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
  33static inline unsigned int xa_lock_type(const struct xarray *xa)
  34{
  35	return (__force unsigned int)xa->xa_flags & 3;
  36}
  37
  38static 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
  48static 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
  58static inline bool xa_track_free(const struct xarray *xa)
  59{
  60	return xa->xa_flags & XA_FLAGS_TRACK_FREE;
  61}
  62
  63static inline bool xa_zero_busy(const struct xarray *xa)
  64{
  65	return xa->xa_flags & XA_FLAGS_ZERO_BUSY;
  66}
  67
  68static 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
  74static 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
  80static inline unsigned long *node_marks(struct xa_node *node, xa_mark_t mark)
  81{
  82	return node->marks[(__force unsigned)mark];
  83}
  84
  85static 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 */
  92static 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 */
  99static 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
 105static 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
 110static 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 */
 126static 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 */
 144static unsigned int get_offset(unsigned long index, struct xa_node *node)
 145{
 146	return (index >> node->shift) & XA_CHUNK_MASK;
 147}
 148
 149static 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) */
 155static 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
 162static void xas_next_offset(struct xa_state *xas)
 163{
 164	xas->xa_offset++;
 165	xas_move_index(xas, xas->xa_offset);
 166}
 167
 168static 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 */
 181static 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
 203static __always_inline void *xas_descend(struct xa_state *xas,
 204					struct xa_node *node)
 205{
 206	unsigned int offset = get_offset(xas->xa_index, node);
 207	void *entry = xa_entry(xas->xa, node, offset);
 208
 209	xas->xa_node = node;
 210	while (xa_is_sibling(entry)) {
 211		offset = xa_to_sibling(entry);
 212		entry = xa_entry(xas->xa, node, offset);
 213		if (node->shift && xa_is_node(entry))
 214			entry = XA_RETRY_ENTRY;
 215	}
 216
 217	xas->xa_offset = offset;
 218	return entry;
 219}
 220
 221/**
 222 * xas_load() - Load an entry from the XArray (advanced).
 223 * @xas: XArray operation state.
 224 *
 225 * Usually walks the @xas to the appropriate state to load the entry
 226 * stored at xa_index.  However, it will do nothing and return %NULL if
 227 * @xas is in an error state.  xas_load() will never expand the tree.
 228 *
 229 * If the xa_state is set up to operate on a multi-index entry, xas_load()
 230 * may return %NULL or an internal entry, even if there are entries
 231 * present within the range specified by @xas.
 232 *
 233 * Context: Any context.  The caller should hold the xa_lock or the RCU lock.
 234 * Return: Usually an entry in the XArray, but see description for exceptions.
 235 */
 236void *xas_load(struct xa_state *xas)
 237{
 238	void *entry = xas_start(xas);
 239
 240	while (xa_is_node(entry)) {
 241		struct xa_node *node = xa_to_node(entry);
 242
 243		if (xas->xa_shift > node->shift)
 244			break;
 245		entry = xas_descend(xas, node);
 246		if (node->shift == 0)
 247			break;
 248	}
 249	return entry;
 250}
 251EXPORT_SYMBOL_GPL(xas_load);
 252
 
 
 
 
 253#define XA_RCU_FREE	((struct xarray *)1)
 254
 255static void xa_node_free(struct xa_node *node)
 256{
 257	XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
 258	node->array = XA_RCU_FREE;
 259	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
 260}
 261
 262/*
 263 * xas_destroy() - Free any resources allocated during the XArray operation.
 264 * @xas: XArray operation state.
 265 *
 266 * Most users will not need to call this function; it is called for you
 267 * by xas_nomem().
 268 */
 269void xas_destroy(struct xa_state *xas)
 270{
 271	struct xa_node *next, *node = xas->xa_alloc;
 272
 273	while (node) {
 274		XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
 275		next = rcu_dereference_raw(node->parent);
 276		radix_tree_node_rcu_free(&node->rcu_head);
 277		xas->xa_alloc = node = next;
 278	}
 279}
 280
 281/**
 282 * xas_nomem() - Allocate memory if needed.
 283 * @xas: XArray operation state.
 284 * @gfp: Memory allocation flags.
 285 *
 286 * If we need to add new nodes to the XArray, we try to allocate memory
 287 * with GFP_NOWAIT while holding the lock, which will usually succeed.
 288 * If it fails, @xas is flagged as needing memory to continue.  The caller
 289 * should drop the lock and call xas_nomem().  If xas_nomem() succeeds,
 290 * the caller should retry the operation.
 291 *
 292 * Forward progress is guaranteed as one node is allocated here and
 293 * stored in the xa_state where it will be found by xas_alloc().  More
 294 * nodes will likely be found in the slab allocator, but we do not tie
 295 * them up here.
 296 *
 297 * Return: true if memory was needed, and was successfully allocated.
 298 */
 299bool xas_nomem(struct xa_state *xas, gfp_t gfp)
 300{
 301	if (xas->xa_node != XA_ERROR(-ENOMEM)) {
 302		xas_destroy(xas);
 303		return false;
 304	}
 305	if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
 306		gfp |= __GFP_ACCOUNT;
 307	xas->xa_alloc = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
 308	if (!xas->xa_alloc)
 309		return false;
 310	xas->xa_alloc->parent = NULL;
 311	XA_NODE_BUG_ON(xas->xa_alloc, !list_empty(&xas->xa_alloc->private_list));
 312	xas->xa_node = XAS_RESTART;
 313	return true;
 314}
 315EXPORT_SYMBOL_GPL(xas_nomem);
 316
 317/*
 318 * __xas_nomem() - Drop locks and allocate memory if needed.
 319 * @xas: XArray operation state.
 320 * @gfp: Memory allocation flags.
 321 *
 322 * Internal variant of xas_nomem().
 323 *
 324 * Return: true if memory was needed, and was successfully allocated.
 325 */
 326static bool __xas_nomem(struct xa_state *xas, gfp_t gfp)
 327	__must_hold(xas->xa->xa_lock)
 328{
 329	unsigned int lock_type = xa_lock_type(xas->xa);
 330
 331	if (xas->xa_node != XA_ERROR(-ENOMEM)) {
 332		xas_destroy(xas);
 333		return false;
 334	}
 335	if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
 336		gfp |= __GFP_ACCOUNT;
 337	if (gfpflags_allow_blocking(gfp)) {
 338		xas_unlock_type(xas, lock_type);
 339		xas->xa_alloc = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
 340		xas_lock_type(xas, lock_type);
 341	} else {
 342		xas->xa_alloc = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
 343	}
 344	if (!xas->xa_alloc)
 345		return false;
 346	xas->xa_alloc->parent = NULL;
 347	XA_NODE_BUG_ON(xas->xa_alloc, !list_empty(&xas->xa_alloc->private_list));
 348	xas->xa_node = XAS_RESTART;
 349	return true;
 350}
 351
 352static void xas_update(struct xa_state *xas, struct xa_node *node)
 353{
 354	if (xas->xa_update)
 355		xas->xa_update(node);
 356	else
 357		XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
 358}
 359
 360static void *xas_alloc(struct xa_state *xas, unsigned int shift)
 361{
 362	struct xa_node *parent = xas->xa_node;
 363	struct xa_node *node = xas->xa_alloc;
 364
 365	if (xas_invalid(xas))
 366		return NULL;
 367
 368	if (node) {
 369		xas->xa_alloc = NULL;
 370	} else {
 371		gfp_t gfp = GFP_NOWAIT | __GFP_NOWARN;
 372
 373		if (xas->xa->xa_flags & XA_FLAGS_ACCOUNT)
 374			gfp |= __GFP_ACCOUNT;
 375
 376		node = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
 377		if (!node) {
 378			xas_set_err(xas, -ENOMEM);
 379			return NULL;
 380		}
 381	}
 382
 383	if (parent) {
 384		node->offset = xas->xa_offset;
 385		parent->count++;
 386		XA_NODE_BUG_ON(node, parent->count > XA_CHUNK_SIZE);
 387		xas_update(xas, parent);
 388	}
 389	XA_NODE_BUG_ON(node, shift > BITS_PER_LONG);
 390	XA_NODE_BUG_ON(node, !list_empty(&node->private_list));
 391	node->shift = shift;
 392	node->count = 0;
 393	node->nr_values = 0;
 394	RCU_INIT_POINTER(node->parent, xas->xa_node);
 395	node->array = xas->xa;
 396
 397	return node;
 398}
 399
 400#ifdef CONFIG_XARRAY_MULTI
 401/* Returns the number of indices covered by a given xa_state */
 402static unsigned long xas_size(const struct xa_state *xas)
 403{
 404	return (xas->xa_sibs + 1UL) << xas->xa_shift;
 405}
 406#endif
 407
 408/*
 409 * Use this to calculate the maximum index that will need to be created
 410 * in order to add the entry described by @xas.  Because we cannot store a
 411 * multi-index entry at index 0, the calculation is a little more complex
 412 * than you might expect.
