/* $OpenBSD: mke2fs.c,v 1.18 2019/07/01 07:17:26 kevlo Exp $ */
/*      $NetBSD: mke2fs.c,v 1.13 2009/10/19 18:41:08 bouyer Exp $       */

/*-
 * Copyright (c) 2007 Izumi Tsutsui.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * Copyright (c) 1980, 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Copyright (c) 1997 Manuel Bouyer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * mke2fs.c: "re-invent (dumb but non-GPLed) wheel as a fun project"
 *
 *      In spite of this name, there is no piece of code
 *      derived from GPLed e2fsprogs written for Linux.
 *      I referred them only to see how each structure
 *      member should be initialized.
 *
 * Reference:
 *      - All NetBSD sources under src/sys/ufs/ext2fs and src/sbin/fsck_ext2fs
 *      - Ext2fs Home Page
 *              http://e2fsprogs.sourceforge.net/ext2.html
 *      - Design and Implementation of the Second Extended Filesystem
 *              http://e2fsprogs.sourceforge.net/ext2intro.html
 *      - Linux Documentation "The Second Extended Filesystem"
 *              src/linux/Documentation/filesystems/ext2.txt
 *                  in the Linux kernel distribution
 */

#include <sys/param.h>  /* MAXBSIZE powerof2 roundup setbit isset MIN */
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/time.h>
#include <ufs/ext2fs/ext2fs_dinode.h>
#include <ufs/ext2fs/ext2fs_dir.h>
#include <ufs/ext2fs/ext2fs.h>
#include <sys/ioctl.h>

#include <err.h>
#include <errno.h>
#include <inttypes.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>

#include "extern.h"

static void initcg(uint);
static void zap_old_sblock(daddr32_t);
static uint cgoverhead(uint);
static int fsinit(const struct timeval *);
static int makedir(struct ext2fs_direct *, int);
static void copy_dir(struct ext2fs_direct *, struct ext2fs_direct *);
static void init_resizeino(const struct timeval *);
static uint32_t alloc(uint32_t, uint16_t);
static void iput(struct ext2fs_dinode *, ino_t);
static void rdfs(daddr32_t, int, void *);
static void wtfs(daddr32_t, int, void *);
static int ilog2(uint);
static int skpc(int, size_t, uint8_t *);
static void uuid_get(struct m_ext2fs *);

/* XXX: some of these macro should be into <ufs/ext2fs/ext2fs.h>? */
#define EXT2_DEF_MAX_MNT_COUNT  20
#define EXT2_DEF_FSCKINTV       (180 * 24 * 60 * 60)    /* 180 days */
#define EXT2_RESERVED_INODES    (EXT2_FIRSTINO - 1)
#define EXT2_UMASK              0755

#define EXT2_INO_INDEX(ino)     ((ino) - 1)             /* no inode zero */

#define EXT2_LOSTFOUNDSIZE      16384
#define EXT2_LOSTFOUNDINO       EXT2_FIRSTINO           /* XXX: not quite */
#define EXT2_LOSTFOUNDUMASK     0700

#define EXT2_RESIZEINOUMASK     0600

#define NBLOCK_SUPERBLOCK       1
#define NBLOCK_BLOCK_BITMAP     1
#define NBLOCK_INODE_BITMAP     1

#define cgbase(fs, c)   \
        ((fs)->e2fs.e2fs_first_dblock + (fs)->e2fs.e2fs_bpg * (c))

#define       rounddown(x,y)  (((x)/(y))*(y))

/*
 * ext2fs super block and group descriptor structures
 *
 *   We don't have to use or setup whole in-memory m_ext2fs structure,
 *   but prepare it to use several macro defined in kernel headers.
 */
union {
        struct m_ext2fs m_ext2fs;
        char pad[SBSIZE];
} ext2fsun;
#define sblock  ext2fsun.m_ext2fs
#define gd      ext2fsun.m_ext2fs.e2fs_gd

static uint8_t *iobuf;          /* for superblock and group descriptors */
static int iobufsize;

static uint8_t buf[MAXBSIZE];   /* for initcg() and makedir() ops */

static int fd;

extern int max_cols;

void
mke2fs(const char *fsys, int f)
{
        struct timeval tv;
        int64_t minfssize;
        uint bcount, fbcount, ficount;
        uint blocks_gd, blocks_per_cg, inodes_per_cg, iblocks_per_cg;
        uint minblocks_per_cg, blocks_lastcg;
        uint ncg, cylno, sboff;
        int i, len, col, delta, fld_width;

        gettimeofday(&tv, NULL);
        fd = f;

        /*
         * collect and verify the block and fragment sizes
         */
        if (!powerof2(bsize)) {
                errx(EXIT_FAILURE,
                    "block size must be a power of 2, not %u\n",
                    bsize);
        }
        if (!powerof2(fsize)) {
                errx(EXIT_FAILURE,
                    "fragment size must be a power of 2, not %u\n",
                    fsize);
        }
        if (fsize < sectorsize) {
                errx(EXIT_FAILURE,
                    "fragment size %u is too small, minimum is %u\n",
                    fsize, sectorsize);
        }
        if (bsize < MINBSIZE) {
                errx(EXIT_FAILURE,
                    "block size %u is too small, minimum is %u\n",
                    bsize, MINBSIZE);
        }
        if (bsize > EXT2_MAXBSIZE) {
                errx(EXIT_FAILURE,
                    "block size %u is too large, maximum is %u\n",
                    bsize, MAXBSIZE);
        }
        if (bsize != fsize) {
                /*
                 * There is no fragment support on current ext2fs (yet?),
                 * but some kernel code refers fsize or fpg as bsize or bpg
                 * and Linux seems to set the same values to them.
                 */
                errx(EXIT_FAILURE,
                    "block size (%u) can't be different from "
                    "fragment size (%u)\n",
                    bsize, fsize);
        }

        /* variable inodesize is REV1 feature */
        if (Oflag == 0 && inodesize != EXT2_REV0_DINODE_SIZE) {
                errx(EXIT_FAILURE, "GOOD_OLD_REV file system format"
                    " doesn't support %d byte inode\n", inodesize);
        }

        sblock.e2fs.e2fs_log_bsize = ilog2(bsize) - LOG_MINBSIZE;
        sblock.e2fs.e2fs_log_fsize = ilog2(fsize) - LOG_MINFSIZE;

        sblock.e2fs_bsize = bsize;
        sblock.e2fs_fsize = fsize;
        sblock.e2fs_bshift = sblock.e2fs.e2fs_log_bsize + LOG_MINBSIZE;
        sblock.e2fs_qbmask = sblock.e2fs_bsize - 1;
        sblock.e2fs_bmask = ~sblock.e2fs_qbmask;
        sblock.e2fs_fsbtodb = ilog2(sblock.e2fs_bsize) - ilog2(sectorsize);
        sblock.e2fs_ipb = sblock.e2fs_bsize / inodesize;

