Ejemplo n.º 1
0
/*
 * Search a pathname.
 * This is a very central and rather complicated routine.
 *
 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
 * The starting directory is taken from ni_startdir. The pathname is
 * descended until done, or a symbolic link is encountered. The variable
 * ni_more is clear if the path is completed; it is set to one if a
 * symbolic link needing interpretation is encountered.
 *
 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
 * whether the name is to be looked up, created, renamed, or deleted.
 * When CREATE, RENAME, or DELETE is specified, information usable in
 * creating, renaming, or deleting a directory entry may be calculated.
 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
 * returned unlocked. Otherwise the parent directory is not returned. If
 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
 * the target is returned locked, otherwise it is returned unlocked.
 * When creating or renaming and LOCKPARENT is specified, the target may not
 * be ".".  When deleting and LOCKPARENT is specified, the target may be ".".
 * 
 * Overall outline of lookup:
 *
 * dirloop:
 *	identify next component of name at ndp->ni_ptr
 *	handle degenerate case where name is null string
 *	if .. and crossing mount points and on mounted filesys, find parent
 *	call VNOP_LOOKUP routine for next component name
 *	    directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
 *	    component vnode returned in ni_vp (if it exists), locked.
 *	if result vnode is mounted on and crossing mount points,
 *	    find mounted on vnode
 *	if more components of name, do next level at dirloop
 *	return the answer in ni_vp, locked if LOCKLEAF set
 *	    if LOCKPARENT set, return locked parent in ni_dvp
 *	    if WANTPARENT set, return unlocked parent in ni_dvp
 *
 * Returns:	0			Success
 *		ENOENT			No such file or directory
 *		EBADF			Bad file descriptor
 *		ENOTDIR			Not a directory
 *		EROFS			Read-only file system [CREATE]
 *		EISDIR			Is a directory [CREATE]
 *		cache_lookup_path:ERECYCLE  (vnode was recycled from underneath us, redrive lookup again)
 *		vnode_authorize:EROFS
 *		vnode_authorize:EACCES
 *		vnode_authorize:EPERM
 *		vnode_authorize:???
 *		VNOP_LOOKUP:ENOENT	No such file or directory
 *		VNOP_LOOKUP:EJUSTRETURN	Restart system call (INTERNAL)
 *		VNOP_LOOKUP:???
 *		VFS_ROOT:ENOTSUP
 *		VFS_ROOT:ENOENT
 *		VFS_ROOT:???
 */
int
lookup(struct nameidata *ndp)
{
	char	*cp;		/* pointer into pathname argument */
	vnode_t		tdp;		/* saved dp */
	vnode_t		dp;		/* the directory we are searching */
	int docache = 1;		/* == 0 do not cache last component */
	int wantparent;			/* 1 => wantparent or lockparent flag */
	int rdonly;			/* lookup read-only flag bit */
	int dp_authorized = 0;
	int error = 0;
	struct componentname *cnp = &ndp->ni_cnd;
	vfs_context_t ctx = cnp->cn_context;
	int vbusyflags = 0;
	int nc_generation = 0;
	vnode_t last_dp = NULLVP;
	int keep_going;
	int atroot;

	/*
	 * Setup: break out flag bits into variables.
	 */
	if (cnp->cn_flags & (NOCACHE | DOWHITEOUT)) {
	        if ((cnp->cn_flags & NOCACHE) || (cnp->cn_nameiop == DELETE))
		        docache = 0;
	}
	wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
	rdonly = cnp->cn_flags & RDONLY;
	cnp->cn_flags &= ~ISSYMLINK;
	cnp->cn_consume = 0;

	dp = ndp->ni_startdir;
	ndp->ni_startdir = NULLVP;

	if ((cnp->cn_flags & CN_NBMOUNTLOOK) != 0)
			vbusyflags = LK_NOWAIT;
	cp = cnp->cn_nameptr;

	if (*cp == '\0') {
	        if ( (vnode_getwithref(dp)) ) {
			dp = NULLVP;
		        error = ENOENT;
			goto bad;
		}
		ndp->ni_vp = dp;
		error = lookup_handle_emptyname(ndp, cnp, wantparent);
		if (error) {
			goto bad;
		}

		return 0;
	}
dirloop: 
	atroot = 0;
	ndp->ni_vp = NULLVP;

	if ( (error = cache_lookup_path(ndp, cnp, dp, ctx, &dp_authorized, last_dp)) ) {
		dp = NULLVP;
		goto bad;
	}
	if ((cnp->cn_flags & ISLASTCN)) {
	        if (docache)
		        cnp->cn_flags |= MAKEENTRY;
	} else
	        cnp->cn_flags |= MAKEENTRY;

	dp = ndp->ni_dvp;

