sys/vm/vm_radix.c

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
   3  *
   4  * Copyright (c) 2013 EMC Corp.
   5  * Copyright (c) 2011 Jeffrey Roberson <jeff@freebsd.org>
   6  * Copyright (c) 2008 Mayur Shardul <mayur.shardul@gmail.com>
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  *
  18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  19  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  20  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  21  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  22  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  23  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  24  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  27  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGE.
  29  *
  30  */
  31
  32 /*
  33  * Path-compressed radix trie implementation.
  34  * The following code is not generalized into a general purpose library
  35  * because there are way too many parameters embedded that should really
  36  * be decided by the library consumers.  At the same time, consumers
  37  * of this code must achieve highest possible performance.
  38  *
  39  * The implementation takes into account the following rationale:
  40  * - Size of the nodes should be as small as possible but still big enough
  41  *   to avoid a large maximum depth for the trie.  This is a balance
  42  *   between the necessity to not wire too much physical memory for the nodes
  43  *   and the necessity to avoid too much cache pollution during the trie
  44  *   operations.
  45  * - There is not a huge bias toward the number of lookup operations over
  46  *   the number of insert and remove operations.  This basically implies
  47  *   that optimizations supposedly helping one operation but hurting the
  48  *   other might be carefully evaluated.
  49  * - On average not many nodes are expected to be fully populated, hence
  50  *   level compression may just complicate things.
  51  */
  52
  53 #include <sys/cdefs.h>
  54 __FBSDID("$FreeBSD$");
  55
  56 #include "opt_ddb.h"
  57
  58 #include <sys/param.h>
  59 #include <sys/systm.h>
  60 #include <sys/kernel.h>
  61 #include <sys/vmmeter.h>
  62
  63 #include <vm/uma.h>
  64 #include <vm/vm.h>
  65 #include <vm/vm_param.h>
  66 #include <vm/vm_page.h>
  67 #include <vm/vm_radix.h>
  68
  69 #ifdef DDB
  70 #include <ddb/ddb.h>
  71 #endif
  72
  73 /*
  74  * These widths should allow the pointers to a node's children to fit within
  75  * a single cache line.  The extra levels from a narrow width should not be
  76  * a problem thanks to path compression.
  77  */
  78 #ifdef __LP64__
  79 #define VM_RADIX_WIDTH  4
  80 #else
  81 #define VM_RADIX_WIDTH  3
  82 #endif
  83
  84 #define VM_RADIX_COUNT  (1 << VM_RADIX_WIDTH)
  85 #define VM_RADIX_MASK   (VM_RADIX_COUNT - 1)
  86 #define VM_RADIX_LIMIT                                                  \
  87         (howmany(sizeof(vm_pindex_t) * NBBY, VM_RADIX_WIDTH) - 1)
  88
  89 /* Flag bits stored in node pointers. */
  90 #define VM_RADIX_ISLEAF 0x1
  91 #define VM_RADIX_FLAGS  0x1
  92 #define VM_RADIX_PAD    VM_RADIX_FLAGS
  93
  94 /* Returns one unit associated with specified level. */
  95 #define VM_RADIX_UNITLEVEL(lev)                                         \
  96         ((vm_pindex_t)1 << ((lev) * VM_RADIX_WIDTH))
  97
  98 struct vm_radix_node {
  99         vm_pindex_t      rn_owner;                      /* Owner of record. */
 100         uint16_t         rn_count;                      /* Valid children. */
 101         uint16_t         rn_clev;                       /* Current level. */
 102         void            *rn_child[VM_RADIX_COUNT];      /* Child nodes. */
 103 };
 104
 105 static uma_zone_t vm_radix_node_zone;
 106
 107 /*
 108  * Allocate a radix node.
 109  */
 110 static __inline struct vm_radix_node *
 111 vm_radix_node_get(vm_pindex_t owner, uint16_t count, uint16_t clevel)
 112 {
 113         struct vm_radix_node *rnode;
 114
 115         rnode = uma_zalloc(vm_radix_node_zone, M_NOWAIT | M_ZERO);
 116         if (rnode == NULL)
 117                 return (NULL);
 118         rnode->rn_owner = owner;
 119         rnode->rn_count = count;
 120         rnode->rn_clev = clevel;
 121         return (rnode);
 122 }
 123
 124 /*
 125  * Free radix node.
