'\" t
.\"     Title: blk_attempt_plug_merge
.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
.\" Generator: DocBook XSL Stylesheets v1.78.1 <http://docbook.sf.net/>
.\"      Date: May 2018
.\"    Manual: Block Devices
.\"    Source: Kernel Hackers Manual 3.16.56
.\"  Language: English
.\"
.TH "BLK_ATTEMPT_PLUG_MER" "9" "May 2018" "Kernel Hackers Manual 3\&.16\&" "Block Devices"
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.SH "NAME"
blk_attempt_plug_merge \- try to merge with \fBcurrent\fR\*(Aqs plugged list
.SH "SYNOPSIS"
.HP \w'bool\ blk_attempt_plug_merge('u
.BI "bool blk_attempt_plug_merge(struct\ request_queue\ *\ " "q" ", struct\ bio\ *\ " "bio" ", unsigned\ int\ *\ " "request_count" ");"
.SH "ARGUMENTS"
.PP
\fIq\fR
.RS 4
request_queue new bio is being queued at
.RE
.PP
\fIbio\fR
.RS 4
new bio being queued
.RE
.PP
\fIrequest_count\fR
.RS 4
out parameter for number of traversed plugged requests
.RE
.SH "DESCRIPTION"
.PP
Determine whether
\fIbio\fR
being queued on
\fIq\fR
can be merged with a request on
\fBcurrent\fR\*(Aqs plugged list\&. Returns
\fBtrue\fR
if merge was successful, otherwise
\fBfalse\fR\&.
.PP
Plugging coalesces IOs from the same issuer for the same purpose without going through
\fIq\fR\->queue_lock\&. As such it\*(Aqs more of an issuing mechanism than scheduling, and the request, while may have elvpriv data, is not added on the elevator at this point\&. In addition, we don\*(Aqt have reliable access to the elevator outside queue lock\&. Only check basic merging parameters without querying the elevator\&.
.PP
Caller must ensure !blk_queue_nomerges(q) beforehand\&.
.SH "COPYRIGHT"
.br