	if (ndp->ni_vp != NULLVP) {
	        /*
		 * cache_lookup_path returned a non-NULL ni_vp then,
		 * we're guaranteed that the dp is a VDIR, it's 
		 * been authorized, and vp is not ".."
		 *
		 * make sure we don't try to enter the name back into
		 * the cache if this vp is purged before we get to that
		 * check since we won't have serialized behind whatever
		 * activity is occurring in the FS that caused the purge
		 */
	        if (dp != NULLVP)
		        nc_generation = dp->v_nc_generation - 1;

	        goto returned_from_lookup_path;
	}

	/*
	 * Handle "..": two special cases.
	 * 1. If at root directory (e.g. after chroot)
	 *    or at absolute root directory
	 *    then ignore it so can't get out.
	 * 2. If this vnode is the root of a mounted
	 *    filesystem, then replace it with the
	 *    vnode which was mounted on so we take the
	 *    .. in the other file system.
	 */
	if ( (cnp->cn_flags & ISDOTDOT) ) {
		for (;;) {
		        if (dp == ndp->ni_rootdir || dp == rootvnode) {
			        ndp->ni_dvp = dp;
				ndp->ni_vp = dp;
				/*
				 * we're pinned at the root
				 * we've already got one reference on 'dp'
				 * courtesy of cache_lookup_path... take
				 * another one for the ".."
				 * if we fail to get the new reference, we'll
				 * drop our original down in 'bad'
				 */
				if ( (vnode_get(dp)) ) {
					error = ENOENT;
					goto bad;
				}
				atroot = 1;
				goto returned_from_lookup_path;
			}
			if ((dp->v_flag & VROOT) == 0 ||
			    (cnp->cn_flags & NOCROSSMOUNT))
			        break;
			if (dp->v_mount == NULL) {	/* forced umount */
			        error = EBADF;
				goto bad;
			}
			tdp = dp;
			dp = tdp->v_mount->mnt_vnodecovered;

			vnode_put(tdp);

			if ( (vnode_getwithref(dp)) ) {
			        dp = NULLVP;
				error = ENOENT;
				goto bad;
			}
			ndp->ni_dvp = dp;
			dp_authorized = 0;
		}
	}

	/*
	 * We now have a segment name to search for, and a directory to search.
	 */
unionlookup:
	ndp->ni_vp = NULLVP;

	if (dp->v_type != VDIR) {
	        error = ENOTDIR;
	        goto lookup_error;
	}
	if ( (cnp->cn_flags & DONOTAUTH) != DONOTAUTH ) {
		error = lookup_authorize_search(dp, cnp, dp_authorized, ctx);
		if (error) {
			goto lookup_error;
		}
	}

	/*
	 * Now that we've authorized a lookup, can bail out if the filesystem
	 * will be doing a batched operation.  Return an iocount on dvp.
	 */
#if NAMEDRSRCFORK
	if ((cnp->cn_flags & ISLASTCN) && namei_compound_available(dp, ndp) && !(cnp->cn_flags & CN_WANTSRSRCFORK)) {
#else 
	if ((cnp->cn_flags & ISLASTCN) && namei_compound_available(dp, ndp)) {
#endif /* NAMEDRSRCFORK */
		ndp->ni_flag |= NAMEI_UNFINISHED;
		ndp->ni_ncgeneration = dp->v_nc_generation;
		return 0;
	}

        nc_generation = dp->v_nc_generation;

	error = VNOP_LOOKUP(dp, &ndp->ni_vp, cnp, ctx);


	if ( error ) {
lookup_error:
		if ((error == ENOENT) &&
		    (dp->v_flag & VROOT) && (dp->v_mount != NULL) &&
		    (dp->v_mount->mnt_flag & MNT_UNION)) {
#if CONFIG_VFS_FUNNEL
		        if ((cnp->cn_flags & FSNODELOCKHELD)) {
			        cnp->cn_flags &= ~FSNODELOCKHELD;
				unlock_fsnode(dp, NULL);
			}	
#endif /* CONFIG_VFS_FUNNEL */
			tdp = dp;
			dp = tdp->v_mount->mnt_vnodecovered;

			vnode_put(tdp);

			if ( (vnode_getwithref(dp)) ) {
			        dp = NULLVP;
				error = ENOENT;
				goto bad;
			}
			ndp->ni_dvp = dp;
			dp_authorized = 0;
			goto unionlookup;
		}

		if (error != EJUSTRETURN)
			goto bad;

		if (ndp->ni_vp != NULLVP)
			panic("leaf should be empty");

