[PATCH] RAID-6

From: "H. Peter Anvin" <hpa@zytor.com>

RAID6 implementation.  See Kconfig help for usage details.

The next release of `mdadm' has raid6 userspace support.

drivers/md/Kconfig

@@ -107,6 +107,39 @@ config MD_RAID5
 
 	  If unsure, say Y.
 
+config MD_RAID6
+	tristate "RAID-6 mode (EXPERIMENTAL)"
+	depends on BLK_DEV_MD && EXPERIMENTAL
+	---help---
+	  WARNING: RAID-6 is currently highly experimental.  If you
+	  use it, there is no guarantee whatsoever that it won't
+	  destroy your data, eat your disk drives, insult your mother,
+	  or re-appoint George W. Bush.
+
+	  A RAID-6 set of N drives with a capacity of C MB per drive
+	  provides the capacity of C * (N - 2) MB, and protects
+	  against a failure of any two drives. For a given sector
+	  (row) number, (N - 2) drives contain data sectors, and two
+	  drives contains two independent redundancy syndromes.  Like
+	  RAID-5, RAID-6 distributes the syndromes across the drives
+	  in one of the available parity distribution methods.
+
+	  RAID-6 currently requires a specially patched version of
+	  mdadm; the patch is available at:
+
+	  ftp://ftp.kernel.org/pub/linux/kernel/people/hpa/
+
+	  ... and the mdadm source code at ...
+
+	  ftp://ftp.kernel.org/pub/linux/utils/raid/mdadm/
+
+	  If you want to use such a RAID-6 set, say Y.  To compile
+	  this code as a module, choose M here: the module will be
+	  called raid6.
+
+
+	  If unsure, say N.
+
 config MD_MULTIPATH
 	tristate "Multipath I/O support"
 	depends on BLK_DEV_MD

drivers/md/Makefile

@@ -4,6 +4,11 @@
 
 dm-mod-objs	:= dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
 		   dm-ioctl.o
+raid6-objs	:= raid6main.o raid6algos.o raid6recov.o raid6tables.o \
+		   raid6int1.o raid6int2.o raid6int4.o \
+		   raid6int8.o raid6int16.o raid6int32.o \
+		   raid6mmx.o raid6sse1.o raid6sse2.o
+host-progs	:= mktables
 
 # Note: link order is important.  All raid personalities
 # and xor.o must come before md.o, as they each initialise 
@@ -14,6 +19,31 @@ obj-$(CONFIG_MD_LINEAR)		+= linear.o
 obj-$(CONFIG_MD_RAID0)		+= raid0.o
 obj-$(CONFIG_MD_RAID1)		+= raid1.o
 obj-$(CONFIG_MD_RAID5)		+= raid5.o xor.o
+obj-$(CONFIG_MD_RAID6)		+= raid6.o xor.o
 obj-$(CONFIG_MD_MULTIPATH)	+= multipath.o
 obj-$(CONFIG_BLK_DEV_MD)	+= md.o
 obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o
+
+# Files generated that shall be removed upon make clean
+clean-files := raid6int*.c raid6tables.c mktables
+
+$(obj)/raid6int1.c:   $(src)/raid6int.uc $(src)/unroll.pl
+	$(PERL) $(src)/unroll.pl 1 < $< > $@ || ( rm -f $@ && exit 1 )
+
+$(obj)/raid6int2.c:   $(src)/raid6int.uc $(src)/unroll.pl
+	$(PERL) $(src)/unroll.pl 2 < $< > $@ || ( rm -f $@ && exit 1 )
+
+$(obj)/raid6int4.c:   $(src)/raid6int.uc $(src)/unroll.pl
+	$(PERL) $(src)/unroll.pl 4 < $< > $@ || ( rm -f $@ && exit 1 )
+
+$(obj)/raid6int8.c:   $(src)/raid6int.uc $(src)/unroll.pl
+	$(PERL) $(src)/unroll.pl 8 < $< > $@ || ( rm -f $@ && exit 1 )
+
+$(obj)/raid6int16.c:  $(src)/raid6int.uc $(src)/unroll.pl
+	$(PERL) $(src)/unroll.pl 16 < $< > $@ || ( rm -f $@ && exit 1 )
+
+$(obj)/raid6int32.c:  $(src)/raid6int.uc $(src)/unroll.pl
+	$(PERL) $(src)/unroll.pl 32 < $< > $@ || ( rm -f $@ && exit 1 )
+
+$(obj)/raid6tables.c: $(obj)/mktables
+	$(obj)/mktables > $@ || ( rm -f $@ && exit 1 )

drivers/md/md.c

@@ -7,6 +7,7 @@
    Changes:
 
    - RAID-1/RAID-5 extensions by Miguel de Icaza, Gadi Oxman, Ingo Molnar
+   - RAID-6 extensions by H. Peter Anvin <hpa@zytor.com>
    - boot support for linear and striped mode by Harald Hoyer <HarryH@Royal.Net>
    - kerneld support by Boris Tobotras <boris@xtalk.msk.su>
    - kmod support by: Cyrus Durgin
@@ -1435,11 +1436,12 @@ static int analyze_sbs(mddev_t * mddev)
 		goto abort;
 	}
 
-	if ((mddev->recovery_cp != MaxSector) && ((mddev->level == 1) ||
-			(mddev->level == 4) || (mddev->level == 5)))
+	if ((mddev->recovery_cp != MaxSector) &&
+	    ((mddev->level == 1) ||
+	     ((mddev->level >= 4) && (mddev->level <= 6))))
 		printk(KERN_ERR "md: md%d: raid array is not clean"
-			" -- starting background reconstruction\n", 
-			mdidx(mddev));
+		       " -- starting background reconstruction\n",
+		       mdidx(mddev));
 
 	return 0;
 abort:
@@ -3014,7 +3016,9 @@ static struct file_operations md_seq_fops = {
 int register_md_personality(int pnum, mdk_personality_t *p)
 {
 	if (pnum >= MAX_PERSONALITY) {
-		MD_BUG();
+		printk(KERN_ERR
+		       "md: tried to install personality %s as nr %d, but max is %lu\n",
+		       p->name, pnum, MAX_PERSONALITY-1);
 		return -EINVAL;
 	}
 

drivers/md/mktables.c

+#ident "$Id: mktables.c,v 1.2 2002/12/12 22:41:27 hpa Exp $"
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, 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.
+ */
+
+#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 \"raid6.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, ", gfmul(i,j+k));
+      }
+      printf("\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, ", v);
+      v = gfmul(v,2);
+      if ( v == 1 ) v = 0;	/* For entry 255, not a real entry */
+    }
+    printf("\n");
+  }
+  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, ", v);
+    }
+    printf("\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, ", invtbl[exptbl[i+j]^1]);
+    }
+    printf("\n");
+  }
+  printf("};\n\n");
+
+  return 0;
+}

drivers/md/raid6.h

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2003 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+#ifndef LINUX_RAID_RAID6_H
+#define LINUX_RAID_RAID6_H
+
+#ifdef __KERNEL__
+
+/* Set to 1 to use kernel-wide empty_zero_page */
+#define RAID6_USE_EMPTY_ZERO_PAGE 0
+
+#include <linux/module.h>
+#include <linux/stddef.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/mempool.h>
+#include <linux/list.h>
+#include <linux/vmalloc.h>
+#include <linux/raid/md.h>
+#include <linux/raid/raid5.h>
+
+typedef raid5_conf_t raid6_conf_t; /* Same configuration */
+
+/* Additional compute_parity mode -- updates the parity w/o LOCKING */
+#define UPDATE_PARITY	4
+
+/* We need a pre-zeroed page... if we don't want to use the kernel-provided
+   one define it here */
+#if RAID6_USE_EMPTY_ZERO_PAGE
+# define raid6_empty_zero_page empty_zero_page
+#else
+extern const char raid6_empty_zero_page[PAGE_SIZE];
+#endif
+
+#else /* ! __KERNEL__ */
+/* Used for testing in user space */
+
+#include <stddef.h>
+#include <sys/types.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <sys/mman.h>
+
+typedef uint8_t  u8;
+typedef uint16_t u16;
+typedef uint32_t u32;
+typedef uint64_t u64;
+
+#ifndef PAGE_SIZE
+# define PAGE_SIZE 4096
+#endif
+extern const char raid6_empty_zero_page[PAGE_SIZE];
+
+#define __init
+#define __exit
+
+#define preempt_enable()
+#define preempt_disable()
+
+#endif /* __KERNEL__ */
+
+/* Change this from BITS_PER_LONG if there is something better... */
+#if BITS_PER_LONG == 64
+# define NBYTES(x) ((x) * 0x0101010101010101UL)
+# define NSIZE  8
+# define NSHIFT 3
+# define NSTRING "64"
+typedef u64 unative_t;
+#else
+# define NBYTES(x) ((x) * 0x01010101U)
+# define NSIZE  4
+# define NSHIFT 2
+# define NSTRING "32"
+typedef u32 unative_t;
+#endif
+
+/* Routine choices */
+struct raid6_calls {
+	void (*gen_syndrome)(int, size_t, void **);
+	int  (*valid)(void);	/* Returns 1 if this routine set is usable */
+	const char *name;	/* Name of this routine set */
+	int prefer;		/* Has special performance attribute */
+};
+
+/* Selected algorithm */
+extern struct raid6_calls raid6_call;
+
+/* Algorithm list */
+extern const struct raid6_calls * const raid6_algos[];
+int raid6_select_algo(void);
+
+/* Return values from chk_syndrome */
+#define RAID6_OK	0
+#define RAID6_P_BAD	1
+#define RAID6_Q_BAD	2
+#define RAID6_PQ_BAD	3
+
+/* Galois field tables */
+extern const u8 raid6_gfmul[256][256] __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)));
+
+/* Recovery routines */
+void raid6_2data_recov(int disks, size_t bytes, int faila, int failb, void **ptrs);
+void raid6_datap_recov(int disks, size_t bytes, int faila, void **ptrs);
+void raid6_dual_recov(int disks, size_t bytes, int faila, int failb, void **ptrs);
+
+/* Some definitions to allow code to be compiled for testing in userspace */
+#ifndef __KERNEL__
+
+# define jiffies	raid6_jiffies()
+# define printk 	printf
+# define GFP_KERNEL	0
+# define __get_free_pages(x,y)	((unsigned long)mmap(NULL, PAGE_SIZE << (y), PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0))
+# define free_pages(x,y)	munmap((void *)(x), (y)*PAGE_SIZE)
+
+static inline void cpu_relax(void)
+{
+	/* Nothing */
+}
+
+#undef  HZ
+#define HZ 1000
+static inline uint32_t raid6_jiffies(void)
+{
+	struct timeval tv;
+	gettimeofday(&tv, NULL);
+	return tv.tv_sec*1000 + tv.tv_usec/1000;
+}
+
+#endif /* ! __KERNEL__ */
+
+#endif /* LINUX_RAID_RAID6_H */

drivers/md/raid6algos.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * raid6algos.c
+ *
+ * Algorithm list and algorithm selection for RAID-6
+ */
+
+#include "raid6.h"
+#ifndef __KERNEL__
+#include <sys/mman.h>
+#endif
+
+struct raid6_calls raid6_call;
+
+/* Various routine sets */
+extern const struct raid6_calls raid6_intx1;
+extern const struct raid6_calls raid6_intx2;
+extern const struct raid6_calls raid6_intx4;
+extern const struct raid6_calls raid6_intx8;
+extern const struct raid6_calls raid6_intx16;
+extern const struct raid6_calls raid6_mmxx1;
+extern const struct raid6_calls raid6_mmxx2;
+extern const struct raid6_calls raid6_sse1x1;
+extern const struct raid6_calls raid6_sse1x2;
+extern const struct raid6_calls raid6_sse2x1;
+extern const struct raid6_calls raid6_sse2x2;
+extern const struct raid6_calls raid6_sse2x4;
+
+const struct raid6_calls * const raid6_algos[] = {
+	&raid6_intx1,
+	&raid6_intx2,
+	&raid6_intx4,
+	&raid6_intx8,
+#if defined(__ia64__)
+	&raid6_intx16,
+	&raid6_intx32,
+#endif
+#if defined(__i386__) || defined(__x86_64__)
+	&raid6_mmxx1,
+	&raid6_mmxx2,
+	&raid6_sse1x1,
+	&raid6_sse1x2,
+	&raid6_sse2x1,
+	&raid6_sse2x2,
+#endif
+#if defined(__x86_64__)
+	&raid6_sse2x4,
+#endif
+	NULL
+};
+
+#ifdef __KERNEL__
+#define RAID6_TIME_JIFFIES_LG2	4
+#else
+/* Need more time to be stable in userspace */
+#define RAID6_TIME_JIFFIES_LG2	9
+#endif
+
+/* Try to pick the best algorithm */
+/* This code uses the gfmul table as convenient data set to abuse */
+
+int __init raid6_select_algo(void)
+{
+	const struct raid6_calls * const * algo;
+	const struct raid6_calls * best;
+	char *syndromes;
+	void *dptrs[(65536/PAGE_SIZE)+2];
+	int i, disks;
+	unsigned long perf, bestperf;
+	int bestprefer;
+	unsigned long j0, j1;
+
+	disks = (65536/PAGE_SIZE)+2;
+	for ( i = 0 ; i < disks-2 ; i++ ) {
+		dptrs[i] = ((char *)raid6_gfmul) + PAGE_SIZE*i;
+	}
+
+	/* Normal code - use a 2-page allocation to avoid D$ conflict */
+	syndromes = (void *) __get_free_pages(GFP_KERNEL, 1);
+
+	if ( !syndromes ) {
+		printk("raid6: Yikes!  No memory available.\n");
+		return -ENOMEM;
+	}
+
+	dptrs[disks-2] = syndromes;
+	dptrs[disks-1] = syndromes + PAGE_SIZE;
+
+	bestperf = 0;  bestprefer = 0;  best = NULL;
+
+	for ( algo = raid6_algos ; *algo ; algo++ ) {
+		if ( !(*algo)->valid || (*algo)->valid() ) {
+			perf = 0;
+
+			preempt_disable();
+			j0 = jiffies;
+			while ( (j1 = jiffies) == j0 )
+				cpu_relax();
+			while ( (jiffies-j1) < (1 << RAID6_TIME_JIFFIES_LG2) ) {
+				(*algo)->gen_syndrome(disks, PAGE_SIZE, dptrs);
+				perf++;
+			}
+			preempt_enable();
+
+			if ( (*algo)->prefer > bestprefer ||
+			     ((*algo)->prefer == bestprefer &&
+			      perf > bestperf) ) {
+				best = *algo;
+				bestprefer = best->prefer;
+				bestperf = perf;
+			}
+			printk("raid6: %-8s %5ld MB/s\n", (*algo)->name,
+			       (perf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
+		}
+	}
+
+	if ( best )
+		printk("raid6: using algorithm %s (%ld MB/s)\n",
+		       best->name,
+		       (bestperf*HZ) >> (20-16+RAID6_TIME_JIFFIES_LG2));
+	else
+		printk("raid6: Yikes!  No algorithm found!\n");
+
+	raid6_call = *best;
+
+	free_pages((unsigned long)syndromes, 1);
+
+	return best ? 0 : -EINVAL;
+}

drivers/md/raid6int.uc

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * raid6int$#.c
+ *
+ * $#-way unrolled portable integer math RAID-6 instruction set
+ *
+ * This file is postprocessed using unroller.pl
+ */
+
+#include "raid6.h"
+
+/*
+ * IA-64 wants insane amounts of unrolling.  On other architectures that
+ * is just a waste of space.
+ */
+
+#if ($# <= 8) || defined(_ia64__)
+
+static void raid6_int$#_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+
+	unative_t wd$$, wq$$, wp$$, w1$$, w2$$;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	for ( d = 0 ; d < bytes ; d += NSIZE*$# ) {
+		wq$$ = wp$$ = *(unative_t *)&dptr[z0][d+$$*NSIZE];
+		for ( z = z0-1 ; z >= 0 ; z-- ) {
+			wd$$ = *(unative_t *)&dptr[z][d+$$*NSIZE];
+			wp$$ ^= wd$$;
+			w2$$ = wq$$ & NBYTES(0x80);
+			w1$$ = (wq$$ << 1) & NBYTES(0xfe);
+			w2$$ = (w2$$ << 1) - (w2$$ >> 7);
+			w2$$ &= NBYTES(0x1d);
+			w1$$ ^= w2$$;
+			wq$$ = w1$$ ^ wd$$;
+		}
+		*(unative_t *)&p[d+NSIZE*$$] = wp$$;
+		*(unative_t *)&q[d+NSIZE*$$] = wq$$;
+	}
+}
+
+const struct raid6_calls raid6_intx$# = {
+	raid6_int$#_gen_syndrome,
+	NULL,		/* always valid */
+	"int" NSTRING "x$#",
+	0
+};
+
+#endif