 126  */
 127 static __inline void
 128 vm_radix_node_put(struct vm_radix_node *rnode)
 129 {
 130
 131         uma_zfree(vm_radix_node_zone, rnode);
 132 }
 133
 134 /*
 135  * Return the position in the array for a given level.
 136  */
 137 static __inline int
 138 vm_radix_slot(vm_pindex_t index, uint16_t level)
 139 {
 140
 141         return ((index >> (level * VM_RADIX_WIDTH)) & VM_RADIX_MASK);
 142 }
 143
 144 /* Trims the key after the specified level. */
 145 static __inline vm_pindex_t
 146 vm_radix_trimkey(vm_pindex_t index, uint16_t level)
 147 {
 148         vm_pindex_t ret;
 149
 150         ret = index;
 151         if (level > 0) {
 152                 ret >>= level * VM_RADIX_WIDTH;
 153                 ret <<= level * VM_RADIX_WIDTH;
 154         }
 155         return (ret);
 156 }
 157
 158 /*
 159  * Get the root node for a radix tree.
 160  */
 161 static __inline struct vm_radix_node *
 162 vm_radix_getroot(struct vm_radix *rtree)
 163 {
 164
 165         return ((struct vm_radix_node *)rtree->rt_root);
 166 }
 167
 168 /*
 169  * Set the root node for a radix tree.
 170  */
 171 static __inline void
 172 vm_radix_setroot(struct vm_radix *rtree, struct vm_radix_node *rnode)
 173 {
 174
 175         rtree->rt_root = (uintptr_t)rnode;
 176 }
 177
 178 /*
 179  * Returns TRUE if the specified radix node is a leaf and FALSE otherwise.
 180  */
 181 static __inline boolean_t
 182 vm_radix_isleaf(struct vm_radix_node *rnode)
 183 {
 184
 185         return (((uintptr_t)rnode & VM_RADIX_ISLEAF) != 0);
 186 }
 187
 188 /*
 189  * Returns the associated page extracted from rnode.
 190  */
 191 static __inline vm_page_t
 192 vm_radix_topage(struct vm_radix_node *rnode)
 193 {
 194
 195         return ((vm_page_t)((uintptr_t)rnode & ~VM_RADIX_FLAGS));
 196 }
 197
 198 /*
 199  * Adds the page as a child of the provided node.
 200  */
 201 static __inline void
 202 vm_radix_addpage(struct vm_radix_node *rnode, vm_pindex_t index, uint16_t clev,
 203     vm_page_t page)
 204 {
 205         int slot;
 206
 207         slot = vm_radix_slot(index, clev);
 208         rnode->rn_child[slot] = (void *)((uintptr_t)page | VM_RADIX_ISLEAF);
 209 }
 210
 211 /*
 212  * Returns the slot where two keys differ.
 213  * It cannot accept 2 equal keys.
 214  */
 215 static __inline uint16_t
 216 vm_radix_keydiff(vm_pindex_t index1, vm_pindex_t index2)
 217 {
 218         uint16_t clev;
 219
 220         KASSERT(index1 != index2, ("%s: passing the same key value %jx",
 221             __func__, (uintmax_t)index1));
 222
 223         index1 ^= index2;
 224         for (clev = VM_RADIX_LIMIT;; clev--)
 225                 if (vm_radix_slot(index1, clev) != 0)
 226                         return (clev);
 227 }
 228
 229 /*
 230  * Returns TRUE if it can be determined that key does not belong to the
 231  * specified rnode.  Otherwise, returns FALSE.
 232  */
 233 static __inline boolean_t
 234 vm_radix_keybarr(struct vm_radix_node *rnode, vm_pindex_t idx)
 235 {
 236
 237         if (rnode->rn_clev < VM_RADIX_LIMIT) {
 238                 idx = vm_radix_trimkey(idx, rnode->rn_clev + 1);
 239                 return (idx != rnode->rn_owner);
 240         }
 241         return (FALSE);
 242 }
 243
 244 /*
 245  * Internal helper for vm_radix_reclaim_allnodes().
 246  * This function is recursive.