		error = lookup_validate_creation_path(ndp);
		if (error)
			goto bad;
		/*
		 * We return with ni_vp NULL to indicate that the entry
		 * doesn't currently exist, leaving a pointer to the
		 * referenced directory vnode in ndp->ni_dvp.
		 */
		if (cnp->cn_flags & SAVESTART) {
			if ( (vnode_get(ndp->ni_dvp)) ) {
				error = ENOENT;
				goto bad;
			}
			ndp->ni_startdir = ndp->ni_dvp;
		}
		if (!wantparent)
		        vnode_put(ndp->ni_dvp);

		if (kdebug_enable)
		        kdebug_lookup(ndp->ni_dvp, cnp);
		return (0);
	}
returned_from_lookup_path:
	/* We'll always have an iocount on ni_vp when this finishes. */
	error = lookup_handle_found_vnode(ndp, cnp, rdonly, vbusyflags, &keep_going, nc_generation, wantparent, atroot, ctx);
	if (error != 0) {
		goto bad2; 
	}

	if (keep_going) {
		dp = ndp->ni_vp;

		/* namei() will handle symlinks */
		if ((dp->v_type == VLNK) &&
				((cnp->cn_flags & FOLLOW) || (ndp->ni_flag & NAMEI_TRAILINGSLASH) || *ndp->ni_next == '/')) {
			return 0; 
		}

		/*
		 * Otherwise, there's more path to process.  
		 * cache_lookup_path is now responsible for dropping io ref on dp
		 * when it is called again in the dirloop.  This ensures we hold
		 * a ref on dp until we complete the next round of lookup.
		 */
		last_dp = dp;

		goto dirloop;
	}

	return (0);
bad2:
#if CONFIG_VFS_FUNNEL
	if ((cnp->cn_flags & FSNODELOCKHELD)) {
	        cnp->cn_flags &= ~FSNODELOCKHELD;
		unlock_fsnode(ndp->ni_dvp, NULL);
	}
#endif /* CONFIG_VFS_FUNNEL */
	if (ndp->ni_dvp)
		vnode_put(ndp->ni_dvp);

	vnode_put(ndp->ni_vp);
	ndp->ni_vp = NULLVP;

	if (kdebug_enable)
	        kdebug_lookup(dp, cnp);
	return (error);

bad:
#if CONFIG_VFS_FUNNEL
	if ((cnp->cn_flags & FSNODELOCKHELD)) {
	        cnp->cn_flags &= ~FSNODELOCKHELD;
		unlock_fsnode(ndp->ni_dvp, NULL);
	}	
#endif /* CONFIG_VFS_FUNNEL */
	if (dp)
	        vnode_put(dp);
	ndp->ni_vp = NULLVP;

	if (kdebug_enable)
	        kdebug_lookup(dp, cnp);
	return (error);
}

int 
lookup_validate_creation_path(struct nameidata *ndp)
{
	struct componentname *cnp = &ndp->ni_cnd;

	/*
	 * If creating and at end of pathname, then can consider
	 * allowing file to be created.
	 */
	if (cnp->cn_flags & RDONLY) {
		return EROFS;
	}
	if ((cnp->cn_flags & ISLASTCN) && (ndp->ni_flag & NAMEI_TRAILINGSLASH) && !(cnp->cn_flags & WILLBEDIR)) {
		return ENOENT;
	}
	
	return 0;
}

/*
 * Modifies only ni_vp.  Always returns with ni_vp still valid (iocount held).
 */
int
lookup_traverse_mountpoints(struct nameidata *ndp, struct componentname *cnp, vnode_t dp, 
		int vbusyflags, vfs_context_t ctx)
{
	mount_t mp;
	vnode_t tdp;
	int error = 0;
	uthread_t uth;
	uint32_t depth = 0;
	int dont_cache_mp = 0;
	vnode_t	mounted_on_dp;
	int current_mount_generation = 0;
	
	mounted_on_dp = dp;
	current_mount_generation = mount_generation;

	while ((dp->v_type == VDIR) && dp->v_mountedhere &&
			((cnp->cn_flags & NOCROSSMOUNT) == 0)) {
#if CONFIG_TRIGGERS
		/*
		 * For a trigger vnode, call its resolver when crossing its mount (if requested)
		 */
		if (dp->v_resolve) {
			(void) vnode_trigger_resolve(dp, ndp, ctx);
		}
#endif
		vnode_lock(dp);

		if ((dp->v_type == VDIR) && (mp = dp->v_mountedhere)) {

			mp->mnt_crossref++;
			vnode_unlock(dp);


			if (vfs_busy(mp, vbusyflags)) {
				mount_dropcrossref(mp, dp, 0);
				if (vbusyflags == LK_NOWAIT) {
					error = ENOENT;
					goto out;
				}

