tnc_commit.c

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

/* This file implements TNC functions for committing */

#include <linux/random.h>
#include "ubifs.h"

static int make_idx_node(struct ubifs_info *c, struct ubifs_idx_node *idx,
             struct ubifs_znode *znode, int lnum, int offs, int len)
{
    struct ubifs_znode *zp;
    int i, err;

    /* Make index node */
    idx->ch.node_type = UBIFS_IDX_NODE;
    idx->child_cnt = cpu_to_le16(znode->child_cnt);
    idx->level = cpu_to_le16(znode->level);
    for (i = 0; i < znode->child_cnt; i++) {
        struct ubifs_branch *br = ubifs_idx_branch(c, idx, i);
        struct ubifs_zbranch *zbr = &znode->zbranch[i];

        key_write_idx(c, &zbr->key, &br->key);
        br->lnum = cpu_to_le32(zbr->lnum);
        br->offs = cpu_to_le32(zbr->offs);
        br->len = cpu_to_le32(zbr->len);
        if (!zbr->lnum || !zbr->len) {
            ubifs_err("bad ref in znode");
            ubifs_dump_znode(c, znode);
            if (zbr->znode)
                ubifs_dump_znode(c, zbr->znode);
        }
    }
    ubifs_prepare_node(c, idx, len, 0);

    znode->lnum = lnum;
    znode->offs = offs;
    znode->len = len;

    err = insert_old_idx_znode(c, znode);

    /* Update the parent */
    zp = znode->parent;
    if (zp) {
        struct ubifs_zbranch *zbr;

        zbr = &zp->zbranch[znode->iip];
        zbr->lnum = lnum;
        zbr->offs = offs;
        zbr->len = len;
    } else {
        c->zroot.lnum = lnum;
        c->zroot.offs = offs;
        c->zroot.len = len;
    }
    c->calc_idx_sz += ALIGN(len, 8);

    atomic_long_dec(&c->dirty_zn_cnt);

    ubifs_assert(ubifs_zn_dirty(znode));
    ubifs_assert(ubifs_zn_cow(znode));

    /*
     * Note, unlike 'write_index()' we do not add memory barriers here
     * because this function is called with @c->tnc_mutex locked.
     */
    __clear_bit(DIRTY_ZNODE, &znode->flags);
    __clear_bit(COW_ZNODE, &znode->flags);

    return err;
}

static int fill_gap(struct ubifs_info *c, int lnum, int gap_start, int gap_end,
            int *dirt)
{
    int len, gap_remains, gap_pos, written, pad_len;

    ubifs_assert((gap_start & 7) == 0);
    ubifs_assert((gap_end & 7) == 0);
    ubifs_assert(gap_end >= gap_start);

    gap_remains = gap_end - gap_start;
    if (!gap_remains)
        return 0;
    gap_pos = gap_start;
    written = 0;
    while (c->enext) {
        len = ubifs_idx_node_sz(c, c->enext->child_cnt);
        if (len < gap_remains) {
            struct ubifs_znode *znode = c->enext;
            const int alen = ALIGN(len, 8);
            int err;

            ubifs_assert(alen <= gap_remains);
            err = make_idx_node(c, c->ileb_buf + gap_pos, znode,
                        lnum, gap_pos, len);
            if (err)
                return err;
            gap_remains -= alen;
            gap_pos += alen;
            c->enext = znode->cnext;
            if (c->enext == c->cnext)
                c->enext = NULL;
            written += 1;
        } else
            break;
    }
    if (gap_end == c->leb_size) {
        c->ileb_len = ALIGN(gap_pos, c->min_io_size);
        /* Pad to end of min_io_size */
        pad_len = c->ileb_len - gap_pos;
    } else
        /* Pad to end of gap */
        pad_len = gap_remains;
    dbg_gc("LEB %d:%d to %d len %d nodes written %d wasted bytes %d",
           lnum, gap_start, gap_end, gap_end - gap_start, written, pad_len);
    ubifs_pad(c, c->ileb_buf + gap_pos, pad_len);
    *dirt += pad_len;
    return written;
}

static int find_old_idx(struct ubifs_info *c, int lnum, int offs)
{
    struct ubifs_old_idx *o;
    struct rb_node *p;

    p = c->old_idx.rb_node;
    while (p) {
        o = rb_entry(p, 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
            return 1;
    }
    return 0;
}

static int is_idx_node_in_use(struct ubifs_info *c, union ubifs_key *key,
                  int level, int lnum, int offs)
{
    int ret;

