/*      $NetBSD: msdosfs_vfsops.c,v 1.138 2022/04/16 07:58:21 hannken Exp $     */

/*-
 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
 * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
 * All rights reserved.
 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by TooLs GmbH.
 * 4. The name of TooLs GmbH may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``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 TOOLS GMBH 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.
 */
/*
 * Written by Paul Popelka (paulp@uts.amdahl.com)
 *
 * You can do anything you want with this software, just don't say you wrote
 * it, and don't remove this notice.
 *
 * This software is provided "as is".
 *
 * The author supplies this software to be publicly redistributed on the
 * understanding that the author is not responsible for the correct
 * functioning of this software in any circumstances and is not liable for
 * any damages caused by this software.
 *
 * October 1992
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: msdosfs_vfsops.c,v 1.138 2022/04/16 07:58:21 hannken Exp $");

#if defined(_KERNEL_OPT)
#include "opt_compat_netbsd.h"
#endif

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysctl.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <miscfs/genfs/genfs.h>
#include <miscfs/specfs/specdev.h> /* XXX */    /* defines v_rdev */
#include <sys/mount.h>
#include <sys/buf.h>
#include <sys/file.h>
#include <sys/device.h>
#include <sys/disklabel.h>
#include <sys/disk.h>
#include <sys/ioctl.h>
#include <sys/malloc.h>
#include <sys/dirent.h>
#include <sys/stat.h>
#include <sys/conf.h>
#include <sys/kauth.h>
#include <sys/module.h>

#include <fs/msdosfs/bpb.h>
#include <fs/msdosfs/bootsect.h>
#include <fs/msdosfs/direntry.h>
#include <fs/msdosfs/denode.h>
#include <fs/msdosfs/msdosfsmount.h>
#include <fs/msdosfs/fat.h>

MODULE(MODULE_CLASS_VFS, msdos, NULL);

#ifdef MSDOSFS_DEBUG
#define DPRINTF(fmt, ...) uprintf("%s(): " fmt "\n", __func__, ##__VA_ARGS__)
#else
#define DPRINTF(fmt, ...)
#endif

#define GEMDOSFS_BSIZE  512

#define MSDOSFS_NAMEMAX(pmp) \
        (pmp)->pm_flags & MSDOSFSMNT_LONGNAME ? WIN_MAXLEN : 12

int msdosfs_mountfs(struct vnode *, struct mount *, struct lwp *,
    struct msdosfs_args *);

static int update_mp(struct mount *, struct msdosfs_args *);

MALLOC_JUSTDEFINE(M_MSDOSFSMNT, "MSDOSFS mount", "MSDOS FS mount structure");
MALLOC_JUSTDEFINE(M_MSDOSFSFAT, "MSDOSFS FAT", "MSDOS FS FAT table");
MALLOC_JUSTDEFINE(M_MSDOSFSTMP, "MSDOSFS temp", "MSDOS FS temp. structures");

extern const struct vnodeopv_desc msdosfs_vnodeop_opv_desc;

const struct vnodeopv_desc * const msdosfs_vnodeopv_descs[] = {
        &msdosfs_vnodeop_opv_desc,
        NULL,
};

struct vfsops msdosfs_vfsops = {
        .vfs_name = MOUNT_MSDOS,
        .vfs_min_mount_data = sizeof (struct msdosfs_args),
        .vfs_mount = msdosfs_mount,
        .vfs_start = msdosfs_start,
        .vfs_unmount = msdosfs_unmount,
        .vfs_root = msdosfs_root,
        .vfs_quotactl = (void *)eopnotsupp,
        .vfs_statvfs = msdosfs_statvfs,
        .vfs_sync = msdosfs_sync,
        .vfs_vget = msdosfs_vget,
        .vfs_loadvnode = msdosfs_loadvnode,
        .vfs_fhtovp = msdosfs_fhtovp,
        .vfs_vptofh = msdosfs_vptofh,
        .vfs_init = msdosfs_init,
        .vfs_reinit = msdosfs_reinit,
        .vfs_done = msdosfs_done,
        .vfs_mountroot = msdosfs_mountroot,
        .vfs_snapshot = (void *)eopnotsupp,
        .vfs_extattrctl = vfs_stdextattrctl,
        .vfs_suspendctl = genfs_suspendctl,
        .vfs_renamelock_enter = genfs_renamelock_enter,
        .vfs_renamelock_exit = genfs_renamelock_exit,
        .vfs_fsync = (void *)eopnotsupp,
        .vfs_opv_descs = msdosfs_vnodeopv_descs
};

SYSCTL_SETUP(msdosfs_sysctl_setup, "msdosfs sysctl")
{
        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "msdosfs",
                       SYSCTL_DESCR("MS-DOS file system"),
                       NULL, 0, NULL, 0,
                       CTL_VFS, 4, CTL_EOL);
        /*
         * XXX the "4" above could be dynamic, thereby eliminating one
         * more instance of the "number to vfs" mapping problem, but
         * "4" is the order as taken from sys/mount.h
         */
}

static int
msdos_modcmd(modcmd_t cmd, void *arg)
{
        int error;

        switch (cmd) {
        case MODULE_CMD_INIT:
                error = vfs_attach(&msdosfs_vfsops);
                if (error != 0)
                        break;
                break;
        case MODULE_CMD_FINI:
                error = vfs_detach(&msdosfs_vfsops);
                if (error != 0)
                        break;
                break;
        default:
                error = ENOTTY;
                break;
        }

        return (error);
}

static int
update_mp(struct mount *mp, struct msdosfs_args *argp)
{
        struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
        int error;

        pmp->pm_gid = argp->gid;
        pmp->pm_uid = argp->uid;
        pmp->pm_mask = argp->mask & ALLPERMS;
        pmp->pm_dirmask = argp->dirmask & ALLPERMS;
        pmp->pm_gmtoff = argp->gmtoff;
        pmp->pm_flags |= argp->flags & MSDOSFSMNT_MNTOPT;

        /*
         * GEMDOS knows nothing about win95 long filenames
         */
        if (pmp->pm_flags & MSDOSFSMNT_GEMDOSFS)
                pmp->pm_flags |= MSDOSFSMNT_NOWIN95;

        if (pmp->pm_flags & MSDOSFSMNT_NOWIN95)
                pmp->pm_flags |= MSDOSFSMNT_SHORTNAME;
        else if (!(pmp->pm_flags &
            (MSDOSFSMNT_SHORTNAME | MSDOSFSMNT_LONGNAME))) {
                struct vnode *rtvp;

                /*
                 * Try to divine whether to support Win'95 long filenames
                 */
                if (FAT32(pmp))
                        pmp->pm_flags |= MSDOSFSMNT_LONGNAME;
                else {
                        error = msdosfs_root(mp, LK_EXCLUSIVE, &rtvp);
                        if (error != 0)
                                return error;
                        pmp->pm_flags |= msdosfs_findwin95(VTODE(rtvp))
                                ? MSDOSFSMNT_LONGNAME
                                        : MSDOSFSMNT_SHORTNAME;
                        vput(rtvp);
                }
        }

        mp->mnt_stat.f_namemax = MSDOSFS_NAMEMAX(pmp);

        return 0;
}

int
msdosfs_mountroot(void)
{
        struct mount *mp;
        struct lwp *l = curlwp; /* XXX */
        int error;
        struct msdosfs_args args;

        if (device_class(root_device) != DV_DISK)
                return (ENODEV);

        if ((error = vfs_rootmountalloc(MOUNT_MSDOS, "root_device", &mp))) {
                vrele(rootvp);
                return (error);
        }

        args.flags = MSDOSFSMNT_VERSIONED;
        args.uid = 0;
        args.gid = 0;
        args.mask = 0777;
        args.version = MSDOSFSMNT_VERSION;
        args.dirmask = 0777;

        if ((error = msdosfs_mountfs(rootvp, mp, l, &args)) != 0) {
                vfs_unbusy(mp);
                vfs_rele(mp);
                return (error);
        }

        if ((error = update_mp(mp, &args)) != 0) {
                (void)msdosfs_unmount(mp, 0);
                vfs_unbusy(mp);
                vfs_rele(mp);
                vrele(rootvp);
                return (error);
        }

        mountlist_append(mp);
        (void)msdosfs_statvfs(mp, &mp->mnt_stat);
        vfs_unbusy(mp);
        return (0);
}

/*
 * mp - path - addr in user space of mount point (ie /usr or whatever)
 * data - addr in user space of mount params including the name of the block
 * special file to treat as a filesystem.
 */
int
msdosfs_mount(struct mount *mp, const char *path, void *data, size_t *data_len)
{
        struct lwp *l = curlwp;
        struct vnode *devvp;      /* vnode for blk device to mount */
        struct msdosfs_args *args = data; /* holds data from mount request */
        /* msdosfs specific mount control block */
        struct msdosfsmount *pmp = NULL;
        int error, flags;
        mode_t accessmode;

        if (args == NULL)
                return EINVAL;
        if (*data_len < sizeof *args)
                return EINVAL;

        if (mp->mnt_flag & MNT_GETARGS) {
                pmp = VFSTOMSDOSFS(mp);
                if (pmp == NULL)
                        return EIO;
                args->fspec = NULL;
                args->uid = pmp->pm_uid;
                args->gid = pmp->pm_gid;
                args->mask = pmp->pm_mask;
                args->flags = pmp->pm_flags;
                args->version = MSDOSFSMNT_VERSION;
                args->dirmask = pmp->pm_dirmask;
                args->gmtoff = pmp->pm_gmtoff;
                *data_len = sizeof *args;
                return 0;
        }

        /*
         * If not versioned (i.e. using old mount_msdos(8)), fill in
         * the additional structure items with suitable defaults.
         */
        if ((args->flags & MSDOSFSMNT_VERSIONED) == 0) {
                args->version = 1;
                args->dirmask = args->mask;
        }

        /*
         * Reset GMT offset for pre-v3 mount structure args.
         */
        if (args->version < 3)
                args->gmtoff = 0;