				continue;
			}


			/*
			 * XXX - if this is the last component of the
			 * pathname, and it's either not a lookup operation
			 * or the NOTRIGGER flag is set for the operation,
			 * set a uthread flag to let VFS_ROOT() for autofs
			 * know it shouldn't trigger a mount.
			 */
			uth = (struct uthread *)get_bsdthread_info(current_thread());
			if ((cnp->cn_flags & ISLASTCN) &&
					(cnp->cn_nameiop != LOOKUP ||
					 (cnp->cn_flags & NOTRIGGER))) {
				uth->uu_notrigger = 1;
				dont_cache_mp = 1;
			}

			error = VFS_ROOT(mp, &tdp, ctx);
			/* XXX - clear the uthread flag */
			uth->uu_notrigger = 0;

			mount_dropcrossref(mp, dp, 0);
			vfs_unbusy(mp);

			if (error) {
				goto out;
			}

			vnode_put(dp);
			ndp->ni_vp = dp = tdp;
			depth++;

#if CONFIG_TRIGGERS
			/*
			 * Check if root dir is a trigger vnode
			 */
			if (dp->v_resolve) {
				error = vnode_trigger_resolve(dp, ndp, ctx);
				if (error) {
					goto out;
				}
			}
#endif			

		} else { 
			vnode_unlock(dp);
			break;
		}
	}

	if (depth && !dont_cache_mp) {
	        mp = mounted_on_dp->v_mountedhere;

		if (mp) {
		        mount_lock_spin(mp);
			mp->mnt_realrootvp_vid = dp->v_id;
			mp->mnt_realrootvp = dp;
			mp->mnt_generation = current_mount_generation;
			mount_unlock(mp);
		}
	}

	return 0;

out:
	return error;
}
Ejemplo n.º 2
0
/*
 * Search a pathname.
 * This is a very central and rather complicated routine.
 *
 * The pathname is pointed to by ni_ptr and is of length ni_pathlen.
 * The starting directory is taken from ni_startdir. The pathname is
 * descended until done, or a symbolic link is encountered. The variable
 * ni_more is clear if the path is completed; it is set to one if a
 * symbolic link needing interpretation is encountered.
 *
 * The flag argument is LOOKUP, CREATE, RENAME, or DELETE depending on
 * whether the name is to be looked up, created, renamed, or deleted.
 * When CREATE, RENAME, or DELETE is specified, information usable in
 * creating, renaming, or deleting a directory entry may be calculated.
 * If flag has LOCKPARENT or'ed into it, the parent directory is returned
 * locked. If flag has WANTPARENT or'ed into it, the parent directory is
 * returned unlocked. Otherwise the parent directory is not returned. If
 * the target of the pathname exists and LOCKLEAF is or'ed into the flag
 * the target is returned locked, otherwise it is returned unlocked.
 * When creating or renaming and LOCKPARENT is specified, the target may not
 * be ".".  When deleting and LOCKPARENT is specified, the target may be ".".
 * 
 * Overall outline of lookup:
 *
 * dirloop:
 *	identify next component of name at ndp->ni_ptr
 *	handle degenerate case where name is null string
 *	if .. and crossing mount points and on mounted filesys, find parent
 *	call VNOP_LOOKUP routine for next component name
 *	    directory vnode returned in ni_dvp, unlocked unless LOCKPARENT set
 *	    component vnode returned in ni_vp (if it exists), locked.
 *	if result vnode is mounted on and crossing mount points,
 *	    find mounted on vnode
 *	if more components of name, do next level at dirloop
 *	return the answer in ni_vp, locked if LOCKLEAF set
 *	    if LOCKPARENT set, return locked parent in ni_dvp
 *	    if WANTPARENT set, return unlocked parent in ni_dvp
 *
 * Returns:	0			Success
 *		ENOENT			No such file or directory
 *		EBADF			Bad file descriptor
 *		ENOTDIR			Not a directory
 *		EROFS			Read-only file system [CREATE]
 *		EISDIR			Is a directory [CREATE]
 *		cache_lookup_path:ERECYCLE  (vnode was recycled from underneath us, redrive lookup again)
 *		vnode_authorize:EROFS
 *		vnode_authorize:EACCES
 *		vnode_authorize:EPERM
 *		vnode_authorize:???
 *		VNOP_LOOKUP:ENOENT	No such file or directory
 *		VNOP_LOOKUP:EJUSTRETURN	Restart system call (INTERNAL)
 *		VNOP_LOOKUP:???
 *		VFS_ROOT:ENOTSUP
 *		VFS_ROOT:ENOENT
 *		VFS_ROOT:???
 */
int
lookup(struct nameidata *ndp)
{
	char	*cp;		/* pointer into pathname argument */
	vnode_t		tdp;		/* saved dp */
	vnode_t		dp;		/* the directory we are searching */
	mount_t		mp;		/* mount table entry */
	int docache = 1;		/* == 0 do not cache last component */
	int wantparent;			/* 1 => wantparent or lockparent flag */
	int rdonly;			/* lookup read-only flag bit */
	int trailing_slash = 0;
	int dp_authorized = 0;
	int error = 0;
	struct componentname *cnp = &ndp->ni_cnd;
	vfs_context_t ctx = cnp->cn_context;
	int mounted_on_depth = 0;
	int dont_cache_mp = 0;
	vnode_t	mounted_on_dp = NULLVP;
	int current_mount_generation = 0;
	int vbusyflags = 0;
	int nc_generation = 0;
	vnode_t last_dp = NULLVP;