 247  */
 248 static void
 249 vm_radix_reclaim_allnodes_int(struct vm_radix_node *rnode)
 250 {
 251         int slot;
 252
 253         KASSERT(rnode->rn_count <= VM_RADIX_COUNT,
 254             ("vm_radix_reclaim_allnodes_int: bad count in rnode %p", rnode));
 255         for (slot = 0; rnode->rn_count != 0; slot++) {
 256                 if (rnode->rn_child[slot] == NULL)
 257                         continue;
 258                 if (!vm_radix_isleaf(rnode->rn_child[slot]))
 259                         vm_radix_reclaim_allnodes_int(rnode->rn_child[slot]);
 260                 rnode->rn_child[slot] = NULL;
 261                 rnode->rn_count--;
 262         }
 263         vm_radix_node_put(rnode);
 264 }
 265
 266 #ifdef INVARIANTS
 267 /*
 268  * Radix node zone destructor.
 269  */
 270 static void
 271 vm_radix_node_zone_dtor(void *mem, int size __unused, void *arg __unused)
 272 {
 273         struct vm_radix_node *rnode;
 274         int slot;
 275
 276         rnode = mem;
 277         KASSERT(rnode->rn_count == 0,
 278             ("vm_radix_node_put: rnode %p has %d children", rnode,
 279             rnode->rn_count));
 280         for (slot = 0; slot < VM_RADIX_COUNT; slot++)
 281                 KASSERT(rnode->rn_child[slot] == NULL,
 282                     ("vm_radix_node_put: rnode %p has a child", rnode));
 283 }
 284 #endif
 285
 286 #ifndef UMA_MD_SMALL_ALLOC
 287 void vm_radix_reserve_kva(void);
 288 /*
 289  * Reserve the KVA necessary to satisfy the node allocation.
 290  * This is mandatory in architectures not supporting direct
 291  * mapping as they will need otherwise to carve into the kernel maps for
 292  * every node allocation, resulting into deadlocks for consumers already
 293  * working with kernel maps.
 294  */
 295 void
 296 vm_radix_reserve_kva(void)
 297 {
 298
 299         /*
 300          * Calculate the number of reserved nodes, discounting the pages that
 301          * are needed to store them.
 302          */
 303         if (!uma_zone_reserve_kva(vm_radix_node_zone,
 304             ((vm_paddr_t)vm_cnt.v_page_count * PAGE_SIZE) / (PAGE_SIZE +
 305             sizeof(struct vm_radix_node))))
 306                 panic("%s: unable to reserve KVA", __func__);
 307 }
 308 #endif
 309
 310 /*
 311  * Initialize the UMA slab zone.
 312  */
 313 void
 314 vm_radix_zinit(void)
 315 {
 316
 317         vm_radix_node_zone = uma_zcreate("RADIX NODE",
 318             sizeof(struct vm_radix_node), NULL,
 319 #ifdef INVARIANTS
 320             vm_radix_node_zone_dtor,
 321 #else
 322             NULL,
 323 #endif
 324             NULL, NULL, VM_RADIX_PAD, UMA_ZONE_VM);
 325 }
 326
 327 /*
 328  * Inserts the key-value pair into the trie.
 329  * Panics if the key already exists.
 330  */
 331 int
 332 vm_radix_insert(struct vm_radix *rtree, vm_page_t page)
 333 {
 334         vm_pindex_t index, newind;
 335         void **parentp;
 336         struct vm_radix_node *rnode, *tmp;
 337         vm_page_t m;
 338         int slot;
 339         uint16_t clev;
 340
 341         index = page->pindex;
 342
 343         /*
 344          * The owner of record for root is not really important because it
 345          * will never be used.
 346          */
 347         rnode = vm_radix_getroot(rtree);
 348         if (rnode == NULL) {
 349                 rtree->rt_root = (uintptr_t)page | VM_RADIX_ISLEAF;
 350                 return (0);
 351         }
 352         parentp = (void **)&rtree->rt_root;
 353         for (;;) {
 354                 if (vm_radix_isleaf(rnode)) {
 355                         m = vm_radix_topage(rnode);
 356                         if (m->pindex == index)
 357                                 panic("%s: key %jx is already present",
 358                                     __func__, (uintmax_t)index);
 359                         clev = vm_radix_keydiff(m->pindex, index);
 360                         tmp = vm_radix_node_get(vm_radix_trimkey(index,
 361                             clev + 1), 2, clev);
 362                         if (tmp == NULL)
 363                                 return (ENOMEM);
 364                         *parentp = tmp;
 365                         vm_radix_addpage(tmp, index, clev, page);
 366                         vm_radix_addpage(tmp, m->pindex, clev, m);
 367                         return (0);
 368                 } else if (vm_radix_keybarr(rnode, index))
 369                         break;
 370                 slot = vm_radix_slot(index, rnode->rn_clev);
 371                 if (rnode->rn_child[slot] == NULL) {
 372                         rnode->rn_count++;
 373                         vm_radix_addpage(rnode, index, rnode->rn_clev, page);
 374                         return (0);
 375                 }
 376                 parentp = &rnode->rn_child[slot];
 377                 rnode = rnode->rn_child[slot];
 378         }
 379
 380         /*
 381          * A new node is needed because the right insertion level is reached.