    ret = is_idx_node_in_tnc(c, key, level, lnum, offs);
    if (ret < 0)
        return ret; /* Error code */
    if (ret == 0)
        if (find_old_idx(c, lnum, offs))
            return 1;
    return ret;
}

static int layout_leb_in_gaps(struct ubifs_info *c, int *p)
{
    struct ubifs_scan_leb *sleb;
    struct ubifs_scan_node *snod;
    int lnum, dirt = 0, gap_start, gap_end, err, written, tot_written;

    tot_written = 0;
    /* Get an index LEB with lots of obsolete index nodes */
    lnum = ubifs_find_dirty_idx_leb(c);
    if (lnum < 0)
        /*
         * There also may be dirt in the index head that could be
         * filled, however we do not check there at present.
         */
        return lnum; /* Error code */
    *p = lnum;
    dbg_gc("LEB %d", lnum);
    /*
     * Scan the index LEB.  We use the generic scan for this even though
     * it is more comprehensive and less efficient than is needed for this
     * purpose.
     */
    sleb = ubifs_scan(c, lnum, 0, c->ileb_buf, 0);
    c->ileb_len = 0;
    if (IS_ERR(sleb))
        return PTR_ERR(sleb);
    gap_start = 0;
    list_for_each_entry(snod, &sleb->nodes, list) {
        struct ubifs_idx_node *idx;
        int in_use, level;

        ubifs_assert(snod->type == UBIFS_IDX_NODE);
        idx = snod->node;
        key_read(c, ubifs_idx_key(c, idx), &snod->key);
        level = le16_to_cpu(idx->level);
        /* Determine if the index node is in use (not obsolete) */
        in_use = is_idx_node_in_use(c, &snod->key, level, lnum,
                        snod->offs);
        if (in_use < 0) {
            ubifs_scan_destroy(sleb);
            return in_use; /* Error code */
        }
        if (in_use) {
            if (in_use == 1)
                dirt += ALIGN(snod->len, 8);
            /*
             * The obsolete index nodes form gaps that can be
             * overwritten.  This gap has ended because we have
             * found an index node that is still in use
             * i.e. not obsolete
             */
            gap_end = snod->offs;
            /* Try to fill gap */
            written = fill_gap(c, lnum, gap_start, gap_end, &dirt);
            if (written < 0) {
                ubifs_scan_destroy(sleb);
                return written; /* Error code */
            }
            tot_written += written;
            gap_start = ALIGN(snod->offs + snod->len, 8);
        }
    }
    ubifs_scan_destroy(sleb);
    c->ileb_len = c->leb_size;
    gap_end = c->leb_size;
    /* Try to fill gap */
    written = fill_gap(c, lnum, gap_start, gap_end, &dirt);
    if (written < 0)
        return written; /* Error code */
    tot_written += written;
    if (tot_written == 0) {
        struct ubifs_lprops lp;

        dbg_gc("LEB %d wrote %d index nodes", lnum, tot_written);
        err = ubifs_read_one_lp(c, lnum, &lp);
        if (err)
            return err;
        if (lp.free == c->leb_size) {
            /*
             * We must have snatched this LEB from the idx_gc list
             * so we need to correct the free and dirty space.
             */
            err = ubifs_change_one_lp(c, lnum,
                          c->leb_size - c->ileb_len,
                          dirt, 0, 0, 0);
            if (err)
                return err;
        }
        return 0;
    }
    err = ubifs_change_one_lp(c, lnum, c->leb_size - c->ileb_len, dirt,
                  0, 0, 0);
    if (err)
        return err;
    err = ubifs_leb_change(c, lnum, c->ileb_buf, c->ileb_len);
    if (err)
        return err;
    dbg_gc("LEB %d wrote %d index nodes", lnum, tot_written);
    return tot_written;
}

static int get_leb_cnt(struct ubifs_info *c, int cnt)
{
    int d;

