[apple/xnu.git] / bsd / miscfs / bindfs / bind_subr.c

/*
 * Copyright (c) 2019 Apple Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 *
 * The 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_LICENSE_HEADER_END@
 */

/*-
 * Portions Copyright (c) 1992, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software donated to Berkeley by
 * Jan-Simon Pendry.
 *
 * 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_subr.c 8.7 (Berkeley) 5/14/95
 *
 * $FreeBSD$
 */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/vnode.h>

#include "bindfs.h"

/*
 * Null layer cache:
 * Each cache entry holds a reference to the lower vnode
 * along with a pointer to the alias vnode.  When an
 * entry is added the lower vnode is VREF'd.  When the
 * alias is removed the lower vnode is vrele'd.
 */

#define BIND_HASH_SIZE (desiredvnodes / 10)

/* xnu doesn't really have the functionality freebsd uses here..gonna try this
 * hacked hash...*/
#define BIND_NHASH(vp) (&bind_node_hashtbl[((((uintptr_t)vp) >> vnsz2log) + (uintptr_t)vnode_mount(vp)) & bind_hash_mask])

static LIST_HEAD(bind_node_hashhead, bind_node) * bind_node_hashtbl;
static LCK_GRP_DECLARE(bind_hashlck_grp, "com.apple.filesystems.bindfs");
static LCK_MTX_DECLARE(bind_hashmtx, &bind_hashlck_grp);
static u_long bind_hash_mask;

/*  xnu doesn't have hashes built into vnodes. This mimics what freebsd does
 *  9 is an eyeball of the log 2 size of vnode */
static int vnsz2log = 9;

static int bind_hashins(struct mount *, struct bind_node *, struct vnode **);

/*
 * Initialise cache headers
 */
int
bindfs_init(__unused struct vfsconf * vfsp)
{
	BINDFSDEBUG("%s\n", __FUNCTION__);

	bind_node_hashtbl = hashinit(BIND_HASH_SIZE, M_TEMP, &bind_hash_mask);
	if (bind_node_hashtbl == NULL) {
		goto error;
	}

	BINDFSDEBUG("%s finished\n", __FUNCTION__);
	return 0;
error:
	printf("BINDFS: failed to initialize globals\n");
	return KERN_FAILURE;
}

int
bindfs_destroy(void)
{
	/* This gets called when the fs is uninstalled, there wasn't an exact
	 * equivalent in vfsops */
	hashdestroy(bind_node_hashtbl, M_TEMP, bind_hash_mask);
	return 0;
}

/*
 * Find the bindfs vnode mapped to lowervp. Return it in *vpp with an iocount if found.
 * Return 0 on success. On failure *vpp will be NULL and a non-zero error code will be returned.
 */
int
bind_hashget(struct mount * mp, struct vnode * lowervp, struct vnode ** vpp)
{
	struct bind_node_hashhead * hd;
	struct bind_node * a;
	struct vnode * vp = NULL;
	uint32_t vp_vid = 0;
	int error = ENOENT;

	/*
	 * Find hash base, and then search the (two-way) linked
	 * list looking for a bind_node structure which is referencing
	 * the lower vnode. We only give up our reference at reclaim so
	 * just check whether the lowervp has gotten pulled from under us
	 */
	hd = BIND_NHASH(lowervp);
	lck_mtx_lock(&bind_hashmtx);
	LIST_FOREACH(a, hd, bind_hash)
	{
		if (a->bind_lowervp == lowervp && vnode_mount(BINDTOV(a)) == mp) {
			vp = BINDTOV(a);
			if (a->bind_lowervid != vnode_vid(lowervp)) {
				/*lowervp has reved */
				error = EIO;
				vp = NULL;
			} else {
				vp_vid = a->bind_myvid;
			}
			break;
		}
	}
	lck_mtx_unlock(&bind_hashmtx);

	if (vp != NULL) {
		error = vnode_getwithvid(vp, vp_vid);
		if (error == 0) {
			*vpp = vp;
		}
	}
	return error;
}

