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
30struct 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
42struct 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
79void *idr_find_slowpath(struct idr *idp, int id);
80void idr_preload(gfp_t gfp_mask);
81int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
82int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);
83int idr_for_each(struct idr *idp,
84		 int (*fn)(int id, void *p, void *data), void *data);
85void *idr_get_next(struct idr *idp, int *nextid);
86void *idr_replace(struct idr *idp, void *ptr, int id);
87void idr_remove(struct idr *idp, int id);
88void idr_destroy(struct idr *idp);
89void idr_init(struct idr *idp);
90bool 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 */
98static 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 */
115static 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
149struct ida_bitmap {
150	long			nr_busy;
151	unsigned long		bitmap[IDA_BITMAP_LONGS];
152};
153
154struct 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
162int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
163int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
164void ida_remove(struct ida *ida, int id);
165void ida_destroy(struct ida *ida);
166void ida_init(struct ida *ida);
167
168int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
169		   gfp_t gfp_mask);
170void 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 */
179static inline int ida_get_new(struct ida *ida, int *p_id)
180{
181	return ida_get_new_above(ida, 0, p_id);
182}
183
184void __init idr_init_cache(void);
185
186#endif /* __IDR_H__ */
187