Adding upstream version 4.3.upstream/4.3

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1038 insertions, 0 deletions

diff --git a/restripe.c b/restripe.c
new file mode 100644
index 0000000..a7a7229
--- /dev/null
+++ b/restripe.c
@@ -0,0 +1,1038 @@
+/*
+ * mdadm - manage Linux "md" devices aka RAID arrays.
+ *
+ * Copyright (C) 2006-2009 Neil Brown <neilb@suse.de>
+ *
+ *
+ *    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 of the License, or
+ *    (at your option) any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program; if not, write to the Free Software
+ *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ *    Author: Neil Brown
+ *    Email: <neilb@suse.de>
+ */
+
+#include "mdadm.h"
+#include <stdint.h>
+
+/* To restripe, we read from old geometry to a buffer, and
+ * read from buffer to new geometry.
+ * When reading, we might have missing devices and so could need
+ * to reconstruct.
+ * When writing, we need to create correct parity and Q.
+ *
+ */
+
+int geo_map(int block, unsigned long long stripe, int raid_disks,
+		   int level, int layout)
+{
+	/* On the given stripe, find which disk in the array will have
+	 * block numbered 'block'.
+	 * '-1' means the parity block.
+	 * '-2' means the Q syndrome.
+	 */
+	int pd;
+
+	/* layout is not relevant for raid0 and raid4 */
+	if ((level == 0) ||
+	    (level == 4))
+		layout = 0;
+
+	switch(level*100 + layout) {
+	case 000:
+	case 400:
+	case 500 + ALGORITHM_PARITY_N:
+		/* raid 4 isn't messed around by parity blocks */
+		if (block == -1)
+			return raid_disks-1; /* parity block */
+		return block;
+	case 500 + ALGORITHM_LEFT_ASYMMETRIC:
+		pd = (raid_disks-1) - stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		if (block >= pd)
+			block++;
+		return block;
+
+	case 500 + ALGORITHM_RIGHT_ASYMMETRIC:
+		pd = stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		if (block >= pd)
+			block++;
+		return block;
+
+	case 500 + ALGORITHM_LEFT_SYMMETRIC:
+		pd = (raid_disks - 1) - stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		return (pd + 1 + block) % raid_disks;
+
+	case 500 + ALGORITHM_RIGHT_SYMMETRIC:
+		pd = stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		return (pd + 1 + block) % raid_disks;
+
+	case 500 + ALGORITHM_PARITY_0:
+		return block + 1;
+
+	case 600 + ALGORITHM_PARITY_N_6:
+		if (block == -2)
+			return raid_disks - 1;
+		if (block == -1)
+			return raid_disks - 2; /* parity block */
+		return block;
+	case 600 + ALGORITHM_LEFT_ASYMMETRIC_6:
+		if (block == -2)
+			return raid_disks - 1;
+		raid_disks--;
+		pd = (raid_disks-1) - stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		if (block >= pd)
+			block++;
+		return block;
+
+	case 600 + ALGORITHM_RIGHT_ASYMMETRIC_6:
+		if (block == -2)
+			return raid_disks - 1;
+		raid_disks--;
+		pd = stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		if (block >= pd)
+			block++;
+		return block;
+
+	case 600 + ALGORITHM_LEFT_SYMMETRIC_6:
+		if (block == -2)
+			return raid_disks - 1;
+		raid_disks--;
+		pd = (raid_disks - 1) - stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		return (pd + 1 + block) % raid_disks;
