AIO_FSYNC(2)              FreeBSD System Calls Manual             AIO_FSYNC(2)

NAME
     aio_fsync - asynchronous file synchronization (REALTIME)

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <aio.h>

     int
     aio_fsync(int op, struct aiocb *iocb);

DESCRIPTION
     The aio_fsync() system call allows the calling process to move all
     modified data associated with the descriptor iocb->aio_fildes to a
     permanent storage device.  The call returns immediately after the
     synchronization request has been enqueued to the descriptor; the
     synchronization may or may not have completed at the time the call
     returns.

     The op argument can be set to O_SYNC to cause all currently queued I/O
     operations to be completed as if by a call to fsync(2), or O_DSYNC for
     the behavior of fdatasync(2).

     If _POSIX_PRIORITIZED_IO is defined, and the descriptor supports it, then
     the enqueued operation is submitted at a priority equal to that of the
     calling process minus iocb->aio_reqprio.

     The iocb pointer may be subsequently used as an argument to aio_return()
     and aio_error() in order to determine return or error status for the
     enqueued operation while it is in progress.

     If the request could not be enqueued (generally due to invalid
     arguments), the call returns without having enqueued the request.

     The iocb->aio_sigevent structure can be used to request notification of
     the operation's completion as described in aio(4).

RESTRICTIONS
     The Asynchronous I/O Control Block structure pointed to by iocb must
     remain valid until the operation has completed.

     The asynchronous I/O control buffer iocb should be zeroed before the
     aio_fsync() call to avoid passing bogus context information to the
     kernel.

     Modification of the Asynchronous I/O Control Block structure is not
     allowed while the request is queued.

RETURN VALUES
     The aio_fsync() function returns the value 0 if successful; otherwise the
     value -1 is returned and the global variable errno is set to indicate the
     error.

ERRORS
     The aio_fsync() system call will fail if:

     [EAGAIN]           The request was not queued because of system resource
                        limitations.

     [EINVAL]           The asynchronous notification method in
                        iocb->aio_sigevent.sigev_notify is invalid or not
                        supported.

     [EOPNOTSUPP]       Asynchronous file synchronization operations on the
                        file descriptor iocb->aio_fildes are unsafe and unsafe
                        asynchronous I/O operations are disabled.

     [EINVAL]           A value of the op argument is not set to O_SYNC or
                        O_DSYNC.

     The following conditions may be synchronously detected when the
     aio_fsync() system call is made, or asynchronously, at any time
     thereafter.  If they are detected at call time, aio_fsync() returns -1
     and sets errno appropriately; otherwise the aio_return() system call must
     be called, and will return -1, and aio_error() must be called to
     determine the actual value that would have been returned in errno.

     [EBADF]            The iocb->aio_fildes argument is not a valid
                        descriptor.

     [EINVAL]           This implementation does not support synchronized I/O
                        for this file.

     If the request is successfully enqueued, but subsequently cancelled or an
     error occurs, the value returned by the aio_return() system call is per
     the read(2) and write(2) system calls, and the value returned by the
     aio_error() system call is one of the error returns from the read(2) or
     write(2) system calls.

SEE ALSO
     aio_cancel(2), aio_error(2), aio_read(2), aio_return(2), aio_suspend(2),
     aio_waitcomplete(2), aio_write(2), fsync(2), sigevent(3), siginfo(3),
     aio(4)

STANDARDS
     The aio_fsync() system call is expected to conform to the IEEE Std 1003.1
     ("POSIX.1") standard.

HISTORY
     The aio_fsync() system call first appeared in FreeBSD 7.0.  The O_DSYNC
     option appeared in FreeBSD 13.0.

FreeBSD 13.1-RELEASE-p6         January 6, 2021        FreeBSD 13.1-RELEASE-p6