Merge tag 'perf-urgent-for-mingo-4.20-20181106' of git://git.kernel.org/pub/scm/linux...

[mirror_ubuntu-eoan-kernel.git] / fs / ubifs / lpt_commit.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 implements commit-related functionality of the LEB properties
 * subsystem.
 */

#include <linux/crc16.h>
#include <linux/slab.h>
#include <linux/random.h>
#include "ubifs.h"

static int dbg_populate_lsave(struct ubifs_info *c);

/**
 * first_dirty_cnode - find first dirty cnode.
 * @c: UBIFS file-system description object
 * @nnode: nnode at which to start
 *
 * This function returns the first dirty cnode or %NULL if there is not one.
 */
static struct ubifs_cnode *first_dirty_cnode(const struct ubifs_info *c, struct ubifs_nnode *nnode)
{
        ubifs_assert(c, nnode);
        while (1) {
                int i, cont = 0;

                for (i = 0; i < UBIFS_LPT_FANOUT; i++) {
                        struct ubifs_cnode *cnode;

                        cnode = nnode->nbranch[i].cnode;
                        if (cnode &&
                            test_bit(DIRTY_CNODE, &cnode->flags)) {
                                if (cnode->level == 0)
                                        return cnode;
                                nnode = (struct ubifs_nnode *)cnode;
                                cont = 1;
                                break;
                        }
                }
                if (!cont)
                        return (struct ubifs_cnode *)nnode;
        }
}

/**
 * next_dirty_cnode - find next dirty cnode.
 * @c: UBIFS file-system description object
 * @cnode: cnode from which to begin searching
 *
 * This function returns the next dirty cnode or %NULL if there is not one.
 */
static struct ubifs_cnode *next_dirty_cnode(const struct ubifs_info *c, struct ubifs_cnode *cnode)
{
        struct ubifs_nnode *nnode;
        int i;

        ubifs_assert(c, cnode);
        nnode = cnode->parent;
        if (!nnode)
                return NULL;
        for (i = cnode->iip + 1; i < UBIFS_LPT_FANOUT; i++) {
                cnode = nnode->nbranch[i].cnode;
                if (cnode && test_bit(DIRTY_CNODE, &cnode->flags)) {
                        if (cnode->level == 0)
                                return cnode; /* cnode is a pnode */
                        /* cnode is a nnode */
                        return first_dirty_cnode(c, (struct ubifs_nnode *)cnode);
                }
        }
        return (struct ubifs_cnode *)nnode;
}

/**
 * get_cnodes_to_commit - create list of dirty cnodes to commit.
 * @c: UBIFS file-system description object
 *
 * This function returns the number of cnodes to commit.
 */
static int get_cnodes_to_commit(struct ubifs_info *c)
{
        struct ubifs_cnode *cnode, *cnext;
        int cnt = 0;

        if (!c->nroot)
                return 0;

        if (!test_bit(DIRTY_CNODE, &c->nroot->flags))
                return 0;

        c->lpt_cnext = first_dirty_cnode(c, c->nroot);
        cnode = c->lpt_cnext;
        if (!cnode)
                return 0;
        cnt += 1;
        while (1) {
                ubifs_assert(c, !test_bit(COW_CNODE, &cnode->flags));
                __set_bit(COW_CNODE, &cnode->flags);
                cnext = next_dirty_cnode(c, cnode);
                if (!cnext) {
                        cnode->cnext = c->lpt_cnext;
                        break;
                }
                cnode->cnext = cnext;
                cnode = cnext;
                cnt += 1;
        }
        dbg_cmt("committing %d cnodes", cnt);
        dbg_lp("committing %d cnodes", cnt);
        ubifs_assert(c, cnt == c->dirty_nn_cnt + c->dirty_pn_cnt);
        return cnt;
}

/**
 * upd_ltab - update LPT LEB properties.
 * @c: UBIFS file-system description object
 * @lnum: LEB number
 * @free: amount of free space
 * @dirty: amount of dirty space to add
 */
static void upd_ltab(struct ubifs_info *c, int lnum, int free, int dirty)
{
        dbg_lp("LEB %d free %d dirty %d to %d +%d",
               lnum, c->ltab[lnum - c->lpt_first].free,
               c->ltab[lnum - c->lpt_first].dirty, free, dirty);
        ubifs_assert(c, lnum >= c->lpt_first && lnum <= c->lpt_last);
        c->ltab[lnum - c->lpt_first].free = free;
        c->ltab[lnum - c->lpt_first].dirty += dirty;
}

/**
 * alloc_lpt_leb - allocate an LPT LEB that is empty.
 * @c: UBIFS file-system description object
 * @lnum: LEB number is passed and returned here
 *
 * This function finds the next empty LEB in the ltab starting from @lnum. If a
 * an empty LEB is found it is returned in @lnum and the function returns %0.
 * Otherwise the function returns -ENOSPC.  Note however, that LPT is designed
 * never to run out of space.
 */
static int alloc_lpt_leb(struct ubifs_info *c, int *lnum)
{
        int i, n;

        n = *lnum - c->lpt_first + 1;
        for (i = n; i < c->lpt_lebs; i++) {
                if (c->ltab[i].tgc || c->ltab[i].cmt)
                        continue;
                if (c->ltab[i].free == c->leb_size) {
                        c->ltab[i].cmt = 1;
                        *lnum = i + c->lpt_first;
                        return 0;
                }
        }

        for (i = 0; i < n; i++) {
                if (c->ltab[i].tgc || c->ltab[i].cmt)
                        continue;
                if (c->ltab[i].free == c->leb_size) {
                        c->ltab[i].cmt = 1;
                        *lnum = i + c->lpt_first;
                        return 0;
                }
        }
        return -ENOSPC;
}

/**
 * layout_cnodes - layout cnodes for commit.
 * @c: UBIFS file-system description object
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int layout_cnodes(struct ubifs_info *c)
{
        int lnum, offs, len, alen, done_lsave, done_ltab, err;
        struct ubifs_cnode *cnode;

        err = dbg_chk_lpt_sz(c, 0, 0);
        if (err)
                return err;
        cnode = c->lpt_cnext;
        if (!cnode)
                return 0;
        lnum = c->nhead_lnum;
        offs = c->nhead_offs;
        /* Try to place lsave and ltab nicely */
        done_lsave = !c->big_lpt;
        done_ltab = 0;
        if (!done_lsave && offs + c->lsave_sz <= c->leb_size) {
                done_lsave = 1;
                c->lsave_lnum = lnum;
                c->lsave_offs = offs;
                offs += c->lsave_sz;
                dbg_chk_lpt_sz(c, 1, c->lsave_sz);
        }

        if (offs + c->ltab_sz <= c->leb_size) {
                done_ltab = 1;
                c->ltab_lnum = lnum;
                c->ltab_offs = offs;
                offs += c->ltab_sz;
                dbg_chk_lpt_sz(c, 1, c->ltab_sz);
        }

        do {
                if (cnode->level) {
                        len = c->nnode_sz;
                        c->dirty_nn_cnt -= 1;
                } else {
                        len = c->pnode_sz;
                        c->dirty_pn_cnt -= 1;
                }
                while (offs + len > c->leb_size) {
                        alen = ALIGN(offs, c->min_io_size);
                        upd_ltab(c, lnum, c->leb_size - alen, alen - offs);
                        dbg_chk_lpt_sz(c, 2, c->leb_size - offs);
                        err = alloc_lpt_leb(c, &lnum);
                        if (err)
                                goto no_space;
                        offs = 0;
                        ubifs_assert(c, lnum >= c->lpt_first &&
                                     lnum <= c->lpt_last);
                        /* Try to place lsave and ltab nicely */
                        if (!done_lsave) {
                                done_lsave = 1;
                                c->lsave_lnum = lnum;
                                c->lsave_offs = offs;
                                offs += c->lsave_sz;
                                dbg_chk_lpt_sz(c, 1, c->lsave_sz);
                                continue;
                        }
                        if (!done_ltab) {
                                done_ltab = 1;
                                c->ltab_lnum = lnum;
                                c->ltab_offs = offs;
                                offs += c->ltab_sz;
                                dbg_chk_lpt_sz(c, 1, c->ltab_sz);
                                continue;
                        }
                        break;
                }
                if (cnode->parent) {
                        cnode->parent->nbranch[cnode->iip].lnum = lnum;
                        cnode->parent->nbranch[cnode->iip].offs = offs;
                } else {
                        c->lpt_lnum = lnum;
                        c->lpt_offs = offs;
                }
                offs += len;
                dbg_chk_lpt_sz(c, 1, len);
                cnode = cnode->cnext;
        } while (cnode && cnode != c->lpt_cnext);

