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 * 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 * raid6/recov.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 <linux/raid/pq.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} 66EXPORT_SYMBOL_GPL(raid6_2data_recov); 67 68/* Recover failure of one data block plus the P block */ 69void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs) 70{ 71 u8 *p, *q, *dq; 72 const u8 *qmul; /* Q multiplier table */ 73 74 p = (u8 *)ptrs[disks-2]; 75 q = (u8 *)ptrs[disks-1]; 76 77 /* Compute syndrome with zero for the missing data page 78 Use the dead data page as temporary storage for delta q */ 79 dq = (u8 *)ptrs[faila]; 80 ptrs[faila] = (void *)raid6_empty_zero_page; 81 ptrs[disks-1] = dq; 82 83 raid6_call.gen_syndrome(disks, bytes, ptrs); 84 85 /* Restore pointer table */ 86 ptrs[faila] = dq; 87 ptrs[disks-1] = q; 88 89 /* Now, pick the proper data tables */ 90 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]]; 91 92 /* Now do it... */ 93 while ( bytes-- ) { 94 *p++ ^= *dq = qmul[*q ^ *dq]; 95 q++; dq++; 96 } 97} 98EXPORT_SYMBOL_GPL(raid6_datap_recov); 99 100#ifndef __KERNEL__ 101/* Testing only */ 102 103/* Recover two failed blocks. */ 104void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) 105{ 106 if ( faila > failb ) { 107 int tmp = faila; 108 faila = failb; 109 failb = tmp; 110 } 111 112 if ( failb == disks-1 ) { 113 if ( faila == disks-2 ) { 114 /* P+Q failure. Just rebuild the syndrome. */ 115 raid6_call.gen_syndrome(disks, bytes, ptrs); 116 } else { 117 /* data+Q failure. Reconstruct data from P, 118 then rebuild syndrome. */ 119 /* NOT IMPLEMENTED - equivalent to RAID-5 */ 120 } 121 } else { 122 if ( failb == disks-2 ) { 123 /* data+P failure. */ 124 raid6_datap_recov(disks, bytes, faila, ptrs); 125 } else { 126 /* data+data failure. */ 127 raid6_2data_recov(disks, bytes, faila, failb, ptrs); 128 } 129 } 130} 131 132#endif 133