gc.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 garbage collection. The procedure for garbage collection
 * is different depending on whether a LEB as an index LEB (contains index
 * nodes) or not. For non-index LEBs, garbage collection finds a LEB which
 * contains a lot of dirty space (obsolete nodes), and copies the non-obsolete
 * nodes to the journal, at which point the garbage-collected LEB is free to be
 * reused. For index LEBs, garbage collection marks the non-obsolete index nodes
 * dirty in the TNC, and after the next commit, the garbage-collected LEB is
 * to be reused. Garbage collection will cause the number of dirty index nodes
 * to grow, however sufficient space is reserved for the index to ensure the
 * commit will never run out of space.
 *
 * Notes about dead watermark. At current UBIFS implementation we assume that
 * LEBs which have less than @c->dead_wm bytes of free + dirty space are full
 * and not worth garbage-collecting. The dead watermark is one min. I/O unit
 * size, or min. UBIFS node size, depending on what is greater. Indeed, UBIFS
 * Garbage Collector has to synchronize the GC head's write buffer before
 * returning, so this is about wasting one min. I/O unit. However, UBIFS GC can
 * actually reclaim even very small pieces of dirty space by garbage collecting
 * enough dirty LEBs, but we do not bother doing this at this implementation.
 *
 * Notes about dark watermark. The results of GC work depends on how big are
 * the UBIFS nodes GC deals with. Large nodes make GC waste more space. Indeed,
 * if GC move data from LEB A to LEB B and nodes in LEB A are large, GC would
 * have to waste large pieces of free space at the end of LEB B, because nodes
 * from LEB A would not fit. And the worst situation is when all nodes are of
 * maximum size. So dark watermark is the amount of free + dirty space in LEB
 * which are guaranteed to be reclaimable. If LEB has less space, the GC might
 * be unable to reclaim it. So, LEBs with free + dirty greater than dark
 * watermark are "good" LEBs from GC's point of few. The other LEBs are not so
 * good, and GC takes extra care when moving them.
 */

#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/list_sort.h>
#include "ubifs.h"

/*
 * GC may need to move more than one LEB to make progress. The below constants
 * define "soft" and "hard" limits on the number of LEBs the garbage collector
 * may move.
 */
#define SOFT_LEBS_LIMIT 4
#define HARD_LEBS_LIMIT 32

static int switch_gc_head(struct ubifs_info *c)
{
    int err, gc_lnum = c->gc_lnum;
    struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;

    ubifs_assert(gc_lnum != -1);
    dbg_gc("switch GC head from LEB %d:%d to LEB %d (waste %d bytes)",
           wbuf->lnum, wbuf->offs + wbuf->used, gc_lnum,
           c->leb_size - wbuf->offs - wbuf->used);

    err = ubifs_wbuf_sync_nolock(wbuf);
    if (err)
        return err;

    /*
     * The GC write-buffer was synchronized, we may safely unmap
     * 'c->gc_lnum'.
     */
    err = ubifs_leb_unmap(c, gc_lnum);
    if (err)
        return err;

    err = ubifs_wbuf_sync_nolock(wbuf);
    if (err)
        return err;

    err = ubifs_add_bud_to_log(c, GCHD, gc_lnum, 0);
    if (err)
        return err;

    c->gc_lnum = -1;
    err = ubifs_wbuf_seek_nolock(wbuf, gc_lnum, 0);
    return err;
}

static int data_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
{
    ino_t inuma, inumb;
    struct ubifs_info *c = priv;
    struct ubifs_scan_node *sa, *sb;

    cond_resched();
    if (a == b)
        return 0;

    sa = list_entry(a, struct ubifs_scan_node, list);
    sb = list_entry(b, struct ubifs_scan_node, list);

    ubifs_assert(key_type(c, &sa->key) == UBIFS_DATA_KEY);
    ubifs_assert(key_type(c, &sb->key) == UBIFS_DATA_KEY);
    ubifs_assert(sa->type == UBIFS_DATA_NODE);
    ubifs_assert(sb->type == UBIFS_DATA_NODE);

    inuma = key_inum(c, &sa->key);
    inumb = key_inum(c, &sb->key);

    if (inuma == inumb) {
        unsigned int blka = key_block(c, &sa->key);
        unsigned int blkb = key_block(c, &sb->key);

