kernel/os/id_space.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 /*
  22  * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
  23  */
  24
  25 #include <sys/types.h>
  26 #include <sys/id_space.h>
  27 #include <sys/debug.h>
  28
  29 /*
  30  * ID Spaces
  31  *
  32  *   The id_space_t provides a simple implementation of a managed range of
  33  *   integer identifiers using a vmem arena.  An ID space guarantees that the
  34  *   next identifer returned by an allocation is larger than the previous one,
  35  *   unless there are no larger slots remaining in the range.  In this case,
  36  *   the ID space will return the first available slot in the lower part of the
  37  *   range (viewing the previous identifier as a partitioning element).  If no
  38  *   slots are available, id_alloc()/id_allocff() will sleep until an
  39  *   identifier becomes available.  Accordingly, id_space allocations must be
  40  *   initiated from contexts where sleeping is acceptable.  id_alloc_nosleep()/
  41  *   id_allocff_nosleep() will return -1 if no slots are available or if the
  42  *   system is low on memory.  If id_alloc_nosleep() fails, callers should
  43  *   not try to extend the ID space.  This is to avoid making a possible
  44  *   low-memory situation worse.
  45  *
  46  *   As an ID space is designed for representing a range of id_t's, there
  47  *   is a preexisting maximal range: [0, MAXUID].  ID space requests outside
  48  *   that range will fail on a DEBUG kernel.  The id_allocff*() functions
  49  *   return the first available id, and should be used when there is benefit
  50  *   to having a compact allocated range.
  51  *
  52  *   (Presently, the id_space_t abstraction supports only direct allocations; ID
  53  *   reservation, in which an ID is allocated but placed in a internal
  54  *   dictionary for later use, should be added when a consuming subsystem
  55  *   arrives.)
  56  */
  57
  58 #define ID_TO_ADDR(id) ((void *)(uintptr_t)(id + 1))
  59 #define ADDR_TO_ID(addr) ((id_t)((uintptr_t)addr - 1))
  60
  61 /*
  62  * Create an arena to represent the range [low, high).
  63  * Caller must be in a context in which VM_SLEEP is legal.
  64  */
  65 id_space_t *
  66 id_space_create(const char *name, id_t low, id_t high)
  67 {
  68         ASSERT(low >= 0);
  69         ASSERT(low < high);
  70
  71         return (vmem_create(name, ID_TO_ADDR(low), high - low, 1,
  72             NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER));
  73 }
  74
  75 /*
  76  * Destroy a previously created ID space.
  77  * No restrictions on caller's context.
  78  */
  79 void
  80 id_space_destroy(id_space_t *isp)
  81 {
  82         vmem_destroy(isp);
  83 }
  84
  85 void
  86 id_space_extend(id_space_t *isp, id_t low, id_t high)
  87 {
  88         (void) vmem_add(isp, ID_TO_ADDR(low), high - low, VM_SLEEP);
  89 }
  90
  91 /*
  92  * Allocate an id_t from specified ID space.
  93  * Caller must be in a context in which VM_SLEEP is legal.
  94  */
  95 id_t
  96 id_alloc(id_space_t *isp)
  97 {
  98         return (ADDR_TO_ID(vmem_alloc(isp, 1, VM_SLEEP | VM_NEXTFIT)));
  99 }
 100
 101 /*
 102  * Allocate an id_t from specified ID space.
 103  * Returns -1 on failure (see module block comments for more information on
 104  * failure modes).
 105  */
 106 id_t
 107 id_alloc_nosleep(id_space_t *isp)
 108 {
 109         return (ADDR_TO_ID(vmem_alloc(isp, 1, VM_NOSLEEP | VM_NEXTFIT)));
 110 }
 111
 112 /*
 113  * Allocate an id_t from specified ID space using FIRSTFIT.
 114  * Caller must be in a context in which VM_SLEEP is legal.
 115  */
 116 id_t
 117 id_allocff(id_space_t *isp)
 118 {
 119         return (ADDR_TO_ID(vmem_alloc(isp, 1, VM_SLEEP | VM_FIRSTFIT)));
 120 }
 121
 122 /*
 123  * Allocate an id_t from specified ID space using FIRSTFIT
 124  * Returns -1 on failure (see module block comments for more information on
 125  * failure modes).
 126  */
 127 id_t
 128 id_allocff_nosleep(id_space_t *isp)
 129 {
 130         return (ADDR_TO_ID(vmem_alloc(isp, 1, VM_NOSLEEP | VM_FIRSTFIT)));
 131 }
 132
 133 /*
 134  * Allocate a specific identifier if possible, returning the id if
 135  * successful, or -1 on failure.
 136  */
 137 id_t
 138 id_alloc_specific_nosleep(id_space_t *isp, id_t id)
 139 {
 140         void *minaddr = ID_TO_ADDR(id);
 141         void *maxaddr = ID_TO_ADDR(id + 1);
 142
 143         /*
 144          * Note that even though we're vmem_free()ing this later, it
 145          * should be OK, since there's no quantum cache.
 146          */
 147         return (ADDR_TO_ID(vmem_xalloc(isp, 1, 1, 0, 0,
 148             minaddr, maxaddr, VM_NOSLEEP)));
 149 }
 150
 151 /*
 152  * Free a previously allocated ID.
 153  * No restrictions on caller's context.
 154  */
 155 void
 156 id_free(id_space_t *isp, id_t id)
 157 {
 158         vmem_free(isp, ID_TO_ADDR(id), 1);
 159 }