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1// SPDX-License-Identifier: GPL-2.0-or-later2/* -*- linux-c -*- ------------------------------------------------------- *3 *4 * Copyright 2002 H. Peter Anvin - All Rights Reserved5 *6 * ----------------------------------------------------------------------- */7 8/*9 * raid6/recov.c10 *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 reconstruct13 * the syndrome.)14 */15 16#include <linux/raid/pq.h>17 18/* Recover two failed data blocks. */19static void raid6_2data_recov_intx1(int disks, size_t bytes, int faila,20 int failb, void **ptrs)21{22 u8 *p, *q, *dp, *dq;23 u8 px, qx, db;24 const u8 *pbmul; /* P multiplier table for B data */25 const u8 *qmul; /* Q multiplier table (for both) */26 27 p = (u8 *)ptrs[disks-2];28 q = (u8 *)ptrs[disks-1];29 30 /* Compute syndrome with zero for the missing data pages31 Use the dead data pages as temporary storage for32 delta p and delta q */33 dp = (u8 *)ptrs[faila];34 ptrs[faila] = (void *)raid6_empty_zero_page;35 ptrs[disks-2] = dp;36 dq = (u8 *)ptrs[failb];37 ptrs[failb] = (void *)raid6_empty_zero_page;38 ptrs[disks-1] = dq;39 40 raid6_call.gen_syndrome(disks, bytes, ptrs);41 42 /* Restore pointer table */43 ptrs[faila] = dp;44 ptrs[failb] = dq;45 ptrs[disks-2] = p;46 ptrs[disks-1] = q;47 48 /* Now, pick the proper data tables */49 pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];50 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];51 52 /* Now do it... */53 while ( bytes-- ) {54 px = *p ^ *dp;55 qx = qmul[*q ^ *dq];56 *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */57 *dp++ = db ^ px; /* Reconstructed A */58 p++; q++;59 }60}61 62/* Recover failure of one data block plus the P block */63static void raid6_datap_recov_intx1(int disks, size_t bytes, int faila,64 void **ptrs)65{66 u8 *p, *q, *dq;67 const u8 *qmul; /* Q multiplier table */68 69 p = (u8 *)ptrs[disks-2];70 q = (u8 *)ptrs[disks-1];71 72 /* Compute syndrome with zero for the missing data page73 Use the dead data page as temporary storage for delta q */74 dq = (u8 *)ptrs[faila];75 ptrs[faila] = (void *)raid6_empty_zero_page;76 ptrs[disks-1] = dq;77 78 raid6_call.gen_syndrome(disks, bytes, ptrs);79 80 /* Restore pointer table */81 ptrs[faila] = dq;82 ptrs[disks-1] = q;83 84 /* Now, pick the proper data tables */85 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];86 87 /* Now do it... */88 while ( bytes-- ) {89 *p++ ^= *dq = qmul[*q ^ *dq];90 q++; dq++;91 }92}93 94 95const struct raid6_recov_calls raid6_recov_intx1 = {96 .data2 = raid6_2data_recov_intx1,97 .datap = raid6_datap_recov_intx1,98 .valid = NULL,99 .name = "intx1",100 .priority = 0,101};102 103#ifndef __KERNEL__104/* Testing only */105 106/* Recover two failed blocks. */107void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs)108{109 if ( faila > failb ) {110 int tmp = faila;111 faila = failb;112 failb = tmp;113 }114 115 if ( failb == disks-1 ) {116 if ( faila == disks-2 ) {117 /* P+Q failure. Just rebuild the syndrome. */118 raid6_call.gen_syndrome(disks, bytes, ptrs);119 } else {120 /* data+Q failure. Reconstruct data from P,121 then rebuild syndrome. */122 /* NOT IMPLEMENTED - equivalent to RAID-5 */123 }124 } else {125 if ( failb == disks-2 ) {126 /* data+P failure. */127 raid6_datap_recov(disks, bytes, faila, ptrs);128 } else {129 /* data+data failure. */130 raid6_2data_recov(disks, bytes, faila, failb, ptrs);131 }132 }133}134 135#endif136