restripe.c - pub/scm/utils/mdadm/mdadm - Git at Google

 /*
  * mdadm - manage Linux "md" devices aka RAID arrays.
  *
  * Copyright (C) 2006 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"

 /* To restripe, we read from old geometry to a buffer, and
  * read from buffer to new geometry.
  * When reading we don't worry about parity. When writing we do.
  *
  */

 static 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;

 	switch(level*100 + layout) {
 	case 000:
 	case 400:
 		/* 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 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_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;
 	}
 	return -1;
 }


 static 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;
 	}
 }

 static void qsyndrome(char *p, char *q, char **sources, int disks, int size)
 {
 	int d, z;
 	char 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;
 	}
 }

 /* Save data:
  * We are given:
  *  A list of 'fds' of the active disks.  For now we require all to be present.
  *  A geometry: raid_disks, chunk_size, level, layout
  *  A list of 'fds' for mirrored targets.  They are already seeked to
  *    right (Write) location
  *  A start and length
  */

 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[8192];
 	int cpos = start % chunk_size; /* where in chunk we are up to */
 	int len;
 	int data_disks = raid_disks - (level == 0 ? 0 : level <=5 ? 1 : 2);
 	int disk;

 	while (length > 0) {
 		unsigned long long offset;
 		int i;
 		len = chunk_size - cpos;
 		if (len > sizeof(buf)) len = sizeof(buf);
 		if (len > length) len = length;
 		/* len bytes to be moved from one device */

 		offset = (start/chunk_size/data_disks)*chunk_size + cpos;
 		disk = start/chunk_size % data_disks;
 		disk = geo_map(disk, start/chunk_size/data_disks,
 			       raid_disks, level, layout);
 		if (lseek64(source[disk], offsets[disk]+offset, 0) < 0)
 			return -1;
 		if (read(source[disk], buf, len) != len)
 			return -1;
 		for (i=0; i<nwrites; i++)
 			if (write(dest[i], buf, len) != len)
 				return -1;
 		length -= len;
 		start += len;
 		cpos += len;
 		while (cpos >= chunk_size) cpos -= chunk_size;
 	}
 	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 *stripe_buf = malloc(raid_disks * chunk_size);
 	char **stripes = malloc(raid_disks * sizeof(char*));
 	char **blocks = malloc(raid_disks * sizeof(char*));
 	int i;

 	int data_disks = raid_disks - (level == 0 ? 0 : level <=5 ? 1 : 2);

 	if (stripe_buf == NULL || stripes == NULL || blocks == NULL) {
 		free(stripe_buf);
 		free(stripes);
 		free(blocks);
 		return -2;
 	}
 	for (i=0; i<raid_disks; i++)
 		stripes[i] = stripe_buf + i * chunk_size;
 	while (length > 0) {
 		int len = data_disks * chunk_size;
 		unsigned long long offset;
 		int disk, qdisk;
 		if (length < len)
 			return -3;
 		for (i=0; i < data_disks; i++) {
 			int disk = geo_map(i, start/chunk_size/data_disks,
 					   raid_disks, level, layout);
 			blocks[i] = stripes[disk];
 			if (lseek64(source, read_offset, 0) != read_offset)
 				return -1;
 			if (read(source, stripes[disk], chunk_size) != chunk_size)
 				return -1;
 			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);
 			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);

 			qsyndrome(stripes[disk], stripes[qdisk], blocks,
 				  data_disks, chunk_size);
 			break;
 		}
 		for (i=0; i < raid_disks ; i++)
 			if (dest[i] >= 0) {
 				if (lseek64(dest[i], offsets[i]+offset, 0) < 0)
 					return -1;
 				if (write(dest[i], stripes[i], chunk_size) != chunk_size)
 					return -1;
 			}
 		length -= len;
 		start += len;
 	}
 	return 0;
 }

 #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 = malloc(raid_disks * chunk_size);
 	char **stripes = malloc(raid_disks * sizeof(char*));
 	char **blocks = malloc(raid_disks * sizeof(char*));
 	char *p = malloc(chunk_size);
 	char *q = malloc(chunk_size);

 	int i;
 	int data_disks = raid_disks - (level == 5 ? 1: 2);
 	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++) {
 			lseek64(source[i], offsets[i]+start, 0);
 			read(source[i], stripes[i], chunk_size);
 		}
 		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, blocks, data_disks, chunk_size);
 			disk = geo_map(-1, start/chunk_size, raid_disks,
 				       level, layout);
 			if (memcmp(p, stripes[disk], chunk_size) != 0) {
 				printf("P(%d) wrong at %llu\n", disk,
 				       start / chunk_size);
 			}
 			disk = geo_map(-2, start/chunk_size, raid_disks,
 				       level, layout);
 			if (memcmp(q, stripes[disk], chunk_size) != 0) {
 				printf("Q(%d) wrong at %llu\n", disk,
 				       start / chunk_size);
 			}
 			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;
 }

 main(int argc, char *argv[])
 {
 	/* save/restore file raid_disks chunk_size level layout start length devices...
 	 */
 	int save;
 	int *fds;
 	char *file;
 	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 = malloc(raid_disks * sizeof(*fds));
 	offsets = malloc(raid_disks * sizeof(*offsets));
 	memset(offsets, 0, 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++) {
 		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);
 		}
 	}

 	if (save == 1) {
 		int rv = save_stripes(fds, offsets,
 				      raid_disks, chunk_size, level, layout,
 				      1, &storefd,
 				      start, length);
 		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);
 		if (rv != 0) {
 			fprintf(stderr,
 				"test_stripe: restore_stripes returned %d\n",
 				rv);
 			exit(1);
 		}
 	}
 	exit(0);
 }

