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g_destroy_consumer.9freebsd

BSD mandoc

NAME

g_new_consumer g_destroy_consumer - GEOM consumers management

SYNOPSIS

In geom/geom.h Ft struct g_consumer * Fn g_new_consumer struct g_geom *gp Ft void Fn 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 Fn g_new_consumer function creates a new consumer on geom Fa gp . Before using the new consumer, it has to be attached to a provider with g_attach9 and opened with g_access9.

The Fn 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

Fn g_new_consumer :

The geom

Fa gp has to have an orphan method defined.

The topology lock has to be held.

Fn 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 Fn 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_CLASS9, g_access9, g_attach9, g_bio9, g_data9, g_event9, g_geom9, g_provider9, g_provider_by_name9, g_wither_geom9

AUTHORS

An -nosplit This manual page was written by An Pawel Jakub Dawidek Aq pjd@FreeBSD.org .