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.TH "BLK_QUEUE_MAKE_REQUEST" "9" "17 July 2003" "" ""

.SH NAME
blk_queue_make_request \- define an alternate make_request function for a device
.SH SYNOPSIS
.sp
\fB
.sp
void blk_queue_make_request  (request_queue_t * \fIq\fB, make_request_fn * \fImfn\fB);
\fR
.SH "ARGUMENTS"
.TP
\fB\fIq\fB\fR
the request queue for the device to be affected
.TP
\fB\fImfn\fB\fR
the alternate make_request function
.SH "DESCRIPTION"
.PP
The normal way for &struct bios to be passed to a device
driver is for them to be collected into requests on a request
queue, and then to allow the device driver to select requests
off that queue when it is ready.  This works well for many block
devices. However some block devices (typically virtual devices
such as md or lvm) do not benefit from the processing on the
request queue, and are served best by having the requests passed
directly to them.  This can be achieved by providing a function
to \fBblk_queue_make_request\fR.
.SH "CAVEAT"
.PP
The driver that does this *must* be able to deal appropriately
with buffers in ``highmemory''. This can be accomplished by either calling
\fB__bio_kmap_atomic\fR to get a temporary kernel mapping, or by calling
\fBblk_queue_bounce\fR to create a buffer in normal memory.
.SH "ABOUT THIS DOCUMENT"
.PP
This documentation is free software; you can redistribute
it and/or modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later
version.
.PP
This program is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU General Public License for more details.
.PP
You should have received a copy of the GNU General Public
License along with this program; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
MA 02111-1307 USA
.PP
For more details see the file COPYING in the source
distribution of Linux.
.PP
If you have comments on the formatting of this manpage, then please contact
Michael Still (mikal@stillhq.com).
.PP
This documentation was generated with kernel version 2.5.71.