The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_blist.c

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    1 /*-
    2  * Copyright (c) 1998 Matthew Dillon.  All Rights Reserved.
    3  * Redistribution and use in source and binary forms, with or without
    4  * modification, are permitted provided that the following conditions
    5  * are met:
    6  * 1. Redistributions of source code must retain the above copyright
    7  *    notice, this list of conditions and the following disclaimer.
    8  * 2. Redistributions in binary form must reproduce the above copyright
    9  *    notice, this list of conditions and the following disclaimer in the
   10  *    documentation and/or other materials provided with the distribution.
   11  * 4. Neither the name of the University nor the names of its contributors
   12  *    may be used to endorse or promote products derived from this software
   13  *    without specific prior written permission.
   14  *
   15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
   16  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   17  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
   19  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
   21  * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
   22  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
   23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   24  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   25  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   26  */
   27 /*
   28  * BLIST.C -    Bitmap allocator/deallocator, using a radix tree with hinting
   29  *
   30  *      This module implements a general bitmap allocator/deallocator.  The
   31  *      allocator eats around 2 bits per 'block'.  The module does not 
   32  *      try to interpret the meaning of a 'block' other than to return 
   33  *      SWAPBLK_NONE on an allocation failure.
   34  *
   35  *      A radix tree is used to maintain the bitmap.  Two radix constants are
   36  *      involved:  One for the bitmaps contained in the leaf nodes (typically
   37  *      32), and one for the meta nodes (typically 16).  Both meta and leaf
   38  *      nodes have a hint field.  This field gives us a hint as to the largest
   39  *      free contiguous range of blocks under the node.  It may contain a
   40  *      value that is too high, but will never contain a value that is too 
   41  *      low.  When the radix tree is searched, allocation failures in subtrees
   42  *      update the hint. 
   43  *
   44  *      The radix tree also implements two collapsed states for meta nodes:
   45  *      the ALL-ALLOCATED state and the ALL-FREE state.  If a meta node is
   46  *      in either of these two states, all information contained underneath
   47  *      the node is considered stale.  These states are used to optimize
   48  *      allocation and freeing operations.
   49  *
   50  *      The hinting greatly increases code efficiency for allocations while
   51  *      the general radix structure optimizes both allocations and frees.  The
   52  *      radix tree should be able to operate well no matter how much 
   53  *      fragmentation there is and no matter how large a bitmap is used.
   54  *
   55  *      The blist code wires all necessary memory at creation time.  Neither
   56  *      allocations nor frees require interaction with the memory subsystem.
   57  *      The non-blocking features of the blist code are used in the swap code
   58  *      (vm/swap_pager.c).
   59  *
   60  *      LAYOUT: The radix tree is laid out recursively using a
   61  *      linear array.  Each meta node is immediately followed (laid out
   62  *      sequentially in memory) by BLIST_META_RADIX lower level nodes.  This
   63  *      is a recursive structure but one that can be easily scanned through
   64  *      a very simple 'skip' calculation.  In order to support large radixes, 
   65  *      portions of the tree may reside outside our memory allocation.  We 
   66  *      handle this with an early-termination optimization (when bighint is 
   67  *      set to -1) on the scan.  The memory allocation is only large enough 
   68  *      to cover the number of blocks requested at creation time even if it
   69  *      must be encompassed in larger root-node radix.
   70  *
   71  *      NOTE: the allocator cannot currently allocate more than 
   72  *      BLIST_BMAP_RADIX blocks per call.  It will panic with 'allocation too 
   73  *      large' if you try.  This is an area that could use improvement.  The 
   74  *      radix is large enough that this restriction does not effect the swap 
   75  *      system, though.  Currently only the allocation code is effected by
   76  *      this algorithmic unfeature.  The freeing code can handle arbitrary
   77  *      ranges.
   78  *
   79  *      This code can be compiled stand-alone for debugging.