        /*
         * Ext2fs preserves BBSIZE (1024 bytes) space at the top for
         * bootloader (though it is not enough at all for our bootloader).
         * If bsize == BBSIZE we have to preserve one block.
         * If bsize > BBSIZE, the first block already contains BBSIZE space
         * before superblock because superblock is allocated at SBOFF and
         * bsize is a power of two (i.e. 2048 bytes or more).
         */
        sblock.e2fs.e2fs_first_dblock = (sblock.e2fs_bsize > BBSIZE) ? 0 : 1;
        minfssize = fsbtodb(&sblock,
            sblock.e2fs.e2fs_first_dblock +
            NBLOCK_SUPERBLOCK +
            1 /* at least one group descriptor */ +
            NBLOCK_BLOCK_BITMAP +
            NBLOCK_INODE_BITMAP +
            1 /* at least one inode table block */ +
            1 /* at least one data block for rootdir */ +
            1 /* at least one data block for data */
            );                  /* XXX and more? */

        if (fssize < minfssize)
                errx(EXIT_FAILURE, "Filesystem size %" PRId64
                    " < minimum size of %" PRId64 "\n", fssize, minfssize);

        bcount = dbtofsb(&sblock, fssize);

        /*
         * While many people claim that ext2fs is a (bad) clone of ufs/ffs,
         * it isn't actual ffs so maybe we should call it "block group"
         * as their native name rather than ffs derived "cylinder group."
         * But we'll use the latter here since other kernel sources use it.
         * (I also agree "cylinder" based allocation is obsolete though)
         */

        /* maybe "simple is the best" */
        blocks_per_cg = sblock.e2fs_bsize * NBBY;

        ncg = howmany(bcount - sblock.e2fs.e2fs_first_dblock, blocks_per_cg);
        blocks_gd = howmany(sizeof(struct ext2_gd) * ncg, bsize);

        /* check range of inode number */
        if (num_inodes < EXT2_FIRSTINO)
                num_inodes = EXT2_FIRSTINO;     /* needs reserved inodes + 1 */
        if (num_inodes > UINT16_MAX * ncg)
                num_inodes = UINT16_MAX * ncg;  /* ext2bgd_nifree is uint16_t */

        inodes_per_cg = num_inodes / ncg;
        iblocks_per_cg = howmany(inodesize * inodes_per_cg, bsize);

        /* Check that the last cylinder group has enough space for inodes */
        minblocks_per_cg =
            NBLOCK_BLOCK_BITMAP +
            NBLOCK_INODE_BITMAP +
            iblocks_per_cg +
            1;  /* at least one data block */
        if (Oflag == 0 || cg_has_sb(ncg - 1) != 0)
                minblocks_per_cg += NBLOCK_SUPERBLOCK + blocks_gd;

        blocks_lastcg = bcount - sblock.e2fs.e2fs_first_dblock -
            blocks_per_cg * (ncg - 1);
        if (blocks_lastcg < minblocks_per_cg) {
                /*
                 * Since we make all the cylinder groups the same size, the
                 * last will only be small if there are more than one
                 * cylinder groups. If the last one is too small to store
                 * filesystem data, just kill it.
                 *
                 * XXX: Does fsck_ext2fs(8) properly handle this case?
                 */
                bcount -= blocks_lastcg;
                ncg--;
                blocks_lastcg = blocks_per_cg;
                blocks_gd = howmany(sizeof(struct ext2_gd) * ncg, bsize);
                inodes_per_cg = num_inodes / ncg;
        }
        /* roundup inodes_per_cg to make it use whole inode table blocks */
        inodes_per_cg = roundup(inodes_per_cg, sblock.e2fs_ipb);
        num_inodes = inodes_per_cg * ncg;
        iblocks_per_cg = inodes_per_cg / sblock.e2fs_ipb;

        /* XXX: probably we should check these adjusted values again */

        sblock.e2fs.e2fs_bcount = bcount;
        sblock.e2fs.e2fs_icount = num_inodes;

        sblock.e2fs_ncg = ncg;
        sblock.e2fs_ngdb = blocks_gd;
        sblock.e2fs_itpg = iblocks_per_cg;

        sblock.e2fs.e2fs_rbcount = sblock.e2fs.e2fs_bcount * minfree / 100;
        /* e2fs_fbcount will be accounted later */
        /* e2fs_ficount will be accounted later */

        sblock.e2fs.e2fs_bpg = blocks_per_cg;
        sblock.e2fs.e2fs_fpg = blocks_per_cg;

        sblock.e2fs.e2fs_ipg = inodes_per_cg;

        sblock.e2fs.e2fs_mtime = 0;
        sblock.e2fs.e2fs_wtime = (u_int32_t)tv.tv_sec;
        sblock.e2fs.e2fs_mnt_count = 0;
        /* XXX: should add some entropy to avoid checking all fs at once? */
        sblock.e2fs.e2fs_max_mnt_count = EXT2_DEF_MAX_MNT_COUNT;

        sblock.e2fs.e2fs_magic = E2FS_MAGIC;
        sblock.e2fs.e2fs_state = E2FS_ISCLEAN;
        sblock.e2fs.e2fs_beh = E2FS_BEH_DEFAULT;
        sblock.e2fs.e2fs_minrev = 0;
        sblock.e2fs.e2fs_lastfsck = (u_int32_t)tv.tv_sec;
        sblock.e2fs.e2fs_fsckintv = EXT2_DEF_FSCKINTV;

        /*
         * Maybe we can use E2FS_OS_FREEBSD here and it would be more proper,
         * but the purpose of this newfs_ext2fs(8) command is to provide
         * a filesystem which can be recognized by firmware on some
         * Linux based appliances that can load bootstrap files only from
         * (their native) ext2fs, and anyway we will (and should) try to
         * act like them as much as possible.
         *
         * Anyway, I hope that all newer such boxes will keep their support
         * for the "GOOD_OLD_REV" ext2fs.
         */
        sblock.e2fs.e2fs_creator = E2FS_OS_LINUX;

        if (Oflag == 0) {
                sblock.e2fs.e2fs_rev = E2FS_REV0;
                sblock.e2fs.e2fs_features_compat   = 0;
                sblock.e2fs.e2fs_features_incompat = 0;
                sblock.e2fs.e2fs_features_rocompat = 0;
        } else {
                sblock.e2fs.e2fs_rev = E2FS_REV1;
                /*
                 * e2fsprogs say "REV1" is "dynamic" so
                 * it isn't quite a version and maybe it means
                 * "extended from REV0 so check compat features."
                 *
                 * XXX: We don't have any native tool to activate
                 *      the EXT2F_COMPAT_RESIZE feature and
                 *      fsck_ext2fs(8) might not fix structures for it.
                 */
                sblock.e2fs.e2fs_features_compat   = EXT2F_COMPAT_RESIZE;
                sblock.e2fs.e2fs_features_incompat = EXT2F_INCOMPAT_FTYPE;
                sblock.e2fs.e2fs_features_rocompat =
                    EXT2F_ROCOMPAT_SPARSE_SUPER | EXT2F_ROCOMPAT_LARGE_FILE;
        }

        sblock.e2fs.e2fs_ruid = geteuid();
        sblock.e2fs.e2fs_rgid = getegid();

        sblock.e2fs.e2fs_first_ino = EXT2_FIRSTINO;
        sblock.e2fs.e2fs_inode_size = inodesize;

