ext4: fix error pointer dereference

[linux/fpc-iii.git] / fs / ubifs / log.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2006-2008 Nokia Corporation.
 *
 * Authors: Artem Bityutskiy (Битюцкий Артём)
 *          Adrian Hunter
 */

/*
 * This file is a part of UBIFS journal implementation and contains various
 * functions which manipulate the log. The log is a fixed area on the flash
 * which does not contain any data but refers to buds. The log is a part of the
 * journal.
 */

#include "ubifs.h"

static int dbg_check_bud_bytes(struct ubifs_info *c);

/**
 * ubifs_search_bud - search bud LEB.
 * @c: UBIFS file-system description object
 * @lnum: logical eraseblock number to search
 *
 * This function searches bud LEB @lnum. Returns bud description object in case
 * of success and %NULL if there is no bud with this LEB number.
 */
struct ubifs_bud *ubifs_search_bud(struct ubifs_info *c, int lnum)
{
        struct rb_node *p;
        struct ubifs_bud *bud;

        spin_lock(&c->buds_lock);
        p = c->buds.rb_node;
        while (p) {
                bud = rb_entry(p, struct ubifs_bud, rb);
                if (lnum < bud->lnum)
                        p = p->rb_left;
                else if (lnum > bud->lnum)
                        p = p->rb_right;
                else {
                        spin_unlock(&c->buds_lock);
                        return bud;
                }
        }
        spin_unlock(&c->buds_lock);
        return NULL;
}

/**
 * ubifs_get_wbuf - get the wbuf associated with a LEB, if there is one.
 * @c: UBIFS file-system description object
 * @lnum: logical eraseblock number to search
 *
 * This functions returns the wbuf for @lnum or %NULL if there is not one.
 */
struct ubifs_wbuf *ubifs_get_wbuf(struct ubifs_info *c, int lnum)
{
        struct rb_node *p;
        struct ubifs_bud *bud;
        int jhead;

        if (!c->jheads)
                return NULL;

        spin_lock(&c->buds_lock);
        p = c->buds.rb_node;
        while (p) {
                bud = rb_entry(p, struct ubifs_bud, rb);
                if (lnum < bud->lnum)
                        p = p->rb_left;
                else if (lnum > bud->lnum)
                        p = p->rb_right;
                else {
                        jhead = bud->jhead;
                        spin_unlock(&c->buds_lock);
                        return &c->jheads[jhead].wbuf;
                }
        }
        spin_unlock(&c->buds_lock);
        return NULL;
}

/**
 * empty_log_bytes - calculate amount of empty space in the log.
 * @c: UBIFS file-system description object
 */
static inline long long empty_log_bytes(const struct ubifs_info *c)
{
        long long h, t;

        h = (long long)c->lhead_lnum * c->leb_size + c->lhead_offs;
        t = (long long)c->ltail_lnum * c->leb_size;

        if (h > t)
                return c->log_bytes - h + t;
        else if (h != t)
                return t - h;
        else if (c->lhead_lnum != c->ltail_lnum)
                return 0;
        else
                return c->log_bytes;
}

/**
 * ubifs_add_bud - add bud LEB to the tree of buds and its journal head list.
 * @c: UBIFS file-system description object
 * @bud: the bud to add
 */
void ubifs_add_bud(struct ubifs_info *c, struct ubifs_bud *bud)
{
        struct rb_node **p, *parent = NULL;
        struct ubifs_bud *b;
        struct ubifs_jhead *jhead;

        spin_lock(&c->buds_lock);
        p = &c->buds.rb_node;
        while (*p) {
                parent = *p;
                b = rb_entry(parent, struct ubifs_bud, rb);
                ubifs_assert(c, bud->lnum != b->lnum);
                if (bud->lnum < b->lnum)
                        p = &(*p)->rb_left;
                else
                        p = &(*p)->rb_right;
        }

        rb_link_node(&bud->rb, parent, p);
        rb_insert_color(&bud->rb, &c->buds);
        if (c->jheads) {
                jhead = &c->jheads[bud->jhead];
                list_add_tail(&bud->list, &jhead->buds_list);
        } else
                ubifs_assert(c, c->replaying && c->ro_mount);

