xref: /freebsd/sys/fs/msdosfs/msdosfs_vnops.c (revision dd4f32ae62426a10a84b4322756d82c06c202c4e)

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

/*-
 * SPDX-License-Identifier: BSD-4-Clause
 *
 * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
 * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
 * All rights reserved.
 * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by TooLs GmbH.
 * 4. The name of TooLs GmbH may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
/*-
 * Written by Paul Popelka (paulp@uts.amdahl.com)
 *
 * You can do anything you want with this software, just don't say you wrote
 * it, and don't remove this notice.
 *
 * This software is provided "as is".
 *
 * The author supplies this software to be publicly redistributed on the
 * understanding that the author is not responsible for the correct
 * functioning of this software in any circumstances and is not liable for
 * any damages caused by this software.
 *
 * October 1992
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/clock.h>
#include <sys/dirent.h>
#include <sys/lock.h>
#include <sys/lockf.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/unistd.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>

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

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

/*
 * Prototypes for MSDOSFS vnode operations
 */
static vop_create_t	msdosfs_create;
static vop_mknod_t	msdosfs_mknod;
static vop_open_t	msdosfs_open;
static vop_close_t	msdosfs_close;
static vop_access_t	msdosfs_access;
static vop_getattr_t	msdosfs_getattr;
static vop_setattr_t	msdosfs_setattr;
static vop_read_t	msdosfs_read;
static vop_write_t	msdosfs_write;
static vop_fsync_t	msdosfs_fsync;
static vop_remove_t	msdosfs_remove;
static vop_link_t	msdosfs_link;
static vop_rename_t	msdosfs_rename;
static vop_mkdir_t	msdosfs_mkdir;
static vop_rmdir_t	msdosfs_rmdir;
static vop_symlink_t	msdosfs_symlink;
static vop_readdir_t	msdosfs_readdir;
static vop_bmap_t	msdosfs_bmap;
static vop_getpages_t	msdosfs_getpages;
static vop_strategy_t	msdosfs_strategy;
static vop_print_t	msdosfs_print;
static vop_pathconf_t	msdosfs_pathconf;
static vop_vptofh_t	msdosfs_vptofh;

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

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

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

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

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

	ndirent.de_Attributes = ATTR_ARCHIVE;
	ndirent.de_LowerCase = 0;
	ndirent.de_StartCluster = 0;
	ndirent.de_FileSize = 0;
	ndirent.de_pmp = pdep->de_pmp;
	ndirent.de_flag = DE_ACCESS | DE_CREATE | DE_UPDATE;
	vfs_timestamp(&ts);
	DETIMES(&ndirent, &ts, &ts, &ts);
	error = createde(&ndirent, pdep, &dep, cnp);
	if (error)
		goto bad;
	*ap->a_vpp = DETOV(dep);
	if ((cnp->cn_flags & MAKEENTRY) != 0)
		cache_enter(ap->a_dvp, *ap->a_vpp, cnp);
	return (0);

bad:
	return (error);
}

static int
msdosfs_mknod(struct vop_mknod_args *ap)
{

    return (EINVAL);
}

static int
msdosfs_open(struct vop_open_args *ap)
{
	struct denode *dep = VTODE(ap->a_vp);
	vnode_create_vobject(ap->a_vp, dep->de_FileSize, ap->a_td);
	return 0;
}

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

	VI_LOCK(vp);
	if (vp->v_usecount > 1) {
		vfs_timestamp(&ts);
		DETIMES(dep, &ts, &ts, &ts);
	}
	VI_UNLOCK(vp);
	return 0;
}

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

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

	/*
	 * Disallow writing to directories and regular files if the
	 * filesystem is read-only.
	 */
	if (accmode & VWRITE) {
		switch (vp->v_type) {
		case VREG:
		case VDIR:
			if (vp->v_mount->mnt_flag & MNT_RDONLY)
				return (EROFS);
			break;
		default:
			break;
		}
	}

	return (vaccess(vp->v_type, file_mode, pmp->pm_uid, pmp->pm_gid,
	    ap->a_accmode, ap->a_cred));
}

