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G_CONSUMER (9) | Kernel routines | Unix Manual Pages | :man▋

NAME

g_new_consumer, g_destroy_consumer - "GEOM consumers management"

CONTENTS

Synopsis
Description
Restrictions/conditions
Return Values
Examples
See Also
Authors

SYNOPSIS


.In 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 start and access methods 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

 
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