        /*
         * Note, although this is a new bud, we anyway account this space now,
         * before any data has been written to it, because this is about to
         * guarantee fixed mount time, and this bud will anyway be read and
         * scanned.
         */
        c->bud_bytes += c->leb_size - bud->start;

        dbg_log("LEB %d:%d, jhead %s, bud_bytes %lld", bud->lnum,
                bud->start, dbg_jhead(bud->jhead), c->bud_bytes);
        spin_unlock(&c->buds_lock);
}

/**
 * ubifs_add_bud_to_log - add a new bud to the log.
 * @c: UBIFS file-system description object
 * @jhead: journal head the bud belongs to
 * @lnum: LEB number of the bud
 * @offs: starting offset of the bud
 *
 * This function writes a reference node for the new bud LEB @lnum to the log,
 * and adds it to the buds trees. It also makes sure that log size does not
 * exceed the 'c->max_bud_bytes' limit. Returns zero in case of success,
 * %-EAGAIN if commit is required, and a negative error code in case of
 * failure.
 */
int ubifs_add_bud_to_log(struct ubifs_info *c, int jhead, int lnum, int offs)
{
        int err;
        struct ubifs_bud *bud;
        struct ubifs_ref_node *ref;

        bud = kmalloc(sizeof(struct ubifs_bud), GFP_NOFS);
        if (!bud)
                return -ENOMEM;
        ref = kzalloc(c->ref_node_alsz, GFP_NOFS);
        if (!ref) {
                kfree(bud);
                return -ENOMEM;
        }

        mutex_lock(&c->log_mutex);
        ubifs_assert(c, !c->ro_media && !c->ro_mount);
        if (c->ro_error) {
                err = -EROFS;
                goto out_unlock;
        }

        /* Make sure we have enough space in the log */
        if (empty_log_bytes(c) - c->ref_node_alsz < c->min_log_bytes) {
                dbg_log("not enough log space - %lld, required %d",
                        empty_log_bytes(c), c->min_log_bytes);
                ubifs_commit_required(c);
                err = -EAGAIN;
                goto out_unlock;
        }

        /*
         * Make sure the amount of space in buds will not exceed the
         * 'c->max_bud_bytes' limit, because we want to guarantee mount time
         * limits.
         *
         * It is not necessary to hold @c->buds_lock when reading @c->bud_bytes
         * because we are holding @c->log_mutex. All @c->bud_bytes take place
         * when both @c->log_mutex and @c->bud_bytes are locked.
         */
        if (c->bud_bytes + c->leb_size - offs > c->max_bud_bytes) {
                dbg_log("bud bytes %lld (%lld max), require commit",
                        c->bud_bytes, c->max_bud_bytes);
                ubifs_commit_required(c);
                err = -EAGAIN;
                goto out_unlock;
        }

        /*
         * If the journal is full enough - start background commit. Note, it is
         * OK to read 'c->cmt_state' without spinlock because integer reads
         * are atomic in the kernel.
         */
        if (c->bud_bytes >= c->bg_bud_bytes &&
            c->cmt_state == COMMIT_RESTING) {
                dbg_log("bud bytes %lld (%lld max), initiate BG commit",
                        c->bud_bytes, c->max_bud_bytes);
                ubifs_request_bg_commit(c);
        }

        bud->lnum = lnum;
        bud->start = offs;
        bud->jhead = jhead;
        bud->log_hash = NULL;

        ref->ch.node_type = UBIFS_REF_NODE;
        ref->lnum = cpu_to_le32(bud->lnum);
        ref->offs = cpu_to_le32(bud->start);
        ref->jhead = cpu_to_le32(jhead);

        if (c->lhead_offs > c->leb_size - c->ref_node_alsz) {
                c->lhead_lnum = ubifs_next_log_lnum(c, c->lhead_lnum);
                ubifs_assert(c, c->lhead_lnum != c->ltail_lnum);
                c->lhead_offs = 0;
        }

        if (c->lhead_offs == 0) {
                /* Must ensure next log LEB has been unmapped */
                err = ubifs_leb_unmap(c, c->lhead_lnum);
                if (err)
                        goto out_unlock;
        }