+
+	case 600 + ALGORITHM_RIGHT_SYMMETRIC_6:
+		if (block == -2)
+			return raid_disks - 1;
+		raid_disks--;
+		pd = stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		return (pd + 1 + block) % raid_disks;
+
+	case 600 + ALGORITHM_PARITY_0_6:
+		if (block == -2)
+			return raid_disks - 1;
+		return block + 1;
+
+	case 600 + ALGORITHM_PARITY_0:
+		if (block == -1)
+			return 0;
+		if (block == -2)
+			return 1;
+		return block + 2;
+
+	case 600 + ALGORITHM_LEFT_ASYMMETRIC:
+		pd = raid_disks - 1 - (stripe % raid_disks);
+		if (block == -1)
+			return pd;
+		if (block == -2)
+			return (pd+1) % raid_disks;
+		if (pd == raid_disks - 1)
+			return block+1;
+		if (block >= pd)
+			return block+2;
+		return block;
+
+	case 600 + ALGORITHM_ROTATING_ZERO_RESTART:
+		/* Different order for calculating Q, otherwize same as ... */
+	case 600 + ALGORITHM_RIGHT_ASYMMETRIC:
+		pd = stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		if (block == -2)
+			return (pd+1) % raid_disks;
+		if (pd == raid_disks - 1)
+			return block+1;
+		if (block >= pd)
+			return block+2;
+		return block;
+
+	case 600 + ALGORITHM_LEFT_SYMMETRIC:
+		pd = raid_disks - 1 - (stripe % raid_disks);
+		if (block == -1)
+			return pd;
+		if (block == -2)
+			return (pd+1) % raid_disks;
+		return (pd + 2 + block) % raid_disks;
+
+	case 600 + ALGORITHM_RIGHT_SYMMETRIC:
+		pd = stripe % raid_disks;
+		if (block == -1)
+			return pd;
+		if (block == -2)
+			return (pd+1) % raid_disks;
+		return (pd + 2 + block) % raid_disks;
+
+	case 600 + ALGORITHM_ROTATING_N_RESTART:
+		/* Same a left_asymmetric, by first stripe is
+		 * D D D P Q  rather than
+		 * Q D D D P
+		 */
+		pd = raid_disks - 1 - ((stripe + 1) % raid_disks);
+		if (block == -1)
+			return pd;
+		if (block == -2)
+			return (pd+1) % raid_disks;
+		if (pd == raid_disks - 1)
+			return block+1;
+		if (block >= pd)
+			return block+2;
+		return block;
+
+	case 600 + ALGORITHM_ROTATING_N_CONTINUE:
+		/* Same as left_symmetric but Q is before P */
+		pd = raid_disks - 1 - (stripe % raid_disks);
+		if (block == -1)
+			return pd;
+		if (block == -2)
+			return (pd+raid_disks-1) % raid_disks;
+		return (pd + 1 + block) % raid_disks;
+	}
+	return -1;
+}
+
+int is_ddf(int layout)
+{
+	switch (layout)
+	{
+	default:
+		return 0;
+	case ALGORITHM_ROTATING_N_CONTINUE:
+	case ALGORITHM_ROTATING_N_RESTART:
+	case ALGORITHM_ROTATING_ZERO_RESTART:
+		return 1;
+	}
+}
+
+void xor_blocks(char *target, char **sources, int disks, int size)
+{
+	int i, j;
+	/* Amazingly inefficient... */
+	for (i=0; i<size; i++) {
+		char c = 0;
+		for (j=0 ; j<disks; j++)
+			c ^= sources[j][i];
+		target[i] = c;
+	}
+}
+
+void qsyndrome(uint8_t *p, uint8_t *q, uint8_t **sources, int disks, int size)
+{
+	int d, z;
+	uint8_t wq0, wp0, wd0, w10, w20;
+	for ( d = 0; d < size; d++) {
+		wq0 = wp0 = sources[disks-1][d];
+		for ( z = disks-2 ; z >= 0 ; z-- ) {
+			wd0 = sources[z][d];
+			wp0 ^= wd0;
+			w20 = (wq0&0x80) ? 0xff : 0x00;
+			w10 = (wq0 << 1) & 0xff;
+			w20 &= 0x1d;
+			w10 ^= w20;
+			wq0 = w10 ^ wd0;
