1 /*
2  * Copyright (C) 2001 Momchil Velikov
3  * Portions Copyright (C) 2001 Christoph Hellwig
4  * Copyright (C) 2005 SGI, Christoph Lameter
5  * Copyright (C) 2006 Nick Piggin
6  * Copyright (C) 2012 Konstantin Khlebnikov
7  * Copyright (C) 2016 Intel, Matthew Wilcox
8  * Copyright (C) 2016 Intel, Ross Zwisler
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public License as
12  * published by the Free Software Foundation; either version 2, or (at
13  * your option) any later version.
14  *
15  * This program is distributed in the hope that it will be useful, but
16  * WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
18  * General Public License for more details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with this program; if not, write to the Free Software
22  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
23  */
24 
25 #include <linux/bitmap.h>
26 #include <linux/bitops.h>
27 #include <linux/bug.h>
28 #include <linux/cpu.h>
29 #include <linux/errno.h>
30 #include <linux/export.h>
31 #include <linux/idr.h>
32 #include <linux/init.h>
33 #include <linux/kernel.h>
34 #include <linux/kmemleak.h>
35 #include <linux/percpu.h>
36 #include <linux/preempt.h>		/* in_interrupt() */
37 #include <linux/radix-tree.h>
38 #include <linux/rcupdate.h>
39 #include <linux/slab.h>
40 #include <linux/string.h>
41 
42 
43 /* Number of nodes in fully populated tree of given height */
44 static unsigned long height_to_maxnodes[RADIX_TREE_MAX_PATH + 1] __read_mostly;
45 
46 /*
47  * Radix tree node cache.
48  */
49 static struct kmem_cache *radix_tree_node_cachep;
50 
51 /*
52  * The radix tree is variable-height, so an insert operation not only has
53  * to build the branch to its corresponding item, it also has to build the
54  * branch to existing items if the size has to be increased (by
55  * radix_tree_extend).
56  *
57  * The worst case is a zero height tree with just a single item at index 0,
58  * and then inserting an item at index ULONG_MAX. This requires 2 new branches
59  * of RADIX_TREE_MAX_PATH size to be created, with only the root node shared.
60  * Hence:
61  */
62 #define RADIX_TREE_PRELOAD_SIZE (RADIX_TREE_MAX_PATH * 2 - 1)
63 
64 /*
65  * The IDR does not have to be as high as the radix tree since it uses
66  * signed integers, not unsigned longs.
67  */
68 #define IDR_INDEX_BITS		(8 /* CHAR_BIT */ * sizeof(int) - 1)
69 #define IDR_MAX_PATH		(DIV_ROUND_UP(IDR_INDEX_BITS, \
70 						RADIX_TREE_MAP_SHIFT))
71 #define IDR_PRELOAD_SIZE	(IDR_MAX_PATH * 2 - 1)
72 
73 /*
74  * The IDA is even shorter since it uses a bitmap at the last level.
75  */
76 #define IDA_INDEX_BITS		(8 * sizeof(int) - 1 - ilog2(IDA_BITMAP_BITS))
77 #define IDA_MAX_PATH		(DIV_ROUND_UP(IDA_INDEX_BITS, \
78 						RADIX_TREE_MAP_SHIFT))
79 #define IDA_PRELOAD_SIZE	(IDA_MAX_PATH * 2 - 1)
80 
81 /*
82  * Per-cpu pool of preloaded nodes
83  */
84 struct radix_tree_preload {
85 	unsigned nr;
86 	/* nodes->parent points to next preallocated node */
87 	struct radix_tree_node *nodes;
88 };
89 static DEFINE_PER_CPU(struct radix_tree_preload, radix_tree_preloads) = { 0, };
90 
entry_to_node(void * ptr)91 static inline struct radix_tree_node *entry_to_node(void *ptr)
92 {
93 	return (void *)((unsigned long)ptr & ~RADIX_TREE_INTERNAL_NODE);
94 }
95 
node_to_entry(void * ptr)96 static inline void *node_to_entry(void *ptr)
97 {
98 	return (void *)((unsigned long)ptr | RADIX_TREE_INTERNAL_NODE);
99 }
100 
101 #define RADIX_TREE_RETRY	node_to_entry(NULL)
102 
103 #ifdef CONFIG_RADIX_TREE_MULTIORDER
104 /* Sibling slots point directly to another slot in the same node */
105 static inline
is_sibling_entry(const struct radix_tree_node * parent,void * node)106 bool is_sibling_entry(const struct radix_tree_node *parent, void *node)
107 {
108 	void __rcu **ptr = node;
109 	return (parent->slots <= ptr) &&
110 			(ptr < parent->slots + RADIX_TREE_MAP_SIZE);
111 }
112 #else
113 static inline
is_sibling_entry(const struct radix_tree_node * parent,void * node)114 bool is_sibling_entry(const struct radix_tree_node *parent, void *node)
115 {
116 	return false;
117 }
118 #endif
119 
120 static inline unsigned long
get_slot_offset(const struct radix_tree_node * parent,void __rcu ** slot)121 get_slot_offset(const struct radix_tree_node *parent, void __rcu **slot)
122 {
123 	return parent ? slot - parent->slots : 0;
124 }
125 
radix_tree_descend(const struct radix_tree_node * parent,struct radix_tree_node ** nodep,unsigned long index)126 static unsigned int radix_tree_descend(const struct radix_tree_node *parent,
127 			struct radix_tree_node **nodep, unsigned long index)
128 {
129 	unsigned int offset = (index >> parent->shift) & RADIX_TREE_MAP_MASK;
130 	void __rcu **entry = rcu_dereference_raw(parent->slots[offset]);
131 
132 #ifdef CONFIG_RADIX_TREE_MULTIORDER
133 	if (radix_tree_is_internal_node(entry)) {
134 		if (is_sibling_entry(parent, entry)) {
135 			void __rcu **sibentry;
136 			sibentry = (void __rcu **) entry_to_node(entry);
137 			offset = get_slot_offset(parent, sibentry);
138 			entry = rcu_dereference_raw(*sibentry);
139 		}
140 	}
141 #endif
142 
143 	*nodep = (void *)entry;
144 	return offset;
145 }
146 
root_gfp_mask(const struct radix_tree_root * root)147 static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
148 {
149 	return root->gfp_mask & (__GFP_BITS_MASK & ~GFP_ZONEMASK);
150 }
151 
tag_set(struct radix_tree_node * node,unsigned int tag,int offset)152 static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
153 		int offset)
154 {
155 	__set_bit(offset, node->tags[tag]);
156 }
157 
tag_clear(struct radix_tree_node * node,unsigned int tag,int offset)158 static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
159 		int offset)
160 {
161 	__clear_bit(offset, node->tags[tag]);
162 }
163 
tag_get(const struct radix_tree_node * node,unsigned int tag,int offset)164 static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
165 		int offset)
166 {
167 	return test_bit(offset, node->tags[tag]);
168 }
169 
root_tag_set(struct radix_tree_root * root,unsigned tag)170 static inline void root_tag_set(struct radix_tree_root *root, unsigned tag)
171 {
172 	root->gfp_mask |= (__force gfp_t)(1 << (tag + ROOT_TAG_SHIFT));
173 }
174 
root_tag_clear(struct radix_tree_root * root,unsigned tag)175 static inline void root_tag_clear(struct radix_tree_root *root, unsigned tag)
176 {
177 	root->gfp_mask &= (__force gfp_t)~(1 << (tag + ROOT_TAG_SHIFT));
178 }
179 
root_tag_clear_all(struct radix_tree_root * root)180 static inline void root_tag_clear_all(struct radix_tree_root *root)
181 {
182 	root->gfp_mask &= (1 << ROOT_TAG_SHIFT) - 1;
183 }
184 
root_tag_get(const struct radix_tree_root * root,unsigned tag)185 static inline int root_tag_get(const struct radix_tree_root *root, unsigned tag)
186 {
187 	return (__force int)root->gfp_mask & (1 << (tag + ROOT_TAG_SHIFT));
188 }
189 
root_tags_get(const struct radix_tree_root * root)190 static inline unsigned root_tags_get(const struct radix_tree_root *root)
191 {
192 	return (__force unsigned)root->gfp_mask >> ROOT_TAG_SHIFT;
193 }
194 
is_idr(const struct radix_tree_root * root)195 static inline bool is_idr(const struct radix_tree_root *root)
196 {
197 	return !!(root->gfp_mask & ROOT_IS_IDR);
198 }
199 
200 /*
201  * Returns 1 if any slot in the node has this tag set.
202  * Otherwise returns 0.
203  */
any_tag_set(const struct radix_tree_node * node,unsigned int tag)204 static inline int any_tag_set(const struct radix_tree_node *node,
205 							unsigned int tag)
206 {
207 	unsigned idx;
208 	for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
209 		if (node->tags[tag][idx])
210 			return 1;
211 	}
212 	return 0;
213 }
214 
all_tag_set(struct radix_tree_node * node,unsigned int tag)215 static inline void all_tag_set(struct radix_tree_node *node, unsigned int tag)
216 {
217 	bitmap_fill(node->tags[tag], RADIX_TREE_MAP_SIZE);
218 }
219 
220 /**
221  * radix_tree_find_next_bit - find the next set bit in a memory region
222  *
223  * @addr: The address to base the search on
224  * @size: The bitmap size in bits
225  * @offset: The bitnumber to start searching at
226  *
227  * Unrollable variant of find_next_bit() for constant size arrays.
228  * Tail bits starting from size to roundup(size, BITS_PER_LONG) must be zero.
229  * Returns next bit offset, or size if nothing found.
