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linux
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raid6
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recov.c
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/* -*- linux-c -*- ------------------------------------------------------- * * * Copyright 2002 H. Peter Anvin - All Rights Reserved * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, Inc., 53 Temple Place Ste 330, * Boston MA 02111-1307, USA; either version 2 of the License, or * (at your option) any later version; incorporated herein by reference. * * ----------------------------------------------------------------------- */ /* * raid6/recov.c * * RAID-6 data recovery in dual failure mode. In single failure mode, * use the RAID-5 algorithm (or, in the case of Q failure, just reconstruct * the syndrome.) */ #include <linux/raid/pq.h> /* Recover two failed data blocks. */ void raid6_2data_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) { u8 *p, *q, *dp, *dq; u8 px, qx, db; const u8 *pbmul; /* P multiplier table for B data */ const u8 *qmul; /* Q multiplier table (for both) */ p = (u8 *)ptrs[disks-2]; q = (u8 *)ptrs[disks-1]; /* Compute syndrome with zero for the missing data pages Use the dead data pages as temporary storage for delta p and delta q */ dp = (u8 *)ptrs[faila]; ptrs[faila] = (void *)raid6_empty_zero_page; ptrs[disks-2] = dp; dq = (u8 *)ptrs[failb]; ptrs[failb] = (void *)raid6_empty_zero_page; ptrs[disks-1] = dq; raid6_call.gen_syndrome(disks, bytes, ptrs); /* Restore pointer table */ ptrs[faila] = dp; ptrs[failb] = dq; ptrs[disks-2] = p; ptrs[disks-1] = q; /* Now, pick the proper data tables */ pbmul = raid6_gfmul[raid6_gfexi[failb-faila]]; qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]]; /* Now do it... */ while ( bytes-- ) { px = *p ^ *dp; qx = qmul[*q ^ *dq]; *dq++ = db = pbmul[px] ^ qx; /* Reconstructed B */ *dp++ = db ^ px; /* Reconstructed A */ p++; q++; } } EXPORT_SYMBOL_GPL(raid6_2data_recov); /* Recover failure of one data block plus the P block */ void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs) { u8 *p, *q, *dq; const u8 *qmul; /* Q multiplier table */ p = (u8 *)ptrs[disks-2]; q = (u8 *)ptrs[disks-1]; /* Compute syndrome with zero for the missing data page Use the dead data page as temporary storage for delta q */ dq = (u8 *)ptrs[faila]; ptrs[faila] = (void *)raid6_empty_zero_page; ptrs[disks-1] = dq; raid6_call.gen_syndrome(disks, bytes, ptrs); /* Restore pointer table */ ptrs[faila] = dq; ptrs[disks-1] = q; /* Now, pick the proper data tables */ qmul = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]]; /* Now do it... */ while ( bytes-- ) { *p++ ^= *dq = qmul[*q ^ *dq]; q++; dq++; } } EXPORT_SYMBOL_GPL(raid6_datap_recov); #ifndef __KERNEL__ /* Testing only */ /* Recover two failed blocks. */ void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs) { if ( faila > failb ) { int tmp = faila; faila = failb; failb = tmp; } if ( failb == disks-1 ) { if ( faila == disks-2 ) { /* P+Q failure. Just rebuild the syndrome. */ raid6_call.gen_syndrome(disks, bytes, ptrs); } else { /* data+Q failure. Reconstruct data from P, then rebuild syndrome. */ /* NOT IMPLEMENTED - equivalent to RAID-5 */ } } else { if ( failb == disks-2 ) { /* data+P failure. */ raid6_datap_recov(disks, bytes, faila, ptrs); } else { /* data+data failure. */ raid6_2data_recov(disks, bytes, faila, failb, ptrs); } } } #endif
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