drivers/md/raid6main.c

+/*
+ * raid6main.c : Multiple Devices driver for Linux
+ *	   Copyright (C) 1996, 1997 Ingo Molnar, Miguel de Icaza, Gadi Oxman
+ *	   Copyright (C) 1999, 2000 Ingo Molnar
+ *	   Copyright (C) 2002, 2003 H. Peter Anvin
+ *
+ * RAID-6 management functions.  This code is derived from raid5.c.
+ * Last merge from raid5.c bkcvs version 1.79 (kernel 2.6.1).
+ *
+ * Thanks to Penguin Computing for making the RAID-6 development possible
+ * by donating a test server!
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * You should have received a copy of the GNU General Public License
+ * (for example /usr/src/linux/COPYING); if not, write to the Free
+ * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/highmem.h>
+#include <asm/bitops.h>
+#include <asm/atomic.h>
+#include "raid6.h"
+
+/*
+ * Stripe cache
+ */
+
+#define NR_STRIPES		256
+#define STRIPE_SIZE		PAGE_SIZE
+#define STRIPE_SHIFT		(PAGE_SHIFT - 9)
+#define STRIPE_SECTORS		(STRIPE_SIZE>>9)
+#define	IO_THRESHOLD		1
+#define HASH_PAGES		1
+#define HASH_PAGES_ORDER	0
+#define NR_HASH			(HASH_PAGES * PAGE_SIZE / sizeof(struct stripe_head *))
+#define HASH_MASK		(NR_HASH - 1)
+
+#define stripe_hash(conf, sect)	((conf)->stripe_hashtbl[((sect) >> STRIPE_SHIFT) & HASH_MASK])
+
+/* bio's attached to a stripe+device for I/O are linked together in bi_sector
+ * order without overlap.  There may be several bio's per stripe+device, and
+ * a bio could span several devices.
+ * When walking this list for a particular stripe+device, we must never proceed
+ * beyond a bio that extends past this device, as the next bio might no longer
+ * be valid.
+ * This macro is used to determine the 'next' bio in the list, given the sector
+ * of the current stripe+device
+ */
+#define r5_next_bio(bio, sect) ( ( bio->bi_sector + (bio->bi_size>>9) < sect + STRIPE_SECTORS) ? bio->bi_next : NULL)
+/*
+ * The following can be used to debug the driver
+ */
+#define RAID6_DEBUG	0	/* Extremely verbose printk */
+#define RAID6_PARANOIA	1	/* Check spinlocks */
+#define RAID6_DUMPSTATE 0	/* Include stripe cache state in /proc/mdstat */
+#if RAID6_PARANOIA && CONFIG_SMP
+# define CHECK_DEVLOCK() if (!spin_is_locked(&conf->device_lock)) BUG()
+#else
+# define CHECK_DEVLOCK()
+#endif
+
+#define PRINTK(x...) ((void)(RAID6_DEBUG && printk(KERN_DEBUG x)))
+#if RAID6_DEBUG
+#undef inline
+#undef __inline__
+#define inline
+#define __inline__
+#endif
+
+#if !RAID6_USE_EMPTY_ZERO_PAGE
+/* In .bss so it's zeroed */
+const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
+#endif
+
+static inline int raid6_next_disk(int disk, int raid_disks)
+{
+	disk++;
+	return (disk < raid_disks) ? disk : 0;
+}
+
+static void print_raid6_conf (raid6_conf_t *conf);
+
+static inline void __release_stripe(raid6_conf_t *conf, struct stripe_head *sh)
+{
+	if (atomic_dec_and_test(&sh->count)) {
+		if (!list_empty(&sh->lru))
+			BUG();
+		if (atomic_read(&conf->active_stripes)==0)
+			BUG();
+		if (test_bit(STRIPE_HANDLE, &sh->state)) {
+			if (test_bit(STRIPE_DELAYED, &sh->state))
+				list_add_tail(&sh->lru, &conf->delayed_list);
+			else
+				list_add_tail(&sh->lru, &conf->handle_list);
+			md_wakeup_thread(conf->mddev->thread);
+		} else {
+			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+				atomic_dec(&conf->preread_active_stripes);
+				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
+					md_wakeup_thread(conf->mddev->thread);
+			}
+			list_add_tail(&sh->lru, &conf->inactive_list);
+			atomic_dec(&conf->active_stripes);
+			if (!conf->inactive_blocked ||
+			    atomic_read(&conf->active_stripes) < (NR_STRIPES*3/4))
+				wake_up(&conf->wait_for_stripe);
+		}
+	}
+}
+static void release_stripe(struct stripe_head *sh)
+{
+	raid6_conf_t *conf = sh->raid_conf;
+	unsigned long flags;
+
+	spin_lock_irqsave(&conf->device_lock, flags);
+	__release_stripe(conf, sh);
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+}
+
+static void remove_hash(struct stripe_head *sh)
+{
+	PRINTK("remove_hash(), stripe %llu\n", (unsigned long long)sh->sector);
+
+	if (sh->hash_pprev) {
+		if (sh->hash_next)
+			sh->hash_next->hash_pprev = sh->hash_pprev;
+		*sh->hash_pprev = sh->hash_next;
+		sh->hash_pprev = NULL;
+	}
+}
+
+static __inline__ void insert_hash(raid6_conf_t *conf, struct stripe_head *sh)
+{
+	struct stripe_head **shp = &stripe_hash(conf, sh->sector);
+
+	PRINTK("insert_hash(), stripe %llu\n", (unsigned long long)sh->sector);
+
+	CHECK_DEVLOCK();
+	if ((sh->hash_next = *shp) != NULL)
+		(*shp)->hash_pprev = &sh->hash_next;
+	*shp = sh;
+	sh->hash_pprev = shp;
+}
+
+
+/* find an idle stripe, make sure it is unhashed, and return it. */
+static struct stripe_head *get_free_stripe(raid6_conf_t *conf)
+{
+	struct stripe_head *sh = NULL;
+	struct list_head *first;
+
+	CHECK_DEVLOCK();
+	if (list_empty(&conf->inactive_list))
+		goto out;
+	first = conf->inactive_list.next;
+	sh = list_entry(first, struct stripe_head, lru);
+	list_del_init(first);
+	remove_hash(sh);
+	atomic_inc(&conf->active_stripes);
+out:
+	return sh;
+}
+
+static void shrink_buffers(struct stripe_head *sh, int num)
+{
+	struct page *p;
+	int i;
+
+	for (i=0; i<num ; i++) {
+		p = sh->dev[i].page;
+		if (!p)
+			continue;
+		sh->dev[i].page = NULL;
+		page_cache_release(p);
+	}
+}
+
+static int grow_buffers(struct stripe_head *sh, int num)
+{
+	int i;
+
+	for (i=0; i<num; i++) {
+		struct page *page;
+
+		if (!(page = alloc_page(GFP_KERNEL))) {
+			return 1;
+		}
+		sh->dev[i].page = page;
+	}
+	return 0;
+}
+
+static void raid6_build_block (struct stripe_head *sh, int i);
+
+static inline void init_stripe(struct stripe_head *sh, unsigned long sector, int pd_idx)
+{
+	raid6_conf_t *conf = sh->raid_conf;
+	int disks = conf->raid_disks, i;
+
+	if (atomic_read(&sh->count) != 0)
+		BUG();
+	if (test_bit(STRIPE_HANDLE, &sh->state))
+		BUG();
+
+	CHECK_DEVLOCK();
+	PRINTK("init_stripe called, stripe %llu\n",
+		(unsigned long long)sh->sector);
+
+	remove_hash(sh);
+
+	sh->sector = sector;
+	sh->pd_idx = pd_idx;
+	sh->state = 0;
+
+	for (i=disks; i--; ) {
+		struct r5dev *dev = &sh->dev[i];
+
+		if (dev->toread || dev->towrite || dev->written ||
+		    test_bit(R5_LOCKED, &dev->flags)) {
+			PRINTK("sector=%llx i=%d %p %p %p %d\n",
+			       (unsigned long long)sh->sector, i, dev->toread,
+			       dev->towrite, dev->written,
+			       test_bit(R5_LOCKED, &dev->flags));
+			BUG();
+		}
+		dev->flags = 0;
+		raid6_build_block(sh, i);
+	}
+	insert_hash(conf, sh);
+}
+
+static struct stripe_head *__find_stripe(raid6_conf_t *conf, unsigned long sector)
+{
+	struct stripe_head *sh;
+
+	CHECK_DEVLOCK();
+	PRINTK("__find_stripe, sector %lu\n", sector);
+	for (sh = stripe_hash(conf, sector); sh; sh = sh->hash_next)
+		if (sh->sector == sector)
+			return sh;
+	PRINTK("__stripe %lu not in cache\n", sector);
+	return NULL;
+}
+
+static struct stripe_head *get_active_stripe(raid6_conf_t *conf, unsigned long sector,
+					     int pd_idx, int noblock)
+{
+	struct stripe_head *sh;
+
+	PRINTK("get_stripe, sector %lu\n", sector);
+
+	spin_lock_irq(&conf->device_lock);
+
+	do {
+		sh = __find_stripe(conf, sector);
+		if (!sh) {
+			if (!conf->inactive_blocked)
+				sh = get_free_stripe(conf);
+			if (noblock && sh == NULL)
+				break;
+			if (!sh) {
+				conf->inactive_blocked = 1;
+				wait_event_lock_irq(conf->wait_for_stripe,
+						    !list_empty(&conf->inactive_list) &&
+						    (atomic_read(&conf->active_stripes) < (NR_STRIPES *3/4)
+						     || !conf->inactive_blocked),
+						    conf->device_lock);
+				conf->inactive_blocked = 0;
+			} else
+				init_stripe(sh, sector, pd_idx);
+		} else {
+			if (atomic_read(&sh->count)) {
+				if (!list_empty(&sh->lru))
+					BUG();
+			} else {
+				if (!test_bit(STRIPE_HANDLE, &sh->state))
+					atomic_inc(&conf->active_stripes);
+				if (list_empty(&sh->lru))
+					BUG();
+				list_del_init(&sh->lru);
+			}
+		}
+	} while (sh == NULL);
+
+	if (sh)
+		atomic_inc(&sh->count);
+
+	spin_unlock_irq(&conf->device_lock);
+	return sh;
+}
+
+static int grow_stripes(raid6_conf_t *conf, int num)
+{
+	struct stripe_head *sh;
+	kmem_cache_t *sc;
+	int devs = conf->raid_disks;
+
+	sprintf(conf->cache_name, "md/raid6-%d", conf->mddev->__minor);
+
+	sc = kmem_cache_create(conf->cache_name,
+			       sizeof(struct stripe_head)+(devs-1)*sizeof(struct r5dev),
+			       0, 0, NULL, NULL);
+	if (!sc)
+		return 1;
+	conf->slab_cache = sc;
+	while (num--) {
+		sh = kmem_cache_alloc(sc, GFP_KERNEL);
+		if (!sh)
+			return 1;
+		memset(sh, 0, sizeof(*sh) + (devs-1)*sizeof(struct r5dev));
+		sh->raid_conf = conf;
+		sh->lock = SPIN_LOCK_UNLOCKED;
+
+		if (grow_buffers(sh, conf->raid_disks)) {
+			shrink_buffers(sh, conf->raid_disks);
+			kmem_cache_free(sc, sh);
+			return 1;
+		}
+		/* we just created an active stripe so... */
+		atomic_set(&sh->count, 1);
+		atomic_inc(&conf->active_stripes);
+		INIT_LIST_HEAD(&sh->lru);
+		release_stripe(sh);
+	}
+	return 0;
+}
+
+static void shrink_stripes(raid6_conf_t *conf)
+{
+	struct stripe_head *sh;
+
+	while (1) {
+		spin_lock_irq(&conf->device_lock);
+		sh = get_free_stripe(conf);
+		spin_unlock_irq(&conf->device_lock);
+		if (!sh)
+			break;
+		if (atomic_read(&sh->count))
+			BUG();
+		shrink_buffers(sh, conf->raid_disks);
+		kmem_cache_free(conf->slab_cache, sh);
+		atomic_dec(&conf->active_stripes);
+	}
+	kmem_cache_destroy(conf->slab_cache);
+	conf->slab_cache = NULL;
+}
+
+static int raid6_end_read_request (struct bio * bi, unsigned int bytes_done,
+				   int error)
+{
+ 	struct stripe_head *sh = bi->bi_private;
+	raid6_conf_t *conf = sh->raid_conf;
+	int disks = conf->raid_disks, i;
+	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
+
+	if (bi->bi_size)
+		return 1;
+
+	for (i=0 ; i<disks; i++)
+		if (bi == &sh->dev[i].req)
+			break;
+
+	PRINTK("end_read_request %llu/%d, count: %d, uptodate %d.\n",
+		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
+		uptodate);
+	if (i == disks) {
+		BUG();
+		return 0;
+	}
+
+	if (uptodate) {
+#if 0
+		struct bio *bio;
+		unsigned long flags;
+		spin_lock_irqsave(&conf->device_lock, flags);
+		/* we can return a buffer if we bypassed the cache or
+		 * if the top buffer is not in highmem.  If there are
+		 * multiple buffers, leave the extra work to
+		 * handle_stripe
+		 */
+		buffer = sh->bh_read[i];
+		if (buffer &&
+		    (!PageHighMem(buffer->b_page)
+		     || buffer->b_page == bh->b_page )
+			) {
+			sh->bh_read[i] = buffer->b_reqnext;
+			buffer->b_reqnext = NULL;
+		} else
+			buffer = NULL;
+		spin_unlock_irqrestore(&conf->device_lock, flags);
+		if (sh->bh_page[i]==bh->b_page)
+			set_buffer_uptodate(bh);
+		if (buffer) {
+			if (buffer->b_page != bh->b_page)
+				memcpy(buffer->b_data, bh->b_data, bh->b_size);
+			buffer->b_end_io(buffer, 1);
+		}
+#else
+		set_bit(R5_UPTODATE, &sh->dev[i].flags);
+#endif
+	} else {
+		md_error(conf->mddev, conf->disks[i].rdev);
+		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
+	}
+	atomic_dec(&conf->disks[i].rdev->nr_pending);
+#if 0
+	/* must restore b_page before unlocking buffer... */
+	if (sh->bh_page[i] != bh->b_page) {
+		bh->b_page = sh->bh_page[i];
+		bh->b_data = page_address(bh->b_page);
+		clear_buffer_uptodate(bh);
+	}
+#endif
+	clear_bit(R5_LOCKED, &sh->dev[i].flags);
+	set_bit(STRIPE_HANDLE, &sh->state);
+	release_stripe(sh);
+	return 0;
+}
+
+static int raid6_end_write_request (struct bio *bi, unsigned int bytes_done,
+				    int error)
+{
+ 	struct stripe_head *sh = bi->bi_private;
+	raid6_conf_t *conf = sh->raid_conf;
+	int disks = conf->raid_disks, i;
+	unsigned long flags;
+	int uptodate = test_bit(BIO_UPTODATE, &bi->bi_flags);
+
+	if (bi->bi_size)
+		return 1;
+
+	for (i=0 ; i<disks; i++)
+		if (bi == &sh->dev[i].req)
+			break;
+
+	PRINTK("end_write_request %llu/%d, count %d, uptodate: %d.\n",
+		(unsigned long long)sh->sector, i, atomic_read(&sh->count),
+		uptodate);
+	if (i == disks) {
+		BUG();
+		return 0;
+	}
+
+	spin_lock_irqsave(&conf->device_lock, flags);
+	if (!uptodate)
+		md_error(conf->mddev, conf->disks[i].rdev);
+
+	atomic_dec(&conf->disks[i].rdev->nr_pending);
+
+	clear_bit(R5_LOCKED, &sh->dev[i].flags);
+	set_bit(STRIPE_HANDLE, &sh->state);
+	__release_stripe(conf, sh);
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+	return 0;
+}
+
+
+static sector_t compute_blocknr(struct stripe_head *sh, int i);
+
+static void raid6_build_block (struct stripe_head *sh, int i)
+{
+	struct r5dev *dev = &sh->dev[i];
+	int pd_idx = sh->pd_idx;
+	int qd_idx = raid6_next_disk(pd_idx, sh->raid_conf->raid_disks);
+
+	bio_init(&dev->req);
+	dev->req.bi_io_vec = &dev->vec;
+	dev->req.bi_vcnt++;
+	dev->vec.bv_page = dev->page;
+	dev->vec.bv_len = STRIPE_SIZE;
+	dev->vec.bv_offset = 0;
+
+	dev->req.bi_sector = sh->sector;
+	dev->req.bi_private = sh;
+
+	dev->flags = 0;
+	if (i != pd_idx && i != qd_idx)
+		dev->sector = compute_blocknr(sh, i);
+}
+
+static void error(mddev_t *mddev, mdk_rdev_t *rdev)
+{
+	char b[BDEVNAME_SIZE];
+	raid6_conf_t *conf = (raid6_conf_t *) mddev->private;
+	PRINTK("raid6: error called\n");
+
+	if (!rdev->faulty) {
+		mddev->sb_dirty = 1;
+		conf->working_disks--;
+		if (rdev->in_sync) {
+			mddev->degraded++;
+			conf->failed_disks++;
+			rdev->in_sync = 0;
+			/*
+			 * if recovery was running, make sure it aborts.
+			 */
+			set_bit(MD_RECOVERY_ERR, &mddev->recovery);
+		}
+		rdev->faulty = 1;
+		printk (KERN_ALERT
+			"raid6: Disk failure on %s, disabling device."
+			" Operation continuing on %d devices\n",
+			bdevname(rdev->bdev,b), conf->working_disks);
+	}
+}
+
+/*
+ * Input: a 'big' sector number,
+ * Output: index of the data and parity disk, and the sector # in them.
+ */
+static unsigned long raid6_compute_sector(sector_t r_sector, unsigned int raid_disks,
+			unsigned int data_disks, unsigned int * dd_idx,
+			unsigned int * pd_idx, raid6_conf_t *conf)
+{
+	long stripe;
+	unsigned long chunk_number;
+	unsigned int chunk_offset;
+	sector_t new_sector;
+	int sectors_per_chunk = conf->chunk_size >> 9;
+
+	/* First compute the information on this sector */
+
+	/*
+	 * Compute the chunk number and the sector offset inside the chunk
+	 */
+	chunk_offset = sector_div(r_sector, sectors_per_chunk);
+	chunk_number = r_sector;
+	if ( r_sector != chunk_number ) {
+		printk(KERN_CRIT "raid6: ERROR: r_sector = %llu, chunk_number = %lu\n",
+		       (unsigned long long)r_sector, (unsigned long)chunk_number);