 413 */
 414static unsigned long xas_max(struct xa_state *xas)
 415{
 416	unsigned long max = xas->xa_index;
 417
 418#ifdef CONFIG_XARRAY_MULTI
 419	if (xas->xa_shift || xas->xa_sibs) {
 420		unsigned long mask = xas_size(xas) - 1;
 421		max |= mask;
 422		if (mask == max)
 423			max++;
 424	}
 425#endif
 426
 427	return max;
 428}
 429
 430/* The maximum index that can be contained in the array without expanding it */
 431static unsigned long max_index(void *entry)
 432{
 433	if (!xa_is_node(entry))
 434		return 0;
 435	return (XA_CHUNK_SIZE << xa_to_node(entry)->shift) - 1;
 436}
 437
 438static void xas_shrink(struct xa_state *xas)
 439{
 440	struct xarray *xa = xas->xa;
 441	struct xa_node *node = xas->xa_node;
 442
 443	for (;;) {
 444		void *entry;
 445
 446		XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
 447		if (node->count != 1)
 448			break;
 449		entry = xa_entry_locked(xa, node, 0);
 450		if (!entry)
 451			break;
 452		if (!xa_is_node(entry) && node->shift)
 453			break;
 454		if (xa_is_zero(entry) && xa_zero_busy(xa))
 455			entry = NULL;
 456		xas->xa_node = XAS_BOUNDS;
 457
 458		RCU_INIT_POINTER(xa->xa_head, entry);
 459		if (xa_track_free(xa) && !node_get_mark(node, 0, XA_FREE_MARK))
 460			xa_mark_clear(xa, XA_FREE_MARK);
 461
 462		node->count = 0;
 463		node->nr_values = 0;
 464		if (!xa_is_node(entry))
 465			RCU_INIT_POINTER(node->slots[0], XA_RETRY_ENTRY);
 466		xas_update(xas, node);
 467		xa_node_free(node);
 468		if (!xa_is_node(entry))
 469			break;
 470		node = xa_to_node(entry);
 471		node->parent = NULL;
 472	}
 473}
 474
 475/*
 476 * xas_delete_node() - Attempt to delete an xa_node
 477 * @xas: Array operation state.
 478 *
 479 * Attempts to delete the @xas->xa_node.  This will fail if xa->node has
 480 * a non-zero reference count.
 481 */
 482static void xas_delete_node(struct xa_state *xas)
 483{
 484	struct xa_node *node = xas->xa_node;
 485
 486	for (;;) {
 487		struct xa_node *parent;
 488
 489		XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
 490		if (node->count)
 491			break;
 492
 493		parent = xa_parent_locked(xas->xa, node);
 494		xas->xa_node = parent;
 495		xas->xa_offset = node->offset;
 496		xa_node_free(node);
 497
 498		if (!parent) {
 499			xas->xa->xa_head = NULL;
 500			xas->xa_node = XAS_BOUNDS;
 501			return;
 502		}
 503
 504		parent->slots[xas->xa_offset] = NULL;
 505		parent->count--;
 506		XA_NODE_BUG_ON(parent, parent->count > XA_CHUNK_SIZE);
 507		node = parent;
 508		xas_update(xas, node);
 509	}
 510
 511	if (!node->parent)
 512		xas_shrink(xas);
 513}
 514
 515/**
 516 * xas_free_nodes() - Free this node and all nodes that it references
 517 * @xas: Array operation state.
 518 * @top: Node to free
 519 *
 520 * This node has been removed from the tree.  We must now free it and all
 521 * of its subnodes.  There may be RCU walkers with references into the tree,
 522 * so we must replace all entries with retry markers.
 523 */
 524static void xas_free_nodes(struct xa_state *xas, struct xa_node *top)
 525{
 526	unsigned int offset = 0;
 527	struct xa_node *node = top;
 528
 529	for (;;) {
 530		void *entry = xa_entry_locked(xas->xa, node, offset);
 531
 532		if (node->shift && xa_is_node(entry)) {
 533			node = xa_to_node(entry);
 534			offset = 0;
 535			continue;
 536		}
 537		if (entry)
 538			RCU_INIT_POINTER(node->slots[offset], XA_RETRY_ENTRY);
 539		offset++;
 540		while (offset == XA_CHUNK_SIZE) {
 541			struct xa_node *parent;
 542
 543			parent = xa_parent_locked(xas->xa, node);
 544			offset = node->offset + 1;
 545			node->count = 0;
 546			node->nr_values = 0;
 547			xas_update(xas, node);
 548			xa_node_free(node);
 549			if (node == top)
 550				return;
 551			node = parent;
 552		}
 553	}
 554}
 555
 556/*
 557 * xas_expand adds nodes to the head of the tree until it has reached
 558 * sufficient height to be able to contain @xas->xa_index
 559 */
 560static int xas_expand(struct xa_state *xas, void *head)
 561{
 562	struct xarray *xa = xas->xa;
 563	struct xa_node *node = NULL;
 564	unsigned int shift = 0;
 565	unsigned long max = xas_max(xas);
 566
 567	if (!head) {
 568		if (max == 0)
 569			return 0;
 570		while ((max >> shift) >= XA_CHUNK_SIZE)
 571			shift += XA_CHUNK_SHIFT;
 572		return shift + XA_CHUNK_SHIFT;
 573	} else if (xa_is_node(head)) {
 574		node = xa_to_node(head);
 575		shift = node->shift + XA_CHUNK_SHIFT;
 576	}
 577	xas->xa_node = NULL;
 578
 579	while (max > max_index(head)) {
 580		xa_mark_t mark = 0;
 581
 582		XA_NODE_BUG_ON(node, shift > BITS_PER_LONG);
 583		node = xas_alloc(xas, shift);
 584		if (!node)
 585			return -ENOMEM;
 586
 587		node->count = 1;
 588		if (xa_is_value(head))
 589			node->nr_values = 1;
 590		RCU_INIT_POINTER(node->slots[0], head);
 591
 592		/* Propagate the aggregated mark info to the new child */
 593		for (;;) {
 594			if (xa_track_free(xa) && mark == XA_FREE_MARK) {
 595				node_mark_all(node, XA_FREE_MARK);
 596				if (!xa_marked(xa, XA_FREE_MARK)) {
 597					node_clear_mark(node, 0, XA_FREE_MARK);
 598					xa_mark_set(xa, XA_FREE_MARK);
 599				}
 600			} else if (xa_marked(xa, mark)) {
 601				node_set_mark(node, 0, mark);
 602			}
 603			if (mark == XA_MARK_MAX)
 604				break;
 605			mark_inc(mark);
 606		}
 607
 608		/*
 609		 * Now that the new node is fully initialised, we can add
 610		 * it to the tree
 611		 */
 612		if (xa_is_node(head)) {
 613			xa_to_node(head)->offset = 0;
 614			rcu_assign_pointer(xa_to_node(head)->parent, node);
 615		}
 616		head = xa_mk_node(node);
 617		rcu_assign_pointer(xa->xa_head, head);
 618		xas_update(xas, node);
 619
 620		shift += XA_CHUNK_SHIFT;
 621	}
 622
 623	xas->xa_node = node;
 624	return shift;
 625}
 626
 627/*
 628 * xas_create() - Create a slot to store an entry in.
 629 * @xas: XArray operation state.
 630 * @allow_root: %true if we can store the entry in the root directly
 631 *
 632 * Most users will not need to call this function directly, as it is called
 633 * by xas_store().  It is useful for doing conditional store operations
 634 * (see the xa_cmpxchg() implementation for an example).
 635 *
 636 * Return: If the slot already existed, returns the contents of this slot.
 637 * If the slot was newly created, returns %NULL.  If it failed to create the
 638 * slot, returns %NULL and indicates the error in @xas.
 639 */
 640static void *xas_create(struct xa_state *xas, bool allow_root)
 641{
 642	struct xarray *xa = xas->xa;
 643	void *entry;
 644	void __rcu **slot;
 645	struct xa_node *node = xas->xa_node;
 646	int shift;
 647	unsigned int order = xas->xa_shift;
 648
 649	if (xas_top(node)) {
 650		entry = xa_head_locked(xa);
 651		xas->xa_node = NULL;
 652		if (!entry && xa_zero_busy(xa))
 653			entry = XA_ZERO_ENTRY;
 654		shift = xas_expand(xas, entry);
 655		if (shift < 0)
 656			return NULL;
 657		if (!shift && !allow_root)
 658			shift = XA_CHUNK_SHIFT;
 659		entry = xa_head_locked(xa);
 660		slot = &xa->xa_head;
 661	} else if (xas_error(xas)) {
 662		return NULL;
 663	} else if (node) {
 664		unsigned int offset = xas->xa_offset;
 665
 666		shift = node->shift;
 667		entry = xa_entry_locked(xa, node, offset);
 668		slot = &node->slots[offset];
 669	} else {
 670		shift = 0;
 671		entry = xa_head_locked(xa);
 672		slot = &xa->xa_head;
 673	}
 674
 675	while (shift > order) {
 676		shift -= XA_CHUNK_SHIFT;
 677		if (!entry) {
 678			node = xas_alloc(xas, shift);
 679			if (!node)
 680				break;
 681			if (xa_track_free(xa))
 682				node_mark_all(node, XA_FREE_MARK);
 683			rcu_assign_pointer(*slot, xa_mk_node(node));
 684		} else if (xa_is_node(entry)) {
 685			node = xa_to_node(entry);
 686		} else {
 687			break;
 688		}
 689		entry = xas_descend(xas, node);
 690		slot = &node->slots[xas->xa_offset];
 691	}
 692
 693	return entry;
 694}
 695
 696/**
 697 * xas_create_range() - Ensure that stores to this range will succeed
 698 * @xas: XArray operation state.
 699 *
 700 * Creates all of the slots in the range covered by @xas.  Sets @xas to
 701 * create single-index entries and positions it at the beginning of the
 702 * range.  This is for the benefit of users which have not yet been
 703 * converted to use multi-index entries.