 382          * Setup the new intermediate node and add the 2 children: the
 383          * new object and the older edge.
 384          */
 385         newind = rnode->rn_owner;
 386         clev = vm_radix_keydiff(newind, index);
 387         tmp = vm_radix_node_get(vm_radix_trimkey(index, clev + 1), 2, clev);
 388         if (tmp == NULL)
 389                 return (ENOMEM);
 390         *parentp = tmp;
 391         vm_radix_addpage(tmp, index, clev, page);
 392         slot = vm_radix_slot(newind, clev);
 393         tmp->rn_child[slot] = rnode;
 394         return (0);
 395 }
 396
 397 /*
 398  * Returns TRUE if the specified radix tree contains a single leaf and FALSE
 399  * otherwise.
 400  */
 401 boolean_t
 402 vm_radix_is_singleton(struct vm_radix *rtree)
 403 {
 404         struct vm_radix_node *rnode;
 405
 406         rnode = vm_radix_getroot(rtree);
 407         if (rnode == NULL)
 408                 return (FALSE);
 409         return (vm_radix_isleaf(rnode));
 410 }
 411
 412 /*
 413  * Returns the value stored at the index.  If the index is not present,
 414  * NULL is returned.
 415  */
 416 vm_page_t
 417 vm_radix_lookup(struct vm_radix *rtree, vm_pindex_t index)
 418 {
 419         struct vm_radix_node *rnode;
 420         vm_page_t m;
 421         int slot;
 422
 423         rnode = vm_radix_getroot(rtree);
 424         while (rnode != NULL) {
 425                 if (vm_radix_isleaf(rnode)) {
 426                         m = vm_radix_topage(rnode);
 427                         if (m->pindex == index)
 428                                 return (m);
 429                         else
 430                                 break;
 431                 } else if (vm_radix_keybarr(rnode, index))
 432                         break;
 433                 slot = vm_radix_slot(index, rnode->rn_clev);
 434                 rnode = rnode->rn_child[slot];
 435         }
 436         return (NULL);
 437 }
 438
 439 /*
 440  * Look up the nearest entry at a position bigger than or equal to index.
 441  */
 442 vm_page_t
 443 vm_radix_lookup_ge(struct vm_radix *rtree, vm_pindex_t index)
 444 {
 445         struct vm_radix_node *stack[VM_RADIX_LIMIT];
 446         vm_pindex_t inc;
 447         vm_page_t m;
 448         struct vm_radix_node *child, *rnode;
 449 #ifdef INVARIANTS
 450         int loops = 0;
 451 #endif
 452         int slot, tos;
 453
 454         rnode = vm_radix_getroot(rtree);
 455         if (rnode == NULL)
 456                 return (NULL);
 457         else if (vm_radix_isleaf(rnode)) {
 458                 m = vm_radix_topage(rnode);
 459                 if (m->pindex >= index)
 460                         return (m);
 461                 else
 462                         return (NULL);
 463         }
 464         tos = 0;
 465         for (;;) {
 466                 /*
 467                  * If the keys differ before the current bisection node,
 468                  * then the search key might rollback to the earliest
 469                  * available bisection node or to the smallest key
 470                  * in the current node (if the owner is bigger than the
 471                  * search key).
 472                  */
 473                 if (vm_radix_keybarr(rnode, index)) {
 474                         if (index > rnode->rn_owner) {
 475 ascend:
 476                                 KASSERT(++loops < 1000,
 477                                     ("vm_radix_lookup_ge: too many loops"));
 478
 479                                 /*
 480                                  * Pop nodes from the stack until either the
 481                                  * stack is empty or a node that could have a
 482                                  * matching descendant is found.