        /*
         * If updating, check whether changing from read-only to
         * read/write; if there is no device name, that's all we do.
         */
        if (mp->mnt_flag & MNT_UPDATE) {
                pmp = VFSTOMSDOSFS(mp);
                error = 0;
                if (!(pmp->pm_flags & MSDOSFSMNT_RONLY) &&
                    (mp->mnt_flag & MNT_RDONLY)) {
                        flags = WRITECLOSE;
                        if (mp->mnt_flag & MNT_FORCE)
                                flags |= FORCECLOSE;
                        error = vflush(mp, NULLVP, flags);
                }
                if (!error && (mp->mnt_flag & MNT_RELOAD))
                        /* not yet implemented */
                        error = EOPNOTSUPP;
                if (error) {
                        DPRINTF("vflush %d", error);
                        return (error);
                }
                if ((pmp->pm_flags & MSDOSFSMNT_RONLY) &&
                    (mp->mnt_iflag & IMNT_WANTRDWR)) {
                        /*
                         * If upgrade to read-write by non-root, then verify
                         * that user has necessary permissions on the device.
                         *
                         * Permission to update a mount is checked higher, so
                         * here we presume updating the mount is okay (for
                         * example, as far as securelevel goes) which leaves us
                         * with the normal check.
                         */
                        devvp = pmp->pm_devvp;
                        vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                        error = kauth_authorize_system(l->l_cred,
                            KAUTH_SYSTEM_MOUNT, KAUTH_REQ_SYSTEM_MOUNT_DEVICE,
                            mp, devvp, KAUTH_ARG(VREAD | VWRITE));
                        VOP_UNLOCK(devvp);
                        DPRINTF("KAUTH_REQ_SYSTEM_MOUNT_DEVICE %d", error);
                        if (error)
                                return (error);

                        pmp->pm_flags &= ~MSDOSFSMNT_RONLY;
                }
                if (args->fspec == NULL) {
                        DPRINTF("missing fspec");
                        return EINVAL;
                }
        }
        /*
         * Not an update, or updating the name: look up the name
         * and verify that it refers to a sensible block device.
         */
        error = namei_simple_user(args->fspec,
                                NSM_FOLLOW_NOEMULROOT, &devvp);
        if (error != 0) {
                DPRINTF("namei %d", error);
                return (error);
        }

        if (devvp->v_type != VBLK) {
                DPRINTF("not block");
                vrele(devvp);
                return (ENOTBLK);
        }
        if (bdevsw_lookup(devvp->v_rdev) == NULL) {
                DPRINTF("no block switch");
                vrele(devvp);
                return (ENXIO);
        }
        /*
         * If mount by non-root, then verify that user has necessary
         * permissions on the device.
         */
        accessmode = VREAD;
        if ((mp->mnt_flag & MNT_RDONLY) == 0)
                accessmode |= VWRITE;
        vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
        error = kauth_authorize_system(l->l_cred, KAUTH_SYSTEM_MOUNT,
            KAUTH_REQ_SYSTEM_MOUNT_DEVICE, mp, devvp, KAUTH_ARG(accessmode));
        VOP_UNLOCK(devvp);
        if (error) {
                DPRINTF("KAUTH_REQ_SYSTEM_MOUNT_DEVICE %d", error);
                vrele(devvp);
                return (error);
        }
        if ((mp->mnt_flag & MNT_UPDATE) == 0) {
                int xflags;

                if (mp->mnt_flag & MNT_RDONLY)
                        xflags = FREAD;
                else
                        xflags = FREAD|FWRITE;
                vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                error = VOP_OPEN(devvp, xflags, FSCRED);
                VOP_UNLOCK(devvp);
                if (error) {
                        DPRINTF("VOP_OPEN %d", error);
                        goto fail;
                }
                error = msdosfs_mountfs(devvp, mp, l, args);
                if (error) {
                        DPRINTF("msdosfs_mountfs %d", error);
                        vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                        (void) VOP_CLOSE(devvp, xflags, NOCRED);
                        VOP_UNLOCK(devvp);
                        goto fail;
                }
#ifdef MSDOSFS_DEBUG            /* only needed for the printf below */
                pmp = VFSTOMSDOSFS(mp);
#endif
        } else {
                vrele(devvp);
                if (devvp != pmp->pm_devvp) {
                        DPRINTF("devvp %p pmp %p", devvp, pmp->pm_devvp);
                        return (EINVAL);        /* needs translation */
                }
        }
        if ((error = update_mp(mp, args)) != 0) {
                msdosfs_unmount(mp, MNT_FORCE);
                DPRINTF("update_mp %d", error);
                return error;
        }

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_mount(): mp %p, pmp %p, inusemap %p\n", mp, pmp, pmp->pm_inusemap);
#endif
        return set_statvfs_info(path, UIO_USERSPACE, args->fspec, UIO_USERSPACE,
            mp->mnt_op->vfs_name, mp, l);

fail:
        vrele(devvp);
        return (error);
}

int
msdosfs_mountfs(struct vnode *devvp, struct mount *mp, struct lwp *l, struct msdosfs_args *argp)
{
        struct msdosfsmount *pmp;
        struct buf *bp;
        dev_t dev = devvp->v_rdev;
        union bootsector *bsp;
        struct byte_bpb33 *b33;
        struct byte_bpb50 *b50;
        struct byte_bpb710 *b710;
        uint8_t SecPerClust;
        int     ronly, error, BlkPerSec;
        uint64_t psize;
        unsigned secsize;
        u_long fatbytes, fatblocksecs;

