1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>blk_start_plug</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="blkdev.html" title="Chapter&#160;14.&#160;Block Devices"><link rel="prev" href="API-blk-rq-prep-clone.html" title="blk_rq_prep_clone"><link rel="next" href="API-blk-pm-runtime-init.html" title="blk_pm_runtime_init"></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">blk_start_plug</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-blk-rq-prep-clone.html">Prev</a>&#160;</td><th width="60%" align="center">Chapter&#160;14.&#160;Block Devices</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-blk-pm-runtime-init.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-blk-start-plug"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>blk_start_plug &#8212; 
2     initialize blk_plug and track it inside the task_struct
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">blk_start_plug </b>(</code></td><td>struct blk_plug * <var class="pdparam">plug</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1128144860"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>plug</code></em></span></dt><dd><p>
4     The <span class="structname">struct blk_plug</span> that needs to be initialized
5    </p></dd></dl></div></div><div class="refsect1"><a name="idp1128146708"></a><h2>Description</h2><p>
6   Tracking blk_plug inside the task_struct will help with auto-flushing the
7   pending I/O should the task end up blocking between <code class="function">blk_start_plug</code> and
8   <code class="function">blk_finish_plug</code>. This is important from a performance perspective, but
9   also ensures that we don't deadlock. For instance, if the task is blocking
10   for a memory allocation, memory reclaim could end up wanting to free a
11   page belonging to that request that is currently residing in our private
12   plug. By flushing the pending I/O when the process goes to sleep, we avoid
13   this kind of deadlock.
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