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1 : : /* SPDX-License-Identifier: GPL-2.0+ */
2 : : #ifndef _LINUX_XARRAY_H
3 : : #define _LINUX_XARRAY_H
4 : : /*
5 : : * eXtensible Arrays
6 : : * Copyright (c) 2017 Microsoft Corporation
7 : : * Author: Matthew Wilcox <willy@infradead.org>
8 : : *
9 : : * See Documentation/core-api/xarray.rst for how to use the XArray.
10 : : */
11 : :
12 : : #include <linux/bug.h>
13 : : #include <linux/compiler.h>
14 : : #include <linux/gfp.h>
15 : : #include <linux/kconfig.h>
16 : : #include <linux/kernel.h>
17 : : #include <linux/rcupdate.h>
18 : : #include <linux/spinlock.h>
19 : : #include <linux/types.h>
20 : :
21 : : /*
22 : : * The bottom two bits of the entry determine how the XArray interprets
23 : : * the contents:
24 : : *
25 : : * 00: Pointer entry
26 : : * 10: Internal entry
27 : : * x1: Value entry or tagged pointer
28 : : *
29 : : * Attempting to store internal entries in the XArray is a bug.
30 : : *
31 : : * Most internal entries are pointers to the next node in the tree.
32 : : * The following internal entries have a special meaning:
33 : : *
34 : : * 0-62: Sibling entries
35 : : * 256: Zero entry
36 : : * 257: Retry entry
37 : : *
38 : : * Errors are also represented as internal entries, but use the negative
39 : : * space (-4094 to -2). They're never stored in the slots array; only
40 : : * returned by the normal API.
41 : : */
42 : :
43 : : #define BITS_PER_XA_VALUE (BITS_PER_LONG - 1)
44 : :
45 : : /**
46 : : * xa_mk_value() - Create an XArray entry from an integer.
47 : : * @v: Value to store in XArray.
48 : : *
49 : : * Context: Any context.
50 : : * Return: An entry suitable for storing in the XArray.
51 : : */
52 : 3 : static inline void *xa_mk_value(unsigned long v)
53 : : {
54 : 3 : WARN_ON((long)v < 0);
55 : 3 : return (void *)((v << 1) | 1);
56 : : }
57 : :
58 : : /**
59 : : * xa_to_value() - Get value stored in an XArray entry.
60 : : * @entry: XArray entry.
61 : : *
62 : : * Context: Any context.
63 : : * Return: The value stored in the XArray entry.
64 : : */
65 : : static inline unsigned long xa_to_value(const void *entry)
66 : : {
67 : 3 : return (unsigned long)entry >> 1;
68 : : }
69 : :
70 : : /**
71 : : * xa_is_value() - Determine if an entry is a value.
72 : : * @entry: XArray entry.
73 : : *
74 : : * Context: Any context.
75 : : * Return: True if the entry is a value, false if it is a pointer.
76 : : */
77 : : static inline bool xa_is_value(const void *entry)
78 : : {
79 : 3 : return (unsigned long)entry & 1;
80 : : }
81 : :
82 : : /**
83 : : * xa_tag_pointer() - Create an XArray entry for a tagged pointer.
84 : : * @p: Plain pointer.
85 : : * @tag: Tag value (0, 1 or 3).
86 : : *
87 : : * If the user of the XArray prefers, they can tag their pointers instead
88 : : * of storing value entries. Three tags are available (0, 1 and 3).
89 : : * These are distinct from the xa_mark_t as they are not replicated up
90 : : * through the array and cannot be searched for.
91 : : *
92 : : * Context: Any context.
93 : : * Return: An XArray entry.
94 : : */
95 : : static inline void *xa_tag_pointer(void *p, unsigned long tag)
96 : : {
97 : : return (void *)((unsigned long)p | tag);
98 : : }
99 : :
100 : : /**
101 : : * xa_untag_pointer() - Turn an XArray entry into a plain pointer.
102 : : * @entry: XArray entry.
103 : : *
104 : : * If you have stored a tagged pointer in the XArray, call this function
105 : : * to get the untagged version of the pointer.
106 : : *
107 : : * Context: Any context.
108 : : * Return: A pointer.
109 : : */
110 : : static inline void *xa_untag_pointer(void *entry)
111 : : {
112 : : return (void *)((unsigned long)entry & ~3UL);
113 : : }
114 : :
115 : : /**
116 : : * xa_pointer_tag() - Get the tag stored in an XArray entry.
117 : : * @entry: XArray entry.
118 : : *
119 : : * If you have stored a tagged pointer in the XArray, call this function
120 : : * to get the tag of that pointer.
121 : : *
122 : : * Context: Any context.
123 : : * Return: A tag.
124 : : */
125 : : static inline unsigned int xa_pointer_tag(void *entry)
126 : : {
127 : : return (unsigned long)entry & 3UL;
128 : : }
129 : :
130 : : /*
131 : : * xa_mk_internal() - Create an internal entry.
132 : : * @v: Value to turn into an internal entry.
133 : : *
134 : : * Internal entries are used for a number of purposes. Entries 0-255 are
135 : : * used for sibling entries (only 0-62 are used by the current code). 256
136 : : * is used for the retry entry. 257 is used for the reserved / zero entry.
137 : : * Negative internal entries are used to represent errnos. Node pointers
138 : : * are also tagged as internal entries in some situations.
139 : : *
140 : : * Context: Any context.
141 : : * Return: An XArray internal entry corresponding to this value.
142 : : */
143 : : static inline void *xa_mk_internal(unsigned long v)
144 : : {
145 : 0 : return (void *)((v << 2) | 2);
146 : : }
147 : :
148 : : /*
149 : : * xa_to_internal() - Extract the value from an internal entry.
150 : : * @entry: XArray entry.
151 : : *
152 : : * Context: Any context.
153 : : * Return: The value which was stored in the internal entry.
154 : : */
155 : : static inline unsigned long xa_to_internal(const void *entry)
156 : : {
157 : : return (unsigned long)entry >> 2;
158 : : }
159 : :
160 : : /*
161 : : * xa_is_internal() - Is the entry an internal entry?
162 : : * @entry: XArray entry.
163 : : *
164 : : * Context: Any context.
165 : : * Return: %true if the entry is an internal entry.
166 : : */
167 : : static inline bool xa_is_internal(const void *entry)
168 : : {
169 : 3 : return ((unsigned long)entry & 3) == 2;
170 : : }
171 : :
172 : : #define XA_ZERO_ENTRY xa_mk_internal(257)
173 : :
174 : : /**
175 : : * xa_is_zero() - Is the entry a zero entry?
176 : : * @entry: Entry retrieved from the XArray
177 : : *
178 : : * The normal API will return NULL as the contents of a slot containing
179 : : * a zero entry. You can only see zero entries by using the advanced API.
180 : : *
181 : : * Return: %true if the entry is a zero entry.
182 : : */
183 : : static inline bool xa_is_zero(const void *entry)
184 : : {
185 : 3 : return unlikely(entry == XA_ZERO_ENTRY);
186 : : }
187 : :
188 : : /**
189 : : * xa_is_err() - Report whether an XArray operation returned an error
190 : : * @entry: Result from calling an XArray function
191 : : *
192 : : * If an XArray operation cannot complete an operation, it will return
193 : : * a special value indicating an error. This function tells you
194 : : * whether an error occurred; xa_err() tells you which error occurred.
195 : : *
196 : : * Context: Any context.
197 : : * Return: %true if the entry indicates an error.
198 : : */
199 : : static inline bool xa_is_err(const void *entry)
200 : : {
201 : 3 : return unlikely(xa_is_internal(entry) &&
202 : : entry >= xa_mk_internal(-MAX_ERRNO));
203 : : }
204 : :
205 : : /**
206 : : * xa_err() - Turn an XArray result into an errno.
207 : : * @entry: Result from calling an XArray function.
208 : : *
209 : : * If an XArray operation cannot complete an operation, it will return
210 : : * a special pointer value which encodes an errno. This function extracts
211 : : * the errno from the pointer value, or returns 0 if the pointer does not
212 : : * represent an errno.
213 : : *
214 : : * Context: Any context.
215 : : * Return: A negative errno or 0.
216 : : */
217 : : static inline int xa_err(void *entry)
218 : : {
219 : : /* xa_to_internal() would not do sign extension. */
220 : 3 : if (xa_is_err(entry))
221 : 3 : return (long)entry >> 2;
222 : : return 0;
223 : : }
224 : :
225 : : /**
226 : : * struct xa_limit - Represents a range of IDs.
227 : : * @min: The lowest ID to allocate (inclusive).
228 : : * @max: The maximum ID to allocate (inclusive).
229 : : *
230 : : * This structure is used either directly or via the XA_LIMIT() macro
231 : : * to communicate the range of IDs that are valid for allocation.
232 : : * Two common ranges are predefined for you:
233 : : * * xa_limit_32b - [0 - UINT_MAX]
234 : : * * xa_limit_31b - [0 - INT_MAX]
235 : : */
236 : : struct xa_limit {
237 : : u32 max;
238 : : u32 min;
239 : : };
240 : :
241 : : #define XA_LIMIT(_min, _max) (struct xa_limit) { .min = _min, .max = _max }
242 : :
243 : : #define xa_limit_32b XA_LIMIT(0, UINT_MAX)
244 : : #define xa_limit_31b XA_LIMIT(0, INT_MAX)
245 : :
246 : : typedef unsigned __bitwise xa_mark_t;
247 : : #define XA_MARK_0 ((__force xa_mark_t)0U)
248 : : #define XA_MARK_1 ((__force xa_mark_t)1U)
249 : : #define XA_MARK_2 ((__force xa_mark_t)2U)
250 : : #define XA_PRESENT ((__force xa_mark_t)8U)
251 : : #define XA_MARK_MAX XA_MARK_2
252 : : #define XA_FREE_MARK XA_MARK_0
253 : :
254 : : enum xa_lock_type {
255 : : XA_LOCK_IRQ = 1,
256 : : XA_LOCK_BH = 2,
257 : : };
258 : :
259 : : /*
260 : : * Values for xa_flags. The radix tree stores its GFP flags in the xa_flags,
261 : : * and we remain compatible with that.
