/*      $NetBSD: msdosfs_lookup.c,v 1.41 2022/08/06 18:26:42 andvar 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
 */

#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: msdosfs_lookup.c,v 1.41 2022/08/06 18:26:42 andvar Exp $");

#include <sys/param.h>

#ifdef _KERNEL
#include <sys/systm.h>
#include <sys/mount.h>
#include <sys/kauth.h>
#include <sys/namei.h>
#include <sys/dirent.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/atomic.h>
#else
#include <ffs/buf.h>
#endif /* _KERNEL */

#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>


#ifdef _KERNEL
/*
 * When we search a directory the blocks containing directory entries are
 * read and examined.  The directory entries contain information that would
 * normally be in the inode of a unix filesystem.  This means that some of
 * a directory's contents may also be in memory resident denodes (sort of
 * an inode).  This can cause problems if we are searching while some other
 * process is modifying a directory.  To prevent one process from accessing
 * incompletely modified directory information we depend upon being the
 * sole owner of a directory block.  bread/brelse provide this service.
 * This being the case, when a process modifies a directory it must first
 * acquire the disk block that contains the directory entry to be modified.
 * Then update the disk block and the denode, and then write the disk block
 * out to disk.  This way disk blocks containing directory entries and in
 * memory denode's will be in synch.
 */
int
msdosfs_lookup(void *v)
{
        struct vop_lookup_v2_args /* {
                struct vnode *a_dvp;
                struct vnode **a_vpp;
                struct componentname *a_cnp;
        } */ *ap = v;
        struct vnode *vdp = ap->a_dvp;
        struct vnode **vpp = ap->a_vpp;
        struct componentname *cnp = ap->a_cnp;
        daddr_t bn;
        int error;
        int slotcount;
        int slotoffset = 0;
        int frcn;
        u_long cluster;
        int blkoff;
        int diroff;
        int blsize;
        int isadir;             /* ~0 if found direntry is a directory   */
        u_long scn;             /* starting cluster number               */
        struct denode *dp;
        struct msdosfsmount *pmp;
        struct buf *bp = 0;
        struct direntry *dep;
        u_char dosfilename[12];
        int flags;
        int nameiop = cnp->cn_nameiop;
        int wincnt = 1;
        int chksum = -1, chksum_ok;
        int olddos = 1;

        flags = cnp->cn_flags;

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_lookup(): looking for %.*s\n",
                (int)cnp->cn_namelen, cnp->cn_nameptr);
#endif
        dp = VTODE(vdp);
        pmp = dp->de_pmp;
        *vpp = NULL;
#ifdef MSDOSFS_DEBUG
        printf("msdosfs_lookup(): vdp %p, dp %p, Attr %02x\n",
            vdp, dp, dp->de_Attributes);
#endif

        /*
         * Check accessibility of directory.
         */
        if ((error = VOP_ACCESS(vdp, VEXEC, cnp->cn_cred)) != 0)
                return (error);

        if ((flags & ISLASTCN) && (vdp->v_mount->mnt_flag & MNT_RDONLY) &&
            (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
                return (EROFS);

        /*
         * We now have a segment name to search for, and a directory to search.
         *
         * Before tediously performing a linear scan of the directory,
         * check the name cache to see if the directory/name pair
         * we are looking for is known already.
         */
        if (cache_lookup(vdp, cnp->cn_nameptr, cnp->cn_namelen,
                         cnp->cn_nameiop, cnp->cn_flags, NULL, vpp)) {
                return *vpp == NULLVP ? ENOENT: 0;
        }

        /* May need to restart the lookup with an exclusive lock. */
        if (VOP_ISLOCKED(vdp) != LK_EXCLUSIVE)
                return ENOLCK;

