Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1998-07-13
2001-07-03
Amsbury, Wayne (Department: 2171)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C707S793000, C707S793000, C707S793000
Reexamination Certificate
active
06256646
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to the field of electronic systems, and more specifically to a method and system for identifying the state of a media device by monitoring file system calls.
BACKGROUND OF THE INVENTION
Computers systems typically have operating systems that access media devices, such as disk drives, through low level device drivers. Applications generally execute above the operating system and pass file system calls through the operating system to store or access data on media devices. The file system calls are typically handled at a low level by the device driver associated with the particular media device.
There can be situations when it is desirable for an application to perform a direct media I/O to a media device. In this case, the access would not pass through the file system. However, this direct I/O can be dangerous in that there must be an assurance that the structure of data on the media device is known. Otherwise, active data could be improperly handled or overwritten. One means for obtaining this assurance is to obtain a lock on the media device by which only the locking application has access to the media device. However, some media devices, such as boot volumes in WINDOWS NT, are non-lockable. In other words, there is no defined interface that allows an application to gain exclusive access to the media device.
In conventional systems, if the operating system is not running on a media device (e.g., a volume of a disk drive), the system will often allow a user program or application to obtain exclusive access to the media device. If a media device is deemed non-lockable, an application could always boot from another operating system with the desired media device attached as a “lockable” device and perform the desired action with the media device under an exclusive lock. However, there are no conventional options for providing “error free” direct I/O to a media device, such as a volume of a fixed disk, while an operating system is up and running and has deemed the media device non-lockable.
Further, it can be desirable to “flush” or “clean” file system residue from a media device, such as a disk volume, thus making it impossible for any data to be recovered from what was once a deleted file on the file system. In general, file system residue includes all aspects of deleted files that remain on the media device. For example, freed data on a volume of a disk drive will reside in many places on the format of the volume. Inactive data can reside in any freed allocations on the disk and also in the descriptors (attributes of the data) that house the name of old files along with pointers to where the old file data once resided. Despite the desirability of flushing all such file system residue, conventional flushing products only operate to flush the free allocations on the file system. This does not remove all of the file system residue from a deleted file. Rather, it only handles data that is in an unallocated state on the media device.
SUMMARY OF THE INVENTION
In accordance with the present invention, a method and system for identifying the state of a media device by monitoring file system calls are disclosed that provide advantages over conventional methods and applications.
According to one aspect of the present invention, file system calls are monitored and information is obtained therefrom. It is determined from this whether the file system call originated from a specified high level application. If the file system call did not originate from the specified high level application, a state for a monitored media device is set to indicate an unknown state if the file system call will modify the monitored media device. If the file system call did originate from the specified high level application, a state for the monitored media device is set to indicate a known state if the file system call is a read request. Further, in one embodiment, if the file system call is a write request that originated from the specified high level application and the monitored media device is in a known state, the file system call is allowed to pass to a low level driver for the monitored media device. On the other hand, if the file system call is a write request that originated from the specified high level application and the monitored media device is in an unknown state, the file system call is rejected. In one implementation, the high level application writes to the monitored media device in order to perform a flushing process on the monitored media device to securely delete inactive data.
A technical advantage of the present invention is the ability to allow a native operating system to continue to run and function as normal, while direct read/writes are performed to a non-lockable media device (e.g., a WINDOWS NT boot volume) without corruption of data stored on the media device. This ability can be particularly helpful for performing a flush of inactive data on the media device such that the inactive data is securely deleted and rendered unrecoverable.
Another technical advantage is the provision of a robust flushing process that can remove all file attribute data (e.g., file control block data in WINDOWS NT), can remove slack space at the end of every file up to the next cluster, and can securely clean free clusters to make any data from file system residue unrecoverable.
Additional technical advantages should be readily apparent from the drawings, description, and claims.
REFERENCES:
patent: 5239437 (1992-04-01), Hoge et al.
patent: 5827453 (1996-06-01), Roberts
patent: 5832513 (1996-06-01), Kennedy
patent: 5946278 (1997-09-01), Tower
patent: 6003041 (1998-01-01), Wugofski
patent: 6044436 (1997-11-01), Otsuka
Murdock Carlos A.
Starek Robert Phillip
Amsbury Wayne
Do Thuy
Infraworks Corporation
Schnader Harrison Segal & Lewis LLP
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