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[dragonfly.git] / sys / vfs / msdosfs / msdosfs_vnops.c

/* $FreeBSD$ */
/*      $NetBSD: msdosfs_vnops.c,v 1.68 1998/02/10 14:10:04 mrg Exp $   */

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * 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/param.h>
#include <sys/systm.h>
#include <sys/uio.h>
#include <sys/resourcevar.h>    /* defines plimit structure in proc struct */
#include <sys/kernel.h>
#include <sys/stat.h>
#include <sys/buf.h>
#include <sys/proc.h>
#include <sys/caps.h>
#include <sys/namei.h>
#include <sys/mount.h>
#include <sys/unistd.h>
#include <sys/vnode.h>
#include <sys/malloc.h>
#include <sys/dirent.h>
#include <sys/signalvar.h>
#include <sys/time.h>

#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_zone.h>
#include <vm/vnode_pager.h>
#include <vm/vm_page2.h>

#include <sys/buf2.h>

#include <machine/inttypes.h>

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

/*
 * Some general notes:
 *
 * In the ufs filesystem the inodes, superblocks, and indirect blocks are
 * read/written using the vnode for the filesystem. Blocks that represent
 * the contents of a file are read/written using the vnode for the file
 * (including directories when they are read/written as files). This
 * presents problems for the dos filesystem because data that should be in
 * an inode (if dos had them) resides in the directory itself.  Since we
 * must update directory entries without the benefit of having the vnode
 * for the directory we must use the vnode for the filesystem.  This means
 * that when a directory is actually read/written (via read, write, or
 * readdir, or seek) we must use the vnode for the filesystem instead of
 * the vnode for the directory as would happen in ufs. This is to insure we
 * retrieve the correct block from the buffer cache since the hash value is
 * based upon the vnode address and the desired block number.
 */

/*
 * Create a regular file. On entry the directory to contain the file being
 * created is locked.  We must release before we return. We must also free
 * the pathname buffer pointed at by cnp->cn_pnbuf, always on error, or
 * only if the SAVESTART bit in cn_flags is clear on success.
 */
static int
msdosfs_create(struct vop_old_create_args *ap)
{
        struct componentname *cnp = ap->a_cnp;
        struct denode ndirent;
        struct denode *dep;
        struct denode *pdep = VTODE(ap->a_dvp);
        struct timespec ts;
        int error;

        mprintf("msdosfs_create(cnp %p, vap %p\n", cnp, ap->a_vap);

        /*
         * If this is the root directory and there is no space left we
         * can't do anything.  This is because the root directory can not
         * change size.
         */
        if (pdep->de_StartCluster == MSDOSFSROOT
            && pdep->de_fndoffset >= pdep->de_FileSize) {
                error = ENOSPC;
                goto bad;
        }

        /*
         * Create a directory entry for the file, then call createde() to
         * have it installed. NOTE: DOS files are always executable.  We
         * use the absence of the owner write bit to make the file
         * readonly.
         */
        memset(&ndirent, 0, sizeof(ndirent));
        error = uniqdosname(pdep, cnp, ndirent.de_Name);
        if (error)
                goto bad;

        ndirent.de_Attributes = (ap->a_vap->va_mode & VWRITE) ?
                                ATTR_ARCHIVE : ATTR_ARCHIVE | ATTR_READONLY;
        ndirent.de_LowerCase = 0;
        ndirent.de_StartCluster = 0;
        ndirent.de_FileSize = 0;
        ndirent.de_dev = pdep->de_dev;
        ndirent.de_devvp = pdep->de_devvp;
        ndirent.de_pmp = pdep->de_pmp;
        ndirent.de_flag = DE_ACCESS | DE_CREATE | DE_UPDATE;
        vfs_timestamp(&ts);
        DETIMES(&ndirent, &ts, &ts, &ts);
        error = createde(&ndirent, pdep, &dep, cnp);
        if (error)
                goto bad;
        *ap->a_vpp = DETOV(dep);
        return (0);

bad:
        return (error);
}

static int
msdosfs_mknod(struct vop_old_mknod_args *ap)
{
        return (EINVAL);
}

static int
msdosfs_open(struct vop_open_args *ap)
{
        return(vop_stdopen(ap));
}

static int
msdosfs_close(struct vop_close_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct denode *dep = VTODE(vp);
        struct timespec ts;

        if (VREFCNT(vp) > 1) {
                vfs_timestamp(&ts);
                DETIMES(dep, &ts, &ts, &ts);
        }
        return (vop_stdclose(ap));
}

static int
msdosfs_access(struct vop_access_args *ap)
{
        struct denode *dep = VTODE(ap->a_vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        mode_t file_mode;

        file_mode = (S_IXUSR|S_IXGRP|S_IXOTH) | (S_IRUSR|S_IRGRP|S_IROTH) |
            ((dep->de_Attributes & ATTR_READONLY) ?
            0 : (S_IWUSR|S_IWGRP|S_IWOTH));
        file_mode &= (ap->a_vp->v_type == VDIR ? pmp->pm_dirmask : pmp->pm_mask);

        return (vop_helper_access(ap, pmp->pm_uid, pmp->pm_gid, file_mode, 0));
}

static int
msdosfs_getattr(struct vop_getattr_args *ap)
{
        struct denode *dep = VTODE(ap->a_vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        struct vattr *vap = ap->a_vap;
        mode_t mode;
        struct timespec ts;
        u_long dirsperblk = pmp->pm_BytesPerSec / sizeof(struct direntry);
        uint64_t fileid;

        vfs_timestamp(&ts);
        DETIMES(dep, &ts, &ts, &ts);
        vap->va_fsid = devid_from_dev(dep->de_dev);
        /*
         * The following computation of the fileid must be the same as that
         * used in msdosfs_readdir() to compute d_fileno. If not, pwd
         * doesn't work.
         */
        if (dep->de_Attributes & ATTR_DIRECTORY) {
                fileid = (uint64_t)cntobn(pmp, dep->de_StartCluster) *
                    dirsperblk;
                if (dep->de_StartCluster == MSDOSFSROOT)
                        fileid = 1;
        } else {
                fileid = (uint64_t)cntobn(pmp, dep->de_dirclust) *
                    dirsperblk;
                if (dep->de_dirclust == MSDOSFSROOT)
                        fileid = (uint64_t)roottobn(pmp, 0) * dirsperblk;
                fileid += (uoff_t)dep->de_diroffset / sizeof(struct direntry);
        }
        vap->va_fileid = fileid;
        if ((dep->de_Attributes & ATTR_READONLY) == 0)
                mode = S_IRWXU|S_IRWXG|S_IRWXO;
        else
                mode = S_IRUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH;
        vap->va_mode = mode &
            (ap->a_vp->v_type == VDIR ? pmp->pm_dirmask : pmp->pm_mask);
        vap->va_uid = pmp->pm_uid;
        vap->va_gid = pmp->pm_gid;
        vap->va_nlink = 1;
        vap->va_rmajor = VNOVAL;
        vap->va_rminor = VNOVAL;
        vap->va_size = dep->de_FileSize;
        fattime2timespec(dep->de_MDate, dep->de_MTime, 0, 0, &vap->va_mtime);
        if (pmp->pm_flags & MSDOSFSMNT_LONGNAME) {
                fattime2timespec(dep->de_ADate, 0, 0, 0, &vap->va_atime);
                fattime2timespec(dep->de_CDate, dep->de_CTime, dep->de_CHun,
                    0, &vap->va_ctime);
        } else {
                vap->va_atime = vap->va_mtime;
                vap->va_ctime = vap->va_mtime;
        }
        vap->va_flags = 0;
        if ((dep->de_Attributes & ATTR_ARCHIVE) == 0)
                vap->va_flags |= SF_ARCHIVED;
        vap->va_gen = 0;
        vap->va_blocksize = pmp->pm_bpcluster;
        vap->va_bytes =
            (dep->de_FileSize + pmp->pm_crbomask) & ~pmp->pm_crbomask;
        vap->va_type = ap->a_vp->v_type;
        vap->va_filerev = dep->de_modrev;
        return (0);
}

static int
msdosfs_setattr(struct vop_setattr_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct denode *dep = VTODE(vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        struct vattr *vap = ap->a_vap;
        struct ucred *cred = ap->a_cred;
        int error = 0;

        mprintf("msdosfs_setattr(): vp %p, vap %p, cred %p\n", vp, vap, cred);