        /* Make sure to place LPT's save table */
        if (!done_lsave) {
                if (offs + c->lsave_sz > c->leb_size) {
                        alen = ALIGN(offs, c->min_io_size);
                        upd_ltab(c, lnum, c->leb_size - alen, alen - offs);
                        dbg_chk_lpt_sz(c, 2, c->leb_size - offs);
                        err = alloc_lpt_leb(c, &lnum);
                        if (err)
                                goto no_space;
                        offs = 0;
                        ubifs_assert(c, lnum >= c->lpt_first &&
                                     lnum <= c->lpt_last);
                }
                done_lsave = 1;
                c->lsave_lnum = lnum;
                c->lsave_offs = offs;
                offs += c->lsave_sz;
                dbg_chk_lpt_sz(c, 1, c->lsave_sz);
        }

        /* Make sure to place LPT's own lprops table */
        if (!done_ltab) {
                if (offs + c->ltab_sz > c->leb_size) {
                        alen = ALIGN(offs, c->min_io_size);
                        upd_ltab(c, lnum, c->leb_size - alen, alen - offs);
                        dbg_chk_lpt_sz(c, 2, c->leb_size - offs);
                        err = alloc_lpt_leb(c, &lnum);
                        if (err)
                                goto no_space;
                        offs = 0;
                        ubifs_assert(c, lnum >= c->lpt_first &&
                                     lnum <= c->lpt_last);
                }
                c->ltab_lnum = lnum;
                c->ltab_offs = offs;
                offs += c->ltab_sz;
                dbg_chk_lpt_sz(c, 1, c->ltab_sz);
        }

        alen = ALIGN(offs, c->min_io_size);
        upd_ltab(c, lnum, c->leb_size - alen, alen - offs);
        dbg_chk_lpt_sz(c, 4, alen - offs);
        err = dbg_chk_lpt_sz(c, 3, alen);
        if (err)
                return err;
        return 0;

no_space:
        ubifs_err(c, "LPT out of space at LEB %d:%d needing %d, done_ltab %d, done_lsave %d",
                  lnum, offs, len, done_ltab, done_lsave);
        ubifs_dump_lpt_info(c);
        ubifs_dump_lpt_lebs(c);
        dump_stack();
        return err;
}

/**
 * realloc_lpt_leb - allocate an LPT LEB that is empty.
 * @c: UBIFS file-system description object
 * @lnum: LEB number is passed and returned here
 *
 * This function duplicates exactly the results of the function alloc_lpt_leb.
 * It is used during end commit to reallocate the same LEB numbers that were
 * allocated by alloc_lpt_leb during start commit.
 *
 * This function finds the next LEB that was allocated by the alloc_lpt_leb
 * function starting from @lnum. If a LEB is found it is returned in @lnum and
 * the function returns %0. Otherwise the function returns -ENOSPC.
 * Note however, that LPT is designed never to run out of space.
 */
static int realloc_lpt_leb(struct ubifs_info *c, int *lnum)
{
        int i, n;

        n = *lnum - c->lpt_first + 1;
        for (i = n; i < c->lpt_lebs; i++)
                if (c->ltab[i].cmt) {
                        c->ltab[i].cmt = 0;
                        *lnum = i + c->lpt_first;
                        return 0;
                }

        for (i = 0; i < n; i++)
                if (c->ltab[i].cmt) {
                        c->ltab[i].cmt = 0;
                        *lnum = i + c->lpt_first;
                        return 0;
                }
        return -ENOSPC;
}

/**
 * write_cnodes - write cnodes for commit.
 * @c: UBIFS file-system description object
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int write_cnodes(struct ubifs_info *c)
{
        int lnum, offs, len, from, err, wlen, alen, done_ltab, done_lsave;
        struct ubifs_cnode *cnode;
        void *buf = c->lpt_buf;

        cnode = c->lpt_cnext;
        if (!cnode)
                return 0;
        lnum = c->nhead_lnum;
        offs = c->nhead_offs;
        from = offs;
        /* Ensure empty LEB is unmapped */
        if (offs == 0) {
                err = ubifs_leb_unmap(c, lnum);
                if (err)
                        return err;
        }
        /* Try to place lsave and ltab nicely */
        done_lsave = !c->big_lpt;
        done_ltab = 0;
        if (!done_lsave && offs + c->lsave_sz <= c->leb_size) {
                done_lsave = 1;
                ubifs_pack_lsave(c, buf + offs, c->lsave);
                offs += c->lsave_sz;
                dbg_chk_lpt_sz(c, 1, c->lsave_sz);
        }

        if (offs + c->ltab_sz <= c->leb_size) {
                done_ltab = 1;
                ubifs_pack_ltab(c, buf + offs, c->ltab_cmt);
                offs += c->ltab_sz;
                dbg_chk_lpt_sz(c, 1, c->ltab_sz);
        }

        /* Loop for each cnode */
        do {
                if (cnode->level)
                        len = c->nnode_sz;
                else
                        len = c->pnode_sz;
                while (offs + len > c->leb_size) {
                        wlen = offs - from;
                        if (wlen) {
                                alen = ALIGN(wlen, c->min_io_size);
                                memset(buf + offs, 0xff, alen - wlen);
                                err = ubifs_leb_write(c, lnum, buf + from, from,
                                                       alen);
                                if (err)
                                        return err;
                        }
                        dbg_chk_lpt_sz(c, 2, c->leb_size - offs);
                        err = realloc_lpt_leb(c, &lnum);
                        if (err)
                                goto no_space;
                        offs = from = 0;
                        ubifs_assert(c, lnum >= c->lpt_first &&
                                     lnum <= c->lpt_last);
                        err = ubifs_leb_unmap(c, lnum);
                        if (err)
                                return err;
                        /* Try to place lsave and ltab nicely */
                        if (!done_lsave) {
                                done_lsave = 1;
                                ubifs_pack_lsave(c, buf + offs, c->lsave);
                                offs += c->lsave_sz;
                                dbg_chk_lpt_sz(c, 1, c->lsave_sz);
                                continue;
                        }
                        if (!done_ltab) {
                                done_ltab = 1;
                                ubifs_pack_ltab(c, buf + offs, c->ltab_cmt);
                                offs += c->ltab_sz;
                                dbg_chk_lpt_sz(c, 1, c->ltab_sz);
                                continue;
                        }
                        break;
                }
                if (cnode->level)
                        ubifs_pack_nnode(c, buf + offs,
                                         (struct ubifs_nnode *)cnode);
                else
                        ubifs_pack_pnode(c, buf + offs,
                                         (struct ubifs_pnode *)cnode);
                /*
                 * The reason for the barriers is the same as in case of TNC.
                 * See comment in 'write_index()'. 'dirty_cow_nnode()' and
                 * 'dirty_cow_pnode()' are the functions for which this is
                 * important.
                 */
                clear_bit(DIRTY_CNODE, &cnode->flags);
                smp_mb__before_atomic();
                clear_bit(COW_CNODE, &cnode->flags);
                smp_mb__after_atomic();
                offs += len;
                dbg_chk_lpt_sz(c, 1, len);
                cnode = cnode->cnext;
        } while (cnode && cnode != c->lpt_cnext);

        /* Make sure to place LPT's save table */
        if (!done_lsave) {
                if (offs + c->lsave_sz > c->leb_size) {
                        wlen = offs - from;
                        alen = ALIGN(wlen, c->min_io_size);
                        memset(buf + offs, 0xff, alen - wlen);
                        err = ubifs_leb_write(c, lnum, buf + from, from, alen);
                        if (err)
                                return err;
                        dbg_chk_lpt_sz(c, 2, c->leb_size - offs);
                        err = realloc_lpt_leb(c, &lnum);
                        if (err)
                                goto no_space;
                        offs = from = 0;
                        ubifs_assert(c, lnum >= c->lpt_first &&
                                     lnum <= c->lpt_last);
                        err = ubifs_leb_unmap(c, lnum);
                        if (err)
                                return err;
                }
                done_lsave = 1;
                ubifs_pack_lsave(c, buf + offs, c->lsave);
                offs += c->lsave_sz;
                dbg_chk_lpt_sz(c, 1, c->lsave_sz);
        }