   80  */
   81 
   82 #include <sys/cdefs.h>
   83 __FBSDID("$FreeBSD: stable/10/sys/kern/subr_blist.c 321459 2017-07-25 04:13:43Z alc $");
   84 
   85 #ifdef _KERNEL
   86 
   87 #include <sys/param.h>
   88 #include <sys/systm.h>
   89 #include <sys/lock.h>
   90 #include <sys/kernel.h>
   91 #include <sys/blist.h>
   92 #include <sys/malloc.h>
   93 #include <sys/proc.h>
   94 #include <sys/mutex.h> 
   95 
   96 #else
   97 
   98 #ifndef BLIST_NO_DEBUG
   99 #define BLIST_DEBUG
  100 #endif
  101 
  102 #include <sys/types.h>
  103 #include <sys/malloc.h>
  104 #include <stdio.h>
  105 #include <string.h>
  106 #include <stdlib.h>
  107 #include <stdarg.h>
  108 #include <stdbool.h>
  109 
  110 #define bitcount64(x)   __bitcount64((uint64_t)(x))
  111 #define malloc(a,b,c)   calloc(a, 1)
  112 #define free(a,b)       free(a)
  113 
  114 #include <sys/blist.h>
  115 
  116 void panic(const char *ctl, ...);
  117 
  118 #endif
  119 
  120 /*
  121  * static support functions
  122  */
  123 
  124 static daddr_t  blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int count,
  125                     daddr_t cursor);
  126 static daddr_t  blst_meta_alloc(blmeta_t *scan, daddr_t blk, daddr_t count,
  127                     daddr_t radix, daddr_t skip, daddr_t cursor);
  128 static void blst_leaf_free(blmeta_t *scan, daddr_t relblk, int count);
  129 static void blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count, 
  130                     daddr_t radix, daddr_t skip, daddr_t blk);
  131 static void blst_copy(blmeta_t *scan, daddr_t blk, daddr_t radix, 
  132                                 daddr_t skip, blist_t dest, daddr_t count);
  133 static daddr_t blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count);
  134 static daddr_t blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count,
  135                     daddr_t radix, daddr_t skip, daddr_t blk);
  136 static daddr_t  blst_radix_init(blmeta_t *scan, daddr_t radix, daddr_t skip,
  137                     daddr_t count);
  138 #ifndef _KERNEL
  139 static void     blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix,
  140                     daddr_t skip, int tab);
  141 #endif
  142 
  143 #ifdef _KERNEL
  144 static MALLOC_DEFINE(M_SWAP, "SWAP", "Swap space");
  145 #endif
  146 
  147 /*
  148  * blist_create() - create a blist capable of handling up to the specified
  149  *                  number of blocks
  150  *
  151  *      blocks - must be greater than 0
  152  *      flags  - malloc flags
  153  *
  154  *      The smallest blist consists of a single leaf node capable of 
  155  *      managing BLIST_BMAP_RADIX blocks.
  156  */
  157 
  158 blist_t 
  159 blist_create(daddr_t blocks, int flags)
  160 {
  161         blist_t bl;
  162         daddr_t nodes, radix, skip;
  163 
  164         /*
  165          * Calculate radix and skip field used for scanning.
  166          */
  167         radix = BLIST_BMAP_RADIX;
  168         skip = 0;
  169         while (radix < blocks) {
  170                 radix *= BLIST_META_RADIX;
  171                 skip = (skip + 1) * BLIST_META_RADIX;
  172         }
  173         nodes = 1 + blst_radix_init(NULL, radix, skip, blocks);
  174 
  175         bl = malloc(sizeof(struct blist), M_SWAP, flags);
  176         if (bl == NULL)
  177                 return (NULL);
  178 
  179         bl->bl_blocks = blocks;
  180         bl->bl_radix = radix;
  181         bl->bl_skip = skip;
  182         bl->bl_cursor = 0;
  183         bl->bl_root = malloc(nodes * sizeof(blmeta_t), M_SWAP, flags);
  184         if (bl->bl_root == NULL) {
  185                 free(bl, M_SWAP);
  186                 return (NULL);
  187         }
  188         blst_radix_init(bl->bl_root, radix, skip, blocks);
  189 
  190 #if defined(BLIST_DEBUG)
  191         printf(
  192                 "BLIST representing %lld blocks (%lld MB of swap)"
  193                 ", requiring %lldK of ram\n",
  194                 (long long)bl->bl_blocks,
  195                 (long long)bl->bl_blocks * 4 / 1024,
  196                 (long long)(nodes * sizeof(blmeta_t) + 1023) / 1024
  197         );
  198         printf("BLIST raw radix tree contains %lld records\n",
  199             (long long)nodes);
  200 #endif
  201 
  202         return (bl);
  203 }
  204 
  205 void 
  206 blist_destroy(blist_t bl)
  207 {
  208         free(bl->bl_root, M_SWAP);
  209         free(bl, M_SWAP);
  210 }
  211 
  212 /*
  213  * blist_alloc() -   reserve space in the block bitmap.  Return the base
  214  *                   of a contiguous region or SWAPBLK_NONE if space could
  215  *                   not be allocated.
  216  */
  217 
  218 daddr_t 
  219 blist_alloc(blist_t bl, daddr_t count)
  220 {
  221         daddr_t blk;
  222 
  223         /*
  224          * This loop iterates at most twice.  An allocation failure in the
  225          * first iteration leads to a second iteration only if the cursor was
  226          * non-zero.  When the cursor is zero, an allocation failure will
  227          * reduce the hint, stopping further iterations.
  228          */
  229         while (count <= bl->bl_root->bm_bighint) {
  230                 if (bl->bl_radix == BLIST_BMAP_RADIX)
  231                         blk = blst_leaf_alloc(bl->bl_root, 0, count,
  232                             bl->bl_cursor);
  233                 else
  234                         blk = blst_meta_alloc(bl->bl_root, 0, count,
  235                             bl->bl_radix, bl->bl_skip, bl->bl_cursor);
  236                 if (blk != SWAPBLK_NONE) {
  237                         bl->bl_cursor = blk + count;
  238                         return (blk);
  239                 } else if (bl->bl_cursor != 0)
  240                         bl->bl_cursor = 0;
  241         }
  242         return (SWAPBLK_NONE);
  243 }
  244 
  245 /*
  246  * blist_avail() -      return the number of free blocks.