        /*
         * If they are going after the . or .. entry in the root directory,
         * they won't find it.  DOS filesystems don't have them in the root
         * directory.  So, we fake it. deget() is in on this scam too.
         */
        if ((vdp->v_vflag & VV_ROOT) && cnp->cn_nameptr[0] == '.' &&
            (cnp->cn_namelen == 1 ||
                (cnp->cn_namelen == 2 && cnp->cn_nameptr[1] == '.'))) {
                isadir = ATTR_DIRECTORY;
                scn = MSDOSFSROOT;
#ifdef MSDOSFS_DEBUG
                printf("msdosfs_lookup(): looking for . or .. in root directory\n");
#endif
                cluster = MSDOSFSROOT;
                blkoff = MSDOSFSROOT_OFS;
                goto foundroot;
        }

        switch (msdosfs_unix2dosfn((const u_char *)cnp->cn_nameptr, dosfilename,
            cnp->cn_namelen, 0)) {
        case 0:
                return (EINVAL);
        case 1:
                break;
        case 2:
                wincnt = msdosfs_winSlotCnt((const u_char *)cnp->cn_nameptr,
                    cnp->cn_namelen, pmp->pm_flags & MSDOSFSMNT_UTF8) + 1;
                break;
        case 3:
                olddos = 0;
                wincnt = msdosfs_winSlotCnt((const u_char *)cnp->cn_nameptr,
                    cnp->cn_namelen, pmp->pm_flags & MSDOSFSMNT_UTF8) + 1;
                break;
        }
        if (pmp->pm_flags & MSDOSFSMNT_SHORTNAME)
                wincnt = 1;

        /*
         * Suppress search for slots unless creating
         * file and at end of pathname, in which case
         * we watch for a place to put the new file in
         * case it doesn't already exist.
         */
        slotcount = wincnt;
        if ((nameiop == CREATE || nameiop == RENAME) &&
            (flags & ISLASTCN))
                slotcount = 0;

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_lookup(): dos filename: %s\n", dosfilename);
#endif
        /*
         * Search the directory pointed at by vdp for the name pointed at
         * by cnp->cn_nameptr.
         */

        /*
         * The outer loop ranges over the clusters that make up the
         * directory.  Note that the root directory is different from all
         * other directories.  It has a fixed number of blocks that are not
         * part of the pool of allocatable clusters.  So, we treat it a
         * little differently. The root directory starts at "cluster" 0.
         */
        diroff = 0;
        for (frcn = 0; diroff < dp->de_FileSize; frcn++) {
                if ((error = msdosfs_pcbmap(dp, frcn, &bn, &cluster,
                    &blsize)) != 0) {
                        if (error == E2BIG)
                                break;
                        return (error);
                }
                error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
                    0, &bp);
                if (error) {
                        return (error);
                }
                for (blkoff = 0; blkoff < blsize;
                     blkoff += sizeof(struct direntry),
                     diroff += sizeof(struct direntry)) {
                        dep = (struct direntry *)((char *)bp->b_data + blkoff);
                        /*
                         * If the slot is empty and we are still looking
                         * for an empty then remember this one.  If the
                         * slot is not empty then check to see if it
                         * matches what we are looking for.  If the slot
                         * has never been filled with anything, then the
                         * remainder of the directory has never been used,
                         * so there is no point in searching it.
                         */
                        if (dep->deName[0] == SLOT_EMPTY ||
                            dep->deName[0] == SLOT_DELETED) {
                                /*
                                 * Drop memory of previous long matches
                                 */
                                chksum = -1;

                                if (slotcount < wincnt) {
                                        slotcount++;
                                        slotoffset = diroff;
                                }
                                if (dep->deName[0] == SLOT_EMPTY) {
                                        brelse(bp, 0);
                                        goto notfound;
                                }
                        } else {
                                /*
                                 * If there wasn't enough space for our
                                 * winentries, forget about the empty space
                                 */
                                if (slotcount < wincnt)
                                        slotcount = 0;

                                /*
                                 * Check for Win95 long filename entry
                                 */
                                if (dep->deAttributes == ATTR_WIN95) {
                                        if (pmp->pm_flags & MSDOSFSMNT_SHORTNAME)
                                                continue;

                                        chksum = msdosfs_winChkName((const u_char *)cnp->cn_nameptr,
                                                            cnp->cn_namelen,
                                                            (struct winentry *)dep,
                                                            chksum,
                                                            pmp->pm_flags & MSDOSFSMNT_UTF8);
                                        continue;
                                }

                                /*
                                 * Ignore volume labels (anywhere, not just
                                 * the root directory).
                                 */
                                if (dep->deAttributes & ATTR_VOLUME) {
                                        chksum = -1;
                                        continue;
                                }