/*
 * Act like bind_hashget, but add passed bind_node to hash if no existing
 * node found.
 * If we find a vnode in the hash table it is returned via vpp. If we don't
 * find a hit in the table, then vpp is NULL on return and xp is added to the table.
 * 0 is returned if a hash table hit occurs or if we insert the bind_node.
 * EIO is returned if we found a hash table hit but the lower vnode was recycled.
 */
static int
bind_hashins(struct mount * mp, struct bind_node * xp, struct vnode ** vpp)
{
	struct bind_node_hashhead * hd;
	struct bind_node * oxp;
	struct vnode * ovp = NULL;
	uint32_t oxp_vid = 0;
	int error = 0;

	hd = BIND_NHASH(xp->bind_lowervp);
	lck_mtx_lock(&bind_hashmtx);
	LIST_FOREACH(oxp, hd, bind_hash)
	{
		if (oxp->bind_lowervp == xp->bind_lowervp && vnode_mount(BINDTOV(oxp)) == mp) {
			ovp = BINDTOV(oxp);
			if (oxp->bind_lowervid != vnode_vid(oxp->bind_lowervp)) {
				/*	vp doesn't exist so return null (not sure we are actually gonna catch
				 *  recycle right now
				 *  This is an exceptional case right now, it suggests the vnode we are
				 *  trying to add has been recycled
				 *  don't add it.*/
				error = EIO;
				ovp = NULL;
			} else {
				oxp_vid = oxp->bind_myvid;
			}
			goto end;
		}
	}
	/* if it wasn't in the hash map then the vnode pointed to by xp already has a
	 * iocount so don't get another. */
	LIST_INSERT_HEAD(hd, xp, bind_hash);
	xp->bind_flags |= BIND_FLAG_HASHED;
end:
	lck_mtx_unlock(&bind_hashmtx);
	if (ovp != NULL) {
		/* if we found something in the hash map then grab an iocount */
		error = vnode_getwithvid(ovp, oxp_vid);
		if (error == 0) {
			*vpp = ovp;
		}
	}
	return error;
}

/*
 * Remove node from hash.
 */
void
bind_hashrem(struct bind_node * xp)
{
	if (xp->bind_flags & BIND_FLAG_HASHED) {
		lck_mtx_lock(&bind_hashmtx);
		LIST_REMOVE(xp, bind_hash);
		lck_mtx_unlock(&bind_hashmtx);
	}
}

static struct bind_node *
bind_nodecreate(struct vnode * lowervp)
{
	struct bind_node * xp;

	MALLOC(xp, struct bind_node *, sizeof(struct bind_node), M_TEMP, M_WAITOK | M_ZERO);
	if (xp != NULL) {
		if (lowervp) {
			xp->bind_lowervp  = lowervp;
			xp->bind_lowervid = vnode_vid(lowervp);
		}
	}
	return xp;
}

/* assumption is that vnode has iocount on it after vnode create */
int
bind_getnewvnode(
	struct mount * mp, struct vnode * lowervp, struct vnode * dvp, struct vnode ** vpp, struct componentname * cnp, int root)
{
	struct vnode_fsparam vnfs_param;
	int error             = 0;
	enum vtype type       = VDIR;
	struct bind_node * xp = bind_nodecreate(lowervp);

	if (xp == NULL) {
		return ENOMEM;
	}

	if (lowervp) {
		type = vnode_vtype(lowervp);
	}

	vnfs_param.vnfs_mp         = mp;
	vnfs_param.vnfs_vtype      = type;
	vnfs_param.vnfs_str        = "bindfs";
	vnfs_param.vnfs_dvp        = dvp;
	vnfs_param.vnfs_fsnode     = (void *)xp;
	vnfs_param.vnfs_vops       = bindfs_vnodeop_p;
	vnfs_param.vnfs_markroot   = root;
	vnfs_param.vnfs_marksystem = 0;
	vnfs_param.vnfs_rdev       = 0;
	vnfs_param.vnfs_filesize   = 0; // set this to 0 since we should only be shadowing non-regular files
	vnfs_param.vnfs_cnp        = cnp;
	vnfs_param.vnfs_flags      = VNFS_ADDFSREF;

	error = vnode_create(VNCREATE_FLAVOR, VCREATESIZE, &vnfs_param, vpp);
	if (error == 0) {
		xp->bind_vnode = *vpp;
		xp->bind_myvid = vnode_vid(*vpp);
		vnode_settag(*vpp, VT_BINDFS);
	} else {
		FREE(xp, M_TEMP);
	}
	return error;
}

