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/bitmap.h>
13#include <linux/bug.h>
14#include <linux/compiler.h>
15#include <linux/err.h>
16#include <linux/gfp.h>
17#include <linux/kconfig.h>
18#include <linux/limits.h>
19#include <linux/lockdep.h>
20#include <linux/rcupdate.h>
21#include <linux/sched/mm.h>
22#include <linux/spinlock.h>
23#include <linux/types.h>
24
25struct list_lru;
26
27/*
28 * The bottom two bits of the entry determine how the XArray interprets
29 * the contents:
30 *
31 * 00: Pointer entry
32 * 10: Internal entry
33 * x1: Value entry or tagged pointer
34 *
35 * Attempting to store internal entries in the XArray is a bug.
36 *
37 * Most internal entries are pointers to the next node in the tree.
38 * The following internal entries have a special meaning:
39 *
40 * 0-62: Sibling entries
41 * 256: Retry entry
42 * 257: Zero entry
43 *
44 * Errors are also represented as internal entries, but use the negative
45 * space (-4094 to -2). They're never stored in the slots array; only
46 * returned by the normal API.
47 */
48
49#define BITS_PER_XA_VALUE (BITS_PER_LONG - 1)
50
51/**
52 * xa_mk_value() - Create an XArray entry from an integer.
53 * @v: Value to store in XArray.
54 *
55 * Context: Any context.
56 * Return: An entry suitable for storing in the XArray.
57 */
58static inline void *xa_mk_value(unsigned long v)
59{
60 WARN_ON((long)v < 0);
61 return (void *)((v << 1) | 1);
62}
63
64/**
65 * xa_to_value() - Get value stored in an XArray entry.
66 * @entry: XArray entry.
67 *
68 * Context: Any context.
69 * Return: The value stored in the XArray entry.
70 */
71static inline unsigned long xa_to_value(const void *entry)
72{
73 return (unsigned long)entry >> 1;
74}
75
76/**
77 * xa_is_value() - Determine if an entry is a value.
78 * @entry: XArray entry.
79 *
80 * Context: Any context.
81 * Return: True if the entry is a value, false if it is a pointer.
82 */
83static inline bool xa_is_value(const void *entry)
84{
85 return (unsigned long)entry & 1;
86}
87
88/**
89 * xa_tag_pointer() - Create an XArray entry for a tagged pointer.
90 * @p: Plain pointer.
91 * @tag: Tag value (0, 1 or 3).
92 *
93 * If the user of the XArray prefers, they can tag their pointers instead
94 * of storing value entries. Three tags are available (0, 1 and 3).
95 * These are distinct from the xa_mark_t as they are not replicated up
96 * through the array and cannot be searched for.
97 *
98 * Context: Any context.
99 * Return: An XArray entry.
100 */
101static inline void *xa_tag_pointer(void *p, unsigned long tag)
102{
103 return (void *)((unsigned long)p | tag);
104}
105
106/**
107 * xa_untag_pointer() - Turn an XArray entry into a plain pointer.
108 * @entry: XArray entry.
109 *
110 * If you have stored a tagged pointer in the XArray, call this function
111 * to get the untagged version of the pointer.
112 *
113 * Context: Any context.
114 * Return: A pointer.
115 */
116static inline void *xa_untag_pointer(void *entry)
117{
118 return (void *)((unsigned long)entry & ~3UL);
119}
120
121/**
122 * xa_pointer_tag() - Get the tag stored in an XArray entry.
123 * @entry: XArray entry.
124 *
125 * If you have stored a tagged pointer in the XArray, call this function
126 * to get the tag of that pointer.
127 *
128 * Context: Any context.
129 * Return: A tag.
130 */
131static inline unsigned int xa_pointer_tag(void *entry)
132{
133 return (unsigned long)entry & 3UL;
134}
135
136/*
137 * xa_mk_internal() - Create an internal entry.
138 * @v: Value to turn into an internal entry.
139 *
140 * Internal entries are used for a number of purposes. Entries 0-255 are
141 * used for sibling entries (only 0-62 are used by the current code). 256
142 * is used for the retry entry. 257 is used for the reserved / zero entry.
143 * Negative internal entries are used to represent errnos. Node pointers
144 * are also tagged as internal entries in some situations.
145 *
146 * Context: Any context.
147 * Return: An XArray internal entry corresponding to this value.
148 */
149static inline void *xa_mk_internal(unsigned long v)
150{
151 return (void *)((v << 2) | 2);
152}
153
154/*
155 * xa_to_internal() - Extract the value from an internal entry.
156 * @entry: XArray entry.
157 *
158 * Context: Any context.
159 * Return: The value which was stored in the internal entry.
160 */
161static inline unsigned long xa_to_internal(const void *entry)
162{
163 return (unsigned long)entry >> 2;
164}
165
166/*
167 * xa_is_internal() - Is the entry an internal entry?
168 * @entry: XArray entry.
169 *
170 * Context: Any context.
171 * Return: %true if the entry is an internal entry.
172 */
173static inline bool xa_is_internal(const void *entry)
174{
175 return ((unsigned long)entry & 3) == 2;
176}
177
178#define XA_ZERO_ENTRY xa_mk_internal(257)
179
180/**
181 * xa_is_zero() - Is the entry a zero entry?
182 * @entry: Entry retrieved from the XArray
183 *
184 * The normal API will return NULL as the contents of a slot containing
185 * a zero entry. You can only see zero entries by using the advanced API.
186 *
187 * Return: %true if the entry is a zero entry.
188 */
189static inline bool xa_is_zero(const void *entry)
190{
191 return unlikely(entry == XA_ZERO_ENTRY);
192}
193
194/**
195 * xa_is_err() - Report whether an XArray operation returned an error
196 * @entry: Result from calling an XArray function
197 *
198 * If an XArray operation cannot complete an operation, it will return
199 * a special value indicating an error. This function tells you
200 * whether an error occurred; xa_err() tells you which error occurred.
201 *
202 * Context: Any context.
203 * Return: %true if the entry indicates an error.
204 */
205static inline bool xa_is_err(const void *entry)
206{
207 return unlikely(xa_is_internal(entry) &&
208 entry >= xa_mk_internal(-MAX_ERRNO));
209}
210
211/**
212 * xa_err() - Turn an XArray result into an errno.
213 * @entry: Result from calling an XArray function.
214 *
215 * If an XArray operation cannot complete an operation, it will return
216 * a special pointer value which encodes an errno. This function extracts
217 * the errno from the pointer value, or returns 0 if the pointer does not
218 * represent an errno.
219 *
220 * Context: Any context.
221 * Return: A negative errno or 0.
222 */
223static inline int xa_err(void *entry)
224{
225 /* xa_to_internal() would not do sign extension. */
226 if (xa_is_err(entry))
227 return (long)entry >> 2;
228 return 0;
229}
230
231/**
232 * struct xa_limit - Represents a range of IDs.
233 * @min: The lowest ID to allocate (inclusive).
234 * @max: The maximum ID to allocate (inclusive).
235 *
236 * This structure is used either directly or via the XA_LIMIT() macro
237 * to communicate the range of IDs that are valid for allocation.
238 * Three common ranges are predefined for you:
239 * * xa_limit_32b - [0 - UINT_MAX]
240 * * xa_limit_31b - [0 - INT_MAX]
241 * * xa_limit_16b - [0 - USHRT_MAX]
242 */
243struct xa_limit {
244 u32 max;
245 u32 min;
246};
247
248#define XA_LIMIT(_min, _max) (struct xa_limit) { .min = _min, .max = _max }
249
250#define xa_limit_32b XA_LIMIT(0, UINT_MAX)
251#define xa_limit_31b XA_LIMIT(0, INT_MAX)
252#define xa_limit_16b XA_LIMIT(0, USHRT_MAX)
253
254typedef unsigned __bitwise xa_mark_t;
255#define XA_MARK_0 ((__force xa_mark_t)0U)
256#define XA_MARK_1 ((__force xa_mark_t)1U)
257#define XA_MARK_2 ((__force xa_mark_t)2U)
258#define XA_PRESENT ((__force xa_mark_t)8U)
259#define XA_MARK_MAX XA_MARK_2
260#define XA_FREE_MARK XA_MARK_0
261
262enum xa_lock_type {
263 XA_LOCK_IRQ = 1,
264 XA_LOCK_BH = 2,
265};
266
267/*
268 * Values for xa_flags. The radix tree stores its GFP flags in the xa_flags,
269 * and we remain compatible with that.