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

	vfs_timestamp(&ts);
	DETIMES(dep, &ts, &ts, &ts);
	vap->va_fsid = dev2udev(pmp->pm_dev);
	/*
	 * The following computation of the fileid must be the same as that
	 * used in msdosfs_readdir() to compute d_fileno. If not, pwd
	 * doesn't work.
	 */
	if (dep->de_Attributes & ATTR_DIRECTORY) {
		fileid = (uint64_t)cntobn(pmp, dep->de_StartCluster) *
		    dirsperblk;
		if (dep->de_StartCluster == MSDOSFSROOT)
			fileid = 1;
	} else {
		fileid = (uint64_t)cntobn(pmp, dep->de_dirclust) *
		    dirsperblk;
		if (dep->de_dirclust == MSDOSFSROOT)
			fileid = (uint64_t)roottobn(pmp, 0) * dirsperblk;
		fileid += (uoff_t)dep->de_diroffset / sizeof(struct direntry);
	}
	vap->va_fileid = fileid;

	mode = S_IRWXU|S_IRWXG|S_IRWXO;
	if (dep->de_Attributes & ATTR_READONLY)
		mode &= ~(S_IWUSR|S_IWGRP|S_IWOTH);
	vap->va_mode = mode &
	    (ap->a_vp->v_type == VDIR ? pmp->pm_dirmask : pmp->pm_mask);
	vap->va_uid = pmp->pm_uid;
	vap->va_gid = pmp->pm_gid;
	vap->va_nlink = 1;
	vap->va_rdev = NODEV;
	vap->va_size = dep->de_FileSize;
	fattime2timespec(dep->de_MDate, dep->de_MTime, 0, 0, &vap->va_mtime);
	vap->va_ctime = vap->va_mtime;
	if (pmp->pm_flags & MSDOSFSMNT_LONGNAME) {
		fattime2timespec(dep->de_ADate, 0, 0, 0, &vap->va_atime);
		fattime2timespec(dep->de_CDate, dep->de_CTime, dep->de_CHun,
		    0, &vap->va_birthtime);
	} else {
		vap->va_atime = vap->va_mtime;
		vap->va_birthtime.tv_sec = -1;
		vap->va_birthtime.tv_nsec = 0;
	}
	vap->va_flags = 0;
	if (dep->de_Attributes & ATTR_ARCHIVE)
		vap->va_flags |= UF_ARCHIVE;
	if (dep->de_Attributes & ATTR_HIDDEN)
		vap->va_flags |= UF_HIDDEN;
	if (dep->de_Attributes & ATTR_READONLY)
		vap->va_flags |= UF_READONLY;
	if (dep->de_Attributes & ATTR_SYSTEM)
		vap->va_flags |= UF_SYSTEM;
	vap->va_gen = 0;
	vap->va_blocksize = pmp->pm_bpcluster;
	if (dep->de_StartCluster != MSDOSFSROOT)
		vap->va_bytes =
		    (dep->de_FileSize + pmp->pm_crbomask) & ~pmp->pm_crbomask;
	else
		vap->va_bytes = 0; /* FAT12/FAT16 root dir in reserved area */
	vap->va_type = ap->a_vp->v_type;
	vap->va_filerev = dep->de_modrev;
	return (0);
}

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

#ifdef MSDOSFS_DEBUG
	printf("msdosfs_setattr(): vp %p, vap %p, cred %p\n",
	    ap->a_vp, vap, cred);
#endif

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

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

	if (vap->va_flags != VNOVAL) {
		if (vp->v_mount->mnt_flag & MNT_RDONLY)
			return (EROFS);
		if (cred->cr_uid != pmp->pm_uid) {
			error = priv_check_cred(cred, PRIV_VFS_ADMIN);
			if (error)
				return (error);
		}
		/*
		 * We are very inconsistent about handling unsupported
		 * attributes.  We ignored the access time and the
		 * read and execute bits.  We were strict for the other
		 * attributes.
		 */
		if (vap->va_flags & ~(UF_ARCHIVE | UF_HIDDEN | UF_READONLY |
		    UF_SYSTEM))
			return EOPNOTSUPP;
		if (vap->va_flags & UF_ARCHIVE)
			dep->de_Attributes |= ATTR_ARCHIVE;
		else
			dep->de_Attributes &= ~ATTR_ARCHIVE;
		if (vap->va_flags & UF_HIDDEN)
			dep->de_Attributes |= ATTR_HIDDEN;
		else
			dep->de_Attributes &= ~ATTR_HIDDEN;
		/* We don't allow changing the readonly bit on directories. */
		if (vp->v_type != VDIR) {
			if (vap->va_flags & UF_READONLY)
				dep->de_Attributes |= ATTR_READONLY;
			else
				dep->de_Attributes &= ~ATTR_READONLY;
		}
		if (vap->va_flags & UF_SYSTEM)
			dep->de_Attributes |= ATTR_SYSTEM;
		else
			dep->de_Attributes &= ~ATTR_SYSTEM;
		dep->de_flag |= DE_MODIFIED;
	}

