/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2006-2008 Nokia Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * Authors: Adrian Hunter
 *          Artem Bityutskiy (Битюцкий Артём)
 */

/*
 * This file contains miscelanious TNC-related functions shared betweend
 * different files. This file does not form any logically separate TNC
 * sub-system. The file was created because there is a lot of TNC code and
 * putting it all in one file would make that file too big and unreadable.
 */

#include "ubifs.h"

/**
 * ubifs_tnc_levelorder_next - next TNC tree element in levelorder traversal.
 * @zr: root of the subtree to traverse
 * @znode: previous znode
 *
 * This function implements levelorder TNC traversal. The LNC is ignored.
 * Returns the next element or %NULL if @znode is already the last one.
 */
struct ubifs_znode *ubifs_tnc_levelorder_next(struct ubifs_znode *zr,
                                              struct ubifs_znode *znode)
{
        int level, iip, level_search = 0;
        struct ubifs_znode *zn;

        ubifs_assert(zr);

        if (unlikely(!znode))
                return zr;

        if (unlikely(znode == zr)) {
                if (znode->level == 0)
                        return NULL;
                return ubifs_tnc_find_child(zr, 0);
        }

        level = znode->level;

        iip = znode->iip;
        while (1) {
                ubifs_assert(znode->level <= zr->level);

                /*
                 * First walk up until there is a znode with next branch to
                 * look at.
                 */
                while (znode->parent != zr && iip >= znode->parent->child_cnt) {
                        znode = znode->parent;
                        iip = znode->iip;
                }

                if (unlikely(znode->parent == zr &&
                             iip >= znode->parent->child_cnt)) {
                        /* This level is done, switch to the lower one */
                        level -= 1;
                        if (level_search || level < 0)
                                /*
                                 * We were already looking for znode at lower
                                 * level ('level_search'). As we are here
                                 * again, it just does not exist. Or all levels
                                 * were finished ('level < 0').
                                 */
                                return NULL;

                        level_search = 1;
                        iip = -1;
                        znode = ubifs_tnc_find_child(zr, 0);
                        ubifs_assert(znode);
                }

                /* Switch to the next index */
                zn = ubifs_tnc_find_child(znode->parent, iip + 1);
                if (!zn) {
                        /* No more children to look at, we have walk up */
                        iip = znode->parent->child_cnt;
                        continue;
                }

                /* Walk back down to the level we came from ('level') */
                while (zn->level != level) {
                        znode = zn;
                        zn = ubifs_tnc_find_child(zn, 0);
                        if (!zn) {
                                /*
                                 * This path is not too deep so it does not
                                 * reach 'level'. Try next path.
                                 */
                                iip = znode->iip;
                                break;
                        }
                }

                if (zn) {
                        ubifs_assert(zn->level >= 0);
                        return zn;
                }
        }
}

/**
 * ubifs_search_zbranch - search znode branch.
 * @c: UBIFS file-system description object
 * @znode: znode to search in
 * @key: key to search for
 * @n: znode branch slot number is returned here
 *
 * This is a helper function which search branch with key @key in @znode using
 * binary search. The result of the search may be:
 *   o exact match, then %1 is returned, and the slot number of the branch is
 *     stored in @n;
 *   o no exact match, then %0 is returned and the slot number of the left
 *     closest branch is returned in @n; the slot if all keys in this znode are
 *     greater than @key, then %-1 is returned in @n.
 */
int ubifs_search_zbranch(const struct ubifs_info *c,
                         const struct ubifs_znode *znode,
                         const union ubifs_key *key, int *n)
{
        int beg = 0, end = znode->child_cnt, uninitialized_var(mid);
        int uninitialized_var(cmp);
        const struct ubifs_zbranch *zbr = &znode->zbranch[0];

        ubifs_assert(end > beg);

        while (end > beg) {
                mid = (beg + end) >> 1;
                cmp = keys_cmp(c, key, &zbr[mid].key);
                if (cmp > 0)
                        beg = mid + 1;
                else if (cmp < 0)
                        end = mid;
                else {
                        *n = mid;
                        return 1;
                }
        }

        *n = end - 1;

        /* The insert point is after *n */
        ubifs_assert(*n >= -1 && *n < znode->child_cnt);
        if (*n == -1)
                ubifs_assert(keys_cmp(c, key, &zbr[0].key) < 0);
        else
                ubifs_assert(keys_cmp(c, key, &zbr[*n].key) > 0);
        if (*n + 1 < znode->child_cnt)
                ubifs_assert(keys_cmp(c, key, &zbr[*n + 1].key) < 0);

        return 0;
}

/**
 * ubifs_tnc_postorder_first - find first znode to do postorder tree traversal.
 * @znode: znode to start at (root of the sub-tree to traverse)
 *
 * Find the lowest leftmost znode in a subtree of the TNC tree. The LNC is
 * ignored.
 */
struct ubifs_znode *ubifs_tnc_postorder_first(struct ubifs_znode *znode)
{
        if (unlikely(!znode))
                return NULL;

