xref: /linux/lib/xarray.c (revision 36ec807b627b4c0a0a382f0ae48eac7187d14b2b)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * XArray implementation
4  * Copyright (c) 2017-2018 Microsoft Corporation
5  * Copyright (c) 2018-2020 Oracle
6  * Author: Matthew Wilcox <willy@infradead.org>
7  */
8 
9 #include <linux/bitmap.h>
10 #include <linux/export.h>
11 #include <linux/list.h>
12 #include <linux/slab.h>
13 #include <linux/xarray.h>
14 
15 #include "radix-tree.h"
16 
17 /*
18  * Coding conventions in this file:
19  *
20  * @xa is used to refer to the entire xarray.
21  * @xas is the 'xarray operation state'.  It may be either a pointer to
22  * an xa_state, or an xa_state stored on the stack.  This is an unfortunate
23  * ambiguity.
24  * @index is the index of the entry being operated on
25  * @mark is an xa_mark_t; a small number indicating one of the mark bits.
26  * @node refers to an xa_node; usually the primary one being operated on by
27  * this function.
28  * @offset is the index into the slots array inside an xa_node.
29  * @parent refers to the @xa_node closer to the head than @node.
30  * @entry refers to something stored in a slot in the xarray
31  */
32 
33 static inline unsigned int xa_lock_type(const struct xarray *xa)
34 {
35 	return (__force unsigned int)xa->xa_flags & 3;
36 }
37 
38 static inline void xas_lock_type(struct xa_state *xas, unsigned int lock_type)
39 {
40 	if (lock_type == XA_LOCK_IRQ)
41 		xas_lock_irq(xas);
42 	else if (lock_type == XA_LOCK_BH)
43 		xas_lock_bh(xas);
44 	else
45 		xas_lock(xas);
46 }
47 
48 static inline void xas_unlock_type(struct xa_state *xas, unsigned int lock_type)
49 {
50 	if (lock_type == XA_LOCK_IRQ)
51 		xas_unlock_irq(xas);
52 	else if (lock_type == XA_LOCK_BH)
53 		xas_unlock_bh(xas);
54 	else
55 		xas_unlock(xas);
56 }
57 
58 static inline bool xa_track_free(const struct xarray *xa)
59 {
60 	return xa->xa_flags & XA_FLAGS_TRACK_FREE;
61 }
62 
63 static inline bool xa_zero_busy(const struct xarray *xa)
64 {
65 	return xa->xa_flags & XA_FLAGS_ZERO_BUSY;
66 }
67 
68 static inline void xa_mark_set(struct xarray *xa, xa_mark_t mark)
69 {
70 	if (!(xa->xa_flags & XA_FLAGS_MARK(mark)))
71 		xa->xa_flags |= XA_FLAGS_MARK(mark);
72 }
73 
74 static inline void xa_mark_clear(struct xarray *xa, xa_mark_t mark)
75 {
76 	if (xa->xa_flags & XA_FLAGS_MARK(mark))
77 		xa->xa_flags &= ~(XA_FLAGS_MARK(mark));
78 }
79 
80 static inline unsigned long *node_marks(struct xa_node *node, xa_mark_t mark)
81 {
82 	return node->marks[(__force unsigned)mark];
83 }
84 
85 static inline bool node_get_mark(struct xa_node *node,
86 		unsigned int offset, xa_mark_t mark)
87 {
88 	return test_bit(offset, node_marks(node, mark));
89 }
90 
91 /* returns true if the bit was set */
92 static inline bool node_set_mark(struct xa_node *node, unsigned int offset,
93 				xa_mark_t mark)
94 {
95 	return __test_and_set_bit(offset, node_marks(node, mark));
96 }
97 
98 /* returns true if the bit was set */
99 static inline bool node_clear_mark(struct xa_node *node, unsigned int offset,
100 				xa_mark_t mark)
101 {
102 	return __test_and_clear_bit(offset, node_marks(node, mark));
103 }
104 
105 static inline bool node_any_mark(struct xa_node *node, xa_mark_t mark)
106 {
107 	return !bitmap_empty(node_marks(node, mark), XA_CHUNK_SIZE);
108 }
109 
110 static inline void node_mark_all(struct xa_node *node, xa_mark_t mark)
111 {
112 	bitmap_fill(node_marks(node, mark), XA_CHUNK_SIZE);
113 }
114 
115 #define mark_inc(mark) do { \
116 	mark = (__force xa_mark_t)((__force unsigned)(mark) + 1); \
117 } while (0)
118 
119 /*
120  * xas_squash_marks() - Merge all marks to the first entry
121  * @xas: Array operation state.
122  *
123  * Set a mark on the first entry if any entry has it set.  Clear marks on
124  * all sibling entries.
125  */
126 static void xas_squash_marks(const struct xa_state *xas)
127 {
128 	unsigned int mark = 0;
129 	unsigned int limit = xas->xa_offset + xas->xa_sibs + 1;
130 
131 	if (!xas->xa_sibs)
132 		return;
133 
134 	do {
135 		unsigned long *marks = xas->xa_node->marks[mark];
136 		if (find_next_bit(marks, limit, xas->xa_offset + 1) == limit)
137 			continue;
138 		__set_bit(xas->xa_offset, marks);
139 		bitmap_clear(marks, xas->xa_offset + 1, xas->xa_sibs);
140 	} while (mark++ != (__force unsigned)XA_MARK_MAX);
141 }
142 
143 /* extracts the offset within this node from the index */
144 static unsigned int get_offset(unsigned long index, struct xa_node *node)
145 {
146 	return (index >> node->shift) & XA_CHUNK_MASK;
147 }
148 
149 static void xas_set_offset(struct xa_state *xas)
150 {
151 	xas->xa_offset = get_offset(xas->xa_index, xas->xa_node);
152 }
153 
154 /* move the index either forwards (find) or backwards (sibling slot) */
155 static void xas_move_index(struct xa_state *xas, unsigned long offset)
156 {
157 	unsigned int shift = xas->xa_node->shift;
158 	xas->xa_index &= ~XA_CHUNK_MASK << shift;
159 	xas->xa_index += offset << shift;
160 }
161 
162 static void xas_next_offset(struct xa_state *xas)
163 {
164 	xas->xa_offset++;
165 	xas_move_index(xas, xas->xa_offset);
166 }
167 
168 static void *set_bounds(struct xa_state *xas)
169 {
170 	xas->xa_node = XAS_BOUNDS;
171 	return NULL;
172 }
173 
174 /*
175  * Starts a walk.  If the @xas is already valid, we assume that it's on
176  * the right path and just return where we've got to.  If we're in an
177  * error state, return NULL.  If the index is outside the current scope
178  * of the xarray, return NULL without changing @xas->xa_node.  Otherwise
179  * set @xas->xa_node to NULL and return the current head of the array.
180  */
181 static void *xas_start(struct xa_state *xas)
182 {
183 	void *entry;
184 
185 	if (xas_valid(xas))
186 		return xas_reload(xas);
187 	if (xas_error(xas))
188 		return NULL;
189 
190 	entry = xa_head(xas->xa);
191 	if (!xa_is_node(entry)) {
192 		if (xas->xa_index)
193 			return set_bounds(xas);
194 	} else {
195 		if ((xas->xa_index >> xa_to_node(entry)->shift) > XA_CHUNK_MASK)
196 			return set_bounds(xas);
197 	}
198 
199 	xas->xa_node = NULL;
200 	return entry;
201 }
202 
203 static __always_inline void *xas_descend(struct xa_state *xas,
204 					struct xa_node *node)
205 {
206 	unsigned int offset = get_offset(xas->xa_index, node);
207 	void *entry = xa_entry(xas->xa, node, offset);
208 
209 	xas->xa_node = node;
210 	while (xa_is_sibling(entry)) {
211 		offset = xa_to_sibling(entry);
212 		entry = xa_entry(xas->xa, node, offset);
213 		if (node->shift && xa_is_node(entry))
214 			entry = XA_RETRY_ENTRY;
215 	}
216 
217 	xas->xa_offset = offset;
218 	return entry;
219 }
220 
221 /**
222  * xas_load() - Load an entry from the XArray (advanced).
223  * @xas: XArray operation state.
224  *
225  * Usually walks the @xas to the appropriate state to load the entry
226  * stored at xa_index.  However, it will do nothing and return %NULL if
227  * @xas is in an error state.  xas_load() will never expand the tree.
228  *
229  * If the xa_state is set up to operate on a multi-index entry, xas_load()
230  * may return %NULL or an internal entry, even if there are entries
231  * present within the range specified by @xas.
232  *
233  * Context: Any context.  The caller should hold the xa_lock or the RCU lock.
234  * Return: Usually an entry in the XArray, but see description for exceptions.
235  */
236 void *xas_load(struct xa_state *xas)
237 {
238 	void *entry = xas_start(xas);
239 
240 	while (xa_is_node(entry)) {
241 		struct xa_node *node = xa_to_node(entry);
242 
243 		if (xas->xa_shift > node->shift)
244 			break;
245 		entry = xas_descend(xas, node);
246 		if (node->shift == 0)
247 			break;
248 	}
249 	return entry;
250 }
251 EXPORT_SYMBOL_GPL(xas_load);
252 
253 #define XA_RCU_FREE	((struct xarray *)1)
254 
255 static void xa_node_free(struct xa_node *node)
256 {
257 	XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
258 	node->array = XA_RCU_FREE;
259 	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
260 }
261 
262 /*
263  * xas_destroy() - Free any resources allocated during the XArray operation.
264  * @xas: XArray operation state.
265  *
266  * Most users will not need to call this function; it is called for you
267  * by xas_nomem().
268  */
269 void xas_destroy(struct xa_state *xas)
270 {
271 	struct xa_node *next, *node = xas->xa_alloc;
272 
273 	while (node) {
274 		XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
275 		next = rcu_dereference_raw(node->parent);
276 		radix_tree_node_rcu_free(&node->rcu_head);
277 		xas->xa_alloc = node = next;
278 	}
279 }
280 
281 /**
282  * xas_nomem() - Allocate memory if needed.
283  * @xas: XArray operation state.
284  * @gfp: Memory allocation flags.
285  *
286  * If we need to add new nodes to the XArray, we try to allocate memory
287  * with GFP_NOWAIT while holding the lock, which will usually succeed.
288  * If it fails, @xas is flagged as needing memory to continue.  The caller
289  * should drop the lock and call xas_nomem().  If xas_nomem() succeeds,
290  * the caller should retry the operation.