        /* Flush out any old buffers remaining from a previous use. */
        vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
        error = vinvalbuf(devvp, V_SAVE, l->l_cred, l, 0, 0);
        VOP_UNLOCK(devvp);
        if (error)
                return (error);

        ronly = (mp->mnt_flag & MNT_RDONLY) != 0;

        bp  = NULL; /* both used in error_exit */
        pmp = NULL;

        error = getdisksize(devvp, &psize, &secsize);
        if (error) {
                if (argp->flags & MSDOSFSMNT_GEMDOSFS)
                        goto error_exit;

                /* ok, so it failed.  we most likely don't need the info */
                secsize = DEV_BSIZE;
                psize = 0;
                error = 0;
        }
        if (secsize < DEV_BSIZE) {
                DPRINTF("Invalid block secsize (%d < DEV_BSIZE)", secsize);
                error = EINVAL;
                goto error_exit;
        }

        if (argp->flags & MSDOSFSMNT_GEMDOSFS) {
                if (secsize != GEMDOSFS_BSIZE) {
                        DPRINTF("Invalid block secsize %d for GEMDOS", secsize);
                        error = EINVAL;
                        goto error_exit;
                }
        }

        /*
         * Read the boot sector of the filesystem, and then check the
         * boot signature.  If not a dos boot sector then error out.
         */
        if (secsize < sizeof(*b50)) {
                DPRINTF("50 bootsec %u\n", secsize);
                error = EINVAL;
                goto error_exit;
        }
        if ((error = bread(devvp, 0, secsize, 0, &bp)) != 0)
                goto error_exit;
        bsp = (union bootsector *)bp->b_data;
        b33 = (struct byte_bpb33 *)bsp->bs33.bsBPB;
        b50 = (struct byte_bpb50 *)bsp->bs50.bsBPB;
        b710 = (struct byte_bpb710 *)bsp->bs710.bsBPB;

#if 0
        /*
         * Some FAT partition, for example Raspberry Pi Pico's
         * USB mass storage, does not have exptected BOOTSIGs.
         * According to FreeBSD's comment, some PC-9800/9821
         * FAT floppy disks have similar problems.
         */
        if (!(argp->flags & MSDOSFSMNT_GEMDOSFS)) {
                if (bsp->bs50.bsBootSectSig0 != BOOTSIG0
                    || bsp->bs50.bsBootSectSig1 != BOOTSIG1) {
                        DPRINTF("bootsig0 %d bootsig1 %d", 
                            bsp->bs50.bsBootSectSig0,
                            bsp->bs50.bsBootSectSig1);
                        error = EINVAL;
                        goto error_exit;
                }
        }
#endif

        pmp = malloc(sizeof(*pmp), M_MSDOSFSMNT, M_WAITOK|M_ZERO);
        pmp->pm_mountp = mp;

        /*
         * Compute several useful quantities from the bpb in the
         * bootsector.  Copy in the dos 5 variant of the bpb then fix up
         * the fields that are different between dos 5 and dos 3.3.
         */
        SecPerClust = b50->bpbSecPerClust;
        pmp->pm_BytesPerSec = getushort(b50->bpbBytesPerSec);
        pmp->pm_ResSectors = getushort(b50->bpbResSectors);
        pmp->pm_FATs = b50->bpbFATs;
        pmp->pm_RootDirEnts = getushort(b50->bpbRootDirEnts);
        pmp->pm_Sectors = getushort(b50->bpbSectors);
        pmp->pm_FATsecs = getushort(b50->bpbFATsecs);
        pmp->pm_SecPerTrack = getushort(b50->bpbSecPerTrack);
        pmp->pm_Heads = getushort(b50->bpbHeads);
        pmp->pm_Media = b50->bpbMedia;

        if (pmp->pm_Sectors == 0) {
                pmp->pm_HiddenSects = getulong(b50->bpbHiddenSecs);
                pmp->pm_HugeSectors = getulong(b50->bpbHugeSectors);
        } else {
                if (secsize < sizeof(*b33)) {
                        DPRINTF("33 bootsec %u\n", secsize);
                        error = EINVAL;
                        goto error_exit;
                }
                pmp->pm_HiddenSects = getushort(b33->bpbHiddenSecs);
                pmp->pm_HugeSectors = pmp->pm_Sectors;
        }

        /*
         * Sanity checks, from the FAT specification:
         * - sectors per cluster: >= 1, power of 2
         * - logical sector size: >= 1, power of 2
         * - cluster size:        <= max FS block size
         * - number of sectors:   >= 1
         */
        if ((SecPerClust == 0) || !powerof2(SecPerClust) ||
            (pmp->pm_BytesPerSec == 0) || !powerof2(pmp->pm_BytesPerSec) ||
            (SecPerClust * pmp->pm_BytesPerSec > MAXBSIZE) ||
            (pmp->pm_HugeSectors == 0)) {
                DPRINTF("consistency checks");
                error = EINVAL;
                goto error_exit;
        }

        if (!(argp->flags & MSDOSFSMNT_GEMDOSFS) &&
            (pmp->pm_SecPerTrack > 63)) {
                DPRINTF("SecPerTrack %d", pmp->pm_SecPerTrack);
                error = EINVAL;
                goto error_exit;
        }

