Hi Michael,
What is wrong with this patch?
On Mon, Nov 06, 2017 at 11:34:17PM -0800, Andrei Vagin wrote:
> The man page describes that vmsplice can splice pages from
> memory to a pipe, but it can work to anonther direction as well.
>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
> ---
> man2/vmsplice.2 | 24 +++++++++++++++++++++---
> 1 file changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/man2/vmsplice.2 b/man2/vmsplice.2
> index e3e61cf27..8f48b8809 100644
> --- a/man2/vmsplice.2
> +++ b/man2/vmsplice.2
> @@ -25,7 +25,7 @@
> .\"
> .TH VMSPLICE 2 2014-10-02 "Linux" "Linux Programmer's Manual"
> .SH NAME
> -vmsplice \- splice user pages into a pipe
> +vmsplice \- splice user pages to/from a pipe
> .SH SYNOPSIS
> .nf
> .BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */"
> @@ -44,13 +44,25 @@ vmsplice \- splice user pages into a pipe
> .\" the kernel-space one (contrast this to "write()", which copies
> .\" the actual data, and you can thus reuse the buffer immediately
> .\" after a successful write), but that is often easy to do.
> -The
> +If
> +.I fd
> +is opened for writting, the
> .BR vmsplice ()
> system call maps
> .I nr_segs
> ranges of user memory described by
> .I iov
> into a pipe.
> +.\" commit 6a14b90bb6bc7cd83e2a444bf457a2ea645cbfe7
> +If
> +.I fd
> +is opened for reading, the
> +.BR vmsplice ()
> +system call fills
> +.I nr_segs
> +ranges of user memory described by
> +.I iov
> +from a pipe.
> The file descriptor
> .I fd
> must refer to a pipe.
> @@ -70,7 +82,6 @@ struct iovec {
> };
> .in
> .fi
> -
> The
> .I flags
> argument is a bit mask that is composed by ORing together
> @@ -163,6 +174,13 @@ as defined in
> Currently,
> .\" UIO_MAXIOV in kernel source
> this limit is 1024.
> +
> +.\" commit 6a14b90bb6bc7cd83e2a444bf457a2ea645cbfe7
> +.BR vmsplice ()
> +only really supports true splicing from user memory to a pipe. In another
> +direction, it actually just copies the data to userspace. But this makes
> +the interface nice and symmetric and enables people to build on splice,
> +with room for future improvement in performance.
> .SH SEE ALSO
> .BR splice (2),
> .BR tee (2)
> --
> 2.13.6
>
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