291  *
292  * Forward progress is guaranteed as one node is allocated here and
293  * stored in the xa_state where it will be found by xas_alloc().  More
294  * nodes will likely be found in the slab allocator, but we do not tie
295  * them up here.
296  *
297  * Return: true if memory was needed, and was successfully allocated.
298  */
299 bool xas_nomem(struct xa_state *xas, gfp_t gfp)
300 {
301 	if (xas->xa_node != XA_ERROR(-ENOMEM)) {
302 		xas_destroy(xas);
303 		return false;
304 	}
305 	if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
306 		gfp |= __GFP_ACCOUNT;
307 	xas->xa_alloc = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
308 	if (!xas->xa_alloc)
309 		return false;
310 	xas->xa_alloc->parent = NULL;
311 	XA_NODE_BUG_ON(xas->xa_alloc, !list_empty(&xas->xa_alloc->private_list));
312 	xas->xa_node = XAS_RESTART;
313 	return true;
314 }
315 EXPORT_SYMBOL_GPL(xas_nomem);
316 
317 /*
318  * __xas_nomem() - Drop locks and allocate memory if needed.
319  * @xas: XArray operation state.
320  * @gfp: Memory allocation flags.
321  *
322  * Internal variant of xas_nomem().
323  *
324  * Return: true if memory was needed, and was successfully allocated.
325  */
326 static bool __xas_nomem(struct xa_state *xas, gfp_t gfp)
327 	__must_hold(xas->xa->xa_lock)
328 {
329 	unsigned int lock_type = xa_lock_type(xas->xa);
330 
331 	if (xas->xa_node != XA_ERROR(-ENOMEM)) {
332 		xas_destroy(xas);
333 		return false;
334 	}
335 	if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
336 		gfp |= __GFP_ACCOUNT;
337 	if (gfpflags_allow_blocking(gfp)) {
338 		xas_unlock_type(xas, lock_type);
339 		xas->xa_alloc = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
340 		xas_lock_type(xas, lock_type);
341 	} else {
342 		xas->xa_alloc = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
343 	}
344 	if (!xas->xa_alloc)
345 		return false;
346 	xas->xa_alloc->parent = NULL;
347 	XA_NODE_BUG_ON(xas->xa_alloc, !list_empty(&xas->xa_alloc->private_list));
348 	xas->xa_node = XAS_RESTART;
349 	return true;
350 }
351 
352 static void xas_update(struct xa_state *xas, struct xa_node *node)
353 {
354 	if (xas->xa_update)
355 		xas->xa_update(node);
356 	else
357 		XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
358 }
359 
360 static void *xas_alloc(struct xa_state *xas, unsigned int shift)
361 {
362 	struct xa_node *parent = xas->xa_node;
363 	struct xa_node *node = xas->xa_alloc;
364 
365 	if (xas_invalid(xas))
366 		return NULL;
367 
368 	if (node) {
369 		xas->xa_alloc = NULL;
370 	} else {
371 		gfp_t gfp = GFP_NOWAIT | __GFP_NOWARN;
372 
373 		if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
374 			gfp |= __GFP_ACCOUNT;
375 
376 		node = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
377 		if (!node) {
378 			xas_set_err(xas, -ENOMEM);
379 			return NULL;
380 		}
381 	}
382 
383 	if (parent) {
384 		node->offset = xas->xa_offset;
385 		parent->count++;
386 		XA_NODE_BUG_ON(node, parent->count > XA_CHUNK_SIZE);
387 		xas_update(xas, parent);
388 	}
389 	XA_NODE_BUG_ON(node, shift > BITS_PER_LONG);
390 	XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
391 	node->shift = shift;
392 	node->count = 0;
393 	node->nr_values = 0;
394 	RCU_INIT_POINTER(node->parent, xas->xa_node);
395 	node->array = xas->xa;
396 
397 	return node;
398 }
399 
400 #ifdef CONFIG_XARRAY_MULTI
401 /* Returns the number of indices covered by a given xa_state */
402 static unsigned long xas_size(const struct xa_state *xas)
403 {
404 	return (xas->xa_sibs + 1UL) << xas->xa_shift;
405 }
406 #endif
407 
408 /*
409  * Use this to calculate the maximum index that will need to be created
410  * in order to add the entry described by @xas.  Because we cannot store a
411  * multi-index entry at index 0, the calculation is a little more complex
412  * than you might expect.
413  */
414 static unsigned long xas_max(struct xa_state *xas)
415 {
416 	unsigned long max = xas->xa_index;
417 
418 #ifdef CONFIG_XARRAY_MULTI
419 	if (xas->xa_shift || xas->xa_sibs) {
420 		unsigned long mask = xas_size(xas) - 1;
421 		max |= mask;
422 		if (mask == max)
423 			max++;
424 	}
425 #endif
426 
427 	return max;
428 }
429 
430 /* The maximum index that can be contained in the array without expanding it */
431 static unsigned long max_index(void *entry)
432 {
433 	if (!xa_is_node(entry))
434 		return 0;
435 	return (XA_CHUNK_SIZE << xa_to_node(entry)->shift) - 1;
436 }
437 
438 static void xas_shrink(struct xa_state *xas)
439 {
440 	struct xarray *xa = xas->xa;
441 	struct xa_node *node = xas->xa_node;
442 
443 	for (;;) {
444 		void *entry;
445 
446 		XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
447 		if (node->count != 1)
448 			break;
449 		entry = xa_entry_locked(xa, node, 0);
450 		if (!entry)
451 			break;
452 		if (!xa_is_node(entry) && node->shift)
453 			break;
454 		if (xa_is_zero(entry) && xa_zero_busy(xa))
455 			entry = NULL;
456 		xas->xa_node = XAS_BOUNDS;
457 
458 		RCU_INIT_POINTER(xa->xa_head, entry);
459 		if (xa_track_free(xa) && !node_get_mark(node, 0, XA_FREE_MARK))
460 			xa_mark_clear(xa, XA_FREE_MARK);
461 
462 		node->count = 0;
463 		node->nr_values = 0;
464 		if (!xa_is_node(entry))
465 			RCU_INIT_POINTER(node->slots[0], XA_RETRY_ENTRY);
466 		xas_update(xas, node);
467 		xa_node_free(node);
468 		if (!xa_is_node(entry))
469 			break;
470 		node = xa_to_node(entry);
471 		node->parent = NULL;
472 	}
473 }
474 
475 /*
476  * xas_delete_node() - Attempt to delete an xa_node
477  * @xas: Array operation state.
478  *
479  * Attempts to delete the @xas->xa_node.  This will fail if xa->node has
480  * a non-zero reference count.
481  */
482 static void xas_delete_node(struct xa_state *xas)
483 {
484 	struct xa_node *node = xas->xa_node;
485 
486 	for (;;) {
487 		struct xa_node *parent;
488 
489 		XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
490 		if (node->count)
491 			break;
492 
493 		parent = xa_parent_locked(xas->xa, node);
494 		xas->xa_node = parent;
495 		xas->xa_offset = node->offset;
496 		xa_node_free(node);
497 
498 		if (!parent) {
499 			xas->xa->xa_head = NULL;
500 			xas->xa_node = XAS_BOUNDS;
501 			return;
502 		}
503 
504 		parent->slots[xas->xa_offset] = NULL;
505 		parent->count--;
506 		XA_NODE_BUG_ON(parent, parent->count > XA_CHUNK_SIZE);
507 		node = parent;
508 		xas_update(xas, node);
509 	}
510 
511 	if (!node->parent)
512 		xas_shrink(xas);
513 }
514 
515 /**
516  * xas_free_nodes() - Free this node and all nodes that it references
517  * @xas: Array operation state.
518  * @top: Node to free
519  *
520  * This node has been removed from the tree.  We must now free it and all
521  * of its subnodes.  There may be RCU walkers with references into the tree,
522  * so we must replace all entries with retry markers.
523  */
524 static void xas_free_nodes(struct xa_state *xas, struct xa_node *top)
525 {
526 	unsigned int offset = 0;
527 	struct xa_node *node = top;
528 
529 	for (;;) {
530 		void *entry = xa_entry_locked(xas->xa, node, offset);
531 
532 		if (node->shift && xa_is_node(entry)) {
533 			node = xa_to_node(entry);
534 			offset = 0;
535 			continue;
536 		}
537 		if (entry)
538 			RCU_INIT_POINTER(node->slots[offset], XA_RETRY_ENTRY);
539 		offset++;
540 		while (offset == XA_CHUNK_SIZE) {
541 			struct xa_node *parent;
542 
543 			parent = xa_parent_locked(xas->xa, node);
544 			offset = node->offset + 1;
545 			node->count = 0;
546 			node->nr_values = 0;
547 			xas_update(xas, node);
548 			xa_node_free(node);
549 			if (node == top)
550 				return;
551 			node = parent;
552 		}
553 	}
554 }
555 
556 /*
557  * xas_expand adds nodes to the head of the tree until it has reached
558  * sufficient height to be able to contain @xas->xa_index
559  */
560 static int xas_expand(struct xa_state *xas, void *head)
561 {
562 	struct xarray *xa = xas->xa;
563 	struct xa_node *node = NULL;
564 	unsigned int shift = 0;
565 	unsigned long max = xas_max(xas);
566 
567 	if (!head) {
568 		if (max == 0)
569 			return 0;
570 		while ((max >> shift) >= XA_CHUNK_SIZE)
571 			shift += XA_CHUNK_SHIFT;
572 		return shift + XA_CHUNK_SHIFT;
573 	} else if (xa_is_node(head)) {
574 		node = xa_to_node(head);
575 		shift = node->shift + XA_CHUNK_SHIFT;
576 	}
577 	xas->xa_node = NULL;
578 
579 	while (max > max_index(head)) {
580 		xa_mark_t mark = 0;
581 
582 		XA_NODE_BUG_ON(node, shift > BITS_PER_LONG);
583 		node = xas_alloc(xas, shift);
584 		if (!node)
585 			return -ENOMEM;
586 
587 		node->count = 1;
588 		if (xa_is_value(head))
589 			node->nr_values = 1;
590 		RCU_INIT_POINTER(node->slots[0], head);
591 
592 		/* Propagate the aggregated mark info to the new child */
593 		for (;;) {
594 			if (xa_track_free(xa) && mark == XA_FREE_MARK) {
595 				node_mark_all(node, XA_FREE_MARK);
596 				if (!xa_marked(xa, XA_FREE_MARK)) {
597 					node_clear_mark(node, 0, XA_FREE_MARK);
598 					xa_mark_set(xa, XA_FREE_MARK);
599 				}
600 			} else if (xa_marked(xa, mark)) {
601 				node_set_mark(node, 0, mark);
602 			}
603 			if (mark == XA_MARK_MAX)
604 				break;
605 			mark_inc(mark);
606 		}
607 
608 		/*
609 		 * Now that the new node is fully initialised, we can add
610 		 * it to the tree
611 		 */
612 		if (xa_is_node(head)) {
613 			xa_to_node(head)->offset = 0;
614 			rcu_assign_pointer(xa_to_node(head)->parent, node);
615 		}
616 		head = xa_mk_node(node);
617 		rcu_assign_pointer(xa->xa_head, head);
618 		xas_update(xas, node);
619 
620 		shift += XA_CHUNK_SHIFT;
621 	}
622 
623 	xas->xa_node = node;
624 	return shift;
625 }
626 
627 /*
628  * xas_create() - Create a slot to store an entry in.
