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NAME

       io_submit - submit asynchronous I/O blocks for processing

SYNOPSIS

       #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

       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_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 4.7)
                     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_HIPRI (since Linux 4.6)
                     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 4.7)
                     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).

       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 performed.

       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 asynchronous 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

       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

       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

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

CONFORMING TO

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

NOTES

       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

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

COLOPHON

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