node to match
+ * @offs: offset of dent node to match
+ *
+ * This function returns %1 and sets @zn and @nn if the collision is resolved.
+ * %0 is returned if @lnum:@offs is not found and @zn and @nn are set to the
+ * next directory entry.  %-ENOENT is returned if there are no
+ * following directory entries for the same inode.  Otherwise a negative error
+ * code is returned.
+ */
+static int resolve_collision_directly(struct ubifs_info *c,
+				      const union ubifs_key *key,
+				      struct ubifs_znode **zn, int *nn,
+				      int lnum, int offs)
+{
+	struct ubifs_znode *znode;
+	union ubifs_key *okey;
+	int n, err;
+
+	dbg_tnc_key(c, key, "key");
+	dbg_mnt_key(c, key, "LEB %d:%d", lnum, offs);
+	znode = *zn;
+	n = *nn;
+	if (matches_position(&znode->zbranch[n], lnum, offs))
+		return 1;
+
+	/* Look left */
+	while (1) {
+		err = tnc_prev(c, &znode, &n);
+		if (err == -ENOENT)
+			break;
+		if (err)
+			return err;
+		if (keys_cmp(c, &znode->zbranch[n].key, key))
+			break;
+		if (matches_position(&znode->zbranch[n], lnum, offs)) {
+			dbg_tnc_key(c, key, "collision resolved");
+			dbg_mnt_key(c, key, "LEB %d:%d collision resolved",
+				    lnum, offs);
+			*zn = znode;
+			*nn = n;
+			return 1;
+		}
+	}
+
+	/* Look right */
+	znode = *zn;
+	n = *nn;
+	while (1) {
+		err = tnc_next(c, &znode, &n);
+		if (err)
+			return err;
+		okey = &znode->zbranch[n].key;
+		if (keys_cmp(c, okey, key))
+			return 0;
+		if (matches_position(&znode->zbranch[n], lnum, offs)) {
+			dbg_tnc_key(c, key, "collision resolved");
+			dbg_mnt_key(c, key, "LEB %d:%d collision resolved",
+				    lnum, offs);
+			*zn = znode;
+			*nn = n;
+			return 1;
+		}
+	}
+}
+
+/**
+ * ubifs_tnc_lookup - look up a file-system node.
+ * @c: UBIFS file-system description object
+ * @key: node key to lookup
+ * @node: the node is returned here
+ *
+ * This function look up and reads node with key @key. The caller has to make
+ * sure the @node buffer is large enough to fit the node. Returns zero in case
+ * of success, %-ENOENT if the node was not found, and a negative error code in
+ * case of failure.
+ */
+int ubifs_tnc_lookup(struct ubifs_info *c, const union ubifs_key *key,
+		     void *node)
+{
+	int found, n, err;
+	struct ubifs_znode *znode;
+	struct ubifs_zbranch zbr, *zt;
+
+	mutex_lock(&c->tnc_mutex);
+	found = lookup_level0(c, key, &znode, &n);
+	if (!found) {
+		err = -ENOENT;
+		goto out;
+	} else if (found < 0) {
+		err = found;
+		goto out;
+	}
+	zt = &znode->zbranch[n];
+	if (is_hash_key(c, key)) {
+		/*
+		 * In this case the leaf-node-cache gets used, so we pass the
+		 * address of the zbranch and keep the mutex locked
+		 */
+		err = tnc_read_node(c, zt, node);
+		goto out;
+	}
+	zbr = znode->zbranch[n];
+	mutex_unlock(&c->tnc_mutex);
+
+	err = tnc_read_node(c, &zbr, node);
+	return err;
+
+out:
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
+ * ubifs_tnc_locate - look up a file-system node and return it and its location.
+ * @c: UBIFS file-system description object
+ * @key: node key to lookup
+ * @node: the node is returned here
+ * @lnum: LEB number is returned here
+ * @offs: offset is returned here
+ *
+ * This function is the same as 'ubifs_tnc_lookup()' but it returns the node
+ * location also. See 'ubifs_tnc_lookup()'.
