1 files changed, 136 insertions, 0 deletions
diff --git a/lib/raid6/recov.c b/lib/raid6/recov.c
new file mode 100644
index 000000000..e49d519de
--- /dev/null
+++ b/lib/raid6/recov.c
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * 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/export.h>
+#include <linux/raid/pq.h>
+
+/* Recover two failed data blocks. */
+static void raid6_2data_recov_intx1(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++;
+	}
+}
+
+/* Recover failure of one data block plus the P block */
+static void raid6_datap_recov_intx1(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++;
+	}
+}
+
+
+const struct raid6_recov_calls raid6_recov_intx1 = {
+	.data2 = raid6_2data_recov_intx1,
+	.datap = raid6_datap_recov_intx1,
+	.valid = NULL,
+	.name = "intx1",
+	.priority = 0,
+};
+
+#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