Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target...

[linux-btrfs-devel.git] / fs / ubifs / replay.c

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

/*
 * This file contains journal replay code. It runs when the file-system is being
 * mounted and requires no locking.
 *
 * The larger is the journal, the longer it takes to scan it, so the longer it
 * takes to mount UBIFS. This is why the journal has limited size which may be
 * changed depending on the system requirements. But a larger journal gives
 * faster I/O speed because it writes the index less frequently. So this is a
 * trade-off. Also, the journal is indexed by the in-memory index (TNC), so the
 * larger is the journal, the more memory its index may consume.
 */

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

/**
 * struct replay_entry - replay list entry.
 * @lnum: logical eraseblock number of the node
 * @offs: node offset
 * @len: node length
 * @deletion: non-zero if this entry corresponds to a node deletion
 * @sqnum: node sequence number
 * @list: links the replay list
 * @key: node key
 * @nm: directory entry name
 * @old_size: truncation old size
 * @new_size: truncation new size
 *
 * The replay process first scans all buds and builds the replay list, then
 * sorts the replay list in nodes sequence number order, and then inserts all
 * the replay entries to the TNC.
 */
struct replay_entry {
        int lnum;
        int offs;
        int len;
        unsigned int deletion:1;
        unsigned long long sqnum;
        struct list_head list;
        union ubifs_key key;
        union {
                struct qstr nm;
                struct {
                        loff_t old_size;
                        loff_t new_size;
                };
        };
};

/**
 * struct bud_entry - entry in the list of buds to replay.
 * @list: next bud in the list
 * @bud: bud description object
 * @sqnum: reference node sequence number
 * @free: free bytes in the bud
 * @dirty: dirty bytes in the bud
 */
struct bud_entry {
        struct list_head list;
        struct ubifs_bud *bud;
        unsigned long long sqnum;
        int free;
        int dirty;
};

/**
 * set_bud_lprops - set free and dirty space used by a bud.
 * @c: UBIFS file-system description object
 * @b: bud entry which describes the bud
 *
 * This function makes sure the LEB properties of bud @b are set correctly
 * after the replay. Returns zero in case of success and a negative error code
 * in case of failure.
 */
static int set_bud_lprops(struct ubifs_info *c, struct bud_entry *b)
{
        const struct ubifs_lprops *lp;
        int err = 0, dirty;

        ubifs_get_lprops(c);

        lp = ubifs_lpt_lookup_dirty(c, b->bud->lnum);
        if (IS_ERR(lp)) {
                err = PTR_ERR(lp);
                goto out;
        }

        dirty = lp->dirty;
        if (b->bud->start == 0 && (lp->free != c->leb_size || lp->dirty != 0)) {
                /*
                 * The LEB was added to the journal with a starting offset of
                 * zero which means the LEB must have been empty. The LEB
                 * property values should be @lp->free == @c->leb_size and
                 * @lp->dirty == 0, but that is not the case. The reason is that
                 * the LEB had been garbage collected before it became the bud,
                 * and there was not commit inbetween. The garbage collector
                 * resets the free and dirty space without recording it
                 * anywhere except lprops, so if there was no commit then
                 * lprops does not have that information.
                 *
                 * We do not need to adjust free space because the scan has told
                 * us the exact value which is recorded in the replay entry as
                 * @b->free.
                 *
                 * However we do need to subtract from the dirty space the
                 * amount of space that the garbage collector reclaimed, which
                 * is the whole LEB minus the amount of space that was free.
                 */
                dbg_mnt("bud LEB %d was GC'd (%d free, %d dirty)", b->bud->lnum,
                        lp->free, lp->dirty);
                dbg_gc("bud LEB %d was GC'd (%d free, %d dirty)", b->bud->lnum,
                        lp->free, lp->dirty);
                dirty -= c->leb_size - lp->free;
                /*
                 * If the replay order was perfect the dirty space would now be
                 * zero. The order is not perfect because the journal heads
                 * race with each other. This is not a problem but is does mean
                 * that the dirty space may temporarily exceed c->leb_size
                 * during the replay.
                 */
                if (dirty != 0)
                        dbg_msg("LEB %d lp: %d free %d dirty "
                                "replay: %d free %d dirty", b->bud->lnum,
                                lp->free, lp->dirty, b->free, b->dirty);
        }
        lp = ubifs_change_lp(c, lp, b->free, dirty + b->dirty,
                             lp->flags | LPROPS_TAKEN, 0);
        if (IS_ERR(lp)) {
                err = PTR_ERR(lp);
                goto out;
        }

