io_uring_prep_readv2(3) — Linux manual page


io_uring_prep_readv2(3)      liburing Manual     io_uring_prep_readv2(3)

NAME         top

       io_uring_prep_readv2 - prepare vector I/O read request with flags

SYNOPSIS         top

       #include <sys/uio.h>
       #include <liburing.h>

       void io_uring_prep_readv2(struct io_uring_sqe *sqe,
                                 int fd,
                                 const struct iovec *iovecs,
                                 unsigned nr_vecs,
                                 __u64 offset,
                                 int flags);

DESCRIPTION         top

       The io_uring_prep_readv2(3) prepares a vectored IO read request.
       The submission queue entry sqe is setup to use the file
       descriptor fd to start reading nr_vecs into the iovecs array at
       the specified offset.  The behavior of the function can be
       controlled with the flags parameter.

       Supported values for flags are:

              High priority request, poll if possible

              per-IO O_DSYNC

              per-IO O_SYNC

              per-IO, return -EAGAIN if operation would block

              per-IO O_APPEND

       On files that support seeking, if the offset is set to -1, the
       read operation commences at the file offset, and the file offset
       is incremented by the number of bytes read. See read(2) for more
       details. Note that for an async API, reading and updating the
       current file offset may result in unpredictable behavior, unless
       access to the file is serialized. It is not encouraged to use
       this feature, if it's possible to provide the desired IO offset
       from the application or library.

       On files that are not capable of seeking, the offset must be 0 or

       After the read has been prepared, it can be submitted with one of
       the submit functions.

RETURN VALUE         top


ERRORS         top

       The CQE res field will contain the result of the operation. See
       the related man page for details on possible values. Note that
       where synchronous system calls will return -1 on failure and set
       errno to the actual error value, io_uring never uses errno.
       Instead it returns the negated errno directly in the CQE res

NOTES         top

       Unless an application explicitly needs to pass in more than one
       iovec, it is more efficient to use io_uring_prep_read(3) rather
       than this function, as no state has to be maintained for a non-
       vectored IO request.  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

SEE ALSO         top

       io_uring_get_sqe(3), io_uring_prep_read(3),
       io_uring_prep_readv(3), io_uring_submit(3)

COLOPHON         top

       This page is part of the liburing (A library for io_uring)
       project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report for
       this manual page, send it to  This page
       was obtained from the project's upstream Git repository
       ⟨⟩ on 2022-12-17.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2022-12-12.)  If you discover any rendering
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       (which is not part of the original manual page), send a mail to

liburing-2.1                November 15, 2021    io_uring_prep_readv2(3)

Pages that refer to this page: io_uring_prep_read(3)io_uring_prep_readv2(3)io_uring_prep_readv(3)