  247  */
  248 
  249 daddr_t
  250 blist_avail(blist_t bl)
  251 {
  252 
  253         if (bl->bl_radix == BLIST_BMAP_RADIX)
  254                 return (bitcount64(bl->bl_root->u.bmu_bitmap));
  255         else
  256                 return (bl->bl_root->u.bmu_avail);
  257 }
  258 
  259 /*
  260  * blist_free() -       free up space in the block bitmap.  Return the base
  261  *                      of a contiguous region.  Panic if an inconsistancy is
  262  *                      found.
  263  */
  264 
  265 void 
  266 blist_free(blist_t bl, daddr_t blkno, daddr_t count)
  267 {
  268         if (bl) {
  269                 if (bl->bl_radix == BLIST_BMAP_RADIX)
  270                         blst_leaf_free(bl->bl_root, blkno, count);
  271                 else
  272                         blst_meta_free(bl->bl_root, blkno, count,
  273                             bl->bl_radix, bl->bl_skip, 0);
  274         }
  275 }
  276 
  277 /*
  278  * blist_fill() -       mark a region in the block bitmap as off-limits
  279  *                      to the allocator (i.e. allocate it), ignoring any
  280  *                      existing allocations.  Return the number of blocks
  281  *                      actually filled that were free before the call.
  282  */
  283 
  284 daddr_t
  285 blist_fill(blist_t bl, daddr_t blkno, daddr_t count)
  286 {
  287         daddr_t filled;
  288 
  289         if (bl) {
  290                 if (bl->bl_radix == BLIST_BMAP_RADIX)
  291                         filled = blst_leaf_fill(bl->bl_root, blkno, count);
  292                 else
  293                         filled = blst_meta_fill(bl->bl_root, blkno, count,
  294                             bl->bl_radix, bl->bl_skip, 0);
  295                 return (filled);
  296         }
  297         return (0);
  298 }
  299 
  300 /*
  301  * blist_resize() -     resize an existing radix tree to handle the
  302  *                      specified number of blocks.  This will reallocate
  303  *                      the tree and transfer the previous bitmap to the new
  304  *                      one.  When extending the tree you can specify whether
  305  *                      the new blocks are to left allocated or freed.
  306  */
  307 
  308 void
  309 blist_resize(blist_t *pbl, daddr_t count, int freenew, int flags)
  310 {
  311     blist_t newbl = blist_create(count, flags);
  312     blist_t save = *pbl;
  313 
  314     *pbl = newbl;
  315     if (count > save->bl_blocks)
  316             count = save->bl_blocks;
  317     blst_copy(save->bl_root, 0, save->bl_radix, save->bl_skip, newbl, count);
  318 
  319     /*
  320      * If resizing upwards, should we free the new space or not?
  321      */
  322     if (freenew && count < newbl->bl_blocks) {
  323             blist_free(newbl, count, newbl->bl_blocks - count);
  324     }
  325     blist_destroy(save);
  326 }
  327 
  328 #ifdef BLIST_DEBUG
  329 
  330 /*
  331  * blist_print()    - dump radix tree
  332  */
  333 
  334 void
  335 blist_print(blist_t bl)
  336 {
  337         printf("BLIST {\n");
  338         blst_radix_print(bl->bl_root, 0, bl->bl_radix, bl->bl_skip, 4);
  339         printf("}\n");
  340 }
  341 
  342 #endif
  343 
  344 /************************************************************************
  345  *                        ALLOCATION SUPPORT FUNCTIONS                  *
  346  ************************************************************************
  347  *
  348  *      These support functions do all the actual work.  They may seem 
  349  *      rather longish, but that's because I've commented them up.  The
  350  *      actual code is straight forward.
  351  *
  352  */
  353 
  354 /*
  355  * blist_leaf_alloc() - allocate at a leaf in the radix tree (a bitmap).
  356  *
  357  *      This is the core of the allocator and is optimized for the
  358  *      BLIST_BMAP_RADIX block allocation case.  Otherwise, execution
  359  *      time is proportional to log2(count) + log2(BLIST_BMAP_RADIX).
  360  */
  361 
  362 static daddr_t
  363 blst_leaf_alloc(blmeta_t *scan, daddr_t blk, int count, daddr_t cursor)
  364 {
  365         u_daddr_t mask;
  366         int count1, hi, lo, mid, num_shifts, range1, range_ext;
  367 
  368         if (count == BLIST_BMAP_RADIX) {
  369                 /*
  370                  * Optimize allocation of BLIST_BMAP_RADIX bits.  If this wasn't
  371                  * a special case, then forming the final value of 'mask' below
  372                  * would require special handling to avoid an invalid left shift
  373                  * when count equals the number of bits in mask.
