/*      $OpenBSD: msdosfs_lookup.c,v 1.35 2022/08/23 20:37:16 cheloha Exp $     */
/*      $NetBSD: msdosfs_lookup.c,v 1.34 1997/10/18 22:12:27 ws 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/param.h>
#include <sys/systm.h>
#include <sys/namei.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/lock.h>
#include <sys/mount.h>
#include <sys/dirent.h>

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

/*
 * 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_args *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 lockparent;
        int wantparent;
        int slotcount;
        int slotoffset = 0;
        int frcn;
        uint32_t cluster;
        int blkoff;
        int diroff;
        int blsize;
        int isadir;             /* ~0 if found direntry is a directory   */
        uint32_t scn;           /* starting cluster number               */
        struct vnode *pdp;
        struct denode *dp;
        struct denode *tdp;
        struct msdosfsmount *pmp;
        struct buf *bp = 0;
        struct direntry *dep;
        u_char dosfilename[11];
        u_char *adjp;
        int adjlen;
        int flags;
        int nameiop = cnp->cn_nameiop;
        int wincnt = 1;
        int chksum = -1, chksum_ok;
        int olddos = 1;

        cnp->cn_flags &= ~PDIRUNLOCK; /* XXX why this ?? */
        flags = cnp->cn_flags;

#ifdef MSDOSFS_DEBUG
        printf("msdosfs_lookup(): looking for %s\n", cnp->cn_nameptr);
#endif
        dp = VTODE(vdp);
        pmp = dp->de_pmp;
        *vpp = NULL;
        lockparent = flags & LOCKPARENT;
        wantparent = flags & (LOCKPARENT | WANTPARENT);
#ifdef MSDOSFS_DEBUG
        printf("msdosfs_lookup(): vdp %p, dp %p, Attr %02x\n",
            vdp, dp, dp->de_Attributes);
#endif

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

        /*
         * 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 ((error = cache_lookup(vdp, vpp, cnp)) >= 0)
                return (error);

        /*
         * 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_flag & VROOT) && 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 (unix2dosfn((u_char *)cnp->cn_nameptr, dosfilename, cnp->cn_namelen, 0)) {
        case 0:
                return (EINVAL);
        case 1:
                break;
        case 2:
                wincnt = winSlotCnt((u_char *)cnp->cn_nameptr, cnp->cn_namelen) + 1;
                break;
        case 3:
                olddos = 0;
                wincnt = winSlotCnt((u_char *)cnp->cn_nameptr, cnp->cn_namelen) + 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 version of filename '%.11s', "
            "length %ld\n", dosfilename, cnp->cn_namelen);
#endif

        /*
         * We want to search the directory pointed to by vdp for the name
         * pointed to by cnp->cn_nameptr.
         *
         * XXX UNIX allows filenames with trailing dots and blanks; we don't.
         *     Most of the routines in msdosfs_conv.c adjust for this, but
         *     winChkName() does not, so we do it here.  Otherwise, a file
         *     such as ".foobar." cannot be retrieved properly.
         *
         *     (Note that this is also faster: perform the adjustment once,
         *     rather than on each call to winChkName.  However, it is still
         *     a nasty hack.)
         */
        adjp = cnp->cn_nameptr;
        adjlen = cnp->cn_namelen;

        for (adjp += adjlen; adjlen > 0; adjlen--)
                if (*--adjp != ' ' && *adjp != '.')
                        break;

