/*-
 *  modified for Lites 1.1
 *
 *  Aug 1995, Godmar Back (gback@cs.utah.edu)
 *  University of Utah, Department of Computer Science
 */
/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1982, 1986, 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.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/vnode.h>
#include <sys/sdt.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/buf.h>
#include <sys/endian.h>

#include <fs/ext2fs/fs.h>
#include <fs/ext2fs/inode.h>
#include <fs/ext2fs/ext2_mount.h>
#include <fs/ext2fs/ext2fs.h>
#include <fs/ext2fs/ext2_extern.h>

SDT_PROVIDER_DEFINE(ext2fs);
/*
 * ext2fs trace probe:
 * arg0: verbosity. Higher numbers give more verbose messages
 * arg1: Textual message
 */
SDT_PROBE_DEFINE2(ext2fs, , alloc, trace, "int", "char*");
SDT_PROBE_DEFINE3(ext2fs, , alloc, ext2_reallocblks_realloc,
    "ino_t", "e2fs_lbn_t", "e2fs_lbn_t");
SDT_PROBE_DEFINE1(ext2fs, , alloc, ext2_reallocblks_bap, "uint32_t");
SDT_PROBE_DEFINE1(ext2fs, , alloc, ext2_reallocblks_blkno, "e2fs_daddr_t");
SDT_PROBE_DEFINE2(ext2fs, , alloc, ext2_b_bitmap_validate_error, "char*", "int");
SDT_PROBE_DEFINE3(ext2fs, , alloc, ext2_nodealloccg_bmap_corrupted,
    "int", "daddr_t", "char*");
SDT_PROBE_DEFINE2(ext2fs, , alloc, ext2_blkfree_bad_block, "ino_t", "e4fs_daddr_t");
SDT_PROBE_DEFINE2(ext2fs, , alloc, ext2_vfree_doublefree, "char*", "ino_t");

static daddr_t  ext2_alloccg(struct inode *, int, daddr_t, int);
static daddr_t  ext2_clusteralloc(struct inode *, int, daddr_t, int);
static u_long   ext2_dirpref(struct inode *);
static e4fs_daddr_t ext2_hashalloc(struct inode *, int, long, int,
    daddr_t (*)(struct inode *, int, daddr_t, 
                                                int));
static daddr_t  ext2_nodealloccg(struct inode *, int, daddr_t, int);
static daddr_t  ext2_mapsearch(struct m_ext2fs *, char *, daddr_t);

/*
 * Allocate a block in the filesystem.
 *
 * A preference may be optionally specified. If a preference is given
 * the following hierarchy is used to allocate a block:
 *   1) allocate the requested block.
 *   2) allocate a rotationally optimal block in the same cylinder.
 *   3) allocate a block in the same cylinder group.
 *   4) quadratically rehash into other cylinder groups, until an
 *        available block is located.
 * If no block preference is given the following hierarchy is used
 * to allocate a block:
 *   1) allocate a block in the cylinder group that contains the
 *        inode for the file.
 *   2) quadratically rehash into other cylinder groups, until an
 *        available block is located.
 */
int
ext2_alloc(struct inode *ip, daddr_t lbn, e4fs_daddr_t bpref, int size,
    struct ucred *cred, e4fs_daddr_t *bnp)
{
        struct m_ext2fs *fs;
        struct ext2mount *ump;
        e4fs_daddr_t bno;
        int cg;

        *bnp = 0;
        fs = ip->i_e2fs;
        ump = ip->i_ump;
        mtx_assert(EXT2_MTX(ump), MA_OWNED);
#ifdef INVARIANTS
        if ((u_int)size > fs->e2fs_bsize || blkoff(fs, size) != 0) {
                vn_printf(ip->i_devvp, "bsize = %lu, size = %d, fs = %s\n",
                    (long unsigned int)fs->e2fs_bsize, size, fs->e2fs_fsmnt);
                panic("ext2_alloc: bad size");
        }
        if (cred == NOCRED)
                panic("ext2_alloc: missing credential");
#endif          /* INVARIANTS */
        if (size == fs->e2fs_bsize && fs->e2fs_fbcount == 0)
                goto nospace;
        if (cred->cr_uid != 0 &&
            fs->e2fs_fbcount < fs->e2fs_rbcount)
                goto nospace;
        if (bpref >= fs->e2fs_bcount)
                bpref = 0;
        if (bpref == 0)
                cg = ino_to_cg(fs, ip->i_number);
        else
                cg = dtog(fs, bpref);
        bno = (daddr_t)ext2_hashalloc(ip, cg, bpref, fs->e2fs_bsize,
            ext2_alloccg);
        if (bno > 0) {
                /* set next_alloc fields as done in block_getblk */
                ip->i_next_alloc_block = lbn;
                ip->i_next_alloc_goal = bno;

                ip->i_blocks += btodb(fs->e2fs_bsize);
                ip->i_flag |= IN_CHANGE | IN_UPDATE;
                *bnp = bno;
                return (0);
        }
nospace:
        EXT2_UNLOCK(ump);
        SDT_PROBE2(ext2fs, , alloc, trace, 1, "cannot allocate data block");
        return (ENOSPC);
}

/*
 * Allocate EA's block for inode.
 */
e4fs_daddr_t
ext2_alloc_meta(struct inode *ip)
{
        struct m_ext2fs *fs;
        daddr_t blk;

        fs = ip->i_e2fs;

        EXT2_LOCK(ip->i_ump);
        blk = ext2_hashalloc(ip, ino_to_cg(fs, ip->i_number), 0, fs->e2fs_bsize,
            ext2_alloccg);
        if (0 == blk) {
                EXT2_UNLOCK(ip->i_ump);
                SDT_PROBE2(ext2fs, , alloc, trace, 1, "cannot allocate meta block");
        }

        return (blk);
}

/*
 * Reallocate a sequence of blocks into a contiguous sequence of blocks.
 *
 * The vnode and an array of buffer pointers for a range of sequential
 * logical blocks to be made contiguous is given. The allocator attempts
 * to find a range of sequential blocks starting as close as possible to
 * an fs_rotdelay offset from the end of the allocation for the logical
 * block immediately preceding the current range. If successful, the
 * physical block numbers in the buffer pointers and in the inode are
 * changed to reflect the new allocation. If unsuccessful, the allocation
 * is left unchanged. The success in doing the reallocation is returned.
 * Note that the error return is not reflected back to the user. Rather
 * the previous block allocation will be used.
 */

static SYSCTL_NODE(_vfs, OID_AUTO, ext2fs, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "EXT2FS filesystem");

static int doasyncfree = 1;

SYSCTL_INT(_vfs_ext2fs, OID_AUTO, doasyncfree, CTLFLAG_RW, &doasyncfree, 0,
    "Use asynchronous writes to update block pointers when freeing blocks");

static int doreallocblks = 0;

