1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
133 lines
3.4 KiB
C
133 lines
3.4 KiB
C
/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright 2002 H. Peter Anvin - All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, Inc., 53 Temple Place Ste 330,
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* Bostom MA 02111-1307, USA; either version 2 of the License, or
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* (at your option) any later version; incorporated herein by reference.
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*
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* ----------------------------------------------------------------------- */
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/*
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* raid6recov.c
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*
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* RAID-6 data recovery in dual failure mode. In single failure mode,
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* use the RAID-5 algorithm (or, in the case of Q failure, just reconstruct
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* the syndrome.)
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*/
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#include "raid6.h"
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/* Recover two failed data blocks. */
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void raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
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void **ptrs)
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{
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u8 *p, *q, *dp, *dq;
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u8 px, qx, db;
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const u8 *pbmul; /* P multiplier table for B data */
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const u8 *qmul; /* Q multiplier table (for both) */
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p = (u8 *)ptrs[disks-2];
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q = (u8 *)ptrs[disks-1];
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/* Compute syndrome with zero for the missing data pages
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Use the dead data pages as temporary storage for
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delta p and delta q */
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dp = (u8 *)ptrs[faila];
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ptrs[faila] = (void *)raid6_empty_zero_page;
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ptrs[disks-2] = dp;
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dq = (u8 *)ptrs[failb];
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ptrs[failb] = (void *)raid6_empty_zero_page;
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ptrs[disks-1] = dq;
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raid6_call.gen_syndrome(disks, bytes, ptrs);
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/* Restore pointer table */
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ptrs[faila] = dp;
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ptrs[failb] = dq;
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ptrs[disks-2] = p;
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ptrs[disks-1] = q;
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/* Now, pick the proper data tables */
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pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];
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qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];
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/* Now do it... */
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while ( bytes-- ) {
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px = *p ^ *dp;
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qx = qmul[*q ^ *dq];
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*dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */
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*dp++ = db ^ px; /* Reconstructed A */
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p++; q++;
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}
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}
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/* Recover failure of one data block plus the P block */
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void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs)
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{
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u8 *p, *q, *dq;
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const u8 *qmul; /* Q multiplier table */
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p = (u8 *)ptrs[disks-2];
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q = (u8 *)ptrs[disks-1];
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/* Compute syndrome with zero for the missing data page
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Use the dead data page as temporary storage for delta q */
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dq = (u8 *)ptrs[faila];
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ptrs[faila] = (void *)raid6_empty_zero_page;
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ptrs[disks-1] = dq;
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raid6_call.gen_syndrome(disks, bytes, ptrs);
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/* Restore pointer table */
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ptrs[faila] = dq;
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ptrs[disks-1] = q;
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/* Now, pick the proper data tables */
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qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];
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/* Now do it... */
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while ( bytes-- ) {
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*p++ ^= *dq = qmul[*q ^ *dq];
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q++; dq++;
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}
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}
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#ifndef __KERNEL__ /* Testing only */
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/* Recover two failed blocks. */
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void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs)
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{
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if ( faila > failb ) {
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int tmp = faila;
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faila = failb;
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failb = tmp;
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}
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if ( failb == disks-1 ) {
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if ( faila == disks-2 ) {
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/* P+Q failure. Just rebuild the syndrome. */
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raid6_call.gen_syndrome(disks, bytes, ptrs);
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} else {
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/* data+Q failure. Reconstruct data from P,
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then rebuild syndrome. */
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/* NOT IMPLEMENTED - equivalent to RAID-5 */
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}
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} else {
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if ( failb == disks-2 ) {
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/* data+P failure. */
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raid6_datap_recov(disks, bytes, faila, ptrs);
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} else {
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/* data+data failure. */
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raid6_2data_recov(disks, bytes, faila, failb, ptrs);
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}
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}
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}
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#endif
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