100f241571
This option just adds complexity and the new implementation no longer will support it, so axing it now that it is unused is probabilly the better idea. FreeBSD version is bumped in order to reflect the KPI breakage introduced by this patch. In the ports tree, kris found that only old OSKit code uses it, but as it is thought to work only on 2.x kernels serie, version bumping will solve any problem.
186 lines
4.4 KiB
Groff
186 lines
4.4 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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.\" $FreeBSD$
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.\"
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.Dd December 27, 2007
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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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.Nm vn_lock
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.Nd serialize access to a vnode
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/lock.h
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.In sys/vnode.h
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.Ft int
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.Fn VOP_LOCK "struct vnode *vp" "int flags" "struct thread *td"
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.Ft int
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.Fn VOP_UNLOCK "struct vnode *vp" "int flags" "struct thread *td"
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.Ft int
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.Fn VOP_ISLOCKED "struct vnode *vp" "struct thread *td"
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.Ft int
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.Fn vn_lock "struct vnode *vp" "int flags" "struct thread *td"
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.Sh DESCRIPTION
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These calls are used to serialize access to the file system, such as
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to prevent two writes to the same file from happening at the
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same time.
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.Pp
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The arguments are:
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.Bl -tag -width flags
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.It Fa vp
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The vnode being locked or unlocked.
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.It Fa flags
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One of the lock request types:
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.Pp
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.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact
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.It Dv LK_SHARED
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Shared lock.
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.It Dv LK_EXCLUSIVE
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Exclusive lock.
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.It Dv LK_UPGRADE
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Shared-to-exclusive upgrade.
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.It Dv LK_DOWNGRADE
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Exclusive-to-shared downgrade.
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.It Dv LK_RELEASE
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Release any type of lock.
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.It Dv LK_DRAIN
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Wait for all lock activity to end.
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.El
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.Pp
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The lock type may be
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.Em or Ns 'ed
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with these lock flags:
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.Pp
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.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact
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.It Dv LK_NOWAIT
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Do not sleep to wait for lock.
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.It Dv LK_SLEEPFAIL
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Sleep, then return failure.
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.It Dv LK_CANRECURSE
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Allow recursive exclusive lock.
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.El
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.Pp
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The lock type may be
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.Em or Ns 'ed
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with these control flags:
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.Pp
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.Bl -tag -width ".Dv LK_CANRECURSE" -offset indent -compact
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.It Dv LK_INTERLOCK
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Specify when the caller already has a simple lock
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.Fn ( VOP_LOCK
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will unlock the simple lock after getting the lock).
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.It Dv LK_RETRY
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Retry until locked.
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.El
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.It Fa td
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Thread context to use for the locks.
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.El
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.Pp
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Kernel code should use
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.Fn vn_lock
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to lock a vnode rather than calling
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.Fn VOP_LOCK
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directly.
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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 file system 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 manual page was written by
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.An Doug Rabson .
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