Pageable filter driver for prospective implementation of disk space quotas
A filter driver for implementing disk space quotas is described. Quota limits on disk space taken up by files in the file system are established for users and directories, and an internal database is established to track quotas against actual disk space utilization. A driver in accordance with the invention uses kernel resources of the operating system to prevent execution of file system I/O operations which would violate any established quota. In doing so, the driver executes a logic in kernel mode which serializes file allocation operations and also serializes access to the internal database. The first step in this logic is to intercept file system I/O requests before they reach the file system driver. Then the driver determines prospectively—before the I/O request is completed—whether any quota would be exceeded by completion of the I/O request. If a quota would be exceeded, completion of the I/O request is blocked and an error status is issued. If a quota would not be exceeded, the I/O request is allowed to complete and the driver's internal database is updated with revised disk space utilization data.
1. A filter driver for use with an operating system, comprising:
means for establishing disk space quotas, said quotas being established in relation to a plurality of quota parameters;
means for determining disk space utilization in relation to each of said quota parameters;
means for storing said disk space quotas and said disk space utilization in a file structure;
means for monitoring disk I/O;
means for prospectively evaluating the effect of said disk I/O on said disk space utilization, said effect being a revised disk space utilization in relation to said disk space quotas;
means for terminating said disk I/O if said revised disk space utilization exceeds any of said disk space quotas; and
means for updating said file structure to reflect completion of said disk I/O if said revised disk space utilization does not exceed any of said disk space quotas.
2. The filter driver of claim 1 , wherein said monitoring means further comprises:
means for detecting disk I/O operations, each said disk I/O operation being associated with a named disk file;
means for serializing operations on said named disk file.
3. The filter driver of claim 2 , wherein said serializing means further comprises:
means for locking a synchronizing object, said synchronizing object being associated with said named disk file, and said locking means serving to block further disk I/O operations on said named disk file.
4. The filter driver of claim 3 , wherein said synchronizing object is a kernel event in the Windows NT operating system.
5. The filter driver of claim 1 , wherein said plurality of quota parameters comprises one or more ownership quotas and one or more directory quotas, each said ownership quota being a maximum quantity of said disk space in use by files associated with a particular owner, and each said directory quota being a maximum quantity of said disk space in use by files associated with a particular directory.
6. The filter driver of claim 1 , wherein access to said file structure is serialized.
7. The filter driver of claim 1 , wherein said monitoring means ignores paging I/O.
8. The filter driver of claim 1 , wherein said prospective evaluation means further comprises:
means for determining said revised disk space utilization; and
means for comparing said revised disk space utilization to said disk space quotas.
9. A computerized method for implementing disk space quotas comprising the steps of:
maintaining a database of disk space quotas and disk space utilization data;
intercepting an I/O request before it reaches a file system driver;
determining whether any disk space quota would be exceeded by completion of the I/O request;
blocking completion of the I/O request if any disk space quota would be exceeded by completion of the I/O request; and
allowing the I/O request to complete and updating the disk space utilization data to reflect completion if a disk space quota would not be exceeded.
10. The method of claim 9 , further comprising the step of issuing an error message if a disk space quota would be exceeded by completion of the I/O request.
11. The method of claim 9 , further comprising the step of serializing I/O requests.
12. The method of claim 11 , wherein the step of serializing I/O requests includes the step of locking a synchronizing object for the file when an I/O request for that file is detected.
13. The method of claim 12 , wherein the synchronizing object is a kernel event.
14. The method of claim 9 , wherein the disk space quotas comprise at least one ownership quota and at least one directory quota, the ownership quota being a maximum quantity of disk space in use by files associated with a particular owner, the directory quota being a maximum quantity of disk space in use by files associated with a particular directory.
15. The method of claim 9 , further comprising the step of serializing access to the database.
16. The method of claim 15 , wherein the serializing step is performed using a simple kernel mutex.
17. The method of claim 9 , wherein paging I/O requests are ignored.
18. A computerized method for implementing disk space quotas comprising the steps of:
maintaining a database of disk space quotas;
intercepting an I/O request before it reaches a file system driver;
determining whether any disk space quota would be exceeded by completion of the I/O request; and
allowing the I/O request to complete only if a disk space quota would not be exceeded.
19. The method of claim 18 , further comprising the step of issuing an error message if a disk space quota would be exceeded by completion of the I/O request.
20. The method of claim 18 , further comprising the step of serializing I/O requests.
21. The method of claim 20 , wherein the step of serializing I/O requests includes the step of locking a synchronizing object for the file when an I/O request for that file is detected.
22. The method of claim 21 , wherein the synchronizing object is a kernel event.
23. The method of claim 18 , further comprising the step of:
maintaining disk space utilization data; and
updating the disk space utilization data to reflect completion of the I/O request.