NAME

       io_uring_prep_files_update - prepare a registered file update request

SYNOPSIS

       #include <liburing.h>

       void io_uring_prep_files_update(struct io_uring_sqe *sqe,
                                       int *fds,
                                       unsigned nr_fds,
                                       int offset);

DESCRIPTION

       The  io_uring_prep_files_update(3)  function  prepares  a  request  for  updating  a number of previously
       registered file descriptors. The submission queue entry sqe is setup to use  the  file  descriptor  array
       pointed  to  by fds and of nr_fds in length to update that amount of previously registered files starting
       at offset offset.

       Once a previously registered file is updated with a new one, the  existing  entry  is  updated  and  then
       removed from the table. This operation is equivalent to first unregistering that entry and then inserting
       a new one, just bundled into one combined operation.

       If offset is specified as IORING_FILE_INDEX_ALLOC, io_uring will allocate free direct descriptors instead
       of  having  the application to pass, and store allocated direct descriptors into fds array, cqe->res will
       return the number of direct descriptors allocated.

RETURN VALUE

       None

ERRORS

       These are the errors that are reported in the CQE res field. On success, res will contain the  number  of
       successfully updated file descriptors. On error, the following errors can occur.

       -ENOMEM
              The kernel was unable to allocate memory for the request.

       -EINVAL
              One of the fields set in the SQE was invalid.

       -EFAULT
              The kernel was unable to copy in the memory pointed to by fds.

       -EBADF On  of  the descriptors located in fds didn't refer to a valid file descriptor, or one of the file
              descriptors in the array referred to an io_uring instance.

       -EOVERFLOW
              The product of offset and nr_fds exceed the valid amount or overflowed.

NOTES

       As with any request that passes in data in a struct, that data must remain valid until  the  request  has
       been  successfully  submitted.  It  need  not  remain  valid  until  completion.  Once a request has been
       submitted, the in-kernel state is stable. Very early kernels (5.4  and  earlier)  required  state  to  be
       stable  until  the  completion  occurred.  Applications  can  test  for  this  behavior by inspecting the
       IORING_FEAT_SUBMIT_STABLE flag passed back from io_uring_queue_init_params(3).

SEE ALSO

       io_uring_get_sqe(3), io_uring_submit(3), io_uring_register(2)

liburing-2.2                                     March 13, 2022                    io_uring_prep_files_update(3)