 704 */
 705void xas_create_range(struct xa_state *xas)
 706{
 707	unsigned long index = xas->xa_index;
 708	unsigned char shift = xas->xa_shift;
 709	unsigned char sibs = xas->xa_sibs;
 710
 711	xas->xa_index |= ((sibs + 1UL) << shift) - 1;
 712	if (xas_is_node(xas) && xas->xa_node->shift == xas->xa_shift)
 713		xas->xa_offset |= sibs;
 714	xas->xa_shift = 0;
 715	xas->xa_sibs = 0;
 716
 717	for (;;) {
 718		xas_create(xas, true);
 719		if (xas_error(xas))
 720			goto restore;
 721		if (xas->xa_index <= (index | XA_CHUNK_MASK))
 722			goto success;
 723		xas->xa_index -= XA_CHUNK_SIZE;
 724
 725		for (;;) {
 726			struct xa_node *node = xas->xa_node;
 727			if (node->shift >= shift)
 728				break;
 729			xas->xa_node = xa_parent_locked(xas->xa, node);
 730			xas->xa_offset = node->offset - 1;
 731			if (node->offset != 0)
 732				break;
 733		}
 734	}
 735
 736restore:
 737	xas->xa_shift = shift;
 738	xas->xa_sibs = sibs;
 739	xas->xa_index = index;
 740	return;
 741success:
 742	xas->xa_index = index;
 743	if (xas->xa_node)
 744		xas_set_offset(xas);
 745}
 746EXPORT_SYMBOL_GPL(xas_create_range);
 747
 748static void update_node(struct xa_state *xas, struct xa_node *node,
 749		int count, int values)
 750{
 751	if (!node || (!count && !values))
 752		return;
 753
 754	node->count += count;
 755	node->nr_values += values;
 756	XA_NODE_BUG_ON(node, node->count > XA_CHUNK_SIZE);
 757	XA_NODE_BUG_ON(node, node->nr_values > XA_CHUNK_SIZE);
 758	xas_update(xas, node);
 759	if (count < 0)
 760		xas_delete_node(xas);
 761}
 762
 763/**
 764 * xas_store() - Store this entry in the XArray.
 765 * @xas: XArray operation state.
 766 * @entry: New entry.
 767 *
 768 * If @xas is operating on a multi-index entry, the entry returned by this
 769 * function is essentially meaningless (it may be an internal entry or it
 770 * may be %NULL, even if there are non-NULL entries at some of the indices
 771 * covered by the range).  This is not a problem for any current users,
 772 * and can be changed if needed.
 773 *
 774 * Return: The old entry at this index.
 775 */
 776void *xas_store(struct xa_state *xas, void *entry)
 777{
 778	struct xa_node *node;
 779	void __rcu **slot = &xas->xa->xa_head;
 780	unsigned int offset, max;
 781	int count = 0;
 782	int values = 0;
 783	void *first, *next;
 784	bool value = xa_is_value(entry);
 785
 786	if (entry) {
 787		bool allow_root = !xa_is_node(entry) && !xa_is_zero(entry);
 788		first = xas_create(xas, allow_root);
 789	} else {
 790		first = xas_load(xas);
 791	}
 792
 793	if (xas_invalid(xas))
 794		return first;
 795	node = xas->xa_node;
 796	if (node && (xas->xa_shift < node->shift))
 797		xas->xa_sibs = 0;
 798	if ((first == entry) && !xas->xa_sibs)
 799		return first;
 800
 801	next = first;
 802	offset = xas->xa_offset;
 803	max = xas->xa_offset + xas->xa_sibs;
 804	if (node) {
 805		slot = &node->slots[offset];
 806		if (xas->xa_sibs)
 807			xas_squash_marks(xas);
 808	}
 809	if (!entry)
 810		xas_init_marks(xas);
 811
 812	for (;;) {
 813		/*
 814		 * Must clear the marks before setting the entry to NULL,
 815		 * otherwise xas_for_each_marked may find a NULL entry and
 816		 * stop early.  rcu_assign_pointer contains a release barrier
 817		 * so the mark clearing will appear to happen before the
 818		 * entry is set to NULL.
 819		 */
 820		rcu_assign_pointer(*slot, entry);
 821		if (xa_is_node(next) && (!node || node->shift))
 822			xas_free_nodes(xas, xa_to_node(next));
 823		if (!node)
 824			break;
 825		count += !next - !entry;
 826		values += !xa_is_value(first) - !value;
 827		if (entry) {
 828			if (offset == max)
 829				break;
 830			if (!xa_is_sibling(entry))
 831				entry = xa_mk_sibling(xas->xa_offset);
 832		} else {
 833			if (offset == XA_CHUNK_MASK)
 834				break;
 835		}
 836		next = xa_entry_locked(xas->xa, node, ++offset);
 837		if (!xa_is_sibling(next)) {
 838			if (!entry && (offset > max))
 839				break;
 840			first = next;
 841		}
 842		slot++;
 843	}
 844
 845	update_node(xas, node, count, values);
 846	return first;
 847}
 848EXPORT_SYMBOL_GPL(xas_store);
 849
 850/**
 851 * xas_get_mark() - Returns the state of this mark.
 852 * @xas: XArray operation state.
 853 * @mark: Mark number.
 854 *
 855 * Return: true if the mark is set, false if the mark is clear or @xas
 856 * is in an error state.
 857 */
 858bool xas_get_mark(const struct xa_state *xas, xa_mark_t mark)
 859{
 860	if (xas_invalid(xas))
 861		return false;
 862	if (!xas->xa_node)
 863		return xa_marked(xas->xa, mark);
 864	return node_get_mark(xas->xa_node, xas->xa_offset, mark);
 865}
 866EXPORT_SYMBOL_GPL(xas_get_mark);
 867
 868/**
 869 * xas_set_mark() - Sets the mark on this entry and its parents.
 870 * @xas: XArray operation state.
 871 * @mark: Mark number.
 872 *
 873 * Sets the specified mark on this entry, and walks up the tree setting it
 874 * on all the ancestor entries.  Does nothing if @xas has not been walked to
 875 * an entry, or is in an error state.
 876 */
 877void xas_set_mark(const struct xa_state *xas, xa_mark_t mark)
 878{
 879	struct xa_node *node = xas->xa_node;
 880	unsigned int offset = xas->xa_offset;
 881
 882	if (xas_invalid(xas))
 883		return;
 884
 885	while (node) {
 886		if (node_set_mark(node, offset, mark))
 887			return;
 888		offset = node->offset;
 889		node = xa_parent_locked(xas->xa, node);
 890	}
 891
 892	if (!xa_marked(xas->xa, mark))
 893		xa_mark_set(xas->xa, mark);
 894}
 895EXPORT_SYMBOL_GPL(xas_set_mark);
 896
 897/**
 898 * xas_clear_mark() - Clears the mark on this entry and its parents.
 899 * @xas: XArray operation state.
 900 * @mark: Mark number.
 901 *
 902 * Clears the specified mark on this entry, and walks back to the head
 903 * attempting to clear it on all the ancestor entries.  Does nothing if
 904 * @xas has not been walked to an entry, or is in an error state.
 905 */
 906void xas_clear_mark(const struct xa_state *xas, xa_mark_t mark)
 907{
 908	struct xa_node *node = xas->xa_node;
 909	unsigned int offset = xas->xa_offset;
 910
 911	if (xas_invalid(xas))
 912		return;
 913
 914	while (node) {
 915		if (!node_clear_mark(node, offset, mark))
 916			return;
 917		if (node_any_mark(node, mark))
 918			return;
 919
 920		offset = node->offset;
 921		node = xa_parent_locked(xas->xa, node);
 922	}
 923
 924	if (xa_marked(xas->xa, mark))
 925		xa_mark_clear(xas->xa, mark);
 926}
 927EXPORT_SYMBOL_GPL(xas_clear_mark);
 928
 929/**
 930 * xas_init_marks() - Initialise all marks for the entry
 931 * @xas: Array operations state.
 932 *
 933 * Initialise all marks for the entry specified by @xas.  If we're tracking
 934 * free entries with a mark, we need to set it on all entries.  All other
 935 * marks are cleared.
 936 *
 937 * This implementation is not as efficient as it could be; we may walk
 938 * up the tree multiple times.
 939 */
 940void xas_init_marks(const struct xa_state *xas)
 941{
 942	xa_mark_t mark = 0;
 943
 944	for (;;) {
 945		if (xa_track_free(xas->xa) && mark == XA_FREE_MARK)
 946			xas_set_mark(xas, mark);
 947		else
 948			xas_clear_mark(xas, mark);
 949		if (mark == XA_MARK_MAX)
 950			break;
 951		mark_inc(mark);
 952	}
 953}
 954EXPORT_SYMBOL_GPL(xas_init_marks);
 955
 956#ifdef CONFIG_XARRAY_MULTI
 957static unsigned int node_get_marks(struct xa_node *node, unsigned int offset)
 958{
 959	unsigned int marks = 0;
 960	xa_mark_t mark = XA_MARK_0;
 961
 962	for (;;) {
 963		if (node_get_mark(node, offset, mark))
 964			marks |= 1 << (__force unsigned int)mark;
 965		if (mark == XA_MARK_MAX)
 966			break;
 967		mark_inc(mark);
 968	}
 969
 970	return marks;
 971}
 972
 973static inline void node_mark_slots(struct xa_node *node, unsigned int sibs,
 974		xa_mark_t mark)
 975{
 976	int i;
 977
 978	if (sibs == 0)
 979		node_mark_all(node, mark);
 980	else {
 981		for (i = 0; i < XA_CHUNK_SIZE; i += sibs + 1)
 982			node_set_mark(node, i, mark);
 983	}
 984}
 985
 986static void node_set_marks(struct xa_node *node, unsigned int offset,
 987			struct xa_node *child, unsigned int sibs,
 988			unsigned int marks)
 989{
 990	xa_mark_t mark = XA_MARK_0;
 991
 992	for (;;) {
 993		if (marks & (1 << (__force unsigned int)mark)) {
 994			node_set_mark(node, offset, mark);
 995			if (child)
 996				node_mark_slots(child, sibs, mark);
 997		}
 998		if (mark == XA_MARK_MAX)
 999			break;
1000		mark_inc(mark);
1001	}
1002}
1003
1004/**
1005 * xas_split_alloc() - Allocate memory for splitting an entry.
