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