.\"/* sys_io_submit:
.\" *      Queue the nr iocbs pointed to by iocbpp for processing.  Returns
.\" *      the number of iocbs queued.  May return -EINVAL if the aio_context
.\" *      specified by ctx is invalid, if nr is < 0, if the iocb at
.\" *      *iocbpp[0] is not properly initialized, if the operation specified
.\" *      is invalid for the file descriptor in the iocb.  May fail with
.\" *      -EFAULT if any of the data structures point to invalid data.  May
.\" *      fail with -EBADF if the file descriptor specified in the first
.\" *      iocb is invalid.  May fail with -EAGAIN if insufficient resources
.\" *      are available to queue any iocbs.  Will return 0 if nr is 0.  Will
.\" *      fail with -ENOSYS if not implemented.
.\" */
.TH io_submit 3 2019-07-23 "Linux" "Linux AIO"
.SH NAME
io_submit \- Submit io requests
.SH SYNOPSIS
.nf
.B #include <errno.h>
.br
.sp
.B #include <libaio.h>
.br
.sp
.BI "int io_submit(io_context_t " ctx ", long " nr ", struct iocb *" iocbs "[]);"
.sp
struct iocb {
	void		*data;
	unsigned	key;
	short		aio_lio_opcode;
	short		aio_reqprio;
	int		aio_fildes;
};
.fi
.SH DESCRIPTION
.BR io_submit ()
submits
.I nr
iocbs for processing for a given io context ctx.

The 
.BR io_submit ()
function can be used to enqueue an arbitrary
number of read and write requests at one time.  The requests can all be
meant for the same file, all for different files or every solution in
between.

.BR io_submit ()
gets the 
.I nr
requests from the array pointed to by
.IR "iocbs" .
The operation to be performed is determined by the
.IR "aio_lio_opcode"
member in each element of 
.IR "iocbs" .
If this field is
.B "IO_CMD_PREAD"
a read operation is enqueued, similar to a call of
.IR "io_prep_pread"
for this element of the array (except that the way
the termination is signalled is different, as we will see below).  If
the 
.IR "aio_lio_opcode"
member is 
.B "IO_CMD_PWRITE"
a write operation
is enqueued.  Otherwise the 
.IR "aio_lio_opcode"
must be 
.B "IO_CMD_NOP"
in which case this element of 
.IR "iocbs"
is simply ignored.  This
``operation'' is useful in situations where one has a fixed array of
.B struct iocb
elements from which only a few need to be handled at
a time.  Another situation is where the 
.BR io_submit (3)
call was
canceled before all requests are processed  and the remaining requests have to be reissued.

The other members of each element of the array pointed to by
.IR "iocbs"
must have values suitable for the operation as described in
the documentation for 
.BR io_prep_pread (3)
and 
.BR io_prep_pwrite (3)
above.

The function returns immediately after
having enqueued all the requests.  
On success,
.BR io_submit ()
returns the number of iocbs submitted successfully.  Otherwise, -error is return, where 
error is one of the Exxx values defined in the Errors section.
.PP
If an error is detected, then the behavior is undefined.
.PP
Simultaneous asynchronous operations using the same iocb produce
undefined results.
.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
.I iocb
contains a file descriptor that does not exist.
.TP
.B EINVAL
The file specified in the
.I iocb
does not support the given io operation.
.SH "SEE ALSO"
.BR io (3),
.BR io_cancel (3),
.BR io_fsync (3),
.BR io_getevents (3),
.BR io_prep_fsync (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 errno (3).