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 * Using 6 bits at each layer allows us to allocate 7 layers out of each page. 22 * 8 bits only gave us 3 layers out of every pair of pages, which is less 23 * efficient except for trees with a largest element between 192-255 inclusive. 24 */ 25 #define IDR_BITS 6 26 #define IDR_SIZE (1 << IDR_BITS) 27 #define IDR_MASK ((1 << IDR_BITS)-1) 28 29 struct idr_layer { 30 int prefix; /* the ID prefix of this idr_layer */ 31 int layer; /* distance from leaf */ 32 struct idr_layer __rcu *ary[1<<IDR_BITS]; 33 int count; /* When zero, we can release it */ 34 union { 35 /* A zero bit means "space here" */ 36 DECLARE_BITMAP(bitmap, IDR_SIZE); 37 struct rcu_head rcu_head; 38 }; 39 }; 40 41 struct idr { 42 struct idr_layer __rcu *hint; /* the last layer allocated from */ 43 struct idr_layer __rcu *top; 44 int layers; /* only valid w/o concurrent changes */ 45 int cur; /* current pos for cyclic allocation */ 46 spinlock_t lock; 47 int id_free_cnt; 48 struct idr_layer *id_free; 49 }; 50 51 #define IDR_INIT(name) \ 52 { \ 53 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ 54 } 55 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name) 56 57 /** 58 * idr_get_cursor - Return the current position of the cyclic allocator 59 * @idr: idr handle 60 * 61 * The value returned is the value that will be next returned from 62 * idr_alloc_cyclic() if it is free (otherwise the search will start from 63 * this position). 64 */ 65 static inline unsigned int idr_get_cursor(struct idr *idr) 66 { 67 return READ_ONCE(idr->cur); 68 } 69 70 /** 71 * idr_set_cursor - Set the current position of the cyclic allocator 72 * @idr: idr handle 73 * @val: new position 74 * 75 * The next call to idr_alloc_cyclic() will return @val if it is free 76 * (otherwise the search will start from this position). 77 */ 78 static inline void idr_set_cursor(struct idr *idr, unsigned int val) 79 { 80 WRITE_ONCE(idr->cur, val); 81 } 82 83 /** 84 * DOC: idr sync 85 * idr synchronization (stolen from radix-tree.h) 86 * 87 * idr_find() is able to be called locklessly, using RCU. The caller must 88 * ensure calls to this function are made within rcu_read_lock() regions. 89 * Other readers (lock-free or otherwise) and modifications may be running 90 * concurrently. 91 * 92 * It is still required that the caller manage the synchronization and 93 * lifetimes of the items. So if RCU lock-free lookups are used, typically 94 * this would mean that the items have their own locks, or are amenable to 95 * lock-free access; and that the items are freed by RCU (or only freed after 96 * having been deleted from the idr tree *and* a synchronize_rcu() grace 97 * period). 98 */ 99 100 /* 101 * This is what we export. 102 */ 103 104 void *idr_find_slowpath(struct idr *idp, int id); 105 void idr_preload(gfp_t gfp_mask); 106 int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask); 107 int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask); 108 int idr_for_each(struct idr *idp, 109 int (*fn)(int id, void *p, void *data), void *data); 110 void *idr_get_next(struct idr *idp, int *nextid); 111 void *idr_replace(struct idr *idp, void *ptr, int id); 112 void idr_remove(struct idr *idp, int id); 113 void idr_destroy(struct idr *idp); 114 void idr_init(struct idr *idp); 115 bool idr_is_empty(struct idr *idp); 116 117 /** 118 * idr_preload_end - end preload section started with idr_preload() 119 * 120 * Each idr_preload() should be matched with an invocation of this 121 * function. See idr_preload() for details. 122 */ 123 static inline void idr_preload_end(void) 124 { 125 preempt_enable(); 126 } 127 128 /** 129 * idr_find - return pointer for given id 130 * @idr: idr handle 131 * @id: lookup key 132 * 133 * Return the pointer given the id it has been registered with. A %NULL 134 * return indicates that @id is not valid or you passed %NULL in 135 * idr_get_new(). 136 * 137 * This function can be called under rcu_read_lock(), given that the leaf 138 * pointers lifetimes are correctly managed. 139 */ 140 static inline void *idr_find(struct idr *idr, int id) 141 { 142 struct idr_layer *hint = rcu_dereference_raw(idr->hint); 143 144 if (hint && (id & ~IDR_MASK) == hint->prefix) 145 return rcu_dereference_raw(hint->ary[id & IDR_MASK]); 146 147 return idr_find_slowpath(idr, id); 148 } 149 150 /** 151 * idr_for_each_entry - iterate over an idr's elements of a given type 152 * @idp: idr handle 153 * @entry: the type * to use as cursor 154 * @id: id entry's key 155 * 156 * @entry and @id do not need to be initialized before the loop, and 157 * after normal terminatinon @entry is left with the value NULL. This 158 * is convenient for a "not found" value. 159 */ 160 #define idr_for_each_entry(idp, entry, id) \ 161 for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id) 162 163 /** 164 * idr_for_each_entry - continue iteration over an idr's elements of a given type 165 * @idp: idr handle 166 * @entry: the type * to use as cursor 167 * @id: id entry's key 168 * 169 * Continue to iterate over list of given type, continuing after 170 * the current position. 171 */ 172 #define idr_for_each_entry_continue(idp, entry, id) \ 173 for ((entry) = idr_get_next((idp), &(id)); \ 174 entry; \ 175 ++id, (entry) = idr_get_next((idp), &(id))) 176 177 /* 178 * IDA - IDR based id allocator, use when translation from id to 179 * pointer isn't necessary. 180 * 181 * IDA_BITMAP_LONGS is calculated to be one less to accommodate 182 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes. 183 */ 184 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ 185 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1) 186 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) 187 188 struct ida_bitmap { 189 long nr_busy; 190 unsigned long bitmap[IDA_BITMAP_LONGS]; 191 }; 192 193 struct ida { 194 struct idr idr; 195 struct ida_bitmap *free_bitmap; 196 }; 197 198 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, } 199 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name) 200 201 int ida_pre_get(struct ida *ida, gfp_t gfp_mask); 202 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id); 203 void ida_remove(struct ida *ida, int id); 204 void ida_destroy(struct ida *ida); 205 void ida_init(struct ida *ida); 206 207 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end, 208 gfp_t gfp_mask); 209 void ida_simple_remove(struct ida *ida, unsigned int id); 210 211 /** 212 * ida_get_new - allocate new ID 213 * @ida: idr handle 214 * @p_id: pointer to the allocated handle 215 * 216 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero. 217 */ 218 static inline int ida_get_new(struct ida *ida, int *p_id) 219 { 220 return ida_get_new_above(ida, 0, p_id); 221 } 222 223 static inline bool ida_is_empty(struct ida *ida) 224 { 225 return idr_is_empty(&ida->idr); 226 } 227 228 void __init idr_init_cache(void); 229 230 #endif /* __IDR_H__ */ 231