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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/types.h>
 16 #include <linux/bitops.h>
 17 #include <linux/init.h>
 18 #include <linux/rcupdate.h>
 19 
 20 /*
 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
 24  * 1k on 32bit.
 25  */
 26 #define IDR_BITS 8
 27 #define IDR_SIZE (1 << IDR_BITS)
 28 #define IDR_MASK ((1 << IDR_BITS)-1)
 29 
 30 struct idr_layer {
 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;
 37 };
 38 
 39 struct idr {
 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 */
 44         int                     id_free_cnt;
 45         int                     cur;    /* current pos for cyclic allocation */
 46         spinlock_t              lock;
 47 };
 48 
 49 #define IDR_INIT(name)                                                  \
 50 {                                                                       \
 51         .lock                   = __SPIN_LOCK_UNLOCKED(name.lock),      \
 52 }
 53 #define DEFINE_IDR(name)        struct idr name = IDR_INIT(name)
 54 
 55 /**
 56  * DOC: idr sync
 57  * idr synchronization (stolen from radix-tree.h)
 58  *
 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
 62  * concurrently.
 63  *
 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
 69  * period).
 70  */
 71 
 72 /*
 73  * This is what we export.
 74  */
 75 
 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_free(struct idr *idp, int id);
 86 void idr_destroy(struct idr *idp);
 87 void idr_init(struct idr *idp);
 88 
 89 /**
 90  * idr_preload_end - end preload section started with idr_preload()
 91  *
 92  * Each idr_preload() should be matched with an invocation of this
 93  * function.  See idr_preload() for details.
 94  */
 95 static inline void idr_preload_end(void)
 96 {
 97         preempt_enable();
 98 }
 99 
100 /**
101  * idr_find - return pointer for given id
102  * @idr: idr handle
103  * @id: lookup key
104  *
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
107  * idr_get_new().
108  *
109  * This function can be called under rcu_read_lock(), given that the leaf
110  * pointers lifetimes are correctly managed.
111  */
112 static inline void *idr_find(struct idr *idr, int id)
113 {
114         struct idr_layer *hint = rcu_dereference_raw(idr->hint);
115 
116         if (hint && (id & ~IDR_MASK) == hint->prefix)
117                 return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
118 
119         return idr_find_slowpath(idr, id);
120 }
121 
122 /**
123  * idr_for_each_entry - iterate over an idr's elements of a given type
124  * @idp:     idr handle
125  * @entry:   the type * to use as cursor
126  * @id:      id entry's key
127  *
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.
131  */
132 #define idr_for_each_entry(idp, entry, id)                      \
133         for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
134 
135 /*
136  * Don't use the following functions.  These exist only to suppress
137  * deprecated warnings on EXPORT_SYMBOL()s.
138  */
139 int __idr_pre_get(struct idr *idp, gfp_t gfp_mask);
140 int __idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
141 void __idr_remove_all(struct idr *idp);
142 
143 /**
144  * idr_pre_get - reserve resources for idr allocation
145  * @idp:        idr handle
146  * @gfp_mask:   memory allocation flags
147  *
148  * Part of old alloc interface.  This is going away.  Use
149  * idr_preload[_end]() and idr_alloc() instead.
150  */
151 static inline int __deprecated idr_pre_get(struct idr *idp, gfp_t gfp_mask)
152 {
153         return __idr_pre_get(idp, gfp_mask);
154 }
155 
156 /**
157  * idr_get_new_above - allocate new idr entry above or equal to a start id
158  * @idp: idr handle
159  * @ptr: pointer you want associated with the id
160  * @starting_id: id to start search at
161  * @id: pointer to the allocated handle
162  *
163  * Part of old alloc interface.  This is going away.  Use
164  * idr_preload[_end]() and idr_alloc() instead.
165  */
166 static inline int __deprecated idr_get_new_above(struct idr *idp, void *ptr,
167                                                  int starting_id, int *id)
168 {
169         return __idr_get_new_above(idp, ptr, starting_id, id);
170 }
171 
172 /**
173  * idr_get_new - allocate new idr entry
174  * @idp: idr handle
175  * @ptr: pointer you want associated with the id
176  * @id: pointer to the allocated handle
177  *
178  * Part of old alloc interface.  This is going away.  Use
179  * idr_preload[_end]() and idr_alloc() instead.
180  */
181 static inline int __deprecated idr_get_new(struct idr *idp, void *ptr, int *id)
182 {
183         return __idr_get_new_above(idp, ptr, 0, id);
184 }
185 
186 /**
187  * idr_remove_all - remove all ids from the given idr tree
188  * @idp: idr handle
189  *
190  * If you're trying to destroy @idp, calling idr_destroy() is enough.
191  * This is going away.  Don't use.
192  */
193 static inline void __deprecated idr_remove_all(struct idr *idp)
194 {
195         __idr_remove_all(idp);
196 }
197 
198 /*
199  * IDA - IDR based id allocator, use when translation from id to
200  * pointer isn't necessary.
201  *
202  * IDA_BITMAP_LONGS is calculated to be one less to accommodate
203  * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
204  */
205 #define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
206 #define IDA_BITMAP_LONGS        (IDA_CHUNK_SIZE / sizeof(long) - 1)
207 #define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
208 
209 struct ida_bitmap {
210         long                    nr_busy;
211         unsigned long           bitmap[IDA_BITMAP_LONGS];
212 };
213 
214 struct ida {
215         struct idr              idr;
216         struct ida_bitmap       *free_bitmap;
217 };
218 
219 #define IDA_INIT(name)          { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
220 #define DEFINE_IDA(name)        struct ida name = IDA_INIT(name)
221 
222 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
223 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
224 void ida_remove(struct ida *ida, int id);
225 void ida_destroy(struct ida *ida);
226 void ida_init(struct ida *ida);
227 
228 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
229                    gfp_t gfp_mask);
230 void ida_simple_remove(struct ida *ida, unsigned int id);
231 
232 /**
233  * ida_get_new - allocate new ID
234  * @ida:        idr handle
235  * @p_id:       pointer to the allocated handle
236  *
237  * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
238  */
239 static inline int ida_get_new(struct ida *ida, int *p_id)
240 {
241         return ida_get_new_above(ida, 0, p_id);
242 }
243 
244 void __init idr_init_cache(void);
245 
246 #endif /* __IDR_H__ */
247 

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