'\" t
.\"     Title: blk_init_queue
.\"    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_INIT_QUEUE" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Block Devices"
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.SH "NAME"
blk_init_queue \- prepare a request queue for use with a block device
.SH "SYNOPSIS"
.HP \w'struct\ request_queue\ *\ blk_init_queue('u
.BI "struct request_queue * blk_init_queue(request_fn_proc\ *\ " "rfn" ", spinlock_t\ *\ " "lock" ");"
.SH "ARGUMENTS"
.PP
\fIrfn\fR
.RS 4
The function to be called to process requests that have been placed on the queue\&.
.RE
.PP
\fIlock\fR
.RS 4
Request queue spin lock
.RE
.SH "DESCRIPTION"
.PP
If a block device wishes to use the standard request handling procedures, which sorts requests and coalesces adjacent requests, then it must call
\fBblk_init_queue\fR\&. The function
\fIrfn\fR
will be called when there are requests on the queue that need to be processed\&. If the device supports plugging, then
\fIrfn\fR
may not be called immediately when requests are available on the queue, but may be called at some time later instead\&. Plugged queues are generally unplugged when a buffer belonging to one of the requests on the queue is needed, or due to memory pressure\&.
.PP
\fIrfn\fR
is not required, or even expected, to remove all requests off the queue, but only as many as it can handle at a time\&. If it does leave requests on the queue, it is responsible for arranging that the requests get dealt with eventually\&.
.PP
The queue spin lock must be held while manipulating the requests on the request queue; this lock will be taken also from interrupt context, so irq disabling is needed for it\&.
.PP
Function returns a pointer to the initialized request queue, or
\fBNULL\fR
if it didn\*(Aqt succeed\&.
.SH "NOTE"
.PP
\fBblk_init_queue\fR
must be paired with a
\fBblk_cleanup_queue\fR
call when the block device is deactivated (such as at module unload)\&.
.SH "COPYRIGHT"
.br