Manual repair of RAID5 (Version which actually ran)

fix-raid5.c

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>

#define STRIPESIZE (64 * 1024)
#define BUFSIZE (2 * STRIPESIZE)
#define MIB16 (16 * 1024 * 1024)
#define GIB (1024 * 1024 * 1024)

void xor(uint8_t* src1, uint8_t* src2, uint32_t len) {
        uint32_t  i, count = len / 4;
        uint32_t *s1, *s2;

        s1 = (uint32_t *)src1;
        s2 = (uint32_t *)src2;

        for(i = 0; i < count; i += 4) {
                s1[i+0] ^= s2[i+0];
                s1[i+1] ^= s2[i+1];
                s1[i+2] ^= s2[i+2];
                s1[i+3] ^= s2[i+3];
        }
}

int main(int argc, char** argv) {
        if(argc <= 4) {
                printf("I'm not even going to explain what this does.\n");
                printf("\n");
                printf(" 1: Source disk 1\n");
                printf(" 2: Source disk 2\n");
                printf(" 3: Destination disk\n");
                printf(" 4: Source disk offset\n");

                return 1;
        }

        int fd0, fd1, fdd;
        uint64_t maxoffset, offset, dstoffset, numrows, cur;
        uint8_t *buf0, *buf1, *tmp;

        /* Try opening all files */
        fd0 = open(argv[1], O_RDONLY);
        if(fd0 == -1) { fprintf(stderr, "%s\n", strerror(errno)); }

        fd1 = open(argv[2], O_RDONLY);
        if(fd1 == -1) { fprintf(stderr, "%s\n", strerror(errno)); }

        fdd = open(argv[3], O_WRONLY);
        if(fdd == -1) { fprintf(stderr, "%s\n", strerror(errno)); }

        /* Read maxoffset */
        maxoffset = strtoull(argv[4], NULL, 16);
        numrows = maxoffset / STRIPESIZE;
        printf("Number of stripe rows: %#llx\n\n", numrows);

        /* Alloc buffers */
        buf0 = (uint8_t*) malloc(STRIPESIZE);
        buf1 = (uint8_t*) malloc(STRIPESIZE);
        if(!buf0 || !buf1) {
                fprintf(stderr, "Could not allocate memory");
                return 2;
        }

        offset = 0; dstoffset = 0;
        for(cur = 0; cur < numrows; cur++) {
                // Always in reversed order
                // printf("fd0 => buf0 | offset 0x%12llx\n", offset);
                read(fd0, buf0, STRIPESIZE);
                // printf("fd1 => buf1 | offset 0x%12llx\n", offset);
                read(fd1, buf1, STRIPESIZE);
                offset += STRIPESIZE;

                switch(cur % 3) {
                        case 0:
                                // printf("buf0 ^= buf1\n");
                                xor(buf0, buf1, STRIPESIZE);
                                break;
                        case 1:
                                // printf("buf1 ^= buf0\n");
                                xor(buf1, buf0, STRIPESIZE);
                                // printf("buf0 <> buf1\n");
                                tmp = buf0; buf0 = buf1; buf1 = tmp;
                                break;
                        case 2:
                                // printf("buf0 <> buf1\n");
                                tmp = buf0; buf0 = buf1; buf1 = tmp;
                                break;
                        default:
                                fprintf(stderr, "Switch not possible\n");
                                return 3;
                }

                // printf("buf0 => fdd | offset 0x%12llx\n", dstoffset);
                write(fdd, buf0, STRIPESIZE);
                dstoffset += STRIPESIZE;
                // printf("buf1 => fdd | offset 0x%12llx\n", dstoffset);
                write(fdd, buf1, STRIPESIZE);
                dstoffset += STRIPESIZE;
                
                if(!((dstoffset + BUFSIZE) & (MIB16 - 1)))
                {
                        printf(".");

                        if(!((dstoffset + BUFSIZE) & (GIB - 1)))
                                printf(" %3lld GiB\n", dstoffset / GIB);
                }
        }
}