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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * This file is part of UBIFS.
  *
  * Copyright (C) 2006-2008 Nokia Corporation.
  *
  * 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 <linux/slab.h>
 #include "ubifs.h"
 
 static int try_read_node(const struct ubifs_info *c, void *buf, int type,
              struct ubifs_zbranch *zbr);
 static int fallible_read_node(struct ubifs_info *c, const union ubifs_key *key,
                   struct ubifs_zbranch *zbr, void *node);
 
 /*
  * 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(c, "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 ubifs_old_idx *old_idx, *n;
 
     rbtree_postorder_for_each_entry_safe(old_idx, n, &c->old_idx, rb)
         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 = kmemdup(znode, c->max_znode_sz, GFP_NOFS);
     if (unlikely(!zn))
         return ERR_PTR(-ENOMEM);
 
     zn->cnext = NULL;
     __set_bit(DIRTY_ZNODE, &zn->flags);
     __clear_bit(COW_ZNODE, &zn->flags);
 
     ubifs_assert(c, !ubifs_zn_obsolete(znode));
     __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 (!ubifs_zn_cow(znode)) {
         /* 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(c, !zbr->leaf);
     ubifs_assert(c, zbr->len != 0);
     ubifs_assert(c, is_hash_key(c, &zbr->key));
 
     err = ubifs_validate_entry(c, dent);
     if (err) {
         dump_stack();
         ubifs_dump_node(c, dent, zbr->len);
         return err;
     }
 
     lnc_node = kmemdup(node, zbr->len, GFP_NOFS);
     if (!lnc_node)
         /* We don't have to have the cache, so no error */
         return 0;
 
     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(c, !zbr->leaf);
     ubifs_assert(c, zbr->len != 0);
 
     err = ubifs_validate_entry(c, node);
     if (err) {
         dump_stack();
         ubifs_dump_node(c, node, zbr->len);
         return err;
     }
 
     zbr->leaf = node;
     return 0;
 }
 
 /**
  * lnc_free - remove a leaf node from the leaf node cache.
  * @zbr: zbranch of leaf node
  */
 static void lnc_free(struct ubifs_zbranch *zbr)
 {
     if (!zbr->leaf)
         return;
     kfree(zbr->leaf);
     zbr->leaf = NULL;
 }
 
 /**
  * tnc_read_hashed_node - 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 error
  * code in case of failure.
  */
 static int tnc_read_hashed_node(struct ubifs_info *c, struct ubifs_zbranch *zbr,
                 void *node)
 {
     int err;
 
     ubifs_assert(c, is_hash_key(c, &zbr->key));
 
     if (zbr->leaf) {
         /* Read from the leaf node cache */
         ubifs_assert(c, zbr->len != 0);
         memcpy(node, zbr->leaf, zbr->len);
         return 0;
     }
 
     if (c->replaying) {
         err = fallible_read_node(c, &zbr->key, zbr, node);
         /*
          * When the node was not found, return -ENOENT, 0 otherwise.
          * Negative return codes stay as-is.
          */
         if (err == 0)
             err = -ENOENT;
         else if (err == 1)
             err = 0;
     } else {
         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
  * @zbr: the zbranch describing the 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->mounting or @c->remounting_rw is true (we are mounting or re-mounting to
  * R/W mode), @c->no_chk_data_crc is ignored and CRC is checked. This is
  * because during mounting or re-mounting from R/O mode to R/W mode we may read
  * journal nodes (when replying the journal or doing the recovery) and the
  * journal nodes may potentially be corrupted, so checking is required.
  */
 static int try_read_node(const struct ubifs_info *c, void *buf, int type,
              struct ubifs_zbranch *zbr)
 {
     int len = zbr->len;
     int lnum = zbr->lnum;
     int offs = zbr->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 = ubifs_leb_read(c, lnum, buf, offs, len, 1);
     if (err) {
         ubifs_err(c, "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->no_chk_data_crc || c->mounting ||
         c->remounting_rw) {
         crc = crc32(UBIFS_CRC32_INIT, buf + 8, node_len - 8);
         node_crc = le32_to_cpu(ch->crc);
         if (crc != node_crc)
             return 0;
     }
 
     err = ubifs_node_check_hash(c, buf, zbr->hash);
     if (err) {
         ubifs_bad_hash(c, buf, zbr->hash, lnum, offs);
         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_tnck(key, "LEB %d:%d, key ", zbr->lnum, zbr->offs);
 