        /*
         * Check for unsettable attributes.
         */
        if ((vap->va_type != VNON) || (vap->va_nlink != VNOVAL) ||
            (vap->va_fsid != VNOVAL) || (vap->va_fileid != VNOVAL) ||
            (vap->va_blocksize != VNOVAL) || (vap->va_rmajor != VNOVAL) ||
            (vap->va_bytes != VNOVAL) || (vap->va_gen != VNOVAL)) {
                mprintf("msdosfs_setattr(): returning EINVAL\n");
                mprintf("    va_type %d, va_nlink %llx, va_fsid %llx, va_fileid %llx\n",
                    vap->va_type, (unsigned long long)vap->va_nlink,
                    (unsigned long long)vap->va_fsid,
                    (unsigned long long)vap->va_fileid);
                mprintf("    va_blocksize %lx, va_rdev %llx, va_bytes %llx, va_gen %lx\n",
                    vap->va_blocksize, (unsigned long long)0,
                    (unsigned long long)vap->va_bytes, vap->va_gen);
                mprintf("    va_uid %x, va_gid %x\n",
                    vap->va_uid, vap->va_gid);
                return (EINVAL);
        }

        /*
         * We don't allow setting attributes on the root directory.
         * The special case for the root directory is because before
         * FAT32, the root directory didn't have an entry for itself
         * (and was otherwise special).  With FAT32, the root
         * directory is not so special, but still doesn't have an
         * entry for itself.
         */
        if (vp->v_flag & VROOT)
                return (EINVAL);

        if (vap->va_flags != VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY)
                        return (EROFS);
                if (cred->cr_uid != pmp->pm_uid &&
                    (error = caps_priv_check(cred, SYSCAP_NOVFS_SETATTR)))
                {
                        return (error);
                }

                /*
                 * We are very inconsistent about handling unsupported
                 * attributes.  We ignored the access time and the
                 * read and execute bits.  We were strict for the other
                 * attributes.
                 *
                 * Here we are strict, stricter than ufs in not allowing
                 * users to attempt to set SF_SETTABLE bits or anyone to
                 * set unsupported bits.  However, we ignore attempts to
                 * set ATTR_ARCHIVE for directories `cp -pr' from a more
                 * sensible file system attempts it a lot.
                 */
                if (cred->cr_uid != 0) {
                        if (vap->va_flags & SF_SETTABLE)
                                return EPERM;
                }
                if (vap->va_flags & ~SF_ARCHIVED)
                        return EOPNOTSUPP;
                if (vap->va_flags & SF_ARCHIVED)
                        dep->de_Attributes &= ~ATTR_ARCHIVE;
                else if (!(dep->de_Attributes & ATTR_DIRECTORY))
                        dep->de_Attributes |= ATTR_ARCHIVE;
                dep->de_flag |= DE_MODIFIED;
        }

        if (vap->va_uid != (uid_t)VNOVAL || vap->va_gid != (gid_t)VNOVAL) {
                uid_t uid;
                gid_t gid;

                if (vp->v_mount->mnt_flag & MNT_RDONLY)
                        return (EROFS);
                uid = vap->va_uid;
                if (uid == (uid_t)VNOVAL)
                        uid = pmp->pm_uid;
                gid = vap->va_gid;
                if (gid == (gid_t)VNOVAL)
                        gid = pmp->pm_gid;
                if ((cred->cr_uid != pmp->pm_uid || uid != pmp->pm_uid ||
                    (gid != pmp->pm_gid && !groupmember(gid, cred))) &&
                    (error = caps_priv_check(cred, SYSCAP_NOVFS_SETATTR)))
                {
                        return error;
                }
                if (uid != pmp->pm_uid || gid != pmp->pm_gid)
                        return EINVAL;
        }

        if (vap->va_size != VNOVAL) {
                switch (vp->v_type) {
                case VDIR:
                        return (EISDIR);
                case VREG:
                        /*
                         * Truncation is only supported for regular files,
                         * Disallow it if the filesystem is read-only.
                         */
                        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                                return (EROFS);
                        break;
                default:
                        /*
                         * According to POSIX, the result is unspecified
                         * for file types other than regular files,
                         * directories and shared memory objects.  We
                         * don't support any file types except regular
                         * files and directories in this file system, so
                         * this (default) case is unreachable and can do
                         * anything.  Keep falling through to detrunc()
                         * for now.
                         */
                        break;
                }
                error = detrunc(dep, vap->va_size, 0);
                if (error)
                        return error;
        }
        if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY)
                        return (EROFS);
                if (cred->cr_uid != pmp->pm_uid &&
                    (error = caps_priv_check(cred, SYSCAP_NOVFS_SETATTR)) &&
                    ((vap->va_vaflags & VA_UTIMES_NULL) == 0 ||
                    (error = VOP_EACCESS(vp, VWRITE, cred))))
                {
                        return (error);
                }
                if (vp->v_type != VDIR) {
                        if ((pmp->pm_flags & MSDOSFSMNT_NOWIN95) == 0 &&
                            vap->va_atime.tv_sec != VNOVAL) {
                                dep->de_flag &= ~DE_ACCESS;
                                timespec2fattime(&vap->va_atime, 0,
                                    &dep->de_ADate, NULL, NULL);
                        }
                        if (vap->va_mtime.tv_sec != VNOVAL) {
                                dep->de_flag &= ~DE_UPDATE;
                                timespec2fattime(&vap->va_mtime, 0,
                                    &dep->de_MDate, &dep->de_MTime, NULL);
                        }
                        dep->de_Attributes |= ATTR_ARCHIVE;
                        dep->de_flag |= DE_MODIFIED;
                }
        }
        /*
         * DOS files only have the ability to have their writability
         * attribute set, so we use the owner write bit to set the readonly
         * attribute.
         */
        if (vap->va_mode != (mode_t)VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY)
                        return (EROFS);
                if (cred->cr_uid != pmp->pm_uid &&
                    (error = caps_priv_check(cred, SYSCAP_NOVFS_SETATTR)))
                {
                        return (error);
                }
                if (vp->v_type != VDIR) {
                        /* We ignore the read and execute bits. */
                        if (vap->va_mode & VWRITE)
                                dep->de_Attributes &= ~ATTR_READONLY;
                        else
                                dep->de_Attributes |= ATTR_READONLY;
                        dep->de_Attributes |= ATTR_ARCHIVE;
                        dep->de_flag |= DE_MODIFIED;
                }
        }
        return (deupdat(dep, 0));
}

static int
msdosfs_read(struct vop_read_args *ap)
{
        int error = 0;
        int blsize;
        int isadir;
        size_t orig_resid;
        u_int n;
        u_long diff;
        u_long on;
        u_long cn;
        daddr_t lbn;
        daddr_t rablock;
        off_t loffset;
        int rasize;
        int seqcount;
        struct buf *bp;
        struct vnode *vp = ap->a_vp;
        struct denode *dep = VTODE(vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        struct uio *uio = ap->a_uio;

        if (uio->uio_offset < 0)
                return (EINVAL);

        if ((uoff_t)uio->uio_offset > MSDOSFS_FILESIZE_MAX)
                return (0);
        /*
         * If they didn't ask for any data, then we are done.
         */
        orig_resid = uio->uio_resid;
        if (orig_resid == 0)
                return (0);

        /*
         * The caller is supposed to ensure that
         * uio->uio_offset >= 0 and uio->uio_resid >= 0.
         * We don't need to check for large offsets as in ffs because
         * dep->de_FileSize <= MSDOSFS_FILESIZE_MAX < OFF_MAX, so large
         * offsets cannot cause overflow even in theory.
         */

        seqcount = ap->a_ioflag >> IO_SEQSHIFT;

        isadir = dep->de_Attributes & ATTR_DIRECTORY;
        do {
                if (uio->uio_offset >= dep->de_FileSize)
                        break;

                cn = de_cluster(pmp, uio->uio_offset);
                loffset = de_cn2doff(pmp, cn);
                rablock = cn + 1;
                blsize = pmp->pm_bpcluster;
                on = uio->uio_offset & pmp->pm_crbomask;

