xref: /freebsd/sys/fs/devfs/devfs_vnops.c (revision 6d79564f)

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2000-2004
 *	Poul-Henning Kamp.  All rights reserved.
 * Copyright (c) 1989, 1992-1993, 1995
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software donated to Berkeley by
 * Jan-Simon Pendry.
 *
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 THE REGENTS OR CONTRIBUTORS 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.
 * From: FreeBSD: src/sys/miscfs/kernfs/kernfs_vnops.c 1.43
 */

/*
 * TODO:
 *	mkdir: want it ?
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/dirent.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/filio.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/stat.h>
#include <sys/sx.h>
#include <sys/sysctl.h>
#include <sys/time.h>
#include <sys/ttycom.h>
#include <sys/unistd.h>
#include <sys/vnode.h>

static struct vop_vector devfs_vnodeops;
static struct vop_vector devfs_specops;
static struct fileops devfs_ops_f;

#include <fs/devfs/devfs.h>
#include <fs/devfs/devfs_int.h>

#include <security/mac/mac_framework.h>

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

static MALLOC_DEFINE(M_CDEVPDATA, "DEVFSP", "Metainfo for cdev-fp data");

struct mtx	devfs_de_interlock;
MTX_SYSINIT(devfs_de_interlock, &devfs_de_interlock, "devfs interlock", MTX_DEF);
struct mtx	cdevpriv_mtx;
MTX_SYSINIT(cdevpriv_mtx, &cdevpriv_mtx, "cdevpriv lock", MTX_DEF);

SYSCTL_DECL(_vfs_devfs);

static int devfs_dotimes;
SYSCTL_INT(_vfs_devfs, OID_AUTO, dotimes, CTLFLAG_RW,
    &devfs_dotimes, 0, "Update timestamps on DEVFS with default precision");

/*
 * Update devfs node timestamp.  Note that updates are unlocked and
 * stat(2) could see partially updated times.
 */
static void
devfs_timestamp(struct timespec *tsp)
{
	time_t ts;

	if (devfs_dotimes) {
		vfs_timestamp(tsp);
	} else {
		ts = time_second;
		if (tsp->tv_sec != ts) {
			tsp->tv_sec = ts;
			tsp->tv_nsec = 0;
		}
	}
}

static int
devfs_fp_check(struct file *fp, struct cdev **devp, struct cdevsw **dswp,
    int *ref)
{
	*dswp = devvn_refthread(fp->f_vnode, devp, ref);
	if (*dswp == NULL || *devp != fp->f_data) {
		if (*dswp != NULL)
			dev_relthread(*devp, *ref);
		return (ENXIO);
	}
	KASSERT((*devp)->si_refcount > 0,
	    ("devfs: un-referenced struct cdev *(%s)", devtoname(*devp)));
	if (*dswp == NULL)
		return (ENXIO);
	curthread->td_fpop = fp;
	return (0);
}

int
devfs_get_cdevpriv(void **datap)
{
	struct file *fp;
	struct cdev_privdata *p;
	int error;

	fp = curthread->td_fpop;
	if (fp == NULL)
		return (EBADF);
	p = fp->f_cdevpriv;
	if (p != NULL) {
		error = 0;
		*datap = p->cdpd_data;
	} else
		error = ENOENT;
	return (error);
}

int
devfs_set_cdevpriv(void *priv, d_priv_dtor_t *priv_dtr)
{
	struct file *fp;
	struct cdev_priv *cdp;
	struct cdev_privdata *p;
	int error;

	fp = curthread->td_fpop;
	if (fp == NULL)
		return (ENOENT);
	cdp = cdev2priv((struct cdev *)fp->f_data);
	p = malloc(sizeof(struct cdev_privdata), M_CDEVPDATA, M_WAITOK);
	p->cdpd_data = priv;
	p->cdpd_dtr = priv_dtr;
	p->cdpd_fp = fp;
	mtx_lock(&cdevpriv_mtx);
	if (fp->f_cdevpriv == NULL) {
		LIST_INSERT_HEAD(&cdp->cdp_fdpriv, p, cdpd_list);
		fp->f_cdevpriv = p;
		mtx_unlock(&cdevpriv_mtx);
		error = 0;
	} else {
		mtx_unlock(&cdevpriv_mtx);
		free(p, M_CDEVPDATA);
		error = EBUSY;
	}
	return (error);
}

int
devfs_foreach_cdevpriv(struct cdev *dev, int (*cb)(void *data, void *arg),
    void *arg)
{
	struct cdev_priv *cdp;
	struct cdev_privdata *p;
	int error;

	cdp = cdev2priv(dev);
	error = 0;
	mtx_lock(&cdevpriv_mtx);
	LIST_FOREACH(p, &cdp->cdp_fdpriv, cdpd_list) {
		error = cb(p->cdpd_data, arg);
		if (error != 0)
			break;
	}
	mtx_unlock(&cdevpriv_mtx);
	return (error);
}

void
devfs_destroy_cdevpriv(struct cdev_privdata *p)
{

	mtx_assert(&cdevpriv_mtx, MA_OWNED);
	KASSERT(p->cdpd_fp->f_cdevpriv == p,
	    ("devfs_destoy_cdevpriv %p != %p", p->cdpd_fp->f_cdevpriv, p));
	p->cdpd_fp->f_cdevpriv = NULL;
	LIST_REMOVE(p, cdpd_list);
	mtx_unlock(&cdevpriv_mtx);
	(p->cdpd_dtr)(p->cdpd_data);
	free(p, M_CDEVPDATA);
}

static void
devfs_fpdrop(struct file *fp)
{
	struct cdev_privdata *p;

	mtx_lock(&cdevpriv_mtx);
	if ((p = fp->f_cdevpriv) == NULL) {
		mtx_unlock(&cdevpriv_mtx);
		return;
	}
	devfs_destroy_cdevpriv(p);
}

void
devfs_clear_cdevpriv(void)
{
	struct file *fp;

	fp = curthread->td_fpop;
	if (fp == NULL)
		return;
	devfs_fpdrop(fp);
}

static void
devfs_usecount_add(struct vnode *vp)
{
	struct devfs_dirent *de;
	struct cdev *dev;

	mtx_lock(&devfs_de_interlock);
	VI_LOCK(vp);
	VNPASS(vp->v_type == VCHR || vp->v_type == VBAD, vp);
	if (VN_IS_DOOMED(vp)) {
		goto out_unlock;
	}

	de = vp->v_data;
	dev = vp->v_rdev;
	MPASS(de != NULL);
	MPASS(dev != NULL);
	dev->si_usecount++;
	de->de_usecount++;
out_unlock:
	VI_UNLOCK(vp);
	mtx_unlock(&devfs_de_interlock);
}

static void
devfs_usecount_subl(struct vnode *vp)
{
	struct devfs_dirent *de;
	struct cdev *dev;

	mtx_assert(&devfs_de_interlock, MA_OWNED);
	ASSERT_VI_LOCKED(vp, __func__);
	VNPASS(vp->v_type == VCHR || vp->v_type == VBAD, vp);

	de = vp->v_data;
	dev = vp->v_rdev;
	if (de == NULL)
		return;
	if (dev == NULL) {
		MPASS(de->de_usecount == 0);
		return;
	}
	if (dev->si_usecount < de->de_usecount)
		panic("%s: si_usecount underflow for dev %p "
		    "(has %ld, dirent has %d)\n",
		    __func__, dev, dev->si_usecount, de->de_usecount);
	if (VN_IS_DOOMED(vp)) {
		dev->si_usecount -= de->de_usecount;
		de->de_usecount = 0;
	} else {
		if (de->de_usecount == 0)
			panic("%s: de_usecount underflow for dev %p\n",
			    __func__, dev);
		dev->si_usecount--;
		de->de_usecount--;
	}
}

static void
devfs_usecount_sub(struct vnode *vp)
{

	mtx_lock(&devfs_de_interlock);
	VI_LOCK(vp);
	devfs_usecount_subl(vp);
	VI_UNLOCK(vp);
	mtx_unlock(&devfs_de_interlock);
}

static int
devfs_usecountl(struct vnode *vp)
{

	VNPASS(vp->v_type == VCHR, vp);
	mtx_assert(&devfs_de_interlock, MA_OWNED);
	ASSERT_VI_LOCKED(vp, __func__);
	return (vp->v_rdev->si_usecount);
}

int
devfs_usecount(struct vnode *vp)
{
	int count;