    /* Assume maximum index node size (i.e. overestimate space needed) */
    cnt -= (c->leb_size - c->ihead_offs) / c->max_idx_node_sz;
    if (cnt < 0)
        cnt = 0;
    d = c->leb_size / c->max_idx_node_sz;
    return DIV_ROUND_UP(cnt, d);
}

static int layout_in_gaps(struct ubifs_info *c, int cnt)
{
    int err, leb_needed_cnt, written, *p;

    dbg_gc("%d znodes to write", cnt);

    c->gap_lebs = kmalloc(sizeof(int) * (c->lst.idx_lebs + 1), GFP_NOFS);
    if (!c->gap_lebs)
        return -ENOMEM;

    p = c->gap_lebs;
    do {
        ubifs_assert(p < c->gap_lebs + sizeof(int) * c->lst.idx_lebs);
        written = layout_leb_in_gaps(c, p);
        if (written < 0) {
            err = written;
            if (err != -ENOSPC) {
                kfree(c->gap_lebs);
                c->gap_lebs = NULL;
                return err;
            }
            if (!dbg_is_chk_index(c)) {
                /*
                 * Do not print scary warnings if the debugging
                 * option which forces in-the-gaps is enabled.
                 */
                ubifs_warn("out of space");
                ubifs_dump_budg(c, &c->bi);
                ubifs_dump_lprops(c);
            }
            /* Try to commit anyway */
            err = 0;
            break;
        }
        p++;
        cnt -= written;
        leb_needed_cnt = get_leb_cnt(c, cnt);
        dbg_gc("%d znodes remaining, need %d LEBs, have %d", cnt,
               leb_needed_cnt, c->ileb_cnt);
    } while (leb_needed_cnt > c->ileb_cnt);

    *p = -1;
    return 0;
}

static int layout_in_empty_space(struct ubifs_info *c)
{
    struct ubifs_znode *znode, *cnext, *zp;
    int lnum, offs, len, next_len, buf_len, buf_offs, used, avail;
    int wlen, blen, err;

    cnext = c->enext;
    if (!cnext)
        return 0;

    lnum = c->ihead_lnum;
    buf_offs = c->ihead_offs;

    buf_len = ubifs_idx_node_sz(c, c->fanout);
    buf_len = ALIGN(buf_len, c->min_io_size);
    used = 0;
    avail = buf_len;

    /* Ensure there is enough room for first write */
    next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
    if (buf_offs + next_len > c->leb_size)
        lnum = -1;

    while (1) {
        znode = cnext;

        len = ubifs_idx_node_sz(c, znode->child_cnt);

        /* Determine the index node position */
        if (lnum == -1) {
            if (c->ileb_nxt >= c->ileb_cnt) {
                ubifs_err("out of space");
                return -ENOSPC;
            }
            lnum = c->ilebs[c->ileb_nxt++];
            buf_offs = 0;
            used = 0;
            avail = buf_len;
        }

        offs = buf_offs + used;

        znode->lnum = lnum;
        znode->offs = offs;
        znode->len = len;

        /* Update the parent */
        zp = znode->parent;
        if (zp) {
            struct ubifs_zbranch *zbr;
            int i;

            i = znode->iip;
            zbr = &zp->zbranch[i];
            zbr->lnum = lnum;
            zbr->offs = offs;
            zbr->len = len;
        } else {
            c->zroot.lnum = lnum;
            c->zroot.offs = offs;
            c->zroot.len = len;
        }
        c->calc_idx_sz += ALIGN(len, 8);

        /*
         * Once lprops is updated, we can decrease the dirty znode count
         * but it is easier to just do it here.
         */
        atomic_long_dec(&c->dirty_zn_cnt);

        /*
         * Calculate the next index node length to see if there is
         * enough room for it
         */
        cnext = znode->cnext;
        if (cnext == c->cnext)
            next_len = 0;
        else
            next_len = ubifs_idx_node_sz(c, cnext->child_cnt);

        /* Update buffer positions */
        wlen = used + len;
        used += ALIGN(len, 8);
        avail -= ALIGN(len, 8);

        if (next_len != 0 &&
            buf_offs + used + next_len <= c->leb_size &&
            avail > 0)
            continue;

        if (avail <= 0 && next_len &&
            buf_offs + used + next_len <= c->leb_size)
            blen = buf_len;
        else
            blen = ALIGN(wlen, c->min_io_size);

        /* The buffer is full or there are no more znodes to do */
        buf_offs += blen;
        if (next_len) {
            if (buf_offs + next_len > c->leb_size) {
                err = ubifs_update_one_lp(c, lnum,
                    c->leb_size - buf_offs, blen - used,
                    0, 0);
                if (err)
                    return err;
                lnum = -1;
            }
            used -= blen;
            if (used < 0)
                used = 0;
            avail = buf_len - used;
            continue;
        }
        err = ubifs_update_one_lp(c, lnum, c->leb_size - buf_offs,
                      blen - used, 0, 0);
        if (err)
            return err;
        break;
    }

    c->dbg->new_ihead_lnum = lnum;
    c->dbg->new_ihead_offs = buf_offs;