        /* Make sure the journal head points to the latest bud */
        err = ubifs_wbuf_seek_nolock(&c->jheads[b->bud->jhead].wbuf,
                                     b->bud->lnum, c->leb_size - b->free,
                                     UBI_SHORTTERM);

out:
        ubifs_release_lprops(c);
        return err;
}

/**
 * set_buds_lprops - set free and dirty space for all replayed buds.
 * @c: UBIFS file-system description object
 *
 * This function sets LEB properties for all replayed buds. Returns zero in
 * case of success and a negative error code in case of failure.
 */
static int set_buds_lprops(struct ubifs_info *c)
{
        struct bud_entry *b;
        int err;

        list_for_each_entry(b, &c->replay_buds, list) {
                err = set_bud_lprops(c, b);
                if (err)
                        return err;
        }

        return 0;
}

/**
 * trun_remove_range - apply a replay entry for a truncation to the TNC.
 * @c: UBIFS file-system description object
 * @r: replay entry of truncation
 */
static int trun_remove_range(struct ubifs_info *c, struct replay_entry *r)
{
        unsigned min_blk, max_blk;
        union ubifs_key min_key, max_key;
        ino_t ino;

        min_blk = r->new_size / UBIFS_BLOCK_SIZE;
        if (r->new_size & (UBIFS_BLOCK_SIZE - 1))
                min_blk += 1;

        max_blk = r->old_size / UBIFS_BLOCK_SIZE;
        if ((r->old_size & (UBIFS_BLOCK_SIZE - 1)) == 0)
                max_blk -= 1;

        ino = key_inum(c, &r->key);

        data_key_init(c, &min_key, ino, min_blk);
        data_key_init(c, &max_key, ino, max_blk);

        return ubifs_tnc_remove_range(c, &min_key, &max_key);
}

/**
 * apply_replay_entry - apply a replay entry to the TNC.
 * @c: UBIFS file-system description object
 * @r: replay entry to apply
 *
 * Apply a replay entry to the TNC.
 */
static int apply_replay_entry(struct ubifs_info *c, struct replay_entry *r)
{
        int err;

        dbg_mnt("LEB %d:%d len %d deletion %d sqnum %llu %s", r->lnum,
                r->offs, r->len, r->deletion, r->sqnum, DBGKEY(&r->key));

        /* Set c->replay_sqnum to help deal with dangling branches. */
        c->replay_sqnum = r->sqnum;

        if (is_hash_key(c, &r->key)) {
                if (r->deletion)
                        err = ubifs_tnc_remove_nm(c, &r->key, &r->nm);
                else
                        err = ubifs_tnc_add_nm(c, &r->key, r->lnum, r->offs,
                                               r->len, &r->nm);
        } else {
                if (r->deletion)
                        switch (key_type(c, &r->key)) {
                        case UBIFS_INO_KEY:
                        {
                                ino_t inum = key_inum(c, &r->key);

                                err = ubifs_tnc_remove_ino(c, inum);
                                break;
                        }
                        case UBIFS_TRUN_KEY:
                                err = trun_remove_range(c, r);
                                break;
                        default:
                                err = ubifs_tnc_remove(c, &r->key);
                                break;
                        }
                else
                        err = ubifs_tnc_add(c, &r->key, r->lnum, r->offs,
                                            r->len);
                if (err)
                        return err;

                if (c->need_recovery)
                        err = ubifs_recover_size_accum(c, &r->key, r->deletion,
                                                       r->new_size);
        }

        return err;
}

/**
 * replay_entries_cmp - compare 2 replay entries.
 * @priv: UBIFS file-system description object
 * @a: first replay entry
 * @a: second replay entry
 *
 * This is a comparios function for 'list_sort()' which compares 2 replay
 * entries @a and @b by comparing their sequence numer.  Returns %1 if @a has
 * greater sequence number and %-1 otherwise.
 */
static int replay_entries_cmp(void *priv, struct list_head *a,
                              struct list_head *b)
{
        struct replay_entry *ra, *rb;

