s3/doc: add man page for aio_fork vfs module

thanks to Volker for the content

Autobuild-User: Björn Jacke <bj@sernet.de>
Autobuild-Date: Tue Oct 18 12:24:35 CEST 2011 on sn-devel-104

diff --git a/docs-xml/manpages-3/vfs_aio_fork.8.xml b/docs-xml/manpages-3/vfs_aio_fork.8.xml
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+<?xml version="1.0" encoding="iso-8859-1"?>
+<!DOCTYPE refentry PUBLIC "-//Samba-Team//DTD DocBook V4.2-Based Variant V1.0//EN" "http://www.samba.org/samba/DTD/samba-doc">
+<refentry id="vfs_aio_fork.8">
+
+<refmeta>
+       <refentrytitle>vfs_aio_fork</refentrytitle>
+       <manvolnum>8</manvolnum>
+       <refmiscinfo class="source">Samba</refmiscinfo>
+       <refmiscinfo class="manual">System Administration tools</refmiscinfo>
+       <refmiscinfo class="version">3.6</refmiscinfo>
+</refmeta>
+
+
+<refnamediv>
+       <refname>vfs_aio_fork</refname>
+       <refpurpose>implement async I/O in Samba vfs</refpurpose>
+</refnamediv>
+
+<refsynopsisdiv>
+       <cmdsynopsis>
+               <command>vfs objects = aio_fork</command>
+       </cmdsynopsis>
+</refsynopsisdiv>
+
+<refsect1>
+       <title>DESCRIPTION</title>
+
+       <para>This VFS module is part of the
+       <citerefentry><refentrytitle>samba</refentrytitle>
+       <manvolnum>7</manvolnum></citerefentry> suite.</para>
+
+       <para>The <command>aio_fork</command> VFS module enables async
+       I/O for Samba on platforms where the system level Posix AIO
+       interface is insufficient. Posix AIO can suffer from severe
+       limitations.  For example, on some Linux versions the
+       real-time signals that it uses are broken under heavy load.
+       Other systems only allow AIO when special kernel modules are
+       loaded or only allow a certain system-wide amount of async
+       requests being scheduled. Systems based on glibc (most Linux
+       systems) only allow a single outstanding request per file
+       descriptor.  </para>
+
+       <para>To work around all these limitations, the aio_fork module
+       was written. It uses forked helper processes instead of the
+       internal Posix AIO interface to create asynchronousity for
+       read and write calls. It has no parameters, it will create
+       helper processes when async requests come in as needed. Idle
+       helper processes will be removed every 30 seconds.
+       </para>
+
+       <para>This module is stackable.</para>
+
+</refsect1>
+
+
+<refsect1>
+       <title>EXAMPLES</title>
+
+       <para>Straight forward use:</para>
+
+<programlisting>
+        <smbconfsection name="[cooldata]"/>
+       <smbconfoption name="path">/data/ice</smbconfoption>
+       <smbconfoption name="vfs objects">aio_fork</smbconfoption>
+</programlisting>
+
+</refsect1>
+
+<refsect1>
+       <title>VERSION</title>
+
+       <para>This man page is correct for version 3.6.0 of the Samba suite.
+       </para>
+</refsect1>
+
+<refsect1>
+       <title>AUTHOR</title>
+
+       <para>The original Samba software and related utilities
+       were created by Andrew Tridgell. Samba is now developed
+       by the Samba Team as an Open Source project similar
+       to the way the Linux kernel is developed.</para>
+
+</refsect1>
+
+</refentry>