config root man

/*-
 * Copyright (c) 2007 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 * All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: release/9.1.0/sys/cddl/compat/opensolaris/kern/opensolaris_lookup.c 191990 2009-05-11 15:33:26Z attilio $");
 
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/pathname.h>
#include <sys/vfs.h>
#include <sys/vnode.h>

int
lookupname(char *dirname, enum uio_seg seg, enum symfollow follow,
    vnode_t **dirvpp, vnode_t **compvpp)
{

	return (lookupnameat(dirname, seg, follow, dirvpp, compvpp, NULL));
}

int
lookupnameat(char *dirname, enum uio_seg seg, enum symfollow follow,
    vnode_t **dirvpp, vnode_t **compvpp, vnode_t *startvp)
{
	struct nameidata nd;
	int error, ltype;

	ASSERT(dirvpp == NULL);

	vref(startvp);
	ltype = VOP_ISLOCKED(startvp);
	VOP_UNLOCK(startvp, 0);
	NDINIT_ATVP(&nd, LOOKUP, LOCKLEAF | MPSAFE | follow, seg, dirname,
	    startvp, curthread);
	error = namei(&nd);
	*compvpp = nd.ni_vp;
	NDFREE(&nd, NDF_ONLY_PNBUF);
	vn_lock(startvp, ltype | LK_RETRY);
	return (error);
}

int
traverse(vnode_t **cvpp, int lktype)
{
	vnode_t *cvp;
	vnode_t *tvp;
	vfs_t *vfsp;
	int error;

	cvp = *cvpp;
	tvp = NULL;

	/*
	 * If this vnode is mounted on, then we transparently indirect
	 * to the vnode which is the root of the mounted file system.
	 * Before we do this we must check that an unmount is not in
	 * progress on this vnode.
	 */

	for (;;) {
		/*
		 * Reached the end of the mount chain?
		 */
		vfsp = vn_mountedvfs(cvp);
		if (vfsp == NULL)
			break;
		/*
		 * tvp is NULL for *cvpp vnode, which we can't unlock.
		 */
		if (tvp != NULL)
			vput(cvp);
		else
			vrele(cvp);

		/*
		 * The read lock must be held across the call to VFS_ROOT() to
		 * prevent a concurrent unmount from destroying the vfs.
		 */
		error = VFS_ROOT(vfsp, lktype, &tvp);
		if (error != 0)
			return (error);
		cvp = tvp;
	}

	*cvpp = cvp;
	return (0);
}