linux-kernel - Re: [PATCH v2 0/4] open/accept directly into io

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Date:   Mon, 16 Aug 2021 17:45:36 +0200
From:   Stefan Metzmacher <metze@...ba.org>
To:     Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        Josh Triplett <josh@...htriplett.org>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v2 0/4] open/accept directly into io_uring fixed file
 table

Hi Pavel,

> The behaviour is controlled by setting sqe->file_index, where 0 implies
> the old behaviour. If non-zero value is specified, then it will behave
> as described and place the file into a fixed file slot
> sqe->file_index - 1. A file table should be already created, the slot
> should be valid and empty, otherwise the operation will fail.
> 
> Note 1: we can't use IOSQE_FIXED_FILE to switch between modes, because
> accept takes a file, and it already uses the flag with a different
> meaning.

Would it be hard to support IOSQE_FIXED_FILE for the dirfd of openat*, renameat, unlinkat, statx?
(And mkdirat, linkat, symlinkat when they arrive)
renameat and linkat might be trickier as they take two dirfds, but it
would make the feature more complete and useful.

metze