1006 * @xas: XArray operation state.
1007 * @entry: New entry which will be stored in the array.
1008 * @order: Current entry order.
1009 * @gfp: Memory allocation flags.
1010 *
1011 * This function should be called before calling xas_split().
1012 * If necessary, it will allocate new nodes (and fill them with @entry)
1013 * to prepare for the upcoming split of an entry of @order size into
1014 * entries of the order stored in the @xas.
1015 *
1016 * Context: May sleep if @gfp flags permit.
1017 */
1018void xas_split_alloc(struct xa_state *xas, void *entry, unsigned int order,
1019		gfp_t gfp)
1020{
1021	unsigned int sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1022	unsigned int mask = xas->xa_sibs;
1023
1024	/* XXX: no support for splitting really large entries yet */
1025	if (WARN_ON(xas->xa_shift + 2 * XA_CHUNK_SHIFT < order))
1026		goto nomem;
1027	if (xas->xa_shift + XA_CHUNK_SHIFT > order)
1028		return;
1029
1030	do {
1031		unsigned int i;
1032		void *sibling = NULL;
1033		struct xa_node *node;
1034
1035		node = kmem_cache_alloc_lru(radix_tree_node_cachep, xas->xa_lru, gfp);
1036		if (!node)
1037			goto nomem;
1038		node->array = xas->xa;
1039		for (i = 0; i < XA_CHUNK_SIZE; i++) {
1040			if ((i & mask) == 0) {
1041				RCU_INIT_POINTER(node->slots[i], entry);
1042				sibling = xa_mk_sibling(i);
1043			} else {
1044				RCU_INIT_POINTER(node->slots[i], sibling);
1045			}
1046		}
1047		RCU_INIT_POINTER(node->parent, xas->xa_alloc);
1048		xas->xa_alloc = node;
1049	} while (sibs-- > 0);
1050
1051	return;
1052nomem:
1053	xas_destroy(xas);
1054	xas_set_err(xas, -ENOMEM);
1055}
1056EXPORT_SYMBOL_GPL(xas_split_alloc);
1057
1058/**
1059 * xas_split() - Split a multi-index entry into smaller entries.
1060 * @xas: XArray operation state.
1061 * @entry: New entry to store in the array.
1062 * @order: Current entry order.
1063 *
1064 * The size of the new entries is set in @xas.  The value in @entry is
1065 * copied to all the replacement entries.
1066 *
1067 * Context: Any context.  The caller should hold the xa_lock.
1068 */
1069void xas_split(struct xa_state *xas, void *entry, unsigned int order)
1070{
1071	unsigned int sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
1072	unsigned int offset, marks;
1073	struct xa_node *node;
1074	void *curr = xas_load(xas);
1075	int values = 0;
1076
1077	node = xas->xa_node;
1078	if (xas_top(node))
1079		return;
1080
1081	marks = node_get_marks(node, xas->xa_offset);
1082
1083	offset = xas->xa_offset + sibs;
1084	do {
1085		if (xas->xa_shift < node->shift) {
1086			struct xa_node *child = xas->xa_alloc;
1087
1088			xas->xa_alloc = rcu_dereference_raw(child->parent);
1089			child->shift = node->shift - XA_CHUNK_SHIFT;
1090			child->offset = offset;
1091			child->count = XA_CHUNK_SIZE;
1092			child->nr_values = xa_is_value(entry) ?
1093					XA_CHUNK_SIZE : 0;
1094			RCU_INIT_POINTER(child->parent, node);
1095			node_set_marks(node, offset, child, xas->xa_sibs,
1096					marks);
1097			rcu_assign_pointer(node->slots[offset],
1098					xa_mk_node(child));
1099			if (xa_is_value(curr))
1100				values--;
1101			xas_update(xas, child);
1102		} else {
1103			unsigned int canon = offset - xas->xa_sibs;
1104
1105			node_set_marks(node, canon, NULL, 0, marks);
1106			rcu_assign_pointer(node->slots[canon], entry);
1107			while (offset > canon)
1108				rcu_assign_pointer(node->slots[offset--],
1109						xa_mk_sibling(canon));
1110			values += (xa_is_value(entry) - xa_is_value(curr)) *
1111					(xas->xa_sibs + 1);
1112		}
1113	} while (offset-- > xas->xa_offset);
1114
1115	node->nr_values += values;
1116	xas_update(xas, node);
1117}
1118EXPORT_SYMBOL_GPL(xas_split);
1119#endif
1120
1121/**
1122 * xas_pause() - Pause a walk to drop a lock.
1123 * @xas: XArray operation state.
1124 *
1125 * Some users need to pause a walk and drop the lock they're holding in
1126 * order to yield to a higher priority thread or carry out an operation
1127 * on an entry.  Those users should call this function before they drop
1128 * the lock.  It resets the @xas to be suitable for the next iteration
1129 * of the loop after the user has reacquired the lock.  If most entries
1130 * found during a walk require you to call xas_pause(), the xa_for_each()
1131 * iterator may be more appropriate.
1132 *
1133 * Note that xas_pause() only works for forward iteration.  If a user needs
1134 * to pause a reverse iteration, we will need a xas_pause_rev().
1135 */
1136void xas_pause(struct xa_state *xas)
1137{
1138	struct xa_node *node = xas->xa_node;
1139
1140	if (xas_invalid(xas))
1141		return;
1142
1143	xas->xa_node = XAS_RESTART;
1144	if (node) {
1145		unsigned long offset = xas->xa_offset;
1146		while (++offset < XA_CHUNK_SIZE) {
1147			if (!xa_is_sibling(xa_entry(xas->xa, node, offset)))
1148				break;
1149		}
1150		xas->xa_index += (offset - xas->xa_offset) << node->shift;
1151		if (xas->xa_index == 0)
1152			xas->xa_node = XAS_BOUNDS;
1153	} else {
1154		xas->xa_index++;
1155	}
1156}
1157EXPORT_SYMBOL_GPL(xas_pause);
1158
1159/*
1160 * __xas_prev() - Find the previous entry in the XArray.
1161 * @xas: XArray operation state.
1162 *
1163 * Helper function for xas_prev() which handles all the complex cases
1164 * out of line.
1165 */
1166void *__xas_prev(struct xa_state *xas)
1167{
1168	void *entry;
1169
1170	if (!xas_frozen(xas->xa_node))
1171		xas->xa_index--;
1172	if (!xas->xa_node)
1173		return set_bounds(xas);
1174	if (xas_not_node(xas->xa_node))
1175		return xas_load(xas);
1176
1177	if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
1178		xas->xa_offset--;
1179
1180	while (xas->xa_offset == 255) {
1181		xas->xa_offset = xas->xa_node->offset - 1;
1182		xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1183		if (!xas->xa_node)
1184			return set_bounds(xas);
1185	}
1186
1187	for (;;) {
1188		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1189		if (!xa_is_node(entry))
1190			return entry;
1191
1192		xas->xa_node = xa_to_node(entry);
1193		xas_set_offset(xas);
1194	}
1195}
1196EXPORT_SYMBOL_GPL(__xas_prev);
1197
1198/*
1199 * __xas_next() - Find the next entry in the XArray.
1200 * @xas: XArray operation state.
1201 *
1202 * Helper function for xas_next() which handles all the complex cases
1203 * out of line.
1204 */
1205void *__xas_next(struct xa_state *xas)
1206{
1207	void *entry;
1208
1209	if (!xas_frozen(xas->xa_node))
1210		xas->xa_index++;
1211	if (!xas->xa_node)
1212		return set_bounds(xas);
1213	if (xas_not_node(xas->xa_node))
1214		return xas_load(xas);
1215
1216	if (xas->xa_offset != get_offset(xas->xa_index, xas->xa_node))
1217		xas->xa_offset++;
1218
1219	while (xas->xa_offset == XA_CHUNK_SIZE) {
1220		xas->xa_offset = xas->xa_node->offset + 1;
1221		xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1222		if (!xas->xa_node)
1223			return set_bounds(xas);
1224	}
1225
1226	for (;;) {
1227		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1228		if (!xa_is_node(entry))
1229			return entry;
1230
1231		xas->xa_node = xa_to_node(entry);
1232		xas_set_offset(xas);
1233	}
1234}
1235EXPORT_SYMBOL_GPL(__xas_next);
1236
1237/**
1238 * xas_find() - Find the next present entry in the XArray.
1239 * @xas: XArray operation state.
1240 * @max: Highest index to return.
1241 *
1242 * If the @xas has not yet been walked to an entry, return the entry
1243 * which has an index >= xas.xa_index.  If it has been walked, the entry
1244 * currently being pointed at has been processed, and so we move to the
1245 * next entry.
1246 *
1247 * If no entry is found and the array is smaller than @max, the iterator
1248 * is set to the smallest index not yet in the array.  This allows @xas
1249 * to be immediately passed to xas_store().
1250 *
1251 * Return: The entry, if found, otherwise %NULL.