+		BUG();
+	}
+
+	/*
+	 * Compute the stripe number
+	 */
+	stripe = chunk_number / data_disks;
+
+	/*
+	 * Compute the data disk and parity disk indexes inside the stripe
+	 */
+	*dd_idx = chunk_number % data_disks;
+
+	/*
+	 * Select the parity disk based on the user selected algorithm.
+	 */
+
+	/**** FIX THIS ****/
+	switch (conf->algorithm) {
+	case ALGORITHM_LEFT_ASYMMETRIC:
+		*pd_idx = raid_disks - 1 - (stripe % raid_disks);
+		if (*pd_idx == raid_disks-1)
+		  	(*dd_idx)++; 	/* Q D D D P */
+		else if (*dd_idx >= *pd_idx)
+		  	(*dd_idx) += 2; /* D D P Q D */
+		break;
+	case ALGORITHM_RIGHT_ASYMMETRIC:
+		*pd_idx = stripe % raid_disks;
+		if (*pd_idx == raid_disks-1)
+		  	(*dd_idx)++; 	/* Q D D D P */
+		else if (*dd_idx >= *pd_idx)
+		  	(*dd_idx) += 2; /* D D P Q D */
+		break;
+	case ALGORITHM_LEFT_SYMMETRIC:
+		*pd_idx = raid_disks - 1 - (stripe % raid_disks);
+		*dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
+		break;
+	case ALGORITHM_RIGHT_SYMMETRIC:
+		*pd_idx = stripe % raid_disks;
+		*dd_idx = (*pd_idx + 2 + *dd_idx) % raid_disks;
+		break;
+	default:
+		printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
+			conf->algorithm);
+	}
+
+	PRINTK("raid6: chunk_number = %lu, pd_idx = %u, dd_idx = %u\n",
+	       chunk_number, *pd_idx, *dd_idx);
+
+	/*
+	 * Finally, compute the new sector number
+	 */
+	new_sector = stripe * sectors_per_chunk + chunk_offset;
+	return new_sector;
+}
+
+
+static sector_t compute_blocknr(struct stripe_head *sh, int i)
+{
+	raid6_conf_t *conf = sh->raid_conf;
+	int raid_disks = conf->raid_disks, data_disks = raid_disks - 2;
+	sector_t new_sector = sh->sector, check;
+	int sectors_per_chunk = conf->chunk_size >> 9;
+	long stripe;
+	int chunk_offset;
+	int chunk_number, dummy1, dummy2, dd_idx = i;
+	sector_t r_sector;
+	int i0 = i;
+
+	chunk_offset = sector_div(new_sector, sectors_per_chunk);
+	stripe = new_sector;
+	if ( new_sector != stripe ) {
+		printk(KERN_CRIT "raid6: ERROR: new_sector = %llu, stripe = %lu\n",
+		       (unsigned long long)new_sector, (unsigned long)stripe);
+		BUG();
+	}
+
+	switch (conf->algorithm) {
+		case ALGORITHM_LEFT_ASYMMETRIC:
+		case ALGORITHM_RIGHT_ASYMMETRIC:
+		  	if (sh->pd_idx == raid_disks-1)
+				i--; 	/* Q D D D P */
+			else if (i > sh->pd_idx)
+				i -= 2; /* D D P Q D */
+			break;
+		case ALGORITHM_LEFT_SYMMETRIC:
+		case ALGORITHM_RIGHT_SYMMETRIC:
+			if (sh->pd_idx == raid_disks-1)
+				i--; /* Q D D D P */
+			else {
+				/* D D P Q D */
+				if (i < sh->pd_idx)
+					i += raid_disks;
+				i -= (sh->pd_idx + 2);
+			}
+			break;
+		default:
+			printk (KERN_CRIT "raid6: unsupported algorithm %d\n",
+				conf->algorithm);
+	}
+
+	PRINTK("raid6: compute_blocknr: pd_idx = %u, i0 = %u, i = %u\n", sh->pd_idx, i0, i);
+
+	chunk_number = stripe * data_disks + i;
+	r_sector = (sector_t)chunk_number * sectors_per_chunk + chunk_offset;
+
+	check = raid6_compute_sector (r_sector, raid_disks, data_disks, &dummy1, &dummy2, conf);
+	if (check != sh->sector || dummy1 != dd_idx || dummy2 != sh->pd_idx) {
+		printk(KERN_CRIT "raid6: compute_blocknr: map not correct\n");
+		return 0;
+	}
+	return r_sector;
+}
+
+
+
+/*
+ * Copy data between a page in the stripe cache, and one or more bion
+ * The page could align with the middle of the bio, or there could be
+ * several bion, each with several bio_vecs, which cover part of the page
+ * Multiple bion are linked together on bi_next.  There may be extras
+ * at the end of this list.  We ignore them.
+ */
+static void copy_data(int frombio, struct bio *bio,
+		     struct page *page,
+		     sector_t sector)
+{
+	char *pa = page_address(page);
+	struct bio_vec *bvl;
+	int i;
+
+	for (;bio && bio->bi_sector < sector+STRIPE_SECTORS;
+	      bio = r5_next_bio(bio, sector) ) {
+		int page_offset;
+		if (bio->bi_sector >= sector)
+			page_offset = (signed)(bio->bi_sector - sector) * 512;
+		else
+			page_offset = (signed)(sector - bio->bi_sector) * -512;
+		bio_for_each_segment(bvl, bio, i) {
+			int len = bio_iovec_idx(bio,i)->bv_len;
+			int clen;
+			int b_offset = 0;
+
+			if (page_offset < 0) {
+				b_offset = -page_offset;
+				page_offset += b_offset;
+				len -= b_offset;
+			}
+
+			if (len > 0 && page_offset + len > STRIPE_SIZE)
+				clen = STRIPE_SIZE - page_offset;
+			else clen = len;
+
+			if (clen > 0) {
+				char *ba = __bio_kmap_atomic(bio, i, KM_USER0);
+				if (frombio)
+					memcpy(pa+page_offset, ba+b_offset, clen);
+				else
+					memcpy(ba+b_offset, pa+page_offset, clen);
+				__bio_kunmap_atomic(ba, KM_USER0);
+			}
+			if (clen < len) /* hit end of page */
+				break;
+			page_offset +=  len;
+		}
+	}
+}
+
+#define check_xor() 	do { 						\
+			   if (count == MAX_XOR_BLOCKS) {		\
+				xor_block(count, STRIPE_SIZE, ptr);	\
+				count = 1;				\
+			   }						\
+			} while(0)
+
+/* Compute P and Q syndromes */
+static void compute_parity(struct stripe_head *sh, int method)
+{
+	raid6_conf_t *conf = sh->raid_conf;
+	int i, pd_idx = sh->pd_idx, qd_idx, d0_idx, disks = conf->raid_disks, count;
+	struct bio *chosen;
+	/**** FIX THIS: This could be very bad if disks is close to 256 ****/
+	void *ptrs[disks];
+
+	qd_idx = raid6_next_disk(pd_idx, disks);
+	d0_idx = raid6_next_disk(qd_idx, disks);
+
+	PRINTK("compute_parity, stripe %llu, method %d\n",
+		(unsigned long long)sh->sector, method);
+
+	switch(method) {
+	case READ_MODIFY_WRITE:
+		BUG();		/* READ_MODIFY_WRITE N/A for RAID-6 */
+	case RECONSTRUCT_WRITE:
+	case UPDATE_PARITY:	/* Is this right? */
+		for (i= disks; i-- ;)
+			if ( i != pd_idx && i != qd_idx && sh->dev[i].towrite ) {
+				chosen = sh->dev[i].towrite;
+				sh->dev[i].towrite = NULL;
+				if (sh->dev[i].written) BUG();
+				sh->dev[i].written = chosen;
+			}
+		break;
+	case CHECK_PARITY:
+		BUG();		/* Not implemented yet */
+	}
+
+	for (i = disks; i--;)
+		if (sh->dev[i].written) {
+			sector_t sector = sh->dev[i].sector;
+			struct bio *wbi = sh->dev[i].written;
+			while (wbi && wbi->bi_sector < sector + STRIPE_SECTORS) {
+				copy_data(1, wbi, sh->dev[i].page, sector);
+				wbi = r5_next_bio(wbi, sector);
+			}
+
+			set_bit(R5_LOCKED, &sh->dev[i].flags);
+			set_bit(R5_UPTODATE, &sh->dev[i].flags);
+		}
+
+//	switch(method) {
+//	case RECONSTRUCT_WRITE:
+//	case CHECK_PARITY:
+//	case UPDATE_PARITY:
+		/* Note that unlike RAID-5, the ordering of the disks matters greatly. */
+		/* FIX: Is this ordering of drives even remotely optimal? */
+		count = 0;
+		i = d0_idx;
+		do {
+			ptrs[count++] = page_address(sh->dev[i].page);
+
+			i = raid6_next_disk(i, disks);
+		} while ( i != d0_idx );
+//		break;
+//	}
+
+	raid6_call.gen_syndrome(disks, STRIPE_SIZE, ptrs);
+
+	switch(method) {
+	case RECONSTRUCT_WRITE:
+		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+		set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
+		set_bit(R5_LOCKED,   &sh->dev[pd_idx].flags);
+		set_bit(R5_LOCKED,   &sh->dev[qd_idx].flags);
+		break;
+	case UPDATE_PARITY:
+		set_bit(R5_UPTODATE, &sh->dev[pd_idx].flags);
+		set_bit(R5_UPTODATE, &sh->dev[qd_idx].flags);
+		break;
+	}
+}
+
+/* Compute one missing block */
+static void compute_block_1(struct stripe_head *sh, int dd_idx)
+{
+	raid6_conf_t *conf = sh->raid_conf;
+	int i, count, disks = conf->raid_disks;
+	void *ptr[MAX_XOR_BLOCKS], *p;
+	int pd_idx = sh->pd_idx;
+	int qd_idx = raid6_next_disk(pd_idx, disks);
+
+	PRINTK("compute_block_1, stripe %llu, idx %d\n",
+		(unsigned long long)sh->sector, dd_idx);
+
+	if ( dd_idx == qd_idx ) {
+		/* We're actually computing the Q drive */
+		compute_parity(sh, UPDATE_PARITY);
+	} else {
+		ptr[0] = page_address(sh->dev[dd_idx].page);
+		memset(ptr[0], 0, STRIPE_SIZE);
+		count = 1;
+		for (i = disks ; i--; ) {
+			if (i == dd_idx || i == qd_idx)
+				continue;
+			p = page_address(sh->dev[i].page);
+			if (test_bit(R5_UPTODATE, &sh->dev[i].flags))
+				ptr[count++] = p;
+			else
+				PRINTK("compute_block() %d, stripe %llu, %d"
+				       " not present\n", dd_idx,
+				       (unsigned long long)sh->sector, i);
+
+			check_xor();
+		}
+		if (count != 1)
+			xor_block(count, STRIPE_SIZE, ptr);
+		set_bit(R5_UPTODATE, &sh->dev[dd_idx].flags);
+	}
+}
+
+/* Compute two missing blocks */
+static void compute_block_2(struct stripe_head *sh, int dd_idx1, int dd_idx2)
+{
+	raid6_conf_t *conf = sh->raid_conf;
+	int i, count, disks = conf->raid_disks;
+	int pd_idx = sh->pd_idx;
+	int qd_idx = raid6_next_disk(pd_idx, disks);
+	int d0_idx = raid6_next_disk(qd_idx, disks);
+	int faila, failb;
+
+	/* faila and failb are disk numbers relative to d0_idx */
+	/* pd_idx become disks-2 and qd_idx become disks-1 */
+	faila = (dd_idx1 < d0_idx) ? dd_idx1+(disks-d0_idx) : dd_idx1-d0_idx;
+	failb = (dd_idx2 < d0_idx) ? dd_idx2+(disks-d0_idx) : dd_idx2-d0_idx;
+
+	BUG_ON(faila == failb);
+	if ( failb < faila ) { int tmp = faila; faila = failb; failb = tmp; }
+
+	PRINTK("compute_block_2, stripe %llu, idx %d,%d (%d,%d)\n",
+	       (unsigned long long)sh->sector, dd_idx1, dd_idx2, faila, failb);
+
+	if ( failb == disks-1 ) {
+		/* Q disk is one of the missing disks */
+		if ( faila == disks-2 ) {
+			/* Missing P+Q, just recompute */
+			compute_parity(sh, UPDATE_PARITY);
+			return;
+		} else {
+			/* We're missing D+Q; recompute D from P */
+			compute_block_1(sh, (dd_idx1 == qd_idx) ? dd_idx2 : dd_idx1);
+			compute_parity(sh, UPDATE_PARITY); /* Is this necessary? */
+			return;
+		}
+	}
+
+	/* We're missing D+P or D+D; build pointer table */
+	{
+		/**** FIX THIS: This could be very bad if disks is close to 256 ****/
+		void *ptrs[disks];
+
+		count = 0;
+		i = d0_idx;
+		do {
+			ptrs[count++] = page_address(sh->dev[i].page);
+			i = raid6_next_disk(i, disks);
+		} while ( i != d0_idx );
+
+		if ( failb == disks-2 ) {
+			/* We're missing D+P. */
+			raid6_datap_recov(disks, STRIPE_SIZE, faila, ptrs);
+		} else {
+			/* We're missing D+D. */
+			raid6_2data_recov(disks, STRIPE_SIZE, faila, failb, ptrs);
+		}
+
+		/* Both the above update both missing blocks */
+		set_bit(R5_UPTODATE, &sh->dev[dd_idx1].flags);
+		set_bit(R5_UPTODATE, &sh->dev[dd_idx2].flags);
+	}
+}
+
+
+/*
+ * Each stripe/dev can have one or more bion attached.
+ * toread/towrite point to the first in a chain.
+ * The bi_next chain must be in order.
+ */
+static void add_stripe_bio (struct stripe_head *sh, struct bio *bi, int dd_idx, int forwrite)
+{
+	struct bio **bip;
+	raid6_conf_t *conf = sh->raid_conf;
+
+	PRINTK("adding bh b#%llu to stripe s#%llu\n",
+		(unsigned long long)bi->bi_sector,
+		(unsigned long long)sh->sector);
+
+
+	spin_lock(&sh->lock);
+	spin_lock_irq(&conf->device_lock);
+	if (forwrite)
+		bip = &sh->dev[dd_idx].towrite;
+	else
+		bip = &sh->dev[dd_idx].toread;
+	while (*bip && (*bip)->bi_sector < bi->bi_sector) {
+		BUG_ON((*bip)->bi_sector + ((*bip)->bi_size >> 9) > bi->bi_sector);
+		bip = & (*bip)->bi_next;
+	}
+/* FIXME do I need to worry about overlapping bion */
+	if (*bip && bi->bi_next && (*bip) != bi->bi_next)
+		BUG();
+	if (*bip)
+		bi->bi_next = *bip;
+	*bip = bi;
+	bi->bi_phys_segments ++;
+	spin_unlock_irq(&conf->device_lock);
+	spin_unlock(&sh->lock);
+
+	PRINTK("added bi b#%llu to stripe s#%llu, disk %d.\n",
+		(unsigned long long)bi->bi_sector,
+		(unsigned long long)sh->sector, dd_idx);
+
+	if (forwrite) {
+		/* check if page is coverred */
+		sector_t sector = sh->dev[dd_idx].sector;
+		for (bi=sh->dev[dd_idx].towrite;
+		     sector < sh->dev[dd_idx].sector + STRIPE_SECTORS &&
+			     bi && bi->bi_sector <= sector;
+		     bi = r5_next_bio(bi, sh->dev[dd_idx].sector)) {
+			if (bi->bi_sector + (bi->bi_size>>9) >= sector)
+				sector = bi->bi_sector + (bi->bi_size>>9);
+		}
+		if (sector >= sh->dev[dd_idx].sector + STRIPE_SECTORS)
+			set_bit(R5_OVERWRITE, &sh->dev[dd_idx].flags);
+	}
+}
+
+
+/*
+ * handle_stripe - do things to a stripe.
+ *
+ * We lock the stripe and then examine the state of various bits
+ * to see what needs to be done.
+ * Possible results:
+ *    return some read request which now have data
+ *    return some write requests which are safely on disc
+ *    schedule a read on some buffers
+ *    schedule a write of some buffers
+ *    return confirmation of parity correctness
+ *
+ * Parity calculations are done inside the stripe lock
+ * buffers are taken off read_list or write_list, and bh_cache buffers
+ * get BH_Lock set before the stripe lock is released.
+ *
+ */
+
+static void handle_stripe(struct stripe_head *sh)
+{
+	raid6_conf_t *conf = sh->raid_conf;
+	int disks = conf->raid_disks;
+	struct bio *return_bi= NULL;
+	struct bio *bi;
+	int i;
+	int syncing;
+	int locked=0, uptodate=0, to_read=0, to_write=0, failed=0, written=0;
+	int non_overwrite = 0;
+	int failed_num[2] = {0, 0};
+	struct r5dev *dev, *pdev, *qdev;
+	int pd_idx = sh->pd_idx;
+	int qd_idx = raid6_next_disk(pd_idx, disks);
+	int p_failed, q_failed;
+
+	PRINTK("handling stripe %llu, state=%#lx cnt=%d, pd_idx=%d, qd_idx=%d\n",
+	       (unsigned long long)sh->sector, sh->state, atomic_read(&sh->count),
+	       pd_idx, qd_idx);
+
+	spin_lock(&sh->lock);
+	clear_bit(STRIPE_HANDLE, &sh->state);
+	clear_bit(STRIPE_DELAYED, &sh->state);
+
+	syncing = test_bit(STRIPE_SYNCING, &sh->state);
+	/* Now to look around and see what can be done */
+
+	for (i=disks; i--; ) {
+		mdk_rdev_t *rdev;
+		dev = &sh->dev[i];
+		clear_bit(R5_Insync, &dev->flags);
+		clear_bit(R5_Syncio, &dev->flags);
+
+		PRINTK("check %d: state 0x%lx read %p write %p written %p\n",
+			i, dev->flags, dev->toread, dev->towrite, dev->written);
+		/* maybe we can reply to a read */
+		if (test_bit(R5_UPTODATE, &dev->flags) && dev->toread) {
+			struct bio *rbi, *rbi2;
+			PRINTK("Return read for disc %d\n", i);
+			spin_lock_irq(&conf->device_lock);
+			rbi = dev->toread;
+			dev->toread = NULL;
+			spin_unlock_irq(&conf->device_lock);
+			while (rbi && rbi->bi_sector < dev->sector + STRIPE_SECTORS) {
+				copy_data(0, rbi, dev->page, dev->sector);
+				rbi2 = r5_next_bio(rbi, dev->sector);
+				spin_lock_irq(&conf->device_lock);
+				if (--rbi->bi_phys_segments == 0) {
+					rbi->bi_next = return_bi;
+					return_bi = rbi;
+				}
+				spin_unlock_irq(&conf->device_lock);
+				rbi = rbi2;
+			}
+		}
+
+		/* now count some things */
+		if (test_bit(R5_LOCKED, &dev->flags)) locked++;
+		if (test_bit(R5_UPTODATE, &dev->flags)) uptodate++;
+
+
+		if (dev->toread) to_read++;