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

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

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

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

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

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

	seqcount = ap->a_ioflag >> IO_SEQSHIFT;

	isadir = dep->de_Attributes & ATTR_DIRECTORY;
	do {
		if (uio->uio_offset >= dep->de_FileSize)
			break;
		lbn = de_cluster(pmp, uio->uio_offset);
		rablock = lbn + 1;
		blsize = pmp->pm_bpcluster;
		on = uio->uio_offset & pmp->pm_crbomask;
		/*
		 * If we are operating on a directory file then be sure to
		 * do i/o with the vnode for the filesystem instead of the
		 * vnode for the directory.
		 */
		if (isadir) {
			/* convert cluster # to block # */
			error = pcbmap(dep, lbn, &lbn, 0, &blsize);
			if (error == E2BIG) {
				error = EINVAL;
				break;
			} else if (error)
				break;
			error = bread(pmp->pm_devvp, lbn, blsize, NOCRED, &bp);
		} else if (de_cn2off(pmp, rablock) >= dep->de_FileSize) {
			error = bread(vp, lbn, blsize, NOCRED, &bp);
		} else if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
			error = cluster_read(vp, dep->de_FileSize, lbn, blsize,
			    NOCRED, on + uio->uio_resid, seqcount, 0, &bp);
		} else if (seqcount > 1) {
			rasize = blsize;
			error = breadn(vp, lbn,
			    blsize, &rablock, &rasize, 1, NOCRED, &bp);
		} else {
			error = bread(vp, lbn, blsize, NOCRED, &bp);
		}
		if (error) {
			brelse(bp);
			break;
		}
		diff = pmp->pm_bpcluster - on;
		n = diff > uio->uio_resid ? uio->uio_resid : diff;
		diff = dep->de_FileSize - uio->uio_offset;
		if (diff < n)
			n = diff;
		diff = blsize - bp->b_resid;
		if (diff < n)
			n = diff;
		error = vn_io_fault_uiomove(bp->b_data + on, (int) n, uio);
		brelse(bp);
	} while (error == 0 && uio->uio_resid > 0 && n != 0);
	if (!isadir && (error == 0 || uio->uio_resid != orig_resid) &&
	    (vp->v_mount->mnt_flag & (MNT_NOATIME | MNT_RDONLY)) == 0)
		dep->de_flag |= DE_ACCESS;
	return (error);
}

/*
 * Write data to a file or directory.
 */
static int
msdosfs_write(struct vop_write_args *ap)
{
	int n;
	int croffset;
	ssize_t resid, r;
	u_long osize;
	int error = 0;
	u_long count;
	int seqcount;
	daddr_t bn, lastcn;
	struct buf *bp;
	int ioflag = ap->a_ioflag;
	struct uio *uio = ap->a_uio;
	struct vnode *vp = ap->a_vp;
	struct vnode *thisvp;
	struct denode *dep = VTODE(vp);
	struct msdosfsmount *pmp = dep->de_pmp;
	struct ucred *cred = ap->a_cred;

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

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

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

	/*
	 * The caller is supposed to ensure that
	 * uio->uio_offset >= 0 and uio->uio_resid >= 0.
	 *
	 * If they've exceeded their filesize limit, tell them about it.
	 */
	error = vn_rlimit_fsizex(vp, uio, MSDOSFS_FILESIZE_MAX, &r,
	    uio->uio_td);
	if (error != 0) {
		vn_rlimit_fsizex_res(uio, r);
		return (error);
	}

	/*
	 * If the offset we are starting the write at is beyond the end of
	 * the file, then they've done a seek.  Unix filesystems allow
	 * files with holes in them, DOS doesn't so we must fill the hole
	 * with zeroed blocks.
	 */
	if (uio->uio_offset > dep->de_FileSize) {
		error = deextend(dep, uio->uio_offset, cred);
		if (error != 0) {
			vn_rlimit_fsizex_res(uio, r);
			return (error);
		}
	}