    return 0;
}

static int layout_commit(struct ubifs_info *c, int no_space, int cnt)
{
    int err;

    if (no_space) {
        err = layout_in_gaps(c, cnt);
        if (err)
            return err;
    }
    err = layout_in_empty_space(c);
    return err;
}

static struct ubifs_znode *find_first_dirty(struct ubifs_znode *znode)
{
    int i, cont;

    if (!znode)
        return NULL;

    while (1) {
        if (znode->level == 0) {
            if (ubifs_zn_dirty(znode))
                return znode;
            return NULL;
        }
        cont = 0;
        for (i = 0; i < znode->child_cnt; i++) {
            struct ubifs_zbranch *zbr = &znode->zbranch[i];

            if (zbr->znode && ubifs_zn_dirty(zbr->znode)) {
                znode = zbr->znode;
                cont = 1;
                break;
            }
        }
        if (!cont) {
            if (ubifs_zn_dirty(znode))
                return znode;
            return NULL;
        }
    }
}

static struct ubifs_znode *find_next_dirty(struct ubifs_znode *znode)
{
    int n = znode->iip + 1;

    znode = znode->parent;
    if (!znode)
        return NULL;
    for (; n < znode->child_cnt; n++) {
        struct ubifs_zbranch *zbr = &znode->zbranch[n];

        if (zbr->znode && ubifs_zn_dirty(zbr->znode))
            return find_first_dirty(zbr->znode);
    }
    return znode;
}

static int get_znodes_to_commit(struct ubifs_info *c)
{
    struct ubifs_znode *znode, *cnext;
    int cnt = 0;

    c->cnext = find_first_dirty(c->zroot.znode);
    znode = c->enext = c->cnext;
    if (!znode) {
        dbg_cmt("no znodes to commit");
        return 0;
    }
    cnt += 1;
    while (1) {
        ubifs_assert(!ubifs_zn_cow(znode));
        __set_bit(COW_ZNODE, &znode->flags);
        znode->alt = 0;
        cnext = find_next_dirty(znode);
        if (!cnext) {
            znode->cnext = c->cnext;
            break;
        }
        znode->cnext = cnext;
        znode = cnext;
        cnt += 1;
    }
    dbg_cmt("committing %d znodes", cnt);
    ubifs_assert(cnt == atomic_long_read(&c->dirty_zn_cnt));
    return cnt;
}

static int alloc_idx_lebs(struct ubifs_info *c, int cnt)
{
    int i, leb_cnt, lnum;

    c->ileb_cnt = 0;
    c->ileb_nxt = 0;
    leb_cnt = get_leb_cnt(c, cnt);
    dbg_cmt("need about %d empty LEBS for TNC commit", leb_cnt);
    if (!leb_cnt)
        return 0;
    c->ilebs = kmalloc(leb_cnt * sizeof(int), GFP_NOFS);
    if (!c->ilebs)
        return -ENOMEM;
    for (i = 0; i < leb_cnt; i++) {
        lnum = ubifs_find_free_leb_for_idx(c);
        if (lnum < 0)
            return lnum;
        c->ilebs[c->ileb_cnt++] = lnum;
        dbg_cmt("LEB %d", lnum);
    }
    if (dbg_is_chk_index(c) && !(random32() & 7))
        return -ENOSPC;
    return 0;
}

static int free_unused_idx_lebs(struct ubifs_info *c)
{
    int i, err = 0, lnum, er;

    for (i = c->ileb_nxt; i < c->ileb_cnt; i++) {
        lnum = c->ilebs[i];
        dbg_cmt("LEB %d", lnum);
        er = ubifs_change_one_lp(c, lnum, LPROPS_NC, LPROPS_NC, 0,
                     LPROPS_INDEX | LPROPS_TAKEN, 0);
        if (!err)
            err = er;
    }
    return err;
}

static int free_idx_lebs(struct ubifs_info *c)
{
    int err;

    err = free_unused_idx_lebs(c);
    kfree(c->ilebs);
    c->ilebs = NULL;
    return err;
}

int ubifs_tnc_start_commit(struct ubifs_info *c, struct ubifs_zbranch *zroot)
{
    int err = 0, cnt;

    mutex_lock(&c->tnc_mutex);
    err = dbg_check_tnc(c, 1);
    if (err)
        goto out;
    cnt = get_znodes_to_commit(c);
    if (cnt != 0) {
        int no_space = 0;