        if (bud->start == 0) {
                /*
                 * Before writing the LEB reference which refers an empty LEB
                 * to the log, we have to make sure it is mapped, because
                 * otherwise we'd risk to refer an LEB with garbage in case of
                 * an unclean reboot, because the target LEB might have been
                 * unmapped, but not yet physically erased.
                 */
                err = ubifs_leb_map(c, bud->lnum);
                if (err)
                        goto out_unlock;
        }

        dbg_log("write ref LEB %d:%d",
                c->lhead_lnum, c->lhead_offs);
        err = ubifs_write_node(c, ref, UBIFS_REF_NODE_SZ, c->lhead_lnum,
                               c->lhead_offs);
        if (err)
                goto out_unlock;

        err = ubifs_shash_update(c, c->log_hash, ref, UBIFS_REF_NODE_SZ);
        if (err)
                goto out_unlock;

        err = ubifs_shash_copy_state(c, c->log_hash, c->jheads[jhead].log_hash);
        if (err)
                goto out_unlock;

        c->lhead_offs += c->ref_node_alsz;

        ubifs_add_bud(c, bud);

        mutex_unlock(&c->log_mutex);
        kfree(ref);
        return 0;

out_unlock:
        mutex_unlock(&c->log_mutex);
        kfree(ref);
        kfree(bud);
        return err;
}

/**
 * remove_buds - remove used buds.
 * @c: UBIFS file-system description object
 *
 * This function removes use buds from the buds tree. It does not remove the
 * buds which are pointed to by journal heads.
 */
static void remove_buds(struct ubifs_info *c)
{
        struct rb_node *p;

        ubifs_assert(c, list_empty(&c->old_buds));
        c->cmt_bud_bytes = 0;
        spin_lock(&c->buds_lock);
        p = rb_first(&c->buds);
        while (p) {
                struct rb_node *p1 = p;
                struct ubifs_bud *bud;
                struct ubifs_wbuf *wbuf;

                p = rb_next(p);
                bud = rb_entry(p1, struct ubifs_bud, rb);
                wbuf = &c->jheads[bud->jhead].wbuf;

                if (wbuf->lnum == bud->lnum) {
                        /*
                         * Do not remove buds which are pointed to by journal
                         * heads (non-closed buds).
                         */
                        c->cmt_bud_bytes += wbuf->offs - bud->start;
                        dbg_log("preserve %d:%d, jhead %s, bud bytes %d, cmt_bud_bytes %lld",
                                bud->lnum, bud->start, dbg_jhead(bud->jhead),
                                wbuf->offs - bud->start, c->cmt_bud_bytes);
                        bud->start = wbuf->offs;
                } else {
                        c->cmt_bud_bytes += c->leb_size - bud->start;
                        dbg_log("remove %d:%d, jhead %s, bud bytes %d, cmt_bud_bytes %lld",
                                bud->lnum, bud->start, dbg_jhead(bud->jhead),
                                c->leb_size - bud->start, c->cmt_bud_bytes);
                        rb_erase(p1, &c->buds);
                        /*
                         * If the commit does not finish, the recovery will need
                         * to replay the journal, in which case the old buds
                         * must be unchanged. Do not release them until post
                         * commit i.e. do not allow them to be garbage
                         * collected.
                         */
                        list_move(&bud->list, &c->old_buds);
                }
        }
        spin_unlock(&c->buds_lock);
}

/**
 * ubifs_log_start_commit - start commit.
 * @c: UBIFS file-system description object
 * @ltail_lnum: return new log tail LEB number
 *
 * The commit operation starts with writing "commit start" node to the log and
 * reference nodes for all journal heads which will define new journal after
 * the commit has been finished. The commit start and reference nodes are
 * written in one go to the nearest empty log LEB (hence, when commit is
 * finished UBIFS may safely unmap all the previous log LEBs). This function
 * returns zero in case of success and a negative error code in case of
 * failure.
 */
int ubifs_log_start_commit(struct ubifs_info *c, int *ltail_lnum)
{
        void *buf;
        struct ubifs_cs_node *cs;
        struct ubifs_ref_node *ref;
        int err, i, max_len, len;