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

        ra = list_entry(a, struct replay_entry, list);
        rb = list_entry(b, struct replay_entry, list);
        ubifs_assert(ra->sqnum != rb->sqnum);
        if (ra->sqnum > rb->sqnum)
                return 1;
        return -1;
}

/**
 * apply_replay_list - apply the replay list to the TNC.
 * @c: UBIFS file-system description object
 *
 * Apply all entries in the replay list to the TNC. Returns zero in case of
 * success and a negative error code in case of failure.
 */
static int apply_replay_list(struct ubifs_info *c)
{
        struct replay_entry *r;
        int err;

        list_sort(c, &c->replay_list, &replay_entries_cmp);

        list_for_each_entry(r, &c->replay_list, list) {
                cond_resched();

                err = apply_replay_entry(c, r);
                if (err)
                        return err;
        }

        return 0;
}

/**
 * destroy_replay_list - destroy the replay.
 * @c: UBIFS file-system description object
 *
 * Destroy the replay list.
 */
static void destroy_replay_list(struct ubifs_info *c)
{
        struct replay_entry *r, *tmp;

        list_for_each_entry_safe(r, tmp, &c->replay_list, list) {
                if (is_hash_key(c, &r->key))
                        kfree(r->nm.name);
                list_del(&r->list);
                kfree(r);
        }
}

/**
 * insert_node - insert a node to the replay list
 * @c: UBIFS file-system description object
 * @lnum: node logical eraseblock number
 * @offs: node offset
 * @len: node length
 * @key: node key
 * @sqnum: sequence number
 * @deletion: non-zero if this is a deletion
 * @used: number of bytes in use in a LEB
 * @old_size: truncation old size
 * @new_size: truncation new size
 *
 * This function inserts a scanned non-direntry node to the replay list. The
 * replay list contains @struct replay_entry elements, and we sort this list in
 * sequence number order before applying it. The replay list is applied at the
 * very end of the replay process. Since the list is sorted in sequence number
 * order, the older modifications are applied first. This function returns zero
 * in case of success and a negative error code in case of failure.
 */
static int insert_node(struct ubifs_info *c, int lnum, int offs, int len,
                       union ubifs_key *key, unsigned long long sqnum,
                       int deletion, int *used, loff_t old_size,
                       loff_t new_size)
{
        struct replay_entry *r;

        dbg_mnt("add LEB %d:%d, key %s", lnum, offs, DBGKEY(key));

        if (key_inum(c, key) >= c->highest_inum)
                c->highest_inum = key_inum(c, key);

        r = kzalloc(sizeof(struct replay_entry), GFP_KERNEL);
        if (!r)
                return -ENOMEM;

        if (!deletion)
                *used += ALIGN(len, 8);
        r->lnum = lnum;
        r->offs = offs;
        r->len = len;
        r->deletion = !!deletion;
        r->sqnum = sqnum;
        key_copy(c, key, &r->key);
        r->old_size = old_size;
        r->new_size = new_size;

        list_add_tail(&r->list, &c->replay_list);
        return 0;
}

/**
 * insert_dent - insert a directory entry node into the replay list.
 * @c: UBIFS file-system description object
 * @lnum: node logical eraseblock number
 * @offs: node offset
 * @len: node length
 * @key: node key
 * @name: directory entry name
 * @nlen: directory entry name length
 * @sqnum: sequence number
 * @deletion: non-zero if this is a deletion
 * @used: number of bytes in use in a LEB
 *
 * This function inserts a scanned directory entry node or an extended
 * attribute entry to the replay list. Returns zero in case of success and a
 * negative error code in case of failure.
 */
static int insert_dent(struct ubifs_info *c, int lnum, int offs, int len,
                       union ubifs_key *key, const char *name, int nlen,
                       unsigned long long sqnum, int deletion, int *used)
{
        struct replay_entry *r;
        char *nbuf;

        dbg_mnt("add LEB %d:%d, key %s", lnum, offs, DBGKEY(key));
        if (key_inum(c, key) >= c->highest_inum)
                c->highest_inum = key_inum(c, key);

        r = kzalloc(sizeof(struct replay_entry), GFP_KERNEL);
        if (!r)
                return -ENOMEM;

        nbuf = kmalloc(nlen + 1, GFP_KERNEL);
        if (!nbuf) {
                kfree(r);
                return -ENOMEM;
        }

