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)
{
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struct g_consumer *cp; |
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g_topology_assert(); |
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/* Create new consumer on ’mygeom’ geom. */ |
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cp = g_new_consumer(mygeom); |
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/* Attach newly created consumer to given provider. */ |
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if (g_attach(cp, pp) != 0) { |
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g_destroy_consumer(cp); |
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return; |
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} |
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/* Open provider for reading through our consumer. */ |
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if (g_access(cp, 1, 0, 0) != 0) { |
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g_detach(cp); |
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g_destroy_consumer(cp); |
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return; |
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} |
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g_topology_unlock(); |
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/* |
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* Read data from provider. |
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*/ |
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g_topology_lock(); |
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/* Disconnect from provider (release access count). */ |
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g_access(cp, -1, 0, 0); |
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/* Detach from provider. */ |
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g_detach(cp); |
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/* Destroy consumer. */ |
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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 [AT] FreeBSD.org>.
BSD January 16, 2004 BSD