+		if (dev->towrite) {
+			to_write++;
+			if (!test_bit(R5_OVERWRITE, &dev->flags))
+				non_overwrite++;
+		}
+		if (dev->written) written++;
+		rdev = conf->disks[i].rdev; /* FIXME, should I be looking rdev */
+		if (!rdev || !rdev->in_sync) {
+			if ( failed < 2 )
+				failed_num[failed] = i;
+			failed++;
+		} else
+			set_bit(R5_Insync, &dev->flags);
+	}
+	PRINTK("locked=%d uptodate=%d to_read=%d"
+	       " to_write=%d failed=%d failed_num=%d,%d\n",
+	       locked, uptodate, to_read, to_write, failed,
+	       failed_num[0], failed_num[1]);
+	/* check if the array has lost >2 devices and, if so, some requests might
+	 * need to be failed
+	 */
+	if (failed > 2 && to_read+to_write+written) {
+		spin_lock_irq(&conf->device_lock);
+		for (i=disks; i--; ) {
+			/* fail all writes first */
+			bi = sh->dev[i].towrite;
+			sh->dev[i].towrite = NULL;
+			if (bi) to_write--;
+
+			while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
+				struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
+				clear_bit(BIO_UPTODATE, &bi->bi_flags);
+				if (--bi->bi_phys_segments == 0) {
+					md_write_end(conf->mddev);
+					bi->bi_next = return_bi;
+					return_bi = bi;
+				}
+				bi = nextbi;
+			}
+			/* and fail all 'written' */
+			bi = sh->dev[i].written;
+			sh->dev[i].written = NULL;
+			while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS) {
+				struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
+				clear_bit(BIO_UPTODATE, &bi->bi_flags);
+				if (--bi->bi_phys_segments == 0) {
+					md_write_end(conf->mddev);
+					bi->bi_next = return_bi;
+					return_bi = bi;
+				}
+				bi = bi2;
+			}
+
+			/* fail any reads if this device is non-operational */
+			if (!test_bit(R5_Insync, &sh->dev[i].flags)) {
+				bi = sh->dev[i].toread;
+				sh->dev[i].toread = NULL;
+				if (bi) to_read--;
+				while (bi && bi->bi_sector < sh->dev[i].sector + STRIPE_SECTORS){
+					struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
+					clear_bit(BIO_UPTODATE, &bi->bi_flags);
+					if (--bi->bi_phys_segments == 0) {
+						bi->bi_next = return_bi;
+						return_bi = bi;
+					}
+					bi = nextbi;
+				}
+			}
+		}
+		spin_unlock_irq(&conf->device_lock);
+	}
+	if (failed > 2 && syncing) {
+		md_done_sync(conf->mddev, STRIPE_SECTORS,0);
+		clear_bit(STRIPE_SYNCING, &sh->state);
+		syncing = 0;
+	}
+
+	/*
+	 * might be able to return some write requests if the parity blocks
+	 * are safe, or on a failed drive
+	 */
+	pdev = &sh->dev[pd_idx];
+	p_failed = (failed >= 1 && failed_num[0] == pd_idx)
+		|| (failed >= 2 && failed_num[1] == pd_idx);
+	qdev = &sh->dev[qd_idx];
+	q_failed = (failed >= 1 && failed_num[0] == qd_idx)
+		|| (failed >= 2 && failed_num[1] == qd_idx);
+
+	if ( written &&
+	     ( p_failed || ((test_bit(R5_Insync, &pdev->flags)
+			     && !test_bit(R5_LOCKED, &pdev->flags)
+			     && test_bit(R5_UPTODATE, &pdev->flags))) ) &&
+	     ( q_failed || ((test_bit(R5_Insync, &qdev->flags)
+			     && !test_bit(R5_LOCKED, &qdev->flags)
+			     && test_bit(R5_UPTODATE, &qdev->flags))) ) ) {
+		/* any written block on an uptodate or failed drive can be
+		 * returned.  Note that if we 'wrote' to a failed drive,
+		 * it will be UPTODATE, but never LOCKED, so we don't need
+		 * to test 'failed' directly.
+		 */
+		for (i=disks; i--; )
+			if (sh->dev[i].written) {
+				dev = &sh->dev[i];
+				if (!test_bit(R5_LOCKED, &dev->flags) &&
+				    test_bit(R5_UPTODATE, &dev->flags) ) {
+					/* We can return any write requests */
+					struct bio *wbi, *wbi2;
+					PRINTK("Return write for stripe %llu disc %d\n",
+					       (unsigned long long)sh->sector, i);
+					spin_lock_irq(&conf->device_lock);
+					wbi = dev->written;
+					dev->written = NULL;
+					while (wbi && wbi->bi_sector < dev->sector + STRIPE_SECTORS) {
+						wbi2 = r5_next_bio(wbi, dev->sector);
+						if (--wbi->bi_phys_segments == 0) {
+							md_write_end(conf->mddev);
+							wbi->bi_next = return_bi;
+							return_bi = wbi;
+						}
+						wbi = wbi2;
+					}
+					spin_unlock_irq(&conf->device_lock);
+				}
+			}
+	}
+
+	/* Now we might consider reading some blocks, either to check/generate
+	 * parity, or to satisfy requests
+	 * or to load a block that is being partially written.
+	 */
+	if (to_read || non_overwrite || (syncing && (uptodate+failed < disks))) {
+		for (i=disks; i--;) {
+			dev = &sh->dev[i];
+			if (!test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
+			    (dev->toread ||
+			     (dev->towrite && !test_bit(R5_OVERWRITE, &dev->flags)) ||
+			     syncing ||
+			     (failed >= 1 && (sh->dev[failed_num[0]].toread ||
+					 (sh->dev[failed_num[0]].towrite && !test_bit(R5_OVERWRITE, &sh->dev[failed_num[0]].flags)))) ||
+			     (failed >= 2 && (sh->dev[failed_num[1]].toread ||
+					 (sh->dev[failed_num[1]].towrite && !test_bit(R5_OVERWRITE, &sh->dev[failed_num[1]].flags))))
+				    )
+				) {
+				/* we would like to get this block, possibly
+				 * by computing it, but we might not be able to
+				 */
+				if (uptodate == disks-1) {
+					PRINTK("Computing stripe %llu block %d\n",
+					       (unsigned long long)sh->sector, i);
+					compute_block_1(sh, i);
+					uptodate++;
+				} else if ( uptodate == disks-2 && failed >= 2 ) {
+					/* Computing 2-failure is *very* expensive; only do it if failed >= 2 */
+					int other;
+					for (other=disks; other--;) {
+						if ( other == i )
+							continue;
+						if ( !test_bit(R5_UPTODATE, &sh->dev[other].flags) )
+							break;
+					}
+					BUG_ON(other < 0);
+					PRINTK("Computing stripe %llu blocks %d,%d\n",
+					       (unsigned long long)sh->sector, i, other);
+					compute_block_2(sh, i, other);
+					uptodate += 2;
+				} else if (test_bit(R5_Insync, &dev->flags)) {
+					set_bit(R5_LOCKED, &dev->flags);
+					set_bit(R5_Wantread, &dev->flags);
+#if 0
+					/* if I am just reading this block and we don't have
+					   a failed drive, or any pending writes then sidestep the cache */
+					if (sh->bh_read[i] && !sh->bh_read[i]->b_reqnext &&
+					    ! syncing && !failed && !to_write) {
+						sh->bh_cache[i]->b_page =  sh->bh_read[i]->b_page;
+						sh->bh_cache[i]->b_data =  sh->bh_read[i]->b_data;
+					}
+#endif
+					locked++;
+					PRINTK("Reading block %d (sync=%d)\n",
+						i, syncing);
+					if (syncing)
+						md_sync_acct(conf->disks[i].rdev, STRIPE_SECTORS);
+				}
+			}
+		}
+		set_bit(STRIPE_HANDLE, &sh->state);
+	}
+
+	/* now to consider writing and what else, if anything should be read */
+	if (to_write) {
+		int rcw=0, must_compute=0;
+		for (i=disks ; i--;) {
+			dev = &sh->dev[i];
+			/* Would I have to read this buffer for reconstruct_write */
+			if (!test_bit(R5_OVERWRITE, &dev->flags)
+			    && i != pd_idx && i != qd_idx
+			    && (!test_bit(R5_LOCKED, &dev->flags)
+#if 0
+				|| sh->bh_page[i] != bh->b_page
+#endif
+				    ) &&
+			    !test_bit(R5_UPTODATE, &dev->flags)) {
+				if (test_bit(R5_Insync, &dev->flags)) rcw++;
+				else {
+					PRINTK("raid6: must_compute: disk %d flags=%#lx\n", i, dev->flags);
+					must_compute++;
+				}
+			}
+		}
+		PRINTK("for sector %llu, rcw=%d, must_compute=%d\n",
+		       (unsigned long long)sh->sector, rcw, must_compute);
+		set_bit(STRIPE_HANDLE, &sh->state);
+
+		if (rcw > 0)
+			/* want reconstruct write, but need to get some data */
+			for (i=disks; i--;) {
+				dev = &sh->dev[i];
+				if (!test_bit(R5_OVERWRITE, &dev->flags)
+				    && !(failed == 0 && (i == pd_idx || i == qd_idx))
+				    && !test_bit(R5_LOCKED, &dev->flags) && !test_bit(R5_UPTODATE, &dev->flags) &&
+				    test_bit(R5_Insync, &dev->flags)) {
+					if (test_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+					{
+						PRINTK("Read_old stripe %llu block %d for Reconstruct\n",
+						       (unsigned long long)sh->sector, i);
+						set_bit(R5_LOCKED, &dev->flags);
+						set_bit(R5_Wantread, &dev->flags);
+						locked++;
+					} else {
+						PRINTK("Request delayed stripe %llu block %d for Reconstruct\n",
+						       (unsigned long long)sh->sector, i);
+						set_bit(STRIPE_DELAYED, &sh->state);
+						set_bit(STRIPE_HANDLE, &sh->state);
+					}
+				}
+			}
+		/* now if nothing is locked, and if we have enough data, we can start a write request */
+		if (locked == 0 && rcw == 0) {
+			if ( must_compute > 0 ) {
+				/* We have failed blocks and need to compute them */
+				switch ( failed ) {
+				case 0:	BUG();
+				case 1: compute_block_1(sh, failed_num[0]); break;
+				case 2: compute_block_2(sh, failed_num[0], failed_num[1]); break;
+				default: BUG();	/* This request should have been failed? */
+				}
+			}
+
+			PRINTK("Computing parity for stripe %llu\n", (unsigned long long)sh->sector);
+			compute_parity(sh, RECONSTRUCT_WRITE);
+			/* now every locked buffer is ready to be written */
+			for (i=disks; i--;)
+				if (test_bit(R5_LOCKED, &sh->dev[i].flags)) {
+					PRINTK("Writing stripe %llu block %d\n",
+					       (unsigned long long)sh->sector, i);
+					locked++;
+					set_bit(R5_Wantwrite, &sh->dev[i].flags);
+#if 0 /**** FIX: I don't understand the logic here... ****/
+					if (!test_bit(R5_Insync, &sh->dev[i].flags)
+					    || ((i==pd_idx || i==qd_idx) && failed == 0)) /* FIX? */
+						set_bit(STRIPE_INSYNC, &sh->state);
+#endif
+				}
+			if (test_and_clear_bit(STRIPE_PREREAD_ACTIVE, &sh->state)) {
+				atomic_dec(&conf->preread_active_stripes);
+				if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD)
+					md_wakeup_thread(conf->mddev->thread);
+			}
+		}
+	}
+
+	/* maybe we need to check and possibly fix the parity for this stripe
+	 * Any reads will already have been scheduled, so we just see if enough data
+	 * is available
+	 */
+	if (syncing && locked == 0 &&
+	    !test_bit(STRIPE_INSYNC, &sh->state) && failed <= 2) {
+		set_bit(STRIPE_HANDLE, &sh->state);
+#if 0 /* RAID-6: Don't support CHECK PARITY yet */
+		if (failed == 0) {
+			char *pagea;
+			if (uptodate != disks)
+				BUG();
+			compute_parity(sh, CHECK_PARITY);
+			uptodate--;
+			pagea = page_address(sh->dev[pd_idx].page);
+			if ((*(u32*)pagea) == 0 &&
+			    !memcmp(pagea, pagea+4, STRIPE_SIZE-4)) {
+				/* parity is correct (on disc, not in buffer any more) */
+				set_bit(STRIPE_INSYNC, &sh->state);
+			}
+		}
+#endif
+		if (!test_bit(STRIPE_INSYNC, &sh->state)) {
+			int failed_needupdate[2];
+			struct r5dev *adev, *bdev;
+
+			if ( failed < 1 )
+				failed_num[0] = pd_idx;
+			if ( failed < 2 )
+				failed_num[1] = (failed_num[0] == qd_idx) ? pd_idx : qd_idx;
+
+			failed_needupdate[0] = !test_bit(R5_UPTODATE, &sh->dev[failed_num[0]].flags);
+			failed_needupdate[1] = !test_bit(R5_UPTODATE, &sh->dev[failed_num[1]].flags);
+
+			PRINTK("sync: failed=%d num=%d,%d fnu=%u%u\n",
+			       failed, failed_num[0], failed_num[1], failed_needupdate[0], failed_needupdate[1]);
+
+#if 0  /* RAID-6: This code seems to require that CHECK_PARITY destroys the uptodateness of the parity */
+			/* should be able to compute the missing block(s) and write to spare */
+			if ( failed_needupdate[0] ^ failed_needupdate[1] ) {
+				if (uptodate+1 != disks)
+					BUG();
+				compute_block_1(sh, failed_needupdate[0] ? failed_num[0] : failed_num[1]);
+				uptodate++;
+			} else if ( failed_needupdate[0] & failed_needupdate[1] ) {
+				if (uptodate+2 != disks)
+					BUG();
+				compute_block_2(sh, failed_num[0], failed_num[1]);
+				uptodate += 2;
+			}
+#else
+			compute_block_2(sh, failed_num[0], failed_num[1]);
+			uptodate += failed_needupdate[0] + failed_needupdate[1];
+#endif
+
+			if (uptodate != disks)
+				BUG();
+
+			PRINTK("Marking for sync stripe %llu blocks %d,%d\n",
+			       (unsigned long long)sh->sector, failed_num[0], failed_num[1]);
+
+			/**** FIX: Should we really do both of these unconditionally? ****/
+			adev = &sh->dev[failed_num[0]];
+			locked += !test_bit(R5_LOCKED, &adev->flags);
+			set_bit(R5_LOCKED, &adev->flags);
+			set_bit(R5_Wantwrite, &adev->flags);
+			bdev = &sh->dev[failed_num[1]];
+			locked += !test_bit(R5_LOCKED, &bdev->flags);
+			set_bit(R5_LOCKED, &bdev->flags);
+			set_bit(R5_Wantwrite, &bdev->flags);
+
+			set_bit(STRIPE_INSYNC, &sh->state);
+			set_bit(R5_Syncio, &adev->flags);
+			set_bit(R5_Syncio, &bdev->flags);
+		}
+	}
+	if (syncing && locked == 0 && test_bit(STRIPE_INSYNC, &sh->state)) {
+		md_done_sync(conf->mddev, STRIPE_SECTORS,1);
+		clear_bit(STRIPE_SYNCING, &sh->state);
+	}
+
+	spin_unlock(&sh->lock);
+
+	while ((bi=return_bi)) {
+		int bytes = bi->bi_size;
+
+		return_bi = bi->bi_next;
+		bi->bi_next = NULL;
+		bi->bi_size = 0;
+		bi->bi_end_io(bi, bytes, 0);
+	}
+	for (i=disks; i-- ;) {
+		int rw;
+		struct bio *bi;
+		mdk_rdev_t *rdev;
+		if (test_and_clear_bit(R5_Wantwrite, &sh->dev[i].flags))
+			rw = 1;
+		else if (test_and_clear_bit(R5_Wantread, &sh->dev[i].flags))
+			rw = 0;
+		else
+			continue;
+
+		bi = &sh->dev[i].req;
+
+		bi->bi_rw = rw;
+		if (rw)
+			bi->bi_end_io = raid6_end_write_request;
+		else
+			bi->bi_end_io = raid6_end_read_request;
+
+		spin_lock_irq(&conf->device_lock);
+		rdev = conf->disks[i].rdev;
+		if (rdev && rdev->faulty)
+			rdev = NULL;
+		if (rdev)
+			atomic_inc(&rdev->nr_pending);
+		spin_unlock_irq(&conf->device_lock);
+
+		if (rdev) {
+			if (test_bit(R5_Syncio, &sh->dev[i].flags))
+				md_sync_acct(rdev, STRIPE_SECTORS);
+
+			bi->bi_bdev = rdev->bdev;
+			PRINTK("for %llu schedule op %ld on disc %d\n",
+				(unsigned long long)sh->sector, bi->bi_rw, i);
+			atomic_inc(&sh->count);
+			bi->bi_sector = sh->sector + rdev->data_offset;
+			bi->bi_flags = 1 << BIO_UPTODATE;
+			bi->bi_vcnt = 1;
+			bi->bi_idx = 0;
+			bi->bi_io_vec = &sh->dev[i].vec;
+			bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
+			bi->bi_io_vec[0].bv_offset = 0;
+			bi->bi_size = STRIPE_SIZE;
+			bi->bi_next = NULL;
+			generic_make_request(bi);
+		} else {
+			PRINTK("skip op %ld on disc %d for sector %llu\n",
+				bi->bi_rw, i, (unsigned long long)sh->sector);
+			clear_bit(R5_LOCKED, &sh->dev[i].flags);
+			set_bit(STRIPE_HANDLE, &sh->state);
+		}
+	}
+}
+
+static inline void raid6_activate_delayed(raid6_conf_t *conf)
+{
+	if (atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD) {
+		while (!list_empty(&conf->delayed_list)) {
+			struct list_head *l = conf->delayed_list.next;
+			struct stripe_head *sh;
+			sh = list_entry(l, struct stripe_head, lru);
+			list_del_init(l);
+			clear_bit(STRIPE_DELAYED, &sh->state);
