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,
* Boston 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
|