     ret = try_read_node(c, node, key_type(c, key), zbr);
     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_mntk(key, "dangling branch LEB %d:%d len %d, key ",
             zbr->lnum, zbr->offs, zbr->len);
     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 fscrypt_name *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, fname_name(nm), min_t(int, nlen, fname_len(nm)));
     if (err == 0) {
         if (nlen == fname_len(nm))
             return NAME_MATCHES;
         else if (nlen < fname_len(nm))
             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 fscrypt_name *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(c, *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(c, 0);
                         if (err == -ENOENT)
                             err = -EINVAL;
                         return err;
                     }
                     ubifs_assert(c, *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(c, 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(c, 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 fscrypt_name *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(c, 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, fname_name(nm), min_t(int, nlen, fname_len(nm)));
     if (err == 0) {
         if (nlen == fname_len(nm))
             return NAME_MATCHES;
         else if (nlen < fname_len(nm))
             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 fscrypt_name *nm,
                       int adding)
 {
     struct ubifs_znode *o_znode = NULL, *znode = *zn;
     int 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(c, *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(c, 0);
                         if (err == -ENOENT)
                             err = -EINVAL;
                         return err;
                     }
                     ubifs_assert(c, *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_mntk(key, "dangling match LEB %d:%d len %d key ",
         o_znode->zbranch[o_n].lnum, o_znode->zbranch[o_n].offs,
         o_znode->zbranch[o_n].len);
     *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, c->zroot.znode);
     ubifs_assert(c, znode);
     if (c->zroot.znode->level > BOTTOM_UP_HEIGHT) {
         kfree(c->bottom_up_buf);
         c->bottom_up_buf = kmalloc_array(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(c, 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(c, path[p - 1] >= 0);
             ubifs_assert(c, path[p - 1] < zp->child_cnt);
             zbr = &zp->zbranch[path[--p]];
             znode = dirty_cow_znode(c, zbr);
         } else {
             ubifs_assert(c, znode == c->zroot.znode);
             znode = dirty_cow_znode(c, &c->zroot);
         }
         if (IS_ERR(znode) || !p)
             break;
         ubifs_assert(c, path[p - 1] >= 0);
         ubifs_assert(c, 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 closest branch or %-1
  *     is stored in @n; In this case calling tnc_next() is mandatory.
  *   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;
     time64_t time = ktime_get_seconds();
 
     dbg_tnck(key, "search key ");
     ubifs_assert(c, key_type(c, key) < UBIFS_INVALID_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 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;
     time64_t time = ktime_get_seconds();
 
     dbg_tnck(key, "search and dirty 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)
 {
     int gc_seq2, gced_lnum;
 
     gced_lnum = c->gced_lnum;
     smp_rmb();
     gc_seq2 = c->gc_seq;
     /* Same seq means no GC */
     if (gc_seq1 == gc_seq2)
         return 0;
     /* Different by more than 1 means we don't know */
     if (gc_seq1 + 1 != gc_seq2)
         return 1;
     /*
      * We have seen the sequence number has increased by 1. Now we need to
      * be sure we read the right LEB number, so read it again.
      */
     smp_rmb();
     if (gced_lnum != c->gced_lnum)
         return 1;
     /* Finally we can check lnum */
     if (gced_lnum == lnum)
         return 1;
     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 looks 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_hashed_node(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);
 
     if (ubifs_get_wbuf(c, zbr.lnum)) {
         /* We do not GC journal heads */
         err = ubifs_tnc_read_node(c, &zbr, node);
         return err;
     }
 
     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, offs;
     int 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;
 }
 
 /**
  * read_wbuf - bulk-read from a LEB with a wbuf.
  * @wbuf: wbuf that may overlap the read
  * @buf: buffer into which to read
  * @len: read length
  * @lnum: LEB number from which to read
  * @offs: offset from which to read
  *
  * This functions returns %0 on success or a negative error code on failure.
  */
 static int read_wbuf(struct ubifs_wbuf *wbuf, void *buf, int len, int lnum,
              int offs)
 {
     const struct ubifs_info *c = wbuf->c;
     int rlen, overlap;
 
     dbg_io("LEB %d:%d, length %d", lnum, offs, len);
     ubifs_assert(c, wbuf && lnum >= 0 && lnum < c->leb_cnt && offs >= 0);
     ubifs_assert(c, !(offs & 7) && offs < c->leb_size);
     ubifs_assert(c, offs + len <= c->leb_size);
 
     spin_lock(&wbuf->lock);
     overlap = (lnum == wbuf->lnum && offs + len > wbuf->offs);
     if (!overlap) {
         /* We may safely unlock the write-buffer and read the data */
         spin_unlock(&wbuf->lock);
         return ubifs_leb_read(c, lnum, buf, offs, len, 0);
     }
 
