From 7e67e1e73230219ea55118f095cc1800faf2c534 Mon Sep 17 00:00:00 2001
From: dfr <dfr@FreeBSD.org>
Date: Mon, 3 Mar 1997 18:01:01 +0000
Subject: This is the current draft of my filesystem manpages.  Some files are
 incomplete and some are just placeholders but I wanted to try to get
 something at least into 2.2 on the grounds that what I have is a lot better
 than nothing.  I also wanted to commit something which documents the
 interfaces in 2.2 before I start updating the documentation for 3.0.

This is a definite 2.2 candidate and is also relavent to 2.1 if people
still care about that branch.
---
 share/man/man9/VOP_LOCK.9 | 129 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 share/man/man9/VOP_LOCK.9

(limited to 'share/man/man9/VOP_LOCK.9')

diff --git a/share/man/man9/VOP_LOCK.9 b/share/man/man9/VOP_LOCK.9
new file mode 100644
index 0000000..03cf51e
--- /dev/null
+++ b/share/man/man9/VOP_LOCK.9
@@ -0,0 +1,129 @@
+.\" -*- nroff -*-
+.\"
+.\" Copyright (c) 1996 Doug Rabson
+.\"
+.\" All rights reserved.
+.\"
+.\" This program is free software.
+.\"
+.\" 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.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``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 DEVELOPERS 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.
+.\"
+.\" $Id$
+.\"
+.Dd July 24, 1996
+.Os
+.Dt VOP_LOCK 9
+.Sh NAME
+.Nm VOP_LOCK ,
+.Nm VOP_UNLOCK ,
+.Nm VOP_ISLOCKED
+.Nd serialize access to a vnode
+.Sh SYNOPSIS
+.Fd #include <sys/vnode.h>
+.Ft int
+.Fn VOP_LOCK "struct vnode *vp"
+.Ft int
+.Fn VOP_UNLOCK "struct vnode *vp"
+.Ft int
+.Fn VOP_ISLOCKED "struct vnode *vp"
+.Sh DESCRIPTION
+.Pp
+The arguments are:
+.Bl -tag -width vp
+.It Ar vp
+the vnode being locked or unlocked
+.El
+.Pp
+These calls are used to serialise access to the filesystem, for
+instance to prevent two writes to the same file from happening at the
+same time.
+.Sh RETURN VALUES
+Zero is returned on success, otherwise an error is returned.
+.Sh PSEUDOCODE
+.Bd -literal
+struct vopnode {
+    int von_flag;
+    /*
+     * Other filesystem specific data.
+     */
+    ...;
+};
+#define VON_LOCKED	1
+#define VON_WANTED	2
+#define VTOVON(vp)	((struct vopnode *) (vp)->v_data)
+
+int
+vop_lock(struct vnode *vp)
+{
+    struct vopnode* vop;
+
+start:
+    while (vp->v_flag & VXLOCK) {
+	vp->v_flag |= VXWANT;
+	tsleep((caddr_t)vp, PINOD, "voplk1", 0);
+    }
+    if (vp->v_tag == VT_NON)
+	return ENOENT;
+    
+    vop = VTOVON(vp);
+    if (vop->von_flag & VON_LOCKED) {
+	vop->von_flag |= VON_WANTED;
+	tsleep((caddr_t) vop, PINOD, "voplk2", 0);
+	goto start;
+    }
+
+    vop->von_flag |= VON_LOCKED;
+
+    return 0;
+}
+
+int
+vop_unlock(struct vnode *vp)
+{
+    struct vopnode *vop = VTOVON(vp);
+
+    if ((vop->von_flag & VON_LOCKED) == 0) {
+	panic("vop_unlock not locked");
+    }
+    vop->von_flag &= ~VON_LOCKED;
+    if (vop->von_flag & VON_WANTED) {
+	vop->von_flag &= ~VON_WANTED;
+	wakeup((caddr_t) vop);
+    }
+
+    return 0;
+}
+
+int
+vop_islocked(struct vnode *vp)
+{
+    struct vopnode *vop = VTOVON(vp);
+
+    if (vop->von_flag & VON_LOCKED)
+	return 1;
+    else
+	return 0;
+}
+.Ed
+.Sh SEE ALSO
+.Xr vnode 9
+.Sh AUTHORS
+This man page was written by Doug Rabson.
-- 
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