+		}
+		p[d] = wp0;
+		q[d] = wq0;
+	}
+}
+
+/*
+ * The following was taken from linux/drivers/md/mktables.c, and modified
+ * to create in-memory tables rather than C code
+ */
+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 tables_ready = 0;
+uint8_t raid6_gfmul[256][256];
+uint8_t raid6_gfexp[256];
+uint8_t raid6_gfinv[256];
+uint8_t raid6_gfexi[256];
+uint8_t raid6_gflog[256];
+uint8_t raid6_gfilog[256];
+void make_tables(void)
+{
+	int i, j;
+	uint8_t v;
+	uint32_t b, log;
+
+	/* Compute multiplication table */
+	for (i = 0; i < 256; i++)
+		for (j = 0; j < 256; j++)
+				raid6_gfmul[i][j] = gfmul(i, j);
+
+	/* Compute power-of-2 table (exponent) */
+	v = 1;
+	for (i = 0; i < 256; i++) {
+		raid6_gfexp[i] = v;
+		v = gfmul(v, 2);
+		if (v == 1)
+			v = 0;	/* For entry 255, not a real entry */
+	}
+
+	/* Compute inverse table x^-1 == x^254 */
+	for (i = 0; i < 256; i++)
+		raid6_gfinv[i] = gfpow(i, 254);
+
+	/* Compute inv(2^x + 1) (exponent-xor-inverse) table */
+	for (i = 0; i < 256; i ++)
+		raid6_gfexi[i] = raid6_gfinv[raid6_gfexp[i] ^ 1];
+
+	/* Compute log and inverse log */
+	/* Modified code from:
+	 *    https://web.eecs.utk.edu/~plank/plank/papers/CS-96-332.html
+	 */
+	b = 1;
+	raid6_gflog[0] = 0;
+	raid6_gfilog[255] = 0;
+
+	for (log = 0; log < 255; log++) {
+		raid6_gflog[b] = (uint8_t) log;
+		raid6_gfilog[log] = (uint8_t) b;
+		b = b << 1;
+		if (b & 256) b = b ^ 0435;
+	}
+
+	tables_ready = 1;
+}
+
+uint8_t *zero;
+int zero_size;
+
+void ensure_zero_has_size(int chunk_size)
+{
+	if (zero == NULL || chunk_size > zero_size) {
+		if (zero)
+			free(zero);
+		zero = xcalloc(1, chunk_size);
+		zero_size = chunk_size;
+	}
+}
+
+/* Following was taken from linux/drivers/md/raid6recov.c */
+
+/* Recover two failed data blocks. */
+
+void raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
+		       uint8_t **ptrs, int neg_offset)
+{
+	uint8_t *p, *q, *dp, *dq;
+	uint8_t px, qx, db;
+	const uint8_t *pbmul;	/* P multiplier table for B data */
+	const uint8_t *qmul;		/* Q multiplier table (for both) */
+
+	if (faila > failb) {
+		int t = faila;
+		faila = failb;
+		failb = t;
+	}
+
+	if (neg_offset) {
+		p = ptrs[-1];
+		q = ptrs[-2];
+	} else {
+		p = ptrs[disks-2];
+		q = 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 = ptrs[faila];
+	ptrs[faila] = zero;
+	dq = ptrs[failb];
+	ptrs[failb] = zero;
+
+	qsyndrome(dp, dq, ptrs, disks-2, bytes);
+
+	/* Restore pointer table */
+	ptrs[faila]   = dp;
+	ptrs[failb]   = dq;
+
+	/* 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, uint8_t **ptrs,
+		       int neg_offset)
+{
+	uint8_t *p, *q, *dq;
+	const uint8_t *qmul;		/* Q multiplier table */
+
+	if (neg_offset) {
+		p = ptrs[-1];
+		q = ptrs[-2];
+	} else {
+		p = ptrs[disks-2];
+		q = ptrs[disks-1];
+	}
+
+	/* Compute syndrome with zero for the missing data page
+	   Use the dead data page as temporary storage for delta q */
+	dq = ptrs[faila];
+	ptrs[faila] = zero;
+
+	qsyndrome(p, dq, ptrs, disks-2, bytes);
+
+	/* Restore pointer table */
+	ptrs[faila]   = dq;
+
+	/* 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++;