        tdp = NULL;
        /*
         * 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;; frcn++) {
                if ((error = pcbmap(dp, frcn, &bn, &cluster, &blsize)) != 0) {
                        if (error == E2BIG)
                                break;
                        return (error);
                }
                error = bread(pmp->pm_devvp, bn, blsize, &bp);
                if (error) {
                        brelse(bp);
                        return (error);
                }
                for (blkoff = 0; blkoff < blsize;
                     blkoff += sizeof(struct direntry),
                     diroff += sizeof(struct direntry)) {
                        dep = (struct direntry *)(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);
                                        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 = winChkName((u_char *)cnp->cn_nameptr,
                                                            adjlen,
                                                            (struct winentry *)dep,
                                                            chksum);
                                        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 == winChksum(dep->deName));
                                if (!chksum_ok
                                    && (!olddos || bcmp(dosfilename, dep->deName, 11))) {
                                        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_fndoffset = diroff;
                                if (chksum_ok && nameiop == RENAME) {
                                        /*
                                         * Target had correct long name
                                         * directory entries, reuse them as
                                         * needed.
                                         */
                                        dp->de_fndcnt = wincnt - 1;
                                } else {
                                        /*
                                         * Long name directory entries not
                                         * present or corrupt, can only reuse
                                         * dos directory entry.
                                         */
                                        dp->de_fndcnt = 0;
                                }
                                goto found;
                        }
                }       /* for (blkoff = 0; .... */
                /*
                 * Release the buffer holding the directory cluster just
                 * searched.
                 */
                brelse(bp);
        }       /* for (frcn = 0; ; frcn++) */

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

        /*
         * 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);

        /*
         * 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\n",
            nameiop, dp->de_refcnt);
        printf("               slotcount %d, slotoffset %d\n",
            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, cnp->cn_proc);
                if (error)
                        return (error);
                /*
                 * Return an indication of where the new directory
                 * entry should be put.
                 */
                dp->de_fndoffset = slotoffset;
                dp->de_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.
                 * The pathname buffer is saved so that the name
                 * can be obtained later.
                 *
                 * NB - if the directory is unlocked, then this
                 * information cannot be used.
                 */
                cnp->cn_flags |= SAVENAME;
                if (!lockparent) {
                        VOP_UNLOCK(vdp);
                        cnp->cn_flags |= PDIRUNLOCK;
                }
                return (EJUSTRETURN);
        }
        /*
         * Insert name into cache (as non-existent) if appropriate.
         */
        if ((cnp->cn_flags & MAKEENTRY) && nameiop != CREATE)
                cache_enter(vdp, *vpp, cnp);
        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 (cluster == MSDOSFSROOT)
                blkoff = diroff;

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

        /*
         * 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);

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.
         * If the wantparent flag isn't set, we return only
         * the directory (in ndp->ni_dvp), otherwise we go
         * on and lock the inode, being careful with ".".
         */
        if (nameiop == DELETE && (flags & ISLASTCN)) {
                /*
                 * Don't allow deleting the root.
                 */
                if (blkoff == MSDOSFSROOT_OFS)
                        return EROFS;                           /* really? XXX */

                /*
                 * Write access to directory required to delete files.
                 */
                error = VOP_ACCESS(vdp, VWRITE, cnp->cn_cred, cnp->cn_proc);
                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);
                }
                if ((error = deget(pmp, cluster, blkoff, &tdp)) != 0)
                        return (error);
                *vpp = DETOV(tdp);
                if (!lockparent) {
                        VOP_UNLOCK(vdp);
                        cnp->cn_flags |= PDIRUNLOCK;
                }
                return (0);
        }

        /*
         * 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 && wantparent &&
            (flags & ISLASTCN)) {
                if (blkoff == MSDOSFSROOT_OFS)
                        return EROFS;                           /* really? XXX */

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

                if ((error = deget(pmp, cluster, blkoff, &tdp)) != 0)
                        return (error);
                *vpp = DETOV(tdp);
                cnp->cn_flags |= SAVENAME;
                if (!lockparent)
                        VOP_UNLOCK(vdp);
                return (0);
        }