262 : : */
263 : : #define XA_FLAGS_LOCK_IRQ ((__force gfp_t)XA_LOCK_IRQ)
264 : : #define XA_FLAGS_LOCK_BH ((__force gfp_t)XA_LOCK_BH)
265 : : #define XA_FLAGS_TRACK_FREE ((__force gfp_t)4U)
266 : : #define XA_FLAGS_ZERO_BUSY ((__force gfp_t)8U)
267 : : #define XA_FLAGS_ALLOC_WRAPPED ((__force gfp_t)16U)
268 : : #define XA_FLAGS_ACCOUNT ((__force gfp_t)32U)
269 : : #define XA_FLAGS_MARK(mark) ((__force gfp_t)((1U << __GFP_BITS_SHIFT) << \
270 : : (__force unsigned)(mark)))
271 : :
272 : : /* ALLOC is for a normal 0-based alloc. ALLOC1 is for an 1-based alloc */
273 : : #define XA_FLAGS_ALLOC (XA_FLAGS_TRACK_FREE | XA_FLAGS_MARK(XA_FREE_MARK))
274 : : #define XA_FLAGS_ALLOC1 (XA_FLAGS_TRACK_FREE | XA_FLAGS_ZERO_BUSY)
275 : :
276 : : /**
277 : : * struct xarray - The anchor of the XArray.
278 : : * @xa_lock: Lock that protects the contents of the XArray.
279 : : *
280 : : * To use the xarray, define it statically or embed it in your data structure.
281 : : * It is a very small data structure, so it does not usually make sense to
282 : : * allocate it separately and keep a pointer to it in your data structure.
283 : : *
284 : : * You may use the xa_lock to protect your own data structures as well.
285 : : */
286 : : /*
287 : : * If all of the entries in the array are NULL, @xa_head is a NULL pointer.
288 : : * If the only non-NULL entry in the array is at index 0, @xa_head is that
289 : : * entry. If any other entry in the array is non-NULL, @xa_head points
290 : : * to an @xa_node.
291 : : */
292 : : struct xarray {
293 : : spinlock_t xa_lock;
294 : : /* private: The rest of the data structure is not to be used directly. */
295 : : gfp_t xa_flags;
296 : : void __rcu * xa_head;
297 : : };
298 : :
299 : : #define XARRAY_INIT(name, flags) { \
300 : : .xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock), \
301 : : .xa_flags = flags, \
302 : : .xa_head = NULL, \
303 : : }
304 : :
305 : : /**
306 : : * DEFINE_XARRAY_FLAGS() - Define an XArray with custom flags.
307 : : * @name: A string that names your XArray.
308 : : * @flags: XA_FLAG values.
309 : : *
310 : : * This is intended for file scope definitions of XArrays. It declares
311 : : * and initialises an empty XArray with the chosen name and flags. It is
312 : : * equivalent to calling xa_init_flags() on the array, but it does the
313 : : * initialisation at compiletime instead of runtime.
314 : : */
315 : : #define DEFINE_XARRAY_FLAGS(name, flags) \
316 : : struct xarray name = XARRAY_INIT(name, flags)
317 : :
318 : : /**
319 : : * DEFINE_XARRAY() - Define an XArray.
320 : : * @name: A string that names your XArray.
321 : : *
322 : : * This is intended for file scope definitions of XArrays. It declares
323 : : * and initialises an empty XArray with the chosen name. It is equivalent
324 : : * to calling xa_init() on the array, but it does the initialisation at
325 : : * compiletime instead of runtime.
326 : : */
327 : : #define DEFINE_XARRAY(name) DEFINE_XARRAY_FLAGS(name, 0)
328 : :
329 : : /**
330 : : * DEFINE_XARRAY_ALLOC() - Define an XArray which allocates IDs starting at 0.
331 : : * @name: A string that names your XArray.
332 : : *
333 : : * This is intended for file scope definitions of allocating XArrays.
334 : : * See also DEFINE_XARRAY().
335 : : */
336 : : #define DEFINE_XARRAY_ALLOC(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC)
337 : :
338 : : /**
339 : : * DEFINE_XARRAY_ALLOC1() - Define an XArray which allocates IDs starting at 1.
340 : : * @name: A string that names your XArray.
341 : : *
342 : : * This is intended for file scope definitions of allocating XArrays.
343 : : * See also DEFINE_XARRAY().
344 : : */
345 : : #define DEFINE_XARRAY_ALLOC1(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC1)
346 : :
347 : : void *xa_load(struct xarray *, unsigned long index);
348 : : void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
349 : : void *xa_erase(struct xarray *, unsigned long index);
350 : : void *xa_store_range(struct xarray *, unsigned long first, unsigned long last,
351 : : void *entry, gfp_t);
352 : : bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t);
353 : : void xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
354 : : void xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
355 : : void *xa_find(struct xarray *xa, unsigned long *index,
356 : : unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
357 : : void *xa_find_after(struct xarray *xa, unsigned long *index,
358 : : unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
359 : : unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,
360 : : unsigned long max, unsigned int n, xa_mark_t);
361 : : void xa_destroy(struct xarray *);
362 : :
363 : : /**
364 : : * xa_init_flags() - Initialise an empty XArray with flags.
365 : : * @xa: XArray.
366 : : * @flags: XA_FLAG values.
367 : : *
368 : : * If you need to initialise an XArray with special flags (eg you need
369 : : * to take the lock from interrupt context), use this function instead
370 : : * of xa_init().
371 : : *
372 : : * Context: Any context.
373 : : */
374 : : static inline void xa_init_flags(struct xarray *xa, gfp_t flags)
375 : : {
376 : 3 : spin_lock_init(&xa->xa_lock);
377 : 3 : xa->xa_flags = flags;
378 : 3 : xa->xa_head = NULL;
379 : : }
380 : :
381 : : /**
382 : : * xa_init() - Initialise an empty XArray.
383 : : * @xa: XArray.
384 : : *
385 : : * An empty XArray is full of NULL entries.
386 : : *
387 : : * Context: Any context.
388 : : */
389 : : static inline void xa_init(struct xarray *xa)
390 : : {
391 : : xa_init_flags(xa, 0);
392 : : }
393 : :
394 : : /**
395 : : * xa_empty() - Determine if an array has any present entries.
396 : : * @xa: XArray.
397 : : *
398 : : * Context: Any context.
399 : : * Return: %true if the array contains only NULL pointers.
400 : : */
401 : : static inline bool xa_empty(const struct xarray *xa)
402 : : {
403 : : return xa->xa_head == NULL;
404 : : }
405 : :
406 : : /**
407 : : * xa_marked() - Inquire whether any entry in this array has a mark set
408 : : * @xa: Array
409 : : * @mark: Mark value
410 : : *
411 : : * Context: Any context.
412 : : * Return: %true if any entry has this mark set.
413 : : */
414 : : static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
415 : : {
416 : 3 : return xa->xa_flags & XA_FLAGS_MARK(mark);
417 : : }
418 : :
419 : : /**
420 : : * xa_for_each_start() - Iterate over a portion of an XArray.
421 : : * @xa: XArray.
422 : : * @index: Index of @entry.
423 : : * @entry: Entry retrieved from array.
424 : : * @start: First index to retrieve from array.
425 : : *
426 : : * During the iteration, @entry will have the value of the entry stored
427 : : * in @xa at @index. You may modify @index during the iteration if you
428 : : * want to skip or reprocess indices. It is safe to modify the array
429 : : * during the iteration. At the end of the iteration, @entry will be set
430 : : * to NULL and @index will have a value less than or equal to max.
431 : : *
432 : : * xa_for_each_start() is O(n.log(n)) while xas_for_each() is O(n). You have
433 : : * to handle your own locking with xas_for_each(), and if you have to unlock
434 : : * after each iteration, it will also end up being O(n.log(n)).
435 : : * xa_for_each_start() will spin if it hits a retry entry; if you intend to
436 : : * see retry entries, you should use the xas_for_each() iterator instead.
437 : : * The xas_for_each() iterator will expand into more inline code than
438 : : * xa_for_each_start().
439 : : *
440 : : * Context: Any context. Takes and releases the RCU lock.
441 : : */
442 : : #define xa_for_each_start(xa, index, entry, start) \
443 : : for (index = start, \
444 : : entry = xa_find(xa, &index, ULONG_MAX, XA_PRESENT); \
445 : : entry; \
446 : : entry = xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT))
447 : :
448 : : /**
449 : : * xa_for_each() - Iterate over present entries in an XArray.
450 : : * @xa: XArray.
451 : : * @index: Index of @entry.
452 : : * @entry: Entry retrieved from array.
453 : : *
454 : : * During the iteration, @entry will have the value of the entry stored
455 : : * in @xa at @index. You may modify @index during the iteration if you want
456 : : * to skip or reprocess indices. It is safe to modify the array during the
457 : : * iteration. At the end of the iteration, @entry will be set to NULL and
458 : : * @index will have a value less than or equal to max.
