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/bitops.h>
17 #include <linux/init.h>
18 #include <linux/rcupdate.h>
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
27 #define IDR_SIZE (1 << IDR_BITS)
28 #define IDR_MASK ((1 << IDR_BITS)-1)
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 */
36 /* A zero bit means "space here" */
37 DECLARE_BITMAP(bitmap
, IDR_SIZE
);
38 struct rcu_head rcu_head
;
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 */
49 struct idr_layer
*id_free
;
52 #define IDR_INIT(name) \
54 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
56 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
60 * idr synchronization (stolen from radix-tree.h)
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
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
76 * This is what we export.
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
);
93 * idr_preload_end - end preload section started with idr_preload()
95 * Each idr_preload() should be matched with an invocation of this
96 * function. See idr_preload() for details.
98 static inline void idr_preload_end(void)
104 * idr_find - return pointer for given id
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
112 * This function can be called under rcu_read_lock(), given that the leaf
113 * pointers lifetimes are correctly managed.
115 static inline void *idr_find(struct idr
*idr
, int id
)
117 struct idr_layer
*hint
= rcu_dereference_raw(idr
->hint
);
119 if (hint
&& (id
& ~IDR_MASK
) == hint
->prefix
)
120 return rcu_dereference_raw(hint
->ary
[id
& IDR_MASK
]);
122 return idr_find_slowpath(idr
, id
);
126 * idr_for_each_entry - iterate over an idr's elements of a given type
128 * @entry: the type * to use as cursor
129 * @id: id entry's key
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.
135 #define idr_for_each_entry(idp, entry, id) \
136 for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
139 * idr_for_each_entry - continue iteration over an idr's elements of a given type
141 * @entry: the type * to use as cursor
142 * @id: id entry's key
144 * Continue to iterate over list of given type, continuing after
145 * the current position.
147 #define idr_for_each_entry_continue(idp, entry, id) \
148 for ((entry) = idr_get_next((idp), &(id)); \
150 ++id, (entry) = idr_get_next((idp), &(id)))
153 * IDA - IDR based id allocator, use when translation from id to
154 * pointer isn't necessary.
156 * IDA_BITMAP_LONGS is calculated to be one less to accommodate
157 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
159 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
160 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)
161 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
165 unsigned long bitmap
[IDA_BITMAP_LONGS
];
170 struct ida_bitmap
*free_bitmap
;
173 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
174 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
176 int ida_pre_get(struct ida
*ida
, gfp_t gfp_mask
);
177 int ida_get_new_above(struct ida
*ida
, int starting_id
, int *p_id
);
178 void ida_remove(struct ida
*ida
, int id
);
179 void ida_destroy(struct ida
*ida
);
180 void ida_init(struct ida
*ida
);
182 int ida_simple_get(struct ida
*ida
, unsigned int start
, unsigned int end
,
184 void ida_simple_remove(struct ida
*ida
, unsigned int id
);
187 * ida_get_new - allocate new ID
189 * @p_id: pointer to the allocated handle
191 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
193 static inline int ida_get_new(struct ida
*ida
, int *p_id
)
195 return ida_get_new_above(ida
, 0, p_id
);
198 void __init
idr_init_cache(void);
200 #endif /* __IDR_H__ */
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