1252 */
1253void *xas_find(struct xa_state *xas, unsigned long max)
1254{
1255	void *entry;
1256
1257	if (xas_error(xas) || xas->xa_node == XAS_BOUNDS)
1258		return NULL;
1259	if (xas->xa_index > max)
1260		return set_bounds(xas);
1261
1262	if (!xas->xa_node) {
1263		xas->xa_index = 1;
1264		return set_bounds(xas);
1265	} else if (xas->xa_node == XAS_RESTART) {
1266		entry = xas_load(xas);
1267		if (entry || xas_not_node(xas->xa_node))
1268			return entry;
1269	} else if (!xas->xa_node->shift &&
1270		    xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)) {
1271		xas->xa_offset = ((xas->xa_index - 1) & XA_CHUNK_MASK) + 1;
1272	}
1273
1274	xas_next_offset(xas);
1275
1276	while (xas->xa_node && (xas->xa_index <= max)) {
1277		if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) {
1278			xas->xa_offset = xas->xa_node->offset + 1;
1279			xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1280			continue;
1281		}
1282
1283		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1284		if (xa_is_node(entry)) {
1285			xas->xa_node = xa_to_node(entry);
1286			xas->xa_offset = 0;
1287			continue;
1288		}
1289		if (entry && !xa_is_sibling(entry))
1290			return entry;
1291
1292		xas_next_offset(xas);
1293	}
1294
1295	if (!xas->xa_node)
1296		xas->xa_node = XAS_BOUNDS;
1297	return NULL;
1298}
1299EXPORT_SYMBOL_GPL(xas_find);
1300
1301/**
1302 * xas_find_marked() - Find the next marked entry in the XArray.
1303 * @xas: XArray operation state.
1304 * @max: Highest index to return.
1305 * @mark: Mark number to search for.
1306 *
1307 * If the @xas has not yet been walked to an entry, return the marked entry
1308 * which has an index >= xas.xa_index.  If it has been walked, the entry
1309 * currently being pointed at has been processed, and so we return the
1310 * first marked entry with an index > xas.xa_index.
1311 *
1312 * If no marked entry is found and the array is smaller than @max, @xas is
1313 * set to the bounds state and xas->xa_index is set to the smallest index
1314 * not yet in the array.  This allows @xas to be immediately passed to
1315 * xas_store().
1316 *
1317 * If no entry is found before @max is reached, @xas is set to the restart
1318 * state.
1319 *
1320 * Return: The entry, if found, otherwise %NULL.
1321 */
1322void *xas_find_marked(struct xa_state *xas, unsigned long max, xa_mark_t mark)
1323{
1324	bool advance = true;
1325	unsigned int offset;
1326	void *entry;
1327
1328	if (xas_error(xas))
1329		return NULL;
1330	if (xas->xa_index > max)
1331		goto max;
1332
1333	if (!xas->xa_node) {
1334		xas->xa_index = 1;
1335		goto out;
1336	} else if (xas_top(xas->xa_node)) {
1337		advance = false;
1338		entry = xa_head(xas->xa);
1339		xas->xa_node = NULL;
1340		if (xas->xa_index > max_index(entry))
1341			goto out;
1342		if (!xa_is_node(entry)) {
1343			if (xa_marked(xas->xa, mark))
1344				return entry;
1345			xas->xa_index = 1;
1346			goto out;
1347		}
1348		xas->xa_node = xa_to_node(entry);
1349		xas->xa_offset = xas->xa_index >> xas->xa_node->shift;
1350	}
1351
1352	while (xas->xa_index <= max) {
1353		if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) {
1354			xas->xa_offset = xas->xa_node->offset + 1;
1355			xas->xa_node = xa_parent(xas->xa, xas->xa_node);
1356			if (!xas->xa_node)
1357				break;
1358			advance = false;
1359			continue;
1360		}
1361
1362		if (!advance) {
1363			entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1364			if (xa_is_sibling(entry)) {
1365				xas->xa_offset = xa_to_sibling(entry);
1366				xas_move_index(xas, xas->xa_offset);
1367			}
1368		}
1369
1370		offset = xas_find_chunk(xas, advance, mark);
1371		if (offset > xas->xa_offset) {
1372			advance = false;
1373			xas_move_index(xas, offset);
1374			/* Mind the wrap */
1375			if ((xas->xa_index - 1) >= max)
1376				goto max;
1377			xas->xa_offset = offset;
1378			if (offset == XA_CHUNK_SIZE)
1379				continue;
1380		}
1381
1382		entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset);
1383		if (!entry && !(xa_track_free(xas->xa) && mark == XA_FREE_MARK))
1384			continue;
1385		if (!xa_is_node(entry))
1386			return entry;
1387		xas->xa_node = xa_to_node(entry);
1388		xas_set_offset(xas);
1389	}
1390
1391out:
1392	if (xas->xa_index > max)
1393		goto max;
1394	return set_bounds(xas);
1395max:
1396	xas->xa_node = XAS_RESTART;
1397	return NULL;
1398}
1399EXPORT_SYMBOL_GPL(xas_find_marked);
1400
1401/**
1402 * xas_find_conflict() - Find the next present entry in a range.
1403 * @xas: XArray operation state.
1404 *
1405 * The @xas describes both a range and a position within that range.
1406 *
1407 * Context: Any context.  Expects xa_lock to be held.
1408 * Return: The next entry in the range covered by @xas or %NULL.
1409 */
1410void *xas_find_conflict(struct xa_state *xas)
1411{
1412	void *curr;
1413
1414	if (xas_error(xas))
1415		return NULL;
1416
1417	if (!xas->xa_node)
1418		return NULL;
1419
1420	if (xas_top(xas->xa_node)) {
1421		curr = xas_start(xas);
1422		if (!curr)
1423			return NULL;
1424		while (xa_is_node(curr)) {
1425			struct xa_node *node = xa_to_node(curr);
1426			curr = xas_descend(xas, node);
1427		}
1428		if (curr)
1429			return curr;
1430	}
1431
1432	if (xas->xa_node->shift > xas->xa_shift)
1433		return NULL;
1434
1435	for (;;) {
1436		if (xas->xa_node->shift == xas->xa_shift) {
1437			if ((xas->xa_offset & xas->xa_sibs) == xas->xa_sibs)
1438				break;
1439		} else if (xas->xa_offset == XA_CHUNK_MASK) {
1440			xas->xa_offset = xas->xa_node->offset;
1441			xas->xa_node = xa_parent_locked(xas->xa, xas->xa_node);
1442			if (!xas->xa_node)
1443				break;
1444			continue;
1445		}
1446		curr = xa_entry_locked(xas->xa, xas->xa_node, ++xas->xa_offset);
1447		if (xa_is_sibling(curr))
1448			continue;
1449		while (xa_is_node(curr)) {
1450			xas->xa_node = xa_to_node(curr);
1451			xas->xa_offset = 0;
1452			curr = xa_entry_locked(xas->xa, xas->xa_node, 0);
1453		}
1454		if (curr)
1455			return curr;
1456	}
1457	xas->xa_offset -= xas->xa_sibs;
1458	return NULL;
1459}
1460EXPORT_SYMBOL_GPL(xas_find_conflict);
1461
1462/**
1463 * xa_load() - Load an entry from an XArray.
1464 * @xa: XArray.
1465 * @index: index into array.
1466 *
1467 * Context: Any context.  Takes and releases the RCU lock.
1468 * Return: The entry at @index in @xa.
1469 */
1470void *xa_load(struct xarray *xa, unsigned long index)
1471{
1472	XA_STATE(xas, xa, index);
1473	void *entry;
1474
1475	rcu_read_lock();
1476	do {
1477		entry = xas_load(&xas);
1478		if (xa_is_zero(entry))
1479			entry = NULL;
1480	} while (xas_retry(&xas, entry));
1481	rcu_read_unlock();
1482
1483	return entry;
1484}
1485EXPORT_SYMBOL(xa_load);
1486
1487static void *xas_result(struct xa_state *xas, void *curr)
1488{
1489	if (xa_is_zero(curr))
1490		return NULL;
1491	if (xas_error(xas))
1492		curr = xas->xa_node;
1493	return curr;
1494}
1495
1496/**
1497 * __xa_erase() - Erase this entry from the XArray while locked.
1498 * @xa: XArray.
1499 * @index: Index into array.
1500 *
1501 * After this function returns, loading from @index will return %NULL.
1502 * If the index is part of a multi-index entry, all indices will be erased
1503 * and none of the entries will be part of a multi-index entry.
1504 *
1505 * Context: Any context.  Expects xa_lock to be held on entry.
1506 * Return: The entry which used to be at this index.
1507 */
1508void *__xa_erase(struct xarray *xa, unsigned long index)
1509{
1510	XA_STATE(xas, xa, index);
1511	return xas_result(&xas, xas_store(&xas, NULL));
1512}
1513EXPORT_SYMBOL(__xa_erase);
1514
1515/**
1516 * xa_erase() - Erase this entry from the XArray.
1517 * @xa: XArray.
1518 * @index: Index of entry.
1519 *
1520 * After this function returns, loading from @index will return %NULL.
1521 * If the index is part of a multi-index entry, all indices will be erased
1522 * and none of the entries will be part of a multi-index entry.
1523 *
1524 * Context: Any context.  Takes and releases the xa_lock.
1525 * Return: The entry which used to be at this index.
1526 */
1527void *xa_erase(struct xarray *xa, unsigned long index)
1528{
1529	void *entry;
1530
1531	xa_lock(xa);
1532	entry = __xa_erase(xa, index);
1533	xa_unlock(xa);
1534
1535	return entry;
1536}
1537EXPORT_SYMBOL(xa_erase);
1538
1539/**
1540 * __xa_store() - Store this entry in the XArray.
1541 * @xa: XArray.
1542 * @index: Index into array.
1543 * @entry: New entry.
1544 * @gfp: Memory allocation flags.
1545 *
1546 * You must already be holding the xa_lock when calling this function.
1547 * It will drop the lock if needed to allocate memory, and then reacquire
1548 * it afterwards.
1549 *
1550 * Context: Any context.  Expects xa_lock to be held on entry.  May
1551 * release and reacquire xa_lock if @gfp flags permit.