SYSCTL_INT(_vfs_ext2fs, OID_AUTO, doreallocblks, CTLFLAG_RW, &doreallocblks, 0, "");

int
ext2_reallocblks(struct vop_reallocblks_args *ap)
{
        struct m_ext2fs *fs;
        struct inode *ip;
        struct vnode *vp;
        struct buf *sbp, *ebp;
        uint32_t *bap, *sbap, *ebap;
        struct ext2mount *ump;
        struct cluster_save *buflist;
        struct indir start_ap[EXT2_NIADDR + 1], end_ap[EXT2_NIADDR + 1], *idp;
        e2fs_lbn_t start_lbn, end_lbn;
        int soff;
        e2fs_daddr_t newblk, blkno;
        int i, len, start_lvl, end_lvl, pref, ssize;

        if (doreallocblks == 0)
                return (ENOSPC);

        vp = ap->a_vp;
        ip = VTOI(vp);
        fs = ip->i_e2fs;
        ump = ip->i_ump;

        if (fs->e2fs_contigsumsize <= 0 || ip->i_flag & IN_E4EXTENTS)
                return (ENOSPC);

        buflist = ap->a_buflist;
        len = buflist->bs_nchildren;
        start_lbn = buflist->bs_children[0]->b_lblkno;
        end_lbn = start_lbn + len - 1;
#ifdef INVARIANTS
        for (i = 1; i < len; i++)
                if (buflist->bs_children[i]->b_lblkno != start_lbn + i)
                        panic("ext2_reallocblks: non-cluster");
#endif
        /*
         * If the cluster crosses the boundary for the first indirect
         * block, leave space for the indirect block. Indirect blocks
         * are initially laid out in a position after the last direct
         * block. Block reallocation would usually destroy locality by
         * moving the indirect block out of the way to make room for
         * data blocks if we didn't compensate here. We should also do
         * this for other indirect block boundaries, but it is only
         * important for the first one.
         */
        if (start_lbn < EXT2_NDADDR && end_lbn >= EXT2_NDADDR)
                return (ENOSPC);
        /*
         * If the latest allocation is in a new cylinder group, assume that
         * the filesystem has decided to move and do not force it back to
         * the previous cylinder group.
         */
        if (dtog(fs, dbtofsb(fs, buflist->bs_children[0]->b_blkno)) !=
            dtog(fs, dbtofsb(fs, buflist->bs_children[len - 1]->b_blkno)))
                return (ENOSPC);
        if (ext2_getlbns(vp, start_lbn, start_ap, &start_lvl) ||
            ext2_getlbns(vp, end_lbn, end_ap, &end_lvl))
                return (ENOSPC);
        /*
         * Get the starting offset and block map for the first block.
         */
        if (start_lvl == 0) {
                sbap = &ip->i_db[0];
                soff = start_lbn;
        } else {
                idp = &start_ap[start_lvl - 1];
                if (bread(vp, idp->in_lbn, (int)fs->e2fs_bsize, NOCRED, &sbp)) {
                        brelse(sbp);
                        return (ENOSPC);
                }
                sbap = (u_int *)sbp->b_data;
                soff = idp->in_off;
        }
        /*
         * If the block range spans two block maps, get the second map.
         */
        ebap = NULL;
        if (end_lvl == 0 || (idp = &end_ap[end_lvl - 1])->in_off + 1 >= len) {
                ssize = len;
        } else {
#ifdef INVARIANTS
                if (start_ap[start_lvl - 1].in_lbn == idp->in_lbn)
                        panic("ext2_reallocblks: start == end");
#endif
                ssize = len - (idp->in_off + 1);
                if (bread(vp, idp->in_lbn, (int)fs->e2fs_bsize, NOCRED, &ebp))
                        goto fail;
                ebap = (u_int *)ebp->b_data;
        }
        /*
         * Find the preferred location for the cluster.
         */
        EXT2_LOCK(ump);
        pref = ext2_blkpref(ip, start_lbn, soff, sbap, 0);
        /*
         * Search the block map looking for an allocation of the desired size.
         */
        if ((newblk = (e2fs_daddr_t)ext2_hashalloc(ip, dtog(fs, pref), pref,
            len, ext2_clusteralloc)) == 0) {
                EXT2_UNLOCK(ump);
                goto fail;
        }
        /*
         * We have found a new contiguous block.
         *
         * First we have to replace the old block pointers with the new
         * block pointers in the inode and indirect blocks associated
         * with the file.
         */
        SDT_PROBE3(ext2fs, , alloc, ext2_reallocblks_realloc,
            ip->i_number, start_lbn, end_lbn);
        blkno = newblk;
        for (bap = &sbap[soff], i = 0; i < len; i++, blkno += fs->e2fs_fpb) {
                if (i == ssize) {
                        bap = ebap;
                        soff = -i;
                }
#ifdef INVARIANTS
                if (buflist->bs_children[i]->b_blkno != fsbtodb(fs, *bap))
                        panic("ext2_reallocblks: alloc mismatch");
#endif
                SDT_PROBE1(ext2fs, , alloc, ext2_reallocblks_bap, *bap);
                *bap++ = blkno;
        }
        /*
         * Next we must write out the modified inode and indirect blocks.
         * For strict correctness, the writes should be synchronous since
         * the old block values may have been written to disk. In practise
         * they are almost never written, but if we are concerned about
         * strict correctness, the `doasyncfree' flag should be set to zero.
         *
         * The test on `doasyncfree' should be changed to test a flag
         * that shows whether the associated buffers and inodes have
         * been written. The flag should be set when the cluster is
         * started and cleared whenever the buffer or inode is flushed.
         * We can then check below to see if it is set, and do the
         * synchronous write only when it has been cleared.
         */
        if (sbap != &ip->i_db[0]) {
                if (doasyncfree)
                        bdwrite(sbp);
                else
                        bwrite(sbp);
        } else {
                ip->i_flag |= IN_CHANGE | IN_UPDATE;
                if (!doasyncfree)
                        ext2_update(vp, 1);
        }
        if (ssize < len) {
                if (doasyncfree)
                        bdwrite(ebp);
                else
                        bwrite(ebp);
        }
        /*
         * Last, free the old blocks and assign the new blocks to the buffers.
         */
        for (blkno = newblk, i = 0; i < len; i++, blkno += fs->e2fs_fpb) {
                ext2_blkfree(ip, dbtofsb(fs, buflist->bs_children[i]->b_blkno),
                    fs->e2fs_bsize);
                buflist->bs_children[i]->b_blkno = fsbtodb(fs, blkno);
                SDT_PROBE1(ext2fs, , alloc, ext2_reallocblks_blkno, blkno);
        }

        return (0);

fail:
        if (ssize < len)
                brelse(ebp);
        if (sbap != &ip->i_db[0])
                brelse(sbp);
        return (ENOSPC);
}