        if (!deletion)
                *used += ALIGN(len, 8);
        r->lnum = lnum;
        r->offs = offs;
        r->len = len;
        r->deletion = !!deletion;
        r->sqnum = sqnum;
        key_copy(c, key, &r->key);
        r->nm.len = nlen;
        memcpy(nbuf, name, nlen);
        nbuf[nlen] = '\0';
        r->nm.name = nbuf;

        list_add_tail(&r->list, &c->replay_list);
        return 0;
}

/**
 * ubifs_validate_entry - validate directory or extended attribute entry node.
 * @c: UBIFS file-system description object
 * @dent: the node to validate
 *
 * This function validates directory or extended attribute entry node @dent.
 * Returns zero if the node is all right and a %-EINVAL if not.
 */
int ubifs_validate_entry(struct ubifs_info *c,
                         const struct ubifs_dent_node *dent)
{
        int key_type = key_type_flash(c, dent->key);
        int nlen = le16_to_cpu(dent->nlen);

        if (le32_to_cpu(dent->ch.len) != nlen + UBIFS_DENT_NODE_SZ + 1 ||
            dent->type >= UBIFS_ITYPES_CNT ||
            nlen > UBIFS_MAX_NLEN || dent->name[nlen] != 0 ||
            strnlen(dent->name, nlen) != nlen ||
            le64_to_cpu(dent->inum) > MAX_INUM) {
                ubifs_err("bad %s node", key_type == UBIFS_DENT_KEY ?
                          "directory entry" : "extended attribute entry");
                return -EINVAL;
        }

        if (key_type != UBIFS_DENT_KEY && key_type != UBIFS_XENT_KEY) {
                ubifs_err("bad key type %d", key_type);
                return -EINVAL;
        }

        return 0;
}

/**
 * is_last_bud - check if the bud is the last in the journal head.
 * @c: UBIFS file-system description object
 * @bud: bud description object
 *
 * This function checks if bud @bud is the last bud in its journal head. This
 * information is then used by 'replay_bud()' to decide whether the bud can
 * have corruptions or not. Indeed, only last buds can be corrupted by power
 * cuts. Returns %1 if this is the last bud, and %0 if not.
 */
static int is_last_bud(struct ubifs_info *c, struct ubifs_bud *bud)
{
        struct ubifs_jhead *jh = &c->jheads[bud->jhead];
        struct ubifs_bud *next;
        uint32_t data;
        int err;

        if (list_is_last(&bud->list, &jh->buds_list))
                return 1;

        /*
         * The following is a quirk to make sure we work correctly with UBIFS
         * images used with older UBIFS.
         *
         * Normally, the last bud will be the last in the journal head's list
         * of bud. However, there is one exception if the UBIFS image belongs
         * to older UBIFS. This is fairly unlikely: one would need to use old
         * UBIFS, then have a power cut exactly at the right point, and then
         * try to mount this image with new UBIFS.
         *
         * The exception is: it is possible to have 2 buds A and B, A goes
         * before B, and B is the last, bud B is contains no data, and bud A is
         * corrupted at the end. The reason is that in older versions when the
         * journal code switched the next bud (from A to B), it first added a
         * log reference node for the new bud (B), and only after this it
         * synchronized the write-buffer of current bud (A). But later this was
         * changed and UBIFS started to always synchronize the write-buffer of
         * the bud (A) before writing the log reference for the new bud (B).
         *
         * But because older UBIFS always synchronized A's write-buffer before
         * writing to B, we can recognize this exceptional situation but
         * checking the contents of bud B - if it is empty, then A can be
         * treated as the last and we can recover it.
         *
         * TODO: remove this piece of code in a couple of years (today it is
         * 16.05.2011).
         */
        next = list_entry(bud->list.next, struct ubifs_bud, list);
        if (!list_is_last(&next->list, &jh->buds_list))
                return 0;

        err = ubifs_leb_read(c, next->lnum, (char *)&data, next->start, 4, 1);
        if (err)
                return 0;