230  */
231 static __always_inline unsigned long
radix_tree_find_next_bit(struct radix_tree_node * node,unsigned int tag,unsigned long offset)232 radix_tree_find_next_bit(struct radix_tree_node *node, unsigned int tag,
233 			 unsigned long offset)
234 {
235 	const unsigned long *addr = node->tags[tag];
236 
237 	if (offset < RADIX_TREE_MAP_SIZE) {
238 		unsigned long tmp;
239 
240 		addr += offset / BITS_PER_LONG;
241 		tmp = *addr >> (offset % BITS_PER_LONG);
242 		if (tmp)
243 			return __ffs(tmp) + offset;
244 		offset = (offset + BITS_PER_LONG) & ~(BITS_PER_LONG - 1);
245 		while (offset < RADIX_TREE_MAP_SIZE) {
246 			tmp = *++addr;
247 			if (tmp)
248 				return __ffs(tmp) + offset;
249 			offset += BITS_PER_LONG;
250 		}
251 	}
252 	return RADIX_TREE_MAP_SIZE;
253 }
254 
iter_offset(const struct radix_tree_iter * iter)255 static unsigned int iter_offset(const struct radix_tree_iter *iter)
256 {
257 	return (iter->index >> iter_shift(iter)) & RADIX_TREE_MAP_MASK;
258 }
259 
260 /*
261  * The maximum index which can be stored in a radix tree
262  */
shift_maxindex(unsigned int shift)263 static inline unsigned long shift_maxindex(unsigned int shift)
264 {
265 	return (RADIX_TREE_MAP_SIZE << shift) - 1;
266 }
267 
node_maxindex(const struct radix_tree_node * node)268 static inline unsigned long node_maxindex(const struct radix_tree_node *node)
269 {
270 	return shift_maxindex(node->shift);
271 }
272 
next_index(unsigned long index,const struct radix_tree_node * node,unsigned long offset)273 static unsigned long next_index(unsigned long index,
274 				const struct radix_tree_node *node,
275 				unsigned long offset)
276 {
277 	return (index & ~node_maxindex(node)) + (offset << node->shift);
278 }
279 
280 #ifndef __KERNEL__
dump_node(struct radix_tree_node * node,unsigned long index)281 static void dump_node(struct radix_tree_node *node, unsigned long index)
282 {
283 	unsigned long i;
284 
285 	pr_debug("radix node: %p offset %d indices %lu-%lu parent %p tags %lx %lx %lx shift %d count %d exceptional %d\n",
286 		node, node->offset, index, index | node_maxindex(node),
287 		node->parent,
288 		node->tags[0][0], node->tags[1][0], node->tags[2][0],
289 		node->shift, node->count, node->exceptional);
290 
291 	for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
292 		unsigned long first = index | (i << node->shift);
293 		unsigned long last = first | ((1UL << node->shift) - 1);
294 		void *entry = node->slots[i];
295 		if (!entry)
296 			continue;
297 		if (entry == RADIX_TREE_RETRY) {
298 			pr_debug("radix retry offset %ld indices %lu-%lu parent %p\n",
299 					i, first, last, node);
300 		} else if (!radix_tree_is_internal_node(entry)) {
301 			pr_debug("radix entry %p offset %ld indices %lu-%lu parent %p\n",
302 					entry, i, first, last, node);
303 		} else if (is_sibling_entry(node, entry)) {
304 			pr_debug("radix sblng %p offset %ld indices %lu-%lu parent %p val %p\n",
305 					entry, i, first, last, node,
306 					*(void **)entry_to_node(entry));
307 		} else {
308 			dump_node(entry_to_node(entry), first);
309 		}
310 	}
311 }
312 
313 /* For debug */
radix_tree_dump(struct radix_tree_root * root)314 static void radix_tree_dump(struct radix_tree_root *root)
315 {
316 	pr_debug("radix root: %p rnode %p tags %x\n",
317 			root, root->rnode,
318 			root->gfp_mask >> ROOT_TAG_SHIFT);
319 	if (!radix_tree_is_internal_node(root->rnode))
320 		return;
321 	dump_node(entry_to_node(root->rnode), 0);
322 }
323 
dump_ida_node(void * entry,unsigned long index)324 static void dump_ida_node(void *entry, unsigned long index)
325 {
326 	unsigned long i;
327 
328 	if (!entry)
329 		return;
330 
331 	if (radix_tree_is_internal_node(entry)) {
332 		struct radix_tree_node *node = entry_to_node(entry);
333 
334 		pr_debug("ida node: %p offset %d indices %lu-%lu parent %p free %lx shift %d count %d\n",
335 			node, node->offset, index * IDA_BITMAP_BITS,
336 			((index | node_maxindex(node)) + 1) *
337 				IDA_BITMAP_BITS - 1,
338 			node->parent, node->tags[0][0], node->shift,
339 			node->count);
340 		for (i = 0; i < RADIX_TREE_MAP_SIZE; i++)
341 			dump_ida_node(node->slots[i],
342 					index | (i << node->shift));
343 	} else if (radix_tree_exceptional_entry(entry)) {
344 		pr_debug("ida excp: %p offset %d indices %lu-%lu data %lx\n",
345 				entry, (int)(index & RADIX_TREE_MAP_MASK),
346 				index * IDA_BITMAP_BITS,
347 				index * IDA_BITMAP_BITS + BITS_PER_LONG -
348 					RADIX_TREE_EXCEPTIONAL_SHIFT,
349 				(unsigned long)entry >>
350 					RADIX_TREE_EXCEPTIONAL_SHIFT);
351 	} else {
352 		struct ida_bitmap *bitmap = entry;
353 
354 		pr_debug("ida btmp: %p offset %d indices %lu-%lu data", bitmap,
355 				(int)(index & RADIX_TREE_MAP_MASK),
356 				index * IDA_BITMAP_BITS,
357 				(index + 1) * IDA_BITMAP_BITS - 1);
358 		for (i = 0; i < IDA_BITMAP_LONGS; i++)
359 			pr_cont(" %lx", bitmap->bitmap[i]);
360 		pr_cont("\n");
361 	}
362 }
363 
ida_dump(struct ida * ida)364 static void ida_dump(struct ida *ida)
365 {
366 	struct radix_tree_root *root = &ida->ida_rt;
367 	pr_debug("ida: %p node %p free %d\n", ida, root->rnode,
368 				root->gfp_mask >> ROOT_TAG_SHIFT);
369 	dump_ida_node(root->rnode, 0);
370 }
371 #endif
372 
373 /*
374  * This assumes that the caller has performed appropriate preallocation, and
375  * that the caller has pinned this thread of control to the current CPU.
376  */
377 static struct radix_tree_node *
radix_tree_node_alloc(gfp_t gfp_mask,struct radix_tree_node * parent,struct radix_tree_root * root,unsigned int shift,unsigned int offset,unsigned int count,unsigned int exceptional)378 radix_tree_node_alloc(gfp_t gfp_mask, struct radix_tree_node *parent,
379 			struct radix_tree_root *root,
380 			unsigned int shift, unsigned int offset,
381 			unsigned int count, unsigned int exceptional)
382 {
383 	struct radix_tree_node *ret = NULL;
384 
385 	/*
386 	 * Preload code isn't irq safe and it doesn't make sense to use
387 	 * preloading during an interrupt anyway as all the allocations have
388 	 * to be atomic. So just do normal allocation when in interrupt.
389 	 */
390 	if (!gfpflags_allow_blocking(gfp_mask) && !in_interrupt()) {
391 		struct radix_tree_preload *rtp;
392 
393 		/*
394 		 * Even if the caller has preloaded, try to allocate from the
395 		 * cache first for the new node to get accounted to the memory
396 		 * cgroup.
397 		 */
398 		ret = kmem_cache_alloc(radix_tree_node_cachep,
399 				       gfp_mask | __GFP_NOWARN);
400 		if (ret)
401 			goto out;
402 
403 		/*
404 		 * Provided the caller has preloaded here, we will always
405 		 * succeed in getting a node here (and never reach
406 		 * kmem_cache_alloc)
407 		 */
408 		rtp = this_cpu_ptr(&radix_tree_preloads);
409 		if (rtp->nr) {
410 			ret = rtp->nodes;
411 			rtp->nodes = ret->parent;
412 			rtp->nr--;
413 		}
414 		/*
415 		 * Update the allocation stack trace as this is more useful
416 		 * for debugging.
417 		 */
418 		kmemleak_update_trace(ret);
419 		goto out;
420 	}
421 	ret = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
422 out:
423 	BUG_ON(radix_tree_is_internal_node(ret));
424 	if (ret) {
425 		ret->shift = shift;
426 		ret->offset = offset;
427 		ret->count = count;
428 		ret->exceptional = exceptional;
429 		ret->parent = parent;
430 		ret->root = root;
431 	}
432 	return ret;
433 }
434 
radix_tree_node_rcu_free(struct rcu_head * head)435 static void radix_tree_node_rcu_free(struct rcu_head *head)
436 {
437 	struct radix_tree_node *node =
438 			container_of(head, struct radix_tree_node, rcu_head);
439 
440 	/*
441 	 * Must only free zeroed nodes into the slab.  We can be left with
442 	 * non-NULL entries by radix_tree_free_nodes, so clear the entries
443 	 * and tags here.
444 	 */
445 	memset(node->slots, 0, sizeof(node->slots));
446 	memset(node->tags, 0, sizeof(node->tags));
447 	INIT_LIST_HEAD(&node->private_list);
448 
449 	kmem_cache_free(radix_tree_node_cachep, node);
450 }
451 
452 static inline void
radix_tree_node_free(struct radix_tree_node * node)453 radix_tree_node_free(struct radix_tree_node *node)
454 {
455 	call_rcu(&node->rcu_head, radix_tree_node_rcu_free);
456 }
457 
458 /*
459  * Load up this CPU's radix_tree_node buffer with sufficient objects to
460  * ensure that the addition of a single element in the tree cannot fail.  On
461  * success, return zero, with preemption disabled.  On error, return -ENOMEM
462  * with preemption not disabled.
463  *
464  * To make use of this facility, the radix tree must be initialised without
465  * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
466  */
__radix_tree_preload(gfp_t gfp_mask,unsigned nr)467 static __must_check int __radix_tree_preload(gfp_t gfp_mask, unsigned nr)
468 {
469 	struct radix_tree_preload *rtp;
470 	struct radix_tree_node *node;
471 	int ret = -ENOMEM;
472 
473 	/*
474 	 * Nodes preloaded by one cgroup can be be used by another cgroup, so
475 	 * they should never be accounted to any particular memory cgroup.
476 	 */
477 	gfp_mask &= ~__GFP_ACCOUNT;
478 
479 	preempt_disable();
480 	rtp = this_cpu_ptr(&radix_tree_preloads);
481 	while (rtp->nr < nr) {
482 		preempt_enable();
483 		node = kmem_cache_alloc(radix_tree_node_cachep, gfp_mask);
484 		if (node == NULL)
485 			goto out;
486 		preempt_disable();
487 		rtp = this_cpu_ptr(&radix_tree_preloads);
488 		if (rtp->nr < nr) {
489 			node->parent = rtp->nodes;
490 			rtp->nodes = node;
491 			rtp->nr++;
492 		} else {
493 			kmem_cache_free(radix_tree_node_cachep, node);
494 		}
495 	}
496 	ret = 0;
497 out:
498 	return ret;
499 }
500 
501 /*
502  * Load up this CPU's radix_tree_node buffer with sufficient objects to
503  * ensure that the addition of a single element in the tree cannot fail.  On
504  * success, return zero, with preemption disabled.  On error, return -ENOMEM
505  * with preemption not disabled.
506  *
507  * To make use of this facility, the radix tree must be initialised without
508  * __GFP_DIRECT_RECLAIM being passed to INIT_RADIX_TREE().
509  */
radix_tree_preload(gfp_t gfp_mask)510 int radix_tree_preload(gfp_t gfp_mask)
511 {
512 	/* Warn on non-sensical use... */
513 	WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
514 	return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
515 }
516 EXPORT_SYMBOL(radix_tree_preload);
517 
518 /*
519  * The same as above function, except we don't guarantee preloading happens.
520  * We do it, if we decide it helps. On success, return zero with preemption
521  * disabled. On error, return -ENOMEM with preemption not disabled.
522  */
radix_tree_maybe_preload(gfp_t gfp_mask)523 int radix_tree_maybe_preload(gfp_t gfp_mask)
524 {
525 	if (gfpflags_allow_blocking(gfp_mask))
526 		return __radix_tree_preload(gfp_mask, RADIX_TREE_PRELOAD_SIZE);
527 	/* Preloading doesn't help anything with this gfp mask, skip it */
528 	preempt_disable();
529 	return 0;
530 }
531 EXPORT_SYMBOL(radix_tree_maybe_preload);
532 
533 #ifdef CONFIG_RADIX_TREE_MULTIORDER
534 /*
535  * Preload with enough objects to ensure that we can split a single entry
536  * of order @old_order into many entries of size @new_order
537  */
radix_tree_split_preload(unsigned int old_order,unsigned int new_order,gfp_t gfp_mask)538 int radix_tree_split_preload(unsigned int old_order, unsigned int new_order,
539 							gfp_t gfp_mask)
540 {
541 	unsigned top = 1 << (old_order % RADIX_TREE_MAP_SHIFT);
542 	unsigned layers = (old_order / RADIX_TREE_MAP_SHIFT) -
543 				(new_order / RADIX_TREE_MAP_SHIFT);
544 	unsigned nr = 0;
545 
546 	WARN_ON_ONCE(!gfpflags_allow_blocking(gfp_mask));
547 	BUG_ON(new_order >= old_order);
548 
549 	while (layers--)
550 		nr = nr * RADIX_TREE_MAP_SIZE + 1;
551 	return __radix_tree_preload(gfp_mask, top * nr);
552 }
553 #endif
554 
555 /*
556  * The same as function above, but preload number of nodes required to insert
557  * (1 << order) continuous naturally-aligned elements.