        /* e2fs_block_group_nr is set on writing superblock to each group */

        uuid_get(&sblock);
        if (volname != NULL) {
                if (strlen(volname) > sizeof(sblock.e2fs.e2fs_vname))
                        errx(EXIT_FAILURE, "Volume name is too long");
                strlcpy(sblock.e2fs.e2fs_vname, volname,
                    sizeof(sblock.e2fs.e2fs_vname));
        }

        sblock.e2fs.e2fs_fsmnt[0] = '\0';
        sblock.e2fs_fsmnt[0] = '\0';

        sblock.e2fs.e2fs_algo = 0;              /* XXX unsupported? */
        sblock.e2fs.e2fs_prealloc = 0;          /* XXX unsupported? */
        sblock.e2fs.e2fs_dir_prealloc = 0;      /* XXX unsupported? */

        /* calculate blocks for reserved group descriptors for resize */
        sblock.e2fs.e2fs_reserved_ngdb = 0;
        if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
            (sblock.e2fs.e2fs_features_compat & EXT2F_COMPAT_RESIZE) != 0) {
                uint64_t target_blocks;
                uint target_ncg, target_ngdb, reserved_ngdb;

                /* reserve descriptors for size as 1024 times as current */
                target_blocks =
                    (sblock.e2fs.e2fs_bcount - sblock.e2fs.e2fs_first_dblock)
                    * 1024ULL;
                /* number of blocks must be in uint32_t */
                if (target_blocks > UINT32_MAX)
                        target_blocks = UINT32_MAX;
                target_ncg = howmany(target_blocks, sblock.e2fs.e2fs_bpg);
                target_ngdb = howmany(sizeof(struct ext2_gd) * target_ncg,
                    sblock.e2fs_bsize);
                /*
                 * Reserved group descriptor blocks are preserved as
                 * the second level double indirect reference blocks in
                 * the EXT2_RESIZEINO inode, so the maximum number of
                 * the blocks is NINDIR(fs).
                 * (see also descriptions in init_resizeino() function)
                 *
                 * We check a number including current e2fs_ngdb here
                 * because they will be moved into reserved gdb on
                 * possible future size shrink, though e2fsprogs don't
                 * seem to care about it.
                 */
                if (target_ngdb > NINDIR(&sblock))
                        target_ngdb = NINDIR(&sblock);

                reserved_ngdb = target_ngdb - sblock.e2fs_ngdb;

                /* make sure reserved_ngdb fits in the last cg */
                if (reserved_ngdb >= blocks_lastcg - cgoverhead(ncg - 1))
                        reserved_ngdb = blocks_lastcg - cgoverhead(ncg - 1);
                if (reserved_ngdb == 0) {
                        /* if no space for reserved gdb, disable the feature */
                        sblock.e2fs.e2fs_features_compat &=
                            ~EXT2F_COMPAT_RESIZE;
                }
                sblock.e2fs.e2fs_reserved_ngdb = reserved_ngdb;
        }

        /*
         * Initialize group descriptors
         */
        gd = calloc(sblock.e2fs_ngdb, bsize);
        if (gd == NULL)
                errx(EXIT_FAILURE, "Can't allocate descriptors buffer");

        fbcount = 0;
        ficount = 0;
        for (cylno = 0; cylno < ncg; cylno++) {
                uint boffset;

                boffset = cgbase(&sblock, cylno);
                if (sblock.e2fs.e2fs_rev == E2FS_REV0 ||
                    (sblock.e2fs.e2fs_features_rocompat &
                     EXT2F_ROCOMPAT_SPARSE_SUPER) == 0 ||
                    cg_has_sb(cylno)) {
                        boffset += NBLOCK_SUPERBLOCK + sblock.e2fs_ngdb;
                        if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
                            (sblock.e2fs.e2fs_features_compat &
                             EXT2F_COMPAT_RESIZE) != 0)
                                boffset += sblock.e2fs.e2fs_reserved_ngdb;
                }
                gd[cylno].ext2bgd_b_bitmap = boffset;
                boffset += NBLOCK_BLOCK_BITMAP;
                gd[cylno].ext2bgd_i_bitmap = boffset;
                boffset += NBLOCK_INODE_BITMAP;
                gd[cylno].ext2bgd_i_tables = boffset;
                if (cylno == (ncg - 1))
                        gd[cylno].ext2bgd_nbfree =
                            blocks_lastcg - cgoverhead(cylno);
                else
                        gd[cylno].ext2bgd_nbfree =
                            sblock.e2fs.e2fs_bpg - cgoverhead(cylno);
                fbcount += gd[cylno].ext2bgd_nbfree;
                gd[cylno].ext2bgd_nifree = sblock.e2fs.e2fs_ipg;
                if (cylno == 0) {
                        /* take reserved inodes off nifree */
                        gd[cylno].ext2bgd_nifree -= EXT2_RESERVED_INODES;
                }
                ficount += gd[cylno].ext2bgd_nifree;
                gd[cylno].ext2bgd_ndirs = 0;
        }
        sblock.e2fs.e2fs_fbcount = fbcount;
        sblock.e2fs.e2fs_ficount = ficount;

        /*
         * Dump out summary information about file system.
         */
        if (verbosity > 0) {
                printf("%s: %u.%1uMB (%" PRId64 " sectors) "
                    "block size %u, fragment size %u\n",
                    fsys,
                    (uint)(((uint64_t)bcount * bsize) / (1024 * 1024)),
                    (uint)((uint64_t)bcount * bsize -
                    rounddown((uint64_t)bcount * bsize, 1024 * 1024))
                    / 1024 / 100,
                    fssize, bsize, fsize);
                printf("\tusing %u block groups of %u.0MB, %u blks, "
                    "%u inodes.\n",
                    ncg, bsize * sblock.e2fs.e2fs_bpg / (1024 * 1024),
                    sblock.e2fs.e2fs_bpg, sblock.e2fs.e2fs_ipg);
        }

        /*
         * allocate space for superblock and group descriptors
         */
        iobufsize = (NBLOCK_SUPERBLOCK + sblock.e2fs_ngdb) * sblock.e2fs_bsize;
        iobuf = mmap(0, iobufsize, PROT_READ|PROT_WRITE,
            MAP_ANON|MAP_PRIVATE, -1, 0);
        if (iobuf == MAP_FAILED)
                errx(EXIT_FAILURE, "Cannot allocate I/O buffer\n");