        return data == 0xFFFFFFFF;
}

/**
 * replay_bud - replay a bud logical eraseblock.
 * @c: UBIFS file-system description object
 * @b: bud entry which describes the bud
 *
 * This function replays bud @bud, recovers it if needed, and adds all nodes
 * from this bud to the replay list. Returns zero in case of success and a
 * negative error code in case of failure.
 */
static int replay_bud(struct ubifs_info *c, struct bud_entry *b)
{
        int is_last = is_last_bud(c, b->bud);
        int err = 0, used = 0, lnum = b->bud->lnum, offs = b->bud->start;
        struct ubifs_scan_leb *sleb;
        struct ubifs_scan_node *snod;

        dbg_mnt("replay bud LEB %d, head %d, offs %d, is_last %d",
                lnum, b->bud->jhead, offs, is_last);

        if (c->need_recovery && is_last)
                /*
                 * Recover only last LEBs in the journal heads, because power
                 * cuts may cause corruptions only in these LEBs, because only
                 * these LEBs could possibly be written to at the power cut
                 * time.
                 */
                sleb = ubifs_recover_leb(c, lnum, offs, c->sbuf, b->bud->jhead);
        else
                sleb = ubifs_scan(c, lnum, offs, c->sbuf, 0);
        if (IS_ERR(sleb))
                return PTR_ERR(sleb);

        /*
         * The bud does not have to start from offset zero - the beginning of
         * the 'lnum' LEB may contain previously committed data. One of the
         * things we have to do in replay is to correctly update lprops with
         * newer information about this LEB.
         *
         * At this point lprops thinks that this LEB has 'c->leb_size - offs'
         * bytes of free space because it only contain information about
         * committed data.
         *
         * But we know that real amount of free space is 'c->leb_size -
         * sleb->endpt', and the space in the 'lnum' LEB between 'offs' and
         * 'sleb->endpt' is used by bud data. We have to correctly calculate
         * how much of these data are dirty and update lprops with this
         * information.
         *
         * The dirt in that LEB region is comprised of padding nodes, deletion
         * nodes, truncation nodes and nodes which are obsoleted by subsequent
         * nodes in this LEB. So instead of calculating clean space, we
         * calculate used space ('used' variable).
         */

        list_for_each_entry(snod, &sleb->nodes, list) {
                int deletion = 0;

                cond_resched();

                if (snod->sqnum >= SQNUM_WATERMARK) {
                        ubifs_err("file system's life ended");
                        goto out_dump;
                }

                if (snod->sqnum > c->max_sqnum)
                        c->max_sqnum = snod->sqnum;

                switch (snod->type) {
                case UBIFS_INO_NODE:
                {
                        struct ubifs_ino_node *ino = snod->node;
                        loff_t new_size = le64_to_cpu(ino->size);

                        if (le32_to_cpu(ino->nlink) == 0)
                                deletion = 1;
                        err = insert_node(c, lnum, snod->offs, snod->len,
                                          &snod->key, snod->sqnum, deletion,
                                          &used, 0, new_size);
                        break;
                }
                case UBIFS_DATA_NODE:
                {
                        struct ubifs_data_node *dn = snod->node;
                        loff_t new_size = le32_to_cpu(dn->size) +
                                          key_block(c, &snod->key) *
                                          UBIFS_BLOCK_SIZE;

                        err = insert_node(c, lnum, snod->offs, snod->len,
                                          &snod->key, snod->sqnum, deletion,
                                          &used, 0, new_size);
                        break;
                }
                case UBIFS_DENT_NODE:
                case UBIFS_XENT_NODE:
                {
                        struct ubifs_dent_node *dent = snod->node;

                        err = ubifs_validate_entry(c, dent);
                        if (err)
                                goto out_dump;

                        err = insert_dent(c, lnum, snod->offs, snod->len,
                                          &snod->key, dent->name,
                                          le16_to_cpu(dent->nlen), snod->sqnum,
                                          !le64_to_cpu(dent->inum), &used);
                        break;
                }
                case UBIFS_TRUN_NODE:
                {
                        struct ubifs_trun_node *trun = snod->node;
                        loff_t old_size = le64_to_cpu(trun->old_size);
                        loff_t new_size = le64_to_cpu(trun->new_size);
                        union ubifs_key key;

                        /* Validate truncation node */
                        if (old_size < 0 || old_size > c->max_inode_sz ||
                            new_size < 0 || new_size > c->max_inode_sz ||
                            old_size <= new_size) {
                                ubifs_err("bad truncation node");
                                goto out_dump;
                        }