        err = alloc_idx_lebs(c, cnt);
        if (err == -ENOSPC)
            no_space = 1;
        else if (err)
            goto out_free;
        err = layout_commit(c, no_space, cnt);
        if (err)
            goto out_free;
        ubifs_assert(atomic_long_read(&c->dirty_zn_cnt) == 0);
        err = free_unused_idx_lebs(c);
        if (err)
            goto out;
    }
    destroy_old_idx(c);
    memcpy(zroot, &c->zroot, sizeof(struct ubifs_zbranch));

    err = ubifs_save_dirty_idx_lnums(c);
    if (err)
        goto out;

    spin_lock(&c->space_lock);
    /*
     * Although we have not finished committing yet, update size of the
     * committed index ('c->bi.old_idx_sz') and zero out the index growth
     * budget. It is OK to do this now, because we've reserved all the
     * space which is needed to commit the index, and it is save for the
     * budgeting subsystem to assume the index is already committed,
     * even though it is not.
     */
    ubifs_assert(c->bi.min_idx_lebs == ubifs_calc_min_idx_lebs(c));
    c->bi.old_idx_sz = c->calc_idx_sz;
    c->bi.uncommitted_idx = 0;
    c->bi.min_idx_lebs = ubifs_calc_min_idx_lebs(c);
    spin_unlock(&c->space_lock);
    mutex_unlock(&c->tnc_mutex);

    dbg_cmt("number of index LEBs %d", c->lst.idx_lebs);
    dbg_cmt("size of index %llu", c->calc_idx_sz);
    return err;

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

static int write_index(struct ubifs_info *c)
{
    struct ubifs_idx_node *idx;
    struct ubifs_znode *znode, *cnext;
    int i, lnum, offs, len, next_len, buf_len, buf_offs, used;
    int avail, wlen, err, lnum_pos = 0, blen, nxt_offs;

    cnext = c->enext;
    if (!cnext)
        return 0;

    /*
     * Always write index nodes to the index head so that index nodes and
     * other types of nodes are never mixed in the same erase block.
     */
    lnum = c->ihead_lnum;
    buf_offs = c->ihead_offs;

    /* Allocate commit buffer */
    buf_len = ALIGN(c->max_idx_node_sz, c->min_io_size);
    used = 0;
    avail = buf_len;

    /* Ensure there is enough room for first write */
    next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
    if (buf_offs + next_len > c->leb_size) {
        err = ubifs_update_one_lp(c, lnum, LPROPS_NC, 0, 0,
                      LPROPS_TAKEN);
        if (err)
            return err;
        lnum = -1;
    }

    while (1) {
        cond_resched();

        znode = cnext;
        idx = c->cbuf + used;

        /* Make index node */
        idx->ch.node_type = UBIFS_IDX_NODE;
        idx->child_cnt = cpu_to_le16(znode->child_cnt);
        idx->level = cpu_to_le16(znode->level);
        for (i = 0; i < znode->child_cnt; i++) {
            struct ubifs_branch *br = ubifs_idx_branch(c, idx, i);
            struct ubifs_zbranch *zbr = &znode->zbranch[i];

            key_write_idx(c, &zbr->key, &br->key);
            br->lnum = cpu_to_le32(zbr->lnum);
            br->offs = cpu_to_le32(zbr->offs);
            br->len = cpu_to_le32(zbr->len);
            if (!zbr->lnum || !zbr->len) {
                ubifs_err("bad ref in znode");
                ubifs_dump_znode(c, znode);
                if (zbr->znode)
                    ubifs_dump_znode(c, zbr->znode);
            }
        }
        len = ubifs_idx_node_sz(c, znode->child_cnt);
        ubifs_prepare_node(c, idx, len, 0);

        /* Determine the index node position */
        if (lnum == -1) {
            lnum = c->ilebs[lnum_pos++];
            buf_offs = 0;
            used = 0;
            avail = buf_len;
        }
        offs = buf_offs + used;

        if (lnum != znode->lnum || offs != znode->offs ||
            len != znode->len) {
            ubifs_err("inconsistent znode posn");
            return -EINVAL;
        }

        /* Grab some stuff from znode while we still can */
        cnext = znode->cnext;

        ubifs_assert(ubifs_zn_dirty(znode));
        ubifs_assert(ubifs_zn_cow(znode));

        /*
         * It is important that other threads should see %DIRTY_ZNODE
         * flag cleared before %COW_ZNODE. Specifically, it matters in
         * the 'dirty_cow_znode()' function. This is the reason for the
         * first barrier. Also, we want the bit changes to be seen to
         * other threads ASAP, to avoid unnecesarry copying, which is
         * the reason for the second barrier.
         */
        clear_bit(DIRTY_ZNODE, &znode->flags);
        smp_mb__before_clear_bit();
        clear_bit(COW_ZNODE, &znode->flags);
        smp_mb__after_clear_bit();

