xref: /src/sys/kern/vfs_vnops.c

/*	$NetBSD: vfs_vnops.c,v 1.72.2.1 2003/07/02 15:26:47 darrenr Exp $	*/

/*
 * Copyright (c) 1982, 1986, 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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 the University of
 *	California, Berkeley and its contributors.
 * 4. 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.
 *
 *	@(#)vfs_vnops.c	8.14 (Berkeley) 6/15/95
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: vfs_vnops.c,v 1.72.2.1 2003/07/02 15:26:47 darrenr Exp $");

#include "fs_union.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/file.h>
#include <sys/stat.h>
#include <sys/buf.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/vnode.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
#include <sys/poll.h>

#include <uvm/uvm_extern.h>

#ifdef UNION
#include <fs/union/union.h>
#endif

#if defined(LKM) || defined(UNION)
int (*vn_union_readdir_hook) (struct vnode **, struct file *, struct proc *);
#endif

#ifdef VERIFIED_EXEC
#include <sys/verified_exec.h>

extern LIST_HEAD(veriexec_devhead, veriexec_dev_list) veriexec_dev_head;
extern struct veriexec_devhead veriexec_file_dev_head;
#endif

static int vn_read(struct file *fp, off_t *offset, struct uio *uio,
	    struct ucred *cred, int flags);
static int vn_write(struct file *fp, off_t *offset, struct uio *uio,
	    struct ucred *cred, int flags);
static int vn_closefile(struct file *fp, struct lwp *l);
static int vn_poll(struct file *fp, int events, struct lwp *l);
static int vn_fcntl(struct file *fp, u_int com, void *data, struct lwp *l);
static int vn_statfile(struct file *fp, struct stat *sb, struct lwp *l);
static int vn_ioctl(struct file *fp, u_long com, void *data, struct lwp *l);

struct 	fileops vnops = {
	vn_read, vn_write, vn_ioctl, vn_fcntl, vn_poll,
	vn_statfile, vn_closefile, vn_kqfilter
};

/*
 * Common code for vnode open operations.
 * Check permissions, and call the VOP_OPEN or VOP_CREATE routine.
 */
int
vn_open(ndp, fmode, cmode)
	struct nameidata *ndp;
	int fmode, cmode;
{
	struct vnode *vp;
	struct lwp *l = ndp->ni_cnd.cn_lwp;
	struct ucred *cred = l->l_proc->p_ucred;
	struct vattr va;
	int error;
#ifdef VERIFIED_EXEC
	char got_dev;
	struct veriexec_inode_list *veriexec_node;
	char fingerprint[MAXFINGERPRINTLEN];
#endif

	if (fmode & O_CREAT) {
		ndp->ni_cnd.cn_nameiop = CREATE;
		ndp->ni_cnd.cn_flags = LOCKPARENT | LOCKLEAF;
		if ((fmode & O_EXCL) == 0 &&
		    ((fmode & O_NOFOLLOW) == 0))
			ndp->ni_cnd.cn_flags |= FOLLOW;
		if ((error = namei(ndp)) != 0)
			return (error);
		if (ndp->ni_vp == NULL) {
			VATTR_NULL(&va);
			va.va_type = VREG;
			va.va_mode = cmode;
			if (fmode & O_EXCL)
				 va.va_vaflags |= VA_EXCLUSIVE;
			VOP_LEASE(ndp->ni_dvp, l, cred, LEASE_WRITE);
			error = VOP_CREATE(ndp->ni_dvp, &ndp->ni_vp,
					   &ndp->ni_cnd, &va);
			if (error)
				return (error);
			fmode &= ~O_TRUNC;
			vp = ndp->ni_vp;
		} else {
			VOP_ABORTOP(ndp->ni_dvp, &ndp->ni_cnd);
			if (ndp->ni_dvp == ndp->ni_vp)
				vrele(ndp->ni_dvp);
			else
				vput(ndp->ni_dvp);
			ndp->ni_dvp = NULL;
			vp = ndp->ni_vp;
			if (fmode & O_EXCL) {
				error = EEXIST;
				goto bad;
			}
			if (ndp->ni_vp->v_type == VLNK) {
				error = EFTYPE;
				goto bad;
			}
			fmode &= ~O_CREAT;
		}
	} else {
		ndp->ni_cnd.cn_nameiop = LOOKUP;
		ndp->ni_cnd.cn_flags = FOLLOW | LOCKLEAF;
		if ((error = namei(ndp)) != 0)
			return (error);
		vp = ndp->ni_vp;
	}
	if (vp->v_type == VSOCK) {
		error = EOPNOTSUPP;
		goto bad;
	}