+			if (!test_and_set_bit(STRIPE_PREREAD_ACTIVE, &sh->state))
+				atomic_inc(&conf->preread_active_stripes);
+			list_add_tail(&sh->lru, &conf->handle_list);
+		}
+	}
+}
+static void raid6_unplug_device(void *data)
+{
+	request_queue_t *q = data;
+	mddev_t *mddev = q->queuedata;
+	raid6_conf_t *conf = mddev_to_conf(mddev);
+	unsigned long flags;
+
+	spin_lock_irqsave(&conf->device_lock, flags);
+
+	if (blk_remove_plug(q))
+		raid6_activate_delayed(conf);
+	md_wakeup_thread(mddev->thread);
+
+	spin_unlock_irqrestore(&conf->device_lock, flags);
+}
+
+static inline void raid6_plug_device(raid6_conf_t *conf)
+{
+	spin_lock_irq(&conf->device_lock);
+	blk_plug_device(conf->mddev->queue);
+	spin_unlock_irq(&conf->device_lock);
+}
+
+static int make_request (request_queue_t *q, struct bio * bi)
+{
+	mddev_t *mddev = q->queuedata;
+	raid6_conf_t *conf = mddev_to_conf(mddev);
+	const unsigned int raid_disks = conf->raid_disks;
+	const unsigned int data_disks = raid_disks - 2;
+	unsigned int dd_idx, pd_idx;
+	sector_t new_sector;
+	sector_t logical_sector, last_sector;
+	struct stripe_head *sh;
+
+	logical_sector = bi->bi_sector & ~(STRIPE_SECTORS-1);
+	last_sector = bi->bi_sector + (bi->bi_size>>9);
+
+	bi->bi_next = NULL;
+	bi->bi_phys_segments = 1;	/* over-loaded to count active stripes */
+	if ( bio_data_dir(bi) == WRITE )
+		md_write_start(mddev);
+	for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) {
+
+		new_sector = raid6_compute_sector(logical_sector,
+						  raid_disks, data_disks, &dd_idx, &pd_idx, conf);
+
+		PRINTK("raid6: make_request, sector %Lu logical %Lu\n",
+		       (unsigned long long)new_sector,
+		       (unsigned long long)logical_sector);
+
+		sh = get_active_stripe(conf, new_sector, pd_idx, (bi->bi_rw&RWA_MASK));
+		if (sh) {
+
+			add_stripe_bio(sh, bi, dd_idx, (bi->bi_rw&RW_MASK));
+
+			raid6_plug_device(conf);
+			handle_stripe(sh);
+			release_stripe(sh);
+		} else {
+			/* cannot get stripe for read-ahead, just give-up */
+			clear_bit(BIO_UPTODATE, &bi->bi_flags);
+			break;
+		}
+
+	}
+	spin_lock_irq(&conf->device_lock);
+	if (--bi->bi_phys_segments == 0) {
+		int bytes = bi->bi_size;
+
+		if ( bio_data_dir(bi) == WRITE )
+			md_write_end(mddev);
+		bi->bi_size = 0;
+		bi->bi_end_io(bi, bytes, 0);
+	}
+	spin_unlock_irq(&conf->device_lock);
+	return 0;
+}
+
+/* FIXME go_faster isn't used */
+static int sync_request (mddev_t *mddev, sector_t sector_nr, int go_faster)
+{
+	raid6_conf_t *conf = (raid6_conf_t *) mddev->private;
+	struct stripe_head *sh;
+	int sectors_per_chunk = conf->chunk_size >> 9;
+	sector_t x;
+	unsigned long stripe;
+	int chunk_offset;
+	int dd_idx, pd_idx;
+	unsigned long first_sector;
+	int raid_disks = conf->raid_disks;
+	int data_disks = raid_disks - 2;
+
+	if (sector_nr >= mddev->size <<1)
+		/* just being told to finish up .. nothing to do */
+		return 0;
+
+	x = sector_nr;
+	chunk_offset = sector_div(x, sectors_per_chunk);
+	stripe = x;
+	BUG_ON(x != stripe);
+
+	first_sector = raid6_compute_sector(stripe*data_disks*sectors_per_chunk
+		+ chunk_offset, raid_disks, data_disks, &dd_idx, &pd_idx, conf);
+	sh = get_active_stripe(conf, sector_nr, pd_idx, 1);
+	if (sh == NULL) {
+		sh = get_active_stripe(conf, sector_nr, pd_idx, 0);
+		/* make sure we don't swamp the stripe cache if someone else
+		 * is trying to get access
+		 */
+		yield();
+	}
+	spin_lock(&sh->lock);
+	set_bit(STRIPE_SYNCING, &sh->state);
+	clear_bit(STRIPE_INSYNC, &sh->state);
+	spin_unlock(&sh->lock);
+
+	handle_stripe(sh);
+	release_stripe(sh);
+
+	return STRIPE_SECTORS;
+}
+
+/*
+ * This is our raid6 kernel thread.
+ *
+ * We scan the hash table for stripes which can be handled now.
+ * During the scan, completed stripes are saved for us by the interrupt
+ * handler, so that they will not have to wait for our next wakeup.
+ */
+static void raid6d (mddev_t *mddev)
+{
+	struct stripe_head *sh;
+	raid6_conf_t *conf = mddev_to_conf(mddev);
+	int handled;
+
+	PRINTK("+++ raid6d active\n");
+
+	md_check_recovery(mddev);
+	md_handle_safemode(mddev);
+
+	handled = 0;
+	spin_lock_irq(&conf->device_lock);
+	while (1) {
+		struct list_head *first;
+
+		if (list_empty(&conf->handle_list) &&
+		    atomic_read(&conf->preread_active_stripes) < IO_THRESHOLD &&
+		    !blk_queue_plugged(mddev->queue) &&
+		    !list_empty(&conf->delayed_list))
+			raid6_activate_delayed(conf);
+
+		if (list_empty(&conf->handle_list))
+			break;
+
+		first = conf->handle_list.next;
+		sh = list_entry(first, struct stripe_head, lru);
+
+		list_del_init(first);
+		atomic_inc(&sh->count);
+		if (atomic_read(&sh->count)!= 1)
+			BUG();
+		spin_unlock_irq(&conf->device_lock);
+
+		handled++;
+		handle_stripe(sh);
+		release_stripe(sh);
+
+		spin_lock_irq(&conf->device_lock);
+	}
+	PRINTK("%d stripes handled\n", handled);
+
+	spin_unlock_irq(&conf->device_lock);
+
+	PRINTK("--- raid6d inactive\n");
+}
+
+static int run (mddev_t *mddev)
+{
+	raid6_conf_t *conf;
+	int raid_disk, memory;
+	mdk_rdev_t *rdev;
+	struct disk_info *disk;
+	struct list_head *tmp;
+
+	if (mddev->level != 6) {
+		PRINTK("raid6: md%d: raid level not set to 6 (%d)\n", mdidx(mddev), mddev->level);
+		return -EIO;
+	}
+
+	mddev->private = kmalloc (sizeof (raid6_conf_t)
+				  + mddev->raid_disks * sizeof(struct disk_info),
+				  GFP_KERNEL);
+	if ((conf = mddev->private) == NULL)
+		goto abort;
+	memset (conf, 0, sizeof (*conf) + mddev->raid_disks * sizeof(struct disk_info) );
+	conf->mddev = mddev;
+
+	if ((conf->stripe_hashtbl = (struct stripe_head **) __get_free_pages(GFP_ATOMIC, HASH_PAGES_ORDER)) == NULL)
+		goto abort;
+	memset(conf->stripe_hashtbl, 0, HASH_PAGES * PAGE_SIZE);
+
+	conf->device_lock = SPIN_LOCK_UNLOCKED;
+	init_waitqueue_head(&conf->wait_for_stripe);
+	INIT_LIST_HEAD(&conf->handle_list);
+	INIT_LIST_HEAD(&conf->delayed_list);
+	INIT_LIST_HEAD(&conf->inactive_list);
+	atomic_set(&conf->active_stripes, 0);
+	atomic_set(&conf->preread_active_stripes, 0);
+
+	mddev->queue->unplug_fn = raid6_unplug_device;
+
+	PRINTK("raid6: run(md%d) called.\n", mdidx(mddev));
+
+	ITERATE_RDEV(mddev,rdev,tmp) {
+		raid_disk = rdev->raid_disk;
+		if (raid_disk >= mddev->raid_disks
+		    || raid_disk < 0)
+			continue;
+		disk = conf->disks + raid_disk;
+
+		disk->rdev = rdev;
+
+		if (rdev->in_sync) {
+			char b[BDEVNAME_SIZE];
+			printk(KERN_INFO "raid6: device %s operational as raid"
+			       " disk %d\n", bdevname(rdev->bdev,b),
+			       raid_disk);
+			conf->working_disks++;
+		}
+	}
+
+	conf->raid_disks = mddev->raid_disks;
+
+	/*
+	 * 0 for a fully functional array, 1 or 2 for a degraded array.
+	 */
+	mddev->degraded = conf->failed_disks = conf->raid_disks - conf->working_disks;
+	conf->mddev = mddev;
+	conf->chunk_size = mddev->chunk_size;
+	conf->level = mddev->level;
+	conf->algorithm = mddev->layout;
+	conf->max_nr_stripes = NR_STRIPES;
+
+	if (conf->raid_disks < 4) {
+		printk(KERN_ERR "raid6: not enough configured devices for md%d (%d, minimum 4)\n",
+		       mdidx(mddev), conf->raid_disks);
+		goto abort;
+	}
+	if (!conf->chunk_size || conf->chunk_size % 4) {
+		printk(KERN_ERR "raid6: invalid chunk size %d for md%d\n",
+		       conf->chunk_size, mdidx(mddev));
+		goto abort;
+	}
+	if (conf->algorithm > ALGORITHM_RIGHT_SYMMETRIC) {
+		printk(KERN_ERR
+		       "raid6: unsupported parity algorithm %d for md%d\n",
+		       conf->algorithm, mdidx(mddev));
+		goto abort;
+	}
+	if (mddev->degraded > 2) {
+		printk(KERN_ERR "raid6: not enough operational devices for md%d"
+		       " (%d/%d failed)\n",
+		       mdidx(mddev), conf->failed_disks, conf->raid_disks);
+		goto abort;
+	}
+
+#if 0				/* FIX: For now */
+	if (mddev->degraded > 0 &&
+	    mddev->recovery_cp != MaxSector) {
+		printk(KERN_ERR "raid6: cannot start dirty degraded array for md%d\n", mdidx(mddev));
+		goto abort;
+	}
+#endif
+
+	{
+		mddev->thread = md_register_thread(raid6d, mddev, "md%d_raid6");
+		if (!mddev->thread) {
+			printk(KERN_ERR
+			       "raid6: couldn't allocate thread for md%d\n",
+			       mdidx(mddev));
+			goto abort;
+		}
+	}
+
+	memory = conf->max_nr_stripes * (sizeof(struct stripe_head) +
+		 conf->raid_disks * ((sizeof(struct bio) + PAGE_SIZE))) / 1024;
+	if (grow_stripes(conf, conf->max_nr_stripes)) {
+		printk(KERN_ERR
+		       "raid6: couldn't allocate %dkB for buffers\n", memory);
+		shrink_stripes(conf);
+		md_unregister_thread(mddev->thread);
+		goto abort;
+	} else
+		printk(KERN_INFO "raid6: allocated %dkB for md%d\n",
+		       memory, mdidx(mddev));
+
+	if (mddev->degraded == 0)
+		printk(KERN_INFO "raid6: raid level %d set md%d active with %d out of %d"
+		       " devices, algorithm %d\n", conf->level, mdidx(mddev),
+		       mddev->raid_disks-mddev->degraded, mddev->raid_disks,
+		       conf->algorithm);
+	else
+		printk(KERN_ALERT "raid6: raid level %d set md%d active with %d"
+		       " out of %d devices, algorithm %d\n", conf->level,
+		       mdidx(mddev), mddev->raid_disks - mddev->degraded,
+		       mddev->raid_disks, conf->algorithm);
+
+	print_raid6_conf(conf);
+
+	/* read-ahead size must cover a whole stripe, which is
+	 * (n-2) * chunksize where 'n' is the number of raid devices
+	 */
+	{
+		int stripe = (mddev->raid_disks-2) * mddev->chunk_size
+			/ PAGE_CACHE_SIZE;
+		if (mddev->queue->backing_dev_info.ra_pages < stripe)
+			mddev->queue->backing_dev_info.ra_pages = stripe;
+	}
+
+	/* Ok, everything is just fine now */
+	mddev->array_size =  mddev->size * (mddev->raid_disks - 2);
+	return 0;
+abort:
+	if (conf) {
+		print_raid6_conf(conf);
+		if (conf->stripe_hashtbl)
+			free_pages((unsigned long) conf->stripe_hashtbl,
+							HASH_PAGES_ORDER);
+		kfree(conf);
+	}
+	mddev->private = NULL;
+	printk(KERN_ALERT "raid6: failed to run raid set md%d\n", mdidx(mddev));
+	return -EIO;
+}
+
+
+
+static int stop (mddev_t *mddev)
+{
+	raid6_conf_t *conf = (raid6_conf_t *) mddev->private;
+
+	md_unregister_thread(mddev->thread);
+	mddev->thread = NULL;
+	shrink_stripes(conf);
+	free_pages((unsigned long) conf->stripe_hashtbl, HASH_PAGES_ORDER);
+	kfree(conf);
+	mddev->private = NULL;
+	return 0;
+}
+
+#if RAID6_DUMPSTATE
+static void print_sh (struct seq_file *seq, struct stripe_head *sh)
+{
+	int i;
+
+	seq_printf(seq, "sh %llu, pd_idx %d, state %ld.\n",
+		   (unsigned long long)sh->sector, sh->pd_idx, sh->state);
+	seq_printf(seq, "sh %llu,  count %d.\n",
+		   (unsigned long long)sh->sector, atomic_read(&sh->count));
+	seq_printf(seq, "sh %llu, ", (unsigned long long)sh->sector);
+	for (i = 0; i < sh->raid_conf->raid_disks; i++) {
+		seq_printf(seq, "(cache%d: %p %ld) ",
+			   i, sh->dev[i].page, sh->dev[i].flags);
+	}
+	seq_printf(seq, "\n");
+}
+
+static void printall (struct seq_file *seq, raid6_conf_t *conf)
+{
+	struct stripe_head *sh;
+	int i;
+
+	spin_lock_irq(&conf->device_lock);
+	for (i = 0; i < NR_HASH; i++) {
+		sh = conf->stripe_hashtbl[i];
+		for (; sh; sh = sh->hash_next) {
+			if (sh->raid_conf != conf)
+				continue;
+			print_sh(seq, sh);
+		}
+	}
+	spin_unlock_irq(&conf->device_lock);
+}
+#endif
+
+static void status (struct seq_file *seq, mddev_t *mddev)
+{
+	raid6_conf_t *conf = (raid6_conf_t *) mddev->private;
+	int i;
+
+	seq_printf (seq, " level %d, %dk chunk, algorithm %d", mddev->level, mddev->chunk_size >> 10, mddev->layout);
+	seq_printf (seq, " [%d/%d] [", conf->raid_disks, conf->working_disks);
+	for (i = 0; i < conf->raid_disks; i++)
+ 		seq_printf (seq, "%s",
+			    conf->disks[i].rdev &&
+			    conf->disks[i].rdev->in_sync ? "U" : "_");
+	seq_printf (seq, "]");
+#if RAID6_DUMPSTATE
+	seq_printf (seq, "\n");
+	printall(seq, conf);
+#endif
+}
+
+static void print_raid6_conf (raid6_conf_t *conf)
+{
+	int i;
+	struct disk_info *tmp;
+
+	printk("RAID6 conf printout:\n");
+	if (!conf) {
+		printk("(conf==NULL)\n");
+		return;
+	}
+	printk(" --- rd:%d wd:%d fd:%d\n", conf->raid_disks,
+		 conf->working_disks, conf->failed_disks);
+
+	for (i = 0; i < conf->raid_disks; i++) {
+		char b[BDEVNAME_SIZE];
+		tmp = conf->disks + i;
+		if (tmp->rdev)
+		printk(" disk %d, o:%d, dev:%s\n",
+			i, !tmp->rdev->faulty,
+			bdevname(tmp->rdev->bdev,b));
+	}
+}
+
+static int raid6_spare_active(mddev_t *mddev)
+{
+	int i;
+	raid6_conf_t *conf = mddev->private;
+	struct disk_info *tmp;
+
+	spin_lock_irq(&conf->device_lock);
+	for (i = 0; i < conf->raid_disks; i++) {
+		tmp = conf->disks + i;
+		if (tmp->rdev
+		    && !tmp->rdev->faulty
+		    && !tmp->rdev->in_sync) {
+			mddev->degraded--;
+			conf->failed_disks--;
+			conf->working_disks++;
+			tmp->rdev->in_sync = 1;
+		}
+	}
+	spin_unlock_irq(&conf->device_lock);
+	print_raid6_conf(conf);
+	return 0;
+}
+
+static int raid6_remove_disk(mddev_t *mddev, int number)
+{
+	raid6_conf_t *conf = mddev->private;
+	int err = 1;
+	struct disk_info *p = conf->disks + number;
+
+	print_raid6_conf(conf);
+	spin_lock_irq(&conf->device_lock);
+
+	if (p->rdev) {
+		if (p->rdev->in_sync ||
+		    atomic_read(&p->rdev->nr_pending)) {
+			err = -EBUSY;
+			goto abort;
+		}
+		p->rdev = NULL;
+		err = 0;
+	}
+	if (err)
+		MD_BUG();
+abort:
+	spin_unlock_irq(&conf->device_lock);
+	print_raid6_conf(conf);
+	return err;
+}
+
+static int raid6_add_disk(mddev_t *mddev, mdk_rdev_t *rdev)
+{
+	raid6_conf_t *conf = mddev->private;
+	int found = 0;
+	int disk;
+	struct disk_info *p;
+
+	spin_lock_irq(&conf->device_lock);
+	/*
+	 * find the disk ...
+	 */
+	for (disk=0; disk < mddev->raid_disks; disk++)
+		if ((p=conf->disks + disk)->rdev == NULL) {
+			p->rdev = rdev;
+			rdev->in_sync = 0;
+			rdev->raid_disk = disk;
+			found = 1;
+			break;
+		}
+	spin_unlock_irq(&conf->device_lock);
+	print_raid6_conf(conf);
+	return found;
+}
+
+static mdk_personality_t raid6_personality=
+{
+	.name		= "raid6",
+	.owner		= THIS_MODULE,
+	.make_request	= make_request,
+	.run		= run,
+	.stop		= stop,
+	.status		= status,
+	.error_handler	= error,
+	.hot_add_disk	= raid6_add_disk,
+	.hot_remove_disk= raid6_remove_disk,
+	.spare_active	= raid6_spare_active,
+	.sync_request	= sync_request,
+};
+
+static int __init raid6_init (void)
+{
+	int e;
+
+	e = raid6_select_algo();
+	if ( e )
+		return e;
+
+	return register_md_personality (RAID6, &raid6_personality);
+}
+
+static void raid6_exit (void)
+{
+	unregister_md_personality (RAID6);
+}
+
+module_init(raid6_init);
+module_exit(raid6_exit);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("md-personality-8"); /* RAID6 */

