Each file system implementation is free to decide how it recognizes its
own file system type. The UDFS file system (at least on my XP box) has
registered for both CD and DISK mount events, so I would assume it can
recognize a UDFS formatted disk drive type. With a tool like objdir or
winobj or the debugger, you should be able to determine what the UDFS
driver has registered as well (the device objects with names have
normally been registered for mount events.)
The media type does matter - Windows only supports mount on four media
types: FILE_DEVICE_DISK, FILE_DEVICE_TAPE, FILE_DEVICE_CD_ROM,
FILE_DEVICE_VIRTUAL_DISK - with the latter being “lumped into” the same
file system type as the first one. File systems of type
FILE_DEVICE_DISK_FILE_SYSTEM are given the opportunity to mount
FILE_DEVICE_DISK or FILE_DEVICE_VIRTUAL_DISK media. File systems of
type FILE_DEVICE_CD_ROM_FILE_SYSTEM are given the opportunity to mount
FILE_DEVICE_CD_ROM, etc.
To achieve this, the file system must create a unique device object and
register that device object with the I/O Manager (IoRegisterFileSystem).
The I/O Manager then maintains a LIFO call table of file systems (last
registered, first called) that are invoked to check a media device and
determine if the volume in question has the right format.
One issue I’ve seen interfere with mounting in the past is that the I/O
Manager is very sensitive to errors returned by the mounting file
system. It expects STATUS_UNRECOGNIZED_VOLUME (see FatMountVolume in
fsctrl.c for FAT). Other errors can (and do) cause mounting problems.
For example, we had an FSD that was written to work with WORM media.
If NTFS were asked to mount the volume first and it attempted to read an
unrecorded area on the media it would get an I/O error (indicating that
the sector had not yet been recorded). NTFS would report this error to
the I/O Manager and the I/O Manager would abort the mount processing -
so our file system never was given an opportunity to mount. Different
media, or different load ordering and the mount proceeded correctly.
This was many years ago and at the time I lobbied for changes to the I/O
Manager to be a bit more liberal in its decision to continue mount
processing but was told that this wouldn’t happen because it only
affected a non-MS file system.
Bottom line: mount processing is an elaborate dance with multiple
players, each of whom must behave in a proscribed manner. A failure to
do so may lead to cases where a volume may not behave the way that you
expect.
Regards,
Tony
Tony Mason
Consulting Partner
OSR Open Systems Resources, Inc.
http://www.osr.com
Looking forward to seeing you at the next OSR File Systems class in
Boston, MA April 18-21, 2006 (note new date - MS scheduled plugfest the
same week again.)
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Saritha Vinod
Sent: Monday, March 06, 2006 7:16 AM
To: ntfsd redirect
Subject: [ntfsd] Does windows detects UDF formatted hard disk?
Hi all,
I am trying to format a hard disk partition using UDF file system. Since
windows 2000 does not have write support for UDF, I formatted using
Linux and was able to read and write to it. The UDF version used was
1.50. I tried accessing that partition again in Windows. But windows
failed to recognize it and showed that it is not formatted. Can anybody
please tell me the reason for this? Is it that windows will not
recognize UDF on hard disk, since it tries to mount UDF only for CD/DVD
devices?
Is the media type in anyway related to this behaviour?
Thanks in advance.
Saritha.
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