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Linux/include/linux/radix-tree.h

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  1 /* SPDX-License-Identifier: GPL-2.0-or-later */
  2 /*
  3  * Copyright (C) 2001 Momchil Velikov
  4  * Portions Copyright (C) 2001 Christoph Hellwig
  5  * Copyright (C) 2006 Nick Piggin
  6  * Copyright (C) 2012 Konstantin Khlebnikov
  7  */
  8 #ifndef _LINUX_RADIX_TREE_H
  9 #define _LINUX_RADIX_TREE_H
 10 
 11 #include <linux/bitops.h>
 12 #include <linux/kernel.h>
 13 #include <linux/list.h>
 14 #include <linux/percpu.h>
 15 #include <linux/preempt.h>
 16 #include <linux/rcupdate.h>
 17 #include <linux/spinlock.h>
 18 #include <linux/types.h>
 19 #include <linux/xarray.h>
 20 #include <linux/local_lock.h>
 21 
 22 /* Keep unconverted code working */
 23 #define radix_tree_root         xarray
 24 #define radix_tree_node         xa_node
 25 
 26 struct radix_tree_preload {
 27         local_lock_t lock;
 28         unsigned nr;
 29         /* nodes->parent points to next preallocated node */
 30         struct radix_tree_node *nodes;
 31 };
 32 DECLARE_PER_CPU(struct radix_tree_preload, radix_tree_preloads);
 33 
 34 /*
 35  * The bottom two bits of the slot determine how the remaining bits in the
 36  * slot are interpreted:
 37  *
 38  * 00 - data pointer
 39  * 10 - internal entry
 40  * x1 - value entry
 41  *
 42  * The internal entry may be a pointer to the next level in the tree, a
 43  * sibling entry, or an indicator that the entry in this slot has been moved
 44  * to another location in the tree and the lookup should be restarted.  While
 45  * NULL fits the 'data pointer' pattern, it means that there is no entry in
 46  * the tree for this index (no matter what level of the tree it is found at).
 47  * This means that storing a NULL entry in the tree is the same as deleting
 48  * the entry from the tree.
 49  */
 50 #define RADIX_TREE_ENTRY_MASK           3UL
 51 #define RADIX_TREE_INTERNAL_NODE        2UL
 52 
 53 static inline bool radix_tree_is_internal_node(void *ptr)
 54 {
 55         return ((unsigned long)ptr & RADIX_TREE_ENTRY_MASK) ==
 56                                 RADIX_TREE_INTERNAL_NODE;
 57 }
 58 
 59 /*** radix-tree API starts here ***/
 60 
 61 #define RADIX_TREE_MAP_SHIFT    XA_CHUNK_SHIFT
 62 #define RADIX_TREE_MAP_SIZE     (1UL << RADIX_TREE_MAP_SHIFT)
 63 #define RADIX_TREE_MAP_MASK     (RADIX_TREE_MAP_SIZE-1)
 64 
 65 #define RADIX_TREE_MAX_TAGS     XA_MAX_MARKS
 66 #define RADIX_TREE_TAG_LONGS    XA_MARK_LONGS
 67 
 68 #define RADIX_TREE_INDEX_BITS  (8 /* CHAR_BIT */ * sizeof(unsigned long))
 69 #define RADIX_TREE_MAX_PATH (DIV_ROUND_UP(RADIX_TREE_INDEX_BITS, \
 70                                           RADIX_TREE_MAP_SHIFT))
 71 
 72 /* The IDR tag is stored in the low bits of xa_flags */
 73 #define ROOT_IS_IDR     ((__force gfp_t)4)
 74 /* The top bits of xa_flags are used to store the root tags */
 75 #define ROOT_TAG_SHIFT  (__GFP_BITS_SHIFT)
 76 
 77 #define RADIX_TREE_INIT(name, mask)     XARRAY_INIT(name, mask)
 78 
 79 #define RADIX_TREE(name, mask) \
 80         struct radix_tree_root name = RADIX_TREE_INIT(name, mask)
 81 
 82 #define INIT_RADIX_TREE(root, mask) xa_init_flags(root, mask)
 83 
 84 static inline bool radix_tree_empty(const struct radix_tree_root *root)
 85 {
 86         return root->xa_head == NULL;
 87 }
 88 
 89 /**
 90  * struct radix_tree_iter - radix tree iterator state
 91  *
 92  * @index:      index of current slot
 93  * @next_index: one beyond the last index for this chunk
 94  * @tags:       bit-mask for tag-iterating
 95  * @node:       node that contains current slot
 96  *
 97  * This radix tree iterator works in terms of "chunks" of slots.  A chunk is a
 98  * subinterval of slots contained within one radix tree leaf node.  It is
 99  * described by a pointer to its first slot and a struct radix_tree_iter
100  * which holds the chunk's position in the tree and its size.  For tagged
101  * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
102  * radix tree tag.
