xref: /openbmc/linux/lib/xarray.c (revision d9d6b822)
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 /*
16  * Coding conventions in this file:
17  *
18  * @xa is used to refer to the entire xarray.
19  * @xas is the 'xarray operation state'.  It may be either a pointer to
20  * an xa_state, or an xa_state stored on the stack.  This is an unfortunate
21  * ambiguity.
22  * @index is the index of the entry being operated on
23  * @mark is an xa_mark_t; a small number indicating one of the mark bits.
24  * @node refers to an xa_node; usually the primary one being operated on by
25  * this function.
26  * @offset is the index into the slots array inside an xa_node.
27  * @parent refers to the @xa_node closer to the head than @node.
28  * @entry refers to something stored in a slot in the xarray
29  */
30 
31 static inline unsigned int xa_lock_type(const struct xarray *xa)
32 {
33 	return (__force unsigned int)xa->xa_flags & 3;
34 }
35 
36 static inline void xas_lock_type(struct xa_state *xas, unsigned int lock_type)
37 {
38 	if (lock_type == XA_LOCK_IRQ)
39 		xas_lock_irq(xas);
40 	else if (lock_type == XA_LOCK_BH)
41 		xas_lock_bh(xas);
42 	else
43 		xas_lock(xas);
44 }
45 
46 static inline void xas_unlock_type(struct xa_state *xas, unsigned int lock_type)
47 {
48 	if (lock_type == XA_LOCK_IRQ)
49 		xas_unlock_irq(xas);
50 	else if (lock_type == XA_LOCK_BH)
51 		xas_unlock_bh(xas);
52 	else
53 		xas_unlock(xas);
54 }
55 
56 static inline bool xa_track_free(const struct xarray *xa)
57 {
58 	return xa->xa_flags & XA_FLAGS_TRACK_FREE;
59 }
60 
61 static inline bool xa_zero_busy(const struct xarray *xa)
62 {
63 	return xa->xa_flags & XA_FLAGS_ZERO_BUSY;
64 }
65 
66 static inline void xa_mark_set(struct xarray *xa, xa_mark_t mark)
67 {
68 	if (!(xa->xa_flags & XA_FLAGS_MARK(mark)))
69 		xa->xa_flags |= XA_FLAGS_MARK(mark);
70 }
71 
72 static inline void xa_mark_clear(struct xarray *xa, xa_mark_t mark)
73 {
74 	if (xa->xa_flags & XA_FLAGS_MARK(mark))
75 		xa->xa_flags &= ~(XA_FLAGS_MARK(mark));
76 }
77 
78 static inline unsigned long *node_marks(struct xa_node *node, xa_mark_t mark)
79 {
80 	return node->marks[(__force unsigned)mark];
81 }
82 
83 static inline bool node_get_mark(struct xa_node *node,
84 		unsigned int offset, xa_mark_t mark)
85 {
86 	return test_bit(offset, node_marks(node, mark));
87 }
88 
89 /* returns true if the bit was set */
90 static inline bool node_set_mark(struct xa_node *node, unsigned int offset,
91 				xa_mark_t mark)
92 {
93 	return __test_and_set_bit(offset, node_marks(node, mark));
94 }
95 
96 /* returns true if the bit was set */
97 static inline bool node_clear_mark(struct xa_node *node, unsigned int offset,
98 				xa_mark_t mark)
99 {
100 	return __test_and_clear_bit(offset, node_marks(node, mark));
101 }
102 
103 static inline bool node_any_mark(struct xa_node *node, xa_mark_t mark)
104 {
105 	return !bitmap_empty(node_marks(node, mark), XA_CHUNK_SIZE);
106 }
107 
108 static inline void node_mark_all(struct xa_node *node, xa_mark_t mark)
109 {
110 	bitmap_fill(node_marks(node, mark), XA_CHUNK_SIZE);
111 }
112 
113 #define mark_inc(mark) do { \
114 	mark = (__force xa_mark_t)((__force unsigned)(mark) + 1); \
115 } while (0)
116 
117 /*
118  * xas_squash_marks() - Merge all marks to the first entry
119  * @xas: Array operation state.
120  *
121  * Set a mark on the first entry if any entry has it set.  Clear marks on
122  * all sibling entries.
123  */
124 static void xas_squash_marks(const struct xa_state *xas)
125 {
126 	unsigned int mark = 0;
127 	unsigned int limit = xas->xa_offset + xas->xa_sibs + 1;
128 
129 	if (!xas->xa_sibs)
130 		return;
131 
132 	do {
133 		unsigned long *marks = xas->xa_node->marks[mark];
134 		if (find_next_bit(marks, limit, xas->xa_offset + 1) == limit)
135 			continue;
136 		__set_bit(xas->xa_offset, marks);
137 		bitmap_clear(marks, xas->xa_offset + 1, xas->xa_sibs);
138 	} while (mark++ != (__force unsigned)XA_MARK_MAX);
139 }
140 
141 /* extracts the offset within this node from the index */
142 static unsigned int get_offset(unsigned long index, struct xa_node *node)
143 {
144 	return (index >> node->shift) & XA_CHUNK_MASK;
145 }
146 
147 static void xas_set_offset(struct xa_state *xas)
148 {
149 	xas->xa_offset = get_offset(xas->xa_index, xas->xa_node);
150 }
151 
152 /* move the index either forwards (find) or backwards (sibling slot) */
153 static void xas_move_index(struct xa_state *xas, unsigned long offset)
154 {
155 	unsigned int shift = xas->xa_node->shift;
156 	xas->xa_index &= ~XA_CHUNK_MASK << shift;
157 	xas->xa_index += offset << shift;
158 }
159 
160 static void xas_advance(struct xa_state *xas)
161 {
162 	xas->xa_offset++;
163 	xas_move_index(xas, xas->xa_offset);
164 }
165 
166 static void *set_bounds(struct xa_state *xas)
167 {
168 	xas->xa_node = XAS_BOUNDS;
169 	return NULL;
170 }
171 
172 /*
173  * Starts a walk.  If the @xas is already valid, we assume that it's on
174  * the right path and just return where we've got to.  If we're in an
175  * error state, return NULL.  If the index is outside the current scope
176  * of the xarray, return NULL without changing @xas->xa_node.  Otherwise
177  * set @xas->xa_node to NULL and return the current head of the array.
178  */
179 static void *xas_start(struct xa_state *xas)
180 {
181 	void *entry;
182 
183 	if (xas_valid(xas))
184 		return xas_reload(xas);
185 	if (xas_error(xas))
186 		return NULL;
187 
188 	entry = xa_head(xas->xa);
189 	if (!xa_is_node(entry)) {
190 		if (xas->xa_index)
191 			return set_bounds(xas);
192 	} else {
193 		if ((xas->xa_index >> xa_to_node(entry)->shift) > XA_CHUNK_MASK)
194 			return set_bounds(xas);
195 	}
196 
197 	xas->xa_node = NULL;
198 	return entry;
199 }
200 
201 static void *xas_descend(struct xa_state *xas, struct xa_node *node)
202 {
203 	unsigned int offset = get_offset(xas->xa_index, node);
204 	void *entry = xa_entry(xas->xa, node, offset);
205 
206 	xas->xa_node = node;
207 	if (xa_is_sibling(entry)) {
208 		offset = xa_to_sibling(entry);
209 		entry = xa_entry(xas->xa, node, offset);
210 	}
211 
212 	xas->xa_offset = offset;
213 	return entry;
214 }
215 
216 /**
217  * xas_load() - Load an entry from the XArray (advanced).
218  * @xas: XArray operation state.
219  *
220  * Usually walks the @xas to the appropriate state to load the entry
221  * stored at xa_index.  However, it will do nothing and return %NULL if
222  * @xas is in an error state.  xas_load() will never expand the tree.
223  *
224  * If the xa_state is set up to operate on a multi-index entry, xas_load()
225  * may return %NULL or an internal entry, even if there are entries
226  * present within the range specified by @xas.
227  *
228  * Context: Any context.  The caller should hold the xa_lock or the RCU lock.
229  * Return: Usually an entry in the XArray, but see description for exceptions.
230  */
231 void *xas_load(struct xa_state *xas)
232 {
233 	void *entry = xas_start(xas);
234 
235 	while (xa_is_node(entry)) {
236 		struct xa_node *node = xa_to_node(entry);
237 
238 		if (xas->xa_shift > node->shift)
239 			break;
240 		entry = xas_descend(xas, node);
241 		if (node->shift == 0)
242 			break;
243 	}
244 	return entry;
245 }
246 EXPORT_SYMBOL_GPL(xas_load);
247 
248 /* Move the radix tree node cache here */
249 extern struct kmem_cache *radix_tree_node_cachep;
250 extern void radix_tree_node_rcu_free(struct rcu_head *head);
251 
252 #define XA_RCU_FREE	((struct xarray *)1)
253 
254 static void xa_node_free(struct xa_node *node)
255 {
256 	XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
257 	node->array = XA_RCU_FREE;
258 	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
259 }
260 
261 /*
262  * xas_destroy() - Free any resources allocated during the XArray operation.
263  * @xas: XArray operation state.
264  *
265  * This function is now internal-only.
266  */
267 static void xas_destroy(struct xa_state *xas)
268 {
269 	struct xa_node *next, *node = xas->xa_alloc;
270 
271 	while (node) {
272 		XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
273 		next = rcu_dereference_raw(node->parent);
274 		radix_tree_node_rcu_free(&node->rcu_head);
275 		xas->xa_alloc = node = next;
276 	}
277 }
278 
279 /**
280  * xas_nomem() - Allocate memory if needed.
281  * @xas: XArray operation state.
282  * @gfp: Memory allocation flags.
283  *
284  * If we need to add new nodes to the XArray, we try to allocate memory
285  * with GFP_NOWAIT while holding the lock, which will usually succeed.
286  * If it fails, @xas is flagged as needing memory to continue.  The caller
287  * should drop the lock and call xas_nomem().  If xas_nomem() succeeds,
288  * the caller should retry the operation.
289  *
290  * Forward progress is guaranteed as one node is allocated here and
291  * stored in the xa_state where it will be found by xas_alloc().  More
292  * nodes will likely be found in the slab allocator, but we do not tie
293  * them up here.
294  *
295  * Return: true if memory was needed, and was successfully allocated.