+ */
+int ubifs_tnc_locate(struct ubifs_info *c, const union ubifs_key *key,
+		     void *node, int *lnum, int *offs)
+{
+	int found, n, err;
+	struct ubifs_znode *znode;
+	struct ubifs_zbranch zbr, *zt;
+
+	mutex_lock(&c->tnc_mutex);
+	found = lookup_level0(c, key, &znode, &n);
+	if (!found) {
+		err = -ENOENT;
+		goto out;
+	} else if (found < 0) {
+		err = found;
+		goto out;
+	}
+	zt = &znode->zbranch[n];
+	if (is_hash_key(c, key)) {
+		/*
+		 * In this case the leaf-node-cache gets used, so we pass the
+		 * address of the zbranch and keep the mutex locked
+		 */
+		*lnum = zt->lnum;
+		*offs = zt->offs;
+		err = tnc_read_node(c, zt, node);
+		goto out;
+	}
+	zbr = znode->zbranch[n];
+	mutex_unlock(&c->tnc_mutex);
+
+	*lnum = zbr.lnum;
+	*offs = zbr.offs;
+
+	err = tnc_read_node(c, &zbr, node);
+	return err;
+
+out:
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
+ * do_lookup_nm- look up a "hashed" node.
+ * directory entry file-system node.
+ * @c: UBIFS file-system description object
+ * @key: node key to lookup
+ * @node: the node is returned here
+ * @nm: node name
+ *
+ * This function look up and reads a node which contains name hash in the key.
+ * Since the hash may have collisions, there may be many nodes with the same
+ * key, so we have to sequentially look to all of them until the needed one is
+ * found. This function returns zero in case of success, %-ENOENT if the node
+ * was not found, and a negative error code in case of failure.
+ */
+static int do_lookup_nm(struct ubifs_info *c, const union ubifs_key *key,
+			void *node, const struct qstr *nm)
+{
+	int found, n, err;
+	struct ubifs_znode *znode;
+	struct ubifs_zbranch zbr;
+
+	dbg_tnc_key(c, key, "key");
+	mutex_lock(&c->tnc_mutex);
+	found = lookup_level0(c, key, &znode, &n);
+	if (!found) {
+		err = -ENOENT;
+		goto out;
+	} else if (found < 0) {
+		err = found;
+		goto out;
+	}
+
+	ubifs_assert(n >= 0);
+
+	err = resolve_collision(c, key, &znode, &n, nm);
+	if (err < 0)
+		goto out;
+	if (err == 0) {
+		err = -ENOENT;
+		goto out;
+	}
+
+	zbr = znode->zbranch[n];
+	mutex_unlock(&c->tnc_mutex);
+
+	err = tnc_read_node(c, &zbr, node);
+
+	return err;
+
+out:
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
+ * ubifs_tnc_lookup_nm- look up a "hashed" node.
+ * directory entry file-system node.
+ * @c: UBIFS file-system description object
+ * @key: node key to lookup
+ * @node: the node is returned here
+ * @nm: node name
+ *
+ * This function look up and reads a node which contains name hash in the key.
+ * Since the hash may have collisions, there may be many nodes with the same
+ * key, so we have to sequentially look to all of them until the needed one is
+ * found. This function returns zero in case of success, %-ENOENT if the node
+ * was not found, and a negative error code in case of failure.
+ */
+int ubifs_tnc_lookup_nm(struct ubifs_info *c, const union ubifs_key *key,
+			void *node, const struct qstr *nm)
+{
+	int err, len;
+	const struct ubifs_dent_node *dent = node;
+
+	/*
+	 * We assume that in most of the cases there are no name collisions and
+	 * 'ubifs_tnc_lookup()' returns us the right direntry.
+	 */
+	err = ubifs_tnc_lookup(c, key, node);
+	if (err)
+		return err;
+
+	len = le16_to_cpu(dent->nlen);
+	if (nm->len == len && !memcmp(dent->name, nm->name, len))
+		return 0;
+
+	/*
+	 * Unluckily, there are hash collisions and we have to iterate over
+	 * them look at each direntry with colliding name hash sequentially.
