Expand PMF_FN_* macros.

[netbsd-mini2440.git] / sys / miscfs / genfs / layer_vnops.c

/*      $NetBSD: layer_vnops.c,v 1.38 2009/03/14 21:04:25 dsl Exp $     */

/*
 * Copyright (c) 1999 National Aeronautics & Space Administration
 * All rights reserved.
 *
 * This software was written by William Studenmund of the
 * Numerical Aerospace Simulation Facility, NASA Ames Research Center.
 *
 * 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 National Aeronautics & Space Administration
 *    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 NATIONAL AERONAUTICS & SPACE ADMINISTRATION
 * ``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 ADMINISTRATION OR CONTRIB-
 * UTORS 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.
 */
/*
 * 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
 *      Id: lofs_vnops.c,v 1.11 1992/05/30 10:05:43 jsp Exp jsp
 *      ...and...
 *      @(#)null_vnodeops.c 1.20 92/07/07 UCLA Ficus project
 */

/*
 * Null Layer vnode routines.
 *
 * (See mount_null(8) for more information.)
 *
 * The layer.h, layer_extern.h, layer_vfs.c, and layer_vnops.c files provide
 * the core implementation of the null file system and most other stacked
 * fs's. The description below refers to the null file system, but the
 * services provided by the layer* files are useful for all layered fs's.
 *
 * 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 the 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.
 *
 * It is conceivable that other overlay filesystems will take different
 * parameters. For instance, data migration or access controll layers might
 * only take one pathname which will serve both as the target-pn and
 * alias-pn described above.
 *
 *
 * 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, through 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 layered nodes by their
 * lower-layer equivalents.  It then invokes the operation
 * on the lower layer.  Finally, it replaces the layered nodes
 * in the arguments and, if a vnode is return by the operation,
 * stacks a layered node on top of the returned vnode.
 *
 * The bypass routine in this file, layer_bypass(), is suitable for use
 * by many different layered filesystems. It can be used by multiple
 * filesystems simultaneously. Alternatively, a layered fs may provide
 * its own bypass routine, in which case layer_bypass() should be used as
 * a model. For instance, the main functionality provided by umapfs, the user
 * identity mapping file system, is handled by a custom bypass routine.
 *
 * Typically a layered fs registers its selected bypass routine as the
 * default vnode operation in its vnodeopv_entry_desc table. Additionally
 * the filesystem must store the bypass entry point in the layerm_bypass
 * field of struct layer_mount. All other layer routines in this file will
 * use the layerm_bypass routine.
 *
 * Although the bypass routine handles most operations outright, a number
 * of operations are special cased, and handled by the layered fs. One
 * group, layer_setattr, layer_getattr, layer_access, layer_open, and
 * layer_fsync, perform layer-specific manipulation in addition to calling
 * the bypass routine. The other group

 * Although bypass handles most operations, vop_getattr, vop_lock,
 * vop_unlock, vop_inactive, vop_reclaim, and vop_print are not
 * bypassed. Vop_getattr must change the fsid being returned.
 * Vop_lock and vop_unlock must handle any locking for the
 * current vnode as well as pass the lock request down.
 * Vop_inactive and vop_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 existence 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 vop_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".  layer_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 handled 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 invoke 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 manually mapped.
 *
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: layer_vnops.c,v 1.38 2009/03/14 21:04:25 dsl Exp $");

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/kmem.h>
#include <sys/buf.h>
#include <sys/kauth.h>

#include <miscfs/genfs/layer.h>
#include <miscfs/genfs/layer_extern.h>
#include <miscfs/genfs/genfs.h>


/*
 * This is the 08-June-99 bypass routine, based on the 10-Apr-92 bypass
 *              routine by John Heidemann.
 *      The new element for this version is that the whole nullfs
 * system gained the concept of locks on the lower node, and locks on
 * our nodes. When returning from a call to the lower layer, we may
 * need to update lock state ONLY on our layer. The LAYERFS_UPPER*LOCK()
 * macros provide this functionality.
 *    The 10-Apr-92 version was optimized for speed, throwing away some
 * safety checks.  It should still always work, but it's not as
 * robust to programmer errors.
 *
 * In general, we map all vnodes going down and unmap them on the way back.
 *
 * Also, some BSD vnode operations have the side effect of vrele'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.
 *
 * New for the 08-June-99 version: we also handle operations which unlock
 * the passed-in node (typically they vput the node).
 *
 * This makes the following assumptions:
 * - only one returned vpp
 * - no INOUT vpp's (Sun's vop_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
layer_bypass(void *v)
{
        struct vop_generic_args /* {
                struct vnodeop_desc *a_desc;
                <other random data follows, presumably>
        } */ *ap = v;
        int (**our_vnodeop_p)(void *);
        struct vnode **this_vp_p;
        int error, error1;
        struct vnode *old_vps[VDESC_MAX_VPS], *vp0;
        struct vnode **vps_p[VDESC_MAX_VPS];
        struct vnode ***vppp;
        struct mount *mp;
        struct vnodeop_desc *descp = ap->a_desc;
        int reles, i, flags;