                                /*
                                 * Check for a checksum or name match
                                 */
                                chksum_ok =
                                    (chksum == msdosfs_winChksum(dep->deName));
                                if (!chksum_ok && (
                                        !olddos ||
                                        memcmp(&dosfilename[0],dep->deName,8) ||
                                        memcmp(&dosfilename[8],dep->deExtension,3))) {
                                        chksum = -1;
                                        continue;
                                }
#ifdef MSDOSFS_DEBUG
                                printf("msdosfs_lookup(): match blkoff %d, diroff %d\n",
                                    blkoff, diroff);
#endif
                                /*
                                 * Remember where this directory
                                 * entry came from for whoever did
                                 * this lookup.
                                 */
                                dp->de_crap.mlr_fndoffset = diroff;
                                if (chksum_ok && nameiop == RENAME) {
                                        /*
                                         * Target had correct long name
                                         * directory entries, reuse them
                                         * as needed.
                                         */
                                        dp->de_crap.mlr_fndcnt = wincnt - 1;
                                } else {
                                        /*
                                         * Long name directory entries
                                         * not present or corrupt, can only
                                         * reuse dos directory entry.
                                         */
                                        dp->de_crap.mlr_fndcnt = 0;
                                }

                                goto found;
                        }
                }       /* for (blkoff = 0; .... */
                /*
                 * Release the buffer holding the directory cluster just
                 * searched.
                 */
                brelse(bp, 0);
        }       /* for (frcn = 0; ; frcn++) */

notfound:
        /*
         * We hold no disk buffers at this point.
         */

        /*
         * If we get here we didn't find the entry we were looking for. But
         * that's ok if we are creating or renaming and are at the end of
         * the pathname and the directory hasn't been removed.
         */
#ifdef MSDOSFS_DEBUG
        printf("msdosfs_lookup(): op %d, refcnt %ld, slotcount %d, slotoffset %d\n",
            nameiop, dp->de_refcnt, slotcount, slotoffset);
#endif
        if ((nameiop == CREATE || nameiop == RENAME) &&
            (flags & ISLASTCN) && dp->de_refcnt != 0) {
                /*
                 * Access for write is interpreted as allowing
                 * creation of files in the directory.
                 */
                error = VOP_ACCESS(vdp, VWRITE, cnp->cn_cred);
                if (error)
                        return (error);

                /*
                 * Fixup the slot description to point to the place where
                 * we might put the new DOS direntry (putting the Win95
                 * long name entries before that)
                 */
                if (!slotcount) {
                        slotcount = 1;
                        slotoffset = diroff;
                }
                if (wincnt > slotcount) {
                        slotoffset +=
                                sizeof(struct direntry) * (wincnt - slotcount);
                }

                /*
                 * Return an indication of where the new directory
                 * entry should be put.
                 */
                dp->de_crap.mlr_fndoffset = slotoffset;
                dp->de_crap.mlr_fndcnt = wincnt - 1;

                /*
                 * We return with the directory locked, so that
                 * the parameters we set up above will still be
                 * valid if we actually decide to do a direnter().
                 * We return ni_vp == NULL to indicate that the entry
                 * does not currently exist; we leave a pointer to
                 * the (locked) directory inode in ndp->ni_dvp.
                 *
                 * NB - if the directory is unlocked, then this
                 * information cannot be used.
                 */
                return (EJUSTRETURN);
        }

#if 0
        /*
         * Insert name into cache (as non-existent) if appropriate.
         *
         * XXX Negative caching is broken for msdosfs because the name
         * cache doesn't understand peculiarities such as case insensitivity
         * and 8.3 filenames.  Hence, it may not invalidate all negative
         * entries if a file with this name is later created.
         * e.g. creating a file 'foo' won't invalidate a negative entry 
         * for 'FOO'.
         */
        if (nameiop != CREATE)
                cache_enter(vdp, *vpp, cnp->cn_nameptr, cnp->cn_namelen,
                            cnp->cn_flags);
#endif

        return (ENOENT);