        /*
         * We have marked the znode as clean but have not updated the
         * @c->clean_zn_cnt counter. If this znode becomes dirty again
         * before 'free_obsolete_znodes()' is called, then
         * @c->clean_zn_cnt will be decremented before it gets
         * incremented (resulting in 2 decrements for the same znode).
         * This means that @c->clean_zn_cnt may become negative for a
         * while.
         *
         * Q: why we cannot increment @c->clean_zn_cnt?
         * A: because we do not have the @c->tnc_mutex locked, and the
         *    following code would be racy and buggy:
         *
         *    if (!ubifs_zn_obsolete(znode)) {
         *            atomic_long_inc(&c->clean_zn_cnt);
         *            atomic_long_inc(&ubifs_clean_zn_cnt);
         *    }
         *
         *    Thus, we just delay the @c->clean_zn_cnt update until we
         *    have the mutex locked.
         */

        /* Do not access znode from this point on */

        /* Update buffer positions */
        wlen = used + len;
        used += ALIGN(len, 8);
        avail -= ALIGN(len, 8);

        /*
         * Calculate the next index node length to see if there is
         * enough room for it
         */
        if (cnext == c->cnext)
            next_len = 0;
        else
            next_len = ubifs_idx_node_sz(c, cnext->child_cnt);

        nxt_offs = buf_offs + used + next_len;
        if (next_len && nxt_offs <= c->leb_size) {
            if (avail > 0)
                continue;
            else
                blen = buf_len;
        } else {
            wlen = ALIGN(wlen, 8);
            blen = ALIGN(wlen, c->min_io_size);
            ubifs_pad(c, c->cbuf + wlen, blen - wlen);
        }

        /* The buffer is full or there are no more znodes to do */
        err = ubifs_leb_write(c, lnum, c->cbuf, buf_offs, blen);
        if (err)
            return err;
        buf_offs += blen;
        if (next_len) {
            if (nxt_offs > c->leb_size) {
                err = ubifs_update_one_lp(c, lnum, LPROPS_NC, 0,
                              0, LPROPS_TAKEN);
                if (err)
                    return err;
                lnum = -1;
            }
            used -= blen;
            if (used < 0)
                used = 0;
            avail = buf_len - used;
            memmove(c->cbuf, c->cbuf + blen, used);
            continue;
        }
        break;
    }

    if (lnum != c->dbg->new_ihead_lnum ||
        buf_offs != c->dbg->new_ihead_offs) {
        ubifs_err("inconsistent ihead");
        return -EINVAL;
    }

    c->ihead_lnum = lnum;
    c->ihead_offs = buf_offs;

    return 0;
}

static void free_obsolete_znodes(struct ubifs_info *c)
{
    struct ubifs_znode *znode, *cnext;

    cnext = c->cnext;
    do {
        znode = cnext;
        cnext = znode->cnext;
        if (ubifs_zn_obsolete(znode))
            kfree(znode);
        else {
            znode->cnext = NULL;
            atomic_long_inc(&c->clean_zn_cnt);
            atomic_long_inc(&ubifs_clean_zn_cnt);
        }
    } while (cnext != c->cnext);
}

static int return_gap_lebs(struct ubifs_info *c)
{
    int *p, err;

    if (!c->gap_lebs)
        return 0;

    dbg_cmt("");
    for (p = c->gap_lebs; *p != -1; p++) {
        err = ubifs_change_one_lp(c, *p, LPROPS_NC, LPROPS_NC, 0,
                      LPROPS_TAKEN, 0);
        if (err)
            return err;
    }

    kfree(c->gap_lebs);
    c->gap_lebs = NULL;
    return 0;
}

int ubifs_tnc_end_commit(struct ubifs_info *c)
{
    int err;

    if (!c->cnext)
        return 0;

    err = return_gap_lebs(c);
    if (err)
        return err;

    err = write_index(c);
    if (err)
        return err;

    mutex_lock(&c->tnc_mutex);

    dbg_cmt("TNC height is %d", c->zroot.znode->level + 1);

    free_obsolete_znodes(c);

    c->cnext = NULL;
    kfree(c->ilebs);
    c->ilebs = NULL;

    mutex_unlock(&c->tnc_mutex);

    return 0;
}