270 */
271#define XA_FLAGS_LOCK_IRQ ((__force gfp_t)XA_LOCK_IRQ)
272#define XA_FLAGS_LOCK_BH ((__force gfp_t)XA_LOCK_BH)
273#define XA_FLAGS_TRACK_FREE ((__force gfp_t)4U)
274#define XA_FLAGS_ZERO_BUSY ((__force gfp_t)8U)
275#define XA_FLAGS_ALLOC_WRAPPED ((__force gfp_t)16U)
276#define XA_FLAGS_ACCOUNT ((__force gfp_t)32U)
277#define XA_FLAGS_MARK(mark) ((__force gfp_t)((1U << __GFP_BITS_SHIFT) << \
278 (__force unsigned)(mark)))
279
280/* ALLOC is for a normal 0-based alloc. ALLOC1 is for an 1-based alloc */
281#define XA_FLAGS_ALLOC (XA_FLAGS_TRACK_FREE | XA_FLAGS_MARK(XA_FREE_MARK))
282#define XA_FLAGS_ALLOC1 (XA_FLAGS_TRACK_FREE | XA_FLAGS_ZERO_BUSY)
283
284/**
285 * struct xarray - The anchor of the XArray.
286 * @xa_lock: Lock that protects the contents of the XArray.
287 *
288 * To use the xarray, define it statically or embed it in your data structure.
289 * It is a very small data structure, so it does not usually make sense to
290 * allocate it separately and keep a pointer to it in your data structure.
291 *
292 * You may use the xa_lock to protect your own data structures as well.
293 */
294/*
295 * If all of the entries in the array are NULL, @xa_head is a NULL pointer.
296 * If the only non-NULL entry in the array is at index 0, @xa_head is that
297 * entry. If any other entry in the array is non-NULL, @xa_head points
298 * to an @xa_node.
299 */
300struct xarray {
301 spinlock_t xa_lock;
302/* private: The rest of the data structure is not to be used directly. */
303 gfp_t xa_flags;
304 void __rcu * xa_head;
305};
306
307#define XARRAY_INIT(name, flags) { \
308 .xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock), \
309 .xa_flags = flags, \
310 .xa_head = NULL, \
311}
312
313/**
314 * DEFINE_XARRAY_FLAGS() - Define an XArray with custom flags.
315 * @name: A string that names your XArray.
316 * @flags: XA_FLAG values.
317 *
318 * This is intended for file scope definitions of XArrays. It declares
319 * and initialises an empty XArray with the chosen name and flags. It is
320 * equivalent to calling xa_init_flags() on the array, but it does the
321 * initialisation at compiletime instead of runtime.
322 */
323#define DEFINE_XARRAY_FLAGS(name, flags) \
324 struct xarray name = XARRAY_INIT(name, flags)
325
326/**
327 * DEFINE_XARRAY() - Define an XArray.
328 * @name: A string that names your XArray.
329 *
330 * This is intended for file scope definitions of XArrays. It declares
331 * and initialises an empty XArray with the chosen name. It is equivalent
332 * to calling xa_init() on the array, but it does the initialisation at
333 * compiletime instead of runtime.
334 */
335#define DEFINE_XARRAY(name) DEFINE_XARRAY_FLAGS(name, 0)
336
337/**
338 * DEFINE_XARRAY_ALLOC() - Define an XArray which allocates IDs starting at 0.
339 * @name: A string that names your XArray.
340 *
341 * This is intended for file scope definitions of allocating XArrays.
342 * See also DEFINE_XARRAY().
343 */
344#define DEFINE_XARRAY_ALLOC(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC)
345
346/**
347 * DEFINE_XARRAY_ALLOC1() - Define an XArray which allocates IDs starting at 1.
348 * @name: A string that names your XArray.
349 *
350 * This is intended for file scope definitions of allocating XArrays.
351 * See also DEFINE_XARRAY().
352 */
353#define DEFINE_XARRAY_ALLOC1(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC1)
354
355void *xa_load(struct xarray *, unsigned long index);
356void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
357void *xa_erase(struct xarray *, unsigned long index);
358void *xa_store_range(struct xarray *, unsigned long first, unsigned long last,
359 void *entry, gfp_t);
360bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t);
361void xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
362void xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
363void *xa_find(struct xarray *xa, unsigned long *index,
364 unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
365void *xa_find_after(struct xarray *xa, unsigned long *index,
366 unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
367unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,
368 unsigned long max, unsigned int n, xa_mark_t);
369void xa_destroy(struct xarray *);
370
371/**
372 * xa_init_flags() - Initialise an empty XArray with flags.
373 * @xa: XArray.
374 * @flags: XA_FLAG values.
375 *
376 * If you need to initialise an XArray with special flags (eg you need
377 * to take the lock from interrupt context), use this function instead
378 * of xa_init().
379 *
380 * Context: Any context.
381 */
382static inline void xa_init_flags(struct xarray *xa, gfp_t flags)
383{
384 spin_lock_init(&xa->xa_lock);
385 xa->xa_flags = flags;
386 xa->xa_head = NULL;
387}
388
389/**
390 * xa_init() - Initialise an empty XArray.
391 * @xa: XArray.
392 *
393 * An empty XArray is full of NULL entries.
394 *
395 * Context: Any context.
396 */
397static inline void xa_init(struct xarray *xa)
398{
399 xa_init_flags(xa, flags: 0);
400}
401
402/**
403 * xa_empty() - Determine if an array has any present entries.
404 * @xa: XArray.
405 *
406 * Context: Any context.
407 * Return: %true if the array contains only NULL pointers.
408 */
409static inline bool xa_empty(const struct xarray *xa)
410{
411 return xa->xa_head == NULL;
412}
413
414/**
415 * xa_marked() - Inquire whether any entry in this array has a mark set
416 * @xa: Array
417 * @mark: Mark value
418 *
419 * Context: Any context.
420 * Return: %true if any entry has this mark set.
421 */
422static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
423{
424 return xa->xa_flags & XA_FLAGS_MARK(mark);
425}
426
427/**
428 * xa_for_each_range() - Iterate over a portion of an XArray.
429 * @xa: XArray.
430 * @index: Index of @entry.
431 * @entry: Entry retrieved from array.
432 * @start: First index to retrieve from array.
433 * @last: Last index to retrieve from array.
434 *
435 * During the iteration, @entry will have the value of the entry stored
436 * in @xa at @index. You may modify @index during the iteration if you
437 * want to skip or reprocess indices. It is safe to modify the array
438 * during the iteration. At the end of the iteration, @entry will be set
439 * to NULL and @index will have a value less than or equal to max.
440 *
441 * xa_for_each_range() is O(n.log(n)) while xas_for_each() is O(n). You have
442 * to handle your own locking with xas_for_each(), and if you have to unlock
443 * after each iteration, it will also end up being O(n.log(n)).
444 * xa_for_each_range() will spin if it hits a retry entry; if you intend to
445 * see retry entries, you should use the xas_for_each() iterator instead.
446 * The xas_for_each() iterator will expand into more inline code than
447 * xa_for_each_range().
448 *
449 * Context: Any context. Takes and releases the RCU lock.
450 */
451#define xa_for_each_range(xa, index, entry, start, last) \
452 for (index = start, \
453 entry = xa_find(xa, &index, last, XA_PRESENT); \
454 entry; \
455 entry = xa_find_after(xa, &index, last, XA_PRESENT))
456
457/**
458 * xa_for_each_start() - Iterate over a portion of an XArray.
459 * @xa: XArray.
460 * @index: Index of @entry.
461 * @entry: Entry retrieved from array.
462 * @start: First index to retrieve from array.
463 *
464 * During the iteration, @entry will have the value of the entry stored
465 * in @xa at @index. You may modify @index during the iteration if you
466 * want to skip or reprocess indices. It is safe to modify the array
467 * during the iteration. At the end of the iteration, @entry will be set
468 * to NULL and @index will have a value less than or equal to max.
469 *
470 * xa_for_each_start() is O(n.log(n)) while xas_for_each() is O(n). You have
471 * to handle your own locking with xas_for_each(), and if you have to unlock
472 * after each iteration, it will also end up being O(n.log(n)).
473 * xa_for_each_start() will spin if it hits a retry entry; if you intend to
474 * see retry entries, you should use the xas_for_each() iterator instead.
475 * The xas_for_each() iterator will expand into more inline code than
476 * xa_for_each_start().
477 *
478 * Context: Any context. Takes and releases the RCU lock.
479 */
480#define xa_for_each_start(xa, index, entry, start) \
481 xa_for_each_range(xa, index, entry, start, ULONG_MAX)
482
483/**
484 * xa_for_each() - Iterate over present entries in an XArray.
485 * @xa: XArray.
486 * @index: Index of @entry.
487 * @entry: Entry retrieved from array.
488 *
489 * During the iteration, @entry will have the value of the entry stored
490 * in @xa at @index. You may modify @index during the iteration if you want
491 * to skip or reprocess indices. It is safe to modify the array during the
492 * iteration. At the end of the iteration, @entry will be set to NULL and
493 * @index will have a value less than or equal to max.
494 *
495 * xa_for_each() is O(n.log(n)) while xas_for_each() is O(n). You have
496 * to handle your own locking with xas_for_each(), and if you have to unlock
497 * after each iteration, it will also end up being O(n.log(n)). xa_for_each()
498 * will spin if it hits a retry entry; if you intend to see retry entries,
499 * you should use the xas_for_each() iterator instead. The xas_for_each()
500 * iterator will expand into more inline code than xa_for_each().
