1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* -*- linux-c -*- ------------------------------------------------------- * 3 * 4 * Copyright 2002 H. Peter Anvin - All Rights Reserved 5 * 6 * ----------------------------------------------------------------------- */ 7 8 /* 9 * raid6/recov.c 10 * 11 * RAID-6 data recovery in dual failure mode. In single failure mode, 12 * use the RAID-5 algorithm (or, in the case of Q failure, just reconstruct 13 * the syndrome.) 14 */ 15 16 #include <linux/export.h> 17 #include <linux/raid/pq.h> 18 19 /* Recover two failed data blocks. */ 20 static void raid6_2data_recov_intx1(int disks, size_t bytes, int faila, 21 int failb, void **ptrs) 22 { 23 u8 *p, *q, *dp, *dq; 24 u8 px, qx, db; 25 const u8 *pbmul; /* P multiplier table for B data */ 26 const u8 *qmul; /* Q multiplier table (for both) */ 27 28 p = (u8 *)ptrs[disks-2]; 29 q = (u8 *)ptrs[disks-1]; 30 31 /* Compute syndrome with zero for the missing data pages 32 Use the dead data pages as temporary storage for 33 delta p and delta q */ 34 dp = (u8 *)ptrs[faila]; 35 ptrs[faila] = (void *)raid6_empty_zero_page; 36 ptrs[disks-2] = dp; 37 dq = (u8 *)ptrs[failb]; 38 ptrs[failb] = (void *)raid6_empty_zero_page; 39 ptrs[disks-1] = dq; 40 41 raid6_call.gen_syndrome(disks, bytes, ptrs); 42 43 /* Restore pointer table */ 44 ptrs[faila] = dp; 45 ptrs[failb] = dq; 46 ptrs[disks-2] = p; 47 ptrs[disks-1] = q; 48 49 /* Now, pick the proper data tables */ 50 pbmul = raid6_gfmul[raid6_gfexi[failb-faila]]; 51 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]]; 52 53 /* Now do it... */ 54 while ( bytes-- ) { 55 px = *p ^ *dp; 56 qx = qmul[*q ^ *dq]; 57 *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */ 58 *dp++ = db ^ px; /* Reconstructed A */ 59 p++; q++; 60 } 61 } 62 63 /* Recover failure of one data block plus the P block */ 64 static void raid6_datap_recov_intx1(int disks, size_t bytes, int faila, 65 void **ptrs) 66 { 67 u8 *p, *q, *dq; 68 const u8 *qmul; /* Q multiplier table */ 69 70 p = (u8 *)ptrs[disks-2]; 71 q = (u8 *)ptrs[disks-1]; 72 73 /* Compute syndrome with zero for the missing data page 74 Use the dead data page as temporary storage for delta q */ 75 dq = (u8 *)ptrs[faila]; 76 ptrs[faila] = (void *)raid6_empty_zero_page; 77 ptrs[disks-1] = dq; 78 79 raid6_call.gen_syndrome(disks, bytes, ptrs); 80 81 /* Restore pointer table */ 82 ptrs[faila] = dq; 83 ptrs[disks-1] = q; 84 85 /* Now, pick the proper data tables */ 86 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]]; 87 88 /* Now do it... */ 89 while ( bytes-- ) { 90 *p++ ^= *dq = qmul[*q ^ *dq]; 91 q++; dq++; 92 } 93 } 94 95 96 const struct raid6_recov_calls raid6_recov_intx1 = { 97 .data2 = raid6_2data_recov_intx1, 98 .datap = raid6_datap_recov_intx1, 99 .valid = NULL, 100 .name = "intx1", 101 .priority = 0, 102 }; 103 104 #ifndef __KERNEL__ 105 /* Testing only */ 106 107 /* Recover two failed blocks. */ 108 void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) 109 { 110 if ( faila > failb ) { 111 int tmp = faila; 112 faila = failb; 113 failb = tmp; 114 } 115 116 if ( failb == disks-1 ) { 117 if ( faila == disks-2 ) { 118 /* P+Q failure. Just rebuild the syndrome. */ 119 raid6_call.gen_syndrome(disks, bytes, ptrs); 120 } else { 121 /* data+Q failure. Reconstruct data from P, 122 then rebuild syndrome. */ 123 /* NOT IMPLEMENTED - equivalent to RAID-5 */ 124 } 125 } else { 126 if ( failb == disks-2 ) { 127 /* data+P failure. */ 128 raid6_datap_recov(disks, bytes, faila, ptrs); 129 } else { 130 /* data+data failure. */ 131 raid6_2data_recov(disks, bytes, faila, failb, ptrs); 132 } 133 } 134 } 135 136 #endif 137