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tnc.c

/*
 * 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 "ubifs.h"

/*
 * Returned codes of 'matches_name()' and 'fallible_matches_name()' functions.
 * @NAME_LESS: name corresponding to the first argument is less than second
 * @NAME_MATCHES: names match
 * @NAME_GREATER: name corresponding to the second argument is greater than
 *                first
 * @NOT_ON_MEDIA: node referred by zbranch does not exist on the media
 *
 * These constants were introduce to improve readability.
 */
enum {
      NAME_LESS    = 0,
      NAME_MATCHES = 1,
      NAME_GREATER = 2,
      NOT_ON_MEDIA = 3,
};

/**
 * 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.
 *
 * For recovery, there must always be a complete intact version of the index on
 * flash at all times. That is called the "old index". It is the index as at the
 * time of the last successful commit. Many of the index nodes in the old index
 * may be dirty, but they must not be erased until the next successful commit
 * (at which point that index becomes the old index).
 *
 * That means that the garbage collection and the in-the-gaps method of
 * committing must be able to determine if an index node is in the old index.
 * Most of the old index nodes can be found by looking up the TNC using the
 * 'lookup_znode()' function. However, some of the old index nodes may have
 * been deleted from the current index or may have been changed so much that
 * they cannot be easily found. In those cases, an entry is added to an RB-tree.
 * That is what this function does. The RB-tree is ordered by LEB number and
 * offset because they uniquely identify the old index node.
 */
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;

      old_idx = kmalloc(sizeof(struct ubifs_old_idx), GFP_NOFS);
      if (unlikely(!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;
}

/**
 * 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 = kmalloc(c->max_znode_sz, GFP_NOFS);
      if (unlikely(!zn))
            return ERR_PTR(-ENOMEM);

      memcpy(zn, znode, c->max_znode_sz);
      zn->cnext = NULL;
      __set_bit(DIRTY_ZNODE, &zn->flags);
      __clear_bit(COW_ZNODE, &zn->flags);

      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;
            }
      }

      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 (unlikely(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 (unlikely(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 (unlikely(err))
            return ERR_PTR(err);
      return zn;
}

/**
 * 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
 *
 * Leaf nodes are non-index nodes 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.
 *
 * Note, this function does not add the @node object to LNC directly, but
 * allocates a copy of the object and adds the copy to LNC. The reason for this
 * is that @node has been allocated outside of the TNC subsystem and will be
 * used with @c->tnc_mutex unlock upon return from the TNC subsystem. But LNC
 * may be changed at any time, e.g. freed by the shrinker.
 */
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);
      ubifs_assert(zbr->len != 0);
      ubifs_assert(is_hash_key(c, &zbr->key));

      err = ubifs_validate_entry(c, dent);
      if (err) {
            dbg_dump_stack();
            dbg_dump_node(c, dent);
            return err;
      }

      lnc_node = kmalloc(zbr->len, GFP_NOFS);
      if (!lnc_node)
            /* We don't have to have the cache, so no error */
            return 0;

      memcpy(lnc_node, node, zbr->len);
      zbr->leaf = lnc_node;
      return 0;
}

 /**
 * lnc_add_directly - 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 is similar to 'lnc_add()', but it does not create a copy of
 * @node but inserts @node to TNC directly.
 */
static int lnc_add_directly(struct ubifs_info *c, struct ubifs_zbranch *zbr,
                      void *node)
{
      int err;

      ubifs_assert(!zbr->leaf);
      ubifs_assert(zbr->len != 0);

      err = ubifs_validate_entry(c, node);
      if (err) {
            dbg_dump_stack();
            dbg_dump_node(c, node);
            return err;
      }

      zbr->leaf = node;
      return 0;
}

/**
 * lnc_free - remove a leaf node from the leaf node cache.
 * @zbr: zbranch of leaf node
 * @node: leaf node
 */
static void lnc_free(struct ubifs_zbranch *zbr)
{
      if (!zbr->leaf)
            return;
      kfree(zbr->leaf);
      zbr->leaf = NULL;
}

/**
 * tnc_read_node_nm - read a "hashed" leaf node.
 * @c: UBIFS file-system description object
 * @zbr: key and position of the node
 * @node: node is returned here
 *
 * This function reads a "hashed" node defined by @zbr from the leaf node cache
 * (in it is there) or from the hash media, in which case the node is also
 * added to LNC. Returns zero in case of success or a negative negative error
 * code in case of failure.
 */
static int tnc_read_node_nm(struct ubifs_info *c, struct ubifs_zbranch *zbr,
                      void *node)
{
      int err;

      ubifs_assert(is_hash_key(c, &zbr->key));

      if (zbr->leaf) {
            /* Read from the leaf node cache */
            ubifs_assert(zbr->len != 0);
            memcpy(node, zbr->leaf, zbr->len);
            return 0;
      }

      err = ubifs_tnc_read_node(c, zbr, node);
      if (err)
            return err;

      /* Add the node to the leaf node cache */
      err = lnc_add(c, zbr, node);
      return err;
}

/**
 * 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.
 *
 * Note, this function does not check CRC of data nodes if @c->no_chk_data_crc
 * is true (it is controlled by corresponding mount option). However, if
 * @c->always_chk_crc is true, @c->no_chk_data_crc is ignored and CRC is always
 * checked.
 */
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);

      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;

      if (type == UBIFS_DATA_NODE && !c->always_chk_crc && c->no_chk_data_crc)
            return 1;

      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("LEB %d:%d, key %s", zbr->lnum, zbr->offs, DBGKEY(key));

      ret = try_read_node(c, node, key_type(c, key), zbr->len, zbr->lnum,
                      zbr->offs);
      if (ret == 1) {
            union ubifs_key node_key;
            struct ubifs_dent_node *dent = node;

            /* All nodes have key in the same place */
            key_read(c, &dent->key, &node_key);
            if (keys_cmp(c, key, &node_key) != 0)
                  ret = 0;
      }
      if (ret == 0 && c->replaying)
            dbg_mnt("dangling branch LEB %d:%d len %d, key %s",
                  zbr->lnum, zbr->offs, zbr->len, DBGKEY(key));
      return ret;
}

/**
 * matches_name - determine if a direntry or xattr entry matches a given name.
 * @c: UBIFS file-system description object
 * @zbr: zbranch of dent
 * @nm: name to match
 *
 * This function checks if xentry/direntry referred by zbranch @zbr matches name
 * @nm. Returns %NAME_MATCHES if it does, %NAME_LESS if the name referred by
 * @zbr is less than @nm, and %NAME_GREATER if it is greater than @nm. In case
 * of failure, a negative error code is returned.
 */
static int matches_name(struct ubifs_info *c, struct ubifs_zbranch *zbr,
                  const struct qstr *nm)
{
      struct ubifs_dent_node *dent;
      int nlen, err;

