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author | Gil Cukierman <cukie@google.com> | 2022-10-31 14:51:59 +0000 |
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committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | 2022-10-31 14:51:59 +0000 |
commit | 7ba7e81400b122a5e3b9dd1ec938fbeda8215899 (patch) | |
tree | ebe9c872e416346e4b333e5062da32401c8e0a73 /man/io_uring_prep_writev.3 | |
parent | d53db6851ea17b2d219d084e1afc683b8b62b105 (diff) | |
parent | dae12c7b40c255ad7c6612591e2908a266f2cfd5 (diff) | |
download | liburing-7ba7e81400b122a5e3b9dd1ec938fbeda8215899.tar.gz |
Update liburing to version 2.2 am: d0a2042580 am: dae12c7b40android-u-beta-1-gpl
Original change: https://android-review.googlesource.com/c/platform/external/liburing/+/2276974
Change-Id: Ie4d6c0c023d49198c105b3d2fc1e5d51edef6398
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
Diffstat (limited to 'man/io_uring_prep_writev.3')
-rw-r--r-- | man/io_uring_prep_writev.3 | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/man/io_uring_prep_writev.3 b/man/io_uring_prep_writev.3 new file mode 100644 index 0000000..9fb83d9 --- /dev/null +++ b/man/io_uring_prep_writev.3 @@ -0,0 +1,85 @@ +.\" Copyright (C) 2021 Stefan Roesch <shr@fb.com> +.\" +.\" SPDX-License-Identifier: LGPL-2.0-or-later +.\" +.TH io_uring_prep_writev 3 "November 15, 2021" "liburing-2.1" "liburing Manual" +.SH NAME +io_uring_prep_writev \- prepare vector I/O write request +.SH SYNOPSIS +.nf +.B #include <sys/uio.h> +.B #include <liburing.h> +.PP +.BI "void io_uring_prep_writev(struct io_uring_sqe *" sqe "," +.BI " int " fd "," +.BI " const struct iovec *" iovecs "," +.BI " unsigned " nr_vecs "," +.BI " __u64 " offset ");" +.fi +.SH DESCRIPTION +.PP +The +.BR io_uring_prep_writev (3) +prepares a vectored IO write request. The submission queue entry +.I sqe +is setup to use the file descriptor +.I fd +to start writing +.I nr_vecs +from the +.I iovecs +array at the specified +.IR offset . + +On files that support seeking, if the offset is set to +.BR -1 , +the write operation commences at the file offset, and the file offset is +incremented by the number of bytes written. See +.BR write (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 is ignored. + +After the write has been prepared it can be submitted with one of the submit +functions. + +.SH RETURN VALUE +None +.SH ERRORS +The CQE +.I 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 +.B -1 +on failure and set +.I errno +to the actual error value, io_uring never uses +.IR errno . +Instead it returns the negated +.I errno +directly in the CQE +.I res +field. +.SH NOTES +Unless an application explicitly needs to pass in more than iovec, it is more +efficient to use +.BR io_uring_prep_write (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 +.B IORING_FEAT_SUBMIT_STABLE +flag passed back from +.BR io_uring_queue_init_params (3). +.SH SEE ALSO +.BR io_uring_get_sqe (3), +.BR io_uring_prep_write (3), +.BR io_uring_prep_writev2 (3), +.BR io_uring_submit (3) |