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* mdadm - manage Linux "md" devices aka RAID arrays.
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* Copyright (C) 2006 Neil Brown <neilb@suse.de>
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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* Email: <neilb@suse.de>
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/* To restripe, we read from old geometry to a buffer, and
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* read from buffer to new geometry.
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* When reading we don't worry about parity. When writing we do.
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static int geo_map(int block, unsigned long long stripe, int raid_disks, int level, int layout)
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/* On the given stripe, find which disk in the array with have
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* block numbered 'block'.
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switch(level*100 + layout) {
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/* raid 4 isn't messed around by parity blocks */
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return raid_disks-1; /* parity block */
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case 500 + ALGORITHM_LEFT_ASYMMETRIC:
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pd = (raid_disks-1) - stripe % raid_disks;
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if (block == -1) return pd;
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case 500 + ALGORITHM_RIGHT_ASYMMETRIC:
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pd = stripe % raid_disks;
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if (block == -1) return pd;
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case 500 + ALGORITHM_LEFT_SYMMETRIC:
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pd = (raid_disks - 1) - stripe % raid_disks;
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if (block == -1) return pd;
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return (pd + 1 + block) % raid_disks;
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case 500 + ALGORITHM_RIGHT_SYMMETRIC:
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pd = stripe % raid_disks;
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if (block == -1) return pd;
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return (pd + 1 + block) % raid_disks;
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case 600 + ALGORITHM_LEFT_ASYMMETRIC:
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pd = raid_disks - 1 - (stripe % raid_disks);
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if (block == -1) return pd;
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if (pd == raid_disks - 1)
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case 600 + ALGORITHM_RIGHT_ASYMMETRIC:
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pd = stripe % raid_disks;
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if (block == -1) return pd;
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if (pd == raid_disks - 1)
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case 600 + ALGORITHM_LEFT_SYMMETRIC:
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pd = raid_disks - 1 - (stripe % raid_disks);
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if (block == -1) return pd;
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return (pd + 2 + block) % raid_disks;
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case 600 + ALGORITHM_RIGHT_SYMMETRIC:
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pd = stripe % raid_disks;
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if (block == -1) return pd;
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return (pd + 2 + block) % raid_disks;
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static void xor_blocks(char *target, char **sources, int disks, int size)
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/* Amazingly inefficient... */
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for (i=0; i<size; i++) {
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for (j=0 ; j<disks; j++)
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* A list of 'fds' of the active disks. For now we require all to be present.
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* A geomtry: raid_disks, chunk_size, level, layout
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* A list of 'fds' for mirrored targets. They are already seeked to
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* right (Write) location
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int save_stripes(int *source, unsigned long long *offsets,
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int raid_disks, int chunk_size, int level, int layout,
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int nwrites, int *dest,
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unsigned long long start, unsigned long long length)
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int cpos = start % chunk_size; /* where in chunk we are up to */
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int data_disks = raid_disks - (level == 0 ? 0 : level <=5 ? 1 : 2);
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unsigned long long offset;
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len = chunk_size - cpos;
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if (len > sizeof(buf)) len = sizeof(buf);
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if (len > length) len = length;
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/* len bytes to be moved from one device */
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offset = (start/chunk_size/data_disks)*chunk_size + cpos;
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disk = start/chunk_size % data_disks;
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disk = geo_map(disk, start/chunk_size/data_disks,
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raid_disks, level, layout);
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if (lseek64(source[disk], offsets[disk]+offset, 0) < 0)
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if (read(source[disk], buf, len) != len)
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for (i=0; i<nwrites; i++)
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if (write(dest[i], buf, len) != len)
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while (cpos >= chunk_size) cpos -= chunk_size;
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* A list of 'fds' of the active disks. Some may be '-1' for not-available.
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* A geometry: raid_disks, chunk_size, level, layout
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* An 'fd' to read from. It is already seeked to the right (Read) location.
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* A start and length.
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* The length must be a multiple of the stripe size.
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* We build a full stripe in memory and then write it out.
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* We assume that there are enough working devices.
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int restore_stripes(int *dest, unsigned long long *offsets,
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int raid_disks, int chunk_size, int level, int layout,
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int source, unsigned long long read_offset,
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unsigned long long start, unsigned long long length)
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char *stripe_buf = malloc(raid_disks * chunk_size);
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char **stripes = malloc(raid_disks * sizeof(char*));
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char **blocks = malloc(raid_disks * sizeof(char*));
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int data_disks = raid_disks - (level == 0 ? 0 : level <=5 ? 1 : 2);
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if (stripe_buf == NULL || stripes == NULL || blocks == NULL) {
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for (i=0; i<raid_disks; i++)
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stripes[i] = stripe_buf + i * chunk_size;
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int len = data_disks * chunk_size;
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unsigned long long offset;
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for (i=0; i < data_disks; i++) {
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int disk = geo_map(i, start/chunk_size/data_disks,
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raid_disks, level, layout);
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blocks[i] = stripes[disk];
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if (lseek64(source, read_offset, 0) != read_offset)
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if (read(source, stripes[disk], chunk_size) != chunk_size)
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read_offset += chunk_size;
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/* We have the data, now do the parity */
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offset = (start/chunk_size/data_disks) * chunk_size;
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int disk = geo_map(-1, start/chunk_size/data_disks,
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raid_disks, level, layout);
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xor_blocks(stripes[disk], blocks, data_disks, chunk_size);
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/* FIXME need to do raid6 Q as well */
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for (i=0; i < raid_disks ; i++)
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if (lseek64(dest[i], offsets[i]+offset, 0) < 0)
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if (write(dest[i], stripes[i], chunk_size) != chunk_size)
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unsigned long long getnum(char *str, char **err)
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unsigned long long rv = strtoull(str, &e, 10);
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main(int argc, char *argv[])
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/* save/restore file raid_disks chunk_size level layout start length devices...
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unsigned long long *offsets;
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int raid_disks, chunk_size, level, layout;
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unsigned long long start, length;
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fprintf(stderr, "Usage: test_stripe save/restore file raid_disks"
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" chunk_size level layout start length devices...\n");
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if (strcmp(argv[1], "save")==0)
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else if (strcmp(argv[1], "restore") == 0)
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fprintf(stderr, "test_stripe: must give 'save' or 'restore'.\n");
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raid_disks = getnum(argv[3], &err);
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chunk_size = getnum(argv[4], &err);
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level = getnum(argv[5], &err);
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layout = getnum(argv[6], &err);
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start = getnum(argv[7], &err);
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length = getnum(argv[8], &err);
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fprintf(stderr, "test_stripe: Bad number: %s\n", err);
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if (argc != raid_disks + 9) {
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fprintf(stderr, "test_stripe: wrong number of devices: want %d found %d\n",
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fds = malloc(raid_disks * sizeof(*fds));
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offsets = malloc(raid_disks * sizeof(*offsets));
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memset(offsets, 0, raid_disks * sizeof(*offsets));
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storefd = open(file, O_RDWR);
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fprintf(stderr, "test_stripe: could not open %s.\n", file);
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for (i=0; i<raid_disks; i++) {
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fds[i] = open(argv[9+i], O_RDWR);
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fprintf(stderr,"test_stripe: cannot open %s.\n", argv[9+i]);
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int rv = save_stripes(fds, offsets,
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raid_disks, chunk_size, level, layout,
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fprintf(stderr, "test_stripe: save_stripes returned %d\n", rv);
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int rv = restore_stripes(fds, offsets,
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raid_disks, chunk_size, level, layout,
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fprintf(stderr, "test_stripe: restore_stripes returned %d\n", rv);