sbin/dump/cache.c

   1 /*
   2  * Copyright (c) 2005 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  * $FreeBSD: src/sbin/dump/cache.c,v 1.1.2.1 2003/01/25 18:54:59 dillon Exp $
  35  */
  36 /*
  37  * Block cache for dump
  38  */
  39
  40 #include <sys/param.h>
  41 #include <sys/stat.h>
  42 #include <sys/mman.h>
  43
  44 #include <vfs/ufs/dir.h>
  45 #include <vfs/ufs/dinode.h>
  46 #include <vfs/ufs/fs.h>
  47
  48 #include <protocols/dumprestore.h>
  49
  50 #include <ctype.h>
  51 #include <stdio.h>
  52 #include <errno.h>
  53 #include <string.h>
  54 #include <stdlib.h>
  55 #include <unistd.h>
  56
  57 #include "dump.h"
  58
  59 typedef struct Block {
  60         struct Block    *b_HNext;       /* must be first field */
  61         off_t           b_Offset;
  62         char            *b_Data;
  63 } Block;
  64
  65 #define HFACTOR         4
  66 #define BLKFACTOR       4
  67
  68 static char  *DataBase;
  69 static Block **BlockHash;
  70 static int   BlockSize;
  71 static int   HSize;
  72 static int   NBlocks;
  73
  74 static void
  75 cinit(void)
  76 {
  77         int i;
  78         int hi;
  79         Block *base;
  80
  81         if ((BlockSize = sblock->fs_bsize * BLKFACTOR) > MAXBSIZE)
  82                 BlockSize = MAXBSIZE;
  83         NBlocks = cachesize / BlockSize;
  84         HSize = NBlocks / HFACTOR;
  85
  86         msg("Cache %d MB, blocksize = %d\n",
  87             NBlocks * BlockSize / (1024 * 1024), BlockSize);
  88
  89         base = calloc(sizeof(Block), NBlocks);
  90         BlockHash = calloc(sizeof(Block *), HSize);
  91         DataBase = mmap(NULL, NBlocks * BlockSize,
  92                         PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);
  93         for (i = 0; i < NBlocks; ++i) {
  94                 base[i].b_Data = DataBase + i * BlockSize;
  95                 base[i].b_Offset = (off_t)-1;
  96                 hi = i / HFACTOR;
  97                 base[i].b_HNext = BlockHash[hi];
  98                 BlockHash[hi] = &base[i];
  99         }
 100 }
 101
 102 ssize_t
 103 cread(int fd, void *buf, size_t nbytes, off_t offset)
 104 {
 105         Block *blk;
 106         Block **pblk;
 107         Block **ppblk;
 108         int hi;
 109         int n;
 110         off_t mask;
 111
 112         /*
 113          * If the cache is disabled, or we do not yet know the filesystem
 114          * block size, then revert to pread.  Otherwise initialize the
 115          * cache as necessary and continue.
 116          */
 117         if (cachesize <= 0 || sblock->fs_bsize == 0)
 118                 return(pread(fd, buf, nbytes, offset));
 119         if (DataBase == NULL)
 120                 cinit();
 121
 122         /*
 123          * If the request crosses a cache block boundary, or the
 124          * request is larger or equal to the cache block size,
 125          * revert to pread().  Full-block-reads are typically
 126          * one-time calls and caching would be detrimental.
 127          */
 128         mask = ~(off_t)(BlockSize - 1);
 129         if (nbytes >= (unsigned)BlockSize ||
 130             ((offset ^ (offset + nbytes - 1)) & mask) != 0) {
 131                 return(pread(fd, buf, nbytes, offset));
 132         }
 133
 134         /*
 135          * Obtain and access the cache block.  Cache a successful
 136          * result.  If an error occurs, revert to pread() (this might
 137          * occur near the end of the media).
 138          */
 139         hi = (offset / BlockSize) % HSize;
 140         pblk = &BlockHash[hi];
 141         ppblk = NULL;
 142         while ((blk = *pblk) != NULL) {
 143                 if (((blk->b_Offset ^ offset) & mask) == 0)
 144                         break;
 145                 ppblk = pblk;
 146                 pblk = &blk->b_HNext;
 147         }
 148         if (blk == NULL) {
 149                 blk = *ppblk;
 150                 pblk = ppblk;
 151                 blk->b_Offset = offset & mask;
 152                 n = pread(fd, blk->b_Data, BlockSize, blk->b_Offset);
 153                 if (n != BlockSize) {
 154                         blk->b_Offset = (off_t)-1;
 155                         blk = NULL;
 156                 }
 157         }
 158         if (blk) {
 159                 bcopy(blk->b_Data + (offset - blk->b_Offset), buf, nbytes);
 160                 *pblk = blk->b_HNext;
 161                 blk->b_HNext = BlockHash[hi];
 162                 BlockHash[hi] = blk;
 163                 return(nbytes);
 164         } else {
 165                 return(pread(fd, buf, nbytes, offset));
 166         }
 167 }
 168