558  */
radix_tree_maybe_preload_order(gfp_t gfp_mask,int order)559 int radix_tree_maybe_preload_order(gfp_t gfp_mask, int order)
560 {
561 	unsigned long nr_subtrees;
562 	int nr_nodes, subtree_height;
563 
564 	/* Preloading doesn't help anything with this gfp mask, skip it */
565 	if (!gfpflags_allow_blocking(gfp_mask)) {
566 		preempt_disable();
567 		return 0;
568 	}
569 
570 	/*
571 	 * Calculate number and height of fully populated subtrees it takes to
572 	 * store (1 << order) elements.
573 	 */
574 	nr_subtrees = 1 << order;
575 	for (subtree_height = 0; nr_subtrees > RADIX_TREE_MAP_SIZE;
576 			subtree_height++)
577 		nr_subtrees >>= RADIX_TREE_MAP_SHIFT;
578 
579 	/*
580 	 * The worst case is zero height tree with a single item at index 0 and
581 	 * then inserting items starting at ULONG_MAX - (1 << order).
582 	 *
583 	 * This requires RADIX_TREE_MAX_PATH nodes to build branch from root to
584 	 * 0-index item.
585 	 */
586 	nr_nodes = RADIX_TREE_MAX_PATH;
587 
588 	/* Plus branch to fully populated subtrees. */
589 	nr_nodes += RADIX_TREE_MAX_PATH - subtree_height;
590 
591 	/* Root node is shared. */
592 	nr_nodes--;
593 
594 	/* Plus nodes required to build subtrees. */
595 	nr_nodes += nr_subtrees * height_to_maxnodes[subtree_height];
596 
597 	return __radix_tree_preload(gfp_mask, nr_nodes);
598 }
599 
radix_tree_load_root(const struct radix_tree_root * root,struct radix_tree_node ** nodep,unsigned long * maxindex)600 static unsigned radix_tree_load_root(const struct radix_tree_root *root,
601 		struct radix_tree_node **nodep, unsigned long *maxindex)
602 {
603 	struct radix_tree_node *node = rcu_dereference_raw(root->rnode);
604 
605 	*nodep = node;
606 
607 	if (likely(radix_tree_is_internal_node(node))) {
608 		node = entry_to_node(node);
609 		*maxindex = node_maxindex(node);
610 		return node->shift + RADIX_TREE_MAP_SHIFT;
611 	}
612 
613 	*maxindex = 0;
614 	return 0;
615 }
616 
617 /*
618  *	Extend a radix tree so it can store key @index.
619  */
radix_tree_extend(struct radix_tree_root * root,gfp_t gfp,unsigned long index,unsigned int shift)620 static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
621 				unsigned long index, unsigned int shift)
622 {
623 	void *entry;
624 	unsigned int maxshift;
625 	int tag;
626 
627 	/* Figure out what the shift should be.  */
628 	maxshift = shift;
629 	while (index > shift_maxindex(maxshift))
630 		maxshift += RADIX_TREE_MAP_SHIFT;
631 
632 	entry = rcu_dereference_raw(root->rnode);
633 	if (!entry && (!is_idr(root) || root_tag_get(root, IDR_FREE)))
634 		goto out;
635 
636 	do {
637 		struct radix_tree_node *node = radix_tree_node_alloc(gfp, NULL,
638 							root, shift, 0, 1, 0);
639 		if (!node)
640 			return -ENOMEM;
641 
642 		if (is_idr(root)) {
643 			all_tag_set(node, IDR_FREE);
644 			if (!root_tag_get(root, IDR_FREE)) {
645 				tag_clear(node, IDR_FREE, 0);
646 				root_tag_set(root, IDR_FREE);
647 			}
648 		} else {
649 			/* Propagate the aggregated tag info to the new child */
650 			for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
651 				if (root_tag_get(root, tag))
652 					tag_set(node, tag, 0);
653 			}
654 		}
655 
656 		BUG_ON(shift > BITS_PER_LONG);
657 		if (radix_tree_is_internal_node(entry)) {
658 			entry_to_node(entry)->parent = node;
659 		} else if (radix_tree_exceptional_entry(entry)) {
660 			/* Moving an exceptional root->rnode to a node */
661 			node->exceptional = 1;
662 		}
663 		/*
664 		 * entry was already in the radix tree, so we do not need
665 		 * rcu_assign_pointer here
666 		 */
667 		node->slots[0] = (void __rcu *)entry;
668 		entry = node_to_entry(node);
669 		rcu_assign_pointer(root->rnode, entry);
670 		shift += RADIX_TREE_MAP_SHIFT;
671 	} while (shift <= maxshift);
672 out:
673 	return maxshift + RADIX_TREE_MAP_SHIFT;
674 }
675 
676 /**
677  *	radix_tree_shrink    -    shrink radix tree to minimum height
678  *	@root		radix tree root
679  */
radix_tree_shrink(struct radix_tree_root * root,radix_tree_update_node_t update_node)680 static inline bool radix_tree_shrink(struct radix_tree_root *root,
681 				     radix_tree_update_node_t update_node)
682 {
683 	bool shrunk = false;
684 
685 	for (;;) {
686 		struct radix_tree_node *node = rcu_dereference_raw(root->rnode);
687 		struct radix_tree_node *child;
688 
689 		if (!radix_tree_is_internal_node(node))
690 			break;
691 		node = entry_to_node(node);
692 
693 		/*
694 		 * The candidate node has more than one child, or its child
695 		 * is not at the leftmost slot, or the child is a multiorder
696 		 * entry, we cannot shrink.
697 		 */
698 		if (node->count != 1)
699 			break;
700 		child = rcu_dereference_raw(node->slots[0]);
701 		if (!child)
702 			break;
703 		if (!radix_tree_is_internal_node(child) && node->shift)
704 			break;
705 
706 		if (radix_tree_is_internal_node(child))
707 			entry_to_node(child)->parent = NULL;
708 
709 		/*
710 		 * We don't need rcu_assign_pointer(), since we are simply
711 		 * moving the node from one part of the tree to another: if it
712 		 * was safe to dereference the old pointer to it
713 		 * (node->slots[0]), it will be safe to dereference the new
714 		 * one (root->rnode) as far as dependent read barriers go.
715 		 */
716 		root->rnode = (void __rcu *)child;
717 		if (is_idr(root) && !tag_get(node, IDR_FREE, 0))
718 			root_tag_clear(root, IDR_FREE);
719 
720 		/*
721 		 * We have a dilemma here. The node's slot[0] must not be
722 		 * NULLed in case there are concurrent lookups expecting to
723 		 * find the item. However if this was a bottom-level node,
724 		 * then it may be subject to the slot pointer being visible
725 		 * to callers dereferencing it. If item corresponding to
726 		 * slot[0] is subsequently deleted, these callers would expect
727 		 * their slot to become empty sooner or later.
728 		 *
729 		 * For example, lockless pagecache will look up a slot, deref
730 		 * the page pointer, and if the page has 0 refcount it means it
731 		 * was concurrently deleted from pagecache so try the deref
732 		 * again. Fortunately there is already a requirement for logic
733 		 * to retry the entire slot lookup -- the indirect pointer
734 		 * problem (replacing direct root node with an indirect pointer
735 		 * also results in a stale slot). So tag the slot as indirect
736 		 * to force callers to retry.
737 		 */
738 		node->count = 0;
739 		if (!radix_tree_is_internal_node(child)) {
740 			node->slots[0] = (void __rcu *)RADIX_TREE_RETRY;
741 			if (update_node)
742 				update_node(node);
743 		}
744 
745 		WARN_ON_ONCE(!list_empty(&node->private_list));
746 		radix_tree_node_free(node);
747 		shrunk = true;
748 	}
749 
750 	return shrunk;
751 }
752 
delete_node(struct radix_tree_root * root,struct radix_tree_node * node,radix_tree_update_node_t update_node)753 static bool delete_node(struct radix_tree_root *root,
754 			struct radix_tree_node *node,
755 			radix_tree_update_node_t update_node)
756 {
757 	bool deleted = false;
758 
759 	do {
760 		struct radix_tree_node *parent;
761 
762 		if (node->count) {
763 			if (node_to_entry(node) ==
764 					rcu_dereference_raw(root->rnode))
765 				deleted |= radix_tree_shrink(root,
766 								update_node);
767 			return deleted;
768 		}
769 
770 		parent = node->parent;
771 		if (parent) {
772 			parent->slots[node->offset] = NULL;
773 			parent->count--;
774 		} else {
775 			/*
776 			 * Shouldn't the tags already have all been cleared
777 			 * by the caller?
778 			 */
779 			if (!is_idr(root))
780 				root_tag_clear_all(root);
781 			root->rnode = NULL;
782 		}
783 
784 		WARN_ON_ONCE(!list_empty(&node->private_list));
785 		radix_tree_node_free(node);
786 		deleted = true;
787 
788 		node = parent;
789 	} while (node);
790 
791 	return deleted;
792 }
793 
794 /**
795  *	__radix_tree_create	-	create a slot in a radix tree
796  *	@root:		radix tree root
797  *	@index:		index key
798  *	@order:		index occupies 2^order aligned slots
799  *	@nodep:		returns node
800  *	@slotp:		returns slot
801  *
802  *	Create, if necessary, and return the node and slot for an item
803  *	at position @index in the radix tree @root.
804  *
805  *	Until there is more than one item in the tree, no nodes are
806  *	allocated and @root->rnode is used as a direct slot instead of
807  *	pointing to a node, in which case *@nodep will be NULL.
808  *
809  *	Returns -ENOMEM, or 0 for success.
810  */
__radix_tree_create(struct radix_tree_root * root,unsigned long index,unsigned order,struct radix_tree_node ** nodep,void __rcu *** slotp)811 int __radix_tree_create(struct radix_tree_root *root, unsigned long index,
812 			unsigned order, struct radix_tree_node **nodep,
813 			void __rcu ***slotp)
814 {
815 	struct radix_tree_node *node = NULL, *child;
816 	void __rcu **slot = (void __rcu **)&root->rnode;
817 	unsigned long maxindex;
818 	unsigned int shift, offset = 0;
819 	unsigned long max = index | ((1UL << order) - 1);
820 	gfp_t gfp = root_gfp_mask(root);
821 
822 	shift = radix_tree_load_root(root, &child, &maxindex);
823 
824 	/* Make sure the tree is high enough.  */
825 	if (order > 0 && max == ((1UL << order) - 1))
826 		max++;
827 	if (max > maxindex) {
828 		int error = radix_tree_extend(root, gfp, max, shift);
829 		if (error < 0)
830 			return error;
831 		shift = error;
832 		child = rcu_dereference_raw(root->rnode);
833 	}
834 
835 	while (shift > order) {
836 		shift -= RADIX_TREE_MAP_SHIFT;
837 		if (child == NULL) {
838 			/* Have to add a child node.  */
839 			child = radix_tree_node_alloc(gfp, node, root, shift,
840 							offset, 0, 0);
841 			if (!child)
842 				return -ENOMEM;
843 			rcu_assign_pointer(*slot, node_to_entry(child));
844 			if (node)
845 				node->count++;
846 		} else if (!radix_tree_is_internal_node(child))
847 			break;
848 
849 		/* Go a level down */
850 		node = entry_to_node(child);
851 		offset = radix_tree_descend(node, &child, index);
852 		slot = &node->slots[offset];
853 	}
854 
855 	if (nodep)
856 		*nodep = node;
857 	if (slotp)
858 		*slotp = slot;
859 	return 0;
860 }
861 
862 /*
863  * Free any nodes below this node.  The tree is presumed to not need
864  * shrinking, and any user data in the tree is presumed to not need a
865  * destructor called on it.  If we need to add a destructor, we can
866  * add that functionality later.  Note that we may not clear tags or
867  * slots from the tree as an RCU walker may still have a pointer into
868  * this subtree.  We could replace the entries with RADIX_TREE_RETRY,
869  * but we'll still have to clear those in rcu_free.
