US Patent 9792294 Using byte-range locks to manage multiple concurrent accesses to a file in a distributed filesystem

The disclosed embodiments disclose techniques for using byte-range locks to manage multiple concurrent accesses to a file in a distributed filesystem. Two or more cloud controllers collectively manage distributed filesystem data that is stored in the cloud storage systems; the cloud controllers ensure data consistency for the stored data, and each cloud controller caches portions of the distributed filesystem. During operation, a cloud controller receives from a first client a request to access a portion of the file. The cloud controller contacts the owning cloud controller for the portion of the file to request a byte-range lock for that portion of the file. The owning cloud controller returns a byte-range lock to the requesting cloud controller if no other clients of the distributed filesystem are currently locking the requested portion of the file with conflicting accesses.