459 : : *
460 : : * xa_for_each() is O(n.log(n)) while xas_for_each() is O(n). You have
461 : : * to handle your own locking with xas_for_each(), and if you have to unlock
462 : : * after each iteration, it will also end up being O(n.log(n)). xa_for_each()
463 : : * will spin if it hits a retry entry; if you intend to see retry entries,
464 : : * you should use the xas_for_each() iterator instead. The xas_for_each()
465 : : * iterator will expand into more inline code than xa_for_each().
466 : : *
467 : : * Context: Any context. Takes and releases the RCU lock.
468 : : */
469 : : #define xa_for_each(xa, index, entry) \
470 : : xa_for_each_start(xa, index, entry, 0)
471 : :
472 : : /**
473 : : * xa_for_each_marked() - Iterate over marked entries in an XArray.
474 : : * @xa: XArray.
475 : : * @index: Index of @entry.
476 : : * @entry: Entry retrieved from array.
477 : : * @filter: Selection criterion.
478 : : *
479 : : * During the iteration, @entry will have the value of the entry stored
480 : : * in @xa at @index. The iteration will skip all entries in the array
481 : : * which do not match @filter. You may modify @index during the iteration
482 : : * if you want to skip or reprocess indices. It is safe to modify the array
483 : : * during the iteration. At the end of the iteration, @entry will be set to
484 : : * NULL and @index will have a value less than or equal to max.
485 : : *
486 : : * xa_for_each_marked() is O(n.log(n)) while xas_for_each_marked() is O(n).
487 : : * You have to handle your own locking with xas_for_each(), and if you have
488 : : * to unlock after each iteration, it will also end up being O(n.log(n)).
489 : : * xa_for_each_marked() will spin if it hits a retry entry; if you intend to
490 : : * see retry entries, you should use the xas_for_each_marked() iterator
491 : : * instead. The xas_for_each_marked() iterator will expand into more inline
492 : : * code than xa_for_each_marked().
493 : : *
494 : : * Context: Any context. Takes and releases the RCU lock.
495 : : */
496 : : #define xa_for_each_marked(xa, index, entry, filter) \
497 : : for (index = 0, entry = xa_find(xa, &index, ULONG_MAX, filter); \
498 : : entry; entry = xa_find_after(xa, &index, ULONG_MAX, filter))
499 : :
500 : : #define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
501 : : #define xa_lock(xa) spin_lock(&(xa)->xa_lock)
502 : : #define xa_unlock(xa) spin_unlock(&(xa)->xa_lock)
503 : : #define xa_lock_bh(xa) spin_lock_bh(&(xa)->xa_lock)
504 : : #define xa_unlock_bh(xa) spin_unlock_bh(&(xa)->xa_lock)
505 : : #define xa_lock_irq(xa) spin_lock_irq(&(xa)->xa_lock)
506 : : #define xa_unlock_irq(xa) spin_unlock_irq(&(xa)->xa_lock)
507 : : #define xa_lock_irqsave(xa, flags) \
508 : : spin_lock_irqsave(&(xa)->xa_lock, flags)
509 : : #define xa_unlock_irqrestore(xa, flags) \
510 : : spin_unlock_irqrestore(&(xa)->xa_lock, flags)
511 : :
512 : : /*
513 : : * Versions of the normal API which require the caller to hold the
514 : : * xa_lock. If the GFP flags allow it, they will drop the lock to
515 : : * allocate memory, then reacquire it afterwards. These functions
516 : : * may also re-enable interrupts if the XArray flags indicate the
517 : : * locking should be interrupt safe.
518 : : */
519 : : void *__xa_erase(struct xarray *, unsigned long index);
520 : : void *__xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
521 : : void *__xa_cmpxchg(struct xarray *, unsigned long index, void *old,
522 : : void *entry, gfp_t);
523 : : int __must_check __xa_insert(struct xarray *, unsigned long index,
524 : : void *entry, gfp_t);
525 : : int __must_check __xa_alloc(struct xarray *, u32 *id, void *entry,
526 : : struct xa_limit, gfp_t);
527 : : int __must_check __xa_alloc_cyclic(struct xarray *, u32 *id, void *entry,
528 : : struct xa_limit, u32 *next, gfp_t);
529 : : void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
530 : : void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
531 : :
532 : : /**
533 : : * xa_store_bh() - Store this entry in the XArray.
534 : : * @xa: XArray.
535 : : * @index: Index into array.
536 : : * @entry: New entry.
537 : : * @gfp: Memory allocation flags.
538 : : *
539 : : * This function is like calling xa_store() except it disables softirqs
540 : : * while holding the array lock.
541 : : *
542 : : * Context: Any context. Takes and releases the xa_lock while
543 : : * disabling softirqs.
544 : : * Return: The entry which used to be at this index.
545 : : */
546 : : static inline void *xa_store_bh(struct xarray *xa, unsigned long index,
547 : : void *entry, gfp_t gfp)
548 : : {
549 : : void *curr;
550 : :
551 : : xa_lock_bh(xa);
552 : : curr = __xa_store(xa, index, entry, gfp);
553 : : xa_unlock_bh(xa);
554 : :
555 : : return curr;
556 : : }
557 : :
558 : : /**
559 : : * xa_store_irq() - Store this entry in the XArray.
560 : : * @xa: XArray.
561 : : * @index: Index into array.
562 : : * @entry: New entry.
563 : : * @gfp: Memory allocation flags.
564 : : *
565 : : * This function is like calling xa_store() except it disables interrupts
566 : : * while holding the array lock.
567 : : *
568 : : * Context: Process context. Takes and releases the xa_lock while
569 : : * disabling interrupts.
570 : : * Return: The entry which used to be at this index.
571 : : */
572 : : static inline void *xa_store_irq(struct xarray *xa, unsigned long index,
573 : : void *entry, gfp_t gfp)
574 : : {
575 : : void *curr;
576 : :
577 : : xa_lock_irq(xa);
578 : : curr = __xa_store(xa, index, entry, gfp);
579 : : xa_unlock_irq(xa);
580 : :
581 : : return curr;
582 : : }
583 : :
584 : : /**
585 : : * xa_erase_bh() - Erase this entry from the XArray.
586 : : * @xa: XArray.
587 : : * @index: Index of entry.
588 : : *
589 : : * After this function returns, loading from @index will return %NULL.
590 : : * If the index is part of a multi-index entry, all indices will be erased
591 : : * and none of the entries will be part of a multi-index entry.
592 : : *
593 : : * Context: Any context. Takes and releases the xa_lock while
594 : : * disabling softirqs.
595 : : * Return: The entry which used to be at this index.
596 : : */
597 : : static inline void *xa_erase_bh(struct xarray *xa, unsigned long index)
598 : : {
599 : : void *entry;
600 : :
601 : : xa_lock_bh(xa);
602 : : entry = __xa_erase(xa, index);
603 : : xa_unlock_bh(xa);
604 : :
605 : : return entry;
606 : : }
607 : :
608 : : /**
609 : : * xa_erase_irq() - Erase this entry from the XArray.
610 : : * @xa: XArray.
611 : : * @index: Index of entry.
612 : : *
613 : : * After this function returns, loading from @index will return %NULL.
614 : : * If the index is part of a multi-index entry, all indices will be erased
615 : : * and none of the entries will be part of a multi-index entry.
616 : : *
617 : : * Context: Process context. Takes and releases the xa_lock while
618 : : * disabling interrupts.
619 : : * Return: The entry which used to be at this index.
620 : : */
621 : : static inline void *xa_erase_irq(struct xarray *xa, unsigned long index)
622 : : {
623 : : void *entry;
624 : :
625 : : xa_lock_irq(xa);
626 : : entry = __xa_erase(xa, index);
627 : : xa_unlock_irq(xa);
628 : :
629 : : return entry;
630 : : }
631 : :
632 : : /**
633 : : * xa_cmpxchg() - Conditionally replace an entry in the XArray.
634 : : * @xa: XArray.
635 : : * @index: Index into array.
636 : : * @old: Old value to test against.
637 : : * @entry: New value to place in array.
638 : : * @gfp: Memory allocation flags.
639 : : *
640 : : * If the entry at @index is the same as @old, replace it with @entry.
641 : : * If the return value is equal to @old, then the exchange was successful.
642 : : *
643 : : * Context: Any context. Takes and releases the xa_lock. May sleep
644 : : * if the @gfp flags permit.
645 : : * Return: The old value at this index or xa_err() if an error happened.
646 : : */
647 : : static inline void *xa_cmpxchg(struct xarray *xa, unsigned long index,
648 : : void *old, void *entry, gfp_t gfp)
649 : : {
650 : : void *curr;
651 : :
652 : : xa_lock(xa);
653 : : curr = __xa_cmpxchg(xa, index, old, entry, gfp);
654 : : xa_unlock(xa);
655 : :
656 : : return curr;
657 : : }
658 : :
659 : : /**
660 : : * xa_cmpxchg_bh() - Conditionally replace an entry in the XArray.
661 : : * @xa: XArray.
662 : : * @index: Index into array.
663 : : * @old: Old value to test against.
664 : : * @entry: New value to place in array.
665 : : * @gfp: Memory allocation flags.
666 : : *
667 : : * This function is like calling xa_cmpxchg() except it disables softirqs
668 : : * while holding the array lock.
669 : : *
670 : : * Context: Any context. Takes and releases the xa_lock while
671 : : * disabling softirqs. May sleep if the @gfp flags permit.
672 : : * Return: The old value at this index or xa_err() if an error happened.
