82 lines
1.7 KiB
C
82 lines
1.7 KiB
C
#include <unistd.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <sys/mount.h>
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/*
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* This is a tiny test program to endian-swap
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* the superblock on a given device.
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* We simply read 4k from where the superblock should be
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* do the swap, and write it back
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* Don't use this on a real array, use mdadm.
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*/
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#define MD_RESERVED_BYTES (64 * 1024)
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#define MD_RESERVED_SECTORS (MD_RESERVED_BYTES / 512)
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#define MD_NEW_SIZE_SECTORS(x) ((x & ~(MD_RESERVED_SECTORS - 1)) - MD_RESERVED_SECTORS)
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extern long long lseek64(int, long long, int);
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int main(int argc, char *argv[])
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{
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int fd, i;
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unsigned long size;
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unsigned long long offset;
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char super[4096];
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if (argc != 2) {
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fprintf(stderr, "Usage: swap_super device\n");
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exit(1);
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}
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fd = open(argv[1], O_RDWR);
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if (fd<0) {
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perror(argv[1]);
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exit(1);
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}
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if (ioctl(fd, BLKGETSIZE, &size)) {
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perror("BLKGETSIZE");
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exit(1);
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}
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offset = MD_NEW_SIZE_SECTORS(size) * 512LL;
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if (lseek64(fd, offset, 0) < 0LL) {
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perror("lseek64");
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exit(1);
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}
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if (read(fd, super, 4096) != 4096) {
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perror("read");
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exit(1);
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}
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for (i=0; i < 4096 ; i+=4) {
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char t = super[i];
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super[i] = super[i+3];
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super[i+3] = t;
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t=super[i+1];
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super[i+1]=super[i+2];
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super[i+2]=t;
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}
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/* swap the u64 events counters */
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for (i=0; i<4; i++) {
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/* events_hi and events_lo */
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char t=super[32*4+7*4 +i];
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super[32*4+7*4 +i] = super[32*4+8*4 +i];
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super[32*4+8*4 +i] = t;
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/* cp_events_hi and cp_events_lo */
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t=super[32*4+9*4 +i];
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super[32*4+9*4 +i] = super[32*4+10*4 +i];
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super[32*4+10*4 +i] = t;
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}
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if (lseek64(fd, offset, 0) < 0LL) {
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perror("lseek64");
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exit(1);
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}
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if (write(fd, super, 4096) != 4096) {
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perror("write");
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exit(1);
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}
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exit(0);
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}
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