        if (blka <= blkb)
            return -1;
    } else if (inuma <= inumb)
        return -1;

    return 1;
}

/*
 * nondata_nodes_cmp - compare 2 non-data nodes.
 * @priv: UBIFS file-system description object
 * @a: first node
 * @a: second node
 *
 * This function compares nodes @a and @b. It makes sure that inode nodes go
 * first and sorted by length in descending order. Directory entry nodes go
 * after inode nodes and are sorted in ascending hash valuer order.
 */
static int nondata_nodes_cmp(void *priv, struct list_head *a,
                 struct list_head *b)
{
    ino_t inuma, inumb;
    struct ubifs_info *c = priv;
    struct ubifs_scan_node *sa, *sb;

    cond_resched();
    if (a == b)
        return 0;

    sa = list_entry(a, struct ubifs_scan_node, list);
    sb = list_entry(b, struct ubifs_scan_node, list);

    ubifs_assert(key_type(c, &sa->key) != UBIFS_DATA_KEY &&
             key_type(c, &sb->key) != UBIFS_DATA_KEY);
    ubifs_assert(sa->type != UBIFS_DATA_NODE &&
             sb->type != UBIFS_DATA_NODE);

    /* Inodes go before directory entries */
    if (sa->type == UBIFS_INO_NODE) {
        if (sb->type == UBIFS_INO_NODE)
            return sb->len - sa->len;
        return -1;
    }
    if (sb->type == UBIFS_INO_NODE)
        return 1;

    ubifs_assert(key_type(c, &sa->key) == UBIFS_DENT_KEY ||
             key_type(c, &sa->key) == UBIFS_XENT_KEY);
    ubifs_assert(key_type(c, &sb->key) == UBIFS_DENT_KEY ||
             key_type(c, &sb->key) == UBIFS_XENT_KEY);
    ubifs_assert(sa->type == UBIFS_DENT_NODE ||
             sa->type == UBIFS_XENT_NODE);
    ubifs_assert(sb->type == UBIFS_DENT_NODE ||
             sb->type == UBIFS_XENT_NODE);

    inuma = key_inum(c, &sa->key);
    inumb = key_inum(c, &sb->key);

    if (inuma == inumb) {
        uint32_t hasha = key_hash(c, &sa->key);
        uint32_t hashb = key_hash(c, &sb->key);

        if (hasha <= hashb)
            return -1;
    } else if (inuma <= inumb)
        return -1;

    return 1;
}

static int sort_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
              struct list_head *nondata, int *min)
{
    int err;
    struct ubifs_scan_node *snod, *tmp;

    *min = INT_MAX;

    /* Separate data nodes and non-data nodes */
    list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
        ubifs_assert(snod->type == UBIFS_INO_NODE  ||
                 snod->type == UBIFS_DATA_NODE ||
                 snod->type == UBIFS_DENT_NODE ||
                 snod->type == UBIFS_XENT_NODE ||
                 snod->type == UBIFS_TRUN_NODE);

        if (snod->type != UBIFS_INO_NODE  &&
            snod->type != UBIFS_DATA_NODE &&
            snod->type != UBIFS_DENT_NODE &&
            snod->type != UBIFS_XENT_NODE) {
            /* Probably truncation node, zap it */
            list_del(&snod->list);
            kfree(snod);
            continue;
        }

        ubifs_assert(key_type(c, &snod->key) == UBIFS_DATA_KEY ||
                 key_type(c, &snod->key) == UBIFS_INO_KEY  ||
                 key_type(c, &snod->key) == UBIFS_DENT_KEY ||
                 key_type(c, &snod->key) == UBIFS_XENT_KEY);

        err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
                     snod->offs, 0);
        if (err < 0)
            return err;

        if (!err) {
            /* The node is obsolete, remove it from the list */
            list_del(&snod->list);
            kfree(snod);
            continue;
        }

        if (snod->len < *min)
            *min = snod->len;

        if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
            list_move_tail(&snod->list, nondata);
    }