        /*
         * Step through the translation in the name.  We do not `vput' the
         * directory because we may need it again if a symbolic link
         * is relative to the current directory.  Instead we save it
         * unlocked as "pdp".  We must get the target inode before unlocking
         * the directory to insure that the inode will not be removed
         * before we get it.  We prevent deadlock by always fetching
         * inodes from the root, moving down the directory tree. Thus
         * when following backward pointers ".." we must unlock the
         * parent directory before getting the requested directory.
         * There is a potential race condition here if both the current
         * and parent directories are removed before the VFS_VGET for the
         * inode associated with ".." returns.  We hope that this occurs
         * infrequently since we cannot avoid this race condition without
         * implementing a sophisticated deadlock detection algorithm.
         * Note also that this simple deadlock detection scheme will not
         * work if the file system has any hard links other than ".."
         * that point backwards in the directory structure.
         */
        pdp = vdp;
        if (flags & ISDOTDOT) {
                VOP_UNLOCK(pdp);        /* race to get the inode */
                cnp->cn_flags |= PDIRUNLOCK;
                if ((error = deget(pmp, cluster, blkoff, &tdp)) != 0) {
                        if (vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY) == 0)
                                cnp->cn_flags &= ~PDIRUNLOCK;
                        return (error);
                }
                if (lockparent && (flags & ISLASTCN)) {
                        if ((error = vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY))) {
                                vput(DETOV(tdp));
                                return (error);
                        }
                        cnp->cn_flags &= ~PDIRUNLOCK;
                }
                *vpp = DETOV(tdp);
        } else if (dp->de_StartCluster == scn && isadir) {
                vref(vdp);      /* we want ourself, ie "." */
                *vpp = vdp;
        } else {
                if ((error = deget(pmp, cluster, blkoff, &tdp)) != 0)
                        return (error);
                if (!lockparent || !(flags & ISLASTCN)) {
                        VOP_UNLOCK(pdp);
                        cnp->cn_flags |= PDIRUNLOCK;
                }
                *vpp = DETOV(tdp);
        }

        /*
         * Insert name into cache if appropriate.
         */
        if (cnp->cn_flags & MAKEENTRY)
                cache_enter(vdp, *vpp, cnp);
        return (0);
}

/*
 * 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
createde(struct denode *dep, struct denode *ddep, struct denode **depp,
    struct componentname *cnp)
{
        int error;
        uint32_t dirclust, diroffset;
        struct direntry *ndep;
        struct msdosfsmount *pmp = ddep->de_pmp;
        struct buf *bp;
        daddr_t bn;
        int blsize;

#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 (ddep->de_fndoffset >= ddep->de_FileSize) {
                diroffset = ddep->de_fndoffset + sizeof(struct direntry)
                    - ddep->de_FileSize;
                dirclust = de_clcount(pmp, diroffset);
                if ((error = extendfile(ddep, dirclust, 0, 0, DE_CLEAR)) != 0) {
                        (void)detrunc(ddep, ddep->de_FileSize, 0, NOCRED,
                            cnp->cn_proc);
                        return error;
                }

                /*
                 * 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 = pcbmap(ddep, de_cluster(pmp, ddep->de_fndoffset),
                       &bn, &dirclust, &blsize);
        if (error)
                return error;
        diroffset = ddep->de_fndoffset;
        if (dirclust != MSDOSFSROOT)
                diroffset &= pmp->pm_crbomask;
        if ((error = bread(pmp->pm_devvp, bn, blsize, &bp)) != 0) {
                brelse(bp);
                return error;
        }
        ndep = bptoep(pmp, bp, ddep->de_fndoffset);

        DE_EXTERNALIZE(ndep, dep);

        /*
         * Now write the Win95 long name
         */
        if (ddep->de_fndcnt > 0) {
                u_int8_t chksum = winChksum(ndep->deName);
                u_char *un = (u_char *)cnp->cn_nameptr;
                int unlen = cnp->cn_namelen;
                int cnt = 1;

                while (--ddep->de_fndcnt >= 0) {
                        if (!(ddep->de_fndoffset & pmp->pm_crbomask)) {
                                if ((error = bwrite(bp)) != 0)
                                        return error;