	VNPASS(vp->v_type == VCHR, vp);
	mtx_lock(&devfs_de_interlock);
	VI_LOCK(vp);
	count = devfs_usecountl(vp);
	VI_UNLOCK(vp);
	mtx_unlock(&devfs_de_interlock);
	return (count);
}

void
devfs_ctty_ref(struct vnode *vp)
{

	vrefact(vp);
	devfs_usecount_add(vp);
}

void
devfs_ctty_unref(struct vnode *vp)
{

	devfs_usecount_sub(vp);
	vrele(vp);
}

/*
 * On success devfs_populate_vp() returns with dmp->dm_lock held.
 */
static int
devfs_populate_vp(struct vnode *vp)
{
	struct devfs_dirent *de;
	struct devfs_mount *dmp;
	int locked;

	ASSERT_VOP_LOCKED(vp, "devfs_populate_vp");

	dmp = VFSTODEVFS(vp->v_mount);
	if (!devfs_populate_needed(dmp)) {
		sx_xlock(&dmp->dm_lock);
		goto out_nopopulate;
	}

	locked = VOP_ISLOCKED(vp);

	sx_xlock(&dmp->dm_lock);
	DEVFS_DMP_HOLD(dmp);

	/* Can't call devfs_populate() with the vnode lock held. */
	VOP_UNLOCK(vp);
	devfs_populate(dmp);

	sx_xunlock(&dmp->dm_lock);
	vn_lock(vp, locked | LK_RETRY);
	sx_xlock(&dmp->dm_lock);
	if (DEVFS_DMP_DROP(dmp)) {
		sx_xunlock(&dmp->dm_lock);
		devfs_unmount_final(dmp);
		return (ERESTART);
	}
out_nopopulate:
	if (VN_IS_DOOMED(vp)) {
		sx_xunlock(&dmp->dm_lock);
		return (ERESTART);
	}
	de = vp->v_data;
	KASSERT(de != NULL,
	    ("devfs_populate_vp: vp->v_data == NULL but vnode not doomed"));
	if ((de->de_flags & DE_DOOMED) != 0) {
		sx_xunlock(&dmp->dm_lock);
		return (ERESTART);
	}

	return (0);
}

static int
devfs_vptocnp(struct vop_vptocnp_args *ap)
{
	struct vnode *vp = ap->a_vp;
	struct vnode **dvp = ap->a_vpp;
	struct devfs_mount *dmp;
	char *buf = ap->a_buf;
	size_t *buflen = ap->a_buflen;
	struct devfs_dirent *dd, *de;
	int i, error;

	dmp = VFSTODEVFS(vp->v_mount);

	error = devfs_populate_vp(vp);
	if (error != 0)
		return (error);

	if (vp->v_type != VCHR && vp->v_type != VDIR) {
		error = ENOENT;
		goto finished;
	}

	dd = vp->v_data;
	if (vp->v_type == VDIR && dd == dmp->dm_rootdir) {
		*dvp = vp;
		vref(*dvp);
		goto finished;
	}

	i = *buflen;
	i -= dd->de_dirent->d_namlen;
	if (i < 0) {
		error = ENOMEM;
		goto finished;
	}
	bcopy(dd->de_dirent->d_name, buf + i, dd->de_dirent->d_namlen);
	*buflen = i;
	de = devfs_parent_dirent(dd);
	if (de == NULL) {
		error = ENOENT;
		goto finished;
	}
	mtx_lock(&devfs_de_interlock);
	*dvp = de->de_vnode;
	if (*dvp != NULL) {
		VI_LOCK(*dvp);
		mtx_unlock(&devfs_de_interlock);
		vholdl(*dvp);
		VI_UNLOCK(*dvp);
		vref(*dvp);
		vdrop(*dvp);
	} else {
		mtx_unlock(&devfs_de_interlock);
		error = ENOENT;
	}
finished:
	sx_xunlock(&dmp->dm_lock);
	return (error);
}

/*
 * Construct the fully qualified path name relative to the mountpoint.
 * If a NULL cnp is provided, no '/' is appended to the resulting path.
 */
char *
devfs_fqpn(char *buf, struct devfs_mount *dmp, struct devfs_dirent *dd,
    struct componentname *cnp)
{
	int i;
	struct devfs_dirent *de;

	sx_assert(&dmp->dm_lock, SA_LOCKED);

	i = SPECNAMELEN;
	buf[i] = '\0';
	if (cnp != NULL)
		i -= cnp->cn_namelen;
	if (i < 0)
		 return (NULL);
	if (cnp != NULL)
		bcopy(cnp->cn_nameptr, buf + i, cnp->cn_namelen);
	de = dd;
	while (de != dmp->dm_rootdir) {
		if (cnp != NULL || i < SPECNAMELEN) {
			i--;
			if (i < 0)
				 return (NULL);
			buf[i] = '/';
		}
		i -= de->de_dirent->d_namlen;
		if (i < 0)
			 return (NULL);
		bcopy(de->de_dirent->d_name, buf + i,
		    de->de_dirent->d_namlen);
		de = devfs_parent_dirent(de);
		if (de == NULL)
			return (NULL);
	}
	return (buf + i);
}

static int
devfs_allocv_drop_refs(int drop_dm_lock, struct devfs_mount *dmp,
	struct devfs_dirent *de)
{
	int not_found;

	not_found = 0;
	if (de->de_flags & DE_DOOMED)
		not_found = 1;
	if (DEVFS_DE_DROP(de)) {
		KASSERT(not_found == 1, ("DEVFS de dropped but not doomed"));
		devfs_dirent_free(de);
	}
	if (DEVFS_DMP_DROP(dmp)) {
		KASSERT(not_found == 1,
			("DEVFS mount struct freed before dirent"));
		not_found = 2;
		sx_xunlock(&dmp->dm_lock);
		devfs_unmount_final(dmp);
	}
	if (not_found == 1 || (drop_dm_lock && not_found != 2))
		sx_unlock(&dmp->dm_lock);
	return (not_found);
}

/*
 * devfs_allocv shall be entered with dmp->dm_lock held, and it drops
 * it on return.
 */
int
devfs_allocv(struct devfs_dirent *de, struct mount *mp, int lockmode,
    struct vnode **vpp)
{
	int error;
	struct vnode *vp;
	struct cdev *dev;
	struct devfs_mount *dmp;
	struct cdevsw *dsw;
	enum vgetstate vs;

	dmp = VFSTODEVFS(mp);
	if (de->de_flags & DE_DOOMED) {
		sx_xunlock(&dmp->dm_lock);
		return (ENOENT);
	}
loop:
	DEVFS_DE_HOLD(de);
	DEVFS_DMP_HOLD(dmp);
	mtx_lock(&devfs_de_interlock);
	vp = de->de_vnode;
	if (vp != NULL) {
		vs = vget_prep(vp);
		mtx_unlock(&devfs_de_interlock);
		sx_xunlock(&dmp->dm_lock);
		vget_finish(vp, lockmode | LK_RETRY, vs);
		sx_xlock(&dmp->dm_lock);
		if (devfs_allocv_drop_refs(0, dmp, de)) {
			vput(vp);
			return (ENOENT);
		} else if (VN_IS_DOOMED(vp)) {
			mtx_lock(&devfs_de_interlock);
			if (de->de_vnode == vp) {
				de->de_vnode = NULL;
				vp->v_data = NULL;
			}
			mtx_unlock(&devfs_de_interlock);
			vput(vp);
			goto loop;
		}
		sx_xunlock(&dmp->dm_lock);
		*vpp = vp;
		return (0);
	}
	mtx_unlock(&devfs_de_interlock);
	if (de->de_dirent->d_type == DT_CHR) {
		if (!(de->de_cdp->cdp_flags & CDP_ACTIVE)) {
			devfs_allocv_drop_refs(1, dmp, de);
			return (ENOENT);
		}
		dev = &de->de_cdp->cdp_c;
	} else {
		dev = NULL;
	}
	error = getnewvnode("devfs", mp, &devfs_vnodeops, &vp);
	if (error != 0) {
		devfs_allocv_drop_refs(1, dmp, de);
		printf("devfs_allocv: failed to allocate new vnode\n");
		return (error);
	}