                /*
                 * If we are operating on a directory file then be sure to
                 * do i/o with the vnode for the filesystem instead of the
                 * vnode for the directory.
                 */
                bp = NULL;
                if (isadir) {
                        /* convert cluster # to block # */
                        error = pcbmap(dep, cn, &lbn, NULL, &blsize);
                        loffset = de_bn2doff(pmp, lbn);
                        if (error == E2BIG) {
                                error = EINVAL;
                                break;
                        } else if (error)
                                break;
                        error = bread(pmp->pm_devvp, loffset, blsize, &bp);
                } else if (de_cn2off(pmp, rablock) >= dep->de_FileSize) {
                        error = bread(vp, loffset, blsize, &bp);
                } else if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
                        error = cluster_readx(vp,
                            ((dep->de_FileSize + blsize - 1) / blsize) * blsize,
                            loffset, blsize, B_NOTMETA, on + uio->uio_resid,
                            seqcount * MAXBSIZE, &bp);
                        bp->b_flags |= B_CLUSTEROK;
                } else if (seqcount > 1) {
                        off_t raoffset = de_cn2doff(pmp, rablock);
                        rasize = blsize;
                        error = breadn(vp, loffset,
                            blsize, &raoffset, &rasize, 1, &bp);
                } else {
                        error = bread(vp, loffset, blsize, &bp);
                }
                if (error) {
                        brelse(bp);
                        break;
                }
                diff = pmp->pm_bpcluster - on;
                n = szmin(uio->uio_resid, diff);
                diff = dep->de_FileSize - uio->uio_offset;
                if (diff < n)
                        n = diff;
                diff = blsize - bp->b_resid;
                if (diff < n)
                        n = diff;
                error = uiomovebp(bp, bp->b_data + on, (size_t)n, uio);
                bqrelse(bp);
        } while (error == 0 && uio->uio_resid > 0 && n != 0);

        if (!isadir && (error == 0 || uio->uio_resid != orig_resid) &&
            (vp->v_mount->mnt_flag & (MNT_NOATIME | MNT_RDONLY)) == 0)
                dep->de_flag |= DE_ACCESS;
        return (error);
}

/*
 * Write data to a file or directory.
 */
static int
msdosfs_write(struct vop_write_args *ap)
{
        int n;
        int croffset;
        size_t resid;
        u_long osize;
        int error = 0;
        u_long count;
        int seqcount;
        daddr_t cn, lastcn;
        struct buf *bp = NULL;
        int ioflag = ap->a_ioflag;
        struct uio *uio = ap->a_uio;
        struct thread *td = uio->uio_td;
        struct vnode *vp = ap->a_vp;
        struct vnode *thisvp;
        struct denode *dep = VTODE(vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        struct proc *p = (td ? td->td_proc : NULL);
        struct lwp *lp = (td ? td->td_lwp : NULL);

        mprintf("msdosfs_write(vp %p, uio %p, ioflag %x, cred %p\n",
            vp, uio, ioflag, ap->a_cred);
        mprintf("msdosfs_write(): diroff %lu, dirclust %lu, startcluster %lu\n",
            dep->de_diroffset, dep->de_dirclust, dep->de_StartCluster);

        switch (vp->v_type) {
        case VREG:
                if (ioflag & IO_APPEND)
                        uio->uio_offset = dep->de_FileSize;
                thisvp = vp;
                break;
        case VDIR:
                return EISDIR;
        default:
                panic("msdosfs_write(): bad file type");
        }

        if (uio->uio_offset < 0)
                return (EFBIG);

        /*
         * This is needed (unlike in ffs_write()) because we extend the
         * file outside of the loop but we don't want to extend the file
         * for writes of 0 bytes.
         */
        if (uio->uio_resid == 0)
                return (0);

        /*
         * The caller is supposed to ensure that
         * uio->uio_offset >= 0 and uio->uio_resid >= 0.
         */
        if ((uoff_t)uio->uio_offset + uio->uio_resid > MSDOSFS_FILESIZE_MAX)
                return (EFBIG);

        /*
         * If they've exceeded their filesize limit, tell them about it.
         */
        if (p &&
            ((uoff_t)uio->uio_offset + uio->uio_resid >
            p->p_rlimit[RLIMIT_FSIZE].rlim_cur)) {
                lwpsignal(p, lp, SIGXFSZ);
                return (EFBIG);
        }

        /*
         * If the offset we are starting the write at is beyond the end of
         * the file, then they've done a seek.  Unix filesystems allow
         * files with holes in them, DOS doesn't so we must fill the hole
         * with zeroed blocks.
         */
        if (uio->uio_offset > dep->de_FileSize) {
                error = deextend(dep, uio->uio_offset);
                if (error)
                        return (error);
        }

        /*
         * Remember some values in case the write fails.
         */
        resid = uio->uio_resid;
        osize = dep->de_FileSize;

        /*
         * If we write beyond the end of the file, extend it to its ultimate
         * size ahead of the time to hopefully get a contiguous area.
         */
        if (uio->uio_offset + resid > osize) {
                count = de_clcount(pmp, uio->uio_offset + resid) -
                        de_clcount(pmp, osize);
                error = extendfile(dep, count, NULL, NULL, 0);
                if (error &&  (error != ENOSPC || (ioflag & IO_UNIT)))
                        goto errexit;
                lastcn = dep->de_fc[FC_LASTFC].fc_frcn;
        } else
                lastcn = de_clcount(pmp, osize) - 1;

        seqcount = ioflag >> IO_SEQSHIFT;
        do {
                if (de_cluster(pmp, uio->uio_offset) > lastcn) {
                        error = ENOSPC;
                        break;
                }

                croffset = uio->uio_offset & pmp->pm_crbomask;
                n = (int)szmin(uio->uio_resid, pmp->pm_bpcluster - croffset);
                if (uio->uio_offset + n > dep->de_FileSize) {
                        dep->de_FileSize = uio->uio_offset + n;
                        /* The object size needs to be set before buffer is allocated */
                        vnode_pager_setsize(vp, dep->de_FileSize);
                }

                /*
                 * If either the whole cluster gets written, or we write
                 * the cluster from its start beyond EOF, then no need to
                 * read data from disk.
                 *
                 * If UIO_NOCOPY is set we have to do a read-before-write
                 * to fill in any missing pieces of the buffer since no
                 * actual overwrite will occur.
                 */
                cn = de_cluster(pmp, uio->uio_offset);
                if ((uio->uio_offset & pmp->pm_crbomask) == 0
                    && uio->uio_segflg != UIO_NOCOPY
                    && (de_cluster(pmp, uio->uio_offset + uio->uio_resid)
                        > de_cluster(pmp, uio->uio_offset)
                        || uio->uio_offset + uio->uio_resid >= dep->de_FileSize)) {
                        bp = getblk(thisvp, de_cn2doff(pmp, cn),
                                    pmp->pm_bpcluster, 0, 0);
                        clrbuf(bp);
                        /*
                         * Do the bmap now, since pcbmap needs buffers
                         * for the FAT table. (see msdosfs_strategy)
                         */
                        if (bp->b_bio2.bio_offset == NOOFFSET) {
                                daddr_t dblkno;

                                error = pcbmap(dep,
                                               de_cluster(pmp, bp->b_loffset),
                                               &dblkno, NULL, NULL);
                                if (error || dblkno == (daddr_t)-1) {
                                        bp->b_bio2.bio_offset = NOOFFSET;
                                } else {
                                        bp->b_bio2.bio_offset = de_bn2doff(pmp,
                                            dblkno);
                                }
                        }
                        if (bp->b_bio2.bio_offset == NOOFFSET) {
                                brelse(bp);
                                if (!error)
                                        error = EIO;            /* XXX */
                                break;
                        }
                } else {
                        /*
                         * The block we need to write into exists, so read
                         * it in.
                         */
                        error = bread(thisvp, de_cn2doff(pmp, cn),
                                      pmp->pm_bpcluster, &bp);
                        if (error) {
                                brelse(bp);
                                break;
                        }
                }

                /*
                 * Should these vnode_pager_* functions be done on dir
                 * files?
                 */

                /*
                 * Copy the data from user space into the buf header.
                 */
                error = uiomovebp(bp, bp->b_data + croffset, (size_t)n, uio);
                if (error) {
                        brelse(bp);
                        break;
                }