  374                  */
  375                 if (~scan->u.bmu_bitmap != 0) {
  376                         scan->bm_bighint = BLIST_BMAP_RADIX - 1;
  377                         return (SWAPBLK_NONE);
  378                 }
  379                 if (cursor != blk)
  380                         return (SWAPBLK_NONE);
  381                 scan->u.bmu_bitmap = 0;
  382                 scan->bm_bighint = 0;
  383                 return (blk);
  384         }
  385         range1 = 0;
  386         count1 = count - 1;
  387         num_shifts = fls(count1);
  388         mask = scan->u.bmu_bitmap;
  389         while (mask != 0 && num_shifts > 0) {
  390                 /*
  391                  * If bit i is set in mask, then bits in [i, i+range1] are set
  392                  * in scan->u.bmu_bitmap.  The value of range1 is equal to
  393                  * count1 >> num_shifts.  Grow range and reduce num_shifts to 0,
  394                  * while preserving these invariants.  The updates to mask leave
  395                  * fewer bits set, but each bit that remains set represents a
  396                  * longer string of consecutive bits set in scan->u.bmu_bitmap.
  397                  */
  398                 num_shifts--;
  399                 range_ext = range1 + ((count1 >> num_shifts) & 1);
  400                 mask &= mask >> range_ext;
  401                 range1 += range_ext;
  402         }
  403         if (mask == 0) {
  404                 /*
  405                  * Update bighint.  There is no allocation bigger than range1
  406                  * available in this leaf.
  407                  */
  408                 scan->bm_bighint = range1;
  409                 return (SWAPBLK_NONE);
  410         }
  411 
  412         /*
  413          * Discard any candidates that appear before the cursor.
  414          */
  415         lo = cursor - blk;
  416         mask &= ~(u_daddr_t)0 << lo;
  417 
  418         if (mask == 0)
  419                 return (SWAPBLK_NONE);
  420 
  421         /*
  422          * The least significant set bit in mask marks the start of the first
  423          * available range of sufficient size.  Clear all the bits but that one,
  424          * and then perform a binary search to find its position.
  425          */
  426         mask &= -mask;
  427         hi = BLIST_BMAP_RADIX - count1;
  428         while (lo + 1 < hi) {
  429                 mid = (lo + hi) >> 1;
  430                 if ((mask >> mid) != 0)
  431                         lo = mid;
  432                 else
  433                         hi = mid;
  434         }
  435 
  436         /*
  437          * Set in mask exactly the bits being allocated, and clear them from
  438          * the set of available bits.
  439          */
  440         mask = (mask << count) - mask;
  441         scan->u.bmu_bitmap &= ~mask;
  442         return (blk + lo);
  443 }
  444 
  445 /*
  446  * blist_meta_alloc() - allocate at a meta in the radix tree.
  447  *
  448  *      Attempt to allocate at a meta node.  If we can't, we update
  449  *      bighint and return a failure.  Updating bighint optimize future
  450  *      calls that hit this node.  We have to check for our collapse cases
  451  *      and we have a few optimizations strewn in as well.
  452  */
  453 
  454 static daddr_t
  455 blst_meta_alloc(blmeta_t *scan, daddr_t blk, daddr_t count, daddr_t radix,
  456     daddr_t skip, daddr_t cursor)
  457 {
  458         daddr_t i, next_skip, r;
  459         int child;
  460         bool scan_from_start;
  461 
  462         if (scan->u.bmu_avail < count) {
  463                 /*
  464                  * The meta node's hint must be too large if the allocation
  465                  * exceeds the number of free blocks.  Reduce the hint, and
  466                  * return failure.
  467                  */
  468                 scan->bm_bighint = scan->u.bmu_avail;
  469                 return (SWAPBLK_NONE);
  470         }
  471         next_skip = skip / BLIST_META_RADIX;
  472 
  473         /*
  474          * An ALL-FREE meta node requires special handling before allocating
  475          * any of its blocks.
  476          */
  477         if (scan->u.bmu_avail == radix) {
  478                 radix /= BLIST_META_RADIX;
  479 
  480                 /*
  481                  * Reinitialize each of the meta node's children.  An ALL-FREE
  482                  * meta node cannot have a terminator in any subtree.
  483                  */
  484                 for (i = 1; i <= skip; i += next_skip) {
  485                         if (next_skip == 1)
  486                                 scan[i].u.bmu_bitmap = (u_daddr_t)-1;
  487                         else
  488                                 scan[i].u.bmu_avail = radix;
  489                         scan[i].bm_bighint = radix;
  490                 }
  491         } else {
  492                 radix /= BLIST_META_RADIX;
  493         }
  494 
  495         if (count > radix) {
  496                 /*
  497                  * The allocation exceeds the number of blocks that are
  498                  * managed by a subtree of this meta node.
  499                  */
  500                 panic("allocation too large");
  501         }
  502         scan_from_start = cursor == blk;
  503         child = (cursor - blk) / radix;
  504         blk += child * radix;
  505         for (i = 1 + child * next_skip; i <= skip; i += next_skip) {
  506                 if (count <= scan[i].bm_bighint) {
  507                         /*
  508                          * The allocation might fit in the i'th subtree.
  509                          */
  510                         if (next_skip == 1) {
  511                                 r = blst_leaf_alloc(&scan[i], blk, count,
  512                                     cursor > blk ? cursor : blk);
  513                         } else {
  514                                 r = blst_meta_alloc(&scan[i], blk, count,
  515                                     radix, next_skip - 1, cursor > blk ?
