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  * Using 6 bits at each layer allows us to allocate 7 layers out of each page.
  22  * 8 bits only gave us 3 layers out of every pair of pages, which is less
  23  * efficient except for trees with a largest element between 192-255 inclusive.
  24  */
  25 #define IDR_BITS 6
  26 #define IDR_SIZE (1 << IDR_BITS)
  27 #define IDR_MASK ((1 << IDR_BITS)-1)
  28
  29 struct idr_layer {
  30         int                     prefix; /* the ID prefix of this idr_layer */
  31         int                     layer;  /* distance from leaf */
  32         struct idr_layer __rcu  *ary[1<<IDR_BITS];
  33         int                     count;  /* When zero, we can release it */
  34         union {
  35                 /* A zero bit means "space here" */
  36                 DECLARE_BITMAP(bitmap, IDR_SIZE);
  37                 struct rcu_head         rcu_head;
  38         };
  39 };
  40
  41 struct idr {
  42         struct idr_layer __rcu  *hint;  /* the last layer allocated from */
  43         struct idr_layer __rcu  *top;
  44         int                     layers; /* only valid w/o concurrent changes */
  45         int                     cur;    /* current pos for cyclic allocation */
  46         spinlock_t              lock;
  47         int                     id_free_cnt;
  48         struct idr_layer        *id_free;
  49 };
  50
  51 #define IDR_INIT(name)                                                  \
  52 {                                                                       \
  53         .lock                   = __SPIN_LOCK_UNLOCKED(name.lock),      \
  54 }
  55 #define DEFINE_IDR(name)        struct idr name = IDR_INIT(name)
  56
  57 /**
  58  * idr_get_cursor - Return the current position of the cyclic allocator
  59  * @idr: idr handle
  60  *
  61  * The value returned is the value that will be next returned from
  62  * idr_alloc_cyclic() if it is free (otherwise the search will start from
  63  * this position).
  64  */
  65 static inline unsigned int idr_get_cursor(struct idr *idr)
  66 {
  67         return READ_ONCE(idr->cur);
  68 }
  69
  70 /**
  71  * idr_set_cursor - Set the current position of the cyclic allocator
  72  * @idr: idr handle
  73  * @val: new position
  74  *
  75  * The next call to idr_alloc_cyclic() will return @val if it is free
  76  * (otherwise the search will start from this position).
  77  */
  78 static inline void idr_set_cursor(struct idr *idr, unsigned int val)
  79 {
  80         WRITE_ONCE(idr->cur, val);
  81 }
  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_slowpath(struct idr *idp, int id);
 105 void idr_preload(gfp_t gfp_mask);
 106 int idr_alloc(struct idr *idp, void *ptr, int start, int end, gfp_t gfp_mask);
 107 int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask);
 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_destroy(struct idr *idp);
 114 void idr_init(struct idr *idp);
 115 bool idr_is_empty(struct idr *idp);
 116
 117 /**
 118  * idr_preload_end - end preload section started with idr_preload()
 119  *
 120  * Each idr_preload() should be matched with an invocation of this
 121  * function.  See idr_preload() for details.
 122  */
 123 static inline void idr_preload_end(void)
 124 {
 125         preempt_enable();
 126 }
 127
 128 /**
 129  * idr_find - return pointer for given id
 130  * @idr: idr handle
 131  * @id: lookup key
 132  *
 133  * Return the pointer given the id it has been registered with.  A %NULL
 134  * return indicates that @id is not valid or you passed %NULL in
 135  * idr_get_new().
 136  *
 137  * This function can be called under rcu_read_lock(), given that the leaf
 138  * pointers lifetimes are correctly managed.
 139  */
 140 static inline void *idr_find(struct idr *idr, int id)
 141 {
 142         struct idr_layer *hint = rcu_dereference_raw(idr->hint);
 143
 144         if (hint && (id & ~IDR_MASK) == hint->prefix)
 145                 return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
 146
 147         return idr_find_slowpath(idr, id);
 148 }
 149
 150 /**
 151  * idr_for_each_entry - iterate over an idr's elements of a given type
 152  * @idp:     idr handle
 153  * @entry:   the type * to use as cursor
 154  * @id:      id entry's key
 155  *
 156  * @entry and @id do not need to be initialized before the loop, and
 157  * after normal terminatinon @entry is left with the value NULL.  This
 158  * is convenient for a "not found" value.
 159  */
 160 #define idr_for_each_entry(idp, entry, id)                      \
 161         for (id = 0; ((entry) = idr_get_next(idp, &(id))) != NULL; ++id)
 162
 163 /**
 164  * idr_for_each_entry - continue iteration over an idr's elements of a given type
 165  * @idp:     idr handle
 166  * @entry:   the type * to use as cursor
 167  * @id:      id entry's key
 168  *
 169  * Continue to iterate over list of given type, continuing after
 170  * the current position.
 171  */
 172 #define idr_for_each_entry_continue(idp, entry, id)                     \
 173         for ((entry) = idr_get_next((idp), &(id));                      \
 174              entry;                                                     \
 175              ++id, (entry) = idr_get_next((idp), &(id)))
 176
 177 /*
 178  * IDA - IDR based id allocator, use when translation from id to
 179  * pointer isn't necessary.
 180  *
 181  * IDA_BITMAP_LONGS is calculated to be one less to accommodate
 182  * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
 183  */
 184 #define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
 185 #define IDA_BITMAP_LONGS        (IDA_CHUNK_SIZE / sizeof(long) - 1)
 186 #define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
 187
 188 struct ida_bitmap {
 189         long                    nr_busy;
 190         unsigned long           bitmap[IDA_BITMAP_LONGS];
 191 };
 192
 193 struct ida {
 194         struct idr              idr;
 195         struct ida_bitmap       *free_bitmap;
 196 };
 197
 198 #define IDA_INIT(name)          { .idr = IDR_INIT((name).idr), .free_bitmap = NULL, }
 199 #define DEFINE_IDA(name)        struct ida name = IDA_INIT(name)
 200
 201 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 202 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
 203 void ida_remove(struct ida *ida, int id);
 204 void ida_destroy(struct ida *ida);
 205 void ida_init(struct ida *ida);
 206
 207 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 208                    gfp_t gfp_mask);
 209 void ida_simple_remove(struct ida *ida, unsigned int id);
 210
 211 /**
 212  * ida_get_new - allocate new ID
 213  * @ida:        idr handle
 214  * @p_id:       pointer to the allocated handle
 215  *
 216  * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
 217  */
 218 static inline int ida_get_new(struct ida *ida, int *p_id)
 219 {
 220         return ida_get_new_above(ida, 0, p_id);
 221 }
 222
 223 static inline bool ida_is_empty(struct ida *ida)
 224 {
 225         return idr_is_empty(&ida->idr);
 226 }
 227
 228 void __init idr_init_cache(void);
 229
 230 #endif /* __IDR_H__ */