/*
 * Make a new or get existing bindfs node.
 * Vp is the alias vnode, lowervp is the lower vnode.
 *
 * lowervp is assumed to have an iocount on it from the caller
 */
int
bind_nodeget(
	struct mount * mp, struct vnode * lowervp, struct vnode * dvp, struct vnode ** vpp, struct componentname * cnp, int root)
{
	struct vnode * vp;
	int error;

	/* Lookup the hash firstly. */
	error = bind_hashget(mp, lowervp, vpp);
	/* ENOENT means it wasn't found, EIO is a failure we should bail from, 0 is it
	 * was found */
	if (error != ENOENT) {
		/* bind_hashget checked the vid, so if we got something here its legit to
		 * the best of our knowledge*/
		/* if we found something then there is an iocount on vpp,
		 *  if we didn't find something then vpp shouldn't be used by the caller */
		return error;
	}

	/*
	 * We do not serialize vnode creation, instead we will check for
	 * duplicates later, when adding new vnode to hash.
	 */
	error = vnode_ref(lowervp); // take a ref on lowervp so we let the system know we care about it
	if (error) {
		// Failed to get a reference on the lower vp so bail. Lowervp may be gone already.
		return error;
	}

	error = bind_getnewvnode(mp, lowervp, dvp, &vp, cnp, root);

	if (error) {
		vnode_rele(lowervp);
		return error;
	}

	/*
	 * Atomically insert our new node into the hash or vget existing
	 * if someone else has beaten us to it.
	 */
	error = bind_hashins(mp, VTOBIND(vp), vpp);
	if (error || *vpp != NULL) {
		/* recycle will call reclaim which will get rid of the internals */
		vnode_recycle(vp);
		vnode_put(vp);
		/* if we found vpp, then bind_hashins put an iocount on it */
		return error;
	}

	/* vp has an iocount from bind_getnewvnode */
	*vpp = vp;

