aio_fsync - asynchronous file synchronisation (REALTIME)
#include <aio.h> int aio_fsync(int op, struct aiocb *aiocbp);
The aio_fsync() function asynchronously forces all I/O operations associated with the file indicated by the file descriptor aio_fildes member of the aiocb structure referenced by the aiocbp argument and queued at the time of the call to aio_fsync() to the synchronised I/O completion state. The function call returns when the synchronisation request has been initiated or queued to the file or device (even when the data cannot be synchronised immediately).
If op is O_DSYNC, all currently queued I/O operations are completed as if by a call to fdatasync(); that is, as defined for synchronised I/O data integrity completion. If op is O_SYNC, all currently queued I/O operations are completed as if by a call to fsync(); that is, as defined for synchronised I/O file integrity completion. If the aio_fsync() function fails, or if the operation queued by aio_fsync() fails, then, as for fsync() and fdatasync(), outstanding I/O operations are not guaranteed to have been completed.
If aio_fsync() succeeds, then it is only the I/O that was queued at the time of the call to aio_fsync() that is guaranteed to be forced to the relevant completion state. The completion of subsequent I/O on the file descriptor is not guaranteed to be completed in a synchronised fashion.
The aiocbp argument refers to an asynchronous I/O control block. The aiocbp value may be used as an argument to aio_error() and aio_return() in order to determine the error status and return status, respectively, of the asynchronous operation while it is proceeding. When the request is queued, the error status for the operation is EINPROGRESS. When all data has been successfully transferred, the error status will be reset to reflect the success or failure of the operation. If the operation does not complete successfully, the error status for the operation will be set to indicate the error. The aio_sigevent member determines the asynchronous notification to occur as specified in
Signal Generation and Deliverywhen all operations have achieved synchronised I/O completion. All other members of the structure referenced by aiocbp are ignored. If the control block referenced by aiocbp becomes an illegal address prior to asynchronous I/O completion, then the behaviour is undefined.
If the aio_fsync() function fails or the aiocbp indicates an error condition, data is not guaranteed to have been successfully transferred.
If aiocbp is NULL, then no status is returned in aiocbp, and no signal is generated upon completion of the operation.
The aio_fsync() function returns the value 0 to the calling process if the I/O operation is successfully queued; otherwise, the function returns the value -1 and sets errno to indicate the error.
The aio_fsync() function will fail if:
- The requested asynchronous operation was not queued due to temporary resource limitations.
- The aio_fildes member of the aiocb structure referenced by the aiocbp argument is not a valid file descriptor open for writing.
- This implementation does not support synchronised I/O for this file.
- A value of op other than O_DSYNC or O_SYNC was specified.
- The aio_fsync() function is not supported by this implementation.
In the event that any of the queued I/O operations fail, aio_fsync() returns the error condition defined for read() and write(). The error will be returned in the error status for the asynchronous fsync() operation, which can be retrieved using aio_error().
fcntl(), fdatasync(), fsync(), open(), read(), write().
Derived from the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995)