1/* -*- linux-c -*- ------------------------------------------------------- * 2 * 3 * Copyright 2002 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 * Bostom 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 * raid6recov.c 15 * 16 * RAID-6 data recovery in dual failure mode. In single failure mode, 17 * use the RAID-5 algorithm (or, in the case of Q failure, just reconstruct 18 * the syndrome.) 19 */ 20 21#include "raid6.h" 22 23/* Recover two failed data blocks. */ 24void raid6_2data_recov(int disks, size_t bytes, int faila, int failb, 25 void **ptrs) 26{ 27 u8 *p, *q, *dp, *dq; 28 u8 px, qx, db; 29 const u8 *pbmul; /* P multiplier table for B data */ 30 const u8 *qmul; /* Q multiplier table (for both) */ 31 32 p = (u8 *)ptrs[disks-2]; 33 q = (u8 *)ptrs[disks-1]; 34 35 /* Compute syndrome with zero for the missing data pages 36 Use the dead data pages as temporary storage for 37 delta p and delta q */ 38 dp = (u8 *)ptrs[faila]; 39 ptrs[faila] = (void *)raid6_empty_zero_page; 40 ptrs[disks-2] = dp; 41 dq = (u8 *)ptrs[failb]; 42 ptrs[failb] = (void *)raid6_empty_zero_page; 43 ptrs[disks-1] = dq; 44 45 raid6_call.gen_syndrome(disks, bytes, ptrs); 46 47 /* Restore pointer table */ 48 ptrs[faila] = dp; 49 ptrs[failb] = dq; 50 ptrs[disks-2] = p; 51 ptrs[disks-1] = q; 52 53 /* Now, pick the proper data tables */ 54 pbmul = raid6_gfmul[raid6_gfexi[failb-faila]]; 55 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]]; 56 57 /* Now do it... */ 58 while ( bytes-- ) { 59 px = *p ^ *dp; 60 qx = qmul[*q ^ *dq]; 61 *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */ 62 *dp++ = db ^ px; /* Reconstructed A */ 63 p++; q++; 64 } 65} 66 67 68 69 70/* Recover failure of one data block plus the P block */ 71void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs) 72{ 73 u8 *p, *q, *dq; 74 const u8 *qmul; /* Q multiplier table */ 75 76 p = (u8 *)ptrs[disks-2]; 77 q = (u8 *)ptrs[disks-1]; 78 79 /* Compute syndrome with zero for the missing data page 80 Use the dead data page as temporary storage for delta q */ 81 dq = (u8 *)ptrs[faila]; 82 ptrs[faila] = (void *)raid6_empty_zero_page; 83 ptrs[disks-1] = dq; 84 85 raid6_call.gen_syndrome(disks, bytes, ptrs); 86 87 /* Restore pointer table */ 88 ptrs[faila] = dq; 89 ptrs[disks-1] = q; 90 91 /* Now, pick the proper data tables */ 92 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]]; 93 94 /* Now do it... */ 95 while ( bytes-- ) { 96 *p++ ^= *dq = qmul[*q ^ *dq]; 97 q++; dq++; 98 } 99} 100 101 102#ifndef __KERNEL__ /* Testing only */ 103 104/* Recover two failed blocks. */ 105void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) 106{ 107 if ( faila > failb ) { 108 int tmp = faila; 109 faila = failb; 110 failb = tmp; 111 } 112 113 if ( failb == disks-1 ) { 114 if ( faila == disks-2 ) { 115 /* P+Q failure. Just rebuild the syndrome. */ 116 raid6_call.gen_syndrome(disks, bytes, ptrs); 117 } else { 118 /* data+Q failure. Reconstruct data from P, 119 then rebuild syndrome. */ 120 /* NOT IMPLEMENTED - equivalent to RAID-5 */ 121 } 122 } else { 123 if ( failb == disks-2 ) { 124 /* data+P failure. */ 125 raid6_datap_recov(disks, bytes, faila, ptrs); 126 } else { 127 /* data+data failure. */ 128 raid6_2data_recov(disks, bytes, faila, failb, ptrs); 129 } 130 } 131} 132 133#endif 134