629  * @xas: XArray operation state.
630  * @allow_root: %true if we can store the entry in the root directly
631  *
632  * Most users will not need to call this function directly, as it is called
633  * by xas_store().  It is useful for doing conditional store operations
634  * (see the xa_cmpxchg() implementation for an example).
635  *
636  * Return: If the slot already existed, returns the contents of this slot.
637  * If the slot was newly created, returns %NULL.  If it failed to create the
638  * slot, returns %NULL and indicates the error in @xas.
639  */
640 static void *xas_create(struct xa_state *xas, bool allow_root)
641 {
642 	struct xarray *xa = xas->xa;
643 	void *entry;
644 	void __rcu **slot;
645 	struct xa_node *node = xas->xa_node;
646 	int shift;
647 	unsigned int order = xas->xa_shift;
648 
649 	if (xas_top(node)) {
650 		entry = xa_head_locked(xa);
651 		xas->xa_node = NULL;
652 		if (!entry && xa_zero_busy(xa))
653 			entry = XA_ZERO_ENTRY;
654 		shift = xas_expand(xas, entry);
655 		if (shift < 0)
656 			return NULL;
657 		if (!shift && !allow_root)
658 			shift = XA_CHUNK_SHIFT;
659 		entry = xa_head_locked(xa);
660 		slot = &xa->xa_head;
661 	} else if (xas_error(xas)) {
662 		return NULL;
663 	} else if (node) {
664 		unsigned int offset = xas->xa_offset;
665 
666 		shift = node->shift;
667 		entry = xa_entry_locked(xa, node, offset);
668 		slot = &node->slots[offset];
669 	} else {
670 		shift = 0;
671 		entry = xa_head_locked(xa);
672 		slot = &xa->xa_head;
673 	}
674 
675 	while (shift > order) {
676 		shift -= XA_CHUNK_SHIFT;
677 		if (!entry) {
678 			node = xas_alloc(xas, shift);
679 			if (!node)
680 				break;
681 			if (xa_track_free(xa))
682 				node_mark_all(node, XA_FREE_MARK);
683 			rcu_assign_pointer(*slot, xa_mk_node(node));
684 		} else if (xa_is_node(entry)) {
685 			node = xa_to_node(entry);
686 		} else {
687 			break;
688 		}
689 		entry = xas_descend(xas, node);
690 		slot = &node->slots[xas->xa_offset];
691 	}
692 
693 	return entry;
694 }
695 
696 /**
697  * xas_create_range() - Ensure that stores to this range will succeed
698  * @xas: XArray operation state.
699  *
700  * Creates all of the slots in the range covered by @xas.  Sets @xas to
701  * create single-index entries and positions it at the beginning of the
702  * range.  This is for the benefit of users which have not yet been
703  * converted to use multi-index entries.
704  */
705 void xas_create_range(struct xa_state *xas)
706 {
707 	unsigned long index = xas->xa_index;
708 	unsigned char shift = xas->xa_shift;
709 	unsigned char sibs = xas->xa_sibs;
710 
711 	xas->xa_index |= ((sibs + 1UL) << shift) - 1;
712 	if (xas_is_node(xas) && xas->xa_node->shift == xas->xa_shift)
713 		xas->xa_offset |= sibs;
714 	xas->xa_shift = 0;
715 	xas->xa_sibs = 0;
716 
717 	for (;;) {
718 		xas_create(xas, true);
719 		if (xas_error(xas))
720 			goto restore;
721 		if (xas->xa_index <= (index | XA_CHUNK_MASK))
722 			goto success;
723 		xas->xa_index -= XA_CHUNK_SIZE;
724 
725 		for (;;) {
726 			struct xa_node *node = xas->xa_node;
727 			if (node->shift >= shift)
728 				break;
729 			xas->xa_node = xa_parent_locked(xas->xa, node);
730 			xas->xa_offset = node->offset - 1;
731 			if (node->offset != 0)
732 				break;
733 		}
734 	}
735 
736 restore:
737 	xas->xa_shift = shift;
738 	xas->xa_sibs = sibs;
739 	xas->xa_index = index;
740 	return;
741 success:
742 	xas->xa_index = index;
743 	if (xas->xa_node)
744 		xas_set_offset(xas);
745 }
746 EXPORT_SYMBOL_GPL(xas_create_range);
747 
748 static void update_node(struct xa_state *xas, struct xa_node *node,
749 		int count, int values)
750 {
751 	if (!node || (!count && !values))
752 		return;
753 
754 	node->count += count;
755 	node->nr_values += values;
756 	XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
757 	XA_NODE_BUG_ON(node, node->nr_values > XA_CHUNK_SIZE);
758 	xas_update(xas, node);
759 	if (count < 0)
760 		xas_delete_node(xas);
761 }
762 
763 /**
764  * xas_store() - Store this entry in the XArray.
765  * @xas: XArray operation state.
766  * @entry: New entry.
767  *
768  * If @xas is operating on a multi-index entry, the entry returned by this
769  * function is essentially meaningless (it may be an internal entry or it
770  * may be %NULL, even if there are non-NULL entries at some of the indices
771  * covered by the range).  This is not a problem for any current users,
772  * and can be changed if needed.
773  *
774  * Return: The old entry at this index.
775  */
776 void *xas_store(struct xa_state *xas, void *entry)
777 {
778 	struct xa_node *node;
779 	void __rcu **slot = &xas->xa->xa_head;
780 	unsigned int offset, max;
781 	int count = 0;
782 	int values = 0;
783 	void *first, *next;
784 	bool value = xa_is_value(entry);
785 
786 	if (entry) {
787 		bool allow_root = !xa_is_node(entry) && !xa_is_zero(entry);
788 		first = xas_create(xas, allow_root);
789 	} else {
790 		first = xas_load(xas);
791 	}
792 
793 	if (xas_invalid(xas))
794 		return first;
795 	node = xas->xa_node;
796 	if (node && (xas->xa_shift < node->shift))
797 		xas->xa_sibs = 0;
798 	if ((first == entry) && !xas->xa_sibs)
799 		return first;
800 
801 	next = first;
802 	offset = xas->xa_offset;
803 	max = xas->xa_offset + xas->xa_sibs;
804 	if (node) {
805 		slot = &node->slots[offset];
806 		if (xas->xa_sibs)
807 			xas_squash_marks(xas);
808 	}
809 	if (!entry)
810 		xas_init_marks(xas);
811 
812 	for (;;) {
813 		/*
814 		 * Must clear the marks before setting the entry to NULL,
815 		 * otherwise xas_for_each_marked may find a NULL entry and
816 		 * stop early.  rcu_assign_pointer contains a release barrier
817 		 * so the mark clearing will appear to happen before the
818 		 * entry is set to NULL.
819 		 */
820 		rcu_assign_pointer(*slot, entry);
821 		if (xa_is_node(next) && (!node || node->shift))
822 			xas_free_nodes(xas, xa_to_node(next));
823 		if (!node)
824 			break;
825 		count += !next - !entry;
826 		values += !xa_is_value(first) - !value;
827 		if (entry) {
828 			if (offset == max)
829 				break;
830 			if (!xa_is_sibling(entry))
831 				entry = xa_mk_sibling(xas->xa_offset);
832 		} else {
833 			if (offset == XA_CHUNK_MASK)
834 				break;
835 		}
836 		next = xa_entry_locked(xas->xa, node, ++offset);
837 		if (!xa_is_sibling(next)) {
838 			if (!entry && (offset > max))
839 				break;
840 			first = next;
841 		}
842 		slot++;
843 	}
844 
845 	update_node(xas, node, count, values);
846 	return first;
847 }
848 EXPORT_SYMBOL_GPL(xas_store);
849 
850 /**
851  * xas_get_mark() - Returns the state of this mark.
852  * @xas: XArray operation state.
853  * @mark: Mark number.
854  *
855  * Return: true if the mark is set, false if the mark is clear or @xas
856  * is in an error state.
857  */
858 bool xas_get_mark(const struct xa_state *xas, xa_mark_t mark)
859 {
860 	if (xas_invalid(xas))
861 		return false;
862 	if (!xas->xa_node)
863 		return xa_marked(xas->xa, mark);
864 	return node_get_mark(xas->xa_node, xas->xa_offset, mark);
865 }
866 EXPORT_SYMBOL_GPL(xas_get_mark);
867 
868 /**
869  * xas_set_mark() - Sets the mark on this entry and its parents.
870  * @xas: XArray operation state.
871  * @mark: Mark number.
872  *
873  * Sets the specified mark on this entry, and walks up the tree setting it
874  * on all the ancestor entries.  Does nothing if @xas has not been walked to
875  * an entry, or is in an error state.
876  */
877 void xas_set_mark(const struct xa_state *xas, xa_mark_t mark)
878 {
879 	struct xa_node *node = xas->xa_node;
880 	unsigned int offset = xas->xa_offset;
881 
882 	if (xas_invalid(xas))
883 		return;
884 
885 	while (node) {
886 		if (node_set_mark(node, offset, mark))
887 			return;
888 		offset = node->offset;
889 		node = xa_parent_locked(xas->xa, node);
890 	}
891 
892 	if (!xa_marked(xas->xa, mark))
893 		xa_mark_set(xas->xa, mark);
894 }
895 EXPORT_SYMBOL_GPL(xas_set_mark);
896 
897 /**
898  * xas_clear_mark() - Clears the mark on this entry and its parents.
899  * @xas: XArray operation state.
900  * @mark: Mark number.
901  *
902  * Clears the specified mark on this entry, and walks back to the head
903  * attempting to clear it on all the ancestor entries.  Does nothing if
904  * @xas has not been walked to an entry, or is in an error state.