                                ddep->de_fndoffset -= sizeof(struct direntry);
                                error = pcbmap(ddep,
                                               de_cluster(pmp,
                                                          ddep->de_fndoffset),
                                               &bn, 0, &blsize);
                                if (error)
                                        return error;

                                error = bread(pmp->pm_devvp, bn, blsize, &bp);
                                if (error) {
                                        brelse(bp);
                                        return error;
                                }
                                ndep = bptoep(pmp, bp, ddep->de_fndoffset);
                        } else {
                                ndep--;
                                ddep->de_fndoffset -= sizeof(struct direntry);
                        }
                        if (!unix2winfn(un, unlen, (struct winentry *)ndep, cnt++, chksum))
                                break;
                }
        }

        if ((error = bwrite(bp)) != 0)
                return error;

        /*
         * If they want us to return with the denode gotten.
         */
        if (depp) {
                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;
                }
                return deget(pmp, dirclust, diroffset, depp);
        }

        return 0;
}

/*
 * Be sure a directory is empty except for "." and "..". Return 1 if empty,
 * return 0 if not empty or error.
 */
int
dosdirempty(struct denode *dep)
{
        int blsize;
        int error;
        uint32_t 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 = pcbmap(dep, cn, &bn, 0, &blsize)) != 0) {
                        if (error == E2BIG)
                                return (1);     /* it's empty */
                        return (0);
                }
                error = bread(pmp->pm_devvp, bn, blsize, &bp);
                if (error) {
                        brelse(bp);
                        return (0);
                }
                for (dentp = (struct direntry *)bp->b_data;
                     (char *)dentp < 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);
                                        return (1);
                                }
                                /*
                                 * Any names other than "." and ".." in a
                                 * directory mean it is not empty.
                                 */
                                if (bcmp(dentp->deName, ".          ", 11) &&
                                    bcmp(dentp->deName, "..         ", 11)) {
                                        brelse(bp);
#ifdef MSDOSFS_DEBUG
                                        printf("dosdirempty(): entry found %02x, %02x\n",
                                            dentp->deName[0], dentp->deName[1]);
#endif
                                        return (0);     /* not empty */
                                }
                        }
                }
                brelse(bp);
        }
        /* NOTREACHED */
}

/*
 * Check to see if the directory described by target is in some
 * subdirectory of source.  This prevents something like the following from
 * succeeding and leaving a bunch or files and directories orphaned. mv
 * /a/b/c /a/b/c/d/e/f Where c and f are directories.
 *
 * source - the inode for /a/b/c
 * target - the inode for /a/b/c/d/e/f
 *
 * Returns 0 if target is NOT a subdirectory of source.
 * Otherwise returns a non-zero error number.
 * The target inode is always unlocked on return.
 */
int
doscheckpath(struct denode *source, struct denode *target)
{
        uint32_t scn;
        struct msdosfsmount *pmp;
        struct direntry *ep;
        struct denode *dep;
        struct buf *bp = NULL;
        int error = 0;

        dep = target;
        if ((target->de_Attributes & ATTR_DIRECTORY) == 0 ||
            (source->de_Attributes & ATTR_DIRECTORY) == 0) {
                error = ENOTDIR;
                goto out;
        }
        if (dep->de_StartCluster == source->de_StartCluster) {
                error = EEXIST;
                goto out;
        }
        if (dep->de_StartCluster == MSDOSFSROOT)
                goto out;
        pmp = dep->de_pmp;
#ifdef  DIAGNOSTIC
        if (pmp != source->de_pmp)
                panic("doscheckpath: source and target on different filesystems");
#endif
        if (FAT32(pmp) && dep->de_StartCluster == pmp->pm_rootdirblk)
                goto out;

        for (;;) {
                if ((dep->de_Attributes & ATTR_DIRECTORY) == 0) {
                        error = ENOTDIR;
                        break;
                }
                scn = dep->de_StartCluster;
                error = bread(pmp->pm_devvp, cntobn(pmp, scn),
                              pmp->pm_bpcluster, &bp);
                if (error)
                        break;