#ifdef VERIFIED_EXEC
	veriexec_node = NULL;

	if ((error = VOP_GETATTR(vp, &va, cred, l)) != 0)
		goto bad;
#endif

	if ((fmode & O_CREAT) == 0) {
#ifdef VERIFIED_EXEC
		  /*
		   * Look for the file on the fingerprint lists iff
		   * it has not been seen before.
		   */
		if ((vp->fp_status == FINGERPRINT_INVALID) ||
		    (vp->fp_status == FINGERPRINT_NODEV)) {
			  /* check the file list for the finger print */
			veriexec_node = get_veriexec_inode(&veriexec_file_dev_head,
						     va.va_fsid,
						     va.va_fileid,
						     &got_dev);
			if (veriexec_node == NULL) {
				/* failing that, check the exec list */
				veriexec_node = get_veriexec_inode(
					&veriexec_dev_head, va.va_fsid,
					va.va_fileid, &got_dev);
			}

			if ((veriexec_node == NULL) && (got_dev == 1))
				vp->fp_status = FINGERPRINT_NOENTRY;

			if (veriexec_node != NULL) {
				if ((error = evaluate_fingerprint(vp,
						veriexec_node, l, va.va_size,
						fingerprint)) != 0)
					goto bad;

				if (fingerprintcmp(veriexec_node,
						   fingerprint) == 0) {
					  /* fingerprint ok */
					vp->fp_status =	FINGERPRINT_VALID;
#ifdef VERIFIED_EXEC_DEBUG
					printf(
			"file fingerprint matches for dev %lu, file %lu\n",
						va.va_fsid, va.va_fileid);
#endif
				} else {
					vp->fp_status =	FINGERPRINT_NOMATCH;
				}
			}
		}
#endif

		if (fmode & FREAD) {
			if ((error = VOP_ACCESS(vp, VREAD, cred, l)) != 0)
				goto bad;

#ifdef VERIFIED_EXEC
				/* file is on finger print list */
			if (vp->fp_status == FINGERPRINT_NOMATCH) {
				  /* fingerprint bad */
				printf(
		"file fingerprint does not match on dev %lu, file %lu\n",
					va.va_fsid, va.va_fileid);
				if (securelevel > 2) {
					error = EPERM;
					goto bad;
				}
			}
#endif
		}
		if (fmode & (FWRITE | O_TRUNC)) {
			if (vp->v_type == VDIR) {
				error = EISDIR;
				goto bad;
			}
			if ((error = vn_writechk(vp)) != 0 ||
			    (error = VOP_ACCESS(vp, VWRITE, cred, l)) != 0)
				goto bad;
#ifdef VERIFIED_EXEC
			  /*
			   * If file has a fingerprint then
			   * deny the write request, otherwise
			   * invalidate the status so we don't
			   * keep checking for the file having
			   * a fingerprint.
			   */
			if (vp->fp_status == FINGERPRINT_VALID) {
				printf(
		      "writing to fingerprinted file for dev %lu, file %lu\n",
		      va.va_fsid, va.va_fileid);
				if (securelevel > 2) {
					error = EPERM;
					goto bad;
				} else {
					vp->fp_status =	FINGERPRINT_INVALID;
				}
			}
#endif
		}
	}
	if (fmode & O_TRUNC) {
		VOP_UNLOCK(vp, 0);			/* XXX */
		VOP_LEASE(vp, l, cred, LEASE_WRITE);
		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);	/* XXX */
		VATTR_NULL(&va);
		va.va_size = 0;
		if ((error = VOP_SETATTR(vp, &va, cred, l)) != 0)
			goto bad;
	}
	if ((error = VOP_OPEN(vp, fmode, cred, l)) != 0)
		goto bad;
	if (vp->v_type == VREG &&
	    uvn_attach(vp, fmode & FWRITE ? VM_PROT_WRITE : 0) == NULL) {
		error = EIO;
		goto bad;
	}
	if (fmode & FWRITE)
		vp->v_writecount++;

	return (0);
bad:
	vput(vp);
	return (error);
}

/*
 * Check for write permissions on the specified vnode.
 * Prototype text segments cannot be written.
 */
int
vn_writechk(vp)
	struct vnode *vp;
{

	/*
	 * If the vnode is in use as a process's text,
	 * we can't allow writing.
	 */
	if (vp->v_flag & VTEXT)
		return (ETXTBSY);
	return (0);
}