	/*
	 * Setup: break out flag bits into variables.
	 */
	if (cnp->cn_flags & (NOCACHE | DOWHITEOUT)) {
	        if ((cnp->cn_flags & NOCACHE) || (cnp->cn_nameiop == DELETE))
		        docache = 0;
	}
	wantparent = cnp->cn_flags & (LOCKPARENT | WANTPARENT);
	rdonly = cnp->cn_flags & RDONLY;
	cnp->cn_flags &= ~ISSYMLINK;
	cnp->cn_consume = 0;

	dp = ndp->ni_startdir;
	ndp->ni_startdir = NULLVP;

	if ((cnp->cn_flags & CN_NBMOUNTLOOK) != 0)
			vbusyflags = LK_NOWAIT;
	cp = cnp->cn_nameptr;

	if (*cp == '\0') {
	        if ( (vnode_getwithref(dp)) ) {
			dp = NULLVP;
		        error = ENOENT;
			goto bad;
		}
		goto emptyname;
	}
dirloop: 
	ndp->ni_vp = NULLVP;

	if ( (error = cache_lookup_path(ndp, cnp, dp, ctx, &trailing_slash, &dp_authorized, last_dp)) ) {
		dp = NULLVP;
		goto bad;
	}
	if ((cnp->cn_flags & ISLASTCN)) {
	        if (docache)
		        cnp->cn_flags |= MAKEENTRY;
	} else
	        cnp->cn_flags |= MAKEENTRY;

	dp = ndp->ni_dvp;

	if (ndp->ni_vp != NULLVP) {
	        /*
		 * cache_lookup_path returned a non-NULL ni_vp then,
		 * we're guaranteed that the dp is a VDIR, it's 
		 * been authorized, and vp is not ".."
		 *
		 * make sure we don't try to enter the name back into
		 * the cache if this vp is purged before we get to that
		 * check since we won't have serialized behind whatever
		 * activity is occurring in the FS that caused the purge
		 */
	        if (dp != NULLVP)
		        nc_generation = dp->v_nc_generation - 1;

	        goto returned_from_lookup_path;
	}

	/*
	 * Handle "..": two special cases.
	 * 1. If at root directory (e.g. after chroot)
	 *    or at absolute root directory
	 *    then ignore it so can't get out.
	 * 2. If this vnode is the root of a mounted
	 *    filesystem, then replace it with the
	 *    vnode which was mounted on so we take the
	 *    .. in the other file system.
	 */
	if ( (cnp->cn_flags & ISDOTDOT) ) {
		for (;;) {
		        if (dp == ndp->ni_rootdir || dp == rootvnode) {
			        ndp->ni_dvp = dp;
				ndp->ni_vp = dp;
				/*
				 * we're pinned at the root
				 * we've already got one reference on 'dp'
				 * courtesy of cache_lookup_path... take
				 * another one for the ".."
				 * if we fail to get the new reference, we'll
				 * drop our original down in 'bad'
				 */
				if ( (vnode_get(dp)) ) {
					error = ENOENT;
					goto bad;
				}
				goto nextname;
			}
			if ((dp->v_flag & VROOT) == 0 ||
			    (cnp->cn_flags & NOCROSSMOUNT))
			        break;
			if (dp->v_mount == NULL) {	/* forced umount */
			        error = EBADF;
				goto bad;
			}
			tdp = dp;
			dp = tdp->v_mount->mnt_vnodecovered;

			vnode_put(tdp);

			if ( (vnode_getwithref(dp)) ) {
			        dp = NULLVP;
				error = ENOENT;
				goto bad;
			}
			ndp->ni_dvp = dp;
			dp_authorized = 0;
		}
	}