	if (de->de_dirent->d_type == DT_CHR) {
		vp->v_type = VCHR;
		VI_LOCK(vp);
		dev_lock();
		dev_refl(dev);
		/* XXX: v_rdev should be protect by vnode lock */
		vp->v_rdev = dev;
		VNPASS(vp->v_usecount == 1, vp);
		/* Special casing of ttys for deadfs.  Probably redundant. */
		dsw = dev->si_devsw;
		if (dsw != NULL && (dsw->d_flags & D_TTY) != 0)
			vp->v_vflag |= VV_ISTTY;
		dev_unlock();
		VI_UNLOCK(vp);
		if ((dev->si_flags & SI_ETERNAL) != 0)
			vp->v_vflag |= VV_ETERNALDEV;
		vp->v_op = &devfs_specops;
	} else if (de->de_dirent->d_type == DT_DIR) {
		vp->v_type = VDIR;
	} else if (de->de_dirent->d_type == DT_LNK) {
		vp->v_type = VLNK;
	} else {
		vp->v_type = VBAD;
	}
	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY | LK_NOWITNESS);
	VN_LOCK_ASHARE(vp);
	mtx_lock(&devfs_de_interlock);
	vp->v_data = de;
	de->de_vnode = vp;
	mtx_unlock(&devfs_de_interlock);
	error = insmntque1(vp, mp);
	if (error != 0) {
		mtx_lock(&devfs_de_interlock);
		vp->v_data = NULL;
		de->de_vnode = NULL;
		mtx_unlock(&devfs_de_interlock);
		vgone(vp);
		vput(vp);
		(void) devfs_allocv_drop_refs(1, dmp, de);
		return (error);
	}
	if (devfs_allocv_drop_refs(0, dmp, de)) {
		vgone(vp);
		vput(vp);
		return (ENOENT);
	}
#ifdef MAC
	mac_devfs_vnode_associate(mp, de, vp);
#endif
	sx_xunlock(&dmp->dm_lock);
	vn_set_state(vp, VSTATE_CONSTRUCTED);
	*vpp = vp;
	return (0);
}

static int
devfs_access(struct vop_access_args *ap)
{
	struct vnode *vp = ap->a_vp;
	struct devfs_dirent *de;
	struct proc *p;
	int error;

	de = vp->v_data;
	if (vp->v_type == VDIR)
		de = de->de_dir;

	error = vaccess(vp->v_type, de->de_mode, de->de_uid, de->de_gid,
	    ap->a_accmode, ap->a_cred);
	if (error == 0)
		return (0);
	if (error != EACCES)
		return (error);
	p = ap->a_td->td_proc;
	/* We do, however, allow access to the controlling terminal */
	PROC_LOCK(p);
	if (!(p->p_flag & P_CONTROLT)) {
		PROC_UNLOCK(p);
		return (error);
	}
	if (p->p_session->s_ttydp == de->de_cdp)
		error = 0;
	PROC_UNLOCK(p);
	return (error);
}

_Static_assert(((FMASK | FCNTLFLAGS) & (FLASTCLOSE | FREVOKE)) == 0,
    "devfs-only flag reuse failed");

static int
devfs_close(struct vop_close_args *ap)
{
	struct vnode *vp = ap->a_vp, *oldvp;
	struct thread *td = ap->a_td;
	struct proc *p;
	struct cdev *dev = vp->v_rdev;
	struct cdevsw *dsw;
	struct devfs_dirent *de = vp->v_data;
	int dflags, error, ref, vp_locked;

	/*
	 * XXX: Don't call d_close() if we were called because of
	 * XXX: insmntque() failure.
	 */
	if (vp->v_data == NULL)
		return (0);

	/*
	 * Hack: a tty device that is a controlling terminal
	 * has a reference from the session structure.
	 * We cannot easily tell that a character device is
	 * a controlling terminal, unless it is the closing
	 * process' controlling terminal.  In that case,
	 * if the reference count is 2 (this last descriptor
	 * plus the session), release the reference from the session.
	 */
	if (de->de_usecount == 2 && td != NULL) {
		p = td->td_proc;
		PROC_LOCK(p);
		if (vp == p->p_session->s_ttyvp) {
			PROC_UNLOCK(p);
			oldvp = NULL;
			sx_xlock(&proctree_lock);
			if (vp == p->p_session->s_ttyvp) {
				SESS_LOCK(p->p_session);
				mtx_lock(&devfs_de_interlock);
				VI_LOCK(vp);
				if (devfs_usecountl(vp) == 2 && !VN_IS_DOOMED(vp)) {
					p->p_session->s_ttyvp = NULL;
					p->p_session->s_ttydp = NULL;
					oldvp = vp;
				}
				VI_UNLOCK(vp);
				mtx_unlock(&devfs_de_interlock);
				SESS_UNLOCK(p->p_session);
			}
			sx_xunlock(&proctree_lock);
			if (oldvp != NULL)
				devfs_ctty_unref(oldvp);
		} else
			PROC_UNLOCK(p);
	}
	/*
	 * We do not want to really close the device if it
	 * is still in use unless we are trying to close it
	 * forcibly. Since every use (buffer, vnode, swap, cmap)
	 * holds a reference to the vnode, and because we mark
	 * any other vnodes that alias this device, when the
	 * sum of the reference counts on all the aliased
	 * vnodes descends to one, we are on last close.
	 */
	dsw = dev_refthread(dev, &ref);
	if (dsw == NULL)
		return (ENXIO);
	dflags = 0;
	mtx_lock(&devfs_de_interlock);
	VI_LOCK(vp);
	if (devfs_usecountl(vp) == 1)
		dflags |= FLASTCLOSE;
	devfs_usecount_subl(vp);
	mtx_unlock(&devfs_de_interlock);
	if (VN_IS_DOOMED(vp)) {
		/* Forced close. */
		dflags |= FREVOKE | FNONBLOCK;
	} else if (dsw->d_flags & D_TRACKCLOSE) {
		/* Keep device updated on status. */
	} else if ((dflags & FLASTCLOSE) == 0) {
		VI_UNLOCK(vp);
		dev_relthread(dev, ref);
		return (0);
	}
	vholdnz(vp);
	VI_UNLOCK(vp);
	vp_locked = VOP_ISLOCKED(vp);
	VOP_UNLOCK(vp);
	KASSERT(dev->si_refcount > 0,
	    ("devfs_close() on un-referenced struct cdev *(%s)", devtoname(dev)));
	error = dsw->d_close(dev, ap->a_fflag | dflags, S_IFCHR, td);
	dev_relthread(dev, ref);
	vn_lock(vp, vp_locked | LK_RETRY);
	vdrop(vp);
	return (error);
}

static int
devfs_close_f(struct file *fp, struct thread *td)
{
	int error;
	struct file *fpop;

	/*
	 * NB: td may be NULL if this descriptor is closed due to
	 * garbage collection from a closed UNIX domain socket.
	 */
	fpop = curthread->td_fpop;
	curthread->td_fpop = fp;
	error = vnops.fo_close(fp, td);
	curthread->td_fpop = fpop;

	/*
	 * The f_cdevpriv cannot be assigned non-NULL value while we
	 * are destroying the file.
	 */
	if (fp->f_cdevpriv != NULL)
		devfs_fpdrop(fp);
	return (error);
}

static int
devfs_getattr(struct vop_getattr_args *ap)
{
	struct vnode *vp = ap->a_vp;
	struct vattr *vap = ap->a_vap;
	struct devfs_dirent *de;
	struct devfs_mount *dmp;
	struct cdev *dev;
	struct timeval boottime;
	int error;

	error = devfs_populate_vp(vp);
	if (error != 0)
		return (error);

	dmp = VFSTODEVFS(vp->v_mount);
	sx_xunlock(&dmp->dm_lock);

	de = vp->v_data;
	KASSERT(de != NULL, ("Null dirent in devfs_getattr vp=%p", vp));
	if (vp->v_type == VDIR) {
		de = de->de_dir;
		KASSERT(de != NULL,
		    ("Null dir dirent in devfs_getattr vp=%p", vp));
	}
	vap->va_uid = de->de_uid;
	vap->va_gid = de->de_gid;
	vap->va_mode = de->de_mode;
	if (vp->v_type == VLNK)
		vap->va_size = strlen(de->de_symlink);
	else if (vp->v_type == VDIR)
		vap->va_size = vap->va_bytes = DEV_BSIZE;
	else
		vap->va_size = 0;
	if (vp->v_type != VDIR)
		vap->va_bytes = 0;
	vap->va_blocksize = DEV_BSIZE;
	vap->va_type = vp->v_type;

	getboottime(&boottime);
#define fix(aa)							\
	do {							\
		if ((aa).tv_sec <= 3600) {			\
			(aa).tv_sec = boottime.tv_sec;		\
			(aa).tv_nsec = boottime.tv_usec * 1000; \
		}						\
	} while (0)