                /* Prepare for clustered writes in some else clauses. */
                if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0)
                        bp->b_flags |= B_CLUSTEROK;

                /*
                 * If IO_SYNC, then each buffer is written synchronously.
                 * Otherwise, if we have a severe page deficiency then
                 * write the buffer asynchronously.  Otherwise, if on a
                 * cluster boundary then write the buffer asynchronously,
                 * combining it with contiguous clusters if permitted and
                 * possible, since we don't expect more writes into this
                 * buffer soon.  Otherwise, do a delayed write because we
                 * expect more writes into this buffer soon.
                 */
                if (ioflag & IO_SYNC)
                        bwrite(bp);
                else if (vm_paging_severe() || buf_dirty_count_severe())
                        bawrite(bp);
                else if (n + croffset == pmp->pm_bpcluster) {
                        if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0)
                                cluster_write(bp, dep->de_FileSize,
                                    pmp->pm_bpcluster, seqcount);
                        else
                                bawrite(bp);
                } else
                        bdwrite(bp);
                dep->de_flag |= DE_UPDATE;
        } while (error == 0 && uio->uio_resid > 0);

        /*
         * If the write failed and they want us to, truncate the file back
         * to the size it was before the write was attempted.
         */
errexit:
        if (error) {
                if (ioflag & IO_UNIT) {
                        detrunc(dep, osize, ioflag & IO_SYNC);
                        uio->uio_offset -= resid - uio->uio_resid;
                        uio->uio_resid = resid;
                } else {
                        detrunc(dep, dep->de_FileSize, ioflag & IO_SYNC);
                        if (uio->uio_resid != resid)
                                error = 0;
                }
        } else if (ioflag & IO_SYNC)
                error = deupdat(dep, 1);
        return (error);
}

/*
 * Flush the blocks of a file to disk.
 */
static int
msdosfs_fsync(struct vop_fsync_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vnode *devvp;
        int allerror, error;

        /*
         * Flush all dirty buffers associated with a vnode.
         */
#ifdef DIAGNOSTIC
loop:
#endif
        vfsync(vp, ap->a_waitfor, 0, NULL, NULL);
#ifdef DIAGNOSTIC
        if (ap->a_waitfor == MNT_WAIT && !RB_EMPTY(&vp->v_rbdirty_tree)) {
                vprint("msdosfs_fsync: dirty", vp);
                goto loop;
        }
#endif
        /*
        * If the syncing request comes from fsync(2), sync the entire
        * FAT and any other metadata that happens to be on devvp.  We
        * need this mainly for the FAT.  We write the FAT sloppily, and
        * syncing it all now is the best we can easily do to get all
        * directory entries associated with the file (not just the file)
        * fully synced.  The other metadata includes critical metadata
        * for all directory entries, but only in the MNT_ASYNC case.  We
        * will soon sync all metadata in the file's directory entry.
        * Non-critical metadata for associated directory entries only
        * gets synced accidentally, as in most file systems.
        */
        if (ap->a_waitfor == MNT_WAIT) {
                devvp = VTODE(ap->a_vp)->de_pmp->pm_devvp;
                vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                allerror = VOP_FSYNC(devvp, MNT_WAIT, 0);
                vn_unlock(devvp);
        } else
                allerror = 0;

        error = deupdat(VTODE(ap->a_vp), ap->a_waitfor == MNT_WAIT);
        if (allerror == 0)
                allerror = error;
        return (allerror);
}

static int
msdosfs_remove(struct vop_old_remove_args *ap)
{
        struct denode *dep = VTODE(ap->a_vp);
        struct denode *ddep = VTODE(ap->a_dvp);
        int error;

        if (ap->a_vp->v_type == VDIR)
                error = EPERM;
        else
                error = removede(ddep, dep);
        mprintf("msdosfs_remove(), dep %p, v_refcnt 0x%08x\n",
                dep, ap->a_vp->v_refcnt);
        return (error);
}

/*
 * DOS filesystems don't know what links are.
 */
static int
msdosfs_link(struct vop_old_link_args *ap)
{
        return (EOPNOTSUPP);
}

/*
 * Renames on files require moving the denode to a new hash queue since the
 * denode's location is used to compute which hash queue to put the file
 * in. Unless it is a rename in place.  For example "mv a b".
 *
 * What follows is the basic algorithm:
 *
 * if (file move) {
 *      if (dest file exists) {
 *              remove dest file
 *      }
 *      if (dest and src in same directory) {
 *              rewrite name in existing directory slot
 *      } else {
 *              write new entry in dest directory
 *              update offset and dirclust in denode
 *              move denode to new hash chain
 *              clear old directory entry
 *      }
 * } else {
 *      directory move
 *      if (dest directory exists) {
 *              if (dest is not empty) {
 *                      return ENOTEMPTY
 *              }
 *              remove dest directory
 *      }
 *      if (dest and src in same directory) {
 *              rewrite name in existing entry
 *      } else {
 *              be sure dest is not a child of src directory
 *              write entry in dest directory
 *              update "." and ".." in moved directory
 *              clear old directory entry for moved directory
 *      }
 * }
 *
 * On entry:
 *      source's parent directory is unlocked
 *      source file or directory is unlocked
 *      destination's parent directory is locked
 *      destination file or directory is locked if it exists
 *
 * On exit:
 *      all denodes should be released
 */
static int
msdosfs_rename(struct vop_old_rename_args *ap)
{
        struct vnode *tdvp = ap->a_tdvp;
        struct vnode *fvp = ap->a_fvp;
        struct vnode *fdvp = ap->a_fdvp;
        struct vnode *tvp = ap->a_tvp;
        struct componentname *tcnp = ap->a_tcnp;
        struct componentname *fcnp = ap->a_fcnp;
        struct denode *ip, *xp, *dp, *zp;
        u_char toname[12], oldname[11];
        u_long from_diroffset, to_diroffset;
        u_char to_count;
        int doingdirectory = 0, newparent = 0;
        int error;
        u_long cn, pcl;
        daddr_t bn;
        struct msdosfsmount *pmp;
        struct direntry *dotdotp;
        struct buf *bp = NULL;

        pmp = VFSTOMSDOSFS(fdvp->v_mount);

        /*
         * Check for cross-device rename.
         */
        if (fvp->v_mount != tdvp->v_mount ||
            (tvp && fvp->v_mount != tvp->v_mount)) {
                error = EXDEV;
abortit:
                if (tdvp == tvp)
                        vrele(tdvp);
                else
                        vput(tdvp);
                if (tvp)
                        vput(tvp);
                vrele(fdvp);
                vrele(fvp);
                return (error);
        }

        /*
         * If source and dest are the same, do nothing.
         */
        if (tvp == fvp) {
                error = 0;
                goto abortit;
        }

        /*
         * fvp is unlocked, fdvp, tvp, tdvp are locked.  Lock fvp and note
         * that we have to unlock it to use the abortit target.
         */
        error = vn_lock(fvp, LK_EXCLUSIVE | LK_FAILRECLAIM);
        if (error)
                goto abortit;
        dp = VTODE(fdvp);
        ip = VTODE(fvp);

        /*
         * Be sure we are not renaming ".", "..", or an alias of ".". This
         * leads to a crippled directory tree.  It's pretty tough to do a
         * "ls" or "pwd" with the "." directory entry missing, and "cd .."
         * doesn't work if the ".." entry is missing.
         */
        if (ip->de_Attributes & ATTR_DIRECTORY) {
                /*
                 * Avoid ".", "..", and aliases of "." for obvious reasons.
                 */
                if ((fcnp->cn_namelen == 1 && fcnp->cn_nameptr[0] == '.') ||
                    dp == ip ||
                    (fcnp->cn_flags & CNP_ISDOTDOT) ||
                    (tcnp->cn_flags & CNP_ISDOTDOT) ||
                    (ip->de_flag & DE_RENAME)) {
                        vn_unlock(fvp);
                        error = EINVAL;
                        goto abortit;
                }
                ip->de_flag |= DE_RENAME;
                doingdirectory++;
        }

        /*
         * fvp locked, fdvp unlocked, tvp, tdvp locked.  DE_RENAME only
         * set if doingdirectory.  We will get fvp unlocked in fairly
         * short order.  dp and xp must be setup and fvp must be unlocked
         * for the out and bad targets to work properly.
         */
        dp = VTODE(tdvp);
        xp = tvp ? VTODE(tvp) : NULL;

