/* * mdadm - manage Linux "md" devices aka RAID arrays. * * Copyright (C) 2006-2009 Neil Brown * * * 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: */ #include "mdadm.h" #include "xmalloc.h" #include /* 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= 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