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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 
xa_lock_type(const struct xarray * xa)31 static inline unsigned int xa_lock_type(const struct xarray *xa)
32 {
33 	return (__force unsigned int)xa->xa_flags & 3;
34 }
35 
xas_lock_type(struct xa_state * xas,unsigned int lock_type)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 
xas_unlock_type(struct xa_state * xas,unsigned int lock_type)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 
xa_track_free(const struct xarray * xa)56 static inline bool xa_track_free(const struct xarray *xa)
57 {
58 	return xa->xa_flags & XA_FLAGS_TRACK_FREE;
59 }
60 
xa_zero_busy(const struct xarray * xa)61 static inline bool xa_zero_busy(const struct xarray *xa)
62 {
63 	return xa->xa_flags & XA_FLAGS_ZERO_BUSY;
64 }
65 
xa_mark_set(struct xarray * xa,xa_mark_t mark)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 
xa_mark_clear(struct xarray * xa,xa_mark_t mark)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 
node_marks(struct xa_node * node,xa_mark_t mark)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 
node_get_mark(struct xa_node * node,unsigned int offset,xa_mark_t mark)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 */
node_set_mark(struct xa_node * node,unsigned int offset,xa_mark_t mark)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 */
node_clear_mark(struct xa_node * node,unsigned int offset,xa_mark_t mark)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 
node_any_mark(struct xa_node * node,xa_mark_t mark)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 
node_mark_all(struct xa_node * node,xa_mark_t mark)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  */
xas_squash_marks(const struct xa_state * xas)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 */
get_offset(unsigned long index,struct xa_node * node)142 static unsigned int get_offset(unsigned long index, struct xa_node *node)
143 {
144 	return (index >> node->shift) & XA_CHUNK_MASK;
145 }
146 
xas_set_offset(struct xa_state * xas)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) */
xas_move_index(struct xa_state * xas,unsigned long offset)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 
xas_advance(struct xa_state * xas)160 static void xas_advance(struct xa_state *xas)
161 {
162 	xas->xa_offset++;
163 	xas_move_index(xas, xas->xa_offset);
164 }
165 
set_bounds(struct xa_state * xas)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  */
xas_start(struct xa_state * xas)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 
xas_descend(struct xa_state * xas,struct xa_node * node)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  */
xas_load(struct xa_state * xas)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 
xa_node_free(struct xa_node * node)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  */
xas_destroy(struct xa_state * xas)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  */
xas_nomem(struct xa_state * xas,gfp_t gfp)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  */
__xas_nomem(struct xa_state * xas,gfp_t gfp)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 
xas_update(struct xa_state * xas,struct xa_node * node)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 
xas_alloc(struct xa_state * xas,unsigned int shift)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 */
xas_size(const struct xa_state * xas)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  */
xas_max(struct xa_state * xas)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 */
max_index(void * entry)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 
xas_shrink(struct xa_state * xas)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  */
xas_delete_node(struct xa_state * xas)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  */
xas_free_nodes(struct xa_state * xas,struct xa_node * top)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  */
xas_expand(struct xa_state * xas,void * head)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  */
xas_create(struct xa_state * xas,bool allow_root)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  */
xas_create_range(struct xa_state * xas)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 			if (node->shift >= shift)
726 				break;
727 			xas->xa_node = xa_parent_locked(xas->xa, node);
728 			xas->xa_offset = node->offset - 1;
729 			if (node->offset != 0)
730 				break;
731 		}
732 	}
733 
734 restore:
735 	xas->xa_shift = shift;
736 	xas->xa_sibs = sibs;
737 	xas->xa_index = index;
738 	return;
739 success:
740 	xas->xa_index = index;
741 	if (xas->xa_node)
742 		xas_set_offset(xas);
743 }
744 EXPORT_SYMBOL_GPL(xas_create_range);
745 
update_node(struct xa_state * xas,struct xa_node * node,int count,int values)746 static void update_node(struct xa_state *xas, struct xa_node *node,
747 		int count, int values)
748 {
749 	if (!node || (!count && !values))
750 		return;
751 
752 	node->count += count;
753 	node->nr_values += values;
754 	XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
755 	XA_NODE_BUG_ON(node, node->nr_values > XA_CHUNK_SIZE);
756 	xas_update(xas, node);
757 	if (count < 0)
758 		xas_delete_node(xas);
759 }
760 
761 /**
762  * xas_store() - Store this entry in the XArray.
763  * @xas: XArray operation state.
764  * @entry: New entry.
765  *
766  * If @xas is operating on a multi-index entry, the entry returned by this
767  * function is essentially meaningless (it may be an internal entry or it
768  * may be %NULL, even if there are non-NULL entries at some of the indices
769  * covered by the range).  This is not a problem for any current users,
770  * and can be changed if needed.
771  *
772  * Return: The old entry at this index.
773  */
xas_store(struct xa_state * xas,void * entry)774 void *xas_store(struct xa_state *xas, void *entry)
775 {
776 	struct xa_node *node;
777 	void __rcu **slot = &xas->xa->xa_head;
778 	unsigned int offset, max;
779 	int count = 0;
780 	int values = 0;
781 	void *first, *next;
782 	bool value = xa_is_value(entry);
783 
784 	if (entry) {
785 		bool allow_root = !xa_is_node(entry) && !xa_is_zero(entry);
786 		first = xas_create(xas, allow_root);
787 	} else {
788 		first = xas_load(xas);
789 	}
790 
791 	if (xas_invalid(xas))
792 		return first;
793 	node = xas->xa_node;
794 	if (node && (xas->xa_shift < node->shift))
795 		xas->xa_sibs = 0;
796 	if ((first == entry) && !xas->xa_sibs)
797 		return first;
798 
799 	next = first;
800 	offset = xas->xa_offset;
801 	max = xas->xa_offset + xas->xa_sibs;
802 	if (node) {
803 		slot = &node->slots[offset];
804 		if (xas->xa_sibs)
805 			xas_squash_marks(xas);
806 	}
807 	if (!entry)
808 		xas_init_marks(xas);
809 
810 	for (;;) {
811 		/*
812 		 * Must clear the marks before setting the entry to NULL,
813 		 * otherwise xas_for_each_marked may find a NULL entry and
814 		 * stop early.  rcu_assign_pointer contains a release barrier
815 		 * so the mark clearing will appear to happen before the
816 		 * entry is set to NULL.
817 		 */
818 		rcu_assign_pointer(*slot, entry);
819 		if (xa_is_node(next) && (!node || node->shift))
820 			xas_free_nodes(xas, xa_to_node(next));
821 		if (!node)
822 			break;
823 		count += !next - !entry;
824 		values += !xa_is_value(first) - !value;
825 		if (entry) {
826 			if (offset == max)
827 				break;
828 			if (!xa_is_sibling(entry))
829 				entry = xa_mk_sibling(xas->xa_offset);
830 		} else {
831 			if (offset == XA_CHUNK_MASK)
832 				break;
833 		}
834 		next = xa_entry_locked(xas->xa, node, ++offset);
835 		if (!xa_is_sibling(next)) {
836 			if (!entry && (offset > max))
837 				break;
838 			first = next;
839 		}
840 		slot++;
841 	}
842 
843 	update_node(xas, node, count, values);
844 	return first;
845 }
846 EXPORT_SYMBOL_GPL(xas_store);
847 
848 /**
849  * xas_get_mark() - Returns the state of this mark.
850  * @xas: XArray operation state.
851  * @mark: Mark number.
852  *
853  * Return: true if the mark is set, false if the mark is clear or @xas
854  * is in an error state.
855  */
xas_get_mark(const struct xa_state * xas,xa_mark_t mark)856 bool xas_get_mark(const struct xa_state *xas, xa_mark_t mark)
857 {
858 	if (xas_invalid(xas))
859 		return false;
860 	if (!xas->xa_node)
861 		return xa_marked(xas->xa, mark);
862 	return node_get_mark(xas->xa_node, xas->xa_offset, mark);
863 }
864 EXPORT_SYMBOL_GPL(xas_get_mark);
865 
866 /**
867  * xas_set_mark() - Sets the mark on this entry and its parents.
