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.\" Copyright (c) 1996 Doug Rabson
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.\" $FreeBSD: head/share/man/man9/vref.9 294299 2016-01-18 22:21:46Z markj $
.\"
.Dd January 18, 2016
.Dt VREF 9
.Os
.Sh NAME
.Nm vref , vrefl
.Nd increment the use count for a vnode
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft void
.Fn vref "struct vnode *vp"
.Ft void
.Fn vrefl "struct vnode *vp"
.Sh DESCRIPTION
Increment the
.Va v_usecount
field of a vnode.
.Bl -tag -width 2n
.It Fa vp
the vnode to increment
.El
.Pp
Each vnode maintains a reference count of how many parts of the system
are using the vnode.
This allows the system to detect when a vnode is
no longer being used and can be safely recycled for a different file.
.Pp
Any code in the system which is using a vnode (e.g.\& during the
operation of some algorithm or to store in a data structure) should
call
.Fn vref
or
.Fn vrefl .
.Pp
.Fn vref
locks the vnode interlock while
.Fn vrefl
expects the interlock to already be held.
.Sh SEE ALSO
.Xr vget 9 ,
.Xr vnode 9 ,
.Xr vput 9 ,
.Xr vrefcnt 9 ,
.Xr vrele 9
.Sh AUTHORS
This manual page was written by
.An Doug Rabson .