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 /*
21 * We want shallower trees and thus more bits covered at each layer. 8
22 * bits gives us large enough first layer for most use cases and maximum
23 * tree depth of 4. Each idr_layer is slightly larger than 2k on 64bit and
24 * 1k on 32bit.
25 */
26 #define IDR_BITS 8
27 #define IDR_SIZE (1 << IDR_BITS)
28 #define IDR_MASK ((1 << IDR_BITS)-1)
29
30 struct idr_layer {
31 int prefix; /* the ID prefix of this idr_layer */
32 int layer; /* distance from leaf */
33 struct idr_layer __rcu *ary[1<<IDR_BITS];
34 int count; /* When zero, we can release it */
35 union {
36 /* A zero bit means "space here" */
37 DECLARE_BITMAP(bitmap, IDR_SIZE);
38 struct rcu_head rcu_head;
39 };
40 };
41
42 struct idr {
43 struct idr_layer __rcu *hint; /* the last layer allocated from */
44 struct idr_layer __rcu *top;
45 int layers; /* only valid w/o concurrent changes */
46 int cur; /* current pos for cyclic allocation */
47 spinlock_t lock;
48 int id_free_cnt;
49 struct idr_layer *id_free;
50 };
51
52 #define IDR_INIT(name) \
53 { \
54 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
55 }
56 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
57
58 /**
59 * DOC: idr sync
60 * idr synchronization (stolen from radix-tree.h)
61 *
62 * idr_find() is able to be called locklessly, using RCU. The caller must
63 * ensure calls to this function are made within rcu_read_lock() regions.
64 * Other readers (lock-free or otherwise) and modifications may be running
65 * concurrently.
66 *
67 * It is still required that the caller manage the synchronization and
68 * lifetimes of the items. So if RCU lock-free lookups are used, typically
69 * this would mean that the items have their own locks, or are amenable to
70 * lock-free access; and that the items are freed by RCU (or only freed after
71 * having been deleted from the idr tree *and* a synchronize_rcu() grace
72 * period).
73 */
74
75 /*
76 * This is what we export.
77 */
78
79 void *idr_find_slowpath(struct idr *idp, int id);
80 void idr_preload(gfp_t gfp_mask);
81 int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
82 int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);
83 int idr_for_each(struct idr *idp,
84 int (*fn)(int id, void *p, void *data), void *data);
85 void *idr_get_next(struct idr *idp, int *nextid);
86 void *idr_replace(struct idr *idp, void *ptr, int id);
87 void idr_remove(struct idr *idp, int id);
88 void idr_destroy(struct idr *idp);
89 void idr_init(struct idr *idp);
90 bool idr_is_empty(struct idr *idp);
91
92 /**
93 * idr_preload_end - end preload section started with idr_preload()
94 *
95 * Each idr_preload() should be matched with an invocation of this
96 * function. See idr_preload() for details.
97 */
idr_preload_end(void)98 static inline void idr_preload_end(void)
99 {
100 preempt_enable();
101 }
102
103 /**
104 * idr_find - return pointer for given id
105 * @idr: idr handle
106 * @id: lookup key
107 *
108 * Return the pointer given the id it has been registered with. A %NULL
109 * return indicates that @id is not valid or you passed %NULL in
110 * idr_get_new().
111 *
112 * This function can be called under rcu_read_lock(), given that the leaf
113 * pointers lifetimes are correctly managed.
114 */
idr_find(struct idr * idr,int id)115 static inline void *idr_find(struct idr *idr, int id)
116 {
117 struct idr_layer *hint = rcu_dereference_raw(idr->hint);
118
119 if (hint && (id & ~IDR_MASK) == hint->prefix)
120 return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
121
122 return idr_find_slowpath(idr, id);
123 }
124
125 /**
126 * idr_for_each_entry - iterate over an idr's elements of a given type
127 * @idp: idr handle
128 * @entry: the type * to use as cursor
129 * @id: id entry's key
130 *
131 * @entry and @id do not need to be initialized before the loop, and
132 * after normal terminatinon @entry is left with the value NULL. This
133 * is convenient for a "not found" value.
134 */
135 #define idr_for_each_entry(idp, entry, id) \
136 for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
137
138 /*
139 * IDA - IDR based id allocator, use when translation from id to
140 * pointer isn't necessary.
141 *
142 * IDA_BITMAP_LONGS is calculated to be one less to accommodate
143 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
144 */
145 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
146 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)
147 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
148
149 struct ida_bitmap {
150 long nr_busy;
151 unsigned long bitmap[IDA_BITMAP_LONGS];
152 };
153
154 struct ida {
155 struct idr idr;
156 struct ida_bitmap *free_bitmap;
157 };
158
159 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
160 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
161
162 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
163 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
164 void ida_remove(struct ida *ida, int id);
165 void ida_destroy(struct ida *ida);
166 void ida_init(struct ida *ida);
167
168 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
169 gfp_t gfp_mask);
170 void ida_simple_remove(struct ida *ida, unsigned int id);
171
172 /**
173 * ida_get_new - allocate new ID
174 * @ida: idr handle
175 * @p_id: pointer to the allocated handle
176 *
177 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
178 */
ida_get_new(struct ida * ida,int * p_id)179 static inline int ida_get_new(struct ida *ida, int *p_id)
180 {
181 return ida_get_new_above(ida, 0, p_id);
182 }
183
184 void __init idr_init_cache(void);
185
186 #endif /* __IDR_H__ */
187