905  */
906 void xas_clear_mark(const struct xa_state *xas, xa_mark_t mark)
907 {
908 	struct xa_node *node = xas->xa_node;
909 	unsigned int offset = xas->xa_offset;
910 
911 	if (xas_invalid(xas))
912 		return;
913 
914 	while (node) {
915 		if (!node_clear_mark(node, offset, mark))
916 			return;
917 		if (node_any_mark(node, mark))
918 			return;
919 
920 		offset = node->offset;
921 		node = xa_parent_locked(xas->xa, node);
922 	}
923 
924 	if (xa_marked(xas->xa, mark))
925 		xa_mark_clear(xas->xa, mark);
926 }
927 EXPORT_SYMBOL_GPL(xas_clear_mark);
928 
929 /**
930  * xas_init_marks() - Initialise all marks for the entry
931  * @xas: Array operations state.
932  *
933  * Initialise all marks for the entry specified by @xas.  If we're tracking
934  * free entries with a mark, we need to set it on all entries.  All other
935  * marks are cleared.
936  *
937  * This implementation is not as efficient as it could be; we may walk
938  * up the tree multiple times.
939  */
940 void xas_init_marks(const struct xa_state *xas)
941 {
942 	xa_mark_t mark = 0;
943 
944 	for (;;) {
945 		if (xa_track_free(xas->xa) && mark == XA_FREE_MARK)
946 			xas_set_mark(xas, mark);
947 		else
948 			xas_clear_mark(xas, mark);
949 		if (mark == XA_MARK_MAX)
950 			break;
951 		mark_inc(mark);
952 	}
953 }
954 EXPORT_SYMBOL_GPL(xas_init_marks);
955 
956 #ifdef CONFIG_XARRAY_MULTI
957 static unsigned int node_get_marks(struct xa_node *node, unsigned int offset)
958 {
959 	unsigned int marks = 0;
960 	xa_mark_t mark = XA_MARK_0;
961 
962 	for (;;) {
963 		if (node_get_mark(node, offset, mark))
964 			marks |= 1 << (__force unsigned int)mark;
965 		if (mark == XA_MARK_MAX)
966 			break;
967 		mark_inc(mark);
968 	}
969 
970 	return marks;
971 }
972 
973 static inline void node_mark_slots(struct xa_node *node, unsigned int sibs,
974 		xa_mark_t mark)
975 {
976 	int i;
977 
978 	if (sibs == 0)
979 		node_mark_all(node, mark);
980 	else {
981 		for (i = 0; i < XA_CHUNK_SIZE; i += sibs + 1)
982 			node_set_mark(node, i, mark);
983 	}
984 }
985 
986 static void node_set_marks(struct xa_node *node, unsigned int offset,
987 			struct xa_node *child, unsigned int sibs,
988 			unsigned int marks)
989 {
990 	xa_mark_t mark = XA_MARK_0;
991 
992 	for (;;) {
993 		if (marks & (1 << (__force unsigned int)mark)) {
994 			node_set_mark(node, offset, mark);
995 			if (child)
996 				node_mark_slots(child, sibs, mark);
997 		}
998 		if (mark == XA_MARK_MAX)
999 			break;
1000 		mark_inc(mark);
1001 	}
1002 }
1003 
1004 /**
1005  * xas_split_alloc() - Allocate memory for splitting an entry.
1006  * @xas: XArray operation state.
1007  * @entry: New entry which will be stored in the array.
1008  * @order: Current entry order.
1009  * @gfp: Memory allocation flags.
1010  *
1011  * This function should be called before calling xas_split().
1012  * If necessary, it will allocate new nodes (and fill them with @entry)
1013  * to prepare for the upcoming split of an entry of @order size into
1014  * entries of the order stored in the @xas.
1015  *
1016  * Context: May sleep if @gfp flags permit.
1017  */
1018 void xas_split_alloc(struct xa_state *xas, void *entry, unsigned int order,
1019 		gfp_t gfp)
1020 {
1021 	unsigned int sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1022 	unsigned int mask = xas->xa_sibs;
1023 
1024 	/* XXX: no support for splitting really large entries yet */
1025 	if (WARN_ON(xas->xa_shift + 2 * XA_CHUNK_SHIFT < order))
1026 		goto nomem;
1027 	if (xas->xa_shift + XA_CHUNK_SHIFT > order)
1028 		return;
1029 
1030 	do {
1031 		unsigned int i;
1032 		void *sibling = NULL;
1033 		struct xa_node *node;
1034 
1035 		node = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
1036 		if (!node)
1037 			goto nomem;
1038 		node->array = xas->xa;
1039 		for (i = 0; i < XA_CHUNK_SIZE; i++) {
1040 			if ((i & mask) == 0) {
1041 				RCU_INIT_POINTER(node->slots[i], entry);
1042 				sibling = xa_mk_sibling(i);
1043 			} else {
1044 				RCU_INIT_POINTER(node->slots[i], sibling);
1045 			}
1046 		}
1047 		RCU_INIT_POINTER(node->parent, xas->xa_alloc);
1048 		xas->xa_alloc = node;
1049 	} while (sibs-- > 0);
1050 
1051 	return;
1052 nomem:
1053 	xas_destroy(xas);
1054 	xas_set_err(xas, -ENOMEM);
1055 }
1056 EXPORT_SYMBOL_GPL(xas_split_alloc);
1057 
1058 /**
1059  * xas_split() - Split a multi-index entry into smaller entries.
1060  * @xas: XArray operation state.
1061  * @entry: New entry to store in the array.
1062  * @order: Current entry order.
1063  *
1064  * The size of the new entries is set in @xas.  The value in @entry is
1065  * copied to all the replacement entries.
1066  *
1067  * Context: Any context.  The caller should hold the xa_lock.
1068  */
1069 void xas_split(struct xa_state *xas, void *entry, unsigned int order)
1070 {
1071 	unsigned int sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1072 	unsigned int offset, marks;
1073 	struct xa_node *node;
1074 	void *curr = xas_load(xas);
1075 	int values = 0;
1076 
1077 	node = xas->xa_node;
1078 	if (xas_top(node))
1079 		return;
1080 
1081 	marks = node_get_marks(node, xas->xa_offset);
1082 
1083 	offset = xas->xa_offset + sibs;
1084 	do {
1085 		if (xas->xa_shift < node->shift) {
1086 			struct xa_node *child = xas->xa_alloc;
1087 
1088 			xas->xa_alloc = rcu_dereference_raw(child->parent);
1089 			child->shift = node->shift - XA_CHUNK_SHIFT;
1090 			child->offset = offset;
1091 			child->count = XA_CHUNK_SIZE;
1092 			child->nr_values = xa_is_value(entry) ?
1093 					XA_CHUNK_SIZE : 0;
1094 			RCU_INIT_POINTER(child->parent, node);
1095 			node_set_marks(node, offset, child, xas->xa_sibs,
1096 					marks);
1097 			rcu_assign_pointer(node->slots[offset],
1098 					xa_mk_node(child));
1099 			if (xa_is_value(curr))
1100 				values--;
1101 			xas_update(xas, child);
1102 		} else {
1103 			unsigned int canon = offset - xas->xa_sibs;
1104 
1105 			node_set_marks(node, canon, NULL, 0, marks);
1106 			rcu_assign_pointer(node->slots[canon], entry);
1107 			while (offset > canon)
1108 				rcu_assign_pointer(node->slots[offset--],
1109 						xa_mk_sibling(canon));
1110 			values += (xa_is_value(entry) - xa_is_value(curr)) *
1111 					(xas->xa_sibs + 1);
1112 		}
1113 	} while (offset-- > xas->xa_offset);
1114 
1115 	node->nr_values += values;
1116 	xas_update(xas, node);
1117 }
1118 EXPORT_SYMBOL_GPL(xas_split);
1119 #endif
1120 
1121 /**
1122  * xas_pause() - Pause a walk to drop a lock.
1123  * @xas: XArray operation state.
1124  *
1125  * Some users need to pause a walk and drop the lock they're holding in
1126  * order to yield to a higher priority thread or carry out an operation
1127  * on an entry.  Those users should call this function before they drop
1128  * the lock.  It resets the @xas to be suitable for the next iteration
1129  * of the loop after the user has reacquired the lock.  If most entries
1130  * found during a walk require you to call xas_pause(), the xa_for_each()
1131  * iterator may be more appropriate.
1132  *
1133  * Note that xas_pause() only works for forward iteration.  If a user needs
1134  * to pause a reverse iteration, we will need a xas_pause_rev().
1135  */
1136 void xas_pause(struct xa_state *xas)
1137 {
1138 	struct xa_node *node = xas->xa_node;
1139 
1140 	if (xas_invalid(xas))
1141 		return;
1142 
1143 	xas->xa_node = XAS_RESTART;
1144 	if (node) {
1145 		unsigned long offset = xas->xa_offset;
1146 		while (++offset < XA_CHUNK_SIZE) {
1147 			if (!xa_is_sibling(xa_entry(xas->xa, node, offset)))
1148 				break;
1149 		}
1150 		xas->xa_index += (offset - xas->xa_offset) << node->shift;
1151 		if (xas->xa_index == 0)
1152 			xas->xa_node = XAS_BOUNDS;
1153 	} else {
1154 		xas->xa_index++;
1155 	}
1156 }
1157 EXPORT_SYMBOL_GPL(xas_pause);
1158 
1159 /*
1160  * __xas_prev() - Find the previous entry in the XArray.
1161  * @xas: XArray operation state.
1162  *
1163  * Helper function for xas_prev() which handles all the complex cases
1164  * out of line.
1165  */
1166 void *__xas_prev(struct xa_state *xas)
1167 {
1168 	void *entry;
1169 
1170 	if (!xas_frozen(xas->xa_node))
1171 		xas->xa_index--;
1172 	if (!xas->xa_node)
1173 		return set_bounds(xas);
1174 	if (xas_not_node(xas->xa_node))
1175 		return xas_load(xas);
1176 
1177 	if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
1178 		xas->xa_offset--;
1179 
1180 	while (xas->xa_offset == 255) {
1181 		xas->xa_offset = xas->xa_node->offset - 1;
1182 		xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1183 		if (!xas->xa_node)
1184 			return set_bounds(xas);
1185 	}
1186 
1187 	for (;;) {
1188 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1189 		if (!xa_is_node(entry))
1190 			return entry;
1191 
1192 		xas->xa_node = xa_to_node(entry);
1193 		xas_set_offset(xas);
1194 	}
1195 }
1196 EXPORT_SYMBOL_GPL(__xas_prev);
1197 
1198 /*
1199  * __xas_next() - Find the next entry in the XArray.
1200  * @xas: XArray operation state.
1201  *
1202  * Helper function for xas_next() which handles all the complex cases
1203  * out of line.