+	 */
+	return do_lookup_nm(c, key, node, nm);
+}
+
+/**
+ * correct_parent_keys - correct parent znodes' keys.
+ * @c: UBIFS file-system description object
+ * @znode: znode to correct parent znodes for
+ *
+ * This is a helper function for 'tnc_insert()'. When the key of the leftmost
+ * zbranch changes, keys of parent znodes have to be corrected. This helper
+ * function is called in such situations and corrects the keys if needed.
+ */
+static void correct_parent_keys(const struct ubifs_info *c,
+				struct ubifs_znode *znode)
+{
+	union ubifs_key *key, *key1;
+
+	ubifs_assert(znode->parent);
+	ubifs_assert(znode->iip == 0);
+
+	key = &znode->zbranch[0].key;
+	key1 = &znode->parent->zbranch[0].key;
+
+	while (keys_cmp(c, key, key1) < 0) {
+		key_copy(c, key, key1);
+		znode = znode->parent;
+		if (!znode->parent || znode->iip)
+			break;
+		key1 = &znode->parent->zbranch[0].key;
+	}
+}
+
+/**
+ * insert_zbranch - insert a zbranch into a znode.
+ * @znode: znode into which to insert
+ * @zbr: zbranch to insert
+ * @n: slot number to insert to
+ *
+ * This is a helper function for 'tnc_insert()'. UBIFS does not allow "gaps" in
+ * znode's array of zbranches and keeps zbranches consolidated, so when a new
+ * zbranch has to be inserted to the @znode->zbranches[]' array at the @n-th
+ * slot, zbranches starting from @n have to be moved right.
+ */
+static void insert_zbranch(struct ubifs_znode *znode,
+			   const struct ubifs_zbranch *zbr, int n)
+{
+	int i;
+
+	ubifs_assert(ubifs_zn_dirty(znode));
+
+	if (znode->level) {
+		for (i = znode->child_cnt; i > n; i--) {
+			znode->zbranch[i] = znode->zbranch[i - 1];
+			if (znode->zbranch[i].znode)
+				znode->zbranch[i].znode->iip = i;
+		}
+		if (zbr->znode)
+			zbr->znode->iip = n;
+	} else
+		for (i = znode->child_cnt; i > n; i--)
+			znode->zbranch[i] = znode->zbranch[i - 1];
+
+	znode->zbranch[n] = *zbr;
+	znode->child_cnt += 1;
+	/*
+	 * After inserting at slot zero, the lower bound of the key range of
+	 * this znode may have changed. If this znode is subsequently split
+	 * then the upper bound of the key range may change, and furthermore
+	 * it could change to be lower than the original lower bound. If that
+	 * happens, then it will no longer be possible to find this znode in the
+	 * TNC using the key from the index node on flash. That is bad because
+	 * if it is not found, we will assume it is obsolete and may overwrite
+	 * it. Then if there is an unclean unmount, we will start using the
+	 * old index which will be broken.
+	 *
+	 * So we first mark znodes that have insertions at slot zero, and then
+	 * if they are split we add their lnum/offs to the old_idx tree.
+	 */
+	if (n == 0)
+		znode->alt = 1;
+}
+
+/**
+ * tnc_insert - insert a node into TNC.
+ * @c: UBIFS file-system description object
+ * @znode: znode to insert into
+ * @zbr: branch to insert
+ * @n: slot number to insert new zbranch to
+ *
+ * This function inserts a new node described by @zbr into znode @znode. If
+ * znode does not have a free slot for new zbranch, it is split. Parent znodes
+ * are splat as well if needed. Returns zero in case of success or a negative
+ * error code in case of failure.
