raid5extend.c

   1
   2 int phys2log(int phys, int stripe, int n, int layout)
   3 {
   4     /* In an 'n' disk array using 'layout',
   5      * in stripe 'stripe', the physical disc 'phys'
   6      * stores what logical chunk?
   7      * -1 mean parity.
   8      *
   9      */
  10     switch(layout) {
  11     case ALGORITHM_LEFT_ASYMMETRIC:
  12         pd = (n-1) - (stripe % n);
  13         if (phys < pd)
  14             return phys;
  15         else if (phys == pd)
  16             return -1;
  17         else return phys-1;
  18
  19     case ALGORITHM_RIGHT_ASYMMETRIC:
  20         pd = stripe % n;
  21         if (phys < pd)
  22             return phys;
  23         else if (phys == pd)
  24             return -1;
  25         else return phys-1;
  26
  27     case ALGORITHM_LEFT_SYMMETRIC:
  28         pd = (n-1) - (stripe %n);
  29         if (phys < pd)
  30             return phys+ n-1-pd;
  31         else if (phys == pd)
  32             return -1;
  33         else return phys-pd-1;
  34
  35     case ALGORITHM_RIGHT_SYMMETRIC:
  36         pd = stripe % n;
  37         if (phys < pd)
  38             return phys+ n-1-pd;
  39         else if (phys == pd)
  40             return -1;
  41         else return phys-pd-1;
  42     }
  43     return -2;
  44 }
  45
  46 raid5_extend(unsigned long len, int chunksize, int layout, int n, int m, int rfds[], int wfds[])
  47 {
  48
  49     static char buf[4096];
  50
  51     unsigned long blocks = len/4;
  52     unsigned int blocksperchunk= chunksize/4096;
  53
  54     unsigned long b;
  55
  56     for (b=0; b<blocks; b++) {
  57         unsigned long stripe = b / blocksperchunk;
  58         unsigned int offset = b - (stripe*blocksperchunk);
  59         unsigned long chunk = stripe * (n-1);
  60         int src;
  61         for (src=0; src<n; src++) {
  62             int dnum, snum;
  63             if (read(rfds[src], buf, sizeof(buf)) != sizeof(buf)) {
  64                 error();
  65                 return 0;
  66             }
  67
  68             snum = phys2log(src, stripe, n, layout);
  69
  70             if (snum == -1)
  71                 continue;
  72             chunk = stripe*(n-1)+snum;
  73
  74             dstripe = chunk/(m-1);
  75             dnum = log2phys(chunk-(stripe*(m-1)), dstripe, m, layout);
  76             llseek(wfds[dnum], dstripe*chunksize+(offset*4096), 0);
  77             write(wfds[dnum], buf, sizeof(buf));
  78         }
  79     }
  80 }