673 : : */
674 : : static inline void *xa_cmpxchg_bh(struct xarray *xa, unsigned long index,
675 : : void *old, void *entry, gfp_t gfp)
676 : : {
677 : : void *curr;
678 : :
679 : : xa_lock_bh(xa);
680 : : curr = __xa_cmpxchg(xa, index, old, entry, gfp);
681 : : xa_unlock_bh(xa);
682 : :
683 : : return curr;
684 : : }
685 : :
686 : : /**
687 : : * xa_cmpxchg_irq() - Conditionally replace an entry in the XArray.
688 : : * @xa: XArray.
689 : : * @index: Index into array.
690 : : * @old: Old value to test against.
691 : : * @entry: New value to place in array.
692 : : * @gfp: Memory allocation flags.
693 : : *
694 : : * This function is like calling xa_cmpxchg() except it disables interrupts
695 : : * while holding the array lock.
696 : : *
697 : : * Context: Process context. Takes and releases the xa_lock while
698 : : * disabling interrupts. May sleep if the @gfp flags permit.
699 : : * Return: The old value at this index or xa_err() if an error happened.
700 : : */
701 : 0 : static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
702 : : void *old, void *entry, gfp_t gfp)
703 : : {
704 : : void *curr;
705 : :
706 : : xa_lock_irq(xa);
707 : 0 : curr = __xa_cmpxchg(xa, index, old, entry, gfp);
708 : : xa_unlock_irq(xa);
709 : :
710 : 0 : return curr;
711 : : }
712 : :
713 : : /**
714 : : * xa_insert() - Store this entry in the XArray unless another entry is
715 : : * already present.
716 : : * @xa: XArray.
717 : : * @index: Index into array.
718 : : * @entry: New entry.
719 : : * @gfp: Memory allocation flags.
720 : : *
721 : : * Inserting a NULL entry will store a reserved entry (like xa_reserve())
722 : : * if no entry is present. Inserting will fail if a reserved entry is
723 : : * present, even though loading from this index will return NULL.
724 : : *
725 : : * Context: Any context. Takes and releases the xa_lock. May sleep if
726 : : * the @gfp flags permit.
727 : : * Return: 0 if the store succeeded. -EBUSY if another entry was present.
728 : : * -ENOMEM if memory could not be allocated.
729 : : */
730 : : static inline int __must_check xa_insert(struct xarray *xa,
731 : : unsigned long index, void *entry, gfp_t gfp)
732 : : {
733 : : int err;
734 : :
735 : : xa_lock(xa);
736 : : err = __xa_insert(xa, index, entry, gfp);
737 : : xa_unlock(xa);
738 : :
739 : : return err;
740 : : }
741 : :
742 : : /**
743 : : * xa_insert_bh() - Store this entry in the XArray unless another entry is
744 : : * already present.
745 : : * @xa: XArray.
746 : : * @index: Index into array.
747 : : * @entry: New entry.
748 : : * @gfp: Memory allocation flags.
749 : : *
750 : : * Inserting a NULL entry will store a reserved entry (like xa_reserve())
751 : : * if no entry is present. Inserting will fail if a reserved entry is
752 : : * present, even though loading from this index will return NULL.
753 : : *
754 : : * Context: Any context. Takes and releases the xa_lock while
755 : : * disabling softirqs. May sleep if the @gfp flags permit.
756 : : * Return: 0 if the store succeeded. -EBUSY if another entry was present.
757 : : * -ENOMEM if memory could not be allocated.
758 : : */
759 : : static inline int __must_check xa_insert_bh(struct xarray *xa,
760 : : unsigned long index, void *entry, gfp_t gfp)
761 : : {
762 : : int err;
763 : :
764 : : xa_lock_bh(xa);
765 : : err = __xa_insert(xa, index, entry, gfp);
766 : : xa_unlock_bh(xa);
767 : :
768 : : return err;
769 : : }
770 : :
771 : : /**
772 : : * xa_insert_irq() - Store this entry in the XArray unless another entry is
773 : : * already present.
774 : : * @xa: XArray.
775 : : * @index: Index into array.
776 : : * @entry: New entry.
777 : : * @gfp: Memory allocation flags.
778 : : *
779 : : * Inserting a NULL entry will store a reserved entry (like xa_reserve())
780 : : * if no entry is present. Inserting will fail if a reserved entry is
781 : : * present, even though loading from this index will return NULL.
782 : : *
783 : : * Context: Process context. Takes and releases the xa_lock while
784 : : * disabling interrupts. May sleep if the @gfp flags permit.
785 : : * Return: 0 if the store succeeded. -EBUSY if another entry was present.
786 : : * -ENOMEM if memory could not be allocated.
787 : : */
788 : : static inline int __must_check xa_insert_irq(struct xarray *xa,
789 : : unsigned long index, void *entry, gfp_t gfp)
790 : : {
791 : : int err;
792 : :
793 : : xa_lock_irq(xa);
794 : : err = __xa_insert(xa, index, entry, gfp);
795 : : xa_unlock_irq(xa);
796 : :
797 : : return err;
798 : : }
799 : :
800 : : /**
801 : : * xa_alloc() - Find somewhere to store this entry in the XArray.
802 : : * @xa: XArray.
803 : : * @id: Pointer to ID.
804 : : * @entry: New entry.
805 : : * @limit: Range of ID to allocate.
806 : : * @gfp: Memory allocation flags.
807 : : *
808 : : * Finds an empty entry in @xa between @limit.min and @limit.max,
809 : : * stores the index into the @id pointer, then stores the entry at
810 : : * that index. A concurrent lookup will not see an uninitialised @id.
811 : : *
812 : : * Context: Any context. Takes and releases the xa_lock. May sleep if
813 : : * the @gfp flags permit.
814 : : * Return: 0 on success, -ENOMEM if memory could not be allocated or
815 : : * -EBUSY if there are no free entries in @limit.
816 : : */
817 : 3 : static inline __must_check int xa_alloc(struct xarray *xa, u32 *id,
818 : : void *entry, struct xa_limit limit, gfp_t gfp)
819 : : {
820 : : int err;
821 : :
822 : : xa_lock(xa);
823 : 3 : err = __xa_alloc(xa, id, entry, limit, gfp);
824 : : xa_unlock(xa);
825 : :
826 : 3 : return err;
827 : : }
828 : :
829 : : /**
830 : : * xa_alloc_bh() - Find somewhere to store this entry in the XArray.
831 : : * @xa: XArray.
832 : : * @id: Pointer to ID.
833 : : * @entry: New entry.
834 : : * @limit: Range of ID to allocate.
835 : : * @gfp: Memory allocation flags.
836 : : *
837 : : * Finds an empty entry in @xa between @limit.min and @limit.max,
838 : : * stores the index into the @id pointer, then stores the entry at
839 : : * that index. A concurrent lookup will not see an uninitialised @id.
840 : : *
841 : : * Context: Any context. Takes and releases the xa_lock while
842 : : * disabling softirqs. May sleep if the @gfp flags permit.
843 : : * Return: 0 on success, -ENOMEM if memory could not be allocated or
844 : : * -EBUSY if there are no free entries in @limit.
845 : : */
846 : : static inline int __must_check xa_alloc_bh(struct xarray *xa, u32 *id,
847 : : void *entry, struct xa_limit limit, gfp_t gfp)
848 : : {
849 : : int err;
850 : :
851 : : xa_lock_bh(xa);
852 : : err = __xa_alloc(xa, id, entry, limit, gfp);
853 : : xa_unlock_bh(xa);
854 : :
855 : : return err;
856 : : }
857 : :
858 : : /**
859 : : * xa_alloc_irq() - Find somewhere to store this entry in the XArray.
860 : : * @xa: XArray.
861 : : * @id: Pointer to ID.
862 : : * @entry: New entry.
863 : : * @limit: Range of ID to allocate.
864 : : * @gfp: Memory allocation flags.
865 : : *
866 : : * Finds an empty entry in @xa between @limit.min and @limit.max,
867 : : * stores the index into the @id pointer, then stores the entry at
868 : : * that index. A concurrent lookup will not see an uninitialised @id.
869 : : *
870 : : * Context: Process context. Takes and releases the xa_lock while
871 : : * disabling interrupts. May sleep if the @gfp flags permit.
872 : : * Return: 0 on success, -ENOMEM if memory could not be allocated or
873 : : * -EBUSY if there are no free entries in @limit.
874 : : */
875 : : static inline int __must_check xa_alloc_irq(struct xarray *xa, u32 *id,
876 : : void *entry, struct xa_limit limit, gfp_t gfp)
877 : : {
878 : : int err;
879 : :
880 : : xa_lock_irq(xa);
881 : : err = __xa_alloc(xa, id, entry, limit, gfp);
882 : : xa_unlock_irq(xa);
883 : :
884 : : return err;
885 : : }
886 : :
887 : : /**
888 : : * xa_alloc_cyclic() - Find somewhere to store this entry in the XArray.
889 : : * @xa: XArray.
890 : : * @id: Pointer to ID.
891 : : * @entry: New entry.
892 : : * @limit: Range of allocated ID.
893 : : * @next: Pointer to next ID to allocate.
894 : : * @gfp: Memory allocation flags.
895 : : *
896 : : * Finds an empty entry in @xa between @limit.min and @limit.max,
897 : : * stores the index into the @id pointer, then stores the entry at
898 : : * that index. A concurrent lookup will not see an uninitialised @id.
899 : : * The search for an empty entry will start at @next and will wrap
900 : : * around if necessary.
901 : : *
902 : : * Context: Any context. Takes and releases the xa_lock. May sleep if
903 : : * the @gfp flags permit.
