G_CONSUMER(9) MidnightBSD Kernel Developer’s Manual G_CONSUMER(9)

NAME

g_new_consumer, g_destroy_consumer — GEOM consumers management

SYNOPSIS

#include <geom/geom.h>

struct g_consumer *

g_new_consumer(struct g_geom *gp);

void

g_destroy_consumer(struct g_consumer *cp);

DESCRIPTION

A GEOM consumer is the backdoor through which a geom connects to another GEOM provider and through which I/O requests are sent.

The g_new_consumer() function creates a new consumer on geom gp. Before using the new consumer, it has to be attached to a provider with g_attach(9) and opened with g_access(9).

The g_destroy_consumer() function destroys the given consumer and cancels all related pending events. This function is the last stage of killing an unwanted consumer.

RESTRICTIONS/CONDITIONS

g_new_consumer():

The geom gp has to have an orphan method defined.

The topology lock has to be held.

g_destroy_consumer():

The consumer must not be attached to a provider.

The access count has to be 0.

The topology lock has to be held.

RETURN VALUES

The g_new_consumer() function returns a pointer to the newly created consumer.

EXAMPLES

Create consumer, attach it to given provider, gain read access and clean up.

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);

}

SEE ALSO

geom(4), DECLARE_GEOM_CLASS(9), g_access(9), g_attach(9), g_bio(9), g_data(9), g_event(9), g_geom(9), g_provider(9), g_provider_by_name(9), g_wither_geom(9)

AUTHORS

This manual page was written by Pawel Jakub Dawidek 〈pjd@FreeBSD.org〉.

MidnightBSD 0.3 January 16, 2004 MidnightBSD 0.3