+	}
+}
+
+/* Try to find out if a specific disk has a problem */
+int raid6_check_disks(int data_disks, int start, int chunk_size,
+		      int level, int layout, int diskP, int diskQ,
+		      uint8_t *p, uint8_t *q, char **stripes)
+{
+	int i;
+	int data_id, diskD;
+	uint8_t Px, Qx;
+	int curr_broken_disk = -1;
+	int prev_broken_disk = -1;
+	int broken_status = 0;
+
+	for(i = 0; i < chunk_size; i++) {
+		Px = (uint8_t)stripes[diskP][i] ^ (uint8_t)p[i];
+		Qx = (uint8_t)stripes[diskQ][i] ^ (uint8_t)q[i];
+
+		if((Px != 0) && (Qx == 0))
+			curr_broken_disk = diskP;
+
+		if((Px == 0) && (Qx != 0))
+			curr_broken_disk = diskQ;
+
+		if((Px != 0) && (Qx != 0)) {
+			data_id = (raid6_gflog[Qx] - raid6_gflog[Px]);
+			if(data_id < 0) data_id += 255;
+			diskD = geo_map(data_id, start/chunk_size,
+					data_disks + 2, level, layout);
+			curr_broken_disk = diskD;
+		}
+
+		if((Px == 0) && (Qx == 0))
+			curr_broken_disk = prev_broken_disk;
+
+		if(curr_broken_disk >= data_disks + 2)
+			broken_status = 2;
+
+		switch(broken_status) {
+		case 0:
+			if(curr_broken_disk != -1) {
+				prev_broken_disk = curr_broken_disk;
+				broken_status = 1;
+			}
+			break;
+
+		case 1:
+			if(curr_broken_disk != prev_broken_disk)
+				broken_status = 2;
+			break;
+
+		case 2:
+		default:
+			curr_broken_disk = prev_broken_disk = -2;
+			break;
+		}
+	}
+
+	return curr_broken_disk;
+}
+
+/*******************************************************************************
+ * Function:	save_stripes
+ * Description:
+ *	Function reads data (only data without P and Q) from array and writes
+ * it to buf and opcjonaly to backup files
+ * Parameters:
+ *	source		: A list of 'fds' of the active disks.
+ *			  Some may be absent
+ *	offsets		: A list of offsets on disk belonging
+ *			 to the array [bytes]
+ *	raid_disks	: geometry: number of disks in the array
+ *	chunk_size	: geometry: chunk size [bytes]
+ *	level		: geometry: RAID level
+ *	layout		: geometry: layout
+ *	nwrites		: number of backup files
+ *	dest		: A list of 'fds' for mirrored targets
+ *			  (e.g. backup files). They are already seeked to right
+ *			  (write) location. If NULL, data will be wrote
+ *			  to the buf only
+ *	start		: start address of data to read (must be stripe-aligned)
+ *			  [bytes]
+ *	length	-	: length of data to read (must be stripe-aligned)
+ *			  [bytes]
+ *	buf		: buffer for data. It is large enough to hold
+ *			  one stripe. It is stripe aligned
+ * Returns:
+ *	 0 : success
+ *	-1 : fail
+ ******************************************************************************/
+int save_stripes(int *source, unsigned long long *offsets,
+		 int raid_disks, int chunk_size, int level, int layout,
+		 int nwrites, int *dest,
+		 unsigned long long start, unsigned long long length,
+		 char *buf)
+{
+	int len;
+	int data_disks = raid_disks - (level == 0 ? 0 : level <=5 ? 1 : 2);
+	int disk;
+	int i;
+	unsigned long long length_test;
+
+	if (!tables_ready)
+		make_tables();
+	ensure_zero_has_size(chunk_size);
+
+	len = data_disks * chunk_size;
+	length_test = length / len;
