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 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_destroy(struct idr *idp); 86 void idr_init(struct idr *idp); 87 bool idr_is_empty(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 * IDA - IDR based id allocator, use when translation from id to 137 * pointer isn't necessary. 138 * 139 * IDA_BITMAP_LONGS is calculated to be one less to accommodate 140 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes. 141 */ 142 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ 143 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1) 144 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) 145 146 struct ida_bitmap { 147 long nr_busy; 148 unsigned long bitmap[IDA_BITMAP_LONGS]; 149 }; 150 151 struct ida { 152 struct idr idr; 153 struct ida_bitmap *free_bitmap; 154 }; 155 156 #define IDA_INIT(name) { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, } 157 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name) 158 159 int ida_pre_get(struct ida *ida, gfp_t gfp_mask); 160 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id); 161 void ida_remove(struct ida *ida, int id); 162 void ida_destroy(struct ida *ida); 163 void ida_init(struct ida *ida); 164 165 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end, 166 gfp_t gfp_mask); 167 void ida_simple_remove(struct ida *ida, unsigned int id); 168 169 /** 170 * ida_get_new - allocate new ID 171 * @ida: idr handle 172 * @p_id: pointer to the allocated handle 173 * 174 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero. 175 */ 176 static inline int ida_get_new(struct ida *ida, int *p_id) 177 { 178 return ida_get_new_above(ida, 0, p_id); 179 } 180 181 void __init idr_init_cache(void); 182 183 #endif /* __IDR_H__ */ 184