Non-privileged access to data independent of filesystem implementation

• US 8,073,886 B2
• Filed: 02/20/2009
• Issued: 12/06/2011
• Est. Priority Date: 02/20/2009
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Ou-Yang, Darwin, Garson, Matt, Thind, Ravinder S.
• Primary Examiner(s): STACE, BRENT S
• Application Number:
  US12/390,357
• Publication Number:
  US 20100228797A1
• Time in Patent Office: 1,019 Days
• Field of Search: 707/999.2, 707/999.205, 707/999.009, 707/999.1, 707/999.101, 707/999.102, 707821-831, 707781-788, 707/802, 707/803, 707/790
• US Class Current: 707/831
• CPC Class Codes: G06F 16/10 File systems; File servers

Abstract

An application programming interface (API) module provides access to data, independent of filesystem implementation in a non-privileged user mode. A discovery volume having a filesystem recognizable by an operating system has cover files which prevent damage to data stored in an unrecognizable primary volume. The discovery volume also includes a data access API available for execution in a non-privileged user mode to render the primary volume accessible by operating systems which would otherwise find the primary volume unrecognizable.

Claims

1. One or more computer-readable storage media storing instructions that, when executed, instruct a processor to perform acts comprising:

calling a data access application programming interface (API), the data access API having an access library module and a discovery volume management module;

building a discovery volume using the discovery volume management module, the building comprising;

initializing the discovery volume having a discovery volume filesystem;

implementing a primary volume in the discovery volume filesystem, the primary volume having a primary filesystem storing primary data;

initializing a virtualized volume boot region in the discovery volume;

moving contents of one or more original boot regions of the primary volume from a beginning of the discovery volume to a new location in the primary volume or creating a discovery volume boot region and writing the original boot region in the primary volume at a location other than the beginning of the discovery volume;

constructing a pointer in the discovery volume boot region of the discovery volume pointing to a data structure containing information referring to an original boot region for the primary filesystem and writing the pointer to the discovery volume boot region;

constructing at least one cover file entry in the discovery volume filesystem, the at least one cover file entry configured to present the discovery volume as full by claiming blocks used by the primary volume filesystem as being used in the discovery volume filesystem; and

accessing the primary volume in a non-privileged user mode with the access library module of the API.

2. The computer-readable storage media of claim 1, further comprising returning contents of the original boot region when a read request comprising a boot region location is received.

3. The computer-readable storage media of claim 1, further comprising storing the data access API in the discovery volume.

4. The computer-readable storage media of claim 1, further comprising redirecting a write request to the virtualized volume boot region to the original boot region, such that the original boot region is written-to and not the virtualized volume boot region at the beginning of the volume.

5. One or more computer-readable storage media storing instructions that when executed instruct a processor to perform acts comprising:

calling a data access application programming interface (API), the data access API having an access library module configured to execute in a non-privileged user mode and a discovery volume management module;

employing the discovery volume management module to initialize a discovery volume boot region in a discovery volume, the discovery volume boot region including discovery volume boot information one or more pointers to one or more original boot regions;

initializing the discovery volume and a discovery volume filesystem, the discovery volume filesystem including at least one cover file entry configured to present the discovery volume as full;

accessing primary data stored in a primary volume of the discovery volume in the non-privileged user mode with the access library module of the API;

moving contents of the one or more original boot regions from a beginning of the discovery volume to a new location in the primary volume, or creating the discovery volume boot region and writing the one or more original boot regions at a location other than the beginning of the discovery volume; and

constructing the one or more pointers pointing to at least one data structure containing information referring to the one or more original boot regions, and writing the one or more pointers to the discovery volume boot region in the discovery volume.

6. The computer-readable storage media of claim 5, wherein the discovery volume management module is configured to execute in the non-privileged user-mode.

7. The computer-readable storage media of claim 5, further comprising:

building the discovery volume with the discovery volume management module, the discovery volume having the discovery volume filesystem, the discovery volume filesystem containing the primary volume and having a primary volume filesystem storing the primary data.

8. The computer-readable storage media of claim 7, wherein the building further comprises constructing the at least one cover file entry in the discovery volume filesystem, the at least one cover file entry configured to claim blocks used by the primary volume as in use by the discovery volume filesystem.

9. The computer-readable storage media of claim 7, wherein the discovery volume filesystem comprises FAT12, FAT16, FAT32, exFAT, FATX, UDF, NTFS, ext2, ext3, ext4, or Tux3.

10. The computer-readable storage media of claim 5, wherein writing the one or more original boot regions in the primary volume comprises writing the one or more original boot regions to a single stash file within the primary volume.

11. The computer-readable storage media of claim 5, further comprising mounting the primary volume in the operating system in user-mode using the access library module of the API.

12. A system comprising:

a processor;

a memory coupled to the processor;

a data access application programming interface (API) stored in the memory and configured to execute on the processor;

an operating system stored in the memory and configured to execute on the processor; and

a storage device separate from the memory and coupled to the processor, the storage device storing a discovery volume having a discovery volume filesystem recognizable by the operating system and a primary volume within the discovery volume, the primary volume having a primary volume filesystem storing primary data unrecognizable by the operating system, wherein the discovery volume filesystem includes at least one cover file that is configured to present the discovery volume as apparently full, and wherein discovery volume further includes a virtualized boot region that includes a pointer to an original boot region stored in a stash file in the primary volume.

13. The system of claim 12, wherein the API further comprises an access library module configured to allow access to the primary volume when executed in a non-privileged user mode and a discovery volume management module configured to build a discovery volume when executed.

14. The system of claim 12, wherein the data access API is stored initially on the storage device and copied to the memory upon coupling of the storage device to the processor.

15. The system of claim 12, wherein the discovery volume comprises an information file comprising information about the primary volume.

16. The system of claim 13, wherein the discovery volume management module is configured to build the at least one cover file in the discovery volume filesystem, the at least one cover file comprising at least one entry in the discovery volume filesystem configured to claim blocks used by the primary volume as being used in the discovery volume filesystem.

17. The system of claim 13, wherein the access library module is configured to allow read and write operation to the primary volume.