142 lines
3.8 KiB
Groff
142 lines
3.8 KiB
Groff
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.\"
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.\" Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 16, 2004
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.Dt g_consumer 9
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.Os
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.Sh NAME
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.Nm g_new_consumer ,
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.Nm g_destroy_consumer
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.Nd "GEOM consumers management"
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.Sh SYNOPSIS
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.In geom/geom.h
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.Ft "struct g_consumer *"
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.Fn g_new_consumer "struct g_geom *gp"
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.Ft void
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.Fn g_destroy_consumer "struct g_consumer *cp"
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.Sh DESCRIPTION
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The GEOM consumer is the backdoor through which a geom connects to
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another GEOM provider and through which I/O requests are sent.
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.Pp
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The
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.Fn g_new_consumer
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function creates a new consumer releated to geom
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.Fa gp .
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The consumer is unusable prior attaching to a provider and gaining access
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to it.
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To serve its purpose, the consumer has to be attached to a provider
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with the
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.Xr g_attach 9
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function.
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.Pp
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The
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.Fn g_destroy_consumer
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function destroys given consumer and cancels all related pending events.
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This function is the last stage of killing an unwanted consumer.
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.Pp
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.Sh RESTRICTIONS/CONDITIONS
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.Fn g_new_consumer :
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.Bl -item -offset indent
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.It
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The geom related to the created consumer must have the
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.Fa start
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and
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.Fa access
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fields defined.
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.It
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The topology lock has to be held.
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.El
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.Pp
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.Fn g_destroy_consumer :
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.Bl -item -offset indent
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.It
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The consumer can not be attached.
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.It
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The access count has to be 0.
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.It
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The topology lock has to be held.
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.El
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.Sh RETURN VALUES
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.Fn g_new_consumer
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returns a pointer to the newly created consumer or
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.Dv NULL
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if an error occured.
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.Sh EXAMPLES
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Create consumer, attach it to given provider, gain read access and clean up.
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.Bd -literal -offset indent
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void
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some_function(struct g_geom *mygeom, struct g_provider *pp)
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{
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struct g_consumer *cp;
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g_topology_assert();
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/* Create new consumer on 'mygeom' geom. */
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cp = g_new_consumer(mygeom);
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if (cp == NULL)
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return;
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/* Attach newly created consumer to given provider. */
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if (g_attach(cp, pp) != 0) {
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g_destroy_consumer(cp);
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return;
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}
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/* Open provider for reading through our consumer. */
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if (g_access_rel(cp, 1, 0, 0) != 0) {
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g_detach(cp);
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g_destroy_consumer(cp);
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return;
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}
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g_topology_unlock();
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/*
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* Read data from provider.
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*/
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g_topology_lock();
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/* Disconnect from provider (release access count). */
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g_access_rel(cp, -1, 0, 0);
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/* Detach from provider. */
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g_detach(cp);
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/* Destroy consumer. */
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g_destroy_consumer(cp);
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}
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.Ed
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.Sh SEE ALSO
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.Xr DECLARE_GEOM_CLASS 9 ,
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.Xr geom 4 ,
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.Xr g_attach 9 ,
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.Xr g_bio 9 ,
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.Xr g_data 9 ,
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.Xr g_event 9 ,
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.Xr g_geom 9 ,
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.Xr g_provider 9 ,
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.Xr g_provider_by_name 9 ,
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.Xr g_wither_geom 9
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.Sh AUTHORS
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.An -nosplit
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This manual page was written by
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.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .
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