etc/protocols - sync with NetBSD-8

[minix.git] / sys / fs / msdosfs / msdosfs_vnops.c

/*      $NetBSD: msdosfs_vnops.c,v 1.93 2015/04/04 12:34:44 riastradh 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_vnops.c,v 1.93 2015/04/04 12:34:44 riastradh Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/namei.h>
#include <sys/resourcevar.h>    /* defines plimit structure in proc struct */
#include <sys/kernel.h>
#include <sys/file.h>           /* define FWRITE ... */
#include <sys/stat.h>
#include <sys/buf.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/fstrans.h>
#include <sys/vnode.h>
#include <sys/signalvar.h>
#include <sys/malloc.h>
#include <sys/dirent.h>
#include <sys/lockf.h>
#include <sys/kauth.h>

#include <miscfs/genfs/genfs.h>
#include <miscfs/specfs/specdev.h> /* XXX */    /* defines v_rdev */

#include <uvm/uvm_extern.h>

#include <fs/msdosfs/bpb.h>
#include <fs/msdosfs/direntry.h>
#include <fs/msdosfs/denode.h>
#include <fs/msdosfs/msdosfsmount.h>
#include <fs/msdosfs/fat.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.
 */
int
msdosfs_create(void *v)
{
        struct vop_create_v3_args /* {
                struct vnode *a_dvp;
                struct vnode **a_vpp;
                struct componentname *a_cnp;
                struct vattr *a_vap;
        } */ *ap = v;
        struct componentname *cnp = ap->a_cnp;
        struct denode ndirent;
        struct denode *dep;
        struct denode *pdep = VTODE(ap->a_dvp);
        int error;

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_create(cnp %p, vap %p\n", cnp, ap->a_vap);
#endif

        fstrans_start(ap->a_dvp->v_mount, FSTRANS_SHARED);
        /*
         * 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));
        if ((error = uniqdosname(pdep, cnp, ndirent.de_Name)) != 0)
                goto bad;

        ndirent.de_Attributes = (ap->a_vap->va_mode & S_IWUSR) ?
                                ATTR_ARCHIVE : ATTR_ARCHIVE | ATTR_READONLY;
        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;
        DETIMES(&ndirent, NULL, NULL, NULL, pdep->de_pmp->pm_gmtoff);
        if ((error = createde(&ndirent, pdep, &dep, cnp)) != 0)
                goto bad;
        fstrans_done(ap->a_dvp->v_mount);
        VN_KNOTE(ap->a_dvp, NOTE_WRITE);
        *ap->a_vpp = DETOV(dep);
        return (0);

bad:
        fstrans_done(ap->a_dvp->v_mount);
        return (error);
}

int
msdosfs_close(void *v)
{
        struct vop_close_args /* {
                struct vnode *a_vp;
                int a_fflag;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct denode *dep = VTODE(vp);

        fstrans_start(vp->v_mount, FSTRANS_SHARED);
        mutex_enter(vp->v_interlock);
        if (vp->v_usecount > 1)
                DETIMES(dep, NULL, NULL, NULL, dep->de_pmp->pm_gmtoff);
        mutex_exit(vp->v_interlock);
        fstrans_done(vp->v_mount);
        return (0);
}

static int
msdosfs_check_possible(struct vnode *vp, struct denode *dep, mode_t mode)
{

        /*
         * Disallow write attempts on read-only file systems;
         * unless the file is a socket, fifo, or a block or
         * character device resident on the file system.
         */
        if (mode & VWRITE) {
                switch (vp->v_type) {
                case VDIR:
                case VLNK:
                case VREG:
                        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                                return (EROFS);
                default:
                        break;
                }
        }

        return 0;
}

static int
msdosfs_check_permitted(struct vnode *vp, struct denode *dep, mode_t mode,
    kauth_cred_t cred)
{
        struct msdosfsmount *pmp = dep->de_pmp;
        mode_t file_mode;

        if ((dep->de_Attributes & ATTR_READONLY) == 0)
                file_mode = S_IRWXU|S_IRWXG|S_IRWXO;
        else
                file_mode = S_IRUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH;

        file_mode &= (vp->v_type == VDIR ? pmp->pm_dirmask : pmp->pm_mask);

        return kauth_authorize_vnode(cred, KAUTH_ACCESS_ACTION(mode,
            vp->v_type, file_mode), vp, NULL, genfs_can_access(vp->v_type,
            file_mode, pmp->pm_uid, pmp->pm_gid, mode, cred));
}

int
msdosfs_access(void *v)
{
        struct vop_access_args /* {
                struct vnode *a_vp;
                int a_mode;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct denode *dep = VTODE(vp);
        int error;

        error = msdosfs_check_possible(vp, dep, ap->a_mode);
        if (error)
                return error;

        error = msdosfs_check_permitted(vp, dep, ap->a_mode, ap->a_cred);

        return error;
}

int
msdosfs_getattr(void *v)
{
        struct vop_getattr_args /* {
                struct vnode *a_vp;
                struct vattr *a_vap;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct denode *dep = VTODE(ap->a_vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        struct vattr *vap = ap->a_vap;
        mode_t mode;
        u_long dirsperblk = pmp->pm_BytesPerSec / sizeof(struct direntry);
        ino_t fileid;

        fstrans_start(ap->a_vp->v_mount, FSTRANS_SHARED);
        DETIMES(dep, NULL, NULL, NULL, pmp->pm_gmtoff);
        vap->va_fsid = 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 = cntobn(pmp, (ino_t)dep->de_StartCluster) * dirsperblk;
                if (dep->de_StartCluster == MSDOSFSROOT)
                        fileid = 1;
        } else {
                fileid = cntobn(pmp, (ino_t)dep->de_dirclust) * dirsperblk;
                if (dep->de_dirclust == MSDOSFSROOT)
                        fileid = roottobn(pmp, 0) * dirsperblk;
                fileid += 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_rdev = 0;
        vap->va_size = ap->a_vp->v_size;
        dos2unixtime(dep->de_MDate, dep->de_MTime, 0, pmp->pm_gmtoff,
            &vap->va_mtime);
        if (dep->de_pmp->pm_flags & MSDOSFSMNT_LONGNAME) {
                dos2unixtime(dep->de_ADate, 0, 0, pmp->pm_gmtoff,
                    &vap->va_atime);
                dos2unixtime(dep->de_CDate, dep->de_CTime, dep->de_CHun,
                    pmp->pm_gmtoff, &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_mode  |= S_ARCH1;
        }
        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;
        fstrans_done(ap->a_vp->v_mount);
        return (0);
}

int
msdosfs_setattr(void *v)
{
        struct vop_setattr_args /* {
                struct vnode *a_vp;
                struct vattr *a_vap;
                kauth_cred_t a_cred;
        } */ *ap = v;
        int error = 0, de_changed = 0;
        struct denode *dep = VTODE(ap->a_vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        struct vnode *vp  = ap->a_vp;
        struct vattr *vap = ap->a_vap;
        kauth_cred_t cred = ap->a_cred;