	return 0;
}
Commit	Line	Data
f427ee49 A	1	/*
	2	* Copyright (c) 2019 Apple Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
	6	* This file contains Original Code and/or Modifications of Original Code
	7	* as defined in and that are subject to the Apple Public Source License
	8	* Version 2.0 (the 'License'). You may not use this file except in
	9	* compliance with the License. Please obtain a copy of the License at
	10	* http://www.opensource.apple.com/apsl/ and read it before using this
	11	* file.
	12	*
	13	* The Original Code and all software distributed under the License are
	14	* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
	15	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
	16	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
	17	* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
	18	* Please see the License for the specific language governing rights and
	19	* limitations under the License.
	20	*
	21	* @APPLE_LICENSE_HEADER_END@
	22	*/
	23
	24	/*-
	25	* Portions Copyright (c) 1992, 1993
	26	* The Regents of the University of California. All rights reserved.
	27	*
	28	* This code is derived from software donated to Berkeley by
	29	* Jan-Simon Pendry.
	30	*
	31	* Redistribution and use in source and binary forms, with or without
	32	* modification, are permitted provided that the following conditions
	33	* are met:
	34	* 1. Redistributions of source code must retain the above copyright
	35	* notice, this list of conditions and the following disclaimer.
	36	* 2. Redistributions in binary form must reproduce the above copyright
	37	* notice, this list of conditions and the following disclaimer in the
	38	* documentation and/or other materials provided with the distribution.
	39	* 4. Neither the name of the University nor the names of its contributors
	40	* may be used to endorse or promote products derived from this software
	41	* without specific prior written permission.
	42	*
	43	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	44	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	45	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	46	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	47	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	48	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	49	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	50	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	51	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	52	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	53	* SUCH DAMAGE.
	54	*
	55	* @(#)null_subr.c 8.7 (Berkeley) 5/14/95
	56	*
	57	* $FreeBSD$
	58	*/
	59	#include <sys/param.h>
	60	#include <sys/systm.h>
	61	#include <sys/kernel.h>
	62	#include <sys/lock.h>
	63	#include <sys/malloc.h>
	64	#include <sys/mount.h>
65	#include <sys/proc.h>
66	#include <sys/vnode.h>
67
68	#include "bindfs.h"
69
70	/*
71	* Null layer cache:
72	* Each cache entry holds a reference to the lower vnode
73	* along with a pointer to the alias vnode. When an
74	* entry is added the lower vnode is VREF'd. When the
75	* alias is removed the lower vnode is vrele'd.
76	*/
77
78	#define BIND_HASH_SIZE (desiredvnodes / 10)
79
80	/* xnu doesn't really have the functionality freebsd uses here..gonna try this
81	* hacked hash...*/
82	#define BIND_NHASH(vp) (&bind_node_hashtbl[((((uintptr_t)vp) >> vnsz2log) + (uintptr_t)vnode_mount(vp)) & bind_hash_mask])
83
84	static LIST_HEAD(bind_node_hashhead, bind_node) * bind_node_hashtbl;
c3c9b80d A	85	static LCK_GRP_DECLARE(bind_hashlck_grp, "com.apple.filesystems.bindfs");
c3c9b80d A	86	static LCK_MTX_DECLARE(bind_hashmtx, &bind_hashlck_grp);
f427ee49 A	87	static u_long bind_hash_mask;
	88
	89	/* xnu doesn't have hashes built into vnodes. This mimics what freebsd does
	90	* 9 is an eyeball of the log 2 size of vnode */
	91	static int vnsz2log = 9;
	92
	93	static int bind_hashins(struct mount , struct bind_node , struct vnode **);
	94