/*
 * Mark a vnode as having executable mappings.
 */
void
vn_markexec(vp)
	struct vnode *vp;
{
	if ((vp->v_flag & VEXECMAP) == 0) {
		uvmexp.filepages -= vp->v_uobj.uo_npages;
		uvmexp.execpages += vp->v_uobj.uo_npages;
	}
	vp->v_flag |= VEXECMAP;
}

/*
 * Mark a vnode as being the text of a process.
 * Fail if the vnode is currently writable.
 */
int
vn_marktext(vp)
	struct vnode *vp;
{

	if (vp->v_writecount != 0) {
		KASSERT((vp->v_flag & VTEXT) == 0);
		return (ETXTBSY);
	}
	vp->v_flag |= VTEXT;
	vn_markexec(vp);
	return (0);
}

/*
 * Vnode close call
 *
 * Note: takes an unlocked vnode, while VOP_CLOSE takes a locked node.
 */
int
vn_close(vp, flags, cred, l)
	struct vnode *vp;
	int flags;
	struct ucred *cred;
	struct lwp *l;
{
	int error;

	if (flags & FWRITE)
		vp->v_writecount--;
	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	error = VOP_CLOSE(vp, flags, cred, l);
	vput(vp);
	return (error);
}

/*
 * Package up an I/O request on a vnode into a uio and do it.
 */
int
vn_rdwr(rw, vp, base, len, offset, segflg, ioflg, cred, aresid, l)
	enum uio_rw rw;
	struct vnode *vp;
	caddr_t base;
	int len;
	off_t offset;
	enum uio_seg segflg;
	int ioflg;
	struct ucred *cred;
	size_t *aresid;
	struct lwp *l;
{
	struct uio auio;
	struct iovec aiov;
	int error;

	if ((ioflg & IO_NODELOCKED) == 0) {
		if (rw == UIO_READ) {
			vn_lock(vp, LK_SHARED | LK_RETRY);
		} else {
			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
		}
	}
	auio.uio_iov = &aiov;
	auio.uio_iovcnt = 1;
	aiov.iov_base = base;
	aiov.iov_len = len;
	auio.uio_resid = len;
	auio.uio_offset = offset;
	auio.uio_segflg = segflg;
	auio.uio_rw = rw;
	auio.uio_lwp = l;
	if (rw == UIO_READ) {
		error = VOP_READ(vp, &auio, ioflg, cred);
	} else {
		error = VOP_WRITE(vp, &auio, ioflg, cred);
	}
	if (aresid)
		*aresid = auio.uio_resid;
	else
		if (auio.uio_resid && error == 0)
			error = EIO;
	if ((ioflg & IO_NODELOCKED) == 0)
		VOP_UNLOCK(vp, 0);
	return (error);
}

int
vn_readdir(fp, buf, segflg, count, done, l, cookies, ncookies)
	struct file *fp;
	char *buf;
	int segflg, *done, *ncookies;
	u_int count;
	struct lwp *l;
	off_t **cookies;
{
	struct vnode *vp = (struct vnode *)fp->f_data;
	struct iovec aiov;
	struct uio auio;
	int error, eofflag;

unionread:
	if (vp->v_type != VDIR)
		return (EINVAL);
	aiov.iov_base = buf;
	aiov.iov_len = count;
	auio.uio_iov = &aiov;
	auio.uio_iovcnt = 1;
	auio.uio_rw = UIO_READ;
	auio.uio_segflg = segflg;
	auio.uio_lwp = l;
	auio.uio_resid = count;
	vn_lock(vp, LK_SHARED | LK_RETRY);
	auio.uio_offset = fp->f_offset;
	error = VOP_READDIR(vp, &auio, fp->f_cred, &eofflag, cookies,
		    ncookies);
	fp->f_offset = auio.uio_offset;
	VOP_UNLOCK(vp, 0);
	if (error)
		return (error);

#if defined(UNION) || defined(LKM)
	if (count == auio.uio_resid && vn_union_readdir_hook) {
		struct vnode *ovp = vp;

		error = (*vn_union_readdir_hook)(&vp, fp, l->l_proc);
		if (error)
			return (error);
		if (vp != ovp)
			goto unionread;
	}
#endif /* UNION || LKM */

	if (count == auio.uio_resid && (vp->v_flag & VROOT) &&
	    (vp->v_mount->mnt_flag & MNT_UNION)) {
		struct vnode *tvp = vp;
		vp = vp->v_mount->mnt_vnodecovered;
		VREF(vp);
		fp->f_data = vp;
		fp->f_offset = 0;
		vrele(tvp);
		goto unionread;
	}
	*done = count - auio.uio_resid;
	return error;
}