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

        max_len = UBIFS_CS_NODE_SZ + c->jhead_cnt * UBIFS_REF_NODE_SZ;
        max_len = ALIGN(max_len, c->min_io_size);
        buf = cs = kmalloc(max_len, GFP_NOFS);
        if (!buf)
                return -ENOMEM;

        cs->ch.node_type = UBIFS_CS_NODE;
        cs->cmt_no = cpu_to_le64(c->cmt_no);
        ubifs_prepare_node(c, cs, UBIFS_CS_NODE_SZ, 0);

        err = ubifs_shash_init(c, c->log_hash);
        if (err)
                goto out;

        err = ubifs_shash_update(c, c->log_hash, cs, UBIFS_CS_NODE_SZ);
        if (err < 0)
                goto out;

        /*
         * Note, we do not lock 'c->log_mutex' because this is the commit start
         * phase and we are exclusively using the log. And we do not lock
         * write-buffer because nobody can write to the file-system at this
         * phase.
         */

        len = UBIFS_CS_NODE_SZ;
        for (i = 0; i < c->jhead_cnt; i++) {
                int lnum = c->jheads[i].wbuf.lnum;
                int offs = c->jheads[i].wbuf.offs;

                if (lnum == -1 || offs == c->leb_size)
                        continue;

                dbg_log("add ref to LEB %d:%d for jhead %s",
                        lnum, offs, dbg_jhead(i));
                ref = buf + len;
                ref->ch.node_type = UBIFS_REF_NODE;
                ref->lnum = cpu_to_le32(lnum);
                ref->offs = cpu_to_le32(offs);
                ref->jhead = cpu_to_le32(i);

                ubifs_prepare_node(c, ref, UBIFS_REF_NODE_SZ, 0);
                len += UBIFS_REF_NODE_SZ;

                err = ubifs_shash_update(c, c->log_hash, ref,
                                         UBIFS_REF_NODE_SZ);
                if (err)
                        goto out;
                ubifs_shash_copy_state(c, c->log_hash, c->jheads[i].log_hash);
        }

        ubifs_pad(c, buf + len, ALIGN(len, c->min_io_size) - len);

        /* Switch to the next log LEB */
        if (c->lhead_offs) {
                c->lhead_lnum = ubifs_next_log_lnum(c, c->lhead_lnum);
                ubifs_assert(c, c->lhead_lnum != c->ltail_lnum);
                c->lhead_offs = 0;
        }

        /* Must ensure next LEB has been unmapped */
        err = ubifs_leb_unmap(c, c->lhead_lnum);
        if (err)
                goto out;

        len = ALIGN(len, c->min_io_size);
        dbg_log("writing commit start at LEB %d:0, len %d", c->lhead_lnum, len);
        err = ubifs_leb_write(c, c->lhead_lnum, cs, 0, len);
        if (err)
                goto out;

        *ltail_lnum = c->lhead_lnum;

        c->lhead_offs += len;
        ubifs_assert(c, c->lhead_offs < c->leb_size);

        remove_buds(c);

        /*
         * We have started the commit and now users may use the rest of the log
         * for new writes.
         */
        c->min_log_bytes = 0;

out:
        kfree(buf);
        return err;
}

/**
 * ubifs_log_end_commit - end commit.
 * @c: UBIFS file-system description object
 * @ltail_lnum: new log tail LEB number
 *
 * This function is called on when the commit operation was finished. It
 * moves log tail to new position and updates the master node so that it stores
 * the new log tail LEB number. Returns zero in case of success and a negative
 * error code in case of failure.
 */
int ubifs_log_end_commit(struct ubifs_info *c, int ltail_lnum)
{
        int err;

        /*
         * At this phase we have to lock 'c->log_mutex' because UBIFS allows FS
         * writes during commit. Its only short "commit" start phase when
         * writers are blocked.
         */
        mutex_lock(&c->log_mutex);

        dbg_log("old tail was LEB %d:0, new tail is LEB %d:0",
                c->ltail_lnum, ltail_lnum);

        c->ltail_lnum = ltail_lnum;
        /*
         * The commit is finished and from now on it must be guaranteed that
         * there is always enough space for the next commit.
         */
        c->min_log_bytes = c->leb_size;

        spin_lock(&c->buds_lock);
        c->bud_bytes -= c->cmt_bud_bytes;
        spin_unlock(&c->buds_lock);