	if (vp->v_type != VCHR)  {
		fix(de->de_atime);
		vap->va_atime = de->de_atime;
		fix(de->de_mtime);
		vap->va_mtime = de->de_mtime;
		fix(de->de_ctime);
		vap->va_ctime = de->de_ctime;
	} else {
		dev = vp->v_rdev;
		fix(dev->si_atime);
		vap->va_atime = dev->si_atime;
		fix(dev->si_mtime);
		vap->va_mtime = dev->si_mtime;
		fix(dev->si_ctime);
		vap->va_ctime = dev->si_ctime;

		vap->va_rdev = cdev2priv(dev)->cdp_inode;
	}
	vap->va_gen = 0;
	vap->va_flags = 0;
	vap->va_filerev = 0;
	vap->va_nlink = de->de_links;
	vap->va_fileid = de->de_inode;

	return (error);
}

/* ARGSUSED */
static int
devfs_ioctl_f(struct file *fp, u_long com, void *data, struct ucred *cred, struct thread *td)
{
	struct file *fpop;
	int error;

	fpop = td->td_fpop;
	td->td_fpop = fp;
	error = vnops.fo_ioctl(fp, com, data, cred, td);
	td->td_fpop = fpop;
	return (error);
}

void *
fiodgname_buf_get_ptr(void *fgnp, u_long com)
{
	union {
		struct fiodgname_arg	fgn;
#ifdef COMPAT_FREEBSD32
		struct fiodgname_arg32	fgn32;
#endif
	} *fgnup;

	fgnup = fgnp;
	switch (com) {
	case FIODGNAME:
		return (fgnup->fgn.buf);
#ifdef COMPAT_FREEBSD32
	case FIODGNAME_32:
		return ((void *)(uintptr_t)fgnup->fgn32.buf);
#endif
	default:
		panic("Unhandled ioctl command %ld", com);
	}
}

static int
devfs_ioctl(struct vop_ioctl_args *ap)
{
	struct fiodgname_arg *fgn;
	struct vnode *vpold, *vp;
	struct cdevsw *dsw;
	struct thread *td;
	struct session *sess;
	struct cdev *dev;
	int error, ref, i;
	const char *p;
	u_long com;

	vp = ap->a_vp;
	com = ap->a_command;
	td = ap->a_td;

	dsw = devvn_refthread(vp, &dev, &ref);
	if (dsw == NULL)
		return (ENXIO);
	KASSERT(dev->si_refcount > 0,
	    ("devfs: un-referenced struct cdev *(%s)", devtoname(dev)));

	switch (com) {
	case FIODTYPE:
		*(int *)ap->a_data = dsw->d_flags & D_TYPEMASK;
		error = 0;
		break;
	case FIODGNAME:
#ifdef	COMPAT_FREEBSD32
	case FIODGNAME_32:
#endif
		fgn = ap->a_data;
		p = devtoname(dev);
		i = strlen(p) + 1;
		if (i > fgn->len)
			error = EINVAL;
		else
			error = copyout(p, fiodgname_buf_get_ptr(fgn, com), i);
		break;
	default:
		error = dsw->d_ioctl(dev, com, ap->a_data, ap->a_fflag, td);
	}

	dev_relthread(dev, ref);
	if (error == ENOIOCTL)
		error = ENOTTY;

	if (error == 0 && com == TIOCSCTTY) {
		/*
		 * Do nothing if reassigning same control tty, or if the
		 * control tty has already disappeared.  If it disappeared,
		 * it's because we were racing with TIOCNOTTY.  TIOCNOTTY
		 * already took care of releasing the old vnode and we have
		 * nothing left to do.
		 */
		sx_slock(&proctree_lock);
		sess = td->td_proc->p_session;
		if (sess->s_ttyvp == vp || sess->s_ttyp == NULL) {
			sx_sunlock(&proctree_lock);
			return (0);
		}

		devfs_ctty_ref(vp);
		SESS_LOCK(sess);
		vpold = sess->s_ttyvp;
		sess->s_ttyvp = vp;
		sess->s_ttydp = cdev2priv(dev);
		SESS_UNLOCK(sess);

		sx_sunlock(&proctree_lock);

		/* Get rid of reference to old control tty */
		if (vpold)
			devfs_ctty_unref(vpold);
	}
	return (error);
}

/* ARGSUSED */
static int
devfs_kqfilter_f(struct file *fp, struct knote *kn)
{
	struct cdev *dev;
	struct cdevsw *dsw;
	int error, ref;
	struct file *fpop;
	struct thread *td;

	td = curthread;
	fpop = td->td_fpop;
	error = devfs_fp_check(fp, &dev, &dsw, &ref);
	if (error)
		return (error);
	error = dsw->d_kqfilter(dev, kn);
	td->td_fpop = fpop;
	dev_relthread(dev, ref);
	return (error);
}

static inline int
devfs_prison_check(struct devfs_dirent *de, struct thread *td)
{
	struct cdev_priv *cdp;
	struct ucred *dcr;
	struct proc *p;
	int error;

	cdp = de->de_cdp;
	if (cdp == NULL)
		return (0);
	dcr = cdp->cdp_c.si_cred;
	if (dcr == NULL)
		return (0);

	error = prison_check(td->td_ucred, dcr);
	if (error == 0)
		return (0);
	/* We do, however, allow access to the controlling terminal */
	p = td->td_proc;
	PROC_LOCK(p);
	if (!(p->p_flag & P_CONTROLT)) {
		PROC_UNLOCK(p);
		return (error);
	}
	if (p->p_session->s_ttydp == cdp)
		error = 0;
	PROC_UNLOCK(p);
	return (error);
}

static int
devfs_lookupx(struct vop_lookup_args *ap, int *dm_unlock)
{
	struct componentname *cnp;
	struct vnode *dvp, **vpp;
	struct thread *td;
	struct devfs_dirent *de, *dd;
	struct devfs_dirent **dde;
	struct devfs_mount *dmp;
	struct mount *mp;
	struct cdev *cdev;
	int error, flags, nameiop, dvplocked;
	char specname[SPECNAMELEN + 1], *pname;

	td = curthread;
	cnp = ap->a_cnp;
	vpp = ap->a_vpp;
	dvp = ap->a_dvp;
	pname = cnp->cn_nameptr;
	flags = cnp->cn_flags;
	nameiop = cnp->cn_nameiop;
	mp = dvp->v_mount;
	dmp = VFSTODEVFS(mp);
	dd = dvp->v_data;
	*vpp = NULLVP;

	if ((flags & ISLASTCN) && nameiop == RENAME)
		return (EOPNOTSUPP);

	if (dvp->v_type != VDIR)
		return (ENOTDIR);

	if ((flags & ISDOTDOT) && (dvp->v_vflag & VV_ROOT))
		return (EIO);

	error = vn_dir_check_exec(dvp, cnp);
	if (error != 0)
		return (error);

	if (cnp->cn_namelen == 1 && *pname == '.') {
		if ((flags & ISLASTCN) && nameiop != LOOKUP)
			return (EINVAL);
		*vpp = dvp;
		VREF(dvp);
		return (0);
	}

	if (flags & ISDOTDOT) {
		if ((flags & ISLASTCN) && nameiop != LOOKUP)
			return (EINVAL);
		de = devfs_parent_dirent(dd);
		if (de == NULL)
			return (ENOENT);
		dvplocked = VOP_ISLOCKED(dvp);
		VOP_UNLOCK(dvp);
		error = devfs_allocv(de, mp, cnp->cn_lkflags & LK_TYPE_MASK,
		    vpp);
		*dm_unlock = 0;
		vn_lock(dvp, dvplocked | LK_RETRY);
		return (error);
	}

	dd = dvp->v_data;
	de = devfs_find(dd, cnp->cn_nameptr, cnp->cn_namelen, 0);
	while (de == NULL) {	/* While(...) so we can use break */

		if (nameiop == DELETE)
			return (ENOENT);

