System and method for performing an on-line check of a file system

• US 20030182389A1
• Filed: 03/22/2002
• Published: 09/25/2003
• Est. Priority Date: 03/22/2002
• Status: Active Grant

• Current Assignee: NetApp, Inc.
• Original Assignee: Network Appliance Incorporated (NetApp, Inc.)
• Inventors: Edwards, John K.
• Granted Patent: US 6,895,413 B2
• Time in Patent Office: Days
• US Class Current: 709/213
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A system and method for performing an on-line check of a file system modifies various function calls within a file system layer of a storage operating system so that each time the particular inode is retrieved using the modified function calls, a check is performed on the inode and associated buffer trees before returning the requested inode to the calling process.

Claims

1. A method for on-line checking of a file system, the method comprising the steps of:

detecting a request for a file system structure;

accessing the requested file system structure;

checking the requested file system structure for coherency;

repairing, in response to the requested file system structure not being coherent, the requested file system structure; and

returning the requested file system structure.

2. The method of claim 1 wherein the file system structure further comprises an inode.

3. The method of claim 1 wherein the file system structure further comprises a directory.

4. A method for checking a file system implemented by a storage operating system while the file system is available for data access, the method comprising the steps of:

suspend data access to the file system

unmounting a volume associated with the file system;

modifying a load function in the storage operating system so that the load function performs a checking procedure before returning a requested file system structure;

mounting the volume; and

resume data access to the file system.

5. The method of claim 4 wherein the step of unmounting the volume further comprises the step of flushing a set of caches to a set of storage devices comprising the volume.

6. The method of claim 4 wherein the step of mounting the volume further comprises the step of loading a set of file system metafiles, wherein the step of loading the set of file system metafiles utilizes the modified load function whereby each of the set of file system metafiles is checked by the modified load function.

7. The method of claim 4 wherein the checking procedure further comprises the steps of:

loading a file system structure requested by the modified load function;

determining a type of the file system structure;

performing, in response to the file system structure being a directory, a directory checking procedure; and

performing, in response to the file system structure being a regular file, an inode checking procedure.

8. The method of claim 7 wherein the file system structure further comprises a directory.

9. The method of claim 7 wherein the file system structure further comprises an inode.

10. The method of claim 7 wherein the inode checking procedure further comprises the steps of:

verifying a set of pointers in a buffer tree associated with the inode;

removing any cross links within any buffer tree associated with the inode;

removing all but a first pointer to any block within a buffer tree associated with the inode; and

marking the inode as being checked.

11. The method of claim 10 wherein the step of marking the inode as being checked further comprises modifying an entry in a tracking file, the tracking file stored in the file system.

12. The method of claim 7 wherein the directory checking procedure further comprises the steps of:

determining if the directory links to a root directory;

determining, in response to the directory not linking to the root directory, if the directory comprises of a special directory;

linking, in response to the directory not linking to the root directory and the directory not comprising a special directory, the directory to a lost and found directory;

loading, using the modified load function, all file system objects in a layer immediately beneath the directory;

verifying a set of pointers in a buffer tree associated with the directory;

removing any cross links within any buffer tree associated with the directory;

removing all but a first pointer to any block within a buffer tree associated with the directory; and

marking the directory as being checked.

13. The method of claim 12 wherein the file system objects in a layer immediately beneath the directory comprises directories.

14. The method of claim 12 wherein the file system objects in a layer immediately beneath the directory comprises files.

15. A method for on-line checking of a file system, the method comprising:

a detector that detects a request for a file system structure;

mean for accessing the requested file system structure;

means for checking the requested file system structure for coherency;

a repair process, responsive to the requested file system structure not being coherent, that repairs the requested file system structure; and

means for returning the requested file system structure.

16. The method of claim 15 wherein the file system structure further comprises an inode.

17. The method of claim 15 wherein the file system structure further comprises a directory