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Diffstat (limited to 'lib/raid6/recov.c')
| -rw-r--r-- | lib/raid6/recov.c | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/lib/raid6/recov.c b/lib/raid6/recov.c new file mode 100644 index 000000000000..2609f00e0d61 --- /dev/null +++ b/lib/raid6/recov.c @@ -0,0 +1,132 @@ +/* -*- 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. + * + * ----------------------------------------------------------------------- */ + +/* + * raid6recov.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 |