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1da177e4 LT |
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 | * Bostom 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 | * raid6recov.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 "raid6.h" | |
22 | ||
23 | /* Recover two failed data blocks. */ | |
24 | void raid6_2data_recov(int disks, size_t bytes, int faila, int failb, | |
25 | void **ptrs) | |
26 | { | |
27 | u8 *p, *q, *dp, *dq; | |
28 | u8 px, qx, db; | |
29 | const u8 *pbmul; /* P multiplier table for B data */ | |
30 | const u8 *qmul; /* Q multiplier table (for both) */ | |
31 | ||
32 | p = (u8 *)ptrs[disks-2]; | |
33 | q = (u8 *)ptrs[disks-1]; | |
34 | ||
35 | /* Compute syndrome with zero for the missing data pages | |
36 | Use the dead data pages as temporary storage for | |
37 | delta p and delta q */ | |
38 | dp = (u8 *)ptrs[faila]; | |
39 | ptrs[faila] = (void *)raid6_empty_zero_page; | |
40 | ptrs[disks-2] = dp; | |
41 | dq = (u8 *)ptrs[failb]; | |
42 | ptrs[failb] = (void *)raid6_empty_zero_page; | |
43 | ptrs[disks-1] = dq; | |
44 | ||
45 | raid6_call.gen_syndrome(disks, bytes, ptrs); | |
46 | ||
47 | /* Restore pointer table */ | |
48 | ptrs[faila] = dp; | |
49 | ptrs[failb] = dq; | |
50 | ptrs[disks-2] = p; | |
51 | ptrs[disks-1] = q; | |
52 | ||
53 | /* Now, pick the proper data tables */ | |
54 | pbmul = raid6_gfmul[raid6_gfexi[failb-faila]]; | |
55 | qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]]; | |
56 | ||
57 | /* Now do it... */ | |
58 | while ( bytes-- ) { | |
59 | px = *p ^ *dp; | |
60 | qx = qmul[*q ^ *dq]; | |
61 | *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */ | |
62 | *dp++ = db ^ px; /* Reconstructed A */ | |
63 | p++; q++; | |
64 | } | |
65 | } | |
66 | ||
67 | ||
68 | ||
69 | ||
70 | /* Recover failure of one data block plus the P block */ | |
71 | void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs) | |
72 | { | |
73 | u8 *p, *q, *dq; | |
74 | const u8 *qmul; /* Q multiplier table */ | |
75 | ||
76 | p = (u8 *)ptrs[disks-2]; | |
77 | q = (u8 *)ptrs[disks-1]; | |
78 | ||
79 | /* Compute syndrome with zero for the missing data page | |
80 | Use the dead data page as temporary storage for delta q */ | |
81 | dq = (u8 *)ptrs[faila]; | |
82 | ptrs[faila] = (void *)raid6_empty_zero_page; | |
83 | ptrs[disks-1] = dq; | |
84 | ||
85 | raid6_call.gen_syndrome(disks, bytes, ptrs); | |
86 | ||
87 | /* Restore pointer table */ | |
88 | ptrs[faila] = dq; | |
89 | ptrs[disks-1] = q; | |
90 | ||
91 | /* Now, pick the proper data tables */ | |
92 | qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]]; | |
93 | ||
94 | /* Now do it... */ | |
95 | while ( bytes-- ) { | |
96 | *p++ ^= *dq = qmul[*q ^ *dq]; | |
97 | q++; dq++; | |
98 | } | |
99 | } | |
100 | ||
101 | ||
102 | #ifndef __KERNEL__ /* Testing only */ | |
103 | ||
104 | /* Recover two failed blocks. */ | |
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 |