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 de-
       fines 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:

              This data is copied into the data field of the  io_event  struc-
              ture upon I/O completion (see io_getevents(2)).

              This  is  an  internal  field used by the kernel.  Do not modify
              this field after an io_submit() call.

              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)  as  well  as
                     the  description  of O_APPEND in open(2).  The aio_offset
                     field is ignored.  The file offset is not changed.

              RWF_DSYNC (since Linux 4.13)
                     Write operation complete according to requirement of syn-
                     chronized I/O data integrity.  See the description of the
                     flag of the same name in pwritev2(2) as well the descrip-
                     tion of O_DSYNC in open(2).

              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 io_event structure (see io_getevents(2)).

              RWF_SYNC (since Linux 4.13)
                     Write operation complete according to requirement of syn-
                     chronized I/O file integrity.  See the description of the
                     flag of the same name in pwritev2(2) as well the descrip-
                     tion of O_SYNC in open(2).

              This  defines the type of I/O to be performed by the iocb struc-
              ture.  The valid values are  defined  by  the  enum  defined  in

                  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,

              This defines the requests priority.

              The  file  descriptor  on  which the I/O operation is to be per-

              This is the buffer used to transfer data for a read or write op-

              This is the size of the buffer pointed to by aio_buf.

              This is the file offset at which the I/O operation is to be per-

              This is the set of flags associated  with  the  iocb  structure.
              The valid values are:

                     Asynchronous  I/O control must signal the file descriptor
                     mentioned in aio_resfd upon completion.

              IOCB_FLAG_IOPRIO (since Linux 4.18)
                     Interpret the aio_reqprio field as an IOPRIO_VALUE as de-
                     fined by linux/ioprio.h.

              The  file  descriptor to signal in the event of asynchronous I/O

       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

       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, the op-
              eration specified is invalid for  the  file  descriptor  in  the
              iocb, or the value in the aio_reqprio field is invalid.

       ENOSYS io_submit() is not implemented on this architecture.

       EPERM  The aio_reqprio field is set with the class IOPRIO_CLASS_RT, but
              the submitting context does not have the CAP_SYS_ADMIN  capabil-

       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_con-
       text_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 in-
       dicating an error: -1, with errno set to a (positive) value that  indi-
       cates the error.

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

       This  page  is  part of release 5.05 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

Linux                             2019-10-10                      IO_SUBMIT(2)
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