The aio_fsync() function shall asynchronously force 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 synchronized
I/O completion state. The function call shall return when the synchronization
request has been initiated or queued to the file or device (even when the data
cannot be synchronized immediately).
If op is O_DSYNC, all currently queued I/O operations shall be completed
as if by a call to fdatasync(); that is, as defined for synchronized
I/O data integrity completion. If op is O_SYNC, all currently queued
I/O operations shall be completed as if by a call to fsync(); that is,
as defined for synchronized 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 synchronized 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 shall be reset to
reflect the success or failure of the operation. If the operation does not
complete successfully, the error status for the operation shall be set to
indicate the error. The aio_sigevent member determines the asynchronous
notification to occur as specified in Signal Generation and Delivery
when all operations have achieved synchronized 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 behavior is undefined.
If the aio_fsync() function fails or aiocbp indicates an error
condition, data is not guaranteed to have been successfully transferred.
The aio_fsync() function shall return the value 0 to the calling process
if the I/O operation is successfully queued; otherwise, the function shall
return the value -1 and set errno to indicate the error.
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 synchronized I/O for
A value of op other than O_DSYNC or O_SYNC was
In the event that any of the queued I/O operations fail, aio_fsync()
shall return the error condition defined for read() and write().
The error is returned in the error status for the asynchronous fsync()
operation, which can be retrieved using aio_error().
The following sections are informative.
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html