        /* Make sure to place LPT's own lprops table */
        if (!done_ltab) {
                if (offs + c->ltab_sz > c->leb_size) {
                        wlen = offs - from;
                        alen = ALIGN(wlen, c->min_io_size);
                        memset(buf + offs, 0xff, alen - wlen);
                        err = ubifs_leb_write(c, lnum, buf + from, from, alen);
                        if (err)
                                return err;
                        dbg_chk_lpt_sz(c, 2, c->leb_size - offs);
                        err = realloc_lpt_leb(c, &lnum);
                        if (err)
                                goto no_space;
                        offs = from = 0;
                        ubifs_assert(c, lnum >= c->lpt_first &&
                                     lnum <= c->lpt_last);
                        err = ubifs_leb_unmap(c, lnum);
                        if (err)
                                return err;
                }
                ubifs_pack_ltab(c, buf + offs, c->ltab_cmt);
                offs += c->ltab_sz;
                dbg_chk_lpt_sz(c, 1, c->ltab_sz);
        }

        /* Write remaining data in buffer */
        wlen = offs - from;
        alen = ALIGN(wlen, c->min_io_size);
        memset(buf + offs, 0xff, alen - wlen);
        err = ubifs_leb_write(c, lnum, buf + from, from, alen);
        if (err)
                return err;

        dbg_chk_lpt_sz(c, 4, alen - wlen);
        err = dbg_chk_lpt_sz(c, 3, ALIGN(offs, c->min_io_size));
        if (err)
                return err;

        c->nhead_lnum = lnum;
        c->nhead_offs = ALIGN(offs, c->min_io_size);

        dbg_lp("LPT root is at %d:%d", c->lpt_lnum, c->lpt_offs);
        dbg_lp("LPT head is at %d:%d", c->nhead_lnum, c->nhead_offs);
        dbg_lp("LPT ltab is at %d:%d", c->ltab_lnum, c->ltab_offs);
        if (c->big_lpt)
                dbg_lp("LPT lsave is at %d:%d", c->lsave_lnum, c->lsave_offs);

        return 0;

no_space:
        ubifs_err(c, "LPT out of space mismatch at LEB %d:%d needing %d, done_ltab %d, done_lsave %d",
                  lnum, offs, len, done_ltab, done_lsave);
        ubifs_dump_lpt_info(c);
        ubifs_dump_lpt_lebs(c);
        dump_stack();
        return err;
}

/**
 * next_pnode_to_dirty - find next pnode to dirty.
 * @c: UBIFS file-system description object
 * @pnode: pnode
 *
 * This function returns the next pnode to dirty or %NULL if there are no more
 * pnodes.  Note that pnodes that have never been written (lnum == 0) are
 * skipped.
 */
static struct ubifs_pnode *next_pnode_to_dirty(struct ubifs_info *c,
                                               struct ubifs_pnode *pnode)
{
        struct ubifs_nnode *nnode;
        int iip;

        /* Try to go right */
        nnode = pnode->parent;
        for (iip = pnode->iip + 1; iip < UBIFS_LPT_FANOUT; iip++) {
                if (nnode->nbranch[iip].lnum)
                        return ubifs_get_pnode(c, nnode, iip);
        }

        /* Go up while can't go right */
        do {
                iip = nnode->iip + 1;
                nnode = nnode->parent;
                if (!nnode)
                        return NULL;
                for (; iip < UBIFS_LPT_FANOUT; iip++) {
                        if (nnode->nbranch[iip].lnum)
                                break;
                }
        } while (iip >= UBIFS_LPT_FANOUT);

        /* Go right */
        nnode = ubifs_get_nnode(c, nnode, iip);
        if (IS_ERR(nnode))
                return (void *)nnode;

        /* Go down to level 1 */
        while (nnode->level > 1) {
                for (iip = 0; iip < UBIFS_LPT_FANOUT; iip++) {
                        if (nnode->nbranch[iip].lnum)
                                break;
                }
                if (iip >= UBIFS_LPT_FANOUT) {
                        /*
                         * Should not happen, but we need to keep going
                         * if it does.
                         */
                        iip = 0;
                }
                nnode = ubifs_get_nnode(c, nnode, iip);
                if (IS_ERR(nnode))
                        return (void *)nnode;
        }

        for (iip = 0; iip < UBIFS_LPT_FANOUT; iip++)
                if (nnode->nbranch[iip].lnum)
                        break;
        if (iip >= UBIFS_LPT_FANOUT)
                /* Should not happen, but we need to keep going if it does */
                iip = 0;
        return ubifs_get_pnode(c, nnode, iip);
}

/**
 * add_pnode_dirt - add dirty space to LPT LEB properties.
 * @c: UBIFS file-system description object
 * @pnode: pnode for which to add dirt
 */
static void add_pnode_dirt(struct ubifs_info *c, struct ubifs_pnode *pnode)
{
        ubifs_add_lpt_dirt(c, pnode->parent->nbranch[pnode->iip].lnum,
                           c->pnode_sz);
}

/**
 * do_make_pnode_dirty - mark a pnode dirty.
 * @c: UBIFS file-system description object
 * @pnode: pnode to mark dirty
 */
static void do_make_pnode_dirty(struct ubifs_info *c, struct ubifs_pnode *pnode)
{
        /* Assumes cnext list is empty i.e. not called during commit */
        if (!test_and_set_bit(DIRTY_CNODE, &pnode->flags)) {
                struct ubifs_nnode *nnode;

                c->dirty_pn_cnt += 1;
                add_pnode_dirt(c, pnode);
                /* Mark parent and ancestors dirty too */
                nnode = pnode->parent;
                while (nnode) {
                        if (!test_and_set_bit(DIRTY_CNODE, &nnode->flags)) {
                                c->dirty_nn_cnt += 1;
                                ubifs_add_nnode_dirt(c, nnode);
                                nnode = nnode->parent;
                        } else
                                break;
                }
        }
}

/**
 * make_tree_dirty - mark the entire LEB properties tree dirty.
 * @c: UBIFS file-system description object
 *
 * This function is used by the "small" LPT model to cause the entire LEB
 * properties tree to be written.  The "small" LPT model does not use LPT
 * garbage collection because it is more efficient to write the entire tree
 * (because it is small).
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int make_tree_dirty(struct ubifs_info *c)
{
        struct ubifs_pnode *pnode;

        pnode = ubifs_pnode_lookup(c, 0);
        if (IS_ERR(pnode))
                return PTR_ERR(pnode);

        while (pnode) {
                do_make_pnode_dirty(c, pnode);
                pnode = next_pnode_to_dirty(c, pnode);
                if (IS_ERR(pnode))
                        return PTR_ERR(pnode);
        }
        return 0;
}

/**
 * need_write_all - determine if the LPT area is running out of free space.
 * @c: UBIFS file-system description object
 *
 * This function returns %1 if the LPT area is running out of free space and %0
 * if it is not.
 */
static int need_write_all(struct ubifs_info *c)
{
        long long free = 0;
        int i;

        for (i = 0; i < c->lpt_lebs; i++) {
                if (i + c->lpt_first == c->nhead_lnum)
                        free += c->leb_size - c->nhead_offs;
                else if (c->ltab[i].free == c->leb_size)
                        free += c->leb_size;
                else if (c->ltab[i].free + c->ltab[i].dirty == c->leb_size)
                        free += c->leb_size;
        }
        /* Less than twice the size left */
        if (free <= c->lpt_sz * 2)
                return 1;
        return 0;
}

/**
 * lpt_tgc_start - start trivial garbage collection of LPT LEBs.
 * @c: UBIFS file-system description object
 *
 * LPT trivial garbage collection is where a LPT LEB contains only dirty and
 * free space and so may be reused as soon as the next commit is completed.
 * This function is called during start commit to mark LPT LEBs for trivial GC.
 */
static void lpt_tgc_start(struct ubifs_info *c)
{
        int i;

        for (i = 0; i < c->lpt_lebs; i++) {
                if (i + c->lpt_first == c->nhead_lnum)
                        continue;
                if (c->ltab[i].dirty > 0 &&
                    c->ltab[i].free + c->ltab[i].dirty == c->leb_size) {
                        c->ltab[i].tgc = 1;
                        c->ltab[i].free = c->leb_size;
                        c->ltab[i].dirty = 0;
                        dbg_lp("LEB %d", i + c->lpt_first);
                }
        }
}