found:
        /*
         * NOTE:  We still have the buffer with matched directory entry at
         * this point.
         */
        isadir = dep->deAttributes & ATTR_DIRECTORY;
        scn = getushort(dep->deStartCluster);
        if (FAT32(pmp)) {
                scn |= getushort(dep->deHighClust) << 16;
                if (scn == pmp->pm_rootdirblk) {
                        /*
                         * There should actually be 0 here.
                         * Just ignore the error.
                         */
                        scn = MSDOSFSROOT;
                }
        }

        if (isadir) {
                cluster = scn;
                if (cluster == MSDOSFSROOT)
                        blkoff = MSDOSFSROOT_OFS;
                else
                        blkoff = 0;
        } else if (cluster == MSDOSFSROOT)
                blkoff = diroff;

        /*
         * Now release buf to allow deget to read the entry again.
         * Reserving it here and giving it to deget could result
         * in a deadlock.
         */
        brelse(bp, 0);

foundroot:
        /*
         * If we entered at foundroot, then we are looking for the . or ..
         * entry of the filesystems root directory.  isadir and scn were
         * setup before jumping here.  And, bp is already null.
         */
        if (FAT32(pmp) && scn == MSDOSFSROOT)
                scn = pmp->pm_rootdirblk;

        /*
         * If deleting, and at end of pathname, return
         * parameters which can be used to remove file.
         * Lock the inode, being careful with ".".
         */
        if (nameiop == DELETE && (flags & ISLASTCN)) {
                /*
                 * Don't allow deleting the root.
                 */
                if (blkoff == MSDOSFSROOT_OFS)
                        return EINVAL;

                /*
                 * Write access to directory required to delete files.
                 */
                error = VOP_ACCESS(vdp, VWRITE, cnp->cn_cred);
                if (error)
                        return (error);

                /*
                 * Return pointer to current entry in dp->i_offset.
                 * Save directory inode pointer in ndp->ni_dvp for dirremove().
                 */
                if (dp->de_StartCluster == scn && isadir) {     /* "." */
                        vref(vdp);
                        *vpp = vdp;
                        return (0);
                }
                error = msdosfs_deget(pmp, cluster, blkoff, vpp);
                return error;
        }

        /*
         * If rewriting (RENAME), return the inode and the
         * information required to rewrite the present directory
         * Must get inode of directory entry to verify it's a
         * regular file, or empty directory.
         */
        if (nameiop == RENAME && (flags & ISLASTCN)) {

                if (vdp->v_mount->mnt_flag & MNT_RDONLY)
                        return (EROFS);

                if (blkoff == MSDOSFSROOT_OFS)
                        return EINVAL;

                error = VOP_ACCESS(vdp, VWRITE, cnp->cn_cred);
                if (error)
                        return (error);

                /*
                 * Careful about locking second inode.
                 * This can only occur if the target is ".".
                 */
                if (dp->de_StartCluster == scn && isadir)
                        return (EISDIR);

                error = msdosfs_deget(pmp, cluster, blkoff, vpp);
                return error;
        }

        if (dp->de_StartCluster == scn && isadir) {
                vref(vdp);      /* we want ourself, ie "." */
                *vpp = vdp;
        } else if ((error = msdosfs_deget(pmp, cluster, blkoff, vpp)) != 0) {
                return error;
        }

        /*
         * Insert name into cache if appropriate.
         */
        cache_enter(vdp, *vpp, cnp->cn_nameptr, cnp->cn_namelen, cnp->cn_flags);

        return 0;
}
#endif /* _KERNEL */

/*
 * dep  - directory entry to copy into the directory
 * ddep - directory to add to
 * depp - return the address of the denode for the created directory entry
 *        if depp != 0
 * cnp  - componentname needed for Win95 long filenames
 */
int
msdosfs_createde(struct denode *dep, struct denode *ddep,
    const struct msdosfs_lookup_results *mlr,
    struct denode **depp, struct componentname *cnp)
{
        int error, rberror;
        u_long dirclust, clusoffset;
        u_long fndoffset, havecnt = 0, wcnt = 1, i;
        struct direntry *ndep;
        struct msdosfsmount *pmp = ddep->de_pmp;
        struct buf *bp;
        daddr_t bn;
        int blsize;
#ifdef _KERNEL
        int async = ddep->de_pmp->pm_mountp->mnt_flag & MNT_ASYNC;
#else
#define async 0
#endif

