Merging file system directories

• US 20080005133A1
• Filed: 06/30/2006
• Published: 01/03/2008
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Khalidi, Yousef A., Talluri, Madhusudhan, Smith, Frederick J.
• Granted Patent: US 8,280,908 B2
• Time in Patent Office: Days
• US Class Current: 707/100
• CPC Class Codes: G06F 16/192 Implementing virtual folder structures

Abstract

Two or more separate physical file system directories are presented as one merged (virtual) file system directory to a process running in a silo. The operating system controls the level of access to the files in the merge directory. The operating system provides the merged view of the file system directories by monitoring file system requests made by processes in silos on a computer or computer system and in response to detecting certain types of file system access requests, provides the view of the seemingly merged directories by performing special processing. The types of requests which trigger the special processing include: enumeration, open, create, rename or close.

Claims

1. A system for controlling file sharing and file access comprising:

an operating system that provides a silo-specific view of a plurality of file system directories for processes running in a silo, wherein the operating system creates the silo-specific view by monitoring file system access requests initiating from the processes running in the silo and in response to detecting a file system access, performs callback processing that creates the silo-specific view of the plurality of the file system directories that appears to the processes running in the silo to be a single directory comprising entries in the plurality of file system directories.

2. The system of claim 1, wherein each of the plurality of file system directories is associated with a rank.

3. The system of claim 2, wherein the rank associated with each of the plurality of file system directories is used as a tiebreaker to determine entries included in the silo-specific view when more than one entry in the plurality of directories is known by a particular name.

4. The system of claim 1, wherein the silo is a first silo, and the first silo includes a second silo nested within the first silo, wherein the first silo is a parent of the second silo and the second silo is a child of the first silo.

5. The system of claim 1, wherein the operating system includes a filter driver that detects file system access requests via callbacks inserted in file request access processing paths.

6. The system of claim 5, wherein the file system access requests include a file system access request comprising an open file request, an open directory request, a create file request, a create directory request, an enumerate file request, an enumerate directory request, a query file request, a query directory request, a rename file request, a rename directory request, a close file request or a close directory request.

7. A method for providing a view of a plurality of file system directories to processes running in a silo comprising:

using a filter driver in an operating system to monitor the processes running in the silo, wherein the filter driver detects a file access request made by a process running in the silo;

in response to detecting the file access request, performing processing associated with a type of file access request wherein the view of the plurality of file system directories is provided to the process, wherein the view presents the plurality of file system directories to the process as a single directory comprising entries of the plurality of file system directories, wherein the plurality of file system directories include a first file directory comprising a global shared directory and a second file directory comprising a silo-specific local unshared directory.

8. The method of claim 7, wherein selection of entries for inclusion in the view depends on a rank associated with each of the plurality of file system directories, wherein the rank is used as a tiebreaker when more than one entry in the directories is known by a particular name.

9. The method of claim 7, wherein in response to determining that the file access request is a create file or create directory operation, metadata associated with the plurality of directories is retrieved, and the second file directory is examined first for a particular file or directory specified in the file access request.

10. The method of claim 7, wherein in response to determining that the file access request is an enumerate file or enumerate directory operation, the operating system returns the view wherein the view comprises a list of entries in the first file directory and the second file directory.

11. The method of claim 7, wherein in response to determining that the file access request is a rename file or rename directory operation, the view is examined for existence of a new name to be used.

12. The method of claim 7, wherein in response to determining that the file access request is a close file or close directory operation, metadata associated with the file or directory is deleted.

13. The method of claim 7, wherein access of the process to entries in the first file directory is restricted to read-only access via creation of the view.

14. The method of claim 7, wherein access of the process to entries in the second file directory is read-write access.

15. A computer-readable medium having program code stored thereon that, when executed by a computing environment, causes the computing environment to:

use a filter driver of an operating system to monitor processes running in a silo, wherein the filter driver detects a file access request made by a process running in the silo;

in response to detecting the file access request, perform processing associated with a type of file access request wherein a view of a plurality of physical file directories is provided to the process, wherein the view presents the plurality of physical file directories to the process as a single virtual directory comprising entries of the plurality of physical file directories.

16. The computer-readable medium of claim 15, having further program code stored thereon, that when executed by the computing environment, causes the computing environment to:

associate metadata with the view of the plurality of physical directories, wherein the view comprises a first portion of the view and a second portion of the view, wherein the first portion of the view comprises entries from a first file directory comprising a global shared directory and the second portion of the view comprises entries from a second file directory comprising a silo-specific local unshared directory, wherein the metadata determines degree of access to the entries.

17. The computer-readable medium of claim 16, having further program code stored thereon, that when executed by the computing environment, causes the computing environment to:

examine the local unshared directory first for an entry specified in the file access request when creating the view when the file access request is an open operation.

18. The computer-readable medium of claim 16, having further program code stored thereon, that when executed by a computing environment, causes the computing environment to:

examine the global shared directory first for an entry specified in the file access request when creating the view when the file access request is a create operation.

19. The computer-readable medium of claim 16, having further program code stored thereon, that when executed by the computing environment, causes the computing environment to:

enumerate entries comprising a union of the first file directory and the second file directory when the file access request is an enumeration operation.

20. The computer-readable medium of claim 16, having further program code stored thereon, that when executed by the computing environment, causes the computing environment to:

update the name of the entry to reflect a resolvable name for a requestor, the requestor comprising a process inside a silo or a process outside the silo.