     /* Don't read under wbuf */
     rlen = wbuf->offs - offs;
     if (rlen < 0)
         rlen = 0;
 
     /* Copy the rest from the write-buffer */
     memcpy(buf + rlen, wbuf->buf + offs + rlen - wbuf->offs, len - rlen);
     spin_unlock(&wbuf->lock);
 
     if (rlen > 0)
         /* Read everything that goes before write-buffer */
         return ubifs_leb_read(c, lnum, buf, offs, rlen, 0);
 
     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(c, "bad node type (%d but expected %d)",
               ch->node_type, UBIFS_DATA_NODE);
         goto out_err;
     }
 
     err = ubifs_check_node(c, buf, zbr->len, zbr->lnum, zbr->offs, 0, 0);
     if (err) {
         ubifs_err(c, "expected node type %d", UBIFS_DATA_NODE);
         goto out;
     }
 
     err = ubifs_node_check_hash(c, buf, zbr->hash);
     if (err) {
         ubifs_bad_hash(c, buf, zbr->hash, zbr->lnum, zbr->offs);
         return err;
     }
 
     len = le32_to_cpu(ch->len);
     if (len != zbr->len) {
         ubifs_err(c, "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(c, "bad key in node at LEB %d:%d",
               zbr->lnum, zbr->offs);
         dbg_tnck(&zbr->key, "looked for key ");
         dbg_tnck(&key1, "found node's key ");
         goto out_err;
     }
 
     return 0;
 
 out_err:
     err = -EINVAL;
 out:
     ubifs_err(c, "bad node at LEB %d:%d", zbr->lnum, zbr->offs);
     ubifs_dump_node(c, buf, zbr->len);
     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;
     struct ubifs_wbuf *wbuf;
     void *buf;
 
     len = bu->zbranch[bu->cnt - 1].offs;
     len += bu->zbranch[bu->cnt - 1].len - offs;
     if (len > bu->buf_len) {
         ubifs_err(c, "buffer too small %d vs %d", bu->buf_len, len);
         return -EINVAL;
     }
 
     /* Do the read */
     wbuf = ubifs_get_wbuf(c, lnum);
     if (wbuf)
         err = read_wbuf(wbuf, bu->buf, len, lnum, offs);
     else
         err = ubifs_leb_read(c, lnum, bu->buf, offs, len, 0);
 
     /* Check for a race with GC */
     if (maybe_leb_gced(c, lnum, bu->gc_seq))
         return -EAGAIN;
 
     if (err && err != -EBADMSG) {
         ubifs_err(c, "failed to read from LEB %d:%d, error %d",
               lnum, offs, err);
         dump_stack();
         dbg_tnck(&bu->key, "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 looks 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 fscrypt_name *nm)
 {
     int found, n, err;
     struct ubifs_znode *znode;
 
     dbg_tnck(key, "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(c, 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_hashed_node(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 looks 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 fscrypt_name *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 (fname_len(nm) == len && !memcmp(dent->name, fname_name(nm), 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);
 }
 
 static int search_dh_cookie(struct ubifs_info *c, const union ubifs_key *key,
                 struct ubifs_dent_node *dent, uint32_t cookie,
                 struct ubifs_znode **zn, int *n, int exact)
 {
     int err;
     struct ubifs_znode *znode = *zn;
     struct ubifs_zbranch *zbr;
     union ubifs_key *dkey;
 
     if (!exact) {
         err = tnc_next(c, &znode, n);
         if (err)
             return err;
     }
 
     for (;;) {
         zbr = &znode->zbranch[*n];
         dkey = &zbr->key;
 
         if (key_inum(c, dkey) != key_inum(c, key) ||
             key_type(c, dkey) != key_type(c, key)) {
             return -ENOENT;
         }
 
         err = tnc_read_hashed_node(c, zbr, dent);
         if (err)
             return err;
 
         if (key_hash(c, key) == key_hash(c, dkey) &&
             le32_to_cpu(dent->cookie) == cookie) {
             *zn = znode;
             return 0;
         }
 
         err = tnc_next(c, &znode, n);
         if (err)
             return err;
     }
 }
 
 static int do_lookup_dh(struct ubifs_info *c, const union ubifs_key *key,
             struct ubifs_dent_node *dent, uint32_t cookie)
 {
     int n, err;
     struct ubifs_znode *znode;
     union ubifs_key start_key;
 
     ubifs_assert(c, is_hash_key(c, key));
 
