1 /* 2 * include/linux/idr.h 3 * 4 * 2002-10-18 written by Jim Houston jim.houston@ccur.com 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 #if BITS_PER_LONG == 32 21 # define IDR_BITS 5 22 # define IDR_FULL 0xfffffffful 23 /* We can only use two of the bits in the top level because there is 24 only one possible bit in the top level (5 bits * 7 levels = 35 25 bits, but you only use 31 bits in the id). */ 26 # define TOP_LEVEL_FULL (IDR_FULL >> 30) 27 #elif BITS_PER_LONG == 64 28 # define IDR_BITS 6 29 # define IDR_FULL 0xfffffffffffffffful 30 /* We can only use two of the bits in the top level because there is 31 only one possible bit in the top level (6 bits * 6 levels = 36 32 bits, but you only use 31 bits in the id). */ 33 # define TOP_LEVEL_FULL (IDR_FULL >> 62) 34 #else 35 # error "BITS_PER_LONG is not 32 or 64" 36 #endif 37 38 #define IDR_SIZE (1 << IDR_BITS) 39 #define IDR_MASK ((1 << IDR_BITS)-1) 40 41 #define MAX_ID_SHIFT (sizeof(int)*8 - 1) 42 #define MAX_ID_BIT (1U << MAX_ID_SHIFT) 43 #define MAX_ID_MASK (MAX_ID_BIT - 1) 44 45 /* Leave the possibility of an incomplete final layer */ 46 #define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS 47 48 /* Number of id_layer structs to leave in free list */ 49 #define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL 50 51 struct idr_layer { 52 unsigned long bitmap; /* A zero bit means "space here" */ 53 struct idr_layer __rcu *ary[1<<IDR_BITS]; 54 int count; /* When zero, we can release it */ 55 int layer; /* distance from leaf */ 56 struct rcu_head rcu_head; 57 }; 58 59 struct idr { 60 struct idr_layer __rcu *top; 61 struct idr_layer *id_free; 62 int layers; /* only valid without concurrent changes */ 63 int id_free_cnt; 64 spinlock_t lock; 65 }; 66 67 #define IDR_INIT(name) \ 68 { \ 69 .top = NULL, \ 70 .id_free = NULL, \ 71 .layers = 0, \ 72 .id_free_cnt = 0, \ 73 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ 74 } 75 #define DEFINE_IDR(name) struct idr name = IDR_INIT(name) 76 77 /* Actions to be taken after a call to _idr_sub_alloc */ 78 #define IDR_NEED_TO_GROW -2 79 #define IDR_NOMORE_SPACE -3 80 81 #define _idr_rc_to_errno(rc) ((rc) == -1 ? -EAGAIN : -ENOSPC) 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(struct idr *idp, int id); 105 int idr_pre_get(struct idr *idp, gfp_t gfp_mask); 106 int idr_get_new(struct idr *idp, void *ptr, int *id); 107 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id); 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_remove_all(struct idr *idp); 114 void idr_destroy(struct idr *idp); 115 void idr_init(struct idr *idp); 116 117 118 /* 119 * IDA - IDR based id allocator, use when translation from id to 120 * pointer isn't necessary. 121 * 122 * IDA_BITMAP_LONGS is calculated to be one less to accommodate 123 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes. 124 */ 125 #define IDA_CHUNK_SIZE 128 /* 128 bytes per chunk */ 126 #define IDA_BITMAP_LONGS (IDA_CHUNK_SIZE / sizeof(long) - 1) 127 #define IDA_BITMAP_BITS (IDA_BITMAP_LONGS * sizeof(long) * 8) 128 129 struct ida_bitmap { 130 long nr_busy; 131 unsigned long bitmap[IDA_BITMAP_LONGS]; 132 }; 133 134 struct ida { 135 struct idr idr; 136 struct ida_bitmap *free_bitmap; 137 }; 138 139 #define IDA_INIT(name) { .idr = IDR_INIT(name), .free_bitmap = NULL, } 140 #define DEFINE_IDA(name) struct ida name = IDA_INIT(name) 141 142 int ida_pre_get(struct ida *ida, gfp_t gfp_mask); 143 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id); 144 int ida_get_new(struct ida *ida, int *p_id); 145 void ida_remove(struct ida *ida, int id); 146 void ida_destroy(struct ida *ida); 147 void ida_init(struct ida *ida); 148 149 void __init idr_init_cache(void); 150 151 #endif /* __IDR_H__ */ 152