        /*
         * We now start writing to the filesystem
         */

        if (!Nflag) {
                static const uint pbsize[] = { 1024, 2048, 4096, 0 };
                uint pblock, epblock;
                /*
                 * Validate the given file system size.
                 * Verify that its last block can actually be accessed.
                 * Convert to file system fragment sized units.
                 */
                if (fssize <= 0)
                        errx(EXIT_FAILURE, "Preposterous size %" PRId64 "\n",
                            fssize);
                wtfs(fssize - 1, sectorsize, iobuf);

                /*
                 * Ensure there is nothing that looks like a filesystem
                 * superblock anywhere other than where ours will be.
                 * If fsck_ext2fs finds the wrong one all hell breaks loose!
                 *
                 * XXX: needs to check how fsck_ext2fs programs even
                 *      on other OSes determine alternate superblocks
                 */
                for (i = 0; pbsize[i] != 0; i++) {
                        epblock = (uint64_t)bcount * bsize / pbsize[i];
                        for (pblock = ((pbsize[i] == SBSIZE) ? 1 : 0);
                            pblock < epblock;
                            pblock += pbsize[i] * NBBY /* bpg */)
                                zap_old_sblock((daddr32_t)pblock *
                                    pbsize[i] / sectorsize);
                }
        }

        if (verbosity >= 3)
                printf("super-block backups (for fsck_ext2fs -b #) at:\n");
        /* If we are printing more than one line of numbers, line up columns */
        fld_width = verbosity < 4 ? 1 : snprintf(NULL, 0, "%" PRIu64,
            (uint64_t)cgbase(&sblock, ncg - 1));
        if (Nflag && verbosity == 3)
                /* Leave space to add " ..." after one row of numbers */
                max_cols -= 4;
#define BASE 0x10000    /* For some fixed-point maths */
        col = 0;
        delta = verbosity > 2 ? 0 : max_cols * BASE / ncg;
        for (cylno = 0; cylno < ncg; cylno++) {
                fflush(stdout);
                initcg(cylno);
                if (verbosity < 2)
                        continue;
                /* the first one is a master, not backup */
                if (cylno == 0)
                        continue;
                /* skip if this cylinder doesn't have a backup */
                if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
                    (sblock.e2fs.e2fs_features_rocompat &
                     EXT2F_ROCOMPAT_SPARSE_SUPER) != 0 &&
                    cg_has_sb(cylno) == 0)
                        continue;

                if (delta > 0) {
                        if (Nflag)
                                /* No point doing dots for -N */
                                break;
                        /* Print dots scaled to end near RH margin */
                        for (col += delta; col > BASE; col -= BASE)
                                printf(".");
                        continue;
                }
                /* Print superblock numbers */
                len = printf("%s%*" PRIu64 ",", (col ? " " : ""), fld_width,
                    (uint64_t)cgbase(&sblock, cylno));
                col += len;
                if (col + len < max_cols)
                        /* Next number fits */
                        continue;
                /* Next number won't fit, need a newline */
                if (verbosity <= 3) {
                        /* Print dots for subsequent cylinder groups */
                        delta = sblock.e2fs_ncg - cylno - 1;
                        if (delta != 0) {
                                if (Nflag) {
                                        printf(" ...");
                                        break;
                                }
                                delta = max_cols * BASE / delta;
                        }
                }
                col = 0;
                printf("\n");
        }
#undef BASE
        if (col > 0)
                printf("\n");
        if (Nflag)
                return;

        /*
         * Now construct the initial file system,
         */
        if (fsinit(&tv) == 0)
                errx(EXIT_FAILURE, "Error making filesystem");
        /*
         * Write out the superblock and group descriptors
         */
        sblock.e2fs.e2fs_block_group_nr = 0;
        sboff = 0;
        if (cgbase(&sblock, 0) == 0) {
                /*
                 * If the first block contains the boot block sectors,
                 * (i.e. in case of sblock.e2fs.e2fs_bsize > BBSIZE)
                 * we have to preserve data in it.
                 */
                sboff = SBOFF;
        }
        e2fs_sbsave(&sblock.e2fs, (struct ext2fs *)(iobuf + sboff));
        e2fs_cgsave(gd, (struct ext2_gd *)(iobuf + sblock.e2fs_bsize),
           sizeof(struct ext2_gd) * sblock.e2fs_ncg);
        wtfs(fsbtodb(&sblock, cgbase(&sblock, 0)) + sboff / sectorsize,
            iobufsize - sboff, iobuf + sboff);

        munmap(iobuf, iobufsize);
}

/*
 * Initialize a cylinder (block) group.
 */
void
initcg(uint cylno)
{
        uint nblcg, i, j, sboff;
        struct ext2fs_dinode *dp;

        /*
         * Make a copy of the superblock and group descriptors.
         */
        if (sblock.e2fs.e2fs_rev == E2FS_REV0 ||
            (sblock.e2fs.e2fs_features_rocompat &
             EXT2F_ROCOMPAT_SPARSE_SUPER) == 0 ||
            cg_has_sb(cylno)) {
                sblock.e2fs.e2fs_block_group_nr = cylno;
                sboff = 0;
                if (cgbase(&sblock, cylno) == 0) {
                        /* preserve data in bootblock in cg0 */
                        sboff = SBOFF;
                }
                e2fs_sbsave(&sblock.e2fs, (struct ext2fs *)(iobuf + sboff));
                e2fs_cgsave(gd, (struct ext2_gd *)(iobuf +
                    sblock.e2fs_bsize * NBLOCK_SUPERBLOCK),
                    sizeof(struct ext2_gd) * sblock.e2fs_ncg);
                /* write superblock and group descriptor backups */
                wtfs(fsbtodb(&sblock, cgbase(&sblock, cylno)) +
                    sboff / sectorsize, iobufsize - sboff, iobuf + sboff);
        }

        /*
         * Initialize block bitmap.
         */
        memset(buf, 0, sblock.e2fs_bsize);
        if (cylno == (sblock.e2fs_ncg - 1)) {
                /* The last group could have less blocks than e2fs_bpg. */
                nblcg = sblock.e2fs.e2fs_bcount -
                    cgbase(&sblock, sblock.e2fs_ncg - 1);
                for (i = nblcg; i < roundup(nblcg, NBBY); i++)
                        setbit(buf, i);
                memset(&buf[i / NBBY], ~0U, sblock.e2fs.e2fs_bpg - i);
        }
        /* set overhead (superblock, group descriptor etc.) blocks used */
        for (i = 0; i < cgoverhead(cylno) / NBBY; i++)
                buf[i] = ~0;
        i = i * NBBY;
        for (; i < cgoverhead(cylno); i++)
                setbit(buf, i);
        wtfs(fsbtodb(&sblock, gd[cylno].ext2bgd_b_bitmap), sblock.e2fs_bsize,
            buf);

