225 lines
5.8 KiB
Groff
225 lines
5.8 KiB
Groff
|
.\"
|
||
|
|
.\" Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
|
||
|
|
.\" All rights reserved.
|
||
|
|
.\"
|
||
|
|
.\" Redistribution and use in source and binary forms, with or without
|
||
|
|
.\" modification, are permitted provided that the following conditions
|
||
|
|
.\" are met:
|
||
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
||
|
|
.\" notice, this list of conditions and the following disclaimer.
|
||
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
||
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
||
|
|
.\" documentation and/or other materials provided with the distribution.
|
||
|
|
.\"
|
||
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
|
||
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
||
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
||
|
|
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
|
||
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
||
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
||
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
||
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
||
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
||
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
||
|
|
.\"
|
||
|
|
.\" $FreeBSD$
|
||
|
|
.\"
|
||
|
|
.Dd January 16, 2004
|
||
|
|
.Dt g_bio 9
|
||
|
|
.Os
|
||
|
|
.Sh NAME
|
||
|
|
.Nm g_new_bio ,
|
||
|
|
.Nm g_clone_bio ,
|
||
|
|
.Nm g_destroy_bio
|
||
|
|
.Nd "bio controlling functions"
|
||
|
|
.Sh SYNOPSIS
|
||
|
|
.In sys/bio.h
|
||
|
|
.In geom/geom.h
|
||
|
|
.Ft "struct bio *"
|
||
|
|
.Fn g_new_bio void
|
||
|
|
.Ft "struct bio *"
|
||
|
|
.Fn g_clone_bio "struct bio *bp"
|
||
|
|
.Ft void
|
||
|
|
.Fn g_destroy_bio "struct bio *bp"
|
||
|
|
.Sh DESCRIPTION
|
||
|
|
The
|
||
|
|
.Fa bio
|
||
|
|
structure is used by GEOM to describe I/O requests.
|
||
|
|
Most important fields of
|
||
|
|
.Fa struct bio
|
||
|
|
are described below:
|
||
|
|
.Bl -tag -width ".Va bio_attribute"
|
||
|
|
.It Va bio_cmd
|
||
|
|
I/O request number.
|
||
|
|
There are four I/O requests available in GEOM:
|
||
|
|
.Bl -tag -width BIO_GETATTR
|
||
|
|
.It Dv BIO_READ
|
||
|
|
Self explanatory.
|
||
|
|
.It Dv BIO_WRITE
|
||
|
|
Self explanatory.
|
||
|
|
.It Dv BIO_DELETE
|
||
|
|
Delete indicates that a certain range of data is no longer used and that
|
||
|
|
it can be erased or freed as the underlying technology supports.
|
||
|
|
Technologies like flash adaptation layers can arrange to erase the relevant
|
||
|
|
blocks before they will become reassigned and cryptographic devices may
|
||
|
|
want to fill random bits into the range to reduce the amount of data
|
||
|
|
available for attack.
|
||
|
|
.It Dv BIO_GETATTR
|
||
|
|
Get attribute supports inspection and manipulation of out\-of\-band
|
||
|
|
attributes on a particular provider or path.
|
||
|
|
Attributes are named by ascii strings and are stored in the
|
||
|
|
.Va bio_attribute
|
||
|
|
field.
|
||
|
|
.El
|
||
|
|
.It Va bio_offset
|
||
|
|
Offset into provider.
|
||
|
|
.It Va bio_data
|
||
|
|
Pointer to data buffer.
|
||
|
|
.It Va bio_flags
|
||
|
|
Available flags:
|
||
|
|
.Bl -tag -width BIO_GETATTR
|
||
|
|
.It Dv BIO_ERROR
|
||
|
|
Request failed (error value is stored in
|
||
|
|
.Va bio_error )
|
||
|
|
field.
|
||
|
|
.It Dv BIO_DONE
|
||
|
|
Request finished.
|
||
|
|
.It Dv BIO_FLAG1
|
||
|
|
Avaliable for private use.
|
||
|
|
.It Dv BIO_FLAG2
|
||
|
|
Avaliable for private use.
|
||
|
|
.El
|
||
|
|
.It Va bio_error
|
||
|
|
Error value when BIO_ERROR is set.
|
||
|
|
.It Va bio_done
|
||
|
|
Pointer to function which will be called on request finish.
|
||
|
|
.It Va bio_driver1
|
||
|
|
Private use by the callee (ie: the provider).
|
||
|
|
.It Va bio_driver2
|
||
|
|
Private use by the callee (ie: the provider).
|
||
|
|
.It Va bio_caller1
|
||
|
|
Private use by the caller (ie: the consumer).
|
||
|
|
.It Va bio_caller2
|
||
|
|
Private use by the caller (ie: the consumer).
|
||
|
|
.It Va bio_attribute
|
||
|
|
Attribute string for BIO_GETATTR request.
|
||
|
|
.It Va bio_from
|
||
|
|
Consumer to use for request (attached to provider stored in
|
||
|
|
.Va bio_to
|
||
|
|
field) (typically read\-only for a class).