drivers/md/raid6mmx.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * raid6mmx.c
+ *
+ * MMX implementation of RAID-6 syndrome functions
+ */
+
+#if defined(__i386__) || defined(__x86_64__)
+
+#include "raid6.h"
+#include "raid6x86.h"
+
+/* Shared with raid6sse1.c */
+const struct raid6_mmx_constants {
+	u64 x1d;
+} raid6_mmx_constants = {
+	0x1d1d1d1d1d1d1d1dULL,
+};
+
+static int raid6_have_mmx(void)
+{
+#ifdef __KERNEL__
+	/* Not really "boot_cpu" but "all_cpus" */
+	return boot_cpu_has(X86_FEATURE_MMX);
+#else
+	/* User space test code */
+	u32 features = cpuid_features();
+	return ( (features & (1<<23)) == (1<<23) );
+#endif
+}
+
+/*
+ * Plain MMX implementation
+ */
+static void raid6_mmx1_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+	raid6_mmx_save_t sa;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	raid6_before_mmx(&sa);
+
+	asm volatile("movq %0,%%mm0" : : "m" (raid6_mmx_constants.x1d));
+	asm volatile("pxor %mm5,%mm5");	/* Zero temp */
+
+	for ( d = 0 ; d < bytes ; d += 8 ) {
+		asm volatile("movq %0,%%mm2" : : "m" (dptr[z0][d])); /* P[0] */
+		asm volatile("movq %mm2,%mm4");	/* Q[0] */
+		for ( z = z0-1 ; z >= 0 ; z-- ) {
+			asm volatile("movq %0,%%mm6" : : "m" (dptr[z][d]));
+			asm volatile("pcmpgtb %mm4,%mm5");
+			asm volatile("paddb %mm4,%mm4");
+			asm volatile("pand %mm0,%mm5");
+			asm volatile("pxor %mm5,%mm4");
+			asm volatile("pxor %mm5,%mm5");
+			asm volatile("pxor %mm6,%mm2");
+			asm volatile("pxor %mm6,%mm4");
+		}
+		asm volatile("movq %%mm2,%0" : "=m" (p[d]));
+		asm volatile("pxor %mm2,%mm2");
+		asm volatile("movq %%mm4,%0" : "=m" (q[d]));
+		asm volatile("pxor %mm4,%mm4");
+	}
+
+	raid6_after_mmx(&sa);
+}
+
+const struct raid6_calls raid6_mmxx1 = {
+	raid6_mmx1_gen_syndrome,
+	raid6_have_mmx,
+	"mmxx1",
+	0
+};
+
+/*
+ * Unrolled-by-2 MMX implementation
+ */
+static void raid6_mmx2_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+	raid6_mmx_save_t sa;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	raid6_before_mmx(&sa);
+
+	asm volatile("movq %0,%%mm0" : : "m" (raid6_mmx_constants.x1d));
+	asm volatile("pxor %mm5,%mm5");	/* Zero temp */
+	asm volatile("pxor %mm7,%mm7"); /* Zero temp */
+
+	for ( d = 0 ; d < bytes ; d += 16 ) {
+		asm volatile("movq %0,%%mm2" : : "m" (dptr[z0][d])); /* P[0] */
+		asm volatile("movq %0,%%mm3" : : "m" (dptr[z0][d+8]));
+		asm volatile("movq %mm2,%mm4"); /* Q[0] */
+		asm volatile("movq %mm3,%mm6"); /* Q[1] */
+		for ( z = z0-1 ; z >= 0 ; z-- ) {
+			asm volatile("pcmpgtb %mm4,%mm5");
+			asm volatile("pcmpgtb %mm6,%mm7");
+			asm volatile("paddb %mm4,%mm4");
+			asm volatile("paddb %mm6,%mm6");
+			asm volatile("pand %mm0,%mm5");
+			asm volatile("pand %mm0,%mm7");
+			asm volatile("pxor %mm5,%mm4");
+			asm volatile("pxor %mm7,%mm6");
+			asm volatile("movq %0,%%mm5" : : "m" (dptr[z][d]));
+			asm volatile("movq %0,%%mm7" : : "m" (dptr[z][d+8]));
+			asm volatile("pxor %mm5,%mm2");
+			asm volatile("pxor %mm7,%mm3");
+			asm volatile("pxor %mm5,%mm4");
+			asm volatile("pxor %mm7,%mm6");
+			asm volatile("pxor %mm5,%mm5");
+			asm volatile("pxor %mm7,%mm7");
+		}
+		asm volatile("movq %%mm2,%0" : "=m" (p[d]));
+		asm volatile("movq %%mm3,%0" : "=m" (p[d+8]));
+		asm volatile("movq %%mm4,%0" : "=m" (q[d]));
+		asm volatile("movq %%mm6,%0" : "=m" (q[d+8]));
+	}
+
+	raid6_after_mmx(&sa);
+}
+
+const struct raid6_calls raid6_mmxx2 = {
+	raid6_mmx2_gen_syndrome,
+	raid6_have_mmx,
+	"mmxx2",
+	0
+};
+
+#endif