                        /*
                         * Create a fake truncation key just to use the same
                         * functions which expect nodes to have keys.
                         */
                        trun_key_init(c, &key, le32_to_cpu(trun->inum));
                        err = insert_node(c, lnum, snod->offs, snod->len,
                                          &key, snod->sqnum, 1, &used,
                                          old_size, new_size);
                        break;
                }
                default:
                        ubifs_err("unexpected node type %d in bud LEB %d:%d",
                                  snod->type, lnum, snod->offs);
                        err = -EINVAL;
                        goto out_dump;
                }
                if (err)
                        goto out;
        }

        ubifs_assert(ubifs_search_bud(c, lnum));
        ubifs_assert(sleb->endpt - offs >= used);
        ubifs_assert(sleb->endpt % c->min_io_size == 0);

        b->dirty = sleb->endpt - offs - used;
        b->free = c->leb_size - sleb->endpt;
        dbg_mnt("bud LEB %d replied: dirty %d, free %d", lnum, b->dirty, b->free);

out:
        ubifs_scan_destroy(sleb);
        return err;

out_dump:
        ubifs_err("bad node is at LEB %d:%d", lnum, snod->offs);
        dbg_dump_node(c, snod->node);
        ubifs_scan_destroy(sleb);
        return -EINVAL;
}

/**
 * replay_buds - replay all buds.
 * @c: UBIFS file-system description object
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int replay_buds(struct ubifs_info *c)
{
        struct bud_entry *b;
        int err;
        unsigned long long prev_sqnum = 0;

        list_for_each_entry(b, &c->replay_buds, list) {
                err = replay_bud(c, b);
                if (err)
                        return err;

                ubifs_assert(b->sqnum > prev_sqnum);
                prev_sqnum = b->sqnum;
        }

        return 0;
}

/**
 * destroy_bud_list - destroy the list of buds to replay.
 * @c: UBIFS file-system description object
 */
static void destroy_bud_list(struct ubifs_info *c)
{
        struct bud_entry *b;

        while (!list_empty(&c->replay_buds)) {
                b = list_entry(c->replay_buds.next, struct bud_entry, list);
                list_del(&b->list);
                kfree(b);
        }
}

/**
 * add_replay_bud - add a bud to the list of buds to replay.
 * @c: UBIFS file-system description object
 * @lnum: bud logical eraseblock number to replay
 * @offs: bud start offset
 * @jhead: journal head to which this bud belongs
 * @sqnum: reference node sequence number
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int add_replay_bud(struct ubifs_info *c, int lnum, int offs, int jhead,
                          unsigned long long sqnum)
{
        struct ubifs_bud *bud;
        struct bud_entry *b;

        dbg_mnt("add replay bud LEB %d:%d, head %d", lnum, offs, jhead);

        bud = kmalloc(sizeof(struct ubifs_bud), GFP_KERNEL);
        if (!bud)
                return -ENOMEM;

        b = kmalloc(sizeof(struct bud_entry), GFP_KERNEL);
        if (!b) {
                kfree(bud);
                return -ENOMEM;
        }

        bud->lnum = lnum;
        bud->start = offs;
        bud->jhead = jhead;
        ubifs_add_bud(c, bud);

        b->bud = bud;
        b->sqnum = sqnum;
        list_add_tail(&b->list, &c->replay_buds);

        return 0;
}

/**
 * validate_ref - validate a reference node.
 * @c: UBIFS file-system description object
 * @ref: the reference node to validate
 * @ref_lnum: LEB number of the reference node
 * @ref_offs: reference node offset
 *
 * This function returns %1 if a bud reference already exists for the LEB. %0 is
 * returned if the reference node is new, otherwise %-EINVAL is returned if
 * validation failed.
 */
static int validate_ref(struct ubifs_info *c, const struct ubifs_ref_node *ref)
{
        struct ubifs_bud *bud;
        int lnum = le32_to_cpu(ref->lnum);
        unsigned int offs = le32_to_cpu(ref->offs);
        unsigned int jhead = le32_to_cpu(ref->jhead);

        /*
         * ref->offs may point to the end of LEB when the journal head points
         * to the end of LEB and we write reference node for it during commit.
         * So this is why we require 'offs > c->leb_size'.
         */
        if (jhead >= c->jhead_cnt || lnum >= c->leb_cnt ||
            lnum < c->main_first || offs > c->leb_size ||
            offs & (c->min_io_size - 1))
                return -EINVAL;