        /*
         * Remember direntry place to use for destination
         */
        to_diroffset = dp->de_fndoffset;
        to_count = dp->de_fndcnt;

        /*
         * If ".." must be changed (ie the directory gets a new
         * parent) then the source directory must not be in the
         * directory hierarchy above the target, as this would
         * orphan everything below the source directory. Also
         * the user must have write permission in the source so
         * as to be able to change "..". We must repeat the call
         * to namei, as the parent directory is unlocked by the
         * call to doscheckpath().
         */
        error = VOP_EACCESS(fvp, VWRITE, tcnp->cn_cred);
        vn_unlock(fvp);
        if (VTODE(fdvp)->de_StartCluster != VTODE(tdvp)->de_StartCluster)
                newparent = 1;

        /*
         * ok. fvp, fdvp unlocked, tvp, tdvp locked. tvp may be NULL.
         * DE_RENAME only set if doingdirectory.
         */
        if (doingdirectory && newparent) {
                if (error)      /* write access check above */
                        goto bad;
                if (xp != NULL) {
                        vput(tvp);
                        xp = NULL;
                }
                /*
                 * checkpath vput's tdvp (VTOI(dp)) on return no matter what,
                 * get an extra ref so we wind up with just an unlocked, ref'd
                 * tdvp.  The 'out' target skips tvp and tdvp cleanups (tdvp
                 * isn't locked so we can't use the out target).
                 */
                vref(tdvp);
                error = doscheckpath(ip, dp);
                tcnp->cn_flags |= CNP_PDIRUNLOCK;
                if (error) {
                        vrele(tdvp);
                        goto out;
                }
                /*
                 * relookup no longer messes with the ref count.  tdvp must
                 * be unlocked on entry and on success will be locked on
                 * return.
                 */
                error = relookup(tdvp, &tvp, tcnp);
                if (error) {
                        if (tcnp->cn_flags & CNP_PDIRUNLOCK)
                                vrele(tdvp);
                        else
                                vput(tdvp);
                        goto out;
                }

                /*
                 * tvp and tdvp are now locked again.
                 */
                dp = VTODE(tdvp);
                xp = tvp ? VTODE(tvp) : NULL;
        }

        /*
         * tvp and tdvp are now locked again, the 'bad' target can be used
         * to clean them up again.  Delete an existant target and clean
         * up tvp.  Set xp to NULL to indicate that tvp has been cleaned up.
         */
        if (xp != NULL) {
                /*
                 * Target must be empty if a directory and have no links
                 * to it. Also, ensure source and target are compatible
                 * (both directories, or both not directories).
                 */
                if (xp->de_Attributes & ATTR_DIRECTORY) {
                        if (!dosdirempty(xp)) {
                                error = ENOTEMPTY;
                                goto bad;
                        }
                        if (!doingdirectory) {
                                error = ENOTDIR;
                                goto bad;
                        }
                } else if (doingdirectory) {
                        error = EISDIR;
                        goto bad;
                }
                error = removede(dp, xp);
                if (error)
                        goto bad;
                vput(tvp);
                xp = NULL;
                tvp = NULL;
        }

        /*
         * Convert the filename in tcnp into a dos filename. We copy this
         * into the denode and directory entry for the destination
         * file/directory.
         */
        error = uniqdosname(VTODE(tdvp), tcnp, toname);
        if (error)
                goto bad;

        /*
         * Since from wasn't locked at various places above, we have to do
         * a relookup here.  If the target and source are the same directory
         * we have to unlock the target directory in order to safely relookup
         * the source, because relookup expects its directory to be unlocked.
         *
         * Note that ap->a_fvp is still valid and ref'd.  Any cleanup must
         * now take that into account.
         *
         * The tdvp locking issues make this a real mess.
         */
        fcnp->cn_flags &= ~CNP_MODMASK;
        fcnp->cn_flags |= CNP_LOCKPARENT;
        if (newparent == 0)
                vn_unlock(tdvp);
        error = relookup(fdvp, &fvp, fcnp);
        if (error || fvp == NULL) {
                /*
                 * From name has disappeared.  Note: fdvp might == tdvp.
                 *
                 * DE_RENAME is only set if doingdirectory.
                 */
                if (doingdirectory)
                        panic("rename: lost dir entry");
                if (fcnp->cn_flags & CNP_PDIRUNLOCK)
                        vrele(fdvp);
                else
                        vput(fdvp);
                if (newparent == 0)
                        vrele(tdvp);
                else
                        vput(tdvp);
                vrele(ap->a_fvp);
                return(0);
        }

        /*
         * No error occured.  tdvp, fdvp and fvp are all locked.  If
         * newparent was 0 be aware that fdvp == tdvp.  tvp has been cleaned
         * up.  ap->a_fvp is still refd.
         */
        xp = VTODE(fvp);
        zp = VTODE(fdvp);
        from_diroffset = zp->de_fndoffset;

        /*
         * Ensure that the directory entry still exists and has not
         * changed till now. If the source is a file the entry may
         * have been unlinked or renamed. In either case there is
         * no further work to be done. If the source is a directory
         * then it cannot have been rmdir'ed or renamed; this is
         * prohibited by the DE_RENAME flag.
         *
         * DE_RENAME is only set if doingdirectory.
         */
        if (xp != ip) {
                if (doingdirectory)
                        panic("rename: lost dir entry");
                goto done;
        } else {
                u_long new_dirclust;
                u_long new_diroffset;

                /*
                 * First write a new entry in the destination
                 * directory and mark the entry in the source directory
                 * as deleted.  Then move the denode to the correct hash
                 * chain for its new location in the filesystem.  And, if
                 * we moved a directory, then update its .. entry to point
                 * to the new parent directory.
                 */
                memcpy(oldname, ip->de_Name, 11);
                memcpy(ip->de_Name, toname, 11);        /* update denode */
                dp->de_fndoffset = to_diroffset;
                dp->de_fndcnt = to_count;
                error = createde(ip, dp, NULL, tcnp);
                if (error) {
                        memcpy(ip->de_Name, oldname, 11);
                        goto done;
                }
                /*
                 * If ip is for a directory, then its name should always
                 * be "." since it is for the directory entry in the
                 * directory itself (msdosfs_lookup() always translates
                 * to the "." entry so as to get a unique denode, except
                 * for the root directory there are different
                 * complications).  However, we just corrupted its name
                 * to pass the correct name to createde().  Undo this.
                 */
                if ((ip->de_Attributes & ATTR_DIRECTORY) != 0)
                        memcpy(ip->de_Name, oldname, 11);
                ip->de_refcnt++;
                zp->de_fndoffset = from_diroffset;
                error = removede(zp, ip);
                if (error) {
                        /* XXX should downgrade to ro here, fs is corrupt */
                        goto done;
                }
                if (!doingdirectory) {
                        error = pcbmap(dp, de_cluster(pmp, to_diroffset),
                                       NULL, &new_dirclust, NULL);
                        if (error) {
                                /* XXX should downgrade to ro here, fs is corrupt */
                                goto done;
                        }
                        if (new_dirclust == MSDOSFSROOT)
                                new_diroffset = to_diroffset;
                        else
                                new_diroffset = to_diroffset & pmp->pm_crbomask;
                        msdosfs_reinsert(ip, new_dirclust, new_diroffset);
                }
        }

        /*
         * If we moved a directory to a new parent directory, then we must
         * fixup the ".." entry in the moved directory.
         */
        if (doingdirectory && newparent) {
                cn = ip->de_StartCluster;
                if (cn == MSDOSFSROOT) {
                        /* this should never happen */
                        panic("msdosfs_rename(): updating .. in root directory?");
                } else {
                        bn = cntobn(pmp, cn);
                }
                error = bread(pmp->pm_devvp, de_bn2doff(pmp, bn),
                              pmp->pm_bpcluster, &bp);
                if (error) {
                        /* XXX should downgrade to ro here, fs is corrupt */
                        brelse(bp);
                        goto done;
                }
                dotdotp = (struct direntry *)bp->b_data + 1;
                pcl = dp->de_StartCluster;
                if (FAT32(pmp) && pcl == pmp->pm_rootdirblk)
                        pcl = MSDOSFSROOT;
                putushort(dotdotp->deStartCluster, pcl);
                if (FAT32(pmp))
                        putushort(dotdotp->deHighClust, pcl >> 16);
                if (DOINGASYNC(fvp))
                        bdwrite(bp);
                else if ((error = bwrite(bp)) != 0) {
                        /* XXX should downgrade to ro here, fs is corrupt */
                        goto done;
                }
        }

