int
vop_lookup(struct vnode *dvp,
	   struct vnode **vpp,
	   struct componentname *cnp)
{
    int error;
    int nameiop = cnp->cn_nameiop;
    int flags = cnp->cn_flags;
    int lockparent = flags & LOCKPARENT;
    int islastcn = flags & ISLASTCN;
    struct vnode *vp = NULL;

    /*
     * ?ǥ??쥯?ȥ??Υ????????????????å????ޤ???
     */
    if (dvp->v_type != VDIR)
	return ENOTDIR;

    error = VOP_ACCESS(dvp, VEXEC, cred, cnp->cn_thread);
    if (error)
	return (error);

    if (islastcn && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
	(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
	return (EROFS);

    /*
     * ?ǥ??쥯?ȥ?/̾???Υڥ??Τ?????̾???????å??????????å????ޤ???
     * ?????ϡ?¸?ߤ??Ƥ??ʤ?̾???ξ????ˤ? ENOENT ????̾???????Ĥ??ä?
     * ?????ˤ? -1 ?򡢤????Ǥʤ??????ˤ? 0 ???֤??ޤ???
     */
    error = cache_lookup(dvp, vpp, cnp);
    if (error) {
	int vpid;

	if (error = ENOENT)
	    return error;

	vp = *vpp;
	if (dvp == vp) {	/* "." ????õ???ޤ? */
	    VREF(vp);
	    error = 0;
	} else if (flags & ISDOTDOT) {
            /*
	     * ?ǥåɥ??å????򤱤뤿?ᡢ".." ?Υ??å????줿 vnode ??
	     * ???????????ˡ????Υǥ??쥯?ȥ??򥢥????å?????ɬ?פ?
	     * ?????ޤ???
	     */
	    VOP_UNLOCK(dvp);
	    error = vget(vp, 1);
	    if (!error) {
		if (lockparent && islastcn)
		    error = VOP_LOCK(dvp);
	    }
	} else {
	    error = vget(vp, 1);
	    if (error || !(lockparent && islastcn)) {
		VOP_UNLOCK(dvp);
	    }
	}

	/*
	 * ???å????ԤäƤ????֤??????ο????Ѳ????Ƥ??ʤ????Ȥ?
	 * ?????å????ޤ???
	 */
	if (!error) {
	    if (vpid == vp->v_id) {
		/*
		 * lockparent && islastcn ?ξ????ˤ? dvp ?????å?
		 * ?????ޤ??? vp ?????å??????ޤ???
		 */
		return (0);
	    }
	    vput(vp);

	    if (dvp != vp && lockparent && islastcn)
		VOP_UNLOCK(pdp);
	}

	/*
	 * ?ʲ??Υǥ??쥯?ȥ긡???Τ????? dvp ?????٥??å????ޤ???
	 */
	error = VOP_LOCK(dvp);
	if (error) {
	    return (error);
	}

	*vpp = NULL;
    }

    /*
     * ???? cnp->cn_nameptr ?Τ????? dvp ?򸡺????ޤ???
     */
    ...;

    if (!found) {
	if ((nameiop == CREATE || nameiop == RENAME)
	    && islastcn
	    && directory dvp has not been removed) {
	    /*
	     * ?ǥ??쥯?ȥ??ν????߸????????å????ޤ???
	     */

	    /*
	     * ?Ǥ????¤ꡢ?ǥ??쥯?ȥ??????ο????????Ǥ?̾???Τ?????
	     * ??ʬ???礭???????ΰ??֤???Ͽ???ޤ??? ?????? dvp ?Τ?????
	     * vnode ?λ?Ū?ǡ????????˵?Ͽ?????뤳?Ȥ???ǽ?Ǥ???
	     * VOP_CREATE ?ޤ??? VOP_RENAME ?Ǹ??ǻ??Ѥ??뤿???ˡ?
	     * ?ѥ?̾???ݻ????뤿???? SAVENAME ?ե饰?????ꤷ?ޤ???
	     */
	    cnp->cn_flags |= SAVENAME;
	    if (!lockparent)
		/*
		 * ?嵭?ǵ?Ͽ???줿?ɲäΥǡ????? lockparent ??????
		 * ???줿???ˤΤ?ͭ?ѤǤ??뤳?Ȥ????դ??Ƥ?????????
		 */
		VOP_UNLOCK(dvp);

	    return EJUSTRETURN;
	}

	/*
	 * ?????å?????̾???????????뤳?Ȥ???θ???ޤ???
	 */
	if ((cnp->cn_flags & MAKEENTRY) && nameiop != CREATE)
	    cache_enter(dvp, NULL, cnp);

	return ENOENT;
    } else {
	/*
	 * ?????ǥѥ?̾?κǸ??ξ????ˤϡ??ե??????κ????˻??ѤǤ???
	 * ?ѥ??᡼?????֤??ޤ??? wantparent ?ե饰?????ꤵ???Ƥ??ʤ?
	 * ?????ˤϤ??Υǥ??쥯?ȥ??Τߤ??֤????????Ǥʤ??????ˤ?
	 * ³???Ƥ??? inode ?????å?????"." ?????դ??ޤ???
	 */
	if (nameiop == DELETE && islastcn) {
	    /*
	     * ?ǥ??쥯?ȥ??ν????߸????????å????ޤ???
	     */
	    error = VOP_ACCESS(dvp, VWRITE, cred, cnp->cn_thread);
	    if (error)
		return (error);