drivers/md/raid6recov.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * raid6recov.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 "raid6.h"
+
+/* Recover two failed data blocks. */
+void raid6_2data_recov(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 */
+void raid6_datap_recov(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++;
+	}
+}
+
+
+#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. */
+			/* FIX */
+		}
+	} 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

drivers/md/raid6sse1.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * raid6sse1.c
+ *
+ * SSE-1/MMXEXT implementation of RAID-6 syndrome functions
+ *
+ * This is really an MMX implementation, but it requires SSE-1 or
+ * AMD MMXEXT for prefetch support and a few other features.  The
+ * support for nontemporal memory accesses is enough to make this
+ * worthwhile as a separate implementation.
+ */
+
+#if defined(__i386__) || defined(__x86_64__)
+
+#include "raid6.h"
+#include "raid6x86.h"
+
+/* Defined in raid6mmx.c */
+extern const struct raid6_mmx_constants {
+	u64 x1d;
+} raid6_mmx_constants;
+
+static int raid6_have_sse1_or_mmxext(void)
+{
+#ifdef __KERNEL__
+	/* Not really boot_cpu but "all_cpus" */
+	return boot_cpu_has(X86_FEATURE_MMX) &&
+		(boot_cpu_has(X86_FEATURE_XMM) ||
+		 boot_cpu_has(X86_FEATURE_MMXEXT));
+#else
+	/* User space test code - this incorrectly breaks on some Athlons */
+	u32 features = cpuid_features();
+	return ( (features & (5<<23)) == (5<<23) );
+#endif
+}
+
+/*
+ * Plain SSE1 implementation
+ */
+static void raid6_sse11_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+	raid6_mmx_save_t sa;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	/* This is really MMX code, not SSE */
+	raid6_before_mmx(&sa);
+
+	asm volatile("movq %0,%%mm0" : : "m" (raid6_mmx_constants.x1d));
+	asm volatile("pxor %mm5,%mm5");	/* Zero temp */
+
+	for ( d = 0 ; d < bytes ; d += 8 ) {
+		asm volatile("prefetchnta %0" : : "m" (dptr[z0][d]));
+		asm volatile("movq %0,%%mm2" : : "m" (dptr[z0][d])); /* P[0] */
+		asm volatile("prefetchnta %0" : : "m" (dptr[z0-1][d]));
+		asm volatile("movq %mm2,%mm4");	/* Q[0] */
+		asm volatile("movq %0,%%mm6" : : "m" (dptr[z0-1][d]));
+		for ( z = z0-2 ; z >= 0 ; z-- ) {
+			asm volatile("prefetchnta %0" : : "m" (dptr[z][d]));
+			asm volatile("pcmpgtb %mm4,%mm5");
+			asm volatile("paddb %mm4,%mm4");
+			asm volatile("pand %mm0,%mm5");
+			asm volatile("pxor %mm5,%mm4");
+			asm volatile("pxor %mm5,%mm5");
+			asm volatile("pxor %mm6,%mm2");
+			asm volatile("pxor %mm6,%mm4");
+			asm volatile("movq %0,%%mm6" : : "m" (dptr[z][d]));
+		}
+		asm volatile("pcmpgtb %mm4,%mm5");
+		asm volatile("paddb %mm4,%mm4");
+		asm volatile("pand %mm0,%mm5");
+		asm volatile("pxor %mm5,%mm4");
+		asm volatile("pxor %mm5,%mm5");
+		asm volatile("pxor %mm6,%mm2");
+		asm volatile("pxor %mm6,%mm4");
+
+		asm volatile("movntq %%mm2,%0" : "=m" (p[d]));
+		asm volatile("movntq %%mm4,%0" : "=m" (q[d]));
+	}
+
+	raid6_after_mmx(&sa);
+	asm volatile("sfence" : : : "memory");
+}
+
+const struct raid6_calls raid6_sse1x1 = {
+	raid6_sse11_gen_syndrome,
+	raid6_have_sse1_or_mmxext,
+	"sse1x1",
+	1			/* Has cache hints */
+};
+
+/*
+ * Unrolled-by-2 SSE1 implementation
+ */
+static void raid6_sse12_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+	raid6_mmx_save_t sa;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	raid6_before_mmx(&sa);
+
+	asm volatile("movq %0,%%mm0" : : "m" (raid6_mmx_constants.x1d));
+	asm volatile("pxor %mm5,%mm5");	/* Zero temp */
+	asm volatile("pxor %mm7,%mm7"); /* Zero temp */
+
+	/* We uniformly assume a single prefetch covers at least 16 bytes */
+	for ( d = 0 ; d < bytes ; d += 16 ) {
+		asm volatile("prefetchnta %0" : : "m" (dptr[z0][d]));
+		asm volatile("movq %0,%%mm2" : : "m" (dptr[z0][d])); /* P[0] */
+		asm volatile("movq %0,%%mm3" : : "m" (dptr[z0][d+8])); /* P[1] */
+		asm volatile("movq %mm2,%mm4");	/* Q[0] */
+		asm volatile("movq %mm3,%mm6"); /* Q[1] */
+		for ( z = z0-1 ; z >= 0 ; z-- ) {
+			asm volatile("prefetchnta %0" : : "m" (dptr[z][d]));
+			asm volatile("pcmpgtb %mm4,%mm5");
+			asm volatile("pcmpgtb %mm6,%mm7");
+			asm volatile("paddb %mm4,%mm4");
+			asm volatile("paddb %mm6,%mm6");
+			asm volatile("pand %mm0,%mm5");
+			asm volatile("pand %mm0,%mm7");
+			asm volatile("pxor %mm5,%mm4");
+			asm volatile("pxor %mm7,%mm6");
+			asm volatile("movq %0,%%mm5" : : "m" (dptr[z][d]));
+			asm volatile("movq %0,%%mm7" : : "m" (dptr[z][d+8]));
+			asm volatile("pxor %mm5,%mm2");
+			asm volatile("pxor %mm7,%mm3");
+			asm volatile("pxor %mm5,%mm4");
+			asm volatile("pxor %mm7,%mm6");
+			asm volatile("pxor %mm5,%mm5");
+			asm volatile("pxor %mm7,%mm7");
+		}
+		asm volatile("movntq %%mm2,%0" : "=m" (p[d]));
+		asm volatile("movntq %%mm3,%0" : "=m" (p[d+8]));
+		asm volatile("movntq %%mm4,%0" : "=m" (q[d]));
+		asm volatile("movntq %%mm6,%0" : "=m" (q[d+8]));
+	}
+
+	raid6_after_mmx(&sa);
+	asm volatile("sfence" : :: "memory");
+}
+
+const struct raid6_calls raid6_sse1x2 = {
+	raid6_sse12_gen_syndrome,
+	raid6_have_sse1_or_mmxext,
+	"sse1x2",
+	1			/* Has cache hints */
+};
+
+#endif

drivers/md/raid6sse2.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * raid6sse2.c
+ *
+ * SSE-2 implementation of RAID-6 syndrome functions
+ *
+ */
+
+#if defined(__i386__) || defined(__x86_64__)
+
+#include "raid6.h"
+#include "raid6x86.h"
+
+static const struct raid6_sse_constants {
+	u64 x1d[2];
+} raid6_sse_constants  __attribute__((aligned(16))) = {
+	{ 0x1d1d1d1d1d1d1d1dULL, 0x1d1d1d1d1d1d1d1dULL },
+};
+
+static int raid6_have_sse2(void)
+{
+#ifdef __KERNEL__
+	/* Not really boot_cpu but "all_cpus" */
+	return boot_cpu_has(X86_FEATURE_MMX) &&
+		boot_cpu_has(X86_FEATURE_FXSR) &&
+		boot_cpu_has(X86_FEATURE_XMM) &&
+		boot_cpu_has(X86_FEATURE_XMM2);
+#else
+	/* User space test code */
+	u32 features = cpuid_features();
+	return ( (features & (15<<23)) == (15<<23) );
+#endif
+}
+
+/*
+ * Plain SSE2 implementation
+ */
+static void raid6_sse21_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+	raid6_sse_save_t sa;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	raid6_before_sse2(&sa);
+
+	asm volatile("movdqa %0,%%xmm0" : : "m" (raid6_sse_constants.x1d[0]));
+	asm volatile("pxor %xmm5,%xmm5");	/* Zero temp */
+
+	for ( d = 0 ; d < bytes ; d += 16 ) {
+		asm volatile("prefetchnta %0" : : "m" (dptr[z0][d]));
+		asm volatile("movdqa %0,%%xmm2" : : "m" (dptr[z0][d])); /* P[0] */
+		asm volatile("prefetchnta %0" : : "m" (dptr[z0-1][d]));
+		asm volatile("movdqa %xmm2,%xmm4"); /* Q[0] */
+		asm volatile("movdqa %0,%%xmm6" : : "m" (dptr[z0-1][d]));
+		for ( z = z0-2 ; z >= 0 ; z-- ) {
+			asm volatile("prefetchnta %0" : : "m" (dptr[z][d]));
+			asm volatile("pcmpgtb %xmm4,%xmm5");
+			asm volatile("paddb %xmm4,%xmm4");
+			asm volatile("pand %xmm0,%xmm5");
+			asm volatile("pxor %xmm5,%xmm4");
+			asm volatile("pxor %xmm5,%xmm5");
+			asm volatile("pxor %xmm6,%xmm2");
+			asm volatile("pxor %xmm6,%xmm4");
+			asm volatile("movdqa %0,%%xmm6" : : "m" (dptr[z][d]));
+		}
+		asm volatile("pcmpgtb %xmm4,%xmm5");
+		asm volatile("paddb %xmm4,%xmm4");
+		asm volatile("pand %xmm0,%xmm5");
+		asm volatile("pxor %xmm5,%xmm4");
+		asm volatile("pxor %xmm5,%xmm5");
+		asm volatile("pxor %xmm6,%xmm2");
+		asm volatile("pxor %xmm6,%xmm4");
+
+		asm volatile("movntdq %%xmm2,%0" : "=m" (p[d]));
+		asm volatile("pxor %xmm2,%xmm2");
+		asm volatile("movntdq %%xmm4,%0" : "=m" (q[d]));
+		asm volatile("pxor %xmm4,%xmm4");
+	}
+
+	raid6_after_sse2(&sa);
+	asm volatile("sfence" : : : "memory");
+}
+
+const struct raid6_calls raid6_sse2x1 = {
+	raid6_sse21_gen_syndrome,
+	raid6_have_sse2,
+	"sse2x1",
+	1			/* Has cache hints */
+};
+
+/*
+ * Unrolled-by-2 SSE2 implementation
+ */
+static void raid6_sse22_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+	raid6_sse_save_t sa;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	raid6_before_sse2(&sa);
+
+	asm volatile("movdqa %0,%%xmm0" : : "m" (raid6_sse_constants.x1d[0]));
+	asm volatile("pxor %xmm5,%xmm5"); /* Zero temp */
+	asm volatile("pxor %xmm7,%xmm7"); /* Zero temp */
+
+	/* We uniformly assume a single prefetch covers at least 32 bytes */
+	for ( d = 0 ; d < bytes ; d += 32 ) {
+		asm volatile("prefetchnta %0" : : "m" (dptr[z0][d]));
+		asm volatile("movdqa %0,%%xmm2" : : "m" (dptr[z0][d]));    /* P[0] */
+		asm volatile("movdqa %0,%%xmm3" : : "m" (dptr[z0][d+16])); /* P[1] */
+		asm volatile("movdqa %xmm2,%xmm4"); /* Q[0] */
+		asm volatile("movdqa %xmm3,%xmm6"); /* Q[1] */
+		for ( z = z0-1 ; z >= 0 ; z-- ) {
+			asm volatile("prefetchnta %0" : : "m" (dptr[z][d]));
+			asm volatile("pcmpgtb %xmm4,%xmm5");
+			asm volatile("pcmpgtb %xmm6,%xmm7");
+			asm volatile("paddb %xmm4,%xmm4");
+			asm volatile("paddb %xmm6,%xmm6");
+			asm volatile("pand %xmm0,%xmm5");
+			asm volatile("pand %xmm0,%xmm7");
+			asm volatile("pxor %xmm5,%xmm4");
+			asm volatile("pxor %xmm7,%xmm6");
+			asm volatile("movdqa %0,%%xmm5" : : "m" (dptr[z][d]));
+			asm volatile("movdqa %0,%%xmm7" : : "m" (dptr[z][d+16]));
+			asm volatile("pxor %xmm5,%xmm2");
+			asm volatile("pxor %xmm7,%xmm3");
+			asm volatile("pxor %xmm5,%xmm4");
+			asm volatile("pxor %xmm7,%xmm6");
+			asm volatile("pxor %xmm5,%xmm5");
+			asm volatile("pxor %xmm7,%xmm7");
+		}
+		asm volatile("movntdq %%xmm2,%0" : "=m" (p[d]));
+		asm volatile("movntdq %%xmm3,%0" : "=m" (p[d+16]));
+		asm volatile("movntdq %%xmm4,%0" : "=m" (q[d]));
+		asm volatile("movntdq %%xmm6,%0" : "=m" (q[d+16]));
+	}
+
+	raid6_after_sse2(&sa);
+	asm volatile("sfence" : : : "memory");
+}
+
+const struct raid6_calls raid6_sse2x2 = {
+	raid6_sse22_gen_syndrome,
+	raid6_have_sse2,
+	"sse2x2",
+	1			/* Has cache hints */
+};
+
+#endif
+
+#ifdef __x86_64__
+
+/*
+ * Unrolled-by-4 SSE2 implementation
+ */
+static void raid6_sse24_gen_syndrome(int disks, size_t bytes, void **ptrs)
+{
+	u8 **dptr = (u8 **)ptrs;
+	u8 *p, *q;
+	int d, z, z0;
+	raid6_sse16_save_t sa;
+
+	z0 = disks - 3;		/* Highest data disk */
+	p = dptr[z0+1];		/* XOR parity */
+	q = dptr[z0+2];		/* RS syndrome */
+
+	raid6_before_sse16(&sa);
+
+	asm volatile("movdqa %0,%%xmm0" :: "m" (raid6_sse_constants.x1d[0]));
+	asm volatile("pxor %xmm2,%xmm2");	/* P[0] */
+	asm volatile("pxor %xmm3,%xmm3");	/* P[1] */
+	asm volatile("pxor %xmm4,%xmm4"); 	/* Q[0] */
+	asm volatile("pxor %xmm5,%xmm5");	/* Zero temp */
+	asm volatile("pxor %xmm6,%xmm6"); 	/* Q[1] */
+	asm volatile("pxor %xmm7,%xmm7"); 	/* Zero temp */
+	asm volatile("pxor %xmm10,%xmm10");	/* P[2] */
+	asm volatile("pxor %xmm11,%xmm11");	/* P[3] */
+	asm volatile("pxor %xmm12,%xmm12"); 	/* Q[2] */
+	asm volatile("pxor %xmm13,%xmm13");	/* Zero temp */
+	asm volatile("pxor %xmm14,%xmm14"); 	/* Q[3] */
+	asm volatile("pxor %xmm15,%xmm15"); 	/* Zero temp */
+
+	for ( d = 0 ; d < bytes ; d += 64 ) {
+		for ( z = z0 ; z >= 0 ; z-- ) {
+			/* The second prefetch seems to improve performance... */
+			asm volatile("prefetchnta %0" :: "m" (dptr[z][d]));
+			asm volatile("prefetchnta %0" :: "m" (dptr[z][d+32]));
+			asm volatile("pcmpgtb %xmm4,%xmm5");
+			asm volatile("pcmpgtb %xmm6,%xmm7");
+			asm volatile("pcmpgtb %xmm12,%xmm13");
+			asm volatile("pcmpgtb %xmm14,%xmm15");
+			asm volatile("paddb %xmm4,%xmm4");
+			asm volatile("paddb %xmm6,%xmm6");
+			asm volatile("paddb %xmm12,%xmm12");
+			asm volatile("paddb %xmm14,%xmm14");
+			asm volatile("pand %xmm0,%xmm5");
+			asm volatile("pand %xmm0,%xmm7");
+			asm volatile("pand %xmm0,%xmm13");
+			asm volatile("pand %xmm0,%xmm15");
+			asm volatile("pxor %xmm5,%xmm4");
+			asm volatile("pxor %xmm7,%xmm6");
+			asm volatile("pxor %xmm13,%xmm12");
+			asm volatile("pxor %xmm15,%xmm14");
+			asm volatile("movdqa %0,%%xmm5" :: "m" (dptr[z][d]));
+			asm volatile("movdqa %0,%%xmm7" :: "m" (dptr[z][d+16]));
+			asm volatile("movdqa %0,%%xmm13" :: "m" (dptr[z][d+32]));
+			asm volatile("movdqa %0,%%xmm15" :: "m" (dptr[z][d+48]));
+			asm volatile("pxor %xmm5,%xmm2");
+			asm volatile("pxor %xmm7,%xmm3");
+			asm volatile("pxor %xmm13,%xmm10");
+			asm volatile("pxor %xmm15,%xmm11");
+			asm volatile("pxor %xmm5,%xmm4");
+			asm volatile("pxor %xmm7,%xmm6");
+			asm volatile("pxor %xmm13,%xmm12");
+			asm volatile("pxor %xmm15,%xmm14");
+			asm volatile("pxor %xmm5,%xmm5");
+			asm volatile("pxor %xmm7,%xmm7");
+			asm volatile("pxor %xmm13,%xmm13");
+			asm volatile("pxor %xmm15,%xmm15");
+		}
+		asm volatile("movntdq %%xmm2,%0" : "=m" (p[d]));
+		asm volatile("pxor %xmm2,%xmm2");
+		asm volatile("movntdq %%xmm3,%0" : "=m" (p[d+16]));
+		asm volatile("pxor %xmm3,%xmm3");
+		asm volatile("movntdq %%xmm10,%0" : "=m" (p[d+32]));
+		asm volatile("pxor %xmm10,%xmm10");
+		asm volatile("movntdq %%xmm11,%0" : "=m" (p[d+48]));
+		asm volatile("pxor %xmm11,%xmm11");
+		asm volatile("movntdq %%xmm4,%0" : "=m" (q[d]));
+		asm volatile("pxor %xmm4,%xmm4");
+		asm volatile("movntdq %%xmm6,%0" : "=m" (q[d+16]));
+		asm volatile("pxor %xmm6,%xmm6");
+		asm volatile("movntdq %%xmm12,%0" : "=m" (q[d+32]));
+		asm volatile("pxor %xmm12,%xmm12");
+		asm volatile("movntdq %%xmm14,%0" : "=m" (q[d+48]));
+		asm volatile("pxor %xmm14,%xmm14");
+	}
+	asm volatile("sfence" : : : "memory");
+	raid6_after_sse16(&sa);
+}
+
+const struct raid6_calls raid6_sse2x4 = {
+	raid6_sse24_gen_syndrome,
+	raid6_have_sse2,
+	"sse2x4",
+	1			/* Has cache hints */
+};
+
+#endif