    /* Sort data and non-data nodes */
    list_sort(c, &sleb->nodes, &data_nodes_cmp);
    list_sort(c, nondata, &nondata_nodes_cmp);

    err = dbg_check_data_nodes_order(c, &sleb->nodes);
    if (err)
        return err;
    err = dbg_check_nondata_nodes_order(c, nondata);
    if (err)
        return err;
    return 0;
}

static int move_node(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
             struct ubifs_scan_node *snod, struct ubifs_wbuf *wbuf)
{
    int err, new_lnum = wbuf->lnum, new_offs = wbuf->offs + wbuf->used;

    cond_resched();
    err = ubifs_wbuf_write_nolock(wbuf, snod->node, snod->len);
    if (err)
        return err;

    err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
                snod->offs, new_lnum, new_offs,
                snod->len);
    list_del(&snod->list);
    kfree(snod);
    return err;
}

static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
{
    int err, min;
    LIST_HEAD(nondata);
    struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;

    if (wbuf->lnum == -1) {
        /*
         * The GC journal head is not set, because it is the first GC
         * invocation since mount.
         */
        err = switch_gc_head(c);
        if (err)
            return err;
    }

    err = sort_nodes(c, sleb, &nondata, &min);
    if (err)
        goto out;

    /* Write nodes to their new location. Use the first-fit strategy */
    while (1) {
        int avail;
        struct ubifs_scan_node *snod, *tmp;

        /* Move data nodes */
        list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
            avail = c->leb_size - wbuf->offs - wbuf->used;
            if  (snod->len > avail)
                /*
                 * Do not skip data nodes in order to optimize
                 * bulk-read.
                 */
                break;

            err = move_node(c, sleb, snod, wbuf);
            if (err)
                goto out;
        }

        /* Move non-data nodes */
        list_for_each_entry_safe(snod, tmp, &nondata, list) {
            avail = c->leb_size - wbuf->offs - wbuf->used;
            if (avail < min)
                break;

            if  (snod->len > avail) {
                /*
                 * Keep going only if this is an inode with
                 * some data. Otherwise stop and switch the GC
                 * head. IOW, we assume that data-less inode
                 * nodes and direntry nodes are roughly of the
                 * same size.
                 */
                if (key_type(c, &snod->key) == UBIFS_DENT_KEY ||
                    snod->len == UBIFS_INO_NODE_SZ)
                    break;
                continue;
            }

            err = move_node(c, sleb, snod, wbuf);
            if (err)
                goto out;
        }

        if (list_empty(&sleb->nodes) && list_empty(&nondata))
            break;

        /*
         * Waste the rest of the space in the LEB and switch to the
         * next LEB.
         */
        err = switch_gc_head(c);
        if (err)
            goto out;
    }

    return 0;

out:
    list_splice_tail(&nondata, &sleb->nodes);
    return err;
}

static int gc_sync_wbufs(struct ubifs_info *c)
{
    int err, i;

    for (i = 0; i < c->jhead_cnt; i++) {
        if (i == GCHD)
            continue;
        err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
        if (err)
            return err;
    }
    return 0;
}

int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
{
    struct ubifs_scan_leb *sleb;
    struct ubifs_scan_node *snod;
    struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
    int err = 0, lnum = lp->lnum;

    ubifs_assert(c->gc_lnum != -1 || wbuf->offs + wbuf->used == 0 ||
             c->need_recovery);
    ubifs_assert(c->gc_lnum != lnum);
    ubifs_assert(wbuf->lnum != lnum);

    if (lp->free + lp->dirty == c->leb_size) {
        /* Special case - a free LEB  */
        dbg_gc("LEB %d is free, return it", lp->lnum);
        ubifs_assert(!(lp->flags & LPROPS_INDEX));

        if (lp->free != c->leb_size) {
            /*
             * Write buffers must be sync'd before unmapping
             * freeable LEBs, because one of them may contain data
             * which obsoletes something in 'lp->pnum'.
             */
            err = gc_sync_wbufs(c);
            if (err)
                return err;
            err = ubifs_change_one_lp(c, lp->lnum, c->leb_size,
                          0, 0, 0, 0);
            if (err)
                return err;
        }
        err = ubifs_leb_unmap(c, lp->lnum);
        if (err)
            return err;

        if (c->gc_lnum == -1) {
            c->gc_lnum = lnum;
            return LEB_RETAINED;
        }

