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| Current File : //sys/amd64/compile/hs32/modules/usr/src/sys/modules/arcmsr/@/fs/nullfs/null_vnops.c |
/*-
* 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.
* 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
*
* $FreeBSD: release/9.1.0/sys/fs/nullfs/null_vnops.c 232645 2012-03-07 08:05:12Z kib $
*/
/*
* Null Layer
*
* (See mount_nullfs(8) for more information.)
*
* The null layer duplicates a portion of the filesystem
* name space under a new name. In this respect, it is
* similar to the loopback filesystem. 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 filesystem 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 filesystem 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_nullfs(8).
* Mount_nullfs(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 filesystem 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 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, 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 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_nullfs /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". 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 filesystem 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 a 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 vnode arguments must be manualy mapped.
*
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <sys/namei.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <fs/nullfs/null.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>
#include <vm/vnode_pager.h>
static int null_bug_bypass = 0; /* for debugging: enables bypass printf'ing */
SYSCTL_INT(_debug, OID_AUTO, nullfs_bug_bypass, CTLFLAG_RW,
&null_bug_bypass, 0, "");
/*
* 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.
*
* 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 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.
*
* 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
null_bypass(struct vop_generic_args *ap)
{
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 DIAGNOSTIC
/*
* 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");
#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 == NULLVP ||
(*this_vp_p)->v_op != &null_vnodeops)) {
old_vps[i] = NULLVP;
} else {
old_vps[i] = *this_vp_p;
*(vps_p[i]) = NULLVPTOLOWERVP(*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.
*/
if (vps_p[0] && *vps_p[0])
error = VCALL(ap);
else {
printf("null_bypass: no map for %s\n", descp->vdesc_name);
error = EINVAL;
}
/*
* 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 0
if (reles & VDESC_VP0_WILLUNLOCK)
VOP_UNLOCK(*(vps_p[i]), 0);
#endif
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);
if (*vppp)
error = null_nodeget(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.
*/
static int
null_lookup(struct vop_lookup_args *ap)
{
struct componentname *cnp = ap->a_cnp;
struct vnode *dvp = ap->a_dvp;
int flags = cnp->cn_flags;
struct vnode *vp, *ldvp, *lvp;
int error;
if ((flags & ISLASTCN) && (dvp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME))
return (EROFS);
/*
* Although it is possible to call null_bypass(), we'll do
* a direct call to reduce overhead
*/
ldvp = NULLVPTOLOWERVP(dvp);
vp = lvp = NULL;
error = VOP_LOOKUP(ldvp, &lvp, cnp);
if (error == EJUSTRETURN && (flags & ISLASTCN) &&
(dvp->v_mount->mnt_flag & MNT_RDONLY) &&
(cnp->cn_nameiop == CREATE || cnp->cn_nameiop == RENAME))
error = EROFS;
if ((error == 0 || error == EJUSTRETURN) && lvp != NULL) {
if (ldvp == lvp) {
*ap->a_vpp = dvp;
VREF(dvp);
vrele(lvp);
} else {
error = null_nodeget(dvp->v_mount, lvp, &vp);
if (error == 0)
*ap->a_vpp = vp;
}
}
return (error);
}
static int
null_open(struct vop_open_args *ap)
{
int retval;
struct vnode *vp, *ldvp;
vp = ap->a_vp;
ldvp = NULLVPTOLOWERVP(vp);
retval = null_bypass(&ap->a_gen);
if (retval == 0)
vp->v_object = ldvp->v_object;
return (retval);
}
/*
* Setattr call. Disallow write attempts if the layer is mounted read-only.
*/
static int
null_setattr(struct vop_setattr_args *ap)
{
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:
if (vap->va_flags != VNOVAL)
return (EOPNOTSUPP);
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 (null_bypass((struct vop_generic_args *)ap));
}
/*
* We handle getattr only to change the fsid.
*/
static int
null_getattr(struct vop_getattr_args *ap)
{
int error;
if ((error = null_bypass((struct vop_generic_args *)ap)) != 0)
return (error);
ap->a_vap->va_fsid = ap->a_vp->v_mount->mnt_stat.f_fsid.val[0];
return (0);
}
/*
* Handle to disallow write access if mounted read-only.
*/
static int
null_access(struct vop_access_args *ap)
{
struct vnode *vp = ap->a_vp;
accmode_t accmode = ap->a_accmode;
/*
* Disallow write attempts on read-only layers;
* unless the file is a socket, fifo, or a block or
* character device resident on the filesystem.
*/
if (accmode & 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 (null_bypass((struct vop_generic_args *)ap));
}
static int
null_accessx(struct vop_accessx_args *ap)
{
struct vnode *vp = ap->a_vp;
accmode_t accmode = ap->a_accmode;
/*
* Disallow write attempts on read-only layers;
* unless the file is a socket, fifo, or a block or
* character device resident on the filesystem.
*/
if (accmode & 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 (null_bypass((struct vop_generic_args *)ap));
}
/*
* Increasing refcount of lower vnode is needed at least for the case
* when lower FS is NFS to do sillyrename if the file is in use.