+ */
+static int tnc_insert(struct ubifs_info *c, struct ubifs_znode *znode,
+		      struct ubifs_zbranch *zbr, int n)
+{
+	struct ubifs_znode *zn, *zi, *zp;
+	int i, keep, move, appending = 0;
+	union ubifs_key *key = &zbr->key;
+
+	ubifs_assert(n >= 0 && n <= c->fanout);
+
+	/* Implement naive insert for now */
+again:
+	zp = znode->parent;
+	if (znode->child_cnt < c->fanout) {
+		ubifs_assert(n != c->fanout);
+		dbg_tnc_key(c, key, "inserted at %d level %d, key ", n,
+			    znode->level);
+
+		insert_zbranch(znode, zbr, n);
+
+		/* Ensure parent's key is correct */
+		if (n == 0 && zp && znode->iip == 0)
+			correct_parent_keys(c, znode);
+
+		return 0;
+	}
+
+	/*
+	 * Unfortunately, @znode does not have more empty slots and we have to
+	 * split it.
+	 */
+	dbg_tnc_key(c, key, "splitting level %d, key ", znode->level);
+
+	if (znode->alt)
+		/*
+		 * We can no longer be sure of finding this znode by key, so we
+		 * record it in the old_idx tree.
+		 */
+		ins_clr_old_idx_znode(c, znode);
+
+	zn = kzalloc(c->max_znode_sz, GFP_NOFS);
+	if (!zn)
+		return -ENOMEM;
+	zn->parent = zp;
+	zn->level = znode->level;
+
+	/* Decide where to split */
+	if (znode->level == 0 && n == c->fanout &&
+	    key_type(c, key) == UBIFS_DATA_KEY) {
+		union ubifs_key *key1;
+
+		/*
+		 * If this is an inode which is being appended - do not split
+		 * it because no other zbranches can be inserted between
+		 * zbranches of consecutive data nodes anyway.
+		 */
+		key1 = &znode->zbranch[n - 1].key;
+		if (key_ino(c, key1) == key_ino(c, key) &&
+		    key_type(c, key1) == UBIFS_DATA_KEY &&
+		    key_block(c, key1) == key_block(c, key) - 1)
+			appending = 1;
+	}
+
+	if (appending) {
+		keep = c->fanout;
+		move = 0;
+	} else {
+		keep = (c->fanout + 1) / 2;
+		move = c->fanout - keep;
+	}
+
+	/*
+	 * Although we don't at present, we could look at the neighbors and see
+	 * if we can move some zbranches there.
+	 */
+
+	if (n < keep) {
+		/* Insert into existing znode */
+		zi = znode;
+		move += 1;
+		keep -= 1;
+	} else {
+		/* Insert into new znode */
+		zi = zn;
+		n -= keep;
+		/* Re-parent */
+		if (zn->level != 0)
+			zbr->znode->parent = zn;
+	}
+
+	set_bit(DIRTY_ZNODE, &zn->flags);
+	atomic_long_inc(&c->dirty_zn_cnt);
+
+	zn->child_cnt = move;
+	znode->child_cnt = keep;
+
+	dbg_tnc("moving %d, keeping %d", move, keep);
+
+	/* Move zbranch */
+	for (i = 0; i < move; i++) {
+		zn->zbranch[i] = znode->zbranch[keep + i];
+		/* Re-parent */
+		if (zn->level != 0)
+			if (zn->zbranch[i].znode) {
+				zn->zbranch[i].znode->parent = zn;
+				zn->zbranch[i].znode->iip = i;
+			}
+	}
+
+	/* Insert new key and branch */
+	dbg_tnc_key(c, key, "inserting at %d level %d, key ", n,
+		    zn->level);
+
+	insert_zbranch(zi, zbr, n);