        if (pmp->pm_RootDirEnts == 0) {
                if (secsize < sizeof(*b710)) {
                        DPRINTF("710 bootsec %u\n", secsize);
                        error = EINVAL;
                        goto error_exit;
                }
                unsigned short FSVers = getushort(b710->bpbFSVers);
                unsigned short ExtFlags = getushort(b710->bpbExtFlags);
                /*
                 * Some say that bsBootSectSig[23] must be zero, but
                 * Windows does not require this and some digital cameras
                 * do not set these to zero.  Therefore, do not insist.
                 */
                if (pmp->pm_Sectors || pmp->pm_FATsecs || FSVers) {
                        DPRINTF("Sectors %d FATsecs %lu FSVers %d",
                            pmp->pm_Sectors, pmp->pm_FATsecs, FSVers);
                        error = EINVAL;
                        goto error_exit;
                }
                pmp->pm_fatmask = FAT32_MASK;
                pmp->pm_fatmult = 4;
                pmp->pm_fatdiv = 1;
                pmp->pm_FATsecs = getulong(b710->bpbBigFATsecs);

                /* Mirroring is enabled if the FATMIRROR bit is not set. */
                if ((ExtFlags & FATMIRROR) == 0)
                        pmp->pm_flags |= MSDOSFS_FATMIRROR;
                else
                        pmp->pm_curfat = ExtFlags & FATNUM;
        } else
                pmp->pm_flags |= MSDOSFS_FATMIRROR;

        if (argp->flags & MSDOSFSMNT_GEMDOSFS) {
                if (FAT32(pmp)) {
                        /* GEMDOS doesn't know FAT32. */
                        DPRINTF("FAT32 for GEMDOS");
                        error = EINVAL;
                        goto error_exit;
                }

                /*
                 * Check a few values (could do some more):
                 * - logical sector size: >= block size
                 * - number of sectors:   <= size of partition
                 */
                if ((pmp->pm_BytesPerSec < GEMDOSFS_BSIZE) ||
                    (pmp->pm_HugeSectors *
                     (pmp->pm_BytesPerSec / GEMDOSFS_BSIZE) > psize)) {
                        DPRINTF("consistency checks for GEMDOS");
                        error = EINVAL;
                        goto error_exit;
                }
                /*
                 * XXX - Many parts of the msdosfs driver seem to assume that
                 * the number of bytes per logical sector (BytesPerSec) will
                 * always be the same as the number of bytes per disk block
                 * Let's pretend it is.
                 */
                BlkPerSec = pmp->pm_BytesPerSec / GEMDOSFS_BSIZE;
                pmp->pm_BytesPerSec  = GEMDOSFS_BSIZE;
                pmp->pm_HugeSectors *= BlkPerSec;
                pmp->pm_HiddenSects *= BlkPerSec;
                pmp->pm_ResSectors  *= BlkPerSec;
                pmp->pm_Sectors     *= BlkPerSec;
                pmp->pm_FATsecs     *= BlkPerSec;
                SecPerClust         *= BlkPerSec;
        }

        /* Check that fs has nonzero FAT size */
        if (pmp->pm_FATsecs == 0) {
                DPRINTF("FATsecs is 0");
                error = EINVAL;
                goto error_exit;
        }

        pmp->pm_fatblk = pmp->pm_ResSectors;
        if (FAT32(pmp)) {
                if (secsize < sizeof(*b710)) {
                        DPRINTF("710 bootsec %u\n", secsize);
                        error = EINVAL;
                        goto error_exit;
                }
                pmp->pm_rootdirblk = getulong(b710->bpbRootClust);
                pmp->pm_firstcluster = pmp->pm_fatblk
                        + (pmp->pm_FATs * pmp->pm_FATsecs);
                pmp->pm_fsinfo = getushort(b710->bpbFSInfo);
        } else {
                pmp->pm_rootdirblk = pmp->pm_fatblk +
                        (pmp->pm_FATs * pmp->pm_FATsecs);
                pmp->pm_rootdirsize = (pmp->pm_RootDirEnts * sizeof(struct direntry)
                                       + pmp->pm_BytesPerSec - 1)
                        / pmp->pm_BytesPerSec;/* in sectors */
                pmp->pm_firstcluster = pmp->pm_rootdirblk + pmp->pm_rootdirsize;
        }

        pmp->pm_nmbrofclusters = (pmp->pm_HugeSectors - pmp->pm_firstcluster) /
            SecPerClust;
        pmp->pm_maxcluster = pmp->pm_nmbrofclusters + 1;
        pmp->pm_fatsize = pmp->pm_FATsecs * pmp->pm_BytesPerSec;

        if (argp->flags & MSDOSFSMNT_GEMDOSFS) {
                if (pmp->pm_nmbrofclusters <= (0xff0 - 2)) {
                        pmp->pm_fatmask = FAT12_MASK;
                        pmp->pm_fatmult = 3;
                        pmp->pm_fatdiv = 2;
                } else {
                        pmp->pm_fatmask = FAT16_MASK;
                        pmp->pm_fatmult = 2;
                        pmp->pm_fatdiv = 1;
                }
        } else if (pmp->pm_fatmask == 0) {
                if (pmp->pm_maxcluster
                    <= ((CLUST_RSRVD - CLUST_FIRST) & FAT12_MASK)) {
                        /*
                         * This will usually be a floppy disk. This size makes
                         * sure that one FAT entry will not be split across
                         * multiple blocks.
                         */
                        pmp->pm_fatmask = FAT12_MASK;
                        pmp->pm_fatmult = 3;
                        pmp->pm_fatdiv = 2;
                } else {
                        pmp->pm_fatmask = FAT16_MASK;
                        pmp->pm_fatmult = 2;
                        pmp->pm_fatdiv = 1;
                }
        }

