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

     /*
      * Copyright (c) 2003,2004 The DragonFly Project.  All rights reserved.
      * 
      * This code is derived from software contributed to The DragonFly Project
      * by Matthew Dillon <dillon@backplane.com>
      * 
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in
     *    the documentation and/or other materials provided with the
     *    distribution.
     * 3. Neither the name of The DragonFly Project nor the names of its
     *    contributors may be used to endorse or promote products derived
     *    from this software without specific, prior written permission.
     * 
     * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
     * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
     * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     * 
     * Implements bitmap resource lists.
     *
     *      Usage:
     *              blist = blist_create(blocks)
     *              (void)  blist_destroy(blist)
     *              blkno = blist_alloc(blist, count)
     *              (void)  blist_free(blist, blkno, count)
     *              nblks = blist_fill(blist, blkno, count)
     *              (void)  blist_resize(&blist, count, freeextra)
     *              
     *
     *      Notes:
     *              on creation, the entire list is marked reserved.  You should
     *              first blist_free() the sections you want to make available
     *              for allocation before doing general blist_alloc()/free()
     *              ops.
     *
     *              SWAPBLK_NONE is returned on failure.  This module is typically
     *              capable of managing up to (2^31) blocks per blist, though
     *              the memory utilization would be insane if you actually did
     *              that.  Managing something like 512MB worth of 4K blocks 
     *              eats around 32 KBytes of memory. 
     *
     * $FreeBSD: src/sys/sys/blist.h,v 1.2.2.1 2003/01/12 09:23:12 dillon Exp $
     * $DragonFly: src/sys/sys/blist.h,v 1.7 2008/08/10 22:09:51 dillon Exp $
     */
    
    #ifndef _SYS_BLIST_H_
    #define _SYS_BLIST_H_
    
    #ifndef _SYS_TYPES_H_ 
    #include <sys/types.h>
    #endif
    
    typedef int32_t         swblk_t;
    typedef u_int32_t       u_swblk_t;
    
    /*
     * note: currently use SWAPBLK_NONE as an absolute value rather then
     * a flag bit.
     */
    #define SWAPBLK_MASK    ((swblk_t)((u_swblk_t)-1 >> 1))         /* mask */
    #define SWAPBLK_NONE    ((swblk_t)((u_swblk_t)SWAPBLK_MASK + 1))/* flag */
    
    /*
     * blmeta and bl_bitmap_t MUST be a power of 2 in size.
     */
    
    typedef struct blmeta {
            union {
                swblk_t     bmu_avail;      /* space available under us     */
                u_swblk_t   bmu_bitmap;     /* bitmap if we are a leaf      */
            } u;
            swblk_t         bm_bighint;     /* biggest contiguous block hint*/
    } blmeta_t;
    
    typedef struct blist {
            swblk_t         bl_blocks;      /* area of coverage             */
            int64_t         bl_radix;       /* coverage radix               */
            swblk_t         bl_skip;        /* starting skip                */
            swblk_t         bl_free;        /* number of free blocks        */
            blmeta_t        *bl_root;       /* root of radix tree           */
            swblk_t         bl_rootblks;    /* swblk_t blks allocated for tree */
    } *blist_t;
    
    #define BLIST_META_RADIX        16
   #define BLIST_BMAP_RADIX        (sizeof(u_swblk_t)*8)
   
   /*
    * The radix can be up to x BLIST_BMAP_RADIX the largest skip,
    * based on the initial skip calculation in blist_create().
    *
    * The radix will exceed the size of a 32 bit signed (or unsigned) int
    * when the maximal number of blocks is allocated.  This corresponds
    * to ~1G x PAGE_SIZE = 4096GB.  The swap code usually divides this
    * by 4, leaving us with a capability of up to four 1TB swap devices.
    */
   #define BLIST_MAXBLKS           (0x40000000 /           \
                                    (BLIST_BMAP_RADIX / BLIST_META_RADIX))
   
   #define BLIST_MAX_ALLOC         BLIST_BMAP_RADIX
   
   extern blist_t blist_create(swblk_t blocks);
   extern void blist_destroy(blist_t blist);
   extern swblk_t blist_alloc(blist_t blist, swblk_t count);
   extern swblk_t blist_allocat(blist_t blist, swblk_t count, swblk_t blkat);
   extern void blist_free(blist_t blist, swblk_t blkno, swblk_t count);
   extern swblk_t blist_fill(blist_t blist, swblk_t blkno, swblk_t count);
   extern void blist_print(blist_t blist);
   extern void blist_resize(blist_t *pblist, swblk_t count, int freenew);
   
   #endif  /* _SYS_BLIST_H_ */

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