        /*
         * Initialize inode bitmap.
         *
         *  Assume e2fs_ipg is a multiple of NBBY since
         *  it's a multiple of e2fs_ipb (as we did above).
         *  Note even (possibly smaller) the last group has the same e2fs_ipg.
         */
        i = sblock.e2fs.e2fs_ipg / NBBY;
        memset(buf, 0, i);
        memset(buf + i, ~0U, sblock.e2fs_bsize - i);
        if (cylno == 0) {
                /* mark reserved inodes */
                for (i = 1; i < EXT2_FIRSTINO; i++)
                        setbit(buf, EXT2_INO_INDEX(i));
        }
        wtfs(fsbtodb(&sblock, gd[cylno].ext2bgd_i_bitmap), sblock.e2fs_bsize,
            buf);

        /*
         * Initialize inode tables.
         *
         *  Just initialize generation numbers for NFS security.
         *  XXX: sys/ufs/ext2fs/ext2fs_alloc.c:ext2fs_valloc() seems
         *       to override these generated numbers.
         */
        memset(buf, 0, sblock.e2fs_bsize);
        for (i = 0; i < sblock.e2fs_itpg; i++) {
                for (j = 0; j < sblock.e2fs_ipb; j++) {
                        dp = (struct ext2fs_dinode *)(buf + inodesize * j);
                        /* If there is some bias in arc4random(), keep it. */
                        dp->e2di_gen = htole32(arc4random());
                }
                wtfs(fsbtodb(&sblock, gd[cylno].ext2bgd_i_tables + i),
                    sblock.e2fs_bsize, buf);
        }
}

/*
 * Zap possible lingering old superblock data
 */
static void
zap_old_sblock(daddr32_t sec)
{
        static daddr32_t cg0_data;
        uint32_t oldfs[SBSIZE / sizeof(uint32_t)];
        static const struct fsm {
                uint32_t offset;
                uint32_t magic;
                uint32_t mask;
        } fs_magics[] = {
                {offsetof(struct ext2fs, e2fs_magic) / 4, E2FS_MAGIC, 0xffff},
                {offsetof(struct ext2fs, e2fs_magic) / 4,
                    E2FS_MAGIC << 16, 0xffff0000},
                {14, 0xef530000, 0xffff0000},   /* EXT2FS (big) */
                {0x55c / 4, 0x00011954, ~0U},   /* FS_UFS1_MAGIC */
                {0x55c / 4, 0x19540119, ~0U},   /* FS_UFS2_MAGIC */
                {0, 0x70162, ~0U},              /* LFS_MAGIC */
                {.offset = ~0U},
        };
        const struct fsm *fsm;

        if (Nflag)
                return;

        /* don't override data before superblock */
        if (sec < SBOFF / sectorsize)
                return;

        if (cg0_data == 0) {
                cg0_data =
                    ((daddr32_t)sblock.e2fs.e2fs_first_dblock + cgoverhead(0)) *
                    sblock.e2fs_bsize / sectorsize;
        }

        /* Ignore anything that is beyond our filesystem */
        if (sec >= fssize)
                return;
        /* Zero anything inside our filesystem... */
        if (sec >= sblock.e2fs.e2fs_first_dblock * bsize / sectorsize) {
                /* ...unless we will write that area anyway */
                if (sec >= cg0_data)
                        /* assume iobuf is zero'ed here */
                        wtfs(sec, roundup(SBSIZE, sectorsize), iobuf);
                return;
        }

        /*
         * The sector might contain boot code, so we must validate it
         *
         * XXX: ext2fs won't preserve data after SBOFF,
         *      but first_dblock could have a different value.
         */
        rdfs(sec, sizeof(oldfs), &oldfs);
        for (fsm = fs_magics;; fsm++) {
                uint32_t v;
                if (fsm->mask == 0)
                        return;
                v = oldfs[fsm->offset];
                if ((v & fsm->mask) == fsm->magic ||
                    (swap32(v) & fsm->mask) == fsm->magic)
                        break;
        }

        /* Just zap the magic number */
        oldfs[fsm->offset] = 0;
        wtfs(sec, sizeof(oldfs), &oldfs);
}

/*
 * uint cgoverhead(uint c)
 *
 *      Return a number of reserved blocks on the specified group.
 *      XXX: should be shared with src/sbin/fsck_ext2fs/setup.c
 */
uint
cgoverhead(uint c)
{
        uint overh;

        overh = NBLOCK_BLOCK_BITMAP + NBLOCK_INODE_BITMAP + sblock.e2fs_itpg;

        if (sblock.e2fs.e2fs_rev == E2FS_REV0 ||
            (sblock.e2fs.e2fs_features_rocompat &
             EXT2F_ROCOMPAT_SPARSE_SUPER) == 0 ||
            cg_has_sb(c) != 0) {
                overh += NBLOCK_SUPERBLOCK + sblock.e2fs_ngdb;

                if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
                    (sblock.e2fs.e2fs_features_compat &
                     EXT2F_COMPAT_RESIZE) != 0)
                        overh += sblock.e2fs.e2fs_reserved_ngdb;
        }

        return overh;
}

/*
 * Initialize the file system
 */

#define LOSTDIR         /* e2fsck complains if there is no lost+found */

#define PREDEFDIR       2

#ifdef LOSTDIR
#define PREDEFROOTDIR   (PREDEFDIR + 1)
#else
#define PREDEFROOTDIR   PREDEFDIR
#endif

struct ext2fs_direct root_dir[] = {
        { EXT2_ROOTINO, 0, 1, 0, "." },
        { EXT2_ROOTINO, 0, 2, 0, ".." },
#ifdef LOSTDIR
        { EXT2_LOSTFOUNDINO, 0, 10, 0, "lost+found" },
#endif
};

#ifdef LOSTDIR
struct ext2fs_direct lost_found_dir[] = {
        { EXT2_LOSTFOUNDINO, 0, 1, 0, "." },
        { EXT2_ROOTINO, 0, 2, 0, ".." },
};
struct ext2fs_direct pad_dir = { 0, sizeof(struct ext2fs_direct), 0, 0, "" };
#endif

int
fsinit(const struct timeval *tv)
{
        struct ext2fs_dinode node;
#ifdef LOSTDIR
        uint i, nblks_lostfound, blk;
#endif

        /*
         * Initialize the inode for the resizefs feature
         */
        if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
            (sblock.e2fs.e2fs_features_compat & EXT2F_COMPAT_RESIZE) != 0)
                init_resizeino(tv);

        /*
         * Initialize the node
         */

#ifdef LOSTDIR
        /*
         * Create the lost+found directory
         */
        if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
            sblock.e2fs.e2fs_features_incompat & EXT2F_INCOMPAT_FTYPE) {
                lost_found_dir[0].e2d_type = EXT2_FT_DIR;
                lost_found_dir[1].e2d_type = EXT2_FT_DIR;
        }
        (void)makedir(lost_found_dir, nitems(lost_found_dir));

