NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

IO_SUBMIT(2)              Linux Programmer's Manual             IO_SUBMIT(2)

NAME         top

       io_submit - submit asynchronous I/O blocks for processing

SYNOPSIS         top

       #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.

DESCRIPTION         top

       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.

RETURN VALUE         top

       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.

ERRORS         top

       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.

VERSIONS         top

       The asynchronous I/O system calls first appeared in Linux 2.5.

CONFORMING TO         top

       io_submit() is Linux-specific and should not be used in programs that
       are intended to be portable.

NOTES         top

       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.

SEE ALSO         top

       io_cancel(2), io_destroy(2), io_getevents(2), io_setup(2), aio(7)

COLOPHON         top

       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)