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 int layer; /* distance from leaf */ 33 struct idr_layer __rcu *ary[1<<IDR_BITS]; 34 int count; /* When zero, we can release it */ 35 union { 36 /* A zero bit means "space here" */ 37 DECLARE_BITMAP(bitmap, IDR_SIZE); 38 struct rcu_head rcu_head; 39 }; 40 }; 41 42 struct idr { 43 struct idr_layer __rcu *hint; /* the last layer allocated from */ 44 struct idr_layer __rcu *top; 45 int layers; /* only valid w/o concurrent changes */ 46 int cur; /* current pos for cyclic allocation */ 47 spinlock_t lock; 48 int id_free_cnt; 49 struct idr_layer *id_free; 50 }; 51 52 #define IDR_INIT(name) \ 53 { \ 54 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ 55 } 56 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name) 57 58 /** 59 * DOC: idr sync 60 * idr synchronization (stolen from radix-tree.h) 61 * 62 * idr_find() is able to be called locklessly, using RCU. The caller must 63 * ensure calls to this function are made within rcu_read_lock() regions. 64 * Other readers (lock-free or otherwise) and modifications may be running 65 * concurrently. 66 * 67 * It is still required that the caller manage the synchronization and 68 * lifetimes of the items. So if RCU lock-free lookups are used, typically 69 * this would mean that the items have their own locks, or are amenable to 70 * lock-free access; and that the items are freed by RCU (or only freed after 71 * having been deleted from the idr tree *and* a synchronize_rcu() grace 72 * period). 73 */ 74 75 /* 76 * This is what we export. 77 */ 78 79 void *idr_find_slowpath(struct idr *idp, int id); 80 void idr_preload(gfp_t gfp_mask); 81 int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask); 82 int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask); 83 int idr_for_each(struct idr *idp, 84 int (*fn)(int id, void *p, void *data), void *data); 85 void *idr_get_next(struct idr *idp, int *nextid); 86 void *idr_replace(struct idr *idp, void *ptr, int id); 87 void idr_remove(struct idr *idp, int id); 88 void idr_destroy(struct idr *idp); 89 void idr_init(struct idr *idp); 90 bool idr_is_empty(struct idr *idp); 91 92 /** 93 * idr_preload_end - end preload section started with idr_preload() 94 * 95 * Each idr_preload() should be matched with an invocation of this 96 * function. See idr_preload() for details. 97 */ 98 static inline void idr_preload_end(void) 99 { 100 preempt_enable(); 101 } 102 103 /** 104 * idr_find - return pointer for given id 105 * @idr: idr handle 106 * @id: lookup key 107 * 108 * Return the pointer given the id it has been registered with. A %NULL 109 * return indicates that @id is not valid or you passed %NULL in 110 * idr_get_new(). 111 * 112 * This function can be called under rcu_read_lock(), given that the leaf 113 * pointers lifetimes are correctly managed. 114 */ 115 static inline void *idr_find(struct idr *idr, int id) 116 { 117 struct idr_layer *hint = rcu_dereference_raw(idr->hint); 118 119 if (hint && (id & ~IDR_MASK) == hint->prefix) 120 return rcu_dereference_raw(hint->ary[id & IDR_MASK]); 121 122 return idr_find_slowpath(idr, id); 123 } 124 125 /** 126 * idr_for_each_entry - iterate over an idr's elements of a given type 127 * @idp: idr handle 128 * @entry: the type * to use as cursor 129 * @id: id entry's key 130 * 131 * @entry and @id do not need to be initialized before the loop, and 132 * after normal terminatinon @entry is left with the value NULL. This 133 * is convenient for a "not found" value. 134 */ 135 #define idr_for_each_entry(idp, entry, id) \ 136 for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id) 137 138 /** 139 * idr_for_each_entry - continue iteration over an idr's elements of a given type 140 * @idp: idr handle 141 * @entry: the type * to use as cursor 142 * @id: id entry's key 143 * 144 * Continue to iterate over list of given type, continuing after 145 * the current position. 146 */ 147 #define idr_for_each_entry_continue(idp, entry, id) \ 148 for ((entry) = idr_get_next((idp), &(id)); \ 149 entry; \ 150 ++id, (entry) = idr_get_next((idp), &(id))) 151 152 /* 153 * IDA - IDR based id allocator, use when translation from id to 154 * pointer isn't necessary. 155 * 156 * IDA_BITMAP_LONGS is calculated to be one less to accommodate 157 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes. 158 */ 159 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ 160 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1) 161 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) 162 163 struct ida_bitmap { 164 long nr_busy; 165 unsigned long bitmap[IDA_BITMAP_LONGS]; 166 }; 167 168 struct ida { 169 struct idr idr; 170 struct ida_bitmap *free_bitmap; 171 }; 172 173 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, } 174 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name) 175 176 int ida_pre_get(struct ida *ida, gfp_t gfp_mask); 177 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id); 178 void ida_remove(struct ida *ida, int id); 179 void ida_destroy(struct ida *ida); 180 void ida_init(struct ida *ida); 181 182 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end, 183 gfp_t gfp_mask); 184 void ida_simple_remove(struct ida *ida, unsigned int id); 185 186 /** 187 * ida_get_new - allocate new ID 188 * @ida: idr handle 189 * @p_id: pointer to the allocated handle 190 * 191 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero. 192 */ 193 static inline int ida_get_new(struct ida *ida, int *p_id) 194 { 195 return ida_get_new_above(ida, 0, p_id); 196 } 197 198 void __init idr_init_cache(void); 199 200 #endif /* __IDR_H__ */ 201