     lowest_dent_key(c, &start_key, key_inum(c, key));
 
     mutex_lock(&c->tnc_mutex);
     err = ubifs_lookup_level0(c, &start_key, &znode, &n);
     if (unlikely(err < 0))
         goto out_unlock;
 
     err = search_dh_cookie(c, key, dent, cookie, &znode, &n, err);
 
 out_unlock:
     mutex_unlock(&c->tnc_mutex);
     return err;
 }
 
 /**
  * ubifs_tnc_lookup_dh - look up a "double hashed" node.
  * @c: UBIFS file-system description object
  * @key: node key to lookup
  * @node: the node is returned here
  * @cookie: node cookie for collision resolution
  *
  * This function looks 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
  * with the same cookie value 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_dh(struct ubifs_info *c, const union ubifs_key *key,
             void *node, uint32_t cookie)
 {
     int err;
     const struct ubifs_dent_node *dent = node;
 
     if (!c->double_hash)
         return -EOPNOTSUPP;
 
     /*
      * 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;
 
     if (le32_to_cpu(dent->cookie) == cookie)
         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_dh(c, key, node, cookie);
 }
 
 /**
  * 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(c, znode->parent);
     ubifs_assert(c, 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.
  * @c: UBIFS file-system description object
  * @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_info *c, struct ubifs_znode *znode,
                const struct ubifs_zbranch *zbr, int n)
 {
     int i;
 
     ubifs_assert(c, 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(c, n >= 0 && n <= c->fanout);
 
     /* Implement naive insert for now */
 again:
     zp = znode->parent;
     if (znode->child_cnt < c->fanout) {
         ubifs_assert(c, n != c->fanout);
         dbg_tnck(key, "inserted at %d level %d, key ", n, znode->level);
 
         insert_zbranch(c, 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_tnck(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 && 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_tnck(key, "inserting at %d level %d, key ", n, zn->level);
 
     insert_zbranch(c, 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
  * @hash: The hash over the node
  *
  * 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, const u8 *hash)
 {
     int found, n, err = 0;
     struct ubifs_znode *znode;
 
     mutex_lock(&c->tnc_mutex);
     dbg_tnck(key, "%d:%d, len %d, key ", lnum, offs, len);
     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;
         ubifs_copy_hash(c, hash, zbr.hash);
         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;
         ubifs_copy_hash(c, hash, zbr->hash);
     } 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_tnck(key, "old LEB %d:%d, new LEB %d:%d, len %d, key ", old_lnum,
          old_offs, lnum, offs, len);
     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
  * @hash: The hash over the node
  * @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 u8 *hash,
              const struct fscrypt_name *nm)
 {
     int found, n, err = 0;
     struct ubifs_znode *znode;
 
     mutex_lock(&c->tnc_mutex);
     dbg_tnck(key, "LEB %d:%d, key ", lnum, offs);
     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;
             ubifs_copy_hash(c, hash, zbr->hash);
             goto out_unlock;
         }
     }
 
     if (!found) {
         struct ubifs_zbranch zbr;
 
         zbr.znode = NULL;
         zbr.lnum = lnum;
         zbr.offs = offs;
         zbr.len = len;
         ubifs_copy_hash(c, hash, zbr.hash);
         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 fscrypt_name noname = { .disk_name = { .name = "", .len = 1 } };
 
             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(c, znode->level == 0);
     ubifs_assert(c, n >= 0 && n < c->fanout);
     dbg_tnck(&znode->zbranch[n].key, "deleting key ");
 
     zbr = &znode->zbranch[n];
     lnc_free(zbr);
 
     err = ubifs_add_dirt(c, zbr->lnum, zbr->len);
     if (err) {
         ubifs_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(c, !ubifs_zn_obsolete(znode));
         ubifs_assert(c, 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(c, 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(c, !ubifs_zn_obsolete(zp));
             ubifs_assert(c, ubifs_zn_dirty(zp));
             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_tnck(key, "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 fscrypt_name *nm)
 {
     int n, err;
     struct ubifs_znode *znode;
 
     mutex_lock(&c->tnc_mutex);
     dbg_tnck(key, "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;
 }
 