904 : : * Return: 0 if the allocation succeeded without wrapping. 1 if the
905 : : * allocation succeeded after wrapping, -ENOMEM if memory could not be
906 : : * allocated or -EBUSY if there are no free entries in @limit.
907 : : */
908 : : static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
909 : : struct xa_limit limit, u32 *next, gfp_t gfp)
910 : : {
911 : : int err;
912 : :
913 : : xa_lock(xa);
914 : : err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
915 : : xa_unlock(xa);
916 : :
917 : : return err;
918 : : }
919 : :
920 : : /**
921 : : * xa_alloc_cyclic_bh() - Find somewhere to store this entry in the XArray.
922 : : * @xa: XArray.
923 : : * @id: Pointer to ID.
924 : : * @entry: New entry.
925 : : * @limit: Range of allocated ID.
926 : : * @next: Pointer to next ID to allocate.
927 : : * @gfp: Memory allocation flags.
928 : : *
929 : : * Finds an empty entry in @xa between @limit.min and @limit.max,
930 : : * stores the index into the @id pointer, then stores the entry at
931 : : * that index. A concurrent lookup will not see an uninitialised @id.
932 : : * The search for an empty entry will start at @next and will wrap
933 : : * around if necessary.
934 : : *
935 : : * Context: Any context. Takes and releases the xa_lock while
936 : : * disabling softirqs. May sleep if the @gfp flags permit.
937 : : * Return: 0 if the allocation succeeded without wrapping. 1 if the
938 : : * allocation succeeded after wrapping, -ENOMEM if memory could not be
939 : : * allocated or -EBUSY if there are no free entries in @limit.
940 : : */
941 : : static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry,
942 : : struct xa_limit limit, u32 *next, gfp_t gfp)
943 : : {
944 : : int err;
945 : :
946 : : xa_lock_bh(xa);
947 : : err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
948 : : xa_unlock_bh(xa);
949 : :
950 : : return err;
951 : : }
952 : :
953 : : /**
954 : : * xa_alloc_cyclic_irq() - Find somewhere to store this entry in the XArray.
955 : : * @xa: XArray.
956 : : * @id: Pointer to ID.
957 : : * @entry: New entry.
958 : : * @limit: Range of allocated ID.
959 : : * @next: Pointer to next ID to allocate.
960 : : * @gfp: Memory allocation flags.
961 : : *
962 : : * Finds an empty entry in @xa between @limit.min and @limit.max,
963 : : * stores the index into the @id pointer, then stores the entry at
964 : : * that index. A concurrent lookup will not see an uninitialised @id.
965 : : * The search for an empty entry will start at @next and will wrap
966 : : * around if necessary.
967 : : *
968 : : * Context: Process context. Takes and releases the xa_lock while
969 : : * disabling interrupts. May sleep if the @gfp flags permit.
970 : : * Return: 0 if the allocation succeeded without wrapping. 1 if the
971 : : * allocation succeeded after wrapping, -ENOMEM if memory could not be
972 : : * allocated or -EBUSY if there are no free entries in @limit.
973 : : */
974 : : static inline int xa_alloc_cyclic_irq(struct xarray *xa, u32 *id, void *entry,
975 : : struct xa_limit limit, u32 *next, gfp_t gfp)
976 : : {
977 : : int err;
978 : :
979 : : xa_lock_irq(xa);
980 : : err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
981 : : xa_unlock_irq(xa);
982 : :
983 : : return err;
984 : : }
985 : :
986 : : /**
987 : : * xa_reserve() - Reserve this index in the XArray.
988 : : * @xa: XArray.
989 : : * @index: Index into array.
990 : : * @gfp: Memory allocation flags.
991 : : *
992 : : * Ensures there is somewhere to store an entry at @index in the array.
993 : : * If there is already something stored at @index, this function does
994 : : * nothing. If there was nothing there, the entry is marked as reserved.
995 : : * Loading from a reserved entry returns a %NULL pointer.
996 : : *
997 : : * If you do not use the entry that you have reserved, call xa_release()
998 : : * or xa_erase() to free any unnecessary memory.
999 : : *
1000 : : * Context: Any context. Takes and releases the xa_lock.
1001 : : * May sleep if the @gfp flags permit.
1002 : : * Return: 0 if the reservation succeeded or -ENOMEM if it failed.
1003 : : */
1004 : : static inline __must_check
1005 : : int xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp)
1006 : : {
1007 : : return xa_err(xa_cmpxchg(xa, index, NULL, XA_ZERO_ENTRY, gfp));
1008 : : }
1009 : :
1010 : : /**
1011 : : * xa_reserve_bh() - Reserve this index in the XArray.
1012 : : * @xa: XArray.
1013 : : * @index: Index into array.
1014 : : * @gfp: Memory allocation flags.
1015 : : *
1016 : : * A softirq-disabling version of xa_reserve().
1017 : : *
1018 : : * Context: Any context. Takes and releases the xa_lock while
1019 : : * disabling softirqs.
1020 : : * Return: 0 if the reservation succeeded or -ENOMEM if it failed.
1021 : : */
1022 : : static inline __must_check
1023 : : int xa_reserve_bh(struct xarray *xa, unsigned long index, gfp_t gfp)
1024 : : {
1025 : : return xa_err(xa_cmpxchg_bh(xa, index, NULL, XA_ZERO_ENTRY, gfp));
1026 : : }
1027 : :
1028 : : /**
1029 : : * xa_reserve_irq() - Reserve this index in the XArray.
1030 : : * @xa: XArray.
1031 : : * @index: Index into array.
1032 : : * @gfp: Memory allocation flags.
1033 : : *
1034 : : * An interrupt-disabling version of xa_reserve().
1035 : : *
1036 : : * Context: Process context. Takes and releases the xa_lock while
1037 : : * disabling interrupts.
1038 : : * Return: 0 if the reservation succeeded or -ENOMEM if it failed.
1039 : : */
1040 : : static inline __must_check
1041 : : int xa_reserve_irq(struct xarray *xa, unsigned long index, gfp_t gfp)
1042 : : {
1043 : : return xa_err(xa_cmpxchg_irq(xa, index, NULL, XA_ZERO_ENTRY, gfp));
1044 : : }
1045 : :
1046 : : /**
1047 : : * xa_release() - Release a reserved entry.
1048 : : * @xa: XArray.
1049 : : * @index: Index of entry.
1050 : : *
1051 : : * After calling xa_reserve(), you can call this function to release the
1052 : : * reservation. If the entry at @index has been stored to, this function
1053 : : * will do nothing.
1054 : : */
1055 : : static inline void xa_release(struct xarray *xa, unsigned long index)
1056 : : {
1057 : : xa_cmpxchg(xa, index, XA_ZERO_ENTRY, NULL, 0);
1058 : : }
1059 : :
1060 : : /* Everything below here is the Advanced API. Proceed with caution. */
1061 : :
1062 : : /*
1063 : : * The xarray is constructed out of a set of 'chunks' of pointers. Choosing
1064 : : * the best chunk size requires some tradeoffs. A power of two recommends
1065 : : * itself so that we can walk the tree based purely on shifts and masks.
1066 : : * Generally, the larger the better; as the number of slots per level of the
1067 : : * tree increases, the less tall the tree needs to be. But that needs to be
1068 : : * balanced against the memory consumption of each node. On a 64-bit system,
1069 : : * xa_node is currently 576 bytes, and we get 7 of them per 4kB page. If we
1070 : : * doubled the number of slots per node, we'd get only 3 nodes per 4kB page.
1071 : : */
1072 : : #ifndef XA_CHUNK_SHIFT
1073 : : #define XA_CHUNK_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
1074 : : #endif
1075 : : #define XA_CHUNK_SIZE (1UL << XA_CHUNK_SHIFT)
1076 : : #define XA_CHUNK_MASK (XA_CHUNK_SIZE - 1)
1077 : : #define XA_MAX_MARKS 3
1078 : : #define XA_MARK_LONGS DIV_ROUND_UP(XA_CHUNK_SIZE, BITS_PER_LONG)
1079 : :
1080 : : /*
1081 : : * @count is the count of every non-NULL element in the ->slots array
1082 : : * whether that is a value entry, a retry entry, a user pointer,
1083 : : * a sibling entry or a pointer to the next level of the tree.
1084 : : * @nr_values is the count of every element in ->slots which is
1085 : : * either a value entry or a sibling of a value entry.