+
+	/* Insert new znode (produced by spitting) into the parent */
+	if (zp) {
+		i = n;
+		/* Locate insertion point */
+		n = znode->iip + 1;
+		if (appending && n != c->fanout)
+			appending = 0;
+
+		if (i == 0 && zi == znode && znode->iip == 0)
+			correct_parent_keys(c, znode);
+
+		/* Tail recursion */
+		zbr->key = zn->zbranch[0].key;
+		zbr->znode = zn;
+		zbr->lnum = 0;
+		zbr->offs = 0;
+		zbr->len = 0;
+		znode = zp;
+
+		goto again;
+	}
+
+	/* We have to split root znode */
+	dbg_tnc("creating new zroot at level %d", znode->level + 1);
+
+	zi = kzalloc(c->max_znode_sz, GFP_NOFS);
+	if (!zi)
+		return -ENOMEM;
+
+	zi->child_cnt = 2;
+	zi->level = znode->level + 1;
+
+	set_bit(DIRTY_ZNODE, &zi->flags);
+	atomic_long_inc(&c->dirty_zn_cnt);
+
+	zi->zbranch[0].key = znode->zbranch[0].key;
+	zi->zbranch[0].znode = znode;
+	zi->zbranch[0].lnum = c->zroot.lnum;
+	zi->zbranch[0].offs = c->zroot.offs;
+	zi->zbranch[0].len = c->zroot.len;
+	zi->zbranch[1].key = zn->zbranch[0].key;
+	zi->zbranch[1].znode = zn;
+
+	c->zroot.lnum = 0;
+	c->zroot.offs = 0;
+	c->zroot.len = 0;
+	c->zroot.znode = zi;
+
+	zn->parent = zi;
+	zn->iip = 1;
+	znode->parent = zi;
+	znode->iip = 0;
+
+	return 0;
+}
+
+/**
+ * ubifs_tnc_add - add a node to TNC.
+ * @c: UBIFS file-system description object
+ * @key: key to add
+ * @lnum: LEB number of node
+ * @offs: node offset
+ * @len: node length
+ *
+ * This function adds a node with key @key to TNC. The node may be new or it may
+ * obsolete some existing one. Returns %0 on success or negative error code on
+ * failure.
+ */
+int ubifs_tnc_add(struct ubifs_info *c, const union ubifs_key *key, int lnum,
+		  int offs, int len)
+{
+	int found, n, err = 0;
+	struct ubifs_znode *znode;
+
+	mutex_lock(&c->tnc_mutex);
+	found = lookup_level0_dirty(c, key, &znode, &n);
+	if (!found) {
+		struct ubifs_zbranch zbr;
+
+		zbr.znode = NULL;
+		zbr.lnum = lnum;
+		zbr.offs = offs;
+		zbr.len = len;
+		zbr.key = *key;
+		err = tnc_insert(c, znode, &zbr, n + 1);
+	} else if (found == 1) {
+		struct ubifs_zbranch *zbr = &znode->zbranch[n];
+
+		lnc_free(zbr);
+		err = ubifs_add_dirt(c, zbr->lnum, zbr->len);
+		zbr->lnum = lnum;
+		zbr->offs = offs;
+		zbr->len = len;
+	} else
+		err = found;
+	if (!err)
+		err = dbg_check_tnc(c, 0);
+	mutex_unlock(&c->tnc_mutex);
+
+	return err;
+}
+
+/**
+ * dirty_cow_bottom_up - dirty a znode and its ancestors.
+ * @c: UBIFS file-system description object
+ * @znode: znode to dirty
+ *
+ * If we do not have a unique key that resides in a znode, then we cannot
+ * dirty that znode from the top down (i.e. by using lookup_level0_dirty)
+ * This function records the path back to the last dirty ancestor, and then
+ * dirties the znodes on that path.