501 *
502 * Context: Any context. Takes and releases the RCU lock.
503 */
504#define xa_for_each(xa, index, entry) \
505 xa_for_each_start(xa, index, entry, 0)
506
507/**
508 * xa_for_each_marked() - Iterate over marked entries in an XArray.
509 * @xa: XArray.
510 * @index: Index of @entry.
511 * @entry: Entry retrieved from array.
512 * @filter: Selection criterion.
513 *
514 * During the iteration, @entry will have the value of the entry stored
515 * in @xa at @index. The iteration will skip all entries in the array
516 * which do not match @filter. You may modify @index during the iteration
517 * if you want to skip or reprocess indices. It is safe to modify the array
518 * during the iteration. At the end of the iteration, @entry will be set to
519 * NULL and @index will have a value less than or equal to max.
520 *
521 * xa_for_each_marked() is O(n.log(n)) while xas_for_each_marked() is O(n).
522 * You have to handle your own locking with xas_for_each(), and if you have
523 * to unlock after each iteration, it will also end up being O(n.log(n)).
524 * xa_for_each_marked() will spin if it hits a retry entry; if you intend to
525 * see retry entries, you should use the xas_for_each_marked() iterator
526 * instead. The xas_for_each_marked() iterator will expand into more inline
527 * code than xa_for_each_marked().
528 *
529 * Context: Any context. Takes and releases the RCU lock.
530 */
531#define xa_for_each_marked(xa, index, entry, filter) \
532 for (index = 0, entry = xa_find(xa, &index, ULONG_MAX, filter); \
533 entry; entry = xa_find_after(xa, &index, ULONG_MAX, filter))
534
535#define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
536#define xa_lock(xa) spin_lock(&(xa)->xa_lock)
537#define xa_unlock(xa) spin_unlock(&(xa)->xa_lock)
538#define xa_lock_bh(xa) spin_lock_bh(&(xa)->xa_lock)
539#define xa_unlock_bh(xa) spin_unlock_bh(&(xa)->xa_lock)
540#define xa_lock_irq(xa) spin_lock_irq(&(xa)->xa_lock)
541#define xa_unlock_irq(xa) spin_unlock_irq(&(xa)->xa_lock)
542#define xa_lock_irqsave(xa, flags) \
543 spin_lock_irqsave(&(xa)->xa_lock, flags)
544#define xa_unlock_irqrestore(xa, flags) \
545 spin_unlock_irqrestore(&(xa)->xa_lock, flags)
546#define xa_lock_nested(xa, subclass) \
547 spin_lock_nested(&(xa)->xa_lock, subclass)
548#define xa_lock_bh_nested(xa, subclass) \
549 spin_lock_bh_nested(&(xa)->xa_lock, subclass)
550#define xa_lock_irq_nested(xa, subclass) \
551 spin_lock_irq_nested(&(xa)->xa_lock, subclass)
552#define xa_lock_irqsave_nested(xa, flags, subclass) \
553 spin_lock_irqsave_nested(&(xa)->xa_lock, flags, subclass)
554
555/*
556 * Versions of the normal API which require the caller to hold the
557 * xa_lock. If the GFP flags allow it, they will drop the lock to
558 * allocate memory, then reacquire it afterwards. These functions
559 * may also re-enable interrupts if the XArray flags indicate the
560 * locking should be interrupt safe.
561 */
562void *__xa_erase(struct xarray *, unsigned long index);
563void *__xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
564void *__xa_cmpxchg(struct xarray *, unsigned long index, void *old,
565 void *entry, gfp_t);
566int __must_check __xa_insert(struct xarray *, unsigned long index,
567 void *entry, gfp_t);
568int __must_check __xa_alloc(struct xarray *, u32 *id, void *entry,
569 struct xa_limit, gfp_t);
570int __must_check __xa_alloc_cyclic(struct xarray *, u32 *id, void *entry,
571 struct xa_limit, u32 *next, gfp_t);
572void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
573void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
574
575/**
576 * xa_store_bh() - Store this entry in the XArray.
577 * @xa: XArray.
578 * @index: Index into array.
579 * @entry: New entry.
580 * @gfp: Memory allocation flags.
581 *
582 * This function is like calling xa_store() except it disables softirqs
583 * while holding the array lock.
584 *
585 * Context: Any context. Takes and releases the xa_lock while
586 * disabling softirqs.
587 * Return: The old entry at this index or xa_err() if an error happened.
588 */
589static inline void *xa_store_bh(struct xarray *xa, unsigned long index,
590 void *entry, gfp_t gfp)
591{
592 void *curr;
593
594 might_alloc(gfp_mask: gfp);
595 xa_lock_bh(xa);
596 curr = __xa_store(xa, index, entry, gfp);
597 xa_unlock_bh(xa);
598
599 return curr;
600}
601
602/**
603 * xa_store_irq() - Store this entry in the XArray.
604 * @xa: XArray.
605 * @index: Index into array.
606 * @entry: New entry.
607 * @gfp: Memory allocation flags.
608 *
609 * This function is like calling xa_store() except it disables interrupts
610 * while holding the array lock.
611 *
612 * Context: Process context. Takes and releases the xa_lock while
613 * disabling interrupts.
614 * Return: The old entry at this index or xa_err() if an error happened.
615 */
616static inline void *xa_store_irq(struct xarray *xa, unsigned long index,
617 void *entry, gfp_t gfp)
618{
619 void *curr;
620
621 might_alloc(gfp_mask: gfp);
622 xa_lock_irq(xa);
623 curr = __xa_store(xa, index, entry, gfp);
624 xa_unlock_irq(xa);
625
626 return curr;
627}
628
629/**
630 * xa_erase_bh() - Erase this entry from the XArray.
631 * @xa: XArray.
632 * @index: Index of entry.
633 *
634 * After this function returns, loading from @index will return %NULL.
635 * If the index is part of a multi-index entry, all indices will be erased
636 * and none of the entries will be part of a multi-index entry.
637 *
638 * Context: Any context. Takes and releases the xa_lock while
639 * disabling softirqs.
640 * Return: The entry which used to be at this index.
641 */
642static inline void *xa_erase_bh(struct xarray *xa, unsigned long index)
643{
644 void *entry;
645
646 xa_lock_bh(xa);
647 entry = __xa_erase(xa, index);
648 xa_unlock_bh(xa);
649
650 return entry;
651}
652
653/**
654 * xa_erase_irq() - Erase this entry from the XArray.
655 * @xa: XArray.
656 * @index: Index of entry.
657 *
658 * After this function returns, loading from @index will return %NULL.
659 * If the index is part of a multi-index entry, all indices will be erased
660 * and none of the entries will be part of a multi-index entry.
661 *
662 * Context: Process context. Takes and releases the xa_lock while
663 * disabling interrupts.
664 * Return: The entry which used to be at this index.
665 */
666static inline void *xa_erase_irq(struct xarray *xa, unsigned long index)
667{
668 void *entry;
669
670 xa_lock_irq(xa);
671 entry = __xa_erase(xa, index);
672 xa_unlock_irq(xa);
673
674 return entry;
675}
676
677/**
678 * xa_cmpxchg() - Conditionally replace an entry in the XArray.
679 * @xa: XArray.
680 * @index: Index into array.
681 * @old: Old value to test against.
682 * @entry: New value to place in array.
683 * @gfp: Memory allocation flags.
684 *
685 * If the entry at @index is the same as @old, replace it with @entry.
686 * If the return value is equal to @old, then the exchange was successful.
687 *
688 * Context: Any context. Takes and releases the xa_lock. May sleep
689 * if the @gfp flags permit.
690 * Return: The old value at this index or xa_err() if an error happened.
691 */
692static inline void *xa_cmpxchg(struct xarray *xa, unsigned long index,
693 void *old, void *entry, gfp_t gfp)
694{
695 void *curr;
696
697 might_alloc(gfp_mask: gfp);
698 xa_lock(xa);
699 curr = __xa_cmpxchg(xa, index, old, entry, gfp);
700 xa_unlock(xa);
701
702 return curr;
703}
704
705/**
706 * xa_cmpxchg_bh() - Conditionally replace an entry in the XArray.
707 * @xa: XArray.
708 * @index: Index into array.
709 * @old: Old value to test against.
710 * @entry: New value to place in array.
711 * @gfp: Memory allocation flags.
712 *
713 * This function is like calling xa_cmpxchg() except it disables softirqs
714 * while holding the array lock.
715 *
716 * Context: Any context. Takes and releases the xa_lock while
717 * disabling softirqs. May sleep if the @gfp flags permit.
718 * Return: The old value at this index or xa_err() if an error happened.
719 */
720static inline void *xa_cmpxchg_bh(struct xarray *xa, unsigned long index,
721 void *old, void *entry, gfp_t gfp)
722{
723 void *curr;
724
725 might_alloc(gfp_mask: gfp);
726 xa_lock_bh(xa);
727 curr = __xa_cmpxchg(xa, index, old, entry, gfp);
728 xa_unlock_bh(xa);
729
730 return curr;
731}
732
733/**
734 * xa_cmpxchg_irq() - Conditionally replace an entry in the XArray.