1086 : : */
1087 : : struct xa_node {
1088 : : unsigned char shift; /* Bits remaining in each slot */
1089 : : unsigned char offset; /* Slot offset in parent */
1090 : : unsigned char count; /* Total entry count */
1091 : : unsigned char nr_values; /* Value entry count */
1092 : : struct xa_node __rcu *parent; /* NULL at top of tree */
1093 : : struct xarray *array; /* The array we belong to */
1094 : : union {
1095 : : struct list_head private_list; /* For tree user */
1096 : : struct rcu_head rcu_head; /* Used when freeing node */
1097 : : };
1098 : : void __rcu *slots[XA_CHUNK_SIZE];
1099 : : union {
1100 : : unsigned long tags[XA_MAX_MARKS][XA_MARK_LONGS];
1101 : : unsigned long marks[XA_MAX_MARKS][XA_MARK_LONGS];
1102 : : };
1103 : : };
1104 : :
1105 : : void xa_dump(const struct xarray *);
1106 : : void xa_dump_node(const struct xa_node *);
1107 : :
1108 : : #ifdef XA_DEBUG
1109 : : #define XA_BUG_ON(xa, x) do { \
1110 : : if (x) { \
1111 : : xa_dump(xa); \
1112 : : BUG(); \
1113 : : } \
1114 : : } while (0)
1115 : : #define XA_NODE_BUG_ON(node, x) do { \
1116 : : if (x) { \
1117 : : if (node) xa_dump_node(node); \
1118 : : BUG(); \
1119 : : } \
1120 : : } while (0)
1121 : : #else
1122 : : #define XA_BUG_ON(xa, x) do { } while (0)
1123 : : #define XA_NODE_BUG_ON(node, x) do { } while (0)
1124 : : #endif
1125 : :
1126 : : /* Private */
1127 : : static inline void *xa_head(const struct xarray *xa)
1128 : : {
1129 : 3 : return rcu_dereference_check(xa->xa_head,
1130 : : lockdep_is_held(&xa->xa_lock));
1131 : : }
1132 : :
1133 : : /* Private */
1134 : : static inline void *xa_head_locked(const struct xarray *xa)
1135 : : {
1136 : 3 : return rcu_dereference_protected(xa->xa_head,
1137 : : lockdep_is_held(&xa->xa_lock));
1138 : : }
1139 : :
1140 : : /* Private */
1141 : : static inline void *xa_entry(const struct xarray *xa,
1142 : : const struct xa_node *node, unsigned int offset)
1143 : : {
1144 : : XA_NODE_BUG_ON(node, offset >= XA_CHUNK_SIZE);
1145 : 3 : return rcu_dereference_check(node->slots[offset],
1146 : : lockdep_is_held(&xa->xa_lock));
1147 : : }
1148 : :
1149 : : /* Private */
1150 : : static inline void *xa_entry_locked(const struct xarray *xa,
1151 : : const struct xa_node *node, unsigned int offset)
1152 : : {
1153 : : XA_NODE_BUG_ON(node, offset >= XA_CHUNK_SIZE);
1154 : 3 : return rcu_dereference_protected(node->slots[offset],
1155 : : lockdep_is_held(&xa->xa_lock));
1156 : : }
1157 : :
1158 : : /* Private */
1159 : : static inline struct xa_node *xa_parent(const struct xarray *xa,
1160 : : const struct xa_node *node)
1161 : : {
1162 : 3 : return rcu_dereference_check(node->parent,
1163 : : lockdep_is_held(&xa->xa_lock));
1164 : : }
1165 : :
1166 : : /* Private */
1167 : : static inline struct xa_node *xa_parent_locked(const struct xarray *xa,
1168 : : const struct xa_node *node)
1169 : : {
1170 : 3 : return rcu_dereference_protected(node->parent,
1171 : : lockdep_is_held(&xa->xa_lock));
1172 : : }
1173 : :
1174 : : /* Private */
1175 : : static inline void *xa_mk_node(const struct xa_node *node)
1176 : : {
1177 : 3 : return (void *)((unsigned long)node | 2);
1178 : : }
1179 : :
1180 : : /* Private */
1181 : : static inline struct xa_node *xa_to_node(const void *entry)
1182 : : {
1183 : 3 : return (struct xa_node *)((unsigned long)entry - 2);
1184 : : }
1185 : :
1186 : : /* Private */
1187 : : static inline bool xa_is_node(const void *entry)
1188 : : {
1189 : 3 : return xa_is_internal(entry) && (unsigned long)entry > 4096;
1190 : : }
1191 : :
1192 : : /* Private */
1193 : : static inline void *xa_mk_sibling(unsigned int offset)
1194 : : {
1195 : : return xa_mk_internal(offset);
1196 : : }
1197 : :
1198 : : /* Private */
1199 : : static inline unsigned long xa_to_sibling(const void *entry)
1200 : : {
1201 : : return xa_to_internal(entry);
1202 : : }
1203 : :
1204 : : /**
1205 : : * xa_is_sibling() - Is the entry a sibling entry?
1206 : : * @entry: Entry retrieved from the XArray
1207 : : *
1208 : : * Return: %true if the entry is a sibling entry.
1209 : : */
1210 : : static inline bool xa_is_sibling(const void *entry)
1211 : : {
1212 : : return IS_ENABLED(CONFIG_XARRAY_MULTI) && xa_is_internal(entry) &&
1213 : : (entry < xa_mk_sibling(XA_CHUNK_SIZE - 1));
1214 : : }
1215 : :
1216 : : #define XA_RETRY_ENTRY xa_mk_internal(256)
1217 : :
1218 : : /**
1219 : : * xa_is_retry() - Is the entry a retry entry?
1220 : : * @entry: Entry retrieved from the XArray
1221 : : *
1222 : : * Return: %true if the entry is a retry entry.
1223 : : */
1224 : : static inline bool xa_is_retry(const void *entry)
1225 : : {
1226 : 3 : return unlikely(entry == XA_RETRY_ENTRY);
1227 : : }
1228 : :
1229 : : /**
1230 : : * xa_is_advanced() - Is the entry only permitted for the advanced API?
1231 : : * @entry: Entry to be stored in the XArray.
1232 : : *
1233 : : * Return: %true if the entry cannot be stored by the normal API.
1234 : : */
1235 : : static inline bool xa_is_advanced(const void *entry)
1236 : : {
1237 : 3 : return xa_is_internal(entry) && (entry <= XA_RETRY_ENTRY);
1238 : : }
1239 : :
1240 : : /**
1241 : : * typedef xa_update_node_t - A callback function from the XArray.
1242 : : * @node: The node which is being processed
1243 : : *
1244 : : * This function is called every time the XArray updates the count of
1245 : : * present and value entries in a node. It allows advanced users to
1246 : : * maintain the private_list in the node.
1247 : : *
1248 : : * Context: The xa_lock is held and interrupts may be disabled.
1249 : : * Implementations should not drop the xa_lock, nor re-enable
1250 : : * interrupts.
1251 : : */
1252 : : typedef void (*xa_update_node_t)(struct xa_node *node);
1253 : :
1254 : : /*
1255 : : * The xa_state is opaque to its users. It contains various different pieces
1256 : : * of state involved in the current operation on the XArray. It should be
1257 : : * declared on the stack and passed between the various internal routines.
1258 : : * The various elements in it should not be accessed directly, but only
1259 : : * through the provided accessor functions. The below documentation is for
1260 : : * the benefit of those working on the code, not for users of the XArray.
1261 : : *
1262 : : * @xa_node usually points to the xa_node containing the slot we're operating
1263 : : * on (and @xa_offset is the offset in the slots array). If there is a
1264 : : * single entry in the array at index 0, there are no allocated xa_nodes to
1265 : : * point to, and so we store %NULL in @xa_node. @xa_node is set to
1266 : : * the value %XAS_RESTART if the xa_state is not walked to the correct
1267 : : * position in the tree of nodes for this operation. If an error occurs
1268 : : * during an operation, it is set to an %XAS_ERROR value. If we run off the
1269 : : * end of the allocated nodes, it is set to %XAS_BOUNDS.
1270 : : */
1271 : : struct xa_state {
1272 : : struct xarray *xa;
1273 : : unsigned long xa_index;
1274 : : unsigned char xa_shift;
1275 : : unsigned char xa_sibs;
1276 : : unsigned char xa_offset;
1277 : : unsigned char xa_pad; /* Helps gcc generate better code */
1278 : : struct xa_node *xa_node;
1279 : : struct xa_node *xa_alloc;
1280 : : xa_update_node_t xa_update;
1281 : : };
1282 : :
1283 : : /*
1284 : : * We encode errnos in the xas->xa_node. If an error has happened, we need to
1285 : : * drop the lock to fix it, and once we've done so the xa_state is invalid.
1286 : : */
1287 : : #define XA_ERROR(errno) ((struct xa_node *)(((unsigned long)errno << 2) | 2UL))
1288 : : #define XAS_BOUNDS ((struct xa_node *)1UL)
1289 : : #define XAS_RESTART ((struct xa_node *)3UL)
1290 : :
1291 : : #define __XA_STATE(array, index, shift, sibs) { \
1292 : : .xa = array, \
1293 : : .xa_index = index, \
1294 : : .xa_shift = shift, \
1295 : : .xa_sibs = sibs, \
1296 : : .xa_offset = 0, \
1297 : : .xa_pad = 0, \
1298 : : .xa_node = XAS_RESTART, \
1299 : : .xa_alloc = NULL, \
1300 : : .xa_update = NULL \
1301 : : }
1302 : :
1303 : : /**
1304 : : * XA_STATE() - Declare an XArray operation state.
1305 : : * @name: Name of this operation state (usually xas).
1306 : : * @array: Array to operate on.
1307 : : * @index: Initial index of interest.
1308 : : *
1309 : : * Declare and initialise an xa_state on the stack.
1310 : : */
1311 : : #define XA_STATE(name, array, index) \
1312 : : struct xa_state name = __XA_STATE(array, index, 0, 0)
1313 : :
1314 : : /**
1315 : : * XA_STATE_ORDER() - Declare an XArray operation state.
1316 : : * @name: Name of this operation state (usually xas).
1317 : : * @array: Array to operate on.
1318 : : * @index: Initial index of interest.
1319 : : * @order: Order of entry.
