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/raid/pq.h> |
17 | |
18 | /* Recover two failed data blocks. */ |
19 | static void raid6_2data_recov_intx1(int disks, size_t bytes, int faila, |
20 | int failb, void **ptrs) |
21 | { |
22 | u8 *p, *q, *dp, *dq; |
23 | u8 px, qx, db; |
24 | const u8 *pbmul; /* P multiplier table for B data */ |
25 | const u8 *qmul; /* Q multiplier table (for both) */ |
26 | |
27 | p = (u8 *)ptrs[disks-2]; |
28 | q = (u8 *)ptrs[disks-1]; |
29 | |
30 | /* Compute syndrome with zero for the missing data pages |
31 | Use the dead data pages as temporary storage for |
32 | delta p and delta q */ |
33 | dp = (u8 *)ptrs[faila]; |
34 | ptrs[faila] = (void *)raid6_empty_zero_page; |
35 | ptrs[disks-2] = dp; |
36 | dq = (u8 *)ptrs[failb]; |
37 | ptrs[failb] = (void *)raid6_empty_zero_page; |
38 | ptrs[disks-1] = dq; |
39 | |
40 | raid6_call.gen_syndrome(disks, bytes, ptrs); |
41 | |
42 | /* Restore pointer table */ |
43 | ptrs[faila] = dp; |
44 | ptrs[failb] = dq; |
45 | ptrs[disks-2] = p; |
46 | ptrs[disks-1] = q; |
47 | |
48 | /* Now, pick the proper data tables */ |
49 | pbmul = raid6_gfmul[raid6_gfexi[failb-faila]]; |
50 | qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]]; |
51 | |
52 | /* Now do it... */ |
53 | while ( bytes-- ) { |
54 | px = *p ^ *dp; |
55 | qx = qmul[*q ^ *dq]; |
56 | *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */ |
57 | *dp++ = db ^ px; /* Reconstructed A */ |
58 | p++; q++; |
59 | } |
60 | } |
61 | |
62 | /* Recover failure of one data block plus the P block */ |
63 | static void raid6_datap_recov_intx1(int disks, size_t bytes, int faila, |
64 | void **ptrs) |
65 | { |
66 | u8 *p, *q, *dq; |
67 | const u8 *qmul; /* Q multiplier table */ |
68 | |
69 | p = (u8 *)ptrs[disks-2]; |
70 | q = (u8 *)ptrs[disks-1]; |
71 | |
72 | /* Compute syndrome with zero for the missing data page |
73 | Use the dead data page as temporary storage for delta q */ |
74 | dq = (u8 *)ptrs[faila]; |
75 | ptrs[faila] = (void *)raid6_empty_zero_page; |
76 | ptrs[disks-1] = dq; |
77 | |
78 | raid6_call.gen_syndrome(disks, bytes, ptrs); |
79 | |
80 | /* Restore pointer table */ |
81 | ptrs[faila] = dq; |
82 | ptrs[disks-1] = q; |
83 | |
84 | /* Now, pick the proper data tables */ |
85 | qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]]; |
86 | |
87 | /* Now do it... */ |
88 | while ( bytes-- ) { |
89 | *p++ ^= *dq = qmul[*q ^ *dq]; |
90 | q++; dq++; |
91 | } |
92 | } |
93 | |
94 | |
95 | const struct raid6_recov_calls raid6_recov_intx1 = { |
96 | .data2 = raid6_2data_recov_intx1, |
97 | .datap = raid6_datap_recov_intx1, |
98 | .valid = NULL, |
99 | .name = "intx1" , |
100 | .priority = 0, |
101 | }; |
102 | |
103 | #ifndef __KERNEL__ |
104 | /* Testing only */ |
105 | |
106 | /* Recover two failed blocks. */ |
107 | void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) |
108 | { |
109 | if ( faila > failb ) { |
110 | int tmp = faila; |
111 | faila = failb; |
112 | failb = tmp; |
113 | } |
114 | |
115 | if ( failb == disks-1 ) { |
116 | if ( faila == disks-2 ) { |
117 | /* P+Q failure. Just rebuild the syndrome. */ |
118 | raid6_call.gen_syndrome(disks, bytes, ptrs); |
119 | } else { |
120 | /* data+Q failure. Reconstruct data from P, |
121 | then rebuild syndrome. */ |
122 | /* NOT IMPLEMENTED - equivalent to RAID-5 */ |
123 | } |
124 | } else { |
125 | if ( failb == disks-2 ) { |
126 | /* data+P failure. */ |
127 | raid6_datap_recov(disks, bytes, faila, ptrs); |
128 | } else { |
129 | /* data+data failure. */ |
130 | raid6_2data_recov(disks, bytes, faila, failb, ptrs); |
131 | } |
132 | } |
133 | } |
134 | |
135 | #endif |
136 | |