/*
 * Allocate an inode in the filesystem.
 *
 */
int
ext2_valloc(struct vnode *pvp, int mode, struct ucred *cred, struct vnode **vpp)
{
        struct timespec ts;
        struct m_ext2fs *fs;
        struct ext2mount *ump;
        struct inode *pip;
        struct inode *ip;
        struct vnode *vp;
        struct thread *td;
        ino_t ino, ipref;
        int error, cg;

        *vpp = NULL;
        pip = VTOI(pvp);
        fs = pip->i_e2fs;
        ump = pip->i_ump;

        EXT2_LOCK(ump);
        if (fs->e2fs_ficount == 0)
                goto noinodes;
        /*
         * If it is a directory then obtain a cylinder group based on
         * ext2_dirpref else obtain it using ino_to_cg. The preferred inode is
         * always the next inode.
         */
        if ((mode & IFMT) == IFDIR) {
                cg = ext2_dirpref(pip);
                if (fs->e2fs_contigdirs[cg] < 255)
                        fs->e2fs_contigdirs[cg]++;
        } else {
                cg = ino_to_cg(fs, pip->i_number);
                if (fs->e2fs_contigdirs[cg] > 0)
                        fs->e2fs_contigdirs[cg]--;
        }
        ipref = cg * fs->e2fs_ipg + 1;
        ino = (ino_t)ext2_hashalloc(pip, cg, (long)ipref, mode, ext2_nodealloccg);
        if (ino == 0)
                goto noinodes;

        td = curthread;
        error = vfs_hash_get(ump->um_mountp, ino, LK_EXCLUSIVE, td, vpp, NULL, NULL);
        if (error || *vpp != NULL) {
                return (error);
        }

        ip = malloc(sizeof(struct inode), M_EXT2NODE, M_WAITOK | M_ZERO);

        /* Allocate a new vnode/inode. */
        if ((error = getnewvnode("ext2fs", ump->um_mountp, &ext2_vnodeops, &vp)) != 0) {
                free(ip, M_EXT2NODE);
                return (error);
        }

        lockmgr(vp->v_vnlock, LK_EXCLUSIVE, NULL);
        vp->v_data = ip;
        ip->i_vnode = vp;
        ip->i_e2fs = fs = ump->um_e2fs;
        ip->i_ump = ump;
        ip->i_number = ino;
        ip->i_block_group = ino_to_cg(fs, ino);
        ip->i_next_alloc_block = 0;
        ip->i_next_alloc_goal = 0;

        error = insmntque(vp, ump->um_mountp);
        if (error) {
                free(ip, M_EXT2NODE);
                return (error);
        }

        error = vfs_hash_insert(vp, ino, LK_EXCLUSIVE, td, vpp, NULL, NULL);
        if (error || *vpp != NULL) {
                *vpp = NULL;
                free(ip, M_EXT2NODE);
                return (error);
        }

        if ((error = ext2_vinit(ump->um_mountp, &ext2_fifoops, &vp)) != 0) {
                vput(vp);
                *vpp = NULL;
                free(ip, M_EXT2NODE);
                return (error);
        }

        if (EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_EXTENTS)
            && (S_ISREG(mode) || S_ISDIR(mode)))
                ext4_ext_tree_init(ip);
        else
                memset(ip->i_data, 0, sizeof(ip->i_data));

        /*
         * Set up a new generation number for this inode.
         * Avoid zero values.
         */
        do {
                ip->i_gen = arc4random();
        } while (ip->i_gen == 0);

        vfs_timestamp(&ts);
        ip->i_birthtime = ts.tv_sec;
        ip->i_birthnsec = ts.tv_nsec;

        vn_set_state(vp, VSTATE_CONSTRUCTED);
        *vpp = vp;

        return (0);

noinodes:
        EXT2_UNLOCK(ump);
        SDT_PROBE2(ext2fs, , alloc, trace, 1, "out of inodes");
        return (ENOSPC);
}

/*
 * 64-bit compatible getters and setters for struct ext2_gd from ext2fs.h
 */
uint64_t
e2fs_gd_get_b_bitmap(struct ext2_gd *gd)
{

        return (((uint64_t)(le32toh(gd->ext4bgd_b_bitmap_hi)) << 32) |
            le32toh(gd->ext2bgd_b_bitmap));
}

uint64_t
e2fs_gd_get_i_bitmap(struct ext2_gd *gd)
{

        return (((uint64_t)(le32toh(gd->ext4bgd_i_bitmap_hi)) << 32) |
            le32toh(gd->ext2bgd_i_bitmap));
}

uint64_t
e2fs_gd_get_i_tables(struct ext2_gd *gd)
{

        return (((uint64_t)(le32toh(gd->ext4bgd_i_tables_hi)) << 32) |
            le32toh(gd->ext2bgd_i_tables));
}

static uint32_t
e2fs_gd_get_nbfree(struct ext2_gd *gd)
{

        return (((uint32_t)(le16toh(gd->ext4bgd_nbfree_hi)) << 16) |
            le16toh(gd->ext2bgd_nbfree));
}

static void
e2fs_gd_set_nbfree(struct ext2_gd *gd, uint32_t val)
{

        gd->ext2bgd_nbfree = htole16(val & 0xffff);
        gd->ext4bgd_nbfree_hi = htole16(val >> 16);
}

static uint32_t
e2fs_gd_get_nifree(struct ext2_gd *gd)
{

        return (((uint32_t)(le16toh(gd->ext4bgd_nifree_hi)) << 16) |
            le16toh(gd->ext2bgd_nifree));
}

static void
e2fs_gd_set_nifree(struct ext2_gd *gd, uint32_t val)
{

        gd->ext2bgd_nifree = htole16(val & 0xffff);
        gd->ext4bgd_nifree_hi = htole16(val >> 16);
}

uint32_t
e2fs_gd_get_ndirs(struct ext2_gd *gd)
{

        return (((uint32_t)(le16toh(gd->ext4bgd_ndirs_hi)) << 16) |
            le16toh(gd->ext2bgd_ndirs));
}

static void
e2fs_gd_set_ndirs(struct ext2_gd *gd, uint32_t val)
{

        gd->ext2bgd_ndirs = htole16(val & 0xffff);
        gd->ext4bgd_ndirs_hi = htole16(val >> 16);
}

static uint32_t
e2fs_gd_get_i_unused(struct ext2_gd *gd)
{
        return ((uint32_t)(le16toh(gd->ext4bgd_i_unused_hi) << 16) |
            le16toh(gd->ext4bgd_i_unused));
}

static void
e2fs_gd_set_i_unused(struct ext2_gd *gd, uint32_t val)
{

        gd->ext4bgd_i_unused = htole16(val & 0xffff);
        gd->ext4bgd_i_unused_hi = htole16(val >> 16);
}

