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/export.h> 22 #include <linux/raid/pq.h> 23 24 /* Recover two failed data blocks. */ 25 void raid6_2data_recov_intx1(int disks, size_t bytes, int faila, int failb, 26 void **ptrs) 27 { 28 u8 *p, *q, *dp, *dq; 29 u8 px, qx, db; 30 const u8 *pbmul; /* P multiplier table for B data */ 31 const u8 *qmul; /* Q multiplier table (for both) */ 32 33 p = (u8 *)ptrs[disks-2]; 34 q = (u8 *)ptrs[disks-1]; 35 36 /* Compute syndrome with zero for the missing data pages 37 Use the dead data pages as temporary storage for 38 delta p and delta q */ 39 dp = (u8 *)ptrs[faila]; 40 ptrs[faila] = (void *)raid6_empty_zero_page; 41 ptrs[disks-2] = dp; 42 dq = (u8 *)ptrs[failb]; 43 ptrs[failb] = (void *)raid6_empty_zero_page; 44 ptrs[disks-1] = dq; 45 46 raid6_call.gen_syndrome(disks, bytes, ptrs); 47 48 /* Restore pointer table */ 49 ptrs[faila] = dp; 50 ptrs[failb] = dq; 51 ptrs[disks-2] = p; 52 ptrs[disks-1] = q; 53 54 /* Now, pick the proper data tables */ 55 pbmul = raid6_gfmul[raid6_gfexi[failb-faila]]; 56 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]]; 57 58 /* Now do it... */ 59 while ( bytes-- ) { 60 px = *p ^ *dp; 61 qx = qmul[*q ^ *dq]; 62 *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */ 63 *dp++ = db ^ px; /* Reconstructed A */ 64 p++; q++; 65 } 66 } 67 68 /* Recover failure of one data block plus the P block */ 69 void raid6_datap_recov_intx1(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 } 98 99 100 const struct raid6_recov_calls raid6_recov_intx1 = { 101 .data2 = raid6_2data_recov_intx1, 102 .datap = raid6_datap_recov_intx1, 103 .valid = NULL, 104 .name = "intx1", 105 .priority = 0, 106 }; 107 108 #ifndef __KERNEL__ 109 /* Testing only */ 110 111 /* Recover two failed blocks. */ 112 void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) 113 { 114 if ( faila > failb ) { 115 int tmp = faila; 116 faila = failb; 117 failb = tmp; 118 } 119 120 if ( failb == disks-1 ) { 121 if ( faila == disks-2 ) { 122 /* P+Q failure. Just rebuild the syndrome. */ 123 raid6_call.gen_syndrome(disks, bytes, ptrs); 124 } else { 125 /* data+Q failure. Reconstruct data from P, 126 then rebuild syndrome. */ 127 /* NOT IMPLEMENTED - equivalent to RAID-5 */ 128 } 129 } else { 130 if ( failb == disks-2 ) { 131 /* data+P failure. */ 132 raid6_datap_recov(disks, bytes, faila, ptrs); 133 } else { 134 /* data+data failure. */ 135 raid6_2data_recov(disks, bytes, faila, failb, ptrs); 136 } 137 } 138 } 139 140 #endif 141