/**
 * lpt_tgc_end - end trivial garbage collection of LPT LEBs.
 * @c: UBIFS file-system description object
 *
 * LPT trivial garbage collection is where a LPT LEB contains only dirty and
 * free space and so may be reused as soon as the next commit is completed.
 * This function is called after the commit is completed (master node has been
 * written) and un-maps LPT LEBs that were marked for trivial GC.
 */
static int lpt_tgc_end(struct ubifs_info *c)
{
        int i, err;

        for (i = 0; i < c->lpt_lebs; i++)
                if (c->ltab[i].tgc) {
                        err = ubifs_leb_unmap(c, i + c->lpt_first);
                        if (err)
                                return err;
                        c->ltab[i].tgc = 0;
                        dbg_lp("LEB %d", i + c->lpt_first);
                }
        return 0;
}

/**
 * populate_lsave - fill the lsave array with important LEB numbers.
 * @c: the UBIFS file-system description object
 *
 * This function is only called for the "big" model. It records a small number
 * of LEB numbers of important LEBs.  Important LEBs are ones that are (from
 * most important to least important): empty, freeable, freeable index, dirty
 * index, dirty or free. Upon mount, we read this list of LEB numbers and bring
 * their pnodes into memory.  That will stop us from having to scan the LPT
 * straight away. For the "small" model we assume that scanning the LPT is no
 * big deal.
 */
static void populate_lsave(struct ubifs_info *c)
{
        struct ubifs_lprops *lprops;
        struct ubifs_lpt_heap *heap;
        int i, cnt = 0;

        ubifs_assert(c, c->big_lpt);
        if (!(c->lpt_drty_flgs & LSAVE_DIRTY)) {
                c->lpt_drty_flgs |= LSAVE_DIRTY;
                ubifs_add_lpt_dirt(c, c->lsave_lnum, c->lsave_sz);
        }

        if (dbg_populate_lsave(c))
                return;

        list_for_each_entry(lprops, &c->empty_list, list) {
                c->lsave[cnt++] = lprops->lnum;
                if (cnt >= c->lsave_cnt)
                        return;
        }
        list_for_each_entry(lprops, &c->freeable_list, list) {
                c->lsave[cnt++] = lprops->lnum;
                if (cnt >= c->lsave_cnt)
                        return;
        }
        list_for_each_entry(lprops, &c->frdi_idx_list, list) {
                c->lsave[cnt++] = lprops->lnum;
                if (cnt >= c->lsave_cnt)
                        return;
        }
        heap = &c->lpt_heap[LPROPS_DIRTY_IDX - 1];
        for (i = 0; i < heap->cnt; i++) {
                c->lsave[cnt++] = heap->arr[i]->lnum;
                if (cnt >= c->lsave_cnt)
                        return;
        }
        heap = &c->lpt_heap[LPROPS_DIRTY - 1];
        for (i = 0; i < heap->cnt; i++) {
                c->lsave[cnt++] = heap->arr[i]->lnum;
                if (cnt >= c->lsave_cnt)
                        return;
        }
        heap = &c->lpt_heap[LPROPS_FREE - 1];
        for (i = 0; i < heap->cnt; i++) {
                c->lsave[cnt++] = heap->arr[i]->lnum;
                if (cnt >= c->lsave_cnt)
                        return;
        }
        /* Fill it up completely */
        while (cnt < c->lsave_cnt)
                c->lsave[cnt++] = c->main_first;
}

/**
 * nnode_lookup - lookup a nnode in the LPT.
 * @c: UBIFS file-system description object
 * @i: nnode number
 *
 * This function returns a pointer to the nnode on success or a negative
 * error code on failure.
 */
static struct ubifs_nnode *nnode_lookup(struct ubifs_info *c, int i)
{
        int err, iip;
        struct ubifs_nnode *nnode;

        if (!c->nroot) {
                err = ubifs_read_nnode(c, NULL, 0);
                if (err)
                        return ERR_PTR(err);
        }
        nnode = c->nroot;
        while (1) {
                iip = i & (UBIFS_LPT_FANOUT - 1);
                i >>= UBIFS_LPT_FANOUT_SHIFT;
                if (!i)
                        break;
                nnode = ubifs_get_nnode(c, nnode, iip);
                if (IS_ERR(nnode))
                        return nnode;
        }
        return nnode;
}

/**
 * make_nnode_dirty - find a nnode and, if found, make it dirty.
 * @c: UBIFS file-system description object
 * @node_num: nnode number of nnode to make dirty
 * @lnum: LEB number where nnode was written
 * @offs: offset where nnode was written
 *
 * This function is used by LPT garbage collection.  LPT garbage collection is
 * used only for the "big" LPT model (c->big_lpt == 1).  Garbage collection
 * simply involves marking all the nodes in the LEB being garbage-collected as
 * dirty.  The dirty nodes are written next commit, after which the LEB is free
 * to be reused.
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int make_nnode_dirty(struct ubifs_info *c, int node_num, int lnum,
                            int offs)
{
        struct ubifs_nnode *nnode;

        nnode = nnode_lookup(c, node_num);
        if (IS_ERR(nnode))
                return PTR_ERR(nnode);
        if (nnode->parent) {
                struct ubifs_nbranch *branch;

                branch = &nnode->parent->nbranch[nnode->iip];
                if (branch->lnum != lnum || branch->offs != offs)
                        return 0; /* nnode is obsolete */
        } else if (c->lpt_lnum != lnum || c->lpt_offs != offs)
                        return 0; /* nnode is obsolete */
        /* Assumes cnext list is empty i.e. not called during commit */
        if (!test_and_set_bit(DIRTY_CNODE, &nnode->flags)) {
                c->dirty_nn_cnt += 1;
                ubifs_add_nnode_dirt(c, nnode);
                /* Mark parent and ancestors dirty too */
                nnode = nnode->parent;
                while (nnode) {
                        if (!test_and_set_bit(DIRTY_CNODE, &nnode->flags)) {
                                c->dirty_nn_cnt += 1;
                                ubifs_add_nnode_dirt(c, nnode);
                                nnode = nnode->parent;
                        } else
                                break;
                }
        }
        return 0;
}

/**
 * make_pnode_dirty - find a pnode and, if found, make it dirty.
 * @c: UBIFS file-system description object
 * @node_num: pnode number of pnode to make dirty
 * @lnum: LEB number where pnode was written
 * @offs: offset where pnode was written
 *
 * This function is used by LPT garbage collection.  LPT garbage collection is
 * used only for the "big" LPT model (c->big_lpt == 1).  Garbage collection
 * simply involves marking all the nodes in the LEB being garbage-collected as
 * dirty.  The dirty nodes are written next commit, after which the LEB is free
 * to be reused.
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int make_pnode_dirty(struct ubifs_info *c, int node_num, int lnum,
                            int offs)
{
        struct ubifs_pnode *pnode;
        struct ubifs_nbranch *branch;

        pnode = ubifs_pnode_lookup(c, node_num);
        if (IS_ERR(pnode))
                return PTR_ERR(pnode);
        branch = &pnode->parent->nbranch[pnode->iip];
        if (branch->lnum != lnum || branch->offs != offs)
                return 0;
        do_make_pnode_dirty(c, pnode);
        return 0;
}

/**
 * make_ltab_dirty - make ltab node dirty.
 * @c: UBIFS file-system description object
 * @lnum: LEB number where ltab was written
 * @offs: offset where ltab was written
 *
 * This function is used by LPT garbage collection.  LPT garbage collection is
 * used only for the "big" LPT model (c->big_lpt == 1).  Garbage collection
 * simply involves marking all the nodes in the LEB being garbage-collected as
 * dirty.  The dirty nodes are written next commit, after which the LEB is free
 * to be reused.
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int make_ltab_dirty(struct ubifs_info *c, int lnum, int offs)
{
        if (lnum != c->ltab_lnum || offs != c->ltab_offs)
                return 0; /* This ltab node is obsolete */
        if (!(c->lpt_drty_flgs & LTAB_DIRTY)) {
                c->lpt_drty_flgs |= LTAB_DIRTY;
                ubifs_add_lpt_dirt(c, c->ltab_lnum, c->ltab_sz);
        }
        return 0;
}

/**
 * make_lsave_dirty - make lsave node dirty.
 * @c: UBIFS file-system description object
 * @lnum: LEB number where lsave was written
 * @offs: offset where lsave was written
 *
 * This function is used by LPT garbage collection.  LPT garbage collection is
 * used only for the "big" LPT model (c->big_lpt == 1).  Garbage collection
 * simply involves marking all the nodes in the LEB being garbage-collected as
 * dirty.  The dirty nodes are written next commit, after which the LEB is free
 * to be reused.
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int make_lsave_dirty(struct ubifs_info *c, int lnum, int offs)
{
        if (lnum != c->lsave_lnum || offs != c->lsave_offs)
                return 0; /* This lsave node is obsolete */
        if (!(c->lpt_drty_flgs & LSAVE_DIRTY)) {
                c->lpt_drty_flgs |= LSAVE_DIRTY;
                ubifs_add_lpt_dirt(c, c->lsave_lnum, c->lsave_sz);
        }
        return 0;
}