/*
 * Find a cylinder to place a directory.
 *
 * The policy implemented by this algorithm is to allocate a
 * directory inode in the same cylinder group as its parent
 * directory, but also to reserve space for its files inodes
 * and data. Restrict the number of directories which may be
 * allocated one after another in the same cylinder group
 * without intervening allocation of files.
 *
 * If we allocate a first level directory then force allocation
 * in another cylinder group.
 *
 */
static u_long
ext2_dirpref(struct inode *pip)
{
        struct m_ext2fs *fs;
        int cg, prefcg, cgsize;
        uint64_t avgbfree, minbfree;
        u_int avgifree, avgndir, curdirsize;
        u_int minifree, maxndir;
        u_int mincg, minndir;
        u_int dirsize, maxcontigdirs;

        mtx_assert(EXT2_MTX(pip->i_ump), MA_OWNED);
        fs = pip->i_e2fs;

        avgifree = fs->e2fs_ficount / fs->e2fs_gcount;
        avgbfree = fs->e2fs_fbcount / fs->e2fs_gcount;
        avgndir = fs->e2fs_total_dir / fs->e2fs_gcount;

        /*
         * Force allocation in another cg if creating a first level dir.
         */
        ASSERT_VOP_LOCKED(ITOV(pip), "ext2fs_dirpref");
        if (ITOV(pip)->v_vflag & VV_ROOT) {
                prefcg = arc4random() % fs->e2fs_gcount;
                mincg = prefcg;
                minndir = fs->e2fs_ipg;
                for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
                        if (e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) < minndir &&
                            e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= avgifree &&
                            e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) >= avgbfree) {
                                mincg = cg;
                                minndir = e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]);
                        }
                for (cg = 0; cg < prefcg; cg++)
                        if (e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) < minndir &&
                            e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= avgifree &&
                            e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) >= avgbfree) {
                                mincg = cg;
                                minndir = e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]);
                        }
                return (mincg);
        }
        /*
         * Count various limits which used for
         * optimal allocation of a directory inode.
         */
        maxndir = min(avgndir + fs->e2fs_ipg / 16, fs->e2fs_ipg);
        minifree = avgifree - avgifree / 4;
        if (minifree < 1)
                minifree = 1;
        minbfree = avgbfree - avgbfree / 4;
        if (minbfree < 1)
                minbfree = 1;
        cgsize = fs->e2fs_fsize * fs->e2fs_fpg;
        dirsize = AVGDIRSIZE;
        curdirsize = avgndir ?
            (cgsize - avgbfree * fs->e2fs_bsize) / avgndir : 0;
        if (dirsize < curdirsize)
                dirsize = curdirsize;
        maxcontigdirs = min((avgbfree * fs->e2fs_bsize) / dirsize, 255);
        maxcontigdirs = min(maxcontigdirs, fs->e2fs_ipg / AFPDIR);
        if (maxcontigdirs == 0)
                maxcontigdirs = 1;

        /*
         * Limit number of dirs in one cg and reserve space for
         * regular files, but only if we have no deficit in
         * inodes or space.
         */
        prefcg = ino_to_cg(fs, pip->i_number);
        for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
                if (e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) < maxndir &&
                    e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= minifree &&
                    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) >= minbfree) {
                        if (fs->e2fs_contigdirs[cg] < maxcontigdirs)
                                return (cg);
                }
        for (cg = 0; cg < prefcg; cg++)
                if (e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) < maxndir &&
                    e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= minifree &&
                    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) >= minbfree) {
                        if (fs->e2fs_contigdirs[cg] < maxcontigdirs)
                                return (cg);
                }
        /*
         * This is a backstop when we have deficit in space.
         */
        for (cg = prefcg; cg < fs->e2fs_gcount; cg++)
                if (e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= avgifree)
                        return (cg);
        for (cg = 0; cg < prefcg; cg++)
                if (e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) >= avgifree)
                        break;
        return (cg);
}

/*
 * Select the desired position for the next block in a file.
 *
 * we try to mimic what Remy does in inode_getblk/block_getblk
 *
 * we note: blocknr == 0 means that we're about to allocate either
 * a direct block or a pointer block at the first level of indirection
 * (In other words, stuff that will go in i_db[] or i_ib[])
 *
 * blocknr != 0 means that we're allocating a block that is none
 * of the above. Then, blocknr tells us the number of the block
 * that will hold the pointer
 */
e4fs_daddr_t
ext2_blkpref(struct inode *ip, e2fs_lbn_t lbn, int indx, e2fs_daddr_t *bap,
    e2fs_daddr_t blocknr)
{
        struct m_ext2fs *fs;
        int tmp;

        fs = ip->i_e2fs;

        mtx_assert(EXT2_MTX(ip->i_ump), MA_OWNED);

        /*
         * If the next block is actually what we thought it is, then set the
         * goal to what we thought it should be.
         */
        if (ip->i_next_alloc_block == lbn && ip->i_next_alloc_goal != 0)
                return ip->i_next_alloc_goal;

        /*
         * Now check whether we were provided with an array that basically
         * tells us previous blocks to which we want to stay close.
         */
        if (bap)
                for (tmp = indx - 1; tmp >= 0; tmp--)
                        if (bap[tmp])
                                return (le32toh(bap[tmp]));

        /*
         * Else lets fall back to the blocknr or, if there is none, follow
         * the rule that a block should be allocated near its inode.
         */
        return (blocknr ? blocknr :
            (e2fs_daddr_t)(ip->i_block_group *
            EXT2_BLOCKS_PER_GROUP(fs)) + le32toh(fs->e2fs->e2fs_first_dblock));
}

/*
 * Implement the cylinder overflow algorithm.
 *
 * The policy implemented by this algorithm is:
 *   1) allocate the block in its requested cylinder group.
 *   2) quadratically rehash on the cylinder group number.
 *   3) brute force search for a free block.
 */
static e4fs_daddr_t
ext2_hashalloc(struct inode *ip, int cg, long pref, int size,
    daddr_t (*allocator) (struct inode *, int, daddr_t, int))
{
        struct m_ext2fs *fs;
        e4fs_daddr_t result;
        int i, icg = cg;

        mtx_assert(EXT2_MTX(ip->i_ump), MA_OWNED);
        fs = ip->i_e2fs;
        /*
         * 1: preferred cylinder group
         */
        result = (*allocator)(ip, cg, pref, size);
        if (result)
                return (result);
        /*
         * 2: quadratic rehash
         */
        for (i = 1; i < fs->e2fs_gcount; i *= 2) {
                cg += i;
                if (cg >= fs->e2fs_gcount)
                        cg -= fs->e2fs_gcount;
                result = (*allocator)(ip, cg, 0, size);
                if (result)
                        return (result);
        }
        /*
         * 3: brute force search
         * Note that we start at i == 2, since 0 was checked initially,
         * and 1 is always checked in the quadratic rehash.
         */
        cg = (icg + 2) % fs->e2fs_gcount;
        for (i = 2; i < fs->e2fs_gcount; i++) {
                result = (*allocator)(ip, cg, 0, size);
                if (result)
                        return (result);
                cg++;
                if (cg == fs->e2fs_gcount)
                        cg = 0;
        }
        return (0);
}