868  * @xas: XArray operation state.
869  * @mark: Mark number.
870  *
871  * Sets the specified mark on this entry, and walks up the tree setting it
872  * on all the ancestor entries.  Does nothing if @xas has not been walked to
873  * an entry, or is in an error state.
874  */
xas_set_mark(const struct xa_state * xas,xa_mark_t mark)875 void xas_set_mark(const struct xa_state *xas, xa_mark_t mark)
876 {
877 	struct xa_node *node = xas->xa_node;
878 	unsigned int offset = xas->xa_offset;
879 
880 	if (xas_invalid(xas))
881 		return;
882 
883 	while (node) {
884 		if (node_set_mark(node, offset, mark))
885 			return;
886 		offset = node->offset;
887 		node = xa_parent_locked(xas->xa, node);
888 	}
889 
890 	if (!xa_marked(xas->xa, mark))
891 		xa_mark_set(xas->xa, mark);
892 }
893 EXPORT_SYMBOL_GPL(xas_set_mark);
894 
895 /**
896  * xas_clear_mark() - Clears the mark on this entry and its parents.
897  * @xas: XArray operation state.
898  * @mark: Mark number.
899  *
900  * Clears the specified mark on this entry, and walks back to the head
901  * attempting to clear it on all the ancestor entries.  Does nothing if
902  * @xas has not been walked to an entry, or is in an error state.
903  */
xas_clear_mark(const struct xa_state * xas,xa_mark_t mark)904 void xas_clear_mark(const struct xa_state *xas, xa_mark_t mark)
905 {
906 	struct xa_node *node = xas->xa_node;
907 	unsigned int offset = xas->xa_offset;
908 
909 	if (xas_invalid(xas))
910 		return;
911 
912 	while (node) {
913 		if (!node_clear_mark(node, offset, mark))
914 			return;
915 		if (node_any_mark(node, mark))
916 			return;
917 
918 		offset = node->offset;
919 		node = xa_parent_locked(xas->xa, node);
920 	}
921 
922 	if (xa_marked(xas->xa, mark))
923 		xa_mark_clear(xas->xa, mark);
924 }
925 EXPORT_SYMBOL_GPL(xas_clear_mark);
926 
927 /**
928  * xas_init_marks() - Initialise all marks for the entry
929  * @xas: Array operations state.
930  *
931  * Initialise all marks for the entry specified by @xas.  If we're tracking
932  * free entries with a mark, we need to set it on all entries.  All other
933  * marks are cleared.
934  *
935  * This implementation is not as efficient as it could be; we may walk
936  * up the tree multiple times.
937  */
xas_init_marks(const struct xa_state * xas)938 void xas_init_marks(const struct xa_state *xas)
939 {
940 	xa_mark_t mark = 0;
941 
942 	for (;;) {
943 		if (xa_track_free(xas->xa) && mark == XA_FREE_MARK)
944 			xas_set_mark(xas, mark);
945 		else
946 			xas_clear_mark(xas, mark);
947 		if (mark == XA_MARK_MAX)
948 			break;
949 		mark_inc(mark);
950 	}
951 }
952 EXPORT_SYMBOL_GPL(xas_init_marks);
953 
954 #ifdef CONFIG_XARRAY_MULTI
node_get_marks(struct xa_node * node,unsigned int offset)955 static unsigned int node_get_marks(struct xa_node *node, unsigned int offset)
956 {
957 	unsigned int marks = 0;
958 	xa_mark_t mark = XA_MARK_0;
959 
960 	for (;;) {
961 		if (node_get_mark(node, offset, mark))
962 			marks |= 1 << (__force unsigned int)mark;
963 		if (mark == XA_MARK_MAX)
964 			break;
965 		mark_inc(mark);
966 	}
967 
968 	return marks;
969 }
970 
node_set_marks(struct xa_node * node,unsigned int offset,struct xa_node * child,unsigned int marks)971 static void node_set_marks(struct xa_node *node, unsigned int offset,
972 			struct xa_node *child, unsigned int marks)
973 {
974 	xa_mark_t mark = XA_MARK_0;
975 
976 	for (;;) {
977 		if (marks & (1 << (__force unsigned int)mark)) {
978 			node_set_mark(node, offset, mark);
979 			if (child)
980 				node_mark_all(child, mark);
981 		}
982 		if (mark == XA_MARK_MAX)
983 			break;
984 		mark_inc(mark);
985 	}
986 }
987 
988 /**
989  * xas_split_alloc() - Allocate memory for splitting an entry.
990  * @xas: XArray operation state.
991  * @entry: New entry which will be stored in the array.
992  * @order: New entry order.
993  * @gfp: Memory allocation flags.
994  *
995  * This function should be called before calling xas_split().
996  * If necessary, it will allocate new nodes (and fill them with @entry)
997  * to prepare for the upcoming split of an entry of @order size into
998  * entries of the order stored in the @xas.
999  *
1000  * Context: May sleep if @gfp flags permit.
1001  */
xas_split_alloc(struct xa_state * xas,void * entry,unsigned int order,gfp_t gfp)1002 void xas_split_alloc(struct xa_state *xas, void *entry, unsigned int order,
1003 		gfp_t gfp)
1004 {
1005 	unsigned int sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1006 	unsigned int mask = xas->xa_sibs;
1007 
1008 	/* XXX: no support for splitting really large entries yet */
1009 	if (WARN_ON(xas->xa_shift + 2 * XA_CHUNK_SHIFT < order))
1010 		goto nomem;
1011 	if (xas->xa_shift + XA_CHUNK_SHIFT > order)
1012 		return;
1013 
1014 	do {
1015 		unsigned int i;
1016 		void *sibling = NULL;
1017 		struct xa_node *node;
1018 
1019 		node = kmem_cache_alloc(radix_tree_node_cachep, gfp);
1020 		if (!node)
1021 			goto nomem;
1022 		node->array = xas->xa;
1023 		for (i = 0; i < XA_CHUNK_SIZE; i++) {
1024 			if ((i & mask) == 0) {
1025 				RCU_INIT_POINTER(node->slots[i], entry);
1026 				sibling = xa_mk_sibling(i);
1027 			} else {
1028 				RCU_INIT_POINTER(node->slots[i], sibling);
1029 			}
1030 		}
1031 		RCU_INIT_POINTER(node->parent, xas->xa_alloc);
1032 		xas->xa_alloc = node;
1033 	} while (sibs-- > 0);
1034 
1035 	return;
1036 nomem:
1037 	xas_destroy(xas);
1038 	xas_set_err(xas, -ENOMEM);
1039 }
1040 EXPORT_SYMBOL_GPL(xas_split_alloc);
1041 
1042 /**
1043  * xas_split() - Split a multi-index entry into smaller entries.
1044  * @xas: XArray operation state.
1045  * @entry: New entry to store in the array.
1046  * @order: New entry order.
1047  *
1048  * The value in the entry is copied to all the replacement entries.
1049  *
1050  * Context: Any context.  The caller should hold the xa_lock.
1051  */
xas_split(struct xa_state * xas,void * entry,unsigned int order)1052 void xas_split(struct xa_state *xas, void *entry, unsigned int order)
1053 {
1054 	unsigned int sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1055 	unsigned int offset, marks;
1056 	struct xa_node *node;
1057 	void *curr = xas_load(xas);
1058 	int values = 0;
1059 
1060 	node = xas->xa_node;
1061 	if (xas_top(node))
1062 		return;
1063 
1064 	marks = node_get_marks(node, xas->xa_offset);
1065 
1066 	offset = xas->xa_offset + sibs;
1067 	do {
1068 		if (xas->xa_shift < node->shift) {
1069 			struct xa_node *child = xas->xa_alloc;
1070 
1071 			xas->xa_alloc = rcu_dereference_raw(child->parent);
1072 			child->shift = node->shift - XA_CHUNK_SHIFT;
1073 			child->offset = offset;
1074 			child->count = XA_CHUNK_SIZE;
1075 			child->nr_values = xa_is_value(entry) ?
