The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/sys/blist.h

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    1 /*
    2  * Copyright (c) 2003,2004 The DragonFly Project.  All rights reserved.
    3  * 
    4  * This code is derived from software contributed to The DragonFly Project
    5  * by Matthew Dillon <dillon@backplane.com>
    6  * 
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in
   15  *    the documentation and/or other materials provided with the
   16  *    distribution.
   17  * 3. Neither the name of The DragonFly Project nor the names of its
   18  *    contributors may be used to endorse or promote products derived
   19  *    from this software without specific, prior written permission.
   20  * 
   21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
   25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  * 
   34  * Implements bitmap resource lists.
   35  *
   36  *      Usage:
   37  *              blist = blist_create(blocks)
   38  *              (void)  blist_destroy(blist)
   39  *              blkno = blist_alloc(blist, count)
   40  *              (void)  blist_free(blist, blkno, count)
   41  *              nblks = blist_fill(blist, blkno, count)
   42  *              (void)  blist_resize(&blist, count, freeextra)
   43  *              
   44  *
   45  *      Notes:
   46  *              on creation, the entire list is marked reserved.  You should
   47  *              first blist_free() the sections you want to make available
   48  *              for allocation before doing general blist_alloc()/free()
   49  *              ops.
   50  *
   51  *              SWAPBLK_NONE is returned on failure.  This module is typically
   52  *              capable of managing up to (2^31) blocks per blist, though
   53  *              the memory utilization would be insane if you actually did
   54  *              that.  Managing something like 512MB worth of 4K blocks 
   55  *              eats around 32 KBytes of memory. 
   56  *
   57  * $FreeBSD: src/sys/sys/blist.h,v 1.2.2.1 2003/01/12 09:23:12 dillon Exp $
   58  * $DragonFly: src/sys/sys/blist.h,v 1.7 2008/08/10 22:09:51 dillon Exp $
   59  */
   60 
   61 #ifndef _SYS_BLIST_H_
   62 #define _SYS_BLIST_H_
   63 
   64 #ifndef _SYS_TYPES_H_ 
   65 #include <sys/types.h>
   66 #endif
   67 
   68 typedef int32_t         swblk_t;
   69 typedef u_int32_t       u_swblk_t;
   70 
   71 /*
   72  * note: currently use SWAPBLK_NONE as an absolute value rather then
   73  * a flag bit.
   74  */
   75 #define SWAPBLK_MASK    ((swblk_t)((u_swblk_t)-1 >> 1))         /* mask */
   76 #define SWAPBLK_NONE    ((swblk_t)((u_swblk_t)SWAPBLK_MASK + 1))/* flag */
   77 
   78 /*
   79  * blmeta and bl_bitmap_t MUST be a power of 2 in size.
   80  */
   81 
   82 typedef struct blmeta {
   83         union {
   84             swblk_t     bmu_avail;      /* space available under us     */
   85             u_swblk_t   bmu_bitmap;     /* bitmap if we are a leaf      */
   86         } u;
   87         swblk_t         bm_bighint;     /* biggest contiguous block hint*/
   88 } blmeta_t;
   89 
   90 typedef struct blist {
   91         swblk_t         bl_blocks;      /* area of coverage             */
   92         int64_t         bl_radix;       /* coverage radix               */
   93         swblk_t         bl_skip;        /* starting skip                */
   94         swblk_t         bl_free;        /* number of free blocks        */
   95         blmeta_t        *bl_root;       /* root of radix tree           */
   96         swblk_t         bl_rootblks;    /* swblk_t blks allocated for tree */
   97 } *blist_t;
   98 
   99 #define BLIST_META_RADIX        16
  100 #define BLIST_BMAP_RADIX        (sizeof(u_swblk_t)*8)
  101 
  102 /*
  103  * The radix can be up to x BLIST_BMAP_RADIX the largest skip,
  104  * based on the initial skip calculation in blist_create().
  105  *
  106  * The radix will exceed the size of a 32 bit signed (or unsigned) int
  107  * when the maximal number of blocks is allocated.  This corresponds
  108  * to ~1G x PAGE_SIZE = 4096GB.  The swap code usually divides this
  109  * by 4, leaving us with a capability of up to four 1TB swap devices.
  110  */
  111 #define BLIST_MAXBLKS           (0x40000000 /           \
  112                                  (BLIST_BMAP_RADIX / BLIST_META_RADIX))
  113 
  114 #define BLIST_MAX_ALLOC         BLIST_BMAP_RADIX
  115 
  116 extern blist_t blist_create(swblk_t blocks);
  117 extern void blist_destroy(blist_t blist);
  118 extern swblk_t blist_alloc(blist_t blist, swblk_t count);
  119 extern swblk_t blist_allocat(blist_t blist, swblk_t count, swblk_t blkat);
  120 extern void blist_free(blist_t blist, swblk_t blkno, swblk_t count);
  121 extern swblk_t blist_fill(blist_t blist, swblk_t blkno, swblk_t count);
  122 extern void blist_print(blist_t blist);
  123 extern void blist_resize(blist_t *pblist, swblk_t count, int freenew);
  124 
  125 #endif  /* _SYS_BLIST_H_ */

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