362 lines
9.6 KiB
C
362 lines
9.6 KiB
C
/*-
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* 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/mutex.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 <fs/nullfs/null.h>
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#define LOG2_SIZEVNODE 8 /* log2(sizeof struct vnode) */
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#define NNULLNODECACHE 16
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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_NHASH(vp) \
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(&null_node_hashtbl[(((uintptr_t)vp)>>LOG2_SIZEVNODE) & null_node_hash])
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static LIST_HEAD(null_node_hashhead, null_node) *null_node_hashtbl;
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static u_long null_node_hash;
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struct mtx null_hashmtx;
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static MALLOC_DEFINE(M_NULLFSHASH, "NULLFS hash", "NULLFS hash table");
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MALLOC_DEFINE(M_NULLFSNODE, "NULLFS node", "NULLFS vnode private part");
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static struct vnode * null_hashget(struct mount *, struct vnode *);
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static struct vnode * null_hashins(struct mount *, struct null_node *);
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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(vfsp)
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struct vfsconf *vfsp;
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{
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NULLFSDEBUG("nullfs_init\n"); /* printed during system boot */
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null_node_hashtbl = hashinit(NNULLNODECACHE, M_NULLFSHASH, &null_node_hash);
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mtx_init(&null_hashmtx, "nullhs", NULL, MTX_DEF);
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return (0);
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}
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int
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nullfs_uninit(vfsp)
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struct vfsconf *vfsp;
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{
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mtx_destroy(&null_hashmtx);
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free(null_node_hashtbl, M_NULLFSHASH);
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return (0);
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}
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/*
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* Return a VREF'ed alias for lower vnode if already exists, else 0.
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* Lower vnode should be locked on entry and will be left locked on exit.
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*/
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static struct vnode *
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null_hashget(mp, lowervp)
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struct mount *mp;
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struct vnode *lowervp;
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{
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struct thread *td = curthread; /* XXX */
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struct null_node_hashhead *hd;
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struct null_node *a;
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struct vnode *vp;
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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. If found, the increment the null_node
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* reference count (but NOT the lower vnode's VREF counter).
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*/
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hd = NULL_NHASH(lowervp);
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loop:
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mtx_lock(&null_hashmtx);
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LIST_FOREACH(a, hd, null_hash) {
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if (a->null_lowervp == lowervp && NULLTOV(a)->v_mount == mp) {
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vp = NULLTOV(a);
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mtx_lock(&vp->v_interlock);
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/*
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* Don't block if nullfs vnode is being recycled.
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* We already hold a lock on the lower vnode, thus
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* waiting might deadlock against the thread
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* recycling the nullfs vnode or another thread
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* in vrele() waiting for the vnode lock.
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*/
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if ((vp->v_iflag & VI_XLOCK) != 0) {
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VI_UNLOCK(vp);
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continue;
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}
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mtx_unlock(&null_hashmtx);
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/*
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* We need vget for the VXLOCK
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* stuff, but we don't want to lock
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* the lower node.
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*/
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if (vget(vp, LK_EXCLUSIVE | LK_THISLAYER | LK_INTERLOCK, td))
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goto loop;
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return (vp);
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}
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}
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mtx_unlock(&null_hashmtx);
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return (NULLVP);
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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 struct vnode *
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null_hashins(mp, xp)
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struct mount *mp;
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struct null_node *xp;
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{
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struct thread *td = curthread; /* XXX */
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struct null_node_hashhead *hd;
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struct null_node *oxp;
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struct vnode *ovp;
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hd = NULL_NHASH(xp->null_lowervp);
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loop:
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mtx_lock(&null_hashmtx);
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LIST_FOREACH(oxp, hd, null_hash) {
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if (oxp->null_lowervp == xp->null_lowervp &&
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NULLTOV(oxp)->v_mount == mp) {
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ovp = NULLTOV(oxp);
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mtx_lock(&ovp->v_interlock);
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/*
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* Don't block if nullfs vnode is being recycled.
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* We already hold a lock on the lower vnode, thus
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* waiting might deadlock against the thread
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* recycling the nullfs vnode or another thread
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* in vrele() waiting for the vnode lock.
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*/
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if ((ovp->v_iflag & VI_XLOCK) != 0) {
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VI_UNLOCK(ovp);
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continue;
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}
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mtx_unlock(&null_hashmtx);
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if (vget(ovp, LK_EXCLUSIVE | LK_THISLAYER | LK_INTERLOCK, td))
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goto loop;
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return (ovp);
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}
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}
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LIST_INSERT_HEAD(hd, xp, null_hash);
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mtx_unlock(&null_hashmtx);
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return (NULLVP);
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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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* The lowervp assumed to be locked and having "spare" reference. This routine
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* vrele lowervp if nullfs node was taken from hash. Otherwise it "transfers"
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* the caller's "spare" reference to created nullfs vnode.
