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Linux/include/linux/idr.h

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  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/radix-tree.h>
 16 #include <linux/gfp.h>
 17 #include <linux/percpu.h>
 18 
 19 struct idr {
 20         struct radix_tree_root  idr_rt;
 21         unsigned int            idr_base;
 22         unsigned int            idr_next;
 23 };
 24 
 25 /*
 26  * The IDR API does not expose the tagging functionality of the radix tree
 27  * to users.  Use tag 0 to track whether a node has free space below it.
 28  */
 29 #define IDR_FREE        0
 30 
 31 /* Set the IDR flag and the IDR_FREE tag */
 32 #define IDR_RT_MARKER   (ROOT_IS_IDR | (__force gfp_t)                  \
 33                                         (1 << (ROOT_TAG_SHIFT + IDR_FREE)))
 34 
 35 #define IDR_INIT_BASE(name, base) {                                     \
 36         .idr_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER),                 \
 37         .idr_base = (base),                                             \
 38         .idr_next = 0,                                                  \
 39 }
 40 
 41 /**
 42  * IDR_INIT() - Initialise an IDR.
 43  * @name: Name of IDR.
 44  *
 45  * A freshly-initialised IDR contains no IDs.
 46  */
 47 #define IDR_INIT(name)  IDR_INIT_BASE(name, 0)
 48 
 49 /**
 50  * DEFINE_IDR() - Define a statically-allocated IDR.
 51  * @name: Name of IDR.
 52  *
 53  * An IDR defined using this macro is ready for use with no additional
 54  * initialisation required.  It contains no IDs.
 55  */
 56 #define DEFINE_IDR(name)        struct idr name = IDR_INIT(name)
 57 
 58 /**
 59  * idr_get_cursor - Return the current position of the cyclic allocator
 60  * @idr: idr handle
 61  *
 62  * The value returned is the value that will be next returned from
 63  * idr_alloc_cyclic() if it is free (otherwise the search will start from
 64  * this position).
 65  */
 66 static inline unsigned int idr_get_cursor(const struct idr *idr)
 67 {
 68         return READ_ONCE(idr->idr_next);
 69 }
 70 
 71 /**
 72  * idr_set_cursor - Set the current position of the cyclic allocator
 73  * @idr: idr handle
 74  * @val: new position
 75  *
 76  * The next call to idr_alloc_cyclic() will return @val if it is free
 77  * (otherwise the search will start from this position).
 78  */
 79 static inline void idr_set_cursor(struct idr *idr, unsigned int val)
 80 {
 81         WRITE_ONCE(idr->idr_next, val);
 82 }
 83 
 84 /**
 85  * DOC: idr sync
 86  * idr synchronization (stolen from radix-tree.h)
 87  *
 88  * idr_find() is able to be called locklessly, using RCU. The caller must
 89  * ensure calls to this function are made within rcu_read_lock() regions.
 90  * Other readers (lock-free or otherwise) and modifications may be running
 91  * concurrently.
 92  *
 93  * It is still required that the caller manage the synchronization and
 94  * lifetimes of the items. So if RCU lock-free lookups are used, typically
 95  * this would mean that the items have their own locks, or are amenable to
 96  * lock-free access; and that the items are freed by RCU (or only freed after
 97  * having been deleted from the idr tree *and* a synchronize_rcu() grace
 98  * period).
 99  */
100 
101 void idr_preload(gfp_t gfp_mask);
102 
103 int idr_alloc(struct idr *, void *ptr, int start, int end, gfp_t);
104 int __must_check idr_alloc_u32(struct idr *, void *ptr, u32 *id,
105                                 unsigned long max, gfp_t);
106 int idr_alloc_cyclic(struct idr *, void *ptr, int start, int end, gfp_t);
107 void *idr_remove(struct idr *, unsigned long id);
108 void *idr_find(const struct idr *, unsigned long id);
109 int idr_for_each(const struct idr *,
110                  int (*fn)(int id, void *p, void *data), void *data);
111 void *idr_get_next(struct idr *, int *nextid);
112 void *idr_get_next_ul(struct idr *, unsigned long *nextid);
113 void *idr_replace(struct idr *, void *, unsigned long id);
114 void idr_destroy(struct idr *);
115 
116 /**
117  * idr_init_base() - Initialise an IDR.
118  * @idr: IDR handle.
119  * @base: The base value for the IDR.
120  *
121  * This variation of idr_init() creates an IDR which will allocate IDs
122  * starting at %base.