        /* validate cluster count against FAT */
        if ((pmp->pm_maxcluster & pmp->pm_fatmask) != pmp->pm_maxcluster) {
                DPRINTF("maxcluster %lu outside of mask %#lx\n",
                        pmp->pm_maxcluster, pmp->pm_fatmask);
                error = EINVAL;
                goto error_exit;
        }

        /* validate FAT size */
        fatbytes = (pmp->pm_maxcluster+1) * pmp->pm_fatmult / pmp->pm_fatdiv;
        fatblocksecs = howmany(fatbytes, pmp->pm_BytesPerSec);

        if (pmp->pm_FATsecs < fatblocksecs) {
                DPRINTF("FATsecs %lu < real %lu\n", pmp->pm_FATsecs,
                        fatblocksecs);
                error = EINVAL;
                goto error_exit;
        }

        if (FAT12(pmp)) {
                /*
                 * limit block size to what is needed to read a FAT block
                 * to not exceed MAXBSIZE
                 */
                pmp->pm_fatblocksec = uimin(3, fatblocksecs);
                pmp->pm_fatblocksize = pmp->pm_fatblocksec
                        * pmp->pm_BytesPerSec;
        } else {
                pmp->pm_fatblocksize = MAXBSIZE;
                pmp->pm_fatblocksec = pmp->pm_fatblocksize
                        / pmp->pm_BytesPerSec;
        }

        pmp->pm_bnshift = ffs(pmp->pm_BytesPerSec) - 1;

        /*
         * Compute mask and shift value for isolating cluster relative byte
         * offsets and cluster numbers from a file offset.
         */
        pmp->pm_bpcluster = SecPerClust * pmp->pm_BytesPerSec;
        pmp->pm_crbomask = pmp->pm_bpcluster - 1;
        pmp->pm_cnshift = ffs(pmp->pm_bpcluster) - 1;

        /*
         * Check for valid cluster size
         * must be a power of 2
         */
        if (pmp->pm_bpcluster ^ (1 << pmp->pm_cnshift)) {
                DPRINTF("bpcluster %lu cnshift %lu", pmp->pm_bpcluster,
                    pmp->pm_cnshift);
                error = EINVAL;
                goto error_exit;
        }

        /*
         * Cluster size must be within limit of MAXBSIZE.
         * Many FAT filesystems will not have clusters larger than
         * 32KiB due to limits in Windows versions before Vista.
         */
        if (pmp->pm_bpcluster > MAXBSIZE) {
                DPRINTF("bpcluster %lu > MAXBSIZE %d",
                    pmp->pm_bpcluster, MAXBSIZE);
                error = EINVAL;
                goto error_exit;
        }

        /*
         * Release the bootsector buffer.
         */
        brelse(bp, BC_AGE);
        bp = NULL;

        /*
         * Check FSInfo.
         */
        if (pmp->pm_fsinfo) {
                struct fsinfo *fp;
                const int rdsz = roundup(sizeof(*fp), pmp->pm_BytesPerSec);

                /*
                 * XXX  If the fsinfo block is stored on media with
                 *      2KB or larger sectors, is the fsinfo structure
                 *      padded at the end or in the middle?
                 */
                if ((error = bread(devvp, de_bn2kb(pmp, pmp->pm_fsinfo),
                    rdsz, 0, &bp)) != 0)
                        goto error_exit;
                fp = (struct fsinfo *)bp->b_data;
                if (!memcmp(fp->fsisig1, "RRaA", 4)
                    && !memcmp(fp->fsisig2, "rrAa", 4)
                    && !memcmp(fp->fsisig3, "\0\0\125\252", 4)
                    && !memcmp(fp->fsisig4, "\0\0\125\252", 4))
                        pmp->pm_nxtfree = getulong(fp->fsinxtfree);
                else
                        pmp->pm_fsinfo = 0;
                brelse(bp, 0);
                bp = NULL;
        }

        /*
         * Check and validate (or perhaps invalidate?) the fsinfo structure?
         * XXX
         */
        if (pmp->pm_fsinfo) {
                if ((pmp->pm_nxtfree == 0xffffffffUL) ||
                    (pmp->pm_nxtfree > pmp->pm_maxcluster))
                        pmp->pm_fsinfo = 0;
        }

        /*
         * Allocate memory for the bitmap of allocated clusters, and then
         * fill it in.
         */
        pmp->pm_inusemap = malloc(((pmp->pm_maxcluster + N_INUSEBITS)
                                   / N_INUSEBITS)
                                  * sizeof(*pmp->pm_inusemap),
                                  M_MSDOSFSFAT, M_WAITOK);

        /*
         * fillinusemap() needs pm_devvp.
         */
        pmp->pm_dev = dev;
        pmp->pm_devvp = devvp;