        /*
         * done case fvp, fdvp, tdvp are locked.  ap->a_fvp is refd
         */
done:
        if (doingdirectory)
                ip->de_flag &= ~DE_RENAME;      /* XXX fvp not locked */
        vput(fvp);
        if (newparent)
                vput(fdvp);
        else
                vrele(fdvp);
        vput(tdvp);
        vrele(ap->a_fvp);
        return (error);

        /*
         * 'bad' target: xp governs tvp.  tvp and tdvp are locked, fdvp and fvp
         * are not locked.  ip points to fvp's inode which may have DE_RENAME
         * set.
         */
bad:
        if (xp)
                vput(tvp);
        vput(tdvp);
out:
        /*
         * 'out' target: tvp and tdvp have already been cleaned up.
         */
        if (doingdirectory)
                ip->de_flag &= ~DE_RENAME;
        vrele(fdvp);
        vrele(fvp);
        return (error);

}

static struct {
        struct direntry dot;
        struct direntry dotdot;
} dosdirtemplate = {
        {       ".          ",                          /* the . entry */
                ATTR_DIRECTORY,                         /* file attribute */
                0,                                      /* reserved */
                0, { 0, 0 }, { 0, 0 },                  /* create time & date */
                { 0, 0 },                               /* access date */
                { 0, 0 },                               /* high bits of start cluster */
                { 210, 4 }, { 210, 4 },                 /* modify time & date */
                { 0, 0 },                               /* startcluster */
                { 0, 0, 0, 0 }                          /* filesize */
        },
        {       "..         ",                          /* the .. entry */
                ATTR_DIRECTORY,                         /* file attribute */
                0,                                      /* reserved */
                0, { 0, 0 }, { 0, 0 },                  /* create time & date */
                { 0, 0 },                               /* access date */
                { 0, 0 },                               /* high bits of start cluster */
                { 210, 4 }, { 210, 4 },                 /* modify time & date */
                { 0, 0 },                               /* startcluster */
                { 0, 0, 0, 0 }                          /* filesize */
        }
};

static int
msdosfs_mkdir(struct vop_old_mkdir_args *ap)
{
        struct componentname *cnp = ap->a_cnp;
        struct denode *dep;
        struct denode *pdep = VTODE(ap->a_dvp);
        struct direntry *denp;
        struct msdosfsmount *pmp = pdep->de_pmp;
        struct buf *bp;
        u_long newcluster, pcl;
        int bn;
        int error;
        struct denode ndirent;
        struct timespec ts;

        /*
         * If this is the root directory and there is no space left we
         * can't do anything.  This is because the root directory can not
         * change size.
         */
        if (pdep->de_StartCluster == MSDOSFSROOT
            && pdep->de_fndoffset >= pdep->de_FileSize) {
                error = ENOSPC;
                goto bad2;
        }

        /*
         * Allocate a cluster to hold the about to be created directory.
         */
        error = clusteralloc(pmp, 0, 1, CLUST_EOFE, &newcluster, NULL);
        if (error)
                goto bad2;

        memset(&ndirent, 0, sizeof(ndirent));
        ndirent.de_pmp = pmp;
        ndirent.de_flag = DE_ACCESS | DE_CREATE | DE_UPDATE;
        vfs_timestamp(&ts);
        DETIMES(&ndirent, &ts, &ts, &ts);

        /*
         * Now fill the cluster with the "." and ".." entries. And write
         * the cluster to disk.  This way it is there for the parent
         * directory to be pointing at if there were a crash.
         */
        bn = cntobn(pmp, newcluster);
        /* always succeeds */
        bp = getblk(pmp->pm_devvp, de_bn2doff(pmp, bn),
                    pmp->pm_bpcluster, 0, 0);
        memset(bp->b_data, 0, pmp->pm_bpcluster);
        memcpy(bp->b_data, &dosdirtemplate, sizeof(dosdirtemplate));
        denp = (struct direntry *)bp->b_data;
        putushort(denp[0].deStartCluster, newcluster);
        putushort(denp[0].deCDate, ndirent.de_CDate);
        putushort(denp[0].deCTime, ndirent.de_CTime);
        denp[0].deCHundredth = ndirent.de_CHun;
        putushort(denp[0].deADate, ndirent.de_ADate);
        putushort(denp[0].deMDate, ndirent.de_MDate);
        putushort(denp[0].deMTime, ndirent.de_MTime);
        pcl = pdep->de_StartCluster;
        /*
         * Although the root directory has a non-magic starting cluster
         * number for FAT32, chkdsk and fsck_msdosfs still require
         * references to it in dotdot entries to be magic.
         */
        if (FAT32(pmp) && pcl == pmp->pm_rootdirblk)
                pcl = MSDOSFSROOT;
        putushort(denp[1].deStartCluster, pcl);
        putushort(denp[1].deCDate, ndirent.de_CDate);
        putushort(denp[1].deCTime, ndirent.de_CTime);
        denp[1].deCHundredth = ndirent.de_CHun;
        putushort(denp[1].deADate, ndirent.de_ADate);
        putushort(denp[1].deMDate, ndirent.de_MDate);
        putushort(denp[1].deMTime, ndirent.de_MTime);
        if (FAT32(pmp)) {
                putushort(denp[0].deHighClust, newcluster >> 16);
                putushort(denp[1].deHighClust, pcl >> 16);
        }

        if (DOINGASYNC(ap->a_dvp))
                bdwrite(bp);
        else if ((error = bwrite(bp)) != 0)
                goto bad;

        /*
         * Now build up a directory entry pointing to the newly allocated
         * cluster.  This will be written to an empty slot in the parent
         * directory.
         */
        error = uniqdosname(pdep, cnp, ndirent.de_Name);
        if (error)
                goto bad;

        ndirent.de_Attributes = ATTR_DIRECTORY;
        ndirent.de_LowerCase = 0;
        ndirent.de_StartCluster = newcluster;
        ndirent.de_FileSize = 0;
        ndirent.de_dev = pdep->de_dev;
        ndirent.de_devvp = pdep->de_devvp;
        error = createde(&ndirent, pdep, &dep, cnp);
        if (error)
                goto bad;
        *ap->a_vpp = DETOV(dep);
        return (0);

bad:
        clusterfree(pmp, newcluster);
bad2:
        return (error);
}

static int
msdosfs_rmdir(struct vop_old_rmdir_args *ap)
{
        struct vnode *vp = ap->a_vp;
        struct vnode *dvp = ap->a_dvp;
        struct denode *ip, *dp;
        int error;

        ip = VTODE(vp);
        dp = VTODE(dvp);

        /*
         * Verify the directory is empty (and valid).
         * (Rmdir ".." won't be valid since
         *  ".." will contain a reference to
         *  the current directory and thus be
         *  non-empty.)
         */
        error = 0;
        if (!dosdirempty(ip) || ip->de_flag & DE_RENAME) {
                error = ENOTEMPTY;
                goto out;
        }
        /*
         * Delete the entry from the directory.  For dos filesystems this
         * gets rid of the directory entry on disk, the in memory copy
         * still exists but the de_refcnt is <= 0.  This prevents it from
         * being found by deget().  When the vput() on dep is done we give
         * up access and eventually msdosfs_reclaim() will be called which
         * will remove it from the denode cache.
         */
        error = removede(dp, ip);
        if (error)
                goto out;
        /*
         * Truncate the directory that is being deleted.
         */
        error = detrunc(ip, (u_long)0, IO_SYNC);
out:
        return (error);
}

