/* * Copyright (c) 1992, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * John Heidemann of the UCLA Ficus project. * * 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. 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. * * @(#)null_vnops.c 8.6 (Berkeley) 5/27/95 * * Ancestors: * @(#)lofs_vnops.c 1.2 (Berkeley) 6/18/92 * @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project * * $FreeBSD: src/sys/miscfs/nullfs/null_vnops.c,v 1.38.2.6 2002/07/31 00:32:28 semenu Exp $ */ /* * Null Layer * * (See mount_null(8) for more information.) * * The null layer duplicates a portion of the file system * name space under a new name. In this respect, it is * similar to the loopback file system. It differs from * the loopback fs in two respects: it is implemented using * a stackable layers techniques, and its "null-node"s stack above * all lower-layer vnodes, not just over directory vnodes. * * The null layer has two purposes. First, it serves as a demonstration * of layering by proving a layer which does nothing. (It actually * does everything the loopback file system does, which is slightly * more than nothing.) Second, the null layer can serve as a prototype * layer. Since it provides all necessary layer framework, * new file system layers can be created very easily be starting * with a null layer. * * The remainder of this man page examines the null layer as a basis * for constructing new layers. * * * INSTANTIATING NEW NULL LAYERS * * New null layers are created with mount_null(8). * Mount_null(8) takes two arguments, the pathname * of the lower vfs (target-pn) and the pathname where the null * layer will appear in the namespace (alias-pn). After * the null layer is put into place, the contents * of target-pn subtree will be aliased under alias-pn. * * * OPERATION OF A NULL LAYER * * The null layer is the minimum file system layer, * simply bypassing all possible operations to the lower layer * for processing there. The majority of its activity used to center * on a so-called bypass routine, through which nullfs vnodes * passed on operation to their underlying peer. * * However, with the current implementation nullfs doesn't have any private * vnodes, rather it relies on DragonFly's namecache API. That gives a much * more lightweight null layer, as namecache structures are pure data, with * no private operations, so there is no need of subtle dispatching routines. * * Unlike the old code, this implementation is not a general skeleton overlay * filesystem: to get more comprehensive overlaying, we will need vnode * operation dispatch. Other overlay filesystems might be * able to get on with a hybrid solution: overlay some vnodes, and rely * on namecache API for the rest. */ #include <sys/param.h> #include <sys/systm.h> #include <sys/kernel.h> #include <sys/sysctl.h> #include <sys/vnode.h> #include <sys/mount.h> #include <sys/mountctl.h> #include <sys/proc.h> #include <sys/malloc.h> #include <sys/buf.h> #include "null.h" static int null_nresolve(struct vop_nresolve_args *ap); static int null_ncreate(struct vop_ncreate_args *ap); static int null_nmkdir(struct vop_nmkdir_args *ap); static int null_nmknod(struct vop_nmknod_args *ap); static int null_nlink(struct vop_nlink_args *ap); static int null_nsymlink(struct vop_nsymlink_args *ap); static int null_nwhiteout(struct vop_nwhiteout_args *ap); static int null_nremove(struct vop_nremove_args *ap); static int null_nrmdir(struct vop_nrmdir_args *ap); static int null_nrename(struct vop_nrename_args *ap); static int null_mountctl(struct vop_mountctl_args *ap); static int null_nresolve(struct vop_nresolve_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_nresolve_ap(ap); } static int null_ncreate(struct vop_ncreate_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_ncreate_ap(ap); } static int null_nmkdir(struct vop_nmkdir_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_nmkdir_ap(ap); } static int null_nmknod(struct vop_nmknod_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_nmknod_ap(ap); } static int null_nlink(struct vop_nlink_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_nlink_ap(ap); } static int null_nsymlink(struct vop_nsymlink_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_nsymlink_ap(ap); } static int null_nwhiteout(struct vop_nwhiteout_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_nwhiteout_ap(ap); } static int null_nremove(struct vop_nremove_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_nremove_ap(ap); } static int null_nrmdir(struct vop_nrmdir_args *ap) { ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_nrmdir_ap(ap); } static int null_nrename(struct vop_nrename_args *ap) { struct mount *lmp; lmp = MOUNTTONULLMOUNT(ap->a_fnch->mount)->nullm_vfs; if (lmp != MOUNTTONULLMOUNT(ap->a_tnch->mount)->nullm_vfs) return (EINVAL); ap->a_head.a_ops = lmp->mnt_vn_norm_ops; return vop_nrename_ap(ap); } static int null_mountctl(struct vop_mountctl_args *ap) { struct mount *mp; int error; mp = ap->a_head.a_ops->head.vv_mount; switch(ap->a_op) { case MOUNTCTL_SET_EXPORT: if (ap->a_ctllen != sizeof(struct export_args)) error = EINVAL; else error = nullfs_export(mp, ap->a_op, (const void *)ap->a_ctl); break; case MOUNTCTL_MOUNTFLAGS: error = vop_stdmountctl(ap); break; default: error = EOPNOTSUPP; break; } return (error); #if 0 ap->a_head.a_ops = MOUNTTONULLMOUNT(ap->a_nch->mount)->nullm_vfs->mnt_vn_norm_ops; return vop_mountctl_ap(ap); #endif } /* * Global vfs data structures */ struct vop_ops null_vnode_vops = { .vop_nresolve = null_nresolve, .vop_ncreate = null_ncreate, .vop_nmkdir = null_nmkdir, .vop_nmknod = null_nmknod, .vop_nlink = null_nlink, .vop_nsymlink = null_nsymlink, .vop_nwhiteout = null_nwhiteout, .vop_nremove = null_nremove, .vop_nrmdir = null_nrmdir, .vop_nrename = null_nrename, .vop_mountctl = null_mountctl };