		/*
		 * OK, we didn't have an entry for the name we were asked for
		 * so we try to see if anybody can create it on demand.
		 */
		pname = devfs_fqpn(specname, dmp, dd, cnp);
		if (pname == NULL)
			break;

		cdev = NULL;
		DEVFS_DMP_HOLD(dmp);
		sx_xunlock(&dmp->dm_lock);
		EVENTHANDLER_INVOKE(dev_clone,
		    td->td_ucred, pname, strlen(pname), &cdev);

		if (cdev == NULL)
			sx_xlock(&dmp->dm_lock);
		else if (devfs_populate_vp(dvp) != 0) {
			*dm_unlock = 0;
			sx_xlock(&dmp->dm_lock);
			if (DEVFS_DMP_DROP(dmp)) {
				sx_xunlock(&dmp->dm_lock);
				devfs_unmount_final(dmp);
			} else
				sx_xunlock(&dmp->dm_lock);
			dev_rel(cdev);
			return (ENOENT);
		}
		if (DEVFS_DMP_DROP(dmp)) {
			*dm_unlock = 0;
			sx_xunlock(&dmp->dm_lock);
			devfs_unmount_final(dmp);
			if (cdev != NULL)
				dev_rel(cdev);
			return (ENOENT);
		}

		if (cdev == NULL)
			break;

		dev_lock();
		dde = &cdev2priv(cdev)->cdp_dirents[dmp->dm_idx];
		if (dde != NULL && *dde != NULL)
			de = *dde;
		dev_unlock();
		dev_rel(cdev);
		break;
	}

	if (de == NULL || de->de_flags & DE_WHITEOUT) {
		if ((nameiop == CREATE || nameiop == RENAME) &&
		    (flags & (LOCKPARENT | WANTPARENT)) && (flags & ISLASTCN)) {
			return (EJUSTRETURN);
		}
		return (ENOENT);
	}

	if (devfs_prison_check(de, td))
		return (ENOENT);

	if ((cnp->cn_nameiop == DELETE) && (flags & ISLASTCN)) {
		error = VOP_ACCESS(dvp, VWRITE, cnp->cn_cred, td);
		if (error)
			return (error);
		if (*vpp == dvp) {
			VREF(dvp);
			*vpp = dvp;
			return (0);
		}
	}
	error = devfs_allocv(de, mp, cnp->cn_lkflags & LK_TYPE_MASK, vpp);
	*dm_unlock = 0;
	return (error);
}

static int
devfs_lookup(struct vop_lookup_args *ap)
{
	int j;
	struct devfs_mount *dmp;
	int dm_unlock;

	if (devfs_populate_vp(ap->a_dvp) != 0)
		return (ENOTDIR);

	dmp = VFSTODEVFS(ap->a_dvp->v_mount);
	dm_unlock = 1;
	j = devfs_lookupx(ap, &dm_unlock);
	if (dm_unlock == 1)
		sx_xunlock(&dmp->dm_lock);
	return (j);
}

static int
devfs_mknod(struct vop_mknod_args *ap)
{
	struct componentname *cnp;
	struct vnode *dvp, **vpp;
	struct devfs_dirent *dd, *de;
	struct devfs_mount *dmp;
	int error;

	/*
	 * The only type of node we should be creating here is a
	 * character device, for anything else return EOPNOTSUPP.
	 */
	if (ap->a_vap->va_type != VCHR)
		return (EOPNOTSUPP);
	dvp = ap->a_dvp;
	dmp = VFSTODEVFS(dvp->v_mount);

	cnp = ap->a_cnp;
	vpp = ap->a_vpp;
	dd = dvp->v_data;

	error = ENOENT;
	sx_xlock(&dmp->dm_lock);
	TAILQ_FOREACH(de, &dd->de_dlist, de_list) {
		if (cnp->cn_namelen != de->de_dirent->d_namlen)
			continue;
		if (de->de_dirent->d_type == DT_CHR &&
		    (de->de_cdp->cdp_flags & CDP_ACTIVE) == 0)
			continue;
		if (bcmp(cnp->cn_nameptr, de->de_dirent->d_name,
		    de->de_dirent->d_namlen) != 0)
			continue;
		if (de->de_flags & DE_WHITEOUT)
			break;
		goto notfound;
	}
	if (de == NULL)
		goto notfound;
	de->de_flags &= ~DE_WHITEOUT;
	error = devfs_allocv(de, dvp->v_mount, LK_EXCLUSIVE, vpp);
	return (error);
notfound:
	sx_xunlock(&dmp->dm_lock);
	return (error);
}

/* ARGSUSED */
static int
devfs_open(struct vop_open_args *ap)
{
	struct thread *td = ap->a_td;
	struct vnode *vp = ap->a_vp;
	struct cdev *dev = vp->v_rdev;
	struct file *fp = ap->a_fp;
	int error, ref, vlocked;
	struct cdevsw *dsw;
	struct file *fpop;

	if (vp->v_type == VBLK)
		return (ENXIO);

	if (dev == NULL)
		return (ENXIO);

	/* Make this field valid before any I/O in d_open. */
	if (dev->si_iosize_max == 0)
		dev->si_iosize_max = DFLTPHYS;

	dsw = dev_refthread(dev, &ref);
	if (dsw == NULL)
		return (ENXIO);
	if (fp == NULL && dsw->d_fdopen != NULL) {
		dev_relthread(dev, ref);
		return (ENXIO);
	}

	if (vp->v_type == VCHR)
		devfs_usecount_add(vp);

	vlocked = VOP_ISLOCKED(vp);
	VOP_UNLOCK(vp);

	fpop = td->td_fpop;
	td->td_fpop = fp;
	if (fp != NULL) {
		fp->f_data = dev;
		fp->f_vnode = vp;
	}
	if (dsw->d_fdopen != NULL)
		error = dsw->d_fdopen(dev, ap->a_mode, td, fp);
	else
		error = dsw->d_open(dev, ap->a_mode, S_IFCHR, td);
	/* Clean up any cdevpriv upon error. */
	if (error != 0)
		devfs_clear_cdevpriv();
	td->td_fpop = fpop;

	vn_lock(vp, vlocked | LK_RETRY);
	if (error != 0 && vp->v_type == VCHR)
		devfs_usecount_sub(vp);

	dev_relthread(dev, ref);
	if (error != 0) {
		if (error == ERESTART)
			error = EINTR;
		return (error);
	}

#if 0	/* /dev/console */
	KASSERT(fp != NULL, ("Could not vnode bypass device on NULL fp"));
#else
	if (fp == NULL)
		return (error);
#endif
	if (fp->f_ops == &badfileops)
		finit(fp, fp->f_flag, DTYPE_VNODE, dev, &devfs_ops_f);
	return (error);
}

static int
devfs_pathconf(struct vop_pathconf_args *ap)
{

	switch (ap->a_name) {
	case _PC_FILESIZEBITS:
		*ap->a_retval = 64;
		return (0);
	case _PC_NAME_MAX:
		*ap->a_retval = NAME_MAX;
		return (0);
	case _PC_LINK_MAX:
		*ap->a_retval = INT_MAX;
		return (0);
	case _PC_SYMLINK_MAX:
		*ap->a_retval = MAXPATHLEN;
		return (0);
	case _PC_MAX_CANON:
		if (ap->a_vp->v_vflag & VV_ISTTY) {
			*ap->a_retval = MAX_CANON;
			return (0);
		}
		return (EINVAL);
	case _PC_MAX_INPUT:
		if (ap->a_vp->v_vflag & VV_ISTTY) {
			*ap->a_retval = MAX_INPUT;
			return (0);
		}
		return (EINVAL);
	case _PC_VDISABLE:
		if (ap->a_vp->v_vflag & VV_ISTTY) {
			*ap->a_retval = _POSIX_VDISABLE;
			return (0);
		}
		return (EINVAL);
	case _PC_MAC_PRESENT:
#ifdef MAC
		/*
		 * If MAC is enabled, devfs automatically supports
		 * trivial non-persistent label storage.
		 */
		*ap->a_retval = 1;
#else
		*ap->a_retval = 0;
#endif
		return (0);
	case _PC_CHOWN_RESTRICTED:
		*ap->a_retval = 1;
		return (0);
	default:
		return (vop_stdpathconf(ap));
	}
	/* NOTREACHED */
}

/* ARGSUSED */
static int
devfs_poll_f(struct file *fp, int events, struct ucred *cred, struct thread *td)
{
	struct cdev *dev;
	struct cdevsw *dsw;
	int error, ref;
	struct file *fpop;

	fpop = td->td_fpop;
	error = devfs_fp_check(fp, &dev, &dsw, &ref);
	if (error != 0) {
		error = vnops.fo_poll(fp, events, cred, td);
		return (error);
	}
	error = dsw->d_poll(dev, events, td);
	td->td_fpop = fpop;
	dev_relthread(dev, ref);
	return(error);
}

