1 #include <sys/types.h> 2 #include <sys/stat.h> 3 #include <fcntl.h> 4 #include <stdio.h> 5 #include <stdlib.h> 6 7 #define SB_OFFSET 1024 8 #define SB_SIZE 1024 9 #define EXT4_MAGIC_OFFSET 0x38 10 #define EXT4_STATE_OFFSET 0x3A 11 12 int main(int argc, char *argv[]) 13 { 14 int fd; 15 char me[] = "set_ext4_err_bit"; 16 unsigned char sb[1024]; 17 18 if (argc != 2) { 19 fprintf(stderr, "%s: Usage: %s <ext4_block_device>\n", me, me); 20 exit(1); 21 } 22 23 fd = open(argv[1], O_RDWR); 24 25 if (fd < 0) { 26 fprintf(stderr, "%s: Cannot open block device %s\n", me, argv[1]); 27 exit(1); 28 } 29 30 if (lseek(fd, SB_OFFSET, SEEK_SET) == -1) { 31 fprintf(stderr, "%s: Cannot lseek to superblock to read\n", me); 32 exit(1); 33 } 34 35 if (read(fd, sb, SB_SIZE) != SB_SIZE) { 36 fprintf(stderr, "%s: Cannot read superblock\n", me); 37 exit(1); 38 } 39 40 if ((sb[EXT4_MAGIC_OFFSET] != 0x53) || (sb[EXT4_MAGIC_OFFSET+1] != 0xEF)) { 41 fprintf(stderr, "%s: invalid superblock magic\n", me); 42 exit(1); 43 } 44 45 /* Set the errors detected bit */ 46 sb[EXT4_STATE_OFFSET] |= 0x2; 47 48 if (lseek(fd, SB_OFFSET, SEEK_SET) == -1) { 49 fprintf(stderr, "%s: Cannot lseek to superblock to write\n", me); 50 exit(1); 51 } 52 53 if (write(fd, sb, SB_SIZE) != SB_SIZE) { 54 fprintf(stderr, "%s: Cannot write superblock\n", me); 55 exit(1); 56 } 57 58 close(fd); 59 60 return 0; 61 } 62 63