/*
 * File table vnode read routine.
 */
static int
vn_read(fp, offset, uio, cred, flags)
	struct file *fp;
	off_t *offset;
	struct uio *uio;
	struct ucred *cred;
	int flags;
{
	struct vnode *vp = (struct vnode *)fp->f_data;
	int count, error, ioflag = 0;

	VOP_LEASE(vp, uio->uio_lwp, cred, LEASE_READ);
	if (fp->f_flag & FNONBLOCK)
		ioflag |= IO_NDELAY;
	if ((fp->f_flag & (FFSYNC | FRSYNC)) == (FFSYNC | FRSYNC))
		ioflag |= IO_SYNC;
	if (fp->f_flag & FALTIO)
		ioflag |= IO_ALTSEMANTICS;
	vn_lock(vp, LK_SHARED | LK_RETRY);
	uio->uio_offset = *offset;
	count = uio->uio_resid;
	error = VOP_READ(vp, uio, ioflag, cred);
	if (flags & FOF_UPDATE_OFFSET)
		*offset += count - uio->uio_resid;
	VOP_UNLOCK(vp, 0);
	return (error);
}

/*
 * File table vnode write routine.
 */
static int
vn_write(fp, offset, uio, cred, flags)
	struct file *fp;
	off_t *offset;
	struct uio *uio;
	struct ucred *cred;
	int flags;
{
	struct vnode *vp = (struct vnode *)fp->f_data;
	int count, error, ioflag = IO_UNIT;

	if (vp->v_type == VREG && (fp->f_flag & O_APPEND))
		ioflag |= IO_APPEND;
	if (fp->f_flag & FNONBLOCK)
		ioflag |= IO_NDELAY;
	if (fp->f_flag & FFSYNC ||
	    (vp->v_mount && (vp->v_mount->mnt_flag & MNT_SYNCHRONOUS)))
		ioflag |= IO_SYNC;
	else if (fp->f_flag & FDSYNC)
		ioflag |= IO_DSYNC;
	if (fp->f_flag & FALTIO)
		ioflag |= IO_ALTSEMANTICS;
	VOP_LEASE(vp, uio->uio_lwp, cred, LEASE_WRITE);
	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	uio->uio_offset = *offset;
	count = uio->uio_resid;
	error = VOP_WRITE(vp, uio, ioflag, cred);
	if (flags & FOF_UPDATE_OFFSET) {
		if (ioflag & IO_APPEND)
			*offset = uio->uio_offset;
		else
			*offset += count - uio->uio_resid;
	}
	VOP_UNLOCK(vp, 0);
	return (error);
}

/*
 * File table vnode stat routine.
 */
static int
vn_statfile(fp, sb, l)
	struct file *fp;
	struct stat *sb;
	struct lwp *l;
{
	struct vnode *vp = (struct vnode *)fp->f_data;

	return vn_stat(vp, sb, l);
}

int
vn_stat(vp, sb, l)
	struct vnode *vp;
	struct stat *sb;
	struct lwp *l;
{
	struct vattr va;
	int error;
	mode_t mode;

	error = VOP_GETATTR(vp, &va, l->l_proc->p_ucred, l);
	if (error)
		return (error);
	/*
	 * Copy from vattr table
	 */
	sb->st_dev = va.va_fsid;
	sb->st_ino = va.va_fileid;
	mode = va.va_mode;
	switch (vp->v_type) {
	case VREG:
		mode |= S_IFREG;
		break;
	case VDIR:
		mode |= S_IFDIR;
		break;
	case VBLK:
		mode |= S_IFBLK;
		break;
	case VCHR:
		mode |= S_IFCHR;
		break;
	case VLNK:
		mode |= S_IFLNK;
		break;
	case VSOCK:
		mode |= S_IFSOCK;
		break;
	case VFIFO:
		mode |= S_IFIFO;
		break;
	default:
		return (EBADF);
	};
	sb->st_mode = mode;
	sb->st_nlink = va.va_nlink;
	sb->st_uid = va.va_uid;
	sb->st_gid = va.va_gid;
	sb->st_rdev = va.va_rdev;
	sb->st_size = va.va_size;
	sb->st_atimespec = va.va_atime;
	sb->st_mtimespec = va.va_mtime;
	sb->st_ctimespec = va.va_ctime;
	sb->st_birthtimespec = va.va_birthtime;
	sb->st_blksize = va.va_blocksize;
	sb->st_flags = va.va_flags;
	sb->st_gen = 0;
	sb->st_blocks = va.va_bytes / S_BLKSIZE;
	return (0);
}

