include/linux/idr.h

   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        *ary[1<<IDR_BITS];
  54         int                      count;  /* When zero, we can release it */
  55         struct rcu_head          rcu_head;
  56 };
  57
  58 struct idr {
  59         struct idr_layer *top;
  60         struct idr_layer *id_free;
  61         int               layers;
  62         int               id_free_cnt;
  63         spinlock_t        lock;
  64 };
  65
  66 #define IDR_INIT(name)                                          \
  67 {                                                               \
  68         .top            = NULL,                                 \
  69         .id_free        = NULL,                                 \
  70         .layers         = 0,                                    \
  71         .id_free_cnt    = 0,                                    \
  72         .lock           = __SPIN_LOCK_UNLOCKED(name.lock),      \
  73 }
  74 #define DEFINE_IDR(name)        struct idr name = IDR_INIT(name)
  75
  76 /* Actions to be taken after a call to _idr_sub_alloc */
  77 #define IDR_NEED_TO_GROW -2
  78 #define IDR_NOMORE_SPACE -3
  79
  80 #define _idr_rc_to_errno(rc) ((rc) == -1 ? -EAGAIN : -ENOSPC)
  81
  82 /**
  83  * idr synchronization (stolen from radix-tree.h)
  84  *
  85  * idr_find() is able to be called locklessly, using RCU. The caller must
  86  * ensure calls to this function are made within rcu_read_lock() regions.
  87  * Other readers (lock-free or otherwise) and modifications may be running
  88  * concurrently.
  89  *
  90  * It is still required that the caller manage the synchronization and
  91  * lifetimes of the items. So if RCU lock-free lookups are used, typically
  92  * this would mean that the items have their own locks, or are amenable to
  93  * lock-free access; and that the items are freed by RCU (or only freed after
  94  * having been deleted from the idr tree *and* a synchronize_rcu() grace
  95  * period).
  96  */
  97
  98 /*
  99  * This is what we export.
 100  */
 101
 102 void *idr_find(struct idr *idp, int id);
 103 int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
 104 int idr_get_new(struct idr *idp, void *ptr, int *id);
 105 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
 106 int idr_for_each(struct idr *idp,
 107                  int (*fn)(int id, void *p, void *data), void *data);
 108 void *idr_replace(struct idr *idp, void *ptr, int id);
 109 void idr_remove(struct idr *idp, int id);
 110 void idr_remove_all(struct idr *idp);
 111 void idr_destroy(struct idr *idp);
 112 void idr_init(struct idr *idp);
 113
 114
 115 /*
 116  * IDA - IDR based id allocator, use when translation from id to
 117  * pointer isn't necessary.
 118  */
 119 #define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
 120 #define IDA_BITMAP_LONGS        (128 / sizeof(long) - 1)
 121 #define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
 122
 123 struct ida_bitmap {
 124         long                    nr_busy;
 125         unsigned long           bitmap[IDA_BITMAP_LONGS];
 126 };
 127
 128 struct ida {
 129         struct idr              idr;
 130         struct ida_bitmap       *free_bitmap;
 131 };
 132
 133 #define IDA_INIT(name)          { .idr = IDR_INIT(name), .free_bitmap = NULL, }
 134 #define DEFINE_IDA(name)        struct ida name = IDA_INIT(name)
 135
 136 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 137 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
 138 int ida_get_new(struct ida *ida, int *p_id);
 139 void ida_remove(struct ida *ida, int id);
 140 void ida_destroy(struct ida *ida);
 141 void ida_init(struct ida *ida);
 142
 143 void __init idr_init_cache(void);
 144
 145 #endif /* __IDR_H__ */