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 #include <linux/bug.h>
  19
  20 struct idr {
  21         struct radix_tree_root  idr_rt;
  22         unsigned int            idr_next;
  23 };
  24
  25 /*
  26  * The IDR API does not expose the tagging functionality of the radix tree
  27  * to users.  Use tag 0 to track whether a node has free space below it.
  28  */
  29 #define IDR_FREE        0
  30
  31 /* Set the IDR flag and the IDR_FREE tag */
  32 #define IDR_RT_MARKER           ((__force gfp_t)(3 << __GFP_BITS_SHIFT))
  33
  34 #define IDR_INIT                                                        \
  35 {                                                                       \
  36         .idr_rt = RADIX_TREE_INIT(IDR_RT_MARKER)                        \
  37 }
  38 #define DEFINE_IDR(name)        struct idr name = IDR_INIT
  39
  40 /**
  41  * idr_get_cursor - Return the current position of the cyclic allocator
  42  * @idr: idr handle
  43  *
  44  * The value returned is the value that will be next returned from
  45  * idr_alloc_cyclic() if it is free (otherwise the search will start from
  46  * this position).
  47  */
  48 static inline unsigned int idr_get_cursor(const struct idr *idr)
  49 {
  50         return READ_ONCE(idr->idr_next);
  51 }
  52
  53 /**
  54  * idr_set_cursor - Set the current position of the cyclic allocator
  55  * @idr: idr handle
  56  * @val: new position
  57  *
  58  * The next call to idr_alloc_cyclic() will return @val if it is free
  59  * (otherwise the search will start from this position).
  60  */
  61 static inline void idr_set_cursor(struct idr *idr, unsigned int val)
  62 {
  63         WRITE_ONCE(idr->idr_next, val);
  64 }
  65
  66 /**
  67  * DOC: idr sync
  68  * idr synchronization (stolen from radix-tree.h)
  69  *
  70  * idr_find() is able to be called locklessly, using RCU. The caller must
  71  * ensure calls to this function are made within rcu_read_lock() regions.
  72  * Other readers (lock-free or otherwise) and modifications may be running
  73  * concurrently.
  74  *
  75  * It is still required that the caller manage the synchronization and
  76  * lifetimes of the items. So if RCU lock-free lookups are used, typically
  77  * this would mean that the items have their own locks, or are amenable to
  78  * lock-free access; and that the items are freed by RCU (or only freed after
  79  * having been deleted from the idr tree *and* a synchronize_rcu() grace
  80  * period).
  81  */
  82
  83 void idr_preload(gfp_t gfp_mask);
  84
  85 int idr_alloc_cmn(struct idr *idr, void *ptr, unsigned long *index,
  86                   unsigned long start, unsigned long end, gfp_t gfp,
  87                   bool ext);
  88
  89 /**
  90  * idr_alloc - allocate an id
  91  * @idr: idr handle
  92  * @ptr: pointer to be associated with the new id
  93  * @start: the minimum id (inclusive)
  94  * @end: the maximum id (exclusive)
  95  * @gfp: memory allocation flags
  96  *
  97  * Allocates an unused ID in the range [start, end).  Returns -ENOSPC
  98  * if there are no unused IDs in that range.
  99  *
 100  * Note that @end is treated as max when <= 0.  This is to always allow
 101  * using @start + N as @end as long as N is inside integer range.
 102  *
 103  * Simultaneous modifications to the @idr are not allowed and should be
 104  * prevented by the user, usually with a lock.  idr_alloc() may be called
 105  * concurrently with read-only accesses to the @idr, such as idr_find() and
 106  * idr_for_each_entry().
 107  */
 108 static inline int idr_alloc(struct idr *idr, void *ptr,
 109                             int start, int end, gfp_t gfp)
 110 {
 111         unsigned long id;
 112         int ret;
 113
 114         if (WARN_ON_ONCE(start < 0))
 115                 return -EINVAL;
 116
 117         ret = idr_alloc_cmn(idr, ptr, &id, start, end, gfp, false);
 118
 119         if (ret)
 120                 return ret;
 121
 122         return id;
 123 }
 124
 125 static inline int idr_alloc_ext(struct idr *idr, void *ptr,
 126                                 unsigned long *index,
 127                                 unsigned long start,
 128                                 unsigned long end,
 129                                 gfp_t gfp)
 130 {
 131         return idr_alloc_cmn(idr, ptr, index, start, end, gfp, true);
 132 }
 133
 134 int idr_alloc_cyclic(struct idr *, void *entry, int start, int end, gfp_t);
 135 int idr_for_each(const struct idr *,
 136                  int (*fn)(int id, void *p, void *data), void *data);
 137 void *idr_get_next(struct idr *, int *nextid);
 138 void *idr_get_next_ext(struct idr *idr, unsigned long *nextid);
 139 void *idr_replace(struct idr *, void *, int id);
 140 void *idr_replace_ext(struct idr *idr, void *ptr, unsigned long id);
 141 void idr_destroy(struct idr *);
 142
 143 static inline void *idr_remove_ext(struct idr *idr, unsigned long id)
 144 {
 145         return radix_tree_delete_item(&idr->idr_rt, id, NULL);
 146 }
 147
 148 static inline void *idr_remove(struct idr *idr, int id)
 149 {
 150         return idr_remove_ext(idr, id);
 151 }
 152
 153 static inline void idr_init(struct idr *idr)
 154 {
 155         INIT_RADIX_TREE(&idr->idr_rt, IDR_RT_MARKER);
 156         idr->idr_next = 0;
 157 }
 158
 159 static inline bool idr_is_empty(const struct idr *idr)
 160 {
 161         return radix_tree_empty(&idr->idr_rt) &&
 162                 radix_tree_tagged(&idr->idr_rt, IDR_FREE);
 163 }
 164
 165 /**
 166  * idr_preload_end - end preload section started with idr_preload()
 167  *
 168  * Each idr_preload() should be matched with an invocation of this
 169  * function.  See idr_preload() for details.
