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/radix-tree.h>
  16 #include <linux/gfp.h>
  17 #include <linux/percpu.h>
  18
  19 struct idr {
  20         struct radix_tree_root  idr_rt;
  21         unsigned int            idr_next;
  22 };
  23
  24 /*
  25  * The IDR API does not expose the tagging functionality of the radix tree
  26  * to users.  Use tag 0 to track whether a node has free space below it.
  27  */
  28 #define IDR_FREE        0
  29
  30 /* Set the IDR flag and the IDR_FREE tag */
  31 #define IDR_RT_MARKER           ((__force gfp_t)(3 << __GFP_BITS_SHIFT))
  32
  33 #define IDR_INIT                                                        \
  34 {                                                                       \
  35         .idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER)                        \
  36 }
  37 #define DEFINE_IDR(name)        struct idr name = IDR_INIT
  38
  39 /**
  40  * idr_get_cursor - Return the current position of the cyclic allocator
  41  * @idr: idr handle
  42  *
  43  * The value returned is the value that will be next returned from
  44  * idr_alloc_cyclic() if it is free (otherwise the search will start from
  45  * this position).
  46  */
  47 static inline unsigned int idr_get_cursor(const struct idr *idr)
  48 {
  49         return READ_ONCE(idr->idr_next);
  50 }
  51
  52 /**
  53  * idr_set_cursor - Set the current position of the cyclic allocator
  54  * @idr: idr handle
  55  * @val: new position
  56  *
  57  * The next call to idr_alloc_cyclic() will return @val if it is free
  58  * (otherwise the search will start from this position).
  59  */
  60 static inline void idr_set_cursor(struct idr *idr, unsigned int val)
  61 {
  62         WRITE_ONCE(idr->idr_next, val);
  63 }
  64
  65 /**
  66  * DOC: idr sync
  67  * idr synchronization (stolen from radix-tree.h)
  68  *
  69  * idr_find() is able to be called locklessly, using RCU. The caller must
  70  * ensure calls to this function are made within rcu_read_lock() regions.
  71  * Other readers (lock-free or otherwise) and modifications may be running
  72  * concurrently.
  73  *
  74  * It is still required that the caller manage the synchronization and
  75  * lifetimes of the items. So if RCU lock-free lookups are used, typically
  76  * this would mean that the items have their own locks, or are amenable to
  77  * lock-free access; and that the items are freed by RCU (or only freed after
  78  * having been deleted from the idr tree *and* a synchronize_rcu() grace
  79  * period).
  80  */
  81
  82 void idr_preload(gfp_t gfp_mask);
  83 int idr_alloc(struct idr *, void *entry, int start, int end, gfp_t);
  84 int idr_alloc_cyclic(struct idr *, void *entry, int start, int end, gfp_t);
  85 int idr_for_each(const struct idr *,
  86                  int (*fn)(int id, void *p, void *data), void *data);
  87 void *idr_get_next(struct idr *, int *nextid);
  88 void *idr_replace(struct idr *, void *, int id);
  89 void idr_destroy(struct idr *);
  90
  91 static inline void *idr_remove(struct idr *idr, int id)
  92 {
  93         return radix_tree_delete_item(&idr->idr_rt, id, NULL);
  94 }
  95
  96 static inline void idr_init(struct idr *idr)
  97 {
  98         INIT_RADIX_TREE(&idr->idr_rt, IDR_RT_MARKER);
  99         idr->idr_next = 0;
 100 }
 101
 102 static inline bool idr_is_empty(const struct idr *idr)
 103 {
 104         return radix_tree_empty(&idr->idr_rt) &&
 105                 radix_tree_tagged(&idr->idr_rt, IDR_FREE);
 106 }
 107
 108 /**
 109  * idr_preload_end - end preload section started with idr_preload()
 110  *
 111  * Each idr_preload() should be matched with an invocation of this
 112  * function.  See idr_preload() for details.
 113  */
 114 static inline void idr_preload_end(void)
 115 {
 116         preempt_enable();
 117 }
 118
 119 /**
 120  * idr_find - return pointer for given id
 121  * @idr: idr handle
 122  * @id: lookup key
 123  *
 124  * Return the pointer given the id it has been registered with.  A %NULL
 125  * return indicates that @id is not valid or you passed %NULL in
 126  * idr_get_new().
 127  *
 128  * This function can be called under rcu_read_lock(), given that the leaf
 129  * pointers lifetimes are correctly managed.
 130  */
 131 static inline void *idr_find(const struct idr *idr, int id)
 132 {
 133         return radix_tree_lookup(&idr->idr_rt, id);
 134 }
 135
 136 /**
 137  * idr_for_each_entry - iterate over an idr's elements of a given type
 138  * @idr:     idr handle
 139  * @entry:   the type * to use as cursor
 140  * @id:      id entry's key
 141  *
 142  * @entry and @id do not need to be initialized before the loop, and
 143  * after normal terminatinon @entry is left with the value NULL.  This
 144  * is convenient for a "not found" value.
 145  */
 146 #define idr_for_each_entry(idr, entry, id)                      \
 147         for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; ++id)
 148
 149 /**
 150  * idr_for_each_entry_continue - continue iteration over an idr's elements of a given type
 151  * @idr:     idr handle
 152  * @entry:   the type * to use as cursor
 153  * @id:      id entry's key
 154  *
 155  * Continue to iterate over list of given type, continuing after
 156  * the current position.
 157  */
 158 #define idr_for_each_entry_continue(idr, entry, id)                     \
 159         for ((entry) = idr_get_next((idr), &(id));                      \
 160              entry;                                                     \
 161              ++id, (entry) = idr_get_next((idr), &(id)))
 162
 163 /*
 164  * IDA - IDR based id allocator, use when translation from id to
 165  * pointer isn't necessary.
 166  */
 167 #define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
 168 #define IDA_BITMAP_LONGS        (IDA_CHUNK_SIZE / sizeof(long))
 169 #define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
 170
 171 struct ida_bitmap {
 172         unsigned long           bitmap[IDA_BITMAP_LONGS];
 173 };
 174
 175 DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);
 176
 177 struct ida {
 178         struct radix_tree_root  ida_rt;
 179 };
 180
 181 #define IDA_INIT        {                                               \
 182         .ida_rt = RADIX_TREE_INIT(IDR_RT_MARKER | GFP_NOWAIT),          \
 183 }
 184 #define DEFINE_IDA(name)        struct ida name = IDA_INIT
 185
 186 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 187 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
 188 void ida_remove(struct ida *ida, int id);
 189 void ida_destroy(struct ida *ida);
 190
 191 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 192                    gfp_t gfp_mask);
 193 void ida_simple_remove(struct ida *ida, unsigned int id);
 194
 195 static inline void ida_init(struct ida *ida)
 196 {
 197         INIT_RADIX_TREE(&ida->ida_rt, IDR_RT_MARKER | GFP_NOWAIT);
 198 }
 199
 200 /**
 201  * ida_get_new - allocate new ID
 202  * @ida:        idr handle
 203  * @p_id:       pointer to the allocated handle
 204  *
 205  * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
 206  */
 207 static inline int ida_get_new(struct ida *ida, int *p_id)
 208 {
 209         return ida_get_new_above(ida, 0, p_id);
 210 }
 211
 212 static inline bool ida_is_empty(const struct ida *ida)
 213 {
 214         return radix_tree_empty(&ida->ida_rt);
 215 }
 216 #endif /* __IDR_H__ */