+ */
+static struct ubifs_znode *dirty_cow_bottom_up(struct ubifs_info *c,
+					       struct ubifs_znode *znode)
+{
+	struct ubifs_znode *zp;
+	int *path = NULL, h, p = 0;
+
+	ubifs_assert(c->zroot.znode != NULL);
+	ubifs_assert(znode != NULL);
+	h = c->zroot.znode->level;
+	if (h) {
+		path = kmalloc(sizeof(int) * h, GFP_NOFS);
+		if (!path)
+			return ERR_PTR(-ENOMEM);
+		/* Go up until parent is dirty */
+		while (1) {
+			int n;
+
+			zp = znode->parent;
+			if (!zp)
+				break;
+			n = znode->iip;
+			ubifs_assert(p < h);
+			path[p++] = n;
+			if (!zp->cnext && ubifs_zn_dirty(znode))
+				break;
+			znode = zp;
+		}
+	}
+	/* Come back down, dirtying as we go */
+	while (1) {
+		struct ubifs_zbranch *zbr;
+
+		zp = znode->parent;
+		if (zp) {
+			ubifs_assert(path[p - 1] >= 0);
+			ubifs_assert(path[p - 1] < zp->child_cnt);
+			zbr = &zp->zbranch[path[--p]];
+			znode = dirty_cow_znode(c, zbr);
+		} else {
+			ubifs_assert(znode == c->zroot.znode);
+			znode = dirty_cow_znode(c, &c->zroot);
+		}
+		if (IS_ERR(znode) || !p)
+			break;
+		ubifs_assert(path[p - 1] >= 0);
+		ubifs_assert(path[p - 1] < znode->child_cnt);
+		znode = znode->zbranch[path[p - 1]].znode;
+	}
+	kfree(path);
+	return znode;
+}
+
+/**
+ * ubifs_tnc_replace - replace a node in the TNC only if the old node is found.
+ * @c: UBIFS file-system description object
+ * @key: key to add
+ * @old_lnum: LEB number of old node
+ * @old_offs: old node offset
+ * @lnum: LEB number of node
+ * @offs: node offset
+ * @len: node length
+ *
+ * This function replaces a node with key @key in the TNC only if the old node
+ * is found.  This function is called by garbage collection when node are moved.
+ * Returns %0 on success or negative error code on failure.
+ */
+int ubifs_tnc_replace(struct ubifs_info *c, const union ubifs_key *key,
+		      int old_lnum, int old_offs, int lnum, int offs, int len)
+{
+	int found, n, err = 0;
+	struct ubifs_znode *znode;
+
+	mutex_lock(&c->tnc_mutex);
+	found = lookup_level0_dirty(c, key, &znode, &n);
+	if (found < 0) {
+		err = found;
+		goto out;
+	} else if (found == 1) {
+		struct ubifs_zbranch *zbr = &znode->zbranch[n];
+
+		found = 0;
+		if (zbr->lnum == old_lnum && zbr->offs == old_offs) {
+			lnc_free(zbr);
+			err = ubifs_add_dirt(c, zbr->lnum, zbr->len);
+			if (err)
+				goto out;
+			zbr->lnum = lnum;
+			zbr->offs = offs;
+			zbr->len = len;
+			found = 1;
+		} else if (is_hash_key(c, key)) {
+			found = resolve_collision_directly(c, key, &znode, &n,
+							   old_lnum, old_offs);
+			if (found == -ENOENT)
+				found = 0;
+			if (found < 0) {
+				err = found;
+				goto out;
+			} else if (found) {
+				/* Ensure the znode is dirtied */
+				if (znode->cnext || !ubifs_zn_dirty(znode)) {
+					    znode = dirty_cow_bottom_up(c,
+									znode);
+					    if (IS_ERR(znode)) {
+						    err = PTR_ERR(znode);
+						    goto out;
+					    }
+				}
+				zbr = &znode->zbranch[n];
+				lnc_free(zbr);
+				err = ubifs_add_dirt(c, zbr->lnum,
+						     zbr->len);
+				if (err)
+					goto out;
+				zbr->lnum = lnum;
+				zbr->offs = offs;
+				zbr->len = len;
+			}
+		}
+	}
+
+	if (found == 0) {
+		err = ubifs_add_dirt(c, lnum, len);
+		if (err)
+			goto out;
+	}
+
+	err = dbg_check_tnc(c, 0);
+
+out:
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
+ * ubifs_tnc_add_nm - add a "hashed" node to TNC.
+ * @c: UBIFS file-system description object
+ * @key: key to add
+ * @lnum: LEB number of node
+ * @offs: node offset
+ * @len: node length
+ * @nm: node name
+ *
+ * This is the same as 'ubifs_tnc_add()' but it should be used with keys which
+ * may have collisions, like directory entry keys.