  516                                     cursor : blk);
  517                         }
  518                         if (r != SWAPBLK_NONE) {
  519                                 scan->u.bmu_avail -= count;
  520                                 return (r);
  521                         }
  522                 } else if (scan[i].bm_bighint == (daddr_t)-1) {
  523                         /*
  524                          * Terminator
  525                          */
  526                         break;
  527                 }
  528                 blk += radix;
  529         }
  530 
  531         /*
  532          * We couldn't allocate count in this subtree, update bighint.
  533          */
  534         if (scan_from_start && scan->bm_bighint >= count)
  535                 scan->bm_bighint = count - 1;
  536 
  537         return (SWAPBLK_NONE);
  538 }
  539 
  540 /*
  541  * BLST_LEAF_FREE() -   free allocated block from leaf bitmap
  542  *
  543  */
  544 
  545 static void
  546 blst_leaf_free(
  547         blmeta_t *scan,
  548         daddr_t blk,
  549         int count
  550 ) {
  551         /*
  552          * free some data in this bitmap
  553          *
  554          * e.g.
  555          *      0000111111111110000
  556          *          \_________/\__/
  557          *              v        n
  558          */
  559         int n = blk & (BLIST_BMAP_RADIX - 1);
  560         u_daddr_t mask;
  561 
  562         mask = ((u_daddr_t)-1 << n) &
  563             ((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - count - n));
  564 
  565         if (scan->u.bmu_bitmap & mask)
  566                 panic("blst_radix_free: freeing free block");
  567         scan->u.bmu_bitmap |= mask;
  568 
  569         /*
  570          * We could probably do a better job here.  We are required to make
  571          * bighint at least as large as the biggest contiguous block of 
  572          * data.  If we just shoehorn it, a little extra overhead will
  573          * be incured on the next allocation (but only that one typically).
  574          */
  575         scan->bm_bighint = BLIST_BMAP_RADIX;
  576 }
  577 
  578 /*
  579  * BLST_META_FREE() - free allocated blocks from radix tree meta info
  580  *
  581  *      This support routine frees a range of blocks from the bitmap.
  582  *      The range must be entirely enclosed by this radix node.  If a
  583  *      meta node, we break the range down recursively to free blocks
  584  *      in subnodes (which means that this code can free an arbitrary
  585  *      range whereas the allocation code cannot allocate an arbitrary
  586  *      range).
  587  */
  588 
  589 static void 
  590 blst_meta_free(blmeta_t *scan, daddr_t freeBlk, daddr_t count, daddr_t radix,
  591     daddr_t skip, daddr_t blk)
  592 {
  593         daddr_t i, next_skip, v;
  594         int child;
  595 
  596 #if 0
  597         printf("free (%llx,%lld) FROM (%llx,%lld)\n",
  598             (long long)freeBlk, (long long)count,
  599             (long long)blk, (long long)radix
  600         );
  601 #endif
  602         next_skip = skip / BLIST_META_RADIX;
  603 
  604         if (scan->u.bmu_avail == 0) {
  605                 /*
  606                  * ALL-ALLOCATED special case, with possible
  607                  * shortcut to ALL-FREE special case.
  608                  */
  609                 scan->u.bmu_avail = count;
  610                 scan->bm_bighint = count;
  611 
  612                 if (count != radix)  {
  613                         for (i = 1; i <= skip; i += next_skip) {
  614                                 if (scan[i].bm_bighint == (daddr_t)-1)
  615                                         break;
  616                                 scan[i].bm_bighint = 0;
  617                                 if (next_skip == 1) {
  618                                         scan[i].u.bmu_bitmap = 0;
  619                                 } else {
  620                                         scan[i].u.bmu_avail = 0;
  621                                 }
  622                         }
  623                         /* fall through */
  624                 }
  625         } else {
  626                 scan->u.bmu_avail += count;
  627                 /* scan->bm_bighint = radix; */
  628         }
  629 
  630         /*
  631          * ALL-FREE special case.
  632          */
  633 
  634         if (scan->u.bmu_avail == radix)
  635                 return;
  636         if (scan->u.bmu_avail > radix)
  637                 panic("blst_meta_free: freeing already free blocks (%lld) %lld/%lld",
  638                     (long long)count, (long long)scan->u.bmu_avail,
  639                     (long long)radix);
  640 
  641         /*
  642          * Break the free down into its components
  643          */
  644 
  645         radix /= BLIST_META_RADIX;
  646 
  647         child = (freeBlk - blk) / radix;
  648         blk += child * radix;
  649         i = 1 + child * next_skip;
  650         while (i <= skip && blk < freeBlk + count) {
  651                 v = blk + radix - freeBlk;
  652                 if (v > count)
  653                         v = count;
  654 
  655                 if (scan->bm_bighint == (daddr_t)-1)
  656                         panic("blst_meta_free: freeing unexpected range");
  657 
  658                 if (next_skip == 1) {
  659                         blst_leaf_free(&scan[i], freeBlk, v);
  660                 } else {
  661                         blst_meta_free(&scan[i], freeBlk, v, radix, next_skip - 1, blk);
  662                 }
  663                 if (scan->bm_bighint < scan[i].bm_bighint)
  664                     scan->bm_bighint = scan[i].bm_bighint;
  665                 count -= v;
  666                 freeBlk += v;
  667                 blk += radix;
  668                 i += next_skip;
  669         }
  670 }
  671 
  672 /*
  673  * BLIST_RADIX_COPY() - copy one radix tree to another
  674  *
  675  *      Locates free space in the source tree and frees it in the destination
  676  *      tree.  The space may not already be free in the destination.
