very large FAT16 partition not readable on 2.6.0-test11

very large FAT16 partition not readable on 2.6.0-test11

[Greg KH]

Hi all,

I just bought a new USB/Firewire external drive.  It comes pre-formatted
as FAT16 (or so shows fdisk) as one big 80Gb partition.  Unfortunately,
Linux can't seem to mount this partition, and I get the following dmesg
output when trying to mount the partition:
	FAT: bogus number of reserved sectors
	VFS: Can't find a valid FAT filesystem on dev sdb1.

Now before I blow it away and put a sane filesystem on this disk, I
saved off the MBR and the initial portion of the partitions if anyone
wants to poke around and take a look at it.  I'll keep the filesystem
as-is for a few days if anyone wants me to get any more data from it.

The files are:
	kernel.org/pub/linux/kernel/people/gregkh/fat16_mbr.gz
	(generated by: 'dd if=/udev/sdb  count=1 bs=512 > fat16_mbr')

	kernel.org/pub/linux/kernel/people/gregkh/fat16_sdb.gz
	(generated by: 'dd if=/udev/sdb  count=1000 bs=512 > fat16_sdb')

	kernel.org/pub/linux/kernel/people/gregkh/fat16_sdb1.gz
	(generated by: 'dd if=/udev/sdb  count=1000 bs=512 > fat16_sdb1')

Oh, 2.4.23 also can't seem to read it, so it doesn't look like this is a
regression or anything.

thanks,

greg k-h

Re: very large FAT16 partition not readable on 2.6.0-test11

[Andries Brouwer]

On Tue, Dec 09, 2003 at 03:03:33PM -0800, Greg KH wrote:

> I just bought a new USB/Firewire external drive.  It comes pre-formatted
> as FAT16 (or so shows fdisk) as one big 80Gb partition.  Unfortunately,
> Linux can't seem to mount this partition, and I get the following dmesg
> output when trying to mount the partition:
> 	FAT: bogus number of reserved sectors
> 	VFS: Can't find a valid FAT filesystem on dev sdb1.
> 
> Now before I blow it away and put a sane filesystem on this disk, I
> saved off the MBR and the initial portion of the partitions if anyone
> wants to poke around and take a look at it.  I'll keep the filesystem
> as-is for a few days if anyone wants me to get any more data from it.

Good.

* fat16_sdb1: this is all zeros. No filesystem at all, which explains
  why it won't mount.
* fat16_mbr: nothing wrong here

   Device Boot    Start       End   #sectors  Id  System
fat16_mbr1            63 156360644  156360582   6  FAT16
fat16_mbr2             0         -          0   0  Empty
fat16_mbr3             0         -          0   0  Empty
fat16_mbr4             0         -          0   0  Empty

* fat16_sdb:
There is a little bit of data here - don't know what it is.

Andries

Re: very large FAT16 partition not readable on 2.6.0-test11

[Rogier Wolff]

On Wed, Dec 10, 2003 at 10:34:46AM +0100, Andries Brouwer wrote:
> On Tue, Dec 09, 2003 at 03:03:33PM -0800, Greg KH wrote:
> 
> > I just bought a new USB/Firewire external drive.  It comes pre-formatted
> > as FAT16 (or so shows fdisk) as one big 80Gb partition.  Unfortunately,
> > Linux can't seem to mount this partition, and I get the following dmesg
> > output when trying to mount the partition:
> > 	FAT: bogus number of reserved sectors
> > 	VFS: Can't find a valid FAT filesystem on dev sdb1.

May I make a programming style suggestion? When you find a parameter
out-of-range, don't just print that it's out of range, but print the
actual value as well. This message would have become:

	FAT: Number of reserved sectors (0) out of range. 

Even better would be to print the range as well:

	FAT: Number of reserved sectors (0) out of range (1..16). 

(I just made the number up, I haven't looked in the code what the
valid range actually is...).


		Roger. 

