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