/*
 * DOS filesystems don't know what symlinks are.
 */
static int
msdosfs_symlink(struct vop_old_symlink_args *ap)
{
        return (EOPNOTSUPP);
}

static int
msdosfs_readdir(struct vop_readdir_args *ap)
{
        struct mbnambuf nb;
        int error = 0;
        int diff;
        long n;
        int blsize;
        long on;
        u_long cn;
        u_long dirsperblk;
        long bias = 0;
        daddr_t bn, lbn;
        struct buf *bp = NULL;
        struct denode *dep;
        struct msdosfsmount *pmp;
        struct direntry *dentp;
        struct dirent dirbuf;
        struct uio *uio = ap->a_uio;
        off_t *cookies = NULL;
        int ncookies = 0;
        off_t offset, off;
        int chksum = -1;

        error = vn_lock(ap->a_vp, LK_EXCLUSIVE | LK_RETRY | LK_FAILRECLAIM);
        if (error)
                return (error);

        dep = VTODE(ap->a_vp);
        pmp = dep->de_pmp;

        mprintf("msdosfs_readdir(): vp %p, uio %p, cred %p, eofflagp %p\n",
            ap->a_vp, uio, ap->a_cred, ap->a_eofflag);

        /*
         * msdosfs_readdir() won't operate properly on regular files since
         * it does i/o only with the filesystem vnode, and hence can
         * retrieve the wrong block from the buffer cache for a plain file.
         * So, fail attempts to readdir() on a plain file.
         */
        if ((dep->de_Attributes & ATTR_DIRECTORY) == 0) {
                error = ENOTDIR;
                goto done;
        }

        /*
         * To be safe, initialize dirbuf
         */
        memset(dirbuf.d_name, 0, sizeof(dirbuf.d_name));

        /*
         * If the user buffer is smaller than the size of one dos directory
         * entry or the file offset is not a multiple of the size of a
         * directory entry, then we fail the read.
         */
        off = offset = uio->uio_offset;
        if (uio->uio_resid < sizeof(struct direntry) ||
            (offset & (sizeof(struct direntry) - 1))) {
                error = EINVAL;
                goto done;
        }

        if (ap->a_ncookies) {
                ncookies = uio->uio_resid / 16 + 1;
                if (ncookies > 1024)
                        ncookies = 1024;
                cookies = kmalloc(ncookies * sizeof(off_t), M_TEMP, M_WAITOK);
                *ap->a_cookies = cookies;
                *ap->a_ncookies = ncookies;
        }

        dirsperblk = pmp->pm_BytesPerSec / sizeof(struct direntry);

#define d_fileno d_ino
        /*
         * If they are reading from the root directory then, we simulate
         * the . and .. entries since these don't exist in the root
         * directory.  We also set the offset bias to make up for having to
         * simulate these entries. By this I mean that at file offset 64 we
         * read the first entry in the root directory that lives on disk.
         */
        if (dep->de_StartCluster == MSDOSFSROOT
            || (FAT32(pmp) && dep->de_StartCluster == pmp->pm_rootdirblk)) {
#if 0
                printf("msdosfs_readdir(): going after . or .. in root dir, offset %d\n",
                    offset);
#endif
                bias = 2 * sizeof(struct direntry);
                if (offset < bias) {
                        for (n = (int)offset / sizeof(struct direntry);
                             n < 2; n++) {
                                dirbuf.d_fileno = FAT32(pmp) ?
                                    (uint64_t)cntobn(pmp, pmp->pm_rootdirblk) *
                                    dirsperblk : 1;
                                dirbuf.d_type = DT_DIR;
                                switch (n) {
                                case 0:
                                        dirbuf.d_namlen = 1;
                                        dirbuf.d_name[0] = '.';
                                        break;
                                case 1:
                                        dirbuf.d_namlen = 2;
                                        dirbuf.d_name[0] = '.';
                                        dirbuf.d_name[1] = '.';
                                        break;
                                }
                                if (vop_write_dirent(&error, uio,
                                    dirbuf.d_fileno, dirbuf.d_type,
                                    dirbuf.d_namlen, dirbuf.d_name))
                                        goto out;
                                if (error)
                                        goto out;
                                offset += sizeof(struct direntry);
                                off = offset;
                                if (cookies) {
                                        *cookies++ = offset;
                                        if (--ncookies <= 0)
                                                goto out;
                                }
                        }
                }
        }

        mbnambuf_init(&nb);
        off = offset;

        while (uio->uio_resid > 0) {
                lbn = de_cluster(pmp, offset - bias);
                on = (offset - bias) & pmp->pm_crbomask;
                n = szmin(pmp->pm_bpcluster - on, uio->uio_resid);
                diff = dep->de_FileSize - (offset - bias);
                if (diff <= 0)
                        break;
                n = min(n, diff);
                error = pcbmap(dep, lbn, &bn, &cn, &blsize);
                if (error)
                        break;
                error = bread(pmp->pm_devvp, de_bn2doff(pmp, bn), blsize, &bp);
                if (error) {
                        brelse(bp);
                        goto done;
                }
                n = min(n, blsize - bp->b_resid);
                if (n == 0) {
                        brelse(bp);
                        error = EIO;
                        goto done;
                }

                /*
                 * Convert from dos directory entries to fs-independent
                 * directory entries.
                 */
                for (dentp = (struct direntry *)(bp->b_data + on);
                     (char *)dentp < bp->b_data + on + n;
                     dentp++, offset += sizeof(struct direntry)) {
#if 0
                        printf("rd: dentp %08x prev %08x crnt %08x deName %02x attr %02x\n",
                            dentp, prev, crnt, dentp->deName[0], dentp->deAttributes);
#endif
                        /*
                         * If this is an unused entry, we can stop.
                         */
                        if (dentp->deName[0] == SLOT_EMPTY) {
                                brelse(bp);
                                goto out;
                        }
                        /*
                         * Skip deleted entries.
                         */
                        if (dentp->deName[0] == SLOT_DELETED) {
                                chksum = -1;
                                mbnambuf_init(&nb);
                                continue;
                        }

                        /*
                         * Handle Win95 long directory entries
                         */
                        if (dentp->deAttributes == ATTR_WIN95) {
                                if (pmp->pm_flags & MSDOSFSMNT_SHORTNAME)
                                        continue;
                                chksum = win2unixfn(&nb,
                                    (struct winentry *)dentp, chksum, pmp);
                                continue;
                        }

                        /*
                         * Skip volume labels
                         */
                        if (dentp->deAttributes & ATTR_VOLUME) {
                                chksum = -1;
                                mbnambuf_init(&nb);
                                continue;
                        }
                        /*
                         * This computation of d_fileno must match
                         * the computation of va_fileid in
                         * msdosfs_getattr.
                         */
                        if (dentp->deAttributes & ATTR_DIRECTORY) {
                                cn = getushort(dentp->deStartCluster);
                                if (FAT32(pmp)) {
                                        cn |= getushort(dentp->deHighClust) <<
                                            16;
                                        if (cn == MSDOSFSROOT)
                                                cn = pmp->pm_rootdirblk;
                                }
                                if (cn == MSDOSFSROOT && !FAT32(pmp))
                                        dirbuf.d_fileno = 1;
                                else
                                        dirbuf.d_fileno = cntobn(pmp, cn) *
                                            dirsperblk;
                                dirbuf.d_type = DT_DIR;
                        } else {
                                dirbuf.d_fileno = (uoff_t)offset /
                                    sizeof(struct direntry);
                                dirbuf.d_type = DT_REG;
                        }

                        if (chksum != winChksum(dentp->deName)) {
                                dirbuf.d_namlen = dos2unixfn(dentp->deName,
                                    (u_char *)dirbuf.d_name,
                                    dentp->deLowerCase |
                                        ((pmp->pm_flags & MSDOSFSMNT_SHORTNAME) ?
                                        (LCASE_BASE | LCASE_EXT) : 0),
                                    pmp);
                                mbnambuf_init(&nb);
                        } else
                                mbnambuf_flush(&nb, &dirbuf);
                        chksum = -1;
                        if (vop_write_dirent(&error, uio, dirbuf.d_fileno,
                            dirbuf.d_type, dirbuf.d_namlen, dirbuf.d_name)) {
                                brelse(bp);
                                goto out;
                        }
                        if (error) {
                                brelse(bp);
                                goto out;
                        }

                        if (cookies) {
                                *cookies++ = offset + sizeof(struct direntry);
                                if (--ncookies <= 0) {
                                        brelse(bp);
                                        goto out;
                                }
                        }
                        off = offset + sizeof(struct direntry);
                }
                brelse(bp);
        }
out:
        /* Subtract unused cookies */
        if (ap->a_ncookies)
                *ap->a_ncookies -= ncookies;

        uio->uio_offset = off;