#ifdef DIAGNOSTIC
        /*
         * We require at least one vp.
         */
        if (descp->vdesc_vp_offsets == NULL ||
            descp->vdesc_vp_offsets[0] == VDESC_NO_OFFSET)
                panic("%s: no vp's in map.\n", __func__);
#endif

        vps_p[0] =
            VOPARG_OFFSETTO(struct vnode**, descp->vdesc_vp_offsets[0], ap);
        vp0 = *vps_p[0];
        mp = vp0->v_mount;
        flags = MOUNTTOLAYERMOUNT(mp)->layerm_flags;
        our_vnodeop_p = vp0->v_op;

        if (flags & LAYERFS_MBYPASSDEBUG)
                printf("%s: %s\n", __func__, descp->vdesc_name);

        /*
         * 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 != our_vnodeop_p)) {
                        old_vps[i] = NULL;
                } else {
                        old_vps[i] = *this_vp_p;
                        *(vps_p[i]) = LAYERVPTOLOWERVP(*this_vp_p);
                        /*
                         * XXX - Several operations have the side effect
                         * of vrele'ing their vp's.  We must account for
                         * that.  (This should go away in the future.)
                         */
                        if (reles & VDESC_VP0_WILLRELE)
                                vref(*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 & VDESC_VP0_WILLUNLOCK)
                                LAYERFS_UPPERUNLOCK(*(vps_p[i]), 0, error1);
                        if (reles & VDESC_VP0_WILLRELE)
                                vrele(*(vps_p[i]));
                }
        }

        /*
         * Map the possible out-going vpp
         * (Assumes that the lower layer always returns
         * a VREF'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 vrele 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);
                /*
                 * Only vop_lookup, vop_create, vop_makedir, vop_bmap,
                 * vop_mknod, and vop_symlink return vpp's. vop_bmap
                 * doesn't call bypass as the lower vpp is fine (we're just
                 * going to do i/o on it). vop_lookup doesn't call bypass
                 * as a lookup on "." would generate a locking error.
                 * So all the calls which get us here have a locked vpp. :-)
                 */
                error = layer_node_create(mp, **vppp, *vppp);
                if (error) {
                        vput(**vppp);
                        **vppp = NULL;
                }
        }

 out:
        return (error);
}

/*
 * We have to carry on the locking protocol on the layer vnodes
 * as we progress through the tree. We also have to enforce read-only
 * if this layer is mounted read-only.
 */
int
layer_lookup(void *v)
{
        struct vop_lookup_args /* {
                struct vnodeop_desc *a_desc;
                struct vnode * a_dvp;
                struct vnode ** a_vpp;
                struct componentname * a_cnp;
        } */ *ap = v;
        struct componentname *cnp = ap->a_cnp;
        int flags = cnp->cn_flags;
        struct vnode *dvp, *lvp, *ldvp;
        int error;

        dvp = ap->a_dvp;

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

        ldvp = LAYERVPTOLOWERVP(dvp);
        ap->a_dvp = ldvp;
        error = VCALL(ldvp, ap->a_desc->vdesc_offset, ap);
        lvp = *ap->a_vpp;
        *ap->a_vpp = NULL;

        if (error == EJUSTRETURN && (flags & ISLASTCN) &&
            (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
            (cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME))
                error = EROFS;

        /*
         * We must do the same locking and unlocking at this layer as
         * is done in the layers below us.
         */
        if (ldvp == lvp) {

                /*
                 * Got the same object back, because we looked up ".",
                 * or ".." in the root node of a mount point.
                 * So we make another reference to dvp and return it.
                 */
                vref(dvp);
                *ap->a_vpp = dvp;
                vrele(lvp);
        } else if (lvp != NULL) {
                /* dvp, ldvp and vp are all locked */
                error = layer_node_create(dvp->v_mount, lvp, ap->a_vpp);
                if (error) {
                        vput(lvp);
                }
        }
        return (error);
}