static uint64_t
ext2_cg_number_gdb_nometa(struct m_ext2fs *fs, int cg)
{

        if (!ext2_cg_has_sb(fs, cg))
                return (0);

        if (EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_META_BG))
                return (le32toh(fs->e2fs->e3fs_first_meta_bg));

        return ((fs->e2fs_gcount + EXT2_DESCS_PER_BLOCK(fs) - 1) /
            EXT2_DESCS_PER_BLOCK(fs));
}

static uint64_t
ext2_cg_number_gdb_meta(struct m_ext2fs *fs, int cg)
{
        unsigned long metagroup;
        int first, last;

        metagroup = cg / EXT2_DESCS_PER_BLOCK(fs);
        first = metagroup * EXT2_DESCS_PER_BLOCK(fs);
        last = first + EXT2_DESCS_PER_BLOCK(fs) - 1;

        if (cg == first || cg == first + 1 || cg == last)
                return (1);

        return (0);
}

uint64_t
ext2_cg_number_gdb(struct m_ext2fs *fs, int cg)
{
        unsigned long first_meta_bg, metagroup;

        first_meta_bg = le32toh(fs->e2fs->e3fs_first_meta_bg);
        metagroup = cg / EXT2_DESCS_PER_BLOCK(fs);

        if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_META_BG) ||
            metagroup < first_meta_bg)
                return (ext2_cg_number_gdb_nometa(fs, cg));

        return ext2_cg_number_gdb_meta(fs, cg);
}

static int
ext2_number_base_meta_blocks(struct m_ext2fs *fs, int cg)
{
        int number;

        number = ext2_cg_has_sb(fs, cg);

        if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_META_BG) ||
            cg < le32toh(fs->e2fs->e3fs_first_meta_bg) *
            EXT2_DESCS_PER_BLOCK(fs)) {
                if (number) {
                        number += ext2_cg_number_gdb(fs, cg);
                        number += le16toh(fs->e2fs->e2fs_reserved_ngdb);
                }
        } else {
                number += ext2_cg_number_gdb(fs, cg);
        }

        return (number);
}

static void
ext2_mark_bitmap_end(int start_bit, int end_bit, char *bitmap)
{
        int i;

        if (start_bit >= end_bit)
                return;

        for (i = start_bit; i < ((start_bit + 7) & ~7UL); i++)
                setbit(bitmap, i);
        if (i < end_bit)
                memset(bitmap + (i >> 3), 0xff, (end_bit - i) >> 3);
}

static int
ext2_get_group_number(struct m_ext2fs *fs, e4fs_daddr_t block)
{

        return ((block - le32toh(fs->e2fs->e2fs_first_dblock)) /
            fs->e2fs_bsize);
}

static int
ext2_block_in_group(struct m_ext2fs *fs, e4fs_daddr_t block, int cg)
{

        return ((ext2_get_group_number(fs, block) == cg) ? 1 : 0);
}

static int
ext2_cg_block_bitmap_init(struct m_ext2fs *fs, int cg, struct buf *bp)
{
        int bit, bit_max, inodes_per_block;
        uint64_t start, tmp;

        if (!(le16toh(fs->e2fs_gd[cg].ext4bgd_flags) & EXT2_BG_BLOCK_UNINIT))
                return (0);

        memset(bp->b_data, 0, fs->e2fs_bsize);

        bit_max = ext2_number_base_meta_blocks(fs, cg);
        if ((bit_max >> 3) >= fs->e2fs_bsize)
                return (EINVAL);

        for (bit = 0; bit < bit_max; bit++)
                setbit(bp->b_data, bit);

        start = (uint64_t)cg * fs->e2fs_bpg +
            le32toh(fs->e2fs->e2fs_first_dblock);

        /* Set bits for block and inode bitmaps, and inode table. */
        tmp = e2fs_gd_get_b_bitmap(&fs->e2fs_gd[cg]);
        if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_FLEX_BG) ||
            ext2_block_in_group(fs, tmp, cg))
                setbit(bp->b_data, tmp - start);

        tmp = e2fs_gd_get_i_bitmap(&fs->e2fs_gd[cg]);
        if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_FLEX_BG) ||
            ext2_block_in_group(fs, tmp, cg))
                setbit(bp->b_data, tmp - start);

        tmp = e2fs_gd_get_i_tables(&fs->e2fs_gd[cg]);
        inodes_per_block = fs->e2fs_bsize/EXT2_INODE_SIZE(fs);
        while( tmp < e2fs_gd_get_i_tables(&fs->e2fs_gd[cg]) +
            fs->e2fs_ipg / inodes_per_block ) {
                if (!EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_FLEX_BG) ||
                    ext2_block_in_group(fs, tmp, cg))
                        setbit(bp->b_data, tmp - start);
                tmp++;
        }

        /*
         * Also if the number of blocks within the group is less than
         * the blocksize * 8 ( which is the size of bitmap ), set rest
         * of the block bitmap to 1
         */
        ext2_mark_bitmap_end(fs->e2fs_bpg, fs->e2fs_bsize * 8,
            bp->b_data);

        /* Clean the flag */
        fs->e2fs_gd[cg].ext4bgd_flags = htole16(le16toh(
            fs->e2fs_gd[cg].ext4bgd_flags) & ~EXT2_BG_BLOCK_UNINIT);

        return (0);
}

static int
ext2_b_bitmap_validate(struct m_ext2fs *fs, struct buf *bp, int cg)
{
        struct ext2_gd *gd;
        uint64_t group_first_block;
        unsigned int offset, max_bit;

        if (EXT2_HAS_INCOMPAT_FEATURE(fs, EXT2F_INCOMPAT_FLEX_BG)) {
                /*
                 * It is not possible to check block bitmap in case of this
                 * feature, because the inode and block bitmaps and inode table
                 * blocks may not be in the group at all.
                 * So, skip check in this case.
                 */
                return (0);
        }

        gd = &fs->e2fs_gd[cg];
        max_bit = fs->e2fs_fpg;
        group_first_block = ((uint64_t)cg) * fs->e2fs_fpg +
            le32toh(fs->e2fs->e2fs_first_dblock);

        /* Check block bitmap block number */
        offset = e2fs_gd_get_b_bitmap(gd) - group_first_block;
        if (offset >= max_bit || !isset(bp->b_data, offset)) {
                SDT_PROBE2(ext2fs, , alloc, ext2_b_bitmap_validate_error,
                    "bad block bitmap, group", cg);
                return (EINVAL);
        }

