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