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

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

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

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

		bn = de_cluster(pmp, uio->uio_offset);
		if ((uio->uio_offset & pmp->pm_crbomask) == 0
		    && (de_cluster(pmp, uio->uio_offset + uio->uio_resid)
			> de_cluster(pmp, uio->uio_offset)
			|| uio->uio_offset + uio->uio_resid >= dep->de_FileSize)) {
			/*
			 * If either the whole cluster gets written,
			 * or we write the cluster from its start beyond EOF,
			 * then no need to read data from disk.
			 */
			bp = getblk(thisvp, bn, pmp->pm_bpcluster, 0, 0, 0);
			/*
			 * This call to vfs_bio_clrbuf() ensures that
			 * even if vn_io_fault_uiomove() below faults,
			 * garbage from the newly instantiated buffer
			 * is not exposed to the userspace via mmap().
			 */
			vfs_bio_clrbuf(bp);
			/*
			 * Do the bmap now, since pcbmap needs buffers
			 * for the FAT table. (see msdosfs_strategy)
			 */
			if (bp->b_blkno == bp->b_lblkno) {
				error = pcbmap(dep, bp->b_lblkno, &bn, 0, 0);
				if (error)
					bp->b_blkno = -1;
				else
					bp->b_blkno = bn;
			}
			if (bp->b_blkno == -1) {
				brelse(bp);
				if (!error)
					error = EIO;		/* XXX */
				break;
			}
		} else {
			/*
			 * The block we need to write into exists, so read it in.
			 */
			error = bread(thisvp, bn, pmp->pm_bpcluster, cred, &bp);
			if (error) {
				break;
			}
		}

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

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

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

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

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

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

	vop_stdfsync(ap);

	/*
	* If the syncing request comes from fsync(2), sync the entire
	* FAT and any other metadata that happens to be on devvp.  We
	* need this mainly for the FAT.  We write the FAT sloppily, and
	* syncing it all now is the best we can easily do to get all
	* directory entries associated with the file (not just the file)
	* fully synced.  The other metadata includes critical metadata
	* for all directory entries, but only in the MNT_ASYNC case.  We
	* will soon sync all metadata in the file's directory entry.
	* Non-critical metadata for associated directory entries only
	* gets synced accidentally, as in most file systems.
	*/
	if (ap->a_waitfor != MNT_NOWAIT) {
		devvp = VTODE(ap->a_vp)->de_pmp->pm_devvp;
		vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
		allerror = VOP_FSYNC(devvp, MNT_WAIT, ap->a_td);
		VOP_UNLOCK(devvp);
	} else
		allerror = 0;

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

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

	if (ap->a_vp->v_type == VDIR)
		error = EPERM;
	else
		error = removede(ddep, dep);
#ifdef MSDOSFS_DEBUG
	printf("msdosfs_remove(), dep %p, v_usecount %d\n", dep, ap->a_vp->v_usecount);
#endif
	return (error);
}

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

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

	tdvp = ap->a_tdvp;
	fvp = ap->a_fvp;
	fdvp = ap->a_fdvp;
	tvp = ap->a_tvp;
	tcnp = ap->a_tcnp;
	fcnp = ap->a_fcnp;
	pmp = VFSTOMSDOSFS(fdvp->v_mount);

	/*
	 * Check for cross-device rename.
	 */
	if (fvp->v_mount != tdvp->v_mount ||
	    (tvp != NULL && fvp->v_mount != tvp->v_mount)) {
		error = EXDEV;
		goto abortit;
	}

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

	/*
	 * When the target exists, both the directory
	 * and target vnodes are passed locked.
	 */
	VOP_UNLOCK(tdvp);
	if (tvp != NULL && tvp != tdvp)
		VOP_UNLOCK(tvp);

	checkpath_locked = false;

relock:
	doingdirectory = newparent = false;

	error = vn_lock(fdvp, LK_EXCLUSIVE);
	if (error != 0)
		goto releout;
	if (vn_lock(tdvp, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
		VOP_UNLOCK(fdvp);
		error = vn_lock(tdvp, LK_EXCLUSIVE);
		if (error != 0)
			goto releout;
		VOP_UNLOCK(tdvp);
		goto relock;
	}