1320 : : *
1321 : : * Declare and initialise an xa_state on the stack. This variant of
1322 : : * XA_STATE() allows you to specify the 'order' of the element you
1323 : : * want to operate on.`
1324 : : */
1325 : : #define XA_STATE_ORDER(name, array, index, order) \
1326 : : struct xa_state name = __XA_STATE(array, \
1327 : : (index >> order) << order, \
1328 : : order - (order % XA_CHUNK_SHIFT), \
1329 : : (1U << (order % XA_CHUNK_SHIFT)) - 1)
1330 : :
1331 : : #define xas_marked(xas, mark) xa_marked((xas)->xa, (mark))
1332 : : #define xas_trylock(xas) xa_trylock((xas)->xa)
1333 : : #define xas_lock(xas) xa_lock((xas)->xa)
1334 : : #define xas_unlock(xas) xa_unlock((xas)->xa)
1335 : : #define xas_lock_bh(xas) xa_lock_bh((xas)->xa)
1336 : : #define xas_unlock_bh(xas) xa_unlock_bh((xas)->xa)
1337 : : #define xas_lock_irq(xas) xa_lock_irq((xas)->xa)
1338 : : #define xas_unlock_irq(xas) xa_unlock_irq((xas)->xa)
1339 : : #define xas_lock_irqsave(xas, flags) \
1340 : : xa_lock_irqsave((xas)->xa, flags)
1341 : : #define xas_unlock_irqrestore(xas, flags) \
1342 : : xa_unlock_irqrestore((xas)->xa, flags)
1343 : :
1344 : : /**
1345 : : * xas_error() - Return an errno stored in the xa_state.
1346 : : * @xas: XArray operation state.
1347 : : *
1348 : : * Return: 0 if no error has been noted. A negative errno if one has.
1349 : : */
1350 : : static inline int xas_error(const struct xa_state *xas)
1351 : : {
1352 : 3 : return xa_err(xas->xa_node);
1353 : : }
1354 : :
1355 : : /**
1356 : : * xas_set_err() - Note an error in the xa_state.
1357 : : * @xas: XArray operation state.
1358 : : * @err: Negative error number.
1359 : : *
1360 : : * Only call this function with a negative @err; zero or positive errors
1361 : : * will probably not behave the way you think they should. If you want
1362 : : * to clear the error from an xa_state, use xas_reset().
1363 : : */
1364 : : static inline void xas_set_err(struct xa_state *xas, long err)
1365 : : {
1366 : 3 : xas->xa_node = XA_ERROR(err);
1367 : : }
1368 : :
1369 : : /**
1370 : : * xas_invalid() - Is the xas in a retry or error state?
1371 : : * @xas: XArray operation state.
1372 : : *
1373 : : * Return: %true if the xas cannot be used for operations.
1374 : : */
1375 : : static inline bool xas_invalid(const struct xa_state *xas)
1376 : : {
1377 : 3 : return (unsigned long)xas->xa_node & 3;
1378 : : }
1379 : :
1380 : : /**
1381 : : * xas_valid() - Is the xas a valid cursor into the array?
1382 : : * @xas: XArray operation state.
1383 : : *
1384 : : * Return: %true if the xas can be used for operations.
1385 : : */
1386 : : static inline bool xas_valid(const struct xa_state *xas)
1387 : : {
1388 : : return !xas_invalid(xas);
1389 : : }
1390 : :
1391 : : /**
1392 : : * xas_is_node() - Does the xas point to a node?
1393 : : * @xas: XArray operation state.
1394 : : *
1395 : : * Return: %true if the xas currently references a node.
1396 : : */
1397 : : static inline bool xas_is_node(const struct xa_state *xas)
1398 : : {
1399 : 3 : return xas_valid(xas) && xas->xa_node;
1400 : : }
1401 : :
1402 : : /* True if the pointer is something other than a node */
1403 : : static inline bool xas_not_node(struct xa_node *node)
1404 : : {
1405 : 3 : return ((unsigned long)node & 3) || !node;
1406 : : }
1407 : :
1408 : : /* True if the node represents RESTART or an error */
1409 : : static inline bool xas_frozen(struct xa_node *node)
1410 : : {
1411 : 3 : return (unsigned long)node & 2;
1412 : : }
1413 : :
1414 : : /* True if the node represents head-of-tree, RESTART or BOUNDS */
1415 : : static inline bool xas_top(struct xa_node *node)
1416 : : {
1417 : : return node <= XAS_RESTART;
1418 : : }
1419 : :
1420 : : /**
1421 : : * xas_reset() - Reset an XArray operation state.
1422 : : * @xas: XArray operation state.
1423 : : *
1424 : : * Resets the error or walk state of the @xas so future walks of the
1425 : : * array will start from the root. Use this if you have dropped the
1426 : : * xarray lock and want to reuse the xa_state.
1427 : : *
1428 : : * Context: Any context.
1429 : : */
1430 : : static inline void xas_reset(struct xa_state *xas)
1431 : : {
1432 : 3 : xas->xa_node = XAS_RESTART;
1433 : : }
1434 : :
1435 : : /**
1436 : : * xas_retry() - Retry the operation if appropriate.
1437 : : * @xas: XArray operation state.
1438 : : * @entry: Entry from xarray.
1439 : : *
1440 : : * The advanced functions may sometimes return an internal entry, such as
1441 : : * a retry entry or a zero entry. This function sets up the @xas to restart
1442 : : * the walk from the head of the array if needed.
1443 : : *
1444 : : * Context: Any context.
1445 : : * Return: true if the operation needs to be retried.
1446 : : */
1447 : : static inline bool xas_retry(struct xa_state *xas, const void *entry)
1448 : : {
1449 : 3 : if (xa_is_zero(entry))
1450 : : return true;
1451 : 3 : if (!xa_is_retry(entry))
1452 : : return false;
1453 : : xas_reset(xas);
1454 : : return true;
1455 : : }
1456 : :
1457 : : void *xas_load(struct xa_state *);
1458 : : void *xas_store(struct xa_state *, void *entry);
1459 : : void *xas_find(struct xa_state *, unsigned long max);
1460 : : void *xas_find_conflict(struct xa_state *);
1461 : :
1462 : : bool xas_get_mark(const struct xa_state *, xa_mark_t);
1463 : : void xas_set_mark(const struct xa_state *, xa_mark_t);
1464 : : void xas_clear_mark(const struct xa_state *, xa_mark_t);
1465 : : void *xas_find_marked(struct xa_state *, unsigned long max, xa_mark_t);
1466 : : void xas_init_marks(const struct xa_state *);
1467 : :
1468 : : bool xas_nomem(struct xa_state *, gfp_t);
1469 : : void xas_pause(struct xa_state *);
1470 : :
1471 : : void xas_create_range(struct xa_state *);
1472 : :
1473 : : /**
1474 : : * xas_reload() - Refetch an entry from the xarray.
1475 : : * @xas: XArray operation state.
1476 : : *
1477 : : * Use this function to check that a previously loaded entry still has
1478 : : * the same value. This is useful for the lockless pagecache lookup where
1479 : : * we walk the array with only the RCU lock to protect us, lock the page,
1480 : : * then check that the page hasn't moved since we looked it up.
1481 : : *
1482 : : * The caller guarantees that @xas is still valid. If it may be in an
1483 : : * error or restart state, call xas_load() instead.
1484 : : *
1485 : : * Return: The entry at this location in the xarray.
1486 : : */
1487 : : static inline void *xas_reload(struct xa_state *xas)
1488 : : {
1489 : 3 : struct xa_node *node = xas->xa_node;
1490 : :
1491 : 3 : if (node)
1492 : 3 : return xa_entry(xas->xa, node, xas->xa_offset);
1493 : 3 : return xa_head(xas->xa);
1494 : : }
1495 : :
1496 : : /**
1497 : : * xas_set() - Set up XArray operation state for a different index.
1498 : : * @xas: XArray operation state.
1499 : : * @index: New index into the XArray.
1500 : : *
1501 : : * Move the operation state to refer to a different index. This will
1502 : : * have the effect of starting a walk from the top; see xas_next()
1503 : : * to move to an adjacent index.
1504 : : */
1505 : : static inline void xas_set(struct xa_state *xas, unsigned long index)
1506 : : {
1507 : 3 : xas->xa_index = index;
1508 : 3 : xas->xa_node = XAS_RESTART;
1509 : : }
1510 : :
1511 : : /**
1512 : : * xas_set_order() - Set up XArray operation state for a multislot entry.
1513 : : * @xas: XArray operation state.
1514 : : * @index: Target of the operation.
1515 : : * @order: Entry occupies 2^@order indices.
1516 : : */
1517 : : static inline void xas_set_order(struct xa_state *xas, unsigned long index,
1518 : : unsigned int order)
1519 : : {
1520 : : #ifdef CONFIG_XARRAY_MULTI
1521 : : xas->xa_index = order < BITS_PER_LONG ? (index >> order) << order : 0;
1522 : : xas->xa_shift = order - (order % XA_CHUNK_SHIFT);
1523 : : xas->xa_sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1524 : : xas->xa_node = XAS_RESTART;
1525 : : #else
1526 : 3 : BUG_ON(order > 0);
1527 : : xas_set(xas, index);
1528 : : #endif
1529 : : }
1530 : :
1531 : : /**
1532 : : * xas_set_update() - Set up XArray operation state for a callback.
1533 : : * @xas: XArray operation state.
1534 : : * @update: Function to call when updating a node.
1535 : : *
1536 : : * The XArray can notify a caller after it has updated an xa_node.
1537 : : * This is advanced functionality and is only needed by the page cache.
1538 : : */
1539 : : static inline void xas_set_update(struct xa_state *xas, xa_update_node_t update)
1540 : : {
1541 : 3 : xas->xa_update = update;
1542 : : }
1543 : :
1544 : : /**
1545 : : * xas_next_entry() - Advance iterator to next present entry.
1546 : : * @xas: XArray operation state.
1547 : : * @max: Highest index to return.