        return LEB_FREED;
    }

    /*
     * We scan the entire LEB even though we only really need to scan up to
     * (c->leb_size - lp->free).
     */
    sleb = ubifs_scan(c, lnum, 0, c->sbuf, 0);
    if (IS_ERR(sleb))
        return PTR_ERR(sleb);

    ubifs_assert(!list_empty(&sleb->nodes));
    snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);

    if (snod->type == UBIFS_IDX_NODE) {
        struct ubifs_gced_idx_leb *idx_gc;

        dbg_gc("indexing LEB %d (free %d, dirty %d)",
               lnum, lp->free, lp->dirty);
        list_for_each_entry(snod, &sleb->nodes, list) {
            struct ubifs_idx_node *idx = snod->node;
            int level = le16_to_cpu(idx->level);

            ubifs_assert(snod->type == UBIFS_IDX_NODE);
            key_read(c, ubifs_idx_key(c, idx), &snod->key);
            err = ubifs_dirty_idx_node(c, &snod->key, level, lnum,
                           snod->offs);
            if (err)
                goto out;
        }

        idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
        if (!idx_gc) {
            err = -ENOMEM;
            goto out;
        }

        idx_gc->lnum = lnum;
        idx_gc->unmap = 0;
        list_add(&idx_gc->list, &c->idx_gc);

        /*
         * Don't release the LEB until after the next commit, because
         * it may contain data which is needed for recovery. So
         * although we freed this LEB, it will become usable only after
         * the commit.
         */
        err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0,
                      LPROPS_INDEX, 1);
        if (err)
            goto out;
        err = LEB_FREED_IDX;
    } else {
        dbg_gc("data LEB %d (free %d, dirty %d)",
               lnum, lp->free, lp->dirty);

        err = move_nodes(c, sleb);
        if (err)
            goto out_inc_seq;

        err = gc_sync_wbufs(c);
        if (err)
            goto out_inc_seq;

        err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0, 0, 0);
        if (err)
            goto out_inc_seq;

        /* Allow for races with TNC */
        c->gced_lnum = lnum;
        smp_wmb();
        c->gc_seq += 1;
        smp_wmb();

        if (c->gc_lnum == -1) {
            c->gc_lnum = lnum;
            err = LEB_RETAINED;
        } else {
            err = ubifs_wbuf_sync_nolock(wbuf);
            if (err)
                goto out;

            err = ubifs_leb_unmap(c, lnum);
            if (err)
                goto out;

            err = LEB_FREED;
        }
    }

out:
    ubifs_scan_destroy(sleb);
    return err;

out_inc_seq:
    /* We may have moved at least some nodes so allow for races with TNC */
    c->gced_lnum = lnum;
    smp_wmb();
    c->gc_seq += 1;
    smp_wmb();
    goto out;
}

int ubifs_garbage_collect(struct ubifs_info *c, int anyway)
{
    int i, err, ret, min_space = c->dead_wm;
    struct ubifs_lprops lp;
    struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;

    ubifs_assert_cmt_locked(c);
    ubifs_assert(!c->ro_media && !c->ro_mount);

    if (ubifs_gc_should_commit(c))
        return -EAGAIN;

    mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);

    if (c->ro_error) {
        ret = -EROFS;
        goto out_unlock;
    }

    /* We expect the write-buffer to be empty on entry */
    ubifs_assert(!wbuf->used);

    for (i = 0; ; i++) {
        int space_before = c->leb_size - wbuf->offs - wbuf->used;
        int space_after;

        cond_resched();

        /* Give the commit an opportunity to run */
        if (ubifs_gc_should_commit(c)) {
            ret = -EAGAIN;
            break;
        }

        if (i > SOFT_LEBS_LIMIT && !list_empty(&c->idx_gc)) {
            /*
             * We've done enough iterations. Indexing LEBs were
             * moved and will be available after the commit.
             */
            dbg_gc("soft limit, some index LEBs GC'ed, -EAGAIN");
            ubifs_commit_required(c);
            ret = -EAGAIN;
            break;
        }

        if (i > HARD_LEBS_LIMIT) {
            /*
             * We've moved too many LEBs and have not made
             * progress, give up.
             */
            dbg_gc("hard limit, -ENOSPC");
            ret = -ENOSPC;
            break;
        }