1076 					XA_CHUNK_SIZE : 0;
1077 			RCU_INIT_POINTER(child->parent, node);
1078 			node_set_marks(node, offset, child, marks);
1079 			rcu_assign_pointer(node->slots[offset],
1080 					xa_mk_node(child));
1081 			if (xa_is_value(curr))
1082 				values--;
1083 			xas_update(xas, child);
1084 		} else {
1085 			unsigned int canon = offset - xas->xa_sibs;
1086 
1087 			node_set_marks(node, canon, NULL, marks);
1088 			rcu_assign_pointer(node->slots[canon], entry);
1089 			while (offset > canon)
1090 				rcu_assign_pointer(node->slots[offset--],
1091 						xa_mk_sibling(canon));
1092 			values += (xa_is_value(entry) - xa_is_value(curr)) *
1093 					(xas->xa_sibs + 1);
1094 		}
1095 	} while (offset-- > xas->xa_offset);
1096 
1097 	node->nr_values += values;
1098 	xas_update(xas, node);
1099 }
1100 EXPORT_SYMBOL_GPL(xas_split);
1101 #endif
1102 
1103 /**
1104  * xas_pause() - Pause a walk to drop a lock.
1105  * @xas: XArray operation state.
1106  *
1107  * Some users need to pause a walk and drop the lock they're holding in
1108  * order to yield to a higher priority thread or carry out an operation
1109  * on an entry.  Those users should call this function before they drop
1110  * the lock.  It resets the @xas to be suitable for the next iteration
1111  * of the loop after the user has reacquired the lock.  If most entries
1112  * found during a walk require you to call xas_pause(), the xa_for_each()
1113  * iterator may be more appropriate.
1114  *
1115  * Note that xas_pause() only works for forward iteration.  If a user needs
1116  * to pause a reverse iteration, we will need a xas_pause_rev().
1117  */
xas_pause(struct xa_state * xas)1118 void xas_pause(struct xa_state *xas)
1119 {
1120 	struct xa_node *node = xas->xa_node;
1121 
1122 	if (xas_invalid(xas))
1123 		return;
1124 
1125 	xas->xa_node = XAS_RESTART;
1126 	if (node) {
1127 		unsigned long offset = xas->xa_offset;
1128 		while (++offset < XA_CHUNK_SIZE) {
1129 			if (!xa_is_sibling(xa_entry(xas->xa, node, offset)))
1130 				break;
1131 		}
1132 		xas->xa_index += (offset - xas->xa_offset) << node->shift;
1133 		if (xas->xa_index == 0)
1134 			xas->xa_node = XAS_BOUNDS;
1135 	} else {
1136 		xas->xa_index++;
1137 	}
1138 }
1139 EXPORT_SYMBOL_GPL(xas_pause);
1140 
1141 /*
1142  * __xas_prev() - Find the previous entry in the XArray.
1143  * @xas: XArray operation state.
1144  *
1145  * Helper function for xas_prev() which handles all the complex cases
1146  * out of line.
1147  */
__xas_prev(struct xa_state * xas)1148 void *__xas_prev(struct xa_state *xas)
1149 {
1150 	void *entry;
1151 
1152 	if (!xas_frozen(xas->xa_node))
1153 		xas->xa_index--;
1154 	if (!xas->xa_node)
1155 		return set_bounds(xas);
1156 	if (xas_not_node(xas->xa_node))
1157 		return xas_load(xas);
1158 
1159 	if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
1160 		xas->xa_offset--;
1161 
1162 	while (xas->xa_offset == 255) {
1163 		xas->xa_offset = xas->xa_node->offset - 1;
1164 		xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1165 		if (!xas->xa_node)
1166 			return set_bounds(xas);
1167 	}
1168 
1169 	for (;;) {
1170 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1171 		if (!xa_is_node(entry))
1172 			return entry;
1173 
1174 		xas->xa_node = xa_to_node(entry);
1175 		xas_set_offset(xas);
1176 	}
1177 }
1178 EXPORT_SYMBOL_GPL(__xas_prev);
1179 
1180 /*
1181  * __xas_next() - Find the next entry in the XArray.
1182  * @xas: XArray operation state.
1183  *
1184  * Helper function for xas_next() which handles all the complex cases
1185  * out of line.
1186  */
__xas_next(struct xa_state * xas)1187 void *__xas_next(struct xa_state *xas)
1188 {
1189 	void *entry;
1190 
1191 	if (!xas_frozen(xas->xa_node))
1192 		xas->xa_index++;
1193 	if (!xas->xa_node)
1194 		return set_bounds(xas);
1195 	if (xas_not_node(xas->xa_node))
1196 		return xas_load(xas);
1197 
1198 	if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
1199 		xas->xa_offset++;
1200 
1201 	while (xas->xa_offset == XA_CHUNK_SIZE) {
1202 		xas->xa_offset = xas->xa_node->offset + 1;
1203 		xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1204 		if (!xas->xa_node)
1205 			return set_bounds(xas);
1206 	}
1207 
1208 	for (;;) {
1209 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1210 		if (!xa_is_node(entry))
1211 			return entry;
1212 
1213 		xas->xa_node = xa_to_node(entry);
1214 		xas_set_offset(xas);
1215 	}
1216 }
1217 EXPORT_SYMBOL_GPL(__xas_next);
1218 
1219 /**
1220  * xas_find() - Find the next present entry in the XArray.
1221  * @xas: XArray operation state.
1222  * @max: Highest index to return.
1223  *
1224  * If the @xas has not yet been walked to an entry, return the entry
1225  * which has an index >= xas.xa_index.  If it has been walked, the entry
1226  * currently being pointed at has been processed, and so we move to the
1227  * next entry.
1228  *
1229  * If no entry is found and the array is smaller than @max, the iterator
1230  * is set to the smallest index not yet in the array.  This allows @xas
1231  * to be immediately passed to xas_store().
1232  *
1233  * Return: The entry, if found, otherwise %NULL.
1234  */
xas_find(struct xa_state * xas,unsigned long max)1235 void *xas_find(struct xa_state *xas, unsigned long max)
1236 {
1237 	void *entry;
1238 
1239 	if (xas_error(xas) || xas->xa_node == XAS_BOUNDS)
1240 		return NULL;
1241 	if (xas->xa_index > max)
1242 		return set_bounds(xas);
1243 
1244 	if (!xas->xa_node) {
1245 		xas->xa_index = 1;
1246 		return set_bounds(xas);
1247 	} else if (xas->xa_node == XAS_RESTART) {
1248 		entry = xas_load(xas);
1249 		if (entry || xas_not_node(xas->xa_node))
1250 			return entry;
1251 	} else if (!xas->xa_node->shift &&
1252 		    xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)) {
1253 		xas->xa_offset = ((xas->xa_index - 1) & XA_CHUNK_MASK) + 1;
1254 	}
1255 
1256 	xas_advance(xas);
1257 
1258 	while (xas->xa_node && (xas->xa_index <= max)) {
1259 		if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) {
1260 			xas->xa_offset = xas->xa_node->offset + 1;
1261 			xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1262 			continue;
1263 		}
1264 
1265 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1266 		if (xa_is_node(entry)) {
1267 			xas->xa_node = xa_to_node(entry);
1268 			xas->xa_offset = 0;
1269 			continue;
1270 		}
1271 		if (entry && !xa_is_sibling(entry))
1272 			return entry;
1273 
1274 		xas_advance(xas);
1275 	}
1276 
1277 	if (!xas->xa_node)
1278 		xas->xa_node = XAS_BOUNDS;
1279 	return NULL;
1280 }
1281 EXPORT_SYMBOL_GPL(xas_find);
1282 
1283 /**
1284  * xas_find_marked() - Find the next marked entry in the XArray.
1285  * @xas: XArray operation state.
1286  * @max: Highest index to return.
1287  * @mark: Mark number to search for.
1288  *
1289  * If the @xas has not yet been walked to an entry, return the marked entry
1290  * which has an index >= xas.xa_index.  If it has been walked, the entry
1291  * currently being pointed at has been processed, and so we return the
1292  * first marked entry with an index > xas.xa_index.
1293  *
1294  * If no marked entry is found and the array is smaller than @max, @xas is
1295  * set to the bounds state and xas->xa_index is set to the smallest index
1296  * not yet in the array.  This allows @xas to be immediately passed to
1297  * xas_store().
