/* * Copyright (c) 2000 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * The contents of this file constitute Original Code as defined in and * are subject to the Apple Public Source License Version 1.1 (the * "License"). You may not use this file except in compliance with the * License. Please obtain a copy of the License at * http://www.apple.com/publicsource and read it before using this file. * * This Original Code and all software distributed under the License are * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. Please see the * License for the specific language governing rights and limitations * under the License. * * @APPLE_LICENSE_HEADER_END@ */ /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */ /* * 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. 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. * * @(#)null_vnops.c 8.6 (Berkeley) 5/27/95 * * Ancestors: * @(#)lofs_vnops.c 1.2 (Berkeley) 6/18/92 * ...and... * @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project */ /* * 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 it's "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 centers * on the bypass routine, though which nearly all vnode operations * pass. * * The bypass routine accepts arbitrary vnode operations for * handling by the lower layer. It begins by examing vnode * operation arguments and replacing any null-nodes by their * lower-layer equivlants. It then invokes the operation * on the lower layer. Finally, it replaces the null-nodes * in the arguments and, if a vnode is return by the operation, * stacks a null-node on top of the returned vnode. * * Although bypass handles most operations, vnop_getattr, vnop_lock, * vnop_unlock, vnop_inactive, vnop_reclaim, and vnop_print are not * bypassed. Vop_getattr must change the fsid being returned. * Vop_lock and vnop_unlock must handle any locking for the * current vnode as well as pass the lock request down. * Vop_inactive and vnop_reclaim are not bypassed so that * they can handle freeing null-layer specific data. Vop_print * is not bypassed to avoid excessive debugging information. * Also, certain vnode operations change the locking state within * the operation (create, mknod, remove, link, rename, mkdir, rmdir, * and symlink). Ideally these operations should not change the * lock state, but should be changed to let the caller of the * function unlock them. Otherwise all intermediate vnode layers * (such as union, umapfs, etc) must catch these functions to do * the necessary locking at their layer. * * * INSTANTIATING VNODE STACKS * * Mounting associates the null layer with a lower layer, * effect stacking two VFSes. Vnode stacks are instead * created on demand as files are accessed. * * The initial mount creates a single vnode stack for the * root of the new null layer. All other vnode stacks * are created as a result of vnode operations on * this or other null vnode stacks. * * New vnode stacks come into existance as a result of * an operation which returns a vnode. * The bypass routine stacks a null-node above the new * vnode before returning it to the caller. * * For example, imagine mounting a null layer with * "mount_null /usr/include /dev/layer/null". * Changing directory to /dev/layer/null will assign * the root null-node (which was created when the null layer was mounted). * Now consider opening "sys". A vnop_lookup would be * done on the root null-node. This operation would bypass through * to the lower layer which would return a vnode representing * the UFS "sys". Null_bypass then builds a null-node * aliasing the UFS "sys" and returns this to the caller. * Later operations on the null-node "sys" will repeat this * process when constructing other vnode stacks. * * * CREATING OTHER FILE SYSTEM LAYERS * * One of the easiest ways to construct new file system layers is to make * a copy of the null layer, rename all files and variables, and * then begin modifing the copy. Sed can be used to easily rename * all variables. * * The umap layer is an example of a layer descended from the * null layer. * * * INVOKING OPERATIONS ON LOWER LAYERS * * There are two techniques to invoke operations on a lower layer * when the operation cannot be completely bypassed. Each method * is appropriate in different situations. In both cases, * it is the responsibility of the aliasing layer to make * the operation arguments "correct" for the lower layer * by mapping an vnode arguments to the lower layer. * * The first approach is to call the aliasing layer's bypass routine. * This method is most suitable when