f427ee49 A	95	/*
	96	* Initialise cache headers
	97	*/
	98	int
	99	bindfs_init(__unused struct vfsconf * vfsp)
	100	{
	101	BINDFSDEBUG("%s\n", __FUNCTION__);
	102
f427ee49 A	103	bind_node_hashtbl = hashinit(BIND_HASH_SIZE, M_TEMP, &bind_hash_mask);
	104	if (bind_node_hashtbl == NULL) {
	105	goto error;
	106	}
f427ee49 A	107
	108	BINDFSDEBUG("%s finished\n", __FUNCTION__);
	109	return 0;
	110	error:
	111	printf("BINDFS: failed to initialize globals\n");
f427ee49 A	112	return KERN_FAILURE;
	113	}
	114
	115	int
	116	bindfs_destroy(void)
	117	{
	118	/* This gets called when the fs is uninstalled, there wasn't an exact
	119	* equivalent in vfsops */
f427ee49	120	hashdestroy(bind_node_hashtbl, M_TEMP, bind_hash_mask);
f427ee49 A	121	return 0;
	122	}
	123
	124	/*
	125	* Find the bindfs vnode mapped to lowervp. Return it in *vpp with an iocount if found.
	126	* Return 0 on success. On failure *vpp will be NULL and a non-zero error code will be returned.
	127	*/
	128	int
	129	bind_hashget(struct mount * mp, struct vnode * lowervp, struct vnode ** vpp)
	130	{
	131	struct bind_node_hashhead * hd;
	132	struct bind_node * a;
	133	struct vnode * vp = NULL;
2a1bd2d3	134	uint32_t vp_vid = 0;
f427ee49 A	135	int error = ENOENT;
	136
	137	/*
	138	* Find hash base, and then search the (two-way) linked
	139	* list looking for a bind_node structure which is referencing
	140	* the lower vnode. We only give up our reference at reclaim so
	141	* just check whether the lowervp has gotten pulled from under us
	142	*/
	143	hd = BIND_NHASH(lowervp);
	144	lck_mtx_lock(&bind_hashmtx);
	145	LIST_FOREACH(a, hd, bind_hash)
	146	{
	147	if (a->bind_lowervp == lowervp && vnode_mount(BINDTOV(a)) == mp) {
	148	vp = BINDTOV(a);
	149	if (a->bind_lowervid != vnode_vid(lowervp)) {
	150	/lowervp has reved /
	151	error = EIO;
	152	vp = NULL;
2a1bd2d3 A	153	} else {
2a1bd2d3 A	154	vp_vid = a->bind_myvid;
f427ee49 A	155	}
	156	break;
	157	}
	158	}
	159	lck_mtx_unlock(&bind_hashmtx);
	160
	161	if (vp != NULL) {
2a1bd2d3	162	error = vnode_getwithvid(vp, vp_vid);
f427ee49 A	163	if (error == 0) {
	164	*vpp = vp;
	165	}
	166	}
	167	return error;
	168	}
	169
	170	/*
	171	* Act like bind_hashget, but add passed bind_node to hash if no existing
	172	* node found.
	173	* If we find a vnode in the hash table it is returned via vpp. If we don't
	174	* find a hit in the table, then vpp is NULL on return and xp is added to the table.
	175	* 0 is returned if a hash table hit occurs or if we insert the bind_node.
	176	* EIO is returned if we found a hash table hit but the lower vnode was recycled.
	177	*/
	178	static int
	179	bind_hashins(struct mount * mp, struct bind_node * xp, struct vnode ** vpp)
	180	{
	181	struct bind_node_hashhead * hd;
	182	struct bind_node * oxp;
	183	struct vnode * ovp = NULL;
2a1bd2d3	184	uint32_t oxp_vid = 0;
f427ee49 A	185	int error = 0;
	186
	187	hd = BIND_NHASH(xp->bind_lowervp);
	188	lck_mtx_lock(&bind_hashmtx);
	189	LIST_FOREACH(oxp, hd, bind_hash)
	190	{
	191	if (oxp->bind_lowervp == xp->bind_lowervp && vnode_mount(BINDTOV(oxp)) == mp) {
	192	ovp = BINDTOV(oxp);
	193	if (oxp->bind_lowervid != vnode_vid(oxp->bind_lowervp)) {
	194	/* vp doesn't exist so return null (not sure we are actually gonna catch
	195	* recycle right now
	196	* This is an exceptional case right now, it suggests the vnode we are
	197	* trying to add has been recycled
	198	* don't add it.*/
	199	error = EIO;
	200	ovp = NULL;
2a1bd2d3 A	201	} else {
2a1bd2d3 A	202	oxp_vid = oxp->bind_myvid;
f427ee49 A	203	}
	204	goto end;
	205	}
	206	}
	207	/* if it wasn't in the hash map then the vnode pointed to by xp already has a
	208	* iocount so don't get another. */
	209	LIST_INSERT_HEAD(hd, xp, bind_hash);
	210	xp->bind_flags \|= BIND_FLAG_HASHED;
	211	end:
	212	lck_mtx_unlock(&bind_hashmtx);
	213	if (ovp != NULL) {
	214	/* if we found something in the hash map then grab an iocount */
2a1bd2d3	215	error = vnode_getwithvid(ovp, oxp_vid);