1298  *
1299  * If no entry is found before @max is reached, @xas is set to the restart
1300  * state.
1301  *
1302  * Return: The entry, if found, otherwise %NULL.
1303  */
xas_find_marked(struct xa_state * xas,unsigned long max,xa_mark_t mark)1304 void *xas_find_marked(struct xa_state *xas, unsigned long max, xa_mark_t mark)
1305 {
1306 	bool advance = true;
1307 	unsigned int offset;
1308 	void *entry;
1309 
1310 	if (xas_error(xas))
1311 		return NULL;
1312 	if (xas->xa_index > max)
1313 		goto max;
1314 
1315 	if (!xas->xa_node) {
1316 		xas->xa_index = 1;
1317 		goto out;
1318 	} else if (xas_top(xas->xa_node)) {
1319 		advance = false;
1320 		entry = xa_head(xas->xa);
1321 		xas->xa_node = NULL;
1322 		if (xas->xa_index > max_index(entry))
1323 			goto out;
1324 		if (!xa_is_node(entry)) {
1325 			if (xa_marked(xas->xa, mark))
1326 				return entry;
1327 			xas->xa_index = 1;
1328 			goto out;
1329 		}
1330 		xas->xa_node = xa_to_node(entry);
1331 		xas->xa_offset = xas->xa_index >> xas->xa_node->shift;
1332 	}
1333 
1334 	while (xas->xa_index <= max) {
1335 		if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) {
1336 			xas->xa_offset = xas->xa_node->offset + 1;
1337 			xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1338 			if (!xas->xa_node)
1339 				break;
1340 			advance = false;
1341 			continue;
1342 		}
1343 
1344 		if (!advance) {
1345 			entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1346 			if (xa_is_sibling(entry)) {
1347 				xas->xa_offset = xa_to_sibling(entry);
1348 				xas_move_index(xas, xas->xa_offset);
1349 			}
1350 		}
1351 
1352 		offset = xas_find_chunk(xas, advance, mark);
1353 		if (offset > xas->xa_offset) {
1354 			advance = false;
1355 			xas_move_index(xas, offset);
1356 			/* Mind the wrap */
1357 			if ((xas->xa_index - 1) >= max)
1358 				goto max;
1359 			xas->xa_offset = offset;
1360 			if (offset == XA_CHUNK_SIZE)
1361 				continue;
1362 		}
1363 
1364 		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1365 		if (!entry && !(xa_track_free(xas->xa) && mark == XA_FREE_MARK))
1366 			continue;
1367 		if (!xa_is_node(entry))
1368 			return entry;
1369 		xas->xa_node = xa_to_node(entry);
1370 		xas_set_offset(xas);
1371 	}
1372 
1373 out:
1374 	if (xas->xa_index > max)
1375 		goto max;
1376 	return set_bounds(xas);
1377 max:
1378 	xas->xa_node = XAS_RESTART;
1379 	return NULL;
1380 }
1381 EXPORT_SYMBOL_GPL(xas_find_marked);
1382 
1383 /**
1384  * xas_find_conflict() - Find the next present entry in a range.
1385  * @xas: XArray operation state.
1386  *
1387  * The @xas describes both a range and a position within that range.
1388  *
1389  * Context: Any context.  Expects xa_lock to be held.
1390  * Return: The next entry in the range covered by @xas or %NULL.
1391  */
xas_find_conflict(struct xa_state * xas)1392 void *xas_find_conflict(struct xa_state *xas)
1393 {
1394 	void *curr;
1395 
1396 	if (xas_error(xas))
1397 		return NULL;
1398 
1399 	if (!xas->xa_node)
1400 		return NULL;
1401 
1402 	if (xas_top(xas->xa_node)) {
1403 		curr = xas_start(xas);
1404 		if (!curr)
1405 			return NULL;
1406 		while (xa_is_node(curr)) {
1407 			struct xa_node *node = xa_to_node(curr);
1408 			curr = xas_descend(xas, node);
1409 		}
1410 		if (curr)
1411 			return curr;
1412 	}
1413 
1414 	if (xas->xa_node->shift > xas->xa_shift)
1415 		return NULL;
1416 
1417 	for (;;) {
1418 		if (xas->xa_node->shift == xas->xa_shift) {
1419 			if ((xas->xa_offset & xas->xa_sibs) == xas->xa_sibs)
1420 				break;
1421 		} else if (xas->xa_offset == XA_CHUNK_MASK) {
1422 			xas->xa_offset = xas->xa_node->offset;
1423 			xas->xa_node = xa_parent_locked(xas->xa, xas->xa_node);
1424 			if (!xas->xa_node)
1425 				break;
1426 			continue;
1427 		}
1428 		curr = xa_entry_locked(xas->xa, xas->xa_node, ++xas->xa_offset);
1429 		if (xa_is_sibling(curr))
1430 			continue;
1431 		while (xa_is_node(curr)) {
1432 			xas->xa_node = xa_to_node(curr);
1433 			xas->xa_offset = 0;
1434 			curr = xa_entry_locked(xas->xa, xas->xa_node, 0);
1435 		}
1436 		if (curr)
1437 			return curr;
1438 	}
1439 	xas->xa_offset -= xas->xa_sibs;
1440 	return NULL;
1441 }
1442 EXPORT_SYMBOL_GPL(xas_find_conflict);
1443 
1444 /**
1445  * xa_load() - Load an entry from an XArray.
1446  * @xa: XArray.
1447  * @index: index into array.
1448  *
1449  * Context: Any context.  Takes and releases the RCU lock.
1450  * Return: The entry at @index in @xa.
1451  */
xa_load(struct xarray * xa,unsigned long index)1452 void *xa_load(struct xarray *xa, unsigned long index)
1453 {
1454 	XA_STATE(xas, xa, index);
1455 	void *entry;
1456 
1457 	rcu_read_lock();
1458 	do {
1459 		entry = xas_load(&xas);
1460 		if (xa_is_zero(entry))
1461 			entry = NULL;
1462 	} while (xas_retry(&xas, entry));
1463 	rcu_read_unlock();
1464 
1465 	return entry;
1466 }
1467 EXPORT_SYMBOL(xa_load);
1468 
xas_result(struct xa_state * xas,void * curr)1469 static void *xas_result(struct xa_state *xas, void *curr)
1470 {
1471 	if (xa_is_zero(curr))
1472 		return NULL;
1473 	if (xas_error(xas))
1474 		curr = xas->xa_node;
1475 	return curr;
1476 }
1477 
1478 /**
1479  * __xa_erase() - Erase this entry from the XArray while locked.
1480  * @xa: XArray.
1481  * @index: Index into array.
1482  *
1483  * After this function returns, loading from @index will return %NULL.
1484  * If the index is part of a multi-index entry, all indices will be erased
1485  * and none of the entries will be part of a multi-index entry.
1486  *
1487  * Context: Any context.  Expects xa_lock to be held on entry.
1488  * Return: The entry which used to be at this index.
1489  */
__xa_erase(struct xarray * xa,unsigned long index)1490 void *__xa_erase(struct xarray *xa, unsigned long index)
1491 {
1492 	XA_STATE(xas, xa, index);
1493 	return xas_result(&xas, xas_store(&xas, NULL));
1494 }
1495 EXPORT_SYMBOL(__xa_erase);
1496 
1497 /**
1498  * xa_erase() - Erase this entry from the XArray.
1499  * @xa: XArray.
1500  * @index: Index of entry.
1501  *
1502  * After this function returns, loading from @index will return %NULL.
1503  * If the index is part of a multi-index entry, all indices will be erased
1504  * and none of the entries will be part of a multi-index entry.
1505  *
1506  * Context: Any context.  Takes and releases the xa_lock.
1507  * Return: The entry which used to be at this index.
1508  */
xa_erase(struct xarray * xa,unsigned long index)1509 void *xa_erase(struct xarray *xa, unsigned long index)
1510 {
1511 	void *entry;
1512 
1513 	xa_lock(xa);
1514 	entry = __xa_erase(xa, index);
1515 	xa_unlock(xa);
1516 
1517 	return entry;
1518 }
1519 EXPORT_SYMBOL(xa_erase);
1520 
1521 /**
1522  * __xa_store() - Store this entry in the XArray.
