sbin/dump/cache.c

   1 /*
   2  * CACHE.C
   3  *
   4  *      Block cache for dump
   5  *
   6  * $FreeBSD$
   7  */
   8
   9 #include <sys/param.h>
  10 #include <sys/stat.h>
  11 #include <sys/mman.h>
  12
  13 #ifdef sunos
  14 #include <sys/vnode.h>
  15
  16 #include <ufs/fs.h>
  17 #include <ufs/fsdir.h>
  18 #include <ufs/inode.h>
  19 #else
  20 #include <ufs/ufs/dir.h>
  21 #include <ufs/ufs/dinode.h>
  22 #include <ufs/ffs/fs.h>
  23 #endif
  24
  25 #include <protocols/dumprestore.h>
  26
  27 #include <ctype.h>
  28 #include <stdio.h>
  29 #ifdef __STDC__
  30 #include <errno.h>
  31 #include <string.h>
  32 #include <stdlib.h>
  33 #include <unistd.h>
  34 #endif
  35 #include "dump.h"
  36
  37 typedef struct Block {
  38         struct Block    *b_HNext;       /* must be first field */
  39         off_t           b_Offset;
  40         char            *b_Data;
  41 } Block;
  42
  43 #define HFACTOR         4
  44 #define BLKFACTOR       4
  45
  46 static char  *DataBase;
  47 static Block **BlockHash;
  48 static int   BlockSize;
  49 static int   HSize;
  50 static int   NBlocks;
  51
  52 static void
  53 cinit(void)
  54 {
  55         int i;
  56         int hi;
  57         Block *base;
  58
  59         if ((BlockSize = sblock->fs_bsize * BLKFACTOR) > MAXBSIZE)
  60                 BlockSize = MAXBSIZE;
  61         NBlocks = cachesize / BlockSize;
  62         HSize = NBlocks / HFACTOR;
  63
  64         msg("Cache %d MB, blocksize = %d\n",
  65             NBlocks * BlockSize / (1024 * 1024), BlockSize);
  66
  67         base = calloc(sizeof(Block), NBlocks);
  68         BlockHash = calloc(sizeof(Block *), HSize);
  69         DataBase = mmap(NULL, NBlocks * BlockSize,
  70                         PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);
  71         for (i = 0; i < NBlocks; ++i) {
  72                 base[i].b_Data = DataBase + i * BlockSize;
  73                 base[i].b_Offset = (off_t)-1;
  74                 hi = i / HFACTOR;
  75                 base[i].b_HNext = BlockHash[hi];
  76                 BlockHash[hi] = &base[i];
  77         }
  78 }
  79
  80 ssize_t
  81 cread(int fd, void *buf, size_t nbytes, off_t offset)
  82 {
  83         Block *blk;
  84         Block **pblk;
  85         Block **ppblk;
  86         int hi;
  87         int n;
  88         off_t mask;
  89
  90         /*
  91          * If the cache is disabled, or we do not yet know the filesystem
  92          * block size, then revert to pread.  Otherwise initialize the
  93          * cache as necessary and continue.
  94          */
  95         if (cachesize <= 0 || sblock->fs_bsize == 0)
  96                 return(pread(fd, buf, nbytes, offset));
  97         if (DataBase == NULL)
  98                 cinit();
  99
 100         /*
 101          * If the request crosses a cache block boundary, or the
 102          * request is larger or equal to the cache block size,
 103          * revert to pread().  Full-block-reads are typically
 104          * one-time calls and caching would be detrimental.
 105          */
 106         mask = ~(off_t)(BlockSize - 1);
 107         if (nbytes >= BlockSize ||
 108             ((offset ^ (offset + nbytes - 1)) & mask) != 0) {
 109                 return(pread(fd, buf, nbytes, offset));
 110         }
 111
 112         /*
 113          * Obtain and access the cache block.  Cache a successful
 114          * result.  If an error occurs, revert to pread() (this might
 115          * occur near the end of the media).
 116          */
 117         hi = (offset / BlockSize) % HSize;
 118         pblk = &BlockHash[hi];
 119         ppblk = NULL;
 120         while ((blk = *pblk) != NULL) {
 121                 if (((blk->b_Offset ^ offset) & mask) == 0)
 122                         break;
 123                 ppblk = pblk;
 124                 pblk = &blk->b_HNext;
 125         }
 126         if (blk == NULL) {
 127                 blk = *ppblk;
 128                 pblk = ppblk;
 129                 blk->b_Offset = offset & mask;
 130                 n = pread(fd, blk->b_Data, BlockSize, blk->b_Offset);
 131                 if (n != BlockSize) {
 132                         blk->b_Offset = (off_t)-1;
 133                         blk = NULL;
 134                 }
 135         }
 136         if (blk) {
 137                 bcopy(blk->b_Data + (offset - blk->b_Offset), buf, nbytes);
 138                 *pblk = blk->b_HNext;
 139                 blk->b_HNext = BlockHash[hi];
 140                 BlockHash[hi] = blk;
 141                 return(nbytes);
 142         } else {
 143                 return(pread(fd, buf, nbytes, offset));
 144         }
 145 }
 146