1552 * Return: The old entry at this index or xa_err() if an error happened.
1553 */
1554void *__xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1555{
1556	XA_STATE(xas, xa, index);
1557	void *curr;
1558
1559	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1560		return XA_ERROR(-EINVAL);
1561	if (xa_track_free(xa) && !entry)
1562		entry = XA_ZERO_ENTRY;
1563
1564	do {
1565		curr = xas_store(&xas, entry);
1566		if (xa_track_free(xa))
1567			xas_clear_mark(&xas, XA_FREE_MARK);
1568	} while (__xas_nomem(&xas, gfp));
1569
1570	return xas_result(&xas, curr);
1571}
1572EXPORT_SYMBOL(__xa_store);
1573
1574/**
1575 * xa_store() - Store this entry in the XArray.
1576 * @xa: XArray.
1577 * @index: Index into array.
1578 * @entry: New entry.
1579 * @gfp: Memory allocation flags.
1580 *
1581 * After this function returns, loads from this index will return @entry.
1582 * Storing into an existing multi-index entry updates the entry of every index.
1583 * The marks associated with @index are unaffected unless @entry is %NULL.
1584 *
1585 * Context: Any context.  Takes and releases the xa_lock.
1586 * May sleep if the @gfp flags permit.
1587 * Return: The old entry at this index on success, xa_err(-EINVAL) if @entry
1588 * cannot be stored in an XArray, or xa_err(-ENOMEM) if memory allocation
1589 * failed.
1590 */
1591void *xa_store(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1592{
1593	void *curr;
1594
1595	xa_lock(xa);
1596	curr = __xa_store(xa, index, entry, gfp);
1597	xa_unlock(xa);
1598
1599	return curr;
1600}
1601EXPORT_SYMBOL(xa_store);
1602
1603/**
1604 * __xa_cmpxchg() - Store this entry in the XArray.
1605 * @xa: XArray.
1606 * @index: Index into array.
1607 * @old: Old value to test against.
1608 * @entry: New entry.
1609 * @gfp: Memory allocation flags.
1610 *
1611 * You must already be holding the xa_lock when calling this function.
1612 * It will drop the lock if needed to allocate memory, and then reacquire
1613 * it afterwards.
1614 *
1615 * Context: Any context.  Expects xa_lock to be held on entry.  May
1616 * release and reacquire xa_lock if @gfp flags permit.
1617 * Return: The old entry at this index or xa_err() if an error happened.
1618 */
1619void *__xa_cmpxchg(struct xarray *xa, unsigned long index,
1620			void *old, void *entry, gfp_t gfp)
1621{
1622	XA_STATE(xas, xa, index);
1623	void *curr;
1624
1625	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1626		return XA_ERROR(-EINVAL);
1627
1628	do {
1629		curr = xas_load(&xas);
1630		if (curr == old) {
1631			xas_store(&xas, entry);
1632			if (xa_track_free(xa) && entry && !curr)
1633				xas_clear_mark(&xas, XA_FREE_MARK);
1634		}
1635	} while (__xas_nomem(&xas, gfp));
1636
1637	return xas_result(&xas, curr);
1638}
1639EXPORT_SYMBOL(__xa_cmpxchg);
1640
1641/**
1642 * __xa_insert() - Store this entry in the XArray if no entry is present.
1643 * @xa: XArray.
1644 * @index: Index into array.
1645 * @entry: New entry.
1646 * @gfp: Memory allocation flags.
1647 *
1648 * Inserting a NULL entry will store a reserved entry (like xa_reserve())
1649 * if no entry is present.  Inserting will fail if a reserved entry is
1650 * present, even though loading from this index will return NULL.
1651 *
1652 * Context: Any context.  Expects xa_lock to be held on entry.  May
1653 * release and reacquire xa_lock if @gfp flags permit.
1654 * Return: 0 if the store succeeded.  -EBUSY if another entry was present.
1655 * -ENOMEM if memory could not be allocated.
1656 */
1657int __xa_insert(struct xarray *xa, unsigned long index, void *entry, gfp_t gfp)
1658{
1659	XA_STATE(xas, xa, index);
1660	void *curr;
1661
1662	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1663		return -EINVAL;
1664	if (!entry)
1665		entry = XA_ZERO_ENTRY;
1666
1667	do {
1668		curr = xas_load(&xas);
1669		if (!curr) {
1670			xas_store(&xas, entry);
1671			if (xa_track_free(xa))
1672				xas_clear_mark(&xas, XA_FREE_MARK);
1673		} else {
1674			xas_set_err(&xas, -EBUSY);
1675		}
1676	} while (__xas_nomem(&xas, gfp));
1677
1678	return xas_error(&xas);
1679}
1680EXPORT_SYMBOL(__xa_insert);
1681
1682#ifdef CONFIG_XARRAY_MULTI
1683static void xas_set_range(struct xa_state *xas, unsigned long first,
1684		unsigned long last)
1685{
1686	unsigned int shift = 0;
1687	unsigned long sibs = last - first;
1688	unsigned int offset = XA_CHUNK_MASK;
1689
1690	xas_set(xas, first);
1691
1692	while ((first & XA_CHUNK_MASK) == 0) {
1693		if (sibs < XA_CHUNK_MASK)
1694			break;
1695		if ((sibs == XA_CHUNK_MASK) && (offset < XA_CHUNK_MASK))
1696			break;
1697		shift += XA_CHUNK_SHIFT;
1698		if (offset == XA_CHUNK_MASK)
1699			offset = sibs & XA_CHUNK_MASK;
1700		sibs >>= XA_CHUNK_SHIFT;
1701		first >>= XA_CHUNK_SHIFT;
1702	}
1703
1704	offset = first & XA_CHUNK_MASK;
1705	if (offset + sibs > XA_CHUNK_MASK)
1706		sibs = XA_CHUNK_MASK - offset;
1707	if ((((first + sibs + 1) << shift) - 1) > last)
1708		sibs -= 1;
1709
1710	xas->xa_shift = shift;
1711	xas->xa_sibs = sibs;
1712}
1713
1714/**
1715 * xa_store_range() - Store this entry at a range of indices in the XArray.
1716 * @xa: XArray.
1717 * @first: First index to affect.
1718 * @last: Last index to affect.
1719 * @entry: New entry.
1720 * @gfp: Memory allocation flags.
1721 *
1722 * After this function returns, loads from any index between @first and @last,
1723 * inclusive will return @entry.
1724 * Storing into an existing multi-index entry updates the entry of every index.
1725 * The marks associated with @index are unaffected unless @entry is %NULL.
1726 *
1727 * Context: Process context.  Takes and releases the xa_lock.  May sleep
1728 * if the @gfp flags permit.
1729 * Return: %NULL on success, xa_err(-EINVAL) if @entry cannot be stored in
1730 * an XArray, or xa_err(-ENOMEM) if memory allocation failed.
1731 */
1732void *xa_store_range(struct xarray *xa, unsigned long first,
1733		unsigned long last, void *entry, gfp_t gfp)
1734{
1735	XA_STATE(xas, xa, 0);
1736
1737	if (WARN_ON_ONCE(xa_is_internal(entry)))
1738		return XA_ERROR(-EINVAL);
1739	if (last < first)
1740		return XA_ERROR(-EINVAL);
1741
1742	do {
1743		xas_lock(&xas);
1744		if (entry) {
1745			unsigned int order = BITS_PER_LONG;
1746			if (last + 1)
1747				order = __ffs(last + 1);
1748			xas_set_order(&xas, last, order);
1749			xas_create(&xas, true);
1750			if (xas_error(&xas))
1751				goto unlock;
1752		}
1753		do {
1754			xas_set_range(&xas, first, last);
1755			xas_store(&xas, entry);
1756			if (xas_error(&xas))
1757				goto unlock;
1758			first += xas_size(&xas);
1759		} while (first <= last);
1760unlock:
1761		xas_unlock(&xas);
1762	} while (xas_nomem(&xas, gfp));
1763
1764	return xas_result(&xas, NULL);
1765}
1766EXPORT_SYMBOL(xa_store_range);
1767
1768/**
1769 * xas_get_order() - Get the order of an entry.
1770 * @xas: XArray operation state.
1771 *
1772 * Called after xas_load, the xas should not be in an error state.
1773 *
1774 * Return: A number between 0 and 63 indicating the order of the entry.
1775 */
1776int xas_get_order(struct xa_state *xas)
1777{
 
 
1778	int order = 0;
1779
1780	if (!xas->xa_node)
1781		return 0;
 
 
 
 
 
 
1782
1783	for (;;) {
1784		unsigned int slot = xas->xa_offset + (1 << order);
1785
1786		if (slot >= XA_CHUNK_SIZE)
1787			break;
1788		if (!xa_is_sibling(xa_entry(xas->xa, xas->xa_node, slot)))
1789			break;
1790		order++;
1791	}
1792
1793	order += xas->xa_node->shift;
1794	return order;
1795}
1796EXPORT_SYMBOL_GPL(xas_get_order);
1797
1798/**
1799 * xa_get_order() - Get the order of an entry.
1800 * @xa: XArray.
1801 * @index: Index of the entry.
1802 *
1803 * Return: A number between 0 and 63 indicating the order of the entry.
1804 */
1805int xa_get_order(struct xarray *xa, unsigned long index)
1806{
1807	XA_STATE(xas, xa, index);
1808	int order = 0;
1809	void *entry;
1810
1811	rcu_read_lock();
1812	entry = xas_load(&xas);
1813	if (entry)
1814		order = xas_get_order(&xas);
1815	rcu_read_unlock();
1816
1817	return order;
1818}
1819EXPORT_SYMBOL(xa_get_order);
1820#endif /* CONFIG_XARRAY_MULTI */
1821
1822/**
1823 * __xa_alloc() - Find somewhere to store this entry in the XArray.