+ */
+int ubifs_tnc_add_nm(struct ubifs_info *c, const union ubifs_key *key,
+		     int lnum, int offs, int len, const struct qstr *nm)
+{
+	int found, n, err = 0;
+	struct ubifs_znode *znode;
+
+	mutex_lock(&c->tnc_mutex);
+	found = lookup_level0_dirty(c, key, &znode, &n);
+	if (found < 0) {
+		err = found;
+		goto out;
+	}
+	if (found == 1) {
+		if (c->replaying)
+			found = fallible_resolve_collision(c, key, &znode, &n,
+							   nm);
+		else
+			found = resolve_collision(c, key, &znode, &n, nm);
+		if (found < 0 && found != -ENOENT) {
+			err = found;
+			goto out;
+		}
+		/* Ensure the znode is dirtied */
+		if (znode->cnext || !ubifs_zn_dirty(znode)) {
+			    znode = dirty_cow_bottom_up(c, znode);
+			    if (IS_ERR(znode)) {
+				    err = PTR_ERR(znode);
+				    goto out;
+			    }
+		}
+		if (found == 0)
+			n -= 1;
+		else if (found == -ENOENT)
+			found = 0;
+		else if (found == 1) {
+			struct ubifs_zbranch *zbr = &znode->zbranch[n];
+
+			lnc_free(zbr);
+			err = ubifs_add_dirt(c, zbr->lnum, zbr->len);
+			zbr->lnum = lnum;
+			zbr->offs = offs;
+			zbr->len = len;
+			goto out;
+		}
+	}
+	if (!found) {
+		struct ubifs_zbranch zbr;
+
+		zbr.znode = NULL;
+		zbr.lnum = lnum;
+		zbr.offs = offs;
+		zbr.len = len;
+		zbr.key = *key;
+		err = tnc_insert(c, znode, &zbr, n + 1);
+	}
+
+out:
+	if (!err)
+		err = dbg_check_tnc(c, 0);
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
+ * tnc_delete - delete a znode form TNC.
+ * @c: UBIFS file-system description object
+ * @znode: znode to delete from
+ * @n: zbranch slot number to delete
+ *
+ * This function deletes a leaf node from @n-th slot of @znode. Returns zero in
+ * case of success and a negative error code in case of failure.
+ */
+static int tnc_delete(struct ubifs_info *c, struct ubifs_znode *znode, int n)
+{
+	struct ubifs_zbranch *zbr;
+	struct ubifs_znode *zp;
+	int i, err;
+
+	/* Delete without merge for now */
+	ubifs_assert(znode->level == 0);
+	ubifs_assert(n >= 0 && n < c->fanout);
+	dbg_tnc_key(c, &znode->zbranch[n].key, "deleting");
+
+	zbr = &znode->zbranch[n];
+	lnc_free(zbr);
+
+	err = ubifs_add_dirt(c, zbr->lnum, zbr->len);
+	if (err) {
+		dbg_dump_znode(c, znode);
+		return err;
+	}
+
+	/* We do not "gap" zbranch slots */
+	for (i = n; i < znode->child_cnt - 1; i++)
+		znode->zbranch[i] = znode->zbranch[i + 1];
+	znode->child_cnt -= 1;
+
+	if (znode->child_cnt > 0)
+		return 0;
+
+	/*
+	 * This was the last zbranch, we have to delete this znode from the
+	 * parent.
+	 */
+
+	do {
+		ubifs_assert(!test_bit(OBSOLETE_ZNODE, &znode->flags));
+		ubifs_assert(ubifs_zn_dirty(znode));
+
+		zp = znode->parent;
+		n = znode->iip;
+
+		atomic_long_dec(&c->dirty_zn_cnt);
+
+		err = insert_old_idx_znode(c, znode);
+		if (err)
+			return err;
+
+		if (znode->cnext) {
+			set_bit(OBSOLETE_ZNODE, &znode->flags);
+			atomic_long_inc(&c->clean_zn_cnt);
+			atomic_long_inc(&ubifs_clean_zn_cnt);
+		} else
+			kfree(znode);
+		znode = zp;
+	} while (znode->child_cnt == 1); /* while removing last child */
+
+	/* Remove from znode, entry n - 1 */
+	znode->child_cnt -= 1;
+	ubifs_assert(znode->level != 0);
+	for (i = n; i < znode->child_cnt; i++) {
+		znode->zbranch[i] = znode->zbranch[i + 1];
+		if (znode->zbranch[i].znode)
+			znode->zbranch[i].znode->iip = i;
+	}
+
+	/*
+	 * If this is the root and it has only 1 child then
+	 * collapse the tree.