 170  */
 171 static inline void idr_preload_end(void)
 172 {
 173         preempt_enable();
 174 }
 175
 176 /**
 177  * idr_find - return pointer for given id
 178  * @idr: idr handle
 179  * @id: lookup key
 180  *
 181  * Return the pointer given the id it has been registered with.  A %NULL
 182  * return indicates that @id is not valid or you passed %NULL in
 183  * idr_get_new().
 184  *
 185  * This function can be called under rcu_read_lock(), given that the leaf
 186  * pointers lifetimes are correctly managed.
 187  */
 188 static inline void *idr_find_ext(const struct idr *idr, unsigned long id)
 189 {
 190         return radix_tree_lookup(&idr->idr_rt, id);
 191 }
 192
 193 static inline void *idr_find(const struct idr *idr, int id)
 194 {
 195         return idr_find_ext(idr, id);
 196 }
 197
 198 /**
 199  * idr_for_each_entry - iterate over an idr's elements of a given type
 200  * @idr:     idr handle
 201  * @entry:   the type * to use as cursor
 202  * @id:      id entry's key
 203  *
 204  * @entry and @id do not need to be initialized before the loop, and
 205  * after normal terminatinon @entry is left with the value NULL.  This
 206  * is convenient for a "not found" value.
 207  */
 208 #define idr_for_each_entry(idr, entry, id)                      \
 209         for (id = 0; ((entry) = idr_get_next(idr, &(id))) != NULL; id += 1U)
 210 #define idr_for_each_entry_ext(idr, entry, id)                  \
 211         for (id = 0; ((entry) = idr_get_next_ext(idr, &(id))) != NULL; ++id)
 212
 213 /**
 214  * idr_for_each_entry_continue - continue iteration over an idr's elements of a given type
 215  * @idr:     idr handle
 216  * @entry:   the type * to use as cursor
 217  * @id:      id entry's key
 218  *
 219  * Continue to iterate over list of given type, continuing after
 220  * the current position.
 221  */
 222 #define idr_for_each_entry_continue(idr, entry, id)                     \
 223         for ((entry) = idr_get_next((idr), &(id));                      \
 224              entry;                                                     \
 225              ++id, (entry) = idr_get_next((idr), &(id)))
 226
 227 /*
 228  * IDA - IDR based id allocator, use when translation from id to
 229  * pointer isn't necessary.
 230  */
 231 #define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
 232 #define IDA_BITMAP_LONGS        (IDA_CHUNK_SIZE / sizeof(long))
 233 #define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)
 234
 235 struct ida_bitmap {
 236         unsigned long           bitmap[IDA_BITMAP_LONGS];
 237 };
 238
 239 DECLARE_PER_CPU(struct ida_bitmap *, ida_bitmap);
 240
 241 struct ida {
 242         struct radix_tree_root  ida_rt;
 243 };
 244
 245 #define IDA_INIT        {                                               \
 246         .ida_rt = RADIX_TREE_INIT(IDR_RT_MARKER | GFP_NOWAIT),          \
 247 }
 248 #define DEFINE_IDA(name)        struct ida name = IDA_INIT
 249
 250 int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
 251 int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
 252 void ida_remove(struct ida *ida, int id);
 253 void ida_destroy(struct ida *ida);
 254
 255 int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
 256                    gfp_t gfp_mask);
 257 void ida_simple_remove(struct ida *ida, unsigned int id);
 258
 259 static inline void ida_init(struct ida *ida)
 260 {
 261         INIT_RADIX_TREE(&ida->ida_rt, IDR_RT_MARKER | GFP_NOWAIT);
 262 }
 263
 264 /**
 265  * ida_get_new - allocate new ID
 266  * @ida:        idr handle
 267  * @p_id:       pointer to the allocated handle
 268  *
 269  * Simple wrapper around ida_get_new_above() w/ @starting_id of zero.
 270  */
 271 static inline int ida_get_new(struct ida *ida, int *p_id)
 272 {
 273         return ida_get_new_above(ida, 0, p_id);
 274 }
 275
 276 static inline bool ida_is_empty(const struct ida *ida)
 277 {
 278         return radix_tree_empty(&ida->ida_rt);
 279 }
 280 #endif /* __IDR_H__ */