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_setattr(): vp %p, vap %p, cred %p\n",
            ap->a_vp, vap, cred);
#endif
        /*
         * Note we silently ignore uid or gid changes.
         */
        if ((vap->va_type != VNON) || (vap->va_nlink != (nlink_t)VNOVAL) ||
            (vap->va_fsid != VNOVAL) || (vap->va_fileid != VNOVAL) ||
            (vap->va_blocksize != VNOVAL) || (vap->va_rdev != VNOVAL) ||
            (vap->va_bytes != VNOVAL) || (vap->va_gen != VNOVAL) ||
            (vap->va_uid != VNOVAL && vap->va_uid != pmp->pm_uid) ||
            (vap->va_gid != VNOVAL && vap->va_gid != pmp->pm_gid)) {
#ifdef MSDOSFS_DEBUG
                printf("msdosfs_setattr(): returning EINVAL\n");
                printf("    va_type %d, va_nlink %x, va_fsid %"PRIx64", va_fileid %llx\n",
                    vap->va_type, vap->va_nlink, vap->va_fsid,
                    (unsigned long long)vap->va_fileid);
                printf("    va_blocksize %lx, va_rdev %"PRIx64", va_bytes %"PRIx64", va_gen %lx\n",
                    vap->va_blocksize, vap->va_rdev, vap->va_bytes, vap->va_gen);
#endif
                return (EINVAL);
        }
        /*
         * Silently ignore attributes modifications on directories.
         */
        if (ap->a_vp->v_type == VDIR)
                return 0;

        fstrans_start(vp->v_mount, FSTRANS_SHARED);
        if (vap->va_size != VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY) {
                        error = EROFS;
                        goto bad;
                }
                error = detrunc(dep, (u_long)vap->va_size, 0, cred);
                if (error)
                        goto bad;
                de_changed = 1;
        }
        if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY) {
                        error = EROFS;
                        goto bad;
                }
                error = kauth_authorize_vnode(cred, KAUTH_VNODE_WRITE_TIMES,
                    ap->a_vp, NULL, genfs_can_chtimes(ap->a_vp, vap->va_vaflags,
                    pmp->pm_uid, cred));
                if (error)
                        goto bad;
                if ((pmp->pm_flags & MSDOSFSMNT_NOWIN95) == 0 &&
                    vap->va_atime.tv_sec != VNOVAL)
                        unix2dostime(&vap->va_atime, pmp->pm_gmtoff, &dep->de_ADate, NULL, NULL);
                if (vap->va_mtime.tv_sec != VNOVAL)
                        unix2dostime(&vap->va_mtime, pmp->pm_gmtoff, &dep->de_MDate, &dep->de_MTime, NULL);
                dep->de_Attributes |= ATTR_ARCHIVE;
                dep->de_flag |= DE_MODIFIED;
                de_changed = 1;
        }
        /*
         * 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) {
                        error = EROFS;
                        goto bad;
                }
                error = kauth_authorize_vnode(cred, KAUTH_VNODE_WRITE_FLAGS, vp,
                    NULL, genfs_can_chflags(cred, vp->v_type, pmp->pm_uid, false));
                if (error)
                        goto bad;
                /* We ignore the read and execute bits. */
                if (vap->va_mode & S_IWUSR)
                        dep->de_Attributes &= ~ATTR_READONLY;
                else
                        dep->de_Attributes |= ATTR_READONLY;
                dep->de_flag |= DE_MODIFIED;
                de_changed = 1;
        }
        /*
         * Allow the `archived' bit to be toggled.
         */
        if (vap->va_flags != VNOVAL) {
                if (vp->v_mount->mnt_flag & MNT_RDONLY) {
                        error = EROFS;
                        goto bad;
                }
                error = kauth_authorize_vnode(cred, KAUTH_VNODE_WRITE_FLAGS, vp,
                    NULL, genfs_can_chflags(cred, vp->v_type, pmp->pm_uid, false));
                if (error)
                        goto bad;
                if (vap->va_flags & SF_ARCHIVED)
                        dep->de_Attributes &= ~ATTR_ARCHIVE;
                else
                        dep->de_Attributes |= ATTR_ARCHIVE;
                dep->de_flag |= DE_MODIFIED;
                de_changed = 1;
        }

        if (de_changed) {
                VN_KNOTE(vp, NOTE_ATTRIB);
                error = deupdat(dep, 1);
                if (error)
                        goto bad;
        }

bad:
        fstrans_done(vp->v_mount);
        return error;
}

int
msdosfs_read(void *v)
{
        struct vop_read_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int a_ioflag;
                kauth_cred_t a_cred;
        } */ *ap = v;
        int error = 0;
        int64_t diff;
        int blsize;
        long n;
        long on;
        daddr_t lbn;
        vsize_t bytelen;
        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 they didn't ask for any data, then we are done.
         */

        if (uio->uio_resid == 0)
                return (0);
        if (uio->uio_offset < 0)
                return (EINVAL);
        if (uio->uio_offset >= dep->de_FileSize)
                return (0);

        fstrans_start(vp->v_mount, FSTRANS_SHARED);
        if (vp->v_type == VREG) {
                const int advice = IO_ADV_DECODE(ap->a_ioflag);

                while (uio->uio_resid > 0) {
                        bytelen = MIN(dep->de_FileSize - uio->uio_offset,
                                      uio->uio_resid);

                        if (bytelen == 0)
                                break;
                        error = ubc_uiomove(&vp->v_uobj, uio, bytelen, advice,
                            UBC_READ | UBC_PARTIALOK | UBC_UNMAP_FLAG(vp));
                        if (error)
                                break;
                }
                dep->de_flag |= DE_ACCESS;
                goto out;
        }