296  */
297 bool xas_nomem(struct xa_state *xas, gfp_t gfp)
298 {
299 	if (xas->xa_node != XA_ERROR(-ENOMEM)) {
300 		xas_destroy(xas);
301 		return false;
302 	}
303 	if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
304 		gfp |= __GFP_ACCOUNT;
305 	xas->xa_alloc = kmem_cache_alloc(radix_tree_node_cachep, gfp);
306 	if (!xas->xa_alloc)
307 		return false;
308 	xas->xa_alloc->parent = NULL;
309 	XA_NODE_BUG_ON(xas->xa_alloc, !list_empty(&xas->xa_alloc->private_list));
310 	xas->xa_node = XAS_RESTART;
311 	return true;
312 }
313 EXPORT_SYMBOL_GPL(xas_nomem);
314 
315 /*
316  * __xas_nomem() - Drop locks and allocate memory if needed.
317  * @xas: XArray operation state.
318  * @gfp: Memory allocation flags.
319  *
320  * Internal variant of xas_nomem().
321  *
322  * Return: true if memory was needed, and was successfully allocated.
323  */
324 static bool __xas_nomem(struct xa_state *xas, gfp_t gfp)
325 	__must_hold(xas->xa->xa_lock)
326 {
327 	unsigned int lock_type = xa_lock_type(xas->xa);
328 
329 	if (xas->xa_node != XA_ERROR(-ENOMEM)) {
330 		xas_destroy(xas);
331 		return false;
332 	}
333 	if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
334 		gfp |= __GFP_ACCOUNT;
335 	if (gfpflags_allow_blocking(gfp)) {
336 		xas_unlock_type(xas, lock_type);
337 		xas->xa_alloc = kmem_cache_alloc(radix_tree_node_cachep, gfp);
338 		xas_lock_type(xas, lock_type);
339 	} else {
340 		xas->xa_alloc = kmem_cache_alloc(radix_tree_node_cachep, gfp);
341 	}
342 	if (!xas->xa_alloc)
343 		return false;
344 	xas->xa_alloc->parent = NULL;
345 	XA_NODE_BUG_ON(xas->xa_alloc, !list_empty(&xas->xa_alloc->private_list));
346 	xas->xa_node = XAS_RESTART;
347 	return true;
348 }
349 
350 static void xas_update(struct xa_state *xas, struct xa_node *node)
351 {
352 	if (xas->xa_update)
353 		xas->xa_update(node);
354 	else
355 		XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
356 }
357 
358 static void *xas_alloc(struct xa_state *xas, unsigned int shift)
359 {
360 	struct xa_node *parent = xas->xa_node;
361 	struct xa_node *node = xas->xa_alloc;
362 
363 	if (xas_invalid(xas))
364 		return NULL;
365 
366 	if (node) {
367 		xas->xa_alloc = NULL;
368 	} else {
369 		gfp_t gfp = GFP_NOWAIT | __GFP_NOWARN;
370 
371 		if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
372 			gfp |= __GFP_ACCOUNT;
373 
374 		node = kmem_cache_alloc(radix_tree_node_cachep, gfp);
375 		if (!node) {
376 			xas_set_err(xas, -ENOMEM);
377 			return NULL;
378 		}
379 	}
380 
381 	if (parent) {
382 		node->offset = xas->xa_offset;
383 		parent->count++;
384 		XA_NODE_BUG_ON(node, parent->count > XA_CHUNK_SIZE);
385 		xas_update(xas, parent);
386 	}
387 	XA_NODE_BUG_ON(node, shift > BITS_PER_LONG);
388 	XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
389 	node->shift = shift;
390 	node->count = 0;
391 	node->nr_values = 0;
392 	RCU_INIT_POINTER(node->parent, xas->xa_node);
393 	node->array = xas->xa;
394 
395 	return node;
396 }
397 
398 #ifdef CONFIG_XARRAY_MULTI
399 /* Returns the number of indices covered by a given xa_state */
400 static unsigned long xas_size(const struct xa_state *xas)
401 {
402 	return (xas->xa_sibs + 1UL) << xas->xa_shift;
403 }
404 #endif
405 
406 /*
407  * Use this to calculate the maximum index that will need to be created
408  * in order to add the entry described by @xas.  Because we cannot store a
409  * multi-index entry at index 0, the calculation is a little more complex
410  * than you might expect.
411  */
412 static unsigned long xas_max(struct xa_state *xas)
413 {
414 	unsigned long max = xas->xa_index;
415 
416 #ifdef CONFIG_XARRAY_MULTI
417 	if (xas->xa_shift || xas->xa_sibs) {
418 		unsigned long mask = xas_size(xas) - 1;
419 		max |= mask;
420 		if (mask == max)
421 			max++;
422 	}
423 #endif
424 
425 	return max;
426 }
427 
428 /* The maximum index that can be contained in the array without expanding it */
429 static unsigned long max_index(void *entry)
430 {
431 	if (!xa_is_node(entry))
432 		return 0;
433 	return (XA_CHUNK_SIZE << xa_to_node(entry)->shift) - 1;
434 }
435 
436 static void xas_shrink(struct xa_state *xas)
437 {
438 	struct xarray *xa = xas->xa;
439 	struct xa_node *node = xas->xa_node;
440 
441 	for (;;) {
442 		void *entry;
443 
444 		XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
445 		if (node->count != 1)
446 			break;
447 		entry = xa_entry_locked(xa, node, 0);
448 		if (!entry)
449 			break;
450 		if (!xa_is_node(entry) && node->shift)
451 			break;
452 		if (xa_is_zero(entry) && xa_zero_busy(xa))
453 			entry = NULL;
454 		xas->xa_node = XAS_BOUNDS;
455 
456 		RCU_INIT_POINTER(xa->xa_head, entry);
457 		if (xa_track_free(xa) && !node_get_mark(node, 0, XA_FREE_MARK))
458 			xa_mark_clear(xa, XA_FREE_MARK);
459 
460 		node->count = 0;
461 		node->nr_values = 0;
462 		if (!xa_is_node(entry))
463 			RCU_INIT_POINTER(node->slots[0], XA_RETRY_ENTRY);
464 		xas_update(xas, node);
465 		xa_node_free(node);
466 		if (!xa_is_node(entry))
467 			break;
468 		node = xa_to_node(entry);
469 		node->parent = NULL;
470 	}
471 }
472 
473 /*
474  * xas_delete_node() - Attempt to delete an xa_node
475  * @xas: Array operation state.
476  *
477  * Attempts to delete the @xas->xa_node.  This will fail if xa->node has
478  * a non-zero reference count.
479  */
480 static void xas_delete_node(struct xa_state *xas)
481 {
482 	struct xa_node *node = xas->xa_node;
483 
484 	for (;;) {
485 		struct xa_node *parent;
486 
487 		XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
488 		if (node->count)
489 			break;
490 
491 		parent = xa_parent_locked(xas->xa, node);
492 		xas->xa_node = parent;
493 		xas->xa_offset = node->offset;
494 		xa_node_free(node);
495 
496 		if (!parent) {
497 			xas->xa->xa_head = NULL;
498 			xas->xa_node = XAS_BOUNDS;
499 			return;
500 		}
501 
502 		parent->slots[xas->xa_offset] = NULL;
503 		parent->count--;
504 		XA_NODE_BUG_ON(parent, parent->count > XA_CHUNK_SIZE);
505 		node = parent;
506 		xas_update(xas, node);
507 	}
508 
509 	if (!node->parent)
510 		xas_shrink(xas);
511 }
512 
513 /**
514  * xas_free_nodes() - Free this node and all nodes that it references
515  * @xas: Array operation state.
516  * @top: Node to free
517  *
518  * This node has been removed from the tree.  We must now free it and all
519  * of its subnodes.  There may be RCU walkers with references into the tree,
520  * so we must replace all entries with retry markers.
521  */
522 static void xas_free_nodes(struct xa_state *xas, struct xa_node *top)
523 {
524 	unsigned int offset = 0;
525 	struct xa_node *node = top;
526 
527 	for (;;) {
528 		void *entry = xa_entry_locked(xas->xa, node, offset);
529 
530 		if (node->shift && xa_is_node(entry)) {
531 			node = xa_to_node(entry);
532 			offset = 0;
533 			continue;
534 		}
535 		if (entry)
536 			RCU_INIT_POINTER(node->slots[offset], XA_RETRY_ENTRY);
537 		offset++;
538 		while (offset == XA_CHUNK_SIZE) {
539 			struct xa_node *parent;
540 
541 			parent = xa_parent_locked(xas->xa, node);
542 			offset = node->offset + 1;
543 			node->count = 0;
544 			node->nr_values = 0;
545 			xas_update(xas, node);
546 			xa_node_free(node);
547 			if (node == top)
548 				return;
549 			node = parent;
550 		}
551 	}
552 }
553 
554 /*
555  * xas_expand adds nodes to the head of the tree until it has reached
556  * sufficient height to be able to contain @xas->xa_index
557  */
558 static int xas_expand(struct xa_state *xas, void *head)
559 {
560 	struct xarray *xa = xas->xa;
561 	struct xa_node *node = NULL;
562 	unsigned int shift = 0;
563 	unsigned long max = xas_max(xas);
564 
565 	if (!head) {
566 		if (max == 0)
567 			return 0;
568 		while ((max >> shift) >= XA_CHUNK_SIZE)
569 			shift += XA_CHUNK_SHIFT;
570 		return shift + XA_CHUNK_SHIFT;
571 	} else if (xa_is_node(head)) {
572 		node = xa_to_node(head);
573 		shift = node->shift + XA_CHUNK_SHIFT;
574 	}
575 	xas->xa_node = NULL;
576 
577 	while (max > max_index(head)) {
578 		xa_mark_t mark = 0;
579 
580 		XA_NODE_BUG_ON(node, shift > BITS_PER_LONG);
581 		node = xas_alloc(xas, shift);
582 		if (!node)
583 			return -ENOMEM;
584 
585 		node->count = 1;
586 		if (xa_is_value(head))
587 			node->nr_values = 1;
588 		RCU_INIT_POINTER(node->slots[0], head);
589 
590 		/* Propagate the aggregated mark info to the new child */
591 		for (;;) {
592 			if (xa_track_free(xa) && mark == XA_FREE_MARK) {
593 				node_mark_all(node, XA_FREE_MARK);
594 				if (!xa_marked(xa, XA_FREE_MARK)) {
595 					node_clear_mark(node, 0, XA_FREE_MARK);
596 					xa_mark_set(xa, XA_FREE_MARK);
597 				}
598 			} else if (xa_marked(xa, mark)) {
599 				node_set_mark(node, 0, mark);
600 			}
601 			if (mark == XA_MARK_MAX)
602 				break;
603 			mark_inc(mark);
604 		}
605 
606 		/*
607 		 * Now that the new node is fully initialised, we can add
608 		 * it to the tree
609 		 */
610 		if (xa_is_node(head)) {
611 			xa_to_node(head)->offset = 0;
612 			rcu_assign_pointer(xa_to_node(head)->parent, node);
613 		}
614 		head = xa_mk_node(node);
615 		rcu_assign_pointer(xa->xa_head, head);
616 		xas_update(xas, node);
617 
618 		shift += XA_CHUNK_SHIFT;
619 	}
620 
621 	xas->xa_node = node;
622 	return shift;
623 }
624 
625 /*
626  * xas_create() - Create a slot to store an entry in.
