114 lines
3.5 KiB
Groff
114 lines
3.5 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 2000 Boris Popov
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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 September 10, 2000
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.Os
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.Dt VOP_CREATEVOBJECT 9
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.Sh NAME
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.Nm VOP_CREATEVOBJECT ,
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.Nm VOP_DESTROYVOBJECT ,
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.Nm VOP_GETVOBJECT
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.Nd VM object interaction
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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 int
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.Fn VOP_CREATEVOBJECT "struct vnode *vp" "struct ucred *cred" "struct thread *td"
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.Ft int
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.Fn VOP_DESTROYVOBJECT "struct vnode *vp"
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.Ft int
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.Fn VOP_GETVOBJECT "struct vnode *vp" "struct vm_object **objpp"
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.Sh DESCRIPTION
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These calls are used to control the association of a VM object
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with a particular vnode.
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.Pp
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The arguments specific to these functions are:
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.Bl -tag -width objpp
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.It Fa vp
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The vnode of the file.
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.It Fa objpp
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The VM object being returned, or
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.Dv NULL
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if the caller wants to test for the existence
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of the VM object).
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.El
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.Pp
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.Xr VFS 9
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invokes
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.Fn VOP_CREATEVOBJECT
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when it needs to create a VM object for the given
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.Xr vnode 9 .
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File system code may pass this call down to the underlying file system.
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This VOP can be called multiple times,
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and file system code should ignore any additional calls,
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exiting with a zero return code.
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.Pp
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.Fn VOP_DESTROYVOBJECT
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is called when a
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.Xr vnode 9
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is recycled.
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.Pp
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.Fn VOP_GETVOBJECT
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should be used by all kernel code to get a VM object.
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.\" XXX What is the next sentence trying to tell people?
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The returned VM object may belong to a different file system in the case
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of stacked mounts.
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.Pp
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.Xr VFS 9
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has three functions which perform standard operations by creating
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and destroying VM objects.
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These functions are:
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.Fn vop_stdcreatevobject ,
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.Fn vop_stddestroyvobject
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and
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.Fn vop_stdgetvobject .
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.Pp
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.Em Note :
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a
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.Xr vnode 9
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should be locked on entry and must be left locked on exit.
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.Sh RETURN VALUES
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The
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.Fn VOP_CREATEVOBJECT ,
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.Fn VOP_DESTROYVOBJECT
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and
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.Fn VOP_GETVOBJECT
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functions return zero on success, or a non-zero value on failure.
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Zero is returned on success, otherwise an error is returned.
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.Sh EXAMPLES
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.\" XXX Why is this code here when it does not use the functions
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.\" described in this manual page?
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By default, file systems leave VM object handling to the
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.Fn vop_std*
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functions.
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.Sh SEE ALSO
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.Xr vnode 9 ,
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.Xr VOP_GETPAGES 9 ,
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.Xr VOP_PUTPAGES 9
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.Sh AUTHORS
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This manual page was written by
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.An Boris Popov .
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