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(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 EXPORT_SYMBOL_GPL(raid6_2data_recov); 68 69 /* Recover failure of one data block plus the P block */ 70 void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs) 71 { 72 u8 *p, *q, *dq; 73 const u8 *qmul; /* Q multiplier table */ 74 75 p = (u8 *)ptrs[disks-2]; 76 q = (u8 *)ptrs[disks-1]; 77 78 /* Compute syndrome with zero for the missing data page 79 Use the dead data page as temporary storage for delta q */ 80 dq = (u8 *)ptrs[faila]; 81 ptrs[faila] = (void *)raid6_empty_zero_page; 82 ptrs[disks-1] = dq; 83 84 raid6_call.gen_syndrome(disks, bytes, ptrs); 85 86 /* Restore pointer table */ 87 ptrs[faila] = dq; 88 ptrs[disks-1] = q; 89 90 /* Now, pick the proper data tables */ 91 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]]; 92 93 /* Now do it... */ 94 while ( bytes-- ) { 95 *p++ ^= *dq = qmul[*q ^ *dq]; 96 q++; dq++; 97 } 98 } 99 EXPORT_SYMBOL_GPL(raid6_datap_recov); 100 101 #ifndef __KERNEL__ 102 /* Testing only */ 103 104 /* Recover two failed blocks. */ 105 void 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