you wish to invoke the operation * currently being hanldled on the lower layer. It has the advantage * that the bypass routine already must do argument mapping. * An example of this is null_getattrs in the null layer. * * A second approach is to directly invoked vnode operations on * the lower layer with the VOP_OPERATIONNAME interface. * The advantage of this method is that it is easy to invoke * arbitrary operations on the lower layer. The disadvantage * is that vnodes arguments must be manualy mapped. * */ #include <sys/param.h> #include <sys/systm.h> #include <sys/proc.h> #include <sys/kauth.h> #include <sys/time.h> #include <sys/types.h> #include <sys/vnode.h> #include <sys/mount_internal.h> #include <sys/namei.h> #include <sys/malloc.h> #include <sys/buf.h> #include <miscfs/nullfs/null.h> int null_bug_bypass = 0; /* for debugging: enables bypass printf'ing */ /* * This is the 10-Apr-92 bypass routine. * This version has been optimized for speed, throwing away some * safety checks. It should still always work, but it's not as * robust to programmer errors. * Define SAFETY to include some error checking code. * * In general, we map all vnodes going down and unmap them on the way back. * As an exception to this, vnodes can be marked "unmapped" by setting * the Nth bit in operation's vdesc_flags. * * Also, some BSD vnode operations have the side effect of node_put'ing * their arguments. With stacking, the reference counts are held * by the upper node, not the lower one, so we must handle these * side-effects here. This is not of concern in Sun-derived systems * since there are no such side-effects. * * This makes the following assumptions: * - only one returned vpp * - no INOUT vpp's (Sun's vnop_open has one of these) * - the vnode operation vector of the first vnode should be used * to determine what implementation of the op should be invoked * - all mapped vnodes are of our vnode-type (NEEDSWORK: * problems on rmdir'ing mount points and renaming?) */ int null_bypass(ap) struct vnop_generic_args /* { struct vnodeop_desc *a_desc; <other random data follows, presumably> } */ *ap; { extern int (**null_vnodeop_p)(void *); /* not extern, really "forward" */ register struct vnode **this_vp_p; int error; struct vnode *old_vps[VDESC_MAX_VPS]; struct vnode **vps_p[VDESC_MAX_VPS]; struct vnode ***vppp; struct vnodeop_desc *descp = ap->a_desc; int reles, i; if (null_bug_bypass) printf ("null_bypass: %s\n", descp->vdesc_name); #ifdef SAFETY /* * We require at least one vp. */ if (descp->vdesc_vp_offsets == NULL || descp->vdesc_vp_offsets[0] == VDESC_NO_OFFSET) panic ("null_bypass: no vp's in map.\n"); #endif /* * Map the vnodes going in. * Later, we'll invoke the operation based on * the first mapped vnode's operation vector. */ reles = descp->vdesc_flags; for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) { if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET) break; /* bail out at end of list */ vps_p[i] = this_vp_p = VOPARG_OFFSETTO(struct vnode**,descp->vdesc_vp_offsets[i],ap); /* * We're not guaranteed that any but the first vnode * are of our type. Check for and don't map any * that aren't. (We must always map first vp or vclean fails.) */ if (i && (*this_vp_p == NULL || (*this_vp_p)->v_op != null_vnodeop_p)) { old_vps[i] = NULL; } else { old_vps[i] = *this_vp_p; *(vps_p[i]) = NULLVPTOLOWERVP(*this_vp_p); /* * XXX - Several operations have the side effect * of vnode_put'ing their vp's. We must account for * that. (This should go away in the future.) */ if (reles & 1) vnode_get(*this_vp_p); } } /* * Call the operation on the lower layer * with the modified argument structure. */ error = VCALL(*(vps_p[0]), descp->vdesc_offset, ap); /* * Maintain the illusion of call-by-value * by restoring vnodes in the argument structure * to their original value. */ reles = descp->vdesc_flags; for (i = 0; i < VDESC_MAX_VPS; reles >>= 1, i++) { if (descp->vdesc_vp_offsets[i] == VDESC_NO_OFFSET) break; /* bail out at end of list */ if (old_vps[i]) { *(vps_p[i]) = old_vps[i]; if (reles & 1) vnode_put(*(vps_p[i])); } } /* * Map the possible out-going vpp * (Assumes that the lower layer always returns * a vnode_get'ed vpp unless it gets an error.) */ if (descp->vdesc_vpp_offset != VDESC_NO_OFFSET && !