+	length_test *= len;
+
+	if (length != length_test) {
+		dprintf("Error: save_stripes(): Data are not alligned. EXIT\n");
+		dprintf("\tArea for saving stripes (length) = %llu\n", length);
+		dprintf("\tWork step (len)                  = %i\n", len);
+		dprintf("\tExpected save area (length_test) = %llu\n",
+			length_test);
+		abort();
+	}
+
+	while (length > 0) {
+		int failed = 0;
+		int fdisk[3], fblock[3];
+		for (disk = 0; disk < raid_disks ; disk++) {
+			unsigned long long offset;
+			int dnum;
+
+			offset = (start/chunk_size/data_disks)*chunk_size;
+			dnum = geo_map(disk < data_disks ? disk : data_disks - disk - 1,
+				       start/chunk_size/data_disks,
+				       raid_disks, level, layout);
+			if (dnum < 0) abort();
+			if (source[dnum] < 0 ||
+			    lseek64(source[dnum],
+				    offsets[dnum] + offset, 0) < 0 ||
+			    read(source[dnum], buf+disk * chunk_size,
+				 chunk_size) != chunk_size) {
+				if (failed <= 2) {
+					fdisk[failed] = dnum;
+					fblock[failed] = disk;
+					failed++;
+				}
+			}
+		}
+		if (failed == 0 || fblock[0] >= data_disks)
+			/* all data disks are good */
+			;
+		else if (failed == 1 || fblock[1] >= data_disks+1) {
+			/* one failed data disk and good parity */
+			char *bufs[data_disks];
+			for (i=0; i < data_disks; i++)
+				if (fblock[0] == i)
+					bufs[i] = buf + data_disks*chunk_size;
+				else
+					bufs[i] = buf + i*chunk_size;
+
+			xor_blocks(buf + fblock[0]*chunk_size,
+				   bufs, data_disks, chunk_size);
+		} else if (failed > 2 || level != 6)
+			/* too much failure */
+			return -1;
+		else {
+			/* RAID6 computations needed. */
+			uint8_t *bufs[data_disks+4];
+			int qdisk;
+			int syndrome_disks;
+			disk = geo_map(-1, start/chunk_size/data_disks,
+				       raid_disks, level, layout);
+			qdisk = geo_map(-2, start/chunk_size/data_disks,
+				       raid_disks, level, layout);
+			if (is_ddf(layout)) {
+				/* q over 'raid_disks' blocks, in device order.
+				 * 'p' and 'q' get to be all zero
+				 */
+				for (i = 0; i < raid_disks; i++)
+					bufs[i] = zero;
+				for (i = 0; i < data_disks; i++) {
+					int dnum = geo_map(i,
+							   start/chunk_size/data_disks,
+							   raid_disks, level, layout);
+					int snum;
+					/* i is the logical block number, so is index to 'buf'.
+					 * dnum is physical disk number
+					 * and thus the syndrome number.
+					 */
+					snum = dnum;
+					bufs[snum] = (uint8_t*)buf + chunk_size * i;
+				}
+				syndrome_disks = raid_disks;
+			} else {
+				/* for md, q is over 'data_disks' blocks,
+				 * starting immediately after 'q'
+				 * Note that for the '_6' variety, the p block
+				 * makes a hole that we need to be careful of.
+				 */
+				int j;
+				int snum = 0;
+				for (j = 0; j < raid_disks; j++) {
+					int dnum = (qdisk + 1 + j) % raid_disks;
+					if (dnum == disk || dnum == qdisk)
+						continue;
+					for (i = 0; i < data_disks; i++)
+						if (geo_map(i,
+							    start/chunk_size/data_disks,
+							    raid_disks, level, layout) == dnum)
+							break;
+					/* i is the logical block number, so is index to 'buf'.
