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 int idr_pre_get(struct idr *idp, gfp_t gfp_mask); 77 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id); 78 void idr_preload(gfp_t gfp_mask); 79 int idr_alloc(struct idr *idp, 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 * @idp: 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_get_new - allocate new idr entry 124 * @idp: idr handle 125 * @ptr: pointer you want associated with the id 126 * @id: pointer to the allocated handle 127 * 128 * Simple wrapper around idr_get_new_above() w/ @starting_id of zero. 129 */ 130 static inline int idr_get_new(struct idr *idp, void *ptr, int *id) 131 { 132 return idr_get_new_above(idp, ptr, 0, id); 133 } 134 135 /** 136 * idr_for_each_entry - iterate over an idr's elements of a given type 137 * @idp: idr handle 138 * @entry: the type * to use as cursor 139 * @id: id entry's key 140 */ 141 #define idr_for_each_entry(idp, entry, id) \ 142 for (id = 0, entry = (typeof(entry))idr_get_next((idp), &(id)); \ 143 entry != NULL; \ 144 ++id, entry = (typeof(entry))idr_get_next((idp), &(id))) 145 146 void __idr_remove_all(struct idr *idp); /* don't use */ 147 148 /** 149 * idr_remove_all - remove all ids from the given idr tree 150 * @idp: idr handle 151 * 152 * If you're trying to destroy @idp, calling idr_destroy() is enough. 153 * This is going away. Don't use. 154 */ 155 static inline void __deprecated idr_remove_all(struct idr *idp) 156 { 157 __idr_remove_all(idp); 158 } 159 160 /* 161 * IDA - IDR based id allocator, use when translation from id to 162 * pointer isn't necessary. 163 * 164 * IDA_BITMAP_LONGS is calculated to be one less to accommodate 165 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes. 166 */ 167 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ 168 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1) 169 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) 170 171 struct ida_bitmap { 172 long nr_busy; 173 unsigned long bitmap[IDA_BITMAP_LONGS]; 174 }; 175 176 struct ida { 177 struct idr idr; 178 struct ida_bitmap *free_bitmap; 179 }; 180 181 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, } 182 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name) 183 184 int ida_pre_get(struct ida *ida, gfp_t gfp_mask); 185 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id); 186 void ida_remove(struct ida *ida, int id); 187 void ida_destroy(struct ida *ida); 188 void ida_init(struct ida *ida); 189 190 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end, 191 gfp_t gfp_mask); 192 void ida_simple_remove(struct ida *ida, unsigned int id); 193 194 /** 195 * ida_get_new - allocate new ID 196 * @ida: idr handle 197 * @p_id: pointer to the allocated handle 198 * 199 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero. 200 */ 201 static inline int ida_get_new(struct ida *ida, int *p_id) 202 { 203 return ida_get_new_above(ida, 0, p_id); 204 } 205 206 void __init idr_init_cache(void); 207 208 #endif /* __IDR_H__ */ 209