      /* If possible, match against the dent in the leaf node cache */
      if (!zbr->leaf) {
            dent = kmalloc(zbr->len, GFP_NOFS);
            if (!dent)
                  return -ENOMEM;

            err = ubifs_tnc_read_node(c, zbr, dent);
            if (err)
                  goto out_free;

            /* Add the node to the leaf node cache */
            err = lnc_add_directly(c, zbr, dent);
            if (err)
                  goto out_free;
      } else
            dent = zbr->leaf;

      nlen = le16_to_cpu(dent->nlen);
      err = memcmp(dent->name, nm->name, min_t(int, nlen, nm->len));
      if (err == 0) {
            if (nlen == nm->len)
                  return NAME_MATCHES;
            else if (nlen < nm->len)
                  return NAME_LESS;
            else
                  return NAME_GREATER;
      } else if (err < 0)
            return NAME_LESS;
      else
            return NAME_GREATER;

out_free:
      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 = ubifs_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
 * @n: 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 *n)
{
      struct ubifs_znode *znode = *zn;
      int nn = *n;

      nn += 1;
      if (nn < znode->child_cnt) {
            *n = nn;
            return 0;
      }
      while (1) {
            struct ubifs_znode *zp;

            zp = znode->parent;
            if (!zp)
                  return -ENOENT;
            nn = znode->iip + 1;
            znode = zp;
            if (nn < znode->child_cnt) {
                  znode = get_znode(c, znode, nn);
                  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);
                  }
                  nn = 0;
                  break;
            }
      }
      *zn = znode;
      *n = nn;
      return 0;
}

/**
 * tnc_prev - find previous TNC entry.
 * @c: UBIFS file-system description object
 * @zn: znode is returned here
 * @n: 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 *n)
{
      struct ubifs_znode *znode = *zn;
      int nn = *n;

      if (nn > 0) {
            *n = nn - 1;
            return 0;
      }
      while (1) {
            struct ubifs_znode *zp;

            zp = znode->parent;
            if (!zp)
                  return -ENOENT;
            nn = znode->iip - 1;
            znode = zp;
            if (nn >= 0) {
                  znode = get_znode(c, znode, nn);
                  if (IS_ERR(znode))
                        return PTR_ERR(znode);
                  while (znode->level != 0) {
                        nn = znode->child_cnt - 1;
                        znode = get_znode(c, znode, nn);
                        if (IS_ERR(znode))
                              return PTR_ERR(znode);
                  }
                  nn = znode->child_cnt - 1;
                  break;
            }
      }
      *zn = znode;
      *n = nn;
      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
 * @n: zbranch number is passed and returned here
 * @nm: name of the entry
 *
 * This function is called for "hashed" keys to make sure that the found key
 * really corresponds to the looked up node (directory or extended attribute
 * entry). It returns %1 and sets @zn and @n if the collision is resolved.
 * %0 is returned if @nm is not found and @zn and @n are set to the previous
 * entry, i.e. to the entry after which @nm could follow if it were in TNC.
 * This means that @n may be set to %-1 if the leftmost key in @zn is the
 * previous one. A negative error code is returned on failures.
 */
static int resolve_collision(struct ubifs_info *c, const union ubifs_key *key,
                       struct ubifs_znode **zn, int *n,
                       const struct qstr *nm)
{
      int err;

      err = matches_name(c, &(*zn)->zbranch[*n], nm);
      if (unlikely(err < 0))
            return err;
      if (err == NAME_MATCHES)
            return 1;

      if (err == NAME_GREATER) {
            /* Look left */
            while (1) {
                  err = tnc_prev(c, zn, n);
                  if (err == -ENOENT) {
                        ubifs_assert(*n == 0);
                        *n = -1;
                        return 0;
                  }
                  if (err < 0)
                        return err;
                  if (keys_cmp(c, &(*zn)->zbranch[*n].key, key)) {
                        /*
                         * We have found the branch after which we would
                         * like to insert, but inserting in this znode
                         * may still be wrong. Consider the following 3
                         * znodes, in the case where we are resolving a
                         * collision with Key2.
                         *
                         *                  znode zp
                         *            ----------------------
                         * level 1     |  Key0  |  Key1  |
                         *            -----------------------
                         *                 |            |
                         *       znode za  |            |  znode zb
                         *          ------------      ------------
                         * level 0  |  Key0  |        |  Key2  |
                         *          ------------      ------------
                         *
                         * The lookup finds Key2 in znode zb. Lets say
                         * there is no match and the name is greater so
                         * we look left. When we find Key0, we end up
                         * here. If we return now, we will insert into
                         * znode za at slot n = 1.  But that is invalid
                         * according to the parent's keys.  Key2 must
                         * be inserted into znode zb.
                         *
                         * Note, this problem is not relevant for the
                         * case when we go right, because
                         * 'tnc_insert()' would correct the parent key.
                         */
                        if (*n == (*zn)->child_cnt - 1) {
                              err = tnc_next(c, zn, n);
                              if (err) {
                                    /* Should be impossible */
                                    ubifs_assert(0);
                                    if (err == -ENOENT)
                                          err = -EINVAL;
                                    return err;
                              }
                              ubifs_assert(*n == 0);
                              *n = -1;
                        }
                        return 0;
                  }
                  err = matches_name(c, &(*zn)->zbranch[*n], nm);
                  if (err < 0)
                        return err;
                  if (err == NAME_LESS)
                        return 0;
                  if (err == NAME_MATCHES)
                        return 1;
                  ubifs_assert(err == NAME_GREATER);
            }
      } else {
            int nn = *n;
            struct ubifs_znode *znode = *zn;

            /* Look right */
            while (1) {
                  err = tnc_next(c, &znode, &nn);
                  if (err == -ENOENT)
                        return 0;
                  if (err < 0)
                        return err;
                  if (keys_cmp(c, &znode->zbranch[nn].key, key))
                        return 0;
                  err = matches_name(c, &znode->zbranch[nn], nm);
                  if (err < 0)
                        return err;
                  if (err == NAME_GREATER)
                        return 0;
                  *zn = znode;
                  *n = nn;
                  if (err == NAME_MATCHES)
                        return 1;
                  ubifs_assert(err == NAME_LESS);
            }
      }
}