+					 * dnum is physical disk number
+					 * snum is syndrome disk for which 0 is immediately after Q
+					 */
+					bufs[snum] = (uint8_t*)buf + chunk_size * i;
+
+					if (fblock[0] == i)
+						fdisk[0] = snum;
+					if (fblock[1] == i)
+						fdisk[1] = snum;
+					snum++;
+				}
+
+				syndrome_disks = data_disks;
+			}
+
+			/* Place P and Q blocks at end of bufs */
+			bufs[syndrome_disks] = (uint8_t*)buf + chunk_size * data_disks;
+			bufs[syndrome_disks+1] = (uint8_t*)buf + chunk_size * (data_disks+1);
+
+			if (fblock[1] == data_disks)
+				/* One data failed, and parity failed */
+				raid6_datap_recov(syndrome_disks+2, chunk_size,
+						  fdisk[0], bufs, 0);
+			else {
+				/* Two data blocks failed, P,Q OK */
+				raid6_2data_recov(syndrome_disks+2, chunk_size,
+						  fdisk[0], fdisk[1], bufs, 0);
+			}
+		}
+		if (dest) {
+			for (i = 0; i < nwrites; i++)
+				if (write(dest[i], buf, len) != len)
+					return -1;
+		} else {
+			/* build next stripe in buffer */
+			buf += len;
+		}
+		length -= len;
+		start += len;
+	}
+	return 0;
+}
+
+/* Restore data:
+ * We are given:
+ *  A list of 'fds' of the active disks. Some may be '-1' for not-available.
+ *  A geometry: raid_disks, chunk_size, level, layout
+ *  An 'fd' to read from.  It is already seeked to the right (Read) location.
+ *  A start and length.
+ * The length must be a multiple of the stripe size.
+ *
+ * We build a full stripe in memory and then write it out.
+ * We assume that there are enough working devices.
+ */
+int restore_stripes(int *dest, unsigned long long *offsets,
+		    int raid_disks, int chunk_size, int level, int layout,
+		    int source, unsigned long long read_offset,
+		    unsigned long long start, unsigned long long length,
+		    char *src_buf)
+{
+	char *stripe_buf;
+	char **stripes = xmalloc(raid_disks * sizeof(char*));
+	char **blocks = xmalloc(raid_disks * sizeof(char*));
+	int i;
+	int rv;
+
+	int data_disks = raid_disks - (level == 0 ? 0 : level <= 5 ? 1 : 2);
+
+	if (posix_memalign((void**)&stripe_buf, 4096, raid_disks * chunk_size))
+		stripe_buf = NULL;
+
+	if (zero == NULL || chunk_size > zero_size) {
+		if (zero)
+			free(zero);
+		zero = xcalloc(1, chunk_size);
+		zero_size = chunk_size;
+	}
+
+	if (stripe_buf == NULL || stripes == NULL || blocks == NULL ||
+	    zero == NULL) {
+		rv = -2;
+		goto abort;
+	}
+	for (i = 0; i < raid_disks; i++)
+		stripes[i] = stripe_buf + i * chunk_size;
+	while (length > 0) {
+		unsigned int len = data_disks * chunk_size;
+		unsigned long long offset;
+		int disk, qdisk;
+		int syndrome_disks;
+		if (length < len) {
+			rv = -3;
+			goto abort;
+		}
+		for (i = 0; i < data_disks; i++) {
+			int disk = geo_map(i, start/chunk_size/data_disks,
+					   raid_disks, level, layout);
+			if (src_buf == NULL) {
+				/* read from file */
+				if (lseek64(source, read_offset, 0) !=
+					 (off64_t)read_offset) {
+					rv = -1;
+					goto abort;
+				}
+				if (read(source,
+					 stripes[disk],
+					 chunk_size) != chunk_size) {
+					rv = -1;
+					goto abort;
+				}
+			} else {
+				/* read from input buffer */
+				memcpy(stripes[disk],
+				       src_buf + read_offset,
+				       chunk_size);
+			}
+			read_offset += chunk_size;
+		}
+		/* We have the data, now do the parity */
+		offset = (start/chunk_size/data_disks) * chunk_size;
+		switch (level) {
+		case 4:
+		case 5:
+			disk = geo_map(-1, start/chunk_size/data_disks,
+					   raid_disks, level, layout);
+			for (i = 0; i < data_disks; i++)
+				blocks[i] = stripes[(disk+1+i) % raid_disks];
+			xor_blocks(stripes[disk], blocks, data_disks, chunk_size);
+			break;
+		case 6:
+			disk = geo_map(-1, start/chunk_size/data_disks,
+				       raid_disks, level, layout);
+			qdisk = geo_map(-2, start/chunk_size/data_disks,
+				       raid_disks, level, layout);
+			if (is_ddf(layout)) {
+				/* q over 'raid_disks' blocks, in device order.