/**
 * make_node_dirty - make node dirty.
 * @c: UBIFS file-system description object
 * @node_type: LPT node type
 * @node_num: node number
 * @lnum: LEB number where node was written
 * @offs: offset where node was written
 *
 * This function is used by LPT garbage collection.  LPT garbage collection is
 * used only for the "big" LPT model (c->big_lpt == 1).  Garbage collection
 * simply involves marking all the nodes in the LEB being garbage-collected as
 * dirty.  The dirty nodes are written next commit, after which the LEB is free
 * to be reused.
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int make_node_dirty(struct ubifs_info *c, int node_type, int node_num,
                           int lnum, int offs)
{
        switch (node_type) {
        case UBIFS_LPT_NNODE:
                return make_nnode_dirty(c, node_num, lnum, offs);
        case UBIFS_LPT_PNODE:
                return make_pnode_dirty(c, node_num, lnum, offs);
        case UBIFS_LPT_LTAB:
                return make_ltab_dirty(c, lnum, offs);
        case UBIFS_LPT_LSAVE:
                return make_lsave_dirty(c, lnum, offs);
        }
        return -EINVAL;
}

/**
 * get_lpt_node_len - return the length of a node based on its type.
 * @c: UBIFS file-system description object
 * @node_type: LPT node type
 */
static int get_lpt_node_len(const struct ubifs_info *c, int node_type)
{
        switch (node_type) {
        case UBIFS_LPT_NNODE:
                return c->nnode_sz;
        case UBIFS_LPT_PNODE:
                return c->pnode_sz;
        case UBIFS_LPT_LTAB:
                return c->ltab_sz;
        case UBIFS_LPT_LSAVE:
                return c->lsave_sz;
        }
        return 0;
}

/**
 * get_pad_len - return the length of padding in a buffer.
 * @c: UBIFS file-system description object
 * @buf: buffer
 * @len: length of buffer
 */
static int get_pad_len(const struct ubifs_info *c, uint8_t *buf, int len)
{
        int offs, pad_len;

        if (c->min_io_size == 1)
                return 0;
        offs = c->leb_size - len;
        pad_len = ALIGN(offs, c->min_io_size) - offs;
        return pad_len;
}

/**
 * get_lpt_node_type - return type (and node number) of a node in a buffer.
 * @c: UBIFS file-system description object
 * @buf: buffer
 * @node_num: node number is returned here
 */
static int get_lpt_node_type(const struct ubifs_info *c, uint8_t *buf,
                             int *node_num)
{
        uint8_t *addr = buf + UBIFS_LPT_CRC_BYTES;
        int pos = 0, node_type;

        node_type = ubifs_unpack_bits(c, &addr, &pos, UBIFS_LPT_TYPE_BITS);
        *node_num = ubifs_unpack_bits(c, &addr, &pos, c->pcnt_bits);
        return node_type;
}

/**
 * is_a_node - determine if a buffer contains a node.
 * @c: UBIFS file-system description object
 * @buf: buffer
 * @len: length of buffer
 *
 * This function returns %1 if the buffer contains a node or %0 if it does not.
 */
static int is_a_node(const struct ubifs_info *c, uint8_t *buf, int len)
{
        uint8_t *addr = buf + UBIFS_LPT_CRC_BYTES;
        int pos = 0, node_type, node_len;
        uint16_t crc, calc_crc;

        if (len < UBIFS_LPT_CRC_BYTES + (UBIFS_LPT_TYPE_BITS + 7) / 8)
                return 0;
        node_type = ubifs_unpack_bits(c, &addr, &pos, UBIFS_LPT_TYPE_BITS);
        if (node_type == UBIFS_LPT_NOT_A_NODE)
                return 0;
        node_len = get_lpt_node_len(c, node_type);
        if (!node_len || node_len > len)
                return 0;
        pos = 0;
        addr = buf;
        crc = ubifs_unpack_bits(c, &addr, &pos, UBIFS_LPT_CRC_BITS);
        calc_crc = crc16(-1, buf + UBIFS_LPT_CRC_BYTES,
                         node_len - UBIFS_LPT_CRC_BYTES);
        if (crc != calc_crc)
                return 0;
        return 1;
}

/**
 * lpt_gc_lnum - garbage collect a LPT LEB.
 * @c: UBIFS file-system description object
 * @lnum: LEB number to garbage collect
 *
 * LPT garbage collection is used only for the "big" LPT model
 * (c->big_lpt == 1).  Garbage collection simply involves marking all the nodes
 * in the LEB being garbage-collected as dirty.  The dirty nodes are written
 * next commit, after which the LEB is free to be reused.
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int lpt_gc_lnum(struct ubifs_info *c, int lnum)
{
        int err, len = c->leb_size, node_type, node_num, node_len, offs;
        void *buf = c->lpt_buf;

        dbg_lp("LEB %d", lnum);

        err = ubifs_leb_read(c, lnum, buf, 0, c->leb_size, 1);
        if (err)
                return err;

        while (1) {
                if (!is_a_node(c, buf, len)) {
                        int pad_len;

                        pad_len = get_pad_len(c, buf, len);
                        if (pad_len) {
                                buf += pad_len;
                                len -= pad_len;
                                continue;
                        }
                        return 0;
                }
                node_type = get_lpt_node_type(c, buf, &node_num);
                node_len = get_lpt_node_len(c, node_type);
                offs = c->leb_size - len;
                ubifs_assert(c, node_len != 0);
                mutex_lock(&c->lp_mutex);
                err = make_node_dirty(c, node_type, node_num, lnum, offs);
                mutex_unlock(&c->lp_mutex);
                if (err)
                        return err;
                buf += node_len;
                len -= node_len;
        }
        return 0;
}

/**
 * lpt_gc - LPT garbage collection.
 * @c: UBIFS file-system description object
 *
 * Select a LPT LEB for LPT garbage collection and call 'lpt_gc_lnum()'.
 * Returns %0 on success and a negative error code on failure.
 */
static int lpt_gc(struct ubifs_info *c)
{
        int i, lnum = -1, dirty = 0;

        mutex_lock(&c->lp_mutex);
        for (i = 0; i < c->lpt_lebs; i++) {
                ubifs_assert(c, !c->ltab[i].tgc);
                if (i + c->lpt_first == c->nhead_lnum ||
                    c->ltab[i].free + c->ltab[i].dirty == c->leb_size)
                        continue;
                if (c->ltab[i].dirty > dirty) {
                        dirty = c->ltab[i].dirty;
                        lnum = i + c->lpt_first;
                }
        }
        mutex_unlock(&c->lp_mutex);
        if (lnum == -1)
                return -ENOSPC;
        return lpt_gc_lnum(c, lnum);
}

/**
 * ubifs_lpt_start_commit - UBIFS commit starts.
 * @c: the UBIFS file-system description object
 *
 * This function has to be called when UBIFS starts the commit operation.
 * This function "freezes" all currently dirty LEB properties and does not
 * change them anymore. Further changes are saved and tracked separately
 * because they are not part of this commit. This function returns zero in case
 * of success and a negative error code in case of failure.
 */
int ubifs_lpt_start_commit(struct ubifs_info *c)
{
        int err, cnt;

        dbg_lp("");

        mutex_lock(&c->lp_mutex);
        err = dbg_chk_lpt_free_spc(c);
        if (err)
                goto out;
        err = dbg_check_ltab(c);
        if (err)
                goto out;

        if (c->check_lpt_free) {
                /*
                 * We ensure there is enough free space in
                 * ubifs_lpt_post_commit() by marking nodes dirty. That
                 * information is lost when we unmount, so we also need
                 * to check free space once after mounting also.
                 */
                c->check_lpt_free = 0;
                while (need_write_all(c)) {
                        mutex_unlock(&c->lp_mutex);
                        err = lpt_gc(c);
                        if (err)
                                return err;
                        mutex_lock(&c->lp_mutex);
                }
        }

        lpt_tgc_start(c);

        if (!c->dirty_pn_cnt) {
                dbg_cmt("no cnodes to commit");
                err = 0;
                goto out;
        }

        if (!c->big_lpt && need_write_all(c)) {
                /* If needed, write everything */
                err = make_tree_dirty(c);
                if (err)
                        goto out;
                lpt_tgc_start(c);
        }

        if (c->big_lpt)
                populate_lsave(c);

        cnt = get_cnodes_to_commit(c);
        ubifs_assert(c, cnt != 0);

