793c381706
This API has no in-tree consumers at the moment but is useful to at least one out-of-tree consumer, and naturally complements existing vnode refcount functions (vholdl(9), vdropl(9)). Obtained from: kib (sys/ portion) Sponsored by: EMC / Isilon Storage Division Differential Revision: https://reviews.freebsd.org/D4947 Differential Revision: https://reviews.freebsd.org/D4953
78 lines
2.3 KiB
Groff
78 lines
2.3 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 January 18, 2016
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.Dt VREF 9
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.Os
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.Sh NAME
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.Nm vref , vrefl
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.Nd increment the use count for a vnode
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/vnode.h
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.Ft void
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.Fn vref "struct vnode *vp"
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.Ft void
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.Fn vrefl "struct vnode *vp"
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.Sh DESCRIPTION
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Increment the
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.Va v_usecount
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field of a vnode.
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.Bl -tag -width 2n
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.It Fa vp
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the vnode to increment
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.El
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.Pp
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Each vnode maintains a reference count of how many parts of the system
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are using the vnode.
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This allows the system to detect when a vnode is
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no longer being used and can be safely recycled for a different file.
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.Pp
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Any code in the system which is using a vnode (e.g.\& during the
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operation of some algorithm or to store in a data structure) should
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call
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.Fn vref
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or
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.Fn vrefl .
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.Pp
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.Fn vref
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locks the vnode interlock while
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.Fn vrefl
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expects the interlock to already be held.
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.Sh SEE ALSO
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.Xr vget 9 ,
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.Xr vnode 9 ,
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.Xr vput 9 ,
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.Xr vrefcnt 9 ,
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.Xr vrele 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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