g_attach (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_attach g_detach - attach/detach GEOM consumers to/from providersSYNOPSIS
In geom/geom.h Ft int Fn g_attach struct g_consumer *cp struct g_provider *pp Ft void Fn g_detach struct g_consumer *cpDESCRIPTION
The Fn g_attach function attaches given consumer Fa cp to given provider Fa pp , thus establishing a communication channel between the consumer and the provider that allows to change access counts and perform I/O operations.The Fn g_detach function detaches given consumer Fa cp from its corresponding provider, tearing down the communication channel between them.
RESTRICTIONS/CONDITIONS
Fn g_attach :- The consumer must not be attached to a provider.
- The operation must not create a topology loop.
- The topology lock has to be held.
Fn g_detach :
- The consumer has to be attached.
- The access count has to be 0.
- There must be no active requests.
- The topology lock has to be held.
RETURN VALUES
The Fn g_attach function returns 0 if successful; otherwise an error code is returned.EXAMPLES
Create a consumer, attach it to a 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);
}
ERRORS
Possible errors:- Bq Er ELOOP
- The operation creates a topology loop.