870  */
radix_tree_free_nodes(struct radix_tree_node * node)871 static void radix_tree_free_nodes(struct radix_tree_node *node)
872 {
873 	unsigned offset = 0;
874 	struct radix_tree_node *child = entry_to_node(node);
875 
876 	for (;;) {
877 		void *entry = rcu_dereference_raw(child->slots[offset]);
878 		if (radix_tree_is_internal_node(entry) &&
879 					!is_sibling_entry(child, entry)) {
880 			child = entry_to_node(entry);
881 			offset = 0;
882 			continue;
883 		}
884 		offset++;
885 		while (offset == RADIX_TREE_MAP_SIZE) {
886 			struct radix_tree_node *old = child;
887 			offset = child->offset + 1;
888 			child = child->parent;
889 			WARN_ON_ONCE(!list_empty(&old->private_list));
890 			radix_tree_node_free(old);
891 			if (old == entry_to_node(node))
892 				return;
893 		}
894 	}
895 }
896 
897 #ifdef CONFIG_RADIX_TREE_MULTIORDER
insert_entries(struct radix_tree_node * node,void __rcu ** slot,void * item,unsigned order,bool replace)898 static inline int insert_entries(struct radix_tree_node *node,
899 		void __rcu **slot, void *item, unsigned order, bool replace)
900 {
901 	struct radix_tree_node *child;
902 	unsigned i, n, tag, offset, tags = 0;
903 
904 	if (node) {
905 		if (order > node->shift)
906 			n = 1 << (order - node->shift);
907 		else
908 			n = 1;
909 		offset = get_slot_offset(node, slot);
910 	} else {
911 		n = 1;
912 		offset = 0;
913 	}
914 
915 	if (n > 1) {
916 		offset = offset & ~(n - 1);
917 		slot = &node->slots[offset];
918 	}
919 	child = node_to_entry(slot);
920 
921 	for (i = 0; i < n; i++) {
922 		if (slot[i]) {
923 			if (replace) {
924 				node->count--;
925 				for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
926 					if (tag_get(node, tag, offset + i))
927 						tags |= 1 << tag;
928 			} else
929 				return -EEXIST;
930 		}
931 	}
932 
933 	for (i = 0; i < n; i++) {
934 		struct radix_tree_node *old = rcu_dereference_raw(slot[i]);
935 		if (i) {
936 			rcu_assign_pointer(slot[i], child);
937 			for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
938 				if (tags & (1 << tag))
939 					tag_clear(node, tag, offset + i);
940 		} else {
941 			rcu_assign_pointer(slot[i], item);
942 			for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
943 				if (tags & (1 << tag))
944 					tag_set(node, tag, offset);
945 		}
946 		if (radix_tree_is_internal_node(old) &&
947 					!is_sibling_entry(node, old) &&
948 					(old != RADIX_TREE_RETRY))
949 			radix_tree_free_nodes(old);
950 		if (radix_tree_exceptional_entry(old))
951 			node->exceptional--;
952 	}
953 	if (node) {
954 		node->count += n;
955 		if (radix_tree_exceptional_entry(item))
956 			node->exceptional += n;
957 	}
958 	return n;
959 }
960 #else
insert_entries(struct radix_tree_node * node,void __rcu ** slot,void * item,unsigned order,bool replace)961 static inline int insert_entries(struct radix_tree_node *node,
962 		void __rcu **slot, void *item, unsigned order, bool replace)
963 {
964 	if (*slot)
965 		return -EEXIST;
966 	rcu_assign_pointer(*slot, item);
967 	if (node) {
968 		node->count++;
969 		if (radix_tree_exceptional_entry(item))
970 			node->exceptional++;
971 	}
972 	return 1;
973 }
974 #endif
975 
976 /**
977  *	__radix_tree_insert    -    insert into a radix tree
978  *	@root:		radix tree root
979  *	@index:		index key
980  *	@order:		key covers the 2^order indices around index
981  *	@item:		item to insert
982  *
983  *	Insert an item into the radix tree at position @index.
984  */
__radix_tree_insert(struct radix_tree_root * root,unsigned long index,unsigned order,void * item)985 int __radix_tree_insert(struct radix_tree_root *root, unsigned long index,
986 			unsigned order, void *item)
987 {
988 	struct radix_tree_node *node;
989 	void __rcu **slot;
990 	int error;
991 
992 	BUG_ON(radix_tree_is_internal_node(item));
993 
994 	error = __radix_tree_create(root, index, order, &node, &slot);
995 	if (error)
996 		return error;
997 
998 	error = insert_entries(node, slot, item, order, false);
999 	if (error < 0)
1000 		return error;
1001 
1002 	if (node) {
1003 		unsigned offset = get_slot_offset(node, slot);
1004 		BUG_ON(tag_get(node, 0, offset));
1005 		BUG_ON(tag_get(node, 1, offset));
1006 		BUG_ON(tag_get(node, 2, offset));
1007 	} else {
1008 		BUG_ON(root_tags_get(root));
1009 	}
1010 
1011 	return 0;
1012 }
1013 EXPORT_SYMBOL(__radix_tree_insert);
1014 
1015 /**
1016  *	__radix_tree_lookup	-	lookup an item in a radix tree
1017  *	@root:		radix tree root
1018  *	@index:		index key
1019  *	@nodep:		returns node
1020  *	@slotp:		returns slot
1021  *
1022  *	Lookup and return the item at position @index in the radix
1023  *	tree @root.
1024  *
1025  *	Until there is more than one item in the tree, no nodes are
1026  *	allocated and @root->rnode is used as a direct slot instead of
1027  *	pointing to a node, in which case *@nodep will be NULL.
1028  */
__radix_tree_lookup(const struct radix_tree_root * root,unsigned long index,struct radix_tree_node ** nodep,void __rcu *** slotp)1029 void *__radix_tree_lookup(const struct radix_tree_root *root,
1030 			  unsigned long index, struct radix_tree_node **nodep,
1031 			  void __rcu ***slotp)
1032 {
1033 	struct radix_tree_node *node, *parent;
1034 	unsigned long maxindex;
1035 	void __rcu **slot;
1036 
1037  restart:
1038 	parent = NULL;
1039 	slot = (void __rcu **)&root->rnode;
1040 	radix_tree_load_root(root, &node, &maxindex);
1041 	if (index > maxindex)
1042 		return NULL;
1043 
1044 	while (radix_tree_is_internal_node(node)) {
1045 		unsigned offset;
1046 
1047 		if (node == RADIX_TREE_RETRY)
1048 			goto restart;
1049 		parent = entry_to_node(node);
1050 		offset = radix_tree_descend(parent, &node, index);
1051 		slot = parent->slots + offset;
1052 	}
1053 
1054 	if (nodep)
1055 		*nodep = parent;
1056 	if (slotp)
1057 		*slotp = slot;
1058 	return node;
1059 }
1060 
1061 /**
1062  *	radix_tree_lookup_slot    -    lookup a slot in a radix tree
1063  *	@root:		radix tree root
1064  *	@index:		index key
1065  *
1066  *	Returns:  the slot corresponding to the position @index in the
1067  *	radix tree @root. This is useful for update-if-exists operations.
1068  *
1069  *	This function can be called under rcu_read_lock iff the slot is not
1070  *	modified by radix_tree_replace_slot, otherwise it must be called
1071  *	exclusive from other writers. Any dereference of the slot must be done
1072  *	using radix_tree_deref_slot.
1073  */
radix_tree_lookup_slot(const struct radix_tree_root * root,unsigned long index)1074 void __rcu **radix_tree_lookup_slot(const struct radix_tree_root *root,
1075 				unsigned long index)
1076 {
1077 	void __rcu **slot;
1078 
1079 	if (!__radix_tree_lookup(root, index, NULL, &slot))
1080 		return NULL;
1081 	return slot;
1082 }
1083 EXPORT_SYMBOL(radix_tree_lookup_slot);
1084 
1085 /**
1086  *	radix_tree_lookup    -    perform lookup operation on a radix tree
1087  *	@root:		radix tree root
1088  *	@index:		index key
1089  *
1090  *	Lookup the item at the position @index in the radix tree @root.
1091  *
1092  *	This function can be called under rcu_read_lock, however the caller
1093  *	must manage lifetimes of leaf nodes (eg. RCU may also be used to free
1094  *	them safely). No RCU barriers are required to access or modify the
1095  *	returned item, however.
1096  */
radix_tree_lookup(const struct radix_tree_root * root,unsigned long index)1097 void *radix_tree_lookup(const struct radix_tree_root *root, unsigned long index)
1098 {
1099 	return __radix_tree_lookup(root, index, NULL, NULL);
1100 }
1101 EXPORT_SYMBOL(radix_tree_lookup);
1102 
replace_sibling_entries(struct radix_tree_node * node,void __rcu ** slot,int count,int exceptional)1103 static inline void replace_sibling_entries(struct radix_tree_node *node,
1104 				void __rcu **slot, int count, int exceptional)
1105 {
1106 #ifdef CONFIG_RADIX_TREE_MULTIORDER
1107 	void *ptr = node_to_entry(slot);
1108 	unsigned offset = get_slot_offset(node, slot) + 1;
1109 
1110 	while (offset < RADIX_TREE_MAP_SIZE) {
1111 		if (rcu_dereference_raw(node->slots[offset]) != ptr)
1112 			break;
1113 		if (count < 0) {
1114 			node->slots[offset] = NULL;
1115 			node->count--;
1116 		}
1117 		node->exceptional += exceptional;
1118 		offset++;
1119 	}
1120 #endif
1121 }
1122 
replace_slot(void __rcu ** slot,void * item,struct radix_tree_node * node,int count,int exceptional)1123 static void replace_slot(void __rcu **slot, void *item,
1124 		struct radix_tree_node *node, int count, int exceptional)
1125 {
1126 	if (WARN_ON_ONCE(radix_tree_is_internal_node(item)))
1127 		return;
1128 
1129 	if (node && (count || exceptional)) {
1130 		node->count += count;
1131 		node->exceptional += exceptional;
1132 		replace_sibling_entries(node, slot, count, exceptional);
1133 	}
1134 
1135 	rcu_assign_pointer(*slot, item);
1136 }
1137 
node_tag_get(const struct radix_tree_root * root,const struct radix_tree_node * node,unsigned int tag,unsigned int offset)1138 static bool node_tag_get(const struct radix_tree_root *root,
1139 				const struct radix_tree_node *node,
1140 				unsigned int tag, unsigned int offset)
1141 {
1142 	if (node)
1143 		return tag_get(node, tag, offset);
1144 	return root_tag_get(root, tag);
1145 }
1146 
1147 /*
1148  * IDR users want to be able to store NULL in the tree, so if the slot isn't
1149  * free, don't adjust the count, even if it's transitioning between NULL and
1150  * non-NULL.  For the IDA, we mark slots as being IDR_FREE while they still
1151  * have empty bits, but it only stores NULL in slots when they're being
1152  * deleted.