/**
 * fallible_matches_name - determine if a dent matches a given name.
 * @c: UBIFS file-system description object
 * @zbr: zbranch of dent
 * @nm: name to match
 *
 * This is a "fallible" version of 'matches_name()' function which does not
 * panic if the direntry/xentry referred by @zbr does not exist on the media.
 *
 * This function checks if xentry/direntry referred by zbranch @zbr matches name
 * @nm. Returns %NAME_MATCHES it does, %NAME_LESS if the name referred by @zbr
 * is less than @nm, %NAME_GREATER if it is greater than @nm, and @NOT_ON_MEDIA
 * if xentry/direntry referred by @zbr does not exist on the media. A negative
 * error code is returned in case of failure.
 */
static int fallible_matches_name(struct ubifs_info *c,
                         struct ubifs_zbranch *zbr,
                         const struct qstr *nm)
{
      struct ubifs_dent_node *dent;
      int nlen, err;

      /* If possible, match against the dent in the leaf node cache */
      if (!zbr->leaf) {
            dent = kmalloc(zbr->len, GFP_NOFS);
            if (!dent)
                  return -ENOMEM;

            err = fallible_read_node(c, &zbr->key, zbr, dent);
            if (err < 0)
                  goto out_free;
            if (err == 0) {
                  /* The node was not present */
                  err = NOT_ON_MEDIA;
                  goto out_free;
            }
            ubifs_assert(err == 1);

            err = lnc_add_directly(c, zbr, dent);
            if (err)
                  goto out_free;
      } else
            dent = zbr->leaf;

      nlen = le16_to_cpu(dent->nlen);
      err = memcmp(dent->name, nm->name, min_t(int, nlen, nm->len));
      if (err == 0) {
            if (nlen == nm->len)
                  return NAME_MATCHES;
            else if (nlen < nm->len)
                  return NAME_LESS;
            else
                  return NAME_GREATER;
      } else if (err < 0)
            return NAME_LESS;
      else
            return NAME_GREATER;

out_free:
      kfree(dent);
      return err;
}

/**
 * fallible_resolve_collision - resolve a collision even if nodes are missing.
 * @c: UBIFS file-system description object
 * @key: key
 * @zn: znode is returned here
 * @n: branch number is passed and returned here
 * @nm: name of directory entry
 * @adding: indicates caller is adding a key to the TNC
 *
 * This is a "fallible" version of the 'resolve_collision()' function which
 * does not panic if one of the nodes referred to by TNC does not exist on the
 * media. This may happen when replaying the journal if a deleted node was
 * Garbage-collected and the commit was not done. A branch that refers to a node
 * that is not present is called a dangling branch. The following are the return
 * codes for this function:
 *  o if @nm was found, %1 is returned and @zn and @n are set to the found
 *    branch;
 *  o if we are @adding and @nm was not found, %0 is returned;
 *  o if we are not @adding and @nm was not found, but a dangling branch was
 *    found, then %1 is returned and @zn and @n are set to the dangling branch;
 *  o a negative error code is returned in case of failure.
 */
static int fallible_resolve_collision(struct ubifs_info *c,
                              const union ubifs_key *key,
                              struct ubifs_znode **zn, int *n,
                              const struct qstr *nm, int adding)
{
      struct ubifs_znode *o_znode = NULL, *znode = *zn;
      int uninitialized_var(o_n), err, cmp, unsure = 0, nn = *n;

      cmp = fallible_matches_name(c, &znode->zbranch[nn], nm);
      if (unlikely(cmp < 0))
            return cmp;
      if (cmp == NAME_MATCHES)
            return 1;
      if (cmp == NOT_ON_MEDIA) {
            o_znode = znode;
            o_n = nn;
            /*
             * We are unlucky and hit a dangling branch straight away.
             * Now we do not really know where to go to find the needed
             * branch - to the left or to the right. Well, let's try left.
             */
            unsure = 1;
      } else if (!adding)
            unsure = 1; /* Remove a dangling branch wherever it is */

      if (cmp == NAME_GREATER || unsure) {
            /* Look left */
            while (1) {
                  err = tnc_prev(c, zn, n);
                  if (err == -ENOENT) {
                        ubifs_assert(*n == 0);
                        *n = -1;
                        break;
                  }
                  if (err < 0)
                        return err;
                  if (keys_cmp(c, &(*zn)->zbranch[*n].key, key)) {
                        /* See comments in 'resolve_collision()' */
                        if (*n == (*zn)->child_cnt - 1) {
                              err = tnc_next(c, zn, n);
                              if (err) {
                                    /* Should be impossible */
                                    ubifs_assert(0);
                                    if (err == -ENOENT)
                                          err = -EINVAL;
                                    return err;
                              }
                              ubifs_assert(*n == 0);
                              *n = -1;
                        }
                        break;
                  }
                  err = fallible_matches_name(c, &(*zn)->zbranch[*n], nm);
                  if (err < 0)
                        return err;
                  if (err == NAME_MATCHES)
                        return 1;
                  if (err == NOT_ON_MEDIA) {
                        o_znode = *zn;
                        o_n = *n;
                        continue;
                  }
                  if (!adding)
                        continue;
                  if (err == NAME_LESS)
                        break;
                  else
                        unsure = 0;
            }
      }

      if (cmp == NAME_LESS || unsure) {
            /* Look right */
            *zn = znode;
            *n = nn;
            while (1) {
                  err = tnc_next(c, &znode, &nn);
                  if (err == -ENOENT)
                        break;
                  if (err < 0)
                        return err;
                  if (keys_cmp(c, &znode->zbranch[nn].key, key))
                        break;
                  err = fallible_matches_name(c, &znode->zbranch[nn], nm);
                  if (err < 0)
                        return err;
                  if (err == NAME_GREATER)
                        break;
                  *zn = znode;
                  *n = nn;
                  if (err == NAME_MATCHES)
                        return 1;
                  if (err == NOT_ON_MEDIA) {
                        o_znode = znode;
                        o_n = nn;
                  }
            }
      }

      /* Never match a dangling branch when adding */
      if (adding || !o_znode)
            return 0;

      dbg_mnt("dangling match LEB %d:%d len %d %s",
            o_znode->zbranch[o_n].lnum, o_znode->zbranch[o_n].offs,
            o_znode->zbranch[o_n].len, DBGKEY(key));
      *zn = o_znode;
      *n = o_n;
      return 1;
}