/*
 * Setattr call. Disallow write attempts if the layer is mounted read-only.
 */
int
layer_setattr(void *v)
{
        struct vop_setattr_args /* {
                struct vnodeop_desc *a_desc;
                struct vnode *a_vp;
                struct vattr *a_vap;
                kauth_cred_t a_cred;
                struct lwp *a_l;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct vattr *vap = ap->a_vap;

        if ((vap->va_flags != VNOVAL || vap->va_uid != (uid_t)VNOVAL ||
            vap->va_gid != (gid_t)VNOVAL || vap->va_atime.tv_sec != VNOVAL ||
            vap->va_mtime.tv_sec != VNOVAL || vap->va_mode != (mode_t)VNOVAL) &&
            (vp->v_mount->mnt_flag & MNT_RDONLY))
                return (EROFS);
        if (vap->va_size != VNOVAL) {
                switch (vp->v_type) {
                case VDIR:
                        return (EISDIR);
                case VCHR:
                case VBLK:
                case VSOCK:
                case VFIFO:
                        return (0);
                case VREG:
                case VLNK:
                default:
                        /*
                         * Disallow write attempts if the filesystem is
                         * mounted read-only.
                         */
                        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                                return (EROFS);
                }
        }
        return (LAYERFS_DO_BYPASS(vp, ap));
}

/*
 *  We handle getattr only to change the fsid.
 */
int
layer_getattr(void *v)
{
        struct vop_getattr_args /* {
                struct vnode *a_vp;
                struct vattr *a_vap;
                kauth_cred_t a_cred;
                struct lwp *a_l;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        int error;

        if ((error = LAYERFS_DO_BYPASS(vp, ap)) != 0)
                return (error);
        /* Requires that arguments be restored. */
        ap->a_vap->va_fsid = vp->v_mount->mnt_stat.f_fsidx.__fsid_val[0];
        return (0);
}

int
layer_access(void *v)
{
        struct vop_access_args /* {
                struct vnode *a_vp;
                int  a_mode;
                kauth_cred_t a_cred;
                struct lwp *a_l;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        mode_t mode = ap->a_mode;

        /*
         * Disallow write attempts on read-only layers;
         * unless the file is a socket, fifo, or a block or
         * character device resident on the file system.
         */
        if (mode & VWRITE) {
                switch (vp->v_type) {
                case VDIR:
                case VLNK:
                case VREG:
                        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                                return (EROFS);
                        break;
                default:
                        break;
                }
        }
        return (LAYERFS_DO_BYPASS(vp, ap));
}

/*
 * We must handle open to be able to catch MNT_NODEV and friends.
 */
int
layer_open(void *v)
{
        struct vop_open_args *ap = v;
        struct vnode *vp = ap->a_vp;
        enum vtype lower_type = LAYERVPTOLOWERVP(vp)->v_type;

        if (((lower_type == VBLK) || (lower_type == VCHR)) &&
            (vp->v_mount->mnt_flag & MNT_NODEV))
                return ENXIO;

        return LAYERFS_DO_BYPASS(vp, ap);
}

/*
 * We need to process our own vnode lock and then clear the
 * interlock flag as it applies only to our vnode, not the
 * vnodes below us on the stack.
 */
int
layer_lock(void *v)
{
        struct vop_lock_args /* {
                struct vnode *a_vp;
                int a_flags;
                struct proc *a_p;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp, *lowervp;
        int     flags = ap->a_flags, error;

        if (flags & LK_INTERLOCK) {
                mutex_exit(&vp->v_interlock);
                flags &= ~LK_INTERLOCK;
        }

        if (vp->v_vnlock != NULL) {
                /*
                 * The lower level has exported a struct lock to us. Use
                 * it so that all vnodes in the stack lock and unlock
                 * simultaneously. Note: we don't DRAIN the lock as DRAIN
                 * decommissions the lock - just because our vnode is
                 * going away doesn't mean the struct lock below us is.
                 * LK_EXCLUSIVE is fine.
                 */
                return (vlockmgr(vp->v_vnlock, flags));
        } else {
                /*
                 * Ahh well. It would be nice if the fs we're over would
                 * export a struct lock for us to use, but it doesn't.
                 *
                 * To prevent race conditions involving doing a lookup
                 * on "..", we have to lock the lower node, then lock our
                 * node. Most of the time it won't matter that we lock our
                 * node (as any locking would need the lower one locked
                 * first).
                 */
                lowervp = LAYERVPTOLOWERVP(vp);
                error = VOP_LOCK(lowervp, flags);
                if (error)
                        return (error);
                if ((error = vlockmgr(&vp->v_lock, flags))) {
                        VOP_UNLOCK(lowervp, 0);
                }
                return (error);
        }
}