        /* prepare a bit large directory for preserved files */
        nblks_lostfound = EXT2_LOSTFOUNDSIZE / sblock.e2fs_bsize;
        /* ...but only with direct blocks */
        if (nblks_lostfound > NDADDR)
                nblks_lostfound = NDADDR;

        memset(&node, 0, sizeof(node));
        node.e2di_mode = EXT2_IFDIR | EXT2_LOSTFOUNDUMASK;
        node.e2di_uid_low = geteuid();
        node.e2di_size = sblock.e2fs_bsize * nblks_lostfound;
        node.e2di_atime = (u_int32_t)tv->tv_sec;
        node.e2di_ctime = (u_int32_t)tv->tv_sec;
        node.e2di_mtime = (u_int32_t)tv->tv_sec;
        node.e2di_gid_low = getegid();
        node.e2di_nlink = PREDEFDIR;
        /* e2di_nblock is a number of disk blocks, not ext2fs blocks */
        node.e2di_nblock = fsbtodb(&sblock, nblks_lostfound);
        node.e2di_blocks[0] = alloc(sblock.e2fs_bsize, node.e2di_mode);
        if (node.e2di_blocks[0] == 0) {
                printf("%s: can't allocate block for lost+found\n", __func__);
                return 0;
        }
        for (i = 1; i < nblks_lostfound; i++) {
                blk = alloc(sblock.e2fs_bsize, 0);
                if (blk == 0) {
                        printf("%s: can't allocate blocks for lost+found\n",
                            __func__);
                        return 0;
                }
                node.e2di_blocks[i] = blk;
        }
        wtfs(fsbtodb(&sblock, node.e2di_blocks[0]), sblock.e2fs_bsize, buf);
        pad_dir.e2d_reclen = sblock.e2fs_bsize;
        for (i = 1; i < nblks_lostfound; i++) {
                memset(buf, 0, sblock.e2fs_bsize);
                copy_dir(&pad_dir, (struct ext2fs_direct *)buf);
                wtfs(fsbtodb(&sblock, node.e2di_blocks[i]), sblock.e2fs_bsize,
                    buf);
        }
        iput(&node, EXT2_LOSTFOUNDINO);
#endif
        /*
         * create the root directory
         */
        memset(&node, 0, sizeof(node));
        if (sblock.e2fs.e2fs_rev > E2FS_REV0 &&
            sblock.e2fs.e2fs_features_incompat & EXT2F_INCOMPAT_FTYPE) {
                root_dir[0].e2d_type = EXT2_FT_DIR;
                root_dir[1].e2d_type = EXT2_FT_DIR;
#ifdef LOSTDIR
                root_dir[2].e2d_type = EXT2_FT_DIR;
#endif
        }
        node.e2di_mode = EXT2_IFDIR | EXT2_UMASK;
        node.e2di_uid_low = geteuid();
        node.e2di_size = makedir(root_dir, nitems(root_dir));
        node.e2di_atime = (u_int32_t)tv->tv_sec;
        node.e2di_ctime = (u_int32_t)tv->tv_sec;
        node.e2di_mtime = (u_int32_t)tv->tv_sec;
        node.e2di_gid_low = getegid();
        node.e2di_nlink = PREDEFROOTDIR;
        /* e2di_nblock is a number of disk block, not ext2fs block */
        node.e2di_nblock = fsbtodb(&sblock, 1);
        node.e2di_blocks[0] = alloc(node.e2di_size, node.e2di_mode);
        if (node.e2di_blocks[0] == 0) {
                printf("%s: can't allocate block for root dir\n", __func__);
                return 0;
        }
        wtfs(fsbtodb(&sblock, node.e2di_blocks[0]), sblock.e2fs_bsize, buf);
        iput(&node, EXT2_ROOTINO);
        return 1;
}

/*
 * Construct a set of directory entries in "buf".
 * return size of directory.
 */
int
makedir(struct ext2fs_direct *protodir, int entries)
{
        uint8_t *cp;
        uint i, spcleft;
        uint dirblksiz;

        dirblksiz = sblock.e2fs_bsize;
        memset(buf, 0, dirblksiz);
        spcleft = dirblksiz;
        for (cp = buf, i = 0; i < entries - 1; i++) {
                protodir[i].e2d_reclen = EXT2FS_DIRSIZ(protodir[i].e2d_namlen);
                copy_dir(&protodir[i], (struct ext2fs_direct *)cp);
                cp += protodir[i].e2d_reclen;
                spcleft -= protodir[i].e2d_reclen;
        }
        protodir[i].e2d_reclen = spcleft;
        copy_dir(&protodir[i], (struct ext2fs_direct *)cp);
        return dirblksiz;
}

/*
 * Copy a direntry to a buffer, in fs byte order
 */
static void
copy_dir(struct ext2fs_direct *dir, struct ext2fs_direct *dbuf)
{

        memcpy(dbuf, dir, EXT2FS_DIRSIZ(dir->e2d_namlen));
        dbuf->e2d_ino = htole32(dir->e2d_ino);
        dbuf->e2d_reclen = htole16(dir->e2d_reclen);
}

/*
 * void init_resizeino(const struct timeval *tv);
 *
 *      Initialize the EXT2_RESEIZE_INO inode to preserve
 *      reserved group descriptor blocks for future growth of this ext2fs.
 */
void
init_resizeino(const struct timeval *tv)
{
        struct ext2fs_dinode node;
        uint64_t isize;
        uint32_t *dindir_block, *reserved_gdb;
        uint nblock, i, cylno, n;

        memset(&node, 0, sizeof(node));

        /*
         * Note this function only prepares required structures for
         * future resize. It's a quite different work to implement
         * a utility like resize_ext2fs(8) which handles actual
         * resize ops even on offline.
         *
         * Anyway, I'm not sure if there is any documentation about
         * this resize ext2fs feature and related data structures,
         * and I've written this function based on things what I see
         * on some existing implementation and real file system data
         * created by existing tools. To be honest, they are not
         * so easy to read, so I will try to implement it here without
         * any dumb optimization for people who would eventually
         * work on "yet another wheel" like resize_ext2fs(8).
         */

        /*
         * I'm not sure what type is appropriate for this inode.
         * The release notes of e2fsprogs says they changed e2fsck to allow
         * IFREG for RESIZEINO since a certain resize tool used it. Hmm.
         */
        node.e2di_mode = EXT2_IFREG | EXT2_RESIZEINOUMASK;
        node.e2di_uid_low = geteuid();
        node.e2di_atime = (u_int32_t)tv->tv_sec;
        node.e2di_ctime = (u_int32_t)tv->tv_sec;
        node.e2di_mtime = (u_int32_t)tv->tv_sec;
        node.e2di_gid_low = getegid();
        node.e2di_nlink = 1;