        /* Make sure we have not already looked at this bud */
        bud = ubifs_search_bud(c, lnum);
        if (bud) {
                if (bud->jhead == jhead && bud->start <= offs)
                        return 1;
                ubifs_err("bud at LEB %d:%d was already referred", lnum, offs);
                return -EINVAL;
        }

        return 0;
}

/**
 * replay_log_leb - replay a log logical eraseblock.
 * @c: UBIFS file-system description object
 * @lnum: log logical eraseblock to replay
 * @offs: offset to start replaying from
 * @sbuf: scan buffer
 *
 * This function replays a log LEB and returns zero in case of success, %1 if
 * this is the last LEB in the log, and a negative error code in case of
 * failure.
 */
static int replay_log_leb(struct ubifs_info *c, int lnum, int offs, void *sbuf)
{
        int err;
        struct ubifs_scan_leb *sleb;
        struct ubifs_scan_node *snod;
        const struct ubifs_cs_node *node;

        dbg_mnt("replay log LEB %d:%d", lnum, offs);
        sleb = ubifs_scan(c, lnum, offs, sbuf, c->need_recovery);
        if (IS_ERR(sleb)) {
                if (PTR_ERR(sleb) != -EUCLEAN || !c->need_recovery)
                        return PTR_ERR(sleb);
                /*
                 * Note, the below function will recover this log LEB only if
                 * it is the last, because unclean reboots can possibly corrupt
                 * only the tail of the log.
                 */
                sleb = ubifs_recover_log_leb(c, lnum, offs, sbuf);
                if (IS_ERR(sleb))
                        return PTR_ERR(sleb);
        }

        if (sleb->nodes_cnt == 0) {
                err = 1;
                goto out;
        }

        node = sleb->buf;
        snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
        if (c->cs_sqnum == 0) {
                /*
                 * This is the first log LEB we are looking at, make sure that
                 * the first node is a commit start node. Also record its
                 * sequence number so that UBIFS can determine where the log
                 * ends, because all nodes which were have higher sequence
                 * numbers.
                 */
                if (snod->type != UBIFS_CS_NODE) {
                        dbg_err("first log node at LEB %d:%d is not CS node",
                                lnum, offs);
                        goto out_dump;
                }
                if (le64_to_cpu(node->cmt_no) != c->cmt_no) {
                        dbg_err("first CS node at LEB %d:%d has wrong "
                                "commit number %llu expected %llu",
                                lnum, offs,
                                (unsigned long long)le64_to_cpu(node->cmt_no),
                                c->cmt_no);
                        goto out_dump;
                }

                c->cs_sqnum = le64_to_cpu(node->ch.sqnum);
                dbg_mnt("commit start sqnum %llu", c->cs_sqnum);
        }

        if (snod->sqnum < c->cs_sqnum) {
                /*
                 * This means that we reached end of log and now
                 * look to the older log data, which was already
                 * committed but the eraseblock was not erased (UBIFS
                 * only un-maps it). So this basically means we have to
                 * exit with "end of log" code.
                 */
                err = 1;
                goto out;
        }

        /* Make sure the first node sits at offset zero of the LEB */
        if (snod->offs != 0) {
                dbg_err("first node is not at zero offset");
                goto out_dump;
        }

        list_for_each_entry(snod, &sleb->nodes, list) {
                cond_resched();

                if (snod->sqnum >= SQNUM_WATERMARK) {
                        ubifs_err("file system's life ended");
                        goto out_dump;
                }

                if (snod->sqnum < c->cs_sqnum) {
                        dbg_err("bad sqnum %llu, commit sqnum %llu",
                                snod->sqnum, c->cs_sqnum);
                        goto out_dump;
                }

                if (snod->sqnum > c->max_sqnum)
                        c->max_sqnum = snod->sqnum;

                switch (snod->type) {
                case UBIFS_REF_NODE: {
                        const struct ubifs_ref_node *ref = snod->node;

                        err = validate_ref(c, ref);
                        if (err == 1)
                                break; /* Already have this bud */
                        if (err)
                                goto out_dump;

                        err = add_replay_bud(c, le32_to_cpu(ref->lnum),
                                             le32_to_cpu(ref->offs),
                                             le32_to_cpu(ref->jhead),
                                             snod->sqnum);
                        if (err)
                                goto out;