627  * @xas: XArray operation state.
628  * @allow_root: %true if we can store the entry in the root directly
629  *
630  * Most users will not need to call this function directly, as it is called
631  * by xas_store().  It is useful for doing conditional store operations
632  * (see the xa_cmpxchg() implementation for an example).
633  *
634  * Return: If the slot already existed, returns the contents of this slot.
635  * If the slot was newly created, returns %NULL.  If it failed to create the
636  * slot, returns %NULL and indicates the error in @xas.
637  */
638 static void *xas_create(struct xa_state *xas, bool allow_root)
639 {
640 	struct xarray *xa = xas->xa;
641 	void *entry;
642 	void __rcu **slot;
643 	struct xa_node *node = xas->xa_node;
644 	int shift;
645 	unsigned int order = xas->xa_shift;
646 
647 	if (xas_top(node)) {
648 		entry = xa_head_locked(xa);
649 		xas->xa_node = NULL;
650 		if (!entry && xa_zero_busy(xa))
651 			entry = XA_ZERO_ENTRY;
652 		shift = xas_expand(xas, entry);
653 		if (shift < 0)
654 			return NULL;
655 		if (!shift && !allow_root)
656 			shift = XA_CHUNK_SHIFT;
657 		entry = xa_head_locked(xa);
658 		slot = &xa->xa_head;
659 	} else if (xas_error(xas)) {
660 		return NULL;
661 	} else if (node) {
662 		unsigned int offset = xas->xa_offset;
663 
664 		shift = node->shift;
665 		entry = xa_entry_locked(xa, node, offset);
666 		slot = &node->slots[offset];
667 	} else {
668 		shift = 0;
669 		entry = xa_head_locked(xa);
670 		slot = &xa->xa_head;
671 	}
672 
673 	while (shift > order) {
674 		shift -= XA_CHUNK_SHIFT;
675 		if (!entry) {
676 			node = xas_alloc(xas, shift);
677 			if (!node)
678 				break;
679 			if (xa_track_free(xa))
680 				node_mark_all(node, XA_FREE_MARK);
681 			rcu_assign_pointer(*slot, xa_mk_node(node));
682 		} else if (xa_is_node(entry)) {
683 			node = xa_to_node(entry);
684 		} else {
685 			break;
686 		}
687 		entry = xas_descend(xas, node);
688 		slot = &node->slots[xas->xa_offset];
689 	}
690 
691 	return entry;
692 }
693 
694 /**
695  * xas_create_range() - Ensure that stores to this range will succeed
696  * @xas: XArray operation state.
697  *
698  * Creates all of the slots in the range covered by @xas.  Sets @xas to
699  * create single-index entries and positions it at the beginning of the
700  * range.  This is for the benefit of users which have not yet been
701  * converted to use multi-index entries.
702  */
703 void xas_create_range(struct xa_state *xas)
704 {
705 	unsigned long index = xas->xa_index;
706 	unsigned char shift = xas->xa_shift;
707 	unsigned char sibs = xas->xa_sibs;
708 
709 	xas->xa_index |= ((sibs + 1UL) << shift) - 1;
710 	if (xas_is_node(xas) && xas->xa_node->shift == xas->xa_shift)
711 		xas->xa_offset |= sibs;
712 	xas->xa_shift = 0;
713 	xas->xa_sibs = 0;
714 
715 	for (;;) {
716 		xas_create(xas, true);
717 		if (xas_error(xas))
718 			goto restore;
719 		if (xas->xa_index <= (index | XA_CHUNK_MASK))
720 			goto success;
721 		xas->xa_index -= XA_CHUNK_SIZE;
722 
723 		for (;;) {
724 			struct xa_node *node = xas->xa_node;
725 			xas->xa_node = xa_parent_locked(xas->xa, node);
726 			xas->xa_offset = node->offset - 1;
727 			if (node->offset != 0)
728 				break;
729 		}
730 	}
731 
732 restore:
733 	xas->xa_shift = shift;
734 	xas->xa_sibs = sibs;
735 	xas->xa_index = index;
736 	return;
737 success:
738 	xas->xa_index = index;
739 	if (xas->xa_node)
740 		xas_set_offset(xas);
741 }
742 EXPORT_SYMBOL_GPL(xas_create_range);
743 
744 static void update_node(struct xa_state *xas, struct xa_node *node,
745 		int count, int values)
746 {
747 	if (!node || (!count && !values))
748 		return;
749 
750 	node->count += count;
751 	node->nr_values += values;
752 	XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
753 	XA_NODE_BUG_ON(node, node->nr_values > XA_CHUNK_SIZE);
754 	xas_update(xas, node);
755 	if (count < 0)
756 		xas_delete_node(xas);
757 }
758 
759 /**
760  * xas_store() - Store this entry in the XArray.
761  * @xas: XArray operation state.
762  * @entry: New entry.
763  *
764  * If @xas is operating on a multi-index entry, the entry returned by this
765  * function is essentially meaningless (it may be an internal entry or it
766  * may be %NULL, even if there are non-NULL entries at some of the indices
767  * covered by the range).  This is not a problem for any current users,
768  * and can be changed if needed.
769  *
770  * Return: The old entry at this index.
771  */
772 void *xas_store(struct xa_state *xas, void *entry)
773 {
774 	struct xa_node *node;
775 	void __rcu **slot = &xas->xa->xa_head;
776 	unsigned int offset, max;
777 	int count = 0;
778 	int values = 0;
779 	void *first, *next;
780 	bool value = xa_is_value(entry);
781 
782 	if (entry) {
783 		bool allow_root = !xa_is_node(entry) && !xa_is_zero(entry);
784 		first = xas_create(xas, allow_root);
785 	} else {
786 		first = xas_load(xas);
787 	}
788 
789 	if (xas_invalid(xas))
790 		return first;
791 	node = xas->xa_node;
792 	if (node && (xas->xa_shift < node->shift))
793 		xas->xa_sibs = 0;
794 	if ((first == entry) && !xas->xa_sibs)
795 		return first;
796 
797 	next = first;
798 	offset = xas->xa_offset;
799 	max = xas->xa_offset + xas->xa_sibs;
800 	if (node) {
801 		slot = &node->slots[offset];
802 		if (xas->xa_sibs)
803 			xas_squash_marks(xas);
804 	}
805 	if (!entry)
806 		xas_init_marks(xas);
807 
808 	for (;;) {
809 		/*
810 		 * Must clear the marks before setting the entry to NULL,
811 		 * otherwise xas_for_each_marked may find a NULL entry and
812 		 * stop early.  rcu_assign_pointer contains a release barrier
813 		 * so the mark clearing will appear to happen before the
814 		 * entry is set to NULL.
815 		 */
816 		rcu_assign_pointer(*slot, entry);
817 		if (xa_is_node(next) && (!node || node->shift))
818 			xas_free_nodes(xas, xa_to_node(next));
819 		if (!node)
820 			break;
821 		count += !next - !entry;
822 		values += !xa_is_value(first) - !value;
823 		if (entry) {
824 			if (offset == max)
825 				break;
826 			if (!xa_is_sibling(entry))
827 				entry = xa_mk_sibling(xas->xa_offset);
828 		} else {
829 			if (offset == XA_CHUNK_MASK)
830 				break;
831 		}
832 		next = xa_entry_locked(xas->xa, node, ++offset);
833 		if (!xa_is_sibling(next)) {
834 			if (!entry && (offset > max))
835 				break;
836 			first = next;
837 		}
838 		slot++;
839 	}
840 
841 	update_node(xas, node, count, values);
842 	return first;
843 }
844 EXPORT_SYMBOL_GPL(xas_store);
845 
846 /**
847  * xas_get_mark() - Returns the state of this mark.
848  * @xas: XArray operation state.
849  * @mark: Mark number.
850  *
851  * Return: true if the mark is set, false if the mark is clear or @xas
852  * is in an error state.
853  */
854 bool xas_get_mark(const struct xa_state *xas, xa_mark_t mark)
855 {
856 	if (xas_invalid(xas))
857 		return false;
858 	if (!xas->xa_node)
859 		return xa_marked(xas->xa, mark);
860 	return node_get_mark(xas->xa_node, xas->xa_offset, mark);
861 }
862 EXPORT_SYMBOL_GPL(xas_get_mark);
863 
864 /**
865  * xas_set_mark() - Sets the mark on this entry and its parents.
866  * @xas: XArray operation state.
867  * @mark: Mark number.
868  *
869  * Sets the specified mark on this entry, and walks up the tree setting it
870  * on all the ancestor entries.  Does nothing if @xas has not been walked to
871  * an entry, or is in an error state.
872  */
873 void xas_set_mark(const struct xa_state *xas, xa_mark_t mark)
874 {
875 	struct xa_node *node = xas->xa_node;
876 	unsigned int offset = xas->xa_offset;
877 
878 	if (xas_invalid(xas))
879 		return;
880 
881 	while (node) {
882 		if (node_set_mark(node, offset, mark))
883 			return;
884 		offset = node->offset;
885 		node = xa_parent_locked(xas->xa, node);
886 	}
887 
888 	if (!xa_marked(xas->xa, mark))
889 		xa_mark_set(xas->xa, mark);
890 }
891 EXPORT_SYMBOL_GPL(xas_set_mark);
892 
893 /**
894  * xas_clear_mark() - Clears the mark on this entry and its parents.
895  * @xas: XArray operation state.
896  * @mark: Mark number.
897  *
898  * Clears the specified mark on this entry, and walks back to the head
899  * attempting to clear it on all the ancestor entries.  Does nothing if
900  * @xas has not been walked to an entry, or is in an error state.