        /* this loop is only for directories now */
        do {
                lbn = de_cluster(pmp, uio->uio_offset);
                on = uio->uio_offset & pmp->pm_crbomask;
                n = MIN(pmp->pm_bpcluster - on, uio->uio_resid);
                if (uio->uio_offset >= dep->de_FileSize) {
                        fstrans_done(vp->v_mount);
                        return (0);
                }
                /* file size (and hence diff) may be up to 4GB */
                diff = dep->de_FileSize - uio->uio_offset;
                if (diff < n)
                        n = (long) diff;

                /* convert cluster # to sector # */
                error = pcbmap(dep, lbn, &lbn, 0, &blsize);
                if (error)
                        goto bad;

                /*
                 * 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.
                 */
                error = bread(pmp->pm_devvp, de_bn2kb(pmp, lbn), blsize,
                    0, &bp);
                if (error) {
                        goto bad;
                }
                n = MIN(n, pmp->pm_bpcluster - bp->b_resid);
                error = uiomove((char *)bp->b_data + on, (int) n, uio);
                brelse(bp, 0);
        } while (error == 0 && uio->uio_resid > 0 && n != 0);

out:
        if ((ap->a_ioflag & IO_SYNC) == IO_SYNC) {
                int uerror;

                uerror = deupdat(dep, 1);
                if (error == 0)
                        error = uerror;
        }
bad:
        fstrans_done(vp->v_mount);
        return (error);
}

/*
 * Write data to a file or directory.
 */
int
msdosfs_write(void *v)
{
        struct vop_write_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int a_ioflag;
                kauth_cred_t a_cred;
        } */ *ap = v;
        int resid, extended = 0;
        int error = 0;
        int ioflag = ap->a_ioflag;
        u_long osize;
        u_long count;
        vsize_t bytelen;
        off_t oldoff;
        size_t rem;
        struct uio *uio = ap->a_uio;
        struct vnode *vp = ap->a_vp;
        struct denode *dep = VTODE(vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        kauth_cred_t cred = ap->a_cred;
        bool async;

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_write(vp %p, uio %p, ioflag %x, cred %p\n",
            vp, uio, ioflag, cred);
        printf("msdosfs_write(): diroff %lu, dirclust %lu, startcluster %lu\n",
            dep->de_diroffset, dep->de_dirclust, dep->de_StartCluster);
#endif

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

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

        if (uio->uio_resid == 0)
                return (0);

        /* Don't bother to try to write files larger than the fs limit */
        if (uio->uio_offset + uio->uio_resid > MSDOSFS_FILESIZE_MAX)
                return (EFBIG);

        fstrans_start(vp->v_mount, FSTRANS_SHARED);
        /*
         * 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) {
                if ((error = deextend(dep, uio->uio_offset, cred)) != 0) {
                        fstrans_done(vp->v_mount);
                        return (error);
                }
        }

        /*
         * Remember some values in case the write fails.
         */
        async = vp->v_mount->mnt_flag & MNT_ASYNC;
        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);
                if ((error = extendfile(dep, count, NULL, NULL, 0)))
                        goto errexit;

                dep->de_FileSize = uio->uio_offset + resid;
                /* hint uvm to not read in extended part */
                uvm_vnp_setwritesize(vp, dep->de_FileSize);
                /* zero out the remainder of the last page */
                rem = round_page(dep->de_FileSize) - dep->de_FileSize;
                if (rem > 0)
                        ubc_zerorange(&vp->v_uobj, (off_t)dep->de_FileSize,
                            rem, UBC_UNMAP_FLAG(vp));
                extended = 1;
        }

        do {
                oldoff = uio->uio_offset;
                bytelen = uio->uio_resid;

                error = ubc_uiomove(&vp->v_uobj, uio, bytelen,
                    IO_ADV_DECODE(ioflag), UBC_WRITE | UBC_UNMAP_FLAG(vp));
                if (error)
                        break;

                /*
                 * flush what we just wrote if necessary.
                 * XXXUBC simplistic async flushing.
                 */

                if (!async && oldoff >> 16 != uio->uio_offset >> 16) {
                        mutex_enter(vp->v_interlock);
                        error = VOP_PUTPAGES(vp, (oldoff >> 16) << 16,
                            (uio->uio_offset >> 16) << 16,
                            PGO_CLEANIT | PGO_LAZY);
                }
        } while (error == 0 && uio->uio_resid > 0);

        /* set final size */
        uvm_vnp_setsize(vp, dep->de_FileSize);
        if (error == 0 && ioflag & IO_SYNC) {
                mutex_enter(vp->v_interlock);
                error = VOP_PUTPAGES(vp, trunc_page(oldoff),
                    round_page(oldoff + bytelen), PGO_CLEANIT | PGO_SYNCIO);
        }
        dep->de_flag |= DE_UPDATE;

        /*
         * 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 (resid > uio->uio_resid)
                VN_KNOTE(vp, NOTE_WRITE | (extended ? NOTE_EXTEND : 0));
        if (error) {
                detrunc(dep, osize, ioflag & IO_SYNC, NOCRED);
                uio->uio_offset -= resid - uio->uio_resid;
                uio->uio_resid = resid;
        } else if ((ioflag & IO_SYNC) == IO_SYNC)
                error = deupdat(dep, 1);
        fstrans_done(vp->v_mount);
        KASSERT(vp->v_size == dep->de_FileSize);
        return (error);
}

int
msdosfs_update(struct vnode *vp, const struct timespec *acc,
    const struct timespec *mod, int flags)
{
        struct buf *bp;
        struct direntry *dirp;
        struct denode *dep;
        int error;

        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                return (0);
        dep = VTODE(vp);
        DETIMES(dep, acc, mod, NULL, dep->de_pmp->pm_gmtoff);
        if ((dep->de_flag & DE_MODIFIED) == 0)
                return (0);
        dep->de_flag &= ~DE_MODIFIED;
        if (dep->de_Attributes & ATTR_DIRECTORY)
                return (0);
        if (dep->de_refcnt <= 0)
                return (0);
        error = readde(dep, &bp, &dirp);
        if (error)
                return (error);
        DE_EXTERNALIZE(dirp, dep);
        if (flags & (UPDATE_WAIT|UPDATE_DIROP))
                return (bwrite(bp));
        else {
                bdwrite(bp);
                return (0);
        }
}

