Using byte-range locks to manage multiple concurrent accesses to a file in a distributed filesystem

A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for using byte-range locks to manage multiple concurrent accesses to a file in a distributed filesystem, the method comprising:

• collectivity managing the data of the distributed filesystem using two or more cloud controllers, wherein collectively managing the data comprises storing the data for the distributed filesystem in one or more cloud storage systems, wherein the cloud controllers cache and ensure data consistency for data stored in the cloud storage system;
• receiving at a first cloud controller a request from a first client to access a portion of the file, wherein the request requests exclusive write access to a first portion of the file;
• contacting the owning cloud controller for the portion of the file to request a byte-range lock for the portion of the file, wherein multiple other distributed clients are accessing a second portion of the file that is distinct from the first portion via byte-range locks with shared read permissions, wherein contacting the owning cloud controller further comprises determining a checksum for the byte range in the current version of the file on the first cloud controller and sending the checksum to the owning cloud controller;
• and
• receiving the byte-range lock at the first cloud controller if no other clients of the distributed filesystem are currently locking the portion of the file with conflicting accesses;
• wherein one or more clients that are associated with other cloud controllers are currently accessing portions of the file using granted byte-range locks;
• wherein the owning cloud controller determines that the requested exclusive write access for the first portion does not conflict with the other currently granted byte-range locks for the file and grants the requested byte-range lock;
• wherein byte-range locks for files facilitate fine-granularity file access and sharing that enables concurrent access by multiple clients in a distributed environment;
• wherein the owning cloud controller compares the checksum from the first cloud controller to a second checksum for the byte range in the version of the file on the owning cloud controller;
• and
• wherein if the checksums differ the owning cloud controller sends the updated file contents of the requested byte range from its local version of the file to the first cloud controller when sending a byte-range lock acknowledgement.

A cloud controller that uses a byte-range locks to access a file in a distributed filesystem, comprising:

• a processor;
• a storage mechanism that stores metadata for the distributed filesystem;
• and
• a storage management mechanism;
• wherein two or more cloud controllers collectively manage the data of the distributed filesystem;
• wherein the cloud controller is configured to receive a request from a client to access a portion of the file, wherein the request requests exclusive write access to a first portion of the file;
• wherein the storage management mechanism is configured to contact the owning cloud controller for the portion of the file to request a byte-range lock for the portion of the file, wherein multiple other distributed clients are accessing a second portion of the file that is distinct from the first portion via byte-range locks with shared read permissions, wherein contacting the owning cloud controller further comprises determining a checksum for the byte range in the current version of the file on the cloud controller and sending the checksum to the owning cloud controller;
• and
• wherein if no other clients of the distributed filesystem are currently locking the portion of the file with conflicting accesses the storage management mechanism receives the byte-range lock from the owning cloud controller;
• wherein one or more clients that are associated with other cloud controllers are currently accessing portions of the file using granted byte-range locks;
• wherein the owning cloud controller determines that the requested exclusive write access for the first portion does not conflict with the other currently granted byte-range locks for the file and grants the requested byte-range lock;
• wherein byte-range locks for files facilitate fine-granularity file access and sharing that enables concurrent access by multiple clients in a distributed environment;
• wherein the owning cloud controller compares the checksum from the cloud controller to a second checksum for the byte range in the version of the file on the owning cloud controller;
• and
• wherein if the checksums differ the owning cloud controller sends the updated file contents of the requested byte range from its local version of the file to the cloud controller when sending a byte-range lock acknowledgement.