'\" t
.\"     Title: blk_attempt_plug_merge
.\"    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_ATTEMPT_PLUG_MER" "9" "January 2017" "Kernel Hackers Manual 4\&.8\&." "Block Devices"
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.el       .ds Aq '
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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" ", struct\ request\ **\ " "same_queue_rq" ");"
.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
.PP
\fIsame_queue_rq\fR
.RS 4
pointer to
struct request
that gets filled in when another request associated with
\fIq\fR
is found on the plug list (optional, may be
\fBNULL\fR)
.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