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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON |
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IO_SUBMIT(2) Linux Programmer's Manual IO_SUBMIT(2)
io_submit - submit asynchronous I/O blocks for processing
#include <linux/aio_abi.h> /* Defines needed types */
int io_submit(aio_context_t ctx_id, long nr, struct iocb **iocbpp);
Note: There is no glibc wrapper for this system call; see NOTES.
The io_submit() system call queues nr I/O request blocks for
processing in the AIO context ctx_id. The iocbpp argument should be
an array of nr AIO control blocks, which will be submitted to context
ctx_id.
The iocb (I/O control block) structure defined in linux/aio_abi.h
defines the parameters that control the I/O operation.
#include <linux/aio_abi.h>
struct iocb {
__u64 aio_data;
__u32 PADDED(aio_key, aio_rw_flags);
__u16 aio_lio_opcode;
__s16 aio_reqprio;
__u32 aio_fildes;
__u64 aio_buf;
__u64 aio_nbytes;
__s64 aio_offset;
__u64 aio_reserved2;
__u32 aio_flags;
__u32 aio_resfd;
};
The fields of this structure are as follows:
aio_data
This is an internal field used by the kernel. Do not modify
this field after an io_submit(2) call.
aio_key
This is an internal field used by the kernel. Do not modify
this field after an io_submit(2) call.
aio_rw_flags
This defines the R/W flags passed with structure. The valid
values are:
RWF_HIPRI
High priority request, poll if possible
RWF_DSYNC
Write operation complete according to requirement of
synchronized I/O data integrity. See the description
of the flag of the same name in pwritev2(2) as well the
description of O_DSYNC in open(2).
RWF_SYNC
Write operation complete according to requirement of
synchronized I/O file integrity. See the description
of the flag of the same name in pwritev2(2) as well the
description of O_SYNC in open(2).
RWF_NOWAIT
Don't wait if the I/O will block for operations such as
file block allocations, dirty page flush, mutex locks,
or a congested block device inside the kernel. If any
of these conditions are met, the control block is
returned immediately with a return value of -EAGAIN in
the res field of the io_event structure (see
io_getevents(2)).
aio_lio_opcode
This defines the type of I/O to be performed by the iocb
structure. The valid values are defined by the enum defined
in linux/aio_abi.h:
enum {
IOCB_CMD_PREAD = 0,
IOCB_CMD_PWRITE = 1,
IOCB_CMD_FSYNC = 2,
IOCB_CMD_FDSYNC = 3,
IOCB_CMD_NOOP = 6,
IOCB_CMD_PREADV = 7,
IOCB_CMD_PWRITEV = 8,
};
aio_reqprio
This defines the requests priority.
aio_filedes
The file descriptor on which the I/O operation is to be per‐
formed.
aio_buf
This is the buffer used to transfer data for a read or write
operation.
aio_nbytes
This is the size of the buffer pointed to by aio_buf.
aio_offset
This is the file offset at which the I/O operation is to be
performed.
aio_flags
This is the flag to be passed iocb structure. The only valid
value is IOCB_FLAG_RESFD, which indicates that the asynchro‐
nous I/O control must signal the file descriptor mentioned in
aio_resfd upon completion.
aio_resfd
The file descriptor to signal in the event of asynchronous I/O
completion.
On success, io_submit() returns the number of iocbs submitted (which
may be less than nr, or 0 if nr is zero). For the failure return,
see NOTES.
EAGAIN Insufficient resources are available to queue any iocbs.
EBADF The file descriptor specified in the first iocb is invalid.
EFAULT One of the data structures points to invalid data.
EINVAL The AIO context specified by ctx_id is invalid. nr is less
than 0. The iocb at *iocbpp[0] is not properly initialized,
or the operation specified is invalid for the file descriptor
in the iocb.
ENOSYS io_submit() is not implemented on this architecture.
The asynchronous I/O system calls first appeared in Linux 2.5.
io_submit() is Linux-specific and should not be used in programs that
are intended to be portable.
Glibc does not provide a wrapper function for this system call. You
could invoke it using syscall(2). But instead, you probably want to
use the io_submit() wrapper function provided by libaio.
Note that the libaio wrapper function uses a different type
(io_context_t) for the ctx_id argument. Note also that the libaio
wrapper does not follow the usual C library conventions for
indicating errors: on error it returns a negated error number (the
negative of one of the values listed in ERRORS). If the system call
is invoked via syscall(2), then the return value follows the usual
conventions for indicating an error: -1, with errno set to a
(positive) value that indicates the error.
io_cancel(2), io_destroy(2), io_getevents(2), io_setup(2), aio(7)
This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2017-09-15 IO_SUBMIT(2)
Pages that refer to this page: fcntl(2), io_cancel(2), io_destroy(2), io_getevents(2), io_setup(2), io_submit(2), syscalls(2), aio(7)
Copyright and license for this manual page
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