735 * @xa: XArray.
736 * @index: Index into array.
737 * @old: Old value to test against.
738 * @entry: New value to place in array.
739 * @gfp: Memory allocation flags.
740 *
741 * This function is like calling xa_cmpxchg() except it disables interrupts
742 * while holding the array lock.
743 *
744 * Context: Process context. Takes and releases the xa_lock while
745 * disabling interrupts. May sleep if the @gfp flags permit.
746 * Return: The old value at this index or xa_err() if an error happened.
747 */
748static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
749 void *old, void *entry, gfp_t gfp)
750{
751 void *curr;
752
753 might_alloc(gfp_mask: gfp);
754 xa_lock_irq(xa);
755 curr = __xa_cmpxchg(xa, index, old, entry, gfp);
756 xa_unlock_irq(xa);
757
758 return curr;
759}
760
761/**
762 * xa_insert() - Store this entry in the XArray unless another entry is
763 * already present.
764 * @xa: XArray.
765 * @index: Index into array.
766 * @entry: New entry.
767 * @gfp: Memory allocation flags.
768 *
769 * Inserting a NULL entry will store a reserved entry (like xa_reserve())
770 * if no entry is present. Inserting will fail if a reserved entry is
771 * present, even though loading from this index will return NULL.
772 *
773 * Context: Any context. Takes and releases the xa_lock. May sleep if
774 * the @gfp flags permit.
775 * Return: 0 if the store succeeded. -EBUSY if another entry was present.
776 * -ENOMEM if memory could not be allocated.
777 */
778static inline int __must_check xa_insert(struct xarray *xa,
779 unsigned long index, void *entry, gfp_t gfp)
780{
781 int err;
782
783 might_alloc(gfp_mask: gfp);
784 xa_lock(xa);
785 err = __xa_insert(xa, index, entry, gfp);
786 xa_unlock(xa);
787
788 return err;
789}
790
791/**
792 * xa_insert_bh() - Store this entry in the XArray unless another entry is
793 * already present.
794 * @xa: XArray.
795 * @index: Index into array.
796 * @entry: New entry.
797 * @gfp: Memory allocation flags.
798 *
799 * Inserting a NULL entry will store a reserved entry (like xa_reserve())
800 * if no entry is present. Inserting will fail if a reserved entry is
801 * present, even though loading from this index will return NULL.
802 *
803 * Context: Any context. Takes and releases the xa_lock while
804 * disabling softirqs. May sleep if the @gfp flags permit.
805 * Return: 0 if the store succeeded. -EBUSY if another entry was present.
806 * -ENOMEM if memory could not be allocated.
807 */
808static inline int __must_check xa_insert_bh(struct xarray *xa,
809 unsigned long index, void *entry, gfp_t gfp)
810{
811 int err;
812
813 might_alloc(gfp_mask: gfp);
814 xa_lock_bh(xa);
815 err = __xa_insert(xa, index, entry, gfp);
816 xa_unlock_bh(xa);
817
818 return err;
819}
820
821/**
822 * xa_insert_irq() - Store this entry in the XArray unless another entry is
823 * already present.
824 * @xa: XArray.
825 * @index: Index into array.
826 * @entry: New entry.
827 * @gfp: Memory allocation flags.
828 *
829 * Inserting a NULL entry will store a reserved entry (like xa_reserve())
830 * if no entry is present. Inserting will fail if a reserved entry is
831 * present, even though loading from this index will return NULL.
832 *
833 * Context: Process context. Takes and releases the xa_lock while
834 * disabling interrupts. May sleep if the @gfp flags permit.
835 * Return: 0 if the store succeeded. -EBUSY if another entry was present.
836 * -ENOMEM if memory could not be allocated.
837 */
838static inline int __must_check xa_insert_irq(struct xarray *xa,
839 unsigned long index, void *entry, gfp_t gfp)
840{
841 int err;
842
843 might_alloc(gfp_mask: gfp);
844 xa_lock_irq(xa);
845 err = __xa_insert(xa, index, entry, gfp);
846 xa_unlock_irq(xa);
847
848 return err;
849}
850
851/**
852 * xa_alloc() - Find somewhere to store this entry in the XArray.
853 * @xa: XArray.
854 * @id: Pointer to ID.
855 * @entry: New entry.
856 * @limit: Range of ID to allocate.
857 * @gfp: Memory allocation flags.
858 *
859 * Finds an empty entry in @xa between @limit.min and @limit.max,
860 * stores the index into the @id pointer, then stores the entry at
861 * that index. A concurrent lookup will not see an uninitialised @id.
862 *
863 * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
864 * in xa_init_flags().
865 *
866 * Context: Any context. Takes and releases the xa_lock. May sleep if
867 * the @gfp flags permit.
868 * Return: 0 on success, -ENOMEM if memory could not be allocated or
869 * -EBUSY if there are no free entries in @limit.
870 */
871static inline __must_check int xa_alloc(struct xarray *xa, u32 *id,
872 void *entry, struct xa_limit limit, gfp_t gfp)
873{
874 int err;
875
876 might_alloc(gfp_mask: gfp);
877 xa_lock(xa);
878 err = __xa_alloc(xa, id, entry, limit, gfp);
879 xa_unlock(xa);
880
881 return err;
882}
883
884/**
885 * xa_alloc_bh() - Find somewhere to store this entry in the XArray.
886 * @xa: XArray.
887 * @id: Pointer to ID.
888 * @entry: New entry.
889 * @limit: Range of ID to allocate.
890 * @gfp: Memory allocation flags.
891 *
892 * Finds an empty entry in @xa between @limit.min and @limit.max,
893 * stores the index into the @id pointer, then stores the entry at
894 * that index. A concurrent lookup will not see an uninitialised @id.
895 *
896 * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
897 * in xa_init_flags().
898 *
899 * Context: Any context. Takes and releases the xa_lock while
900 * disabling softirqs. May sleep if the @gfp flags permit.
901 * Return: 0 on success, -ENOMEM if memory could not be allocated or
902 * -EBUSY if there are no free entries in @limit.
903 */
904static inline int __must_check xa_alloc_bh(struct xarray *xa, u32 *id,
905 void *entry, struct xa_limit limit, gfp_t gfp)
906{
907 int err;
908
909 might_alloc(gfp_mask: gfp);
910 xa_lock_bh(xa);
911 err = __xa_alloc(xa, id, entry, limit, gfp);
912 xa_unlock_bh(xa);
913
914 return err;
915}
916
917/**
918 * xa_alloc_irq() - Find somewhere to store this entry in the XArray.
919 * @xa: XArray.
920 * @id: Pointer to ID.
921 * @entry: New entry.
922 * @limit: Range of ID to allocate.
923 * @gfp: Memory allocation flags.
924 *
925 * Finds an empty entry in @xa between @limit.min and @limit.max,
926 * stores the index into the @id pointer, then stores the entry at
927 * that index. A concurrent lookup will not see an uninitialised @id.
928 *
929 * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
930 * in xa_init_flags().
931 *
932 * Context: Process context. Takes and releases the xa_lock while
933 * disabling interrupts. May sleep if the @gfp flags permit.
934 * Return: 0 on success, -ENOMEM if memory could not be allocated or
935 * -EBUSY if there are no free entries in @limit.
936 */
937static inline int __must_check xa_alloc_irq(struct xarray *xa, u32 *id,
938 void *entry, struct xa_limit limit, gfp_t gfp)
939{
940 int err;
941
942 might_alloc(gfp_mask: gfp);
943 xa_lock_irq(xa);
944 err = __xa_alloc(xa, id, entry, limit, gfp);
945 xa_unlock_irq(xa);
946
947 return err;
948}
949
950/**
951 * xa_alloc_cyclic() - Find somewhere to store this entry in the XArray.
952 * @xa: XArray.
953 * @id: Pointer to ID.
954 * @entry: New entry.
955 * @limit: Range of allocated ID.
956 * @next: Pointer to next ID to allocate.
957 * @gfp: Memory allocation flags.
958 *
959 * Finds an empty entry in @xa between @limit.min and @limit.max,
960 * stores the index into the @id pointer, then stores the entry at
961 * that index. A concurrent lookup will not see an uninitialised @id.
962 * The search for an empty entry will start at @next and will wrap
963 * around if necessary.
964 *
965 * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
966 * in xa_init_flags().
967 *
968 * Note that callers interested in whether wrapping has occurred should
969 * use __xa_alloc_cyclic() instead.
970 *
971 * Context: Any context. Takes and releases the xa_lock. May sleep if
972 * the @gfp flags permit.
973 * Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
974 * allocated or -EBUSY if there are no free entries in @limit.