        /*
         * To preserve the reserved group descriptor blocks,
         * EXT2_RESIZEINO uses only double indirect reference
         * blocks in its inode entries.
         *
         * All entries for direct, single indirect and triple
         * indirect references are left zero'ed. Maybe it's safe
         * because no write operation will happen with this inode.
         *
         * We have to allocate a block for the first level double
         * indirect reference block. Indexes of inode entries in
         * this first level dindirect block are corresponding to
         * indexes of group descriptors including both used (e2fs_ngdb)
         * and reserved (e2fs_reserved_ngdb) group descriptor blocks.
         *
         * Inode entries of indexes for used (e2fs_ngdb) descriptors are
         * left zero'ed. Entries for reserved (e2fs_reserved_ngdb) ones
         * have block numbers of actual reserved group descriptors
         * allocated at block group zero. This means e2fs_reserved_ngdb
         * blocks are reserved as the second level dindirect reference
         * blocks, and they actually contain block numbers of indirect
         * references. It may be safe since they don't have to keep any
         * data yet.
         *
         * Each these second dindirect blocks (i.e. reserved group
         * descriptor blocks in the first block group) should have
         * block numbers of its backups in all other block groups.
         * I.e. reserved_ngdb[0] block in block group 0 contains block
         * numbers of resreved_ngdb[0] from group 1 through (e2fs_ncg - 1).
         * The number of backups can be determined by the
         * EXT2_ROCOMPAT_SPARSESUPER feature and cg_has_sb() macro
         * as done in the above initcg() function.
         */

        /* set e2di_size which occupies whole blocks through DINDIR blocks */
        isize = (uint64_t)sblock.e2fs_bsize * NDADDR +
            (uint64_t)sblock.e2fs_bsize * NINDIR(&sblock) +
            (uint64_t)sblock.e2fs_bsize * NINDIR(&sblock) * NINDIR(&sblock);
        if (isize > UINT32_MAX &&
            (sblock.e2fs.e2fs_features_rocompat &
             EXT2F_ROCOMPAT_LARGE_FILE) == 0) {
                /* XXX should enable it here and update all backups? */
                errx(EXIT_FAILURE, "%s: large_file rocompat feature is "
                    "required to enable resize feature for this filesystem\n",
                    __func__);
        }
        /* upper 32bit is stored into e2di_size_hi on REV1 feature */
        node.e2di_size = isize & UINT32_MAX;
        node.e2di_size_hi = isize >> 32;

#define SINGLE  0       /* index of single indirect block */
#define DOUBLE  1       /* index of double indirect block */
#define TRIPLE  2       /* index of triple indirect block */

        /* zero out entries for direct references */
        for (i = 0; i < NDADDR; i++)
                node.e2di_blocks[i] = 0;
        /* also zero out entries for single and triple indirect references */
        node.e2di_blocks[NDADDR + SINGLE] = 0;
        node.e2di_blocks[NDADDR + TRIPLE] = 0;

        /* allocate a block for the first level double indirect reference */
        node.e2di_blocks[NDADDR + DOUBLE] =
            alloc(sblock.e2fs_bsize, node.e2di_mode);
        if (node.e2di_blocks[NDADDR + DOUBLE] == 0)
                errx(EXIT_FAILURE, "%s: Can't allocate a dindirect block",
                    __func__);

        /* account this first block */
        nblock = fsbtodb(&sblock, 1);

        /* allocate buffer to set data in the dindirect block */
        dindir_block = malloc(sblock.e2fs_bsize);
        if (dindir_block == NULL)
                errx(EXIT_FAILURE,
                    "%s: Can't allocate buffer for a dindirect block",
                    __func__);

        /* allocate buffer to set data in the group descriptor blocks */
        reserved_gdb = malloc(sblock.e2fs_bsize);
        if (reserved_gdb == NULL)
                errx(EXIT_FAILURE,
                    "%s: Can't allocate buffer for group descriptor blocks",
                    __func__);

        /*
         * Setup block entries in the first level dindirect blocks
         */
        for (i = 0; i < sblock.e2fs_ngdb; i++) {
                /* no need to handle used group descriptor blocks */
                dindir_block[i] = 0;
        }
        for (; i < sblock.e2fs_ngdb + sblock.e2fs.e2fs_reserved_ngdb; i++) {
                /*
                 * point reserved group descriptor block in the first
                 * (i.e. master) block group
                 * 
                 * XXX: e2fsprogs seem to use "(i % NINDIR(&sblock))" here
                 *      to store maximum NINDIR(&sblock) reserved gdbs.
                 *      I'm not sure what will be done on future filesystem
                 *      shrink in that case on their way.
                 */
                if (i >= NINDIR(&sblock))
                        errx(EXIT_FAILURE, "%s: too many reserved "
                            "group descriptors (%u) for resize inode",
                            __func__, sblock.e2fs.e2fs_reserved_ngdb);
                dindir_block[i] =
                    htole32(cgbase(&sblock, 0) + NBLOCK_SUPERBLOCK + i);

                /*
                 * Setup block entries in the second dindirect blocks
                 * (which are primary reserved group descriptor blocks)
                 * to point their backups.
                 */
                for (n = 0, cylno = 1; cylno < sblock.e2fs_ncg; cylno++) {
                        /* skip block groups without backup */
                        if ((sblock.e2fs.e2fs_features_rocompat &
                             EXT2F_ROCOMPAT_SPARSE_SUPER) != 0 &&
                            cg_has_sb(cylno) == 0)
                                continue;

                        if (n >= NINDIR(&sblock))
                                errx(EXIT_FAILURE, "%s: too many block groups "
                                    "for the resize feature", __func__);
                        /*
                         * These blocks are already reserved in
                         * initcg() so no need to use alloc() here.
                         */
                        reserved_gdb[n++] = htole32(cgbase(&sblock, cylno) +
                            NBLOCK_SUPERBLOCK + i);
                        nblock += fsbtodb(&sblock, 1);
                }
                for (; n < NINDIR(&sblock); n++)
                        reserved_gdb[n] = 0;

                /* write group descriptor block as the second dindirect refs */
                wtfs(fsbtodb(&sblock, letoh32(dindir_block[i])),
                    sblock.e2fs_bsize, reserved_gdb);
                nblock += fsbtodb(&sblock, 1);
        }
        for (; i < NINDIR(&sblock); i++) {
                /* leave trailing entries unallocated */
                dindir_block[i] = 0;
        }
        free(reserved_gdb);