        /* Check inode bitmap block number */
        offset = e2fs_gd_get_i_bitmap(gd) - group_first_block;
        if (offset >= max_bit || !isset(bp->b_data, offset)) {
                SDT_PROBE2(ext2fs, , alloc, ext2_b_bitmap_validate_error,
                    "bad inode bitmap", cg);
                return (EINVAL);
        }

        /* Check inode table */
        offset = e2fs_gd_get_i_tables(gd) - group_first_block;
        if (offset >= max_bit || offset + fs->e2fs_itpg >= max_bit) {
                SDT_PROBE2(ext2fs, , alloc, ext2_b_bitmap_validate_error,
                    "bad inode table, group", cg);
                return (EINVAL);
        }

        return (0);
}

/*
 * Determine whether a block can be allocated.
 *
 * Check to see if a block of the appropriate size is available,
 * and if it is, allocate it.
 */
static daddr_t
ext2_alloccg(struct inode *ip, int cg, daddr_t bpref, int size)
{
        struct m_ext2fs *fs;
        struct buf *bp;
        struct ext2mount *ump;
        daddr_t bno, runstart, runlen;
        int bit, loc, end, error, start;
        char *bbp;
        /* XXX ondisk32 */
        fs = ip->i_e2fs;
        ump = ip->i_ump;
        if (e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) == 0)
                return (0);

        EXT2_UNLOCK(ump);
        error = bread(ip->i_devvp, fsbtodb(fs,
            e2fs_gd_get_b_bitmap(&fs->e2fs_gd[cg])),
            (int)fs->e2fs_bsize, NOCRED, &bp);
        if (error)
                goto fail;

        if (EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_GDT_CSUM) ||
            EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_METADATA_CKSUM)) {
                error = ext2_cg_block_bitmap_init(fs, cg, bp);
                if (error)
                        goto fail;

                ext2_gd_b_bitmap_csum_set(fs, cg, bp);
        }
        error = ext2_gd_b_bitmap_csum_verify(fs, cg, bp);
        if (error)
                goto fail;

        error = ext2_b_bitmap_validate(fs,bp, cg);
        if (error)
                goto fail;

        /*
         * Check, that another thread did not not allocate the last block in
         * this group while we were waiting for the buffer.
         */
        if (e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) == 0)
                goto fail;

        bbp = (char *)bp->b_data;

        if (dtog(fs, bpref) != cg)
                bpref = 0;
        if (bpref != 0) {
                bpref = dtogd(fs, bpref);
                /*
                 * if the requested block is available, use it
                 */
                if (isclr(bbp, bpref)) {
                        bno = bpref;
                        goto gotit;
                }
        }
        /*
         * no blocks in the requested cylinder, so take next
         * available one in this cylinder group.
         * first try to get 8 contigous blocks, then fall back to a single
         * block.
         */
        if (bpref)
                start = dtogd(fs, bpref) / NBBY;
        else
                start = 0;
        end = howmany(fs->e2fs_fpg, NBBY);
retry:
        runlen = 0;
        runstart = 0;
        for (loc = start; loc < end; loc++) {
                if (bbp[loc] == (char)0xff) {
                        runlen = 0;
                        continue;
                }

                /* Start of a run, find the number of high clear bits. */
                if (runlen == 0) {
                        bit = fls(bbp[loc]);
                        runlen = NBBY - bit;
                        runstart = loc * NBBY + bit;
                } else if (bbp[loc] == 0) {
                        /* Continue a run. */
                        runlen += NBBY;
                } else {
                        /*
                         * Finish the current run.  If it isn't long
                         * enough, start a new one.
                         */
                        bit = ffs(bbp[loc]) - 1;
                        runlen += bit;
                        if (runlen >= 8) {
                                bno = runstart;
                                goto gotit;
                        }

                        /* Run was too short, start a new one. */
                        bit = fls(bbp[loc]);
                        runlen = NBBY - bit;
                        runstart = loc * NBBY + bit;
                }

                /* If the current run is long enough, use it. */
                if (runlen >= 8) {
                        bno = runstart;
                        goto gotit;
                }
        }
        if (start != 0) {
                end = start;
                start = 0;
                goto retry;
        }
        bno = ext2_mapsearch(fs, bbp, bpref);
        if (bno < 0)
                goto fail;

gotit:
#ifdef INVARIANTS
        if (isset(bbp, bno)) {
                printf("ext2fs_alloccgblk: cg=%d bno=%jd fs=%s\n",
                    cg, (intmax_t)bno, fs->e2fs_fsmnt);
                panic("ext2fs_alloccg: dup alloc");
        }
#endif
        setbit(bbp, bno);
        EXT2_LOCK(ump);
        ext2_clusteracct(fs, bbp, cg, bno, -1);
        fs->e2fs_fbcount--;
        e2fs_gd_set_nbfree(&fs->e2fs_gd[cg],
            e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) - 1);
        fs->e2fs_fmod = 1;
        EXT2_UNLOCK(ump);
        ext2_gd_b_bitmap_csum_set(fs, cg, bp);
        bdwrite(bp);
        return (((uint64_t)cg) * fs->e2fs_fpg +
            le32toh(fs->e2fs->e2fs_first_dblock) + bno);

fail:
        brelse(bp);
        EXT2_LOCK(ump);
        return (0);
}

/*
 * Determine whether a cluster can be allocated.
 */
static daddr_t
ext2_clusteralloc(struct inode *ip, int cg, daddr_t bpref, int len)
{
        struct m_ext2fs *fs;
        struct ext2mount *ump;
        struct buf *bp;
        char *bbp;
        int bit, error, got, i, loc, run;
        int32_t *lp;
        daddr_t bno;

        fs = ip->i_e2fs;
        ump = ip->i_ump;

        if (fs->e2fs_maxcluster[cg] < len)
                return (0);

        EXT2_UNLOCK(ump);
        error = bread(ip->i_devvp,
            fsbtodb(fs, e2fs_gd_get_b_bitmap(&fs->e2fs_gd[cg])),
            (int)fs->e2fs_bsize, NOCRED, &bp);
        if (error)
                goto fail_lock;

        bbp = (char *)bp->b_data;
        EXT2_LOCK(ump);
        /*
         * Check to see if a cluster of the needed size (or bigger) is
         * available in this cylinder group.
         */
        lp = &fs->e2fs_clustersum[cg].cs_sum[len];
        for (i = len; i <= fs->e2fs_contigsumsize; i++)
                if (*lp++ > 0)
                        break;
        if (i > fs->e2fs_contigsumsize) {
                /*
                 * Update the cluster summary information to reflect
                 * the true maximum-sized cluster so that future cluster
                 * allocation requests can avoid reading the bitmap only
                 * to find no cluster.
                 */
                lp = &fs->e2fs_clustersum[cg].cs_sum[len - 1];
                for (i = len - 1; i > 0; i--)
                        if (*lp-- > 0)
                                break;
                fs->e2fs_maxcluster[cg] = i;
                goto fail;
        }
        EXT2_UNLOCK(ump);