901  */
902 void xas_clear_mark(const struct xa_state *xas, xa_mark_t mark)
903 {
904 	struct xa_node *node = xas->xa_node;
905 	unsigned int offset = xas->xa_offset;
906 
907 	if (xas_invalid(xas))
908 		return;
909 
910 	while (node) {
911 		if (!node_clear_mark(node, offset, mark))
912 			return;
913 		if (node_any_mark(node, mark))
914 			return;
915 
916 		offset = node->offset;
917 		node = xa_parent_locked(xas->xa, node);
918 	}
919 
920 	if (xa_marked(xas->xa, mark))
921 		xa_mark_clear(xas->xa, mark);
922 }
923 EXPORT_SYMBOL_GPL(xas_clear_mark);
924 
925 /**
926  * xas_init_marks() - Initialise all marks for the entry
927  * @xas: Array operations state.
928  *
929  * Initialise all marks for the entry specified by @xas.  If we're tracking
930  * free entries with a mark, we need to set it on all entries.  All other
931  * marks are cleared.
932  *
933  * This implementation is not as efficient as it could be; we may walk
934  * up the tree multiple times.
935  */
936 void xas_init_marks(const struct xa_state *xas)
937 {
938 	xa_mark_t mark = 0;
939 
940 	for (;;) {
941 		if (xa_track_free(xas->xa) && mark == XA_FREE_MARK)
942 			xas_set_mark(xas, mark);
943 		else
944 			xas_clear_mark(xas, mark);
945 		if (mark == XA_MARK_MAX)
946 			break;
947 		mark_inc(mark);
948 	}
949 }
950 EXPORT_SYMBOL_GPL(xas_init_marks);
951 
952 #ifdef CONFIG_XARRAY_MULTI
953 static unsigned int node_get_marks(struct xa_node *node, unsigned int offset)
954 {
955 	unsigned int marks = 0;
956 	xa_mark_t mark = XA_MARK_0;
957 
958 	for (;;) {
959 		if (node_get_mark(node, offset, mark))
960 			marks |= 1 << (__force unsigned int)mark;
961 		if (mark == XA_MARK_MAX)
962 			break;
963 		mark_inc(mark);
964 	}
965 
966 	return marks;
967 }
968 
969 static void node_set_marks(struct xa_node *node, unsigned int offset,
970 			struct xa_node *child, unsigned int marks)
971 {
972 	xa_mark_t mark = XA_MARK_0;
973 
974 	for (;;) {
975 		if (marks & (1 << (__force unsigned int)mark)) {
976 			node_set_mark(node, offset, mark);
977 			if (child)
978 				node_mark_all(child, mark);
979 		}
980 		if (mark == XA_MARK_MAX)
981 			break;
982 		mark_inc(mark);
983 	}
984 }
985 
986 /**
987  * xas_split_alloc() - Allocate memory for splitting an entry.
988  * @xas: XArray operation state.
989  * @entry: New entry which will be stored in the array.
990  * @order: Current entry order.
991  * @gfp: Memory allocation flags.
992  *
993  * This function should be called before calling xas_split().
994  * If necessary, it will allocate new nodes (and fill them with @entry)
995  * to prepare for the upcoming split of an entry of @order size into
996  * entries of the order stored in the @xas.
997  *
998  * Context: May sleep if @gfp flags permit.
999  */
1000 void xas_split_alloc(struct xa_state *xas, void *entry, unsigned int order,
1001 		gfp_t gfp)
1002 {
1003 	unsigned int sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1004 	unsigned int mask = xas->xa_sibs;
1005 
1006 	/* XXX: no support for splitting really large entries yet */
1007 	if (WARN_ON(xas->xa_shift + 2 * XA_CHUNK_SHIFT < order))
1008 		goto nomem;
1009 	if (xas->xa_shift + XA_CHUNK_SHIFT > order)
1010 		return;
1011 
1012 	do {
1013 		unsigned int i;
1014 		void *sibling = NULL;
1015 		struct xa_node *node;
1016 
1017 		node = kmem_cache_alloc(radix_tree_node_cachep, gfp);
1018 		if (!node)
1019 			goto nomem;
1020 		node->array = xas->xa;
1021 		for (i = 0; i < XA_CHUNK_SIZE; i++) {
1022 			if ((i & mask) == 0) {
1023 				RCU_INIT_POINTER(node->slots[i], entry);
1024 				sibling = xa_mk_sibling(i);
1025 			} else {
1026 				RCU_INIT_POINTER(node->slots[i], sibling);
1027 			}
1028 		}
1029 		RCU_INIT_POINTER(node->parent, xas->xa_alloc);
1030 		xas->xa_alloc = node;
1031 	} while (sibs-- > 0);
1032 
1033 	return;
1034 nomem:
1035 	xas_destroy(xas);
1036 	xas_set_err(xas, -ENOMEM);
1037 }
1038 EXPORT_SYMBOL_GPL(xas_split_alloc);
1039 
1040 /**
1041  * xas_split() - Split a multi-index entry into smaller entries.
1042  * @xas: XArray operation state.
1043  * @entry: New entry to store in the array.
1044  * @order: Current entry order.
1045  *
1046  * The size of the new entries is set in @xas.  The value in @entry is
1047  * copied to all the replacement entries.
1048  *
1049  * Context: Any context.  The caller should hold the xa_lock.
1050  */
1051 void xas_split(struct xa_state *xas, void *entry, unsigned int order)
1052 {
1053 	unsigned int sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1054 	unsigned int offset, marks;
1055 	struct xa_node *node;
1056 	void *curr = xas_load(xas);
1057 	int values = 0;
1058 
1059 	node = xas->xa_node;
1060 	if (xas_top(node))
1061 		return;
1062 
1063 	marks = node_get_marks(node, xas->xa_offset);
1064 
1065 	offset = xas->xa_offset + sibs;
1066 	do {
1067 		if (xas->xa_shift < node->shift) {
1068 			struct xa_node *child = xas->xa_alloc;
1069 
1070 			xas->xa_alloc = rcu_dereference_raw(child->parent);
1071 			child->shift = node->shift - XA_CHUNK_SHIFT;
1072 			child->offset = offset;
1073 			child->count = XA_CHUNK_SIZE;
1074 			child->nr_values = xa_is_value(entry) ?
1075 					XA_CHUNK_SIZE : 0;
1076 			RCU_INIT_POINTER(child->parent, node);
1077 			node_set_marks(node, offset, child, marks);
1078 			rcu_assign_pointer(node->slots[offset],
1079 					xa_mk_node(child));
1080 			if (xa_is_value(curr))
1081 				values--;
1082 		} else {
1083 			unsigned int canon = offset - xas->xa_sibs;
1084 
1085 			node_set_marks(node, canon, NULL, marks);
1086 			rcu_assign_pointer(node->slots[canon], entry);
1087 			while (offset > canon)
1088 				rcu_assign_pointer(node->slots[offset--],
1089 						xa_mk_sibling(canon));
1090 			values += (xa_is_value(entry) - xa_is_value(curr)) *
1091 					(xas->xa_sibs + 1);
1092 		}
1093 	} while (offset-- > xas->xa_offset);
1094 
1095 	node->nr_values += values;
1096 }
1097 EXPORT_SYMBOL_GPL(xas_split);
1098 #endif
1099 
1100 /**
1101  * xas_pause() - Pause a walk to drop a lock.
1102  * @xas: XArray operation state.
1103  *
1104  * Some users need to pause a walk and drop the lock they're holding in
1105  * order to yield to a higher priority thread or carry out an operation
1106  * on an entry.  Those users should call this function before they drop
1107  * the lock.  It resets the @xas to be suitable for the next iteration
1108  * of the loop after the user has reacquired the lock.  If most entries
1109  * found during a walk require you to call xas_pause(), the xa_for_each()
1110  * iterator may be more appropriate.
1111  *
1112  * Note that xas_pause() only works for forward iteration.  If a user needs
1113  * to pause a reverse iteration, we will need a xas_pause_rev().
1114  */
1115 void xas_pause(struct xa_state *xas)
1116 {
1117 	struct xa_node *node = xas->xa_node;
1118 
1119 	if (xas_invalid(xas))
1120 		return;
1121 
1122 	xas->xa_node = XAS_RESTART;
1123 	if (node) {
1124 		unsigned long offset = xas->xa_offset;
1125 		while (++offset < XA_CHUNK_SIZE) {
1126 			if (!xa_is_sibling(xa_entry(xas->xa, node, offset)))
1127 				break;
1128 		}
1129 		xas->xa_index += (offset - xas->xa_offset) << node->shift;
1130 		if (xas->xa_index == 0)
1131 			xas->xa_node = XAS_BOUNDS;
1132 	} else {
1133 		xas->xa_index++;
1134 	}
1135 }
1136 EXPORT_SYMBOL_GPL(xas_pause);
1137 
1138 /*
1139  * __xas_prev() - Find the previous entry in the XArray.
1140  * @xas: XArray operation state.
1141  *
1142  * Helper function for xas_prev() which handles all the complex cases
1143  * out of line.
1144  */
1145 void *__xas_prev(struct xa_state *xas)
1146 {
1147 	void *entry;
1148 
1149 	if (!xas_frozen(xas->xa_node))
1150 		xas->xa_index--;
1151 	if (!xas->xa_node)
1152 		return set_bounds(xas);
1153 	if (xas_not_node(xas->xa_node))
1154 		return xas_load(xas);
1155 
1156 	if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
1157 		xas->xa_offset--;
1158 
1159 	while (xas->xa_offset == 255) {
1160 		xas->xa_offset = xas->xa_node->offset - 1;
1161 		xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1162 		if (!xas->xa_node)
1163 			return set_bounds(xas);
1164 	}
1165 
1166 	for (;;) {
1167 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1168 		if (!xa_is_node(entry))
1169 			return entry;
1170 
1171 		xas->xa_node = xa_to_node(entry);
1172 		xas_set_offset(xas);
1173 	}
1174 }
1175 EXPORT_SYMBOL_GPL(__xas_prev);
1176 
1177 /*
1178  * __xas_next() - Find the next entry in the XArray.
1179  * @xas: XArray operation state.
1180  *
1181  * Helper function for xas_next() which handles all the complex cases
1182  * out of line.