-- 
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*-- BitWizard writes Linux device drivers for any device you may have! --*
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Re: very large FAT16 partition not readable on 2.6.0-test11

[Greg KH]

On Wed, Dec 10, 2003 at 10:34:46AM +0100, Andries Brouwer wrote:
> On Tue, Dec 09, 2003 at 03:03:33PM -0800, Greg KH wrote:
> 
> > I just bought a new USB/Firewire external drive.  It comes pre-formatted
> > as FAT16 (or so shows fdisk) as one big 80Gb partition.  Unfortunately,
> > Linux can't seem to mount this partition, and I get the following dmesg
> > output when trying to mount the partition:
> > 	FAT: bogus number of reserved sectors
> > 	VFS: Can't find a valid FAT filesystem on dev sdb1.
> > 
> > Now before I blow it away and put a sane filesystem on this disk, I
> > saved off the MBR and the initial portion of the partitions if anyone
> > wants to poke around and take a look at it.  I'll keep the filesystem
> > as-is for a few days if anyone wants me to get any more data from it.
> 
> Good.
> 
> * fat16_sdb1: this is all zeros. No filesystem at all, which explains
>   why it won't mount.

Ok, you're right.  It can't mount on a Windows box either.  Seems to
need to be formatted for any os that uses it.  So I've just put ext3 on
it and it runs just fine for me.

Sorry for the disruption, and thanks for looking into it.

greg k-h

Re: very large FAT16 partition not readable on 2.6.0-test11

[Dennis Bliefernicht]

Greg KH wrote:
> I just bought a new USB/Firewire external drive.  It comes pre-formatted
> as FAT16 (or so shows fdisk) as one big 80Gb partition.  Unfortunately,
> Linux can't seem to mount this partition, and I get the following dmesg
> output when trying to mount the partition:
> 	FAT: bogus number of reserved sectors
> 	VFS: Can't find a valid FAT filesystem on dev sdb1.

Well, according to my sources FAT16 cannot sustain any partition larger 
than 2GiB, so 80GiB is probably a lot more than it can handle. Anyway, 
sdb1 is lacking any type of header and sdb containt something, but not a 
FAT header afaik. So probably theres just a partition table entry but 
not formatted.

RE: very large FAT16 partition not readable on 2.6.0-test11

[Kevin Krieser]

Actually, there is an extension to 4GB that NT used in the 4.0 days (maybe
earlier?).

Don't know if the Linux driver supports it.

-----Original Message-----
From: linux-kernel-owner@vger.kernel.org
[mailto:linux-kernel-owner@vger.kernel.org]On Behalf Of Dennis
Bliefernicht
Sent: Tuesday, December 09, 2003 5:38 PM
To: linux-kernel@vger.kernel.org
Subject: Re: very large FAT16 partition not readable on 2.6.0-test11


Greg KH wrote:
> I just bought a new USB/Firewire external drive.  It comes pre-formatted
> as FAT16 (or so shows fdisk) as one big 80Gb partition.  Unfortunately,
> Linux can't seem to mount this partition, and I get the following dmesg
> output when trying to mount the partition:
> 	FAT: bogus number of reserved sectors
> 	VFS: Can't find a valid FAT filesystem on dev sdb1.

Well, according to my sources FAT16 cannot sustain any partition larger
than 2GiB, so 80GiB is probably a lot more than it can handle. Anyway,
sdb1 is lacking any type of header and sdb containt something, but not a
FAT header afaik. So probably theres just a partition table entry but
not formatted.

Re: very large FAT16 partition not readable on 2.6.0-test11

[H. Peter Anvin]

Followup to:  <NDBBLFLJADKDMBPPNBALOEDBCLAB.kkrieser@lcisp.com>
By author:    "Kevin Krieser" <kkrieser@lcisp.com>
In newsgroup: linux.dev.kernel
>
> Actually, there is an extension to 4GB that NT used in the 4.0 days (maybe
> earlier?).
> 

One can do that with a 64K cluster size.  This is against the
currently published spec, but was apparently done sometimes.

	-hpa
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