64 lines
1.6 KiB
C
64 lines
1.6 KiB
C
/* This procedure examines a file system and figures out whether it is
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* version 1 or version 2. It returns the result as an int. If the
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* file system is neither, it returns -1. A typical call is:
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*
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* n = fsversion("/dev/hd1", "df");
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*
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* The first argument is the special file for the file system.
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* The second is the program name, which is used in error messages.
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*/
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#include <sys/types.h>
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#include <minix/config.h>
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#include <minix/const.h>
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#include <minix/minlib.h>
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#include <minix/type.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <stdio.h>
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#include <string.h>
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#include "mfs/const.h"
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static char super[SUPER_BLOCK_BYTES];
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#define MAGIC_OFFSET_MFS 0x18
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#define MAGIC_OFFSET_EXT 0x38
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#define MAGIC_VALUE_EXT2 0xef53
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static int check_super(off_t offset, unsigned short magic)
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{
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return (memcmp(super + offset, &magic, sizeof(magic)) == 0) ? 1 : 0;
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}
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int fsversion(dev, prog)
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char *dev, *prog;
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{
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int fd;
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if ((fd = open(dev, O_RDONLY)) < 0) {
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std_err(prog);
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std_err(" cannot open ");
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perror(dev);
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return(-1);
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}
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lseek(fd, (off_t) SUPER_BLOCK_BYTES, SEEK_SET); /* skip boot block */
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if (read(fd, (char *) &super, sizeof(super)) != sizeof(super)) {
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std_err(prog);
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std_err(" cannot read super block on ");
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perror(dev);
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close(fd);
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return(-1);
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}
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close(fd);
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/* first check MFS, a valid MFS may look like EXT but not vice versa */
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if (check_super(MAGIC_OFFSET_MFS, SUPER_MAGIC)) return FSVERSION_MFS1;
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if (check_super(MAGIC_OFFSET_MFS, SUPER_V2)) return FSVERSION_MFS2;
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if (check_super(MAGIC_OFFSET_MFS, SUPER_V3)) return FSVERSION_MFS3;
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if (check_super(MAGIC_OFFSET_EXT, MAGIC_VALUE_EXT2)) return FSVERSION_EXT2;
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return(-1);
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}
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