[PATCH v2 02/19] btrfs-progs: raid56: Introduce tables for RAID6 recovery

From: Qu Wenruo <quwenruo@cn.fujitsu.com>
To: linux-btrfs@vger.kernel.org
Subject: [PATCH v2 02/19] btrfs-progs: raid56: Introduce tables for RAID6 recovery
Date: Mon, 26 Dec 2016 14:29:22 +0800	[thread overview]
Message-ID: <20161226062939.5841-3-quwenruo@cn.fujitsu.com> (raw)
In-Reply-To: <20161226062939.5841-1-quwenruo@cn.fujitsu.com>

Use kernel RAID6 galois tables for later RAID6 recovery.

Galois tables file, kernel-lib/tables.c is generated by user space
program, mktable.

Galois field tables declaration, in kernel-lib/raid56.h, is completely
copied from kernel.

The mktables.c is copied from kernel with minor header/macro
modification, to ensure the generated tables.c works well in
btrfs-progs.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 .gitignore            |   2 +
 Makefile.in           |  15 ++++-
 kernel-lib/mktables.c | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel-lib/raid56.h   |  12 ++++
 4 files changed, 174 insertions(+), 3 deletions(-)
 create mode 100644 kernel-lib/mktables.c

diff --git a/.gitignore b/.gitignore
index 98b3657b..554e8921 100644
--- a/.gitignore
+++ b/.gitignore
@@ -35,6 +35,8 @@ btrfs-select-super
 btrfs-calc-size
 btrfs-crc
 btrfstune
+mktables
+kernel-lib/tables.c
 libbtrfs.a
 libbtrfs.so
 libbtrfs.so.0
diff --git a/Makefile.in b/Makefile.in
index 6e009bff..fecaaa6a 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -98,7 +98,8 @@ objects = ctree.o disk-io.o kernel-lib/radix-tree.o extent-tree.o print-tree.o \
 	  extent-cache.o extent_io.o volumes.o utils.o repair.o \
 	  qgroup.o raid56.o free-space-cache.o kernel-lib/list_sort.o props.o \
 	  ulist.o qgroup-verify.o backref.o string-table.o task-utils.o \
-	  inode.o file.o find-root.o free-space-tree.o help.o send-dump.o
+	  inode.o file.o find-root.o free-space-tree.o help.o send-dump.o \
+	  kernel-lib/tables.o
 cmds_objects = cmds-subvolume.o cmds-filesystem.o cmds-device.o cmds-scrub.o \
 	       cmds-inspect.o cmds-balance.o cmds-send.o cmds-receive.o \
 	       cmds-quota.o cmds-qgroup.o cmds-replace.o cmds-check.o \
@@ -318,6 +319,14 @@ version.h: version.sh version.h.in configure.ac
 	@echo "    [SH]     $@"
 	$(Q)bash ./config.status --silent $@
 
