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1/*
2 * include/linux/idr.h
3 *
4 * 2002-10-18 written by Jim Houston jim.houston@ccur.com
5 * Copyright (C) 2002 by Concurrent Computer Corporation
6 * Distributed under the GNU GPL license version 2.
7 *
8 * Small id to pointer translation service avoiding fixed sized
9 * tables.
10 */
11
12#ifndef __IDR_H__
13#define __IDR_H__
14
15#include <linux/types.h>
16#include <linux/bitops.h>
17#include <linux/init.h>
18#include <linux/rcupdate.h>
19
20#if BITS_PER_LONG == 32
21# define IDR_BITS 5
22# define IDR_FULL 0xfffffffful
23/* We can only use two of the bits in the top level because there is
24 only one possible bit in the top level (5 bits * 7 levels = 35
25 bits, but you only use 31 bits in the id). */
26# define TOP_LEVEL_FULL (IDR_FULL >> 30)
27#elif BITS_PER_LONG == 64
28# define IDR_BITS 6
29# define IDR_FULL 0xfffffffffffffffful
30/* We can only use two of the bits in the top level because there is
31 only one possible bit in the top level (6 bits * 6 levels = 36
32 bits, but you only use 31 bits in the id). */
33# define TOP_LEVEL_FULL (IDR_FULL >> 62)
34#else
35# error "BITS_PER_LONG is not 32 or 64"
36#endif
37
38#define IDR_SIZE (1 << IDR_BITS)
39#define IDR_MASK ((1 << IDR_BITS)-1)
40
41#define MAX_ID_SHIFT (sizeof(int)*8 - 1)
42#define MAX_ID_BIT (1U << MAX_ID_SHIFT)
43#define MAX_ID_MASK (MAX_ID_BIT - 1)
44
45/* Leave the possibility of an incomplete final layer */
46#define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS
47
48/* Number of id_layer structs to leave in free list */
49#define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL
50
51struct idr_layer {
52 unsigned long bitmap; /* A zero bit means "space here" */
53 struct idr_layer __rcu *ary[1<<IDR_BITS];
54 int count; /* When zero, we can release it */
55 int layer; /* distance from leaf */
56 struct rcu_head rcu_head;
57};
58
59struct idr {
60 struct idr_layer __rcu *top;
61 struct idr_layer *id_free;
62 int layers; /* only valid without concurrent changes */
63 int id_free_cnt;
64 spinlock_t lock;
65};
66
67#define IDR_INIT(name) \
68{ \
69 .top = NULL, \
70 .id_free = NULL, \
71 .layers = 0, \
72 .id_free_cnt = 0, \
73 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
74}
75#define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
76
77/* Actions to be taken after a call to _idr_sub_alloc */
78#define IDR_NEED_TO_GROW -2
79#define IDR_NOMORE_SPACE -3
80
81#define _idr_rc_to_errno(rc) ((rc) == -1 ? -EAGAIN : -ENOSPC)
82
83/**
84 * DOC: idr sync
85 * idr synchronization (stolen from radix-tree.h)
86 *
87 * idr_find() is able to be called locklessly, using RCU. The caller must
88 * ensure calls to this function are made within rcu_read_lock() regions.
89 * Other readers (lock-free or otherwise) and modifications may be running
90 * concurrently.
91 *
92 * It is still required that the caller manage the synchronization and
93 * lifetimes of the items. So if RCU lock-free lookups are used, typically
94 * this would mean that the items have their own locks, or are amenable to
95 * lock-free access; and that the items are freed by RCU (or only freed after
96 * having been deleted from the idr tree *and* a synchronize_rcu() grace
97 * period).
98 */
99
100/*
101 * This is what we export.
102 */
103
104void *idr_find(struct idr *idp, int id);
105int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
106int idr_get_new(struct idr *idp, void *ptr, int *id);
107int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
108int idr_for_each(struct idr *idp,
109 int (*fn)(int id, void *p, void *data), void *data);
110void *idr_get_next(struct idr *idp, int *nextid);
111void *idr_replace(struct idr *idp, void *ptr, int id);
112void idr_remove(struct idr *idp, int id);
113void idr_remove_all(struct idr *idp);
114void idr_destroy(struct idr *idp);
115void idr_init(struct idr *idp);
116
117
118/*
119 * IDA - IDR based id allocator, use when translation from id to
120 * pointer isn't necessary.
121 *
122 * IDA_BITMAP_LONGS is calculated to be one less to accommodate
123 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
124 */
125#define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
126#define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)
127#define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
128
129struct ida_bitmap {
130 long nr_busy;
131 unsigned long bitmap[IDA_BITMAP_LONGS];
132};
133
134struct ida {
135 struct idr idr;
136 struct ida_bitmap *free_bitmap;
137};
138
139#define IDA_INIT(name) { .idr = IDR_INIT(name), .free_bitmap = NULL, }
140#define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
141
142int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
143int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
144int ida_get_new(struct ida *ida, int *p_id);
145void ida_remove(struct ida *ida, int id);
146void ida_destroy(struct ida *ida);
147void ida_init(struct ida *ida);
148
149int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
150 gfp_t gfp_mask);
151void ida_simple_remove(struct ida *ida, unsigned int id);
152
153void __init idr_init_cache(void);
154
155#endif /* __IDR_H__ */