gems-kernel/source/THIRDPARTY/xnu/bsd/miscfs/bindfs/bind_subr.c

359 lines
11 KiB
C
Raw Normal View History

2024-06-03 11:29:39 -05:00
/*
* 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;
}
}
if (vp) {
vnode_hold(vp);
}
lck_mtx_unlock(&bind_hashmtx);
if (vp != NULL) {
error = vnode_getwithvid(vp, vp_vid);
if (error == 0) {
*vpp = vp;
}
vnode_drop(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:
if (ovp) {
vnode_hold(ovp);
}
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;
}
vnode_drop(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;
xp = kalloc_type(struct bind_node, Z_WAITOK | Z_ZERO | Z_NOFAIL);
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_ext(VNCREATE_FLAVOR, VCREATESIZE, &vnfs_param, vpp, VNODE_CREATE_DEFAULT);
if (error == 0) {
xp->bind_vnode = *vpp;
xp->bind_myvid = vnode_vid(*vpp);
vnode_settag(*vpp, VT_BINDFS);
} else {
kfree_type(struct bind_node, xp);
}
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;
}