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 * This code is also shared with userland. In userland, we don't have the same
58 * ability to have sleeping variants, so we effectively turn the normal
59 * versions without _nosleep into _nosleep.
60 */
61
62 #define ID_TO_ADDR(id) ((void *)(uintptr_t)(id + 1))
63 #define ADDR_TO_ID(addr) ((id_t)((uintptr_t)addr - 1))
64
65 /*
66 * Create an arena to represent the range [low, high).
67 * Caller must be in a context in which VM_SLEEP is legal,
68 * for the kernel. Always VM_NOSLEEP in userland.
69 */
70 id_space_t *
id_space_create(const char * name,id_t low,id_t high)71 id_space_create(const char *name, id_t low, id_t high)
72 {
73 #ifdef _KERNEL
74 int flag = VM_SLEEP;
75 #else
76 int flag = VM_NOSLEEP;
77 #endif
78 ASSERT(low >= 0);
79 ASSERT(low < high);
80
81 return (vmem_create(name, ID_TO_ADDR(low), high - low, 1,
82 NULL, NULL, NULL, 0, flag | VMC_IDENTIFIER));
83 }
84
85 /*
86 * Destroy a previously created ID space.
87 * No restrictions on caller's context.
88 */
89 void
id_space_destroy(id_space_t * isp)90 id_space_destroy(id_space_t *isp)
91 {
92 vmem_destroy(isp);
93 }
94
95 void
id_space_extend(id_space_t * isp,id_t low,id_t high)96 id_space_extend(id_space_t *isp, id_t low, id_t high)
97 {
98 #ifdef _KERNEL
99 int flag = VM_SLEEP;
100 #else
101 int flag = VM_NOSLEEP;
102 #endif
103 (void) vmem_add(isp, ID_TO_ADDR(low), high - low, flag);
104 }
105
106 /*
107 * Allocate an id_t from specified ID space.
108 * Caller must be in a context in which VM_SLEEP is legal.
109 */
110 id_t
id_alloc(id_space_t * isp)111 id_alloc(id_space_t *isp)
112 {
113 #ifdef _KERNEL
114 int flag = VM_SLEEP;
115 #else
116 int flag = VM_NOSLEEP;
117 #endif
118 return (ADDR_TO_ID(vmem_alloc(isp, 1, flag | VM_NEXTFIT)));
119 }
120
121 /*
122 * Allocate an id_t from specified ID space.
123 * Returns -1 on failure (see module block comments for more information on
124 * failure modes).
125 */
126 id_t
id_alloc_nosleep(id_space_t * isp)127 id_alloc_nosleep(id_space_t *isp)
128 {
129 return (ADDR_TO_ID(vmem_alloc(isp, 1, VM_NOSLEEP | VM_NEXTFIT)));
130 }
131
132 /*
133 * Allocate an id_t from specified ID space using FIRSTFIT.
134 * Caller must be in a context in which VM_SLEEP is legal.
135 */
136 id_t
id_allocff(id_space_t * isp)137 id_allocff(id_space_t *isp)
138 {
139 #ifdef _KERNEL
140 int flag = VM_SLEEP;
141 #else
142 int flag = VM_NOSLEEP;
143 #endif
144 return (ADDR_TO_ID(vmem_alloc(isp, 1, flag | VM_FIRSTFIT)));
145 }
146
147 /*
148 * Allocate an id_t from specified ID space using FIRSTFIT
149 * Returns -1 on failure (see module block comments for more information on
150 * failure modes).
151 */
152 id_t
id_allocff_nosleep(id_space_t * isp)153 id_allocff_nosleep(id_space_t *isp)
154 {
155 return (ADDR_TO_ID(vmem_alloc(isp, 1, VM_NOSLEEP | VM_FIRSTFIT)));
156 }
157
158 /*
159 * Allocate a specific identifier if possible, returning the id if
160 * successful, or -1 on failure.
161 */
162 id_t
id_alloc_specific_nosleep(id_space_t * isp,id_t id)163 id_alloc_specific_nosleep(id_space_t *isp, id_t id)
164 {
165 void *minaddr = ID_TO_ADDR(id);
166 void *maxaddr = ID_TO_ADDR(id + 1);
167
168 /*
169 * Note that even though we're vmem_free()ing this later, it
170 * should be OK, since there's no quantum cache.
171 */
172 return (ADDR_TO_ID(vmem_xalloc(isp, 1, 1, 0, 0,
173 minaddr, maxaddr, VM_NOSLEEP)));
174 }
175
176 /*
177 * Free a previously allocated ID.
178 * No restrictions on caller's context.
179 */
180 void
id_free(id_space_t * isp,id_t id)181 id_free(id_space_t *isp, id_t id)
182 {
183 vmem_free(isp, ID_TO_ADDR(id), 1);
184 }
185