/*
 * Flush the blocks of a file to disk.
 *
 * This function is worthless for vnodes that represent directories. Maybe we
 * could just do a sync if they try an fsync on a directory file.
 */
int
msdosfs_remove(void *v)
{
        struct vop_remove_args /* {
                struct vnode *a_dvp;
                struct vnode *a_vp;
                struct componentname *a_cnp;
        } */ *ap = v;
        struct denode *dep = VTODE(ap->a_vp);
        struct denode *ddep = VTODE(ap->a_dvp);
        int error;

        fstrans_start(ap->a_dvp->v_mount, FSTRANS_SHARED);
        if (ap->a_vp->v_type == VDIR)
                error = EPERM;
        else
                error = removede(ddep, dep);
#ifdef MSDOSFS_DEBUG
        printf("msdosfs_remove(), dep %p, v_usecount %d\n",
                dep, ap->a_vp->v_usecount);
#endif
        VN_KNOTE(ap->a_vp, NOTE_DELETE);
        VN_KNOTE(ap->a_dvp, NOTE_WRITE);
        if (ddep == dep)
                vrele(ap->a_vp);
        else
                vput(ap->a_vp); /* causes msdosfs_inactive() to be called
                                 * via vrele() */
        vput(ap->a_dvp);
        fstrans_done(ap->a_dvp->v_mount);
        return (error);
}

/*
 * 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
 *              update offset and dirclust in denode
 *              move denode to new hash chain
 *              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
 *
 * Notes:
 * I'm not sure how the memory containing the pathnames pointed at by the
 * componentname structures is freed, there may be some memory bleeding
 * for each rename done.
 *
 * --More-- Notes:
 * This routine needs help.  badly.
 */
int
msdosfs_rename(void *v)
{
        struct vop_rename_args /* {
                struct vnode *a_fdvp;
                struct vnode *a_fvp;
                struct componentname *a_fcnp;
                struct vnode *a_tdvp;
                struct vnode *a_tvp;
                struct componentname *a_tcnp;
        } */ *ap = v;
        struct vnode *tvp = ap->a_tvp;
        struct vnode *tdvp = ap->a_tdvp;
        struct vnode *fvp = ap->a_fvp;
        struct vnode *fdvp = ap->a_fdvp;
        struct mount *mp = fdvp->v_mount;
        struct componentname *tcnp = ap->a_tcnp;
        struct componentname *fcnp = ap->a_fcnp;
        struct denode *ip, *xp, *dp, *zp;
        u_char toname[12], oldname[12];
        u_long from_diroffset, to_diroffset;
        u_char to_count;
        int doingdirectory = 0, newparent = 0;
        int error;
        u_long cn;
        daddr_t bn;
        struct msdosfsmount *pmp;
        struct direntry *dotdotp;
        struct buf *bp;

        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:
                VOP_ABORTOP(tdvp, tcnp);
                if (tdvp == tvp)
                        vrele(tdvp);
                else
                        vput(tdvp);
                if (tvp)
                        vput(tvp);
                VOP_ABORTOP(fdvp, fcnp);
                vrele(fdvp);
                vrele(fvp);
                return (error);
        }

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

        /*
         * XXX: This can deadlock since we hold tdvp/tvp locked.
         * But I'm not going to fix it now.
         */
        if ((error = vn_lock(fvp, LK_EXCLUSIVE)) != 0)
                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 & ISDOTDOT) ||
                    (tcnp->cn_flags & ISDOTDOT) ||
                    (ip->de_flag & DE_RENAME)) {
                        VOP_UNLOCK(fvp);
                        error = EINVAL;
                        goto abortit;
                }
                ip->de_flag |= DE_RENAME;
                doingdirectory++;
        }
        VN_KNOTE(fdvp, NOTE_WRITE);             /* XXXLUKEM/XXX: right place? */

        fstrans_start(mp, FSTRANS_SHARED);
        /*
         * When the target exists, both the directory
         * and target vnodes are returned locked.
         */
        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_ACCESS(fvp, VWRITE, tcnp->cn_cred);
        VOP_UNLOCK(fvp);
        if (VTODE(fdvp)->de_StartCluster != VTODE(tdvp)->de_StartCluster)
                newparent = 1;

        if (doingdirectory && newparent) {
                if (error)      /* write access check above */
                        goto tdvpbad;
                if (xp != NULL)
                        vput(tvp);
                tvp = NULL;
                /*
                 * doscheckpath() vput()'s tdvp (dp == VTODE(tdvp)),
                 * so we have to get an extra ref to it first, and
                 * because it's been unlocked we need to do a relookup
                 * afterwards in case tvp has changed.
                 */
                vref(tdvp);
                if ((error = doscheckpath(ip, dp)) != 0)
                        goto bad;
                vn_lock(tdvp, LK_EXCLUSIVE | LK_RETRY);
                if ((error = relookup(tdvp, &tvp, tcnp, 0)) != 0) {
                        VOP_UNLOCK(tdvp);
                        goto bad;
                }
                dp = VTODE(tdvp);
                xp = tvp ? VTODE(tvp) : NULL;
        }

        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 tdvpbad;
                        }
                        if (!doingdirectory) {
                                error = ENOTDIR;
                                goto tdvpbad;
                        }
                } else if (doingdirectory) {
                        error = EISDIR;
                        goto tdvpbad;
                }
                if ((error = removede(dp, xp)) != 0)
                        goto tdvpbad;
                VN_KNOTE(tdvp, NOTE_WRITE);
                VN_KNOTE(tvp, NOTE_DELETE);
                cache_purge(tvp);
                vput(tvp);
                tvp = NULL;
                xp = NULL;
        }

        /*
         * Convert the filename in tcnp into a dos filename. We copy this
         * into the denode and directory entry for the destination
         * file/directory.
         */
        if ((error = uniqdosname(VTODE(tdvp), tcnp, toname)) != 0) {
                fstrans_done(mp);
                goto abortit;
        }

        /*
         * Since from wasn't locked at various places above,
         * have to do a relookup here.
         */
        fcnp->cn_flags &= ~MODMASK;
        fcnp->cn_flags |= LOCKPARENT | LOCKLEAF;
        VOP_UNLOCK(tdvp);
        vn_lock(fdvp, LK_EXCLUSIVE | LK_RETRY);
        if ((error = relookup(fdvp, &fvp, fcnp, 0))) {
                VOP_UNLOCK(fdvp);
                vrele(ap->a_fvp);
                vrele(tdvp);
                fstrans_done(mp);
                return (error);
        }
        if (fvp == NULL) {
                /*
                 * From name has disappeared.
                 */
                if (doingdirectory)
                        panic("rename: lost dir entry");
                vput(fdvp);
                vrele(ap->a_fvp);
                vrele(tdvp);
                fstrans_done(mp);
                return 0;
        }
        VOP_UNLOCK(fdvp);
        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.
         */
        if (xp != ip) {
                if (doingdirectory)
                        panic("rename: lost dir entry");
                vrele(ap->a_fvp);
                xp = NULL;
        } else {
                vrele(fvp);
                xp = NULL;