1204  */
1205 void *__xas_next(struct xa_state *xas)
1206 {
1207 	void *entry;
1208 
1209 	if (!xas_frozen(xas->xa_node))
1210 		xas->xa_index++;
1211 	if (!xas->xa_node)
1212 		return set_bounds(xas);
1213 	if (xas_not_node(xas->xa_node))
1214 		return xas_load(xas);
1215 
1216 	if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
1217 		xas->xa_offset++;
1218 
1219 	while (xas->xa_offset == XA_CHUNK_SIZE) {
1220 		xas->xa_offset = xas->xa_node->offset + 1;
1221 		xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1222 		if (!xas->xa_node)
1223 			return set_bounds(xas);
1224 	}
1225 
1226 	for (;;) {
1227 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1228 		if (!xa_is_node(entry))
1229 			return entry;
1230 
1231 		xas->xa_node = xa_to_node(entry);
1232 		xas_set_offset(xas);
1233 	}
1234 }
1235 EXPORT_SYMBOL_GPL(__xas_next);
1236 
1237 /**
1238  * xas_find() - Find the next present entry in the XArray.
1239  * @xas: XArray operation state.
1240  * @max: Highest index to return.
1241  *
1242  * If the @xas has not yet been walked to an entry, return the entry
1243  * which has an index >= xas.xa_index.  If it has been walked, the entry
1244  * currently being pointed at has been processed, and so we move to the
1245  * next entry.
1246  *
1247  * If no entry is found and the array is smaller than @max, the iterator
1248  * is set to the smallest index not yet in the array.  This allows @xas
1249  * to be immediately passed to xas_store().
1250  *
1251  * Return: The entry, if found, otherwise %NULL.
1252  */
1253 void *xas_find(struct xa_state *xas, unsigned long max)
1254 {
1255 	void *entry;
1256 
1257 	if (xas_error(xas) || xas->xa_node == XAS_BOUNDS)
1258 		return NULL;
1259 	if (xas->xa_index > max)
1260 		return set_bounds(xas);
1261 
1262 	if (!xas->xa_node) {
1263 		xas->xa_index = 1;
1264 		return set_bounds(xas);
1265 	} else if (xas->xa_node == XAS_RESTART) {
1266 		entry = xas_load(xas);
1267 		if (entry || xas_not_node(xas->xa_node))
1268 			return entry;
1269 	} else if (!xas->xa_node->shift &&
1270 		    xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)) {
1271 		xas->xa_offset = ((xas->xa_index - 1) & XA_CHUNK_MASK) + 1;
1272 	}
1273 
1274 	xas_next_offset(xas);
1275 
1276 	while (xas->xa_node && (xas->xa_index <= max)) {
1277 		if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) {
1278 			xas->xa_offset = xas->xa_node->offset + 1;
1279 			xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1280 			continue;
1281 		}
1282 
1283 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1284 		if (xa_is_node(entry)) {
1285 			xas->xa_node = xa_to_node(entry);
1286 			xas->xa_offset = 0;
1287 			continue;
1288 		}
1289 		if (entry && !xa_is_sibling(entry))
1290 			return entry;
1291 
1292 		xas_next_offset(xas);
1293 	}
1294 
1295 	if (!xas->xa_node)
1296 		xas->xa_node = XAS_BOUNDS;
1297 	return NULL;
1298 }
1299 EXPORT_SYMBOL_GPL(xas_find);
1300 
1301 /**
1302  * xas_find_marked() - Find the next marked entry in the XArray.
1303  * @xas: XArray operation state.
1304  * @max: Highest index to return.
1305  * @mark: Mark number to search for.
1306  *
1307  * If the @xas has not yet been walked to an entry, return the marked entry
1308  * which has an index >= xas.xa_index.  If it has been walked, the entry
1309  * currently being pointed at has been processed, and so we return the
1310  * first marked entry with an index > xas.xa_index.
1311  *
1312  * If no marked entry is found and the array is smaller than @max, @xas is
1313  * set to the bounds state and xas->xa_index is set to the smallest index
1314  * not yet in the array.  This allows @xas to be immediately passed to
1315  * xas_store().
1316  *
1317  * If no entry is found before @max is reached, @xas is set to the restart
1318  * state.
1319  *
1320  * Return: The entry, if found, otherwise %NULL.
1321  */
1322 void *xas_find_marked(struct xa_state *xas, unsigned long max, xa_mark_t mark)
1323 {
1324 	bool advance = true;
1325 	unsigned int offset;
1326 	void *entry;
1327 
1328 	if (xas_error(xas))
1329 		return NULL;
1330 	if (xas->xa_index > max)
1331 		goto max;
1332 
1333 	if (!xas->xa_node) {
1334 		xas->xa_index = 1;
1335 		goto out;
1336 	} else if (xas_top(xas->xa_node)) {
1337 		advance = false;
1338 		entry = xa_head(xas->xa);
1339 		xas->xa_node = NULL;
1340 		if (xas->xa_index > max_index(entry))
1341 			goto out;
1342 		if (!xa_is_node(entry)) {
1343 			if (xa_marked(xas->xa, mark))
1344 				return entry;
1345 			xas->xa_index = 1;
1346 			goto out;
1347 		}
1348 		xas->xa_node = xa_to_node(entry);
1349 		xas->xa_offset = xas->xa_index >> xas->xa_node->shift;
1350 	}
1351 
1352 	while (xas->xa_index <= max) {
1353 		if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) {
1354 			xas->xa_offset = xas->xa_node->offset + 1;
1355 			xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1356 			if (!xas->xa_node)
1357 				break;
1358 			advance = false;
1359 			continue;
1360 		}
1361 
1362 		if (!advance) {
1363 			entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1364 			if (xa_is_sibling(entry)) {
1365 				xas->xa_offset = xa_to_sibling(entry);
1366 				xas_move_index(xas, xas->xa_offset);
1367 			}
1368 		}
1369 
1370 		offset = xas_find_chunk(xas, advance, mark);
1371 		if (offset > xas->xa_offset) {
1372 			advance = false;
1373 			xas_move_index(xas, offset);
1374 			/* Mind the wrap */
1375 			if ((xas->xa_index - 1) >= max)
1376 				goto max;
1377 			xas->xa_offset = offset;
1378 			if (offset == XA_CHUNK_SIZE)
1379 				continue;
1380 		}
1381 
1382 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1383 		if (!entry && !(xa_track_free(xas->xa) && mark == XA_FREE_MARK))
1384 			continue;
1385 		if (!xa_is_node(entry))
1386 			return entry;
1387 		xas->xa_node = xa_to_node(entry);
1388 		xas_set_offset(xas);
1389 	}
1390 
1391 out:
1392 	if (xas->xa_index > max)
1393 		goto max;
1394 	return set_bounds(xas);
1395 max:
1396 	xas->xa_node = XAS_RESTART;
1397 	return NULL;
1398 }
1399 EXPORT_SYMBOL_GPL(xas_find_marked);
1400 
1401 /**
1402  * xas_find_conflict() - Find the next present entry in a range.
1403  * @xas: XArray operation state.
1404  *
1405  * The @xas describes both a range and a position within that range.
1406  *
1407  * Context: Any context.  Expects xa_lock to be held.
1408  * Return: The next entry in the range covered by @xas or %NULL.
1409  */
1410 void *xas_find_conflict(struct xa_state *xas)
1411 {
1412 	void *curr;
1413 
1414 	if (xas_error(xas))
1415 		return NULL;
1416 
1417 	if (!xas->xa_node)
1418 		return NULL;
1419 
1420 	if (xas_top(xas->xa_node)) {
1421 		curr = xas_start(xas);
1422 		if (!curr)
1423 			return NULL;
1424 		while (xa_is_node(curr)) {
1425 			struct xa_node *node = xa_to_node(curr);
1426 			curr = xas_descend(xas, node);
1427 		}
1428 		if (curr)
1429 			return curr;
1430 	}
1431 
1432 	if (xas->xa_node->shift > xas->xa_shift)
1433 		return NULL;
1434 
1435 	for (;;) {
1436 		if (xas->xa_node->shift == xas->xa_shift) {
1437 			if ((xas->xa_offset & xas->xa_sibs) == xas->xa_sibs)
1438 				break;
1439 		} else if (xas->xa_offset == XA_CHUNK_MASK) {
1440 			xas->xa_offset = xas->xa_node->offset;
1441 			xas->xa_node = xa_parent_locked(xas->xa, xas->xa_node);
1442 			if (!xas->xa_node)
1443 				break;
1444 			continue;
1445 		}
1446 		curr = xa_entry_locked(xas->xa, xas->xa_node, ++xas->xa_offset);
1447 		if (xa_is_sibling(curr))
1448 			continue;
1449 		while (xa_is_node(curr)) {
1450 			xas->xa_node = xa_to_node(curr);
1451 			xas->xa_offset = 0;
1452 			curr = xa_entry_locked(xas->xa, xas->xa_node, 0);
1453 		}
1454 		if (curr)
1455 			return curr;
1456 	}
1457 	xas->xa_offset -= xas->xa_sibs;
1458 	return NULL;
1459 }
1460 EXPORT_SYMBOL_GPL(xas_find_conflict);
1461 
1462 /**
1463  * xa_load() - Load an entry from an XArray.
1464  * @xa: XArray.
1465  * @index: index into array.
1466  *
1467  * Context: Any context.  Takes and releases the RCU lock.
1468  * Return: The entry at @index in @xa.
1469  */
1470 void *xa_load(struct xarray *xa, unsigned long index)
1471 {
1472 	XA_STATE(xas, xa, index);
1473 	void *entry;
1474 
1475 	rcu_read_lock();
1476 	do {
1477 		entry = xas_load(&xas);
1478 		if (xa_is_zero(entry))
1479 			entry = NULL;
1480 	} while (xas_retry(&xas, entry));
1481 	rcu_read_unlock();
1482 
1483 	return entry;
1484 }
1485 EXPORT_SYMBOL(xa_load);
1486 
1487 static void *xas_result(struct xa_state *xas, void *curr)
1488 {
1489 	if (xa_is_zero(curr))
1490 		return NULL;
1491 	if (xas_error(xas))
1492 		curr = xas->xa_node;
1493 	return curr;
1494 }
1495 
1496 /**
1497  * __xa_erase() - Erase this entry from the XArray while locked.
1498  * @xa: XArray.
1499  * @index: Index into array.
1500  *
1501  * After this function returns, loading from @index will return %NULL.
1502  * If the index is part of a multi-index entry, all indices will be erased
1503  * and none of the entries will be part of a multi-index entry.
