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         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         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
  75 void *idr_find_slowpath(struct idr *idp, int id);
  76 void idr_preload(gfp_t gfp_mask);
  77 int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
  78 int idr_for_each(struct idr *idp,
  79                  int (*fn)(int id, void *p, void *data), void *data);
  80 void *idr_get_next(struct idr *idp, int *nextid);
  81 void *idr_replace(struct idr *idp, void *ptr, int id);
  82 void idr_remove(struct idr *idp, int id);
  83 void idr_free(struct idr *idp, int id);
  84 void idr_destroy(struct idr *idp);
  85 void 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  */
  93 static 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  */
 110 static 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  */
 135 int __idr_pre_get(struct idr *idp, gfp_t gfp_mask);
 136 int __idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
 137 void __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  */
 147 static 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  */
 162 static 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  */
 177 static 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  */
 189 static 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
 205 struct ida_bitmap {
 206         long                    nr_busy;
 207         unsigned long           bitmap[IDA_BITMAP_LONGS];
 208 };
 209
 210 struct 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
 218 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 219 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
 220 void ida_remove(struct ida *ida, int id);
 221 void ida_destroy(struct ida *ida);
 222 void ida_init(struct ida *ida);
 223
 224 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 225                    gfp_t gfp_mask);
 226 void 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  */
 235 static inline int ida_get_new(struct ida *ida, int *p_id)
 236 {
 237         return ida_get_new_above(ida, 0, p_id);
 238 }
 239
 240 void __init idr_init_cache(void);
 241
 242 #endif /* __IDR_H__ */