#ifdef MSDOSFS_DEBUG
        printf("createde(dep %p, ddep %p, depp %p, cnp %p)\n",
            dep, ddep, depp, cnp);
#endif

        /*
         * If no space left in the directory then allocate another cluster
         * and chain it onto the end of the file.  There is one exception
         * to this.  That is, if the root directory has no more space it
         * can NOT be expanded.  extendfile() checks for and fails attempts
         * to extend the root directory.  We just return an error in that
         * case.
         */
        if (mlr->mlr_fndoffset >= ddep->de_FileSize) {
                u_long needlen = ddep->de_crap.mlr_fndoffset
                    + sizeof(struct direntry) - ddep->de_FileSize;
                dirclust = de_clcount(pmp, needlen);
                if ((error = msdosfs_extendfile(ddep, dirclust, 0, 0,
                    DE_CLEAR)) != 0) {
                        (void)msdosfs_detrunc(ddep, ddep->de_FileSize, 0,
                            NOCRED);
                        goto err_norollback;
                }

                /*
                 * Update the size of the directory
                 */
                ddep->de_FileSize += de_cn2off(pmp, dirclust);
        }

        /*
         * We just read in the cluster with space.  Copy the new directory
         * entry in.  Then write it to disk. NOTE:  DOS directories
         * do not get smaller as clusters are emptied.
         */
        error = msdosfs_pcbmap(ddep, de_cluster(pmp, mlr->mlr_fndoffset),
                       &bn, &dirclust, &blsize);
        if (error)
                goto err_norollback;
        clusoffset = mlr->mlr_fndoffset;
        if (dirclust != MSDOSFSROOT)
                clusoffset &= pmp->pm_crbomask;
        if ((error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
            B_MODIFY, &bp)) != 0) {
                goto err_norollback;
        }
        ndep = bptoep(pmp, bp, clusoffset);

        DE_EXTERNALIZE(ndep, dep);

        /*
         * Now write the Win95 long name
         */
        if (mlr->mlr_fndcnt > 0) {
                u_int8_t chksum = msdosfs_winChksum(ndep->deName);
                const u_char *un = (const u_char *)cnp->cn_nameptr;
                int unlen = cnp->cn_namelen;
                u_long xhavecnt;

                fndoffset = mlr->mlr_fndoffset;
                xhavecnt = mlr->mlr_fndcnt + 1;

                for(; wcnt < xhavecnt; wcnt++) {
                        if ((fndoffset & pmp->pm_crbomask) == 0) {
                                /* we should never get here if ddep is root
                                 * directory */

                                if (async)
                                        (void) bdwrite(bp);
                                else if ((error = bwrite(bp)) != 0)
                                        goto rollback;

                                fndoffset -= sizeof(struct direntry);
                                error = msdosfs_pcbmap(ddep,
                                               de_cluster(pmp, fndoffset),
                                               &bn, 0, &blsize);
                                if (error)
                                        goto rollback;

                                error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn),
                                    blsize, B_MODIFY, &bp);
                                if (error) {
                                        goto rollback;
                                }
                                ndep = bptoep(pmp, bp,
                                                fndoffset & pmp->pm_crbomask);
                        } else {
                                ndep--;
                                fndoffset -= sizeof(struct direntry);
                        }
                        if (!msdosfs_unix2winfn(un, unlen,
                                        (struct winentry *)ndep,
                                        wcnt, chksum,
                                        ddep->de_pmp->pm_flags & MSDOSFSMNT_UTF8))
                                break;
                }
        }

        if (async)
                bdwrite(bp);
        else if ((error = bwrite(bp)) != 0)
                goto rollback;

