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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright 2002 H. Peter Anvin - All Rights Reserved
4 *
5 * RAID-6 data recovery in dual failure mode. In single failure mode, use the
6 * RAID-5 algorithm (or, in the case of Q failure, just reconstruct the
7 * syndrome.)
8 */
9
10#include <linux/mm.h>
11#include <linux/raid/pq.h>
12#include "algos.h"
13
14/* Recover two failed data blocks. */
15static void raid6_2data_recov_intx1(int disks, size_t bytes, int faila,
16 int failb, void **ptrs)
17{
18 u8 *p, *q, *dp, *dq;
19 u8 px, qx, db;
20 const u8 *pbmul; /* P multiplier table for B data */
21 const u8 *qmul; /* Q multiplier table (for both) */
22
23 p = (u8 *)ptrs[disks-2];
24 q = (u8 *)ptrs[disks-1];
25
26 /* Compute syndrome with zero for the missing data pages
27 Use the dead data pages as temporary storage for
28 delta p and delta q */
29 dp = (u8 *)ptrs[faila];
30 ptrs[faila] = page_address(ZERO_PAGE(0));
31 ptrs[disks-2] = dp;
32 dq = (u8 *)ptrs[failb];
33 ptrs[failb] = page_address(ZERO_PAGE(0));
34 ptrs[disks-1] = dq;
35
36 raid6_gen_syndrome(disks, bytes, ptrs);
37
38 /* Restore pointer table */
39 ptrs[faila] = dp;
40 ptrs[failb] = dq;
41 ptrs[disks-2] = p;
42 ptrs[disks-1] = q;
43
44 /* Now, pick the proper data tables */
45 pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];
46 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];
47
48 /* Now do it... */
49 while ( bytes-- ) {
50 px = *p ^ *dp;
51 qx = qmul[*q ^ *dq];
52 *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */
53 *dp++ = db ^ px; /* Reconstructed A */
54 p++; q++;
55 }
56}
57
58/* Recover failure of one data block plus the P block */
59static void raid6_datap_recov_intx1(int disks, size_t bytes, int faila,
60 void **ptrs)
61{
62 u8 *p, *q, *dq;
63 const u8 *qmul; /* Q multiplier table */
64
65 p = (u8 *)ptrs[disks-2];
66 q = (u8 *)ptrs[disks-1];
67
68 /* Compute syndrome with zero for the missing data page
69 Use the dead data page as temporary storage for delta q */
70 dq = (u8 *)ptrs[faila];
71 ptrs[faila] = page_address(ZERO_PAGE(0));
72 ptrs[disks-1] = dq;
73
74 raid6_gen_syndrome(disks, bytes, ptrs);
75
76 /* Restore pointer table */
77 ptrs[faila] = dq;
78 ptrs[disks-1] = q;
79
80 /* Now, pick the proper data tables */
81 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];
82
83 /* Now do it... */
84 while ( bytes-- ) {
85 *p++ ^= *dq = qmul[*q ^ *dq];
86 q++; dq++;
87 }
88}
89
90
91const struct raid6_recov_calls raid6_recov_intx1 = {
92 .data2 = raid6_2data_recov_intx1,
93 .datap = raid6_datap_recov_intx1,
94 .name = "intx1",
95};