103  */
104 struct radix_tree_iter {
105         unsigned long   index;
106         unsigned long   next_index;
107         unsigned long   tags;
108         struct radix_tree_node *node;
109 };
110 
111 /**
112  * Radix-tree synchronization
113  *
114  * The radix-tree API requires that users provide all synchronisation (with
115  * specific exceptions, noted below).
116  *
117  * Synchronization of access to the data items being stored in the tree, and
118  * management of their lifetimes must be completely managed by API users.
119  *
120  * For API usage, in general,
121  * - any function _modifying_ the tree or tags (inserting or deleting
122  *   items, setting or clearing tags) must exclude other modifications, and
123  *   exclude any functions reading the tree.
124  * - any function _reading_ the tree or tags (looking up items or tags,
125  *   gang lookups) must exclude modifications to the tree, but may occur
126  *   concurrently with other readers.
127  *
128  * The notable exceptions to this rule are the following functions:
129  * __radix_tree_lookup
130  * radix_tree_lookup
131  * radix_tree_lookup_slot
132  * radix_tree_tag_get
133  * radix_tree_gang_lookup
134  * radix_tree_gang_lookup_tag
135  * radix_tree_gang_lookup_tag_slot
136  * radix_tree_tagged
137  *
138  * The first 7 functions are able to be called locklessly, using RCU. The
139  * caller must ensure calls to these functions are made within rcu_read_lock()
140  * regions. Other readers (lock-free or otherwise) and modifications may be
141  * running concurrently.
142  *
143  * It is still required that the caller manage the synchronization and lifetimes
144  * of the items. So if RCU lock-free lookups are used, typically this would mean
145  * that the items have their own locks, or are amenable to lock-free access; and
146  * that the items are freed by RCU (or only freed after having been deleted from
147  * the radix tree *and* a synchronize_rcu() grace period).
148  *
149  * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
150  * access to data items when inserting into or looking up from the radix tree)
151  *
152  * Note that the value returned by radix_tree_tag_get() may not be relied upon
153  * if only the RCU read lock is held.  Functions to set/clear tags and to
154  * delete nodes running concurrently with it may affect its result such that
155  * two consecutive reads in the same locked section may return different
156  * values.  If reliability is required, modification functions must also be
157  * excluded from concurrency.
158  *
159  * radix_tree_tagged is able to be called without locking or RCU.
160  */
161 
162 /**
163  * radix_tree_deref_slot - dereference a slot
164  * @slot: slot pointer, returned by radix_tree_lookup_slot
165  *
166  * For use with radix_tree_lookup_slot().  Caller must hold tree at least read
167  * locked across slot lookup and dereference. Not required if write lock is
168  * held (ie. items cannot be concurrently inserted).
169  *
170  * radix_tree_deref_retry must be used to confirm validity of the pointer if
171  * only the read lock is held.
172  *
173  * Return: entry stored in that slot.
174  */
175 static inline void *radix_tree_deref_slot(void __rcu **slot)
176 {
177         return rcu_dereference(*slot);
178 }
179 
180 /**
181  * radix_tree_deref_slot_protected - dereference a slot with tree lock held
182  * @slot: slot pointer, returned by radix_tree_lookup_slot
183  *
184  * Similar to radix_tree_deref_slot.  The caller does not hold the RCU read
185  * lock but it must hold the tree lock to prevent parallel updates.
