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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>write_cache_pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><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="re223.html" title="balance_dirty_pages_ratelimited_nr" /><link rel="next" href="re225.html" title="generic_writepages" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>write_cache_pages</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re223.html">Prev</a> </td><th width="60%" align="center">More Memory Management Functions</th><td width="20%" align="right"> <a accesskey="n" href="re225.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="write_cache_pages"><a id="API-write-cache-pages"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>write_cache_pages —
walk the list of dirty pages of the given address space and write all of them.
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <b class="fsfunc">write_cache_pages </b>(</code></td><td>struct address_space * <var class="pdparam">mapping</var>, </td></tr><tr><td> </td><td>struct writeback_control * <var class="pdparam">wbc</var>, </td></tr><tr><td> </td><td>writepage_t <var class="pdparam">writepage</var>, </td></tr><tr><td> </td><td>void * <var class="pdparam">data</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2652790"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>mapping</code></em></span></dt><dd><p>
address space structure to write
</p></dd><dt><span class="term"><em class="parameter"><code>wbc</code></em></span></dt><dd><p>
subtract the number of written pages from *<em class="parameter"><code>wbc</code></em>->nr_to_write
</p></dd><dt><span class="term"><em class="parameter"><code>writepage</code></em></span></dt><dd><p>
function called for each page
</p></dd><dt><span class="term"><em class="parameter"><code>data</code></em></span></dt><dd><p>
data passed to writepage function
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2652875"></a><h2>Description</h2><p>
If a page is already under I/O, <code class="function">write_cache_pages</code> skips it, even
if it's dirty. This is desirable behaviour for memory-cleaning writeback,
but it is INCORRECT for data-integrity system calls such as <code class="function">fsync</code>. <code class="function">fsync</code>
and <code class="function">msync</code> need to guarantee that all the data which was dirty at the time
the call was made get new I/O started against them. If wbc->sync_mode is
WB_SYNC_ALL then we were called for data integrity and we must wait for
existing IO to complete.
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