1824 * @xa: XArray.
1825 * @id: Pointer to ID.
1826 * @limit: Range for allocated ID.
1827 * @entry: New entry.
1828 * @gfp: Memory allocation flags.
1829 *
1830 * Finds an empty entry in @xa between @limit.min and @limit.max,
1831 * stores the index into the @id pointer, then stores the entry at
1832 * that index.  A concurrent lookup will not see an uninitialised @id.
1833 *
1834 * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
1835 * in xa_init_flags().
1836 *
1837 * Context: Any context.  Expects xa_lock to be held on entry.  May
1838 * release and reacquire xa_lock if @gfp flags permit.
1839 * Return: 0 on success, -ENOMEM if memory could not be allocated or
1840 * -EBUSY if there are no free entries in @limit.
1841 */
1842int __xa_alloc(struct xarray *xa, u32 *id, void *entry,
1843		struct xa_limit limit, gfp_t gfp)
1844{
1845	XA_STATE(xas, xa, 0);
1846
1847	if (WARN_ON_ONCE(xa_is_advanced(entry)))
1848		return -EINVAL;
1849	if (WARN_ON_ONCE(!xa_track_free(xa)))
1850		return -EINVAL;
1851
1852	if (!entry)
1853		entry = XA_ZERO_ENTRY;
1854
1855	do {
1856		xas.xa_index = limit.min;
1857		xas_find_marked(&xas, limit.max, XA_FREE_MARK);
1858		if (xas.xa_node == XAS_RESTART)
1859			xas_set_err(&xas, -EBUSY);
1860		else
1861			*id = xas.xa_index;
1862		xas_store(&xas, entry);
1863		xas_clear_mark(&xas, XA_FREE_MARK);
1864	} while (__xas_nomem(&xas, gfp));
1865
1866	return xas_error(&xas);
1867}
1868EXPORT_SYMBOL(__xa_alloc);
1869
1870/**
1871 * __xa_alloc_cyclic() - Find somewhere to store this entry in the XArray.
1872 * @xa: XArray.
1873 * @id: Pointer to ID.
1874 * @entry: New entry.
1875 * @limit: Range of allocated ID.
1876 * @next: Pointer to next ID to allocate.
1877 * @gfp: Memory allocation flags.
1878 *
1879 * Finds an empty entry in @xa between @limit.min and @limit.max,
1880 * stores the index into the @id pointer, then stores the entry at
1881 * that index.  A concurrent lookup will not see an uninitialised @id.
1882 * The search for an empty entry will start at @next and will wrap
1883 * around if necessary.
1884 *
1885 * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set
1886 * in xa_init_flags().
1887 *
1888 * Context: Any context.  Expects xa_lock to be held on entry.  May
1889 * release and reacquire xa_lock if @gfp flags permit.
1890 * Return: 0 if the allocation succeeded without wrapping.  1 if the
1891 * allocation succeeded after wrapping, -ENOMEM if memory could not be
1892 * allocated or -EBUSY if there are no free entries in @limit.
1893 */
1894int __xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
1895		struct xa_limit limit, u32 *next, gfp_t gfp)
1896{
1897	u32 min = limit.min;
1898	int ret;
1899
1900	limit.min = max(min, *next);
1901	ret = __xa_alloc(xa, id, entry, limit, gfp);
1902	if ((xa->xa_flags & XA_FLAGS_ALLOC_WRAPPED) && ret == 0) {
1903		xa->xa_flags &= ~XA_FLAGS_ALLOC_WRAPPED;
1904		ret = 1;
1905	}
1906
1907	if (ret < 0 && limit.min > min) {
1908		limit.min = min;
1909		ret = __xa_alloc(xa, id, entry, limit, gfp);
1910		if (ret == 0)
1911			ret = 1;
1912	}
1913
1914	if (ret >= 0) {
1915		*next = *id + 1;
1916		if (*next == 0)
1917			xa->xa_flags |= XA_FLAGS_ALLOC_WRAPPED;
1918	}
1919	return ret;
1920}
1921EXPORT_SYMBOL(__xa_alloc_cyclic);
1922
1923/**
1924 * __xa_set_mark() - Set this mark on this entry while locked.
1925 * @xa: XArray.
1926 * @index: Index of entry.
1927 * @mark: Mark number.
1928 *
1929 * Attempting to set a mark on a %NULL entry does not succeed.
1930 *
1931 * Context: Any context.  Expects xa_lock to be held on entry.
1932 */
1933void __xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1934{
1935	XA_STATE(xas, xa, index);
1936	void *entry = xas_load(&xas);
1937
1938	if (entry)
1939		xas_set_mark(&xas, mark);
1940}
1941EXPORT_SYMBOL(__xa_set_mark);
1942
1943/**
1944 * __xa_clear_mark() - Clear this mark on this entry while locked.
1945 * @xa: XArray.
1946 * @index: Index of entry.
1947 * @mark: Mark number.
1948 *
1949 * Context: Any context.  Expects xa_lock to be held on entry.
1950 */
1951void __xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1952{
1953	XA_STATE(xas, xa, index);
1954	void *entry = xas_load(&xas);
1955
1956	if (entry)
1957		xas_clear_mark(&xas, mark);
1958}
1959EXPORT_SYMBOL(__xa_clear_mark);
1960
1961/**
1962 * xa_get_mark() - Inquire whether this mark is set on this entry.
1963 * @xa: XArray.
1964 * @index: Index of entry.
1965 * @mark: Mark number.
1966 *
1967 * This function uses the RCU read lock, so the result may be out of date
1968 * by the time it returns.  If you need the result to be stable, use a lock.
1969 *
1970 * Context: Any context.  Takes and releases the RCU lock.
1971 * Return: True if the entry at @index has this mark set, false if it doesn't.
1972 */
1973bool xa_get_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
1974{
1975	XA_STATE(xas, xa, index);
1976	void *entry;
1977
1978	rcu_read_lock();
1979	entry = xas_start(&xas);
1980	while (xas_get_mark(&xas, mark)) {
1981		if (!xa_is_node(entry))
1982			goto found;
1983		entry = xas_descend(&xas, xa_to_node(entry));
1984	}
1985	rcu_read_unlock();
1986	return false;
1987 found:
1988	rcu_read_unlock();
1989	return true;
1990}
1991EXPORT_SYMBOL(xa_get_mark);
1992
1993/**
1994 * xa_set_mark() - Set this mark on this entry.
1995 * @xa: XArray.
1996 * @index: Index of entry.
1997 * @mark: Mark number.
1998 *
1999 * Attempting to set a mark on a %NULL entry does not succeed.
2000 *
2001 * Context: Process context.  Takes and releases the xa_lock.
2002 */
2003void xa_set_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
2004{
2005	xa_lock(xa);
2006	__xa_set_mark(xa, index, mark);
2007	xa_unlock(xa);
2008}
2009EXPORT_SYMBOL(xa_set_mark);
2010
2011/**
2012 * xa_clear_mark() - Clear this mark on this entry.
2013 * @xa: XArray.
2014 * @index: Index of entry.
2015 * @mark: Mark number.
2016 *
2017 * Clearing a mark always succeeds.
2018 *
2019 * Context: Process context.  Takes and releases the xa_lock.
2020 */
2021void xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark)
2022{
2023	xa_lock(xa);
2024	__xa_clear_mark(xa, index, mark);
2025	xa_unlock(xa);
2026}
2027EXPORT_SYMBOL(xa_clear_mark);
2028
2029/**
2030 * xa_find() - Search the XArray for an entry.
2031 * @xa: XArray.
2032 * @indexp: Pointer to an index.
2033 * @max: Maximum index to search to.
2034 * @filter: Selection criterion.
2035 *
2036 * Finds the entry in @xa which matches the @filter, and has the lowest
2037 * index that is at least @indexp and no more than @max.
2038 * If an entry is found, @indexp is updated to be the index of the entry.
2039 * This function is protected by the RCU read lock, so it may not find
2040 * entries which are being simultaneously added.  It will not return an
2041 * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find().
2042 *
2043 * Context: Any context.  Takes and releases the RCU lock.
2044 * Return: The entry, if found, otherwise %NULL.
2045 */
2046void *xa_find(struct xarray *xa, unsigned long *indexp,
2047			unsigned long max, xa_mark_t filter)
2048{
2049	XA_STATE(xas, xa, *indexp);
2050	void *entry;
2051
2052	rcu_read_lock();
2053	do {
2054		if ((__force unsigned int)filter < XA_MAX_MARKS)
2055			entry = xas_find_marked(&xas, max, filter);
2056		else
2057			entry = xas_find(&xas, max);
2058	} while (xas_retry(&xas, entry));
2059	rcu_read_unlock();
2060
2061	if (entry)
2062		*indexp = xas.xa_index;
2063	return entry;
2064}
2065EXPORT_SYMBOL(xa_find);
2066
2067static bool xas_sibling(struct xa_state *xas)
2068{
2069	struct xa_node *node = xas->xa_node;
2070	unsigned long mask;
2071
2072	if (!IS_ENABLED(CONFIG_XARRAY_MULTI) || !node)
2073		return false;
2074	mask = (XA_CHUNK_SIZE << node->shift) - 1;
2075	return (xas->xa_index & mask) >
2076		((unsigned long)xas->xa_offset << node->shift);
2077}
2078
2079/**
2080 * xa_find_after() - Search the XArray for a present entry.
2081 * @xa: XArray.
2082 * @indexp: Pointer to an index.
2083 * @max: Maximum index to search to.
2084 * @filter: Selection criterion.