 /**
  * ubifs_tnc_remove_dh - remove an index entry for a "double hashed" node.
  * @c: UBIFS file-system description object
  * @key: key of node
  * @cookie: node cookie for collision resolution
  *
  * Returns %0 on success or negative error code on failure.
  */
 int ubifs_tnc_remove_dh(struct ubifs_info *c, const union ubifs_key *key,
             uint32_t cookie)
 {
     int n, err;
     struct ubifs_znode *znode;
     struct ubifs_dent_node *dent;
     struct ubifs_zbranch *zbr;
 
     if (!c->double_hash)
         return -EOPNOTSUPP;
 
     mutex_lock(&c->tnc_mutex);
     err = lookup_level0_dirty(c, key, &znode, &n);
     if (err <= 0)
         goto out_unlock;
 
     zbr = &znode->zbranch[n];
     dent = kmalloc(UBIFS_MAX_DENT_NODE_SZ, GFP_NOFS);
     if (!dent) {
         err = -ENOMEM;
         goto out_unlock;
     }
 
     err = tnc_read_hashed_node(c, zbr, dent);
     if (err)
         goto out_free;
 
     /* If the cookie does not match, we're facing a hash collision. */
     if (le32_to_cpu(dent->cookie) != cookie) {
         union ubifs_key start_key;
 
         lowest_dent_key(c, &start_key, key_inum(c, key));
 
         err = ubifs_lookup_level0(c, &start_key, &znode, &n);
         if (unlikely(err < 0))
             goto out_free;
 
         err = search_dh_cookie(c, key, dent, cookie, &znode, &n, err);
         if (err)
             goto out_free;
     }
 
     if (znode->cnext || !ubifs_zn_dirty(znode)) {
         znode = dirty_cow_bottom_up(c, znode);
         if (IS_ERR(znode)) {
             err = PTR_ERR(znode);
             goto out_free;
         }
     }
     err = tnc_delete(c, znode, n);
 
 out_free:
     kfree(dent);
 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) {
                 ubifs_dump_znode(c, znode);
                 goto out_unlock;
             }
             dbg_tnck(key, "removing 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 fscrypt_name nm = {0};
 
     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;
             kfree(pxent);
             return err;
         }
 
         xattr_inum = le64_to_cpu(xent->inum);
         dbg_tnc("xent '%s', ino %lu", xent->name,
             (unsigned long)xattr_inum);
 
         ubifs_evict_xattr_inode(c, xattr_inum);
 
         fname_name(&nm) = xent->name;
         fname_len(&nm) = le16_to_cpu(xent->nlen);
         err = ubifs_tnc_remove_nm(c, &key1, &nm);
         if (err) {
             kfree(pxent);
             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(pxent);
             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 fscrypt_name *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_tnck(key, "key ");
     ubifs_assert(c, 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 (fname_len(nm) > 0) {
         if (err) {
             /* Handle collisions */
             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 (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_hashed_node(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);
 }
 
 /**
  * tnc_destroy_cnext - destroy left-over obsolete znodes from a failed commit.
  * @c: UBIFS file-system description object
  *
  * Destroy left-over obsolete znodes from a failed commit.
  */
 static void tnc_destroy_cnext(struct ubifs_info *c)
 {
     struct ubifs_znode *cnext;
 
     if (!c->cnext)
         return;
     ubifs_assert(c, c->cmt_state == COMMIT_BROKEN);
     cnext = c->cnext;
     do {
         struct ubifs_znode *znode = cnext;
 
         cnext = cnext->cnext;
         if (ubifs_zn_obsolete(znode))
             kfree(znode);
     } while (cnext && cnext != c->cnext);
 }
 
 /**
  * ubifs_tnc_close - close TNC subsystem and free all related resources.
  * @c: UBIFS file-system description object
  */
 void ubifs_tnc_close(struct ubifs_info *c)
 {
     tnc_destroy_cnext(c);
     if (c->zroot.znode) {
         long n, freed;
 
         n = atomic_long_read(&c->clean_zn_cnt);
         freed = ubifs_destroy_tnc_subtree(c, c->zroot.znode);
         ubifs_assert(c, freed == n);
         atomic_long_sub(n, &ubifs_clean_zn_cnt);
     }
     kfree(c->gap_lebs);
     kfree(c->ilebs);
     destroy_old_idx(c);
 }
 
 /**
  * left_znode - get the znode to the left.
  * @c: UBIFS file-system description object
  * @znode: znode
  *
  * This function returns a pointer to the znode to the left of @znode or NULL if
  * there is not one. A negative error code is returned on failure.
  */
 static struct ubifs_znode *left_znode(struct ubifs_info *c,
                       struct ubifs_znode *znode)
 {
     int level = znode->level;
 
     while (1) {
         int n = znode->iip - 1;
 