1523  * @xa: XArray.
1524  * @index: Index into array.
1525  * @entry: New entry.
1526  * @gfp: Memory allocation flags.
1527  *
1528  * You must already be holding the xa_lock when calling this function.
1529  * It will drop the lock if needed to allocate memory, and then reacquire
1530  * it afterwards.
1531  *
1532  * Context: Any context.  Expects xa_lock to be held on entry.  May
1533  * release and reacquire xa_lock if @gfp flags permit.
1534  * Return: The old entry at this index or xa_err() if an error happened.
1535  */
__xa_store(struct xarray * xa,unsigned long index,void * entry,gfp_t gfp)1536 void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1537 {
1538 	XA_STATE(xas, xa, index);
1539 	void *curr;
1540 
1541 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1542 		return XA_ERROR(-EINVAL);
1543 	if (xa_track_free(xa) && !entry)
1544 		entry = XA_ZERO_ENTRY;
1545 
1546 	do {
1547 		curr = xas_store(&xas, entry);
1548 		if (xa_track_free(xa))
1549 			xas_clear_mark(&xas, XA_FREE_MARK);
1550 	} while (__xas_nomem(&xas, gfp));
1551 
1552 	return xas_result(&xas, curr);
1553 }
1554 EXPORT_SYMBOL(__xa_store);
1555 
1556 /**
1557  * xa_store() - Store this entry in the XArray.
1558  * @xa: XArray.
1559  * @index: Index into array.
1560  * @entry: New entry.
1561  * @gfp: Memory allocation flags.
1562  *
1563  * After this function returns, loads from this index will return @entry.
1564  * Storing into an existing multi-index entry updates the entry of every index.
1565  * The marks associated with @index are unaffected unless @entry is %NULL.
1566  *
1567  * Context: Any context.  Takes and releases the xa_lock.
1568  * May sleep if the @gfp flags permit.
1569  * Return: The old entry at this index on success, xa_err(-EINVAL) if @entry
1570  * cannot be stored in an XArray, or xa_err(-ENOMEM) if memory allocation
1571  * failed.
1572  */
xa_store(struct xarray * xa,unsigned long index,void * entry,gfp_t gfp)1573 void *xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1574 {
1575 	void *curr;
1576 
1577 	xa_lock(xa);
1578 	curr = __xa_store(xa, index, entry, gfp);
1579 	xa_unlock(xa);
1580 
1581 	return curr;
1582 }
1583 EXPORT_SYMBOL(xa_store);
1584 
1585 /**
1586  * __xa_cmpxchg() - Store this entry in the XArray.
1587  * @xa: XArray.
1588  * @index: Index into array.
1589  * @old: Old value to test against.
1590  * @entry: New entry.
1591  * @gfp: Memory allocation flags.
1592  *
1593  * You must already be holding the xa_lock when calling this function.
1594  * It will drop the lock if needed to allocate memory, and then reacquire
1595  * it afterwards.
1596  *
1597  * Context: Any context.  Expects xa_lock to be held on entry.  May
1598  * release and reacquire xa_lock if @gfp flags permit.
1599  * Return: The old entry at this index or xa_err() if an error happened.
1600  */
__xa_cmpxchg(struct xarray * xa,unsigned long index,void * old,void * entry,gfp_t gfp)1601 void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
1602 			void *old, void *entry, gfp_t gfp)
1603 {
1604 	XA_STATE(xas, xa, index);
1605 	void *curr;
1606 
1607 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1608 		return XA_ERROR(-EINVAL);
1609 
1610 	do {
1611 		curr = xas_load(&xas);
1612 		if (curr == old) {
1613 			xas_store(&xas, entry);
1614 			if (xa_track_free(xa) && entry && !curr)
1615 				xas_clear_mark(&xas, XA_FREE_MARK);
1616 		}
1617 	} while (__xas_nomem(&xas, gfp));
1618 
1619 	return xas_result(&xas, curr);
1620 }
1621 EXPORT_SYMBOL(__xa_cmpxchg);
1622 
1623 /**
1624  * __xa_insert() - Store this entry in the XArray if no entry is present.
1625  * @xa: XArray.
1626  * @index: Index into array.
1627  * @entry: New entry.
1628  * @gfp: Memory allocation flags.
1629  *
1630  * Inserting a NULL entry will store a reserved entry (like xa_reserve())
1631  * if no entry is present.  Inserting will fail if a reserved entry is
1632  * present, even though loading from this index will return NULL.
1633  *
1634  * Context: Any context.  Expects xa_lock to be held on entry.  May
1635  * release and reacquire xa_lock if @gfp flags permit.
1636  * Return: 0 if the store succeeded.  -EBUSY if another entry was present.
1637  * -ENOMEM if memory could not be allocated.
1638  */
__xa_insert(struct xarray * xa,unsigned long index,void * entry,gfp_t gfp)1639 int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1640 {
1641 	XA_STATE(xas, xa, index);
1642 	void *curr;
1643 
1644 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1645 		return -EINVAL;
1646 	if (!entry)
1647 		entry = XA_ZERO_ENTRY;
1648 
1649 	do {
1650 		curr = xas_load(&xas);
1651 		if (!curr) {
1652 			xas_store(&xas, entry);
1653 			if (xa_track_free(xa))
1654 				xas_clear_mark(&xas, XA_FREE_MARK);
1655 		} else {
1656 			xas_set_err(&xas, -EBUSY);
1657 		}
1658 	} while (__xas_nomem(&xas, gfp));
1659 
1660 	return xas_error(&xas);
1661 }
1662 EXPORT_SYMBOL(__xa_insert);
1663 
1664 #ifdef CONFIG_XARRAY_MULTI
xas_set_range(struct xa_state * xas,unsigned long first,unsigned long last)1665 static void xas_set_range(struct xa_state *xas, unsigned long first,
1666 		unsigned long last)
1667 {
1668 	unsigned int shift = 0;
1669 	unsigned long sibs = last - first;
1670 	unsigned int offset = XA_CHUNK_MASK;
1671 
1672 	xas_set(xas, first);
1673 
1674 	while ((first & XA_CHUNK_MASK) == 0) {
1675 		if (sibs < XA_CHUNK_MASK)
1676 			break;
1677 		if ((sibs == XA_CHUNK_MASK) && (offset < XA_CHUNK_MASK))
1678 			break;
1679 		shift += XA_CHUNK_SHIFT;
1680 		if (offset == XA_CHUNK_MASK)
1681 			offset = sibs & XA_CHUNK_MASK;
1682 		sibs >>= XA_CHUNK_SHIFT;
1683 		first >>= XA_CHUNK_SHIFT;
1684 	}
1685 
1686 	offset = first & XA_CHUNK_MASK;
1687 	if (offset + sibs > XA_CHUNK_MASK)
1688 		sibs = XA_CHUNK_MASK - offset;
1689 	if ((((first + sibs + 1) << shift) - 1) > last)
1690 		sibs -= 1;
1691 
1692 	xas->xa_shift = shift;
1693 	xas->xa_sibs = sibs;
1694 }
1695 
1696 /**
1697  * xa_store_range() - Store this entry at a range of indices in the XArray.
1698  * @xa: XArray.
1699  * @first: First index to affect.
1700  * @last: Last index to affect.
1701  * @entry: New entry.
1702  * @gfp: Memory allocation flags.
1703  *
1704  * After this function returns, loads from any index between @first and @last,
1705  * inclusive will return @entry.
1706  * Storing into an existing multi-index entry updates the entry of every index.
1707  * The marks associated with @index are unaffected unless @entry is %NULL.
1708  *
1709  * Context: Process context.  Takes and releases the xa_lock.  May sleep
1710  * if the @gfp flags permit.
1711  * Return: %NULL on success, xa_err(-EINVAL) if @entry cannot be stored in
1712  * an XArray, or xa_err(-ENOMEM) if memory allocation failed.