2085 *
2086 * Finds the entry in @xa which matches the @filter and has the lowest
2087 * index that is above @indexp and no more than @max.
2088 * If an entry is found, @indexp is updated to be the index of the entry.
2089 * This function is protected by the RCU read lock, so it may miss entries
2090 * which are being simultaneously added.  It will not return an
2091 * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find().
2092 *
2093 * Context: Any context.  Takes and releases the RCU lock.
2094 * Return: The pointer, if found, otherwise %NULL.
2095 */
2096void *xa_find_after(struct xarray *xa, unsigned long *indexp,
2097			unsigned long max, xa_mark_t filter)
2098{
2099	XA_STATE(xas, xa, *indexp + 1);
2100	void *entry;
2101
2102	if (xas.xa_index == 0)
2103		return NULL;
2104
2105	rcu_read_lock();
2106	for (;;) {
2107		if ((__force unsigned int)filter < XA_MAX_MARKS)
2108			entry = xas_find_marked(&xas, max, filter);
2109		else
2110			entry = xas_find(&xas, max);
2111
2112		if (xas_invalid(&xas))
2113			break;
2114		if (xas_sibling(&xas))
2115			continue;
2116		if (!xas_retry(&xas, entry))
2117			break;
2118	}
2119	rcu_read_unlock();
2120
2121	if (entry)
2122		*indexp = xas.xa_index;
2123	return entry;
2124}
2125EXPORT_SYMBOL(xa_find_after);
2126
2127static unsigned int xas_extract_present(struct xa_state *xas, void **dst,
2128			unsigned long max, unsigned int n)
2129{
2130	void *entry;
2131	unsigned int i = 0;
2132
2133	rcu_read_lock();
2134	xas_for_each(xas, entry, max) {
2135		if (xas_retry(xas, entry))
2136			continue;
2137		dst[i++] = entry;
2138		if (i == n)
2139			break;
2140	}
2141	rcu_read_unlock();
2142
2143	return i;
2144}
2145
2146static unsigned int xas_extract_marked(struct xa_state *xas, void **dst,
2147			unsigned long max, unsigned int n, xa_mark_t mark)
2148{
2149	void *entry;
2150	unsigned int i = 0;
2151
2152	rcu_read_lock();
2153	xas_for_each_marked(xas, entry, max, mark) {
2154		if (xas_retry(xas, entry))
2155			continue;
2156		dst[i++] = entry;
2157		if (i == n)
2158			break;
2159	}
2160	rcu_read_unlock();
2161
2162	return i;
2163}
2164
2165/**
2166 * xa_extract() - Copy selected entries from the XArray into a normal array.
2167 * @xa: The source XArray to copy from.
2168 * @dst: The buffer to copy entries into.
2169 * @start: The first index in the XArray eligible to be selected.
2170 * @max: The last index in the XArray eligible to be selected.
2171 * @n: The maximum number of entries to copy.
2172 * @filter: Selection criterion.
2173 *
2174 * Copies up to @n entries that match @filter from the XArray.  The
2175 * copied entries will have indices between @start and @max, inclusive.
2176 *
2177 * The @filter may be an XArray mark value, in which case entries which are
2178 * marked with that mark will be copied.  It may also be %XA_PRESENT, in
2179 * which case all entries which are not %NULL will be copied.
2180 *
2181 * The entries returned may not represent a snapshot of the XArray at a
2182 * moment in time.  For example, if another thread stores to index 5, then
2183 * index 10, calling xa_extract() may return the old contents of index 5
2184 * and the new contents of index 10.  Indices not modified while this
2185 * function is running will not be skipped.
2186 *
2187 * If you need stronger guarantees, holding the xa_lock across calls to this
2188 * function will prevent concurrent modification.
2189 *
2190 * Context: Any context.  Takes and releases the RCU lock.
2191 * Return: The number of entries copied.
2192 */
2193unsigned int xa_extract(struct xarray *xa, void **dst, unsigned long start,
2194			unsigned long max, unsigned int n, xa_mark_t filter)
2195{
2196	XA_STATE(xas, xa, start);
2197
2198	if (!n)
2199		return 0;
2200
2201	if ((__force unsigned int)filter < XA_MAX_MARKS)
2202		return xas_extract_marked(&xas, dst, max, n, filter);
2203	return xas_extract_present(&xas, dst, max, n);
2204}
2205EXPORT_SYMBOL(xa_extract);
2206
2207/**
2208 * xa_delete_node() - Private interface for workingset code.
2209 * @node: Node to be removed from the tree.
2210 * @update: Function to call to update ancestor nodes.
2211 *
2212 * Context: xa_lock must be held on entry and will not be released.
2213 */
2214void xa_delete_node(struct xa_node *node, xa_update_node_t update)
2215{
2216	struct xa_state xas = {
2217		.xa = node->array,
2218		.xa_index = (unsigned long)node->offset <<
2219				(node->shift + XA_CHUNK_SHIFT),
2220		.xa_shift = node->shift + XA_CHUNK_SHIFT,
2221		.xa_offset = node->offset,
2222		.xa_node = xa_parent_locked(node->array, node),
2223		.xa_update = update,
2224	};
2225
2226	xas_store(&xas, NULL);
2227}
2228EXPORT_SYMBOL_GPL(xa_delete_node);	/* For the benefit of the test suite */
2229
2230/**
2231 * xa_destroy() - Free all internal data structures.
2232 * @xa: XArray.
2233 *
2234 * After calling this function, the XArray is empty and has freed all memory
2235 * allocated for its internal data structures.  You are responsible for
2236 * freeing the objects referenced by the XArray.
2237 *
2238 * Context: Any context.  Takes and releases the xa_lock, interrupt-safe.
2239 */
2240void xa_destroy(struct xarray *xa)
2241{
2242	XA_STATE(xas, xa, 0);
2243	unsigned long flags;
2244	void *entry;
2245
2246	xas.xa_node = NULL;
2247	xas_lock_irqsave(&xas, flags);
2248	entry = xa_head_locked(xa);
2249	RCU_INIT_POINTER(xa->xa_head, NULL);
2250	xas_init_marks(&xas);
2251	if (xa_zero_busy(xa))
2252		xa_mark_clear(xa, XA_FREE_MARK);
2253	/* lockdep checks we're still holding the lock in xas_free_nodes() */
2254	if (xa_is_node(entry))
2255		xas_free_nodes(&xas, xa_to_node(entry));
2256	xas_unlock_irqrestore(&xas, flags);
2257}
2258EXPORT_SYMBOL(xa_destroy);
2259
2260#ifdef XA_DEBUG
2261void xa_dump_node(const struct xa_node *node)
2262{
2263	unsigned i, j;
2264
2265	if (!node)
2266		return;
2267	if ((unsigned long)node & 3) {
2268		pr_cont("node %px\n", node);
2269		return;
2270	}
2271
2272	pr_cont("node %px %s %d parent %px shift %d count %d values %d "
2273		"array %px list %px %px marks",
2274		node, node->parent ? "offset" : "max", node->offset,
2275		node->parent, node->shift, node->count, node->nr_values,
2276		node->array, node->private_list.prev, node->private_list.next);
2277	for (i = 0; i < XA_MAX_MARKS; i++)
2278		for (j = 0; j < XA_MARK_LONGS; j++)
2279			pr_cont(" %lx", node->marks[i][j]);
2280	pr_cont("\n");
2281}
2282
2283void xa_dump_index(unsigned long index, unsigned int shift)
2284{
2285	if (!shift)
2286		pr_info("%lu: ", index);
2287	else if (shift >= BITS_PER_LONG)
2288		pr_info("0-%lu: ", ~0UL);
2289	else
2290		pr_info("%lu-%lu: ", index, index | ((1UL << shift) - 1));
2291}
2292
2293void xa_dump_entry(const void *entry, unsigned long index, unsigned long shift)
2294{
2295	if (!entry)
2296		return;
2297
2298	xa_dump_index(index, shift);
2299
2300	if (xa_is_node(entry)) {
2301		if (shift == 0) {
2302			pr_cont("%px\n", entry);
2303		} else {
2304			unsigned long i;
2305			struct xa_node *node = xa_to_node(entry);
2306			xa_dump_node(node);
2307			for (i = 0; i < XA_CHUNK_SIZE; i++)
2308				xa_dump_entry(node->slots[i],
2309				      index + (i << node->shift), node->shift);
2310		}
2311	} else if (xa_is_value(entry))
2312		pr_cont("value %ld (0x%lx) [%px]\n", xa_to_value(entry),
2313						xa_to_value(entry), entry);
2314	else if (!xa_is_internal(entry))
2315		pr_cont("%px\n", entry);
2316	else if (xa_is_retry(entry))
2317		pr_cont("retry (%ld)\n", xa_to_internal(entry));
2318	else if (xa_is_sibling(entry))
2319		pr_cont("sibling (slot %ld)\n", xa_to_sibling(entry));
2320	else if (xa_is_zero(entry))
2321		pr_cont("zero (%ld)\n", xa_to_internal(entry));
2322	else
2323		pr_cont("UNKNOWN ENTRY (%px)\n", entry);
2324}
2325
2326void xa_dump(const struct xarray *xa)
2327{
2328	void *entry = xa->xa_head;
2329	unsigned int shift = 0;
2330
2331	pr_info("xarray: %px head %px flags %x marks %d %d %d\n", xa, entry,
2332			xa->xa_flags, xa_marked(xa, XA_MARK_0),
2333			xa_marked(xa, XA_MARK_1), xa_marked(xa, XA_MARK_2));
2334	if (xa_is_node(entry))
2335		shift = xa_to_node(entry)->shift + XA_CHUNK_SHIFT;
2336	xa_dump_entry(entry, 0, shift);
2337}
2338#endif