        while (znode->level > 0) {
                struct ubifs_znode *child;

                child = ubifs_tnc_find_child(znode, 0);
                if (!child)
                        return znode;
                znode = child;
        }

        return znode;
}

/**
 * ubifs_tnc_postorder_next - next TNC tree element in postorder traversal.
 * @znode: previous znode
 *
 * This function implements postorder TNC traversal. The LNC is ignored.
 * Returns the next element or %NULL if @znode is already the last one.
 */
struct ubifs_znode *ubifs_tnc_postorder_next(struct ubifs_znode *znode)
{
        struct ubifs_znode *zn;

        ubifs_assert(znode);
        if (unlikely(!znode->parent))
                return NULL;

        /* Switch to the next index in the parent */
        zn = ubifs_tnc_find_child(znode->parent, znode->iip + 1);
        if (!zn)
                /* This is in fact the last child, return parent */
                return znode->parent;

        /* Go to the first znode in this new subtree */
        return ubifs_tnc_postorder_first(zn);
}

/**
 * ubifs_destroy_tnc_subtree - destroy all znodes connected to a subtree.
 * @znode: znode defining subtree to destroy
 *
 * This function destroys subtree of the TNC tree. Returns number of clean
 * znodes in the subtree.
 */
long ubifs_destroy_tnc_subtree(struct ubifs_znode *znode)
{
        struct ubifs_znode *zn = ubifs_tnc_postorder_first(znode);
        long clean_freed = 0;
        int n;

        ubifs_assert(zn);
        while (1) {
                for (n = 0; n < zn->child_cnt; n++) {
                        if (!zn->zbranch[n].znode)
                                continue;

                        if (zn->level > 0 &&
                            !ubifs_zn_dirty(zn->zbranch[n].znode))
                                clean_freed += 1;

                        cond_resched();
                        kfree(zn->zbranch[n].znode);
                }

                if (zn == znode) {
                        if (!ubifs_zn_dirty(zn))
                                clean_freed += 1;
                        kfree(zn);
                        return clean_freed;
                }

                zn = ubifs_tnc_postorder_next(zn);
        }
}

/**
 * read_znode - read an indexing node from flash and fill znode.
 * @c: UBIFS file-system description object
 * @lnum: LEB of the indexing node to read
 * @offs: node offset
 * @len: node length
 * @znode: znode to read to
 *
 * This function reads an indexing node from the flash media and fills znode
 * with the read data. Returns zero in case of success and a negative error
 * code in case of failure. The read indexing node is validated and if anything
 * is wrong with it, this function prints complaint messages and returns
 * %-EINVAL.
 */
static int read_znode(struct ubifs_info *c, int lnum, int offs, int len,
                      struct ubifs_znode *znode)
{
        int i, err, type, cmp;
        struct ubifs_idx_node *idx;

        idx = kmalloc(c->max_idx_node_sz, GFP_NOFS);
        if (!idx)
                return -ENOMEM;

        err = ubifs_read_node(c, idx, UBIFS_IDX_NODE, len, lnum, offs);
        if (err < 0) {
                kfree(idx);
                return err;
        }

        znode->child_cnt = le16_to_cpu(idx->child_cnt);
        znode->level = le16_to_cpu(idx->level);

        dbg_tnc("LEB %d:%d, level %d, %d branch",
                lnum, offs, znode->level, znode->child_cnt);

        if (znode->child_cnt > c->fanout || znode->level > UBIFS_MAX_LEVELS) {
                ubifs_err(c, "current fanout %d, branch count %d",
                          c->fanout, znode->child_cnt);
                ubifs_err(c, "max levels %d, znode level %d",
                          UBIFS_MAX_LEVELS, znode->level);
                err = 1;
                goto out_dump;
        }

        for (i = 0; i < znode->child_cnt; i++) {
                const struct ubifs_branch *br = ubifs_idx_branch(c, idx, i);
                struct ubifs_zbranch *zbr = &znode->zbranch[i];

                key_read(c, &br->key, &zbr->key);
                zbr->lnum = le32_to_cpu(br->lnum);
                zbr->offs = le32_to_cpu(br->offs);
                zbr->len  = le32_to_cpu(br->len);
                zbr->znode = NULL;