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

        err = ubifs_lpt_calc_hash(c, c->mst_node->hash_lpt);
        if (err)
                goto out;

        /* Copy the LPT's own lprops for end commit to write */
        memcpy(c->ltab_cmt, c->ltab,
               sizeof(struct ubifs_lpt_lprops) * c->lpt_lebs);
        c->lpt_drty_flgs &= ~(LTAB_DIRTY | LSAVE_DIRTY);

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

/**
 * free_obsolete_cnodes - free obsolete cnodes for commit end.
 * @c: UBIFS file-system description object
 */
static void free_obsolete_cnodes(struct ubifs_info *c)
{
        struct ubifs_cnode *cnode, *cnext;

        cnext = c->lpt_cnext;
        if (!cnext)
                return;
        do {
                cnode = cnext;
                cnext = cnode->cnext;
                if (test_bit(OBSOLETE_CNODE, &cnode->flags))
                        kfree(cnode);
                else
                        cnode->cnext = NULL;
        } while (cnext != c->lpt_cnext);
        c->lpt_cnext = NULL;
}

/**
 * ubifs_lpt_end_commit - finish the commit operation.
 * @c: the UBIFS file-system description object
 *
 * This function has to be called when the commit operation finishes. It
 * flushes the changes which were "frozen" by 'ubifs_lprops_start_commit()' to
 * the media. Returns zero in case of success and a negative error code in case
 * of failure.
 */
int ubifs_lpt_end_commit(struct ubifs_info *c)
{
        int err;

        dbg_lp("");

        if (!c->lpt_cnext)
                return 0;

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

        mutex_lock(&c->lp_mutex);
        free_obsolete_cnodes(c);
        mutex_unlock(&c->lp_mutex);

        return 0;
}

/**
 * ubifs_lpt_post_commit - post commit LPT trivial GC and LPT GC.
 * @c: UBIFS file-system description object
 *
 * LPT trivial GC is completed after a commit. Also LPT GC is done after a
 * commit for the "big" LPT model.
 */
int ubifs_lpt_post_commit(struct ubifs_info *c)
{
        int err;

        mutex_lock(&c->lp_mutex);
        err = lpt_tgc_end(c);
        if (err)
                goto out;
        if (c->big_lpt)
                while (need_write_all(c)) {
                        mutex_unlock(&c->lp_mutex);
                        err = lpt_gc(c);
                        if (err)
                                return err;
                        mutex_lock(&c->lp_mutex);
                }
out:
        mutex_unlock(&c->lp_mutex);
        return err;
}

/**
 * first_nnode - find the first nnode in memory.
 * @c: UBIFS file-system description object
 * @hght: height of tree where nnode found is returned here
 *
 * This function returns a pointer to the nnode found or %NULL if no nnode is
 * found. This function is a helper to 'ubifs_lpt_free()'.
 */
static struct ubifs_nnode *first_nnode(struct ubifs_info *c, int *hght)
{
        struct ubifs_nnode *nnode;
        int h, i, found;

        nnode = c->nroot;
        *hght = 0;
        if (!nnode)
                return NULL;
        for (h = 1; h < c->lpt_hght; h++) {
                found = 0;
                for (i = 0; i < UBIFS_LPT_FANOUT; i++) {
                        if (nnode->nbranch[i].nnode) {
                                found = 1;
                                nnode = nnode->nbranch[i].nnode;
                                *hght = h;
                                break;
                        }
                }
                if (!found)
                        break;
        }
        return nnode;
}

/**
 * next_nnode - find the next nnode in memory.
 * @c: UBIFS file-system description object
 * @nnode: nnode from which to start.
 * @hght: height of tree where nnode is, is passed and returned here
 *
 * This function returns a pointer to the nnode found or %NULL if no nnode is
 * found. This function is a helper to 'ubifs_lpt_free()'.
 */
static struct ubifs_nnode *next_nnode(struct ubifs_info *c,
                                      struct ubifs_nnode *nnode, int *hght)
{
        struct ubifs_nnode *parent;
        int iip, h, i, found;

        parent = nnode->parent;
        if (!parent)
                return NULL;
        if (nnode->iip == UBIFS_LPT_FANOUT - 1) {
                *hght -= 1;
                return parent;
        }
        for (iip = nnode->iip + 1; iip < UBIFS_LPT_FANOUT; iip++) {
                nnode = parent->nbranch[iip].nnode;
                if (nnode)
                        break;
        }
        if (!nnode) {
                *hght -= 1;
                return parent;
        }
        for (h = *hght + 1; h < c->lpt_hght; h++) {
                found = 0;
                for (i = 0; i < UBIFS_LPT_FANOUT; i++) {
                        if (nnode->nbranch[i].nnode) {
                                found = 1;
                                nnode = nnode->nbranch[i].nnode;
                                *hght = h;
                                break;
                        }
                }
                if (!found)
                        break;
        }
        return nnode;
}

/**
 * ubifs_lpt_free - free resources owned by the LPT.
 * @c: UBIFS file-system description object
 * @wr_only: free only resources used for writing
 */
void ubifs_lpt_free(struct ubifs_info *c, int wr_only)
{
        struct ubifs_nnode *nnode;
        int i, hght;

        /* Free write-only things first */

        free_obsolete_cnodes(c); /* Leftover from a failed commit */

        vfree(c->ltab_cmt);
        c->ltab_cmt = NULL;
        vfree(c->lpt_buf);
        c->lpt_buf = NULL;
        kfree(c->lsave);
        c->lsave = NULL;

        if (wr_only)
                return;

        /* Now free the rest */

        nnode = first_nnode(c, &hght);
        while (nnode) {
                for (i = 0; i < UBIFS_LPT_FANOUT; i++)
                        kfree(nnode->nbranch[i].nnode);
                nnode = next_nnode(c, nnode, &hght);
        }
        for (i = 0; i < LPROPS_HEAP_CNT; i++)
                kfree(c->lpt_heap[i].arr);
        kfree(c->dirty_idx.arr);
        kfree(c->nroot);
        vfree(c->ltab);
        kfree(c->lpt_nod_buf);
}

/*
 * Everything below is related to debugging.
 */

/**
 * dbg_is_all_ff - determine if a buffer contains only 0xFF bytes.
 * @buf: buffer
 * @len: buffer length
 */
static int dbg_is_all_ff(uint8_t *buf, int len)
{
        int i;

        for (i = 0; i < len; i++)
                if (buf[i] != 0xff)
                        return 0;
        return 1;
}

/**
 * dbg_is_nnode_dirty - determine if a nnode is dirty.
 * @c: the UBIFS file-system description object
 * @lnum: LEB number where nnode was written
 * @offs: offset where nnode was written
 */
static int dbg_is_nnode_dirty(struct ubifs_info *c, int lnum, int offs)
{
        struct ubifs_nnode *nnode;
        int hght;

        /* Entire tree is in memory so first_nnode / next_nnode are OK */
        nnode = first_nnode(c, &hght);
        for (; nnode; nnode = next_nnode(c, nnode, &hght)) {
                struct ubifs_nbranch *branch;

                cond_resched();
                if (nnode->parent) {
                        branch = &nnode->parent->nbranch[nnode->iip];
                        if (branch->lnum != lnum || branch->offs != offs)
                                continue;
                        if (test_bit(DIRTY_CNODE, &nnode->flags))
                                return 1;
                        return 0;
                } else {
                        if (c->lpt_lnum != lnum || c->lpt_offs != offs)
                                continue;
                        if (test_bit(DIRTY_CNODE, &nnode->flags))
                                return 1;
                        return 0;
                }
        }
        return 1;
}

/**
 * dbg_is_pnode_dirty - determine if a pnode is dirty.
 * @c: the UBIFS file-system description object
 * @lnum: LEB number where pnode was written
 * @offs: offset where pnode was written
 */
static int dbg_is_pnode_dirty(struct ubifs_info *c, int lnum, int offs)
{
        int i, cnt;

        cnt = DIV_ROUND_UP(c->main_lebs, UBIFS_LPT_FANOUT);
        for (i = 0; i < cnt; i++) {
                struct ubifs_pnode *pnode;
                struct ubifs_nbranch *branch;

                cond_resched();
                pnode = ubifs_pnode_lookup(c, i);
                if (IS_ERR(pnode))
                        return PTR_ERR(pnode);
                branch = &pnode->parent->nbranch[pnode->iip];
                if (branch->lnum != lnum || branch->offs != offs)
                        continue;
                if (test_bit(DIRTY_CNODE, &pnode->flags))
                        return 1;
                return 0;
        }
        return 1;
}