  677  */
  678 
  679 static void blst_copy(
  680         blmeta_t *scan, 
  681         daddr_t blk,
  682         daddr_t radix, 
  683         daddr_t skip, 
  684         blist_t dest,
  685         daddr_t count
  686 ) {
  687         daddr_t i, next_skip;
  688 
  689         /*
  690          * Leaf node
  691          */
  692 
  693         if (radix == BLIST_BMAP_RADIX) {
  694                 u_daddr_t v = scan->u.bmu_bitmap;
  695 
  696                 if (v == (u_daddr_t)-1) {
  697                         blist_free(dest, blk, count);
  698                 } else if (v != 0) {
  699                         int i;
  700 
  701                         for (i = 0; i < BLIST_BMAP_RADIX && i < count; ++i) {
  702                                 if (v & ((u_daddr_t)1 << i))
  703                                         blist_free(dest, blk + i, 1);
  704                         }
  705                 }
  706                 return;
  707         }
  708 
  709         /*
  710          * Meta node
  711          */
  712 
  713         if (scan->u.bmu_avail == 0) {
  714                 /*
  715                  * Source all allocated, leave dest allocated
  716                  */
  717                 return;
  718         } 
  719         if (scan->u.bmu_avail == radix) {
  720                 /*
  721                  * Source all free, free entire dest
  722                  */
  723                 if (count < radix)
  724                         blist_free(dest, blk, count);
  725                 else
  726                         blist_free(dest, blk, radix);
  727                 return;
  728         }
  729 
  730 
  731         radix /= BLIST_META_RADIX;
  732         next_skip = skip / BLIST_META_RADIX;
  733 
  734         for (i = 1; count && i <= skip; i += next_skip) {
  735                 if (scan[i].bm_bighint == (daddr_t)-1)
  736                         break;
  737 
  738                 if (count >= radix) {
  739                         blst_copy(
  740                             &scan[i],
  741                             blk,
  742                             radix,
  743                             next_skip - 1,
  744                             dest,
  745                             radix
  746                         );
  747                         count -= radix;
  748                 } else {
  749                         if (count) {
  750                                 blst_copy(
  751                                     &scan[i],
  752                                     blk,
  753                                     radix,
  754                                     next_skip - 1,
  755                                     dest,
  756                                     count
  757                                 );
  758                         }
  759                         count = 0;
  760                 }
  761                 blk += radix;
  762         }
  763 }
  764 
  765 /*
  766  * BLST_LEAF_FILL() -   allocate specific blocks in leaf bitmap
  767  *
  768  *      This routine allocates all blocks in the specified range
  769  *      regardless of any existing allocations in that range.  Returns
  770  *      the number of blocks allocated by the call.
  771  */
  772 
  773 static daddr_t
  774 blst_leaf_fill(blmeta_t *scan, daddr_t blk, int count)
  775 {
  776         int n = blk & (BLIST_BMAP_RADIX - 1);
  777         daddr_t nblks;
  778         u_daddr_t mask;
  779 
  780         mask = ((u_daddr_t)-1 << n) &
  781             ((u_daddr_t)-1 >> (BLIST_BMAP_RADIX - count - n));
  782 
  783         /* Count the number of blocks that we are allocating. */
  784         nblks = bitcount64(scan->u.bmu_bitmap & mask);
  785 
  786         scan->u.bmu_bitmap &= ~mask;
  787         return (nblks);
  788 }
  789 
  790 /*
  791  * BLIST_META_FILL() -  allocate specific blocks at a meta node
  792  *
  793  *      This routine allocates the specified range of blocks,
  794  *      regardless of any existing allocations in the range.  The
  795  *      range must be within the extent of this node.  Returns the
  796  *      number of blocks allocated by the call.
  797  */
  798 static daddr_t
  799 blst_meta_fill(blmeta_t *scan, daddr_t allocBlk, daddr_t count, daddr_t radix,
  800     daddr_t skip, daddr_t blk)
  801 {
  802         daddr_t i, nblks, next_skip, v;
  803         int child;
  804 
  805         if (count > radix) {
  806                 /*
  807                  * The allocation exceeds the number of blocks that are
  808                  * managed by this meta node.
  809                  */
  810                 panic("allocation too large");
  811         }
  812         if (count == radix || scan->u.bmu_avail == 0)  {
  813                 /*
  814                  * ALL-ALLOCATED special case
  815                  */
  816                 nblks = scan->u.bmu_avail;
  817                 scan->u.bmu_avail = 0;
  818                 scan->bm_bighint = 0;
  819                 return nblks;
  820         }
  821         next_skip = skip / BLIST_META_RADIX;
  822 
  823         /*
  824          * An ALL-FREE meta node requires special handling before allocating
  825          * any of its blocks.