(descp->vdesc_flags & VDESC_NOMAP_VPP) && !error) { /* * XXX - even though some ops have vpp returned vp's, * several ops actually vnode_put this before returning. * We must avoid these ops. * (This should go away when these ops are regularized.) */ if (descp->vdesc_flags & VDESC_VPP_WILLRELE) goto out; vppp = VOPARG_OFFSETTO(struct vnode***, descp->vdesc_vpp_offset,ap); error = null_node_create(old_vps[0]->v_mount, **vppp, *vppp); } out: return (error); } /* * We have to carry on the locking protocol on the null layer vnodes * as we progress through the tree. We also have to enforce read-only * if this layer is mounted read-only. */ null_lookup(ap) struct vnop_lookup_args /* { struct vnode * a_dvp; struct vnode ** a_vpp; struct componentname * a_cnp; vfs_context_t a_context; } */ *ap; { struct componentname *cnp = ap->a_cnp; struct proc *p = cnp->cn_proc; int flags = cnp->cn_flags; struct vnode *dvp, *vp; int error; error = null_bypass(ap); /* * We must do the same locking and unlocking at this layer as * is done in the layers below us. We could figure this out * based on the error return and the LASTCN, LOCKPARENT, and * LOCKLEAF flags. However, it is more expidient to just find * out the state of the lower level vnodes and set ours to the * same state. */ dvp = ap->a_dvp; vp = *ap->a_vpp; if (dvp == vp) return (error); return (error); } /* * Setattr call. */ int null_setattr( struct vnop_setattr_args /* { struct vnodeop_desc *a_desc; struct vnode *a_vp; struct vnode_attr *a_vap; kauth_cred_t a_cred; struct proc *a_p; } */ *ap) { struct vnode *vp = ap->a_vp; struct vnode_attr *vap = ap->a_vap; if (VATTR_IS_ACTIVE(vap, va_data_size)) { switch (vp->v_type) { case VDIR: return (EISDIR); case VCHR: case VBLK: case VSOCK: case VFIFO: return (0); case VREG: case VLNK: default: } } return (null_bypass(ap)); } /* * We handle getattr only to change the fsid. */ int null_getattr(ap) struct vnop_getattr_args /* { struct vnode *a_vp; struct vnode_attr *a_vap; vfs_context_t a_context; } */ *ap; { int error; if (error = null_bypass(ap)) return (error); /* Requires that arguments be restored. */ VATTR_RETURN(ap->a_vap, va_fsid, ap->a_vp->v_mount->mnt_vfsstat.f_fsid.val[0]); return (0); } int null_access(ap) struct vnop_access_args /* { struct vnode *a_vp; int a_action; vfs_context_t a_context; } */ *ap; { return (null_bypass(ap)); } int null_inactive(ap) struct vnop_inactive_args /* { struct vnode *a_vp; vfs_context_t a_context; } */ *ap; { /* * Do nothing (and _don't_ bypass). * Wait to vnode_put lowervp until reclaim, * so that until then our null_node is in the * cache and reusable. * * NEEDSWORK: Someday, consider inactive'ing * the lowervp and then trying to reactivate it * with capabilities (v_id) * like they do in the name lookup cache code. * That's too much work for now. */ return (0); } int null_reclaim(ap) struct vnop_reclaim_args /* { struct vnode *a_vp; vfs_context_t a_context; } */ *ap; { struct vnode *vp = ap->a_vp; struct null_node *xp = VTONULL(vp); struct vnode *lowervp = xp->null_lowervp; /* * Note: in vnop_reclaim, vp->v_op == dead_vnodeop_p, * so we can't call VOPs on ourself. */ /* After this assignment, this node will not be re-used. */ xp->null_lowervp = NULL; LIST_REMOVE(xp, null_hash); FREE(vp->v_data, M_TEMP); vp->v_data = NULL; vnode_put (lowervp); return (0); } /* * XXX - vnop_strategy must be hand coded because it has no * vnode in its arguments. * This goes away with a merged VM/buffer cache. */ int null_strategy(ap) struct vnop_strategy_args /* { struct buf *a_bp; } */ *ap; { struct buf *bp = ap->a_bp; int error; struct vnode *savedvp; savedvp = vnode(bp); buf_setvnode(bp, NULLVPTOLOWERVP(savedvp)); error = VNOP_STRATEGY(bp); buf_setvnode(bp, savedvp); return (error); } /* * XXX - like vnop_strategy, vnop_bwrite must be hand coded because it has no * vnode in its arguments. * This goes away with a merged VM/buffer cache. */ int null_bwrite(ap) struct vnop_bwrite_args /* { struct buf *a_bp; } */ *ap; { struct buf *bp = ap->a_bp; int error; struct vnode *savedvp; savedvp = buf_vnode(bp); buf_setvnode(bp, NULLVPTOLOWERVP(savedvp)); error = VNOP_BWRITE(bp); buf_setvnode(bp, savedvp); return (error); } /* * Global vfs data structures */ #define VOPFUNC int (*)(void *) int (**null_vnodeop_p)(void *); struct vnodeopv_entry_desc null_vnodeop_entries[] = { { &vnop_default_desc, (VOPFUNC)null_bypass }, { &vnop_lookup_desc, (VOPFUNC)null_lookup }, { &vnop_setattr_desc, (VOPFUNC)null_setattr }, { &vnop_getattr_desc, (VOPFUNC)null_getattr }, { &vnop_access_desc, (VOPFUNC)null_access }, { &vnop_inactive_desc, (VOPFUNC)null_inactive }, { &vnop_reclaim_desc, (VOPFUNC)null_reclaim }, { &vnop_strategy_desc, (VOPFUNC)null_strategy }, { &vnop_bwrite_desc, (VOPFUNC)null_bwrite }, { (struct vnodeop_desc*)NULL, (int(*)())NULL } }; struct vnodeopv_desc null_vnodeop_opv_desc = { &null_vnodeop_p, null_vnodeop_entries };