LXR linux/lib/raid6/recov

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * RAID-6 data recovery in dual failure mode based on the XC instruction.
   4 *
   5 * Copyright IBM Corp. 2016
   6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
   7 */
   8
   9#include <linux/export.h>
  10#include <linux/raid/pq.h>
  11
  12static inline void xor_block(u8 *p1, u8 *p2)
  13{
  14        typedef struct { u8 _[256]; } addrtype;
  15
  16        asm volatile(
  17                "       xc      0(256,%[p1]),0(%[p2])\n"
  18                : "+m" (*(addrtype *) p1) : "m" (*(addrtype *) p2),
  19                  [p1] "a" (p1), [p2] "a" (p2) : "cc");
  20}
  21
  22/* Recover two failed data blocks. */
  23static void raid6_2data_recov_s390xc(int disks, size_t bytes, int faila,
  24                int failb, void **ptrs)
  25{
  26        u8 *p, *q, *dp, *dq;
  27        const u8 *pbmul;        /* P multiplier table for B data */
  28        const u8 *qmul;         /* Q multiplier table (for both) */
  29        int i;
  30
  31        p = (u8 *)ptrs[disks-2];
  32        q = (u8 *)ptrs[disks-1];
  33
  34        /* Compute syndrome with zero for the missing data pages
  35           Use the dead data pages as temporary storage for
  36           delta p and delta q */
  37        dp = (u8 *)ptrs[faila];
  38        ptrs[faila] = (void *)raid6_empty_zero_page;
  39        ptrs[disks-2] = dp;
  40        dq = (u8 *)ptrs[failb];
  41        ptrs[failb] = (void *)raid6_empty_zero_page;
  42        ptrs[disks-1] = dq;
  43
  44        raid6_call.gen_syndrome(disks, bytes, ptrs);
  45
  46        /* Restore pointer table */
  47        ptrs[faila]   = dp;
  48        ptrs[failb]   = dq;
  49        ptrs[disks-2] = p;
  50        ptrs[disks-1] = q;
  51
  52        /* Now, pick the proper data tables */
  53        pbmul = raid6_gfmul[raid6_gfexi[failb-faila]];
  54        qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]^raid6_gfexp[failb]]];
  55
  56        /* Now do it... */
  57        while (bytes) {
  58                xor_block(dp, p);
  59                xor_block(dq, q);
  60                for (i = 0; i < 256; i++)
  61                        dq[i] = pbmul[dp[i]] ^ qmul[dq[i]];
  62                xor_block(dp, dq);
  63                p += 256;
  64                q += 256;
  65                dp += 256;
  66                dq += 256;
  67                bytes -= 256;
  68        }
  69}
  70
  71/* Recover failure of one data block plus the P block */
  72static void raid6_datap_recov_s390xc(int disks, size_t bytes, int faila,
  73                void **ptrs)
  74{
  75        u8 *p, *q, *dq;
  76        const u8 *qmul;         /* Q multiplier table */
  77        int i;
  78
  79        p = (u8 *)ptrs[disks-2];
  80        q = (u8 *)ptrs[disks-1];
  81
  82        /* Compute syndrome with zero for the missing data page
  83           Use the dead data page as temporary storage for delta q */
  84        dq = (u8 *)ptrs[faila];
  85        ptrs[faila] = (void *)raid6_empty_zero_page;
  86        ptrs[disks-1] = dq;
  87
  88        raid6_call.gen_syndrome(disks, bytes, ptrs);
  89
  90        /* Restore pointer table */
  91        ptrs[faila]   = dq;
  92        ptrs[disks-1] = q;
  93
  94        /* Now, pick the proper data tables */
  95        qmul  = raid6_gfmul[raid6_gfinv[raid6_gfexp[faila]]];
  96
  97        /* Now do it... */
  98        while (bytes) {
  99                xor_block(dq, q);
 100                for (i = 0; i < 256; i++)
 101                        dq[i] = qmul[dq[i]];
 102                xor_block(p, dq);
 103                p += 256;
 104                q += 256;
 105                dq += 256;
 106                bytes -= 256;
 107        }
 108}
 109
 110
 111const struct raid6_recov_calls raid6_recov_s390xc = {
 112        .data2 = raid6_2data_recov_s390xc,
 113        .datap = raid6_datap_recov_s390xc,
 114        .valid = NULL,
 115        .name = "s390xc",
 116        .priority = 1,
 117};
 118