1183  */
1184 void *__xas_next(struct xa_state *xas)
1185 {
1186 	void *entry;
1187 
1188 	if (!xas_frozen(xas->xa_node))
1189 		xas->xa_index++;
1190 	if (!xas->xa_node)
1191 		return set_bounds(xas);
1192 	if (xas_not_node(xas->xa_node))
1193 		return xas_load(xas);
1194 
1195 	if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
1196 		xas->xa_offset++;
1197 
1198 	while (xas->xa_offset == XA_CHUNK_SIZE) {
1199 		xas->xa_offset = xas->xa_node->offset + 1;
1200 		xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1201 		if (!xas->xa_node)
1202 			return set_bounds(xas);
1203 	}
1204 
1205 	for (;;) {
1206 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1207 		if (!xa_is_node(entry))
1208 			return entry;
1209 
1210 		xas->xa_node = xa_to_node(entry);
1211 		xas_set_offset(xas);
1212 	}
1213 }
1214 EXPORT_SYMBOL_GPL(__xas_next);
1215 
1216 /**
1217  * xas_find() - Find the next present entry in the XArray.
1218  * @xas: XArray operation state.
1219  * @max: Highest index to return.
1220  *
1221  * If the @xas has not yet been walked to an entry, return the entry
1222  * which has an index >= xas.xa_index.  If it has been walked, the entry
1223  * currently being pointed at has been processed, and so we move to the
1224  * next entry.
1225  *
1226  * If no entry is found and the array is smaller than @max, the iterator
1227  * is set to the smallest index not yet in the array.  This allows @xas
1228  * to be immediately passed to xas_store().
1229  *
1230  * Return: The entry, if found, otherwise %NULL.
1231  */
1232 void *xas_find(struct xa_state *xas, unsigned long max)
1233 {
1234 	void *entry;
1235 
1236 	if (xas_error(xas) || xas->xa_node == XAS_BOUNDS)
1237 		return NULL;
1238 	if (xas->xa_index > max)
1239 		return set_bounds(xas);
1240 
1241 	if (!xas->xa_node) {
1242 		xas->xa_index = 1;
1243 		return set_bounds(xas);
1244 	} else if (xas->xa_node == XAS_RESTART) {
1245 		entry = xas_load(xas);
1246 		if (entry || xas_not_node(xas->xa_node))
1247 			return entry;
1248 	} else if (!xas->xa_node->shift &&
1249 		    xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)) {
1250 		xas->xa_offset = ((xas->xa_index - 1) & XA_CHUNK_MASK) + 1;
1251 	}
1252 
1253 	xas_advance(xas);
1254 
1255 	while (xas->xa_node && (xas->xa_index <= max)) {
1256 		if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) {
1257 			xas->xa_offset = xas->xa_node->offset + 1;
1258 			xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1259 			continue;
1260 		}
1261 
1262 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1263 		if (xa_is_node(entry)) {
1264 			xas->xa_node = xa_to_node(entry);
1265 			xas->xa_offset = 0;
1266 			continue;
1267 		}
1268 		if (entry && !xa_is_sibling(entry))
1269 			return entry;
1270 
1271 		xas_advance(xas);
1272 	}
1273 
1274 	if (!xas->xa_node)
1275 		xas->xa_node = XAS_BOUNDS;
1276 	return NULL;
1277 }
1278 EXPORT_SYMBOL_GPL(xas_find);
1279 
1280 /**
1281  * xas_find_marked() - Find the next marked entry in the XArray.
1282  * @xas: XArray operation state.
1283  * @max: Highest index to return.
1284  * @mark: Mark number to search for.
1285  *
1286  * If the @xas has not yet been walked to an entry, return the marked entry
1287  * which has an index >= xas.xa_index.  If it has been walked, the entry
1288  * currently being pointed at has been processed, and so we return the
1289  * first marked entry with an index > xas.xa_index.
1290  *
1291  * If no marked entry is found and the array is smaller than @max, @xas is
1292  * set to the bounds state and xas->xa_index is set to the smallest index
1293  * not yet in the array.  This allows @xas to be immediately passed to
1294  * xas_store().
1295  *
1296  * If no entry is found before @max is reached, @xas is set to the restart
1297  * state.
1298  *
1299  * Return: The entry, if found, otherwise %NULL.
1300  */
1301 void *xas_find_marked(struct xa_state *xas, unsigned long max, xa_mark_t mark)
1302 {
1303 	bool advance = true;
1304 	unsigned int offset;
1305 	void *entry;
1306 
1307 	if (xas_error(xas))
1308 		return NULL;
1309 	if (xas->xa_index > max)
1310 		goto max;
1311 
1312 	if (!xas->xa_node) {
1313 		xas->xa_index = 1;
1314 		goto out;
1315 	} else if (xas_top(xas->xa_node)) {
1316 		advance = false;
1317 		entry = xa_head(xas->xa);
1318 		xas->xa_node = NULL;
1319 		if (xas->xa_index > max_index(entry))
1320 			goto out;
1321 		if (!xa_is_node(entry)) {
1322 			if (xa_marked(xas->xa, mark))
1323 				return entry;
1324 			xas->xa_index = 1;
1325 			goto out;
1326 		}
1327 		xas->xa_node = xa_to_node(entry);
1328 		xas->xa_offset = xas->xa_index >> xas->xa_node->shift;
1329 	}
1330 
1331 	while (xas->xa_index <= max) {
1332 		if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) {
1333 			xas->xa_offset = xas->xa_node->offset + 1;
1334 			xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1335 			if (!xas->xa_node)
1336 				break;
1337 			advance = false;
1338 			continue;
1339 		}
1340 
1341 		if (!advance) {
1342 			entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1343 			if (xa_is_sibling(entry)) {
1344 				xas->xa_offset = xa_to_sibling(entry);
1345 				xas_move_index(xas, xas->xa_offset);
1346 			}
1347 		}
1348 
1349 		offset = xas_find_chunk(xas, advance, mark);
1350 		if (offset > xas->xa_offset) {
1351 			advance = false;
1352 			xas_move_index(xas, offset);
1353 			/* Mind the wrap */
1354 			if ((xas->xa_index - 1) >= max)
1355 				goto max;
1356 			xas->xa_offset = offset;
1357 			if (offset == XA_CHUNK_SIZE)
1358 				continue;
1359 		}
1360 
1361 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1362 		if (!entry && !(xa_track_free(xas->xa) && mark == XA_FREE_MARK))
1363 			continue;
1364 		if (!xa_is_node(entry))
1365 			return entry;
1366 		xas->xa_node = xa_to_node(entry);
1367 		xas_set_offset(xas);
1368 	}
1369 
1370 out:
1371 	if (xas->xa_index > max)
1372 		goto max;
1373 	return set_bounds(xas);
1374 max:
1375 	xas->xa_node = XAS_RESTART;
1376 	return NULL;
1377 }
1378 EXPORT_SYMBOL_GPL(xas_find_marked);
1379 
1380 /**
1381  * xas_find_conflict() - Find the next present entry in a range.
1382  * @xas: XArray operation state.
1383  *
1384  * The @xas describes both a range and a position within that range.
1385  *
1386  * Context: Any context.  Expects xa_lock to be held.
1387  * Return: The next entry in the range covered by @xas or %NULL.
1388  */
1389 void *xas_find_conflict(struct xa_state *xas)
1390 {
1391 	void *curr;
1392 
1393 	if (xas_error(xas))
1394 		return NULL;
1395 
1396 	if (!xas->xa_node)
1397 		return NULL;
1398 
1399 	if (xas_top(xas->xa_node)) {
1400 		curr = xas_start(xas);
1401 		if (!curr)
1402 			return NULL;
1403 		while (xa_is_node(curr)) {
1404 			struct xa_node *node = xa_to_node(curr);
1405 			curr = xas_descend(xas, node);
1406 		}
1407 		if (curr)
1408 			return curr;
1409 	}
1410 
1411 	if (xas->xa_node->shift > xas->xa_shift)
1412 		return NULL;
1413 
1414 	for (;;) {
1415 		if (xas->xa_node->shift == xas->xa_shift) {
1416 			if ((xas->xa_offset & xas->xa_sibs) == xas->xa_sibs)
1417 				break;
1418 		} else if (xas->xa_offset == XA_CHUNK_MASK) {
1419 			xas->xa_offset = xas->xa_node->offset;
1420 			xas->xa_node = xa_parent_locked(xas->xa, xas->xa_node);
1421 			if (!xas->xa_node)
1422 				break;
1423 			continue;
1424 		}
1425 		curr = xa_entry_locked(xas->xa, xas->xa_node, ++xas->xa_offset);
1426 		if (xa_is_sibling(curr))
1427 			continue;
1428 		while (xa_is_node(curr)) {
1429 			xas->xa_node = xa_to_node(curr);
1430 			xas->xa_offset = 0;
1431 			curr = xa_entry_locked(xas->xa, xas->xa_node, 0);
1432 		}
1433 		if (curr)
1434 			return curr;
1435 	}
1436 	xas->xa_offset -= xas->xa_sibs;
1437 	return NULL;
1438 }
1439 EXPORT_SYMBOL_GPL(xas_find_conflict);
1440 
1441 /**
1442  * xa_load() - Load an entry from an XArray.
1443  * @xa: XArray.
1444  * @index: index into array.
1445  *
1446  * Context: Any context.  Takes and releases the RCU lock.
1447  * Return: The entry at @index in @xa.
1448  */
1449 void *xa_load(struct xarray *xa, unsigned long index)
1450 {
1451 	XA_STATE(xas, xa, index);
1452 	void *entry;
1453 
1454 	rcu_read_lock();
1455 	do {
1456 		entry = xas_load(&xas);
1457 		if (xa_is_zero(entry))
1458 			entry = NULL;
1459 	} while (xas_retry(&xas, entry));
1460 	rcu_read_unlock();
1461 
1462 	return entry;
1463 }
1464 EXPORT_SYMBOL(xa_load);
1465 
1466 static void *xas_result(struct xa_state *xas, void *curr)
1467 {
1468 	if (xa_is_zero(curr))
1469 		return NULL;
1470 	if (xas_error(xas))
1471 		curr = xas->xa_node;
1472 	return curr;
1473 }
1474 
1475 /**
1476  * __xa_erase() - Erase this entry from the XArray while locked.
1477  * @xa: XArray.
1478  * @index: Index into array.
1479  *
1480  * After this function returns, loading from @index will return %NULL.