        /*
         * If they want us to return with the denode gotten.
         */
        if (depp) {
                u_long diroffset = clusoffset;

                if (dep->de_Attributes & ATTR_DIRECTORY) {
                        dirclust = dep->de_StartCluster;
                        if (FAT32(pmp) && dirclust == pmp->pm_rootdirblk)
                                dirclust = MSDOSFSROOT;
                        if (dirclust == MSDOSFSROOT)
                                diroffset = MSDOSFSROOT_OFS;
                        else
                                diroffset = 0;
                }
#ifdef MAKEFS
                error = msdosfs_deget(pmp, dirclust, diroffset, depp);
#else
                struct vnode *vp;

                error = msdosfs_deget(pmp, dirclust, diroffset, &vp);
                if (error == 0)
                        *depp = VTODE(vp);
                else
                        *depp = NULL;
#endif
                return error;
        }

        return 0;

    rollback:
        /*
         * Mark all slots modified so far as deleted. Note that we
         * can't just call removede(), since directory is not in
         * consistent state.
         */
        fndoffset = mlr->mlr_fndoffset;
        rberror = msdosfs_pcbmap(ddep, de_cluster(pmp, fndoffset),
               &bn, NULL, &blsize);
        if (rberror)
                goto err_norollback;
        if ((rberror = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
            B_MODIFY, &bp)) != 0) {
                goto err_norollback;
        }
        ndep = bptoep(pmp, bp, clusoffset);

        havecnt = mlr->mlr_fndcnt + 1;
        for(i = wcnt; i <= havecnt; i++) {
                /* mark entry as deleted */
                ndep->deName[0] = SLOT_DELETED;

                if ((fndoffset & pmp->pm_crbomask) == 0) {
                        /* we should never get here if ddep is root
                         * directory */

                        if (async)
                                bdwrite(bp);
                        else if ((rberror = bwrite(bp)) != 0)
                                goto err_norollback;

                        fndoffset -= sizeof(struct direntry);
                        rberror = msdosfs_pcbmap(ddep,
                                       de_cluster(pmp, fndoffset),
                                       &bn, 0, &blsize);
                        if (rberror)
                                goto err_norollback;

                        rberror = bread(pmp->pm_devvp, de_bn2kb(pmp, bn),
                            blsize, B_MODIFY, &bp);
                        if (rberror) {
                                goto err_norollback;
                        }
                        ndep = bptoep(pmp, bp, fndoffset);
                } else {
                        ndep--;
                        fndoffset -= sizeof(struct direntry);
                }
        }

        /* ignore any further error */
        if (async)
                (void) bdwrite(bp);
        else
                (void) bwrite(bp);

    err_norollback:
        return error;
}

/*
 * Be sure a directory is empty except for "." and "..". Return 1 if empty,
 * return 0 if not empty or error.
 */
int
msdosfs_dosdirempty(struct denode *dep)
{
        int blsize;
        int error;
        u_long cn;
        daddr_t bn;
        struct buf *bp;
        struct msdosfsmount *pmp = dep->de_pmp;
        struct direntry *dentp;

        /*
         * Since the filesize field in directory entries for a directory is
         * zero, we just have to feel our way through the directory until
         * we hit end of file.
         */
        for (cn = 0;; cn++) {
                if ((error = msdosfs_pcbmap(dep, cn, &bn, 0, &blsize)) != 0) {
                        if (error == E2BIG)
                                return (1);     /* it's empty */
                        return (0);
                }
                error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
                    0, &bp);
                if (error) {
                        return (0);
                }
                for (dentp = (struct direntry *)bp->b_data;
                     (char *)dentp < (char *)bp->b_data + blsize;
                     dentp++) {
                        if (dentp->deName[0] != SLOT_DELETED &&
                            (dentp->deAttributes & ATTR_VOLUME) == 0) {
                                /*
                                 * In dos directories an entry whose name
                                 * starts with SLOT_EMPTY (0) starts the
                                 * beginning of the unused part of the
                                 * directory, so we can just return that it
                                 * is empty.
                                 */
                                if (dentp->deName[0] == SLOT_EMPTY) {
                                        brelse(bp, 0);
                                        return (1);
                                }
                                /*
                                 * Any names other than "." and ".." in a
                                 * directory mean it is not empty.
                                 */
                                if (memcmp(dentp->deName, ".          ", 11) &&
                                    memcmp(dentp->deName, "..         ", 11)) {
                                        brelse(bp, 0);
#ifdef MSDOSFS_DEBUG
                                        printf("dosdirempty(): found %.11s, %d, %d\n",
                                            dentp->deName, dentp->deName[0],
                                                dentp->deName[1]);
#endif
                                        return (0);     /* not empty */
                                }
                        }
                }
                brelse(bp, 0);
        }
        /* NOTREACHED */
}

