364 lines
11 KiB
C
364 lines
11 KiB
C
/*
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* Copyright (c) 2016 Apple Inc. All rights reserved.
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*
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* @APPLE_LICENSE_HEADER_START@
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*
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* This file contains Original Code and/or Modifications of Original Code
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* as defined in and that are subject to the Apple Public Source License
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* Version 2.0 (the 'License'). You may not use this file except in
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* compliance with the License. Please obtain a copy of the License at
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* http://www.opensource.apple.com/apsl/ and read it before using this
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* file.
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*
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* The Original Code and all software distributed under the License are
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* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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* Please see the License for the specific language governing rights and
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* limitations under the License.
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*
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* @APPLE_LICENSE_HEADER_END@
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*/
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/*-
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* Portions Copyright (c) 1992, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software donated to Berkeley by
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* Jan-Simon Pendry.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)null_subr.c 8.7 (Berkeley) 5/14/95
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/mount.h>
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#include <sys/proc.h>
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#include <sys/vnode.h>
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#include "nullfs.h"
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/*
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* Null layer cache:
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* Each cache entry holds a reference to the lower vnode
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* along with a pointer to the alias vnode. When an
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* entry is added the lower vnode is VREF'd. When the
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* alias is removed the lower vnode is vrele'd.
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*/
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#define NULL_HASH_SIZE (desiredvnodes / 10)
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/* osx doesn't really have the functionality freebsd uses here..gonna try this
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* hacked hash...*/
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#define NULL_NHASH(vp) (&null_node_hashtbl[((((uintptr_t)vp) >> vnsz2log) + (uintptr_t)vnode_mount(vp)) & null_hash_mask])
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static LIST_HEAD(null_node_hashhead, null_node) * null_node_hashtbl;
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static LCK_GRP_DECLARE(null_hashlck_grp, "com.apple.filesystems.nullfs");
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static LCK_MTX_DECLARE(null_hashmtx, &null_hashlck_grp);
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static u_long null_hash_mask;
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/* os x doesn't have hashes built into vnode. gonna try doing what freebsd does
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* anyway
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* Don't want to create a dependency on vnode_internal.h and the real struct
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* vnode.
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* 9 is an eyeball of the log 2 size of vnode */
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static int vnsz2log = 9;
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static int null_hashins(struct mount *, struct null_node *, struct vnode **);
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void
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nullfs_init_lck(lck_mtx_t * lck)
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{
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lck_mtx_init(lck, &null_hashlck_grp, LCK_ATTR_NULL);
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}
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void
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nullfs_destroy_lck(lck_mtx_t * lck)
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{
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lck_mtx_destroy(lck, &null_hashlck_grp);
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}
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/*
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* Initialise cache headers
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*/
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int
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nullfs_init(__unused struct vfsconf * vfsp)
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{
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NULLFSDEBUG("%s\n", __FUNCTION__);
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null_node_hashtbl = hashinit(NULL_HASH_SIZE, M_TEMP, &null_hash_mask);
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NULLFSDEBUG("%s finished\n", __FUNCTION__);
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return 0;
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}
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int
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nullfs_uninit(void)
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{
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/* This gets called when the fs is uninstalled, there wasn't an exact
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* equivalent in vfsops */
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hashdestroy(null_node_hashtbl, M_TEMP, null_hash_mask);
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return 0;
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}
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/*
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* Find the nullfs vnode mapped to lowervp. Return it in *vpp with an iocount if found.
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* Return 0 on success. On failure *vpp will be null and a non-zero error code will be returned.
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*/
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int
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null_hashget(struct mount * mp, struct vnode * lowervp, struct vnode ** vpp)
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{
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struct null_node_hashhead * hd = NULL;
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struct null_node * a = NULL;
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struct vnode * vp = NULL;
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uint32_t vp_vid = 0;
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int error = ENOENT;
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/*
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* Find hash base, and then search the (two-way) linked
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* list looking for a null_node structure which is referencing
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* the lower vnode. We only give up our reference at reclaim so
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* just check whether the lowervp has gotten pulled from under us
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*/
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hd = NULL_NHASH(lowervp);
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// In the future we should consider using a per bucket lock
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lck_mtx_lock(&null_hashmtx);
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LIST_FOREACH(a, hd, null_hash)
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{
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if (a->null_lowervp == lowervp && vnode_mount(NULLTOV(a)) == mp) {
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vp = NULLTOV(a);
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if (a->null_lowervid != vnode_vid(lowervp)) {
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/*lowervp has reved */
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error = EIO;
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vp = NULL;
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} else {
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vp_vid = a->null_myvid;
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}
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// In the case of a succesful look-up we should consider moving the object to the top of the head
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break;
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}
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}
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if (vp != NULL) {
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vnode_hold(vp);
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}
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lck_mtx_unlock(&null_hashmtx);
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if (vp != NULL) {
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error = vnode_getwithvid(vp, vp_vid);
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if (error == 0) {
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*vpp = vp;
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}
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vnode_drop(vp);
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}
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return error;
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}
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/*
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* Act like null_hashget, but add passed null_node to hash if no existing
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* node found.
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*/
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static int
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null_hashins(struct mount * mp, struct null_node * xp, struct vnode ** vpp)
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{
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struct null_node_hashhead * hd = NULL;
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struct null_node * oxp = NULL;
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struct vnode * ovp = NULL;
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uint32_t oxp_vid = 0;
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int error = 0;
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hd = NULL_NHASH(xp->null_lowervp);
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lck_mtx_lock(&null_hashmtx);
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LIST_FOREACH(oxp, hd, null_hash)
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{
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if (oxp->null_lowervp == xp->null_lowervp && vnode_mount(NULLTOV(oxp)) == mp) {
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/*
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* See null_hashget for a description of this
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* operation.