1504  *
1505  * Context: Any context.  Expects xa_lock to be held on entry.
1506  * Return: The entry which used to be at this index.
1507  */
1508 void *__xa_erase(struct xarray *xa, unsigned long index)
1509 {
1510 	XA_STATE(xas, xa, index);
1511 	return xas_result(&xas, xas_store(&xas, NULL));
1512 }
1513 EXPORT_SYMBOL(__xa_erase);
1514 
1515 /**
1516  * xa_erase() - Erase this entry from the XArray.
1517  * @xa: XArray.
1518  * @index: Index of entry.
1519  *
1520  * After this function returns, loading from @index will return %NULL.
1521  * If the index is part of a multi-index entry, all indices will be erased
1522  * and none of the entries will be part of a multi-index entry.
1523  *
1524  * Context: Any context.  Takes and releases the xa_lock.
1525  * Return: The entry which used to be at this index.
1526  */
1527 void *xa_erase(struct xarray *xa, unsigned long index)
1528 {
1529 	void *entry;
1530 
1531 	xa_lock(xa);
1532 	entry = __xa_erase(xa, index);
1533 	xa_unlock(xa);
1534 
1535 	return entry;
1536 }
1537 EXPORT_SYMBOL(xa_erase);
1538 
1539 /**
1540  * __xa_store() - Store this entry in the XArray.
1541  * @xa: XArray.
1542  * @index: Index into array.
1543  * @entry: New entry.
1544  * @gfp: Memory allocation flags.
1545  *
1546  * You must already be holding the xa_lock when calling this function.
1547  * It will drop the lock if needed to allocate memory, and then reacquire
1548  * it afterwards.
1549  *
1550  * Context: Any context.  Expects xa_lock to be held on entry.  May
1551  * release and reacquire xa_lock if @gfp flags permit.
1552  * Return: The old entry at this index or xa_err() if an error happened.
1553  */
1554 void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1555 {
1556 	XA_STATE(xas, xa, index);
1557 	void *curr;
1558 
1559 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1560 		return XA_ERROR(-EINVAL);
1561 	if (xa_track_free(xa) && !entry)
1562 		entry = XA_ZERO_ENTRY;
1563 
1564 	do {
1565 		curr = xas_store(&xas, entry);
1566 		if (xa_track_free(xa))
1567 			xas_clear_mark(&xas, XA_FREE_MARK);
1568 	} while (__xas_nomem(&xas, gfp));
1569 
1570 	return xas_result(&xas, curr);
1571 }
1572 EXPORT_SYMBOL(__xa_store);
1573 
1574 /**
1575  * xa_store() - Store this entry in the XArray.
1576  * @xa: XArray.
1577  * @index: Index into array.
1578  * @entry: New entry.
1579  * @gfp: Memory allocation flags.
1580  *
1581  * After this function returns, loads from this index will return @entry.
1582  * Storing into an existing multi-index entry updates the entry of every index.
1583  * The marks associated with @index are unaffected unless @entry is %NULL.
1584  *
1585  * Context: Any context.  Takes and releases the xa_lock.
1586  * May sleep if the @gfp flags permit.
1587  * Return: The old entry at this index on success, xa_err(-EINVAL) if @entry
1588  * cannot be stored in an XArray, or xa_err(-ENOMEM) if memory allocation
1589  * failed.
1590  */
1591 void *xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1592 {
1593 	void *curr;
1594 
1595 	xa_lock(xa);
1596 	curr = __xa_store(xa, index, entry, gfp);
1597 	xa_unlock(xa);
1598 
1599 	return curr;
1600 }
1601 EXPORT_SYMBOL(xa_store);
1602 
1603 /**
1604  * __xa_cmpxchg() - Store this entry in the XArray.
1605  * @xa: XArray.
1606  * @index: Index into array.
1607  * @old: Old value to test against.
1608  * @entry: New entry.
1609  * @gfp: Memory allocation flags.
1610  *
1611  * You must already be holding the xa_lock when calling this function.
1612  * It will drop the lock if needed to allocate memory, and then reacquire
1613  * it afterwards.
1614  *
1615  * Context: Any context.  Expects xa_lock to be held on entry.  May
1616  * release and reacquire xa_lock if @gfp flags permit.
1617  * Return: The old entry at this index or xa_err() if an error happened.
1618  */
1619 void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
1620 			void *old, void *entry, gfp_t gfp)
1621 {
1622 	XA_STATE(xas, xa, index);
1623 	void *curr;
1624 
1625 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1626 		return XA_ERROR(-EINVAL);
1627 
1628 	do {
1629 		curr = xas_load(&xas);
1630 		if (curr == old) {
1631 			xas_store(&xas, entry);
1632 			if (xa_track_free(xa) && entry && !curr)
1633 				xas_clear_mark(&xas, XA_FREE_MARK);
1634 		}
1635 	} while (__xas_nomem(&xas, gfp));
1636 
1637 	return xas_result(&xas, curr);
1638 }
1639 EXPORT_SYMBOL(__xa_cmpxchg);
1640 
1641 /**
1642  * __xa_insert() - Store this entry in the XArray if no entry is present.
1643  * @xa: XArray.
1644  * @index: Index into array.
1645  * @entry: New entry.
1646  * @gfp: Memory allocation flags.
1647  *
1648  * Inserting a NULL entry will store a reserved entry (like xa_reserve())
1649  * if no entry is present.  Inserting will fail if a reserved entry is
1650  * present, even though loading from this index will return NULL.
1651  *
1652  * Context: Any context.  Expects xa_lock to be held on entry.  May
1653  * release and reacquire xa_lock if @gfp flags permit.
1654  * Return: 0 if the store succeeded.  -EBUSY if another entry was present.
1655  * -ENOMEM if memory could not be allocated.
1656  */
1657 int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1658 {
1659 	XA_STATE(xas, xa, index);
1660 	void *curr;
1661 
1662 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1663 		return -EINVAL;
1664 	if (!entry)
1665 		entry = XA_ZERO_ENTRY;
1666 
1667 	do {
1668 		curr = xas_load(&xas);
1669 		if (!curr) {
1670 			xas_store(&xas, entry);
1671 			if (xa_track_free(xa))
1672 				xas_clear_mark(&xas, XA_FREE_MARK);
1673 		} else {
1674 			xas_set_err(&xas, -EBUSY);
1675 		}
1676 	} while (__xas_nomem(&xas, gfp));
1677 
1678 	return xas_error(&xas);
1679 }
1680 EXPORT_SYMBOL(__xa_insert);
1681 
1682 #ifdef CONFIG_XARRAY_MULTI
1683 static void xas_set_range(struct xa_state *xas, unsigned long first,
1684 		unsigned long last)
1685 {
1686 	unsigned int shift = 0;
1687 	unsigned long sibs = last - first;
1688 	unsigned int offset = XA_CHUNK_MASK;
1689 
1690 	xas_set(xas, first);
1691 
1692 	while ((first & XA_CHUNK_MASK) == 0) {
1693 		if (sibs < XA_CHUNK_MASK)
1694 			break;
1695 		if ((sibs == XA_CHUNK_MASK) && (offset < XA_CHUNK_MASK))
1696 			break;
1697 		shift += XA_CHUNK_SHIFT;
1698 		if (offset == XA_CHUNK_MASK)
1699 			offset = sibs & XA_CHUNK_MASK;
1700 		sibs >>= XA_CHUNK_SHIFT;
1701 		first >>= XA_CHUNK_SHIFT;
1702 	}
1703 
1704 	offset = first & XA_CHUNK_MASK;
1705 	if (offset + sibs > XA_CHUNK_MASK)
1706 		sibs = XA_CHUNK_MASK - offset;
1707 	if ((((first + sibs + 1) << shift) - 1) > last)
1708 		sibs -= 1;
1709 
1710 	xas->xa_shift = shift;
1711 	xas->xa_sibs = sibs;
1712 }
1713 
1714 /**
1715  * xa_store_range() - Store this entry at a range of indices in the XArray.
1716  * @xa: XArray.
1717  * @first: First index to affect.
1718  * @last: Last index to affect.
1719  * @entry: New entry.
1720  * @gfp: Memory allocation flags.
1721  *
1722  * After this function returns, loads from any index between @first and @last,
1723  * inclusive will return @entry.
1724  * Storing into an existing multi-index entry updates the entry of every index.
1725  * The marks associated with @index are unaffected unless @entry is %NULL.
1726  *
1727  * Context: Process context.  Takes and releases the xa_lock.  May sleep
1728  * if the @gfp flags permit.
1729  * Return: %NULL on success, xa_err(-EINVAL) if @entry cannot be stored in
1730  * an XArray, or xa_err(-ENOMEM) if memory allocation failed.
1731  */
1732 void *xa_store_range(struct xarray *xa, unsigned long first,
1733 		unsigned long last, void *entry, gfp_t gfp)
1734 {
1735 	XA_STATE(xas, xa, 0);
1736 
1737 	if (WARN_ON_ONCE(xa_is_internal(entry)))
1738 		return XA_ERROR(-EINVAL);
1739 	if (last < first)
1740 		return XA_ERROR(-EINVAL);
1741 
1742 	do {
1743 		xas_lock(&xas);
1744 		if (entry) {
1745 			unsigned int order = BITS_PER_LONG;
1746 			if (last + 1)
1747 				order = __ffs(last + 1);
1748 			xas_set_order(&xas, last, order);
1749 			xas_create(&xas, true);
1750 			if (xas_error(&xas))
1751 				goto unlock;
1752 		}
1753 		do {
1754 			xas_set_range(&xas, first, last);
1755 			xas_store(&xas, entry);
1756 			if (xas_error(&xas))
1757 				goto unlock;
1758 			first += xas_size(&xas);
1759 		} while (first <= last);
1760 unlock:
1761 		xas_unlock(&xas);
1762 	} while (xas_nomem(&xas, gfp));
1763 
1764 	return xas_result(&xas, NULL);
1765 }
1766 EXPORT_SYMBOL(xa_store_range);
1767 
1768 /**
1769  * xas_get_order() - Get the order of an entry.
1770  * @xas: XArray operation state.
1771  *
1772  * Called after xas_load, the xas should not be in an error state.
1773  *
1774  * Return: A number between 0 and 63 indicating the order of the entry.