  826          */
  827         if (scan->u.bmu_avail == radix) {
  828                 radix /= BLIST_META_RADIX;
  829 
  830                 /*
  831                  * Reinitialize each of the meta node's children.  An ALL-FREE
  832                  * meta node cannot have a terminator in any subtree.
  833                  */
  834                 for (i = 1; i <= skip; i += next_skip) {
  835                         if (next_skip == 1) {
  836                                 scan[i].u.bmu_bitmap = (u_daddr_t)-1;
  837                                 scan[i].bm_bighint = BLIST_BMAP_RADIX;
  838                         } else {
  839                                 scan[i].bm_bighint = radix;
  840                                 scan[i].u.bmu_avail = radix;
  841                         }
  842                 }
  843         } else {
  844                 radix /= BLIST_META_RADIX;
  845         }
  846 
  847         nblks = 0;
  848         child = (allocBlk - blk) / radix;
  849         blk += child * radix;
  850         i = 1 + child * next_skip;
  851         while (i <= skip && blk < allocBlk + count) {
  852                 v = blk + radix - allocBlk;
  853                 if (v > count)
  854                         v = count;
  855 
  856                 if (scan->bm_bighint == (daddr_t)-1)
  857                         panic("blst_meta_fill: filling unexpected range");
  858 
  859                 if (next_skip == 1) {
  860                         nblks += blst_leaf_fill(&scan[i], allocBlk, v);
  861                 } else {
  862                         nblks += blst_meta_fill(&scan[i], allocBlk, v,
  863                             radix, next_skip - 1, blk);
  864                 }
  865                 count -= v;
  866                 allocBlk += v;
  867                 blk += radix;
  868                 i += next_skip;
  869         }
  870         scan->u.bmu_avail -= nblks;
  871         return nblks;
  872 }
  873 
  874 /*
  875  * BLST_RADIX_INIT() - initialize radix tree
  876  *
  877  *      Initialize our meta structures and bitmaps and calculate the exact
  878  *      amount of space required to manage 'count' blocks - this space may
  879  *      be considerably less than the calculated radix due to the large
  880  *      RADIX values we use.
  881  */
  882 
  883 static daddr_t  
  884 blst_radix_init(blmeta_t *scan, daddr_t radix, daddr_t skip, daddr_t count)
  885 {
  886         daddr_t i, memindex, next_skip;
  887 
  888         memindex = 0;
  889 
  890         /*
  891          * Leaf node
  892          */
  893 
  894         if (radix == BLIST_BMAP_RADIX) {
  895                 if (scan) {
  896                         scan->bm_bighint = 0;
  897                         scan->u.bmu_bitmap = 0;
  898                 }
  899                 return(memindex);
  900         }
  901 
  902         /*
  903          * Meta node.  If allocating the entire object we can special
  904          * case it.  However, we need to figure out how much memory
  905          * is required to manage 'count' blocks, so we continue on anyway.
  906          */
  907 
  908         if (scan) {
  909                 scan->bm_bighint = 0;
  910                 scan->u.bmu_avail = 0;
  911         }
  912 
  913         radix /= BLIST_META_RADIX;
  914         next_skip = skip / BLIST_META_RADIX;
  915 
  916         for (i = 1; i <= skip; i += next_skip) {
  917                 if (count >= radix) {
  918                         /*
  919                          * Allocate the entire object
  920                          */
  921                         memindex = i + blst_radix_init(
  922                             ((scan) ? &scan[i] : NULL),
  923                             radix,
  924                             next_skip - 1,
  925                             radix
  926                         );
  927                         count -= radix;
  928                 } else if (count > 0) {
  929                         /*
  930                          * Allocate a partial object
  931                          */
  932                         memindex = i + blst_radix_init(
  933                             ((scan) ? &scan[i] : NULL),
  934                             radix,
  935                             next_skip - 1,
  936                             count
  937                         );
  938                         count = 0;
  939                 } else {
  940                         /*
  941                          * Add terminator and break out
  942                          */
  943                         if (scan)
  944                                 scan[i].bm_bighint = (daddr_t)-1;
  945                         break;
  946                 }
  947         }
  948         if (memindex < i)
  949                 memindex = i;
  950         return(memindex);
  951 }
  952 
  953 #ifdef BLIST_DEBUG
  954 
  955 static void     
  956 blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix, daddr_t skip,
  957     int tab)
  958 {
  959         daddr_t i, next_skip;
  960 
  961         if (radix == BLIST_BMAP_RADIX) {
  962                 printf(
  963                     "%*.*s(%08llx,%lld): bitmap %016llx big=%lld\n", 
  964                     tab, tab, "",
  965                     (long long)blk, (long long)radix,
  966                     (long long)scan->u.bmu_bitmap,
  967                     (long long)scan->bm_bighint
  968                 );
  969                 return;
  970         }
  971 
  972         if (scan->u.bmu_avail == 0) {
  973                 printf(
  974                     "%*.*s(%08llx,%lld) ALL ALLOCATED\n",