+				 * 'p' and 'q' get to be all zero
+				 */
+				for (i = 0; i < raid_disks; i++)
+					if (i == disk || i == qdisk)
+						blocks[i] = (char*)zero;
+					else
+						blocks[i] = stripes[i];
+				syndrome_disks = raid_disks;
+			} else {
+				/* for md, q is over 'data_disks' blocks,
+				 * starting immediately after 'q'
+				 */
+				for (i = 0; i < data_disks; i++)
+					blocks[i] = stripes[(qdisk+1+i) % raid_disks];
+
+				syndrome_disks = data_disks;
+			}
+			qsyndrome((uint8_t*)stripes[disk],
+				  (uint8_t*)stripes[qdisk],
+				  (uint8_t**)blocks,
+				  syndrome_disks, chunk_size);
+			break;
+		}
+		for (i=0; i < raid_disks ; i++)
+			if (dest[i] >= 0) {
+				if (lseek64(dest[i],
+					 offsets[i]+offset, 0) < 0) {
+					rv = -1;
+					goto abort;
+				}
+				if (write(dest[i], stripes[i],
+					 chunk_size) != chunk_size) {
+					rv = -1;
+					goto abort;
+				}
+			}
+		length -= len;
+		start += len;
+	}
+	rv = 0;
+
+abort:
+	free(stripe_buf);
+	free(stripes);
+	free(blocks);
+	return rv;
+}
+
+#ifdef MAIN
+
+int test_stripes(int *source, unsigned long long *offsets,
+		 int raid_disks, int chunk_size, int level, int layout,
+		 unsigned long long start, unsigned long long length)
+{
+	/* ready the data and p (and q) blocks, and check we got them right */
+	char *stripe_buf = xmalloc(raid_disks * chunk_size);
+	char **stripes = xmalloc(raid_disks * sizeof(char*));
+	char **blocks = xmalloc(raid_disks * sizeof(char*));
+	uint8_t *p = xmalloc(chunk_size);
+	uint8_t *q = xmalloc(chunk_size);
+
+	int i;
+	int diskP, diskQ;
+	int data_disks = raid_disks - (level == 5 ? 1: 2);
+
+	if (!tables_ready)
+		make_tables();
+
+	for ( i = 0 ; i < raid_disks ; i++)
+		stripes[i] = stripe_buf + i * chunk_size;
+
+	while (length > 0) {
+		int disk;
+
+		for (i = 0 ; i < raid_disks ; i++) {
+			if ((lseek64(source[i], offsets[i]+start, 0) < 0) ||
+			    (read(source[i], stripes[i], chunk_size) !=
+			     chunk_size)) {
+				free(q);
+				free(p);
+				free(blocks);
+				free(stripes);
+				free(stripe_buf);
+				return -1;
+			}
+		}
+		for (i = 0 ; i < data_disks ; i++) {
+			int disk = geo_map(i, start/chunk_size, raid_disks,
+					   level, layout);
+			blocks[i] = stripes[disk];
+			printf("%d->%d\n", i, disk);
+		}
+		switch(level) {
+		case 6:
+			qsyndrome(p, q, (uint8_t**)blocks, data_disks, chunk_size);
+			diskP = geo_map(-1, start/chunk_size, raid_disks,
+				       level, layout);
+			if (memcmp(p, stripes[diskP], chunk_size) != 0) {
+				printf("P(%d) wrong at %llu\n", diskP,
+				       start / chunk_size);
+			}
+			diskQ = geo_map(-2, start/chunk_size, raid_disks,
+				       level, layout);
+			if (memcmp(q, stripes[diskQ], chunk_size) != 0) {
+				printf("Q(%d) wrong at %llu\n", diskQ,
+				       start / chunk_size);
+			}
+			disk = raid6_check_disks(data_disks, start, chunk_size,
+						 level, layout, diskP, diskQ,
+						 p, q, stripes);
+			if(disk >= 0) {
+			  printf("Possible failed disk: %d\n", disk);
+			}
+			if(disk == -2) {
+			  printf("Failure detected, but disk unknown\n");
+			}
+			break;
+		}
+		length -= chunk_size;
+		start += chunk_size;
+	}
+	return 0;
+}
+
+unsigned long long getnum(char *str, char **err)
+{
+	char *e;
+	unsigned long long rv = strtoull(str, &e, 10);
+	if (e==str || *e) {
+		*err = str;
+		return 0;
+	}
+	return rv;
+}
+
+char const Name[] = "test_restripe";
+int main(int argc, char *argv[])
+{
+	/* save/restore file raid_disks chunk_size level layout start length devices...