	/*
	 * We now have a segment name to search for, and a directory to search.
	 */
unionlookup:
	ndp->ni_vp = NULLVP;

	if (dp->v_type != VDIR) {
	        error = ENOTDIR;
	        goto lookup_error;
	}
	if ( (cnp->cn_flags & DONOTAUTH) != DONOTAUTH ) {
		if (!dp_authorized) {
			error = vnode_authorize(dp, NULL, KAUTH_VNODE_SEARCH, ctx);
			if (error)
				goto lookup_error;
		}
#if CONFIG_MACF
		error = mac_vnode_check_lookup(ctx, dp, cnp);
		if (error)
			goto lookup_error;
#endif /* CONFIG_MACF */
	}

        nc_generation = dp->v_nc_generation;

	if ( (error = VNOP_LOOKUP(dp, &ndp->ni_vp, cnp, ctx)) ) {
lookup_error:
		if ((error == ENOENT) &&
		    (dp->v_flag & VROOT) && (dp->v_mount != NULL) &&
		    (dp->v_mount->mnt_flag & MNT_UNION)) {
		        if ((cnp->cn_flags & FSNODELOCKHELD)) {
			        cnp->cn_flags &= ~FSNODELOCKHELD;
				unlock_fsnode(dp, NULL);
			}	
			tdp = dp;
			dp = tdp->v_mount->mnt_vnodecovered;

			vnode_put(tdp);

			if ( (vnode_getwithref(dp)) ) {
			        dp = NULLVP;
				error = ENOENT;
				goto bad;
			}
			ndp->ni_dvp = dp;
			dp_authorized = 0;
			goto unionlookup;
		}

		if (error != EJUSTRETURN)
			goto bad;

		if (ndp->ni_vp != NULLVP)
			panic("leaf should be empty");

		/*
		 * If creating and at end of pathname, then can consider
		 * allowing file to be created.
		 */
		if (rdonly) {
			error = EROFS;
			goto bad;
		}
		if ((cnp->cn_flags & ISLASTCN) && trailing_slash && !(cnp->cn_flags & WILLBEDIR)) {
			error = ENOENT;
			goto bad;
		}
		/*
		 * We return with ni_vp NULL to indicate that the entry
		 * doesn't currently exist, leaving a pointer to the
		 * referenced directory vnode in ndp->ni_dvp.
		 */
		if (cnp->cn_flags & SAVESTART) {
			if ( (vnode_get(ndp->ni_dvp)) ) {
				error = ENOENT;
				goto bad;
			}
			ndp->ni_startdir = ndp->ni_dvp;
		}
		if (!wantparent)
		        vnode_put(ndp->ni_dvp);

		if (kdebug_enable)
		        kdebug_lookup(ndp->ni_dvp, cnp);
		return (0);
	}
returned_from_lookup_path:
	dp = ndp->ni_vp;

	/*
	 * Take into account any additional components consumed by
	 * the underlying filesystem.
	 */
	if (cnp->cn_consume > 0) {
		cnp->cn_nameptr += cnp->cn_consume;
		ndp->ni_next += cnp->cn_consume;
		ndp->ni_pathlen -= cnp->cn_consume;
		cnp->cn_consume = 0;
	} else {
	        if (dp->v_name == NULL || dp->v_parent == NULLVP) {
		        int isdot_or_dotdot;
			int  update_flags = 0;

			isdot_or_dotdot = (cnp->cn_namelen == 1 && cnp->cn_nameptr[0] == '.') || (cnp->cn_flags & ISDOTDOT);
	    
			if (isdot_or_dotdot == 0) {
			        if (dp->v_name == NULL)
					update_flags |= VNODE_UPDATE_NAME;
				if (ndp->ni_dvp != NULLVP && dp->v_parent == NULLVP)
				        update_flags |= VNODE_UPDATE_PARENT;

				if (update_flags)
				        vnode_update_identity(dp, ndp->ni_dvp, cnp->cn_nameptr, cnp->cn_namelen, cnp->cn_hash, update_flags);
			}
		}
		if ( (cnp->cn_flags & MAKEENTRY) && (dp->v_flag & VNCACHEABLE) && LIST_FIRST(&dp->v_nclinks) == NULL) {
		        /*
			 * missing from name cache, but should
			 * be in it... this can happen if volfs
			 * causes the vnode to be created or the
			 * name cache entry got recycled but the
			 * vnode didn't...
			 * check to make sure that ni_dvp is valid
			 * cache_lookup_path may return a NULL
			 * do a quick check to see if the generation of the
			 * directory matches our snapshot... this will get
			 * rechecked behind the name cache lock, but if it
			 * already fails to match, no need to go any further
			 */
		        if (ndp->ni_dvp != NULLVP && (nc_generation == ndp->ni_dvp->v_nc_generation))
			        cache_enter_with_gen(ndp->ni_dvp, dp, cnp, nc_generation);
		}
	}

	mounted_on_dp = dp;
	mounted_on_depth = 0;
	dont_cache_mp = 0;
	current_mount_generation = mount_generation;
	/*
	 * Check to see if the vnode has been mounted on...
	 * if so find the root of the mounted file system.
	 */
check_mounted_on:
	if ((dp->v_type == VDIR) && dp->v_mountedhere &&
            ((cnp->cn_flags & NOCROSSMOUNT) == 0)) {
	  