                /* Validate branch */

                if (zbr->lnum < c->main_first ||
                    zbr->lnum >= c->leb_cnt || zbr->offs < 0 ||
                    zbr->offs + zbr->len > c->leb_size || zbr->offs & 7) {
                        ubifs_err(c, "bad branch %d", i);
                        err = 2;
                        goto out_dump;
                }

                switch (key_type(c, &zbr->key)) {
                case UBIFS_INO_KEY:
                case UBIFS_DATA_KEY:
                case UBIFS_DENT_KEY:
                case UBIFS_XENT_KEY:
                        break;
                default:
                        ubifs_err(c, "bad key type at slot %d: %d",
                                  i, key_type(c, &zbr->key));
                        err = 3;
                        goto out_dump;
                }

                if (znode->level)
                        continue;

                type = key_type(c, &zbr->key);
                if (c->ranges[type].max_len == 0) {
                        if (zbr->len != c->ranges[type].len) {
                                ubifs_err(c, "bad target node (type %d) length (%d)",
                                          type, zbr->len);
                                ubifs_err(c, "have to be %d", c->ranges[type].len);
                                err = 4;
                                goto out_dump;
                        }
                } else if (zbr->len < c->ranges[type].min_len ||
                           zbr->len > c->ranges[type].max_len) {
                        ubifs_err(c, "bad target node (type %d) length (%d)",
                                  type, zbr->len);
                        ubifs_err(c, "have to be in range of %d-%d",
                                  c->ranges[type].min_len,
                                  c->ranges[type].max_len);
                        err = 5;
                        goto out_dump;
                }
        }

        /*
         * Ensure that the next key is greater or equivalent to the
         * previous one.
         */
        for (i = 0; i < znode->child_cnt - 1; i++) {
                const union ubifs_key *key1, *key2;

                key1 = &znode->zbranch[i].key;
                key2 = &znode->zbranch[i + 1].key;

                cmp = keys_cmp(c, key1, key2);
                if (cmp > 0) {
                        ubifs_err(c, "bad key order (keys %d and %d)", i, i + 1);
                        err = 6;
                        goto out_dump;
                } else if (cmp == 0 && !is_hash_key(c, key1)) {
                        /* These can only be keys with colliding hash */
                        ubifs_err(c, "keys %d and %d are not hashed but equivalent",
                                  i, i + 1);
                        err = 7;
                        goto out_dump;
                }
        }

        kfree(idx);
        return 0;

out_dump:
        ubifs_err(c, "bad indexing node at LEB %d:%d, error %d", lnum, offs, err);
        ubifs_dump_node(c, idx);
        kfree(idx);
        return -EINVAL;
}

/**
 * ubifs_load_znode - load znode to TNC cache.
 * @c: UBIFS file-system description object
 * @zbr: znode branch
 * @parent: znode's parent
 * @iip: index in parent
 *
 * This function loads znode pointed to by @zbr into the TNC cache and
 * returns pointer to it in case of success and a negative error code in case
 * of failure.
 */
struct ubifs_znode *ubifs_load_znode(struct ubifs_info *c,
                                     struct ubifs_zbranch *zbr,
                                     struct ubifs_znode *parent, int iip)
{
        int err;
        struct ubifs_znode *znode;

        ubifs_assert(!zbr->znode);
        /*
         * A slab cache is not presently used for znodes because the znode size
         * depends on the fanout which is stored in the superblock.
         */
        znode = kzalloc(c->max_znode_sz, GFP_NOFS);
        if (!znode)
                return ERR_PTR(-ENOMEM);

        err = read_znode(c, zbr->lnum, zbr->offs, zbr->len, znode);
        if (err)
                goto out;

        atomic_long_inc(&c->clean_zn_cnt);

        /*
         * Increment the global clean znode counter as well. It is OK that
         * global and per-FS clean znode counters may be inconsistent for some
         * short time (because we might be preempted at this point), the global
         * one is only used in shrinker.
         */
        atomic_long_inc(&ubifs_clean_zn_cnt);

        zbr->znode = znode;
        znode->parent = parent;
        znode->time = get_seconds();
        znode->iip = iip;

        return znode;

out:
        kfree(znode);
        return ERR_PTR(err);
}

/**
 * ubifs_tnc_read_node - read a leaf node from the flash media.
 * @c: UBIFS file-system description object
 * @zbr: key and position of the node
 * @node: node is returned here
 *
 * This function reads a node defined by @zbr from the flash media. Returns
 * zero in case of success or a negative negative error code in case of
 * failure.
 */
int ubifs_tnc_read_node(struct ubifs_info *c, struct ubifs_zbranch *zbr,
                        void *node)
{
        union ubifs_key key1, *key = &zbr->key;
        int err, type = key_type(c, key);
        struct ubifs_wbuf *wbuf;

        /*
         * 'zbr' has to point to on-flash node. The node may sit in a bud and
         * may even be in a write buffer, so we have to take care about this.
         */
        wbuf = ubifs_get_wbuf(c, zbr->lnum);
        if (wbuf)
                err = ubifs_read_node_wbuf(wbuf, node, type, zbr->len,
                                           zbr->lnum, zbr->offs);
        else
                err = ubifs_read_node(c, node, type, zbr->len, zbr->lnum,
                                      zbr->offs);

        if (err) {
                dbg_tnck(key, "key ");
                return err;
        }

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

        return 0;
}