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 *
id_space_create(const char * name,id_t low,id_t high)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
id_space_destroy(id_space_t * isp)80 id_space_destroy(id_space_t *isp)
81 {
82 vmem_destroy(isp);
83 }
84
85 void
id_space_extend(id_space_t * isp,id_t low,id_t high)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
id_alloc(id_space_t * isp)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
id_alloc_nosleep(id_space_t * isp)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
id_allocff(id_space_t * isp)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
id_allocff_nosleep(id_space_t * isp)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
id_alloc_specific_nosleep(id_space_t * isp,id_t id)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
id_free(id_space_t * isp,id_t id)156 id_free(id_space_t *isp, id_t id)
157 {
158 vmem_free(isp, ID_TO_ADDR(id), 1);
159 }
160