+	 */
+	if (znode->parent == NULL) {
+		while (znode->child_cnt == 1 && znode->level != 0) {
+			zp = znode;
+			zbr = &znode->zbranch[0];
+			znode = get_znode(c, znode, 0);
+			if (IS_ERR(znode))
+				return PTR_ERR(znode);
+			znode = dirty_cow_znode(c, zbr);
+			if (IS_ERR(znode))
+				return PTR_ERR(znode);
+			znode->parent = NULL;
+			znode->iip = 0;
+			if (c->zroot.len) {
+				err = insert_old_idx(c, c->zroot.lnum,
+						     c->zroot.offs);
+				if (err)
+					return err;
+			}
+			c->zroot.lnum = zbr->lnum;
+			c->zroot.offs = zbr->offs;
+			c->zroot.len = zbr->len;
+			c->zroot.znode = znode;
+			ubifs_assert(!test_bit(OBSOLETE_ZNODE,
+				     &zp->flags));
+			ubifs_assert(test_bit(DIRTY_ZNODE, &zp->flags));
+			atomic_long_dec(&c->dirty_zn_cnt);
+
+			if (zp->cnext) {
+				set_bit(OBSOLETE_ZNODE, &zp->flags);
+				atomic_long_inc(&c->clean_zn_cnt);
+				atomic_long_inc(&ubifs_clean_zn_cnt);
+			} else
+				kfree(zp);
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * ubifs_tnc_remove - remove an index entry of a node.
+ * @c: UBIFS file-system description object
+ * @key: key of node
+ *
+ * Returns %0 on success or negative error code on failure.
+ */
+int ubifs_tnc_remove(struct ubifs_info *c, const union ubifs_key *key)
+{
+	int found, n, err = 0;
+	struct ubifs_znode *znode;
+
+	mutex_lock(&c->tnc_mutex);
+	found = lookup_level0_dirty(c, key, &znode, &n);
+	if (found == 1)
+		err = tnc_delete(c, znode, n);
+	else if (found < 0)
+		err = found;
+	if (!err)
+		err = dbg_check_tnc(c, 0);
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
+ * ubifs_tnc_remove_nm - remove an index entry for a "hashed" node.
+ * @c: UBIFS file-system description object
+ * @key: key of node
+ * @nm: directory entry name
+ *
+ * Returns %0 on success or negative error code on failure.
+ */
+int ubifs_tnc_remove_nm(struct ubifs_info *c, const union ubifs_key *key,
+			const struct qstr *nm)
+{
+	int found, n, err = 0;
+	struct ubifs_znode *znode;
+
+	mutex_lock(&c->tnc_mutex);
+	found = lookup_level0_dirty(c, key, &znode, &n);
+	if (found < 0) {
+		err = found;
+		goto out;
+	}
+	if (found) {
+		if (c->replaying)
+			found = fallible_resolve_collision(c, key, &znode, &n,
+							   nm);
+		else
+			found = resolve_collision(c, key, &znode, &n, nm);
+		if (found == -ENOENT)
+			found = 0;
+		if (found < 0) {
+			err = found;
+			goto out;
+		}
+		if (found) {
+			/* Ensure the znode is dirtied */
+			if (znode->cnext || !ubifs_zn_dirty(znode)) {
+				    znode = dirty_cow_bottom_up(c, znode);
+				    if (IS_ERR(znode)) {
+					    err = PTR_ERR(znode);
+					    goto out;
+				    }
+			}
+			err = tnc_delete(c, znode, n);
+		}
+	}
+out:
+	if (!err)
+		err = dbg_check_tnc(c, 0);
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
+ * key_in_range - determine if a key falls wi