/**
 * matches_position - determine if a zbranch matches a given position.
 * @zbr: 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 *zbr, int lnum, int offs)
{
      if (zbr->lnum == lnum && zbr->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
 * @n: zbranch number is passed and returned here
 * @lnum: LEB number of dent node to match
 * @offs: offset of dent node to match
 *
 * This function is used for "hashed" keys to make sure the found directory or
 * extended attribute entry node is what was looked for. It is used when the
 * flash address of the right node is known (@lnum:@offs) which makes it much
 * easier to resolve collisions (no need to read entries and match full
 * names). This function returns %1 and sets @zn and @n if the collision is
 * resolved, %0 if @lnum:@offs is not found and @zn and @n are set to the
 * previous directory entry. 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 *n,
                              int lnum, int offs)
{
      struct ubifs_znode *znode;
      int nn, err;

      znode = *zn;
      nn = *n;
      if (matches_position(&znode->zbranch[nn], lnum, offs))
            return 1;

      /* Look left */
      while (1) {
            err = tnc_prev(c, &znode, &nn);
            if (err == -ENOENT)
                  break;
            if (err < 0)
                  return err;
            if (keys_cmp(c, &znode->zbranch[nn].key, key))
                  break;
            if (matches_position(&znode->zbranch[nn], lnum, offs)) {
                  *zn = znode;
                  *n = nn;
                  return 1;
            }
      }

      /* Look right */
      znode = *zn;
      nn = *n;
      while (1) {
            err = tnc_next(c, &znode, &nn);
            if (err == -ENOENT)
                  return 0;
            if (err < 0)
                  return err;
            if (keys_cmp(c, &znode->zbranch[nn].key, key))
                  return 0;
            *zn = znode;
            *n = nn;
            if (matches_position(&znode->zbranch[nn], lnum, offs))
                  return 1;
      }
}

/**
 * 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 = c->bottom_up_buf, p = 0;

      ubifs_assert(c->zroot.znode);
      ubifs_assert(znode);
      if (c->zroot.znode->level > BOTTOM_UP_HEIGHT) {
            kfree(c->bottom_up_buf);
            c->bottom_up_buf = kmalloc(c->zroot.znode->level * sizeof(int),
                                 GFP_NOFS);
            if (!c->bottom_up_buf)
                  return ERR_PTR(-ENOMEM);
            path = c->bottom_up_buf;
      }
      if (c->zroot.znode->level) {
            /* Go up until parent is dirty */
            while (1) {
                  int n;

                  zp = znode->parent;
                  if (!zp)
                        break;
                  n = znode->iip;
                  ubifs_assert(p < c->zroot.znode->level);
                  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;
      }

      return znode;
}

/**
 * ubifs_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 than 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.
 */
int ubifs_lookup_level0(struct ubifs_info *c, const union ubifs_key *key,
                  struct ubifs_znode **zn, int *n)
{
      int err, exact;
      struct ubifs_znode *znode;
      unsigned long time = get_seconds();

      dbg_tnc("search key %s", DBGKEY(key));

      znode = c->zroot.znode;
      if (unlikely(!znode)) {
            znode = ubifs_load_znode(c, &c->zroot, NULL, 0);
            if (IS_ERR(znode))
                  return PTR_ERR(znode);
      }

      znode->time = time;

      while (1) {
            struct ubifs_zbranch *zbr;

            exact = ubifs_search_zbranch(c, znode, key, n);

            if (znode->level == 0)
                  break;

            if (*n < 0)
                  *n = 0;
            zbr = &znode->zbranch[*n];

            if (zbr->znode) {
                  znode->time = time;
                  znode = zbr->znode;
                  continue;
            }

            /* znode is not in TNC cache, load it from the media */
            znode = ubifs_load_znode(c, zbr, znode, *n);
            if (IS_ERR(znode))
                  return PTR_ERR(znode);
      }

      *zn = znode;
      if (exact || !is_hash_key(c, key) || *n != -1) {
            dbg_tnc("found %d, lvl %d, n %d", exact, znode->level, *n);
            return exact;
      }

      /*
       * Here is a tricky place. We have not found the key and this is a
       * "hashed" key, which may collide. The rest of the code deals with
       * situations like this:
       *
       *                  | 3 | 5 |
       *                  /       \
       *          | 3 | 5 |      | 6 | 7 | (x)
       *
       * Or more a complex example:
       *
       *                | 1 | 5 |
       *                /       \
       *       | 1 | 3 |         | 5 | 8 |
       *              \           /
       *          | 5 | 5 |   | 6 | 7 | (x)
       *
       * In the examples, if we are looking for key "5", we may reach nodes
       * marked with "(x)". In this case what we have do is to look at the
       * left and see if there is "5" key there. If there is, we have to
       * return it.
       *
       * Note, this whole situation is possible because we allow to have
       * elements which are equivalent to the next key in the parent in the
       * children of current znode. For example, this happens if we split a
       * znode like this: | 3 | 5 | 5 | 6 | 7 |, which results in something
       * like this:
       *                      | 3 | 5 |
       *                       /     \
       *                | 3 | 5 |   | 5 | 6 | 7 |
       *                              ^
       * And this becomes what is at the first "picture" after key "5" marked
       * with "^" is removed. What could be done is we could prohibit
       * splitting in the middle of the colliding sequence. Also, when
       * removing the leftmost key, we would have to correct the key of the
       * parent node, which would introduce additional complications. Namely,
       * if we changed the the leftmost key of the parent znode, the garbage
       * collector would be unable to find it (GC is doing this when GC'ing
       * indexing LEBs). Although we already have an additional RB-tree where
       * we save such changed znodes (see 'ins_clr_old_idx_znode()') until
       * after the commit. But anyway, this does not look easy to implement
       * so we did not try this.
       */
      err = tnc_prev(c, &znode, n);
      if (err == -ENOENT) {
            dbg_tnc("found 0, lvl %d, n -1", znode->level);
            *n = -1;
            return 0;
      }
      if (unlikely(err < 0))
            return err;
      if (keys_cmp(c, key, &znode->zbranch[*n].key)) {
            dbg_tnc("found 0, lvl %d, n -1", znode->level);
            *n = -1;
            return 0;
      }

      dbg_tnc("found 1, lvl %d, n %d", znode->level, *n);
      *zn = znode;
      return 1;
}

/**
 * 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 than the lowest key of the
 *     leftmost zero-level node, then %0 is returned and %-1 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 err, exact;
      struct ubifs_znode *znode;
      unsigned long time = get_seconds();

      dbg_tnc("search and dirty key %s", DBGKEY(key));

      znode = c->zroot.znode;
      if (unlikely(!znode)) {
            znode = ubifs_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;

            exact = ubifs_search_zbranch(c, znode, key, n);

            if (znode->level == 0)
                  break;

            if (*n < 0)
                  *n = 0;
            zbr = &znode->zbranch[*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 = ubifs_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;
      if (exact || !is_hash_key(c, key) || *n != -1) {
            dbg_tnc("found %d, lvl %d, n %d", exact, znode->level, *n);
            return exact;
      }