	error = msdosfs_lookup_ino(fdvp, NULL, fcnp, &scn, &blkoff);
	if (error != 0) {
		VOP_UNLOCK(fdvp);
		VOP_UNLOCK(tdvp);
		goto releout;
	}
	error = deget(pmp, scn, blkoff, LK_EXCLUSIVE | LK_NOWAIT, &nip);
	if (error != 0) {
		VOP_UNLOCK(fdvp);
		VOP_UNLOCK(tdvp);
		if (error != EBUSY)
			goto releout;
		error = deget(pmp, scn, blkoff, LK_EXCLUSIVE, &nip);
		if (error != 0)
			goto releout;
		vp = fvp;
		fvp = DETOV(nip);
		VOP_UNLOCK(fvp);
		vrele(vp);
		goto relock;
	}
	vrele(fvp);
	fvp = DETOV(nip);

	error = msdosfs_lookup_ino(tdvp, NULL, tcnp, &scn, &blkoff);
	if (error != 0 && error != EJUSTRETURN) {
		VOP_UNLOCK(fdvp);
		VOP_UNLOCK(tdvp);
		VOP_UNLOCK(fvp);
		goto releout;
	}
	if (error == EJUSTRETURN && tvp != NULL) {
		vrele(tvp);
		tvp = NULL;
	}
	if (error == 0) {
		nip = NULL;
		error = deget(pmp, scn, blkoff, LK_EXCLUSIVE | LK_NOWAIT,
		    &nip);
		if (tvp != NULL) {
			vrele(tvp);
			tvp = NULL;
		}
		if (error != 0) {
			VOP_UNLOCK(fdvp);
			VOP_UNLOCK(tdvp);
			VOP_UNLOCK(fvp);
			if (error != EBUSY)
				goto releout;
			error = deget(pmp, scn, blkoff, LK_EXCLUSIVE,
			    &nip);
			if (error != 0)
				goto releout;
			vput(DETOV(nip));
			goto relock;
		}
		tvp = DETOV(nip);
	}

	fdip = VTODE(fdvp);
	fip = VTODE(fvp);
	tdip = VTODE(tdvp);
	tip = tvp != NULL ? VTODE(tvp) : NULL;

	/*
	 * Remember direntry place to use for destination
	 */
	to_diroffset = tdip->de_fndoffset;

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

	/*
	 * If ".." must be changed (ie the directory gets a new
	 * parent) then the source directory must not be in the
	 * directory hierarchy above the target, as this would
	 * orphan everything below the source directory. Also
	 * the user must have write permission in the source so
	 * as to be able to change "..". We must repeat the call
	 * to namei, as the parent directory is unlocked by the
	 * call to doscheckpath().
	 */
	error = VOP_ACCESS(fvp, VWRITE, tcnp->cn_cred, curthread);
	if (fdip->de_StartCluster != tdip->de_StartCluster)
		newparent = true;
	if (doingdirectory && newparent) {
		if (error != 0)	/* write access check above */
			goto unlock;
		lockmgr(&pmp->pm_checkpath_lock, LK_EXCLUSIVE, NULL);
		checkpath_locked = true;
		error = doscheckpath(fip, tdip, &wait_scn);
		if (wait_scn != 0) {
			lockmgr(&pmp->pm_checkpath_lock, LK_RELEASE, NULL);
			checkpath_locked = false;
			VOP_UNLOCK(fdvp);
			VOP_UNLOCK(tdvp);
			VOP_UNLOCK(fvp);
			if (tvp != NULL && tvp != tdvp)
				VOP_UNLOCK(tvp);
			error = deget(pmp, wait_scn, 0, LK_EXCLUSIVE,
			    &nip);
			if (error == 0) {
				vput(DETOV(nip));
				goto relock;
			}
		}
		if (error != 0)
			goto unlock;
	}

	if (tip != NULL) {
		/*
		 * Target must be empty if a directory and have no links
		 * to it. Also, ensure source and target are compatible
		 * (both directories, or both not directories).
		 */
		if ((tip->de_Attributes & ATTR_DIRECTORY) != 0) {
			if (!dosdirempty(tip)) {
				error = ENOTEMPTY;
				goto unlock;
			}
			if (!doingdirectory) {
				error = ENOTDIR;
				goto unlock;
			}
			cache_purge(tdvp);
		} else if (doingdirectory) {
			error = EISDIR;
			goto unlock;
		}
		error = msdosfs_lookup_ino(tdvp, NULL, tcnp, &scn, &blkoff);
		MPASS(error == 0);
		error = removede(tdip, tip);
		if (error != 0)
			goto unlock;
		vput(tvp);
		tvp = NULL;
		tip = NULL;
	}