f427ee49 A	216	if (error == 0) {
	217	*vpp = ovp;
	218	}
	219	}
	220	return error;
	221	}
	222
	223	/*
	224	* Remove node from hash.
	225	*/
	226	void
	227	bind_hashrem(struct bind_node * xp)
	228	{
	229	if (xp->bind_flags & BIND_FLAG_HASHED) {
	230	lck_mtx_lock(&bind_hashmtx);
	231	LIST_REMOVE(xp, bind_hash);
	232	lck_mtx_unlock(&bind_hashmtx);
	233	}
	234	}
	235
	236	static struct bind_node *
	237	bind_nodecreate(struct vnode * lowervp)
	238	{
	239	struct bind_node * xp;
	240
	241	MALLOC(xp, struct bind_node *, sizeof(struct bind_node), M_TEMP, M_WAITOK \| M_ZERO);
	242	if (xp != NULL) {
	243	if (lowervp) {
	244	xp->bind_lowervp = lowervp;
	245	xp->bind_lowervid = vnode_vid(lowervp);
	246	}
	247	}
	248	return xp;
	249	}
	250
	251	/* assumption is that vnode has iocount on it after vnode create */
	252	int
	253	bind_getnewvnode(
	254	struct mount * mp, struct vnode * lowervp, struct vnode * dvp, struct vnode ** vpp, struct componentname * cnp, int root)
	255	{
	256	struct vnode_fsparam vnfs_param;
	257	int error = 0;
	258	enum vtype type = VDIR;
	259	struct bind_node * xp = bind_nodecreate(lowervp);
	260
	261	if (xp == NULL) {
	262	return ENOMEM;
	263	}
	264
	265	if (lowervp) {
	266	type = vnode_vtype(lowervp);
	267	}
	268
	269	vnfs_param.vnfs_mp = mp;
	270	vnfs_param.vnfs_vtype = type;
	271	vnfs_param.vnfs_str = "bindfs";
	272	vnfs_param.vnfs_dvp = dvp;
	273	vnfs_param.vnfs_fsnode = (void *)xp;
	274	vnfs_param.vnfs_vops = bindfs_vnodeop_p;
	275	vnfs_param.vnfs_markroot = root;
	276	vnfs_param.vnfs_marksystem = 0;
	277	vnfs_param.vnfs_rdev = 0;
	278	vnfs_param.vnfs_filesize = 0; // set this to 0 since we should only be shadowing non-regular files
	279	vnfs_param.vnfs_cnp = cnp;
280	vnfs_param.vnfs_flags = VNFS_ADDFSREF;
281
282	error = vnode_create(VNCREATE_FLAVOR, VCREATESIZE, &vnfs_param, vpp);
283	if (error == 0) {
284	xp->bind_vnode = *vpp;
285	xp->bind_myvid = vnode_vid(*vpp);
286	vnode_settag(*vpp, VT_BINDFS);
287	} else {
288	FREE(xp, M_TEMP);
289	}
290	return error;
291	}
292
293	/*
294	* Make a new or get existing bindfs node.
295	* Vp is the alias vnode, lowervp is the lower vnode.
296	*
297	* lowervp is assumed to have an iocount on it from the caller
298	*/
299	int
300	bind_nodeget(
301	struct mount * mp, struct vnode * lowervp, struct vnode * dvp, struct vnode ** vpp, struct componentname * cnp, int root)
302	{
303	struct vnode * vp;
304	int error;
305
306	/* Lookup the hash firstly. */
307	error = bind_hashget(mp, lowervp, vpp);
308	/* ENOENT means it wasn't found, EIO is a failure we should bail from, 0 is it
309	* was found */
310	if (error != ENOENT) {
311	/* bind_hashget checked the vid, so if we got something here its legit to
312	* the best of our knowledge*/
313	/* if we found something then there is an iocount on vpp,
314	* if we didn't find something then vpp shouldn't be used by the caller */
315	return error;
316	}
317
318	/*
319	* We do not serialize vnode creation, instead we will check for
320	* duplicates later, when adding new vnode to hash.
321	*/
322	error = vnode_ref(lowervp); // take a ref on lowervp so we let the system know we care about it
323	if (error) {
324	// Failed to get a reference on the lower vp so bail. Lowervp may be gone already.
325	return error;
326	}
327
328	error = bind_getnewvnode(mp, lowervp, dvp, &vp, cnp, root);
329
330	if (error) {
331	vnode_rele(lowervp);
332	return error;
333	}
334
335	/*
336	* Atomically insert our new node into the hash or vget existing
337	* if someone else has beaten us to it.
338	*/
339	error = bind_hashins(mp, VTOBIND(vp), vpp);
340	if (error \|\| *vpp != NULL) {
341	/* recycle will call reclaim which will get rid of the internals */
342	vnode_recycle(vp);
343	vnode_put(vp);
344	/* if we found vpp, then bind_hashins put an iocount on it */
345	return error;
346	}
347
348	/* vp has an iocount from bind_getnewvnode */
349	*vpp = vp;
350
351	return 0;
352	}