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

        err = ubifs_write_master(c);

out:
        mutex_unlock(&c->log_mutex);
        return err;
}

/**
 * ubifs_log_post_commit - things to do after commit is completed.
 * @c: UBIFS file-system description object
 * @old_ltail_lnum: old log tail LEB number
 *
 * Release buds only after commit is completed, because they must be unchanged
 * if recovery is needed.
 *
 * Unmap log LEBs only after commit is completed, because they may be needed for
 * recovery.
 *
 * This function returns %0 on success and a negative error code on failure.
 */
int ubifs_log_post_commit(struct ubifs_info *c, int old_ltail_lnum)
{
        int lnum, err = 0;

        while (!list_empty(&c->old_buds)) {
                struct ubifs_bud *bud;

                bud = list_entry(c->old_buds.next, struct ubifs_bud, list);
                err = ubifs_return_leb(c, bud->lnum);
                if (err)
                        return err;
                list_del(&bud->list);
                kfree(bud->log_hash);
                kfree(bud);
        }
        mutex_lock(&c->log_mutex);
        for (lnum = old_ltail_lnum; lnum != c->ltail_lnum;
             lnum = ubifs_next_log_lnum(c, lnum)) {
                dbg_log("unmap log LEB %d", lnum);
                err = ubifs_leb_unmap(c, lnum);
                if (err)
                        goto out;
        }
out:
        mutex_unlock(&c->log_mutex);
        return err;
}

/**
 * struct done_ref - references that have been done.
 * @rb: rb-tree node
 * @lnum: LEB number
 */
struct done_ref {
        struct rb_node rb;
        int lnum;
};

/**
 * done_already - determine if a reference has been done already.
 * @done_tree: rb-tree to store references that have been done
 * @lnum: LEB number of reference
 *
 * This function returns %1 if the reference has been done, %0 if not, otherwise
 * a negative error code is returned.
 */
static int done_already(struct rb_root *done_tree, int lnum)
{
        struct rb_node **p = &done_tree->rb_node, *parent = NULL;
        struct done_ref *dr;

        while (*p) {
                parent = *p;
                dr = rb_entry(parent, struct done_ref, rb);
                if (lnum < dr->lnum)
                        p = &(*p)->rb_left;
                else if (lnum > dr->lnum)
                        p = &(*p)->rb_right;
                else
                        return 1;
        }

        dr = kzalloc(sizeof(struct done_ref), GFP_NOFS);
        if (!dr)
                return -ENOMEM;

        dr->lnum = lnum;

        rb_link_node(&dr->rb, parent, p);
        rb_insert_color(&dr->rb, done_tree);

        return 0;
}

/**
 * destroy_done_tree - destroy the done tree.
 * @done_tree: done tree to destroy
 */
static void destroy_done_tree(struct rb_root *done_tree)
{
        struct done_ref *dr, *n;

        rbtree_postorder_for_each_entry_safe(dr, n, done_tree, rb)
                kfree(dr);
}

/**
 * add_node - add a node to the consolidated log.
 * @c: UBIFS file-system description object
 * @buf: buffer to which to add
 * @lnum: LEB number to which to write is passed and returned here
 * @offs: offset to where to write is passed and returned here
 * @node: node to add
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int add_node(struct ubifs_info *c, void *buf, int *lnum, int *offs,
                    void *node)
{
        struct ubifs_ch *ch = node;
        int len = le32_to_cpu(ch->len), remains = c->leb_size - *offs;

        if (len > remains) {
                int sz = ALIGN(*offs, c->min_io_size), err;

                ubifs_pad(c, buf + *offs, sz - *offs);
                err = ubifs_leb_change(c, *lnum, buf, sz);
                if (err)
                        return err;
                *lnum = ubifs_next_log_lnum(c, *lnum);
                *offs = 0;
        }
        memcpy(buf + *offs, node, len);
        *offs += ALIGN(len, 8);
        return 0;
}