* Unfortunately v_usecount is incremented in many places in
* the kernel and, as such, there may be races that result in
* the NFS client doing an extraneous silly rename, but that seems
* preferable to not doing a silly rename when it is needed.
*/
static int
null_remove(struct vop_remove_args *ap)
{
int retval, vreleit;
struct vnode *lvp;
if (vrefcnt(ap->a_vp) > 1) {
lvp = NULLVPTOLOWERVP(ap->a_vp);
VREF(lvp);
vreleit = 1;
} else
vreleit = 0;
retval = null_bypass(&ap->a_gen);
if (vreleit != 0)
vrele(lvp);
return (retval);
}
/*
* We handle this to eliminate null FS to lower FS
* file moving. Don't know why we don't allow this,
* possibly we should.
*/
static int
null_rename(struct vop_rename_args *ap)
{
struct vnode *tdvp = ap->a_tdvp;
struct vnode *fvp = ap->a_fvp;
struct vnode *fdvp = ap->a_fdvp;
struct vnode *tvp = ap->a_tvp;
/* Check for cross-device rename. */
if ((fvp->v_mount != tdvp->v_mount) ||
(tvp && (fvp->v_mount != tvp->v_mount))) {
if (tdvp == tvp)
vrele(tdvp);
else
vput(tdvp);
if (tvp)
vput(tvp);
vrele(fdvp);
vrele(fvp);
return (EXDEV);
}
return (null_bypass((struct vop_generic_args *)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.
*/
static int
null_lock(struct vop_lock1_args *ap)
{
struct vnode *vp = ap->a_vp;
int flags = ap->a_flags;
struct null_node *nn;
struct vnode *lvp;
int error;
if ((flags & LK_INTERLOCK) == 0) {
VI_LOCK(vp);
ap->a_flags = flags |= LK_INTERLOCK;
}
nn = VTONULL(vp);
/*
* If we're still active we must ask the lower layer to
* lock as ffs has special lock considerations in it's
* vop lock.
*/
if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) {
VI_LOCK_FLAGS(lvp, MTX_DUPOK);
VI_UNLOCK(vp);
/*
* We have to hold the vnode here to solve a potential
* reclaim race. If we're forcibly vgone'd while we
* still have refs, a thread could be sleeping inside
* the lowervp's vop_lock routine. When we vgone we will
* drop our last ref to the lowervp, which would allow it
* to be reclaimed. The lowervp could then be recycled,
* in which case it is not legal to be sleeping in it's VOP.
* We prevent it from being recycled by holding the vnode
* here.
*/
vholdl(lvp);
error = VOP_LOCK(lvp, flags);
/*
* We might have slept to get the lock and someone might have
* clean our vnode already, switching vnode lock from one in
* lowervp to v_lock in our own vnode structure. Handle this
* case by reacquiring correct lock in requested mode.
*/
if (VTONULL(vp) == NULL && error == 0) {
ap->a_flags &= ~(LK_TYPE_MASK | LK_INTERLOCK);
switch (flags & LK_TYPE_MASK) {
case LK_SHARED:
ap->a_flags |= LK_SHARED;
break;
case LK_UPGRADE:
case LK_EXCLUSIVE:
ap->a_flags |= LK_EXCLUSIVE;
break;
default:
panic("Unsupported lock request %d\n",
ap->a_flags);
}
VOP_UNLOCK(lvp, 0);
error = vop_stdlock(ap);
}
vdrop(lvp);
} else
error = vop_stdlock(ap);
return (error);
}
/*
* We need to process our own vnode unlock and then clear the
* interlock flag as it applies only to our vnode, not the
* vnodes below us on the stack.
*/
static int
null_unlock(struct vop_unlock_args *ap)
{
struct vnode *vp = ap->a_vp;
int flags = ap->a_flags;
int mtxlkflag = 0;
struct null_node *nn;
struct vnode *lvp;
int error;
if ((flags & LK_INTERLOCK) != 0)
mtxlkflag = 1;
else if (mtx_owned(VI_MTX(vp)) == 0) {
VI_LOCK(vp);
mtxlkflag = 2;
}
nn = VTONULL(vp);
if (nn != NULL && (lvp = NULLVPTOLOWERVP(vp)) != NULL) {
VI_LOCK_FLAGS(lvp, MTX_DUPOK);
flags |= LK_INTERLOCK;
vholdl(lvp);
VI_UNLOCK(vp);
error = VOP_UNLOCK(lvp, flags);
vdrop(lvp);
if (mtxlkflag == 0)
VI_LOCK(vp);
} else {
if (mtxlkflag == 2)
VI_UNLOCK(vp);
error = vop_stdunlock(ap);
}
return (error);
}
/*
* There is no way to tell that someone issued remove/rmdir operation
* on the underlying filesystem. For now we just have to release lowervp
* as soon as possible.
*
* Note, we can't release any resources nor remove vnode from hash before
* appropriate VXLOCK stuff is done because other process can find this
* vnode in hash during inactivation and may be sitting in vget() and waiting
* for null_inactive to unlock vnode. Thus we will do all those in VOP_RECLAIM.
