1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>page_cache_async_readahead</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="The Linux Kernel API"><link rel="up" href="ch04s03.html" title="More Memory Management Functions"><link rel="prev" href="API-page-cache-sync-readahead.html" title="page_cache_sync_readahead"><link rel="next" href="API-delete-from-page-cache.html" title="delete_from_page_cache"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span class="phrase">page_cache_async_readahead</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-page-cache-sync-readahead.html">Prev</a>&#160;</td><th width="60%" align="center">More Memory Management Functions</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-delete-from-page-cache.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-page-cache-async-readahead"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>page_cache_async_readahead &#8212; 
2     file readahead for marked pages
3 </p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">page_cache_async_readahead </b>(</code></td><td>struct address_space * <var class="pdparam">mapping</var>, </td></tr><tr><td>&#160;</td><td>struct file_ra_state * <var class="pdparam">ra</var>, </td></tr><tr><td>&#160;</td><td>struct file * <var class="pdparam">filp</var>, </td></tr><tr><td>&#160;</td><td>struct page * <var class="pdparam">page</var>, </td></tr><tr><td>&#160;</td><td>pgoff_t <var class="pdparam">offset</var>, </td></tr><tr><td>&#160;</td><td>unsigned long <var class="pdparam">req_size</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1123998076"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>mapping</code></em></span></dt><dd><p>
4     address_space which holds the pagecache and I/O vectors
5    </p></dd><dt><span class="term"><em class="parameter"><code>ra</code></em></span></dt><dd><p>
6     file_ra_state which holds the readahead state
7    </p></dd><dt><span class="term"><em class="parameter"><code>filp</code></em></span></dt><dd><p>
8     passed on to -&gt;<code class="function">readpage</code> and -&gt;<code class="function">readpages</code>
9    </p></dd><dt><span class="term"><em class="parameter"><code>page</code></em></span></dt><dd><p>
10     the page at <em class="parameter"><code>offset</code></em> which has the PG_readahead flag set
11    </p></dd><dt><span class="term"><em class="parameter"><code>offset</code></em></span></dt><dd><p>
12     start offset into <em class="parameter"><code>mapping</code></em>, in pagecache page-sized units
13    </p></dd><dt><span class="term"><em class="parameter"><code>req_size</code></em></span></dt><dd><p>
14     hint: total size of the read which the caller is performing in
15     pagecache pages
16    </p></dd></dl></div></div><div class="refsect1"><a name="idp1124006396"></a><h2>Description</h2><p>
17   <code class="function">page_cache_async_readahead</code> should be called when a page is used which
18   has the PG_readahead flag; this is a marker to suggest that the application
19   has used up enough of the readahead window that we should start pulling in
20   more pages.
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