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>.