Page cache management for a shared file

• US 7,831,642 B1
• Filed: 10/08/2004
• Issued: 11/09/2010
• Est. Priority Date: 09/30/2004
• Status: Active Grant

• Current Assignee: Veritas Technologies, LLC (Whitehouse Group Ltd.)
• Original Assignee: Symantec Operating Corporation (Gen Digital Inc.)
• Inventors: Kumaresan, Balemurughan, Prince, Harold Bailey Jr., Balan, Ramesh
• Primary Examiner(s): Jalil; Neveen Abel
• Assistant Examiner(s): Chbouki; Tarek
• Application Number:
  US10/961,454
• Time in Patent Office: 2,223 Days
• Field of Search: None
• US Class Current: 707/822
• CPC Class Codes: G06F 12/0804 with main memory updating G06F12/0806 takes precedence
• CPC Class Codes: G06F 12/0808 with cache invalidating means G06F12/0815 takes precedence
• CPC Class Codes: G06F 12/084 with a shared cache
• CPC Class Codes: G06F 12/0842 for multiprocessing or multitasking
• CPC Class Codes: G06F 12/0844 Multiple simultaneous or quasi-simultaneous cache accessing

Abstract

A method, system, computer system, and computer-readable medium to efficiently coordinate caching operations between nodes operating on the same file while allowing different regions of the file to be written concurrently. More than one program can concurrently read and write to the same file. Pages of data from the file are proactively and selectively cached and flushed on different nodes. In one embodiment, range locks are used to effectively flush and invalidate only those pages that are accessed on another node.

Claims

1. A method of providing concurrent access to data, said method comprising:

receiving, by a processor of a second network node, a request from a first network node for access to a first portion of a file, wherein

said first portion of said file is a subset of a region of said file,

the second network node has been granted access to said region of said file, and

said access to said region of said file is controlled by a first range lock;

in response to receiving the request from the first network node for access to the first portion of said file,

said processor performing an operation on a set of pages in a page cache stored in a page cache memory coupled to said processor, wherein

the set of pages corresponds to said region of said file,

a first page of the set of pages corresponds to the first portion of the file, and

the performing the operation comprises causing the first page of the set of pages to be provided to the first network node if the second network node has been granted exclusive access to the first portion of the file, and

revoking said first range lock to the first portion if the second network node has been granted exclusive access to the first portion of the file; and

transmitting to said second network node information causing a second range lock to be associated with said first portion of the file.

2. The method of claim 1 wherein

a second page of the set of pages in the page cache corresponds to a second portion of the region of the file, and

the operation is not performed on the second page.

3. The method of claim 1 wherein

if the second network node has been granted exclusive access to the first portion, the performing the operation further comprises causing the first page of the set of pages to be flushed from the page cache to the file.

4. The method of claim 3 further comprising:

causing the first network node to read the first portion from the file.

5. The method of claim 3 further comprising:

causing the first portion to be provided to the first network node.

6. The method of claim 1 further comprising:

if the second network node has been granted shared access to the first portion, the performing the operation comprises causing the first page of the set of pages to be invalidated in the page cache.

7. The method of claim 6 further comprising:

causing the first network node to read the first portion from the file.

8. The method of claim 1 further comprising:

if the operation changes a size of the file, blocking the operation until file size information is obtained.

9. A system for providing concurrent access to data, said system comprising:

a processor of a second network node;

means for causing said processor of said second network node to receive a request from a first network node for access to a first portion of a file, wherein

said first portion of said file is a subset of a region of said file,

said second network node has been granted access to said region of the file, and

said access to said region of said file is controlled by a first range lock;

means for operating on a set of pages in a page cache coupled to said processor of said second network node in response to the request from the first network node, wherein

the set of pages corresponds to the region of the file,

a first page of the set of pages corresponds to the first portion of the file, and

the means for operating causes the first page of the set of pages to be provided to the first network node if the second network node has been granted exclusive access to the first portion of the file;

means for revoking said first range lock to the first portion if the second network node has been granted exclusive access to the first portion of the file; and

means for transmitting to said second network node information causing a second range lock to be associated with the first portion of the file.

10. The system of claim 9 wherein

a second page of the set of pages in the page cache corresponds to a second portion of the region of the file, and

the means for operating does not cause the second page to be provided to the first network node.

11. The system of claim 9 further comprising:

second causing means for causing said processor to flush the first page the set of pages from the page cache to the file if the second network node has exclusive access to the first portion.

12. The system of claim 11 further comprising:

third causing means for causing the first network node to read the first portion from the file.

13. The system of claim 11 further comprising:

third causing means for causing the first portion to be provided to the first network node.

14. A computer-readable storage medium comprising:

receiving instructions to cause a processor of a second network node to receive a request from a first network node for access to a first portion of a file by said first network node, wherein

said first portion of the file is a subset of a region of the file,

said second network node has been granted access to the region of the file, and

said access to said region of the file is controlled by a first range lock;

causing instructions to cause an operation to be performed by said processor of said second network node on a set of pages in a page cache coupled to said processor of said second network node, wherein

the causing instructions are performed in response to the request for access to the first portion of the file by said first network node,

the set of pages corresponds to the region of the file,

a first page of the set of pages corresponds to the first portion of the file, and

the operation comprises causing the first page of the set of pages to be provided to the first network node if the second network node has been granted exclusive access to the first portion of the file;

revoking instructions for revoking said range lock to the first portion if said second network node has been granted exclusive access to said second portion; and

transmitting instructions for transmitting to said second network node information causing a second range lock to be associated with said first portion of said file.

15. The computer-readable storage medium of claim 14 wherein

a second page of the set of pages in the page cache corresponds to a second portion of the region of the file, and

the operation is not performed on the second page.

16. The computer-readable storage medium of claim 14 further comprising:

second causing instructions to cause the first page of the set of pages to be flushed from the page cache to the file if the second network node has been granted exclusive access to the first portion.

17. The computer-readable storage medium of claim 16 further comprising:

third causing instructions to cause the first network node to read the first portion from the file.

18. The computer-readable storage medium of claim 16 further comprising:

third causing instructions to cause the first portion to be provided to the first network node.

19. A system for providing concurrent access to data, said system comprising:

a processor of a second network node;

a receiving module to cause said processor of said second network node to receive a request from a first network node for access to a first portion of a file, wherein

said first portion of said file is a subset of a region of said file,

said second network node has been granted access to the region of the file, and

said access to said region of said file is controlled by a first range lock;

a causing module for operating on a set of pages in a page cache coupled to said processor of the second network node, wherein

the causing module causes the operation to be performed in response to the request for access to a first portion of the file by the first network node, wherein

the set of pages corresponds to the region of the file,

a first page of the set of pages corresponds to the first portion of the file, and

the operation comprises causing the first page of the set of pages to be provided to the first network node if the second network node has been granted exclusive access to the first portion of the file;

a revoking module for revoking said range lock to the first portion if said second network node has been granted exclusive access to said first portion; and

a transmitting module for transmitting to said second network node information causing a second range lock to be associated with said first portion of said file.

20. The system of claim 19 wherein

a second page of the set of pages in the page cache corresponds to a second portion of the region of the file, and

the operation is not performed on the second page.

21. The system of claim 19 further comprising:

a second causing module to cause the processor to flush the first page of the set of pages from the page cache to the file if the second network node has been granted exclusive access to the first portion.

22. The system of claim 21 further comprising:

a third causing module to cause the first network node to read the first portion from the file.

23. The system of claim 21 further comprising:

a third causing module to cause the first portion to be provided to the first network node.