On Thursday August 11, blinux_adm@xxxxxxxxx wrote:
>
> My array is raid5, so I decided to overwrite the
> big-endian superblocks and assemble the array. Your
> patch worked as expected and the array is functioning
> properly. Thanks for the help.
>
> Is there a simple way convert the superblocks back to
> big-endian while the drives are connected to the
> little-endian machine?
Not with mdadm... I could but I don't think I really want to.
However I wrote the following little program to test the byteswapping
code in mdadm. It does a full byteswap of the superblock on the
device that you pass as an argument.
NeilBrown
-----------cut--here--------
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/mount.h>
/*
* This is a tiny test program to endian-swap
* the superblock on a given device.
* We simply read 4k from where the superblock should be
* do the swap, and write it back
* Don't use this on a real array, use mdadm.
*/
#define MD_RESERVED_BYTES (64 * 1024)
#define MD_RESERVED_SECTORS (MD_RESERVED_BYTES / 512)
#define MD_NEW_SIZE_SECTORS(x) ((x & ~(MD_RESERVED_SECTORS - 1)) - MD_RESERVED_SECTORS)
main(int argc, char *argv[])
{
int fd, i;
unsigned long size;
unsigned long long offset;
char super[4096];
if (argc != 2) {
fprintf(stderr, "Usage: swap_super device\n");
exit(1);
}
fd = open(argv[1], O_RDWR);
if (fd<0) {
perror(argv[1]);
exit(1);
}
if (ioctl(fd, BLKGETSIZE, &size)) {
perror("BLKGETSIZE");
exit(1);
}
offset = MD_NEW_SIZE_SECTORS(size) * 512LL;
if (lseek64(fd, offset, 0) < 0LL) {
perror("lseek64");
exit(1);
}
if (read(fd, super, 4096) != 4096) {
perror("read");
exit(1);
}
for (i=0; i < 4096 ; i+=4) {
char t = super[i];
super[i] = super[i+3];
super[i+3] = t;
t=super[i+1];
super[i+1]=super[i+2];
super[i+2]=t;
}
/* swap the u64 events counters */
for (i=0; i<4; i++) {
/* events_hi and events_lo */
char t=super[32*4+7*4 +i];
super[32*4+7*4 +i] = super[32*4+8*4 +i];
super[32*4+8*4 +i] = t;
/* cp_events_hi and cp_events_lo */
t=super[32*4+9*4 +i];
super[32*4+9*4 +i] = super[32*4+10*4 +i];
super[32*4+10*4 +i] = t;
}
if (lseek64(fd, offset, 0) < 0LL) {
perror("lseek64");
exit(1);
}
if (write(fd, super, 4096) != 4096) {
perror("write");
exit(1);
}
exit(0);
}
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