186  *
187  * Return: entry stored in that slot.
188  */
189 static inline void *radix_tree_deref_slot_protected(void __rcu **slot,
190                                                         spinlock_t *treelock)
191 {
192         return rcu_dereference_protected(*slot, lockdep_is_held(treelock));
193 }
194 
195 /**
196  * radix_tree_deref_retry       - check radix_tree_deref_slot
197  * @arg:        pointer returned by radix_tree_deref_slot
198  * Returns:     0 if retry is not required, otherwise retry is required
199  *
200  * radix_tree_deref_retry must be used with radix_tree_deref_slot.
201  */
202 static inline int radix_tree_deref_retry(void *arg)
203 {
204         return unlikely(radix_tree_is_internal_node(arg));
205 }
206 
207 /**
208  * radix_tree_exception - radix_tree_deref_slot returned either exception?
209  * @arg:        value returned by radix_tree_deref_slot
210  * Returns:     0 if well-aligned pointer, non-0 if either kind of exception.
211  */
212 static inline int radix_tree_exception(void *arg)
213 {
214         return unlikely((unsigned long)arg & RADIX_TREE_ENTRY_MASK);
215 }
216 
217 int radix_tree_insert(struct radix_tree_root *, unsigned long index,
218                         void *);
219 void *__radix_tree_lookup(const struct radix_tree_root *, unsigned long index,
220                           struct radix_tree_node **nodep, void __rcu ***slotp);
221 void *radix_tree_lookup(const struct radix_tree_root *, unsigned long);
222 void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *,
223                                         unsigned long index);
224 void __radix_tree_replace(struct radix_tree_root *, struct radix_tree_node *,
225                           void __rcu **slot, void *entry);
226 void radix_tree_iter_replace(struct radix_tree_root *,
227                 const struct radix_tree_iter *, void __rcu **slot, void *entry);
228 void radix_tree_replace_slot(struct radix_tree_root *,
229                              void __rcu **slot, void *entry);
230 void radix_tree_iter_delete(struct radix_tree_root *,
231                         struct radix_tree_iter *iter, void __rcu **slot);
232 void *radix_tree_delete_item(struct radix_tree_root *, unsigned long, void *);
233 void *radix_tree_delete(struct radix_tree_root *, unsigned long);
234 unsigned int radix_tree_gang_lookup(const struct radix_tree_root *,
235                         void **results, unsigned long first_index,
236                         unsigned int max_items);
237 int radix_tree_preload(gfp_t gfp_mask);
238 int radix_tree_maybe_preload(gfp_t gfp_mask);
239 void radix_tree_init(void);
240 void *radix_tree_tag_set(struct radix_tree_root *,
241                         unsigned long index, unsigned int tag);
242 void *radix_tree_tag_clear(struct radix_tree_root *,
243                         unsigned long index, unsigned int tag);
244 int radix_tree_tag_get(const struct radix_tree_root *,
245                         unsigned long index, unsigned int tag);
246 void radix_tree_iter_tag_clear(struct radix_tree_root *,
247                 const struct radix_tree_iter *iter, unsigned int tag);
248 unsigned int radix_tree_gang_lookup_tag(const struct radix_tree_root *,
249                 void **results, unsigned long first_index,
250                 unsigned int max_items, unsigned int tag);
251 unsigned int radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *,
252                 void __rcu ***results, unsigned long first_index,
253                 unsigned int max_items, unsigned int tag);
254 int radix_tree_tagged(const struct radix_tree_root *, unsigned int tag);
255 
256 static inline void radix_tree_preload_end(void)
257 {
258         local_unlock(&radix_tree_preloads.lock);
259 }
260 
261 void __rcu **idr_get_free(struct radix_tree_root *root,
262                               struct radix_tree_iter *iter, gfp_t gfp,
263                               unsigned long max);
264 
265 enum {
266         RADIX_TREE_ITER_TAG_MASK = 0x0f,        /* tag index in lower nybble */
267         RADIX_TREE_ITER_TAGGED   = 0x10,        /* lookup tagged slots */
268         RADIX_TREE_ITER_CONTIG   = 0x20,        /* stop at first hole */
269 };
270 
271 /**
272  * radix_tree_iter_init - initialize radix tree iterator
273  *
274  * @iter:       pointer to iterator state
275  * @start:      iteration starting index
276  * Returns:     NULL
277  */
278 static __always_inline void __rcu **
279 radix_tree_iter_init(struct radix_tree_iter *iter, unsigned long start)
280 {
281         /*
282          * Leave iter->tags uninitialized. radix_tree_next_chunk() will fill it
283          * in the case of a successful tagged chunk lookup.  If the lookup was
284          * unsuccessful or non-tagged then nobody cares about ->tags.
