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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 | /* -*- linux-c -*- ------------------------------------------------------- * * * Copyright 2002 H. Peter Anvin - All Rights Reserved * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, Inc., 53 Temple Place Ste 330, * Bostom MA 02111-1307, USA; either version 2 of the License, or * (at your option) any later version; incorporated herein by reference. * * ----------------------------------------------------------------------- */ /* * raid6recov.c * * RAID-6 data recovery in dual failure mode. In single failure mode, * use the RAID-5 algorithm (or, in the case of Q failure, just reconstruct * the syndrome.) */ #include "raid6.h" /* Recover two failed data blocks. */ void raid6_2data_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) { u8 *p, *q, *dp, *dq; u8 px, qx, db; const u8 *pbmul; /* P multiplier table for B data */ const u8 *qmul; /* Q multiplier table (for both) */ p = (u8 *)ptrs[disks-2]; q = (u8 *)ptrs[disks-1]; /* Compute syndrome with zero for the missing data pages Use the dead data pages as temporary storage for delta p and delta q */ dp = (u8 *)ptrs[faila]; ptrs[faila] = (void *)raid6_empty_zero_page; ptrs[disks-2] = dp; dq = (u8 *)ptrs[failb]; ptrs[failb] = (void *)raid6_empty_zero_page; ptrs[disks-1] = dq; raid6_call.gen_syndrome(disks, bytes, ptrs); /* Restore pointer table */ ptrs[faila] = dp; ptrs[failb] = dq; ptrs[disks-2] = p; ptrs[disks-1] = q; /* Now, pick the proper data tables */ pbmul = raid6_gfmul[raid6_gfexi[failb-faila]]; qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]]; /* Now do it... */ while ( bytes-- ) { px = *p ^ *dp; qx = qmul[*q ^ *dq]; *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */ *dp++ = db ^ px; /* Reconstructed A */ p++; q++; } } /* Recover failure of one data block plus the P block */ void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs) { u8 *p, *q, *dq; const u8 *qmul; /* Q multiplier table */ p = (u8 *)ptrs[disks-2]; q = (u8 *)ptrs[disks-1]; /* Compute syndrome with zero for the missing data page Use the dead data page as temporary storage for delta q */ dq = (u8 *)ptrs[faila]; ptrs[faila] = (void *)raid6_empty_zero_page; ptrs[disks-1] = dq; raid6_call.gen_syndrome(disks, bytes, ptrs); /* Restore pointer table */ ptrs[faila] = dq; ptrs[disks-1] = q; /* Now, pick the proper data tables */ qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]]; /* Now do it... */ while ( bytes-- ) { *p++ ^= *dq = qmul[*q ^ *dq]; q++; dq++; } } #ifndef __KERNEL__ /* Testing only */ /* Recover two failed blocks. */ void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) { if ( faila > failb ) { int tmp = faila; faila = failb; failb = tmp; } if ( failb == disks-1 ) { if ( faila == disks-2 ) { /* P+Q failure. Just rebuild the syndrome. */ raid6_call.gen_syndrome(disks, bytes, ptrs); } else { /* data+Q failure. Reconstruct data from P, then rebuild syndrome. */ /* NOT IMPLEMENTED - equivalent to RAID-5 */ } } else { if ( failb == disks-2 ) { /* data+P failure. */ raid6_datap_recov(disks, bytes, faila, ptrs); } else { /* data+data failure. */ raid6_2data_recov(disks, bytes, faila, failb, ptrs); } } } #endif |