1153  */
calculate_count(struct radix_tree_root * root,struct radix_tree_node * node,void __rcu ** slot,void * item,void * old)1154 static int calculate_count(struct radix_tree_root *root,
1155 				struct radix_tree_node *node, void __rcu **slot,
1156 				void *item, void *old)
1157 {
1158 	if (is_idr(root)) {
1159 		unsigned offset = get_slot_offset(node, slot);
1160 		bool free = node_tag_get(root, node, IDR_FREE, offset);
1161 		if (!free)
1162 			return 0;
1163 		if (!old)
1164 			return 1;
1165 	}
1166 	return !!item - !!old;
1167 }
1168 
1169 /**
1170  * __radix_tree_replace		- replace item in a slot
1171  * @root:		radix tree root
1172  * @node:		pointer to tree node
1173  * @slot:		pointer to slot in @node
1174  * @item:		new item to store in the slot.
1175  * @update_node:	callback for changing leaf nodes
1176  *
1177  * For use with __radix_tree_lookup().  Caller must hold tree write locked
1178  * across slot lookup and replacement.
1179  */
__radix_tree_replace(struct radix_tree_root * root,struct radix_tree_node * node,void __rcu ** slot,void * item,radix_tree_update_node_t update_node)1180 void __radix_tree_replace(struct radix_tree_root *root,
1181 			  struct radix_tree_node *node,
1182 			  void __rcu **slot, void *item,
1183 			  radix_tree_update_node_t update_node)
1184 {
1185 	void *old = rcu_dereference_raw(*slot);
1186 	int exceptional = !!radix_tree_exceptional_entry(item) -
1187 				!!radix_tree_exceptional_entry(old);
1188 	int count = calculate_count(root, node, slot, item, old);
1189 
1190 	/*
1191 	 * This function supports replacing exceptional entries and
1192 	 * deleting entries, but that needs accounting against the
1193 	 * node unless the slot is root->rnode.
1194 	 */
1195 	WARN_ON_ONCE(!node && (slot != (void __rcu **)&root->rnode) &&
1196 			(count || exceptional));
1197 	replace_slot(slot, item, node, count, exceptional);
1198 
1199 	if (!node)
1200 		return;
1201 
1202 	if (update_node)
1203 		update_node(node);
1204 
1205 	delete_node(root, node, update_node);
1206 }
1207 
1208 /**
1209  * radix_tree_replace_slot	- replace item in a slot
1210  * @root:	radix tree root
1211  * @slot:	pointer to slot
1212  * @item:	new item to store in the slot.
1213  *
1214  * For use with radix_tree_lookup_slot(), radix_tree_gang_lookup_slot(),
1215  * radix_tree_gang_lookup_tag_slot().  Caller must hold tree write locked
1216  * across slot lookup and replacement.
1217  *
1218  * NOTE: This cannot be used to switch between non-entries (empty slots),
1219  * regular entries, and exceptional entries, as that requires accounting
1220  * inside the radix tree node. When switching from one type of entry or
1221  * deleting, use __radix_tree_lookup() and __radix_tree_replace() or
1222  * radix_tree_iter_replace().
1223  */
radix_tree_replace_slot(struct radix_tree_root * root,void __rcu ** slot,void * item)1224 void radix_tree_replace_slot(struct radix_tree_root *root,
1225 			     void __rcu **slot, void *item)
1226 {
1227 	__radix_tree_replace(root, NULL, slot, item, NULL);
1228 }
1229 EXPORT_SYMBOL(radix_tree_replace_slot);
1230 
1231 /**
1232  * radix_tree_iter_replace - replace item in a slot
1233  * @root:	radix tree root
1234  * @slot:	pointer to slot
1235  * @item:	new item to store in the slot.
1236  *
1237  * For use with radix_tree_split() and radix_tree_for_each_slot().
1238  * Caller must hold tree write locked across split and replacement.
1239  */
radix_tree_iter_replace(struct radix_tree_root * root,const struct radix_tree_iter * iter,void __rcu ** slot,void * item)1240 void radix_tree_iter_replace(struct radix_tree_root *root,
1241 				const struct radix_tree_iter *iter,
1242 				void __rcu **slot, void *item)
1243 {
1244 	__radix_tree_replace(root, iter->node, slot, item, NULL);
1245 }
1246 
1247 #ifdef CONFIG_RADIX_TREE_MULTIORDER
1248 /**
1249  * radix_tree_join - replace multiple entries with one multiorder entry
1250  * @root: radix tree root
1251  * @index: an index inside the new entry
1252  * @order: order of the new entry
1253  * @item: new entry
1254  *
1255  * Call this function to replace several entries with one larger entry.
1256  * The existing entries are presumed to not need freeing as a result of
1257  * this call.
1258  *
1259  * The replacement entry will have all the tags set on it that were set
1260  * on any of the entries it is replacing.
1261  */
radix_tree_join(struct radix_tree_root * root,unsigned long index,unsigned order,void * item)1262 int radix_tree_join(struct radix_tree_root *root, unsigned long index,
1263 			unsigned order, void *item)
1264 {
1265 	struct radix_tree_node *node;
1266 	void __rcu **slot;
1267 	int error;
1268 
1269 	BUG_ON(radix_tree_is_internal_node(item));
1270 
1271 	error = __radix_tree_create(root, index, order, &node, &slot);
1272 	if (!error)
1273 		error = insert_entries(node, slot, item, order, true);
1274 	if (error > 0)
1275 		error = 0;
1276 
1277 	return error;
1278 }
1279 
1280 /**
1281  * radix_tree_split - Split an entry into smaller entries
1282  * @root: radix tree root
1283  * @index: An index within the large entry
1284  * @order: Order of new entries
1285  *
1286  * Call this function as the first step in replacing a multiorder entry
1287  * with several entries of lower order.  After this function returns,
1288  * loop over the relevant portion of the tree using radix_tree_for_each_slot()
1289  * and call radix_tree_iter_replace() to set up each new entry.
1290  *
1291  * The tags from this entry are replicated to all the new entries.
1292  *
1293  * The radix tree should be locked against modification during the entire
1294  * replacement operation.  Lock-free lookups will see RADIX_TREE_RETRY which
1295  * should prompt RCU walkers to restart the lookup from the root.
1296  */
radix_tree_split(struct radix_tree_root * root,unsigned long index,unsigned order)1297 int radix_tree_split(struct radix_tree_root *root, unsigned long index,
1298 				unsigned order)
1299 {
1300 	struct radix_tree_node *parent, *node, *child;
1301 	void __rcu **slot;
1302 	unsigned int offset, end;
1303 	unsigned n, tag, tags = 0;
1304 	gfp_t gfp = root_gfp_mask(root);
1305 
1306 	if (!__radix_tree_lookup(root, index, &parent, &slot))
1307 		return -ENOENT;
1308 	if (!parent)
1309 		return -ENOENT;
1310 
1311 	offset = get_slot_offset(parent, slot);
1312 
1313 	for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1314 		if (tag_get(parent, tag, offset))
1315 			tags |= 1 << tag;
1316 
1317 	for (end = offset + 1; end < RADIX_TREE_MAP_SIZE; end++) {
1318 		if (!is_sibling_entry(parent,
1319 				rcu_dereference_raw(parent->slots[end])))
1320 			break;
1321 		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1322 			if (tags & (1 << tag))
1323 				tag_set(parent, tag, end);
1324 		/* rcu_assign_pointer ensures tags are set before RETRY */
1325 		rcu_assign_pointer(parent->slots[end], RADIX_TREE_RETRY);
1326 	}
1327 	rcu_assign_pointer(parent->slots[offset], RADIX_TREE_RETRY);
1328 	parent->exceptional -= (end - offset);
1329 
1330 	if (order == parent->shift)
1331 		return 0;
1332 	if (order > parent->shift) {
1333 		while (offset < end)
1334 			offset += insert_entries(parent, &parent->slots[offset],
1335 					RADIX_TREE_RETRY, order, true);
1336 		return 0;
1337 	}
1338 
1339 	node = parent;
1340 
1341 	for (;;) {
1342 		if (node->shift > order) {
1343 			child = radix_tree_node_alloc(gfp, node, root,
1344 					node->shift - RADIX_TREE_MAP_SHIFT,
1345 					offset, 0, 0);
1346 			if (!child)
1347 				goto nomem;
1348 			if (node != parent) {
1349 				node->count++;
1350 				rcu_assign_pointer(node->slots[offset],
1351 							node_to_entry(child));
1352 				for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1353 					if (tags & (1 << tag))
1354 						tag_set(node, tag, offset);
1355 			}
1356 
1357 			node = child;
1358 			offset = 0;
1359 			continue;
1360 		}
1361 
1362 		n = insert_entries(node, &node->slots[offset],
1363 					RADIX_TREE_RETRY, order, false);
1364 		BUG_ON(n > RADIX_TREE_MAP_SIZE);
1365 
1366 		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1367 			if (tags & (1 << tag))
1368 				tag_set(node, tag, offset);
1369 		offset += n;
1370 
1371 		while (offset == RADIX_TREE_MAP_SIZE) {
1372 			if (node == parent)
1373 				break;
1374 			offset = node->offset;
1375 			child = node;
1376 			node = node->parent;
1377 			rcu_assign_pointer(node->slots[offset],
1378 						node_to_entry(child));
1379 			offset++;
1380 		}
1381 		if ((node == parent) && (offset == end))
1382 			return 0;
1383 	}
1384 
1385  nomem:
1386 	/* Shouldn't happen; did user forget to preload? */
1387 	/* TODO: free all the allocated nodes */
1388 	WARN_ON(1);
1389 	return -ENOMEM;
1390 }
1391 #endif
1392 
node_tag_set(struct radix_tree_root * root,struct radix_tree_node * node,unsigned int tag,unsigned int offset)1393 static void node_tag_set(struct radix_tree_root *root,
1394 				struct radix_tree_node *node,
1395 				unsigned int tag, unsigned int offset)
1396 {
1397 	while (node) {
1398 		if (tag_get(node, tag, offset))
1399 			return;
1400 		tag_set(node, tag, offset);
1401 		offset = node->offset;
1402 		node = node->parent;
1403 	}
1404 
1405 	if (!root_tag_get(root, tag))
1406 		root_tag_set(root, tag);
1407 }
1408 
1409 /**
1410  *	radix_tree_tag_set - set a tag on a radix tree node
1411  *	@root:		radix tree root
1412  *	@index:		index key
1413  *	@tag:		tag index
1414  *
1415  *	Set the search tag (which must be < RADIX_TREE_MAX_TAGS)
1416  *	corresponding to @index in the radix tree.  From
1417  *	the root all the way down to the leaf node.
1418  *
1419  *	Returns the address of the tagged item.  Setting a tag on a not-present
1420  *	item is a bug.
