Managing concurrent I/OS in file systems

• US 9,213,717 B1
• Filed: 09/28/2011
• Issued: 12/15/2015
• Est. Priority Date: 09/28/2011
• Status: Active Grant

• Current Assignee: Emc IP Holding Company LLC (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Pawar, Sitaram, Davenport, William, Basov, Ivan
• Primary Examiner(s): Cygiel, Gary W
• Application Number:
  US13/247,753
• Time in Patent Office: 1,539 Days
• Field of Search: 707/704, 707/999.008, 711/150
• US Class Current: 1/1
• CPC Class Codes: G06F 16/1774 Locking methods, e.g. locking methods for file systems allowing shared and concurrent access to files
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database

Abstract

A method is used in managing concurrent I/Os in file systems. A first and second I/O requests are received. The first I/O request is directed to a first portion of a file and the second I/O request is directed to a second portion of the file. A first range lock for the first portion is obtained and a second range lock for the second portion is obtained. The first and second I/O requests are performed concurrently. The second I/O request starts performing I/O on the second portion of the file before the first I/O request finish performing I/O on the first portion of the file.

Claims

1. A method for use in managing concurrent I/Os in file systems, the method comprising:

receiving a first and second I/O requests, wherein the first I/O request is directed to a first portion of a file and the second I/O request is directed to a second portion of the file;

obtaining a first range lock for the first portion and a second range lock for the second portion, wherein the first and second range locks provide access to the first and second portions of the file concurrently;

determining whether the first and second portions of the file overlap;

performing the first and second I/O requests concurrently upon determining that the first and second portions of the file do not overlap, wherein the second I/O request starts performing I/O on the second portion of the file before the first I/O request finishes performing I/O on the first portion of the file; and

writing data associated with the first and second I/O requests to the file organized on a storage system in an order in which the first and second I/O requests are received upon determining that the first and second portions of the file overlap, wherein data associated with the second I/O request for the second portion of the file is written to a buffer in a memory of the storage system upon determining that flushing of the data associated with the first I/O request is in progress for the first portion of the file.

2. The method of claim 1, wherein performing the first and second I/O requests concurrently further comprising:

writing data of the first I/O request to a first memory buffer and writing data of the second I/O request to a second memory buffer;

releasing the first and second range locks;

determining, based on whether the first and second I/O requests are stable write operations, whether to add the first and second memory buffers to a dirty list; and

based on the determination, flushing the first and second memory buffers to the file stored on a storage device.

3. The method of claim 2, further comprising:

receiving a third I/O request, wherein the third I/O request is directed to the first portion of the file;

determining, whether the flushing of the first I/O operation is in progress for the first portion of the file;

based on the determination, creating a copy of the first memory buffer;

modifying the copy based on the third I/O request; and

adding the third I/O request to a dependency list.

4. The method of claim 2, wherein the flushing of the first and second memory buffers further comprising:

obtaining a third range lock for the first portion of the file stored on the storage device and a fourth range lock for the second portion of the file stored on the storage device;

copying contents of the first memory buffer to the first portion of the file stored on the storage device and copying contents of second memory buffer to the second portion of the file stored on the storage device; and

releasing the third and fourth range locks.

5. The method of claim 1, wherein a range lock protects a portion of the file from conflicting I/O operations, wherein a portion of the file is based on a granularity of a size of a data block.

6. The method of claim 1, wherein a range lock is associated with an access mode, wherein the access mode is selected from the group consisting of an exclusive mode and a shared mode.

7. The method of claim 1, wherein the first and second range locks are organized in a dependency list, wherein the dependency list includes a list of granted ranges and a list of waiting ranges.

8. The method of claim 1, further comprising:

determining, whether the first I/O request is a partial block request;

based on the determination, reading contents of the file in a memory buffer, wherein the contents are aligned based on a granularity of a size of a data block; and

modifying data of the memory buffer based on the first I/O request.

9. The method of claim 1, further comprising:

receiving a read I/O request, wherein the read I/O request is directed to a portion of the file;

obtaining a range lock in a shared mode for the portion of the file;

determining, whether data associated with the I/O request is stored in a cache;

based on the determination, reading the data from the cache; and

releasing the range lock.

10. The method of claim 1, wherein a first set of range locks protects a logical portion of the file stored in a memory buffer and a second set of range locks protects a physical portion of the file stored on a storage device.

11. A system for use in managing concurrent I/Os in file systems, the system comprising a processor configured to:

receive a first and second I/O requests, wherein the first I/O request is directed to a first portion of a file and the second I/O request is directed to a second portion of the file;

obtain a first range lock for the first portion and a second range lock for the second portion, wherein the first and second range locks provide access to the first and second portions of the file concurrently;

determine whether the first and second portions of the file overlap

perform the first and second I/O requests concurrently upon determining that the first and second portions of the file do not overlap, wherein the second I/O request starts performing I/O on the second portion of the file before the first I/O request finishes performing I/O on the first portion of the file; and

write data associated with the first and second I/O requests to the file organized on a storage system in an order in which the first and second I/O requests are received upon determining that the first and second portions of the file overlap, wherein data associated with the second I/O request for the second portion of the file is written to a buffer in a memory of the storage system upon determining that flushing of the data associated with the first I/O request is in progress for the first portion of the file.

12. The system of claim 11, wherein performing the first and second I/O requests concurrently further comprising:

write data of the first I/O request to a first memory buffer and writing data of the second I/O request to a second memory buffer;

release the first and second range locks;

determine, based on whether the first and second I/O requests are stable write operations, whether to add the first and second memory buffers to a dirty list; and

flush, based on the determination, the first and second memory buffers to the file stored on a storage device.

13. The system of claim 12, further comprising:

receive a third I/O request, wherein the third I/O request is directed to the first portion of the file;

determine, whether the flushing of the first I/O operation is in progress for the first portion of the file;

create, based on the determination, a copy of the first memory buffer;

modify the copy based on the third I/O request; and

add the third I/O request to a dependency list.

14. The system of claim 12, wherein the flushing of the first and second memory buffers further comprising:

obtain a third range lock for the first portion of the file stored on the storage device and a fourth range lock for the second portion of the file stored on the storage device;

copy contents of the first memory buffer to the first portion of the file stored on the storage device and copying contents of second memory buffer to the second portion of the file stored on the storage device; and

release the third and fourth range locks.

15. The system of claim 11, wherein a range lock protects a portion of the file from conflicting I/O operations, wherein a portion of the file is based on a granularity of a size of a data block.

16. The system of claim 11, wherein a range lock is associated with an access mode, wherein the access mode is selected from the group consisting of an exclusive mode and a shared mode.

17. The system of claim 11, wherein the first and second range locks are organized in a dependency list, wherein the dependency list includes a list of granted ranges and a list of waiting ranges.

18. The system of claim 11, further comprising:

determine, whether the first I/O request is a partial block request;

read, based on the determination, contents of the file in a memory buffer, wherein the contents are aligned based on a granularity of a size of a data block; and

modify data of the memory buffer based on the first I/O request.

19. The system of claim 11, further comprising:

receive a read I/O request, wherein the read I/O request is directed to a portion of the file;

obtain a range lock in a shared mode for the portion of the file;

determine, whether data associated with the I/O request is stored in a cache;

read, based on the determination, the data from the cache; and

release the range lock.

20. The system of claim 11, wherein a first set of range locks protects a logical portion of the file stored in a memory buffer and a second set of range locks protects a physical portion of the file stored on a storage device.