raid6.c

   1 /* -*- linux-c -*- ------------------------------------------------------- *
   2  *
   3  *   Copyright 2002-2004 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
   8  *   Boston MA 02111-1307, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * raid6int1.c
  15  *
  16  * 1-way unrolled portable integer math RAID-6 instruction set
  17  *
  18  * This file was postprocessed using unroll.pl and then ported to userspace
  19  */
  20 #include <stdint.h>
  21 #include <unistd.h>
  22 #include "kerncompat.h"
  23
  24 /*
  25  * This is the C data type to use
  26  */
  27
  28 /* Change this from BITS_PER_LONG if there is something better... */
  29 #if BITS_PER_LONG == 64
  30 # define NBYTES(x) ((x) * 0x0101010101010101UL)
  31 # define NSIZE  8
  32 # define NSHIFT 3
  33 typedef uint64_t unative_t;
  34 #else
  35 # define NBYTES(x) ((x) * 0x01010101U)
  36 # define NSIZE  4
  37 # define NSHIFT 2
  38 typedef uint32_t unative_t;
  39 #endif
  40
  41 /*
  42  * These sub-operations are separate inlines since they can sometimes be
  43  * specially optimized using architecture-specific hacks.
  44  */
  45
  46 /*
  47  * The SHLBYTE() operation shifts each byte left by 1, *not*
  48  * rolling over into the next byte
  49  */
  50 static inline __attribute_const__ unative_t SHLBYTE(unative_t v)
  51 {
  52         unative_t vv;
  53
  54         vv = (v << 1) & NBYTES(0xfe);
  55         return vv;
  56 }
  57
  58 /*
  59  * The MASK() operation returns 0xFF in any byte for which the high
  60  * bit is 1, 0x00 for any byte for which the high bit is 0.
  61  */
  62 static inline __attribute_const__ unative_t MASK(unative_t v)
  63 {
  64         unative_t vv;
  65
  66         vv = v & NBYTES(0x80);
  67         vv = (vv << 1) - (vv >> 7); /* Overflow on the top bit is OK */
  68         return vv;
  69 }
  70
  71
  72 void raid6_gen_syndrome(int disks, size_t bytes, void **ptrs)
  73 {
  74         uint8_t **dptr = (uint8_t **)ptrs;
  75         uint8_t *p, *q;
  76         int d, z, z0;
  77
  78         unative_t wd0, wq0, wp0, w10, w20;
  79
  80         z0 = disks - 3;         /* Highest data disk */
  81         p = dptr[z0+1];         /* XOR parity */
  82         q = dptr[z0+2];         /* RS syndrome */
  83
  84         for ( d = 0 ; d < bytes ; d += NSIZE*1 ) {
  85                 wq0 = wp0 = *(unative_t *)&dptr[z0][d+0*NSIZE];
  86                 for ( z = z0-1 ; z >= 0 ; z-- ) {
  87                         wd0 = *(unative_t *)&dptr[z][d+0*NSIZE];
  88                         wp0 ^= wd0;
  89                         w20 = MASK(wq0);
  90                         w10 = SHLBYTE(wq0);
  91                         w20 &= NBYTES(0x1d);
  92                         w10 ^= w20;
  93                         wq0 = w10 ^ wd0;
  94                 }
  95                 *(unative_t *)&p[d+NSIZE*0] = wp0;
  96                 *(unative_t *)&q[d+NSIZE*0] = wq0;
  97         }
  98 }
  99