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*/
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int
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null_nodeget(mp, lowervp, vpp)
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struct mount *mp;
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struct vnode *lowervp;
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struct vnode **vpp;
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{
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struct thread *td = curthread; /* XXX */
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struct null_node *xp;
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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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*vpp = null_hashget(mp, lowervp);
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if (*vpp != NULL) {
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vrele(lowervp);
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return (0);
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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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* Note that duplicate can only appear in hash if the lowervp is
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* locked LK_SHARED.
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*/
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/*
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* Do the MALLOC before the getnewvnode since doing so afterward
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* might cause a bogus v_data pointer to get dereferenced
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* elsewhere if MALLOC should block.
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*/
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MALLOC(xp, struct null_node *, sizeof(struct null_node),
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M_NULLFSNODE, M_WAITOK);
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error = getnewvnode("null", mp, &null_vnodeops, &vp);
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if (error) {
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FREE(xp, M_NULLFSNODE);
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return (error);
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}
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xp->null_vnode = vp;
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xp->null_lowervp = lowervp;
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xp->null_pending_locks = 0;
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xp->null_drain_wakeup = 0;
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vp->v_type = lowervp->v_type;
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vp->v_data = xp;
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/*
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* From NetBSD:
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* Now lock the new node. We rely on the fact that we were passed
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* a locked vnode. If the lower node is exporting a struct lock
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* (v_vnlock != NULL) then we just set the upper v_vnlock to the
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* lower one, and both are now locked. If the lower node is exporting
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* NULL, then we copy that up and manually lock the new vnode.
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*/
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vp->v_vnlock = lowervp->v_vnlock;
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error = VOP_LOCK(vp, LK_EXCLUSIVE | LK_THISLAYER, td);
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if (error)
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panic("null_nodeget: can't lock new vnode\n");
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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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*vpp = null_hashins(mp, xp);
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if (*vpp != NULL) {
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vrele(lowervp);
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VOP_UNLOCK(vp, LK_THISLAYER, td);
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vp->v_vnlock = NULL;
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xp->null_lowervp = NULL;
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vrele(vp);
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return (0);
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}
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/*
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* XXX We take extra vref just to workaround UFS's XXX:
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* UFS can vrele() vnode in VOP_CLOSE() in some cases. Luckily, this
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* can only happen if v_usecount == 1. To workaround, we just don't
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* let v_usecount be 1, it will be 2 or more.
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*/
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VREF(lowervp);
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*vpp = vp;
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return (0);
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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(xp)
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struct null_node *xp;
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{
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mtx_lock(&null_hashmtx);
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LIST_REMOVE(xp, null_hash);
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mtx_unlock(&null_hashmtx);
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}
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#ifdef DIAGNOSTIC
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#ifdef KDB
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#define null_checkvp_barrier 1
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#else
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#define null_checkvp_barrier 0
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#endif
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struct vnode *
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null_checkvp(vp, fil, lno)
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struct vnode *vp;
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char *fil;
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int lno;
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{
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struct null_node *a = VTONULL(vp);
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#ifdef notyet
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/*
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* Can't do this check because vop_reclaim runs
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* with a funny vop vector.
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*/
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if (vp->v_op != null_vnodeop_p) {
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printf ("null_checkvp: on non-null-node\n");
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while (null_checkvp_barrier) /*WAIT*/ ;
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panic("null_checkvp");
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};
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#endif
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if (a->null_lowervp == NULLVP) {
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/* Should never happen */
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int i; u_long *p;
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printf("vp = %p, ZERO ptr\n", (void *)vp);
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for (p = (u_long *) a, i = 0; i < 8; i++)
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printf(" %lx", p[i]);
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printf("\n");
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/* wait for debugger */
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while (null_checkvp_barrier) /*WAIT*/ ;
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panic("null_checkvp");
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}
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if (vrefcnt(a->null_lowervp) < 1) {
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int i; u_long *p;
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printf("vp = %p, unref'ed lowervp\n", (void *)vp);
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for (p = (u_long *) a, i = 0; i < 8; i++)
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printf(" %lx", p[i]);
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printf("\n");
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/* wait for debugger */
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while (null_checkvp_barrier) /*WAIT*/ ;
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panic ("null with unref'ed lowervp");
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};
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#ifdef notyet
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printf("null %x/%d -> %x/%d [%s, %d]\n",
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NULLTOV(a), vrefcnt(NULLTOV(a)),
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a->null_lowervp, vrefcnt(a->null_lowervp),
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fil, lno);
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#endif
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return a->null_lowervp;
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}
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#endif
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