123  */
124 static inline void idr_init_base(struct idr *idr, int base)
125 {
126         INIT_RADIX_TREE(&idr->idr_rt, IDR_RT_MARKER);
127         idr->idr_base = base;
128         idr->idr_next = 0;
129 }
130 
131 /**
132  * idr_init() - Initialise an IDR.
133  * @idr: IDR handle.
134  *
135  * Initialise a dynamically allocated IDR.  To initialise a
136  * statically allocated IDR, use DEFINE_IDR().
137  */
138 static inline void idr_init(struct idr *idr)
139 {
140         idr_init_base(idr, 0);
141 }
142 
143 /**
144  * idr_is_empty() - Are there any IDs allocated?
145  * @idr: IDR handle.
146  *
147  * Return: %true if any IDs have been allocated from this IDR.
148  */
149 static inline bool idr_is_empty(const struct idr *idr)
150 {
151         return radix_tree_empty(&idr->idr_rt) &&
152                 radix_tree_tagged(&idr->idr_rt, IDR_FREE);
153 }
154 
155 /**
156  * idr_preload_end - end preload section started with idr_preload()
157  *
158  * Each idr_preload() should be matched with an invocation of this
159  * function.  See idr_preload() for details.
160  */
161 static inline void idr_preload_end(void)
162 {
163         preempt_enable();
164 }
165 
166 /**
167  * idr_for_each_entry() - Iterate over an IDR's elements of a given type.
168  * @idr: IDR handle.
169  * @entry: The type * to use as cursor
170  * @id: Entry ID.
171  *
172  * @entry and @id do not need to be initialized before the loop, and
173  * after normal termination @entry is left with the value NULL.  This
174  * is convenient for a "not found" value.
175  */
176 #define idr_for_each_entry(idr, entry, id)                      \
177         for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; ++id)
178 
179 /**
180  * idr_for_each_entry_ul() - Iterate over an IDR's elements of a given type.
181  * @idr: IDR handle.
182  * @entry: The type * to use as cursor.
183  * @id: Entry ID.
184  *
185  * @entry and @id do not need to be initialized before the loop, and
186  * after normal termination @entry is left with the value NULL.  This
187  * is convenient for a "not found" value.
188  */
189 #define idr_for_each_entry_ul(idr, entry, id)                   \
190         for (id = 0; ((entry) = idr_get_next_ul(idr, &(id))) != NULL; ++id)
191 
192 /**
193  * idr_for_each_entry_continue() - Continue iteration over an IDR's elements of a given type
194  * @idr: IDR handle.
195  * @entry: The type * to use as a cursor.
196  * @id: Entry ID.
197  *
198  * Continue to iterate over entries, continuing after the current position.
199  */
200 #define idr_for_each_entry_continue(idr, entry, id)                     \
201         for ((entry) = idr_get_next((idr), &(id));                      \
202              entry;                                                     \
203              ++id, (entry) = idr_get_next((idr), &(id)))
204 
205 /*
206  * IDA - IDR based id allocator, use when translation from id to
207  * pointer isn't necessary.
208  */
209 #define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
210 #define IDA_BITMAP_LONGS        (IDA_CHUNK_SIZE / sizeof(long))
211 #define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
212 
213 struct ida_bitmap {
214         unsigned long           bitmap[IDA_BITMAP_LONGS];
215 };
216 
217 DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);
218 
219 struct ida {
220         struct radix_tree_root  ida_rt;
221 };
222 
223 #define IDA_INIT(name)  {                                               \
224         .ida_rt = RADIX_TREE_INIT(name, IDR_RT_MARKER | GFP_NOWAIT),    \
225 }
226 #define DEFINE_IDA(name)        struct ida name = IDA_INIT(name)
227 
228 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
229 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
230 void ida_remove(struct ida *ida, int id);
231 void ida_destroy(struct ida *ida);
232 
233 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
234                    gfp_t gfp_mask);
235 void ida_simple_remove(struct ida *ida, unsigned int id);
236 
237 static inline void ida_init(struct ida *ida)
238 {
239         INIT_RADIX_TREE(&ida->ida_rt, IDR_RT_MARKER | GFP_NOWAIT);
240 }
241 
242 /**
243  * ida_get_new - allocate new ID
244  * @ida:        idr handle
245  * @p_id:       pointer to the allocated handle
246  *
247  * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
248  */
249 static inline int ida_get_new(struct ida *ida, int *p_id)
250 {
251         return ida_get_new_above(ida, 0, p_id);
252 }
253 
254 static inline bool ida_is_empty(const struct ida *ida)
255 {
256         return radix_tree_empty(&ida->ida_rt);
257 }
258 #endif /* __IDR_H__ */
259 

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