*/
static int
null_inactive(struct vop_inactive_args *ap)
{
struct vnode *vp = ap->a_vp;
struct thread *td = ap->a_td;
vp->v_object = NULL;
/*
* If this is the last reference, then free up the vnode
* so as not to tie up the lower vnodes.
*/
vrecycle(vp, td);
return (0);
}
/*
* Now, the VXLOCK is in force and we're free to destroy the null vnode.
*/
static int
null_reclaim(struct vop_reclaim_args *ap)
{
struct vnode *vp;
struct null_node *xp;
struct vnode *lowervp;
vp = ap->a_vp;
xp = VTONULL(vp);
lowervp = xp->null_lowervp;
KASSERT(lowervp != NULL && vp->v_vnlock != &vp->v_lock,
("Reclaiming inclomplete null vnode %p", vp));
null_hashrem(xp);
/*
* Use the interlock to protect the clearing of v_data to
* prevent faults in null_lock().
*/
lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
VI_LOCK(vp);
vp->v_data = NULL;
vp->v_object = NULL;
vp->v_vnlock = &vp->v_lock;
VI_UNLOCK(vp);
vput(lowervp);
free(xp, M_NULLFSNODE);
return (0);
}
static int
null_print(struct vop_print_args *ap)
{
struct vnode *vp = ap->a_vp;
printf("\tvp=%p, lowervp=%p\n", vp, VTONULL(vp)->null_lowervp);
return (0);
}
/* ARGSUSED */
static int
null_getwritemount(struct vop_getwritemount_args *ap)
{
struct null_node *xp;
struct vnode *lowervp;
struct vnode *vp;
vp = ap->a_vp;
VI_LOCK(vp);
xp = VTONULL(vp);
if (xp && (lowervp = xp->null_lowervp)) {
VI_LOCK_FLAGS(lowervp, MTX_DUPOK);
VI_UNLOCK(vp);
vholdl(lowervp);
VI_UNLOCK(lowervp);
VOP_GETWRITEMOUNT(lowervp, ap->a_mpp);
vdrop(lowervp);
} else {
VI_UNLOCK(vp);
*(ap->a_mpp) = NULL;
}
return (0);
}
static int
null_vptofh(struct vop_vptofh_args *ap)
{
struct vnode *lvp;
lvp = NULLVPTOLOWERVP(ap->a_vp);
return VOP_VPTOFH(lvp, ap->a_fhp);
}
static int
null_vptocnp(struct vop_vptocnp_args *ap)
{
struct vnode *vp = ap->a_vp;
struct vnode **dvp = ap->a_vpp;
struct vnode *lvp, *ldvp;
struct ucred *cred = ap->a_cred;
int error, locked;
if (vp->v_type == VDIR)
return (vop_stdvptocnp(ap));
locked = VOP_ISLOCKED(vp);
lvp = NULLVPTOLOWERVP(vp);
vhold(lvp);
VOP_UNLOCK(vp, 0); /* vp is held by vn_vptocnp_locked that called us */
ldvp = lvp;
vref(lvp);
error = vn_vptocnp(&ldvp, cred, ap->a_buf, ap->a_buflen);
vdrop(lvp);
if (error != 0) {
vn_lock(vp, locked | LK_RETRY);
return (ENOENT);
}
/*
* Exclusive lock is required by insmntque1 call in
* null_nodeget()
*/
error = vn_lock(ldvp, LK_EXCLUSIVE);
if (error != 0) {
vrele(ldvp);
vn_lock(vp, locked | LK_RETRY);
return (ENOENT);
}
vref(ldvp);
error = null_nodeget(vp->v_mount, ldvp, dvp);
if (error == 0) {
#ifdef DIAGNOSTIC
NULLVPTOLOWERVP(*dvp);
#endif
VOP_UNLOCK(*dvp, 0); /* keep reference on *dvp */
}
vn_lock(vp, locked | LK_RETRY);
return (error);
}
static int
null_link(struct vop_link_args *ap)
{
if (ap->a_tdvp->v_mount != ap->a_vp->v_mount)
return (EXDEV);
return (null_bypass((struct vop_generic_args *)ap));
}
/*
* Global vfs data structures
*/
struct vop_vector null_vnodeops = {
.vop_bypass = null_bypass,
.vop_access = null_access,
.vop_accessx = null_accessx,
.vop_advlockpurge = vop_stdadvlockpurge,
.vop_bmap = VOP_EOPNOTSUPP,
.vop_getattr = null_getattr,
.vop_getwritemount = null_getwritemount,
.vop_inactive = null_inactive,
.vop_islocked = vop_stdislocked,
.vop_link = null_link,
.vop_lock1 = null_lock,
.vop_lookup = null_lookup,
.vop_open = null_open,
.vop_print = null_print,
.vop_reclaim = null_reclaim,
.vop_remove = null_remove,
.vop_rename = null_rename,
.vop_setattr = null_setattr,
.vop_strategy = VOP_EOPNOTSUPP,
.vop_unlock = null_unlock,
.vop_vptocnp = null_vptocnp,
.vop_vptofh = null_vptofh,
};