/*
 * Print out the contents of a special device vnode.
 */
static int
devfs_print(struct vop_print_args *ap)
{

	printf("\tdev %s\n", devtoname(ap->a_vp->v_rdev));
	return (0);
}

static int
devfs_read_f(struct file *fp, struct uio *uio, struct ucred *cred,
    int flags, struct thread *td)
{
	struct cdev *dev;
	int ioflag, error, ref;
	ssize_t resid;
	struct cdevsw *dsw;
	struct file *fpop;

	if (uio->uio_resid > DEVFS_IOSIZE_MAX)
		return (EINVAL);
	fpop = td->td_fpop;
	error = devfs_fp_check(fp, &dev, &dsw, &ref);
	if (error != 0) {
		error = vnops.fo_read(fp, uio, cred, flags, td);
		return (error);
	}
	resid = uio->uio_resid;
	ioflag = fp->f_flag & (O_NONBLOCK | O_DIRECT);
	if (ioflag & O_DIRECT)
		ioflag |= IO_DIRECT;

	foffset_lock_uio(fp, uio, flags | FOF_NOLOCK);
	error = dsw->d_read(dev, uio, ioflag);
	if (uio->uio_resid != resid || (error == 0 && resid != 0))
		devfs_timestamp(&dev->si_atime);
	td->td_fpop = fpop;
	dev_relthread(dev, ref);

	foffset_unlock_uio(fp, uio, flags | FOF_NOLOCK | FOF_NEXTOFF_R);
	return (error);
}

static int
devfs_readdir(struct vop_readdir_args *ap)
{
	int error;
	struct uio *uio;
	struct dirent *dp;
	struct devfs_dirent *dd;
	struct devfs_dirent *de;
	struct devfs_mount *dmp;
	off_t off;
	int *tmp_ncookies = NULL;

	if (ap->a_vp->v_type != VDIR)
		return (ENOTDIR);

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

	/*
	 * XXX: This is a temporary hack to get around this filesystem not
	 * supporting cookies. We store the location of the ncookies pointer
	 * in a temporary variable before calling vfs_subr.c:vfs_read_dirent()
	 * and set the number of cookies to 0. We then set the pointer to
	 * NULL so that vfs_read_dirent doesn't try to call realloc() on
	 * ap->a_cookies. Later in this function, we restore the ap->a_ncookies
	 * pointer to its original location before returning to the caller.
	 */
	if (ap->a_ncookies != NULL) {
		tmp_ncookies = ap->a_ncookies;
		*ap->a_ncookies = 0;
		ap->a_ncookies = NULL;
	}

	dmp = VFSTODEVFS(ap->a_vp->v_mount);
	if (devfs_populate_vp(ap->a_vp) != 0) {
		if (tmp_ncookies != NULL)
			ap->a_ncookies = tmp_ncookies;
		return (EIO);
	}
	error = 0;
	de = ap->a_vp->v_data;
	off = 0;
	TAILQ_FOREACH(dd, &de->de_dlist, de_list) {
		KASSERT(dd->de_cdp != (void *)0xdeadc0de, ("%s %d\n", __func__, __LINE__));
		if (dd->de_flags & (DE_COVERED | DE_WHITEOUT))
			continue;
		if (devfs_prison_check(dd, uio->uio_td))
			continue;
		if (dd->de_dirent->d_type == DT_DIR)
			de = dd->de_dir;
		else
			de = dd;
		dp = dd->de_dirent;
		MPASS(dp->d_reclen == GENERIC_DIRSIZ(dp));
		if (dp->d_reclen > uio->uio_resid)
			break;
		dp->d_fileno = de->de_inode;
		/* NOTE: d_off is the offset for the *next* entry. */
		dp->d_off = off + dp->d_reclen;
		if (off >= uio->uio_offset) {
			error = vfs_read_dirent(ap, dp, off);
			if (error)
				break;
		}
		off += dp->d_reclen;
	}
	sx_xunlock(&dmp->dm_lock);
	uio->uio_offset = off;

	/*
	 * Restore ap->a_ncookies if it wasn't originally NULL in the first
	 * place.
	 */
	if (tmp_ncookies != NULL)
		ap->a_ncookies = tmp_ncookies;

	return (error);
}

static int
devfs_readlink(struct vop_readlink_args *ap)
{
	struct devfs_dirent *de;

	de = ap->a_vp->v_data;
	return (uiomove(de->de_symlink, strlen(de->de_symlink), ap->a_uio));
}

static void
devfs_reclaiml(struct vnode *vp)
{
	struct devfs_dirent *de;

	mtx_assert(&devfs_de_interlock, MA_OWNED);
	de = vp->v_data;
	if (de != NULL) {
		MPASS(de->de_usecount == 0);
		de->de_vnode = NULL;
		vp->v_data = NULL;
	}
}

static int
devfs_reclaim(struct vop_reclaim_args *ap)
{
	struct vnode *vp;

	vp = ap->a_vp;
	mtx_lock(&devfs_de_interlock);
	devfs_reclaiml(vp);
	mtx_unlock(&devfs_de_interlock);
	return (0);
}

static int
devfs_reclaim_vchr(struct vop_reclaim_args *ap)
{
	struct vnode *vp;
	struct cdev *dev;

	vp = ap->a_vp;
	MPASS(vp->v_type == VCHR);

	mtx_lock(&devfs_de_interlock);
	VI_LOCK(vp);
	devfs_usecount_subl(vp);
	devfs_reclaiml(vp);
	mtx_unlock(&devfs_de_interlock);
	dev_lock();
	dev = vp->v_rdev;
	vp->v_rdev = NULL;
	dev_unlock();
	VI_UNLOCK(vp);
	if (dev != NULL)
		dev_rel(dev);
	return (0);
}

static int
devfs_remove(struct vop_remove_args *ap)
{
	struct vnode *dvp = ap->a_dvp;
	struct vnode *vp = ap->a_vp;
	struct devfs_dirent *dd;
	struct devfs_dirent *de, *de_covered;
	struct devfs_mount *dmp = VFSTODEVFS(vp->v_mount);

	ASSERT_VOP_ELOCKED(dvp, "devfs_remove");
	ASSERT_VOP_ELOCKED(vp, "devfs_remove");

	sx_xlock(&dmp->dm_lock);
	dd = ap->a_dvp->v_data;
	de = vp->v_data;
	if (de->de_cdp == NULL) {
		TAILQ_REMOVE(&dd->de_dlist, de, de_list);
		if (de->de_dirent->d_type == DT_LNK) {
			de_covered = devfs_find(dd, de->de_dirent->d_name,
			    de->de_dirent->d_namlen, 0);
			if (de_covered != NULL)
				de_covered->de_flags &= ~DE_COVERED;
		}
		/* We need to unlock dvp because devfs_delete() may lock it. */
		VOP_UNLOCK(vp);
		if (dvp != vp)
			VOP_UNLOCK(dvp);
		devfs_delete(dmp, de, 0);
		sx_xunlock(&dmp->dm_lock);
		if (dvp != vp)
			vn_lock(dvp, LK_EXCLUSIVE | LK_RETRY);
		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	} else {
		de->de_flags |= DE_WHITEOUT;
		sx_xunlock(&dmp->dm_lock);
	}
	return (0);
}

/*
 * Revoke is called on a tty when a terminal session ends.  The vnode
 * is orphaned by setting v_op to deadfs so we need to let go of it
 * as well so that we create a new one next time around.
 *
 */
static int
devfs_revoke(struct vop_revoke_args *ap)
{
	struct vnode *vp = ap->a_vp, *vp2;
	struct cdev *dev;
	struct cdev_priv *cdp;
	struct devfs_dirent *de;
	enum vgetstate vs;
	u_int i;

	KASSERT((ap->a_flags & REVOKEALL) != 0, ("devfs_revoke !REVOKEALL"));

	dev = vp->v_rdev;
	cdp = cdev2priv(dev);

	dev_lock();
	cdp->cdp_inuse++;
	dev_unlock();

	vhold(vp);
	vgone(vp);
	vdrop(vp);

