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92 lines
2.9 KiB
Groff
92 lines
2.9 KiB
Groff
.\" -*- nroff -*-
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.\"
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.\" Copyright (c) 2013 Hudson River Trading LLC
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.\" Written by: John H. Baldwin <jhb@FreeBSD.org>
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.\" All rights reserved.
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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 AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 26, 2015
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.Dt VOP_ADVISE 9
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.Os
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.Sh NAME
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.Nm VOP_ADVISE
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.Nd apply advice about use of file data
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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_ADVISE "struct vnode *vp" "off_t start" "off_t end" "int advice"
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.Sh DESCRIPTION
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This call applies advice for a range of a file's data.
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It is used to implement the
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.Xr posix_fadvise
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system call.
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.Pp
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Its arguments are:
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.Bl -tag -width offset
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.It Fa vp
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The vnode of the file.
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.It Fa start
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The start of the range of file data.
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.It Fa end
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The end of the range of file data.
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A value of
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.Dv OFF_MAX
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indicates that the advice is to be applied up to the end of the file.
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.It Fa advice
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The type of operation to apply to the file data.
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Possible values are:
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.Bl -tag -width POSIX_FADV_WILLNEED
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.It Dv POSIX_FADV_WILLNEED
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Initiate an asynchronous read of the file data if it is not already resident.
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.It Dv POSIX_FADV_DONTNEED
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Decrease the in-memory priority of clean file data or discard clean file data.
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.El
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.El
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.Pp
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If the
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.Fa start
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and
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.Fa end
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offsets are both zero,
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then the operation should be applied to the entire file.
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Note that this call is advisory only and may perform the requested
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operation on a subset of the requested range
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.Pq including not performing it at all
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and still return success.
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.Sh LOCKS
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The file should be unlocked on entry.
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.Sh RETURN VALUES
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Zero is returned if the call is successful, otherwise an appropriate
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error code is returned.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EINVAL
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An invalid value was given for
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.Fa advice .
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.El
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.Sh SEE ALSO
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.Xr vnode 9
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