|
||
|
|
.It Va bio_to
|
||
|
|
Destination provider (typically read\-only for a class).
|
||
|
|
.It Va bio_length
|
||
|
|
Request length in bytes.
|
||
|
|
.It Va bio_completed
|
||
|
|
Number of bytes completed, but they may not be completed from
|
||
|
|
the front of the request.
|
||
|
|
.It Va bio_children
|
||
|
|
Number of bio clones (typically read\-only for a class).
|
||
|
|
.It Va bio_inbed
|
||
|
|
Number of finished bio clones.
|
||
|
|
.It Va bio_parent
|
||
|
|
Pointer to parent bio.
|
||
|
|
.El
|
||
|
|
.Pp
|
||
|
|
The
|
||
|
|
.Fn g_new_bio
|
||
|
|
function allocates a new, empty
|
||
|
|
.Vt bio
|
||
|
|
structure.
|
||
|
|
.Pp
|
||
|
|
The
|
||
|
|
.Fn g_clone_bio
|
||
|
|
function allocates a new
|
||
|
|
.Vt bio
|
||
|
|
structure and copies those fields from the
|
||
|
|
.Vt bio
|
||
|
|
structure given as an argument to clone:
|
||
|
|
.Va bio_cmd ,
|
||
|
|
.Va bio_length ,
|
||
|
|
.Va bio_offset ,
|
||
|
|
.Va bio_data ,
|
||
|
|
.Va bio_attribute .
|
||
|
|
The field
|
||
|
|
.Va bio_parent
|
||
|
|
in clone is set to source
|
||
|
|
.Vt bio
|
||
|
|
and the field
|
||
|
|
.Va bio_children
|
||
|
|
in parent is increased.
|
||
|
|
.Pp
|
||
|
|
This function should be used for every request which enters through
|
||
|
|
the provider of a particular geom and needs to be scheduled down.
|
||
|
|
Proper order is:
|
||
|
|
.Pp
|
||
|
|
.Bl -enum -compact
|
||
|
|
.It
|
||
|
|
Clone
|
||
|
|
.Vt "struct bio" .
|
||
|
|
.It
|
||
|
|
Modify the clone.
|
||
|
|
.It
|
||
|
|
Schedule the clone on its own consumer.
|
||
|
|
.El
|
||
|
|
.Pp
|
||
|
|
The
|
||
|
|
.Fn g_destroy_bio
|
||
|
|
function kills the given
|
||
|
|
.Vt bio
|
||
|
|
structure.
|
||
|
|
.Sh EXAMPLES
|
||
|
|
Implementation of
|
||
|
|
.Dq Dv NULL Ns \-transformation ,
|
||
|
|
meaning that an I/O request is cloned and scheduled down without any
|
||
|
|
modifications.
|
||
|
|
Let's assume that field
|
||
|
|
.Va ex_consumer
|
||
|
|
in structure
|
||
|
|
.Vt example_softc
|
||
|
|
contains a consumer attached to the provider we want to operate on.
|
||
|
|
.Bd -literal -offset indent
|
||
|
|
void
|
||
|
|
example_start(struct bio *bp)
|
||
|
|
{
|
||
|
|
struct example_softc *sc;
|
||
|
|
struct bio *cbp;
|
||
|
|
|
||
|
|
sc = bp->bio_to->geom->softc;
|
||
|
|
if (sc == NULL) {
|
||
|
|
g_io_deliver(bp, ENXIO);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Let's clone our bio request. */
|
||
|
|
cbp = g_clone_bio(bp);
|
||
|
|
if (cbp == NULL) {
|
||
|
|
g_io_deliver(bp, ENOMEM);
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
cbp->bio_done = g_std_done; /* Standard 'done' function. */
|
||
|
|
|
||
|
|
/* Ok, schedule it down. */
|
||
|
|
/*
|
||
|
|
* The consumer can be obtained from
|
||
|
|
* LIST_FIRST(&bp->bio_to->geom->consumers) as well,
|
||
|
|
* if there is only one in our geom.
|
||
|
|
*/
|
||
|
|
g_io_request(cbp, sc->ex_consumer);
|
||
|
|
}
|
||
|
|
.Ed
|
||
|
|
.Sh SEE ALSO
|
||
|
|
.Xr DECLARE_GEOM_CLASS 9 ,
|
||
|
|
.Xr geom 4 ,
|
||
|
|
.Xr g_attach 9 ,
|
||
|
|
.Xr g_consumer 9 ,
|
||
|
|
.Xr g_data 9 ,
|
||
|
|
.Xr g_event 9 ,
|
||
|
|
.Xr g_geom 9 ,
|
||
|
|
.Xr g_provider 9 ,
|
||
|
|
.Xr g_provider_by_name 9 ,
|
||
|
|
.Xr g_wither_geom 9
|
||
|
|
.Sh AUTHORS
|
||
|
|
.An -nosplit
|
||
|
|
This manual page was written by
|
||
|
|
.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .
|