+	 */
+	int save;
+	int *fds;
+	char *file;
+	char *buf;
+	int storefd;
+	unsigned long long *offsets;
+	int raid_disks, chunk_size, level, layout;
+	unsigned long long start, length;
+	int i;
+
+	char *err = NULL;
+	if (argc < 10) {
+		fprintf(stderr, "Usage: test_stripe save/restore file raid_disks chunk_size level layout start length devices...\n");
+		exit(1);
+	}
+	if (strcmp(argv[1], "save")==0)
+		save = 1;
+	else if (strcmp(argv[1], "restore") == 0)
+		save = 0;
+	else if (strcmp(argv[1], "test") == 0)
+		save = 2;
+	else {
+		fprintf(stderr, "test_stripe: must give 'save' or 'restore'.\n");
+		exit(2);
+	}
+
+	file = argv[2];
+	raid_disks = getnum(argv[3], &err);
+	chunk_size = getnum(argv[4], &err);
+	level = getnum(argv[5], &err);
+	layout = getnum(argv[6], &err);
+	start = getnum(argv[7], &err);
+	length = getnum(argv[8], &err);
+	if (err) {
+		fprintf(stderr, "test_stripe: Bad number: %s\n", err);
+		exit(2);
+	}
+	if (argc != raid_disks + 9) {
+		fprintf(stderr, "test_stripe: wrong number of devices: want %d found %d\n",
+			raid_disks, argc-9);
+		exit(2);
+	}
+	fds = xmalloc(raid_disks * sizeof(*fds));
+	offsets = xcalloc(raid_disks, sizeof(*offsets));
+
+	storefd = open(file, O_RDWR);
+	if (storefd < 0) {
+		perror(file);
+		fprintf(stderr, "test_stripe: could not open %s.\n", file);
+		exit(3);
+	}
+	for (i=0; i<raid_disks; i++) {
+		char *p;
+		p = strchr(argv[9+i], ':');
+
+		if(p != NULL) {
+			*p++ = '\0';
+			offsets[i] = atoll(p) * 512;
+		}
+
+		fds[i] = open(argv[9+i], O_RDWR);
+		if (fds[i] < 0) {
+			perror(argv[9+i]);
+			fprintf(stderr,"test_stripe: cannot open %s.\n", argv[9+i]);
+			exit(3);
+		}
+	}
+
+	buf = xmalloc(raid_disks * chunk_size);
+
+	if (save == 1) {
+		int rv = save_stripes(fds, offsets,
+				      raid_disks, chunk_size, level, layout,
+				      1, &storefd,
+				      start, length, buf);
+		if (rv != 0) {
+			fprintf(stderr,
+				"test_stripe: save_stripes returned %d\n", rv);
+			exit(1);
+		}
+	} else if (save == 2) {
+		int rv = test_stripes(fds, offsets,
+				      raid_disks, chunk_size, level, layout,
+				      start, length);
+		if (rv != 0) {
+			fprintf(stderr,
+				"test_stripe: test_stripes returned %d\n", rv);
+			exit(1);
+		}
+	} else {
+		int rv = restore_stripes(fds, offsets,
+					 raid_disks, chunk_size, level, layout,
+					 storefd, 0ULL,
+					 start, length, NULL);
+		if (rv != 0) {
+			fprintf(stderr,
+				"test_stripe: restore_stripes returned %d\n",
+				rv);
+			exit(1);
+		}
+	}
+	exit(0);
+}
+
+#endif /* MAIN */