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. */
25static void raid6_2data_recov_intx1(int disks, size_t bytes, int faila,
26		int failb, 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
68/* Recover failure of one data block plus the P block */
69static void raid6_datap_recov_intx1(int disks, size_t bytes, int faila,
70		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
100
101const struct raid6_recov_calls raid6_recov_intx1 = {
102	.data2 = raid6_2data_recov_intx1,
103	.datap = raid6_datap_recov_intx1,
104	.valid = NULL,
105	.name = "intx1",
106	.priority = 0,
107};
108
109#ifndef __KERNEL__
110/* Testing only */
111
112/* Recover two failed blocks. */
113void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs)
114{
115	if ( faila > failb ) {
116		int tmp = faila;
117		faila = failb;
118		failb = tmp;
119	}
120
121	if ( failb == disks-1 ) {
122		if ( faila == disks-2 ) {
123			/* P+Q failure.  Just rebuild the syndrome. */
124			raid6_call.gen_syndrome(disks, bytes, ptrs);
125		} else {
126			/* data+Q failure.  Reconstruct data from P,
127			   then rebuild syndrome. */
128			/* NOT IMPLEMENTED - equivalent to RAID-5 */
129		}
130	} else {
131		if ( failb == disks-2 ) {
132			/* data+P failure. */
133			raid6_datap_recov(disks, bytes, faila, ptrs);
134		} else {
135			/* data+data failure. */
136			raid6_2data_recov(disks, bytes, faila, failb, ptrs);
137		}
138	}
139}
140
141#endif
142