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