mount_guess_fstype.c

Util-linux 软件包包含许多工具。其中比较重要的是加载、卸载、格式化、分区和管理硬盘驱动器

	else if (minixmagic(sb.ms) == MINIX_SUPER_MAGIC ||
		 minixmagic(sb.ms) == MINIX_SUPER_MAGIC2 ||
		 minixmagic(sb.ms) == swapped(MINIX_SUPER_MAGIC2) ||
		 minixmagic(sb.ms) == MINIX2_SUPER_MAGIC ||
		 minixmagic(sb.ms) == MINIX2_SUPER_MAGIC2)
		type = "minix";

	else if (extmagic(sb.es) == EXT_SUPER_MAGIC)
		type = "ext";

	else if (vxfsmagic(sb.vs) == VXFS_SUPER_MAGIC)
		type = "vxfs";
    }

    if (!type) {
	/* block 1 */
        if (lseek(fd, 0x400, SEEK_SET) != 0x400
            || read(fd, (char *) &hfssb, sizeof(hfssb)) != sizeof(hfssb))
             goto io_error;

        /* also check if block size is equal to 512 bytes,
	   or a multiple. (I see 1536 here.) */
        if (hfsmagic(hfssb) == HFS_SUPER_MAGIC &&	/* always BE */
	    hfsblksize(hfssb) != 0 &&
	    (hfsblksize(hfssb) & 0x1ff) == 0)
             type = "hfs";
    }

    if (!type) {
	/* block 3 */
        if (lseek(fd, 0xc00, SEEK_SET) != 0xc00
            || read(fd, (char *) &adfssb, sizeof(adfssb)) != sizeof(adfssb))
             goto io_error;

	/* only a weak test */
        if (may_be_adfs((u_char *) &adfssb)
            && (adfsblksize(adfssb) >= 8 &&
                adfsblksize(adfssb) <= 10))
             type = "adfs";
    }

    if (!type) {
	 int mag;

	 /* block 8 */
	 if (lseek(fd, 8192, SEEK_SET) != 8192
	     || read(fd, (char *) &ufssb, sizeof(ufssb)) != sizeof(ufssb))
	      goto io_error;

	 mag = ufsmagic(ufssb);
	 if (mag == UFS_SUPER_MAGIC_LE || mag == UFS_SUPER_MAGIC_BE)
	      type = "ufs";
    }

    if (!type) {
	/* block 8 */
	if (lseek(fd, REISERFS_OLD_DISK_OFFSET_IN_BYTES, SEEK_SET) !=
				REISERFS_OLD_DISK_OFFSET_IN_BYTES
	    || read(fd, (char *) &reiserfssb, sizeof(reiserfssb)) !=
		sizeof(reiserfssb))
	    goto io_error;
	if (reiserfs_magic_version(reiserfssb.s_magic))
	    type = "reiserfs";
    }

    if (!type) {
	/* block 8 */
        if (lseek(fd, 0x2000, SEEK_SET) != 0x2000
            || read(fd, (char *) &hpfssb, sizeof(hpfssb)) != sizeof(hpfssb))
             goto io_error;

        if (hpfsmagic(hpfssb) == HPFS_SUPER_MAGIC)
             type = "hpfs";
    }

    if (!type) {
	 /* block 32 */
	 if (lseek(fd, JFS_SUPER1_OFF, SEEK_SET) != JFS_SUPER1_OFF
	     || read(fd, (char *) &jfssb, sizeof(jfssb)) != sizeof(jfssb))
	      goto io_error;
	 if (!strncmp(jfssb.s_magic, JFS_MAGIC, 4))
	      type = "jfs";
    }

    if (!type) {
	 /* block 32 */
    try_iso9660:
	 if (lseek(fd, 0x8000, SEEK_SET) != 0x8000
	     || read(fd, (char *) &isosb, sizeof(isosb)) != sizeof(isosb))
	      goto io_error;

	 if (strncmp(isosb.hs.id, HS_STANDARD_ID, sizeof(isosb.hs.id)) == 0) {
		 /* "CDROM" */
		 type = "iso9660";
	 } else if (strncmp(isosb.iso.id, ISO_STANDARD_ID,
			  sizeof(isosb.iso.id)) == 0) {
		 /* CD001 */
		 type = "iso9660";
		 if (is_really_udf(fd))
			 type = "udf";
	 } else if (may_be_udf(isosb.iso.id))
		 type = "udf";
    }

    if (!type) {
	/* block 64 */
	if (lseek(fd, REISERFS_DISK_OFFSET_IN_BYTES, SEEK_SET) !=
		REISERFS_DISK_OFFSET_IN_BYTES
	    || read(fd, (char *) &reiserfssb, sizeof(reiserfssb)) !=
		sizeof(reiserfssb))
	    goto io_error;
	if (reiserfs_magic_version(reiserfssb.s_magic))
	    type = "reiserfs";
    }

    if (!type) {
	    int blksize, blkoff;

	    for (blksize = OCFS2_MIN_BLOCKSIZE;
		 blksize <= OCFS2_MAX_BLOCKSIZE;
		 blksize <<= 1) {
		    blkoff = blksize * OCFS2_SUPER_BLOCK_BLKNO;
		    if (lseek(fd, blkoff, SEEK_SET) != blkoff
			|| read(fd, (char *) &osb, sizeof(osb)) != sizeof(osb))
			    goto io_error;
		    if (strncmp(osb.signature, OCFS2_SUPER_BLOCK_SIGNATURE,
				sizeof(OCFS2_SUPER_BLOCK_SIGNATURE)) == 0)
			    type = "ocfs2";
	    }
    }