285          *
286          * Set index to zero to bypass next_index overflow protection.
287          * See the comment in radix_tree_next_chunk() for details.
288          */
289         iter->index = 0;
290         iter->next_index = start;
291         return NULL;
292 }
293 
294 /**
295  * radix_tree_next_chunk - find next chunk of slots for iteration
296  *
297  * @root:       radix tree root
298  * @iter:       iterator state
299  * @flags:      RADIX_TREE_ITER_* flags and tag index
300  * Returns:     pointer to chunk first slot, or NULL if there no more left
301  *
302  * This function looks up the next chunk in the radix tree starting from
303  * @iter->next_index.  It returns a pointer to the chunk's first slot.
304  * Also it fills @iter with data about chunk: position in the tree (index),
305  * its end (next_index), and constructs a bit mask for tagged iterating (tags).
306  */
307 void __rcu **radix_tree_next_chunk(const struct radix_tree_root *,
308                              struct radix_tree_iter *iter, unsigned flags);
309 
310 /**
311  * radix_tree_iter_lookup - look up an index in the radix tree
312  * @root: radix tree root
313  * @iter: iterator state
314  * @index: key to look up
315  *
316  * If @index is present in the radix tree, this function returns the slot
317  * containing it and updates @iter to describe the entry.  If @index is not
318  * present, it returns NULL.
319  */
320 static inline void __rcu **
321 radix_tree_iter_lookup(const struct radix_tree_root *root,
322                         struct radix_tree_iter *iter, unsigned long index)
323 {
324         radix_tree_iter_init(iter, index);
325         return radix_tree_next_chunk(root, iter, RADIX_TREE_ITER_CONTIG);
326 }
327 
328 /**
329  * radix_tree_iter_retry - retry this chunk of the iteration
330  * @iter:       iterator state
331  *
332  * If we iterate over a tree protected only by the RCU lock, a race
333  * against deletion or creation may result in seeing a slot for which
334  * radix_tree_deref_retry() returns true.  If so, call this function
335  * and continue the iteration.
336  */
337 static inline __must_check
338 void __rcu **radix_tree_iter_retry(struct radix_tree_iter *iter)
339 {
340         iter->next_index = iter->index;
341         iter->tags = 0;
342         return NULL;
343 }
344 
345 static inline unsigned long
346 __radix_tree_iter_add(struct radix_tree_iter *iter, unsigned long slots)
347 {
348         return iter->index + slots;
349 }
350 
351 /**
352  * radix_tree_iter_resume - resume iterating when the chunk may be invalid
353  * @slot: pointer to current slot
354  * @iter: iterator state
355  * Returns: New slot pointer
356  *
357  * If the iterator needs to release then reacquire a lock, the chunk may
358  * have been invalidated by an insertion or deletion.  Call this function
359  * before releasing the lock to continue the iteration from the next index.