1481  * If the index is part of a multi-index entry, all indices will be erased
1482  * and none of the entries will be part of a multi-index entry.
1483  *
1484  * Context: Any context.  Expects xa_lock to be held on entry.
1485  * Return: The entry which used to be at this index.
1486  */
1487 void *__xa_erase(struct xarray *xa, unsigned long index)
1488 {
1489 	XA_STATE(xas, xa, index);
1490 	return xas_result(&xas, xas_store(&xas, NULL));
1491 }
1492 EXPORT_SYMBOL(__xa_erase);
1493 
1494 /**
1495  * xa_erase() - Erase this entry from the XArray.
1496  * @xa: XArray.
1497  * @index: Index of entry.
1498  *
1499  * After this function returns, loading from @index will return %NULL.
1500  * If the index is part of a multi-index entry, all indices will be erased
1501  * and none of the entries will be part of a multi-index entry.
1502  *
1503  * Context: Any context.  Takes and releases the xa_lock.
1504  * Return: The entry which used to be at this index.
1505  */
1506 void *xa_erase(struct xarray *xa, unsigned long index)
1507 {
1508 	void *entry;
1509 
1510 	xa_lock(xa);
1511 	entry = __xa_erase(xa, index);
1512 	xa_unlock(xa);
1513 
1514 	return entry;
1515 }
1516 EXPORT_SYMBOL(xa_erase);
1517 
1518 /**
1519  * __xa_store() - Store this entry in the XArray.
1520  * @xa: XArray.
1521  * @index: Index into array.
1522  * @entry: New entry.
1523  * @gfp: Memory allocation flags.
1524  *
1525  * You must already be holding the xa_lock when calling this function.
1526  * It will drop the lock if needed to allocate memory, and then reacquire
1527  * it afterwards.
1528  *
1529  * Context: Any context.  Expects xa_lock to be held on entry.  May
1530  * release and reacquire xa_lock if @gfp flags permit.
1531  * Return: The old entry at this index or xa_err() if an error happened.
1532  */
1533 void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1534 {
1535 	XA_STATE(xas, xa, index);
1536 	void *curr;
1537 
1538 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1539 		return XA_ERROR(-EINVAL);
1540 	if (xa_track_free(xa) && !entry)
1541 		entry = XA_ZERO_ENTRY;
1542 
1543 	do {
1544 		curr = xas_store(&xas, entry);
1545 		if (xa_track_free(xa))
1546 			xas_clear_mark(&xas, XA_FREE_MARK);
1547 	} while (__xas_nomem(&xas, gfp));
1548 
1549 	return xas_result(&xas, curr);
1550 }
1551 EXPORT_SYMBOL(__xa_store);
1552 
1553 /**
1554  * xa_store() - Store this entry in the XArray.
1555  * @xa: XArray.
1556  * @index: Index into array.
1557  * @entry: New entry.
1558  * @gfp: Memory allocation flags.
1559  *
1560  * After this function returns, loads from this index will return @entry.
1561  * Storing into an existing multi-index entry updates the entry of every index.
1562  * The marks associated with @index are unaffected unless @entry is %NULL.
1563  *
1564  * Context: Any context.  Takes and releases the xa_lock.
1565  * May sleep if the @gfp flags permit.
1566  * Return: The old entry at this index on success, xa_err(-EINVAL) if @entry
1567  * cannot be stored in an XArray, or xa_err(-ENOMEM) if memory allocation
1568  * failed.
1569  */
1570 void *xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1571 {
1572 	void *curr;
1573 
1574 	xa_lock(xa);
1575 	curr = __xa_store(xa, index, entry, gfp);
1576 	xa_unlock(xa);
1577 
1578 	return curr;
1579 }
1580 EXPORT_SYMBOL(xa_store);
1581 
1582 /**
1583  * __xa_cmpxchg() - Store this entry in the XArray.
1584  * @xa: XArray.
1585  * @index: Index into array.
1586  * @old: Old value to test against.
1587  * @entry: New entry.
1588  * @gfp: Memory allocation flags.
1589  *
1590  * You must already be holding the xa_lock when calling this function.
1591  * It will drop the lock if needed to allocate memory, and then reacquire
1592  * it afterwards.
1593  *
1594  * Context: Any context.  Expects xa_lock to be held on entry.  May
1595  * release and reacquire xa_lock if @gfp flags permit.
1596  * Return: The old entry at this index or xa_err() if an error happened.
1597  */
1598 void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
1599 			void *old, void *entry, gfp_t gfp)
1600 {
1601 	XA_STATE(xas, xa, index);
1602 	void *curr;
1603 
1604 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1605 		return XA_ERROR(-EINVAL);
1606 
1607 	do {
1608 		curr = xas_load(&xas);
1609 		if (curr == old) {
1610 			xas_store(&xas, entry);
1611 			if (xa_track_free(xa) && entry && !curr)
1612 				xas_clear_mark(&xas, XA_FREE_MARK);
1613 		}
1614 	} while (__xas_nomem(&xas, gfp));
1615 
1616 	return xas_result(&xas, curr);
1617 }
1618 EXPORT_SYMBOL(__xa_cmpxchg);
1619 
1620 /**
1621  * __xa_insert() - Store this entry in the XArray if no entry is present.
1622  * @xa: XArray.
1623  * @index: Index into array.
1624  * @entry: New entry.
1625  * @gfp: Memory allocation flags.
1626  *
1627  * Inserting a NULL entry will store a reserved entry (like xa_reserve())
1628  * if no entry is present.  Inserting will fail if a reserved entry is
1629  * present, even though loading from this index will return NULL.
1630  *
1631  * Context: Any context.  Expects xa_lock to be held on entry.  May
1632  * release and reacquire xa_lock if @gfp flags permit.
1633  * Return: 0 if the store succeeded.  -EBUSY if another entry was present.
1634  * -ENOMEM if memory could not be allocated.
1635  */
1636 int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1637 {
1638 	XA_STATE(xas, xa, index);
1639 	void *curr;
1640 
1641 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1642 		return -EINVAL;
1643 	if (!entry)
1644 		entry = XA_ZERO_ENTRY;
1645 
1646 	do {
1647 		curr = xas_load(&xas);
1648 		if (!curr) {
1649 			xas_store(&xas, entry);
1650 			if (xa_track_free(xa))
1651 				xas_clear_mark(&xas, XA_FREE_MARK);
1652 		} else {
1653 			xas_set_err(&xas, -EBUSY);
1654 		}
1655 	} while (__xas_nomem(&xas, gfp));
1656 
1657 	return xas_error(&xas);
1658 }
1659 EXPORT_SYMBOL(__xa_insert);
1660 
1661 #ifdef CONFIG_XARRAY_MULTI
1662 static void xas_set_range(struct xa_state *xas, unsigned long first,
1663 		unsigned long last)
1664 {
1665 	unsigned int shift = 0;
1666 	unsigned long sibs = last - first;
1667 	unsigned int offset = XA_CHUNK_MASK;
1668 
1669 	xas_set(xas, first);
1670 
1671 	while ((first & XA_CHUNK_MASK) == 0) {
1672 		if (sibs < XA_CHUNK_MASK)
1673 			break;
1674 		if ((sibs == XA_CHUNK_MASK) && (offset < XA_CHUNK_MASK))
1675 			break;
1676 		shift += XA_CHUNK_SHIFT;
1677 		if (offset == XA_CHUNK_MASK)
1678 			offset = sibs & XA_CHUNK_MASK;
1679 		sibs >>= XA_CHUNK_SHIFT;
1680 		first >>= XA_CHUNK_SHIFT;
1681 	}
1682 
1683 	offset = first & XA_CHUNK_MASK;
1684 	if (offset + sibs > XA_CHUNK_MASK)
1685 		sibs = XA_CHUNK_MASK - offset;
1686 	if ((((first + sibs + 1) << shift) - 1) > last)
1687 		sibs -= 1;
1688 
1689 	xas->xa_shift = shift;
1690 	xas->xa_sibs = sibs;
1691 }
1692 
1693 /**
1694  * xa_store_range() - Store this entry at a range of indices in the XArray.
1695  * @xa: XArray.
1696  * @first: First index to affect.
1697  * @last: Last index to affect.
1698  * @entry: New entry.
1699  * @gfp: Memory allocation flags.
1700  *
1701  * After this function returns, loads from any index between @first and @last,
1702  * inclusive will return @entry.
1703  * Storing into an existing multi-index entry updates the entry of every index.
1704  * The marks associated with @index are unaffected unless @entry is %NULL.
1705  *
1706  * Context: Process context.  Takes and releases the xa_lock.  May sleep
1707  * if the @gfp flags permit.
1708  * Return: %NULL on success, xa_err(-EINVAL) if @entry cannot be stored in
1709  * an XArray, or xa_err(-ENOMEM) if memory allocation failed.
1710  */
1711 void *xa_store_range(struct xarray *xa, unsigned long first,
1712 		unsigned long last, void *entry, gfp_t gfp)
1713 {
1714 	XA_STATE(xas, xa, 0);
1715 
1716 	if (WARN_ON_ONCE(xa_is_internal(entry)))
1717 		return XA_ERROR(-EINVAL);
1718 	if (last < first)
1719 		return XA_ERROR(-EINVAL);
1720 
1721 	do {
1722 		xas_lock(&xas);
1723 		if (entry) {
1724 			unsigned int order = BITS_PER_LONG;
1725 			if (last + 1)
1726 				order = __ffs(last + 1);
1727 			xas_set_order(&xas, last, order);
1728 			xas_create(&xas, true);
1729 			if (xas_error(&xas))
1730 				goto unlock;
1731 		}
1732 		do {
1733 			xas_set_range(&xas, first, last);
1734 			xas_store(&xas, entry);
1735 			if (xas_error(&xas))
1736 				goto unlock;
1737 			first += xas_size(&xas);
1738 		} while (first <= last);
1739 unlock:
1740 		xas_unlock(&xas);
1741 	} while (xas_nomem(&xas, gfp));
1742 
1743 	return xas_result(&xas, NULL);
1744 }
1745 EXPORT_SYMBOL(xa_store_range);
1746 
1747 /**
1748  * xa_get_order() - Get the order of an entry.
1749  * @xa: XArray.
1750  * @index: Index of the entry.
1751  *
1752  * Return: A number between 0 and 63 indicating the order of the entry.