	/*
	 * Convert the filename in tcnp into a dos filename. We copy this
	 * into the denode and directory entry for the destination
	 * file/directory.
	 */
	error = uniqdosname(tdip, tcnp, toname);
	if (error != 0)
		goto unlock;

	/*
	 * First write a new entry in the destination
	 * directory and mark the entry in the source directory
	 * as deleted.  Then move the denode to the correct hash
	 * chain for its new location in the filesystem.  And, if
	 * we moved a directory, then update its .. entry to point
	 * to the new parent directory.
	 */
	memcpy(oldname, fip->de_Name, 11);
	memcpy(fip->de_Name, toname, 11);	/* update denode */
	error = msdosfs_lookup_ino(tdvp, NULL, tcnp, &scn, &blkoff);
	MPASS(error == EJUSTRETURN);
	error = createde(fip, tdip, NULL, tcnp);
	if (error != 0) {
		memcpy(fip->de_Name, oldname, 11);
		goto unlock;
	}

	/*
	 * If fip is for a directory, then its name should always
	 * be "." since it is for the directory entry in the
	 * directory itself (msdosfs_lookup() always translates
	 * to the "." entry so as to get a unique denode, except
	 * for the root directory there are different
	 * complications).  However, we just corrupted its name
	 * to pass the correct name to createde().  Undo this.
	 */
	if ((fip->de_Attributes & ATTR_DIRECTORY) != 0)
		memcpy(fip->de_Name, oldname, 11);
	fip->de_refcnt++;
	error = msdosfs_lookup_ino(fdvp, NULL, fcnp, &scn, &blkoff);
	MPASS(error == 0);
	error = removede(fdip, fip);
	if (error != 0) {
		/* XXX should downgrade to ro here, fs is corrupt */
		goto unlock;
	}
	if (!doingdirectory) {
		error = pcbmap(tdip, de_cluster(pmp, to_diroffset), 0,
		    &fip->de_dirclust, 0);
		if (error != 0) {
			/*
			 * XXX should downgrade to ro here,
			 * fs is corrupt
			 */
			goto unlock;
		}
		if (fip->de_dirclust == MSDOSFSROOT)
			fip->de_diroffset = to_diroffset;
		else
			fip->de_diroffset = to_diroffset & pmp->pm_crbomask;
	}
	reinsert(fip);

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

	/*
	 * The msdosfs lookup is case insensitive. Several aliases may
	 * be inserted for a single directory entry. As a consequnce,
	 * name cache purge done by lookup for fvp when DELETE op for
	 * namei is specified, might be not enough to expunge all
	 * namecache entries that were installed for this direntry.
	 */
	cache_purge(fvp);

unlock:
	if (checkpath_locked)
		lockmgr(&pmp->pm_checkpath_lock, LK_RELEASE, NULL);
	vput(fdvp);
	vput(fvp);
	if (tvp != NULL) {
		if (tvp != tdvp)
			vput(tvp);
		else
			vrele(tvp);
	}
	vput(tdvp);
	return (error);
releout:
	MPASS(!checkpath_locked);
	vrele(tdvp);
	if (tvp != NULL)
		vrele(tvp);
	vrele(fdvp);
	vrele(fvp);
	return (error);
abortit:
	if (tdvp == tvp)
		vrele(tdvp);
	else
		vput(tdvp);
	if (tvp != NULL)
		vput(tvp);
	vrele(fdvp);
	vrele(fvp);
	return (error);
}

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

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

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

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

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

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

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

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

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

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

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

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

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

out:
	return (error);
}

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

static int
msdosfs_readdir(struct vop_readdir_args *ap)
{
	struct mbnambuf nb;
	int error = 0;
	int diff;
	long n;
	int blsize;
	long on;
	u_long cn;
	u_long dirsperblk;
	long bias = 0;
	daddr_t bn, lbn;
	struct buf *bp;
	struct denode *dep = VTODE(ap->a_vp);
	struct msdosfsmount *pmp = dep->de_pmp;
	struct direntry *dentp;
	struct dirent dirbuf;
	struct uio *uio = ap->a_uio;
	uint64_t *cookies = NULL;
	int ncookies = 0;
	off_t offset, off;
	int chksum = -1;