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*/
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ovp = NULLTOV(oxp);
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if (oxp->null_lowervid != vnode_vid(oxp->null_lowervp)) {
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/*vp doesn't exist so return null (not sure we are actually gonna catch
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* recycle right now
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* This is an exceptional case right now, it suggests the vnode we are
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* trying to add has been recycled
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* don't add it.*/
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error = EIO;
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ovp = NULL;
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} else {
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oxp_vid = oxp->null_myvid;
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}
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goto end;
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}
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}
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/* if it wasn't in the hash map then the vnode pointed to by xp already has a
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* iocount so don't bother */
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LIST_INSERT_HEAD(hd, xp, null_hash);
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xp->null_flags |= NULL_FLAG_HASHED;
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end:
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if (ovp != NULL) {
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vnode_hold(ovp);
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}
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lck_mtx_unlock(&null_hashmtx);
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if (ovp != NULL) {
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/* if we found something in the hash map then grab an iocount */
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error = vnode_getwithvid(ovp, oxp_vid);
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if (error == 0) {
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*vpp = ovp;
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}
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vnode_drop(ovp);
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}
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return error;
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}
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/*
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* Remove node from hash.
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*/
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void
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null_hashrem(struct null_node * xp)
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{
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lck_mtx_lock(&null_hashmtx);
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LIST_REMOVE(xp, null_hash);
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lck_mtx_unlock(&null_hashmtx);
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}
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static struct null_node *
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null_nodecreate(struct vnode * lowervp)
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{
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struct null_node * xp;
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xp = kalloc_type(struct null_node, Z_WAITOK | Z_ZERO | Z_NOFAIL);
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if (lowervp) {
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xp->null_lowervp = lowervp;
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xp->null_lowervid = vnode_vid(lowervp);
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}
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return xp;
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}
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/* assumption is that vnode has iocount on it after vnode create */
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int
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null_getnewvnode(
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struct mount * mp, struct vnode * lowervp, struct vnode * dvp, struct vnode ** vpp, struct componentname * cnp, int root)
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{
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struct vnode_fsparam vnfs_param;
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int error = 0;
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enum vtype type = VDIR;
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struct null_node * xp = null_nodecreate(lowervp);
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if (xp == NULL) {
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return ENOMEM;
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}
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if (lowervp) {
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type = vnode_vtype(lowervp);
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}
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vnfs_param.vnfs_mp = mp;
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vnfs_param.vnfs_vtype = type;
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vnfs_param.vnfs_str = "nullfs";
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vnfs_param.vnfs_dvp = dvp;
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vnfs_param.vnfs_fsnode = (void *)xp;
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vnfs_param.vnfs_vops = nullfs_vnodeop_p;
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vnfs_param.vnfs_markroot = root;
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vnfs_param.vnfs_marksystem = 0;
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vnfs_param.vnfs_rdev = 0;
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vnfs_param.vnfs_filesize = 0; // set this to 0 since we should only be shadowing non-regular files
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vnfs_param.vnfs_cnp = cnp;
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vnfs_param.vnfs_flags = VNFS_ADDFSREF;
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error = vnode_create_ext(VNCREATE_FLAVOR, VCREATESIZE, &vnfs_param, vpp, VNODE_CREATE_DEFAULT);
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if (error == 0) {
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xp->null_vnode = *vpp;
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xp->null_myvid = vnode_vid(*vpp);
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vnode_settag(*vpp, VT_NULL);
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} else {
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kfree_type(struct null_node, xp);
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}
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return error;
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}
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/*
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* Make a new or get existing nullfs node.
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* Vp is the alias vnode, lowervp is the lower vnode.
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*
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* lowervp is assumed to have an iocount on it from the caller
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*/
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int
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null_nodeget(
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struct mount * mp, struct vnode * lowervp, struct vnode * dvp, struct vnode ** vpp, struct componentname * cnp, int root)
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{
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struct vnode * vp;
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int error;
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/* Lookup the hash firstly. */
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error = null_hashget(mp, lowervp, vpp);
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/* ENOENT means it wasn't found, EIO is a failure we should bail from, 0 is it
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* was found */
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if (error != ENOENT) {
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/* null_hashget checked the vid, so if we got something here its legit to
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* the best of our knowledge*/
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/* if we found something then there is an iocount on vpp,
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* if we didn't find something then vpp shouldn't be used by the caller */
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return error;
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}
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/*
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* We do not serialize vnode creation, instead we will check for
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* duplicates later, when adding new vnode to hash.
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*/
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error = vnode_ref(lowervp); // take a ref on lowervp so we let the system know we care about it
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if (error) {
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// Failed to get a reference on the lower vp so bail. Lowervp may be gone already.
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return error;
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}
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error = null_getnewvnode(mp, lowervp, dvp, &vp, cnp, root);
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if (error) {
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vnode_rele(lowervp);
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return error;
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}
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/*
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* Atomically insert our new node into the hash or vget existing
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* if someone else has beaten us to it.
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*/
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error = null_hashins(mp, VTONULL(vp), vpp);
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if (error || *vpp != NULL) {
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/* recycle will call reclaim which will get rid of the internals */
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vnode_recycle(vp);
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vnode_put(vp);
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/* if we found vpp, then null_hashins put an iocount on it */
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return error;
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}
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/* vp has an iocount from null_getnewvnode */
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*vpp = vp;
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return 0;
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}
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