/*
 */
int
layer_unlock(void *v)
{
        struct vop_unlock_args /* {
                struct vnode *a_vp;
                int a_flags;
                struct proc *a_p;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        int     flags = ap->a_flags;

        if (flags & LK_INTERLOCK) {
                mutex_exit(&vp->v_interlock);
                flags &= ~LK_INTERLOCK;
        }

        if (vp->v_vnlock != NULL) {
                return (vlockmgr(vp->v_vnlock, ap->a_flags | LK_RELEASE));
        } else {
                VOP_UNLOCK(LAYERVPTOLOWERVP(vp), flags);
                return (vlockmgr(&vp->v_lock, flags | LK_RELEASE));
        }
}

int
layer_islocked(void *v)
{
        struct vop_islocked_args /* {
                struct vnode *a_vp;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        int lkstatus;

        if (vp->v_vnlock != NULL)
                return vlockstatus(vp->v_vnlock);

        lkstatus = VOP_ISLOCKED(LAYERVPTOLOWERVP(vp));
        if (lkstatus)
                return lkstatus;

        return vlockstatus(&vp->v_lock);
}

/*
 * If vinvalbuf is calling us, it's a "shallow fsync" -- don't bother
 * syncing the underlying vnodes, since they'll be fsync'ed when
 * reclaimed; otherwise,
 * pass it through to the underlying layer.
 *
 * XXX Do we still need to worry about shallow fsync?
 */

int
layer_fsync(void *v)
{
        struct vop_fsync_args /* {
                struct vnode *a_vp;
                kauth_cred_t a_cred;
                int  a_flags;
                off_t offlo;
                off_t offhi;
                struct lwp *a_l;
        } */ *ap = v;

        if (ap->a_flags & FSYNC_RECLAIM) {
                return 0;
        }

        return (LAYERFS_DO_BYPASS(ap->a_vp, ap));
}


int
layer_inactive(void *v)
{
        struct vop_inactive_args /* {
                struct vnode *a_vp;
                bool *a_recycle;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;

        /*
         * ..., but don't cache the device node. Also, if we did a
         * remove, don't cache the node.
         */
        *ap->a_recycle = (vp->v_type == VBLK || vp->v_type == VCHR
            || (VTOLAYER(vp)->layer_flags & LAYERFS_REMOVED));

        /*
         * Do nothing (and _don't_ bypass).
         * Wait to vrele lowervp until reclaim,
         * so that until then our layer_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.
         */
        VOP_UNLOCK(vp, 0);

        return (0);
}

int
layer_remove(void *v)
{
        struct vop_remove_args /* {
                struct vonde            *a_dvp;
                struct vnode            *a_vp;
                struct componentname    *a_cnp;
        } */ *ap = v;

        int             error;
        struct vnode    *vp = ap->a_vp;

        vref(vp);
        if ((error = LAYERFS_DO_BYPASS(vp, ap)) == 0)
                VTOLAYER(vp)->layer_flags |= LAYERFS_REMOVED;

        vrele(vp);

        return (error);
}

int
layer_rename(void *v)
{
        struct vop_rename_args  /* {
                struct vnode            *a_fdvp;
                struct vnode            *a_fvp;
                struct componentname    *a_fcnp;
                struct vnode            *a_tdvp;
                struct vnode            *a_tvp;
                struct componentname    *a_tcnp;
        } */ *ap = v;

        int error;
        struct vnode *fdvp = ap->a_fdvp;
        struct vnode *tvp;

        tvp = ap->a_tvp;
        if (tvp) {
                if (tvp->v_mount != fdvp->v_mount)
                        tvp = NULL;
                else
                        vref(tvp);
        }
        error = LAYERFS_DO_BYPASS(fdvp, ap);
        if (tvp) {
                if (error == 0)
                        VTOLAYER(tvp)->layer_flags |= LAYERFS_REMOVED;
                vrele(tvp);
        }

        return (error);
}

int
layer_rmdir(void *v)
{
        struct vop_rmdir_args /* {
                struct vnode            *a_dvp;
                struct vnode            *a_vp;
                struct componentname    *a_cnp;
        } */ *ap = v;
        int             error;
        struct vnode    *vp = ap->a_vp;

        vref(vp);
        if ((error = LAYERFS_DO_BYPASS(vp, ap)) == 0)
                VTOLAYER(vp)->layer_flags |= LAYERFS_REMOVED;

        vrele(vp);

        return (error);
}

int
layer_reclaim(void *v)
{
        struct vop_reclaim_args /* {
                struct vnode *a_vp;
                struct lwp *a_l;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        struct layer_mount *lmp = MOUNTTOLAYERMOUNT(vp->v_mount);
        struct layer_node *xp = VTOLAYER(vp);
        struct vnode *lowervp = xp->layer_lowervp;

