1 /* 2 * include/linux/idr.h 3 * 4 * 2002-10-18 written by Jim Houston [email protected] 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 spinlock_t lock; 46 }; 47 48 #define IDR_INIT(name) \ 49 { \ 50 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ 51 } 52 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name) 53 54 /** 55 * DOC: idr sync 56 * idr synchronization (stolen from radix-tree.h) 57 * 58 * idr_find() is able to be called locklessly, using RCU. The caller must 59 * ensure calls to this function are made within rcu_read_lock() regions. 60 * Other readers (lock-free or otherwise) and modifications may be running 61 * concurrently. 62 * 63 * It is still required that the caller manage the synchronization and 64 * lifetimes of the items. So if RCU lock-free lookups are used, typically 65 * this would mean that the items have their own locks, or are amenable to 66 * lock-free access; and that the items are freed by RCU (or only freed after 67 * having been deleted from the idr tree *and* a synchronize_rcu() grace 68 * period). 69 */ 70 71 /* 72 * This is what we export. 73 */ 74 75 void *idr_find_slowpath(struct idr *idp, int id); 76 void idr_preload(gfp_t gfp_mask); 77 int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask); 78 int idr_for_each(struct idr *idp, 79 int (*fn)(int id, void *p, void *data), void *data); 80 void *idr_get_next(struct idr *idp, int *nextid); 81 void *idr_replace(struct idr *idp, void *ptr, int id); 82 void idr_remove(struct idr *idp, int id); 83 void idr_free(struct idr *idp, int id); 84 void idr_destroy(struct idr *idp); 85 void idr_init(struct idr *idp); 86 87 /** 88 * idr_preload_end - end preload section started with idr_preload() 89 * 90 * Each idr_preload() should be matched with an invocation of this 91 * function. See idr_preload() for details. 92 */ 93 static inline void idr_preload_end(void) 94 { 95 preempt_enable(); 96 } 97 98 /** 99 * idr_find - return pointer for given id 100 * @idr: idr handle 101 * @id: lookup key 102 * 103 * Return the pointer given the id it has been registered with. A %NULL 104 * return indicates that @id is not valid or you passed %NULL in 105 * idr_get_new(). 106 * 107 * This function can be called under rcu_read_lock(), given that the leaf 108 * pointers lifetimes are correctly managed. 109 */ 110 static inline void *idr_find(struct idr *idr, int id) 111 { 112 struct idr_layer *hint = rcu_dereference_raw(idr->hint); 113 114 if (hint && (id & ~IDR_MASK) == hint->prefix) 115 return rcu_dereference_raw(hint->ary[id & IDR_MASK]); 116 117 return idr_find_slowpath(idr, id); 118 } 119 120 /** 121 * idr_for_each_entry - iterate over an idr's elements of a given type 122 * @idp: idr handle 123 * @entry: the type * to use as cursor 124 * @id: id entry's key 125 */ 126 #define idr_for_each_entry(idp, entry, id) \ 127 for (id = 0, entry = (typeof(entry))idr_get_next((idp), &(id)); \ 128 entry != NULL; \ 129 ++id, entry = (typeof(entry))idr_get_next((idp), &(id))) 130 131 /* 132 * Don't use the following functions. These exist only to suppress 133 * deprecated warnings on EXPORT_SYMBOL()s. 134 */ 135 int __idr_pre_get(struct idr *idp, gfp_t gfp_mask); 136 int __idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id); 137 void __idr_remove_all(struct idr *idp); 138 139 /** 140 * idr_pre_get - reserve resources for idr allocation 141 * @idp: idr handle 142 * @gfp_mask: memory allocation flags 143 * 144 * Part of old alloc interface. This is going away. Use 145 * idr_preload[_end]() and idr_alloc() instead. 146 */ 147 static inline int __deprecated idr_pre_get(struct idr *idp, gfp_t gfp_mask) 148 { 149 return __idr_pre_get(idp, gfp_mask); 150 } 151 152 /** 153 * idr_get_new_above - allocate new idr entry above or equal to a start id 154 * @idp: idr handle 155 * @ptr: pointer you want associated with the id 156 * @starting_id: id to start search at 157 * @id: pointer to the allocated handle 158 * 159 * Part of old alloc interface. This is going away. Use 160 * idr_preload[_end]() and idr_alloc() instead. 161 */ 162 static inline int __deprecated idr_get_new_above(struct idr *idp, void *ptr, 163 int starting_id, int *id) 164 { 165 return __idr_get_new_above(idp, ptr, starting_id, id); 166 } 167 168 /** 169 * idr_get_new - allocate new idr entry 170 * @idp: idr handle 171 * @ptr: pointer you want associated with the id 172 * @id: pointer to the allocated handle 173 * 174 * Part of old alloc interface. This is going away. Use 175 * idr_preload[_end]() and idr_alloc() instead. 176 */ 177 static inline int __deprecated idr_get_new(struct idr *idp, void *ptr, int *id) 178 { 179 return __idr_get_new_above(idp, ptr, 0, id); 180 } 181 182 /** 183 * idr_remove_all - remove all ids from the given idr tree 184 * @idp: idr handle 185 * 186 * If you're trying to destroy @idp, calling idr_destroy() is enough. 187 * This is going away. Don't use. 188 */ 189 static inline void __deprecated idr_remove_all(struct idr *idp) 190 { 191 __idr_remove_all(idp); 192 } 193 194 /* 195 * IDA - IDR based id allocator, use when translation from id to 196 * pointer isn't necessary. 197 * 198 * IDA_BITMAP_LONGS is calculated to be one less to accommodate 199 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes. 200 */ 201 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ 202 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1) 203 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) 204 205 struct ida_bitmap { 206 long nr_busy; 207 unsigned long bitmap[IDA_BITMAP_LONGS]; 208 }; 209 210 struct ida { 211 struct idr idr; 212 struct ida_bitmap *free_bitmap; 213 }; 214 215 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, } 216 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name) 217 218 int ida_pre_get(struct ida *ida, gfp_t gfp_mask); 219 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id); 220 void ida_remove(struct ida *ida, int id); 221 void ida_destroy(struct ida *ida); 222 void ida_init(struct ida *ida); 223 224 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end, 225 gfp_t gfp_mask); 226 void ida_simple_remove(struct ida *ida, unsigned int id); 227 228 /** 229 * ida_get_new - allocate new ID 230 * @ida: idr handle 231 * @p_id: pointer to the allocated handle 232 * 233 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero. 234 */ 235 static inline int ida_get_new(struct ida *ida, int *p_id) 236 { 237 return ida_get_new_above(ida, 0, p_id); 238 } 239 240 void __init idr_init_cache(void); 241 242 #endif /* __IDR_H__ */ 243