1421  */
radix_tree_tag_set(struct radix_tree_root * root,unsigned long index,unsigned int tag)1422 void *radix_tree_tag_set(struct radix_tree_root *root,
1423 			unsigned long index, unsigned int tag)
1424 {
1425 	struct radix_tree_node *node, *parent;
1426 	unsigned long maxindex;
1427 
1428 	radix_tree_load_root(root, &node, &maxindex);
1429 	BUG_ON(index > maxindex);
1430 
1431 	while (radix_tree_is_internal_node(node)) {
1432 		unsigned offset;
1433 
1434 		parent = entry_to_node(node);
1435 		offset = radix_tree_descend(parent, &node, index);
1436 		BUG_ON(!node);
1437 
1438 		if (!tag_get(parent, tag, offset))
1439 			tag_set(parent, tag, offset);
1440 	}
1441 
1442 	/* set the root's tag bit */
1443 	if (!root_tag_get(root, tag))
1444 		root_tag_set(root, tag);
1445 
1446 	return node;
1447 }
1448 EXPORT_SYMBOL(radix_tree_tag_set);
1449 
1450 /**
1451  * radix_tree_iter_tag_set - set a tag on the current iterator entry
1452  * @root:	radix tree root
1453  * @iter:	iterator state
1454  * @tag:	tag to set
1455  */
radix_tree_iter_tag_set(struct radix_tree_root * root,const struct radix_tree_iter * iter,unsigned int tag)1456 void radix_tree_iter_tag_set(struct radix_tree_root *root,
1457 			const struct radix_tree_iter *iter, unsigned int tag)
1458 {
1459 	node_tag_set(root, iter->node, tag, iter_offset(iter));
1460 }
1461 
node_tag_clear(struct radix_tree_root * root,struct radix_tree_node * node,unsigned int tag,unsigned int offset)1462 static void node_tag_clear(struct radix_tree_root *root,
1463 				struct radix_tree_node *node,
1464 				unsigned int tag, unsigned int offset)
1465 {
1466 	while (node) {
1467 		if (!tag_get(node, tag, offset))
1468 			return;
1469 		tag_clear(node, tag, offset);
1470 		if (any_tag_set(node, tag))
1471 			return;
1472 
1473 		offset = node->offset;
1474 		node = node->parent;
1475 	}
1476 
1477 	/* clear the root's tag bit */
1478 	if (root_tag_get(root, tag))
1479 		root_tag_clear(root, tag);
1480 }
1481 
1482 /**
1483  *	radix_tree_tag_clear - clear a tag on a radix tree node
1484  *	@root:		radix tree root
1485  *	@index:		index key
1486  *	@tag:		tag index
1487  *
1488  *	Clear the search tag (which must be < RADIX_TREE_MAX_TAGS)
1489  *	corresponding to @index in the radix tree.  If this causes
1490  *	the leaf node to have no tags set then clear the tag in the
1491  *	next-to-leaf node, etc.
1492  *
1493  *	Returns the address of the tagged item on success, else NULL.  ie:
1494  *	has the same return value and semantics as radix_tree_lookup().
1495  */
radix_tree_tag_clear(struct radix_tree_root * root,unsigned long index,unsigned int tag)1496 void *radix_tree_tag_clear(struct radix_tree_root *root,
1497 			unsigned long index, unsigned int tag)
1498 {
1499 	struct radix_tree_node *node, *parent;
1500 	unsigned long maxindex;
1501 	int offset;
1502 
1503 	radix_tree_load_root(root, &node, &maxindex);
1504 	if (index > maxindex)
1505 		return NULL;
1506 
1507 	parent = NULL;
1508 
1509 	while (radix_tree_is_internal_node(node)) {
1510 		parent = entry_to_node(node);
1511 		offset = radix_tree_descend(parent, &node, index);
1512 	}
1513 
1514 	if (node)
1515 		node_tag_clear(root, parent, tag, offset);
1516 
1517 	return node;
1518 }
1519 EXPORT_SYMBOL(radix_tree_tag_clear);
1520 
1521 /**
1522   * radix_tree_iter_tag_clear - clear a tag on the current iterator entry
1523   * @root: radix tree root
1524   * @iter: iterator state
1525   * @tag: tag to clear
1526   */
radix_tree_iter_tag_clear(struct radix_tree_root * root,const struct radix_tree_iter * iter,unsigned int tag)1527 void radix_tree_iter_tag_clear(struct radix_tree_root *root,
1528 			const struct radix_tree_iter *iter, unsigned int tag)
1529 {
1530 	node_tag_clear(root, iter->node, tag, iter_offset(iter));
1531 }
1532 
1533 /**
1534  * radix_tree_tag_get - get a tag on a radix tree node
1535  * @root:		radix tree root
1536  * @index:		index key
1537  * @tag:		tag index (< RADIX_TREE_MAX_TAGS)
1538  *
1539  * Return values:
1540  *
1541  *  0: tag not present or not set
1542  *  1: tag set
1543  *
1544  * Note that the return value of this function may not be relied on, even if
1545  * the RCU lock is held, unless tag modification and node deletion are excluded
1546  * from concurrency.
1547  */
radix_tree_tag_get(const struct radix_tree_root * root,unsigned long index,unsigned int tag)1548 int radix_tree_tag_get(const struct radix_tree_root *root,
1549 			unsigned long index, unsigned int tag)
1550 {
1551 	struct radix_tree_node *node, *parent;
1552 	unsigned long maxindex;
1553 
1554 	if (!root_tag_get(root, tag))
1555 		return 0;
1556 
1557 	radix_tree_load_root(root, &node, &maxindex);
1558 	if (index > maxindex)
1559 		return 0;
1560 
1561 	while (radix_tree_is_internal_node(node)) {
1562 		unsigned offset;
1563 
1564 		parent = entry_to_node(node);
1565 		offset = radix_tree_descend(parent, &node, index);
1566 
1567 		if (!tag_get(parent, tag, offset))
1568 			return 0;
1569 		if (node == RADIX_TREE_RETRY)
1570 			break;
1571 	}
1572 
1573 	return 1;
1574 }
1575 EXPORT_SYMBOL(radix_tree_tag_get);
1576 
__set_iter_shift(struct radix_tree_iter * iter,unsigned int shift)1577 static inline void __set_iter_shift(struct radix_tree_iter *iter,
1578 					unsigned int shift)
1579 {
1580 #ifdef CONFIG_RADIX_TREE_MULTIORDER
1581 	iter->shift = shift;
1582 #endif
1583 }
1584 
1585 /* Construct iter->tags bit-mask from node->tags[tag] array */
set_iter_tags(struct radix_tree_iter * iter,struct radix_tree_node * node,unsigned offset,unsigned tag)1586 static void set_iter_tags(struct radix_tree_iter *iter,
1587 				struct radix_tree_node *node, unsigned offset,
1588 				unsigned tag)
1589 {
1590 	unsigned tag_long = offset / BITS_PER_LONG;
1591 	unsigned tag_bit  = offset % BITS_PER_LONG;
1592 
1593 	if (!node) {
1594 		iter->tags = 1;
1595 		return;
1596 	}
1597 
1598 	iter->tags = node->tags[tag][tag_long] >> tag_bit;
1599 
1600 	/* This never happens if RADIX_TREE_TAG_LONGS == 1 */
1601 	if (tag_long < RADIX_TREE_TAG_LONGS - 1) {
1602 		/* Pick tags from next element */
1603 		if (tag_bit)
1604 			iter->tags |= node->tags[tag][tag_long + 1] <<
1605 						(BITS_PER_LONG - tag_bit);
1606 		/* Clip chunk size, here only BITS_PER_LONG tags */
1607 		iter->next_index = __radix_tree_iter_add(iter, BITS_PER_LONG);
1608 	}
1609 }
1610 
1611 #ifdef CONFIG_RADIX_TREE_MULTIORDER
skip_siblings(struct radix_tree_node ** nodep,void __rcu ** slot,struct radix_tree_iter * iter)1612 static void __rcu **skip_siblings(struct radix_tree_node **nodep,
1613 			void __rcu **slot, struct radix_tree_iter *iter)
1614 {
1615 	while (iter->index < iter->next_index) {
1616 		*nodep = rcu_dereference_raw(*slot);
1617 		if (*nodep && !is_sibling_entry(iter->node, *nodep))
1618 			return slot;
1619 		slot++;
1620 		iter->index = __radix_tree_iter_add(iter, 1);
1621 		iter->tags >>= 1;
1622 	}
1623 
1624 	*nodep = NULL;
1625 	return NULL;
1626 }
1627 
__radix_tree_next_slot(void __rcu ** slot,struct radix_tree_iter * iter,unsigned flags)1628 void __rcu **__radix_tree_next_slot(void __rcu **slot,
1629 				struct radix_tree_iter *iter, unsigned flags)
1630 {
1631 	unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
1632 	struct radix_tree_node *node;
1633 
1634 	slot = skip_siblings(&node, slot, iter);
1635 
1636 	while (radix_tree_is_internal_node(node)) {
1637 		unsigned offset;
1638 		unsigned long next_index;
1639 
1640 		if (node == RADIX_TREE_RETRY)
1641 			return slot;
1642 		node = entry_to_node(node);
1643 		iter->node = node;
1644 		iter->shift = node->shift;
1645 
1646 		if (flags & RADIX_TREE_ITER_TAGGED) {
1647 			offset = radix_tree_find_next_bit(node, tag, 0);
1648 			if (offset == RADIX_TREE_MAP_SIZE)
1649 				return NULL;
1650 			slot = &node->slots[offset];
1651 			iter->index = __radix_tree_iter_add(iter, offset);
1652 			set_iter_tags(iter, node, offset, tag);
1653 			node = rcu_dereference_raw(*slot);
1654 		} else {
1655 			offset = 0;
1656 			slot = &node->slots[0];
1657 			for (;;) {
1658 				node = rcu_dereference_raw(*slot);
1659 				if (node)
1660 					break;
1661 				slot++;
1662 				offset++;
1663 				if (offset == RADIX_TREE_MAP_SIZE)
1664 					return NULL;
1665 			}
1666 			iter->index = __radix_tree_iter_add(iter, offset);
1667 		}
1668 		if ((flags & RADIX_TREE_ITER_CONTIG) && (offset > 0))
1669 			goto none;
1670 		next_index = (iter->index | shift_maxindex(iter->shift)) + 1;
1671 		if (next_index < iter->next_index)
1672 			iter->next_index = next_index;
1673 	}
1674 
1675 	return slot;
1676  none:
1677 	iter->next_index = 0;
1678 	return NULL;
1679 }
1680 EXPORT_SYMBOL(__radix_tree_next_slot);
1681 #else
skip_siblings(struct radix_tree_node ** nodep,void __rcu ** slot,struct radix_tree_iter * iter)1682 static void __rcu **skip_siblings(struct radix_tree_node **nodep,
1683 			void __rcu **slot, struct radix_tree_iter *iter)
1684 {
1685 	return slot;
1686 }
1687 #endif
1688 
radix_tree_iter_resume(void __rcu ** slot,struct radix_tree_iter * iter)1689 void __rcu **radix_tree_iter_resume(void __rcu **slot,
1690 					struct radix_tree_iter *iter)
1691 {
1692 	struct radix_tree_node *node;
1693 
1694 	slot++;
1695 	iter->index = __radix_tree_iter_add(iter, 1);
1696 	skip_siblings(&node, slot, iter);
1697 	iter->next_index = iter->index;
1698 	iter->tags = 0;
1699 	return NULL;
1700 }
1701 EXPORT_SYMBOL(radix_tree_iter_resume);
1702 
1703 /**
1704  * radix_tree_next_chunk - find next chunk of slots for iteration
1705  *
1706  * @root:	radix tree root
1707  * @iter:	iterator state
1708  * @flags:	RADIX_TREE_ITER_* flags and tag index
1709  * Returns:	pointer to chunk first slot, or NULL if iteration is over
1710  */
radix_tree_next_chunk(const struct radix_tree_root * root,struct radix_tree_iter * iter,unsigned flags)1711 void __rcu **radix_tree_next_chunk(const struct radix_tree_root *root,
1712 			     struct radix_tree_iter *iter, unsigned flags)
1713 {
1714 	unsigned tag = flags & RADIX_TREE_ITER_TAG_MASK;
1715 	struct radix_tree_node *node, *child;
1716 	unsigned long index, offset, maxindex;
1717 
1718 	if ((flags & RADIX_TREE_ITER_TAGGED) && !root_tag_get(root, tag))
1719 		return NULL;
1720 
1721 	/*
1722 	 * Catch next_index overflow after ~0UL. iter->index never overflows
1723 	 * during iterating; it can be zero only at the beginning.
1724 	 * And we cannot overflow iter->next_index in a single step,
1725 	 * because RADIX_TREE_MAP_SHIFT < BITS_PER_LONG.
1726 	 *
1727 	 * This condition also used by radix_tree_next_slot() to stop
1728 	 * contiguous iterating, and forbid switching to the next chunk.
