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.\"
.\" 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_ATTACH 9
.Os
.Sh NAME
.Nm g_attach ,
.Nm g_detach
.Nd "attach/detach GEOM consumers to/from providers"
.Sh SYNOPSIS
.In geom/geom.h
.Ft int
.Fn g_attach "struct g_consumer *cp" "struct g_provider *pp"
.Ft void
.Fn g_detach "struct g_consumer *cp"
.Sh DESCRIPTION
The
.Fn g_attach
function attaches given consumer
.Fa cp
to given provider
.Fa pp ,
thus establishing a communication channel between the consumer and the
provider that allows to change access counts and perform I/O operations.
.Pp
The
.Fn g_detach
function detaches given consumer
.Fa cp
from its corresponding provider, tearing down the communication channel
between them.
.Sh RESTRICTIONS/CONDITIONS
.Fn g_attach :
.Bl -item -offset indent
.It
The consumer must not be attached to a provider.
.It
The operation must not create a topology loop.
.It
The topology lock has to be held.
.El
.Pp
.Fn g_detach :
.Bl -item -offset indent
.It
The consumer has to be attached.
.It
The access count has to be 0.
.It
There must be no active requests.
.It
The topology lock has to be held.
.El
.Sh RETURN VALUES
The
.Fn g_attach
function returns 0 if successful; otherwise an error code is returned.
.Sh EXAMPLES
Create a consumer, attach it to a given provider, gain read access and clean up.
.Bd -literal -offset indent
void
some_function(struct g_geom *mygeom, struct g_provider *pp)
{
struct g_consumer *cp;
g_topology_assert();
/* Create new consumer on 'mygeom' geom. */
cp = g_new_consumer(mygeom);
/* Attach newly created consumer to given provider. */
if (g_attach(cp, pp) != 0) {
g_destroy_consumer(cp);
return;
}
/* Open provider for reading through our consumer. */
if (g_access(cp, 1, 0, 0) != 0) {
g_detach(cp);
g_destroy_consumer(cp);
return;
}
g_topology_unlock();
/*
* Read data from provider.
*/
g_topology_lock();
/* Disconnect from provider (release access count). */
g_access(cp, -1, 0, 0);
/* Detach from provider. */
g_detach(cp);
/* Destroy consumer. */
g_destroy_consumer(cp);
}
.Ed
.Sh ERRORS
Possible errors:
.Bl -tag -width Er
.It Bq Er ELOOP
The operation creates a topology loop.
.El
.Sh SEE ALSO
.Xr geom 4 ,
.Xr DECLARE_GEOM_CLASS 9 ,
.Xr g_access 9 ,
.Xr g_bio 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 Mt pjd@FreeBSD.org .
|
