File system viewpath mechanism

• US 5,905,990 A
• Filed: 06/23/1997
• Issued: 05/18/1999
• Est. Priority Date: 06/23/1997
• Status: Expired due to Term

• Current Assignee: Xyratex Technology Limited (Seagate Technology Holdings Plc)
• Original Assignee: International Business Machines Corporation
• Inventors: Inglett, Scott D.
• Primary Examiner(s): Amsbury, Wayne
• Assistant Examiner(s): PARDO, THUY N
• Application Number:
  US08/880,781
• Time in Patent Office: 694 Days
• Field of Search: 84/602, 707/1, 707/8, 707/101, 707/102, 707/200, 707/203, 707/205, 707/602, 707/206, 707/2
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

A computer file system, particularly adapted to UNIX operating systems, for transparently allowing access to and modification of snapshot objects, i.e., files, directories, and symbolic links. The file system creates a mountpoint directory and dynamically searches the computer system to find a requested file object, manifesting a representation of the requested file object in the mountpoint directory if it is found. If an earlier representation of the requested file object already exists (in the mountpoint directory), then any further requests for the file object are directed to the earlier representation. Searching can be performed along a viewpath having two or more independent search paths, including those based on an object name, or based on an object name extension. The binding file translation is done entirely within the kernel to speed up processing, as well as minimize the overhead required to establish mountpoints across different machines.

Claims

1. A file system for a computer having a device for storing data and an operating system for organizing the data into logical file system objects including files and directories, the operating system interacting with the file objects by means of intermediate data structures, the file system comprising:

means for creating a mountpoint directory over an existing directory of the file system;

means for dynamically searching said intermediate data structures to find a requested logical file system object; and

means for manifesting a representation of the requested logical file system object in said mountpoint directory as a separate logical file system object.

2. The file system of claim 1 wherein said dynamic searching means is responsive to calls from the operating system against the requested logical file system object.

3. The file system of claim 2 wherein said dynamic searching means is further responsive to said calls which specify the requested logical file system object as being located in said mountpoint directory.

4. The file system of claim 1 wherein said dynamic searching means first searches said mountpoint directory to determine whether an earlier representation of the requested logical file system object already exists and, if so, directing any further requests for the requested logical file system object to said earlier representation.

5. The file system of claim 4 wherein, if no earlier representation of the requested logical file system object is found in said mountpoint directory, said dynamic searching means thereafter searches for the requested logical file system object along a viewpath comprising one or more independent search paths.

6. The file system of claim 1 further comprising means for indicating when no logical file system object is found matching the requested logical file system object.

7. The file system of claim 1 wherein said dynamic searching means searches for the requested logical file system object along a viewpath comprising at least two independent search paths.

8. The file system of claim 7 further comprising:

means for generating a child directory within said mountpoint directory; and

means for creating child directory search paths corresponding to said independent search paths.

9. The file system of claim 7 wherein there are at least four of said independent search paths each of a different search-path type including:

a regular expression search path instructing said dynamic searching means to search a first set of directories for the requested logical file system object based on a regular expression;

an alternate search path instructing said dynamic searching means to search a second set of directories for the requested logical file system object based on an object name;

an extension search path instructing said dynamic searching means to search a third set of directories for the requested logical file system object based on an object name extension; and

a library search path instructing said dynamic searching means to search a fourth set of directories for the requested logical file system object without regard to said regular expression, said object name or said object name extension.

10. The file system of claim 9 wherein said dynamic searching means searches said second set of directories before searching said first, third or fourth sets of directories, and further searches said first set of directories before searching said third or fourth sets of directories.

11. The file system of claim 1 wherein the operating system supports more than one physical file system each physical file system having physical file system objects corresponding to the logical file system objects.

12. The file system of claim 11 wherein the operating system calls a physical file system routine to implement an input/output call issued against a given logical file system object, and said searching means makes use of said physical file system routine to locate a physical file system object corresponding to said requested logical file system object.

13. The file system of claim 1 wherein:

said operating system has a kernel for low-level, fast operations; and

said manifesting means binds the representation of the requested logical file system object to its corresponding data structure within the kernel.

14. A method of manifesting a representation of a requested file object in a computer system, the file object residing in a storage device and having a corresponding intermediate data structure which is used to access the file object, comprising the steps of:

creating a mountpoint directory over an existing directory of the computer system;

searching the computer system for the intermediate data structure; and

if the intermediate data structure is found, associating the intermediate data structure with a representation of the requested file as a separate logical file system object but, if the intermediate data structure is not found, indicating that the requested file object does not exist.

15. The method of claim 14 wherein said searching step is performed in response to a call from the computer system against the requested file object.

16. The method of claim 14 comprising the additional step of searching said mountpoint directory to determine whether an earlier representation of the requested file object already exists before said searching of the computer system for the intermediate data structure.

17. The method of claim 16 wherein, if no earlier representation of the requested file object is found in said mountpoint directory, said searching step includes thereafter searching for the requested file object along a viewpath comprising one or more search paths.

18. The method of claim 17 wherein:

there are at least four of said independent search paths each of a different search-path type including a regular expression search path instructing said dynamic searching means to search a first set of directories for the requested logical file system object based on a regular expression, an alternate search path instructing said dynamic searching means to search a second set of directories for the requested logical file system object based on an object name, an extension search path instructing said dynamic searching means to search a third set of directories for the requested logical file system object based on an object name extension, and a library search path instructing said dynamic searching means to search a fourth set of directories for the requested logical file system object without regard to said regular expression, said object name or said object name extension; and

said searching step first searches said second set of directories, then searches said first set of directories only if the requested logical file system object is not found in the second set of directories, then searches said third set of directories only if the requested file object is not found in the first or second sets of directories, and thereafter searches said fourth set of directories only if the requested file object is not found in the first, second or third sets of directories.

19. The method of claim 14 wherein said searching step searches for the requested file object along a viewpath comprising at least two independent search paths.

20. The method of claim 14 wherein:

said computer system has a kernel for low-level, fast operations; and

said associating step binds the representation of the requested file object to its corresponding data structure within the kernel.

21. A file system for a computer having access to a device for storing data and an operating system that logically organizes the data into logical file system (LFS) objects, the file system comprising:

means for calling one or more physical file system routines to implement input/output system calls issued against a given LFS object;

means for using one of the physical file system routines to locate a given PFS object beneath a given directory;

means for supporting at least one physical file system which implements the LFS objects by way of corresponding physical file system (PFS) objects;

means for using one of the physical file system routines to mount an instance of the physical file system over a given directory, the contents of which are subsequently implemented by the physical file system;

means for assigning a set of viewpaths to a mountpoint directory; and

means for searching one more of the viewpaths of a given directory for the given LFS object and, if found, manifesting a mirage object associated with the given LFS object in the given directory.

22. The file system of claim 21 wherein said manifesting means manifests the mirage object by creating a second LFS object corresponding to a second PFS object.

23. The file system of claim 22 further comprising means for redirecting operating system calls against the given PFS object to the second PFS object.

24. The file system of claim 21 wherein said mounting means includes means for creating a child directory beneath the mountpoint directory, the child directory inheriting the set of viewpaths.