104 lines
2.9 KiB
Groff
104 lines
2.9 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 1996 Doug Rabson
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.\" Copyright (c) 2010 Konstantin Belousov <kib@FreeBSD.org>
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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 February 24, 2016
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.Dt VRELE 9
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.Os
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.Sh NAME
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.Nm vput ,
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.Nm vrele ,
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.Nm vunref
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.Nd decrement 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 vput "struct vnode *vp"
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.Ft void
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.Fn vrele "struct vnode *vp"
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.Ft void
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.Fn vunref "struct vnode *vp"
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.Sh DESCRIPTION
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Decrement 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 decrement
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.El
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.Pp
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The
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.Fn vrele
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function takes an unlocked vnode and returns with the vnode unlocked.
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.Pp
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The
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.Fn vput
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function should be given a locked vnode as argument, the vnode is unlocked
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after the function returned.
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The
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.Fn vput
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is operationally equivalent to calling
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.Xr VOP_UNLOCK 9
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followed by
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.Xr vrele 9 ,
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with less overhead.
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.Pp
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The
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.Fn vunref
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function takes a locked vnode as argument, and returns with the vnode locked.
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.Pp
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Any code in the system which signified its use of a vnode by usecount
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should call one of the listed function to decrement use counter.
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If the
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.Va v_usecount
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field of the non-doomed vnode reaches zero, then it will be inactivated
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and placed on the free list.
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.Pp
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The
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.Fn vrele
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function may lock the vnode.
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All three functions may sleep.
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.Pp
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The hold count for the vnode is always greater or equal to the usecount.
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Non-forced unmount fails when mount point owns a vnode that has non-zero
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usecount, see
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.Xr vflush 9 .
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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 vref 9 ,
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.Xr vrefcnt 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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and
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.An Konstantin Belousov .
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