        /*
         * Set the eofflag (NFS uses it)
         */
        if (ap->a_eofflag) {
                if (dep->de_FileSize - (offset - bias) <= 0)
                        *ap->a_eofflag = 1;
                else
                        *ap->a_eofflag = 0;
        }
done:
        vn_unlock(ap->a_vp);
        return (error);
}

/*-
 * a_vp   - pointer to the file's vnode
 * a_runp - where to return the "run past" a_bn.  This is the count of logical
 *          blocks whose physical blocks (together with a_bn's physical block)
 *          are contiguous.
 * a_runb - where to return the "run before" a_bn.
 */
static int
msdosfs_bmap(struct vop_bmap_args *ap)
{
        struct fatcache savefc;
        struct denode *dep;
        struct mount *mp;
        struct msdosfsmount *pmp;
        struct vnode *vp;
        daddr_t dbn, runbn;
        u_long cn;
        int bnpercn, error, maxio, maxrun, run;

        vp = ap->a_vp;
        dep = VTODE(vp);
        pmp = dep->de_pmp;

        if (ap->a_doffsetp == NULL)
                return (0);
        if (ap->a_runp != NULL)
                *ap->a_runp = 0;
        if (ap->a_runb != NULL)
                *ap->a_runb = 0;

        KKASSERT(((int)ap->a_loffset & ((1 << pmp->pm_cnshift) - 1)) == 0);
        error = pcbmap(dep, de_cluster(pmp, ap->a_loffset), &dbn, NULL, NULL);
        if (error || dbn == (daddr_t)-1)
                *ap->a_doffsetp = NOOFFSET;
        else
                *ap->a_doffsetp = de_bn2doff(pmp, dbn);
        if (error != 0 || dbn == (daddr_t)-1 ||
            (ap->a_runp == NULL && ap->a_runb == NULL))
                return (error);

        /*
         * Prepare to back out updates of the fatchain cache after the one
         * for the first block done by pcbmap() above.  Without the backout,
         * then whenever the caller doesn't do i/o to all of the blocks that
         * we find, the single useful cache entry would be too far in advance
         * of the actual i/o to work for the next sequential i/o.  Then the
         * FAT would be searched from the beginning.  With the backout, the
         * FAT is searched starting at most a few blocks early.  This wastes
         * much less time.  Time is also wasted finding more blocks than the
         * caller will do i/o to.  This is necessary because the runlength
         * parameters are output-only.
         */
        savefc = dep->de_fc[FC_LASTMAP];

        cn = de_cluster(pmp, ap->a_loffset);
        mp = vp->v_mount;
        maxio = mp->mnt_iosize_max / mp->mnt_stat.f_iosize;
        bnpercn = de_cn2bn(pmp, 1);
        if (ap->a_runp != NULL) {
                maxrun = ulmin(maxio - 1, pmp->pm_maxcluster - cn);
                for (run = 1; run <= maxrun; run++) {
                        if (pcbmap(dep, cn + run, &runbn, NULL, NULL) != 0 ||
                            runbn != dbn + run * bnpercn)
                                break;
                }
                *ap->a_runp = run - 1;
        }
        if (ap->a_runb != NULL) {
                maxrun = ulmin(maxio - 1, cn);
                for (run = 1; run < maxrun; run++) {
                        if (pcbmap(dep, cn - run, &runbn, NULL, NULL) != 0 ||
                            runbn != dbn - run * bnpercn)
                                break;
                }
                *ap->a_runb = run - 1;
        }
        dep->de_fc[FC_LASTMAP] = savefc;

        return (0);
}

static int
msdosfs_strategy(struct vop_strategy_args *ap)
{
        struct bio *bio = ap->a_bio;
        struct bio *nbio;
        struct buf *bp = bio->bio_buf;
        struct vnode *vp = ap->a_vp;
        struct denode *dep = VTODE(vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        int error = 0;
        daddr_t dblkno;

        if (vp->v_type == VBLK || vp->v_type == VCHR)
                panic("msdosfs_strategy: spec");
        /*
         * If we don't already know the filesystem relative block number
         * then get it using pcbmap().  If pcbmap() returns the block
         * number as -1 then we've got a hole in the file.  DOS filesystems
         * don't allow files with holes, so we shouldn't ever see this.
         */
        nbio = push_bio(bio);
        if (nbio->bio_offset == NOOFFSET) {
                error = pcbmap(dep, de_cluster(pmp, bio->bio_offset),
                               &dblkno, NULL, NULL);
                if (error) {
                        bp->b_error = error;
                        bp->b_flags |= B_ERROR;
                        /* I/O was never started on nbio, must biodone(bio) */
                        biodone(bio);
                        return (error);
                }
                if (dblkno == (daddr_t)-1) {
                        nbio->bio_offset = NOOFFSET;
                        vfs_bio_clrbuf(bp);
                } else {
                        nbio->bio_offset = de_bn2doff(pmp, dblkno);
                }
        }
        if (nbio->bio_offset == NOOFFSET) {
                /* I/O was never started on nbio, must biodone(bio) */
                biodone(bio);
                return (0);
        }
        /*
         * Read/write the block from/to the disk that contains the desired
         * file block.
         */
        vn_strategy(dep->de_devvp, nbio);
        return (0);
}

static int
msdosfs_print(struct vop_print_args *ap)
{
        struct denode *dep = VTODE(ap->a_vp);

        kprintf("tag VT_MSDOSFS, startcluster %lu, dircluster %lu, "
                "diroffset %lu, dev %d, %d",
                dep->de_StartCluster, dep->de_dirclust, dep->de_diroffset,
                major(dep->de_dev), minor(dep->de_dev));
        lockmgr_printinfo(&ap->a_vp->v_lock);
        return (0);
}

static int
msdosfs_pathconf(struct vop_pathconf_args *ap)
{
        struct msdosfsmount *pmp = VTODE(ap->a_vp)->de_pmp;

        switch (ap->a_name) {
        case _PC_FILESIZEBITS:
                *ap->a_retval = FAT12(pmp) ? 32 : 33;
                return (0);
        case _PC_LINK_MAX:
                *ap->a_retval = 1;
                return (0);
        case _PC_NAME_MAX:
                *ap->a_retval =
                    pmp->pm_flags & MSDOSFSMNT_LONGNAME ? WIN_MAXLEN : 12;
                return (0);
        case _PC_CHOWN_RESTRICTED:
                *ap->a_retval = 1;
                return (0);
        case _PC_NO_TRUNC:
                *ap->a_retval = 0;
                return (0);
        default:
                return (vop_stdpathconf(ap));
        }
        /* NOTREACHED */
}

/* Global vfs data structures for msdosfs */
struct vop_ops msdosfs_vnode_vops = {
        .vop_default =          vop_defaultop,
        .vop_access =           msdosfs_access,
        .vop_bmap =             msdosfs_bmap,
        .vop_getpages =         vop_stdgetpages,
        .vop_putpages =         vop_stdputpages,
        .vop_open =             msdosfs_open,
        .vop_close =            msdosfs_close,
        .vop_old_create =       msdosfs_create,
        .vop_fsync =            msdosfs_fsync,
        .vop_getattr =          msdosfs_getattr,
        .vop_inactive =         msdosfs_inactive,
        .vop_old_link =         msdosfs_link,
        .vop_old_lookup =       msdosfs_lookup,
        .vop_old_mkdir =        msdosfs_mkdir,
        .vop_old_mknod =        msdosfs_mknod,
        .vop_pathconf =         msdosfs_pathconf,
        .vop_print =            msdosfs_print,
        .vop_read =             msdosfs_read,
        .vop_readdir =          msdosfs_readdir,
        .vop_reclaim =          msdosfs_reclaim,
        .vop_old_remove =       msdosfs_remove,
        .vop_old_rename =       msdosfs_rename,
        .vop_old_rmdir =        msdosfs_rmdir,
        .vop_setattr =          msdosfs_setattr,
        .vop_strategy =         msdosfs_strategy,
        .vop_old_symlink =      msdosfs_symlink,
        .vop_write =            msdosfs_write,
};