        /*
         * Note: in vop_reclaim, the node's struct lock has been
         * decomissioned, so we have to be careful about calling
         * VOP's on ourself.  We must be careful as VXLOCK is set.
         */
        /* After this assignment, this node will not be re-used. */
        if ((vp == lmp->layerm_rootvp)) {
                /*
                 * Oops! We no longer have a root node. Most likely reason is
                 * that someone forcably unmunted the underlying fs.
                 *
                 * Now getting the root vnode will fail. We're dead. :-(
                 */
                lmp->layerm_rootvp = NULL;
        }
        xp->layer_lowervp = NULL;
        mutex_enter(&lmp->layerm_hashlock);
        LIST_REMOVE(xp, layer_hash);
        mutex_exit(&lmp->layerm_hashlock);
        kmem_free(vp->v_data, lmp->layerm_size);
        vp->v_data = NULL;
        vrele(lowervp);

        return (0);
}

/*
 * We just feed the returned vnode up to the caller - there's no need
 * to build a layer node on top of the node on which we're going to do
 * i/o. :-)
 */
int
layer_bmap(void *v)
{
        struct vop_bmap_args /* {
                struct vnode *a_vp;
                daddr_t  a_bn;
                struct vnode **a_vpp;
                daddr_t *a_bnp;
                int *a_runp;
        } */ *ap = v;
        struct vnode *vp;

        ap->a_vp = vp = LAYERVPTOLOWERVP(ap->a_vp);

        return (VCALL(vp, ap->a_desc->vdesc_offset, ap));
}

int
layer_print(void *v)
{
        struct vop_print_args /* {
                struct vnode *a_vp;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        printf ("\ttag VT_LAYERFS, vp=%p, lowervp=%p\n", vp, LAYERVPTOLOWERVP(vp));
        return (0);
}

/*
 * XXX - vop_bwrite must be hand coded because it has no
 * vnode in its arguments.
 * This goes away with a merged VM/buffer cache.
 */
int
layer_bwrite(void *v)
{
        struct vop_bwrite_args /* {
                struct buf *a_bp;
        } */ *ap = v;
        struct buf *bp = ap->a_bp;
        int error;
        struct vnode *savedvp;

        savedvp = bp->b_vp;
        bp->b_vp = LAYERVPTOLOWERVP(bp->b_vp);

        error = VOP_BWRITE(bp);

        bp->b_vp = savedvp;

        return (error);
}

int
layer_getpages(void *v)
{
        struct vop_getpages_args /* {
                struct vnode *a_vp;
                voff_t a_offset;
                struct vm_page **a_m;
                int *a_count;
                int a_centeridx;
                vm_prot_t a_access_type;
                int a_advice;
                int a_flags;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        int error;

        /*
         * just pass the request on to the underlying layer.
         */

        if (ap->a_flags & PGO_LOCKED) {
                return EBUSY;
        }
        ap->a_vp = LAYERVPTOLOWERVP(vp);
        mutex_exit(&vp->v_interlock);
        mutex_enter(&ap->a_vp->v_interlock);
        error = VCALL(ap->a_vp, VOFFSET(vop_getpages), ap);
        return error;
}

int
layer_putpages(void *v)
{
        struct vop_putpages_args /* {
                struct vnode *a_vp;
                voff_t a_offlo;
                voff_t a_offhi;
                int a_flags;
        } */ *ap = v;
        struct vnode *vp = ap->a_vp;
        int error;

        /*
         * just pass the request on to the underlying layer.
         */

        ap->a_vp = LAYERVPTOLOWERVP(vp);
        mutex_exit(&vp->v_interlock);
        if (ap->a_flags & PGO_RECLAIM) {
                return 0;
        }
        mutex_enter(&ap->a_vp->v_interlock);
        error = VCALL(ap->a_vp, VOFFSET(vop_putpages), ap);
        return error;
}