f30a1ae8d5
Allow multiple vector IOs to be started with one system call. aio_readv() and aio_writev() already used these opcodes under the covers. This commit makes them available to user space. Being non-standard extensions, they're only visible if __BSD_VISIBLE is defined, like the functions. Reviewed by: asomers, kib MFC after: 2 weeks Differential Revision: https://reviews.freebsd.org/D31627
238 lines
5.1 KiB
Groff
238 lines
5.1 KiB
Groff
.\" Copyright (c) 2003 Tim J. Robbins
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd August 22, 2021
|
|
.Dt LIO_LISTIO 2
|
|
.Os
|
|
.Sh NAME
|
|
.Nm lio_listio
|
|
.Nd "list directed I/O (REALTIME)"
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In aio.h
|
|
.Ft int
|
|
.Fo lio_listio
|
|
.Fa "int mode"
|
|
.Fa "struct aiocb * const list[]"
|
|
.Fa "int nent"
|
|
.Fa "struct sigevent *sig"
|
|
.Fc
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn lio_listio
|
|
function initiates a list of I/O requests with a single function call.
|
|
The
|
|
.Fa list
|
|
argument is an array of pointers to
|
|
.Vt aiocb
|
|
structures describing each operation to perform,
|
|
with
|
|
.Fa nent
|
|
elements.
|
|
.Dv NULL
|
|
elements are ignored.
|
|
.Pp
|
|
The
|
|
.Va aio_lio_opcode
|
|
field of each
|
|
.Vt aiocb
|
|
specifies the operation to be performed.
|
|
The following operations are supported:
|
|
.Bl -tag -width ".Dv LIO_WRITE"
|
|
.It Dv LIO_READ
|
|
Read data as if by a call to
|
|
.Xr aio_read 2 .
|
|
.It Dv LIO_READV
|
|
Read data as if by a call to
|
|
.Xr aio_readv 2 .
|
|
.It Dv LIO_NOP
|
|
No operation.
|
|
.It Dv LIO_WRITE
|
|
Write data as if by a call to
|
|
.Xr aio_write 2 .
|
|
.It Dv LIO_WRITEV
|
|
Write data as if by a call to
|
|
.Xr aio_writev 2 .
|
|
.El
|
|
.Pp
|
|
If the
|
|
.Fa mode
|
|
argument is
|
|
.Dv LIO_WAIT ,
|
|
.Fn lio_listio
|
|
does not return until all the requested operations have been completed.
|
|
If
|
|
.Fa mode
|
|
is
|
|
.Dv LIO_NOWAIT ,
|
|
.Fa sig
|
|
can be used to request asynchronous notification when all operations have
|
|
completed.
|
|
If
|
|
.Fa sig
|
|
is
|
|
.Dv NULL ,
|
|
no notification is sent.
|
|
.Pp
|
|
For
|
|
.Dv SIGEV_KEVENT
|
|
notifications,
|
|
the posted kevent will contain:
|
|
.Bl -column ".Va filter"
|
|
.It Sy Member Ta Sy Value
|
|
.It Va ident Ta Fa list
|
|
.It Va filter Ta Dv EVFILT_LIO
|
|
.It Va udata Ta
|
|
value stored in
|
|
.Fa sig->sigev_value
|
|
.El
|
|
.Pp
|
|
For
|
|
.Dv SIGEV_SIGNO
|
|
and
|
|
.Dv SIGEV_THREAD_ID
|
|
notifications,
|
|
the information for the queued signal will include
|
|
.Dv SI_ASYNCIO
|
|
in the
|
|
.Va si_code
|
|
field and the value stored in
|
|
.Fa sig->sigev_value
|
|
in the
|
|
.Va si_value
|
|
field.
|
|
.Pp
|
|
For
|
|
.Dv SIGEV_THREAD
|
|
notifications,
|
|
the value stored in
|
|
.Fa sig->sigev_value
|
|
is passed to the
|
|
.Fa sig->sigev_notify_function
|
|
as described in
|
|
.Xr sigevent 3 .
|
|
.Pp
|
|
The order in which the requests are carried out is not specified;
|
|
in particular, there is no guarantee that they will be executed in
|
|
the order 0, 1, ...,
|
|
.Fa nent Ns \-1 .
|
|
.Sh RETURN VALUES
|
|
If
|
|
.Fa mode
|
|
is
|
|
.Dv LIO_WAIT ,
|
|
the
|
|
.Fn lio_listio
|
|
function returns 0 if the operations completed successfully,
|
|
otherwise \-1.
|
|
.Pp
|
|
If
|
|
.Fa mode
|
|
is
|
|
.Dv LIO_NOWAIT ,
|
|
the
|
|
.Fn lio_listio
|
|
function returns 0 if the operations are successfully queued,
|
|
otherwise \-1.
|
|
.Sh ERRORS
|
|
The
|
|
.Fn lio_listio
|
|
function will fail if:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EAGAIN
|
|
There are not enough resources to enqueue the requests.
|
|
.It Bq Er EAGAIN
|
|
The request would cause the system-wide limit
|
|
.Dv {AIO_MAX}
|
|
to be exceeded.
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa mode
|
|
argument is neither
|
|
.Dv LIO_WAIT
|
|
nor
|
|
.Dv LIO_NOWAIT ,
|
|
or
|
|
.Fa nent
|
|
is greater than
|
|
.Dv {AIO_LISTIO_MAX} .
|
|
.It Bq Er EINVAL
|
|
The asynchronous notification method in
|
|
.Fa sig->sigev_notify
|
|
is invalid or not supported.
|
|
.It Bq Er EINTR
|
|
A signal interrupted the system call before it could be completed.
|
|
.It Bq Er EIO
|
|
One or more requests failed.
|
|
.El
|
|
.Pp
|
|
In addition, the
|
|
.Fn lio_listio
|
|
function may fail for any of the reasons listed for
|
|
.Xr aio_read 2
|
|
and
|
|
.Xr aio_write 2 .
|
|
.Pp
|
|
If
|
|
.Fn lio_listio
|
|
succeeds, or fails with an error code of
|
|
.Er EAGAIN , EINTR ,
|
|
or
|
|
.Er EIO ,
|
|
some of the requests may have been initiated.
|
|
The caller should check the error status of each
|
|
.Vt aiocb
|
|
structure individually by calling
|
|
.Xr aio_error 2 .
|
|
.Sh SEE ALSO
|
|
.Xr aio_error 2 ,
|
|
.Xr aio_read 2 ,
|
|
.Xr aio_readv 2 ,
|
|
.Xr aio_write 2 ,
|
|
.Xr aio_writev 2 ,
|
|
.Xr read 2 ,
|
|
.Xr write 2 ,
|
|
.Xr sigevent 3 ,
|
|
.Xr siginfo 3 ,
|
|
.Xr aio 4
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn lio_listio
|
|
function is expected to conform to
|
|
.St -p1003.1-2001 .
|
|
The
|
|
.Dv LIO_READV
|
|
and
|
|
.Dv LIO_WRITEV
|
|
operations are
|
|
.Fx extensions, and should not be used in portable code.
|
|
.Sh HISTORY
|
|
The
|
|
.Fn lio_listio
|
|
system call first appeared in
|
|
.Fx 3.0 .
|