'\" t
.\"     Title: blk_start_plug
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: January 2017
.\"    Manual: Block Devices
.\"    Source: Kernel Hackers Manual 4.8.15
.\"  Language: English
.\"
.TH "BLK_START_PLUG" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Block Devices"
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.SH "NAME"
blk_start_plug \- initialize blk_plug and track it inside the task_struct
.SH "SYNOPSIS"
.HP \w'void\ blk_start_plug('u
.BI "void blk_start_plug(struct\ blk_plug\ *\ " "plug" ");"
.SH "ARGUMENTS"
.PP
\fIplug\fR
.RS 4
The
struct blk_plug
that needs to be initialized
.RE
.SH "DESCRIPTION"
.PP
Tracking blk_plug inside the task_struct will help with auto\-flushing the pending I/O should the task end up blocking between
\fBblk_start_plug\fR
and
\fBblk_finish_plug\fR\&. This is important from a performance perspective, but also ensures that we don\*(Aqt deadlock\&. For instance, if the task is blocking for a memory allocation, memory reclaim could end up wanting to free a page belonging to that request that is currently residing in our private plug\&. By flushing the pending I/O when the process goes to sleep, we avoid this kind of deadlock\&.
.SH "COPYRIGHT"
.br