.\" static inline int io_fsync(io_context_t ctx, struct iocb *iocb, io_callback_t cb, int fd)
.\" {
.\" 	io_prep_fsync(iocb, fd);
.\" 	io_set_callback(iocb, cb);
.\" 	return io_submit(ctx, 1, &iocb);
.\" }
.TH io_fsync 3 2017-12-10 "Linux" "Linux AIO"
.SH NAME
io_fsync \- Synchronize a file's complete in-core state with that on disk
.SH SYNOPSIS
.nf
.B #include <errno.h>
.sp
.br
.B #include <libaio.h>
.sp
.br
.BI "int io_fsync(io_context_t " ctx ", struct iocb *" iocb ", io_callback_t " cb ", int " fd ");"
.sp
struct iocb {
	void		*data;
	unsigned	key;
	short		aio_lio_opcode;
	short		aio_reqprio;
	int		aio_fildes;
};
.sp
typedef void (*io_callback_t)(io_context_t ctx, struct iocb *iocb, long res, long res2);
.sp
.fi
.SH DESCRIPTION
When dealing with asynchronous operations it is sometimes necessary to
get into a consistent state.  This would mean for AIO that one wants to
know whether a certain request or a group of request were processed.
This could be done by waiting for the notification sent by the system
after the operation terminated, but this sometimes would mean wasting
resources (mainly computation time). 
.PP
Calling this function forces all I/O operations operating queued at the
time of the function call operating on the file descriptor
.IR "iocb->io_fildes"
into the synchronized I/O completion state.  The
.BR io_fsync ()
function returns
immediately but the notification through the method described in
.IR "io_callback"
will happen only after all requests for this
file descriptor have terminated and the file is synchronized.  This also
means that requests for this very same file descriptor which are queued
after the synchronization request are not affected.
.SH "RETURN VALUES"
Returns
.BR 0 ,
otherwise returns
.IR errno .
.SH ERRORS
.TP
.B EFAULT
.I iocbs
referenced data outside of the program's accessible address space.
.TP
.B EINVAL
.I ctx
refers to an uninitialized aio context, the iocb pointed to by
.I iocbs
contains an improperly initialized iocb, 
.TP
.B EBADF
The iocb contains a file descriptor that does not exist.
.TP
.B EINVAL
The file specified in the iocb does not support the given io operation.
.SH "SEE ALSO"
.BR io (3),
.BR io_cancel (3),
.BR io_getevents (3),
.BR io_prep_pread (3),
.BR io_prep_pwrite (3),
.BR io_queue_init (3),
.BR io_queue_release (3),
.BR io_queue_run (3),
.BR io_queue_wait (3),
.BR io_set_callback (3),
.BR io_submit (3),
.BR errno (3).