FreeBSD-5.3/share/man/man9/VOP_OPENCLOSE.9

.\" -*- 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.
.\"
.\" $FreeBSD: src/share/man/man9/VOP_OPENCLOSE.9,v 1.15 2004/05/11 14:13:52 hmp Exp $
.\"
.Dd July 24, 1996
.Os
.Dt VOP_OPEN 9
.Sh NAME
.Nm VOP_OPEN ,
.Nm VOP_CLOSE
.Nd open or close a file
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fn VOP_OPEN "struct vnode *vp" "int mode" "struct ucred *cred" "struct thread *td" "int fdidx"
.Ft int
.Fn VOP_CLOSE "struct vnode *vp" "int mode" "struct ucred *cred" "struct thread *td"
.Sh DESCRIPTION
The
.Fn VOP_OPEN
entry point is called before a file is accessed by a process and the
.Fn VOP_CLOSE
entry point is called after a file is finished with by the process.
.Pp
The arguments are:
.Bl -tag -width mode
.It Fa vp
the vnode of the file
.It Fa mode
the access mode required by the calling process
.It Fa td
the thread which is accessing the file
.El
.Pp
Additionally,
.Fn VOP_OPEN
can accept a file descriptor number in
.Fa fdidx ;
this is useful for file systems which require such information, e.g.,
.Xr fdesc 5 .
.Pp
The access mode is a set of flags, including
.Dv FREAD ,
.Dv FWRITE ,
.Dv O_NONBLOCK ,
.Dv O_APPEND .
.Sh LOCKS
.Fn VOP_OPEN
expects
.Fa vp
to be locked on entry and will leave it locked on return.
.Pp
.Fn VOP_CLOSE
expects at least a reference to be associated with the vnode and does not
care whether the vnode is locked or not.
The lock and reference state is left unchanged on return.
Note that
.Fa vn_close
expects an unlocked, referenced vnode and will dereference the vnode prior
to returning.
.Sh IMPLEMENTATION NOTES
The
.Fa fdidx
argument to
.Fn VOP_OPEN
is currently unused, use
.Ql \-1
for the meantime; however, this will change in future.
.Sh RETURN VALUES
Zero is returned on success, otherwise an error code is returned.
.Sh PSEUDOCODE
.Bd -literal
int
vop_open(struct vnode *vp, int mode, struct ucred *cred, struct thread *td)
{
    /*
     * Most file systems don't do much here.
     */
    return 0;
}
.Ed
.Sh SEE ALSO
.Xr vnode 9 ,
.Xr VOP_LOOKUP 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .