Re: [PATCH 01/32] readv2: Note preadv2(..., RWF_NOWAIT) bug in BUGS section

["Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>]

Hello Will and Alex,

On 7/28/21 10:19 PM, Alejandro Colomar wrote:
> From: Will Manley <will@williammanley.net>
> 
> To save the next person before they fall foul of it.  See
> <https://lore.kernel.org/linux-fsdevel/fea8b16d-5a69-40f9-b123-e84dcd6e8f2e@www.fastmail.com/T/#u>
> and <https://github.com/tokio-rs/tokio/issues/3803> for more information.
> 
> Signed-off-by: Will Manley <will@williammanley.net>
> Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>

Patch applied, but see my follow-up mail.

Thanks,

Michael

> ---
>  man2/readv.2 | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/man2/readv.2 b/man2/readv.2
> index df42cf830..3355fa9d7 100644
> --- a/man2/readv.2
> +++ b/man2/readv.2
> @@ -243,7 +243,9 @@ If some data was successfully read, it will return the number of bytes read.
>  If no bytes were read, it will return \-1 and set
>  .IR errno
>  to
> -.BR EAGAIN .
> +.BR EAGAIN
> +(but see
> +.BR BUGS ")."
>  Currently, this flag is meaningful only for
>  .BR preadv2 ().
>  .TP
> @@ -425,6 +427,13 @@ iov[1].iov_len = strlen(str1);
>  nwritten = writev(STDOUT_FILENO, iov, 2);
>  .EE
>  .in
> +.SH BUGS
> +Linux v5.9 and v5.10 have a bug where
> +.BR preadv2()
> +with the
> +.BR RWF_NOWAIT
> +flag may return 0 even when not at end of file.  See
> +https://lore.kernel.org/linux-fsdevel/fea8b16d-5a69-40f9-b123-e84dcd6e8f2e@www.fastmail.com/T/#u
>  .SH SEE ALSO
>  .BR pread (2),
>  .BR read (2),
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/