      /*
       * See huge comment at 'lookup_level0_dirty()' what is the rest of the
       * code.
       */
      err = tnc_prev(c, &znode, n);
      if (err == -ENOENT) {
            *n = -1;
            dbg_tnc("found 0, lvl %d, n -1", znode->level);
            return 0;
      }
      if (unlikely(err < 0))
            return err;
      if (keys_cmp(c, key, &znode->zbranch[*n].key)) {
            *n = -1;
            dbg_tnc("found 0, lvl %d, n -1", znode->level);
            return 0;
      }

      if (znode->cnext || !ubifs_zn_dirty(znode)) {
            znode = dirty_cow_bottom_up(c, znode);
            if (IS_ERR(znode))
                  return PTR_ERR(znode);
      }

      dbg_tnc("found 1, lvl %d, n %d", znode->level, *n);
      *zn = znode;
      return 1;
}

/**
 * maybe_leb_gced - determine if a LEB may have been garbage collected.
 * @c: UBIFS file-system description object
 * @lnum: LEB number
 * @gc_seq1: garbage collection sequence number
 *
 * This function determines if @lnum may have been garbage collected since
 * sequence number @gc_seq1. If it may have been then %1 is returned, otherwise
 * %0 is returned.
 */
static int maybe_leb_gced(struct ubifs_info *c, int lnum, int gc_seq1)
{
      /*
       * No garbage collection in the read-only U-Boot implementation
       */
      return 0;
}

/**
 * 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 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. The node location can be returned in @lnum and @offs.
 */
int ubifs_tnc_locate(struct ubifs_info *c, const union ubifs_key *key,
                 void *node, int *lnum, int *offs)
{
      int found, n, err, safely = 0, gc_seq1;
      struct ubifs_znode *znode;
      struct ubifs_zbranch zbr, *zt;

again:
      mutex_lock(&c->tnc_mutex);
      found = ubifs_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 (lnum) {
            *lnum = zt->lnum;
            *offs = zt->offs;
      }
      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_nm(c, zt, node);
            goto out;
      }
      if (safely) {
            err = ubifs_tnc_read_node(c, zt, node);
            goto out;
      }
      /* Drop the TNC mutex prematurely and race with garbage collection */
      zbr = znode->zbranch[n];
      gc_seq1 = c->gc_seq;
      mutex_unlock(&c->tnc_mutex);

      err = fallible_read_node(c, key, &zbr, node);
      if (err <= 0 || maybe_leb_gced(c, zbr.lnum, gc_seq1)) {
            /*
             * The node may have been GC'ed out from under us so try again
             * while keeping the TNC mutex locked.
             */
            safely = 1;
            goto again;
      }
      return 0;

out:
      mutex_unlock(&c->tnc_mutex);
      return err;
}

/**
 * ubifs_tnc_get_bu_keys - lookup keys for bulk-read.
 * @c: UBIFS file-system description object
 * @bu: bulk-read parameters and results
 *
 * Lookup consecutive data node keys for the same inode that reside
 * consecutively in the same LEB. This function returns zero in case of success
 * and a negative error code in case of failure.
 *
 * Note, if the bulk-read buffer length (@bu->buf_len) is known, this function
 * makes sure bulk-read nodes fit the buffer. Otherwise, this function prepares
 * maximum possible amount of nodes for bulk-read.
 */
int ubifs_tnc_get_bu_keys(struct ubifs_info *c, struct bu_info *bu)
{
      int n, err = 0, lnum = -1, uninitialized_var(offs);
      int uninitialized_var(len);
      unsigned int block = key_block(c, &bu->key);
      struct ubifs_znode *znode;

      bu->cnt = 0;
      bu->blk_cnt = 0;
      bu->eof = 0;

      mutex_lock(&c->tnc_mutex);
      /* Find first key */
      err = ubifs_lookup_level0(c, &bu->key, &znode, &n);
      if (err < 0)
            goto out;
      if (err) {
            /* Key found */
            len = znode->zbranch[n].len;
            /* The buffer must be big enough for at least 1 node */
            if (len > bu->buf_len) {
                  err = -EINVAL;
                  goto out;
            }
            /* Add this key */
            bu->zbranch[bu->cnt++] = znode->zbranch[n];
            bu->blk_cnt += 1;
            lnum = znode->zbranch[n].lnum;
            offs = ALIGN(znode->zbranch[n].offs + len, 8);
      }
      while (1) {
            struct ubifs_zbranch *zbr;
            union ubifs_key *key;
            unsigned int next_block;

            /* Find next key */
            err = tnc_next(c, &znode, &n);
            if (err)
                  goto out;
            zbr = &znode->zbranch[n];
            key = &zbr->key;
            /* See if there is another data key for this file */
            if (key_inum(c, key) != key_inum(c, &bu->key) ||
                key_type(c, key) != UBIFS_DATA_KEY) {
                  err = -ENOENT;
                  goto out;
            }
            if (lnum < 0) {
                  /* First key found */
                  lnum = zbr->lnum;
                  offs = ALIGN(zbr->offs + zbr->len, 8);
                  len = zbr->len;
                  if (len > bu->buf_len) {
                        err = -EINVAL;
                        goto out;
                  }
            } else {
                  /*
                   * The data nodes must be in consecutive positions in
                   * the same LEB.
                   */
                  if (zbr->lnum != lnum || zbr->offs != offs)
                        goto out;
                  offs += ALIGN(zbr->len, 8);
                  len = ALIGN(len, 8) + zbr->len;
                  /* Must not exceed buffer length */
                  if (len > bu->buf_len)
                        goto out;
            }
            /* Allow for holes */
            next_block = key_block(c, key);
            bu->blk_cnt += (next_block - block - 1);
            if (bu->blk_cnt >= UBIFS_MAX_BULK_READ)
                  goto out;
            block = next_block;
            /* Add this key */
            bu->zbranch[bu->cnt++] = *zbr;
            bu->blk_cnt += 1;
            /* See if we have room for more */
            if (bu->cnt >= UBIFS_MAX_BULK_READ)
                  goto out;
            if (bu->blk_cnt >= UBIFS_MAX_BULK_READ)
                  goto out;
      }
out:
      if (err == -ENOENT) {
            bu->eof = 1;
            err = 0;
      }
      bu->gc_seq = c->gc_seq;
      mutex_unlock(&c->tnc_mutex);
      if (err)
            return err;
      /*
       * An enormous hole could cause bulk-read to encompass too many
       * page cache pages, so limit the number here.
       */
      if (bu->blk_cnt > UBIFS_MAX_BULK_READ)
            bu->blk_cnt = UBIFS_MAX_BULK_READ;
      /*
       * Ensure that bulk-read covers a whole number of page cache
       * pages.
       */
      if (UBIFS_BLOCKS_PER_PAGE == 1 ||
          !(bu->blk_cnt & (UBIFS_BLOCKS_PER_PAGE - 1)))
            return 0;
      if (bu->eof) {
            /* At the end of file we can round up */
            bu->blk_cnt += UBIFS_BLOCKS_PER_PAGE - 1;
            return 0;
      }
      /* Exclude data nodes that do not make up a whole page cache page */
      block = key_block(c, &bu->key) + bu->blk_cnt;
      block &= ~(UBIFS_BLOCKS_PER_PAGE - 1);
      while (bu->cnt) {
            if (key_block(c, &bu->zbranch[bu->cnt - 1].key) < block)
                  break;
            bu->cnt -= 1;
      }
      return 0;
}

