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g_consumer (9)

>> g_consumer (9) ( FreeBSD man: Ядро )

BSD mandoc

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 Fa gp . Before using the new consumer, it has to be attached to a provider with g_attach9 and opened with g_access9.

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: Fa 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);
}