xref: /illumos-gate/usr/src/common/idspace/id_space.c (revision 01aad269)
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