        /* finally write the first level dindirect block */
        wtfs(fsbtodb(&sblock, node.e2di_blocks[NDADDR + DOUBLE]),
            sblock.e2fs_bsize, dindir_block);
        free(dindir_block);

        node.e2di_nblock = nblock;
        iput(&node, EXT2_RESIZEINO);
}

/*
 * uint32_t alloc(uint32_t size, uint16_t mode)
 *
 *      Allocate a block (from cylinder group 0)
 *      Reference: src/sys/ufs/ext2fs/ext2fs_alloc.c:ext2fs_alloccg()
 */
uint32_t
alloc(uint32_t size, uint16_t mode)
{
        uint32_t loc, bno;
        uint8_t *bbp;
        uint len, map, i;

        if (gd[0].ext2bgd_nbfree == 0)
                return 0;

        if (size > sblock.e2fs_bsize)
                return 0;

        bbp = malloc(sblock.e2fs_bsize);
        if (bbp == NULL)
                return 0;
        rdfs(fsbtodb(&sblock, gd[0].ext2bgd_b_bitmap), sblock.e2fs_bsize, bbp);

        /* XXX: kernel uses e2fs_fpg here */
        len = sblock.e2fs.e2fs_bpg / NBBY;

#if 0   /* no need block allocation for root or lost+found dir */
        for (loc = 0; loc < len; loc++) {
                if (bbp[loc] == 0) {
                        bno = loc * NBBY;
                        goto gotit;
                }
        }
#endif

        loc = skpc(~0U, len, bbp);
        if (loc == 0) {
                free(bbp);
                return 0;
        }
        loc = len - loc;
        map = bbp[loc];
        bno = loc * NBBY;
        for (i = 0; i < NBBY; i++, bno++) {
                if ((map & (1 << i)) == 0)
                        goto gotit;
        }
        free(bbp);
        return 0;
        
 gotit:
        if (isset(bbp, bno))
                errx(EXIT_FAILURE, "%s: inconsistent bitmap\n", __func__);

        setbit(bbp, bno);
        wtfs(fsbtodb(&sblock, gd[0].ext2bgd_b_bitmap), sblock.e2fs_bsize, bbp);
        free(bbp);
        /* XXX: modified group descriptors won't be written into backups */
        gd[0].ext2bgd_nbfree--;
        if ((mode & EXT2_IFDIR) != 0)
                gd[0].ext2bgd_ndirs++;
        sblock.e2fs.e2fs_fbcount--;

        return sblock.e2fs.e2fs_first_dblock + bno;
}

/*
 * void iput(struct ext2fs_dinode *ip, ino_t ino)
 *
 *      Put an inode entry into the corresponding table.
 */
static void
iput(struct ext2fs_dinode *ip, ino_t ino)
{
        daddr32_t d;
        uint c, i;
        struct ext2fs_dinode *dp;
        uint8_t *bp;

        bp = malloc(sblock.e2fs_bsize);
        if (bp == NULL)
                errx(EXIT_FAILURE, "%s: can't allocate buffer for inode\n",
                    __func__);

        /*
         * Reserved inodes are allocated and accounted in initcg()
         * so skip checks of the bitmap and allocation for them.
         */
        if (ino >= EXT2_FIRSTINO) {
                c = ino_to_cg(&sblock, ino);

                /* sanity check */
                if (gd[c].ext2bgd_nifree == 0)
                        errx(EXIT_FAILURE,
                            "%s: no free inode %" PRIu64 " in block group %u\n",
                            __func__, (uint64_t)ino, c);

                /* update inode bitmap */
                rdfs(fsbtodb(&sblock, gd[0].ext2bgd_i_bitmap),
                    sblock.e2fs_bsize, bp);

                /* more sanity */
                if (isset(bp, EXT2_INO_INDEX(ino)))
                        errx(EXIT_FAILURE, "%s: inode %" PRIu64
                            " already in use\n", __func__, (uint64_t)ino);
                setbit(bp, EXT2_INO_INDEX(ino));
                wtfs(fsbtodb(&sblock, gd[0].ext2bgd_i_bitmap),
                    sblock.e2fs_bsize, bp);
                gd[c].ext2bgd_nifree--;
                sblock.e2fs.e2fs_ficount--;
        }

        if (ino >= sblock.e2fs.e2fs_ipg * sblock.e2fs_ncg)
                errx(EXIT_FAILURE, "%s: inode value out of range (%" PRIu64
                    ").\n", __func__, (uint64_t)ino);

        /* update an inode entry in the table */
        d = fsbtodb(&sblock, ino_to_fsba(&sblock, ino));
        rdfs(d, sblock.e2fs_bsize, bp);

        dp = (struct ext2fs_dinode *)(bp +
            inodesize * ino_to_fsbo(&sblock, ino));
        e2fs_isave(&sblock, ip, dp);
        /* e2fs_i_bswap() doesn't swap e2di_blocks addrs */
        if ((ip->e2di_mode & EXT2_IFMT) != EXT2_IFLNK) {
                for (i = 0; i < NDADDR + NIADDR; i++)
                        dp->e2di_blocks[i] = htole32(ip->e2di_blocks[i]);
        }
        /* If there is some bias in arc4random(), keep it. */
        dp->e2di_gen = htole32(arc4random());

        wtfs(d, sblock.e2fs_bsize, bp);
        free(bp);
}

/*
 * Read a block from the file system
 */
void
rdfs(daddr32_t bno, int size, void *bf)
{
        int n;
        off_t offset;

        offset = bno;
        n = pread(fd, bf, size, offset * sectorsize);
        if (n != size)
                err(EXIT_FAILURE, "%s: read error for sector %" PRId64,
                    __func__, (int64_t)bno);
}

/*
 * Write a block to the file system
 */
void
wtfs(daddr32_t bno, int size, void *bf)
{
        int n;
        off_t offset;

        if (Nflag)
                return;
        offset = bno;
        n = pwrite(fd, bf, size, offset * sectorsize);
        if (n != size)
                err(EXIT_FAILURE, "%s: write error for sector %" PRId64,
                    __func__, (int64_t)bno);
}

int
ilog2(uint val)
{

        if (val == 0 || !powerof2(val))
                errx(EXIT_FAILURE, "%s: %u is not a power of 2\n",
                    __func__, val);

        return ffs(val) - 1;
}

/*
 * int skpc(int mask, size_t size, uint8_t *cp)
 *
 *      Locate an unsigned character of value mask inside cp[].
 *      (from src/sys/lib/libkern/skpc.c)
 */
int
skpc(int mask, size_t size, uint8_t *cp)
{
        uint8_t *end;

        end = &cp[size];
        while (cp < end && *cp == (uint8_t)mask)
                cp++;

        return end - cp;
}

static void
uuid_get(struct m_ext2fs *sb)
{
        unsigned char buf[sizeof(sb->e2fs.e2fs_uuid)];

        arc4random_buf(buf, sizeof(buf));
        /* UUID version 4: random */
        buf[6] &= 0x0f;
        buf[6] |= 0x40;
        /* RFC4122 variant */
        buf[8] &= 0x3f;
        buf[8] |= 0x80;
        memcpy(sb->e2fs.e2fs_uuid, buf, sizeof(sb->e2fs.e2fs_uuid));
}