	        vnode_lock(dp);

		if ((dp->v_type == VDIR) && (mp = dp->v_mountedhere)) {
			struct uthread *uth = (struct uthread *)get_bsdthread_info(current_thread());

			mp->mnt_crossref++;
			vnode_unlock(dp);

				
			if (vfs_busy(mp, vbusyflags)) {
				mount_dropcrossref(mp, dp, 0);
				if (vbusyflags == LK_NOWAIT) {
					error = ENOENT;
					goto bad2;	
				}
				goto check_mounted_on;
			}

			/*
			 * XXX - if this is the last component of the
			 * pathname, and it's either not a lookup operation
			 * or the NOTRIGGER flag is set for the operation,
			 * set a uthread flag to let VFS_ROOT() for autofs
			 * know it shouldn't trigger a mount.
			 */
			if ((cnp->cn_flags & ISLASTCN) &&
			    (cnp->cn_nameiop != LOOKUP ||
			     (cnp->cn_flags & NOTRIGGER))) {
				uth->uu_notrigger = 1;
				dont_cache_mp = 1;
			}
			error = VFS_ROOT(mp, &tdp, ctx);
			/* XXX - clear the uthread flag */
			uth->uu_notrigger = 0;
			/*
			 * mount_dropcrossref does a vnode_put
			 * on dp if the 3rd arg is non-zero
			 */
			mount_dropcrossref(mp, dp, 1);
			dp = NULL;
			vfs_unbusy(mp);

			if (error) {
				goto bad2;
			}
			ndp->ni_vp = dp = tdp;
			mounted_on_depth++;
			
			goto check_mounted_on;
		} 
		vnode_unlock(dp);
	}

#if CONFIG_MACF
	if (vfs_flags(vnode_mount(dp)) & MNT_MULTILABEL) {
		error = vnode_label(vnode_mount(dp), NULL, dp, NULL,
		    VNODE_LABEL_NEEDREF, ctx);
		if (error)
		        goto bad2;
	}
#endif

	if (mounted_on_depth && !dont_cache_mp) {
	        mp = mounted_on_dp->v_mountedhere;

		if (mp) {
		        mount_lock(mp);
			mp->mnt_realrootvp_vid = dp->v_id;
			mp->mnt_realrootvp = dp;
			mp->mnt_generation = current_mount_generation;
			mount_unlock(mp);
		}
	}

	/*
	 * Check for symbolic link
	 */
	if ((dp->v_type == VLNK) &&
	    ((cnp->cn_flags & FOLLOW) || trailing_slash || *ndp->ni_next == '/')) {
		cnp->cn_flags |= ISSYMLINK;
		return (0);
	}

	/*
	 * Check for bogus trailing slashes.
	 */
	if (trailing_slash) {
		if (dp->v_type != VDIR) {
			error = ENOTDIR;
			goto bad2;
		}
		trailing_slash = 0;
	}

nextname:
	/*
	 * Not a symbolic link.  If more pathname,
	 * continue at next component, else return.
	 */
	if (*ndp->ni_next == '/') {
		cnp->cn_nameptr = ndp->ni_next + 1;
		ndp->ni_pathlen--;
		while (*cnp->cn_nameptr == '/') {
			cnp->cn_nameptr++;
			ndp->ni_pathlen--;
		}
		vnode_put(ndp->ni_dvp);

		cp = cnp->cn_nameptr;

		if (*cp == '\0')
			goto emptyname;

		/*
		 * cache_lookup_path is now responsible for dropping io ref on dp
		 * when it is called again in the dirloop.  This ensures we hold
		 * a ref on dp until we complete the next round of lookup.
		 */
		last_dp = dp;
		goto dirloop;
	}
				  
	/*
	 * Disallow directory write attempts on read-only file systems.
	 */
	if (rdonly &&
	    (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)) {
		error = EROFS;
		goto bad2;
	}
	if (cnp->cn_flags & SAVESTART) {
	        /*	
		 * note that we already hold a reference
		 * on both dp and ni_dvp, but for some reason
		 * can't get another one... in this case we
		 * need to do vnode_put on dp in 'bad2'
		 */
	        if ( (vnode_get(ndp->ni_dvp)) ) {
		        error = ENOENT;
			goto bad2;
		}
		ndp->ni_startdir = ndp->ni_dvp;
	}
	if (!wantparent && ndp->ni_dvp) {
		vnode_put(ndp->ni_dvp);
		ndp->ni_dvp = NULLVP;
	}

	if (cnp->cn_flags & AUDITVNPATH1)
		AUDIT_ARG(vnpath, dp, ARG_VNODE1);
	else if (cnp->cn_flags & AUDITVNPATH2)
		AUDIT_ARG(vnpath, dp, ARG_VNODE2);

