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git.proxmox.com Git - mirror_ubuntu-zesty-kernel.git/blob - include/linux/idr.h
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 * Using 6 bits at each layer allows us to allocate 7 layers out of each page.
22 * 8 bits only gave us 3 layers out of every pair of pages, which is less
23 * efficient except for trees with a largest element between 192-255 inclusive.
26 #define IDR_SIZE (1 << IDR_BITS)
27 #define IDR_MASK ((1 << IDR_BITS)-1)
30 int prefix
; /* the ID prefix of this idr_layer */
31 int layer
; /* distance from leaf */
32 struct idr_layer __rcu
*ary
[1<<IDR_BITS
];
33 int count
; /* When zero, we can release it */
35 /* A zero bit means "space here" */
36 DECLARE_BITMAP(bitmap
, IDR_SIZE
);
37 struct rcu_head rcu_head
;
42 struct idr_layer __rcu
*hint
; /* the last layer allocated from */
43 struct idr_layer __rcu
*top
;
44 int layers
; /* only valid w/o concurrent changes */
45 int cur
; /* current pos for cyclic allocation */
48 struct idr_layer
*id_free
;
51 #define IDR_INIT(name) \
53 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
55 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
58 * idr_get_cursor - Return the current position of the cyclic allocator
61 * The value returned is the value that will be next returned from
62 * idr_alloc_cyclic() if it is free (otherwise the search will start from
65 static inline unsigned int idr_get_cursor(struct idr
*idr
)
67 return READ_ONCE(idr
->cur
);
71 * idr_set_cursor - Set the current position of the cyclic allocator
75 * The next call to idr_alloc_cyclic() will return @val if it is free
76 * (otherwise the search will start from this position).
78 static inline void idr_set_cursor(struct idr
*idr
, unsigned int val
)
80 WRITE_ONCE(idr
->cur
, val
);
85 * idr synchronization (stolen from radix-tree.h)
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
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
101 * This is what we export.
104 void *idr_find_slowpath(struct idr
*idp
, int id
);
105 void idr_preload(gfp_t gfp_mask
);
106 int idr_alloc(struct idr
*idp
, void *ptr
, int start
, int end
, gfp_t gfp_mask
);
107 int idr_alloc_cyclic(struct idr
*idr
, void *ptr
, int start
, int end
, gfp_t gfp_mask
);
108 int idr_for_each(struct idr
*idp
,
109 int (*fn
)(int id
, void *p
, void *data
), void *data
);
110 void *idr_get_next(struct idr
*idp
, int *nextid
);
111 void *idr_replace(struct idr
*idp
, void *ptr
, int id
);
112 void idr_remove(struct idr
*idp
, int id
);
113 void idr_destroy(struct idr
*idp
);
114 void idr_init(struct idr
*idp
);
115 bool idr_is_empty(struct idr
*idp
);
118 * idr_preload_end - end preload section started with idr_preload()
120 * Each idr_preload() should be matched with an invocation of this
121 * function. See idr_preload() for details.
123 static inline void idr_preload_end(void)
129 * idr_find - return pointer for given id
133 * Return the pointer given the id it has been registered with. A %NULL
134 * return indicates that @id is not valid or you passed %NULL in
137 * This function can be called under rcu_read_lock(), given that the leaf
138 * pointers lifetimes are correctly managed.
140 static inline void *idr_find(struct idr
*idr
, int id
)
142 struct idr_layer
*hint
= rcu_dereference_raw(idr
->hint
);
144 if (hint
&& (id
& ~IDR_MASK
) == hint
->prefix
)
145 return rcu_dereference_raw(hint
->ary
[id
& IDR_MASK
]);
147 return idr_find_slowpath(idr
, id
);
151 * idr_for_each_entry - iterate over an idr's elements of a given type
153 * @entry: the type * to use as cursor
154 * @id: id entry's key
156 * @entry and @id do not need to be initialized before the loop, and
157 * after normal terminatinon @entry is left with the value NULL. This
158 * is convenient for a "not found" value.
160 #define idr_for_each_entry(idp, entry, id) \
161 for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
164 * idr_for_each_entry - continue iteration over an idr's elements of a given type
166 * @entry: the type * to use as cursor
167 * @id: id entry's key
169 * Continue to iterate over list of given type, continuing after
170 * the current position.
172 #define idr_for_each_entry_continue(idp, entry, id) \
173 for ((entry) = idr_get_next((idp), &(id)); \
175 ++id, (entry) = idr_get_next((idp), &(id)))
178 * IDA - IDR based id allocator, use when translation from id to
179 * pointer isn't necessary.
181 * IDA_BITMAP_LONGS is calculated to be one less to accommodate
182 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
184 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
185 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)
186 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
190 unsigned long bitmap
[IDA_BITMAP_LONGS
];
195 struct ida_bitmap
*free_bitmap
;
198 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
199 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
201 int ida_pre_get(struct ida
*ida
, gfp_t gfp_mask
);
202 int ida_get_new_above(struct ida
*ida
, int starting_id
, int *p_id
);
203 void ida_remove(struct ida
*ida
, int id
);
204 void ida_destroy(struct ida
*ida
);
205 void ida_init(struct ida
*ida
);
207 int ida_simple_get(struct ida
*ida
, unsigned int start
, unsigned int end
,
209 void ida_simple_remove(struct ida
*ida
, unsigned int id
);
212 * ida_get_new - allocate new ID
214 * @p_id: pointer to the allocated handle
216 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
218 static inline int ida_get_new(struct ida
*ida
, int *p_id
)
220 return ida_get_new_above(ida
, 0, p_id
);
223 static inline bool ida_is_empty(struct ida
*ida
)
225 return idr_is_empty(&ida
->idr
);
228 void __init
idr_init_cache(void);
230 #endif /* __IDR_H__ */