1775  */
1776 int xas_get_order(struct xa_state *xas)
1777 {
1778 	int order = 0;
1779 
1780 	if (!xas->xa_node)
1781 		return 0;
1782 
1783 	for (;;) {
1784 		unsigned int slot = xas->xa_offset + (1 << order);
1785 
1786 		if (slot >= XA_CHUNK_SIZE)
1787 			break;
1788 		if (!xa_is_sibling(xa_entry(xas->xa, xas->xa_node, slot)))
1789 			break;
1790 		order++;
1791 	}
1792 
1793 	order += xas->xa_node->shift;
1794 	return order;
1795 }
1796 EXPORT_SYMBOL_GPL(xas_get_order);
1797 
1798 /**
1799  * xa_get_order() - Get the order of an entry.
1800  * @xa: XArray.
1801  * @index: Index of the entry.
1802  *
1803  * Return: A number between 0 and 63 indicating the order of the entry.
1804  */
1805 int xa_get_order(struct xarray *xa, unsigned long index)
1806 {
1807 	XA_STATE(xas, xa, index);
1808 	int order = 0;
1809 	void *entry;
1810 
1811 	rcu_read_lock();
1812 	entry = xas_load(&xas);
1813 	if (entry)
1814 		order = xas_get_order(&xas);
1815 	rcu_read_unlock();
1816 
1817 	return order;
1818 }
1819 EXPORT_SYMBOL(xa_get_order);
1820 #endif /* CONFIG_XARRAY_MULTI */
1821 
1822 /**
1823  * __xa_alloc() - Find somewhere to store this entry in the XArray.
1824  * @xa: XArray.
1825  * @id: Pointer to ID.
1826  * @limit: Range for allocated ID.
1827  * @entry: New entry.
1828  * @gfp: Memory allocation flags.
1829  *
1830  * Finds an empty entry in @xa between @limit.min and @limit.max,
1831  * stores the index into the @id pointer, then stores the entry at
1832  * that index.  A concurrent lookup will not see an uninitialised @id.
1833  *
1834  * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
1835  * in xa_init_flags().
1836  *
1837  * Context: Any context.  Expects xa_lock to be held on entry.  May
1838  * release and reacquire xa_lock if @gfp flags permit.
1839  * Return: 0 on success, -ENOMEM if memory could not be allocated or
1840  * -EBUSY if there are no free entries in @limit.
1841  */
1842 int __xa_alloc(struct xarray *xa, u32 *id, void *entry,
1843 		struct xa_limit limit, gfp_t gfp)
1844 {
1845 	XA_STATE(xas, xa, 0);
1846 
1847 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1848 		return -EINVAL;
1849 	if (WARN_ON_ONCE(!xa_track_free(xa)))
1850 		return -EINVAL;
1851 
1852 	if (!entry)
1853 		entry = XA_ZERO_ENTRY;
1854 
1855 	do {
1856 		xas.xa_index = limit.min;
1857 		xas_find_marked(&xas, limit.max, XA_FREE_MARK);
1858 		if (xas.xa_node == XAS_RESTART)
1859 			xas_set_err(&xas, -EBUSY);
1860 		else
1861 			*id = xas.xa_index;
1862 		xas_store(&xas, entry);
1863 		xas_clear_mark(&xas, XA_FREE_MARK);
1864 	} while (__xas_nomem(&xas, gfp));
1865 
1866 	return xas_error(&xas);
1867 }
1868 EXPORT_SYMBOL(__xa_alloc);
1869 
1870 /**
1871  * __xa_alloc_cyclic() - Find somewhere to store this entry in the XArray.
1872  * @xa: XArray.
1873  * @id: Pointer to ID.
1874  * @entry: New entry.
1875  * @limit: Range of allocated ID.
1876  * @next: Pointer to next ID to allocate.
1877  * @gfp: Memory allocation flags.
1878  *
1879  * Finds an empty entry in @xa between @limit.min and @limit.max,
1880  * stores the index into the @id pointer, then stores the entry at
1881  * that index.  A concurrent lookup will not see an uninitialised @id.
1882  * The search for an empty entry will start at @next and will wrap
1883  * around if necessary.
1884  *
1885  * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
1886  * in xa_init_flags().
1887  *
1888  * Context: Any context.  Expects xa_lock to be held on entry.  May
1889  * release and reacquire xa_lock if @gfp flags permit.
1890  * Return: 0 if the allocation succeeded without wrapping.  1 if the
1891  * allocation succeeded after wrapping, -ENOMEM if memory could not be
1892  * allocated or -EBUSY if there are no free entries in @limit.
1893  */
1894 int __xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
1895 		struct xa_limit limit, u32 *next, gfp_t gfp)
1896 {
1897 	u32 min = limit.min;
1898 	int ret;
1899 
1900 	limit.min = max(min, *next);
1901 	ret = __xa_alloc(xa, id, entry, limit, gfp);
1902 	if ((xa->xa_flags & XA_FLAGS_ALLOC_WRAPPED) && ret == 0) {
1903 		xa->xa_flags &= ~XA_FLAGS_ALLOC_WRAPPED;
1904 		ret = 1;
1905 	}
1906 
1907 	if (ret < 0 && limit.min > min) {
1908 		limit.min = min;
1909 		ret = __xa_alloc(xa, id, entry, limit, gfp);
1910 		if (ret == 0)
1911 			ret = 1;
1912 	}
1913 
1914 	if (ret >= 0) {
1915 		*next = *id + 1;
1916 		if (*next == 0)
1917 			xa->xa_flags |= XA_FLAGS_ALLOC_WRAPPED;
1918 	}
1919 	return ret;
1920 }
1921 EXPORT_SYMBOL(__xa_alloc_cyclic);
1922 
1923 /**
1924  * __xa_set_mark() - Set this mark on this entry while locked.
1925  * @xa: XArray.
1926  * @index: Index of entry.
1927  * @mark: Mark number.
1928  *
1929  * Attempting to set a mark on a %NULL entry does not succeed.
1930  *
1931  * Context: Any context.  Expects xa_lock to be held on entry.
1932  */
1933 void __xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1934 {
1935 	XA_STATE(xas, xa, index);
1936 	void *entry = xas_load(&xas);
1937 
1938 	if (entry)
1939 		xas_set_mark(&xas, mark);
1940 }
1941 EXPORT_SYMBOL(__xa_set_mark);
1942 
1943 /**
1944  * __xa_clear_mark() - Clear this mark on this entry while locked.
1945  * @xa: XArray.
1946  * @index: Index of entry.
1947  * @mark: Mark number.
1948  *
1949  * Context: Any context.  Expects xa_lock to be held on entry.
1950  */
1951 void __xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1952 {
1953 	XA_STATE(xas, xa, index);
1954 	void *entry = xas_load(&xas);
1955 
1956 	if (entry)
1957 		xas_clear_mark(&xas, mark);
1958 }
1959 EXPORT_SYMBOL(__xa_clear_mark);
1960 
1961 /**
1962  * xa_get_mark() - Inquire whether this mark is set on this entry.
1963  * @xa: XArray.
1964  * @index: Index of entry.
1965  * @mark: Mark number.
1966  *
1967  * This function uses the RCU read lock, so the result may be out of date
1968  * by the time it returns.  If you need the result to be stable, use a lock.
1969  *
1970  * Context: Any context.  Takes and releases the RCU lock.
1971  * Return: True if the entry at @index has this mark set, false if it doesn't.
1972  */
1973 bool xa_get_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1974 {
1975 	XA_STATE(xas, xa, index);
1976 	void *entry;
1977 
1978 	rcu_read_lock();
1979 	entry = xas_start(&xas);
1980 	while (xas_get_mark(&xas, mark)) {
1981 		if (!xa_is_node(entry))
1982 			goto found;
1983 		entry = xas_descend(&xas, xa_to_node(entry));
1984 	}
1985 	rcu_read_unlock();
1986 	return false;
1987  found:
1988 	rcu_read_unlock();
1989 	return true;
1990 }
1991 EXPORT_SYMBOL(xa_get_mark);
1992 
1993 /**
1994  * xa_set_mark() - Set this mark on this entry.
1995  * @xa: XArray.
1996  * @index: Index of entry.
1997  * @mark: Mark number.
1998  *
1999  * Attempting to set a mark on a %NULL entry does not succeed.
2000  *
2001  * Context: Process context.  Takes and releases the xa_lock.
2002  */
2003 void xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
2004 {
2005 	xa_lock(xa);
2006 	__xa_set_mark(xa, index, mark);
2007 	xa_unlock(xa);
2008 }
2009 EXPORT_SYMBOL(xa_set_mark);
2010 
2011 /**
2012  * xa_clear_mark() - Clear this mark on this entry.
2013  * @xa: XArray.
2014  * @index: Index of entry.
2015  * @mark: Mark number.
2016  *
2017  * Clearing a mark always succeeds.
2018  *
2019  * Context: Process context.  Takes and releases the xa_lock.
2020  */
2021 void xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
2022 {
2023 	xa_lock(xa);
2024 	__xa_clear_mark(xa, index, mark);
2025 	xa_unlock(xa);
2026 }
2027 EXPORT_SYMBOL(xa_clear_mark);
2028 
2029 /**
2030  * xa_find() - Search the XArray for an entry.
2031  * @xa: XArray.
2032  * @indexp: Pointer to an index.
2033  * @max: Maximum index to search to.
2034  * @filter: Selection criterion.
2035  *
2036  * Finds the entry in @xa which matches the @filter, and has the lowest
2037  * index that is at least @indexp and no more than @max.
2038  * If an entry is found, @indexp is updated to be the index of the entry.
2039  * This function is protected by the RCU read lock, so it may not find
2040  * entries which are being simultaneously added.  It will not return an
2041  * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find().
2042  *
2043  * Context: Any context.  Takes and releases the RCU lock.
2044  * Return: The entry, if found, otherwise %NULL.
2045  */
2046 void *xa_find(struct xarray *xa, unsigned long *indexp,
2047 			unsigned long max, xa_mark_t filter)
2048 {
2049 	XA_STATE(xas, xa, *indexp);
2050 	void *entry;
2051 
2052 	rcu_read_lock();
2053 	do {
2054 		if ((__force unsigned int)filter < XA_MAX_MARKS)
2055 			entry = xas_find_marked(&xas, max, filter);
2056 		else
2057 			entry = xas_find(&xas, max);
2058 	} while (xas_retry(&xas, entry));
2059 	rcu_read_unlock();
2060 
2061 	if (entry)
2062 		*indexp = xas.xa_index;
2063 	return entry;
2064 }
2065 EXPORT_SYMBOL(xa_find);
2066 
2067 static bool xas_sibling(struct xa_state *xas)
2068 {
2069 	struct xa_node *node = xas->xa_node;
2070 	unsigned long mask;
2071 
2072 	if (!IS_ENABLED(CONFIG_XARRAY_MULTI) || !node)
2073 		return false;
2074 	mask = (XA_CHUNK_SIZE << node->shift) - 1;
2075 	return (xas->xa_index & mask) >
2076 		((unsigned long)xas->xa_offset << node->shift);
2077 }
2078 
2079 /**
2080  * xa_find_after() - Search the XArray for a present entry.