         /* Go up until we can go left */
         znode = znode->parent;
         if (!znode)
             return NULL;
         if (n >= 0) {
             /* Now go down the rightmost branch to 'level' */
             znode = get_znode(c, znode, n);
             if (IS_ERR(znode))
                 return znode;
             while (znode->level != level) {
                 n = znode->child_cnt - 1;
                 znode = get_znode(c, znode, n);
                 if (IS_ERR(znode))
                     return znode;
             }
             break;
         }
     }
     return znode;
 }
 
 /**
  * right_znode - get the znode to the right.
  * @c: UBIFS file-system description object
  * @znode: znode
  *
  * This function returns a pointer to the znode to the right of @znode or NULL
  * if there is not one. A negative error code is returned on failure.
  */
 static struct ubifs_znode *right_znode(struct ubifs_info *c,
                        struct ubifs_znode *znode)
 {
     int level = znode->level;
 
     while (1) {
         int n = znode->iip + 1;
 
         /* Go up until we can go right */
         znode = znode->parent;
         if (!znode)
             return NULL;
         if (n < znode->child_cnt) {
             /* Now go down the leftmost branch to 'level' */
             znode = get_znode(c, znode, n);
             if (IS_ERR(znode))
                 return znode;
             while (znode->level != level) {
                 znode = get_znode(c, znode, 0);
                 if (IS_ERR(znode))
                     return znode;
             }
             break;
         }
     }
     return znode;
 }
 
 /**
  * lookup_znode - find a particular indexing node from TNC.
  * @c: UBIFS file-system description object
  * @key: index node key to lookup
  * @level: index node level
  * @lnum: index node LEB number
  * @offs: index node offset
  *
  * This function searches an indexing node by its first key @key and its
  * address @lnum:@offs. It looks up the indexing tree by pulling all indexing
  * nodes it traverses to TNC. This function is called for indexing nodes which
  * were found on the media by scanning, for example when garbage-collecting or
  * when doing in-the-gaps commit. This means that the indexing node which is
  * looked for does not have to have exactly the same leftmost key @key, because
  * the leftmost key may have been changed, in which case TNC will contain a
  * dirty znode which still refers the same @lnum:@offs. This function is clever
  * enough to recognize such indexing nodes.
  *
  * Note, if a znode was deleted or changed too much, then this function will
  * not find it. For situations like this UBIFS has the old index RB-tree
  * (indexed by @lnum:@offs).
  *
  * This function returns a pointer to the znode found or %NULL if it is not
  * found. A negative error code is returned on failure.
  */
 static struct ubifs_znode *lookup_znode(struct ubifs_info *c,
                     union ubifs_key *key, int level,
                     int lnum, int offs)
 {
     struct ubifs_znode *znode, *zn;
     int n, nn;
 
     ubifs_assert(c, key_type(c, key) < UBIFS_INVALID_KEY);
 
     /*
      * The arguments have probably been read off flash, so don't assume
      * they are valid.
      */
     if (level < 0)
         return ERR_PTR(-EINVAL);
 
     /* Get the root znode */
     znode = c->zroot.znode;
     if (!znode) {
         znode = ubifs_load_znode(c, &c->zroot, NULL, 0);
         if (IS_ERR(znode))
             return znode;
     }
     /* Check if it is the one we are looking for */
     if (c->zroot.lnum == lnum && c->zroot.offs == offs)
         return znode;
     /* Descend to the parent level i.e. (level + 1) */
     if (level >= znode->level)
         return NULL;
     while (1) {
         ubifs_search_zbranch(c, znode, key, &n);
         if (n < 0) {
             /*
              * We reached a znode where the leftmost key is greater
              * than the key we are searching for. This is the same
              * situation as the one described in a huge comment at
              * the end of the 'ubifs_lookup_level0()' function. And
              * for exactly the same reasons we have to try to look
              * left before giving up.
              */
             znode = left_znode(c, znode);
             if (!znode)
                 return NULL;
             if (IS_ERR(znode))
                 return znode;
             ubifs_search_zbranch(c, znode, key, &n);
             ubifs_assert(c, n >= 0);
         }
         if (znode->level == level + 1)
             break;
         znode = get_znode(c, znode, n);
         if (IS_ERR(znode))
             return znode;
     }
     /* Check if the child is the one we are looking for */
     if (znode->zbranch[n].lnum == lnum && znode->zbranch[n].offs == offs)
         return get_znode(c, znode, n);
     /* If the key is unique, there is nowhere else to look */
     if (!is_hash_key(c, key))
         return NULL;
     /*
      * The key is not unique and so may be also in the znodes to either
      * side.
      */
     zn = znode;
     nn = n;
     /* Look left */
     while (1) {
         /* Move one branch to the left */
         if (n)
             n -= 1;
         else {
             znode = left_znode(c, znode);
             if (!znode)
                 break;
             if (IS_ERR(znode))
                 return znode;
             n = znode->child_cnt - 1;
         }
         /* Check it */
         if (znode->zbranch[n].lnum == lnum &&
             znode->zbranch[n].offs == offs)
             return get_znode(c, znode, n);
         /* Stop if the key is less than the one we are looking for */
         if (keys_cmp(c, &znode->zbranch[n].key, key) < 0)
             break;
     }
     /* Back to the middle */
     znode = zn;
     n = nn;
     /* Look right */
     while (1) {
         /* Move one branch to the right */
         if (++n >= znode->child_cnt) {
             znode = right_znode(c, znode);
             if (!znode)
                 break;
             if (IS_ERR(znode))
                 return znode;
             n = 0;
         }
         /* Check it */
         if (znode->zbranch[n].lnum == lnum &&
             znode->zbranch[n].offs == offs)
             return get_znode(c, znode, n);
         /* Stop if the key is greater than the one we are looking for */
         if (keys_cmp(c, &znode->zbranch[n].key, key) > 0)
             break;
     }
     return NULL;
 }
 
