g_consumer9
Geom consumers management
Usage
#include <geom/geom.h>
struct g_consumer *
g_new_consumer(struct g_geom *gp);
void
g_destroy_consumer(struct g_consumer *cp);
Overview
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);
}
Releases
52 releases since FreeBSD 5.3-RELEASE; the text changed 32 times.