#if NAMEDRSRCFORK
	/*
	 * Caller wants the resource fork.
	 */
	if ((cnp->cn_flags & CN_WANTSRSRCFORK) && (dp != NULLVP)) {
		vnode_t svp = NULLVP;
		enum nsoperation nsop;

		if (dp->v_type != VREG) {
			error = ENOENT;
			goto bad2;
		}
		switch (cnp->cn_nameiop) {
		case DELETE:
			nsop = NS_DELETE;
			break;
		case CREATE:
			nsop = NS_CREATE;
			break;
		case LOOKUP:
			/* Make sure our lookup of "/..namedfork/rsrc" is allowed. */
			if (cnp->cn_flags & CN_ALLOWRSRCFORK) {
				nsop = NS_OPEN;
			} else {
				error = EPERM;
				goto bad2;
			}
			break;
		default:
			error = EPERM;
			goto bad2;
		}
		/* Ask the file system for the resource fork. */
		error = vnode_getnamedstream(dp, &svp, XATTR_RESOURCEFORK_NAME, nsop, 0, ctx);

		/* During a create, it OK for stream vnode to be missing. */
		if (error == ENOATTR || error == ENOENT) {
			error = (nsop == NS_CREATE) ? 0 : ENOENT;
		}		
		if (error) {
			goto bad2;
		}
		/* The "parent" of the stream is the file. */
		if (wantparent) {
			if (ndp->ni_dvp) {
				if (ndp->ni_cnd.cn_flags & FSNODELOCKHELD) {
					ndp->ni_cnd.cn_flags &= ~FSNODELOCKHELD;
					unlock_fsnode(ndp->ni_dvp, NULL);
				}	
				vnode_put(ndp->ni_dvp);
			}
			ndp->ni_dvp = dp;
		} else {
			vnode_put(dp);
		}
		ndp->ni_vp = dp = svp;  /* on create this may be null */

		/* Restore the truncated pathname buffer (for audits). */
		if (ndp->ni_pathlen == 1 && ndp->ni_next[0] == '\0') {
			ndp->ni_next[0] = '/';
		}
		cnp->cn_flags  &= ~MAKEENTRY;
	}
#endif
	if (kdebug_enable)
	        kdebug_lookup(dp, cnp);
	return (0);

emptyname:
	cnp->cn_namelen = 0;
	/*
	 * A degenerate name (e.g. / or "") which is a way of
	 * talking about a directory, e.g. like "/." or ".".
	 */
	if (dp->v_type != VDIR) {
		error = ENOTDIR;
		goto bad;
	}
	if (cnp->cn_nameiop != LOOKUP) {
		error = EISDIR;
		goto bad;
	}
	if (wantparent) {
	        /*	
		 * note that we already hold a reference
		 * on dp, but for some reason can't
		 * get another one... in this case we
		 * need to do vnode_put on dp in 'bad'
		 */
	        if ( (vnode_get(dp)) ) {
		        error = ENOENT;
			goto bad;
		}
		ndp->ni_dvp = dp;
	}
	cnp->cn_flags &= ~ISDOTDOT;
	cnp->cn_flags |= ISLASTCN;
	ndp->ni_next = cp;
	ndp->ni_vp = dp;

	if (cnp->cn_flags & AUDITVNPATH1)
		AUDIT_ARG(vnpath, dp, ARG_VNODE1);
	else if (cnp->cn_flags & AUDITVNPATH2)
		AUDIT_ARG(vnpath, dp, ARG_VNODE2);
	if (cnp->cn_flags & SAVESTART)
		panic("lookup: SAVESTART");
	return (0);

bad2:
	if ((cnp->cn_flags & FSNODELOCKHELD)) {
	        cnp->cn_flags &= ~FSNODELOCKHELD;
		unlock_fsnode(ndp->ni_dvp, NULL);
	}
	if (ndp->ni_dvp)
	        vnode_put(ndp->ni_dvp);
	if (dp)
	        vnode_put(dp);
	ndp->ni_vp = NULLVP;

	if (kdebug_enable)
	        kdebug_lookup(dp, cnp);
	return (error);

bad:
	if ((cnp->cn_flags & FSNODELOCKHELD)) {
	        cnp->cn_flags &= ~FSNODELOCKHELD;
		unlock_fsnode(ndp->ni_dvp, NULL);
	}	
	if (dp)
	        vnode_put(dp);
	ndp->ni_vp = NULLVP;

	if (kdebug_enable)
	        kdebug_lookup(dp, cnp);
	return (error);
}