.\" Copyright (C) 2003 Free Software Foundation, Inc.
+.\" and Copyright (C) 2017 Goldwyn Rodrigues <rgoldwyn@suse.de>
+.\"
+.\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
.\" This file is distributed according to the GNU General Public License.
-.\" See the file COPYING in the top level source directory for details.
+.\" %%%LICENSE_END
.\"
-.TH IO_SUBMIT 2 2008-06-18 "Linux" "Linux Programmer's Manual"
+.TH IO_SUBMIT 2 2020-04-11 "Linux" "Linux Programmer's Manual"
.SH NAME
io_submit \- submit asynchronous I/O blocks for processing
-.SH "SYNOPSIS"
+.SH SYNOPSIS
.nf
-.B #include <libaio.h>
-.\" #include <linux/aio.h>
-.sp
+.BR "#include <linux/aio_abi.h>" " /* Defines needed types */"
+.PP
.BI "int io_submit(aio_context_t " ctx_id ", long " nr \
", struct iocb **" iocbpp );
-.sp
-Link with \fI\-laio\fP.
.fi
-.SH "DESCRIPTION"
.PP
+.IR Note :
+There is no glibc wrapper for this system call; see NOTES.
+.SH DESCRIPTION
+.PP
+The
.BR io_submit ()
+system call
queues \fInr\fP I/O request blocks for processing in
the AIO context \fIctx_id\fP.
-\fIiocbpp\fP should be an array of \fInr\fP AIO control blocks,
+The
+.I iocbpp
+argument should be an array of \fInr\fP AIO control blocks,
which will be submitted to context \fIctx_id\fP.
-.SH "RETURN VALUE"
+.PP
+The
+.I iocb
+(I/O control block) structure defined in
+.IR linux/aio_abi.h
+defines the parameters that control the I/O operation.
+.PP
+.in +4n
+.EX
+#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;
+};
+.EE
+.in
+.PP
+The fields of this structure are as follows:
+.TP
+.I aio_data
+This data is copied into the
+.I data
+field of the
+.I io_event
+structure upon I/O completion (see
+.BR io_getevents (2)).
+.TP
+.I aio_key
+This is an internal field used by the kernel.
+Do not modify this field after an
+.BR io_submit ()
+call.
+.TP
+.I aio_rw_flags
+This defines the R/W flags passed with structure.
+The valid values are:
+.RS
+.TP
+.BR RWF_APPEND " (since Linux 4.16)"
+.\" commit e1fc742e14e01d84d9693c4aca4ab23da65811fb
+Append data to the end of the file.
+See the description of the flag of the same name in
+.BR pwritev2 (2)
+as well as the description of
+.B O_APPEND
+in
+.BR open (2).
+The
+.I aio_offset
+field is ignored.
+The file offset is not changed.
+.TP
+.BR 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
+.BR pwritev2 (2)
+as well the description of
+.B O_DSYNC
+in
+.BR open (2).
+.TP
+.BR RWF_HIPRI " (since Linux 4.13)"
+High priority request, poll if possible
+.TP
+.BR 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
+.B \-EAGAIN
+in the
+.I res
+field of the
+.I io_event
+structure (see
+.BR io_getevents (2)).
+.TP
+.BR 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
+.BR pwritev2 (2)
+as well the description of
+.B O_SYNC
+in
+.BR open (2).
+.RE
+.TP
+.I aio_lio_opcode
+This defines the type of I/O to be performed by the
+.I iocb
+structure.
+The
+valid values are defined by the enum defined in
+.IR linux/aio_abi.h :
+.IP
+.in +4
+.EX
+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,
+};
+.EE
+.in
+.TP
+.I aio_reqprio
+This defines the requests priority.
+.TP
+.I aio_fildes
+The file descriptor on which the I/O operation is to be performed.
+.TP
+.I aio_buf
+This is the buffer used to transfer data for a read or write operation.
+.TP
+.I aio_nbytes
+This is the size of the buffer pointed to by
+.IR aio_buf .
+.TP
+.I aio_offset
+This is the file offset at which the I/O operation is to be performed.
+.TP
+.I aio_flags
+This is the set of flags associated with the
+.I iocb
+structure.
+The valid values are:
+.RS
+.TP
+.BR IOCB_FLAG_RESFD
+Asynchronous I/O control must signal the file
+descriptor mentioned in
+.I aio_resfd
+upon completion.
+.TP
+.BR IOCB_FLAG_IOPRIO " (since Linux 4.18)"
+.\" commit d9a08a9e616beeccdbd0e7262b7225ffdfa49e92
+Interpret the
+.I aio_reqprio
+field as an
+.B IOPRIO_VALUE
+as defined by
+.IR linux/ioprio.h .
+.RE
+.TP
+.I aio_resfd
+The file descriptor to signal in the event of asynchronous I/O completion.
+.SH RETURN VALUE
On success,
.BR io_submit ()
returns the number of \fIiocb\fPs submitted (which may be
-0 if \fInr\fP is zero).
+less than \fInr\fP, or 0 if \fInr\fP is zero).
For the failure return, see NOTES.
-.SH "ERRORS"
+.SH ERRORS
.TP
.B EAGAIN
Insufficient resources are available to queue any \fIiocb\fPs.
One of the data structures points to invalid data.
.TP
.B EINVAL
-The \fIaio_context\fP specified by \fIctx_id\fP is invalid.
+The AIO context specified by \fIctx_id\fP is invalid.
\fInr\fP is less than 0.
-The \fIiocb\fP at *iocbpp[0] is not properly initialized,
-or the operation specified is invalid for the file descriptor
-in the \fIiocb\fP.
+The \fIiocb\fP at
+.I *iocbpp[0]
+is not properly initialized, the operation specified is invalid for the file
+descriptor in the \fIiocb\fP, or the value in the
+.I aio_reqprio
+field is invalid.
.TP
.B ENOSYS
.BR io_submit ()
is not implemented on this architecture.
-.SH "VERSIONS"
+.TP
+.B EPERM
+The
+.I aio_reqprio
+field is set with the class
+.BR IOPRIO_CLASS_RT ,
+but the submitting context does not have the
+.B CAP_SYS_ADMIN
+capability.
+.SH VERSIONS
.PP
-The asynchronous I/O system calls first appeared in Linux 2.5, August 2002.
-.SH "CONFORMING TO"
+The asynchronous I/O system calls first appeared in Linux 2.5.
+.SH CONFORMING TO
.PP
.BR io_submit ()
is Linux-specific and should not be used in
programs that are intended to be portable.
.SH NOTES
Glibc does not provide a wrapper function for this system call.
-
-The wrapper provided in
-.I libaio
-for
+You could invoke it using
+.BR syscall (2).
+But instead, you probably want to use the
.BR io_submit ()
-does not follow the usual C library conventions for indicating error:
+wrapper function provided by
+.\" http://git.fedorahosted.org/git/?p=libaio.git
+.IR libaio .
+.PP
+Note that the
+.I libaio
+wrapper function uses a different type
+.RI ( io_context_t )
+.\" But glibc is confused, since <libaio.h> uses 'io_context_t' to declare
+.\" the system call.
+for the
+.I ctx_id
+argument.
+Note also that the
+.I 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
indicating an error: \-1, with
.I errno
set to a (positive) value that indicates the error.
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR io_cancel (2),
.BR io_destroy (2),
.BR io_getevents (2),
.BR io_setup (2),
.BR aio (7)
-.\" .SH "NOTES"
-.\" .PP
-.\" The asynchronous I/O system calls were written by Benjamin LaHaise.
.\" .SH AUTHOR
.\" Kent Yoder.
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