1713  */
xa_store_range(struct xarray * xa,unsigned long first,unsigned long last,void * entry,gfp_t gfp)1714 void *xa_store_range(struct xarray *xa, unsigned long first,
1715 		unsigned long last, void *entry, gfp_t gfp)
1716 {
1717 	XA_STATE(xas, xa, 0);
1718 
1719 	if (WARN_ON_ONCE(xa_is_internal(entry)))
1720 		return XA_ERROR(-EINVAL);
1721 	if (last < first)
1722 		return XA_ERROR(-EINVAL);
1723 
1724 	do {
1725 		xas_lock(&xas);
1726 		if (entry) {
1727 			unsigned int order = BITS_PER_LONG;
1728 			if (last + 1)
1729 				order = __ffs(last + 1);
1730 			xas_set_order(&xas, last, order);
1731 			xas_create(&xas, true);
1732 			if (xas_error(&xas))
1733 				goto unlock;
1734 		}
1735 		do {
1736 			xas_set_range(&xas, first, last);
1737 			xas_store(&xas, entry);
1738 			if (xas_error(&xas))
1739 				goto unlock;
1740 			first += xas_size(&xas);
1741 		} while (first <= last);
1742 unlock:
1743 		xas_unlock(&xas);
1744 	} while (xas_nomem(&xas, gfp));
1745 
1746 	return xas_result(&xas, NULL);
1747 }
1748 EXPORT_SYMBOL(xa_store_range);
1749 
1750 /**
1751  * xa_get_order() - Get the order of an entry.
1752  * @xa: XArray.
1753  * @index: Index of the entry.
1754  *
1755  * Return: A number between 0 and 63 indicating the order of the entry.
1756  */
xa_get_order(struct xarray * xa,unsigned long index)1757 int xa_get_order(struct xarray *xa, unsigned long index)
1758 {
1759 	XA_STATE(xas, xa, index);
1760 	void *entry;
1761 	int order = 0;
1762 
1763 	rcu_read_lock();
1764 	entry = xas_load(&xas);
1765 
1766 	if (!entry)
1767 		goto unlock;
1768 
1769 	if (!xas.xa_node)
1770 		goto unlock;
1771 
1772 	for (;;) {
1773 		unsigned int slot = xas.xa_offset + (1 << order);
1774 
1775 		if (slot >= XA_CHUNK_SIZE)
1776 			break;
1777 		if (!xa_is_sibling(xas.xa_node->slots[slot]))
1778 			break;
1779 		order++;
1780 	}
1781 
1782 	order += xas.xa_node->shift;
1783 unlock:
1784 	rcu_read_unlock();
1785 
1786 	return order;
1787 }
1788 EXPORT_SYMBOL(xa_get_order);
1789 #endif /* CONFIG_XARRAY_MULTI */
1790 
1791 /**
1792  * __xa_alloc() - Find somewhere to store this entry in the XArray.
1793  * @xa: XArray.
1794  * @id: Pointer to ID.
1795  * @limit: Range for allocated ID.
1796  * @entry: New entry.
1797  * @gfp: Memory allocation flags.
1798  *
1799  * Finds an empty entry in @xa between @limit.min and @limit.max,
1800  * stores the index into the @id pointer, then stores the entry at
1801  * that index.  A concurrent lookup will not see an uninitialised @id.
1802  *
1803  * Context: Any context.  Expects xa_lock to be held on entry.  May
1804  * release and reacquire xa_lock if @gfp flags permit.
1805  * Return: 0 on success, -ENOMEM if memory could not be allocated or
1806  * -EBUSY if there are no free entries in @limit.
1807  */
__xa_alloc(struct xarray * xa,u32 * id,void * entry,struct xa_limit limit,gfp_t gfp)1808 int __xa_alloc(struct xarray *xa, u32 *id, void *entry,
1809 		struct xa_limit limit, gfp_t gfp)
1810 {
1811 	XA_STATE(xas, xa, 0);
1812 
1813 	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1814 		return -EINVAL;
1815 	if (WARN_ON_ONCE(!xa_track_free(xa)))
1816 		return -EINVAL;
1817 
1818 	if (!entry)
1819 		entry = XA_ZERO_ENTRY;
1820 
1821 	do {
1822 		xas.xa_index = limit.min;
1823 		xas_find_marked(&xas, limit.max, XA_FREE_MARK);
1824 		if (xas.xa_node == XAS_RESTART)
1825 			xas_set_err(&xas, -EBUSY);
1826 		else
1827 			*id = xas.xa_index;
1828 		xas_store(&xas, entry);
1829 		xas_clear_mark(&xas, XA_FREE_MARK);
1830 	} while (__xas_nomem(&xas, gfp));
1831 
1832 	return xas_error(&xas);
1833 }
1834 EXPORT_SYMBOL(__xa_alloc);
1835 
1836 /**
1837  * __xa_alloc_cyclic() - Find somewhere to store this entry in the XArray.
1838  * @xa: XArray.
1839  * @id: Pointer to ID.
1840  * @entry: New entry.
1841  * @limit: Range of allocated ID.
1842  * @next: Pointer to next ID to allocate.
1843  * @gfp: Memory allocation flags.
1844  *
1845  * Finds an empty entry in @xa between @limit.min and @limit.max,
1846  * stores the index into the @id pointer, then stores the entry at
1847  * that index.  A concurrent lookup will not see an uninitialised @id.
1848  * The search for an empty entry will start at @next and will wrap
1849  * around if necessary.
1850  *
1851  * Context: Any context.  Expects xa_lock to be held on entry.  May
1852  * release and reacquire xa_lock if @gfp flags permit.
1853  * Return: 0 if the allocation succeeded without wrapping.  1 if the
1854  * allocation succeeded after wrapping, -ENOMEM if memory could not be
1855  * allocated or -EBUSY if there are no free entries in @limit.
1856  */
__xa_alloc_cyclic(struct xarray * xa,u32 * id,void * entry,struct xa_limit limit,u32 * next,gfp_t gfp)1857 int __xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
1858 		struct xa_limit limit, u32 *next, gfp_t gfp)
1859 {
1860 	u32 min = limit.min;
1861 	int ret;
1862 
1863 	limit.min = max(min, *next);
1864 	ret = __xa_alloc(xa, id, entry, limit, gfp);
1865 	if ((xa->xa_flags & XA_FLAGS_ALLOC_WRAPPED) && ret == 0) {
1866 		xa->xa_flags &= ~XA_FLAGS_ALLOC_WRAPPED;
1867 		ret = 1;
1868 	}
1869 
1870 	if (ret < 0 && limit.min > min) {
1871 		limit.min = min;
1872 		ret = __xa_alloc(xa, id, entry, limit, gfp);
1873 		if (ret == 0)
1874 			ret = 1;
1875 	}
1876 
1877 	if (ret >= 0) {
1878 		*next = *id + 1;
1879 		if (*next == 0)
1880 			xa->xa_flags |= XA_FLAGS_ALLOC_WRAPPED;
1881 	}
1882 	return ret;
1883 }
1884 EXPORT_SYMBOL(__xa_alloc_cyclic);
1885 
1886 /**
1887  * __xa_set_mark() - Set this mark on this entry while locked.
1888  * @xa: XArray.
1889  * @index: Index of entry.
1890  * @mark: Mark number.
1891  *
1892  * Attempting to set a mark on a %NULL entry does not succeed.
1893  *
1894  * Context: Any context.  Expects xa_lock to be held on entry.
1895  */
__xa_set_mark(struct xarray * xa,unsigned long index,xa_mark_t mark)1896 void __xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1897 {
1898 	XA_STATE(xas, xa, index);
1899 	void *entry = xas_load(&xas);
1900 
1901 	if (entry)
1902 		xas_set_mark(&xas, mark);
1903 }
1904 EXPORT_SYMBOL(__xa_set_mark);
1905 
1906 /**
1907  * __xa_clear_mark() - Clear this mark on this entry while locked.
1908  * @xa: XArray.
1909  * @index: Index of entry.
1910  * @mark: Mark number.
1911  *
1912  * Context: Any context.  Expects xa_lock to be held on entry.