+mktables: kernel-lib/mktables.c
+	@echo "    [CC]     $@"
+	$(Q)$(CC) $(CFLAGS) $< -o $@
+
+kernel-lib/tables.c: mktables
+	@echo "    [TABLE]  $@"
+	$(Q)./mktables > $@ || ($(RM) -f $@ && exit 1)
+	
 $(libs_shared): $(libbtrfs_objects) $(lib_links) send.h
 	@echo "    [LD]     $@"
 	$(Q)$(CC) $(CFLAGS) $(libbtrfs_objects) $(LDFLAGS) $(LIBBTRFS_LIBS) \
@@ -490,12 +499,12 @@ clean-all: clean clean-doc clean-gen
 clean: $(CLEANDIRS)
 	@echo "Cleaning"
 	$(Q)$(RM) -f -- $(progs) cscope.out *.o *.o.d \
-		kernel-lib/*.o kernel-lib/*.o.d \
+		kernel-lib/*.o kernel-lib/*.o.d kernel-lib/tables.c \
 		image/*.o image/*.o.d \
 		convert/*.o convert/*.o.d \
 		mkfs/*.o mkfs/*.o.d \
 	      dir-test ioctl-test quick-test library-test library-test-static \
-	      btrfs.static mkfs.btrfs.static \
+	      mktables btrfs.static mkfs.btrfs.static \
 	      $(check_defs) \
 	      $(libs) $(lib_links) \
 	      $(progs_static) $(progs_extra)
diff --git a/kernel-lib/mktables.c b/kernel-lib/mktables.c
new file mode 100644
index 00000000..85f621fe
--- /dev/null
+++ b/kernel-lib/mktables.c
@@ -0,0 +1,148 @@
+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002-2007 H. Peter Anvin - All Rights Reserved
+ *
+ *   This file is part of the Linux kernel, and is made available under
+ *   the terms of the GNU General Public License version 2 or (at your
+ *   option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * mktables.c
+ *
+ * Make RAID-6 tables.  This is a host user space program to be run at
+ * compile time.
+ */
+
+/*
+ * Btrfs-progs port, with following minor fixes:
+ * 1) Use "kerncompat.h"
+ * 2) Get rid of __KERNEL__ related macros
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <time.h>
+
+static uint8_t gfmul(uint8_t a, uint8_t b)
+{
+	uint8_t v = 0;
+
+	while (b) {
+		if (b & 1)
+			v ^= a;
+		a = (a << 1) ^ (a & 0x80 ? 0x1d : 0);
+		b >>= 1;
+	}
+
+	return v;
+}
+
+static uint8_t gfpow(uint8_t a, int b)
+{
+	uint8_t v = 1;
+
+	b %= 255;
+	if (b < 0)
+		b += 255;
+
+	while (b) {
+		if (b & 1)
+			v = gfmul(v, a);
+		a = gfmul(a, a);
+		b >>= 1;
+	}
+
+	return v;
+}
+
+int main(int argc, char *argv[])
+{
+	int i, j, k;
+	uint8_t v;
+	uint8_t exptbl[256], invtbl[256];
+
+	printf("#include \"kerncompat.h\"\n");
+
+	/* Compute multiplication table */
+	printf("\nconst u8  __attribute__((aligned(256)))\n"
+		"raid6_gfmul[256][256] =\n"
+		"{\n");
+	for (i = 0; i < 256; i++) {
+		printf("\t{\n");
+		for (j = 0; j < 256; j += 8) {
+			printf("\t\t");
+			for (k = 0; k < 8; k++)
+				printf("0x%02x,%c", gfmul(i, j + k),
+				       (k == 7) ? '\n' : ' ');
+		}
+		printf("\t},\n");
+	}
+	printf("};\n");
+
+	/* Compute vector multiplication table */
+	printf("\nconst u8  __attribute__((aligned(256)))\n"
+		"raid6_vgfmul[256][32] =\n"
+		"{\n");
+	for (i = 0; i < 256; i++) {
+		printf("\t{\n");
+		for (j = 0; j < 16; j += 8) {
+			printf("\t\t");
+			for (k = 0; k < 8; k++)
+				printf("0x%02x,%c", gfmul(i, j + k),
+				       (k == 7) ? '\n' : ' ');
+		}
+		for (j = 0; j < 16; j += 8) {
+			printf("\t\t");
+			for (k = 0; k < 8; k++)
+				printf("0x%02x,%c", gfmul(i, (j + k) << 4),
+				       (k == 7) ? '\n' : ' ');
+		}
+		printf("\t},\n");
+	}
+	printf("};\n");
+
+	/* Compute power-of-2 table (exponent) */
+	v = 1;
+	printf("\nconst u8 __attribute__((aligned(256)))\n"
+	       "raid6_gfexp[256] =\n" "{\n");
+	for (i = 0; i < 256; i += 8) {
+		printf("\t");
+		for (j = 0; j < 8; j++) {
+			exptbl[i + j] = v;
+			printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
+			v = gfmul(v, 2);
+			if (v == 1)
+				v = 0;	/* For entry 255, not a real entry */
+		}
+	}
+	printf("};\n");
+
+	/* Compute inverse table x^-1 == x^254 */
+	printf("\nconst u8 __attribute__((aligned(256)))\n"
+	       "raid6_gfinv[256] =\n" "{\n");
+	for (i = 0; i < 256; i += 8) {
+		printf("\t");
+		for (j = 0; j < 8; j++) {
+			invtbl[i + j] = v = gfpow(i + j, 254);
+			printf("0x%02x,%c", v, (j == 7) ? '\n' : ' ');
+		}
+	}
+	printf("};\n");
+
+	/* Compute inv(2^x + 1) (exponent-xor-inverse) table */
+	printf("\nconst u8 __attribute__((aligned(256)))\n"
+	       "raid6_gfexi[256] =\n" "{\n");
+	for (i = 0; i < 256; i += 8) {
+		printf("\t");
+		for (j = 0; j < 8; j++)
+			printf("0x%02x,%c", invtbl[exptbl[i + j] ^ 1],
+			       (j == 7) ? '\n' : ' ');
+	}
+	printf("};\n");
+
+	return 0;
+}
diff --git a/kernel-lib/raid56.h b/kernel-lib/raid56.h
index 7d4f4678..1bf2e01a 100644
--- a/kernel-lib/raid56.h
+++ b/kernel-lib/raid56.h
@@ -25,4 +25,16 @@
 
 void raid6_gen_syndrome(int disks, size_t bytes, void **ptrs);
 int raid5_gen_result(int nr_devs, size_t stripe_len, int dest, void **data);
+
+/*
+ * Headers synchronized from kernel include/linux/raid/pq.h
+ * No modification at all.
+ *
+ * Galois field tables.
+ */
+extern const u8 raid6_gfmul[256][256] __attribute__((aligned(256)));
+extern const u8 raid6_vgfmul[256][32] __attribute__((aligned(256)));
+extern const u8 raid6_gfexp[256]      __attribute__((aligned(256)));
+extern const u8 raid6_gfinv[256]      __attribute__((aligned(256)));
+extern const u8 raid6_gfexi[256]      __attribute__((aligned(256)));
 #endif
-- 
2.11.0



