1 /* -*- linux-c -*- ------------------------------------------------------- *
2 *
3 * Copyright 2002 H. Peter Anvin - All Rights Reserved
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation, Inc., 53 Temple Place Ste 330,
8 * Boston MA 02111-1307, USA; either version 2 of the License, or
9 * (at your option) any later version; incorporated herein by reference.
10 *
11 * ----------------------------------------------------------------------- */
12
13 /*
14 * raid6/recov.c
15 *
16 * RAID-6 data recovery in dual failure mode. In single failure mode,
17 * use the RAID-5 algorithm (or, in the case of Q failure, just reconstruct
18 * the syndrome.)
19 */
20
21 #include <linux/export.h>
22 #include <linux/raid/pq.h>
23
24 /* Recover two failed data blocks. */
raid6_2data_recov(int disks,size_t bytes,int faila,int failb,void ** ptrs)25 void raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
26 void **ptrs)
27 {
28 u8 *p, *q, *dp, *dq;
29 u8 px, qx, db;
30 const u8 *pbmul; /* P multiplier table for B data */
31 const u8 *qmul; /* Q multiplier table (for both) */
32
33 p = (u8 *)ptrs[disks-2];
34 q = (u8 *)ptrs[disks-1];
35
36 /* Compute syndrome with zero for the missing data pages
37 Use the dead data pages as temporary storage for
38 delta p and delta q */
39 dp = (u8 *)ptrs[faila];
40 ptrs[faila] = (void *)raid6_empty_zero_page;
41 ptrs[disks-2] = dp;
42 dq = (u8 *)ptrs[failb];
43 ptrs[failb] = (void *)raid6_empty_zero_page;
44 ptrs[disks-1] = dq;
45
46 raid6_call.gen_syndrome(disks, bytes, ptrs);
47
48 /* Restore pointer table */
49 ptrs[faila] = dp;
50 ptrs[failb] = dq;
51 ptrs[disks-2] = p;
52 ptrs[disks-1] = q;
53
54 /* Now, pick the proper data tables */
55 pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];
56 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];
57
58 /* Now do it... */
59 while ( bytes-- ) {
60 px = *p ^ *dp;
61 qx = qmul[*q ^ *dq];
62 *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */
63 *dp++ = db ^ px; /* Reconstructed A */
64 p++; q++;
65 }
66 }
67 EXPORT_SYMBOL_GPL(raid6_2data_recov);
68
69 /* Recover failure of one data block plus the P block */
raid6_datap_recov(int disks,size_t bytes,int faila,void ** ptrs)70 void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs)
71 {
72 u8 *p, *q, *dq;
73 const u8 *qmul; /* Q multiplier table */
74
75 p = (u8 *)ptrs[disks-2];
76 q = (u8 *)ptrs[disks-1];
77
78 /* Compute syndrome with zero for the missing data page
79 Use the dead data page as temporary storage for delta q */
80 dq = (u8 *)ptrs[faila];
81 ptrs[faila] = (void *)raid6_empty_zero_page;
82 ptrs[disks-1] = dq;
83
84 raid6_call.gen_syndrome(disks, bytes, ptrs);
85
86 /* Restore pointer table */
87 ptrs[faila] = dq;
88 ptrs[disks-1] = q;
89
90 /* Now, pick the proper data tables */
91 qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];
92
93 /* Now do it... */
94 while ( bytes-- ) {
95 *p++ ^= *dq = qmul[*q ^ *dq];
96 q++; dq++;
97 }
98 }
99 EXPORT_SYMBOL_GPL(raid6_datap_recov);
100
101 #ifndef __KERNEL__
102 /* Testing only */
103
104 /* Recover two failed blocks. */
raid6_dual_recov(int disks,size_t bytes,int faila,int failb,void ** ptrs)105 void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs)
106 {
107 if ( faila > failb ) {
108 int tmp = faila;
109 faila = failb;
110 failb = tmp;
111 }
112
113 if ( failb == disks-1 ) {
114 if ( faila == disks-2 ) {
115 /* P+Q failure. Just rebuild the syndrome. */
116 raid6_call.gen_syndrome(disks, bytes, ptrs);
117 } else {
118 /* data+Q failure. Reconstruct data from P,
119 then rebuild syndrome. */
120 /* NOT IMPLEMENTED - equivalent to RAID-5 */
121 }
122 } else {
123 if ( failb == disks-2 ) {
124 /* data+P failure. */
125 raid6_datap_recov(disks, bytes, faila, ptrs);
126 } else {
127 /* data+data failure. */
128 raid6_2data_recov(disks, bytes, faila, failb, ptrs);
129 }
130 }
131 }
132
133 #endif
134