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Manual Pages  — G_CONSUMER

NAME

g_new_consumer, g_destroy_consumer – GEOM consumers management

CONTENTS

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 <Mt pjd@FreeBSD.org>.

G_CONSUMER (9) January 16, 2004

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