'\" t .\" Title: blk_lld_busy .\" Author: [FIXME: author] [see http://docbook.sf.net/el/author] .\" Generator: DocBook XSL Stylesheets v1.79.1 .\" Date: April 2019 .\" Manual: Block Devices .\" Source: Kernel Hackers Manual 4.9.168 .\" Language: English .\" .TH "BLK_LLD_BUSY" "9" "April 2019" "Kernel Hackers Manual 4\&.9\&." "Block Devices" .\" ----------------------------------------------------------------- .\" * Define some portability stuff .\" ----------------------------------------------------------------- .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .\" http://bugs.debian.org/507673 .\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html .\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ .ie \n(.g .ds Aq \(aq .el .ds Aq ' .\" ----------------------------------------------------------------- .\" * set default formatting .\" ----------------------------------------------------------------- .\" disable hyphenation .nh .\" disable justification (adjust text to left margin only) .ad l .\" ----------------------------------------------------------------- .\" * MAIN CONTENT STARTS HERE * .\" ----------------------------------------------------------------- .SH "NAME" blk_lld_busy \- Check if underlying low\-level drivers of a device are busy .SH "SYNOPSIS" .HP \w'int\ blk_lld_busy('u .BI "int blk_lld_busy(struct\ request_queue\ *\ " "q" ");" .SH "ARGUMENTS" .PP \fIq\fR .RS 4 the queue of the device being checked .RE .SH "DESCRIPTION" .PP 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 \fBblk_queue_lld_busy\fR first\&. .PP 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\&. .SH "RETURN" .PP 0 \- Not busy (The request stacking driver should dispatch request) 1 \- Busy (The request stacking driver should stop dispatching request) .SH "COPYRIGHT" .br