1913  */
__xa_clear_mark(struct xarray * xa,unsigned long index,xa_mark_t mark)1914 void __xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1915 {
1916 	XA_STATE(xas, xa, index);
1917 	void *entry = xas_load(&xas);
1918 
1919 	if (entry)
1920 		xas_clear_mark(&xas, mark);
1921 }
1922 EXPORT_SYMBOL(__xa_clear_mark);
1923 
1924 /**
1925  * xa_get_mark() - Inquire whether this mark is set on this entry.
1926  * @xa: XArray.
1927  * @index: Index of entry.
1928  * @mark: Mark number.
1929  *
1930  * This function uses the RCU read lock, so the result may be out of date
1931  * by the time it returns.  If you need the result to be stable, use a lock.
1932  *
1933  * Context: Any context.  Takes and releases the RCU lock.
1934  * Return: True if the entry at @index has this mark set, false if it doesn't.
1935  */
xa_get_mark(struct xarray * xa,unsigned long index,xa_mark_t mark)1936 bool xa_get_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1937 {
1938 	XA_STATE(xas, xa, index);
1939 	void *entry;
1940 
1941 	rcu_read_lock();
1942 	entry = xas_start(&xas);
1943 	while (xas_get_mark(&xas, mark)) {
1944 		if (!xa_is_node(entry))
1945 			goto found;
1946 		entry = xas_descend(&xas, xa_to_node(entry));
1947 	}
1948 	rcu_read_unlock();
1949 	return false;
1950  found:
1951 	rcu_read_unlock();
1952 	return true;
1953 }
1954 EXPORT_SYMBOL(xa_get_mark);
1955 
1956 /**
1957  * xa_set_mark() - Set this mark on this entry.
1958  * @xa: XArray.
1959  * @index: Index of entry.
1960  * @mark: Mark number.
1961  *
1962  * Attempting to set a mark on a %NULL entry does not succeed.
1963  *
1964  * Context: Process context.  Takes and releases the xa_lock.
1965  */
xa_set_mark(struct xarray * xa,unsigned long index,xa_mark_t mark)1966 void xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1967 {
1968 	xa_lock(xa);
1969 	__xa_set_mark(xa, index, mark);
1970 	xa_unlock(xa);
1971 }
1972 EXPORT_SYMBOL(xa_set_mark);
1973 
1974 /**
1975  * xa_clear_mark() - Clear this mark on this entry.
1976  * @xa: XArray.
1977  * @index: Index of entry.
1978  * @mark: Mark number.
1979  *
1980  * Clearing a mark always succeeds.
1981  *
1982  * Context: Process context.  Takes and releases the xa_lock.
1983  */
xa_clear_mark(struct xarray * xa,unsigned long index,xa_mark_t mark)1984 void xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1985 {
1986 	xa_lock(xa);
1987 	__xa_clear_mark(xa, index, mark);
1988 	xa_unlock(xa);
1989 }
1990 EXPORT_SYMBOL(xa_clear_mark);
1991 
1992 /**
1993  * xa_find() - Search the XArray for an entry.
1994  * @xa: XArray.
1995  * @indexp: Pointer to an index.
1996  * @max: Maximum index to search to.
1997  * @filter: Selection criterion.
1998  *
1999  * Finds the entry in @xa which matches the @filter, and has the lowest
2000  * index that is at least @indexp and no more than @max.
2001  * If an entry is found, @indexp is updated to be the index of the entry.
2002  * This function is protected by the RCU read lock, so it may not find
2003  * entries which are being simultaneously added.  It will not return an
2004  * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find().
2005  *
2006  * Context: Any context.  Takes and releases the RCU lock.
2007  * Return: The entry, if found, otherwise %NULL.
2008  */
xa_find(struct xarray * xa,unsigned long * indexp,unsigned long max,xa_mark_t filter)2009 void *xa_find(struct xarray *xa, unsigned long *indexp,
2010 			unsigned long max, xa_mark_t filter)
2011 {
2012 	XA_STATE(xas, xa, *indexp);
2013 	void *entry;
2014 
2015 	rcu_read_lock();
2016 	do {
2017 		if ((__force unsigned int)filter < XA_MAX_MARKS)
2018 			entry = xas_find_marked(&xas, max, filter);
2019 		else
2020 			entry = xas_find(&xas, max);
2021 	} while (xas_retry(&xas, entry));
2022 	rcu_read_unlock();
2023 
2024 	if (entry)
2025 		*indexp = xas.xa_index;
2026 	return entry;
2027 }
2028 EXPORT_SYMBOL(xa_find);
2029 
xas_sibling(struct xa_state * xas)2030 static bool xas_sibling(struct xa_state *xas)
2031 {
2032 	struct xa_node *node = xas->xa_node;
2033 	unsigned long mask;
2034 
2035 	if (!IS_ENABLED(CONFIG_XARRAY_MULTI) || !node)
2036 		return false;
2037 	mask = (XA_CHUNK_SIZE << node->shift) - 1;
2038 	return (xas->xa_index & mask) >
2039 		((unsigned long)xas->xa_offset << node->shift);
2040 }
2041 
2042 /**
2043  * xa_find_after() - Search the XArray for a present entry.
2044  * @xa: XArray.
2045  * @indexp: Pointer to an index.
2046  * @max: Maximum index to search to.
2047  * @filter: Selection criterion.
2048  *
2049  * Finds the entry in @xa which matches the @filter and has the lowest
2050  * index that is above @indexp and no more than @max.
2051  * If an entry is found, @indexp is updated to be the index of the entry.
2052  * This function is protected by the RCU read lock, so it may miss entries
2053  * which are being simultaneously added.  It will not return an
2054  * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find().
2055  *
2056  * Context: Any context.  Takes and releases the RCU lock.
2057  * Return: The pointer, if found, otherwise %NULL.
2058  */
xa_find_after(struct xarray * xa,unsigned long * indexp,unsigned long max,xa_mark_t filter)2059 void *xa_find_after(struct xarray *xa, unsigned long *indexp,
2060 			unsigned long max, xa_mark_t filter)
2061 {
2062 	XA_STATE(xas, xa, *indexp + 1);
2063 	void *entry;
2064 
2065 	if (xas.xa_index == 0)
2066 		return NULL;
2067 
2068 	rcu_read_lock();
2069 	for (;;) {
2070 		if ((__force unsigned int)filter < XA_MAX_MARKS)
2071 			entry = xas_find_marked(&xas, max, filter);
2072 		else
2073 			entry = xas_find(&xas, max);
2074 
2075 		if (xas_invalid(&xas))
2076 			break;
2077 		if (xas_sibling(&xas))
2078 			continue;
2079 		if (!xas_retry(&xas, entry))
2080 			break;
2081 	}
2082 	rcu_read_unlock();
2083 
2084 	if (entry)
2085 		*indexp = xas.xa_index;
2086 	return entry;
2087 }
2088 EXPORT_SYMBOL(xa_find_after);
2089 
xas_extract_present(struct xa_state * xas,void ** dst,unsigned long max,unsigned int n)2090 static unsigned int xas_extract_present(struct xa_state *xas, void **dst,
2091 			unsigned long max, unsigned int n)
2092 {
2093 	void *entry;
2094 	unsigned int i = 0;
2095 
2096 	rcu_read_lock();
2097 	xas_for_each(xas, entry, max) {
2098 		if (xas_retry(xas, entry))
2099 			continue;
2100 		dst[i++] = entry;
2101 		if (i == n)
2102 			break;
2103 	}
2104 	rcu_read_unlock();
2105 
2106 	return i;
2107 }
2108 
xas_extract_marked(struct xa_state * xas,void ** dst,unsigned long max,unsigned int n,xa_mark_t mark)2109 static unsigned int xas_extract_marked(struct xa_state *xas, void **dst,
2110 			unsigned long max, unsigned int n, xa_mark_t mark)
2111 {
2112 	void *entry;
2113 	unsigned int i = 0;
2114 
2115 	rcu_read_lock();
2116 	xas_for_each_marked(xas, entry, max, mark) {
2117 		if (xas_retry(xas, entry))
2118 			continue;
2119 		dst[i++] = entry;
2120 		if (i == n)
2121 			break;
2122 	}
2123 	rcu_read_unlock();
2124 
2125 	return i;
2126 }
2127 
2128 /**
2129  * xa_extract() - Copy selected entries from the XArray into a normal array.