                /*
                 * 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, (struct denode **)0, tcnp);
                if (error) {
                        memcpy(ip->de_Name, oldname, 11);
                        VOP_UNLOCK(fvp);
                        goto bad;
                }
                ip->de_refcnt++;
                zp->de_fndoffset = from_diroffset;
                if ((error = removede(zp, ip)) != 0) {
                        /* XXX should really panic here, fs is corrupt */
                        VOP_UNLOCK(fvp);
                        goto bad;
                }
                cache_purge(fvp);
                if (!doingdirectory) {
                        struct denode_key old_key = ip->de_key;
                        struct denode_key new_key = ip->de_key;

                        error = pcbmap(dp, de_cluster(pmp, to_diroffset), 0,
                                       &new_key.dk_dirclust, 0);
                        if (error) {
                                /* XXX should really panic here, fs is corrupt */
                                VOP_UNLOCK(fvp);
                                goto bad;
                        }
                        new_key.dk_diroffset = to_diroffset;
                        if (new_key.dk_dirclust != MSDOSFSROOT)
                                new_key.dk_diroffset &= pmp->pm_crbomask;
                        vcache_rekey_enter(pmp->pm_mountp, fvp, &old_key,
                            sizeof(old_key), &new_key, sizeof(new_key));
                        ip->de_key = new_key;
                        vcache_rekey_exit(pmp->pm_mountp, fvp, &old_key,
                            sizeof(old_key), &ip->de_key, sizeof(ip->de_key));
                }
        }

        /*
         * 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_bn2kb(pmp, bn),
                    pmp->pm_bpcluster, B_MODIFY, &bp);
                if (error) {
                        /* XXX should really panic here, fs is corrupt */
                        VOP_UNLOCK(fvp);
                        goto bad;
                }
                dotdotp = (struct direntry *)bp->b_data + 1;
                putushort(dotdotp->deStartCluster, dp->de_StartCluster);
                if (FAT32(pmp)) {
                        putushort(dotdotp->deHighClust,
                                dp->de_StartCluster >> 16);
                } else {
                        putushort(dotdotp->deHighClust, 0);
                }
                if ((error = bwrite(bp)) != 0) {
                        /* XXX should really panic here, fs is corrupt */
                        VOP_UNLOCK(fvp);
                        goto bad;
                }
        }

        VN_KNOTE(fvp, NOTE_RENAME);
        VOP_UNLOCK(fvp);
bad:
        if (tvp)
                vput(tvp);
        vrele(tdvp);
        ip->de_flag &= ~DE_RENAME;
        vrele(fdvp);
        vrele(fvp);
        fstrans_done(mp);
        return (error);

        /* XXX: uuuh */
tdvpbad:
        VOP_UNLOCK(tdvp);
        goto bad;
}

static const 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 */
        }
};

int
msdosfs_mkdir(void *v)
{
        struct vop_mkdir_v3_args /* {
                struct vnode *a_dvp;
                struvt vnode **a_vpp;
                struvt componentname *a_cnp;
                struct vattr *a_vap;
        } */ *ap = v;
        struct componentname *cnp = ap->a_cnp;
        struct denode ndirent;
        struct denode *dep;
        struct denode *pdep = VTODE(ap->a_dvp);
        int error;
        int bn;
        u_long newcluster, pcl;
        daddr_t lbn;
        struct direntry *denp;
        struct msdosfsmount *pmp = pdep->de_pmp;
        struct buf *bp;
        int async = pdep->de_pmp->pm_mountp->mnt_flag & MNT_ASYNC;

        fstrans_start(ap->a_dvp->v_mount, FSTRANS_SHARED);
        /*
         * 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, &newcluster, NULL);
        if (error)
                goto bad2;

        memset(&ndirent, 0, sizeof(ndirent));
        ndirent.de_pmp = pmp;
        ndirent.de_flag = DE_ACCESS | DE_CREATE | DE_UPDATE;
        DETIMES(&ndirent, NULL, NULL, NULL, pmp->pm_gmtoff);

        /*
         * 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);
        lbn = de_bn2kb(pmp, bn);
        /* always succeeds */
        bp = getblk(pmp->pm_devvp, lbn, 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;
        if (FAT32(pmp) && pcl == pmp->pm_rootdirblk)
                pcl = 0;
        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, pdep->de_StartCluster >> 16);
        } else {
                putushort(denp[0].deHighClust, 0);
                putushort(denp[1].deHighClust, 0);
        }

        if (async)
                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.
         */
        if ((error = uniqdosname(pdep, cnp, ndirent.de_Name)) != 0)
                goto bad;

        ndirent.de_Attributes = ATTR_DIRECTORY;
        ndirent.de_StartCluster = newcluster;
        ndirent.de_FileSize = 0;
        ndirent.de_dev = pdep->de_dev;
        ndirent.de_devvp = pdep->de_devvp;
        if ((error = createde(&ndirent, pdep, &dep, cnp)) != 0)
                goto bad;
        VN_KNOTE(ap->a_dvp, NOTE_WRITE | NOTE_LINK);
        *ap->a_vpp = DETOV(dep);
        fstrans_done(ap->a_dvp->v_mount);
        return (0);

bad:
        clusterfree(pmp, newcluster, NULL);
bad2:
        fstrans_done(ap->a_dvp->v_mount);
        return (error);
}

int
msdosfs_rmdir(void *v)
{
        struct vop_rmdir_args /* {
                struct vnode *a_dvp;
                struct vnode *a_vp;
                struct componentname *a_cnp;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct vnode *dvp = ap->a_dvp;
        struct mount *mp = dvp->v_mount;
        struct componentname *cnp = ap->a_cnp;
        struct denode *ip, *dp;
        int error;