        /*
         * Have the inuse map filled in.
         */
        if ((error = msdosfs_fillinusemap(pmp)) != 0) {
                DPRINTF("fillinusemap %d", error);
                goto error_exit;
        }

        /*
         * If they want FAT updates to be synchronous then let them suffer
         * the performance degradation in exchange for the on disk copy of
         * the FAT being correct just about all the time.  I suppose this
         * would be a good thing to turn on if the kernel is still flakey.
         */
        if (mp->mnt_flag & MNT_SYNCHRONOUS)
                pmp->pm_flags |= MSDOSFSMNT_WAITONFAT;

        /*
         * Finish up.
         */
        if (ronly)
                pmp->pm_flags |= MSDOSFSMNT_RONLY;
        else
                pmp->pm_fmod = 1;
        mp->mnt_data = pmp;
        mp->mnt_stat.f_fsidx.__fsid_val[0] = (long)dev;
        mp->mnt_stat.f_fsidx.__fsid_val[1] = makefstype(MOUNT_MSDOS);
        mp->mnt_stat.f_fsid = mp->mnt_stat.f_fsidx.__fsid_val[0];
        mp->mnt_stat.f_namemax = MSDOSFS_NAMEMAX(pmp);
        mp->mnt_flag |= MNT_LOCAL;
        mp->mnt_iflag |= IMNT_SHRLOOKUP;
        mp->mnt_dev_bshift = pmp->pm_bnshift;
        mp->mnt_fs_bshift = pmp->pm_cnshift;

        /*
         * If we ever do quotas for DOS filesystems this would be a place
         * to fill in the info in the msdosfsmount structure. You dolt,
         * quotas on dos filesystems make no sense because files have no
         * owners on dos filesystems. of course there is some empty space
         * in the directory entry where we could put uid's and gid's.
         */

        spec_node_setmountedfs(devvp, mp);

        return (0);

error_exit:
        if (bp)
                brelse(bp, BC_AGE);
        if (pmp) {
                if (pmp->pm_inusemap)
                        free(pmp->pm_inusemap, M_MSDOSFSFAT);
                free(pmp, M_MSDOSFSMNT);
                mp->mnt_data = NULL;
        }
        return (error);
}

int
msdosfs_start(struct mount *mp, int flags)
{

        return (0);
}

/*
 * Unmount the filesystem described by mp.
 */
int
msdosfs_unmount(struct mount *mp, int mntflags)
{
        struct msdosfsmount *pmp;
        int error, flags;

        flags = 0;
        if (mntflags & MNT_FORCE)
                flags |= FORCECLOSE;
        if ((error = vflush(mp, NULLVP, flags)) != 0)
                return (error);
        pmp = VFSTOMSDOSFS(mp);
        if (pmp->pm_devvp->v_type != VBAD)
                spec_node_setmountedfs(pmp->pm_devvp, NULL);
#ifdef MSDOSFS_DEBUG
        {
                struct vnode *vp = pmp->pm_devvp;

                printf("msdosfs_umount(): just before calling VOP_CLOSE()\n");
                printf("flag %08x, usecount %d, writecount %d, holdcnt %d\n",
                    vp->v_vflag | vp->v_iflag | vp->v_uflag, vrefcnt(vp),
                    vp->v_writecount, vp->v_holdcnt);
                printf("mount %p, op %p\n",
                    vp->v_mount, vp->v_op);
                printf("cleanblkhd %p, dirtyblkhd %p, numoutput %d, type %d\n",
                    vp->v_cleanblkhd.lh_first,
                    vp->v_dirtyblkhd.lh_first,
                    vp->v_numoutput, vp->v_type);
                printf("union %p, tag %d, data[0] %08x, data[1] %08x\n",
                    vp->v_socket, vp->v_tag,
                    ((u_int *)vp->v_data)[0],
                    ((u_int *)vp->v_data)[1]);
        }
#endif
        vn_lock(pmp->pm_devvp, LK_EXCLUSIVE | LK_RETRY);
        (void) VOP_CLOSE(pmp->pm_devvp,
            pmp->pm_flags & MSDOSFSMNT_RONLY ? FREAD : FREAD|FWRITE, NOCRED);
        vput(pmp->pm_devvp);
        msdosfs_fh_destroy(pmp);
        free(pmp->pm_inusemap, M_MSDOSFSFAT);
        free(pmp, M_MSDOSFSMNT);
        mp->mnt_data = NULL;
        mp->mnt_flag &= ~MNT_LOCAL;
        return (0);
}

int
msdosfs_root(struct mount *mp, int lktype, struct vnode **vpp)
{
        struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
        int error;