                ep = (struct direntry *) bp->b_data + 1;
                if ((ep->deAttributes & ATTR_DIRECTORY) == 0 ||
                    bcmp(ep->deName, "..         ", 11) != 0) {
                        error = ENOTDIR;
                        break;
                }
                scn = getushort(ep->deStartCluster);
                if (FAT32(pmp))
                        scn |= getushort(ep->deHighClust) << 16;

                if (scn == source->de_StartCluster) {
                        error = EINVAL;
                        break;
                }
                if (scn == MSDOSFSROOT)
                        break;
                if (FAT32(pmp) && scn == pmp->pm_rootdirblk) {
                        /*
                         * scn should be 0 in this case,
                         * but we silently ignore the error.
                         */
                        break;
                }

                vput(DETOV(dep));
                brelse(bp);
                bp = NULL;
                /* NOTE: deget() clears dep on error */
                if ((error = deget(pmp, scn, 0, &dep)) != 0)
                        break;
        }
out:;
        if (bp)
                brelse(bp);
        if (error == ENOTDIR)
                printf("doscheckpath(): .. not a directory?\n");
        if (dep != NULL)
                vput(DETOV(dep));
        return (error);
}

/*
 * 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
readep(struct msdosfsmount *pmp, uint32_t dirclust, uint32_t 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, bn, blsize, bpp)) != 0) {
                brelse(*bpp);
                *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
readde(struct denode *dep, struct buf **bpp, struct direntry **epp)
{

        return (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.
 *
 * pdep - directory where the entry is removed
 * dep - file to be removed
 */
int
removede(struct denode *pdep, struct denode *dep)
{
        int error;
        struct direntry *ep;
        struct buf *bp;
        daddr_t bn;
        int blsize;
        struct msdosfsmount *pmp = pdep->de_pmp;
        uint32_t offset = pdep->de_fndoffset;

#ifdef MSDOSFS_DEBUG
        printf("removede(): filename %.11s, dep %p, offset %x\n",
            dep->de_Name, dep, offset);
#endif

        dep->de_refcnt--;
        offset += sizeof(struct direntry);
        do {
                offset -= sizeof(struct direntry);
                error = pcbmap(pdep, de_cluster(pmp, offset), &bn, 0, &blsize);
                if (error)
                        return error;
                error = bread(pmp->pm_devvp, bn, blsize, &bp);
                if (error) {
                        brelse(bp);
                        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 != pdep->de_fndoffset) {
                        brelse(bp);
                        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 ((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
uniqdosname(struct denode *dep, struct componentname *cnp, u_char *cp)
{
        struct msdosfsmount *pmp = dep->de_pmp;
        struct direntry *dentp;
        int gen;
        int blsize;
        uint32_t cn;
        daddr_t bn;
        struct buf *bp;
        int error;

        for (gen = 1;; gen++) {
                /*
                 * Generate DOS name with generation number
                 */
                if (!unix2dosfn((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 = pcbmap(dep, cn, &bn, 0, &blsize)) != 0) {
                                if (error == E2BIG)     /* EOF reached and not found */
                                        return 0;
                                return error;
                        }
                        error = bread(pmp->pm_devvp, bn, blsize, &bp);
                        if (error) {
                                brelse(bp);
                                return error;
                        }
                        for (dentp = (struct direntry *)bp->b_data;
                             (char *)dentp < bp->b_data + blsize;
                             dentp++) {
                                if (dentp->deName[0] == SLOT_EMPTY) {
                                        /*
                                         * Last used entry and not found
                                         */
                                        brelse(bp);
                                        return 0;
                                }
                                /*
                                 * Ignore volume labels and Win95 entries
                                 */
                                if (dentp->deAttributes & ATTR_VOLUME)
                                        continue;
                                if (!bcmp(dentp->deName, cp, 11)) {
                                        error = EEXIST;
                                        break;
                                }
                        }
                        brelse(bp);
                }
        }

        return (EEXIST);
}