        ip = VTODE(vp);
        dp = VTODE(dvp);
        /*
         * No rmdir "." please.
         */
        if (dp == ip) {
                vrele(dvp);
                vput(vp);
                return (EINVAL);
        }
        fstrans_start(mp, FSTRANS_SHARED);
        /*
         * 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.
         */
        if ((error = removede(dp, ip)) != 0)
                goto out;
        /*
         * This is where we decrement the link count in the parent
         * directory.  Since dos filesystems don't do this we just purge
         * the name cache and let go of the parent directory denode.
         */
        VN_KNOTE(dvp, NOTE_WRITE | NOTE_LINK);
        cache_purge(dvp);
        vput(dvp);
        dvp = NULL;
        /*
         * Truncate the directory that is being deleted.
         */
        error = detrunc(ip, (u_long)0, IO_SYNC, cnp->cn_cred);
        cache_purge(vp);
out:
        VN_KNOTE(vp, NOTE_DELETE);
        if (dvp)
                vput(dvp);
        vput(vp);
        fstrans_done(mp);
        return (error);
}

int
msdosfs_readdir(void *v)
{
        struct vop_readdir_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                kauth_cred_t a_cred;
                int *a_eofflag;
                off_t **a_cookies;
                int *a_ncookies;
        } */ *ap = v;
        int error = 0;
        int diff;
        long n;
        int blsize;
        long on;
        long lost;
        long count;
        u_long cn;
        ino_t fileno;
        u_long dirsperblk;
        long bias = 0;
        daddr_t bn, lbn;
        struct buf *bp;
        struct denode *dep = VTODE(ap->a_vp);
        struct msdosfsmount *pmp = dep->de_pmp;
        struct direntry *dentp;
        struct dirent *dirbuf;
        struct uio *uio = ap->a_uio;
        off_t *cookies = NULL;
        int ncookies = 0, nc = 0;
        off_t offset, uio_off;
        int chksum = -1;

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_readdir(): vp %p, uio %p, cred %p, eofflagp %p\n",
            ap->a_vp, uio, ap->a_cred, ap->a_eofflag);
#endif

        /*
         * 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)
                return (ENOTDIR);

        /*
         * 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.
         */
        count = uio->uio_resid & ~(sizeof(struct direntry) - 1);
        offset = uio->uio_offset;
        if (count < sizeof(struct direntry) ||
            (offset & (sizeof(struct direntry) - 1)))
                return (EINVAL);
        lost = uio->uio_resid - count;
        uio->uio_resid = count;
        uio_off = uio->uio_offset;
        
        fstrans_start(ap->a_vp->v_mount, FSTRANS_SHARED);

        /* Allocate a temporary dirent buffer. */
        dirbuf = malloc(sizeof(struct dirent), M_MSDOSFSTMP, M_WAITOK | M_ZERO);

        if (ap->a_ncookies) {
                nc = uio->uio_resid / _DIRENT_MINSIZE((struct dirent *)0);
                cookies = malloc(nc * sizeof (off_t), M_TEMP, M_WAITOK);
                *ap->a_cookies = cookies;
        }

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

        /*
         * 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 %" PRIu64 "\n", offset);
#endif
                bias = 2 * sizeof(struct direntry);
                if (offset < bias) {
                        for (n = (int)offset / sizeof(struct direntry);
                             n < 2; n++) {
                                if (FAT32(pmp))
                                        dirbuf->d_fileno = cntobn(pmp,
                                             (ino_t)pmp->pm_rootdirblk)
                                             * dirsperblk;
                                else
                                        dirbuf->d_fileno = 1;
                                dirbuf->d_type = DT_DIR;
                                switch (n) {
                                case 0:
                                        dirbuf->d_namlen = 1;
                                        strlcpy(dirbuf->d_name, ".",
                                            sizeof(dirbuf->d_name));
                                        break;
                                case 1:
                                        dirbuf->d_namlen = 2;
                                        strlcpy(dirbuf->d_name, "..",
                                            sizeof(dirbuf->d_name));
                                        break;
                                }
                                dirbuf->d_reclen = _DIRENT_SIZE(dirbuf);
                                if (uio->uio_resid < dirbuf->d_reclen)
                                        goto out;
                                error = uiomove(dirbuf, dirbuf->d_reclen, uio);
                                if (error)
                                        goto out;
                                offset += sizeof(struct direntry);
                                uio_off = offset;
                                if (cookies) {
                                        *cookies++ = offset;
                                        ncookies++;
                                        if (ncookies >= nc)
                                                goto out;
                                }
                        }
                }
        }

        while (uio->uio_resid > 0) {
                lbn = de_cluster(pmp, offset - bias);
                on = (offset - bias) & pmp->pm_crbomask;
                n = MIN(pmp->pm_bpcluster - on, uio->uio_resid);
                diff = dep->de_FileSize - (offset - bias);
                if (diff <= 0)
                        break;
                n = MIN(n, diff);
                if ((error = pcbmap(dep, lbn, &bn, &cn, &blsize)) != 0)
                        break;
                error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
                    0, &bp);
                if (error) {
                        goto bad;
                }
                n = MIN(n, blsize - bp->b_resid);

                /*
                 * Convert from dos directory entries to fs-independent
                 * directory entries.
                 */
                for (dentp = (struct direntry *)((char *)bp->b_data + on);
                     (char *)dentp < (char *)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, 0);
                                goto out;
                        }
                        /*
                         * Skip deleted entries.
                         */
                        if (dentp->deName[0] == SLOT_DELETED) {
                                chksum = -1;
                                continue;
                        }