/*
 * File table vnode fcntl routine.
 */
static int
vn_fcntl(fp, com, data, l)
	struct file *fp;
	u_int com;
	void *data;
	struct lwp *l;
{
	struct vnode *vp = ((struct vnode *)fp->f_data);
	int error;

	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
	error = VOP_FCNTL(vp, com, data, fp->f_flag, l->l_proc->p_ucred, l);
	VOP_UNLOCK(vp, 0);
	return (error);
}

/*
 * File table vnode ioctl routine.
 */
static int
vn_ioctl(fp, com, data, l)
	struct file *fp;
	u_long com;
	void *data;
	struct lwp *l;
{
	struct vnode *vp = ((struct vnode *)fp->f_data);
	struct proc *p = l->l_proc;
	struct vattr vattr;
	int error;

	switch (vp->v_type) {

	case VREG:
	case VDIR:
		if (com == FIONREAD) {
			error = VOP_GETATTR(vp, &vattr, l->l_proc->p_ucred, l);
			if (error)
				return (error);
			*(int *)data = vattr.va_size - fp->f_offset;
			return (0);
		}
		if (com == FIOGETBMAP) {
			daddr_t *block;

			if (*(daddr_t *)data < 0)
				return (EINVAL);
			block = (daddr_t *)data;
			return (VOP_BMAP(vp, *block, NULL, block, NULL));
		}
		if (com == OFIOGETBMAP) {
			daddr_t ibn, obn;

			if (*(int32_t *)data < 0)
				return (EINVAL);
			ibn = (daddr_t)*(int32_t *)data;
			error = VOP_BMAP(vp, ibn, NULL, &obn, NULL);
			*(int32_t *)data = (int32_t)obn;
			return error;
		}
		if (com == FIONBIO || com == FIOASYNC)	/* XXX */
			return (0);			/* XXX */
		/* fall into ... */

	case VFIFO:
	case VCHR:
	case VBLK:
		error = VOP_IOCTL(vp, com, data, fp->f_flag,
		    l->l_proc->p_ucred, l);
		if (error == 0 && com == TIOCSCTTY) {
			if (p->p_session->s_ttyvp)
				vrele(p->p_session->s_ttyvp);
			p->p_session->s_ttyvp = vp;
			VREF(vp);
		}
		return (error);

	default:
		return (EPASSTHROUGH);
	}
}

/*
 * File table vnode poll routine.
 */
static int
vn_poll(fp, events, l)
	struct file *fp;
	int events;
	struct lwp *l;
{

	return (VOP_POLL(((struct vnode *)fp->f_data), events, l));
}

/*
 * File table vnode kqfilter routine.
 */
int
vn_kqfilter(fp, kn)
	struct file *fp;
	struct knote *kn;
{

	return (VOP_KQFILTER((struct vnode *)fp->f_data, kn));
}

/*
 * Check that the vnode is still valid, and if so
 * acquire requested lock.
 */
int
vn_lock(vp, flags)
	struct vnode *vp;
	int flags;
{
	int error;

	do {
		if ((flags & LK_INTERLOCK) == 0)
			simple_lock(&vp->v_interlock);
		if (vp->v_flag & VXLOCK) {
			if (flags & LK_NOWAIT) {
				simple_unlock(&vp->v_interlock);
				return EBUSY;
			}
			vp->v_flag |= VXWANT;
			ltsleep(vp, PINOD | PNORELOCK,
			    "vn_lock", 0, &vp->v_interlock);
			error = ENOENT;
		} else {
			error = VOP_LOCK(vp, flags | LK_INTERLOCK);
			if (error == 0 || error == EDEADLK || error == EBUSY)
				return (error);
		}
		flags &= ~LK_INTERLOCK;
	} while (flags & LK_RETRY);
	return (error);
}

/*
 * File table vnode close routine.
 */
static int
vn_closefile(fp, l)
	struct file *fp;
	struct lwp *l;
{

	return (vn_close(((struct vnode *)fp->f_data), fp->f_flag,
		fp->f_cred, l));
}

/*
 * Enable LK_CANRECURSE on lock. Return prior status.
 */
u_int
vn_setrecurse(vp)
	struct vnode *vp;
{
	struct lock *lkp = &vp->v_lock;
	u_int retval = lkp->lk_flags & LK_CANRECURSE;

	lkp->lk_flags |= LK_CANRECURSE;
	return retval;
}

/*
 * Called when done with locksetrecurse.
 */
void
vn_restorerecurse(vp, flags)
	struct vnode *vp;
	u_int flags;
{
	struct lock *lkp = &vp->v_lock;

	lkp->lk_flags &= ~LK_CANRECURSE;
	lkp->lk_flags |= flags;
}