RAID/s390: provide raid6 recovery optimization

The XC instruction can be used to improve the speed of the raid6
recovery. The loops now operate on blocks of 256 bytes.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/include/linux/raid/pq.h b/include/linux/raid/pq.h
index c032a6a..395a4c6 100644 (file)
--- a/include/linux/raid/pq.h
+++ b/include/linux/raid/pq.h
@@ -116,6 +116,7 @@ struct raid6_recov_calls {
 extern const struct raid6_recov_calls raid6_recov_intx1;
 extern const struct raid6_recov_calls raid6_recov_ssse3;
 extern const struct raid6_recov_calls raid6_recov_avx2;
+extern const struct raid6_recov_calls raid6_recov_s390xc;
 
 extern const struct raid6_calls raid6_neonx1;
 extern const struct raid6_calls raid6_neonx2;

diff --git a/lib/raid6/Makefile b/lib/raid6/Makefile
index 667b960..29f503e 100644 (file)
--- a/lib/raid6/Makefile
+++ b/lib/raid6/Makefile
@@ -7,7 +7,7 @@ raid6_pq-$(CONFIG_X86) += recov_ssse3.o recov_avx2.o mmx.o sse1.o sse2.o avx2.o
 raid6_pq-$(CONFIG_ALTIVEC) += altivec1.o altivec2.o altivec4.o altivec8.o
 raid6_pq-$(CONFIG_KERNEL_MODE_NEON) += neon.o neon1.o neon2.o neon4.o neon8.o
 raid6_pq-$(CONFIG_TILEGX) += tilegx8.o
-raid6_pq-$(CONFIG_S390) += s390vx8.o
+raid6_pq-$(CONFIG_S390) += s390vx8.o recov_s390xc.o
 
 hostprogs-y    += mktables
 

diff --git a/lib/raid6/algos.c b/lib/raid6/algos.c
index e1923b6..592ff49 100644 (file)
--- a/lib/raid6/algos.c
+++ b/lib/raid6/algos.c
@@ -98,6 +98,9 @@ const struct raid6_recov_calls *const raid6_recov_algos[] = {
 #ifdef CONFIG_AS_SSSE3
        &raid6_recov_ssse3,
 #endif
+#ifdef CONFIG_S390
+       &raid6_recov_s390xc,
+#endif
        &raid6_recov_intx1,
        NULL
 };

diff --git a/lib/raid6/recov_s390xc.c b/lib/raid6/recov_s390xc.c
new file mode 100644 (file)
index 0000000..b042dac
--- /dev/null
+++ b/lib/raid6/recov_s390xc.c
@@ -0,0 +1,116 @@
+/*
+ * RAID-6 data recovery in dual failure mode based on the XC instruction.
+ *
+ * Copyright IBM Corp. 2016
+ * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+
+#include <linux/export.h>
+#include <linux/raid/pq.h>
+
+static inline void xor_block(u8 *p1, u8 *p2)
+{
+       typedef struct { u8 _[256]; } addrtype;
+
+       asm volatile(
+               "       xc      0(256,%[p1]),0(%[p2])\n"
+               : "+m" (*(addrtype *) p1) : "m" (*(addrtype *) p2),
+                 [p1] "a" (p1), [p2] "a" (p2) : "cc");
+}
+
+/* Recover two failed data blocks. */
+static void raid6_2data_recov_s390xc(int disks, size_t bytes, int faila,
+               int failb, void **ptrs)
+{
+       u8 *p, *q, *dp, *dq;
+       const u8 *pbmul;        /* P multiplier table for B data */
+       const u8 *qmul;         /* Q multiplier table (for both) */
+       int i;
+
+       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) {
+               xor_block(dp, p);
+               xor_block(dq, q);
+               for (i = 0; i < 256; i++)
+                       dq[i] = pbmul[dp[i]] ^ qmul[dq[i]];
+               xor_block(dp, dq);
+               p += 256;
+               q += 256;
+               dp += 256;
+               dq += 256;
+               bytes -= 256;
+       }
+}
+
+/* Recover failure of one data block plus the P block */
+static void raid6_datap_recov_s390xc(int disks, size_t bytes, int faila,
+               void **ptrs)
+{
+       u8 *p, *q, *dq;
+       const u8 *qmul;         /* Q multiplier table */
+       int i;
+
+       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) {
+               xor_block(dq, q);
+               for (i = 0; i < 256; i++)
+                       dq[i] = qmul[dq[i]];
+               xor_block(p, dq);
+               p += 256;
+               q += 256;
+               dq += 256;
+               bytes -= 256;
+       }
+}
+
+
+const struct raid6_recov_calls raid6_recov_s390xc = {
+       .data2 = raid6_2data_recov_s390xc,
+       .datap = raid6_datap_recov_s390xc,
+       .valid = NULL,
+       .name = "s390xc",
+       .priority = 1,
+};