id_space.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
#include <sys/types.h>
#include <sys/id_space.h>
#include <sys/debug.h>
/*
* ID Spaces
*
* The id_space_t provides a simple implementation of a managed range of
* integer identifiers using a vmem arena. An ID space guarantees that the
* next identifer returned by an allocation is larger than the previous one,
* unless there are no larger slots remaining in the range. In this case,
* the ID space will return the first available slot in the lower part of the
* range (viewing the previous identifier as a partitioning element). If no
* slots are available, id_alloc() will sleep until an identifier becomes
* available. Accordingly, id_space allocations must be initiated from
* contexts where sleeping is acceptable. id_alloc_nosleep() will return
* -1 if no slots are available or if the system is low on memory. If
* id_alloc_nosleep() fails, callers should not try to extend the ID
* space. This is to avoid making a possible low-memory situation
* worse.
*
* As an ID space is designed for representing a range of id_t's, there
* is a preexisting maximal range: [0, MAXUID]. ID space requests
* outside that range will fail on a DEBUG kernel.
*
* (Presently, the id_space_t abstraction supports only direct allocations; ID
* reservation, in which an ID is allocated but placed in a internal
* dictionary for later use, should be added when a consuming subsystem
* arrives.)
*/
/*
* Create an arena to represent the range [low, high).
* Caller must be in a context in which VM_SLEEP is legal.
*/
id_space_t *
id_space_create(const char *name, id_t low, id_t high)
{
ASSERT(low >= 0);
ASSERT(low < high);
return (vmem_create(name, (void *)(uintptr_t)(low + 1), high - low, 1,
NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER));
}
/*
* Destroy a previously created ID space.
* No restrictions on caller's context.
*/
void
id_space_destroy(id_space_t *isp)
{
vmem_destroy(isp);
}
void
id_space_extend(id_space_t *isp, id_t low, id_t high)
{
(void) vmem_add(isp,
(void *)(uintptr_t)(low + 1), high - low, VM_SLEEP);
}
/*
* Allocate an id_t from specified ID space.
* Caller must be in a context in which VM_SLEEP is legal.
*/
id_t
id_alloc(id_space_t *isp)
{
return ((id_t)(uintptr_t)
vmem_alloc(isp, 1, VM_SLEEP | VM_NEXTFIT) - 1);
}
/*
* Allocate an id_t from specified ID space.
* Returns -1 on failure (see module block comments for more information on
* failure modes).
*/
id_t
id_alloc_nosleep(id_space_t *isp)
{
return ((id_t)(uintptr_t)
vmem_alloc(isp, 1, VM_NOSLEEP | VM_NEXTFIT) - 1);
}
/*
* Free a previously allocated ID.
* No restrictions on caller's context.
*/
void
id_free(id_space_t *isp, id_t id)
{
vmem_free(isp, (void *)(uintptr_t)(id + 1), 1);
}