                        break;
                }
                case UBIFS_CS_NODE:
                        /* Make sure it sits at the beginning of LEB */
                        if (snod->offs != 0) {
                                ubifs_err("unexpected node in log");
                                goto out_dump;
                        }
                        break;
                default:
                        ubifs_err("unexpected node in log");
                        goto out_dump;
                }
        }

        if (sleb->endpt || c->lhead_offs >= c->leb_size) {
                c->lhead_lnum = lnum;
                c->lhead_offs = sleb->endpt;
        }

        err = !sleb->endpt;
out:
        ubifs_scan_destroy(sleb);
        return err;

out_dump:
        ubifs_err("log error detected while replaying the log at LEB %d:%d",
                  lnum, offs + snod->offs);
        dbg_dump_node(c, snod->node);
        ubifs_scan_destroy(sleb);
        return -EINVAL;
}

/**
 * take_ihead - update the status of the index head in lprops to 'taken'.
 * @c: UBIFS file-system description object
 *
 * This function returns the amount of free space in the index head LEB or a
 * negative error code.
 */
static int take_ihead(struct ubifs_info *c)
{
        const struct ubifs_lprops *lp;
        int err, free;

        ubifs_get_lprops(c);

        lp = ubifs_lpt_lookup_dirty(c, c->ihead_lnum);
        if (IS_ERR(lp)) {
                err = PTR_ERR(lp);
                goto out;
        }

        free = lp->free;

        lp = ubifs_change_lp(c, lp, LPROPS_NC, LPROPS_NC,
                             lp->flags | LPROPS_TAKEN, 0);
        if (IS_ERR(lp)) {
                err = PTR_ERR(lp);
                goto out;
        }

        err = free;
out:
        ubifs_release_lprops(c);
        return err;
}

/**
 * ubifs_replay_journal - replay journal.
 * @c: UBIFS file-system description object
 *
 * This function scans the journal, replays and cleans it up. It makes sure all
 * memory data structures related to uncommitted journal are built (dirty TNC
 * tree, tree of buds, modified lprops, etc).
 */
int ubifs_replay_journal(struct ubifs_info *c)
{
        int err, i, lnum, offs, free;

        BUILD_BUG_ON(UBIFS_TRUN_KEY > 5);

        /* Update the status of the index head in lprops to 'taken' */
        free = take_ihead(c);
        if (free < 0)
                return free; /* Error code */

        if (c->ihead_offs != c->leb_size - free) {
                ubifs_err("bad index head LEB %d:%d", c->ihead_lnum,
                          c->ihead_offs);
                return -EINVAL;
        }

        dbg_mnt("start replaying the journal");
        c->replaying = 1;
        lnum = c->ltail_lnum = c->lhead_lnum;
        offs = c->lhead_offs;

        for (i = 0; i < c->log_lebs; i++, lnum++) {
                if (lnum >= UBIFS_LOG_LNUM + c->log_lebs) {
                        /*
                         * The log is logically circular, we reached the last
                         * LEB, switch to the first one.
                         */
                        lnum = UBIFS_LOG_LNUM;
                        offs = 0;
                }
                err = replay_log_leb(c, lnum, offs, c->sbuf);
                if (err == 1)
                        /* We hit the end of the log */
                        break;
                if (err)
                        goto out;
                offs = 0;
        }

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

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

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

        /*
         * UBIFS budgeting calculations use @c->bi.uncommitted_idx variable
         * to roughly estimate index growth. Things like @c->bi.min_idx_lebs
         * depend on it. This means we have to initialize it to make sure
         * budgeting works properly.
         */
        c->bi.uncommitted_idx = atomic_long_read(&c->dirty_zn_cnt);
        c->bi.uncommitted_idx *= c->max_idx_node_sz;

        ubifs_assert(c->bud_bytes <= c->max_bud_bytes || c->need_recovery);
        dbg_mnt("finished, log head LEB %d:%d, max_sqnum %llu, "
                "highest_inum %lu", c->lhead_lnum, c->lhead_offs, c->max_sqnum,
                (unsigned long)c->highest_inum);
out:
        destroy_replay_list(c);
        destroy_bud_list(c);
        c->replaying = 0;
        return err;
}