/**
 * validate_data_node - validate data nodes for bulk-read.
 * @c: UBIFS file-system description object
 * @buf: buffer containing data node to validate
 * @zbr: zbranch of data node to validate
 *
 * This functions returns %0 on success or a negative error code on failure.
 */
static int validate_data_node(struct ubifs_info *c, void *buf,
                        struct ubifs_zbranch *zbr)
{
      union ubifs_key key1;
      struct ubifs_ch *ch = buf;
      int err, len;

      if (ch->node_type != UBIFS_DATA_NODE) {
            ubifs_err("bad node type (%d but expected %d)",
                    ch->node_type, UBIFS_DATA_NODE);
            goto out_err;
      }

      err = ubifs_check_node(c, buf, zbr->lnum, zbr->offs, 0, 0);
      if (err) {
            ubifs_err("expected node type %d", UBIFS_DATA_NODE);
            goto out;
      }

      len = le32_to_cpu(ch->len);
      if (len != zbr->len) {
            ubifs_err("bad node length %d, expected %d", len, zbr->len);
            goto out_err;
      }

      /* Make sure the key of the read node is correct */
      key_read(c, buf + UBIFS_KEY_OFFSET, &key1);
      if (!keys_eq(c, &zbr->key, &key1)) {
            ubifs_err("bad key in node at LEB %d:%d",
                    zbr->lnum, zbr->offs);
            dbg_tnc("looked for key %s found node's key %s",
                  DBGKEY(&zbr->key), DBGKEY1(&key1));
            goto out_err;
      }

      return 0;

out_err:
      err = -EINVAL;
out:
      ubifs_err("bad node at LEB %d:%d", zbr->lnum, zbr->offs);
      dbg_dump_node(c, buf);
      dbg_dump_stack();
      return err;
}

/**
 * ubifs_tnc_bulk_read - read a number of data nodes in one go.
 * @c: UBIFS file-system description object
 * @bu: bulk-read parameters and results
 *
 * This functions reads and validates the data nodes that were identified by the
 * 'ubifs_tnc_get_bu_keys()' function. This functions returns %0 on success,
 * -EAGAIN to indicate a race with GC, or another negative error code on
 * failure.
 */
int ubifs_tnc_bulk_read(struct ubifs_info *c, struct bu_info *bu)
{
      int lnum = bu->zbranch[0].lnum, offs = bu->zbranch[0].offs, len, err, i;
      void *buf;

      len = bu->zbranch[bu->cnt - 1].offs;
      len += bu->zbranch[bu->cnt - 1].len - offs;
      if (len > bu->buf_len) {
            ubifs_err("buffer too small %d vs %d", bu->buf_len, len);
            return -EINVAL;
      }

      /* Do the read */
      err = ubi_read(c->ubi, lnum, bu->buf, offs, len);

      /* Check for a race with GC */
      if (maybe_leb_gced(c, lnum, bu->gc_seq))
            return -EAGAIN;

      if (err && err != -EBADMSG) {
            ubifs_err("failed to read from LEB %d:%d, error %d",
                    lnum, offs, err);
            dbg_dump_stack();
            dbg_tnc("key %s", DBGKEY(&bu->key));
            return err;
      }

      /* Validate the nodes read */
      buf = bu->buf;
      for (i = 0; i < bu->cnt; i++) {
            err = validate_data_node(c, buf, &bu->zbranch[i]);
            if (err)
                  return err;
            buf = buf + ALIGN(bu->zbranch[i].len, 8);
      }

      return 0;
}

/**
 * do_lookup_nm- look up a "hashed" 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;

      dbg_tnc("name '%.*s' key %s", nm->len, nm->name, DBGKEY(key));
      mutex_lock(&c->tnc_mutex);
      found = ubifs_lookup_level0(c, key, &znode, &n);
      if (!found) {
            err = -ENOENT;
            goto out_unlock;
      } else if (found < 0) {
            err = found;
            goto out_unlock;
      }

      ubifs_assert(n >= 0);

      err = resolve_collision(c, key, &znode, &n, nm);
      dbg_tnc("rc returned %d, znode %p, n %d", err, znode, n);
      if (unlikely(err < 0))
            goto out_unlock;
      if (err == 0) {
            err = -ENOENT;
            goto out_unlock;
      }

      err = tnc_read_node_nm(c, &znode->zbranch[n], node);

out_unlock:
      mutex_unlock(&c->tnc_mutex);
      return err;
}

/**
 * ubifs_tnc_lookup_nm - look up a "hashed" 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;
            znode->alt = 1;
            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, *key1;

      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("inserted at %d level %d, key %s", n, znode->level,
                  DBGKEY(key));

            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("splitting level %d, key %s", znode->level, DBGKEY(key));

      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 && key_type(c, key) == UBIFS_DATA_KEY) {
            /* Try not to split consecutive data keys */
            if (n == c->fanout) {
                  key1 = &znode->zbranch[n - 1].key;
                  if (key_inum(c, key1) == key_inum(c, key) &&
                      key_type(c, key1) == UBIFS_DATA_KEY)
                        appending = 1;
            } else
                  goto check_split;
      } else if (appending && n != c->fanout) {
            /* Try not to split consecutive data keys */
            appending = 0;
check_split:
            if (n >= (c->fanout + 1) / 2) {
                  key1 = &znode->zbranch[0].key;
                  if (key_inum(c, key1) == key_inum(c, key) &&
                      key_type(c, key1) == UBIFS_DATA_KEY) {
                        key1 = &znode->zbranch[n].key;
                        if (key_inum(c, key1) != key_inum(c, key) ||
                            key_type(c, key1) != UBIFS_DATA_KEY) {
                              keep = n;
                              move = c->fanout - keep;
                              zi = znode;
                              goto do_split;
                        }
                  }
            }
      }

