<?xml version="1.0" encoding="ANSI_X3.4-1968" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>blk_lld_busy</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="ch14.html" title="Chapter 14. Block Devices" /><link rel="prev" href="re525.html" title="__blk_end_request_err" /><link rel="next" href="re527.html" title="blk_rq_unprep_clone" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>blk_lld_busy</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re525.html">Prev</a> </td><th width="60%" align="center">Chapter 14. Block Devices</th><td width="20%" align="right"> <a accesskey="n" href="re527.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="blk_lld_busy"><a id="API-blk-lld-busy"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>blk_lld_busy — Check if underlying low-level drivers of a device are busy </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">blk_lld_busy </b>(</code></td><td>struct request_queue * <var class="pdparam">q</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2699299"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>q</code></em></span></dt><dd><p> the queue of the device being checked </p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2699326"></a><h2>Description</h2><p> Check if underlying low-level drivers of a device are busy. If the drivers want to export their busy state, they must set own exporting function using <code class="function">blk_queue_lld_busy</code> first. </p><p> Basically, this function is used only by request stacking drivers to stop dispatching requests to underlying devices when underlying devices are busy. This behavior helps more I/O merging on the queue of the request stacking driver and prevents I/O throughput regression on burst I/O load. </p></div><div class="refsect1" title="Return"><a id="id2699352"></a><h2>Return</h2><p> 0 - Not busy (The request stacking driver should dispatch request) 1 - Busy (The request stacking driver should stop dispatching request) </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re525.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch14.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re527.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>__blk_end_request_err</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>blk_rq_unprep_clone</span></td></tr></table></div></body></html>