360  */
361 void __rcu **__must_check radix_tree_iter_resume(void __rcu **slot,
362                                         struct radix_tree_iter *iter);
363 
364 /**
365  * radix_tree_chunk_size - get current chunk size
366  *
367  * @iter:       pointer to radix tree iterator
368  * Returns:     current chunk size
369  */
370 static __always_inline long
371 radix_tree_chunk_size(struct radix_tree_iter *iter)
372 {
373         return iter->next_index - iter->index;
374 }
375 
376 /**
377  * radix_tree_next_slot - find next slot in chunk
378  *
379  * @slot:       pointer to current slot
380  * @iter:       pointer to iterator state
381  * @flags:      RADIX_TREE_ITER_*, should be constant
382  * Returns:     pointer to next slot, or NULL if there no more left
383  *
384  * This function updates @iter->index in the case of a successful lookup.
385  * For tagged lookup it also eats @iter->tags.
386  *
387  * There are several cases where 'slot' can be passed in as NULL to this
388  * function.  These cases result from the use of radix_tree_iter_resume() or
389  * radix_tree_iter_retry().  In these cases we don't end up dereferencing
390  * 'slot' because either:
391  * a) we are doing tagged iteration and iter->tags has been set to 0, or
392  * b) we are doing non-tagged iteration, and iter->index and iter->next_index
393  *    have been set up so that radix_tree_chunk_size() returns 1 or 0.
394  */
395 static __always_inline void __rcu **radix_tree_next_slot(void __rcu **slot,
396                                 struct radix_tree_iter *iter, unsigned flags)
397 {
398         if (flags & RADIX_TREE_ITER_TAGGED) {
399                 iter->tags >>= 1;
400                 if (unlikely(!iter->tags))
401                         return NULL;
402                 if (likely(iter->tags & 1ul)) {
403                         iter->index = __radix_tree_iter_add(iter, 1);
404                         slot++;
405                         goto found;
406                 }
407                 if (!(flags & RADIX_TREE_ITER_CONTIG)) {
408                         unsigned offset = __ffs(iter->tags);
409 
410                         iter->tags >>= offset++;
411                         iter->index = __radix_tree_iter_add(iter, offset);
412                         slot += offset;
413                         goto found;
414                 }
415         } else {
416                 long count = radix_tree_chunk_size(iter);
417 
418                 while (--count > 0) {
419                         slot++;
420                         iter->index = __radix_tree_iter_add(iter, 1);
421 
422                         if (likely(*slot))
423                                 goto found;
424                         if (flags & RADIX_TREE_ITER_CONTIG) {
425                                 /* forbid switching to the next chunk */
426                                 iter->next_index = 0;
427                                 break;
428                         }
429                 }
430         }
431         return NULL;
432 
433  found:
434         return slot;
435 }
436 
437 /**
438  * radix_tree_for_each_slot - iterate over non-empty slots
439  *
440  * @slot:       the void** variable for pointer to slot
441  * @root:       the struct radix_tree_root pointer
442  * @iter:       the struct radix_tree_iter pointer
443  * @start:      iteration starting index
444  *
445  * @slot points to radix tree slot, @iter->index contains its index.
446  */
447 #define radix_tree_for_each_slot(slot, root, iter, start)               \
448         for (slot = radix_tree_iter_init(iter, start) ;                 \
449              slot || (slot = radix_tree_next_chunk(root, iter, 0)) ;    \
450              slot = radix_tree_next_slot(slot, iter, 0))
451 
452 /**
453  * radix_tree_for_each_tagged - iterate over tagged slots
454  *
455  * @slot:       the void** variable for pointer to slot
456  * @root:       the struct radix_tree_root pointer
457  * @iter:       the struct radix_tree_iter pointer
458  * @start:      iteration starting index
459  * @tag:        tag index
460  *
461  * @slot points to radix tree slot, @iter->index contains its index.
462  */
463 #define radix_tree_for_each_tagged(slot, root, iter, start, tag)        \
464         for (slot = radix_tree_iter_init(iter, start) ;                 \
465              slot || (slot = radix_tree_next_chunk(root, iter,          \
466                               RADIX_TREE_ITER_TAGGED | tag)) ;          \
467              slot = radix_tree_next_slot(slot, iter,                    \
468                                 RADIX_TREE_ITER_TAGGED | tag))
469 
470 #endif /* _LINUX_RADIX_TREE_H */
471 

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