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<table class="head">
<tr>
<td class="head-ltitle">VOP_ADVISE(9)</td>
<td class="head-vol">Kernel Developer's Manual</td>
<td class="head-rtitle">VOP_ADVISE(9)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">VOP_ADVISE</code> — <span class="Nd">apply
advice about use of file data</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="In">#include
<<a class="In">sys/param.h</a>></code>
<br/>
<code class="In">#include <<a class="In">sys/vnode.h</a>></code></p>
<p class="Pp"><var class="Ft">int</var>
<br/>
<code class="Fn">VOP_ADVISE</code>(<var class="Fa" style="white-space: nowrap;">struct
vnode *vp</var>, <var class="Fa" style="white-space: nowrap;">off_t
start</var>, <var class="Fa" style="white-space: nowrap;">off_t end</var>,
<var class="Fa" style="white-space: nowrap;">int advice</var>);</p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">This call applies advice for a range of a file's data. It is used
to implement the <a class="Xr">posix_fadvise(2)</a> system call.</p>
<p class="Pp">Its arguments are:</p>
<dl class="Bl-tag">
<dt><var class="Fa">vp</var></dt>
<dd>The vnode of the file.</dd>
<dt><var class="Fa">start</var></dt>
<dd>The start of the range of file data.</dd>
<dt><var class="Fa">end</var></dt>
<dd>The end of the range of file data. A value of
<code class="Dv">OFF_MAX</code> indicates that the advice is to be applied
up to the end of the file.</dd>
<dt><var class="Fa">advice</var></dt>
<dd>The type of operation to apply to the file data. Possible values are:
<dl class="Bl-tag">
<dt id="POSIX_FADV_WILLNEED"><a class="permalink" href="#POSIX_FADV_WILLNEED"><code class="Dv">POSIX_FADV_WILLNEED</code></a></dt>
<dd>Initiate an asynchronous read of the file data if it is not already
resident.</dd>
<dt id="POSIX_FADV_DONTNEED"><a class="permalink" href="#POSIX_FADV_DONTNEED"><code class="Dv">POSIX_FADV_DONTNEED</code></a></dt>
<dd>Decrease the in-memory priority of clean file data or discard clean
file data.</dd>
</dl>
</dd>
</dl>
<p class="Pp">If the <var class="Fa">start</var> and <var class="Fa">end</var>
offsets are both zero, then the operation should be applied to the entire
file. Note that this call is advisory only and may perform the requested
operation on a subset of the requested range (including not performing it at
all) and still return success.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="LOCKS"><a class="permalink" href="#LOCKS">LOCKS</a></h1>
<p class="Pp">The file should be unlocked on entry.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="RETURN_VALUES"><a class="permalink" href="#RETURN_VALUES">RETURN
VALUES</a></h1>
<p class="Pp">Zero is returned if the call is successful, otherwise an
appropriate error code is returned.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="ERRORS"><a class="permalink" href="#ERRORS">ERRORS</a></h1>
<dl class="Bl-tag">
<dt id="EINVAL">[<a class="permalink" href="#EINVAL"><code class="Er">EINVAL</code></a>]</dt>
<dd>An invalid value was given for <var class="Fa">advice</var>.</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">vnode(9)</a></p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">September 26, 2015</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