975 */
976static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
977 struct xa_limit limit, u32 *next, gfp_t gfp)
978{
979 int err;
980
981 might_alloc(gfp_mask: gfp);
982 xa_lock(xa);
983 err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
984 xa_unlock(xa);
985
986 return err < 0 ? err : 0;
987}
988
989/**
990 * xa_alloc_cyclic_bh() - Find somewhere to store this entry in the XArray.
991 * @xa: XArray.
992 * @id: Pointer to ID.
993 * @entry: New entry.
994 * @limit: Range of allocated ID.
995 * @next: Pointer to next ID to allocate.
996 * @gfp: Memory allocation flags.
997 *
998 * Finds an empty entry in @xa between @limit.min and @limit.max,
999 * stores the index into the @id pointer, then stores the entry at
1000 * that index. A concurrent lookup will not see an uninitialised @id.
1001 * The search for an empty entry will start at @next and will wrap
1002 * around if necessary.
1003 *
1004 * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
1005 * in xa_init_flags().
1006 *
1007 * Note that callers interested in whether wrapping has occurred should
1008 * use __xa_alloc_cyclic() instead.
1009 *
1010 * Context: Any context. Takes and releases the xa_lock while
1011 * disabling softirqs. May sleep if the @gfp flags permit.
1012 * Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
1013 * allocated or -EBUSY if there are no free entries in @limit.
1014 */
1015static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry,
1016 struct xa_limit limit, u32 *next, gfp_t gfp)
1017{
1018 int err;
1019
1020 might_alloc(gfp_mask: gfp);
1021 xa_lock_bh(xa);
1022 err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
1023 xa_unlock_bh(xa);
1024
1025 return err < 0 ? err : 0;
1026}
1027
1028/**
1029 * xa_alloc_cyclic_irq() - Find somewhere to store this entry in the XArray.
1030 * @xa: XArray.
1031 * @id: Pointer to ID.
1032 * @entry: New entry.
1033 * @limit: Range of allocated ID.
1034 * @next: Pointer to next ID to allocate.
1035 * @gfp: Memory allocation flags.
1036 *
1037 * Finds an empty entry in @xa between @limit.min and @limit.max,
1038 * stores the index into the @id pointer, then stores the entry at
1039 * that index. A concurrent lookup will not see an uninitialised @id.
1040 * The search for an empty entry will start at @next and will wrap
1041 * around if necessary.
1042 *
1043 * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
1044 * in xa_init_flags().
1045 *
1046 * Note that callers interested in whether wrapping has occurred should
1047 * use __xa_alloc_cyclic() instead.
1048 *
1049 * Context: Process context. Takes and releases the xa_lock while
1050 * disabling interrupts. May sleep if the @gfp flags permit.
1051 * Return: 0 if the allocation succeeded, -ENOMEM if memory could not be
1052 * allocated or -EBUSY if there are no free entries in @limit.
1053 */
1054static inline int xa_alloc_cyclic_irq(struct xarray *xa, u32 *id, void *entry,
1055 struct xa_limit limit, u32 *next, gfp_t gfp)
1056{
1057 int err;
1058
1059 might_alloc(gfp_mask: gfp);
1060 xa_lock_irq(xa);
1061 err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
1062 xa_unlock_irq(xa);
1063
1064 return err < 0 ? err : 0;
1065}
1066
1067/**
1068 * xa_reserve() - Reserve this index in the XArray.
1069 * @xa: XArray.
1070 * @index: Index into array.
1071 * @gfp: Memory allocation flags.
1072 *
1073 * Ensures there is somewhere to store an entry at @index in the array.
1074 * If there is already something stored at @index, this function does
1075 * nothing. If there was nothing there, the entry is marked as reserved.
1076 * Loading from a reserved entry returns a %NULL pointer.
1077 *
1078 * If you do not use the entry that you have reserved, call xa_release()
1079 * or xa_erase() to free any unnecessary memory.
1080 *
1081 * Context: Any context. Takes and releases the xa_lock.
1082 * May sleep if the @gfp flags permit.
1083 * Return: 0 if the reservation succeeded or -ENOMEM if it failed.
1084 */
1085static inline __must_check
1086int xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp)
1087{
1088 return xa_err(entry: xa_cmpxchg(xa, index, NULL, XA_ZERO_ENTRY, gfp));
1089}
1090
1091/**
1092 * xa_reserve_bh() - Reserve this index in the XArray.
1093 * @xa: XArray.
1094 * @index: Index into array.
1095 * @gfp: Memory allocation flags.
1096 *
1097 * A softirq-disabling version of xa_reserve().
1098 *
1099 * Context: Any context. Takes and releases the xa_lock while
1100 * disabling softirqs.
1101 * Return: 0 if the reservation succeeded or -ENOMEM if it failed.
1102 */
1103static inline __must_check
1104int xa_reserve_bh(struct xarray *xa, unsigned long index, gfp_t gfp)
1105{
1106 return xa_err(entry: xa_cmpxchg_bh(xa, index, NULL, XA_ZERO_ENTRY, gfp));
1107}
1108
1109/**
1110 * xa_reserve_irq() - Reserve this index in the XArray.
1111 * @xa: XArray.
1112 * @index: Index into array.
1113 * @gfp: Memory allocation flags.
1114 *
1115 * An interrupt-disabling version of xa_reserve().
1116 *
1117 * Context: Process context. Takes and releases the xa_lock while
1118 * disabling interrupts.
1119 * Return: 0 if the reservation succeeded or -ENOMEM if it failed.
1120 */
1121static inline __must_check
1122int xa_reserve_irq(struct xarray *xa, unsigned long index, gfp_t gfp)
1123{
1124 return xa_err(entry: xa_cmpxchg_irq(xa, index, NULL, XA_ZERO_ENTRY, gfp));
1125}
1126
1127/**
1128 * xa_release() - Release a reserved entry.
1129 * @xa: XArray.
1130 * @index: Index of entry.
1131 *
1132 * After calling xa_reserve(), you can call this function to release the
1133 * reservation. If the entry at @index has been stored to, this function
1134 * will do nothing.
1135 */
1136static inline void xa_release(struct xarray *xa, unsigned long index)
1137{
1138 xa_cmpxchg(xa, index, XA_ZERO_ENTRY, NULL, gfp: 0);
1139}
1140
1141/* Everything below here is the Advanced API. Proceed with caution. */
1142
1143/*
1144 * The xarray is constructed out of a set of 'chunks' of pointers. Choosing
1145 * the best chunk size requires some tradeoffs. A power of two recommends
1146 * itself so that we can walk the tree based purely on shifts and masks.
1147 * Generally, the larger the better; as the number of slots per level of the
1148 * tree increases, the less tall the tree needs to be. But that needs to be
1149 * balanced against the memory consumption of each node. On a 64-bit system,
1150 * xa_node is currently 576 bytes, and we get 7 of them per 4kB page. If we
1151 * doubled the number of slots per node, we'd get only 3 nodes per 4kB page.
1152 */
1153#ifndef XA_CHUNK_SHIFT
1154#define XA_CHUNK_SHIFT (IS_ENABLED(CONFIG_BASE_SMALL) ? 4 : 6)
1155#endif
1156#define XA_CHUNK_SIZE (1UL << XA_CHUNK_SHIFT)
1157#define XA_CHUNK_MASK (XA_CHUNK_SIZE - 1)
1158#define XA_MAX_MARKS 3
1159#define XA_MARK_LONGS BITS_TO_LONGS(XA_CHUNK_SIZE)
1160
1161/*
1162 * @count is the count of every non-NULL element in the ->slots array
1163 * whether that is a value entry, a retry entry, a user pointer,
1164 * a sibling entry or a pointer to the next level of the tree.
1165 * @nr_values is the count of every element in ->slots which is
1166 * either a value entry or a sibling of a value entry.