1729 	 */
1730 	index = iter->next_index;
1731 	if (!index && iter->index)
1732 		return NULL;
1733 
1734  restart:
1735 	radix_tree_load_root(root, &child, &maxindex);
1736 	if (index > maxindex)
1737 		return NULL;
1738 	if (!child)
1739 		return NULL;
1740 
1741 	if (!radix_tree_is_internal_node(child)) {
1742 		/* Single-slot tree */
1743 		iter->index = index;
1744 		iter->next_index = maxindex + 1;
1745 		iter->tags = 1;
1746 		iter->node = NULL;
1747 		__set_iter_shift(iter, 0);
1748 		return (void __rcu **)&root->rnode;
1749 	}
1750 
1751 	do {
1752 		node = entry_to_node(child);
1753 		offset = radix_tree_descend(node, &child, index);
1754 
1755 		if ((flags & RADIX_TREE_ITER_TAGGED) ?
1756 				!tag_get(node, tag, offset) : !child) {
1757 			/* Hole detected */
1758 			if (flags & RADIX_TREE_ITER_CONTIG)
1759 				return NULL;
1760 
1761 			if (flags & RADIX_TREE_ITER_TAGGED)
1762 				offset = radix_tree_find_next_bit(node, tag,
1763 						offset + 1);
1764 			else
1765 				while (++offset	< RADIX_TREE_MAP_SIZE) {
1766 					void *slot = rcu_dereference_raw(
1767 							node->slots[offset]);
1768 					if (is_sibling_entry(node, slot))
1769 						continue;
1770 					if (slot)
1771 						break;
1772 				}
1773 			index &= ~node_maxindex(node);
1774 			index += offset << node->shift;
1775 			/* Overflow after ~0UL */
1776 			if (!index)
1777 				return NULL;
1778 			if (offset == RADIX_TREE_MAP_SIZE)
1779 				goto restart;
1780 			child = rcu_dereference_raw(node->slots[offset]);
1781 		}
1782 
1783 		if (!child)
1784 			goto restart;
1785 		if (child == RADIX_TREE_RETRY)
1786 			break;
1787 	} while (radix_tree_is_internal_node(child));
1788 
1789 	/* Update the iterator state */
1790 	iter->index = (index &~ node_maxindex(node)) | (offset << node->shift);
1791 	iter->next_index = (index | node_maxindex(node)) + 1;
1792 	iter->node = node;
1793 	__set_iter_shift(iter, node->shift);
1794 
1795 	if (flags & RADIX_TREE_ITER_TAGGED)
1796 		set_iter_tags(iter, node, offset, tag);
1797 
1798 	return node->slots + offset;
1799 }
1800 EXPORT_SYMBOL(radix_tree_next_chunk);
1801 
1802 /**
1803  *	radix_tree_gang_lookup - perform multiple lookup on a radix tree
1804  *	@root:		radix tree root
1805  *	@results:	where the results of the lookup are placed
1806  *	@first_index:	start the lookup from this key
1807  *	@max_items:	place up to this many items at *results
1808  *
1809  *	Performs an index-ascending scan of the tree for present items.  Places
1810  *	them at *@results and returns the number of items which were placed at
1811  *	*@results.
1812  *
1813  *	The implementation is naive.
1814  *
1815  *	Like radix_tree_lookup, radix_tree_gang_lookup may be called under
1816  *	rcu_read_lock. In this case, rather than the returned results being
1817  *	an atomic snapshot of the tree at a single point in time, the
1818  *	semantics of an RCU protected gang lookup are as though multiple
1819  *	radix_tree_lookups have been issued in individual locks, and results
1820  *	stored in 'results'.
1821  */
1822 unsigned int
radix_tree_gang_lookup(const struct radix_tree_root * root,void ** results,unsigned long first_index,unsigned int max_items)1823 radix_tree_gang_lookup(const struct radix_tree_root *root, void **results,
1824 			unsigned long first_index, unsigned int max_items)
1825 {
1826 	struct radix_tree_iter iter;
1827 	void __rcu **slot;
1828 	unsigned int ret = 0;
1829 
1830 	if (unlikely(!max_items))
1831 		return 0;
1832 
1833 	radix_tree_for_each_slot(slot, root, &iter, first_index) {
1834 		results[ret] = rcu_dereference_raw(*slot);
1835 		if (!results[ret])
1836 			continue;
1837 		if (radix_tree_is_internal_node(results[ret])) {
1838 			slot = radix_tree_iter_retry(&iter);
1839 			continue;
1840 		}
1841 		if (++ret == max_items)
1842 			break;
1843 	}
1844 
1845 	return ret;
1846 }
1847 EXPORT_SYMBOL(radix_tree_gang_lookup);
1848 
1849 /**
1850  *	radix_tree_gang_lookup_slot - perform multiple slot lookup on radix tree
1851  *	@root:		radix tree root
1852  *	@results:	where the results of the lookup are placed
1853  *	@indices:	where their indices should be placed (but usually NULL)
1854  *	@first_index:	start the lookup from this key
1855  *	@max_items:	place up to this many items at *results
1856  *
1857  *	Performs an index-ascending scan of the tree for present items.  Places
1858  *	their slots at *@results and returns the number of items which were
1859  *	placed at *@results.
1860  *
1861  *	The implementation is naive.
1862  *
1863  *	Like radix_tree_gang_lookup as far as RCU and locking goes. Slots must
1864  *	be dereferenced with radix_tree_deref_slot, and if using only RCU
1865  *	protection, radix_tree_deref_slot may fail requiring a retry.
1866  */
1867 unsigned int
radix_tree_gang_lookup_slot(const struct radix_tree_root * root,void __rcu *** results,unsigned long * indices,unsigned long first_index,unsigned int max_items)1868 radix_tree_gang_lookup_slot(const struct radix_tree_root *root,
1869 			void __rcu ***results, unsigned long *indices,
1870 			unsigned long first_index, unsigned int max_items)
1871 {
1872 	struct radix_tree_iter iter;
1873 	void __rcu **slot;
1874 	unsigned int ret = 0;
1875 
1876 	if (unlikely(!max_items))
1877 		return 0;
1878 
1879 	radix_tree_for_each_slot(slot, root, &iter, first_index) {
1880 		results[ret] = slot;
1881 		if (indices)
1882 			indices[ret] = iter.index;
1883 		if (++ret == max_items)
1884 			break;
1885 	}
1886 
1887 	return ret;
1888 }
1889 EXPORT_SYMBOL(radix_tree_gang_lookup_slot);
1890 
1891 /**
1892  *	radix_tree_gang_lookup_tag - perform multiple lookup on a radix tree
1893  *	                             based on a tag
1894  *	@root:		radix tree root
1895  *	@results:	where the results of the lookup are placed
1896  *	@first_index:	start the lookup from this key
1897  *	@max_items:	place up to this many items at *results
1898  *	@tag:		the tag index (< RADIX_TREE_MAX_TAGS)
1899  *
1900  *	Performs an index-ascending scan of the tree for present items which
1901  *	have the tag indexed by @tag set.  Places the items at *@results and
1902  *	returns the number of items which were placed at *@results.
1903  */
1904 unsigned int
radix_tree_gang_lookup_tag(const struct radix_tree_root * root,void ** results,unsigned long first_index,unsigned int max_items,unsigned int tag)1905 radix_tree_gang_lookup_tag(const struct radix_tree_root *root, void **results,
1906 		unsigned long first_index, unsigned int max_items,
1907 		unsigned int tag)
1908 {
1909 	struct radix_tree_iter iter;
1910 	void __rcu **slot;
1911 	unsigned int ret = 0;
1912 
1913 	if (unlikely(!max_items))
1914 		return 0;
1915 
1916 	radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1917 		results[ret] = rcu_dereference_raw(*slot);
1918 		if (!results[ret])
1919 			continue;
1920 		if (radix_tree_is_internal_node(results[ret])) {
1921 			slot = radix_tree_iter_retry(&iter);
1922 			continue;
1923 		}
1924 		if (++ret == max_items)
1925 			break;
1926 	}
1927 
1928 	return ret;
1929 }
1930 EXPORT_SYMBOL(radix_tree_gang_lookup_tag);
1931 
1932 /**
1933  *	radix_tree_gang_lookup_tag_slot - perform multiple slot lookup on a
1934  *					  radix tree based on a tag
1935  *	@root:		radix tree root
1936  *	@results:	where the results of the lookup are placed
1937  *	@first_index:	start the lookup from this key
1938  *	@max_items:	place up to this many items at *results
1939  *	@tag:		the tag index (< RADIX_TREE_MAX_TAGS)
1940  *
1941  *	Performs an index-ascending scan of the tree for present items which
1942  *	have the tag indexed by @tag set.  Places the slots at *@results and
1943  *	returns the number of slots which were placed at *@results.
1944  */
1945 unsigned int
radix_tree_gang_lookup_tag_slot(const struct radix_tree_root * root,void __rcu *** results,unsigned long first_index,unsigned int max_items,unsigned int tag)1946 radix_tree_gang_lookup_tag_slot(const struct radix_tree_root *root,
1947 		void __rcu ***results, unsigned long first_index,
1948 		unsigned int max_items, unsigned int tag)
1949 {
1950 	struct radix_tree_iter iter;
1951 	void __rcu **slot;
1952 	unsigned int ret = 0;
1953 
1954 	if (unlikely(!max_items))
1955 		return 0;
1956 
1957 	radix_tree_for_each_tagged(slot, root, &iter, first_index, tag) {
1958 		results[ret] = slot;
1959 		if (++ret == max_items)
1960 			break;
1961 	}
1962 
1963 	return ret;
1964 }
1965 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
1966 
1967 /**
1968  *	__radix_tree_delete_node    -    try to free node after clearing a slot
1969  *	@root:		radix tree root
1970  *	@node:		node containing @index
1971  *	@update_node:	callback for changing leaf nodes
1972  *
1973  *	After clearing the slot at @index in @node from radix tree
1974  *	rooted at @root, call this function to attempt freeing the
1975  *	node and shrinking the tree.
1976  */
__radix_tree_delete_node(struct radix_tree_root * root,struct radix_tree_node * node,radix_tree_update_node_t update_node)1977 void __radix_tree_delete_node(struct radix_tree_root *root,
1978 			      struct radix_tree_node *node,
1979 			      radix_tree_update_node_t update_node)
1980 {
1981 	delete_node(root, node, update_node);
1982 }
1983 
__radix_tree_delete(struct radix_tree_root * root,struct radix_tree_node * node,void __rcu ** slot)1984 static bool __radix_tree_delete(struct radix_tree_root *root,
1985 				struct radix_tree_node *node, void __rcu **slot)
1986 {
1987 	void *old = rcu_dereference_raw(*slot);
1988 	int exceptional = radix_tree_exceptional_entry(old) ? -1 : 0;
1989 	unsigned offset = get_slot_offset(node, slot);
1990 	int tag;
1991 
1992 	if (is_idr(root))
1993 		node_tag_set(root, node, IDR_FREE, offset);
1994 	else
1995 		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
1996 			node_tag_clear(root, node, tag, offset);
1997 
1998 	replace_slot(slot, NULL, node, -1, exceptional);
1999 	return node && delete_node(root, node, NULL);
2000 }
2001 
2002 /**
2003  * radix_tree_iter_delete - delete the entry at this iterator position
2004  * @root: radix tree root
2005  * @iter: iterator state
2006  * @slot: pointer to slot
2007  *
2008  * Delete the entry at the position currently pointed to by the iterator.
2009  * This may result in the current node being freed; if it is, the iterator
2010  * is advanced so that it will not reference the freed memory.  This
2011  * function may be called without any locking if there are no other threads
2012  * which can access this tree.
