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