Is there a way to limit VFAT allocation?

[Zoltan Boszormenyi <zboszor@dunaweb.hu>]

Hi,

I have bought a 2GB MP3 player / flash disk
that erroneously partitions and formats its storage.
The built-in firmware has an off-by-one bug that
creates the partition one cylinder larger that the
disk size allows and then it formats the VFAT fs
according to the buggy partition size. No wonder
when I try to copy large amounts of data to the
flash disk it detects errors and then remounts it
read-only.

I tried to repartition and reformat it three times
with different mformat or mkdosfs options
but as soon as I remove it from the USB port,
the device detects changed disk format and
automatically reformats itself again, so it
stays buggy.

Here's the excerpt from the logs on one occasion
I tried to copy some large stuff onto it:

Oct  3 22:56:31 host-81-17-177-202 kernel: SCSI device sdb: 4095765 
512-byte hdwr sectors (2097 MB)
Oct  3 22:56:31 host-81-17-177-202 kernel: sdb: Write Protect is off
Oct  3 22:56:32 host-81-17-177-202 kernel: sdb: assuming drive cache: 
write through
Oct  3 22:56:32 host-81-17-177-202 kernel: SCSI device sdb: 4095765 
512-byte hdwr sectors (2097 MB)
Oct  3 22:56:32 host-81-17-177-202 kernel: sdb: Write Protect is off
Oct  3 22:56:32 host-81-17-177-202 kernel: sdb: assuming drive cache: 
write through
Oct  3 22:56:33 host-81-17-177-202 kernel:  sdb: sdb1
Oct  3 22:56:33 host-81-17-177-202 kernel:  sdb: p1 exceeds device capacity
Oct  3 22:56:33 host-81-17-177-202 kernel: sd 6:0:0:0: Attached scsi 
removable disk sdb
Oct  3 22:56:33 host-81-17-177-202 kernel: sd 6:0:0:0: Attached scsi 
generic sg1 type 0
Oct  3 22:56:33 host-81-17-177-202 kernel: sd 5:0:0:0: Attached scsi 
removable disk sdc
Oct  3 22:56:33 host-81-17-177-202 kernel: sd 5:0:0:0: Attached scsi 
generic sg2 type 0
Oct  3 22:56:33 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095616
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095617
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095618
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095619
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095620
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095621
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095622
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095623
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095616
Oct  3 22:56:34 host-81-17-177-202 kernel: Buffer I/O error on device 
sdb1, logical block 4095617
Oct  3 22:56:34 host-81-17-177-202 kernel: SELinux: initialized (dev 
sdb1, type vfat), uses genfs_contexts
...
Oct  3 23:26:53 host-81-17-177-202 kernel: FAT: Filesystem panic (dev sdb1)
Oct  3 23:26:53 host-81-17-177-202 kernel:     fat_get_cluster: invalid 
cluster chain (i_pos 0)
Oct  3 23:26:53 host-81-17-177-202 kernel:     File system has been set 
read-only
...
Oct  3 23:31:35 host-81-17-177-202 kernel: FAT: Filesystem panic (dev sdb1)
Oct  3 23:31:35 host-81-17-177-202 kernel:     fat_get_cluster: invalid 
cluster chain (i_pos 0)
Oct  3 23:35:33 host-81-17-177-202 kernel: FAT: Filesystem panic (dev sdb1)
Oct  3 23:35:33 host-81-17-177-202 kernel:     fat_bmap_cluster: request 
beyond EOF (i_pos 47395744)
Oct  3 23:35:33 host-81-17-177-202 kernel: FAT: Filesystem panic (dev sdb1)
Oct  3 23:35:33 host-81-17-177-202 kernel:     fat_bmap_cluster: request 
beyond EOF (i_pos 47395744)
Oct  3 23:35:33 host-81-17-177-202 kernel: FAT: Filesystem panic (dev sdb1)
Oct  3 23:35:33 host-81-17-177-202 kernel:     fat_bmap_cluster: request 
beyond EOF (i_pos 47395744)
Oct  3 23:35:33 host-81-17-177-202 kernel: FAT: Filesystem panic (dev sdb1)
Oct  3 23:35:33 host-81-17-177-202 kernel:     fat_bmap_cluster: request 
beyond EOF (i_pos 47395744)
...

Unfortunately, the firmware is not upgradeable.
The device in question is a Telstar UFM-102B.

Is there a way to tell the VFAT driver to exclude
the last N sectors from the allocation strategy?

Best regards,
Zoltán Böszörményi

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