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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 * 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 DECLARE_BITMAP(bitmap
, IDR_SIZE
); /* A zero bit means "space here" */
33 struct idr_layer __rcu
*ary
[1<<IDR_BITS
];
34 int count
; /* When zero, we can release it */
35 int layer
; /* distance from leaf */
36 struct rcu_head rcu_head
;
40 struct idr_layer __rcu
*hint
; /* the last layer allocated from */
41 struct idr_layer __rcu
*top
;
42 struct idr_layer
*id_free
;
43 int layers
; /* only valid w/o concurrent changes */
45 int cur
; /* current pos for cyclic allocation */
49 #define IDR_INIT(name) \
51 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
53 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name)
57 * idr synchronization (stolen from radix-tree.h)
59 * idr_find() is able to be called locklessly, using RCU. The caller must
60 * ensure calls to this function are made within rcu_read_lock() regions.
61 * Other readers (lock-free or otherwise) and modifications may be running
64 * It is still required that the caller manage the synchronization and
65 * lifetimes of the items. So if RCU lock-free lookups are used, typically
66 * this would mean that the items have their own locks, or are amenable to
67 * lock-free access; and that the items are freed by RCU (or only freed after
68 * having been deleted from the idr tree *and* a synchronize_rcu() grace
73 * This is what we export.
76 void *idr_find_slowpath(struct idr
*idp
, int id
);
77 void idr_preload(gfp_t gfp_mask
);
78 int idr_alloc(struct idr
*idp
, void *ptr
, int start
, int end
, gfp_t gfp_mask
);
79 int idr_alloc_cyclic(struct idr
*idr
, void *ptr
, int start
, int end
, gfp_t gfp_mask
);
80 int idr_for_each(struct idr
*idp
,
81 int (*fn
)(int id
, void *p
, void *data
), void *data
);
82 void *idr_get_next(struct idr
*idp
, int *nextid
);
83 void *idr_replace(struct idr
*idp
, void *ptr
, int id
);
84 void idr_remove(struct idr
*idp
, int id
);
85 void idr_destroy(struct idr
*idp
);
86 void idr_init(struct idr
*idp
);
87 bool idr_is_empty(struct idr
*idp
);
90 * idr_preload_end - end preload section started with idr_preload()
92 * Each idr_preload() should be matched with an invocation of this
93 * function. See idr_preload() for details.
95 static inline void idr_preload_end(void)
101 * idr_find - return pointer for given id
105 * Return the pointer given the id it has been registered with. A %NULL
106 * return indicates that @id is not valid or you passed %NULL in
109 * This function can be called under rcu_read_lock(), given that the leaf
110 * pointers lifetimes are correctly managed.
112 static inline void *idr_find(struct idr
*idr
, int id
)
114 struct idr_layer
*hint
= rcu_dereference_raw(idr
->hint
);
116 if (hint
&& (id
& ~IDR_MASK
) == hint
->prefix
)
117 return rcu_dereference_raw(hint
->ary
[id
& IDR_MASK
]);
119 return idr_find_slowpath(idr
, id
);
123 * idr_for_each_entry - iterate over an idr's elements of a given type
125 * @entry: the type * to use as cursor
126 * @id: id entry's key
128 * @entry and @id do not need to be initialized before the loop, and
129 * after normal terminatinon @entry is left with the value NULL. This
130 * is convenient for a "not found" value.
132 #define idr_for_each_entry(idp, entry, id) \
133 for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
136 * IDA - IDR based id allocator, use when translation from id to
137 * pointer isn't necessary.
139 * IDA_BITMAP_LONGS is calculated to be one less to accommodate
140 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
142 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */
143 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1)
144 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8)
148 unsigned long bitmap
[IDA_BITMAP_LONGS
];
153 struct ida_bitmap
*free_bitmap
;
156 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
157 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name)
159 int ida_pre_get(struct ida
*ida
, gfp_t gfp_mask
);
160 int ida_get_new_above(struct ida
*ida
, int starting_id
, int *p_id
);
161 void ida_remove(struct ida
*ida
, int id
);
162 void ida_destroy(struct ida
*ida
);
163 void ida_init(struct ida
*ida
);
165 int ida_simple_get(struct ida
*ida
, unsigned int start
, unsigned int end
,
167 void ida_simple_remove(struct ida
*ida
, unsigned int id
);
170 * ida_get_new - allocate new ID
172 * @p_id: pointer to the allocated handle
174 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
176 static inline int ida_get_new(struct ida
*ida
, int *p_id
)
178 return ida_get_new_above(ida
, 0, p_id
);
181 void __init
idr_init_cache(void);
183 #endif /* __IDR_H__ */