Application-defined object logging through a file system journal

A system, comprising:

• a processor;
• and
• a file system to:
• determine during execution of an operation for an application whether a callback function is specified for the operation, wherein the file system is to log events that have not yet been completed in a file system journal;
• invoke, in response to the determination that the callback function is specified for the operation, the callback function;
• receive an object defined by the application that is returned in response to the invocation of the callback function;
• receive, in response to the invocation, a size of the object defined by the application;
• link a copy of the object with a file system transaction associated with the operation in the file system journal;
• and
• atomically commit the file system transaction and a change log record to an event log file, such that both committing the file system transaction and the change log record occur or neither occur, wherein to atomically commit includes:
• determining whether the file system transaction is committed;
• writing, in response to the determination that the file system transaction is committed, a copy of the object from the file system journal to the event log file;
• and
• allowing the application to determine whether the file system transaction is committed by enabling access to the event log file.

A non-transitory machine-readable storage medium comprising instructions, the instructions executable by a processor to:

• determine, by a file system, during execution of an operation for an application whether a callback function is specified for the operation, wherein the file system is to log events that have not yet been committed to a file system journal;
• invoke, by the file system, the callback function, in response to the determination that the callback function is specified for the operation;
• receive, by the file system, an object defined by the application that is returned in response to the invocation of the callback function;
• link, by the file system, a copy of the object with a file system transaction associated with the operation in the file system journal;
• and
• atomically commit the file system transaction and a change log record to an event log file, such that both committing the file system transaction and the change log record occur or neither occur, wherein to atomically commit includes:
• determining, by the file system, whether the file system transaction is committed;
• writing, by the file system, a copy of the object from the file system journal to the event log file, in response to the determination that the file system transaction is committed;
• and
• allowing, by the file system, the application to access the event log file to determine whether the file system transaction is committed during recovery from a failure of a device that includes the file system to determine whether the copy of the object is present in the event log file.