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G_CONSUMER(9) 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⟩.
January 16, 2004 Debian