  975                     tab, tab, "",
  976                     (long long)blk,
  977                     (long long)radix
  978                 );
  979                 return;
  980         }
  981         if (scan->u.bmu_avail == radix) {
  982                 printf(
  983                     "%*.*s(%08llx,%lld) ALL FREE\n",
  984                     tab, tab, "",
  985                     (long long)blk,
  986                     (long long)radix
  987                 );
  988                 return;
  989         }
  990 
  991         printf(
  992             "%*.*s(%08llx,%lld): subtree (%lld/%lld) big=%lld {\n",
  993             tab, tab, "",
  994             (long long)blk, (long long)radix,
  995             (long long)scan->u.bmu_avail,
  996             (long long)radix,
  997             (long long)scan->bm_bighint
  998         );
  999 
 1000         radix /= BLIST_META_RADIX;
 1001         next_skip = skip / BLIST_META_RADIX;
 1002         tab += 4;
 1003 
 1004         for (i = 1; i <= skip; i += next_skip) {
 1005                 if (scan[i].bm_bighint == (daddr_t)-1) {
 1006                         printf(
 1007                             "%*.*s(%08llx,%lld): Terminator\n",
 1008                             tab, tab, "",
 1009                             (long long)blk, (long long)radix
 1010                         );
 1011                         break;
 1012                 }
 1013                 blst_radix_print(
 1014                     &scan[i],
 1015                     blk,
 1016                     radix,
 1017                     next_skip - 1,
 1018                     tab
 1019                 );
 1020                 blk += radix;
 1021         }
 1022         tab -= 4;
 1023 
 1024         printf(
 1025             "%*.*s}\n",
 1026             tab, tab, ""
 1027         );
 1028 }
 1029 
 1030 #endif
 1031 
 1032 #ifdef BLIST_DEBUG
 1033 
 1034 int
 1035 main(int ac, char **av)
 1036 {
 1037         int size = 1024;
 1038         int i;
 1039         blist_t bl;
 1040 
 1041         for (i = 1; i < ac; ++i) {
 1042                 const char *ptr = av[i];
 1043                 if (*ptr != '-') {
 1044                         size = strtol(ptr, NULL, 0);
 1045                         continue;
 1046                 }
 1047                 ptr += 2;
 1048                 fprintf(stderr, "Bad option: %s\n", ptr - 2);
 1049                 exit(1);
 1050         }
 1051         bl = blist_create(size, M_WAITOK);
 1052         blist_free(bl, 0, size);
 1053 
 1054         for (;;) {
 1055                 char buf[1024];
 1056                 long long da = 0;
 1057                 long long count = 0;
 1058 
 1059                 printf("%lld/%lld/%lld> ", (long long)blist_avail(bl),
 1060                     (long long)size, (long long)bl->bl_radix);
 1061                 fflush(stdout);
 1062                 if (fgets(buf, sizeof(buf), stdin) == NULL)
 1063                         break;
 1064                 switch(buf[0]) {
 1065                 case 'r':
 1066                         if (sscanf(buf + 1, "%lld", &count) == 1) {
 1067                                 blist_resize(&bl, count, 1, M_WAITOK);
 1068                         } else {
 1069                                 printf("?\n");
 1070                         }
 1071                 case 'p':
 1072                         blist_print(bl);
 1073                         break;
 1074                 case 'a':
 1075                         if (sscanf(buf + 1, "%lld", &count) == 1) {
 1076                                 daddr_t blk = blist_alloc(bl, count);
 1077                                 printf("    R=%08llx\n", (long long)blk);
 1078                         } else {
 1079                                 printf("?\n");
 1080                         }
 1081                         break;
 1082                 case 'f':
 1083                         if (sscanf(buf + 1, "%llx %lld", &da, &count) == 2) {
 1084                                 blist_free(bl, da, count);
 1085                         } else {
 1086                                 printf("?\n");
 1087                         }
 1088                         break;
 1089                 case 'l':
 1090                         if (sscanf(buf + 1, "%llx %lld", &da, &count) == 2) {
 1091                                 printf("    n=%jd\n",
 1092                                     (intmax_t)blist_fill(bl, da, count));
 1093                         } else {
 1094                                 printf("?\n");
 1095                         }
 1096                         break;
 1097                 case '?':
 1098                 case 'h':
 1099                         puts(
 1100                             "p          -print\n"
 1101                             "a %d       -allocate\n"
 1102                             "f %x %d    -free\n"
 1103                             "l %x %d    -fill\n"
 1104                             "r %d       -resize\n"
 1105                             "h/?        -help"
 1106                         );
 1107                         break;
 1108                 default:
 1109                         printf("?\n");
 1110                         break;
 1111                 }
 1112         }
 1113         return(0);
 1114 }
 1115 
 1116 void
 1117 panic(const char *ctl, ...)
 1118 {
 1119         va_list va;
 1120 
 1121         va_start(va, ctl);
 1122         vfprintf(stderr, ctl, va);
 1123         fprintf(stderr, "\n");
 1124         va_end(va);
 1125         exit(1);
 1126 }
 1127 
 1128 #endif
 1129 

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