drivers/md/raid6test/Makefile

+#
+# This is a simple Makefile to test some of the RAID-6 code
+# from userspace.
+#
+
+CC	= gcc
+CFLAGS	= -I.. -O2 -g -march=i686
+LD	= ld
+PERL	= perl
+
+.c.o:
+	$(CC) $(CFLAGS) -c -o $@ $<
+
+%.c: ../%.c
+	cp -f $< $@
+
+%.uc: ../%.uc
+	cp -f $< $@
+
+%.pl: ../%.pl
+	cp -f $< $@
+
+all:	raid6.o raid6test
+
+raid6.o: raid6int1.o raid6int2.o raid6int4.o raid6int8.o raid6int16.o \
+	 raid6mmx.o raid6sse1.o raid6sse2.o \
+	 raid6recov.o raid6algos.o \
+	 raid6tables.o
+	$(LD) -r -o $@ $^
+
+raid6test: raid6.o test.c
+	$(CC) $(CFLAGS) -o raid6test $^
+
+raid6int1.c: raid6int.uc unroller.pl
+	$(PERL) ./unroller.pl 1 < raid6int.uc > $@
+
+raid6int2.c: raid6int.uc unroller.pl
+	$(PERL) ./unroller.pl 2 < raid6int.uc > $@
+
+raid6int4.c: raid6int.uc unroller.pl
+	$(PERL) ./unroller.pl 4 < raid6int.uc > $@
+
+raid6int8.c: raid6int.uc unroller.pl
+	$(PERL) ./unroller.pl 8 < raid6int.uc > $@
+
+raid6int16.c: raid6int.uc unroller.pl
+	$(PERL) ./unroller.pl 16 < raid6int.uc > $@
+
+raid6tables.c: mktables
+	./mktables > raid6tables.c
+
+clean:
+	rm -f *.o mktables mktables.c raid6int.uc raid6*.c raid6test
+
+spotless: clean
+	rm -f *~

drivers/md/raid6test/test.c

+/* -*- linux-c -*- ------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * raid6test.c
+ *
+ * Test RAID-6 recovery with various algorithms
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "raid6.h"
+
+#define NDISKS		16	/* Including P and Q */
+
+const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
+struct raid6_calls raid6_call;
+
+char *dataptrs[NDISKS];
+char data[NDISKS][PAGE_SIZE];
+char recovi[PAGE_SIZE], recovj[PAGE_SIZE];
+
+void makedata(void)
+{
+	int i, j;
+
+	for (  i = 0 ; i < NDISKS ; i++ ) {
+		for ( j = 0 ; j < PAGE_SIZE ; j++ ) {
+			data[i][j] = rand();
+		}
+		dataptrs[i] = data[i];
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	const struct raid6_calls * const * algo;
+	int i, j;
+	int erra, errb;
+
+	makedata();
+
+	for ( algo = raid6_algos ; *algo ; algo++ ) {
+		if ( !(*algo)->valid || (*algo)->valid() ) {
+			raid6_call = **algo;
+
+			/* Nuke syndromes */
+			memset(data[NDISKS-2], 0xee, 2*PAGE_SIZE);
+
+			/* Generate assumed good syndrome */
+			raid6_call.gen_syndrome(NDISKS, PAGE_SIZE, (void **)&dataptrs);
+
+			for ( i = 0 ; i < NDISKS-1 ; i++ ) {
+				for ( j = i+1 ; j < NDISKS ; j++ ) {
+					memset(recovi, 0xf0, PAGE_SIZE);
+					memset(recovj, 0xba, PAGE_SIZE);
+
+					dataptrs[i] = recovi;
+					dataptrs[j] = recovj;
+
+					raid6_dual_recov(NDISKS, PAGE_SIZE, i, j, (void **)&dataptrs);
+
+					erra = memcmp(data[i], recovi, PAGE_SIZE);
+					errb = memcmp(data[j], recovj, PAGE_SIZE);
+
+					printf("algo=%-8s  faila=%3d(%c)  failb=%3d(%c)  %s\n",
+					       raid6_call.name,
+					       i, (i==NDISKS-2)?'P':'D',
+					       j, (j==NDISKS-1)?'Q':(j==NDISKS-2)?'P':'D',
+					       (!erra && !errb) ? "OK" :
+					       !erra ? "ERRB" :
+					       !errb ? "ERRA" :
+					       "ERRAB");
+
+					dataptrs[i] = data[i];
+					dataptrs[j] = data[j];
+				}
+			}
+		}
+		printf("\n");
+	}
+
+	printf("\n");
+	/* Pick the best algorithm test */
+	raid6_select_algo();
+
+	return 0;
+}

drivers/md/raid6x86.h

+#ident "$Id: raid6x86.h,v 1.3 2002/12/12 22:41:27 hpa Exp $"
+/* ----------------------------------------------------------------------- *
+ *
+ *   Copyright 2002 H. Peter Anvin - All Rights Reserved
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
+ *   Bostom MA 02111-1307, USA; either version 2 of the License, or
+ *   (at your option) any later version; incorporated herein by reference.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * raid6x86.h
+ *
+ * Definitions common to x86 and x86-64 RAID-6 code only
+ */
+
+#ifndef LINUX_RAID_RAID6X86_H
+#define LINUX_RAID_RAID6X86_H
+
+#if defined(__i386__) || defined(__x86_64__)
+
+typedef struct {
+	unsigned int fsave[27];
+	unsigned int cr0;
+} raid6_mmx_save_t;
+
+/* N.B.: For SSE we only save %xmm0-%xmm7 even for x86-64, since
+   the code doesn't know about the additional x86-64 registers */
+/* The +3 is so we can make sure the area is aligned properly */
+typedef struct {
+	unsigned int sarea[8*4+3];
+	unsigned int cr0;
+} raid6_sse_save_t __attribute__((aligned(16)));
+
+#ifdef __x86_64__
+
+/* This is for x86-64-specific code which uses all 16 XMM registers */
+typedef struct {
+	unsigned int sarea[16*4+3];
+	unsigned int cr0;
+} raid6_sse16_save_t __attribute__((aligned(16)));
+
+#endif
+
+#ifdef __KERNEL__ /* Real code */
+
+ static inline u32 raid6_get_fpu(void)
+{
+	u32 cr0;
+
+	preempt_disable();
+	asm volatile("movl %%cr0,%0 ; clts" : "=r" (cr0));
+	return cr0;
+}
+
+static inline void raid6_put_fpu(u32 cr0)
+{
+	asm volatile("movl %0,%%cr0" : : "r" (cr0));
+	preempt_enable();
+}
+
+#else /* Dummy code for user space testing */
+
+static inline u32 raid6_get_fpu(void)
+{
+	return 0xf00ba6;
+}
+
+static inline void raid6_put_fpu(u32 cr0)
+{
+	(void)cr0;
+}
+
+#endif
+
+static inline void raid6_before_mmx(raid6_mmx_save_t *s)
+{
+	s->cr0 = raid6_get_fpu();
+	asm volatile("fsave %0 ; fwait" : "=m" (s->fsave[0]));
+}
+
+static inline void raid6_after_mmx(raid6_mmx_save_t *s)
+{
+	asm volatile("frstor %0" : : "m" (s->fsave[0]));
+	raid6_put_fpu(s->cr0);
+}
+
+static inline void raid6_before_sse(raid6_sse_save_t *s)
+{
+#ifdef __x86_64__
+	unsigned int *rsa = s->sarea;
+#else
+	/* On i386 the save area may not be aligned */
+	unsigned int *rsa =
+		(unsigned int *)((((unsigned long)&s->sarea)+15) & ~15);
+#endif
+	s->cr0 = raid6_get_fpu();
+
+	asm volatile("movaps %%xmm0,%0" : "=m" (rsa[0]));
+	asm volatile("movaps %%xmm1,%0" : "=m" (rsa[4]));
+	asm volatile("movaps %%xmm2,%0" : "=m" (rsa[8]));
+	asm volatile("movaps %%xmm3,%0" : "=m" (rsa[12]));
+	asm volatile("movaps %%xmm4,%0" : "=m" (rsa[16]));
+	asm volatile("movaps %%xmm5,%0" : "=m" (rsa[20]));
+	asm volatile("movaps %%xmm6,%0" : "=m" (rsa[24]));
+	asm volatile("movaps %%xmm7,%0" : "=m" (rsa[28]));
+}
+
+static inline void raid6_after_sse(raid6_sse_save_t *s)
+{
+#ifdef __x86_64__
+	unsigned int *rsa = s->sarea;
+#else
+	/* On i386 the save area may not be aligned */
+	unsigned int *rsa =
+		(unsigned int *)((((unsigned long)&s->sarea)+15) & ~15);
+#endif
+	asm volatile("movaps %0,%%xmm0" : : "m" (rsa[0]));
+	asm volatile("movaps %0,%%xmm1" : : "m" (rsa[4]));
+	asm volatile("movaps %0,%%xmm2" : : "m" (rsa[8]));
+	asm volatile("movaps %0,%%xmm3" : : "m" (rsa[12]));
+	asm volatile("movaps %0,%%xmm4" : : "m" (rsa[16]));
+	asm volatile("movaps %0,%%xmm5" : : "m" (rsa[20]));
+	asm volatile("movaps %0,%%xmm6" : : "m" (rsa[24]));
+	asm volatile("movaps %0,%%xmm7" : : "m" (rsa[28]));
+
+	raid6_put_fpu(s->cr0);
+}
+
+static inline void raid6_before_sse2(raid6_sse_save_t *s)
+{
+#ifdef __x86_64__
+	unsigned int *rsa = &s->sarea;
+#else
+	/* On i386 the save area may not be aligned */
+	unsigned int *rsa =
+		(unsigned int *)((((unsigned long)&s->sarea)+15) & ~15);
+#endif
+	s->cr0 = raid6_get_fpu();
+
+	asm volatile("movdqa %%xmm0,%0" : "=m" (rsa[0]));
+	asm volatile("movdqa %%xmm1,%0" : "=m" (rsa[4]));
+	asm volatile("movdqa %%xmm2,%0" : "=m" (rsa[8]));
+	asm volatile("movdqa %%xmm3,%0" : "=m" (rsa[12]));
+	asm volatile("movdqa %%xmm4,%0" : "=m" (rsa[16]));
+	asm volatile("movdqa %%xmm5,%0" : "=m" (rsa[20]));
+	asm volatile("movdqa %%xmm6,%0" : "=m" (rsa[24]));
+	asm volatile("movdqa %%xmm7,%0" : "=m" (rsa[28]));
+}
+
+static inline void raid6_after_sse2(raid6_sse_save_t *s)
+{
+#ifdef __x86_64__
+	unsigned int *rsa = s->sarea;
+#else
+	/* On i386 the save area may not be aligned */
+	unsigned int *rsa =
+		(unsigned int *)((((unsigned long)&s->sarea)+15) & ~15);
+#endif
+	asm volatile("movdqa %0,%%xmm0" : : "m" (rsa[0]));
+	asm volatile("movdqa %0,%%xmm1" : : "m" (rsa[4]));
+	asm volatile("movdqa %0,%%xmm2" : : "m" (rsa[8]));
+	asm volatile("movdqa %0,%%xmm3" : : "m" (rsa[12]));
+	asm volatile("movdqa %0,%%xmm4" : : "m" (rsa[16]));
+	asm volatile("movdqa %0,%%xmm5" : : "m" (rsa[20]));
+	asm volatile("movdqa %0,%%xmm6" : : "m" (rsa[24]));
+	asm volatile("movdqa %0,%%xmm7" : : "m" (rsa[28]));
+
+	raid6_put_fpu(s->cr0);
+}
+
+#ifdef __x86_64__
+
+static inline raid6_before_sse16(raid6_sse16_save_t *s)
+{
+	unsigned int *rsa = s->sarea;
+
+	s->cr0 = raid6_get_fpu();
+
+	asm volatile("movdqa %%xmm0,%0" : "=m" (rsa[0]));
+	asm volatile("movdqa %%xmm1,%0" : "=m" (rsa[4]));
+	asm volatile("movdqa %%xmm2,%0" : "=m" (rsa[8]));
+	asm volatile("movdqa %%xmm3,%0" : "=m" (rsa[12]));
+	asm volatile("movdqa %%xmm4,%0" : "=m" (rsa[16]));
+	asm volatile("movdqa %%xmm5,%0" : "=m" (rsa[20]));
+	asm volatile("movdqa %%xmm6,%0" : "=m" (rsa[24]));
+	asm volatile("movdqa %%xmm7,%0" : "=m" (rsa[28]));
+	asm volatile("movdqa %%xmm8,%0" : "=m" (rsa[32]));
+	asm volatile("movdqa %%xmm9,%0" : "=m" (rsa[36]));
+	asm volatile("movdqa %%xmm10,%0" : "=m" (rsa[40]));
+	asm volatile("movdqa %%xmm11,%0" : "=m" (rsa[44]));
+	asm volatile("movdqa %%xmm12,%0" : "=m" (rsa[48]));
+	asm volatile("movdqa %%xmm13,%0" : "=m" (rsa[52]));
+	asm volatile("movdqa %%xmm14,%0" : "=m" (rsa[56]));
+	asm volatile("movdqa %%xmm15,%0" : "=m" (rsa[60]));
+}
+
+static inline raid6_after_sse16(raid6_sse16_save_t *s)
+{
+	unsigned int *rsa = s->sarea;
+
+	asm volatile("movdqa %0,%%xmm0" : : "m" (rsa[0]));
+	asm volatile("movdqa %0,%%xmm1" : : "m" (rsa[4]));
+	asm volatile("movdqa %0,%%xmm2" : : "m" (rsa[8]));
+	asm volatile("movdqa %0,%%xmm3" : : "m" (rsa[12]));
+	asm volatile("movdqa %0,%%xmm4" : : "m" (rsa[16]));
+	asm volatile("movdqa %0,%%xmm5" : : "m" (rsa[20]));
+	asm volatile("movdqa %0,%%xmm6" : : "m" (rsa[24]));
+	asm volatile("movdqa %0,%%xmm7" : : "m" (rsa[28]));
+	asm volatile("movdqa %0,%%xmm8" : : "m" (rsa[32]));
+	asm volatile("movdqa %0,%%xmm9" : : "m" (rsa[36]));
+	asm volatile("movdqa %0,%%xmm10" : : "m" (rsa[40]));
+	asm volatile("movdqa %0,%%xmm11" : : "m" (rsa[44]));
+	asm volatile("movdqa %0,%%xmm12" : : "m" (rsa[48]));
+	asm volatile("movdqa %0,%%xmm13" : : "m" (rsa[52]));
+	asm volatile("movdqa %0,%%xmm14" : : "m" (rsa[56]));
+	asm volatile("movdqa %0,%%xmm15" : : "m" (rsa[60]));
+
+	raid6_put_fpu(s->cr0);
+}
+
+#endif /* __x86_64__ */
+
+/* User space test hack */
+#ifndef __KERNEL__
+static inline int cpuid_features(void)
+{
+	u32 eax = 1;
+	u32 ebx, ecx, edx;
+
+	asm volatile("cpuid" :
+		     "+a" (eax), "=b" (ebx), "=c" (ecx), "=d" (edx));
+
+	return edx;
+}
+#endif /* ndef __KERNEL__ */
+
+#endif
+#endif

drivers/md/unroll.pl

+#!/usr/bin/perl
+#
+# Take a piece of C code and for each line which contains the sequence $$
+# repeat n times with $ replaced by 0...n-1; the sequence $# is replaced
+# by the unrolling factor, and $* with a single $
+#
+
+($n) = @ARGV;
+$n += 0;
+
+while ( defined($line = <STDIN>) ) {
+    if ( $line =~ /\$\$/ ) {
+	$rep = $n;
+    } else {
+	$rep = 1;
+    }
+    for ( $i = 0 ; $i < $rep ; $i++ ) {
+	$tmp = $line;
+	$tmp =~ s/\$\$/$i/g;
+	$tmp =~ s/\$\#/$n/g;
+	$tmp =~ s/\$\*/\$/g;
+	print $tmp;
+    }
+}

include/linux/raid/md_k.h

@@ -23,7 +23,8 @@
 #define TRANSLUCENT       5UL
 #define HSM               6UL
 #define MULTIPATH         7UL
-#define MAX_PERSONALITY   8UL
+#define RAID6		  8UL
+#define MAX_PERSONALITY   9UL
 
 #define	LEVEL_MULTIPATH		(-4)
 #define	LEVEL_LINEAR		(-1)
@@ -41,6 +42,7 @@ static inline int pers_to_level (int pers)
 		case RAID0:		return 0;
 		case RAID1:		return 1;
 		case RAID5:		return 5;
+		case RAID6:		return 6;
 	}
 	BUG();
 	return MD_RESERVED;
@@ -57,6 +59,7 @@ static inline int level_to_pers (int level)
 		case 1: return RAID1;
 		case 4:
 		case 5: return RAID5;
+		case 6: return RAID6;
 	}
 	return MD_RESERVED;
 }