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
  84 int idr_alloc_cmn(struct idr *idr, void *ptr, unsigned long *index,
  85                   unsigned long start, unsigned long end, gfp_t gfp,
  86                   bool ext);
  87
  88 /**
  89  * idr_alloc - allocate an id
  90  * @idr: idr handle
  91  * @ptr: pointer to be associated with the new id
  92  * @start: the minimum id (inclusive)
  93  * @end: the maximum id (exclusive)
  94  * @gfp: memory allocation flags
  95  *
  96  * Allocates an unused ID in the range [start, end).  Returns -ENOSPC
  97  * if there are no unused IDs in that range.
  98  *
  99  * Note that @end is treated as max when <= 0.  This is to always allow
 100  * using @start + N as @end as long as N is inside integer range.
 101  *
 102  * Simultaneous modifications to the @idr are not allowed and should be
 103  * prevented by the user, usually with a lock.  idr_alloc() may be called
 104  * concurrently with read-only accesses to the @idr, such as idr_find() and
 105  * idr_for_each_entry().
 106  */
 107 static inline int idr_alloc(struct idr *idr, void *ptr,
 108                             int start, int end, gfp_t gfp)
 109 {
 110         unsigned long id;
 111         int ret;
 112
 113         if (WARN_ON_ONCE(start < 0))
 114                 return -EINVAL;
 115
 116         ret = idr_alloc_cmn(idr, ptr, &id, start, end, gfp, false);
 117
 118         if (ret)
 119                 return ret;
 120
 121         return id;
 122 }
 123
 124 static inline int idr_alloc_ext(struct idr *idr, void *ptr,
 125                                 unsigned long *index,
 126                                 unsigned long start,
 127                                 unsigned long end,
 128                                 gfp_t gfp)
 129 {
 130         return idr_alloc_cmn(idr, ptr, index, start, end, gfp, true);
 131 }
 132
 133 int idr_alloc_cyclic(struct idr *, void *entry, int start, int end, gfp_t);
 134 int idr_for_each(const struct idr *,
 135                  int (*fn)(int id, void *p, void *data), void *data);
 136 void *idr_get_next(struct idr *, int *nextid);
 137 void *idr_get_next_ext(struct idr *idr, unsigned long *nextid);
 138 void *idr_replace(struct idr *, void *, int id);
 139 void *idr_replace_ext(struct idr *idr, void *ptr, unsigned long id);
 140 void idr_destroy(struct idr *);
 141
 142 static inline void *idr_remove_ext(struct idr *idr, unsigned long id)
 143 {
 144         return radix_tree_delete_item(&idr->idr_rt, id, NULL);
 145 }
 146
 147 static inline void *idr_remove(struct idr *idr, int id)
 148 {
 149         return idr_remove_ext(idr, id);
 150 }
 151
 152 static inline void idr_init(struct idr *idr)
 153 {
 154         INIT_RADIX_TREE(&idr->idr_rt, IDR_RT_MARKER);
 155         idr->idr_next = 0;
 156 }
 157
 158 static inline bool idr_is_empty(const struct idr *idr)
 159 {
 160         return radix_tree_empty(&idr->idr_rt) &&
 161                 radix_tree_tagged(&idr->idr_rt, IDR_FREE);
 162 }
 163
 164 /**
 165  * idr_preload_end - end preload section started with idr_preload()
 166  *
 167  * Each idr_preload() should be matched with an invocation of this
 168  * function.  See idr_preload() for details.
 169  */
 170 static inline void idr_preload_end(void)
 171 {
 172         preempt_enable();
 173 }
 174
 175 /**
 176  * idr_find - return pointer for given id
 177  * @idr: idr handle
 178  * @id: lookup key
 179  *
 180  * Return the pointer given the id it has been registered with.  A %NULL
 181  * return indicates that @id is not valid or you passed %NULL in
 182  * idr_get_new().
 183  *
 184  * This function can be called under rcu_read_lock(), given that the leaf
 185  * pointers lifetimes are correctly managed.
 186  */
 187 static inline void *idr_find_ext(const struct idr *idr, unsigned long id)
 188 {
 189         return radix_tree_lookup(&idr->idr_rt, id);
 190 }
 191
 192 static inline void *idr_find(const struct idr *idr, int id)
 193 {
 194         return idr_find_ext(idr, id);
 195 }
 196
 197 /**
 198  * idr_for_each_entry - iterate over an idr's elements of a given type
 199  * @idr:     idr handle
 200  * @entry:   the type * to use as cursor
 201  * @id:      id entry's key
 202  *
 203  * @entry and @id do not need to be initialized before the loop, and
 204  * after normal terminatinon @entry is left with the value NULL.  This
 205  * is convenient for a "not found" value.
 206  */
 207 #define idr_for_each_entry(idr, entry, id)                      \
 208         for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; ++id)
 209 #define idr_for_each_entry_ext(idr, entry, id)                  \
 210         for (id = 0; ((entry) = idr_get_next_ext(idr, &(id))) != NULL; ++id)
 211
 212 /**
 213  * idr_for_each_entry_continue - continue iteration over an idr's elements of a given type
 214  * @idr:     idr handle
 215  * @entry:   the type * to use as cursor
 216  * @id:      id entry's key
 217  *
 218  * Continue to iterate over list of given type, continuing after
 219  * the current position.
 220  */
 221 #define idr_for_each_entry_continue(idr, entry, id)                     \
 222         for ((entry) = idr_get_next((idr), &(id));                      \
 223              entry;                                                     \
 224              ++id, (entry) = idr_get_next((idr), &(id)))
 225
 226 /*
 227  * IDA - IDR based id allocator, use when translation from id to
 228  * pointer isn't necessary.
 229  */
 230 #define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
 231 #define IDA_BITMAP_LONGS        (IDA_CHUNK_SIZE / sizeof(long))
 232 #define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
 233
 234 struct ida_bitmap {
 235         unsigned long           bitmap[IDA_BITMAP_LONGS];
 236 };
 237
 238 DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);
 239
 240 struct ida {
 241         struct radix_tree_root  ida_rt;
 242 };
 243
 244 #define IDA_INIT        {                                               \
 245         .ida_rt = RADIX_TREE_INIT(IDR_RT_MARKER | GFP_NOWAIT),          \
 246 }
 247 #define DEFINE_IDA(name)        struct ida name = IDA_INIT
 248
 249 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 250 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
 251 void ida_remove(struct ida *ida, int id);
 252 void ida_destroy(struct ida *ida);
 253
 254 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 255                    gfp_t gfp_mask);
 256 void ida_simple_remove(struct ida *ida, unsigned int id);
 257
 258 static inline void ida_init(struct ida *ida)
 259 {
 260         INIT_RADIX_TREE(&ida->ida_rt, IDR_RT_MARKER | GFP_NOWAIT);
 261 }
 262
 263 /**
 264  * ida_get_new - allocate new ID
 265  * @ida:        idr handle
 266  * @p_id:       pointer to the allocated handle
 267  *
 268  * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
 269  */
 270 static inline int ida_get_new(struct ida *ida, int *p_id)
 271 {
 272         return ida_get_new_above(ida, 0, p_id);
 273 }
 274
 275 static inline bool ida_is_empty(const struct ida *ida)
 276 {
 277         return radix_tree_empty(&ida->ida_rt);
 278 }
 279 #endif /* __IDR_H__ */