2081  * @xa: XArray.
2082  * @indexp: Pointer to an index.
2083  * @max: Maximum index to search to.
2084  * @filter: Selection criterion.
2085  *
2086  * Finds the entry in @xa which matches the @filter and has the lowest
2087  * index that is above @indexp and no more than @max.
2088  * If an entry is found, @indexp is updated to be the index of the entry.
2089  * This function is protected by the RCU read lock, so it may miss entries
2090  * which are being simultaneously added.  It will not return an
2091  * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find().
2092  *
2093  * Context: Any context.  Takes and releases the RCU lock.
2094  * Return: The pointer, if found, otherwise %NULL.
2095  */
2096 void *xa_find_after(struct xarray *xa, unsigned long *indexp,
2097 			unsigned long max, xa_mark_t filter)
2098 {
2099 	XA_STATE(xas, xa, *indexp + 1);
2100 	void *entry;
2101 
2102 	if (xas.xa_index == 0)
2103 		return NULL;
2104 
2105 	rcu_read_lock();
2106 	for (;;) {
2107 		if ((__force unsigned int)filter < XA_MAX_MARKS)
2108 			entry = xas_find_marked(&xas, max, filter);
2109 		else
2110 			entry = xas_find(&xas, max);
2111 
2112 		if (xas_invalid(&xas))
2113 			break;
2114 		if (xas_sibling(&xas))
2115 			continue;
2116 		if (!xas_retry(&xas, entry))
2117 			break;
2118 	}
2119 	rcu_read_unlock();
2120 
2121 	if (entry)
2122 		*indexp = xas.xa_index;
2123 	return entry;
2124 }
2125 EXPORT_SYMBOL(xa_find_after);
2126 
2127 static unsigned int xas_extract_present(struct xa_state *xas, void **dst,
2128 			unsigned long max, unsigned int n)
2129 {
2130 	void *entry;
2131 	unsigned int i = 0;
2132 
2133 	rcu_read_lock();
2134 	xas_for_each(xas, entry, max) {
2135 		if (xas_retry(xas, entry))
2136 			continue;
2137 		dst[i++] = entry;
2138 		if (i == n)
2139 			break;
2140 	}
2141 	rcu_read_unlock();
2142 
2143 	return i;
2144 }
2145 
2146 static unsigned int xas_extract_marked(struct xa_state *xas, void **dst,
2147 			unsigned long max, unsigned int n, xa_mark_t mark)
2148 {
2149 	void *entry;
2150 	unsigned int i = 0;
2151 
2152 	rcu_read_lock();
2153 	xas_for_each_marked(xas, entry, max, mark) {
2154 		if (xas_retry(xas, entry))
2155 			continue;
2156 		dst[i++] = entry;
2157 		if (i == n)
2158 			break;
2159 	}
2160 	rcu_read_unlock();
2161 
2162 	return i;
2163 }
2164 
2165 /**
2166  * xa_extract() - Copy selected entries from the XArray into a normal array.
2167  * @xa: The source XArray to copy from.
2168  * @dst: The buffer to copy entries into.
2169  * @start: The first index in the XArray eligible to be selected.
2170  * @max: The last index in the XArray eligible to be selected.
2171  * @n: The maximum number of entries to copy.
2172  * @filter: Selection criterion.
2173  *
2174  * Copies up to @n entries that match @filter from the XArray.  The
2175  * copied entries will have indices between @start and @max, inclusive.
2176  *
2177  * The @filter may be an XArray mark value, in which case entries which are
2178  * marked with that mark will be copied.  It may also be %XA_PRESENT, in
2179  * which case all entries which are not %NULL will be copied.
2180  *
2181  * The entries returned may not represent a snapshot of the XArray at a
2182  * moment in time.  For example, if another thread stores to index 5, then
2183  * index 10, calling xa_extract() may return the old contents of index 5
2184  * and the new contents of index 10.  Indices not modified while this
2185  * function is running will not be skipped.
2186  *
2187  * If you need stronger guarantees, holding the xa_lock across calls to this
2188  * function will prevent concurrent modification.
2189  *
2190  * Context: Any context.  Takes and releases the RCU lock.
2191  * Return: The number of entries copied.
2192  */
2193 unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,
2194 			unsigned long max, unsigned int n, xa_mark_t filter)
2195 {
2196 	XA_STATE(xas, xa, start);
2197 
2198 	if (!n)
2199 		return 0;
2200 
2201 	if ((__force unsigned int)filter < XA_MAX_MARKS)
2202 		return xas_extract_marked(&xas, dst, max, n, filter);
2203 	return xas_extract_present(&xas, dst, max, n);
2204 }
2205 EXPORT_SYMBOL(xa_extract);
2206 
2207 /**
2208  * xa_delete_node() - Private interface for workingset code.
2209  * @node: Node to be removed from the tree.
2210  * @update: Function to call to update ancestor nodes.
2211  *
2212  * Context: xa_lock must be held on entry and will not be released.
2213  */
2214 void xa_delete_node(struct xa_node *node, xa_update_node_t update)
2215 {
2216 	struct xa_state xas = {
2217 		.xa = node->array,
2218 		.xa_index = (unsigned long)node->offset <<
2219 				(node->shift + XA_CHUNK_SHIFT),
2220 		.xa_shift = node->shift + XA_CHUNK_SHIFT,
2221 		.xa_offset = node->offset,
2222 		.xa_node = xa_parent_locked(node->array, node),
2223 		.xa_update = update,
2224 	};
2225 
2226 	xas_store(&xas, NULL);
2227 }
2228 EXPORT_SYMBOL_GPL(xa_delete_node);	/* For the benefit of the test suite */
2229 
2230 /**
2231  * xa_destroy() - Free all internal data structures.
2232  * @xa: XArray.
2233  *
2234  * After calling this function, the XArray is empty and has freed all memory
2235  * allocated for its internal data structures.  You are responsible for
2236  * freeing the objects referenced by the XArray.
2237  *
2238  * Context: Any context.  Takes and releases the xa_lock, interrupt-safe.
2239  */
2240 void xa_destroy(struct xarray *xa)
2241 {
2242 	XA_STATE(xas, xa, 0);
2243 	unsigned long flags;
2244 	void *entry;
2245 
2246 	xas.xa_node = NULL;
2247 	xas_lock_irqsave(&xas, flags);
2248 	entry = xa_head_locked(xa);
2249 	RCU_INIT_POINTER(xa->xa_head, NULL);
2250 	xas_init_marks(&xas);
2251 	if (xa_zero_busy(xa))
2252 		xa_mark_clear(xa, XA_FREE_MARK);
2253 	/* lockdep checks we're still holding the lock in xas_free_nodes() */
2254 	if (xa_is_node(entry))
2255 		xas_free_nodes(&xas, xa_to_node(entry));
2256 	xas_unlock_irqrestore(&xas, flags);
2257 }
2258 EXPORT_SYMBOL(xa_destroy);
2259 
2260 #ifdef XA_DEBUG
2261 void xa_dump_node(const struct xa_node *node)
2262 {
2263 	unsigned i, j;
2264 
2265 	if (!node)
2266 		return;
2267 	if ((unsigned long)node & 3) {
2268 		pr_cont("node %px\n", node);
2269 		return;
2270 	}
2271 
2272 	pr_cont("node %px %s %d parent %px shift %d count %d values %d "
2273 		"array %px list %px %px marks",
2274 		node, node->parent ? "offset" : "max", node->offset,
2275 		node->parent, node->shift, node->count, node->nr_values,
2276 		node->array, node->private_list.prev, node->private_list.next);
2277 	for (i = 0; i < XA_MAX_MARKS; i++)
2278 		for (j = 0; j < XA_MARK_LONGS; j++)
2279 			pr_cont(" %lx", node->marks[i][j]);
2280 	pr_cont("\n");
2281 }
2282 
2283 void xa_dump_index(unsigned long index, unsigned int shift)
2284 {
2285 	if (!shift)
2286 		pr_info("%lu: ", index);
2287 	else if (shift >= BITS_PER_LONG)
2288 		pr_info("0-%lu: ", ~0UL);
2289 	else
2290 		pr_info("%lu-%lu: ", index, index | ((1UL << shift) - 1));
2291 }
2292 
2293 void xa_dump_entry(const void *entry, unsigned long index, unsigned long shift)
2294 {
2295 	if (!entry)
2296 		return;
2297 
2298 	xa_dump_index(index, shift);
2299 
2300 	if (xa_is_node(entry)) {
2301 		if (shift == 0) {
2302 			pr_cont("%px\n", entry);
2303 		} else {
2304 			unsigned long i;
2305 			struct xa_node *node = xa_to_node(entry);
2306 			xa_dump_node(node);
2307 			for (i = 0; i < XA_CHUNK_SIZE; i++)
2308 				xa_dump_entry(node->slots[i],
2309 				      index + (i << node->shift), node->shift);
2310 		}
2311 	} else if (xa_is_value(entry))
2312 		pr_cont("value %ld (0x%lx) [%px]\n", xa_to_value(entry),
2313 						xa_to_value(entry), entry);
2314 	else if (!xa_is_internal(entry))
2315 		pr_cont("%px\n", entry);
2316 	else if (xa_is_retry(entry))
2317 		pr_cont("retry (%ld)\n", xa_to_internal(entry));
2318 	else if (xa_is_sibling(entry))
2319 		pr_cont("sibling (slot %ld)\n", xa_to_sibling(entry));
2320 	else if (xa_is_zero(entry))
2321 		pr_cont("zero (%ld)\n", xa_to_internal(entry));
2322 	else
2323 		pr_cont("UNKNOWN ENTRY (%px)\n", entry);
2324 }
2325 
2326 void xa_dump(const struct xarray *xa)
2327 {
2328 	void *entry = xa->xa_head;
2329 	unsigned int shift = 0;
2330 
2331 	pr_info("xarray: %px head %px flags %x marks %d %d %d\n", xa, entry,
2332 			xa->xa_flags, xa_marked(xa, XA_MARK_0),
2333 			xa_marked(xa, XA_MARK_1), xa_marked(xa, XA_MARK_2));
2334 	if (xa_is_node(entry))
2335 		shift = xa_to_node(entry)->shift + XA_CHUNK_SHIFT;
2336 	xa_dump_entry(entry, 0, shift);
2337 }
2338 #endif
2339