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

                        /*
                         * Skip volume labels
                         */
                        if (dentp->deAttributes & ATTR_VOLUME) {
                                chksum = -1;
                                continue;
                        }
                        /*
                         * This computation of d_fileno must match
                         * the computation of va_fileid in
                         * msdosfs_getattr.
                         */
                        if (dentp->deAttributes & ATTR_DIRECTORY) {
                                fileno = getushort(dentp->deStartCluster);
                                if (FAT32(pmp))
                                        fileno |= ((ino_t)getushort(dentp->deHighClust)) << 16;
                                /* if this is the root directory */
                                if (fileno == MSDOSFSROOT)
                                        if (FAT32(pmp))
                                                fileno = cntobn(pmp,
                                                    (ino_t)pmp->pm_rootdirblk)
                                                    * dirsperblk;
                                        else
                                                fileno = 1;
                                else
                                        fileno = cntobn(pmp, fileno) * dirsperblk;
                                dirbuf->d_fileno = fileno;
                                dirbuf->d_type = DT_DIR;
                        } else {
                                dirbuf->d_fileno =
                                    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,
                                    pmp->pm_flags & MSDOSFSMNT_SHORTNAME);
                        else
                                dirbuf->d_name[dirbuf->d_namlen] = 0;
                        chksum = -1;
                        dirbuf->d_reclen = _DIRENT_SIZE(dirbuf);
                        if (uio->uio_resid < dirbuf->d_reclen) {
                                brelse(bp, 0);
                                goto out;
                        }
                        error = uiomove(dirbuf, dirbuf->d_reclen, uio);
                        if (error) {
                                brelse(bp, 0);
                                goto out;
                        }
                        uio_off = offset + sizeof(struct direntry);
                        if (cookies) {
                                *cookies++ = offset + sizeof(struct direntry);
                                ncookies++;
                                if (ncookies >= nc) {
                                        brelse(bp, 0);
                                        goto out;
                                }
                        }
                }
                brelse(bp, 0);
        }

out:
        uio->uio_offset = uio_off;
        uio->uio_resid += lost;
        if (dep->de_FileSize - (offset - bias) <= 0)
                *ap->a_eofflag = 1;
        else
                *ap->a_eofflag = 0;

        if (ap->a_ncookies) {
                if (error) {
                        free(*ap->a_cookies, M_TEMP);
                        *ap->a_ncookies = 0;
                        *ap->a_cookies = NULL;
                } else
                        *ap->a_ncookies = ncookies;
        }

bad:
        free(dirbuf, M_MSDOSFSTMP);
        fstrans_done(ap->a_vp->v_mount);
        return (error);
}

/*
 * vp  - address of vnode file the file
 * bn  - which cluster we are interested in mapping to a filesystem block number.
 * vpp - returns the vnode for the block special file holding the filesystem
 *       containing the file of interest
 * bnp - address of where to return the filesystem relative block number
 */
int
msdosfs_bmap(void *v)
{
        struct vop_bmap_args /* {
                struct vnode *a_vp;
                daddr_t a_bn;
                struct vnode **a_vpp;
                daddr_t *a_bnp;
                int *a_runp;
        } */ *ap = v;
        struct denode *dep = VTODE(ap->a_vp);
        int run, maxrun;
        daddr_t runbn;
        int status;

        if (ap->a_vpp != NULL)
                *ap->a_vpp = dep->de_devvp;
        if (ap->a_bnp == NULL)
                return (0);
        status = pcbmap(dep, ap->a_bn, ap->a_bnp, 0, 0);

        /*
         * From FreeBSD:
         * A little kludgy, but we loop calling pcbmap until we
         * reach the end of the contiguous piece, or reach MAXPHYS.
         * Since it reduces disk I/Os, the "wasted" CPU is put to
         * good use (4 to 5 fold sequential read I/O improvement on USB
         * drives).
         */
        if (ap->a_runp != NULL) {
                /* taken from ufs_bmap */
                maxrun = ulmin(MAXPHYS / dep->de_pmp->pm_bpcluster - 1,
                               dep->de_pmp->pm_maxcluster - ap->a_bn);
                for (run = 1; run <= maxrun; run++) {
                        if (pcbmap(dep, ap->a_bn + run, &runbn, NULL, NULL)
                            != 0 || runbn !=
                                    *ap->a_bnp + de_cn2bn(dep->de_pmp, run))
                                break;
                }
                *ap->a_runp = run - 1;
        }

        /*
         * We need to scale *ap->a_bnp by sector_size/DEV_BSIZE
         */
        *ap->a_bnp = de_bn2kb(dep->de_pmp, *ap->a_bnp);
        return status;
}

int
msdosfs_strategy(void *v)
{
        struct vop_strategy_args /* {
                struct vnode *a_vp;
                struct buf *a_bp;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct buf *bp = ap->a_bp;
        struct denode *dep = VTODE(bp->b_vp);
        int error = 0;

        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.
         */
        if (bp->b_blkno == bp->b_lblkno) {
                error = pcbmap(dep, de_bn2cn(dep->de_pmp, bp->b_lblkno),
                               &bp->b_blkno, 0, 0);
                if (error)
                        bp->b_blkno = -1;
                if (bp->b_blkno == -1)
                        clrbuf(bp);
                else
                        bp->b_blkno = de_bn2kb(dep->de_pmp, bp->b_blkno);
        }
        if (bp->b_blkno == -1) {
                biodone(bp);
                return (error);
        }

        /*
         * Read/write the block from/to the disk that contains the desired
         * file block.
         */

        vp = dep->de_devvp;
        return (VOP_STRATEGY(vp, bp));
}

int
msdosfs_print(void *v)
{
        struct vop_print_args /* {
                struct vnode *vp;
        } */ *ap = v;
        struct denode *dep = VTODE(ap->a_vp);

        printf(
            "tag VT_MSDOSFS, startcluster %ld, dircluster %ld, diroffset %ld ",
            dep->de_StartCluster, dep->de_dirclust, dep->de_diroffset);
        printf(" dev %llu, %llu ", (unsigned long long)major(dep->de_dev),
            (unsigned long long)minor(dep->de_dev));
        printf("\n");
        return (0);
}

int
msdosfs_advlock(void *v)
{
        struct vop_advlock_args /* {
                struct vnode *a_vp;
                void *a_id;
                int a_op;
                struct flock *a_fl;
                int a_flags;
        } */ *ap = v;
        struct denode *dep = VTODE(ap->a_vp);

        return lf_advlock(ap, &dep->de_lockf, dep->de_FileSize);
}

int
msdosfs_pathconf(void *v)
{
        struct vop_pathconf_args /* {
                struct vnode *a_vp;
                int a_name;
                register_t *a_retval;
        } */ *ap = v;

        switch (ap->a_name) {
        case _PC_LINK_MAX:
                *ap->a_retval = 1;
                return (0);
        case _PC_NAME_MAX:
                *ap->a_retval = ap->a_vp->v_mount->mnt_stat.f_namemax;
                return (0);
        case _PC_PATH_MAX:
                *ap->a_retval = PATH_MAX;
                return (0);
        case _PC_CHOWN_RESTRICTED:
                *ap->a_retval = 1;
                return (0);
        case _PC_NO_TRUNC:
                *ap->a_retval = 1;
                return (0);
        case _PC_SYNC_IO:
                *ap->a_retval = 1;
                return (0);
        case _PC_FILESIZEBITS:
                *ap->a_retval = 32;
                return (0);
        default:
                return (EINVAL);
        }
        /* NOTREACHED */
}