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

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

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

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

	if (ap->a_ncookies) {
		ncookies = uio->uio_resid / 16;
		cookies = malloc(ncookies * sizeof(*cookies), M_TEMP,
		       M_WAITOK);
		*ap->a_cookies = cookies;
		*ap->a_ncookies = ncookies;
	}

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

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

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

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

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

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

			if (chksum != winChksum(dentp->deName)) {
				dirbuf.d_namlen = dos2unixfn(dentp->deName,
				    (u_char *)dirbuf.d_name,
				    dentp->deLowerCase |
					((pmp->pm_flags & MSDOSFSMNT_SHORTNAME) ?
					(LCASE_BASE | LCASE_EXT) : 0),
				    pmp);
				mbnambuf_init(&nb);
			} else
				mbnambuf_flush(&nb, &dirbuf);
			chksum = -1;
			dirbuf.d_reclen = GENERIC_DIRSIZ(&dirbuf);
			/* NOTE: d_off is the offset of the *next* entry. */
			dirbuf.d_off = offset + sizeof(struct direntry);
			dirent_terminate(&dirbuf);
			if (uio->uio_resid < dirbuf.d_reclen) {
				brelse(bp);
				goto out;
			}
			error = uiomove(&dirbuf, dirbuf.d_reclen, uio);
			if (error) {
				brelse(bp);
				goto out;
			}
			if (cookies) {
				*cookies++ = offset + sizeof(struct direntry);
				if (--ncookies <= 0) {
					brelse(bp);
					goto out;
				}
			}
			off = offset + sizeof(struct direntry);
		}
		brelse(bp);
	}
out:
	/* Subtract unused cookies */
	if (ap->a_ncookies)
		*ap->a_ncookies -= ncookies;

	uio->uio_offset = off;

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

/*-
 * a_vp   - pointer to the file's vnode
 * a_bn   - logical block number within the file (cluster number for us)
 * a_bop  - where to return the bufobj of the special file containing the fs
 * a_bnp  - where to return the "physical" block number corresponding to a_bn
 *          (relative to the special file; units are blocks of size DEV_BSIZE)
 * a_runp - where to return the "run past" a_bn.  This is the count of logical
 *          blocks whose physical blocks (together with a_bn's physical block)
 *          are contiguous.
 * a_runb - where to return the "run before" a_bn.
 */
static int
msdosfs_bmap(struct vop_bmap_args *ap)
{
	struct fatcache savefc;
	struct denode *dep;
	struct mount *mp;
	struct msdosfsmount *pmp;
	struct vnode *vp;
	daddr_t runbn;
	u_long cn;
	int bnpercn, error, maxio, maxrun, run;

	vp = ap->a_vp;
	dep = VTODE(vp);
	pmp = dep->de_pmp;
	if (ap->a_bop != NULL)
		*ap->a_bop = &pmp->pm_devvp->v_bufobj;
	if (ap->a_bnp == NULL)
		return (0);
	if (ap->a_runp != NULL)
		*ap->a_runp = 0;
	if (ap->a_runb != NULL)
		*ap->a_runb = 0;
	cn = ap->a_bn;
	if (cn != ap->a_bn)
		return (EFBIG);
	error = pcbmap(dep, cn, ap->a_bnp, NULL, NULL);
	if (error != 0 || (ap->a_runp == NULL && ap->a_runb == NULL))
		return (error);

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

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

SYSCTL_NODE(_vfs, OID_AUTO, msdosfs, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "msdos filesystem");
static int use_buf_pager = 1;
SYSCTL_INT(_vfs_msdosfs, OID_AUTO, use_buf_pager, CTLFLAG_RWTUN,
    &use_buf_pager, 0,
    "Use buffer pager instead of bmap");

