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g_consumer(9) [freebsd man page]

G_CONSUMER(9)						   BSD Kernel Developer's Manual					     G_CONSUMER(9)

NAME
g_new_consumer, g_destroy_consumer -- GEOM consumers management 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 <pjd@FreeBSD.org>. BSD
January 16, 2004 BSD

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G_ATTACH(9)						   BSD Kernel Developer's Manual					       G_ATTACH(9)

NAME
g_attach, g_detach -- attach/detach GEOM consumers to/from providers SYNOPSIS
#include <geom/geom.h> int g_attach(struct g_consumer *cp, struct g_provider *pp); void g_detach(struct g_consumer *cp); DESCRIPTION
The g_attach() function attaches given consumer cp to given provider pp, thus establishing a communication channel between the consumer and the provider that allows to change access counts and perform I/O operations. The g_detach() function detaches given consumer cp from its corresponding provider, tearing down the communication channel between them. RESTRICTIONS
/CONDITIONS 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. 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 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: [ELOOP] The operation creates a topology loop. SEE ALSO
geom(4), DECLARE_GEOM_CLASS(9), g_access(9), g_bio(9), g_consumer(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 <pjd@FreeBSD.org>. BSD
January 16, 2004 BSD

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