        /*
         * Empty and freeable LEBs can turn up while we waited for
         * the wbuf lock, or while we have been running GC. In that
         * case, we should just return one of those instead of
         * continuing to GC dirty LEBs. Hence we request
         * 'ubifs_find_dirty_leb()' to return an empty LEB if it can.
         */
        ret = ubifs_find_dirty_leb(c, &lp, min_space, anyway ? 0 : 1);
        if (ret) {
            if (ret == -ENOSPC)
                dbg_gc("no more dirty LEBs");
            break;
        }

        dbg_gc("found LEB %d: free %d, dirty %d, sum %d (min. space %d)",
               lp.lnum, lp.free, lp.dirty, lp.free + lp.dirty,
               min_space);

        space_before = c->leb_size - wbuf->offs - wbuf->used;
        if (wbuf->lnum == -1)
            space_before = 0;

        ret = ubifs_garbage_collect_leb(c, &lp);
        if (ret < 0) {
            if (ret == -EAGAIN) {
                /*
                 * This is not error, so we have to return the
                 * LEB to lprops. But if 'ubifs_return_leb()'
                 * fails, its failure code is propagated to the
                 * caller instead of the original '-EAGAIN'.
                 */
                err = ubifs_return_leb(c, lp.lnum);
                if (err)
                    ret = err;
                break;
            }
            goto out;
        }

        if (ret == LEB_FREED) {
            /* An LEB has been freed and is ready for use */
            dbg_gc("LEB %d freed, return", lp.lnum);
            ret = lp.lnum;
            break;
        }

        if (ret == LEB_FREED_IDX) {
            /*
             * This was an indexing LEB and it cannot be
             * immediately used. And instead of requesting the
             * commit straight away, we try to garbage collect some
             * more.
             */
            dbg_gc("indexing LEB %d freed, continue", lp.lnum);
            continue;
        }

        ubifs_assert(ret == LEB_RETAINED);
        space_after = c->leb_size - wbuf->offs - wbuf->used;
        dbg_gc("LEB %d retained, freed %d bytes", lp.lnum,
               space_after - space_before);

        if (space_after > space_before) {
            /* GC makes progress, keep working */
            min_space >>= 1;
            if (min_space < c->dead_wm)
                min_space = c->dead_wm;
            continue;
        }

        dbg_gc("did not make progress");

        /*
         * GC moved an LEB bud have not done any progress. This means
         * that the previous GC head LEB contained too few free space
         * and the LEB which was GC'ed contained only large nodes which
         * did not fit that space.
         *
         * We can do 2 things:
         * 1. pick another LEB in a hope it'll contain a small node
         *    which will fit the space we have at the end of current GC
         *    head LEB, but there is no guarantee, so we try this out
         *    unless we have already been working for too long;
         * 2. request an LEB with more dirty space, which will force
         *    'ubifs_find_dirty_leb()' to start scanning the lprops
         *    table, instead of just picking one from the heap
         *    (previously it already picked the dirtiest LEB).
         */
        if (i < SOFT_LEBS_LIMIT) {
            dbg_gc("try again");
            continue;
        }

        min_space <<= 1;
        if (min_space > c->dark_wm)
            min_space = c->dark_wm;
        dbg_gc("set min. space to %d", min_space);
    }

    if (ret == -ENOSPC && !list_empty(&c->idx_gc)) {
        dbg_gc("no space, some index LEBs GC'ed, -EAGAIN");
        ubifs_commit_required(c);
        ret = -EAGAIN;
    }

    err = ubifs_wbuf_sync_nolock(wbuf);
    if (!err)
        err = ubifs_leb_unmap(c, c->gc_lnum);
    if (err) {
        ret = err;
        goto out;
    }
out_unlock:
    mutex_unlock(&wbuf->io_mutex);
    return ret;

out:
    ubifs_assert(ret < 0);
    ubifs_assert(ret != -ENOSPC && ret != -EAGAIN);
    ubifs_wbuf_sync_nolock(wbuf);
    ubifs_ro_mode(c, ret);
    mutex_unlock(&wbuf->io_mutex);
    ubifs_return_leb(c, lp.lnum);
    return ret;
}

int ubifs_gc_start_commit(struct ubifs_info *c)
{
    struct ubifs_gced_idx_leb *idx_gc;
    const struct ubifs_lprops *lp;
    int err = 0, flags;

    ubifs_get_lprops(c);

