Return to msdosfs_lookup.c CVS log

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Fix a bug where the root directory could look corrupted on FAT12.
I'm not sure if this fix is correct but: some comments in the code say that
it should be done this way, it fixes the particular problem, it doesn't break
anything else, noone who got the diff complained (in two months).

/*	$OpenBSD: msdosfs_lookup.c,v 1.11 1999/02/19 17:26:17 art 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/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(v)
	void *v;
{
	struct vop_lookup_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;
	struct proc *p = cnp->cn_proc;
	daddr_t bn;
	int error;
	int lockparent;
	int wantparent;
	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 vnode *pdp;
	struct denode *dp;
	struct denode *tdp;
	struct msdosfsmount *pmp;
	struct buf *bp = 0;
	struct direntry *dep;
	u_char dosfilename[12];
	int flags = cnp->cn_flags;
	int nameiop = cnp->cn_nameiop;
	int wincnt = 1;
	int chksum = -1;
	int olddos = 1;
	
#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 %08x, dp %08x, Attr %02x\n",
	    vdp, dp, dp->de_Attributes);
#endif

	/*
	 * Check accessiblity 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) {
		int vpid;

		if (error == ENOENT)
			return (error);
		/*
		 * Get the next vnode in the path.
		 * See comment below starting `Step through' for
		 * an explaination of the locking protocol.
		 */
		pdp = vdp;
		dp = VTODE(*vpp);
		vdp = *vpp;
		vpid = vdp->v_id;
		if (pdp == vdp) {   /* lookup on "." */
			VREF(vdp);
			error = 0;
		} else if (flags & ISDOTDOT) {
			VOP_UNLOCK(pdp, 0, p);
			error = vget(vdp, LK_EXCLUSIVE, p);
			if (!error && lockparent && (flags & ISLASTCN))
				error =
				    vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY, p);
		} else {
			error = vget(vdp, LK_EXCLUSIVE, p);
			if (!lockparent || error || !(flags & ISLASTCN))
				VOP_UNLOCK(pdp, 0, p);
		}
		/*
		 * Check that the capability number did not change
		 * while we were waiting for the lock.
		 */
		if (!error) {
			if (vpid == vdp->v_id) {
#ifdef MSDOSFS_DEBUG
				printf("msdosfs_lookup(): cache hit, vnode %08x, file %s\n",
				    vdp, dp->de_Name);
#endif
				return (0);
			}
			vput(vdp);
			if (lockparent && pdp != vdp && (flags & ISLASTCN))
				VOP_UNLOCK(pdp, 0, p);
		}
		if ((error = vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY, p)) != 0)
			return (error);
		vdp = pdp;
		dp = VTODE(vdp);
		*vpp = NULL;
	}

	/*
	 * 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 %s, length %d\n",
	    dosfilename, cnp->cn_namelen);
#endif
	/*
	 * Search the directory pointed at by vdp for the name pointed at
	 * by cnp->cn_nameptr.
	 */
	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, NOCRED, &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,
							    cnp->cn_namelen,
							    (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
				 */
				if (chksum != winChksum(dep->deName)
				    && (!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;
				dp->de_fndcnt = 0;	/* unused anyway */
				
				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 %d\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, 0, p);
		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, 0, p);
		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, 0, p);
		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, 0, p);	/* race to get the inode */
		if ((error = deget(pmp, cluster, blkoff, &tdp)) != 0) {
			vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY, p);
			return (error);
		}
		if (lockparent && (flags & ISLASTCN) &&
		    (error = vn_lock(pdp, LK_EXCLUSIVE | LK_RETRY, p))) {
			vput(DETOV(tdp));
			return (error);
		}
		*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, 0, p);
		*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(dep, ddep, depp, cnp)
	struct denode *dep;
	struct denode *ddep;
	struct denode **depp;
	struct componentname *cnp;
{
	int error;
	u_long 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 %08x, ddep %08x, depp %08x, cnp %08x)\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, NULL);
			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, NOCRED, &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,
					      NOCRED, &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(dep)
	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 = pcbmap(dep, cn, &bn, 0, &blsize)) != 0) {
			if (error == E2BIG)
				return (1);	/* it's empty */
			return (0);
		}
		error = bread(pmp->pm_devvp, bn, blsize, NOCRED, &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(source, target)
	struct denode *source;
	struct denode *target;
{
	daddr_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, NOCRED, &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(pmp, dirclust, diroffset, bpp, epp)
	struct msdosfsmount *pmp;
	u_long dirclust, diroffset;
	struct buf **bpp;
	struct direntry **epp;
{
	int error;
	daddr_t bn;
	int blsize;
	u_long boff;

	boff = diroffset & ~pmp->pm_crbomask;
	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, NOCRED, 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(dep, bpp, epp)
	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.
 */
int
removede(pdep, dep)
	struct denode *pdep;	/* directory where the entry is removed */
	struct denode *dep;	/* file to be removed */
{
	int error;
	struct direntry *ep;
	struct buf *bp;
	daddr_t bn;
	int blsize;
	struct msdosfsmount *pmp = pdep->de_pmp;
	u_long offset = pdep->de_fndoffset;
	
#ifdef MSDOSFS_DEBUG
	printf("removede(): filename %s, dep %08x, offset %08x\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, NOCRED, &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 agressive 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(dep, cnp, cp)
	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 (!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, NOCRED, &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);
}

/*
 * Find any Win'95 long filename entry in directory dep
 */
int
findwin95(dep)
	struct denode *dep;
{
	struct msdosfsmount *pmp = dep->de_pmp;
	struct direntry *dentp;
	int blsize;
	u_long cn;
	daddr_t bn;
	struct buf *bp;

	/*
	 * Read through the directory looking for Win'95 entries
	 * Note: Error currently handled just as EOF			XXX
	 */
	for (cn = 0;; cn++) {
		if (pcbmap(dep, cn, &bn, 0, &blsize))
			return 0;
		if (bread(pmp->pm_devvp, bn, blsize, NOCRED, &bp)) {
			brelse(bp);
			return 0;
		}
		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;
			}
			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);
				return 1;
			}
		}
		brelse(bp);
	}
}