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_root(); mp %p, pmp %p\n", mp, pmp);
#endif
        if ((error = msdosfs_deget(pmp, MSDOSFSROOT, MSDOSFSROOT_OFS,
            vpp)) != 0)
                return error;
        error = vn_lock(*vpp, lktype);
        if (error) {
                vrele(*vpp);
                *vpp = NULL;
                return error;
        }
        return 0;
}

int
msdosfs_statvfs(struct mount *mp, struct statvfs *sbp)
{
        struct msdosfsmount *pmp;

        pmp = VFSTOMSDOSFS(mp);
        sbp->f_bsize = pmp->pm_bpcluster;
        sbp->f_frsize = sbp->f_bsize;
        sbp->f_iosize = pmp->pm_bpcluster;
        sbp->f_blocks = pmp->pm_nmbrofclusters;
        sbp->f_bfree = pmp->pm_freeclustercount;
        sbp->f_bavail = pmp->pm_freeclustercount;
        sbp->f_bresvd = 0;
        sbp->f_files = pmp->pm_RootDirEnts;                     /* XXX */
        sbp->f_ffree = 0;       /* what to put in here? */
        sbp->f_favail = 0;      /* what to put in here? */
        sbp->f_fresvd = 0;
        copy_statvfs_info(sbp, mp);
        return (0);
}

struct msdosfs_sync_ctx {
        int waitfor;
};

static bool
msdosfs_sync_selector(void *cl, struct vnode *vp)
{
        struct msdosfs_sync_ctx *c = cl;
        struct denode *dep;

        KASSERT(mutex_owned(vp->v_interlock));

        dep = VTODE(vp);
        if (c->waitfor == MNT_LAZY || vp->v_type == VNON ||
            dep == NULL || (((dep->de_flag &
            (DE_ACCESS | DE_CREATE | DE_UPDATE | DE_MODIFIED)) == 0) &&
             (LIST_EMPTY(&vp->v_dirtyblkhd) &&
              (vp->v_iflag & VI_ONWORKLST) == 0)))
                return false;
        return true;
}

int
msdosfs_sync(struct mount *mp, int waitfor, kauth_cred_t cred)
{
        struct vnode *vp;
        struct vnode_iterator *marker;
        struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
        int error, allerror = 0;
        struct msdosfs_sync_ctx ctx;

        /*
         * If we ever switch to not updating all of the FATs all the time,
         * this would be the place to update them from the first one.
         */
        if (pmp->pm_fmod != 0) {
                if (pmp->pm_flags & MSDOSFSMNT_RONLY)
                        panic("msdosfs_sync: rofs mod");
                else {
                        /* update FATs here */
                }
        }
        /*
         * Write back each (modified) denode.
         */
        vfs_vnode_iterator_init(mp, &marker);
        ctx.waitfor = waitfor;
        while ((vp = vfs_vnode_iterator_next(marker, msdosfs_sync_selector,
            &ctx)))
        {
                error = vn_lock(vp, LK_EXCLUSIVE);
                if (error) {
                        vrele(vp);
                        continue;
                }
                if ((error = VOP_FSYNC(vp, cred,
                    waitfor == MNT_WAIT ? FSYNC_WAIT : 0, 0, 0)) != 0)
                        allerror = error;
                vput(vp);
        }
        vfs_vnode_iterator_destroy(marker);

        /*
         * Force stale file system control information to be flushed.
         */
        vn_lock(pmp->pm_devvp, LK_EXCLUSIVE | LK_RETRY);
        if ((error = VOP_FSYNC(pmp->pm_devvp, cred,
            waitfor == MNT_WAIT ? FSYNC_WAIT : 0, 0, 0)) != 0)
                allerror = error;
        VOP_UNLOCK(pmp->pm_devvp);
        return (allerror);
}

int
msdosfs_fhtovp(struct mount *mp, struct fid *fhp, int lktype, struct vnode **vpp)
{
        struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
        struct defid defh;
        uint32_t gen;
        int error;

        if (fhp->fid_len != sizeof(struct defid)) {
                DPRINTF("fid_len %d %zd", fhp->fid_len, sizeof(struct defid));
                return EINVAL;
        }
        memcpy(&defh, fhp, sizeof(defh));
        error = msdosfs_fh_lookup(pmp, defh.defid_dirclust, defh.defid_dirofs,
            &gen);
        if (error == 0 && gen != defh.defid_gen)
                error = ESTALE;
        if (error) {
                *vpp = NULLVP;
                return error;
        }
        error = msdosfs_deget(pmp, defh.defid_dirclust, defh.defid_dirofs, vpp);
        if (error) {
                DPRINTF("deget %d", error);
                *vpp = NULLVP;
                return error;
        }
        error = vn_lock(*vpp, lktype);
        if (error) {
                vrele(*vpp);
                *vpp = NULLVP;
                return error;
        }
        return 0;
}

int
msdosfs_vptofh(struct vnode *vp, struct fid *fhp, size_t *fh_size)
{
        struct msdosfsmount *pmp = VFSTOMSDOSFS(vp->v_mount);
        struct denode *dep;
        struct defid defh;
        int error;

        if (*fh_size < sizeof(struct defid)) {
                *fh_size = sizeof(struct defid);
                return E2BIG;
        }
        *fh_size = sizeof(struct defid);
        dep = VTODE(vp);
        memset(&defh, 0, sizeof(defh));
        defh.defid_len = sizeof(struct defid);
        defh.defid_dirclust = dep->de_dirclust;
        defh.defid_dirofs = dep->de_diroffset;
        error = msdosfs_fh_enter(pmp, dep->de_dirclust, dep->de_diroffset,
             &defh.defid_gen);
        if (error == 0)
                memcpy(fhp, &defh, sizeof(defh));
        return error;
}

int
msdosfs_vget(struct mount *mp, ino_t ino, int lktype,
    struct vnode **vpp)
{

        return (EOPNOTSUPP);
}