      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;
      }

do_split:

      __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("inserting at %d level %d, key %s", n, zn->level, DBGKEY(key));

      insert_zbranch(zi, zbr, n);

      /* Insert new znode (produced by spitting) into the parent */
      if (zp) {
            if (n == 0 && zi == znode && znode->iip == 0)
                  correct_parent_keys(c, znode);

            /* Locate insertion point */
            n = znode->iip + 1;

            /* 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);
      dbg_tnc("%d:%d, len %d, key %s", lnum, offs, len, DBGKEY(key));
      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;
            key_copy(c, key, &zbr.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;
}

/**
 * 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);
      dbg_tnc("old LEB %d:%d, new LEB %d:%d, len %d, key %s", old_lnum,
            old_offs, lnum, offs, len, DBGKEY(key));
      found = lookup_level0_dirty(c, key, &znode, &n);
      if (found < 0) {
            err = found;
            goto out_unlock;
      }

      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_unlock;
                  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);
                  dbg_tnc("rc returned %d, znode %p, n %d, LEB %d:%d",
                        found, znode, n, old_lnum, old_offs);
                  if (found < 0) {
                        err = found;
                        goto out_unlock;
                  }

                  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_unlock;
                              }
                        }
                        zbr = &znode->zbranch[n];
                        lnc_free(zbr);
                        err = ubifs_add_dirt(c, zbr->lnum,
                                         zbr->len);
                        if (err)
                              goto out_unlock;
                        zbr->lnum = lnum;
                        zbr->offs = offs;
                        zbr->len = len;
                  }
            }
      }

      if (!found)
            err = ubifs_add_dirt(c, lnum, len);

      if (!err)
            err = dbg_check_tnc(c, 0);

out_unlock:
      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);
      dbg_tnc("LEB %d:%d, name '%.*s', key %s", lnum, offs, nm->len, nm->name,
            DBGKEY(key));
      found = lookup_level0_dirty(c, key, &znode, &n);
      if (found < 0) {
            err = found;
            goto out_unlock;
      }

      if (found == 1) {
            if (c->replaying)
                  found = fallible_resolve_collision(c, key, &znode, &n,
                                             nm, 1);
            else
                  found = resolve_collision(c, key, &znode, &n, nm);
            dbg_tnc("rc returned %d, znode %p, n %d", found, znode, n);
            if (found < 0) {
                  err = found;
                  goto out_unlock;
            }

            /* 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_unlock;
                  }
            }

            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_unlock;
            }
      }

      if (!found) {
            struct ubifs_zbranch zbr;

            zbr.znode = NULL;
            zbr.lnum = lnum;
            zbr.offs = offs;
            zbr.len = len;
            key_copy(c, key, &zbr.key);
            err = tnc_insert(c, znode, &zbr, n + 1);
            if (err)
                  goto out_unlock;
            if (c->replaying) {
                  /*
                   * We did not find it in the index so there may be a
                   * dangling branch still in the index. So we remove it
                   * by passing 'ubifs_tnc_remove_nm()' the same key but
                   * an unmatchable name.
                   */
                  struct qstr noname = { .len = 0, .name = "" };

                  err = dbg_check_tnc(c, 0);
                  mutex_unlock(&c->tnc_mutex);
                  if (err)
                        return err;
                  return ubifs_tnc_remove_nm(c, key, &noname);
            }
      }

out_unlock:
      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("deleting %s", DBGKEY(&znode->zbranch[n].key));

      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) {
            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);
      dbg_tnc("key %s", DBGKEY(key));
      found = lookup_level0_dirty(c, key, &znode, &n);
      if (found < 0) {
            err = found;
            goto out_unlock;
      }
      if (found == 1)
            err = tnc_delete(c, znode, n);
      if (!err)
            err = dbg_check_tnc(c, 0);

out_unlock:
      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 n, err;
      struct ubifs_znode *znode;

      mutex_lock(&c->tnc_mutex);
      dbg_tnc("%.*s, key %s", nm->len, nm->name, DBGKEY(key));
      err = lookup_level0_dirty(c, key, &znode, &n);
      if (err < 0)
            goto out_unlock;

      if (err) {
            if (c->replaying)
                  err = fallible_resolve_collision(c, key, &znode, &n,
                                           nm, 0);
            else
                  err = resolve_collision(c, key, &znode, &n, nm);
            dbg_tnc("rc returned %d, znode %p, n %d", err, znode, n);
            if (err < 0)
                  goto out_unlock;
            if (err) {
                  /* 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_unlock;
                            }
                  }
                  err = tnc_delete(c, znode, n);
            }
      }

out_unlock:
      if (!err)
            err = dbg_check_tnc(c, 0);
      mutex_unlock(&c->tnc_mutex);
      return err;
}

/**
 * key_in_range - determine if a key falls within a range of keys.
 * @c: UBIFS file-system description object
 * @key: key to check
 * @from_key: lowest key in range
 * @to_key: highest key in range
 *
 * This function returns %1 if the key is in range and %0 otherwise.
 */
static int key_in_range(struct ubifs_info *c, union ubifs_key *key,
                  union ubifs_key *from_key, union ubifs_key *to_key)
{
      if (keys_cmp(c, key, from_key) < 0)
            return 0;
      if (keys_cmp(c, key, to_key) > 0)
            return 0;
      return 1;
}

/**
 * ubifs_tnc_remove_range - remove index entries in range.
 * @c: UBIFS file-system description object
 * @from_key: lowest key to remove
 * @to_key: highest key to remove
 *
 * This function removes index entries starting at @from_key and ending at
 * @to_key.  This function returns zero in case of success and a negative error
 * code in case of failure.
 */
int ubifs_tnc_remove_range(struct ubifs_info *c, union ubifs_key *from_key,
                     union ubifs_key *to_key)
{
      int i, n, k, err = 0;
      struct ubifs_znode *znode;
      union ubifs_key *key;

      mutex_lock(&c->tnc_mutex);
      while (1) {
            /* Find first level 0 znode that contains keys to remove */
            err = ubifs_lookup_level0(c, from_key, &znode, &n);
            if (err < 0)
                  goto out_unlock;

            if (err)
                  key = from_key;
            else {
                  err = tnc_next(c, &znode, &n);
                  if (err == -ENOENT) {
                        err = 0;
                        goto out_unlock;
                  }
                  if (err < 0)
                        goto out_unlock;
                  key = &znode->zbranch[n].key;
                  if (!key_in_range(c, key, from_key, to_key)) {
                        err = 0;
                        goto out_unlock;
                  }
            }