	VOP_UNLOCK(vp);
 loop:
	for (;;) {
		mtx_lock(&devfs_de_interlock);
		dev_lock();
		vp2 = NULL;
		for (i = 0; i <= cdp->cdp_maxdirent; i++) {
			de = cdp->cdp_dirents[i];
			if (de == NULL)
				continue;

			vp2 = de->de_vnode;
			if (vp2 != NULL) {
				dev_unlock();
				vs = vget_prep(vp2);
				mtx_unlock(&devfs_de_interlock);
				if (vget_finish(vp2, LK_EXCLUSIVE, vs) != 0)
					goto loop;
				vhold(vp2);
				vgone(vp2);
				vdrop(vp2);
				vput(vp2);
				break;
			}
		}
		if (vp2 != NULL) {
			continue;
		}
		dev_unlock();
		mtx_unlock(&devfs_de_interlock);
		break;
	}
	dev_lock();
	cdp->cdp_inuse--;
	if (!(cdp->cdp_flags & CDP_ACTIVE) && cdp->cdp_inuse == 0) {
		KASSERT((cdp->cdp_flags & CDP_ON_ACTIVE_LIST) != 0,
		    ("%s: cdp %p (%s) not on active list",
		    __func__, cdp, dev->si_name));
		cdp->cdp_flags &= ~CDP_ON_ACTIVE_LIST;
		TAILQ_REMOVE(&cdevp_list, cdp, cdp_list);
		dev_unlock();
		dev_rel(&cdp->cdp_c);
	} else
		dev_unlock();

	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	return (0);
}

static int
devfs_rioctl(struct vop_ioctl_args *ap)
{
	struct vnode *vp;
	struct devfs_mount *dmp;
	int error;

	vp = ap->a_vp;
	vn_lock(vp, LK_SHARED | LK_RETRY);
	if (VN_IS_DOOMED(vp)) {
		VOP_UNLOCK(vp);
		return (EBADF);
	}
	dmp = VFSTODEVFS(vp->v_mount);
	sx_xlock(&dmp->dm_lock);
	VOP_UNLOCK(vp);
	DEVFS_DMP_HOLD(dmp);
	devfs_populate(dmp);
	if (DEVFS_DMP_DROP(dmp)) {
		sx_xunlock(&dmp->dm_lock);
		devfs_unmount_final(dmp);
		return (ENOENT);
	}
	error = devfs_rules_ioctl(dmp, ap->a_command, ap->a_data, ap->a_td);
	sx_xunlock(&dmp->dm_lock);
	return (error);
}

static int
devfs_rread(struct vop_read_args *ap)
{

	if (ap->a_vp->v_type != VDIR)
		return (EINVAL);
	return (VOP_READDIR(ap->a_vp, ap->a_uio, ap->a_cred, NULL, NULL, NULL));
}

static int
devfs_setattr(struct vop_setattr_args *ap)
{
	struct devfs_dirent *de;
	struct vattr *vap;
	struct vnode *vp;
	struct thread *td;
	int c, error;
	uid_t uid;
	gid_t gid;

	vap = ap->a_vap;
	vp = ap->a_vp;
	td = curthread;
	if ((vap->va_type != VNON) ||
	    (vap->va_nlink != VNOVAL) ||
	    (vap->va_fsid != VNOVAL) ||
	    (vap->va_fileid != VNOVAL) ||
	    (vap->va_blocksize != VNOVAL) ||
	    (vap->va_flags != VNOVAL && vap->va_flags != 0) ||
	    (vap->va_rdev != VNOVAL) ||
	    ((int)vap->va_bytes != VNOVAL) ||
	    (vap->va_gen != VNOVAL)) {
		return (EINVAL);
	}

	error = devfs_populate_vp(vp);
	if (error != 0)
		return (error);

	de = vp->v_data;
	if (vp->v_type == VDIR)
		de = de->de_dir;

	c = 0;
	if (vap->va_uid == (uid_t)VNOVAL)
		uid = de->de_uid;
	else
		uid = vap->va_uid;
	if (vap->va_gid == (gid_t)VNOVAL)
		gid = de->de_gid;
	else
		gid = vap->va_gid;
	if (uid != de->de_uid || gid != de->de_gid) {
		if ((ap->a_cred->cr_uid != de->de_uid) || uid != de->de_uid ||
		    (gid != de->de_gid && !groupmember(gid, ap->a_cred))) {
			error = priv_check(td, PRIV_VFS_CHOWN);
			if (error != 0)
				goto ret;
		}
		de->de_uid = uid;
		de->de_gid = gid;
		c = 1;
	}

	if (vap->va_mode != (mode_t)VNOVAL) {
		if (ap->a_cred->cr_uid != de->de_uid) {
			error = priv_check(td, PRIV_VFS_ADMIN);
			if (error != 0)
				goto ret;
		}
		de->de_mode = vap->va_mode;
		c = 1;
	}

	if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
		error = vn_utimes_perm(vp, vap, ap->a_cred, td);
		if (error != 0)
			goto ret;
		if (vap->va_atime.tv_sec != VNOVAL) {
			if (vp->v_type == VCHR)
				vp->v_rdev->si_atime = vap->va_atime;
			else
				de->de_atime = vap->va_atime;
		}
		if (vap->va_mtime.tv_sec != VNOVAL) {
			if (vp->v_type == VCHR)
				vp->v_rdev->si_mtime = vap->va_mtime;
			else
				de->de_mtime = vap->va_mtime;
		}
		c = 1;
	}

	if (c) {
		if (vp->v_type == VCHR)
			vfs_timestamp(&vp->v_rdev->si_ctime);
		else
			vfs_timestamp(&de->de_mtime);
	}

ret:
	sx_xunlock(&VFSTODEVFS(vp->v_mount)->dm_lock);
	return (error);
}

#ifdef MAC
static int
devfs_setlabel(struct vop_setlabel_args *ap)
{
	struct vnode *vp;
	struct devfs_dirent *de;

	vp = ap->a_vp;
	de = vp->v_data;

	mac_vnode_relabel(ap->a_cred, vp, ap->a_label);
	mac_devfs_update(vp->v_mount, de, vp);

	return (0);
}
#endif

static int
devfs_stat_f(struct file *fp, struct stat *sb, struct ucred *cred)
{

	return (vnops.fo_stat(fp, sb, cred));
}

static int
devfs_symlink(struct vop_symlink_args *ap)
{
	int i, error;
	struct devfs_dirent *dd;
	struct devfs_dirent *de, *de_covered, *de_dotdot;
	struct devfs_mount *dmp;

	error = priv_check(curthread, PRIV_DEVFS_SYMLINK);
	if (error)
		return(error);
	dmp = VFSTODEVFS(ap->a_dvp->v_mount);
	if (devfs_populate_vp(ap->a_dvp) != 0)
		return (ENOENT);

	dd = ap->a_dvp->v_data;
	de = devfs_newdirent(ap->a_cnp->cn_nameptr, ap->a_cnp->cn_namelen);
	de->de_flags = DE_USER;
	de->de_uid = 0;
	de->de_gid = 0;
	de->de_mode = 0755;
	de->de_inode = alloc_unr(devfs_inos);
	de->de_dir = dd;
	de->de_dirent->d_type = DT_LNK;
	i = strlen(ap->a_target) + 1;
	de->de_symlink = malloc(i, M_DEVFS, M_WAITOK);
	bcopy(ap->a_target, de->de_symlink, i);
#ifdef MAC
	mac_devfs_create_symlink(ap->a_cnp->cn_cred, dmp->dm_mount, dd, de);
#endif
	de_covered = devfs_find(dd, de->de_dirent->d_name,
	    de->de_dirent->d_namlen, 0);
	if (de_covered != NULL) {
		if ((de_covered->de_flags & DE_USER) != 0) {
			devfs_delete(dmp, de, DEVFS_DEL_NORECURSE);
			sx_xunlock(&dmp->dm_lock);
			return (EEXIST);
		}
		KASSERT((de_covered->de_flags & DE_COVERED) == 0,
		    ("devfs_symlink: entry %p already covered", de_covered));
		de_covered->de_flags |= DE_COVERED;
	}

	de_dotdot = TAILQ_FIRST(&dd->de_dlist);		/* "." */
	de_dotdot = TAILQ_NEXT(de_dotdot, de_list);	/* ".." */
	TAILQ_INSERT_AFTER(&dd->de_dlist, de_dotdot, de, de_list);
	devfs_dir_ref_de(dmp, dd);
	devfs_rules_apply(dmp, de);

	return (devfs_allocv(de, ap->a_dvp->v_mount, LK_EXCLUSIVE, ap->a_vpp));
}

static int
devfs_truncate_f(struct file *fp, off_t length, struct ucred *cred, struct thread *td)
{

	return (vnops.fo_truncate(fp, length, cred, td));
}

static int
devfs_write_f(struct file *fp, struct uio *uio, struct ucred *cred,
    int flags, struct thread *td)
{
	struct cdev *dev;
	int error, ioflag, ref;
	ssize_t resid;
	struct cdevsw *dsw;
	struct file *fpop;

