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.
8 * Small id to pointer translation service avoiding fixed sized
15 #include <linux/types.h>
16 #include <linux/bitmap.h>
17 #include <linux/bitops.h>
18 #include <linux/preempt.h>
19 #include <linux/rcupdate.h>
20 #include <linux/spinlock.h>
23 * We want shallower trees and thus more bits covered at each layer. 8
24 * bits gives us large enough first layer for most use cases and maximum
25 * tree depth of 4. Each idr_layer is slightly larger than 2k on 64bit and
29 #define IDR_SIZE (1 << IDR_BITS)
30 #define IDR_MASK ((1 << IDR_BITS)-1)
33 int prefix; /* the ID prefix of this idr_layer */
34 int layer; /* distance from leaf */
35 struct idr_layer __rcu *ary[1<<IDR_BITS];
36 int count; /* When zero, we can release it */
38 /* A zero bit means "space here" */
39 DECLARE_BITMAP(bitmap, IDR_SIZE);
40 struct rcu_head rcu_head;
45 struct idr_layer __rcu *hint; /* the last layer allocated from */
46 struct idr_layer __rcu *top;
47 int layers; /* only valid w/o concurrent changes */
48 int cur; /* current pos for cyclic allocation */
51 struct idr_layer *id_free;
54 #define IDR_INIT(name) \
56 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
58 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
62 * idr synchronization (stolen from radix-tree.h)
64 * idr_find() is able to be called locklessly, using RCU. The caller must
65 * ensure calls to this function are made within rcu_read_lock() regions.
66 * Other readers (lock-free or otherwise) and modifications may be running
69 * It is still required that the caller manage the synchronization and
70 * lifetimes of the items. So if RCU lock-free lookups are used, typically
71 * this would mean that the items have their own locks, or are amenable to
72 * lock-free access; and that the items are freed by RCU (or only freed after
73 * having been deleted from the idr tree *and* a synchronize_rcu() grace
78 * This is what we export.
81 void *idr_find_slowpath(struct idr *idp, int id);
82 void idr_preload(gfp_t gfp_mask);
84 static inline int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask)
89 static inline void idr_remove(struct idr *idp, int id) {}
91 int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);
92 int idr_for_each(struct idr *idp,
93 int (*fn)(int id, void *p, void *data), void *data);
94 void *idr_get_next(struct idr *idp, int *nextid);
95 void *idr_replace(struct idr *idp, void *ptr, int id);
96 void idr_destroy(struct idr *idp);
97 void idr_init(struct idr *idp);
98 bool idr_is_empty(struct idr *idp);
101 * idr_preload_end - end preload section started with idr_preload()
103 * Each idr_preload() should be matched with an invocation of this
104 * function. See idr_preload() for details.
106 static inline void idr_preload_end(void)
112 * idr_find - return pointer for given id
116 * Return the pointer given the id it has been registered with. A %NULL
117 * return indicates that @id is not valid or you passed %NULL in
120 * This function can be called under rcu_read_lock(), given that the leaf
121 * pointers lifetimes are correctly managed.
123 static inline void *idr_find(struct idr *idr, int id)
125 struct idr_layer *hint = rcu_dereference_raw(idr->hint);
127 if (hint && (id & ~IDR_MASK) == hint->prefix)
128 return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
130 return idr_find_slowpath(idr, id);
134 * idr_for_each_entry - iterate over an idr's elements of a given type
136 * @entry: the type * to use as cursor
137 * @id: id entry's key
139 * @entry and @id do not need to be initialized before the loop, and
140 * after normal terminatinon @entry is left with the value NULL. This
141 * is convenient for a "not found" value.
143 #define idr_for_each_entry(idp, entry, id) \
144 for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
147 * idr_for_each_entry - continue iteration over an idr's elements of a given type
149 * @entry: the type * to use as cursor
150 * @id: id entry's key
152 * Continue to iterate over list of given type, continuing after
153 * the current position.
155 #define idr_for_each_entry_continue(idp, entry, id) \
156 for ((entry) = idr_get_next((idp), &(id)); \
158 ++id, (entry) = idr_get_next((idp), &(id)))
161 * IDA - IDR based id allocator, use when translation from id to
162 * pointer isn't necessary.
164 * IDA_BITMAP_LONGS is calculated to be one less to accommodate
165 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
167 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
168 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)
169 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
173 unsigned long bitmap[IDA_BITMAP_LONGS];
178 struct ida_bitmap *free_bitmap;
181 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
182 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
184 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
185 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
186 void ida_remove(struct ida *ida, int id);
187 void ida_destroy(struct ida *ida);
188 void ida_init(struct ida *ida);
190 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
192 void ida_simple_remove(struct ida *ida, unsigned int id);
195 * ida_get_new - allocate new ID
197 * @p_id: pointer to the allocated handle
199 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
201 static inline int ida_get_new(struct ida *ida, int *p_id)
203 return ida_get_new_above(ida, 0, p_id);
206 void __init idr_init_cache(void);
208 #endif /* __IDR_H__ */