/*
 * Read in the disk block containing the directory entry (dirclu, dirofs)
 * and return the address of the buf header, and the address of the
 * directory entry within the block.
 */
int
msdosfs_readep(struct msdosfsmount *pmp, u_long dirclust, u_long diroffset,
    struct buf **bpp, struct direntry **epp)
{
        int error;
        daddr_t bn;
        int blsize;

        blsize = pmp->pm_bpcluster;
        if (dirclust == MSDOSFSROOT
            && de_blk(pmp, diroffset + blsize) > pmp->pm_rootdirsize)
                blsize = de_bn2off(pmp, pmp->pm_rootdirsize) & pmp->pm_crbomask;
        bn = detobn(pmp, dirclust, diroffset);
        if ((error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
            0, bpp)) != 0) {
                *bpp = NULL;
                return (error);
        }
        if (epp)
                *epp = bptoep(pmp, *bpp, diroffset);
        return (0);
}

/*
 * Read in the disk block containing the directory entry dep came from and
 * return the address of the buf header, and the address of the directory
 * entry within the block.
 */
int
msdosfs_readde(struct denode *dep, struct buf **bpp, struct direntry **epp)
{
        return (msdosfs_readep(dep->de_pmp, dep->de_dirclust, dep->de_diroffset,
                        bpp, epp));
}

/*
 * Remove a directory entry. At this point the file represented by the
 * directory entry to be removed is still full length until noone has it
 * open.  When the file no longer being used msdosfs_inactive() is called
 * and will truncate the file to 0 length.  When the vnode containing the
 * denode is needed for some other purpose by VFS it will call
 * msdosfs_reclaim() which will remove the denode from the denode cache.
 */
int
msdosfs_removede(struct denode *pdep, struct denode *dep,
    const struct msdosfs_lookup_results *mlr)
        /* pdep:         directory where the entry is removed */
        /* dep:  file to be removed */
        /* mlr:  position of dep in pdep from lookup */
{
        int error;
        struct direntry *ep;
        struct buf *bp;
        daddr_t bn;
        int blsize;
        struct msdosfsmount *pmp = pdep->de_pmp;
        u_long offset = mlr->mlr_fndoffset;
#ifdef _KERNEL
        int async = pdep->de_pmp->pm_mountp->mnt_flag & MNT_ASYNC;
#else
#define async 0
#endif

#ifdef MSDOSFS_DEBUG
        printf("removede(): filename %s, dep %p, offset %08lx\n",
            dep->de_Name, dep, offset);
#endif

        if (--dep->de_refcnt == 0) {
#ifndef MAKEFS
                struct denode_key old_key = dep->de_key;
                struct denode_key new_key = dep->de_key;

                KASSERT(new_key.dk_dirgen == NULL);
                new_key.dk_dirgen = dep;
                vcache_rekey_enter(pmp->pm_mountp, DETOV(dep), &old_key,
                    sizeof(old_key), &new_key, sizeof(new_key));
                dep->de_key = new_key;
                vcache_rekey_exit(pmp->pm_mountp, DETOV(dep), &old_key,
                    sizeof(old_key), &dep->de_key, sizeof(dep->de_key));
#endif
        }
        offset += sizeof(struct direntry);
        do {
                offset -= sizeof(struct direntry);
                error = msdosfs_pcbmap(pdep, de_cluster(pmp, offset), &bn, 0,
                    &blsize);
                if (error)
                        return error;
                error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
                    B_MODIFY, &bp);
                if (error) {
                        return error;
                }
                ep = bptoep(pmp, bp, offset);
                /*
                 * Check whether, if we came here the second time, i.e.
                 * when underflowing into the previous block, the last
                 * entry in this block is a longfilename entry, too.
                 */
                if (ep->deAttributes != ATTR_WIN95
                    && offset != mlr->mlr_fndoffset) {
                        brelse(bp, 0);
                        break;
                }
                offset += sizeof(struct direntry);
                while (1) {
                        /*
                         * We are a bit aggressive here in that we delete any Win95
                         * entries preceding this entry, not just the ones we "own".
                         * Since these presumably aren't valid anyway,
                         * there should be no harm.
                         */
                        offset -= sizeof(struct direntry);
                        ep--->deName[0] = SLOT_DELETED;
                        if ((pmp->pm_flags & MSDOSFSMNT_NOWIN95)
                            || !(offset & pmp->pm_crbomask)
                            || ep->deAttributes != ATTR_WIN95)
                                break;
                }
                if (async)
                        bdwrite(bp);
                else if ((error = bwrite(bp)) != 0)
                        return error;
        } while (!(pmp->pm_flags & MSDOSFSMNT_NOWIN95)
            && !(offset & pmp->pm_crbomask)
            && offset);
        return 0;
}