 483                                  */
 484                                 do {
 485                                         if (tos == 0)
 486                                                 return (NULL);
 487                                         rnode = stack[--tos];
 488                                 } while (vm_radix_slot(index,
 489                                     rnode->rn_clev) == (VM_RADIX_COUNT - 1));
 490
 491                                 /*
 492                                  * The following computation cannot overflow
 493                                  * because index's slot at the current level
 494                                  * is less than VM_RADIX_COUNT - 1.
 495                                  */
 496                                 index = vm_radix_trimkey(index,
 497                                     rnode->rn_clev);
 498                                 index += VM_RADIX_UNITLEVEL(rnode->rn_clev);
 499                         } else
 500                                 index = rnode->rn_owner;
 501                         KASSERT(!vm_radix_keybarr(rnode, index),
 502                             ("vm_radix_lookup_ge: keybarr failed"));
 503                 }
 504                 slot = vm_radix_slot(index, rnode->rn_clev);
 505                 child = rnode->rn_child[slot];
 506                 if (vm_radix_isleaf(child)) {
 507                         m = vm_radix_topage(child);
 508                         if (m->pindex >= index)
 509                                 return (m);
 510                 } else if (child != NULL)
 511                         goto descend;
 512
 513                 /*
 514                  * Look for an available edge or page within the current
 515                  * bisection node.
 516                  */
 517                 if (slot < (VM_RADIX_COUNT - 1)) {
 518                         inc = VM_RADIX_UNITLEVEL(rnode->rn_clev);
 519                         index = vm_radix_trimkey(index, rnode->rn_clev);
 520                         do {
 521                                 index += inc;
 522                                 slot++;
 523                                 child = rnode->rn_child[slot];
 524                                 if (vm_radix_isleaf(child)) {
 525                                         m = vm_radix_topage(child);
 526                                         if (m->pindex >= index)
 527                                                 return (m);
 528                                 } else if (child != NULL)
 529                                         goto descend;
 530                         } while (slot < (VM_RADIX_COUNT - 1));
 531                 }
 532                 KASSERT(child == NULL || vm_radix_isleaf(child),
 533                     ("vm_radix_lookup_ge: child is radix node"));
 534
 535                 /*
 536                  * If a page or edge bigger than the search slot is not found
 537                  * in the current node, ascend to the next higher-level node.
 538                  */
 539                 goto ascend;
 540 descend:
 541                 KASSERT(rnode->rn_clev > 0,
 542                     ("vm_radix_lookup_ge: pushing leaf's parent"));
 543                 KASSERT(tos < VM_RADIX_LIMIT,
 544                     ("vm_radix_lookup_ge: stack overflow"));
 545                 stack[tos++] = rnode;
 546                 rnode = child;
 547         }
 548 }
 549
 550 /*
 551  * Look up the nearest entry at a position less than or equal to index.
 552  */
 553 vm_page_t
 554 vm_radix_lookup_le(struct vm_radix *rtree, vm_pindex_t index)
 555 {
 556         struct vm_radix_node *stack[VM_RADIX_LIMIT];
 557         vm_pindex_t inc;
 558         vm_page_t m;
 559         struct vm_radix_node *child, *rnode;
 560 #ifdef INVARIANTS
 561         int loops = 0;
 562 #endif
 563         int slot, tos;
 564
 565         rnode = vm_radix_getroot(rtree);
 566         if (rnode == NULL)
 567                 return (NULL);
 568         else if (vm_radix_isleaf(rnode)) {
 569                 m = vm_radix_topage(rnode);
 570                 if (m->pindex <= index)
 571                         return (m);
 572                 else
 573                         return (NULL);
 574         }
 575         tos = 0;
 576         for (;;) {
 577                 /*
 578                  * If the keys differ before the current bisection node,
 579                  * then the search key might rollback to the earliest
 580                  * available bisection node or to the largest key
 581                  * in the current node (if the owner is smaller than the
 582                  * search key).
 583                  */
 584                 if (vm_radix_keybarr(rnode, index)) {
 585                         if (index > rnode->rn_owner) {
 586                                 index = rnode->rn_owner + VM_RADIX_COUNT *
 587                                     VM_RADIX_UNITLEVEL(rnode->rn_clev);
 588                         } else {
 589 ascend:
 590                                 KASSERT(++loops < 1000,
 591                                     ("vm_radix_lookup_le: too many loops"));
 592
 593                                 /*
 594                                  * Pop nodes from the stack until either the
 595                                  * stack is empty or a node that could have a
 596                                  * matching descendant is found.
