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