1753  */
1754 int xa_get_order(struct xarray *xa, unsigned long index)
1755 {
1756 	XA_STATE(xas, xa, index);
1757 	void *entry;
1758 	int order = 0;
1759 
1760 	rcu_read_lock();
1761 	entry = xas_load(&xas);
1762 
1763 	if (!entry)
1764 		goto unlock;
1765 
1766 	if (!xas.xa_node)
1767 		goto unlock;
1768 
1769 	for (;;) {
1770 		unsigned int slot = xas.xa_offset + (1 << order);
1771 
1772 		if (slot >= XA_CHUNK_SIZE)
1773 			break;
1774 		if (!xa_is_sibling(xas.xa_node->slots[slot]))
1775 			break;
1776 		order++;
1777 	}
1778 
1779 	order += xas.xa_node->shift;
1780 unlock:
1781 	rcu_read_unlock();
1782 
1783 	return order;
1784 }
1785 EXPORT_SYMBOL(xa_get_order);
1786 #endif /* CONFIG_XARRAY_MULTI */
1787 
1788 /**
1789  * __xa_alloc() - Find somewhere to store this entry in the XArray.
1790  * @xa: XArray.
1791  * @id: Pointer to ID.
1792  * @limit: Range for allocated ID.
1793  * @entry: New entry.
1794  * @gfp: Memory allocation flags.
1795  *
1796  * Finds an empty entry in @xa between @limit.min and @limit.max,
1797  * stores the index into the @id pointer, then stores the entry at
1798  * that index.  A concurrent lookup will not see an uninitialised @id.
1799  *
1800  * Context: Any context.  Expects xa_lock to be held on entry.  May
1801  * release and reacquire xa_lock if @gfp flags permit.
1802  * Return: 0 on success, -ENOMEM if memory could not be allocated or
1803  * -EBUSY if there are no free entries in @limit.
1804  */
1805 int __xa_alloc(struct xarray *xa, u32 *id, void *entry,
1806 		struct xa_limit limit, gfp_t gfp)
1807 {
1808 	XA_STATE(xas, xa, 0);
1809 
1810 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1811 		return -EINVAL;
1812 	if (WARN_ON_ONCE(!xa_track_free(xa)))
1813 		return -EINVAL;
1814 
1815 	if (!entry)
1816 		entry = XA_ZERO_ENTRY;
1817 
1818 	do {
1819 		xas.xa_index = limit.min;
1820 		xas_find_marked(&xas, limit.max, XA_FREE_MARK);
1821 		if (xas.xa_node == XAS_RESTART)
1822 			xas_set_err(&xas, -EBUSY);
1823 		else
1824 			*id = xas.xa_index;
1825 		xas_store(&xas, entry);
1826 		xas_clear_mark(&xas, XA_FREE_MARK);
1827 	} while (__xas_nomem(&xas, gfp));
1828 
1829 	return xas_error(&xas);
1830 }
1831 EXPORT_SYMBOL(__xa_alloc);
1832 
1833 /**
1834  * __xa_alloc_cyclic() - Find somewhere to store this entry in the XArray.
1835  * @xa: XArray.
1836  * @id: Pointer to ID.
1837  * @entry: New entry.
1838  * @limit: Range of allocated ID.
1839  * @next: Pointer to next ID to allocate.
1840  * @gfp: Memory allocation flags.
1841  *
1842  * Finds an empty entry in @xa between @limit.min and @limit.max,
1843  * stores the index into the @id pointer, then stores the entry at
1844  * that index.  A concurrent lookup will not see an uninitialised @id.
1845  * The search for an empty entry will start at @next and will wrap
1846  * around if necessary.
1847  *
1848  * Context: Any context.  Expects xa_lock to be held on entry.  May
1849  * release and reacquire xa_lock if @gfp flags permit.
1850  * Return: 0 if the allocation succeeded without wrapping.  1 if the
1851  * allocation succeeded after wrapping, -ENOMEM if memory could not be
1852  * allocated or -EBUSY if there are no free entries in @limit.
1853  */
1854 int __xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
1855 		struct xa_limit limit, u32 *next, gfp_t gfp)
1856 {
1857 	u32 min = limit.min;
1858 	int ret;
1859 
1860 	limit.min = max(min, *next);
1861 	ret = __xa_alloc(xa, id, entry, limit, gfp);
1862 	if ((xa->xa_flags & XA_FLAGS_ALLOC_WRAPPED) && ret == 0) {
1863 		xa->xa_flags &= ~XA_FLAGS_ALLOC_WRAPPED;
1864 		ret = 1;
1865 	}
1866 
1867 	if (ret < 0 && limit.min > min) {
1868 		limit.min = min;
1869 		ret = __xa_alloc(xa, id, entry, limit, gfp);
1870 		if (ret == 0)
1871 			ret = 1;
1872 	}
1873 
1874 	if (ret >= 0) {
1875 		*next = *id + 1;
1876 		if (*next == 0)
1877 			xa->xa_flags |= XA_FLAGS_ALLOC_WRAPPED;
1878 	}
1879 	return ret;
1880 }
1881 EXPORT_SYMBOL(__xa_alloc_cyclic);
1882 
1883 /**
1884  * __xa_set_mark() - Set this mark on this entry while locked.
1885  * @xa: XArray.
1886  * @index: Index of entry.
1887  * @mark: Mark number.
1888  *
1889  * Attempting to set a mark on a %NULL entry does not succeed.
1890  *
1891  * Context: Any context.  Expects xa_lock to be held on entry.
1892  */
1893 void __xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1894 {
1895 	XA_STATE(xas, xa, index);
1896 	void *entry = xas_load(&xas);
1897 
1898 	if (entry)
1899 		xas_set_mark(&xas, mark);
1900 }
1901 EXPORT_SYMBOL(__xa_set_mark);
1902 
1903 /**
1904  * __xa_clear_mark() - Clear this mark on this entry while locked.
1905  * @xa: XArray.
1906  * @index: Index of entry.
1907  * @mark: Mark number.
1908  *
1909  * Context: Any context.  Expects xa_lock to be held on entry.
1910  */
1911 void __xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1912 {
1913 	XA_STATE(xas, xa, index);
1914 	void *entry = xas_load(&xas);
1915 
1916 	if (entry)
1917 		xas_clear_mark(&xas, mark);
1918 }
1919 EXPORT_SYMBOL(__xa_clear_mark);
1920 
1921 /**
1922  * xa_get_mark() - Inquire whether this mark is set on this entry.
1923  * @xa: XArray.
1924  * @index: Index of entry.
1925  * @mark: Mark number.
1926  *
1927  * This function uses the RCU read lock, so the result may be out of date
1928  * by the time it returns.  If you need the result to be stable, use a lock.
1929  *
1930  * Context: Any context.  Takes and releases the RCU lock.
1931  * Return: True if the entry at @index has this mark set, false if it doesn't.
1932  */
1933 bool xa_get_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1934 {
1935 	XA_STATE(xas, xa, index);
1936 	void *entry;
1937 
1938 	rcu_read_lock();
1939 	entry = xas_start(&xas);
1940 	while (xas_get_mark(&xas, mark)) {
1941 		if (!xa_is_node(entry))
1942 			goto found;
1943 		entry = xas_descend(&xas, xa_to_node(entry));
1944 	}
1945 	rcu_read_unlock();
1946 	return false;
1947  found:
1948 	rcu_read_unlock();
1949 	return true;
1950 }
1951 EXPORT_SYMBOL(xa_get_mark);
1952 
1953 /**
1954  * xa_set_mark() - Set this mark on this entry.
1955  * @xa: XArray.
1956  * @index: Index of entry.
1957  * @mark: Mark number.
1958  *
1959  * Attempting to set a mark on a %NULL entry does not succeed.
1960  *
1961  * Context: Process context.  Takes and releases the xa_lock.
1962  */
1963 void xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1964 {
1965 	xa_lock(xa);
1966 	__xa_set_mark(xa, index, mark);
1967 	xa_unlock(xa);
1968 }
1969 EXPORT_SYMBOL(xa_set_mark);
1970 
1971 /**
1972  * xa_clear_mark() - Clear this mark on this entry.
1973  * @xa: XArray.
1974  * @index: Index of entry.
1975  * @mark: Mark number.
1976  *
1977  * Clearing a mark always succeeds.
1978  *
1979  * Context: Process context.  Takes and releases the xa_lock.
1980  */
1981 void xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1982 {
1983 	xa_lock(xa);
1984 	__xa_clear_mark(xa, index, mark);
1985 	xa_unlock(xa);
1986 }
1987 EXPORT_SYMBOL(xa_clear_mark);
1988 
1989 /**
1990  * xa_find() - Search the XArray for an entry.
1991  * @xa: XArray.
1992  * @indexp: Pointer to an index.
1993  * @max: Maximum index to search to.
1994  * @filter: Selection criterion.
1995  *
1996  * Finds the entry in @xa which matches the @filter, and has the lowest
1997  * index that is at least @indexp and no more than @max.
1998  * If an entry is found, @indexp is updated to be the index of the entry.
1999  * This function is protected by the RCU read lock, so it may not find
2000  * entries which are being simultaneously added.  It will not return an
2001  * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find().
2002  *
2003  * Context: Any context.  Takes and releases the RCU lock.
2004  * Return: The entry, if found, otherwise %NULL.
2005  */
2006 void *xa_find(struct xarray *xa, unsigned long *indexp,
2007 			unsigned long max, xa_mark_t filter)
2008 {
2009 	XA_STATE(xas, xa, *indexp);
2010 	void *entry;
2011 
2012 	rcu_read_lock();
2013 	do {
2014 		if ((__force unsigned int)filter < XA_MAX_MARKS)
2015 			entry = xas_find_marked(&xas, max, filter);
2016 		else
2017 			entry = xas_find(&xas, max);
2018 	} while (xas_retry(&xas, entry));
2019 	rcu_read_unlock();
2020 
2021 	if (entry)
2022 		*indexp = xas.xa_index;
2023 	return entry;
2024 }
2025 EXPORT_SYMBOL(xa_find);
2026 
2027 static bool xas_sibling(struct xa_state *xas)
2028 {
2029 	struct xa_node *node = xas->xa_node;
2030 	unsigned long mask;
2031 
2032 	if (!IS_ENABLED(CONFIG_XARRAY_MULTI) || !node)
2033 		return false;
2034 	mask = (XA_CHUNK_SIZE << node->shift) - 1;
2035 	return (xas->xa_index & mask) >
2036 		((unsigned long)xas->xa_offset << node->shift);
2037 }
2038 
2039 /**
2040  * xa_find_after() - Search the XArray for a present entry.