        /* Search the bitmap to find a big enough cluster like in FFS. */
        if (dtog(fs, bpref) != cg)
                bpref = 0;
        if (bpref != 0)
                bpref = dtogd(fs, bpref);
        loc = bpref / NBBY;
        bit = 1 << (bpref % NBBY);
        for (run = 0, got = bpref; got < fs->e2fs_fpg; got++) {
                if ((bbp[loc] & bit) != 0)
                        run = 0;
                else {
                        run++;
                        if (run == len)
                                break;
                }
                if ((got & (NBBY - 1)) != (NBBY - 1))
                        bit <<= 1;
                else {
                        loc++;
                        bit = 1;
                }
        }

        if (got >= fs->e2fs_fpg)
                goto fail_lock;

        /* Allocate the cluster that we found. */
        for (i = 1; i < len; i++)
                if (!isclr(bbp, got - run + i))
                        panic("ext2_clusteralloc: map mismatch");

        bno = got - run + 1;
        if (bno >= fs->e2fs_fpg)
                panic("ext2_clusteralloc: allocated out of group");

        EXT2_LOCK(ump);
        for (i = 0; i < len; i += fs->e2fs_fpb) {
                setbit(bbp, bno + i);
                ext2_clusteracct(fs, bbp, cg, bno + i, -1);
                fs->e2fs_fbcount--;
                e2fs_gd_set_nbfree(&fs->e2fs_gd[cg],
                    e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) - 1);
        }
        fs->e2fs_fmod = 1;
        EXT2_UNLOCK(ump);

        bdwrite(bp);
        return (cg * fs->e2fs_fpg + le32toh(fs->e2fs->e2fs_first_dblock)
            + bno);

fail_lock:
        EXT2_LOCK(ump);
fail:
        brelse(bp);
        return (0);
}

static int
ext2_zero_inode_table(struct inode *ip, int cg)
{
        struct m_ext2fs *fs;
        struct buf *bp;
        int i, all_blks, used_blks;

        fs = ip->i_e2fs;

        if (le16toh(fs->e2fs_gd[cg].ext4bgd_flags) & EXT2_BG_INODE_ZEROED)
                return (0);

        all_blks = le16toh(fs->e2fs->e2fs_inode_size) * fs->e2fs_ipg /
            fs->e2fs_bsize;

        used_blks = howmany(fs->e2fs_ipg -
            e2fs_gd_get_i_unused(&fs->e2fs_gd[cg]),
            fs->e2fs_bsize / EXT2_INODE_SIZE(fs));

        for (i = 0; i < all_blks - used_blks; i++) {
                bp = getblk(ip->i_devvp, fsbtodb(fs,
                    e2fs_gd_get_i_tables(&fs->e2fs_gd[cg]) + used_blks + i),
                    fs->e2fs_bsize, 0, 0, 0);
                if (!bp)
                        return (EIO);

                vfs_bio_bzero_buf(bp, 0, fs->e2fs_bsize);
                bawrite(bp);
        }

        fs->e2fs_gd[cg].ext4bgd_flags = htole16(le16toh(
            fs->e2fs_gd[cg].ext4bgd_flags) | EXT2_BG_INODE_ZEROED);

        return (0);
}

static void
ext2_fix_bitmap_tail(unsigned char *bitmap, int first, int last)
{
        int i;

        for (i = first; i <= last; i++)
                bitmap[i] = 0xff;
}

/*
 * Determine whether an inode can be allocated.
 *
 * Check to see if an inode is available, and if it is,
 * allocate it using tode in the specified cylinder group.
 */
static daddr_t
ext2_nodealloccg(struct inode *ip, int cg, daddr_t ipref, int mode)
{
        struct m_ext2fs *fs;
        struct buf *bp;
        struct ext2mount *ump;
        int error, start, len, ifree, ibytes;
        char *ibp, *loc;

        ipref--;        /* to avoid a lot of (ipref -1) */
        if (ipref == -1)
                ipref = 0;
        fs = ip->i_e2fs;
        ump = ip->i_ump;
        if (e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) == 0)
                return (0);
        EXT2_UNLOCK(ump);
        error = bread(ip->i_devvp, fsbtodb(fs,
            e2fs_gd_get_i_bitmap(&fs->e2fs_gd[cg])),
            (int)fs->e2fs_bsize, NOCRED, &bp);
        if (error) {
                EXT2_LOCK(ump);
                return (0);
        }
        if (EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_GDT_CSUM) ||
            EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_METADATA_CKSUM)) {
                if (le16toh(fs->e2fs_gd[cg].ext4bgd_flags) &
                    EXT2_BG_INODE_UNINIT) {
                        ibytes = fs->e2fs_ipg / 8;
                        memset(bp->b_data, 0, ibytes - 1);
                        ext2_fix_bitmap_tail(bp->b_data, ibytes,
                            fs->e2fs_bsize - 1);
                        fs->e2fs_gd[cg].ext4bgd_flags = htole16(le16toh(
                            fs->e2fs_gd[cg].ext4bgd_flags) &
                            ~EXT2_BG_INODE_UNINIT);
                }
                ext2_gd_i_bitmap_csum_set(fs, cg, bp);
                error = ext2_zero_inode_table(ip, cg);
                if (error) {
                        brelse(bp);
                        EXT2_LOCK(ump);
                        return (0);
                }
        }
        error = ext2_gd_i_bitmap_csum_verify(fs, cg, bp);
        if (error) {
                brelse(bp);
                EXT2_LOCK(ump);
                return (0);
        }
        if (e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) == 0) {
                /*
                 * Another thread allocated the last i-node in this
                 * group while we were waiting for the buffer.
                 */
                brelse(bp);
                EXT2_LOCK(ump);
                return (0);
        }
        ibp = (char *)bp->b_data;
        if (ipref) {
                ipref %= fs->e2fs_ipg;
                if (isclr(ibp, ipref))
                        goto gotit;
        }
        start = ipref / NBBY;
        len = howmany(fs->e2fs_ipg - ipref, NBBY);
        loc = memcchr(&ibp[start], 0xff, len);
        if (loc == NULL) {
                len = start + 1;
                start = 0;
                loc = memcchr(&ibp[start], 0xff, len);
                if (loc == NULL) {
                        SDT_PROBE3(ext2fs, , alloc,
                            ext2_nodealloccg_bmap_corrupted, cg, ipref,
                            fs->e2fs_fsmnt);
                        brelse(bp);
                        EXT2_LOCK(ump);
                        return (0);
                }
        }
        ipref = (loc - ibp) * NBBY + ffs(~*loc) - 1;
gotit:
        setbit(ibp, ipref);
        EXT2_LOCK(ump);
        e2fs_gd_set_nifree(&fs->e2fs_gd[cg],
            e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) - 1);
        if (EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_GDT_CSUM) ||
            EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_METADATA_CKSUM)) {
                ifree = fs->e2fs_ipg - e2fs_gd_get_i_unused(&fs->e2fs_gd[cg]);
                if (ipref + 1 > ifree)
                        e2fs_gd_set_i_unused(&fs->e2fs_gd[cg],
                            fs->e2fs_ipg - (ipref + 1));
        }
        fs->e2fs_ficount--;
        fs->e2fs_fmod = 1;
        if ((mode & IFMT) == IFDIR) {
                e2fs_gd_set_ndirs(&fs->e2fs_gd[cg],
                    e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) + 1);
                fs->e2fs_total_dir++;
        }
        EXT2_UNLOCK(ump);
        ext2_gd_i_bitmap_csum_set(fs, cg, bp);
        bdwrite(bp);
        return ((uint64_t)cg * fs->e2fs_ipg + ipref + 1);
}