2013  */
radix_tree_iter_delete(struct radix_tree_root * root,struct radix_tree_iter * iter,void __rcu ** slot)2014 void radix_tree_iter_delete(struct radix_tree_root *root,
2015 				struct radix_tree_iter *iter, void __rcu **slot)
2016 {
2017 	if (__radix_tree_delete(root, iter->node, slot))
2018 		iter->index = iter->next_index;
2019 }
2020 EXPORT_SYMBOL(radix_tree_iter_delete);
2021 
2022 /**
2023  * radix_tree_delete_item - delete an item from a radix tree
2024  * @root: radix tree root
2025  * @index: index key
2026  * @item: expected item
2027  *
2028  * Remove @item at @index from the radix tree rooted at @root.
2029  *
2030  * Return: the deleted entry, or %NULL if it was not present
2031  * or the entry at the given @index was not @item.
2032  */
radix_tree_delete_item(struct radix_tree_root * root,unsigned long index,void * item)2033 void *radix_tree_delete_item(struct radix_tree_root *root,
2034 			     unsigned long index, void *item)
2035 {
2036 	struct radix_tree_node *node = NULL;
2037 	void __rcu **slot = NULL;
2038 	void *entry;
2039 
2040 	entry = __radix_tree_lookup(root, index, &node, &slot);
2041 	if (!slot)
2042 		return NULL;
2043 	if (!entry && (!is_idr(root) || node_tag_get(root, node, IDR_FREE,
2044 						get_slot_offset(node, slot))))
2045 		return NULL;
2046 
2047 	if (item && entry != item)
2048 		return NULL;
2049 
2050 	__radix_tree_delete(root, node, slot);
2051 
2052 	return entry;
2053 }
2054 EXPORT_SYMBOL(radix_tree_delete_item);
2055 
2056 /**
2057  * radix_tree_delete - delete an entry from a radix tree
2058  * @root: radix tree root
2059  * @index: index key
2060  *
2061  * Remove the entry at @index from the radix tree rooted at @root.
2062  *
2063  * Return: The deleted entry, or %NULL if it was not present.
2064  */
radix_tree_delete(struct radix_tree_root * root,unsigned long index)2065 void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
2066 {
2067 	return radix_tree_delete_item(root, index, NULL);
2068 }
2069 EXPORT_SYMBOL(radix_tree_delete);
2070 
radix_tree_clear_tags(struct radix_tree_root * root,struct radix_tree_node * node,void __rcu ** slot)2071 void radix_tree_clear_tags(struct radix_tree_root *root,
2072 			   struct radix_tree_node *node,
2073 			   void __rcu **slot)
2074 {
2075 	if (node) {
2076 		unsigned int tag, offset = get_slot_offset(node, slot);
2077 		for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
2078 			node_tag_clear(root, node, tag, offset);
2079 	} else {
2080 		root_tag_clear_all(root);
2081 	}
2082 }
2083 
2084 /**
2085  *	radix_tree_tagged - test whether any items in the tree are tagged
2086  *	@root:		radix tree root
2087  *	@tag:		tag to test
2088  */
radix_tree_tagged(const struct radix_tree_root * root,unsigned int tag)2089 int radix_tree_tagged(const struct radix_tree_root *root, unsigned int tag)
2090 {
2091 	return root_tag_get(root, tag);
2092 }
2093 EXPORT_SYMBOL(radix_tree_tagged);
2094 
2095 /**
2096  * idr_preload - preload for idr_alloc()
2097  * @gfp_mask: allocation mask to use for preloading
2098  *
2099  * Preallocate memory to use for the next call to idr_alloc().  This function
2100  * returns with preemption disabled.  It will be enabled by idr_preload_end().
2101  */
idr_preload(gfp_t gfp_mask)2102 void idr_preload(gfp_t gfp_mask)
2103 {
2104 	if (__radix_tree_preload(gfp_mask, IDR_PRELOAD_SIZE))
2105 		preempt_disable();
2106 }
2107 EXPORT_SYMBOL(idr_preload);
2108 
ida_pre_get(struct ida * ida,gfp_t gfp)2109 int ida_pre_get(struct ida *ida, gfp_t gfp)
2110 {
2111 	/*
2112 	 * The IDA API has no preload_end() equivalent.  Instead,
2113 	 * ida_get_new() can return -EAGAIN, prompting the caller
2114 	 * to return to the ida_pre_get() step.
2115 	 */
2116 	if (!__radix_tree_preload(gfp, IDA_PRELOAD_SIZE))
2117 		preempt_enable();
2118 
2119 	if (!this_cpu_read(ida_bitmap)) {
2120 		struct ida_bitmap *bitmap = kzalloc(sizeof(*bitmap), gfp);
2121 		if (!bitmap)
2122 			return 0;
2123 		if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))
2124 			kfree(bitmap);
2125 	}
2126 
2127 	return 1;
2128 }
2129 
idr_get_free(struct radix_tree_root * root,struct radix_tree_iter * iter,gfp_t gfp,unsigned long max)2130 void __rcu **idr_get_free(struct radix_tree_root *root,
2131 			      struct radix_tree_iter *iter, gfp_t gfp,
2132 			      unsigned long max)
2133 {
2134 	struct radix_tree_node *node = NULL, *child;
2135 	void __rcu **slot = (void __rcu **)&root->rnode;
2136 	unsigned long maxindex, start = iter->next_index;
2137 	unsigned int shift, offset = 0;
2138 
2139  grow:
2140 	shift = radix_tree_load_root(root, &child, &maxindex);
2141 	if (!radix_tree_tagged(root, IDR_FREE))
2142 		start = max(start, maxindex + 1);
2143 	if (start > max)
2144 		return ERR_PTR(-ENOSPC);
2145 
2146 	if (start > maxindex) {
2147 		int error = radix_tree_extend(root, gfp, start, shift);
2148 		if (error < 0)
2149 			return ERR_PTR(error);
2150 		shift = error;
2151 		child = rcu_dereference_raw(root->rnode);
2152 	}
2153 
2154 	while (shift) {
2155 		shift -= RADIX_TREE_MAP_SHIFT;
2156 		if (child == NULL) {
2157 			/* Have to add a child node.  */
2158 			child = radix_tree_node_alloc(gfp, node, root, shift,
2159 							offset, 0, 0);
2160 			if (!child)
2161 				return ERR_PTR(-ENOMEM);
2162 			all_tag_set(child, IDR_FREE);
2163 			rcu_assign_pointer(*slot, node_to_entry(child));
2164 			if (node)
2165 				node->count++;
2166 		} else if (!radix_tree_is_internal_node(child))
2167 			break;
2168 
2169 		node = entry_to_node(child);
2170 		offset = radix_tree_descend(node, &child, start);
2171 		if (!tag_get(node, IDR_FREE, offset)) {
2172 			offset = radix_tree_find_next_bit(node, IDR_FREE,
2173 							offset + 1);
2174 			start = next_index(start, node, offset);
2175 			if (start > max || start == 0)
2176 				return ERR_PTR(-ENOSPC);
2177 			while (offset == RADIX_TREE_MAP_SIZE) {
2178 				offset = node->offset + 1;
2179 				node = node->parent;
2180 				if (!node)
2181 					goto grow;
2182 				shift = node->shift;
2183 			}
2184 			child = rcu_dereference_raw(node->slots[offset]);
2185 		}
2186 		slot = &node->slots[offset];
2187 	}
2188 
2189 	iter->index = start;
2190 	if (node)
2191 		iter->next_index = 1 + min(max, (start | node_maxindex(node)));
2192 	else
2193 		iter->next_index = 1;
2194 	iter->node = node;
2195 	__set_iter_shift(iter, shift);
2196 	set_iter_tags(iter, node, offset, IDR_FREE);
2197 
2198 	return slot;
2199 }
2200 
2201 /**
2202  * idr_destroy - release all internal memory from an IDR
2203  * @idr: idr handle
2204  *
2205  * After this function is called, the IDR is empty, and may be reused or
2206  * the data structure containing it may be freed.
2207  *
2208  * A typical clean-up sequence for objects stored in an idr tree will use
2209  * idr_for_each() to free all objects, if necessary, then idr_destroy() to
2210  * free the memory used to keep track of those objects.
2211  */
idr_destroy(struct idr * idr)2212 void idr_destroy(struct idr *idr)
2213 {
2214 	struct radix_tree_node *node = rcu_dereference_raw(idr->idr_rt.rnode);
2215 	if (radix_tree_is_internal_node(node))
2216 		radix_tree_free_nodes(node);
2217 	idr->idr_rt.rnode = NULL;
2218 	root_tag_set(&idr->idr_rt, IDR_FREE);
2219 }
2220 EXPORT_SYMBOL(idr_destroy);
2221 
2222 static void
radix_tree_node_ctor(void * arg)2223 radix_tree_node_ctor(void *arg)
2224 {
2225 	struct radix_tree_node *node = arg;
2226 
2227 	memset(node, 0, sizeof(*node));
2228 	INIT_LIST_HEAD(&node->private_list);
2229 }
2230 
__maxindex(unsigned int height)2231 static __init unsigned long __maxindex(unsigned int height)
2232 {
2233 	unsigned int width = height * RADIX_TREE_MAP_SHIFT;
2234 	int shift = RADIX_TREE_INDEX_BITS - width;
2235 
2236 	if (shift < 0)
2237 		return ~0UL;
2238 	if (shift >= BITS_PER_LONG)
2239 		return 0UL;
2240 	return ~0UL >> shift;
2241 }
2242 
radix_tree_init_maxnodes(void)2243 static __init void radix_tree_init_maxnodes(void)
2244 {
2245 	unsigned long height_to_maxindex[RADIX_TREE_MAX_PATH + 1];
2246 	unsigned int i, j;
2247 
2248 	for (i = 0; i < ARRAY_SIZE(height_to_maxindex); i++)
2249 		height_to_maxindex[i] = __maxindex(i);
2250 	for (i = 0; i < ARRAY_SIZE(height_to_maxnodes); i++) {
2251 		for (j = i; j > 0; j--)
2252 			height_to_maxnodes[i] += height_to_maxindex[j - 1] + 1;
2253 	}
2254 }
2255 
radix_tree_cpu_dead(unsigned int cpu)2256 static int radix_tree_cpu_dead(unsigned int cpu)
2257 {
2258 	struct radix_tree_preload *rtp;
2259 	struct radix_tree_node *node;
2260 
2261 	/* Free per-cpu pool of preloaded nodes */
2262 	rtp = &per_cpu(radix_tree_preloads, cpu);
2263 	while (rtp->nr) {
2264 		node = rtp->nodes;
2265 		rtp->nodes = node->parent;
2266 		kmem_cache_free(radix_tree_node_cachep, node);
2267 		rtp->nr--;
2268 	}
2269 	kfree(per_cpu(ida_bitmap, cpu));
2270 	per_cpu(ida_bitmap, cpu) = NULL;
2271 	return 0;
2272 }
2273 
radix_tree_init(void)2274 void __init radix_tree_init(void)
2275 {
2276 	int ret;
2277 
2278 	BUILD_BUG_ON(RADIX_TREE_MAX_TAGS + __GFP_BITS_SHIFT > 32);
2279 	BUILD_BUG_ON(ROOT_IS_IDR & ~GFP_ZONEMASK);
2280 	radix_tree_node_cachep = kmem_cache_create("radix_tree_node",
2281 			sizeof(struct radix_tree_node), 0,
2282 			SLAB_PANIC | SLAB_RECLAIM_ACCOUNT,
2283 			radix_tree_node_ctor);
2284 	radix_tree_init_maxnodes();
2285 	ret = cpuhp_setup_state_nocalls(CPUHP_RADIX_DEAD, "lib/radix:dead",
2286 					NULL, radix_tree_cpu_dead);
2287 	WARN_ON(ret < 0);
2288 }
2289