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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | NOTES | SEE ALSO | COLOPHON |
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io_uring_prep_readv2(3) liburing Manual io_uring_prep_readv2(3)
io_uring_prep_readv2 - prepare vector I/O read request with flags
#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);
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:
RWF_HIPRI
High priority request, poll if possible
RWF_DSYNC
per-IO O_DSYNC
RWF_SYNC
per-IO O_SYNC
RWF_NOWAIT
per-IO, return -EAGAIN if operation would block
RWF_APPEND
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
-1.
After the read has been prepared, it can be submitted with one of
the submit functions.
None
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
field.
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
io_uring_queue_init_params(3).
io_uring_get_sqe(3), io_uring_prep_read(3),
io_uring_prep_readv(3), io_uring_submit(3)
This page is part of the liburing (A library for io_uring)
project. Information about the project can be found at
⟨https://github.com/axboe/liburing⟩. If you have a bug report for
this manual page, send it to [email protected]. This page
was obtained from the project's upstream Git repository
⟨https://github.com/axboe/liburing⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-03.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
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)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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