2130  * @xa: The source XArray to copy from.
2131  * @dst: The buffer to copy entries into.
2132  * @start: The first index in the XArray eligible to be selected.
2133  * @max: The last index in the XArray eligible to be selected.
2134  * @n: The maximum number of entries to copy.
2135  * @filter: Selection criterion.
2136  *
2137  * Copies up to @n entries that match @filter from the XArray.  The
2138  * copied entries will have indices between @start and @max, inclusive.
2139  *
2140  * The @filter may be an XArray mark value, in which case entries which are
2141  * marked with that mark will be copied.  It may also be %XA_PRESENT, in
2142  * which case all entries which are not %NULL will be copied.
2143  *
2144  * The entries returned may not represent a snapshot of the XArray at a
2145  * moment in time.  For example, if another thread stores to index 5, then
2146  * index 10, calling xa_extract() may return the old contents of index 5
2147  * and the new contents of index 10.  Indices not modified while this
2148  * function is running will not be skipped.
2149  *
2150  * If you need stronger guarantees, holding the xa_lock across calls to this
2151  * function will prevent concurrent modification.
2152  *
2153  * Context: Any context.  Takes and releases the RCU lock.
2154  * Return: The number of entries copied.
2155  */
xa_extract(struct xarray * xa,void ** dst,unsigned long start,unsigned long max,unsigned int n,xa_mark_t filter)2156 unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,
2157 			unsigned long max, unsigned int n, xa_mark_t filter)
2158 {
2159 	XA_STATE(xas, xa, start);
2160 
2161 	if (!n)
2162 		return 0;
2163 
2164 	if ((__force unsigned int)filter < XA_MAX_MARKS)
2165 		return xas_extract_marked(&xas, dst, max, n, filter);
2166 	return xas_extract_present(&xas, dst, max, n);
2167 }
2168 EXPORT_SYMBOL(xa_extract);
2169 
2170 /**
2171  * xa_delete_node() - Private interface for workingset code.
2172  * @node: Node to be removed from the tree.
2173  * @update: Function to call to update ancestor nodes.
2174  *
2175  * Context: xa_lock must be held on entry and will not be released.
2176  */
xa_delete_node(struct xa_node * node,xa_update_node_t update)2177 void xa_delete_node(struct xa_node *node, xa_update_node_t update)
2178 {
2179 	struct xa_state xas = {
2180 		.xa = node->array,
2181 		.xa_index = (unsigned long)node->offset <<
2182 				(node->shift + XA_CHUNK_SHIFT),
2183 		.xa_shift = node->shift + XA_CHUNK_SHIFT,
2184 		.xa_offset = node->offset,
2185 		.xa_node = xa_parent_locked(node->array, node),
2186 		.xa_update = update,
2187 	};
2188 
2189 	xas_store(&xas, NULL);
2190 }
2191 EXPORT_SYMBOL_GPL(xa_delete_node);	/* For the benefit of the test suite */
2192 
2193 /**
2194  * xa_destroy() - Free all internal data structures.
2195  * @xa: XArray.
2196  *
2197  * After calling this function, the XArray is empty and has freed all memory
2198  * allocated for its internal data structures.  You are responsible for
2199  * freeing the objects referenced by the XArray.
2200  *
2201  * Context: Any context.  Takes and releases the xa_lock, interrupt-safe.
2202  */
xa_destroy(struct xarray * xa)2203 void xa_destroy(struct xarray *xa)
2204 {
2205 	XA_STATE(xas, xa, 0);
2206 	unsigned long flags;
2207 	void *entry;
2208 
2209 	xas.xa_node = NULL;
2210 	xas_lock_irqsave(&xas, flags);
2211 	entry = xa_head_locked(xa);
2212 	RCU_INIT_POINTER(xa->xa_head, NULL);
2213 	xas_init_marks(&xas);
2214 	if (xa_zero_busy(xa))
2215 		xa_mark_clear(xa, XA_FREE_MARK);
2216 	/* lockdep checks we're still holding the lock in xas_free_nodes() */
2217 	if (xa_is_node(entry))
2218 		xas_free_nodes(&xas, xa_to_node(entry));
2219 	xas_unlock_irqrestore(&xas, flags);
2220 }
2221 EXPORT_SYMBOL(xa_destroy);
2222 
2223 #ifdef XA_DEBUG
xa_dump_node(const struct xa_node * node)2224 void xa_dump_node(const struct xa_node *node)
2225 {
2226 	unsigned i, j;
2227 
2228 	if (!node)
2229 		return;
2230 	if ((unsigned long)node & 3) {
2231 		pr_cont("node %px\n", node);
2232 		return;
2233 	}
2234 
2235 	pr_cont("node %px %s %d parent %px shift %d count %d values %d "
2236 		"array %px list %px %px marks",
2237 		node, node->parent ? "offset" : "max", node->offset,
2238 		node->parent, node->shift, node->count, node->nr_values,
2239 		node->array, node->private_list.prev, node->private_list.next);
2240 	for (i = 0; i < XA_MAX_MARKS; i++)
2241 		for (j = 0; j < XA_MARK_LONGS; j++)
2242 			pr_cont(" %lx", node->marks[i][j]);
2243 	pr_cont("\n");
2244 }
2245 
xa_dump_index(unsigned long index,unsigned int shift)2246 void xa_dump_index(unsigned long index, unsigned int shift)
2247 {
2248 	if (!shift)
2249 		pr_info("%lu: ", index);
2250 	else if (shift >= BITS_PER_LONG)
2251 		pr_info("0-%lu: ", ~0UL);
2252 	else
2253 		pr_info("%lu-%lu: ", index, index | ((1UL << shift) - 1));
2254 }
2255 
xa_dump_entry(const void * entry,unsigned long index,unsigned long shift)2256 void xa_dump_entry(const void *entry, unsigned long index, unsigned long shift)
2257 {
2258 	if (!entry)
2259 		return;
2260 
2261 	xa_dump_index(index, shift);
2262 
2263 	if (xa_is_node(entry)) {
2264 		if (shift == 0) {
2265 			pr_cont("%px\n", entry);
2266 		} else {
2267 			unsigned long i;
2268 			struct xa_node *node = xa_to_node(entry);
2269 			xa_dump_node(node);
2270 			for (i = 0; i < XA_CHUNK_SIZE; i++)
2271 				xa_dump_entry(node->slots[i],
2272 				      index + (i << node->shift), node->shift);
2273 		}
2274 	} else if (xa_is_value(entry))
2275 		pr_cont("value %ld (0x%lx) [%px]\n", xa_to_value(entry),
2276 						xa_to_value(entry), entry);
2277 	else if (!xa_is_internal(entry))
2278 		pr_cont("%px\n", entry);
2279 	else if (xa_is_retry(entry))
2280 		pr_cont("retry (%ld)\n", xa_to_internal(entry));
2281 	else if (xa_is_sibling(entry))
2282 		pr_cont("sibling (slot %ld)\n", xa_to_sibling(entry));
2283 	else if (xa_is_zero(entry))
2284 		pr_cont("zero (%ld)\n", xa_to_internal(entry));
2285 	else
2286 		pr_cont("UNKNOWN ENTRY (%px)\n", entry);
2287 }
2288 
xa_dump(const struct xarray * xa)2289 void xa_dump(const struct xarray *xa)
2290 {
2291 	void *entry = xa->xa_head;
2292 	unsigned int shift = 0;
2293 
2294 	pr_info("xarray: %px head %px flags %x marks %d %d %d\n", xa, entry,
2295 			xa->xa_flags, xa_marked(xa, XA_MARK_0),
2296 			xa_marked(xa, XA_MARK_1), xa_marked(xa, XA_MARK_2));
2297 	if (xa_is_node(entry))
2298 		shift = xa_to_node(entry)->shift + XA_CHUNK_SHIFT;
2299 	xa_dump_entry(entry, 0, shift);
2300 }
2301 #endif
2302