Re: [Q] FAT driver enhancement

OGAWA Hirofumi (
Fri, 29 Mar 2002 04:48:44 +0900

Jos Hulzink <> writes:

> Hi,
> A while ago I initiated a thread about mounting a NTFS partition as FAT
> partition. The problem is that FAT partitions do not have a real
> fingerprint, so the FAT driver mounts almost anything.
> The current 2.5 driver only tests if some values in the bootsector are
> non-zero. IMHO, this is not strict enough. For example, the number of FATs
> is always 1 or 2 (anyone ever seen more ?). Besides, when there are two
> FATs, all entries in those FATs should be equal. If they are not, we deal
> with a non-FAT or broken FAT partition, and we should not mount.
> It's not a real fingerprint, but what are the chances all sectors of what
> we think is the FAT are equal on non-FAT filesystems ? Yes, when you just
> did a
> dd if=/dev/zero of=/dev/partition; mkfs.somefs /dev/partition
> there is a chance, but that's an empty filesystem. Data corruption isn't
> that bad on an empty disk. We know that a FAT is at the beginning of a
> partition and I assume that any other filesystem will fill up those first
> sectors very soon.
> Questions:
> 1) How do you think about the checking of the FAT tables ? It definitely
> will slow down the mount.

Unfortunately if FAT table has bad sector, FAT tables may not be the

> 2) If I implement it, where shoud it go ? At the moment, I hacked
> fat_read_super, for there the FAT fs is validated, but I got the
> feeling this is not the place to be.
> 3) Anyone seen more than two FATs on a filesystem ? Can I assume there is
> a limit ?
> 4) Comments, anyone ?

How about writing the The can
check many of the ordinary FAT status. If the something occurs, output
message to user. And user can handle it by option etc.


OGAWA Hirofumi <>
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

="end" -->