/*
 * Free a block or fragment.
 *
 */
void
ext2_blkfree(struct inode *ip, e4fs_daddr_t bno, long size)
{
        struct m_ext2fs *fs;
        struct buf *bp;
        struct ext2mount *ump;
        int cg, error;
        char *bbp;

        fs = ip->i_e2fs;
        ump = ip->i_ump;
        cg = dtog(fs, bno);
        if (bno >= fs->e2fs_bcount) {
                SDT_PROBE2(ext2fs, , alloc, ext2_blkfree_bad_block,
                    ip->i_number, bno);
                return;
        }
        error = bread(ip->i_devvp,
            fsbtodb(fs, e2fs_gd_get_b_bitmap(&fs->e2fs_gd[cg])),
            (int)fs->e2fs_bsize, NOCRED, &bp);
        if (error) {
                return;
        }
        bbp = (char *)bp->b_data;
        bno = dtogd(fs, bno);
        if (isclr(bbp, bno)) {
                panic("ext2_blkfree: freeing free block %lld, fs=%s",
                    (long long)bno, fs->e2fs_fsmnt);
        }
        clrbit(bbp, bno);
        EXT2_LOCK(ump);
        ext2_clusteracct(fs, bbp, cg, bno, 1);
        fs->e2fs_fbcount++;
        e2fs_gd_set_nbfree(&fs->e2fs_gd[cg],
            e2fs_gd_get_nbfree(&fs->e2fs_gd[cg]) + 1);
        fs->e2fs_fmod = 1;
        EXT2_UNLOCK(ump);
        ext2_gd_b_bitmap_csum_set(fs, cg, bp);
        bdwrite(bp);
}

/*
 * Free an inode.
 *
 */
int
ext2_vfree(struct vnode *pvp, ino_t ino, int mode)
{
        struct m_ext2fs *fs;
        struct inode *pip;
        struct buf *bp;
        struct ext2mount *ump;
        int error, cg;
        char *ibp;

        pip = VTOI(pvp);
        fs = pip->i_e2fs;
        ump = pip->i_ump;
        if ((u_int)ino > fs->e2fs_ipg * fs->e2fs_gcount)
                panic("ext2_vfree: range: devvp = %p, ino = %ju, fs = %s",
                    pip->i_devvp, (uintmax_t)ino, fs->e2fs_fsmnt);

        cg = ino_to_cg(fs, ino);
        error = bread(pip->i_devvp,
            fsbtodb(fs, e2fs_gd_get_i_bitmap(&fs->e2fs_gd[cg])),
            (int)fs->e2fs_bsize, NOCRED, &bp);
        if (error) {
                return (0);
        }
        ibp = (char *)bp->b_data;
        ino = (ino - 1) % fs->e2fs_ipg;
        if (isclr(ibp, ino)) {
                SDT_PROBE2(ext2fs, , alloc, ext2_vfree_doublefree,
                    fs->e2fs_fsmnt, ino);
                if (fs->e2fs_ronly == 0)
                        panic("ext2_vfree: freeing free inode");
        }
        clrbit(ibp, ino);
        EXT2_LOCK(ump);
        fs->e2fs_ficount++;
        e2fs_gd_set_nifree(&fs->e2fs_gd[cg],
            e2fs_gd_get_nifree(&fs->e2fs_gd[cg]) + 1);
        if ((mode & IFMT) == IFDIR) {
                e2fs_gd_set_ndirs(&fs->e2fs_gd[cg],
                    e2fs_gd_get_ndirs(&fs->e2fs_gd[cg]) - 1);
                fs->e2fs_total_dir--;
        }
        fs->e2fs_fmod = 1;
        EXT2_UNLOCK(ump);
        ext2_gd_i_bitmap_csum_set(fs, cg, bp);
        bdwrite(bp);
        return (0);
}

/*
 * Find a block in the specified cylinder group.
 *
 * It is a panic if a request is made to find a block if none are
 * available.
 */
static daddr_t
ext2_mapsearch(struct m_ext2fs *fs, char *bbp, daddr_t bpref)
{
        char *loc;
        int start, len;

        /*
         * find the fragment by searching through the free block
         * map for an appropriate bit pattern
         */
        if (bpref)
                start = dtogd(fs, bpref) / NBBY;
        else
                start = 0;
        len = howmany(fs->e2fs_fpg, NBBY) - start;
        loc = memcchr(&bbp[start], 0xff, len);
        if (loc == NULL) {
                len = start + 1;
                start = 0;
                loc = memcchr(&bbp[start], 0xff, len);
                if (loc == NULL) {
                        panic("ext2_mapsearch: map corrupted: start=%d, len=%d,"
                            "fs=%s", start, len, fs->e2fs_fsmnt);
                        /* NOTREACHED */
                }
        }
        return ((loc - bbp) * NBBY + ffs(~*loc) - 1);
}

int
ext2_cg_has_sb(struct m_ext2fs *fs, int cg)
{
        int a3, a5, a7;

        if (cg == 0)
                return (1);

        if (EXT2_HAS_COMPAT_FEATURE(fs, EXT2F_COMPAT_SPARSESUPER2)) {
                if (cg == le32toh(fs->e2fs->e4fs_backup_bgs[0]) ||
                    cg == le32toh(fs->e2fs->e4fs_backup_bgs[1]))
                        return (1);
                return (0);
        }

        if ((cg <= 1) ||
            !EXT2_HAS_RO_COMPAT_FEATURE(fs, EXT2F_ROCOMPAT_SPARSESUPER))
                return (1);

        if (!(cg & 1))
                return (0);

        for (a3 = 3, a5 = 5, a7 = 7;
            a3 <= cg || a5 <= cg || a7 <= cg;
            a3 *= 3, a5 *= 5, a7 *= 7)
                if (cg == a3 || cg == a5 || cg == a7)
                        return (1);
        return (0);
}