1167 */
1168struct xa_node {
1169 unsigned char shift; /* Bits remaining in each slot */
1170 unsigned char offset; /* Slot offset in parent */
1171 unsigned char count; /* Total entry count */
1172 unsigned char nr_values; /* Value entry count */
1173 struct xa_node __rcu *parent; /* NULL at top of tree */
1174 struct xarray *array; /* The array we belong to */
1175 union {
1176 struct list_head private_list; /* For tree user */
1177 struct rcu_head rcu_head; /* Used when freeing node */
1178 };
1179 void __rcu *slots[XA_CHUNK_SIZE];
1180 union {
1181 unsigned long tags[XA_MAX_MARKS][XA_MARK_LONGS];
1182 unsigned long marks[XA_MAX_MARKS][XA_MARK_LONGS];
1183 };
1184};
1185
1186void xa_dump(const struct xarray *);
1187void xa_dump_node(const struct xa_node *);
1188
1189#ifdef XA_DEBUG
1190#define XA_BUG_ON(xa, x) do { \
1191 if (x) { \
1192 xa_dump(xa); \
1193 BUG(); \
1194 } \
1195 } while (0)
1196#define XA_NODE_BUG_ON(node, x) do { \
1197 if (x) { \
1198 if (node) xa_dump_node(node); \
1199 BUG(); \
1200 } \
1201 } while (0)
1202#else
1203#define XA_BUG_ON(xa, x) do { } while (0)
1204#define XA_NODE_BUG_ON(node, x) do { } while (0)
1205#endif
1206
1207/* Private */
1208static inline void *xa_head(const struct xarray *xa)
1209{
1210 return rcu_dereference_check(xa->xa_head,
1211 lockdep_is_held(&xa->xa_lock));
1212}
1213
1214/* Private */
1215static inline void *xa_head_locked(const struct xarray *xa)
1216{
1217 return rcu_dereference_protected(xa->xa_head,
1218 lockdep_is_held(&xa->xa_lock));
1219}
1220
1221/* Private */
1222static inline void *xa_entry(const struct xarray *xa,
1223 const struct xa_node *node, unsigned int offset)
1224{
1225 XA_NODE_BUG_ON(node, offset >= XA_CHUNK_SIZE);
1226 return rcu_dereference_check(node->slots[offset],
1227 lockdep_is_held(&xa->xa_lock));
1228}
1229
1230/* Private */
1231static inline void *xa_entry_locked(const struct xarray *xa,
1232 const struct xa_node *node, unsigned int offset)
1233{
1234 XA_NODE_BUG_ON(node, offset >= XA_CHUNK_SIZE);
1235 return rcu_dereference_protected(node->slots[offset],
1236 lockdep_is_held(&xa->xa_lock));
1237}
1238
1239/* Private */
1240static inline struct xa_node *xa_parent(const struct xarray *xa,
1241 const struct xa_node *node)
1242{
1243 return rcu_dereference_check(node->parent,
1244 lockdep_is_held(&xa->xa_lock));
1245}
1246
1247/* Private */
1248static inline struct xa_node *xa_parent_locked(const struct xarray *xa,
1249 const struct xa_node *node)
1250{
1251 return rcu_dereference_protected(node->parent,
1252 lockdep_is_held(&xa->xa_lock));
1253}
1254
1255/* Private */
1256static inline void *xa_mk_node(const struct xa_node *node)
1257{
1258 return (void *)((unsigned long)node | 2);
1259}
1260
1261/* Private */
1262static inline struct xa_node *xa_to_node(const void *entry)
1263{
1264 return (struct xa_node *)((unsigned long)entry - 2);
1265}
1266
1267/* Private */
1268static inline bool xa_is_node(const void *entry)
1269{
1270 return xa_is_internal(entry) && (unsigned long)entry > 4096;
1271}
1272
1273/* Private */
1274static inline void *xa_mk_sibling(unsigned int offset)
1275{
1276 return xa_mk_internal(v: offset);
1277}
1278
1279/* Private */
1280static inline unsigned long xa_to_sibling(const void *entry)
1281{
1282 return xa_to_internal(entry);
1283}
1284
1285/**
1286 * xa_is_sibling() - Is the entry a sibling entry?
1287 * @entry: Entry retrieved from the XArray
1288 *
1289 * Return: %true if the entry is a sibling entry.
1290 */
1291static inline bool xa_is_sibling(const void *entry)
1292{
1293 return IS_ENABLED(CONFIG_XARRAY_MULTI) && xa_is_internal(entry) &&
1294 (entry < xa_mk_sibling(XA_CHUNK_SIZE - 1));
1295}
1296
1297#define XA_RETRY_ENTRY xa_mk_internal(256)
1298
1299/**
1300 * xa_is_retry() - Is the entry a retry entry?
1301 * @entry: Entry retrieved from the XArray
1302 *
1303 * Return: %true if the entry is a retry entry.
1304 */
1305static inline bool xa_is_retry(const void *entry)
1306{
1307 return unlikely(entry == XA_RETRY_ENTRY);
1308}
1309
1310/**
1311 * xa_is_advanced() - Is the entry only permitted for the advanced API?
1312 * @entry: Entry to be stored in the XArray.
1313 *
1314 * Return: %true if the entry cannot be stored by the normal API.
1315 */
1316static inline bool xa_is_advanced(const void *entry)
1317{
1318 return xa_is_internal(entry) && (entry <= XA_RETRY_ENTRY);
1319}
1320
1321/**
1322 * typedef xa_update_node_t - A callback function from the XArray.
1323 * @node: The node which is being processed
1324 *
1325 * This function is called every time the XArray updates the count of
1326 * present and value entries in a node. It allows advanced users to
1327 * maintain the private_list in the node.
1328 *
1329 * Context: The xa_lock is held and interrupts may be disabled.
1330 * Implementations should not drop the xa_lock, nor re-enable
1331 * interrupts.
1332 */
1333typedef void (*xa_update_node_t)(struct xa_node *node);
1334
1335void xa_delete_node(struct xa_node *, xa_update_node_t);
1336
1337/*
1338 * The xa_state is opaque to its users. It contains various different pieces
1339 * of state involved in the current operation on the XArray. It should be
1340 * declared on the stack and passed between the various internal routines.
1341 * The various elements in it should not be accessed directly, but only
1342 * through the provided accessor functions. The below documentation is for
1343 * the benefit of those working on the code, not for users of the XArray.
1344 *
1345 * @xa_node usually points to the xa_node containing the slot we're operating
1346 * on (and @xa_offset is the offset in the slots array). If there is a
1347 * single entry in the array at index 0, there are no allocated xa_nodes to
1348 * point to, and so we store %NULL in @xa_node. @xa_node is set to
1349 * the value %XAS_RESTART if the xa_state is not walked to the correct
1350 * position in the tree of nodes for this operation. If an error occurs
1351 * during an operation, it is set to an %XAS_ERROR value. If we run off the
1352 * end of the allocated nodes, it is set to %XAS_BOUNDS.
1353 */
1354struct xa_state {
1355 struct xarray *xa;
1356 unsigned long xa_index;
1357 unsigned char xa_shift;
1358 unsigned char xa_sibs;
1359 unsigned char xa_offset;
1360 unsigned char xa_pad; /* Helps gcc generate better code */
1361 struct xa_node *xa_node;
1362 struct xa_node *xa_alloc;
1363 xa_update_node_t xa_update;
1364 struct list_lru *xa_lru;
1365};
1366
1367/*
1368 * We encode errnos in the xas->xa_node. If an error has happened, we need to
1369 * drop the lock to fix it, and once we've done so the xa_state is invalid.
1370 */
1371#define XA_ERROR(errno) ((struct xa_node *)(((unsigned long)errno << 2) | 2UL))
1372#define XAS_BOUNDS ((struct xa_node *)1UL)
1373#define XAS_RESTART ((struct xa_node *)3UL)
1374
1375#define __XA_STATE(array, index, shift, sibs) { \
1376 .xa = array, \
1377 .xa_index = index, \
1378 .xa_shift = shift, \
1379 .xa_sibs = sibs, \
1380 .xa_offset = 0, \
1381 .xa_pad = 0, \
1382 .xa_node = XAS_RESTART, \
1383 .xa_alloc = NULL, \
1384 .xa_update = NULL, \
1385 .xa_lru = NULL, \
1386}
1387
1388/**
1389 * XA_STATE() - Declare an XArray operation state.
1390 * @name: Name of this operation state (usually xas).
1391 * @array: Array to operate on.
1392 * @index: Initial index of interest.
1393 *
1394 * Declare and initialise an xa_state on the stack.
1395 */
1396#define XA_STATE(name, array, index) \
1397 struct xa_state name = __XA_STATE(array, index, 0, 0)
1398
1399/**
1400 * XA_STATE_ORDER() - Declare an XArray operation state.
1401 * @name: Name of this operation state (usually xas).
1402 * @array: Array to operate on.
1403 * @index: Initial index of interest.
1404 * @order: Order of entry.
1405 *
1406 * Declare and initialise an xa_state on the stack. This variant of
1407 * XA_STATE() allows you to specify the 'order' of the element you
1408 * want to operate on.`
1409 */
1410#define XA_STATE_ORDER(name, array, index, order) \
1411 struct xa_state name = __XA_STATE(array, \
1412 (index >> order) << order, \
1413 order - (order % XA_CHUNK_SHIFT), \
1414 (1U << (order % XA_CHUNK_SHIFT)) - 1)
1415
1416#define xas_marked(xas, mark) xa_marked((xas)->xa, (mark))
1417#define xas_trylock(xas) xa_trylock((xas)->xa)
1418#define xas_lock(xas) xa_lock((xas)->xa)
1419#define xas_unlock(xas) xa_unlock((xas)->xa)
1420#define xas_lock_bh(xas) xa_lock_bh((xas)->xa)
1421#define xas_unlock_bh(xas) xa_unlock_bh((xas)->xa)
1422#define xas_lock_irq(xas) xa_lock_irq((xas)->xa)
1423#define xas_unlock_irq(xas) xa_unlock_irq((xas)->xa)
1424#define xas_lock_irqsave(xas, flags) \
1425 xa_lock_irqsave((xas)->xa, flags)
1426#define xas_unlock_irqrestore(xas, flags) \
1427 xa_unlock_irqrestore((xas)->xa, flags)
1428
1429/**
1430 * xas_error() - Return an errno stored in the xa_state.