/**
 * dbg_is_ltab_dirty - determine if a ltab node is dirty.
 * @c: the UBIFS file-system description object
 * @lnum: LEB number where ltab node was written
 * @offs: offset where ltab node was written
 */
static int dbg_is_ltab_dirty(struct ubifs_info *c, int lnum, int offs)
{
        if (lnum != c->ltab_lnum || offs != c->ltab_offs)
                return 1;
        return (c->lpt_drty_flgs & LTAB_DIRTY) != 0;
}

/**
 * dbg_is_lsave_dirty - determine if a lsave node is dirty.
 * @c: the UBIFS file-system description object
 * @lnum: LEB number where lsave node was written
 * @offs: offset where lsave node was written
 */
static int dbg_is_lsave_dirty(struct ubifs_info *c, int lnum, int offs)
{
        if (lnum != c->lsave_lnum || offs != c->lsave_offs)
                return 1;
        return (c->lpt_drty_flgs & LSAVE_DIRTY) != 0;
}

/**
 * dbg_is_node_dirty - determine if a node is dirty.
 * @c: the UBIFS file-system description object
 * @node_type: node type
 * @lnum: LEB number where node was written
 * @offs: offset where node was written
 */
static int dbg_is_node_dirty(struct ubifs_info *c, int node_type, int lnum,
                             int offs)
{
        switch (node_type) {
        case UBIFS_LPT_NNODE:
                return dbg_is_nnode_dirty(c, lnum, offs);
        case UBIFS_LPT_PNODE:
                return dbg_is_pnode_dirty(c, lnum, offs);
        case UBIFS_LPT_LTAB:
                return dbg_is_ltab_dirty(c, lnum, offs);
        case UBIFS_LPT_LSAVE:
                return dbg_is_lsave_dirty(c, lnum, offs);
        }
        return 1;
}

/**
 * dbg_check_ltab_lnum - check the ltab for a LPT LEB number.
 * @c: the UBIFS file-system description object
 * @lnum: LEB number where node was written
 *
 * This function returns %0 on success and a negative error code on failure.
 */
static int dbg_check_ltab_lnum(struct ubifs_info *c, int lnum)
{
        int err, len = c->leb_size, dirty = 0, node_type, node_num, node_len;
        int ret;
        void *buf, *p;

        if (!dbg_is_chk_lprops(c))
                return 0;

        buf = p = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);
        if (!buf) {
                ubifs_err(c, "cannot allocate memory for ltab checking");
                return 0;
        }

        dbg_lp("LEB %d", lnum);

        err = ubifs_leb_read(c, lnum, buf, 0, c->leb_size, 1);
        if (err)
                goto out;

        while (1) {
                if (!is_a_node(c, p, len)) {
                        int i, pad_len;

                        pad_len = get_pad_len(c, p, len);
                        if (pad_len) {
                                p += pad_len;
                                len -= pad_len;
                                dirty += pad_len;
                                continue;
                        }
                        if (!dbg_is_all_ff(p, len)) {
                                ubifs_err(c, "invalid empty space in LEB %d at %d",
                                          lnum, c->leb_size - len);
                                err = -EINVAL;
                        }
                        i = lnum - c->lpt_first;
                        if (len != c->ltab[i].free) {
                                ubifs_err(c, "invalid free space in LEB %d (free %d, expected %d)",
                                          lnum, len, c->ltab[i].free);
                                err = -EINVAL;
                        }
                        if (dirty != c->ltab[i].dirty) {
                                ubifs_err(c, "invalid dirty space in LEB %d (dirty %d, expected %d)",
                                          lnum, dirty, c->ltab[i].dirty);
                                err = -EINVAL;
                        }
                        goto out;
                }
                node_type = get_lpt_node_type(c, p, &node_num);
                node_len = get_lpt_node_len(c, node_type);
                ret = dbg_is_node_dirty(c, node_type, lnum, c->leb_size - len);
                if (ret == 1)
                        dirty += node_len;
                p += node_len;
                len -= node_len;
        }

        err = 0;
out:
        vfree(buf);
        return err;
}

/**
 * dbg_check_ltab - check the free and dirty space in the ltab.
 * @c: the UBIFS file-system description object
 *
 * This function returns %0 on success and a negative error code on failure.
 */
int dbg_check_ltab(struct ubifs_info *c)
{
        int lnum, err, i, cnt;

        if (!dbg_is_chk_lprops(c))
                return 0;

        /* Bring the entire tree into memory */
        cnt = DIV_ROUND_UP(c->main_lebs, UBIFS_LPT_FANOUT);
        for (i = 0; i < cnt; i++) {
                struct ubifs_pnode *pnode;

                pnode = ubifs_pnode_lookup(c, i);
                if (IS_ERR(pnode))
                        return PTR_ERR(pnode);
                cond_resched();
        }

        /* Check nodes */
        err = dbg_check_lpt_nodes(c, (struct ubifs_cnode *)c->nroot, 0, 0);
        if (err)
                return err;

        /* Check each LEB */
        for (lnum = c->lpt_first; lnum <= c->lpt_last; lnum++) {
                err = dbg_check_ltab_lnum(c, lnum);
                if (err) {
                        ubifs_err(c, "failed at LEB %d", lnum);
                        return err;
                }
        }

        dbg_lp("succeeded");
        return 0;
}

/**
 * dbg_chk_lpt_free_spc - check LPT free space is enough to write entire LPT.
 * @c: the UBIFS file-system description object
 *
 * This function returns %0 on success and a negative error code on failure.
 */
int dbg_chk_lpt_free_spc(struct ubifs_info *c)
{
        long long free = 0;
        int i;

        if (!dbg_is_chk_lprops(c))
                return 0;

        for (i = 0; i < c->lpt_lebs; i++) {
                if (c->ltab[i].tgc || c->ltab[i].cmt)
                        continue;
                if (i + c->lpt_first == c->nhead_lnum)
                        free += c->leb_size - c->nhead_offs;
                else if (c->ltab[i].free == c->leb_size)
                        free += c->leb_size;
        }
        if (free < c->lpt_sz) {
                ubifs_err(c, "LPT space error: free %lld lpt_sz %lld",
                          free, c->lpt_sz);
                ubifs_dump_lpt_info(c);
                ubifs_dump_lpt_lebs(c);
                dump_stack();
                return -EINVAL;
        }
        return 0;
}

/**
 * dbg_chk_lpt_sz - check LPT does not write more than LPT size.
 * @c: the UBIFS file-system description object
 * @action: what to do
 * @len: length written
 *
 * This function returns %0 on success and a negative error code on failure.
 * The @action argument may be one of:
 *   o %0 - LPT debugging checking starts, initialize debugging variables;
 *   o %1 - wrote an LPT node, increase LPT size by @len bytes;
 *   o %2 - switched to a different LEB and wasted @len bytes;
 *   o %3 - check that we've written the right number of bytes.
 *   o %4 - wasted @len bytes;
 */
int dbg_chk_lpt_sz(struct ubifs_info *c, int action, int len)
{
        struct ubifs_debug_info *d = c->dbg;
        long long chk_lpt_sz, lpt_sz;
        int err = 0;

        if (!dbg_is_chk_lprops(c))
                return 0;

