1.\" Copyright (c) 1996 Doug Rabson 2.\" 3.\" All rights reserved. 4.\" 5.\" This program is free software. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 17.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 18.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 19.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 20.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 21.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 22.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 23.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 24.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 25.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 26.\" 27.\" $FreeBSD: src/share/man/man9/vref.9,v 1.6.2.2 2001/12/17 11:30:19 ru Exp $ 28.\" $DragonFly: src/share/man/man9/vref.9,v 1.8 2007/05/11 08:25:24 swildner Exp $ 29.\" 30.Dd May 5, 2007 31.Os 32.Dt VREF 9 33.Sh NAME 34.Nm vref 35.Nd Increment the primary reference count for an active vnode 36.Sh SYNOPSIS 37.In sys/param.h 38.In sys/vnode.h 39.Ft void 40.Fn vref "struct vnode *vp" 41.Sh DESCRIPTION 42The primary reference count for an active vnode is incremented. 43The vnode must already have active references to it, usually acquired 44prior to the vnode pointer being passed to the code making this call 45or when vnode pointers are obtained from structures, such as file pointers, 46which hold an active reference to the vnode. 47Any attempt to use 48.Nm 49on an inactive vnode will result in a panic. 50.Bl -tag -width ".Fa vp" 51.It Fa vp 52The vnode being referenced. 53.El 54.Pp 55Each vnode maintains a Primary and Auxiliary reference count. 56The primary reference count prevents the vnode from being deactivated 57while the auxiliary reference count keeps track of auxiliary structures, 58such as namecache and VM object structures, which are typically kept 59associated with the vnode for caching purposes even after the vnode 60has been deactivated. 61.Pp 62A procedure will often acquire its own primary reference to a vnode 63to prevent the vnode from getting ripped out from under it during 64an operation due to the destruction of the parent data structure. 65For example, one thread may be blocked on a vnode operation related 66to a file descriptor that another thread then closes. 67.Sh SEE ALSO 68.Xr vdrop 9 , 69.Xr vget 9 , 70.Xr vhold 9 , 71.Xr vnode 9 , 72.Xr vn_lock 9 , 73.Xr vn_unlock 9 , 74.Xr vput 9 , 75.Xr vrele 9 76.Sh AUTHORS 77This manual page was written by 78.An Doug Rabson . 79