 /**
  * is_idx_node_in_tnc - determine if an index node is in the TNC.
  * @c: UBIFS file-system description object
  * @key: key of index node
  * @level: index node level
  * @lnum: LEB number of index node
  * @offs: offset of index node
  *
  * This function returns %0 if the index node is not referred to in the TNC, %1
  * if the index node is referred to in the TNC and the corresponding znode is
  * dirty, %2 if an index node is referred to in the TNC and the corresponding
  * znode is clean, and a negative error code in case of failure.
  *
  * Note, the @key argument has to be the key of the first child. Also note,
  * this function relies on the fact that 0:0 is never a valid LEB number and
  * offset for a main-area node.
  */
 int is_idx_node_in_tnc(struct ubifs_info *c, union ubifs_key *key, int level,
                int lnum, int offs)
 {
     struct ubifs_znode *znode;
 
     znode = lookup_znode(c, key, level, lnum, offs);
     if (!znode)
         return 0;
     if (IS_ERR(znode))
         return PTR_ERR(znode);
 
     return ubifs_zn_dirty(znode) ? 1 : 2;
 }
 
 /**
  * is_leaf_node_in_tnc - determine if a non-indexing not is in the TNC.
  * @c: UBIFS file-system description object
  * @key: node key
  * @lnum: node LEB number
  * @offs: node offset
  *
  * This function returns %1 if the node is referred to in the TNC, %0 if it is
  * not, and a negative error code in case of failure.
  *
  * Note, this function relies on the fact that 0:0 is never a valid LEB number
  * and offset for a main-area node.
  */
 static int is_leaf_node_in_tnc(struct ubifs_info *c, union ubifs_key *key,
                    int lnum, int offs)
 {
     struct ubifs_zbranch *zbr;
     struct ubifs_znode *znode, *zn;
     int n, found, err, nn;
     const int unique = !is_hash_key(c, key);
 
     found = ubifs_lookup_level0(c, key, &znode, &n);
     if (found < 0)
         return found; /* Error code */
     if (!found)
         return 0;
     zbr = &znode->zbranch[n];
     if (lnum == zbr->lnum && offs == zbr->offs)
         return 1; /* Found it */
     if (unique)
         return 0;
     /*
      * Because the key is not unique, we have to look left
      * and right as well
      */
     zn = znode;
     nn = n;
     /* Look left */
     while (1) {
         err = tnc_prev(c, &znode, &n);
         if (err == -ENOENT)
             break;
         if (err)
             return err;
         if (keys_cmp(c, key, &znode->zbranch[n].key))
             break;
         zbr = &znode->zbranch[n];
         if (lnum == zbr->lnum && offs == zbr->offs)
             return 1; /* Found it */
     }
     /* Look right */
     znode = zn;
     n = nn;
     while (1) {
         err = tnc_next(c, &znode, &n);
         if (err) {
             if (err == -ENOENT)
                 return 0;
             return err;
         }
         if (keys_cmp(c, key, &znode->zbranch[n].key))
             break;
         zbr = &znode->zbranch[n];
         if (lnum == zbr->lnum && offs == zbr->offs)
             return 1; /* Found it */
     }
     return 0;
 }
 
 /**
  * ubifs_tnc_has_node - determine whether a node is in the TNC.
  * @c: UBIFS file-system description object
  * @key: node key
  * @level: index node level (if it is an index node)
  * @lnum: node LEB number
  * @offs: node offset
  * @is_idx: non-zero if the node is an index node
  *
  * This function returns %1 if the node is in the TNC, %0 if it is not, and a
  * negative error code in case of failure. For index nodes, @key has to be the
  * key of the first child. An index node is considered to be in the TNC only if
  * the corresponding znode is clean or has not been loaded.
  */
 int ubifs_tnc_has_node(struct ubifs_info *c, union ubifs_key *key, int level,
                int lnum, int offs, int is_idx)
 {
     int err;
 
     mutex_lock(&c->tnc_mutex);
     if (is_idx) {
         err = is_idx_node_in_tnc(c, key, level, lnum, offs);
         if (err < 0)
             goto out_unlock;
         if (err == 1)
             /* The index node was found but it was dirty */
             err = 0;
         else if (err == 2)
             /* The index node was found and it was clean */
             err = 1;
         else
             BUG_ON(err != 0);
     } else
         err = is_leaf_node_in_tnc(c, key, lnum, offs);
 
 out_unlock:
     mutex_unlock(&c->tnc_mutex);
     return err;
 }
 
 /**
  * ubifs_dirty_idx_node - dirty an index node.
  * @c: UBIFS file-system description object
  * @key: index node key
  * @level: index node level
  * @lnum: index node LEB number
  * @offs: index node offset
  *
  * This function loads and dirties an index node so that it can be garbage
  * collected. The @key argument has to be the key of the first child. This
  * function relies on the fact that 0:0 is never a valid LEB number and offset
  * for a main-area node. Returns %0 on success and a negative error code on
  * failure.
  */
 int ubifs_dirty_idx_node(struct ubifs_info *c, union ubifs_key *key, int level,
              int lnum, int offs)
 {
     struct ubifs_znode *znode;
     int err = 0;
 
     mutex_lock(&c->tnc_mutex);
     znode = lookup_znode(c, key, level, lnum, offs);
     if (!znode)
         goto out_unlock;
     if (IS_ERR(znode)) {
         err = PTR_ERR(znode);
         goto out_unlock;
     }
     znode = dirty_cow_bottom_up(c, znode);
     if (IS_ERR(znode)) {
         err = PTR_ERR(znode);
         goto out_unlock;
     }
 
 out_unlock:
     mutex_unlock(&c->tnc_mutex);
     return err;
 }
 
 /**
  * dbg_check_inode_size - check if inode size is correct.
  * @c: UBIFS file-system description object
  * @inode: inode to check
  * @size: inode size
  *
  * This function makes sure that the inode size (@size) is correct and it does
  * not have any pages beyond @size. Returns zero if the inode is OK, %-EINVAL
  * if it has a data page beyond @size, and other negative error code in case of
  * other errors.
  */
 int dbg_check_inode_size(struct ubifs_info *c, const struct inode *inode,
              loff_t size)
 {
     int err, n;
     union ubifs_key from_key, to_key, *key;
     struct ubifs_znode *znode;
     unsigned int block;
 
     if (!S_ISREG(inode->i_mode))
         return 0;
     if (!dbg_is_chk_gen(c))
         return 0;
 
     block = (size + UBIFS_BLOCK_SIZE - 1) >> UBIFS_BLOCK_SHIFT;
     data_key_init(c, &from_key, inode->i_ino, block);
     highest_data_key(c, &to_key, inode->i_ino);
 
     mutex_lock(&c->tnc_mutex);
     err = ubifs_lookup_level0(c, &from_key, &znode, &n);
     if (err < 0)
         goto out_unlock;
 
     if (err) {
         key = &from_key;
         goto out_dump;
     }
 
     err = tnc_next(c, &znode, &n);
     if (err == -ENOENT) {
         err = 0;
         goto out_unlock;
     }
     if (err < 0)
         goto out_unlock;
 
     ubifs_assert(c, err == 0);
     key = &znode->zbranch[n].key;
     if (!key_in_range(c, key, &from_key, &to_key))
         goto out_unlock;
 
 out_dump:
     block = key_block(c, key);
     ubifs_err(c, "inode %lu has size %lld, but there are data at offset %lld",
           (unsigned long)inode->i_ino, size,
           ((loff_t)block) << UBIFS_BLOCK_SHIFT);
     mutex_unlock(&c->tnc_mutex);
     ubifs_dump_inode(c, inode);
     dump_stack();
     return -EINVAL;
 
 out_unlock:
     mutex_unlock(&c->tnc_mutex);
     return err;
 }