int
msdosfs_fsync(void *v)
{
        struct vop_fsync_args /* {
                struct vnode *a_vp;
                kauth_cred_t a_cred;
                int a_flags;
                off_t offlo;
                off_t offhi;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        int wait;
        int error;

        fstrans_start(vp->v_mount, FSTRANS_LAZY);
        wait = (ap->a_flags & FSYNC_WAIT) != 0;
        error = vflushbuf(vp, ap->a_flags);
        if (error == 0 && (ap->a_flags & FSYNC_DATAONLY) == 0)
                error = msdosfs_update(vp, NULL, NULL, wait ? UPDATE_WAIT : 0);

        if (error == 0 && ap->a_flags & FSYNC_CACHE) {
                struct denode *dep = VTODE(vp);
                struct vnode *devvp = dep->de_devvp;

                int l = 0;
                error = VOP_IOCTL(devvp, DIOCCACHESYNC, &l, FWRITE,
                                          curlwp->l_cred);
        }
        fstrans_done(vp->v_mount);

        return (error);
}

void
msdosfs_detimes(struct denode *dep, const struct timespec *acc,
    const struct timespec *mod, const struct timespec *cre, int gmtoff)
{
        struct timespec *ts = NULL, tsb;

        KASSERT(dep->de_flag & (DE_UPDATE | DE_CREATE | DE_ACCESS));
        /* XXX just call getnanotime early and use result if needed? */
        dep->de_flag |= DE_MODIFIED;
        if (dep->de_flag & DE_UPDATE) {
                if (mod == NULL) {
                        getnanotime(&tsb);
                        mod = ts = &tsb;
                }
                unix2dostime(mod, gmtoff, &dep->de_MDate, &dep->de_MTime, NULL);
                dep->de_Attributes |= ATTR_ARCHIVE;
        }
        if ((dep->de_pmp->pm_flags & MSDOSFSMNT_NOWIN95) == 0) {
                if (dep->de_flag & DE_ACCESS)  {
                        if (acc == NULL)
                                acc = ts == NULL ?
                                    (getnanotime(&tsb), ts = &tsb) : ts;
                        unix2dostime(acc, gmtoff, &dep->de_ADate, NULL, NULL);
                }
                if (dep->de_flag & DE_CREATE) {
                        if (cre == NULL)
                                cre = ts == NULL ?
                                    (getnanotime(&tsb), ts = &tsb) : ts;
                        unix2dostime(cre, gmtoff, &dep->de_CDate,
                            &dep->de_CTime, &dep->de_CHun);
                }
        }

        dep->de_flag &= ~(DE_UPDATE | DE_CREATE | DE_ACCESS);
}

/* Global vfs data structures for msdosfs */
int (**msdosfs_vnodeop_p)(void *);
const struct vnodeopv_entry_desc msdosfs_vnodeop_entries[] = {
        { &vop_default_desc, vn_default_error },
        { &vop_lookup_desc, msdosfs_lookup },           /* lookup */
        { &vop_create_desc, msdosfs_create },           /* create */
        { &vop_mknod_desc, genfs_eopnotsupp },          /* mknod */
        { &vop_open_desc, genfs_nullop },               /* open */
        { &vop_close_desc, msdosfs_close },             /* close */
        { &vop_access_desc, msdosfs_access },           /* access */
        { &vop_getattr_desc, msdosfs_getattr },         /* getattr */
        { &vop_setattr_desc, msdosfs_setattr },         /* setattr */
        { &vop_read_desc, msdosfs_read },               /* read */
        { &vop_write_desc, msdosfs_write },             /* write */
        { &vop_fallocate_desc, genfs_eopnotsupp },      /* fallocate */
        { &vop_fdiscard_desc, genfs_eopnotsupp },       /* fdiscard */
        { &vop_fcntl_desc, genfs_fcntl },               /* fcntl */
        { &vop_ioctl_desc, msdosfs_ioctl },             /* ioctl */
        { &vop_poll_desc, msdosfs_poll },               /* poll */
        { &vop_kqfilter_desc, genfs_kqfilter },         /* kqfilter */
        { &vop_revoke_desc, msdosfs_revoke },           /* revoke */
        { &vop_mmap_desc, msdosfs_mmap },               /* mmap */
        { &vop_fsync_desc, msdosfs_fsync },             /* fsync */
        { &vop_seek_desc, msdosfs_seek },               /* seek */
        { &vop_remove_desc, msdosfs_remove },           /* remove */
        { &vop_link_desc, genfs_eopnotsupp },           /* link */
        { &vop_rename_desc, msdosfs_rename },           /* rename */
        { &vop_mkdir_desc, msdosfs_mkdir },             /* mkdir */
        { &vop_rmdir_desc, msdosfs_rmdir },             /* rmdir */
        { &vop_symlink_desc, genfs_eopnotsupp },        /* symlink */
        { &vop_readdir_desc, msdosfs_readdir },         /* readdir */
        { &vop_readlink_desc, genfs_einval },           /* readlink */
        { &vop_abortop_desc, msdosfs_abortop },         /* abortop */
        { &vop_inactive_desc, msdosfs_inactive },       /* inactive */
        { &vop_reclaim_desc, msdosfs_reclaim },         /* reclaim */
        { &vop_lock_desc, genfs_lock },                 /* lock */
        { &vop_unlock_desc, genfs_unlock },             /* unlock */
        { &vop_bmap_desc, msdosfs_bmap },               /* bmap */
        { &vop_strategy_desc, msdosfs_strategy },       /* strategy */
        { &vop_print_desc, msdosfs_print },             /* print */
        { &vop_islocked_desc, genfs_islocked },         /* islocked */
        { &vop_pathconf_desc, msdosfs_pathconf },       /* pathconf */
        { &vop_advlock_desc, msdosfs_advlock },         /* advlock */
        { &vop_bwrite_desc, vn_bwrite },                /* bwrite */
        { &vop_getpages_desc, genfs_getpages },         /* getpages */
        { &vop_putpages_desc, genfs_putpages },         /* putpages */
        { NULL, NULL }
};
const struct vnodeopv_desc msdosfs_vnodeop_opv_desc =
        { &msdosfs_vnodeop_p, msdosfs_vnodeop_entries };