    /*
     * Unmap (non-index) freeable LEBs. Note that recovery requires that all
     * wbufs are sync'd before this, which is done in 'do_commit()'.
     */
    while (1) {
        lp = ubifs_fast_find_freeable(c);
        if (IS_ERR(lp)) {
            err = PTR_ERR(lp);
            goto out;
        }
        if (!lp)
            break;
        ubifs_assert(!(lp->flags & LPROPS_TAKEN));
        ubifs_assert(!(lp->flags & LPROPS_INDEX));
        err = ubifs_leb_unmap(c, lp->lnum);
        if (err)
            goto out;
        lp = ubifs_change_lp(c, lp, c->leb_size, 0, lp->flags, 0);
        if (IS_ERR(lp)) {
            err = PTR_ERR(lp);
            goto out;
        }
        ubifs_assert(!(lp->flags & LPROPS_TAKEN));
        ubifs_assert(!(lp->flags & LPROPS_INDEX));
    }

    /* Mark GC'd index LEBs OK to unmap after this commit finishes */
    list_for_each_entry(idx_gc, &c->idx_gc, list)
        idx_gc->unmap = 1;

    /* Record index freeable LEBs for unmapping after commit */
    while (1) {
        lp = ubifs_fast_find_frdi_idx(c);
        if (IS_ERR(lp)) {
            err = PTR_ERR(lp);
            goto out;
        }
        if (!lp)
            break;
        idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
        if (!idx_gc) {
            err = -ENOMEM;
            goto out;
        }
        ubifs_assert(!(lp->flags & LPROPS_TAKEN));
        ubifs_assert(lp->flags & LPROPS_INDEX);
        /* Don't release the LEB until after the next commit */
        flags = (lp->flags | LPROPS_TAKEN) ^ LPROPS_INDEX;
        lp = ubifs_change_lp(c, lp, c->leb_size, 0, flags, 1);
        if (IS_ERR(lp)) {
            err = PTR_ERR(lp);
            kfree(idx_gc);
            goto out;
        }
        ubifs_assert(lp->flags & LPROPS_TAKEN);
        ubifs_assert(!(lp->flags & LPROPS_INDEX));
        idx_gc->lnum = lp->lnum;
        idx_gc->unmap = 1;
        list_add(&idx_gc->list, &c->idx_gc);
    }
out:
    ubifs_release_lprops(c);
    return err;
}

int ubifs_gc_end_commit(struct ubifs_info *c)
{
    struct ubifs_gced_idx_leb *idx_gc, *tmp;
    struct ubifs_wbuf *wbuf;
    int err = 0;

    wbuf = &c->jheads[GCHD].wbuf;
    mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
    list_for_each_entry_safe(idx_gc, tmp, &c->idx_gc, list)
        if (idx_gc->unmap) {
            dbg_gc("LEB %d", idx_gc->lnum);
            err = ubifs_leb_unmap(c, idx_gc->lnum);
            if (err)
                goto out;
            err = ubifs_change_one_lp(c, idx_gc->lnum, LPROPS_NC,
                      LPROPS_NC, 0, LPROPS_TAKEN, -1);
            if (err)
                goto out;
            list_del(&idx_gc->list);
            kfree(idx_gc);
        }
out:
    mutex_unlock(&wbuf->io_mutex);
    return err;
}

void ubifs_destroy_idx_gc(struct ubifs_info *c)
{
    while (!list_empty(&c->idx_gc)) {
        struct ubifs_gced_idx_leb *idx_gc;

        idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb,
                    list);
        c->idx_gc_cnt -= 1;
        list_del(&idx_gc->list);
        kfree(idx_gc);
    }
}

int ubifs_get_idx_gc_leb(struct ubifs_info *c)
{
    struct ubifs_gced_idx_leb *idx_gc;
    int lnum;

    if (list_empty(&c->idx_gc))
        return -ENOSPC;
    idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb, list);
    lnum = idx_gc->lnum;
    /* c->idx_gc_cnt is updated by the caller when lprops are updated */
    list_del(&idx_gc->list);
    kfree(idx_gc);
    return lnum;
}