Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/lib/radix-tree.c

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

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