1431 * @xas: XArray operation state.
1432 *
1433 * Return: 0 if no error has been noted. A negative errno if one has.
1434 */
1435static inline int xas_error(const struct xa_state *xas)
1436{
1437 return xa_err(entry: xas->xa_node);
1438}
1439
1440/**
1441 * xas_set_err() - Note an error in the xa_state.
1442 * @xas: XArray operation state.
1443 * @err: Negative error number.
1444 *
1445 * Only call this function with a negative @err; zero or positive errors
1446 * will probably not behave the way you think they should. If you want
1447 * to clear the error from an xa_state, use xas_reset().
1448 */
1449static inline void xas_set_err(struct xa_state *xas, long err)
1450{
1451 xas->xa_node = XA_ERROR(err);
1452}
1453
1454/**
1455 * xas_invalid() - Is the xas in a retry or error state?
1456 * @xas: XArray operation state.
1457 *
1458 * Return: %true if the xas cannot be used for operations.
1459 */
1460static inline bool xas_invalid(const struct xa_state *xas)
1461{
1462 return (unsigned long)xas->xa_node & 3;
1463}
1464
1465/**
1466 * xas_valid() - Is the xas a valid cursor into the array?
1467 * @xas: XArray operation state.
1468 *
1469 * Return: %true if the xas can be used for operations.
1470 */
1471static inline bool xas_valid(const struct xa_state *xas)
1472{
1473 return !xas_invalid(xas);
1474}
1475
1476/**
1477 * xas_is_node() - Does the xas point to a node?
1478 * @xas: XArray operation state.
1479 *
1480 * Return: %true if the xas currently references a node.
1481 */
1482static inline bool xas_is_node(const struct xa_state *xas)
1483{
1484 return xas_valid(xas) && xas->xa_node;
1485}
1486
1487/* True if the pointer is something other than a node */
1488static inline bool xas_not_node(struct xa_node *node)
1489{
1490 return ((unsigned long)node & 3) || !node;
1491}
1492
1493/* True if the node represents RESTART or an error */
1494static inline bool xas_frozen(struct xa_node *node)
1495{
1496 return (unsigned long)node & 2;
1497}
1498
1499/* True if the node represents head-of-tree, RESTART or BOUNDS */
1500static inline bool xas_top(struct xa_node *node)
1501{
1502 return node <= XAS_RESTART;
1503}
1504
1505/**
1506 * xas_reset() - Reset an XArray operation state.
1507 * @xas: XArray operation state.
1508 *
1509 * Resets the error or walk state of the @xas so future walks of the
1510 * array will start from the root. Use this if you have dropped the
1511 * xarray lock and want to reuse the xa_state.
1512 *
1513 * Context: Any context.
1514 */
1515static inline void xas_reset(struct xa_state *xas)
1516{
1517 xas->xa_node = XAS_RESTART;
1518}
1519
1520/**
1521 * xas_retry() - Retry the operation if appropriate.
1522 * @xas: XArray operation state.
1523 * @entry: Entry from xarray.
1524 *
1525 * The advanced functions may sometimes return an internal entry, such as
1526 * a retry entry or a zero entry. This function sets up the @xas to restart
1527 * the walk from the head of the array if needed.
1528 *
1529 * Context: Any context.
1530 * Return: true if the operation needs to be retried.
1531 */
1532static inline bool xas_retry(struct xa_state *xas, const void *entry)
1533{
1534 if (xa_is_zero(entry))
1535 return true;
1536 if (!xa_is_retry(entry))
1537 return false;
1538 xas_reset(xas);
1539 return true;
1540}
1541
1542void *xas_load(struct xa_state *);
1543void *xas_store(struct xa_state *, void *entry);
1544void *xas_find(struct xa_state *, unsigned long max);
1545void *xas_find_conflict(struct xa_state *);
1546
1547bool xas_get_mark(const struct xa_state *, xa_mark_t);
1548void xas_set_mark(const struct xa_state *, xa_mark_t);
1549void xas_clear_mark(const struct xa_state *, xa_mark_t);
1550void *xas_find_marked(struct xa_state *, unsigned long max, xa_mark_t);
1551void xas_init_marks(const struct xa_state *);
1552
1553bool xas_nomem(struct xa_state *, gfp_t);
1554void xas_destroy(struct xa_state *);
1555void xas_pause(struct xa_state *);
1556
1557void xas_create_range(struct xa_state *);
1558
1559#ifdef CONFIG_XARRAY_MULTI
1560int xa_get_order(struct xarray *, unsigned long index);
1561int xas_get_order(struct xa_state *xas);
1562void xas_split(struct xa_state *, void *entry, unsigned int order);
1563void xas_split_alloc(struct xa_state *, void *entry, unsigned int order, gfp_t);
1564void xas_try_split(struct xa_state *xas, void *entry, unsigned int order);
1565unsigned int xas_try_split_min_order(unsigned int order);
1566#else
1567static inline int xa_get_order(struct xarray *xa, unsigned long index)
1568{
1569 return 0;
1570}
1571
1572static inline int xas_get_order(struct xa_state *xas)
1573{
1574 return 0;
1575}
1576
1577static inline void xas_split(struct xa_state *xas, void *entry,
1578 unsigned int order)
1579{
1580 xas_store(xas, entry);
1581}
1582
1583static inline void xas_split_alloc(struct xa_state *xas, void *entry,
1584 unsigned int order, gfp_t gfp)
1585{
1586}
1587
1588static inline void xas_try_split(struct xa_state *xas, void *entry,
1589 unsigned int order)
1590{
1591}
1592
1593static inline unsigned int xas_try_split_min_order(unsigned int order)
1594{
1595 return 0;
1596}
1597
1598#endif
1599
1600/**
1601 * xas_reload() - Refetch an entry from the xarray.
1602 * @xas: XArray operation state.
1603 *
1604 * Use this function to check that a previously loaded entry still has
1605 * the same value. This is useful for the lockless pagecache lookup where
1606 * we walk the array with only the RCU lock to protect us, lock the page,
1607 * then check that the page hasn't moved since we looked it up.
1608 *
1609 * The caller guarantees that @xas is still valid. If it may be in an
1610 * error or restart state, call xas_load() instead.
1611 *
1612 * Return: The entry at this location in the xarray.
1613 */
1614static inline void *xas_reload(struct xa_state *xas)
1615{
1616 struct xa_node *node = xas->xa_node;
1617 void *entry;
1618 char offset;
1619
1620 if (!node)
1621 return xa_head(xa: xas->xa);
1622 if (IS_ENABLED(CONFIG_XARRAY_MULTI)) {
1623 offset = (xas->xa_index >> node->shift) & XA_CHUNK_MASK;
1624 entry = xa_entry(xa: xas->xa, node, offset);
1625 if (!xa_is_sibling(entry))
1626 return entry;
1627 offset = xa_to_sibling(entry);
1628 } else {
1629 offset = xas->xa_offset;
1630 }
1631 return xa_entry(xa: xas->xa, node, offset);
1632}
1633
1634/**
1635 * xas_set() - Set up XArray operation state for a different index.
1636 * @xas: XArray operation state.
1637 * @index: New index into the XArray.
1638 *
1639 * Move the operation state to refer to a different index. This will
1640 * have the effect of starting a walk from the top; see xas_next()
1641 * to move to an adjacent index.
1642 */
1643static inline void xas_set(struct xa_state *xas, unsigned long index)
1644{
1645 xas->xa_index = index;
1646 xas->xa_node = XAS_RESTART;
1647}
1648
1649/**
1650 * xas_advance() - Skip over sibling entries.
1651 * @xas: XArray operation state.
1652 * @index: Index of last sibling entry.
1653 *
1654 * Move the operation state to refer to the last sibling entry.
1655 * This is useful for loops that normally want to see sibling
1656 * entries but sometimes want to skip them. Use xas_set() if you
1657 * want to move to an index which is not part of this entry.
1658 */
1659static inline void xas_advance(struct xa_state *xas, unsigned long index)
1660{
1661 unsigned char shift = xas_is_node(xas) ? xas->xa_node->shift : 0;
1662
1663 xas->xa_index = index;
1664 xas->xa_offset = (index >> shift) & XA_CHUNK_MASK;
1665}
1666
1667/**
1668 * xas_set_order() - Set up XArray operation state for a multislot entry.
1669 * @xas: XArray operation state.
1670 * @index: Target of the operation.
1671 * @order: Entry occupies 2^@order indices.
1672 */
1673static inline void xas_set_order(struct xa_state *xas, unsigned long index,
1674 unsigned int order)
1675{
1676#ifdef CONFIG_XARRAY_MULTI
1677 xas->xa_index = order < BITS_PER_LONG ? (index >> order) << order : 0;
1678 xas->xa_shift = order - (order % XA_CHUNK_SHIFT);
1679 xas->xa_sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1680 xas->xa_node = XAS_RESTART;
1681#else
1682 BUG_ON(order > 0);
1683 xas_set(xas, index);
1684#endif
1685}
1686
1687/**
1688 * xas_set_update() - Set up XArray operation state for a callback.