/**
 * ubifs_consolidate_log - consolidate the log.
 * @c: UBIFS file-system description object
 *
 * Repeated failed commits could cause the log to be full, but at least 1 LEB is
 * needed for commit. This function rewrites the reference nodes in the log
 * omitting duplicates, and failed CS nodes, and leaving no gaps.
 *
 * This function returns %0 on success and a negative error code on failure.
 */
int ubifs_consolidate_log(struct ubifs_info *c)
{
        struct ubifs_scan_leb *sleb;
        struct ubifs_scan_node *snod;
        struct rb_root done_tree = RB_ROOT;
        int lnum, err, first = 1, write_lnum, offs = 0;
        void *buf;

        dbg_rcvry("log tail LEB %d, log head LEB %d", c->ltail_lnum,
                  c->lhead_lnum);
        buf = vmalloc(c->leb_size);
        if (!buf)
                return -ENOMEM;
        lnum = c->ltail_lnum;
        write_lnum = lnum;
        while (1) {
                sleb = ubifs_scan(c, lnum, 0, c->sbuf, 0);
                if (IS_ERR(sleb)) {
                        err = PTR_ERR(sleb);
                        goto out_free;
                }
                list_for_each_entry(snod, &sleb->nodes, list) {
                        switch (snod->type) {
                        case UBIFS_REF_NODE: {
                                struct ubifs_ref_node *ref = snod->node;
                                int ref_lnum = le32_to_cpu(ref->lnum);

                                err = done_already(&done_tree, ref_lnum);
                                if (err < 0)
                                        goto out_scan;
                                if (err != 1) {
                                        err = add_node(c, buf, &write_lnum,
                                                       &offs, snod->node);
                                        if (err)
                                                goto out_scan;
                                }
                                break;
                        }
                        case UBIFS_CS_NODE:
                                if (!first)
                                        break;
                                err = add_node(c, buf, &write_lnum, &offs,
                                               snod->node);
                                if (err)
                                        goto out_scan;
                                first = 0;
                                break;
                        }
                }
                ubifs_scan_destroy(sleb);
                if (lnum == c->lhead_lnum)
                        break;
                lnum = ubifs_next_log_lnum(c, lnum);
        }
        if (offs) {
                int sz = ALIGN(offs, c->min_io_size);

                ubifs_pad(c, buf + offs, sz - offs);
                err = ubifs_leb_change(c, write_lnum, buf, sz);
                if (err)
                        goto out_free;
                offs = ALIGN(offs, c->min_io_size);
        }
        destroy_done_tree(&done_tree);
        vfree(buf);
        if (write_lnum == c->lhead_lnum) {
                ubifs_err(c, "log is too full");
                return -EINVAL;
        }
        /* Unmap remaining LEBs */
        lnum = write_lnum;
        do {
                lnum = ubifs_next_log_lnum(c, lnum);
                err = ubifs_leb_unmap(c, lnum);
                if (err)
                        return err;
        } while (lnum != c->lhead_lnum);
        c->lhead_lnum = write_lnum;
        c->lhead_offs = offs;
        dbg_rcvry("new log head at %d:%d", c->lhead_lnum, c->lhead_offs);
        return 0;

out_scan:
        ubifs_scan_destroy(sleb);
out_free:
        destroy_done_tree(&done_tree);
        vfree(buf);
        return err;
}

/**
 * dbg_check_bud_bytes - make sure bud bytes calculation are all right.
 * @c: UBIFS file-system description object
 *
 * This function makes sure the amount of flash space used by closed buds
 * ('c->bud_bytes' is correct). Returns zero in case of success and %-EINVAL in
 * case of failure.
 */
static int dbg_check_bud_bytes(struct ubifs_info *c)
{
        int i, err = 0;
        struct ubifs_bud *bud;
        long long bud_bytes = 0;

        if (!dbg_is_chk_gen(c))
                return 0;

        spin_lock(&c->buds_lock);
        for (i = 0; i < c->jhead_cnt; i++)
                list_for_each_entry(bud, &c->jheads[i].buds_list, list)
                        bud_bytes += c->leb_size - bud->start;

        if (c->bud_bytes != bud_bytes) {
                ubifs_err(c, "bad bud_bytes %lld, calculated %lld",
                          c->bud_bytes, bud_bytes);
                err = -EINVAL;
        }
        spin_unlock(&c->buds_lock);

        return err;
}