g_consumer (9)
Leading comments
Copyright (c) 2004 Pawel Jakub Dawidek <pjd@FreeBSD.org> All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the d...
NAME
g_new_consumer g_destroy_consumer - GEOM consumers managementSYNOPSIS
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 *cpDESCRIPTION
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);
}