io_submit(2) - Linux manual page (original) (raw)
iosubmit(2) System Calls Manual iosubmit(2)
NAME top
io_submit - submit asynchronous I/O blocks for processingLIBRARY top
Standard C library (_libc_, _-lc_)
Alternatively, Asynchronous I/O library (_libaio_, _-laio_); see
VERSIONS.SYNOPSIS top
**#include <linux/aio_abi.h>** /* Defines needed types */
**int io_submit(aio_context_t** _ctxid_**, long** _nr_**, struct iocb** _iocbpp_**);**
_Note_: There is no glibc wrapper for this system call; see
VERSIONS.DESCRIPTION top
_Note_: this page describes the raw Linux system call interface.
The wrapper function provided by _libaio_ uses a different type for
the _ctxid_ argument. See VERSIONS.
The **io_submit**() system call queues _nr_ I/O request blocks for
processing in the AIO context _ctxid_. The _iocbpp_ argument should
be an array of _nr_ AIO control blocks, which will be submitted to
context _ctxid_.
The _iocb_ (I/O control block) structure defined in _linux/aioabi.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:
_aiodata_
This data is copied into the _data_ field of the _ioevent_
structure upon I/O completion (see [io_getevents(2)](../man2/io%5Fgetevents.2.html)).
_aiokey_
This is an internal field used by the kernel. Do not
modify this field after an **io_submit**() call.
_aiorwflags_
This defines the R/W flags passed with structure. The
valid values are:
**RWF_APPEND** (since Linux 4.16)
Append data to the end of the file. See the
description of the flag of the same name in
[pwritev2(2)](../man2/pwritev2.2.html) as well as the description of **O_APPEND**
in [open(2)](../man2/open.2.html). The _aiooffset_ field is ignored. The
file offset is not changed.
**RWF_DSYNC** (since Linux 4.13)
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)](../man2/pwritev2.2.html) as well the description of **O_DSYNC** in
[open(2)](../man2/open.2.html).
**RWF_HIPRI** (since Linux 4.13)
High priority request, poll if possible
**RWF_NOWAIT** (since Linux 4.14)
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 _ioevent_
structure (see [io_getevents(2)](../man2/io%5Fgetevents.2.html)).
**RWF_SYNC** (since Linux 4.13)
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)](../man2/pwritev2.2.html) as well the description of **O_SYNC** in
[open(2)](../man2/open.2.html).
**RWF_NOAPPEND** (since Linux 6.9)
Do not honor **O_APPEND open**(2) flag. See the
description of **RWF_NOAPPEND** in [pwritev2(2)](../man2/pwritev2.2.html).
**RWF_ATOMIC** (since Linux 6.11)
Write a block of data such that a write will never
be torn from power fail or similar. See the
description of **RWF_ATOMIC** in [pwritev2(2)](../man2/pwritev2.2.html). For usage
with **IOCB_CMD_PWRITEV**, the upper vector limit is
_stxatomicwritesegmentsmax._ See
**STATX_WRITE_ATOMIC** and _stxatomicwritesegmentsmax_
description in [statx(2)](../man2/statx.2.html).
_aiolioopcode_
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/aioabi.h_:
enum {
IOCB_CMD_PREAD = 0,
IOCB_CMD_PWRITE = 1,
IOCB_CMD_FSYNC = 2,
IOCB_CMD_FDSYNC = 3,
IOCB_CMD_POLL = 5,
IOCB_CMD_NOOP = 6,
IOCB_CMD_PREADV = 7,
IOCB_CMD_PWRITEV = 8,
};
_aioreqprio_
This defines the requests priority.
_aiofildes_
The file descriptor on which the I/O operation is to be
performed.
_aiobuf_
This is the buffer used to transfer data for a read or
write operation.
_aionbytes_
This is the size of the buffer pointed to by _aiobuf_.
_aiooffset_
This is the file offset at which the I/O operation is to be
performed.
_aioflags_
This is the set of flags associated with the _iocb_
structure. The valid values are:
**IOCB_FLAG_RESFD**
Asynchronous I/O control must signal the file
descriptor mentioned in _aioresfd_ upon completion.
**IOCB_FLAG_IOPRIO** (since Linux 4.18)
Interpret the _aioreqprio_ field as an **IOPRIO_VALUE**
as defined by _linux/ioprio.h_.
_aioresfd_
The file descriptor to signal in the event of asynchronous
I/O completion.RETURN VALUE top
On success, **io_submit**() returns the number of _iocb_s submitted
(which may be less than _nr_, or 0 if _nr_ is zero). For the failure
return, see VERSIONS.ERRORS top
**EAGAIN** Insufficient resources are available to queue any _iocb_s.
**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 _ctxid_ is invalid. _nr_ is less
than 0. The _iocb_ at _*iocbpp[0]_ is not properly
initialized, the operation specified is invalid for the
file descriptor in the _iocb_, or the value in the
_aioreqprio_ field is invalid.
**ENOSYS io_submit**() is not implemented on this architecture.
**EPERM** The _aioreqprio_ field is set with the class
**IOPRIO_CLASS_RT**, but the submitting context does not have
the **CAP_SYS_ADMIN** capability.VERSIONS top
glibc does not provide a wrapper for this system call. You could
invoke it using [syscall(2)](../man2/syscall.2.html). 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
(_iocontextt_) for the _ctxid_ 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)](../man2/syscall.2.html), then the return value follows the
usual conventions for indicating an error: -1, with _[errno](../man3/errno.3.html)_ set to a
(positive) value that indicates the error.STANDARDS top
Linux.HISTORY top
Linux 2.5.SEE ALSO top
[io_cancel(2)](../man2/io%5Fcancel.2.html), [io_destroy(2)](../man2/io%5Fdestroy.2.html), [io_getevents(2)](../man2/io%5Fgetevents.2.html), [io_setup(2)](../man2/io%5Fsetup.2.html), [aio(7)](../man7/aio.7.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2025-01-04 iosubmit(2)
Pages that refer to this page:fcntl(2), io_cancel(2), io_destroy(2), io_getevents(2), io_setup(2), syscalls(2), systemd.exec(5), aio(7)