1548 : : *
1549 : : * xas_next_entry() is an inline function to optimise xarray traversal for
1550 : : * speed. It is equivalent to calling xas_find(), and will call xas_find()
1551 : : * for all the hard cases.
1552 : : *
1553 : : * Return: The next present entry after the one currently referred to by @xas.
1554 : : */
1555 : 3 : static inline void *xas_next_entry(struct xa_state *xas, unsigned long max)
1556 : : {
1557 : 3 : struct xa_node *node = xas->xa_node;
1558 : : void *entry;
1559 : :
1560 : 3 : if (unlikely(xas_not_node(node) || node->shift ||
1561 : : xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)))
1562 : 3 : return xas_find(xas, max);
1563 : :
1564 : : do {
1565 : 3 : if (unlikely(xas->xa_index >= max))
1566 : 3 : return xas_find(xas, max);
1567 : 3 : if (unlikely(xas->xa_offset == XA_CHUNK_MASK))
1568 : 3 : return xas_find(xas, max);
1569 : 3 : entry = xa_entry(xas->xa, node, xas->xa_offset + 1);
1570 : 3 : if (unlikely(xa_is_internal(entry)))
1571 : 0 : return xas_find(xas, max);
1572 : 3 : xas->xa_offset++;
1573 : 3 : xas->xa_index++;
1574 : 3 : } while (!entry);
1575 : :
1576 : 3 : return entry;
1577 : : }
1578 : :
1579 : : /* Private */
1580 : : static inline unsigned int xas_find_chunk(struct xa_state *xas, bool advance,
1581 : : xa_mark_t mark)
1582 : : {
1583 : 3 : unsigned long *addr = xas->xa_node->marks[(__force unsigned)mark];
1584 : 3 : unsigned int offset = xas->xa_offset;
1585 : :
1586 : 3 : if (advance)
1587 : 3 : offset++;
1588 : : if (XA_CHUNK_SIZE == BITS_PER_LONG) {
1589 : : if (offset < XA_CHUNK_SIZE) {
1590 : : unsigned long data = *addr & (~0UL << offset);
1591 : : if (data)
1592 : : return __ffs(data);
1593 : : }
1594 : : return XA_CHUNK_SIZE;
1595 : : }
1596 : :
1597 : 3 : return find_next_bit(addr, XA_CHUNK_SIZE, offset);
1598 : : }
1599 : :
1600 : : /**
1601 : : * xas_next_marked() - Advance iterator to next marked entry.
1602 : : * @xas: XArray operation state.
1603 : : * @max: Highest index to return.
1604 : : * @mark: Mark to search for.
1605 : : *
1606 : : * xas_next_marked() is an inline function to optimise xarray traversal for
1607 : : * speed. It is equivalent to calling xas_find_marked(), and will call
1608 : : * xas_find_marked() for all the hard cases.
1609 : : *
1610 : : * Return: The next marked entry after the one currently referred to by @xas.
1611 : : */
1612 : 3 : static inline void *xas_next_marked(struct xa_state *xas, unsigned long max,
1613 : : xa_mark_t mark)
1614 : : {
1615 : 3 : struct xa_node *node = xas->xa_node;
1616 : : void *entry;
1617 : : unsigned int offset;
1618 : :
1619 : 3 : if (unlikely(xas_not_node(node) || node->shift))
1620 : 3 : return xas_find_marked(xas, max, mark);
1621 : : offset = xas_find_chunk(xas, true, mark);
1622 : 3 : xas->xa_offset = offset;
1623 : 3 : xas->xa_index = (xas->xa_index & ~XA_CHUNK_MASK) + offset;
1624 : 3 : if (xas->xa_index > max)
1625 : : return NULL;
1626 : 3 : if (offset == XA_CHUNK_SIZE)
1627 : 3 : return xas_find_marked(xas, max, mark);
1628 : : entry = xa_entry(xas->xa, node, offset);
1629 : 3 : if (!entry)
1630 : 0 : return xas_find_marked(xas, max, mark);
1631 : : return entry;
1632 : : }
1633 : :
1634 : : /*
1635 : : * If iterating while holding a lock, drop the lock and reschedule
1636 : : * every %XA_CHECK_SCHED loops.
1637 : : */
1638 : : enum {
1639 : : XA_CHECK_SCHED = 4096,
1640 : : };
1641 : :
1642 : : /**
1643 : : * xas_for_each() - Iterate over a range of an XArray.
1644 : : * @xas: XArray operation state.
1645 : : * @entry: Entry retrieved from the array.
1646 : : * @max: Maximum index to retrieve from array.
1647 : : *
1648 : : * The loop body will be executed for each entry present in the xarray
1649 : : * between the current xas position and @max. @entry will be set to
1650 : : * the entry retrieved from the xarray. It is safe to delete entries
1651 : : * from the array in the loop body. You should hold either the RCU lock
1652 : : * or the xa_lock while iterating. If you need to drop the lock, call
1653 : : * xas_pause() first.
1654 : : */
1655 : : #define xas_for_each(xas, entry, max) \
1656 : : for (entry = xas_find(xas, max); entry; \
1657 : : entry = xas_next_entry(xas, max))
1658 : :
1659 : : /**
1660 : : * xas_for_each_marked() - Iterate over a range of an XArray.
1661 : : * @xas: XArray operation state.
1662 : : * @entry: Entry retrieved from the array.
1663 : : * @max: Maximum index to retrieve from array.
1664 : : * @mark: Mark to search for.
1665 : : *
1666 : : * The loop body will be executed for each marked entry in the xarray
1667 : : * between the current xas position and @max. @entry will be set to
1668 : : * the entry retrieved from the xarray. It is safe to delete entries
1669 : : * from the array in the loop body. You should hold either the RCU lock
1670 : : * or the xa_lock while iterating. If you need to drop the lock, call
1671 : : * xas_pause() first.
1672 : : */
1673 : : #define xas_for_each_marked(xas, entry, max, mark) \
1674 : : for (entry = xas_find_marked(xas, max, mark); entry; \
1675 : : entry = xas_next_marked(xas, max, mark))
1676 : :
1677 : : /**
1678 : : * xas_for_each_conflict() - Iterate over a range of an XArray.
1679 : : * @xas: XArray operation state.
1680 : : * @entry: Entry retrieved from the array.
1681 : : *
1682 : : * The loop body will be executed for each entry in the XArray that lies
1683 : : * within the range specified by @xas. If the loop completes successfully,
1684 : : * any entries that lie in this range will be replaced by @entry. The caller
1685 : : * may break out of the loop; if they do so, the contents of the XArray will
1686 : : * be unchanged. The operation may fail due to an out of memory condition.
1687 : : * The caller may also call xa_set_err() to exit the loop while setting an
1688 : : * error to record the reason.
1689 : : */
1690 : : #define xas_for_each_conflict(xas, entry) \
1691 : : while ((entry = xas_find_conflict(xas)))
1692 : :
1693 : : void *__xas_next(struct xa_state *);
1694 : : void *__xas_prev(struct xa_state *);
1695 : :
1696 : : /**
1697 : : * xas_prev() - Move iterator to previous index.
1698 : : * @xas: XArray operation state.
1699 : : *
1700 : : * If the @xas was in an error state, it will remain in an error state
1701 : : * and this function will return %NULL. If the @xas has never been walked,
1702 : : * it will have the effect of calling xas_load(). Otherwise one will be
1703 : : * subtracted from the index and the state will be walked to the correct
1704 : : * location in the array for the next operation.
1705 : : *
1706 : : * If the iterator was referencing index 0, this function wraps
1707 : : * around to %ULONG_MAX.
1708 : : *
1709 : : * Return: The entry at the new index. This may be %NULL or an internal
1710 : : * entry.
1711 : : */
1712 : 3 : static inline void *xas_prev(struct xa_state *xas)
1713 : : {
1714 : 3 : struct xa_node *node = xas->xa_node;
1715 : :
1716 : 3 : if (unlikely(xas_not_node(node) || node->shift ||
1717 : : xas->xa_offset == 0))
1718 : 3 : return __xas_prev(xas);
1719 : :
1720 : 3 : xas->xa_index--;
1721 : 3 : xas->xa_offset--;
1722 : 3 : return xa_entry(xas->xa, node, xas->xa_offset);
1723 : : }
1724 : :
1725 : : /**
1726 : : * xas_next() - Move state to next index.
1727 : : * @xas: XArray operation state.
1728 : : *
1729 : : * If the @xas was in an error state, it will remain in an error state
1730 : : * and this function will return %NULL. If the @xas has never been walked,
1731 : : * it will have the effect of calling xas_load(). Otherwise one will be
1732 : : * added to the index and the state will be walked to the correct
1733 : : * location in the array for the next operation.
1734 : : *
1735 : : * If the iterator was referencing index %ULONG_MAX, this function wraps
1736 : : * around to 0.
1737 : : *
1738 : : * Return: The entry at the new index. This may be %NULL or an internal
1739 : : * entry.
1740 : : */
1741 : 3 : static inline void *xas_next(struct xa_state *xas)
1742 : : {
1743 : 3 : struct xa_node *node = xas->xa_node;
1744 : :
1745 : 3 : if (unlikely(xas_not_node(node) || node->shift ||
1746 : : xas->xa_offset == XA_CHUNK_MASK))
1747 : 3 : return __xas_next(xas);
1748 : :
1749 : 3 : xas->xa_index++;
1750 : 3 : xas->xa_offset++;
1751 : 3 : return xa_entry(xas->xa, node, xas->xa_offset);
1752 : : }
1753 : :
1754 : : #endif /* _LINUX_XARRAY_H */
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