linux/include/linux/idr.h
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   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/*
  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
  30struct 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
  39struct 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
  75void *idr_find_slowpath(struct idr *idp, int id);
  76void idr_preload(gfp_t gfp_mask);
  77int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
  78int idr_for_each(struct idr *idp,
  79                 int (*fn)(int id, void *p, void *data), void *data);
  80void *idr_get_next(struct idr *idp, int *nextid);
  81void *idr_replace(struct idr *idp, void *ptr, int id);
  82void idr_remove(struct idr *idp, int id);
  83void idr_free(struct idr *idp, int id);
  84void idr_destroy(struct idr *idp);
  85void idr_init(struct idr *idp);
  86
  87/**
  88 * idr_preload_end - end preload section started with idr_preload()
  89 *
  90 * Each idr_preload() should be matched with an invocation of this
  91 * function.  See idr_preload() for details.
  92 */
  93static inline void idr_preload_end(void)
  94{
  95        preempt_enable();
  96}
  97
  98/**
  99 * idr_find - return pointer for given id
 100 * @idr: idr handle
 101 * @id: lookup key
 102 *
 103 * Return the pointer given the id it has been registered with.  A %NULL
 104 * return indicates that @id is not valid or you passed %NULL in
 105 * idr_get_new().
 106 *
 107 * This function can be called under rcu_read_lock(), given that the leaf
 108 * pointers lifetimes are correctly managed.
 109 */
 110static inline void *idr_find(struct idr *idr, int id)
 111{
 112        struct idr_layer *hint = rcu_dereference_raw(idr->hint);
 113
 114        if (hint && (id & ~IDR_MASK) == hint->prefix)
 115                return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
 116
 117        return idr_find_slowpath(idr, id);
 118}
 119
 120/**
 121 * idr_for_each_entry - iterate over an idr's elements of a given type
 122 * @idp:     idr handle
 123 * @entry:   the type * to use as cursor
 124 * @id:      id entry's key
 125 */
 126#define idr_for_each_entry(idp, entry, id)                              \
 127        for (id = 0, entry = (typeof(entry))idr_get_next((idp), &(id)); \
 128             entry != NULL;                                             \
 129             ++id, entry = (typeof(entry))idr_get_next((idp), &(id)))
 130
 131/*
 132 * Don't use the following functions.  These exist only to suppress
 133 * deprecated warnings on EXPORT_SYMBOL()s.
 134 */
 135int __idr_pre_get(struct idr *idp, gfp_t gfp_mask);
 136int __idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
 137void __idr_remove_all(struct idr *idp);
 138
 139/**
 140 * idr_pre_get - reserve resources for idr allocation
 141 * @idp:        idr handle
 142 * @gfp_mask:   memory allocation flags
 143 *
 144 * Part of old alloc interface.  This is going away.  Use
 145 * idr_preload[_end]() and idr_alloc() instead.
 146 */
 147static inline int __deprecated idr_pre_get(struct idr *idp, gfp_t gfp_mask)
 148{
 149        return __idr_pre_get(idp, gfp_mask);
 150}
 151
 152/**
 153 * idr_get_new_above - allocate new idr entry above or equal to a start id
 154 * @idp: idr handle
 155 * @ptr: pointer you want associated with the id
 156 * @starting_id: id to start search at
 157 * @id: pointer to the allocated handle
 158 *
 159 * Part of old alloc interface.  This is going away.  Use
 160 * idr_preload[_end]() and idr_alloc() instead.
 161 */
 162static inline int __deprecated idr_get_new_above(struct idr *idp, void *ptr,
 163                                                 int starting_id, int *id)
 164{
 165        return __idr_get_new_above(idp, ptr, starting_id, id);
 166}
 167
 168/**
 169 * idr_get_new - allocate new idr entry
 170 * @idp: idr handle
 171 * @ptr: pointer you want associated with the id
 172 * @id: pointer to the allocated handle
 173 *
 174 * Part of old alloc interface.  This is going away.  Use
 175 * idr_preload[_end]() and idr_alloc() instead.
 176 */
 177static inline int __deprecated idr_get_new(struct idr *idp, void *ptr, int *id)
 178{
 179        return __idr_get_new_above(idp, ptr, 0, id);
 180}
 181
 182/**
 183 * idr_remove_all - remove all ids from the given idr tree
 184 * @idp: idr handle
 185 *
 186 * If you're trying to destroy @idp, calling idr_destroy() is enough.
 187 * This is going away.  Don't use.
 188 */
 189static inline void __deprecated idr_remove_all(struct idr *idp)
 190{
 191        __idr_remove_all(idp);
 192}
 193
 194/*
 195 * IDA - IDR based id allocator, use when translation from id to
 196 * pointer isn't necessary.
 197 *
 198 * IDA_BITMAP_LONGS is calculated to be one less to accommodate
 199 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
 200 */
 201#define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
 202#define IDA_BITMAP_LONGS        (IDA_CHUNK_SIZE / sizeof(long) - 1)
 203#define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
 204
 205struct ida_bitmap {
 206        long                    nr_busy;
 207        unsigned long           bitmap[IDA_BITMAP_LONGS];
 208};
 209
 210struct ida {
 211        struct idr              idr;
 212        struct ida_bitmap       *free_bitmap;
 213};
 214
 215#define IDA_INIT(name)          { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
 216#define DEFINE_IDA(name)        struct ida name = IDA_INIT(name)
 217
 218int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 219int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
 220void ida_remove(struct ida *ida, int id);
 221void ida_destroy(struct ida *ida);
 222void ida_init(struct ida *ida);
 223
 224int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 225                   gfp_t gfp_mask);
 226void ida_simple_remove(struct ida *ida, unsigned int id);
 227
 228/**
 229 * ida_get_new - allocate new ID
 230 * @ida:        idr handle
 231 * @p_id:       pointer to the allocated handle
 232 *
 233 * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
 234 */
 235static inline int ida_get_new(struct ida *ida, int *p_id)
 236{
 237        return ida_get_new_above(ida, 0, p_id);
 238}
 239
 240void __init idr_init_cache(void);
 241
 242#endif /* __IDR_H__ */
 243
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