        switch (action) {
        case 0:
                d->chk_lpt_sz = 0;
                d->chk_lpt_sz2 = 0;
                d->chk_lpt_lebs = 0;
                d->chk_lpt_wastage = 0;
                if (c->dirty_pn_cnt > c->pnode_cnt) {
                        ubifs_err(c, "dirty pnodes %d exceed max %d",
                                  c->dirty_pn_cnt, c->pnode_cnt);
                        err = -EINVAL;
                }
                if (c->dirty_nn_cnt > c->nnode_cnt) {
                        ubifs_err(c, "dirty nnodes %d exceed max %d",
                                  c->dirty_nn_cnt, c->nnode_cnt);
                        err = -EINVAL;
                }
                return err;
        case 1:
                d->chk_lpt_sz += len;
                return 0;
        case 2:
                d->chk_lpt_sz += len;
                d->chk_lpt_wastage += len;
                d->chk_lpt_lebs += 1;
                return 0;
        case 3:
                chk_lpt_sz = c->leb_size;
                chk_lpt_sz *= d->chk_lpt_lebs;
                chk_lpt_sz += len - c->nhead_offs;
                if (d->chk_lpt_sz != chk_lpt_sz) {
                        ubifs_err(c, "LPT wrote %lld but space used was %lld",
                                  d->chk_lpt_sz, chk_lpt_sz);
                        err = -EINVAL;
                }
                if (d->chk_lpt_sz > c->lpt_sz) {
                        ubifs_err(c, "LPT wrote %lld but lpt_sz is %lld",
                                  d->chk_lpt_sz, c->lpt_sz);
                        err = -EINVAL;
                }
                if (d->chk_lpt_sz2 && d->chk_lpt_sz != d->chk_lpt_sz2) {
                        ubifs_err(c, "LPT layout size %lld but wrote %lld",
                                  d->chk_lpt_sz, d->chk_lpt_sz2);
                        err = -EINVAL;
                }
                if (d->chk_lpt_sz2 && d->new_nhead_offs != len) {
                        ubifs_err(c, "LPT new nhead offs: expected %d was %d",
                                  d->new_nhead_offs, len);
                        err = -EINVAL;
                }
                lpt_sz = (long long)c->pnode_cnt * c->pnode_sz;
                lpt_sz += (long long)c->nnode_cnt * c->nnode_sz;
                lpt_sz += c->ltab_sz;
                if (c->big_lpt)
                        lpt_sz += c->lsave_sz;
                if (d->chk_lpt_sz - d->chk_lpt_wastage > lpt_sz) {
                        ubifs_err(c, "LPT chk_lpt_sz %lld + waste %lld exceeds %lld",
                                  d->chk_lpt_sz, d->chk_lpt_wastage, lpt_sz);
                        err = -EINVAL;
                }
                if (err) {
                        ubifs_dump_lpt_info(c);
                        ubifs_dump_lpt_lebs(c);
                        dump_stack();
                }
                d->chk_lpt_sz2 = d->chk_lpt_sz;
                d->chk_lpt_sz = 0;
                d->chk_lpt_wastage = 0;
                d->chk_lpt_lebs = 0;
                d->new_nhead_offs = len;
                return err;
        case 4:
                d->chk_lpt_sz += len;
                d->chk_lpt_wastage += len;
                return 0;
        default:
                return -EINVAL;
        }
}

/**
 * dump_lpt_leb - dump an LPT LEB.
 * @c: UBIFS file-system description object
 * @lnum: LEB number to dump
 *
 * This function dumps an LEB from LPT area. Nodes in this area are very
 * different to nodes in the main area (e.g., they do not have common headers,
 * they do not have 8-byte alignments, etc), so we have a separate function to
 * dump LPT area LEBs. Note, LPT has to be locked by the caller.
 */
static void dump_lpt_leb(const struct ubifs_info *c, int lnum)
{
        int err, len = c->leb_size, node_type, node_num, node_len, offs;
        void *buf, *p;

        pr_err("(pid %d) start dumping LEB %d\n", current->pid, lnum);
        buf = p = __vmalloc(c->leb_size, GFP_NOFS, PAGE_KERNEL);
        if (!buf) {
                ubifs_err(c, "cannot allocate memory to dump LPT");
                return;
        }

        err = ubifs_leb_read(c, lnum, buf, 0, c->leb_size, 1);
        if (err)
                goto out;

        while (1) {
                offs = c->leb_size - len;
                if (!is_a_node(c, p, len)) {
                        int pad_len;

                        pad_len = get_pad_len(c, p, len);
                        if (pad_len) {
                                pr_err("LEB %d:%d, pad %d bytes\n",
                                       lnum, offs, pad_len);
                                p += pad_len;
                                len -= pad_len;
                                continue;
                        }
                        if (len)
                                pr_err("LEB %d:%d, free %d bytes\n",
                                       lnum, offs, len);
                        break;
                }

                node_type = get_lpt_node_type(c, p, &node_num);
                switch (node_type) {
                case UBIFS_LPT_PNODE:
                {
                        node_len = c->pnode_sz;
                        if (c->big_lpt)
                                pr_err("LEB %d:%d, pnode num %d\n",
                                       lnum, offs, node_num);
                        else
                                pr_err("LEB %d:%d, pnode\n", lnum, offs);
                        break;
                }
                case UBIFS_LPT_NNODE:
                {
                        int i;
                        struct ubifs_nnode nnode;

                        node_len = c->nnode_sz;
                        if (c->big_lpt)
                                pr_err("LEB %d:%d, nnode num %d, ",
                                       lnum, offs, node_num);
                        else
                                pr_err("LEB %d:%d, nnode, ",
                                       lnum, offs);
                        err = ubifs_unpack_nnode(c, p, &nnode);
                        if (err) {
                                pr_err("failed to unpack_node, error %d\n",
                                       err);
                                break;
                        }
                        for (i = 0; i < UBIFS_LPT_FANOUT; i++) {
                                pr_cont("%d:%d", nnode.nbranch[i].lnum,
                                       nnode.nbranch[i].offs);
                                if (i != UBIFS_LPT_FANOUT - 1)
                                        pr_cont(", ");
                        }
                        pr_cont("\n");
                        break;
                }
                case UBIFS_LPT_LTAB:
                        node_len = c->ltab_sz;
                        pr_err("LEB %d:%d, ltab\n", lnum, offs);
                        break;
                case UBIFS_LPT_LSAVE:
                        node_len = c->lsave_sz;
                        pr_err("LEB %d:%d, lsave len\n", lnum, offs);
                        break;
                default:
                        ubifs_err(c, "LPT node type %d not recognized", node_type);
                        goto out;
                }

                p += node_len;
                len -= node_len;
        }

        pr_err("(pid %d) finish dumping LEB %d\n", current->pid, lnum);
out:
        vfree(buf);
        return;
}

/**
 * ubifs_dump_lpt_lebs - dump LPT lebs.
 * @c: UBIFS file-system description object
 *
 * This function dumps all LPT LEBs. The caller has to make sure the LPT is
 * locked.
 */
void ubifs_dump_lpt_lebs(const struct ubifs_info *c)
{
        int i;

        pr_err("(pid %d) start dumping all LPT LEBs\n", current->pid);
        for (i = 0; i < c->lpt_lebs; i++)
                dump_lpt_leb(c, i + c->lpt_first);
        pr_err("(pid %d) finish dumping all LPT LEBs\n", current->pid);
}

/**
 * dbg_populate_lsave - debugging version of 'populate_lsave()'
 * @c: UBIFS file-system description object
 *
 * This is a debugging version for 'populate_lsave()' which populates lsave
 * with random LEBs instead of useful LEBs, which is good for test coverage.
 * Returns zero if lsave has not been populated (this debugging feature is
 * disabled) an non-zero if lsave has been populated.
 */
static int dbg_populate_lsave(struct ubifs_info *c)
{
        struct ubifs_lprops *lprops;
        struct ubifs_lpt_heap *heap;
        int i;

        if (!dbg_is_chk_gen(c))
                return 0;
        if (prandom_u32() & 3)
                return 0;

        for (i = 0; i < c->lsave_cnt; i++)
                c->lsave[i] = c->main_first;

        list_for_each_entry(lprops, &c->empty_list, list)
                c->lsave[prandom_u32() % c->lsave_cnt] = lprops->lnum;
        list_for_each_entry(lprops, &c->freeable_list, list)
                c->lsave[prandom_u32() % c->lsave_cnt] = lprops->lnum;
        list_for_each_entry(lprops, &c->frdi_idx_list, list)
                c->lsave[prandom_u32() % c->lsave_cnt] = lprops->lnum;

        heap = &c->lpt_heap[LPROPS_DIRTY_IDX - 1];
        for (i = 0; i < heap->cnt; i++)
                c->lsave[prandom_u32() % c->lsave_cnt] = heap->arr[i]->lnum;
        heap = &c->lpt_heap[LPROPS_DIRTY - 1];
        for (i = 0; i < heap->cnt; i++)
                c->lsave[prandom_u32() % c->lsave_cnt] = heap->arr[i]->lnum;
        heap = &c->lpt_heap[LPROPS_FREE - 1];
        for (i = 0; i < heap->cnt; i++)
                c->lsave[prandom_u32() % c->lsave_cnt] = heap->arr[i]->lnum;

        return 1;
}