	if (uio->uio_resid > DEVFS_IOSIZE_MAX)
		return (EINVAL);
	fpop = td->td_fpop;
	error = devfs_fp_check(fp, &dev, &dsw, &ref);
	if (error != 0) {
		error = vnops.fo_write(fp, uio, cred, flags, td);
		return (error);
	}
	KASSERT(uio->uio_td == td, ("uio_td %p is not td %p", uio->uio_td, td));
	ioflag = fp->f_flag & (O_NONBLOCK | O_DIRECT | O_FSYNC);
	if (ioflag & O_DIRECT)
		ioflag |= IO_DIRECT;
	foffset_lock_uio(fp, uio, flags | FOF_NOLOCK);

	resid = uio->uio_resid;

	error = dsw->d_write(dev, uio, ioflag);
	if (uio->uio_resid != resid || (error == 0 && resid != 0)) {
		devfs_timestamp(&dev->si_ctime);
		dev->si_mtime = dev->si_ctime;
	}
	td->td_fpop = fpop;
	dev_relthread(dev, ref);

	foffset_unlock_uio(fp, uio, flags | FOF_NOLOCK | FOF_NEXTOFF_W);
	return (error);
}

static int
devfs_mmap_f(struct file *fp, vm_map_t map, vm_offset_t *addr, vm_size_t size,
    vm_prot_t prot, vm_prot_t cap_maxprot, int flags, vm_ooffset_t foff,
    struct thread *td)
{
	struct cdev *dev;
	struct cdevsw *dsw;
	struct mount *mp;
	struct vnode *vp;
	struct file *fpop;
	vm_object_t object;
	vm_prot_t maxprot;
	int error, ref;

	vp = fp->f_vnode;

	/*
	 * Ensure that file and memory protections are
	 * compatible.
	 */
	mp = vp->v_mount;
	if (mp != NULL && (mp->mnt_flag & MNT_NOEXEC) != 0) {
		maxprot = VM_PROT_NONE;
		if ((prot & VM_PROT_EXECUTE) != 0)
			return (EACCES);
	} else
		maxprot = VM_PROT_EXECUTE;
	if ((fp->f_flag & FREAD) != 0)
		maxprot |= VM_PROT_READ;
	else if ((prot & VM_PROT_READ) != 0)
		return (EACCES);

	/*
	 * If we are sharing potential changes via MAP_SHARED and we
	 * are trying to get write permission although we opened it
	 * without asking for it, bail out.
	 *
	 * Note that most character devices always share mappings.
	 * The one exception is that D_MMAP_ANON devices
	 * (i.e. /dev/zero) permit private writable mappings.
	 *
	 * Rely on vm_mmap_cdev() to fail invalid MAP_PRIVATE requests
	 * as well as updating maxprot to permit writing for
	 * D_MMAP_ANON devices rather than doing that here.
	 */
	if ((flags & MAP_SHARED) != 0) {
		if ((fp->f_flag & FWRITE) != 0)
			maxprot |= VM_PROT_WRITE;
		else if ((prot & VM_PROT_WRITE) != 0)
			return (EACCES);
	}
	maxprot &= cap_maxprot;

	fpop = td->td_fpop;
	error = devfs_fp_check(fp, &dev, &dsw, &ref);
	if (error != 0)
		return (error);

	error = vm_mmap_cdev(td, size, prot, &maxprot, &flags, dev, dsw, &foff,
	    &object);
	td->td_fpop = fpop;
	dev_relthread(dev, ref);
	if (error != 0)
		return (error);

	error = vm_mmap_object(map, addr, size, prot, maxprot, flags, object,
	    foff, FALSE, td);
	if (error != 0)
		vm_object_deallocate(object);
	return (error);
}

dev_t
dev2udev(struct cdev *x)
{
	if (x == NULL)
		return (NODEV);
	return (cdev2priv(x)->cdp_inode);
}

static int
devfs_cmp_f(struct file *fp1, struct file *fp2, struct thread *td)
{
	if (fp2->f_type != DTYPE_VNODE || fp2->f_ops != &devfs_ops_f)
		return (3);
	return (kcmp_cmp((uintptr_t)fp1->f_data, (uintptr_t)fp2->f_data));
}

static struct fileops devfs_ops_f = {
	.fo_read =	devfs_read_f,
	.fo_write =	devfs_write_f,
	.fo_truncate =	devfs_truncate_f,
	.fo_ioctl =	devfs_ioctl_f,
	.fo_poll =	devfs_poll_f,
	.fo_kqfilter =	devfs_kqfilter_f,
	.fo_stat =	devfs_stat_f,
	.fo_close =	devfs_close_f,
	.fo_chmod =	vn_chmod,
	.fo_chown =	vn_chown,
	.fo_sendfile =	vn_sendfile,
	.fo_seek =	vn_seek,
	.fo_fill_kinfo = vn_fill_kinfo,
	.fo_mmap =	devfs_mmap_f,
	.fo_cmp =	devfs_cmp_f,
	.fo_flags =	DFLAG_PASSABLE | DFLAG_SEEKABLE
};

/* Vops for non-CHR vnodes in /dev. */
static struct vop_vector devfs_vnodeops = {
	.vop_default =		&default_vnodeops,

	.vop_access =		devfs_access,
	.vop_getattr =		devfs_getattr,
	.vop_ioctl =		devfs_rioctl,
	.vop_lookup =		devfs_lookup,
	.vop_mknod =		devfs_mknod,
	.vop_pathconf =		devfs_pathconf,
	.vop_read =		devfs_rread,
	.vop_readdir =		devfs_readdir,
	.vop_readlink =		devfs_readlink,
	.vop_reclaim =		devfs_reclaim,
	.vop_remove =		devfs_remove,
	.vop_revoke =		devfs_revoke,
	.vop_setattr =		devfs_setattr,
#ifdef MAC
	.vop_setlabel =		devfs_setlabel,
#endif
	.vop_symlink =		devfs_symlink,
	.vop_vptocnp =		devfs_vptocnp,
	.vop_lock1 =		vop_lock,
	.vop_unlock =		vop_unlock,
	.vop_islocked =		vop_islocked,
	.vop_add_writecount =	vop_stdadd_writecount_nomsync,
};
VFS_VOP_VECTOR_REGISTER(devfs_vnodeops);

/* Vops for VCHR vnodes in /dev. */
static struct vop_vector devfs_specops = {
	.vop_default =		&default_vnodeops,

	.vop_access =		devfs_access,
	.vop_bmap =		VOP_PANIC,
	.vop_close =		devfs_close,
	.vop_create =		VOP_PANIC,
	.vop_fsync =		vop_stdfsync,
	.vop_getattr =		devfs_getattr,
	.vop_ioctl =		devfs_ioctl,
	.vop_link =		VOP_PANIC,
	.vop_mkdir =		VOP_PANIC,
	.vop_mknod =		VOP_PANIC,
	.vop_open =		devfs_open,
	.vop_pathconf =		devfs_pathconf,
	.vop_poll =		dead_poll,
	.vop_print =		devfs_print,
	.vop_read =		dead_read,
	.vop_readdir =		VOP_PANIC,
	.vop_readlink =		VOP_PANIC,
	.vop_reallocblks =	VOP_PANIC,
	.vop_reclaim =		devfs_reclaim_vchr,
	.vop_remove =		devfs_remove,
	.vop_rename =		VOP_PANIC,
	.vop_revoke =		devfs_revoke,
	.vop_rmdir =		VOP_PANIC,
	.vop_setattr =		devfs_setattr,
#ifdef MAC
	.vop_setlabel =		devfs_setlabel,
#endif
	.vop_strategy =		VOP_PANIC,
	.vop_symlink =		VOP_PANIC,
	.vop_vptocnp =		devfs_vptocnp,
	.vop_write =		dead_write,
	.vop_lock1 =		vop_lock,
	.vop_unlock =		vop_unlock,
	.vop_islocked =		vop_islocked,
	.vop_add_writecount =	vop_stdadd_writecount_nomsync,
};
VFS_VOP_VECTOR_REGISTER(devfs_specops);

/*
 * Our calling convention to the device drivers used to be that we passed
 * vnode.h IO_* flags to read()/write(), but we're moving to fcntl.h O_
 * flags instead since that's what open(), close() and ioctl() takes and
 * we don't really want vnode.h in device drivers.
 * We solved the source compatibility by redefining some vnode flags to
 * be the same as the fcntl ones and by sending down the bitwise OR of
 * the respective fcntl/vnode flags.  These CTASSERTS make sure nobody
 * pulls the rug out under this.
 */
CTASSERT(O_NONBLOCK == IO_NDELAY);
CTASSERT(O_FSYNC == IO_SYNC);