 597                                  */
 598                                 do {
 599                                         if (tos == 0)
 600                                                 return (NULL);
 601                                         rnode = stack[--tos];
 602                                 } while (vm_radix_slot(index,
 603                                     rnode->rn_clev) == 0);
 604
 605                                 /*
 606                                  * The following computation cannot overflow
 607                                  * because index's slot at the current level
 608                                  * is greater than 0.
 609                                  */
 610                                 index = vm_radix_trimkey(index,
 611                                     rnode->rn_clev);
 612                         }
 613                         index--;
 614                         KASSERT(!vm_radix_keybarr(rnode, index),
 615                             ("vm_radix_lookup_le: keybarr failed"));
 616                 }
 617                 slot = vm_radix_slot(index, rnode->rn_clev);
 618                 child = rnode->rn_child[slot];
 619                 if (vm_radix_isleaf(child)) {
 620                         m = vm_radix_topage(child);
 621                         if (m->pindex <= index)
 622                                 return (m);
 623                 } else if (child != NULL)
 624                         goto descend;
 625
 626                 /*
 627                  * Look for an available edge or page within the current
 628                  * bisection node.
 629                  */
 630                 if (slot > 0) {
 631                         inc = VM_RADIX_UNITLEVEL(rnode->rn_clev);
 632                         index |= inc - 1;
 633                         do {
 634                                 index -= inc;
 635                                 slot--;
 636                                 child = rnode->rn_child[slot];
 637                                 if (vm_radix_isleaf(child)) {
 638                                         m = vm_radix_topage(child);
 639                                         if (m->pindex <= index)
 640                                                 return (m);
 641                                 } else if (child != NULL)
 642                                         goto descend;
 643                         } while (slot > 0);
 644                 }
 645                 KASSERT(child == NULL || vm_radix_isleaf(child),
 646                     ("vm_radix_lookup_le: child is radix node"));
 647
 648                 /*
 649                  * If a page or edge smaller than the search slot is not found
 650                  * in the current node, ascend to the next higher-level node.
 651                  */
 652                 goto ascend;
 653 descend:
 654                 KASSERT(rnode->rn_clev > 0,
 655                     ("vm_radix_lookup_le: pushing leaf's parent"));
 656                 KASSERT(tos < VM_RADIX_LIMIT,
 657                     ("vm_radix_lookup_le: stack overflow"));
 658                 stack[tos++] = rnode;
 659                 rnode = child;
 660         }
 661 }
 662
 663 /*
 664  * Remove the specified index from the trie, and return the value stored at
 665  * that index.  If the index is not present, return NULL.
 666  */
 667 vm_page_t
 668 vm_radix_remove(struct vm_radix *rtree, vm_pindex_t index)
 669 {
 670         struct vm_radix_node *rnode, *parent;
 671         vm_page_t m;
 672         int i, slot;
 673
 674         rnode = vm_radix_getroot(rtree);
 675         if (vm_radix_isleaf(rnode)) {
 676                 m = vm_radix_topage(rnode);
 677                 if (m->pindex != index)
 678                         return (NULL);
 679                 vm_radix_setroot(rtree, NULL);
 680                 return (m);
 681         }
 682         parent = NULL;
 683         for (;;) {
 684                 if (rnode == NULL)
 685                         return (NULL);
 686                 slot = vm_radix_slot(index, rnode->rn_clev);
 687                 if (vm_radix_isleaf(rnode->rn_child[slot])) {
 688                         m = vm_radix_topage(rnode->rn_child[slot]);
 689                         if (m->pindex != index)
 690                                 return (NULL);
 691                         rnode->rn_child[slot] = NULL;
 692                         rnode->rn_count--;
 693                         if (rnode->rn_count > 1)
 694                                 return (m);
 695                         for (i = 0; i < VM_RADIX_COUNT; i++)
 696                                 if (rnode->rn_child[i] != NULL)
 697                                         break;
 698                         KASSERT(i != VM_RADIX_COUNT,
 699                             ("%s: invalid node configuration", __func__));
 700                         if (parent == NULL)
 701                                 vm_radix_setroot(rtree, rnode->rn_child[i]);
 702                         else {
 703                                 slot = vm_radix_slot(index, parent->rn_clev);
 704                                 KASSERT(parent->rn_child[slot] == rnode,
 705                                     ("%s: invalid child value", __func__));
 706                                 parent->rn_child[slot] = rnode->rn_child[i];
 707                         }
 708                         rnode->rn_count--;
 709                         rnode->rn_child[i] = NULL;
 710                         vm_radix_node_put(rnode);
 711                         return (m);
 712                 }
 713                 parent = rnode;
 714                 rnode = rnode->rn_child[slot];
 715         }
 716 }
 717
 718 /*
 719  * Remove and free all the nodes from the radix tree.