	    if (found entry is same as dvp) {
		VREF(dvp);
		*vpp = dvp;
		return 0;
	    }

	    error = VFS_VGET(dvp->v_mount, ..., &vp);
	    if (error)
		return error;

	    if (directory is sticky
		&& cred->cr_uid != 0
		&& cred->cr_uid != owner of dvp
		&& owner of vp != cred->cr_uid) {
		vput(vp);
		return EPERM;
	    }
	    *vpp = vp;
	    if (!lockparent)
		VOP_UNLOCK(dvp);

	    return 0;
	}

	/*
	 * ?ƽ????? (RENAME) ?ξ????ˤϡ????? inode ?????Ӹ??ߤ?
	 * ?ǥ??쥯?ȥ????ƽ????ߤ??뤿?????׵ᤵ???????????֤??ޤ???
	 * ?̾??ե??????ޤ??϶??Υǥ??쥯?ȥ??Ǥ??뤳?Ȥ???ǧ???뤿???ˡ?
	 * ?ǥ??쥯?ȥꥨ???ȥ??? inode ?????????ʤ????Фʤ??ޤ?????
	 */
	if (nameiop == RENAME && wantparent && islastcn) {
	    error = VOP_ACCESS(dvp, VWRITE, cred, cnp->cn_thread);
	    if (error)
		return (error);

	    /*
	     * "." ???????å????ޤ???
	     */
	    if (found entry is same as dvp)
		return EISDIR;

	    error = VFS_VGET(dvp->v_mount, ..., &vp);
	    if (error)
		return error;
	    *vpp = vp;
	    /*
	     * ???? VOP_RENAME ?ǻ??Ѥ??뤿????̾??????¸???ޤ???
	     */
	    cnp->cn_flags |= SAVENAME;
	    if (!lockparent)
		VOP_UNLOCK(dvp);

	    return 0;
	}

	/*
	 * ̾?????Ѵ??Υ??ƥåפ????ƤǤ??? ?????ܥ??å????󥯤????ߤ?
	 * ?ǥ??쥯?ȥ꤫???????ФǤ????????ˤϡ?????ɬ?פˤʤ??Τǡ?
	 * ?ǥ??쥯?ȥ??? 'vput' ???ޤ????? ???????? "pdp" ?Ȥ???
	 * ???????å????줿?ǥ??쥯?ȥ?????¸???ޤ??? ???????????ˤ???
	 * inode ???????????ʤ????Ȥ??ݾڤ??뤿???ˡ????Υǥ??쥯?ȥ???
	 * ???????å???????????Ū?? inode ?????????ʤ????Фʤ??ޤ?????
	 * ?롼?Ȥ????ǥ??쥯?ȥ??ĥ꡼?򲼤??????? inode ??????????
	 * ???Ȥǡ??ǥåɥ??å???????ͽ?ɤ??ޤ??? ?????äơ??ո?????
	 * ?ݥ????? ".." ??é???Ȥ??ˤϡ??׵ᤵ?줿?ǥ??쥯?ȥ???????????
	 * ???˿ƥǥ??쥯?ȥ??򥢥????å????ʤ????Фʤ??ޤ????? ".." ??
	 * ??Ϣ?դ????줿 inode ?Τ????? VFS_VGET ?????????ˡ????ߤ?
	 * ?????ӿƥǥ??쥯?ȥ???ξ???????????줿?????ˤϡ???????????Ū??
	 * ???????֤??????ޤ??? ????????ʣ???ʥǥåɥ??å????Х??르?ꥺ??
	 * ?μ????ʤ??ˤ??ζ??????֤??򤱤뤳?Ȥ??Ǥ??ʤ??Τǡ?????
	 * ???????֤?ȯ???????Ǥ??뤳?Ȥ????Ԥ??Ƥ??ޤ??? ?ե????륷???ƥब??
	 *  ".." ?ʳ??ˡ??ǥ??쥯?ȥ깽¤???????̤????ؤ??ϡ??ɥ??󥯤?
	 * ???ľ??硢???δ?ñ?ʥǥåɥ??å????е?????Ư???ʤ????Ȥˤ?????
	 * ???Ƥ?????????
	 */
	if (flags & ISDOTDOT) {
	    VOP_UNLOCK(dvp);	/* inode ?????????뤿???ζ????Ǥ? */
	    error = VFS_VGET(dvp->v_mount, ..., &vp);
	    if (error) {
		VOP_LOCK(dvp);
		return (error);
	    }
	    if (lockparent && islastcn) {
		error = VOP_LOCK(dvp);
		if (error) {
		    vput(vp);
		    return error;
		}
	    }
	    *vpp = vp;
	} else if (found entry is same as dvp) {
	    VREF(dvp);	/* ?㤨?? "." ?ʤɡ???ʬ???Ȥ?ɬ?פǤ? */
	    *vpp = dvp;
	} else {
	    error = VFS_VGET(dvp->v_mount, ..., &vp);
	    if (error)
		return (error);
	    if (!lockparent || !islastcn)
		VOP_UNLOCK(dvp);
	    *vpp = vp;
	}

	/*
	 * Ŭ?ڤǤ?????̾???򥭥??å????????????ޤ???
	 */
	if (cnp->cn_flags & MAKEENTRY)
	    cache_enter(dvp, *vpp, cnp);
	return (0);
    }
}