 #endif /* MAIN */
	/*
	* mdadm - manage Linux "md" devices aka RAID arrays.
	*
	* Copyright (C) 2006 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"

	/* To restripe, we read from old geometry to a buffer, and
	* read from buffer to new geometry.
	* When reading we don't worry about parity. When writing we do.
	*
	*/

	static 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;

	switch(level*100 + layout) {
	case 000:
	case 400:
	/* 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 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_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;
	}
	return -1;
	}


	static 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;
	}
	}

	static void qsyndrome(char p, char q, char **sources, int disks, int size)
	{
	int d, z;
	char 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;
	}
	}

	/* Save data:
	* We are given:
	* A list of 'fds' of the active disks. For now we require all to be present.
	* A geometry: raid_disks, chunk_size, level, layout
	* A list of 'fds' for mirrored targets. They are already seeked to
	* right (Write) location
	* A start and length
	*/

	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[8192];
	int cpos = start % chunk_size; /* where in chunk we are up to */
	int len;
	int data_disks = raid_disks - (level == 0 ? 0 : level <=5 ? 1 : 2);
	int disk;

	while (length > 0) {
	unsigned long long offset;
	int i;
	len = chunk_size - cpos;
	if (len > sizeof(buf)) len = sizeof(buf);
	if (len > length) len = length;
	/* len bytes to be moved from one device */

	offset = (start/chunk_size/data_disks)*chunk_size + cpos;
	disk = start/chunk_size % data_disks;
	disk = geo_map(disk, start/chunk_size/data_disks,
	raid_disks, level, layout);
	if (lseek64(source[disk], offsets[disk]+offset, 0) < 0)
	return -1;
	if (read(source[disk], buf, len) != len)
	return -1;
	for (i=0; i<nwrites; i++)
	if (write(dest[i], buf, len) != len)
	return -1;
	length -= len;
	start += len;
	cpos += len;
	while (cpos >= chunk_size) cpos -= chunk_size;
	}
	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 stripe_buf = malloc(raid_disks chunk_size);
	char *stripes = malloc(raid_disks sizeof(char*));
	char *blocks = malloc(raid_disks sizeof(char*));
	int i;

	int data_disks = raid_disks - (level == 0 ? 0 : level <=5 ? 1 : 2);

	if (stripe_buf == NULL \|\| stripes == NULL \|\| blocks == NULL) {
	free(stripe_buf);
	free(stripes);
	free(blocks);
	return -2;
	}
	for (i=0; i<raid_disks; i++)
	stripes[i] = stripe_buf + i * chunk_size;
	while (length > 0) {
	int len = data_disks * chunk_size;
	unsigned long long offset;
	int disk, qdisk;
	if (length < len)
	return -3;
	for (i=0; i < data_disks; i++) {
	int disk = geo_map(i, start/chunk_size/data_disks,
	raid_disks, level, layout);
	blocks[i] = stripes[disk];
	if (lseek64(source, read_offset, 0) != read_offset)
	return -1;
	if (read(source, stripes[disk], chunk_size) != chunk_size)
	return -1;
	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);
	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);

	qsyndrome(stripes[disk], stripes[qdisk], blocks,
	data_disks, chunk_size);
	break;
	}
	for (i=0; i < raid_disks ; i++)
	if (dest[i] >= 0) {
	if (lseek64(dest[i], offsets[i]+offset, 0) < 0)
	return -1;
	if (write(dest[i], stripes[i], chunk_size) != chunk_size)
	return -1;
	}
	length -= len;
	start += len;
	}
	return 0;
	}

	#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 = malloc(raid_disks chunk_size);
	char *stripes = malloc(raid_disks sizeof(char*));
	char *blocks = malloc(raid_disks sizeof(char*));
	char *p = malloc(chunk_size);
	char *q = malloc(chunk_size);

	int i;
	int data_disks = raid_disks - (level == 5 ? 1: 2);
	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++) {
	lseek64(source[i], offsets[i]+start, 0);
	read(source[i], stripes[i], chunk_size);
	}
	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, blocks, data_disks, chunk_size);
	disk = geo_map(-1, start/chunk_size, raid_disks,
	level, layout);
	if (memcmp(p, stripes[disk], chunk_size) != 0) {
	printf("P(%d) wrong at %llu\n", disk,
	start / chunk_size);
	}
	disk = geo_map(-2, start/chunk_size, raid_disks,
	level, layout);
	if (memcmp(q, stripes[disk], chunk_size) != 0) {
	printf("Q(%d) wrong at %llu\n", disk,
	start / chunk_size);
	}
	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;
	}

	main(int argc, char *argv[])
	{
	/* save/restore file raid_disks chunk_size level layout start length devices...
	*/
	int save;
	int *fds;
	char *file;
	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 = malloc(raid_disks * sizeof(*fds));
	offsets = malloc(raid_disks * sizeof(*offsets));
	memset(offsets, 0, 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++) {
	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);
	}
	}

	if (save == 1) {
	int rv = save_stripes(fds, offsets,
	raid_disks, chunk_size, level, layout,
	1, &storefd,
	start, length);
	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);
	if (rv != 0) {
	fprintf(stderr,
	"test_stripe: restore_stripes returned %d\n",
	rv);
	exit(1);
	}
	}
	exit(0);
	}

	#endif /* MAIN */