1689 * @xas: XArray operation state.
1690 * @update: Function to call when updating a node.
1691 *
1692 * The XArray can notify a caller after it has updated an xa_node.
1693 * This is advanced functionality and is only needed by the page
1694 * cache and swap cache.
1695 */
1696static inline void xas_set_update(struct xa_state *xas, xa_update_node_t update)
1697{
1698 xas->xa_update = update;
1699}
1700
1701static inline void xas_set_lru(struct xa_state *xas, struct list_lru *lru)
1702{
1703 xas->xa_lru = lru;
1704}
1705
1706/**
1707 * xas_next_entry() - Advance iterator to next present entry.
1708 * @xas: XArray operation state.
1709 * @max: Highest index to return.
1710 *
1711 * xas_next_entry() is an inline function to optimise xarray traversal for
1712 * speed. It is equivalent to calling xas_find(), and will call xas_find()
1713 * for all the hard cases.
1714 *
1715 * Return: The next present entry after the one currently referred to by @xas.
1716 */
1717static inline void *xas_next_entry(struct xa_state *xas, unsigned long max)
1718{
1719 struct xa_node *node = xas->xa_node;
1720 void *entry;
1721
1722 if (unlikely(xas_not_node(node) || node->shift ||
1723 xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)))
1724 return xas_find(xas, max);
1725
1726 do {
1727 if (unlikely(xas->xa_index >= max))
1728 return xas_find(xas, max);
1729 if (unlikely(xas->xa_offset == XA_CHUNK_MASK))
1730 return xas_find(xas, max);
1731 entry = xa_entry(xa: xas->xa, node, offset: xas->xa_offset + 1);
1732 if (unlikely(xa_is_internal(entry)))
1733 return xas_find(xas, max);
1734 xas->xa_offset++;
1735 xas->xa_index++;
1736 } while (!entry);
1737
1738 return entry;
1739}
1740
1741/* Private */
1742static inline unsigned int xas_find_chunk(struct xa_state *xas, bool advance,
1743 xa_mark_t mark)
1744{
1745 unsigned long *addr = xas->xa_node->marks[(__force unsigned)mark];
1746 unsigned int offset = xas->xa_offset;
1747
1748 if (advance)
1749 offset++;
1750 if (XA_CHUNK_SIZE == BITS_PER_LONG) {
1751 if (offset < XA_CHUNK_SIZE) {
1752 unsigned long data = *addr & (~0UL << offset);
1753 if (data)
1754 return __ffs(data);
1755 }
1756 return XA_CHUNK_SIZE;
1757 }
1758
1759 return find_next_bit(addr, XA_CHUNK_SIZE, offset);
1760}
1761
1762/**
1763 * xas_next_marked() - Advance iterator to next marked entry.
1764 * @xas: XArray operation state.
1765 * @max: Highest index to return.
1766 * @mark: Mark to search for.
1767 *
1768 * xas_next_marked() is an inline function to optimise xarray traversal for
1769 * speed. It is equivalent to calling xas_find_marked(), and will call
1770 * xas_find_marked() for all the hard cases.
1771 *
1772 * Return: The next marked entry after the one currently referred to by @xas.
1773 */
1774static inline void *xas_next_marked(struct xa_state *xas, unsigned long max,
1775 xa_mark_t mark)
1776{
1777 struct xa_node *node = xas->xa_node;
1778 void *entry;
1779 unsigned int offset;
1780
1781 if (unlikely(xas_not_node(node) || node->shift))
1782 return xas_find_marked(xas, max, mark);
1783 offset = xas_find_chunk(xas, advance: true, mark);
1784 xas->xa_offset = offset;
1785 xas->xa_index = (xas->xa_index & ~XA_CHUNK_MASK) + offset;
1786 if (xas->xa_index > max)
1787 return NULL;
1788 if (offset == XA_CHUNK_SIZE)
1789 return xas_find_marked(xas, max, mark);
1790 entry = xa_entry(xa: xas->xa, node, offset);
1791 if (!entry)
1792 return xas_find_marked(xas, max, mark);
1793 return entry;
1794}
1795
1796/*
1797 * If iterating while holding a lock, drop the lock and reschedule
1798 * every %XA_CHECK_SCHED loops.
1799 */
1800enum {
1801 XA_CHECK_SCHED = 4096,
1802};
1803
1804/**
1805 * xas_for_each() - Iterate over a range of an XArray.
1806 * @xas: XArray operation state.
1807 * @entry: Entry retrieved from the array.
1808 * @max: Maximum index to retrieve from array.
1809 *
1810 * The loop body will be executed for each entry present in the xarray
1811 * between the current xas position and @max. @entry will be set to
1812 * the entry retrieved from the xarray. It is safe to delete entries
1813 * from the array in the loop body. You should hold either the RCU lock
1814 * or the xa_lock while iterating. If you need to drop the lock, call
1815 * xas_pause() first.
1816 */
1817#define xas_for_each(xas, entry, max) \
1818 for (entry = xas_find(xas, max); entry; \
1819 entry = xas_next_entry(xas, max))
1820
1821/**
1822 * xas_for_each_marked() - Iterate over a range of an XArray.
1823 * @xas: XArray operation state.
1824 * @entry: Entry retrieved from the array.
1825 * @max: Maximum index to retrieve from array.
1826 * @mark: Mark to search for.
1827 *
1828 * The loop body will be executed for each marked entry in the xarray
1829 * between the current xas position and @max. @entry will be set to
1830 * the entry retrieved from the xarray. It is safe to delete entries
1831 * from the array in the loop body. You should hold either the RCU lock
1832 * or the xa_lock while iterating. If you need to drop the lock, call
1833 * xas_pause() first.
1834 */
1835#define xas_for_each_marked(xas, entry, max, mark) \
1836 for (entry = xas_find_marked(xas, max, mark); entry; \
1837 entry = xas_next_marked(xas, max, mark))
1838
1839/**
1840 * xas_for_each_conflict() - Iterate over a range of an XArray.
1841 * @xas: XArray operation state.
1842 * @entry: Entry retrieved from the array.
1843 *
1844 * The loop body will be executed for each entry in the XArray that
1845 * lies within the range specified by @xas. If the loop terminates
1846 * normally, @entry will be %NULL. The user may break out of the loop,
1847 * which will leave @entry set to the conflicting entry. The caller
1848 * may also call xa_set_err() to exit the loop while setting an error
1849 * to record the reason.
1850 */
1851#define xas_for_each_conflict(xas, entry) \
1852 while ((entry = xas_find_conflict(xas)))
1853
1854void *__xas_next(struct xa_state *);
1855void *__xas_prev(struct xa_state *);
1856
1857/**
1858 * xas_prev() - Move iterator to previous index.
1859 * @xas: XArray operation state.
1860 *
1861 * If the @xas was in an error state, it will remain in an error state
1862 * and this function will return %NULL. If the @xas has never been walked,
1863 * it will have the effect of calling xas_load(). Otherwise one will be
1864 * subtracted from the index and the state will be walked to the correct
1865 * location in the array for the next operation.
1866 *
1867 * If the iterator was referencing index 0, this function wraps
1868 * around to %ULONG_MAX.
1869 *
1870 * Return: The entry at the new index. This may be %NULL or an internal
1871 * entry.
1872 */
1873static inline void *xas_prev(struct xa_state *xas)
1874{
1875 struct xa_node *node = xas->xa_node;
1876
1877 if (unlikely(xas_not_node(node) || node->shift ||
1878 xas->xa_offset == 0))
1879 return __xas_prev(xas);
1880
1881 xas->xa_index--;
1882 xas->xa_offset--;
1883 return xa_entry(xa: xas->xa, node, offset: xas->xa_offset);
1884}
1885
1886/**
1887 * xas_next() - Move state to next index.
1888 * @xas: XArray operation state.
1889 *
1890 * If the @xas was in an error state, it will remain in an error state
1891 * and this function will return %NULL. If the @xas has never been walked,
1892 * it will have the effect of calling xas_load(). Otherwise one will be
1893 * added to the index and the state will be walked to the correct
1894 * location in the array for the next operation.
1895 *
1896 * If the iterator was referencing index %ULONG_MAX, this function wraps
1897 * around to 0.
1898 *
1899 * Return: The entry at the new index. This may be %NULL or an internal
1900 * entry.
1901 */
1902static inline void *xas_next(struct xa_state *xas)
1903{
1904 struct xa_node *node = xas->xa_node;
1905
1906 if (unlikely(xas_not_node(node) || node->shift ||
1907 xas->xa_offset == XA_CHUNK_MASK))
1908 return __xas_next(xas);
1909
1910 xas->xa_index++;
1911 xas->xa_offset++;
1912 return xa_entry(xa: xas->xa, node, offset: xas->xa_offset);
1913}
1914
1915#endif /* _LINUX_XARRAY_H */
1916