    if (!type) {
	    /* perhaps the user tries to mount the swap space
	       on a new disk; warn her before she does mke2fs on it */
	    int pagesize = getpagesize();
	    int rd;
	    char buf[32768];

	    rd = pagesize;
	    if (rd < 8192)
		    rd = 8192;
	    if (rd > sizeof(buf))
		    rd = sizeof(buf);
	    if (lseek(fd, 0, SEEK_SET) != 0
		|| read(fd, buf, rd) != rd)
		    goto io_error;
	    if (may_be_swap(buf+pagesize) ||
		may_be_swap(buf+4096) || may_be_swap(buf+8192))
		    type = "swap";
    }

    close (fd);
    return(type);

io_error:
    if (errno)
	 perror(device);
    else
	 fprintf(stderr, _("mount: error while guessing filesystem type\n"));
    close(fd);
    return 0;
}

#endif

static struct tried {
	struct tried *next;
	char *type;
} *tried = NULL;

static int
was_tested(const char *fstype) {
	struct tried *t;

	if (known_fstype(fstype))
		return 1;
	for (t = tried; t; t = t->next) {
		if (!strcmp(t->type, fstype))
			return 1;
	}
	return 0;
}

static void
set_tested(const char *fstype) {
	struct tried *t = xmalloc(sizeof(struct tried));

	t->next = tried;
	t->type = xstrdup(fstype);
	tried = t;
}

static void
free_tested(void) {
	struct tried *t, *tt;

	t = tried;
	while(t) {
		free(t->type);
		tt = t->next;
		free(t);
		t = tt;
	}
	tried = NULL;
}

char *
guess_fstype(const char *spec) {
	char *type = do_guess_fstype(spec);
	if (verbose) {
	    printf (_("mount: you didn't specify a filesystem type for %s\n"),
		    spec);
	    if (!type)
	      printf (_("       I will try all types mentioned in %s or %s\n"),
		      ETC_FILESYSTEMS, PROC_FILESYSTEMS);
	    else if (!strcmp(type, "swap"))
	      printf (_("       and it looks like this is swapspace\n"));
	    else
	      printf (_("       I will try type %s\n"), type);
	}
	return type;
}

static char *
procfsnext(FILE *procfs) {
   char line[100];
   char fsname[100];

   while (fgets(line, sizeof(line), procfs)) {
      if (sscanf (line, "nodev %[^\n]\n", fsname) == 1) continue;
      if (sscanf (line, " %[^ \n]\n", fsname) != 1) continue;
      return xstrdup(fsname);
   }
   return 0;
}

/* Only use /proc/filesystems here, this is meant to test what
   the kernel knows about, so /etc/filesystems is irrelevant.
   Return: 1: yes, 0: no, -1: cannot open procfs */
int
is_in_procfs(const char *type) {
    FILE *procfs;
    char *fsname;
    int ret = -1;

    procfs = fopen(PROC_FILESYSTEMS, "r");
    if (procfs) {
	ret = 0;
	while ((fsname = procfsnext(procfs)) != NULL)
	    if (!strcmp(fsname, type)) {
		ret = 1;
		break;
	    }
	fclose(procfs);
	procfs = NULL;
    }
    return ret;
}

/* Try all types in FILESYSTEMS, except those in *types,
   in case *types starts with "no" */
/* return: 0: OK, -1: error in errno, 1: type not found */
/* when 0 or -1 is returned, *types contains the type used */
/* when 1 is returned, *types is NULL */
int
procfsloop(int (*mount_fn)(struct mountargs *), struct mountargs *args,
	   const char **types) {
	char *files[2] = { ETC_FILESYSTEMS, PROC_FILESYSTEMS };
	FILE *procfs;
	char *fsname;
	const char *notypes = NULL;
	int no = 0;
	int ret = 1;
	int errsv = 0;
	int i;

	if (*types && !strncmp(*types, "no", 2)) {
		no = 1;
		notypes = (*types) + 2;
	}
	*types = NULL;

	/* Use PROC_FILESYSTEMS only when ETC_FILESYSTEMS does not exist.
	   In some cases trying a filesystem that the kernel knows about
	   on the wrong data will crash the kernel; in such cases
	   ETC_FILESYSTEMS can be used to list the filesystems that we
	   are allowed to try, and in the order they should be tried.
	   End ETC_FILESYSTEMS with a line containing a single '*' only,
	   if PROC_FILESYSTEMS should be tried afterwards. */

	for (i=0; i<2; i++) {
		procfs = fopen(files[i], "r");
		if (!procfs)
			continue;
		while ((fsname = procfsnext(procfs)) != NULL) {
			if (!strcmp(fsname, "*")) {
				fclose(procfs);
				goto nexti;
			}
			if (was_tested (fsname))
				continue;
			if (no && matching_type(fsname, notypes))
				continue;
			set_tested (fsname);
			args->type = fsname;
			if (verbose) {
				printf(_("Trying %s\n"), fsname);
				fflush(stdout);
			}
			if ((*mount_fn) (args) == 0) {
				*types = fsname;
				ret = 0;
				break;
			} else if (errno != EINVAL &&
				   is_in_procfs(fsname) == 1) {
				*types = "guess";
				ret = -1;
				errsv = errno;
				break;
			}
		}
		free_tested();
		fclose(procfs);
		errno = errsv;
		return ret;
	nexti:;
	}
	return 1;
}