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>

1 files changed, 116 insertions, 0 deletions

diff --git a/lib/raid6/recov_s390xc.c b/lib/raid6/recov_s390xc.c
new file mode 100644
index 000000000000..b042dac826cc
--- /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,
+};