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From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org
Subject: Re: [PATCH liburing] man/io_uring_enter.2: add notes about direct open/accept
Date: Tue, 31 Aug 2021 14:04:02 -0600	[thread overview]
Message-ID: <8f82a074-1597-1796-2e26-da3abe722806@kernel.dk> (raw)
In-Reply-To: <e4b7c0f9b585307ac542470c535ef54e419157e0.1630439510.git.asml.silence@gmail.com>

On 8/31/21 1:52 PM, Pavel Begunkov wrote:
> Add a few lines describing openat/openat2/accept bypassing normal file
> tables and installing files right into the fixed file table.
> 
> Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
> ---
>  man/io_uring_enter.2 | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/man/io_uring_enter.2 b/man/io_uring_enter.2
> index 9ccedef..52a5e13 100644
> --- a/man/io_uring_enter.2
> +++ b/man/io_uring_enter.2
> @@ -511,6 +511,18 @@ field. See also
>  .BR accept4(2)
>  for the general description of the related system call. Available since 5.5.
>  
> +If the
> +.I file_index
> +field is set to a non-negative number, the file won't be installed into the
> +normal file table as usual but will be placed into the fixed file table at index
> +.I file_index - 1.
> +In this case, instead of returning a file descriptor, the result will contain
> +0 on success or an error. If there is already a file registered at this index,

I don't think non-negative is correct, it has to be set to a positive
number. non-negative would include 0, which isn't correct.

Should also include a note on if these types of file are used, they
won't work in anything but io_uring. That's obvious to us, but should be
noted that they then only live within the realm of the ring itself, not
the system as a whole.

-- 
Jens Axboe


  reply	other threads:[~2021-08-31 20:04 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-31 19:52 Pavel Begunkov
2021-08-31 20:04 ` Jens Axboe [this message]
2021-08-31 20:07   ` Pavel Begunkov

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