 720  * This function is recursive but there is a tight control on it as the
 721  * maximum depth of the tree is fixed.
 722  */
 723 void
 724 vm_radix_reclaim_allnodes(struct vm_radix *rtree)
 725 {
 726         struct vm_radix_node *root;
 727
 728         root = vm_radix_getroot(rtree);
 729         if (root == NULL)
 730                 return;
 731         vm_radix_setroot(rtree, NULL);
 732         if (!vm_radix_isleaf(root))
 733                 vm_radix_reclaim_allnodes_int(root);
 734 }
 735
 736 /*
 737  * Replace an existing page in the trie with another one.
 738  * Panics if there is not an old page in the trie at the new page's index.
 739  */
 740 vm_page_t
 741 vm_radix_replace(struct vm_radix *rtree, vm_page_t newpage)
 742 {
 743         struct vm_radix_node *rnode;
 744         vm_page_t m;
 745         vm_pindex_t index;
 746         int slot;
 747
 748         index = newpage->pindex;
 749         rnode = vm_radix_getroot(rtree);
 750         if (rnode == NULL)
 751                 panic("%s: replacing page on an empty trie", __func__);
 752         if (vm_radix_isleaf(rnode)) {
 753                 m = vm_radix_topage(rnode);
 754                 if (m->pindex != index)
 755                         panic("%s: original replacing root key not found",
 756                             __func__);
 757                 rtree->rt_root = (uintptr_t)newpage | VM_RADIX_ISLEAF;
 758                 return (m);
 759         }
 760         for (;;) {
 761                 slot = vm_radix_slot(index, rnode->rn_clev);
 762                 if (vm_radix_isleaf(rnode->rn_child[slot])) {
 763                         m = vm_radix_topage(rnode->rn_child[slot]);
 764                         if (m->pindex == index) {
 765                                 rnode->rn_child[slot] =
 766                                     (void *)((uintptr_t)newpage |
 767                                     VM_RADIX_ISLEAF);
 768                                 return (m);
 769                         } else
 770                                 break;
 771                 } else if (rnode->rn_child[slot] == NULL ||
 772                     vm_radix_keybarr(rnode->rn_child[slot], index))
 773                         break;
 774                 rnode = rnode->rn_child[slot];
 775         }
 776         panic("%s: original replacing page not found", __func__);
 777 }
 778
 779 void
 780 vm_radix_wait(void)
 781 {
 782         uma_zwait(vm_radix_node_zone);
 783 }
 784
 785 #ifdef DDB
 786 /*
 787  * Show details about the given radix node.
 788  */
 789 DB_SHOW_COMMAND(radixnode, db_show_radixnode)
 790 {
 791         struct vm_radix_node *rnode;
 792         int i;
 793
 794         if (!have_addr)
 795                 return;
 796         rnode = (struct vm_radix_node *)addr;
 797         db_printf("radixnode %p, owner %jx, children count %u, level %u:\n",
 798             (void *)rnode, (uintmax_t)rnode->rn_owner, rnode->rn_count,
 799             rnode->rn_clev);
 800         for (i = 0; i < VM_RADIX_COUNT; i++)
 801                 if (rnode->rn_child[i] != NULL)
 802                         db_printf("slot: %d, val: %p, page: %p, clev: %d\n",
 803                             i, (void *)rnode->rn_child[i],
 804                             vm_radix_isleaf(rnode->rn_child[i]) ?
 805                             vm_radix_topage(rnode->rn_child[i]) : NULL,
 806                             rnode->rn_clev);
 807 }
 808 #endif /* DDB */