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131 lines
3.3 KiB
Groff
131 lines
3.3 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 1996 Doug Rabson
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.\"
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.\" All rights reserved.
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.\"
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.\" This program is free software.
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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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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $Id: VOP_LOCK.9,v 1.2 1997/03/04 06:20:42 mpp Exp $
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.\"
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.Dd July 24, 1996
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.Os
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.Dt VOP_LOCK 9
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.Sh NAME
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.Nm VOP_LOCK ,
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.Nm VOP_UNLOCK ,
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.Nm VOP_ISLOCKED
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.Nd serialize access to a vnode
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.Sh SYNOPSIS
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.Fd #include <sys/param.h>
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.Fd #include <sys/vnode.h>
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.Ft int
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.Fn VOP_LOCK "struct vnode *vp" "int flags" "struct proc *p"
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.Ft int
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.Fn VOP_UNLOCK "struct vnode *vp" "int flags" "struct proc *p"
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.Ft int
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.Fn VOP_ISLOCKED "struct vnode *vp"
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.Sh DESCRIPTION
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.Pp
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The arguments are:
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.Bl -tag -width vp
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.It Ar vp
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the vnode being locked or unlocked
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.El
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.Pp
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These calls are used to serialize access to the filesystem, for
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instance to prevent two writes to the same file from happening at the
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same time.
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.Sh RETURN VALUES
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Zero is returned on success, otherwise an error is returned.
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.Sh PSEUDOCODE
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.Bd -literal
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struct vopnode {
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int von_flag;
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/*
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* Other filesystem specific data.
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*/
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...;
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};
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#define VON_LOCKED 1
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#define VON_WANTED 2
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#define VTOVON(vp) ((struct vopnode *) (vp)->v_data)
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int
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vop_lock(struct vnode *vp)
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{
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struct vopnode* vop;
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start:
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while (vp->v_flag & VXLOCK) {
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vp->v_flag |= VXWANT;
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tsleep((caddr_t)vp, PINOD, "voplk1", 0);
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}
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if (vp->v_tag == VT_NON)
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return ENOENT;
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vop = VTOVON(vp);
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if (vop->von_flag & VON_LOCKED) {
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vop->von_flag |= VON_WANTED;
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tsleep((caddr_t) vop, PINOD, "voplk2", 0);
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goto start;
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}
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vop->von_flag |= VON_LOCKED;
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return 0;
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}
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int
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vop_unlock(struct vnode *vp)
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{
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struct vopnode *vop = VTOVON(vp);
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if ((vop->von_flag & VON_LOCKED) == 0) {
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panic("vop_unlock not locked");
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}
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vop->von_flag &= ~VON_LOCKED;
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if (vop->von_flag & VON_WANTED) {
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vop->von_flag &= ~VON_WANTED;
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wakeup((caddr_t) vop);
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}
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return 0;
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}
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int
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vop_islocked(struct vnode *vp)
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{
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struct vopnode *vop = VTOVON(vp);
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if (vop->von_flag & VON_LOCKED)
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return 1;
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else
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return 0;
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}
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.Ed
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.Sh SEE ALSO
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.Xr vnode 9
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.Sh AUTHORS
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This man page was written by Doug Rabson.
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