2041  * @xa: XArray.
2042  * @indexp: Pointer to an index.
2043  * @max: Maximum index to search to.
2044  * @filter: Selection criterion.
2045  *
2046  * Finds the entry in @xa which matches the @filter and has the lowest
2047  * index that is above @indexp and no more than @max.
2048  * If an entry is found, @indexp is updated to be the index of the entry.
2049  * This function is protected by the RCU read lock, so it may miss entries
2050  * which are being simultaneously added.  It will not return an
2051  * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find().
2052  *
2053  * Context: Any context.  Takes and releases the RCU lock.
2054  * Return: The pointer, if found, otherwise %NULL.
2055  */
2056 void *xa_find_after(struct xarray *xa, unsigned long *indexp,
2057 			unsigned long max, xa_mark_t filter)
2058 {
2059 	XA_STATE(xas, xa, *indexp + 1);
2060 	void *entry;
2061 
2062 	if (xas.xa_index == 0)
2063 		return NULL;
2064 
2065 	rcu_read_lock();
2066 	for (;;) {
2067 		if ((__force unsigned int)filter < XA_MAX_MARKS)
2068 			entry = xas_find_marked(&xas, max, filter);
2069 		else
2070 			entry = xas_find(&xas, max);
2071 
2072 		if (xas_invalid(&xas))
2073 			break;
2074 		if (xas_sibling(&xas))
2075 			continue;
2076 		if (!xas_retry(&xas, entry))
2077 			break;
2078 	}
2079 	rcu_read_unlock();
2080 
2081 	if (entry)
2082 		*indexp = xas.xa_index;
2083 	return entry;
2084 }
2085 EXPORT_SYMBOL(xa_find_after);
2086 
2087 static unsigned int xas_extract_present(struct xa_state *xas, void **dst,
2088 			unsigned long max, unsigned int n)
2089 {
2090 	void *entry;
2091 	unsigned int i = 0;
2092 
2093 	rcu_read_lock();
2094 	xas_for_each(xas, entry, max) {
2095 		if (xas_retry(xas, entry))
2096 			continue;
2097 		dst[i++] = entry;
2098 		if (i == n)
2099 			break;
2100 	}
2101 	rcu_read_unlock();
2102 
2103 	return i;
2104 }
2105 
2106 static unsigned int xas_extract_marked(struct xa_state *xas, void **dst,
2107 			unsigned long max, unsigned int n, xa_mark_t mark)
2108 {
2109 	void *entry;
2110 	unsigned int i = 0;
2111 
2112 	rcu_read_lock();
2113 	xas_for_each_marked(xas, entry, max, mark) {
2114 		if (xas_retry(xas, entry))
2115 			continue;
2116 		dst[i++] = entry;
2117 		if (i == n)
2118 			break;
2119 	}
2120 	rcu_read_unlock();
2121 
2122 	return i;
2123 }
2124 
2125 /**
2126  * xa_extract() - Copy selected entries from the XArray into a normal array.
2127  * @xa: The source XArray to copy from.
2128  * @dst: The buffer to copy entries into.
2129  * @start: The first index in the XArray eligible to be selected.
2130  * @max: The last index in the XArray eligible to be selected.
2131  * @n: The maximum number of entries to copy.
2132  * @filter: Selection criterion.
2133  *
2134  * Copies up to @n entries that match @filter from the XArray.  The
2135  * copied entries will have indices between @start and @max, inclusive.
2136  *
2137  * The @filter may be an XArray mark value, in which case entries which are
2138  * marked with that mark will be copied.  It may also be %XA_PRESENT, in
2139  * which case all entries which are not %NULL will be copied.
2140  *
2141  * The entries returned may not represent a snapshot of the XArray at a
2142  * moment in time.  For example, if another thread stores to index 5, then
2143  * index 10, calling xa_extract() may return the old contents of index 5
2144  * and the new contents of index 10.  Indices not modified while this
2145  * function is running will not be skipped.
2146  *
2147  * If you need stronger guarantees, holding the xa_lock across calls to this
2148  * function will prevent concurrent modification.
2149  *
2150  * Context: Any context.  Takes and releases the RCU lock.
2151  * Return: The number of entries copied.
2152  */
2153 unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,
2154 			unsigned long max, unsigned int n, xa_mark_t filter)
2155 {
2156 	XA_STATE(xas, xa, start);
2157 
2158 	if (!n)
2159 		return 0;
2160 
2161 	if ((__force unsigned int)filter < XA_MAX_MARKS)
2162 		return xas_extract_marked(&xas, dst, max, n, filter);
2163 	return xas_extract_present(&xas, dst, max, n);
2164 }
2165 EXPORT_SYMBOL(xa_extract);
2166 
2167 /**
2168  * xa_delete_node() - Private interface for workingset code.
2169  * @node: Node to be removed from the tree.
2170  * @update: Function to call to update ancestor nodes.
2171  *
2172  * Context: xa_lock must be held on entry and will not be released.
2173  */
2174 void xa_delete_node(struct xa_node *node, xa_update_node_t update)
2175 {
2176 	struct xa_state xas = {
2177 		.xa = node->array,
2178 		.xa_index = (unsigned long)node->offset <<
2179 				(node->shift + XA_CHUNK_SHIFT),
2180 		.xa_shift = node->shift + XA_CHUNK_SHIFT,
2181 		.xa_offset = node->offset,
2182 		.xa_node = xa_parent_locked(node->array, node),
2183 		.xa_update = update,
2184 	};
2185 
2186 	xas_store(&xas, NULL);
2187 }
2188 EXPORT_SYMBOL_GPL(xa_delete_node);	/* For the benefit of the test suite */
2189 
2190 /**
2191  * xa_destroy() - Free all internal data structures.
2192  * @xa: XArray.
2193  *
2194  * After calling this function, the XArray is empty and has freed all memory
2195  * allocated for its internal data structures.  You are responsible for
2196  * freeing the objects referenced by the XArray.
2197  *
2198  * Context: Any context.  Takes and releases the xa_lock, interrupt-safe.
2199  */
2200 void xa_destroy(struct xarray *xa)
2201 {
2202 	XA_STATE(xas, xa, 0);
2203 	unsigned long flags;
2204 	void *entry;
2205 
2206 	xas.xa_node = NULL;
2207 	xas_lock_irqsave(&xas, flags);
2208 	entry = xa_head_locked(xa);
2209 	RCU_INIT_POINTER(xa->xa_head, NULL);
2210 	xas_init_marks(&xas);
2211 	if (xa_zero_busy(xa))
2212 		xa_mark_clear(xa, XA_FREE_MARK);
2213 	/* lockdep checks we're still holding the lock in xas_free_nodes() */
2214 	if (xa_is_node(entry))
2215 		xas_free_nodes(&xas, xa_to_node(entry));
2216 	xas_unlock_irqrestore(&xas, flags);
2217 }
2218 EXPORT_SYMBOL(xa_destroy);
2219 
2220 #ifdef XA_DEBUG
2221 void xa_dump_node(const struct xa_node *node)
2222 {
2223 	unsigned i, j;
2224 
2225 	if (!node)
2226 		return;
2227 	if ((unsigned long)node & 3) {
2228 		pr_cont("node %px\n", node);
2229 		return;
2230 	}
2231 
2232 	pr_cont("node %px %s %d parent %px shift %d count %d values %d "
2233 		"array %px list %px %px marks",
2234 		node, node->parent ? "offset" : "max", node->offset,
2235 		node->parent, node->shift, node->count, node->nr_values,
2236 		node->array, node->private_list.prev, node->private_list.next);
2237 	for (i = 0; i < XA_MAX_MARKS; i++)
2238 		for (j = 0; j < XA_MARK_LONGS; j++)
2239 			pr_cont(" %lx", node->marks[i][j]);
2240 	pr_cont("\n");
2241 }
2242 
2243 void xa_dump_index(unsigned long index, unsigned int shift)
2244 {
2245 	if (!shift)
2246 		pr_info("%lu: ", index);
2247 	else if (shift >= BITS_PER_LONG)
2248 		pr_info("0-%lu: ", ~0UL);
2249 	else
2250 		pr_info("%lu-%lu: ", index, index | ((1UL << shift) - 1));
2251 }
2252 
2253 void xa_dump_entry(const void *entry, unsigned long index, unsigned long shift)
2254 {
2255 	if (!entry)
2256 		return;
2257 
2258 	xa_dump_index(index, shift);
2259 
2260 	if (xa_is_node(entry)) {
2261 		if (shift == 0) {
2262 			pr_cont("%px\n", entry);
2263 		} else {
2264 			unsigned long i;
2265 			struct xa_node *node = xa_to_node(entry);
2266 			xa_dump_node(node);
2267 			for (i = 0; i < XA_CHUNK_SIZE; i++)
2268 				xa_dump_entry(node->slots[i],
2269 				      index + (i << node->shift), node->shift);
2270 		}
2271 	} else if (xa_is_value(entry))
2272 		pr_cont("value %ld (0x%lx) [%px]\n", xa_to_value(entry),
2273 						xa_to_value(entry), entry);
2274 	else if (!xa_is_internal(entry))
2275 		pr_cont("%px\n", entry);
2276 	else if (xa_is_retry(entry))
2277 		pr_cont("retry (%ld)\n", xa_to_internal(entry));
2278 	else if (xa_is_sibling(entry))
2279 		pr_cont("sibling (slot %ld)\n", xa_to_sibling(entry));
2280 	else if (xa_is_zero(entry))
2281 		pr_cont("zero (%ld)\n", xa_to_internal(entry));
2282 	else
2283 		pr_cont("UNKNOWN ENTRY (%px)\n", entry);
2284 }
2285 
2286 void xa_dump(const struct xarray *xa)
2287 {
2288 	void *entry = xa->xa_head;
2289 	unsigned int shift = 0;
2290 
2291 	pr_info("xarray: %px head %px flags %x marks %d %d %d\n", xa, entry,
2292 			xa->xa_flags, xa_marked(xa, XA_MARK_0),
2293 			xa_marked(xa, XA_MARK_1), xa_marked(xa, XA_MARK_2));
2294 	if (xa_is_node(entry))
2295 		shift = xa_to_node(entry)->shift + XA_CHUNK_SHIFT;
2296 	xa_dump_entry(entry, 0, shift);
2297 }
2298 #endif
2299