static daddr_t
msdosfs_gbp_getblkno(struct vnode *vp, vm_ooffset_t off)
{

	return (de_cluster(VTODE(vp)->de_pmp, off));
}

static int
msdosfs_gbp_getblksz(struct vnode *vp, daddr_t lbn, long *sz)
{

	*sz = VTODE(vp)->de_pmp->pm_bpcluster;
	return (0);
}

static int
msdosfs_getpages(struct vop_getpages_args *ap)
{

	if (use_buf_pager)
		return (vfs_bio_getpages(ap->a_vp, ap->a_m, ap->a_count,
		    ap->a_rbehind, ap->a_rahead, msdosfs_gbp_getblkno,
		    msdosfs_gbp_getblksz));
	return (vnode_pager_generic_getpages(ap->a_vp, ap->a_m, ap->a_count,
	    ap->a_rbehind, ap->a_rahead, NULL, NULL));
}

static int
msdosfs_strategy(struct vop_strategy_args *ap)
{
	struct buf *bp = ap->a_bp;
	struct denode *dep = VTODE(ap->a_vp);
	struct bufobj *bo;
	int error = 0;
	daddr_t blkno;

	/*
	 * If we don't already know the filesystem relative block number
	 * then get it using pcbmap().  If pcbmap() returns the block
	 * number as -1 then we've got a hole in the file.  DOS filesystems
	 * don't allow files with holes, so we shouldn't ever see this.
	 */
	if (bp->b_blkno == bp->b_lblkno) {
		error = pcbmap(dep, bp->b_lblkno, &blkno, 0, 0);
		bp->b_blkno = blkno;
		if (error) {
			bp->b_error = error;
			bp->b_ioflags |= BIO_ERROR;
			bufdone(bp);
			return (0);
		}
		if ((long)bp->b_blkno == -1)
			vfs_bio_clrbuf(bp);
	}
	if (bp->b_blkno == -1) {
		bufdone(bp);
		return (0);
	}
	/*
	 * Read/write the block from/to the disk that contains the desired
	 * file block.
	 */
	bp->b_iooffset = dbtob(bp->b_blkno);
	bo = dep->de_pmp->pm_bo;
	BO_STRATEGY(bo, bp);
	return (0);
}

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

	printf("\tstartcluster %lu, dircluster %lu, diroffset %lu, ",
	       dep->de_StartCluster, dep->de_dirclust, dep->de_diroffset);
	printf("on dev %s\n", devtoname(dep->de_pmp->pm_dev));
	return (0);
}

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

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

static int
msdosfs_vptofh(struct vop_vptofh_args *ap)
{
	struct denode *dep;
	struct defid *defhp;

	dep = VTODE(ap->a_vp);
	defhp = (struct defid *)ap->a_fhp;
	defhp->defid_len = sizeof(struct defid);
	defhp->defid_dirclust = dep->de_dirclust;
	defhp->defid_dirofs = dep->de_diroffset;
	/* defhp->defid_gen = dep->de_gen; */
	return (0);
}

/* Global vfs data structures for msdosfs */
struct vop_vector msdosfs_vnodeops = {
	.vop_default =		&default_vnodeops,

	.vop_access =		msdosfs_access,
	.vop_bmap =		msdosfs_bmap,
	.vop_getpages =		msdosfs_getpages,
	.vop_cachedlookup =	msdosfs_lookup,
	.vop_open =		msdosfs_open,
	.vop_close =		msdosfs_close,
	.vop_create =		msdosfs_create,
	.vop_fsync =		msdosfs_fsync,
	.vop_fdatasync =	vop_stdfdatasync_buf,
	.vop_getattr =		msdosfs_getattr,
	.vop_inactive =		msdosfs_inactive,
	.vop_link =		msdosfs_link,
	.vop_lookup =		vfs_cache_lookup,
	.vop_mkdir =		msdosfs_mkdir,
	.vop_mknod =		msdosfs_mknod,
	.vop_pathconf =		msdosfs_pathconf,
	.vop_print =		msdosfs_print,
	.vop_read =		msdosfs_read,
	.vop_readdir =		msdosfs_readdir,
	.vop_reclaim =		msdosfs_reclaim,
	.vop_remove =		msdosfs_remove,
	.vop_rename =		msdosfs_rename,
	.vop_rmdir =		msdosfs_rmdir,
	.vop_setattr =		msdosfs_setattr,
	.vop_strategy =		msdosfs_strategy,
	.vop_symlink =		msdosfs_symlink,
	.vop_write =		msdosfs_write,
	.vop_vptofh =		msdosfs_vptofh,
};
VFS_VOP_VECTOR_REGISTER(msdosfs_vnodeops);