/*
 * Create a unique DOS name in dvp
 */
int
msdosfs_uniqdosname(struct denode *dep, struct componentname *cnp, u_char *cp)
{
        struct msdosfsmount *pmp = dep->de_pmp;
        struct direntry *dentp;
        int gen;
        int blsize;
        u_long cn;
        daddr_t bn;
        struct buf *bp;
        int error;

        for (gen = 1;; gen++) {
                /*
                 * Generate DOS name with generation number
                 */
                if (!msdosfs_unix2dosfn((const u_char *)cnp->cn_nameptr, cp,
                    cnp->cn_namelen, gen))
                        return gen == 1 ? EINVAL : EEXIST;

                /*
                 * Now look for a dir entry with this exact name
                 */
                for (cn = error = 0; !error; cn++) {
                        if ((error = msdosfs_pcbmap(dep, cn, &bn, 0,
                            &blsize)) != 0) {
                                if (error == E2BIG)     /* EOF reached and not found */
                                        return 0;
                                return error;
                        }
                        error = bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
                            0, &bp);
                        if (error) {
                                return error;
                        }
                        for (dentp = (struct direntry *)bp->b_data;
                             (char *)dentp < (char *)bp->b_data + blsize;
                             dentp++) {
                                if (dentp->deName[0] == SLOT_EMPTY) {
                                        /*
                                         * Last used entry and not found
                                         */
                                        brelse(bp, 0);
                                        return 0;
                                }
                                /*
                                 * Ignore volume labels and Win95 entries
                                 */
                                if (dentp->deAttributes & ATTR_VOLUME)
                                        continue;
                                if (!memcmp(dentp->deName, cp, 11)) {
                                        error = EEXIST;
                                        break;
                                }
                        }
                        brelse(bp, 0);
                }
        }
}

/*
 * Find any Win'95 long filename entry in directory dep
 */
int
msdosfs_findwin95(struct denode *dep)
{
        struct msdosfsmount *pmp = dep->de_pmp;
        struct direntry *dentp;
        int blsize, win95;
        u_long cn;
        daddr_t bn;
        struct buf *bp;

        win95 = 1;
        /*
         * Read through the directory looking for Win'95 entries
         * XXX Note: Error currently handled just as EOF
         */
        for (cn = 0;; cn++) {
                if (msdosfs_pcbmap(dep, cn, &bn, 0, &blsize))
                        return win95;
                if (bread(pmp->pm_devvp, de_bn2kb(pmp, bn), blsize,
                    0, &bp)) {
                        return win95;
                }
                for (dentp = (struct direntry *)bp->b_data;
                     (char *)dentp < (char *)bp->b_data + blsize;
                     dentp++) {
                        if (dentp->deName[0] == SLOT_EMPTY) {
                                /*
                                 * Last used entry and not found
                                 */
                                brelse(bp, 0);
                                return win95;
                        }
                        if (dentp->deName[0] == SLOT_DELETED) {
                                /*
                                 * Ignore deleted files
                                 * Note: might be an indication of Win'95
                                 * anyway       XXX
                                 */
                                continue;
                        }
                        if (dentp->deAttributes == ATTR_WIN95) {
                                brelse(bp, 0);
                                return 1;
                        }
                        win95 = 0;
                }
                brelse(bp, 0);
        }
}