            /* 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_unlock;
                  }
            }

            /* Remove all keys in range except the first */
            for (i = n + 1, k = 0; i < znode->child_cnt; i++, k++) {
                  key = &znode->zbranch[i].key;
                  if (!key_in_range(c, key, from_key, to_key))
                        break;
                  lnc_free(&znode->zbranch[i]);
                  err = ubifs_add_dirt(c, znode->zbranch[i].lnum,
                                   znode->zbranch[i].len);
                  if (err) {
                        dbg_dump_znode(c, znode);
                        goto out_unlock;
                  }
                  dbg_tnc("removing %s", DBGKEY(key));
            }
            if (k) {
                  for (i = n + 1 + k; i < znode->child_cnt; i++)
                        znode->zbranch[i - k] = znode->zbranch[i];
                  znode->child_cnt -= k;
            }

            /* Now delete the first */
            err = tnc_delete(c, znode, n);
            if (err)
                  goto out_unlock;
      }

out_unlock:
      if (!err)
            err = dbg_check_tnc(c, 0);
      mutex_unlock(&c->tnc_mutex);
      return err;
}

/**
 * ubifs_tnc_remove_ino - remove an inode from TNC.
 * @c: UBIFS file-system description object
 * @inum: inode number to remove
 *
 * This function remove inode @inum and all the extended attributes associated
 * with the anode from TNC and returns zero in case of success or a negative
 * error code in case of failure.
 */
int ubifs_tnc_remove_ino(struct ubifs_info *c, ino_t inum)
{
      union ubifs_key key1, key2;
      struct ubifs_dent_node *xent, *pxent = NULL;
      struct qstr nm = { .name = NULL };

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

      /*
       * Walk all extended attribute entries and remove them together with
       * corresponding extended attribute inodes.
       */
      lowest_xent_key(c, &key1, inum);
      while (1) {
            ino_t xattr_inum;
            int err;

            xent = ubifs_tnc_next_ent(c, &key1, &nm);
            if (IS_ERR(xent)) {
                  err = PTR_ERR(xent);
                  if (err == -ENOENT)
                        break;
                  return err;
            }

            xattr_inum = le64_to_cpu(xent->inum);
            dbg_tnc("xent '%s', ino %lu", xent->name,
                  (unsigned long)xattr_inum);

            nm.name = (char *)xent->name;
            nm.len = le16_to_cpu(xent->nlen);
            err = ubifs_tnc_remove_nm(c, &key1, &nm);
            if (err) {
                  kfree(xent);
                  return err;
            }

            lowest_ino_key(c, &key1, xattr_inum);
            highest_ino_key(c, &key2, xattr_inum);
            err = ubifs_tnc_remove_range(c, &key1, &key2);
            if (err) {
                  kfree(xent);
                  return err;
            }

            kfree(pxent);
            pxent = xent;
            key_read(c, &xent->key, &key1);
      }

      kfree(pxent);
      lowest_ino_key(c, &key1, inum);
      highest_ino_key(c, &key2, inum);

      return ubifs_tnc_remove_range(c, &key1, &key2);
}

/**
 * ubifs_tnc_next_ent - walk directory or extended attribute entries.
 * @c: UBIFS file-system description object
 * @key: key of last entry
 * @nm: name of last entry found or %NULL
 *
 * This function finds and reads the next directory or extended attribute entry
 * after the given key (@key) if there is one. @nm is used to resolve
 * collisions.
 *
 * If the name of the current entry is not known and only the key is known,
 * @nm->name has to be %NULL. In this case the semantics of this function is a
 * little bit different and it returns the entry corresponding to this key, not
 * the next one. If the key was not found, the closest "right" entry is
 * returned.
 *
 * If the fist entry has to be found, @key has to contain the lowest possible
 * key value for this inode and @name has to be %NULL.
 *
 * This function returns the found directory or extended attribute entry node
 * in case of success, %-ENOENT is returned if no entry was found, and a
 * negative error code is returned in case of failure.
 */
struct ubifs_dent_node *ubifs_tnc_next_ent(struct ubifs_info *c,
                                 union ubifs_key *key,
                                 const struct qstr *nm)
{
      int n, err, type = key_type(c, key);
      struct ubifs_znode *znode;
      struct ubifs_dent_node *dent;
      struct ubifs_zbranch *zbr;
      union ubifs_key *dkey;

      dbg_tnc("%s %s", nm->name ? (char *)nm->name : "(lowest)", DBGKEY(key));
      ubifs_assert(is_hash_key(c, key));

      mutex_lock(&c->tnc_mutex);
      err = ubifs_lookup_level0(c, key, &znode, &n);
      if (unlikely(err < 0))
            goto out_unlock;

      if (nm->name) {
            if (err) {
                  /* Handle collisions */
                  err = resolve_collision(c, key, &znode, &n, nm);
                  dbg_tnc("rc returned %d, znode %p, n %d",
                        err, znode, n);
                  if (unlikely(err < 0))
                        goto out_unlock;
            }

            /* Now find next entry */
            err = tnc_next(c, &znode, &n);
            if (unlikely(err))
                  goto out_unlock;
      } else {
            /*
             * The full name of the entry was not given, in which case the
             * behavior of this function is a little different and it
             * returns current entry, not the next one.
             */
            if (!err) {
                  /*
                   * However, the given key does not exist in the TNC
                   * tree and @znode/@n variables contain the closest
                   * "preceding" element. Switch to the next one.
                   */
                  err = tnc_next(c, &znode, &n);
                  if (err)
                        goto out_unlock;
            }
      }

      zbr = &znode->zbranch[n];
      dent = kmalloc(zbr->len, GFP_NOFS);
      if (unlikely(!dent)) {
            err = -ENOMEM;
            goto out_unlock;
      }

      /*
       * The above 'tnc_next()' call could lead us to the next inode, check
       * this.
       */
      dkey = &zbr->key;
      if (key_inum(c, dkey) != key_inum(c, key) ||
          key_type(c, dkey) != type) {
            err = -ENOENT;
            goto out_free;
      }

      err = tnc_read_node_nm(c, zbr, dent);
      if (unlikely(err))
            goto out_free;

      mutex_unlock(&c->tnc_mutex);
      return dent;

out_free:
      kfree(dent);
out_unlock:
      mutex_unlock(&c->tnc_mutex);
      return ERR_PTR(err);
}

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