linux-kernel - Re: [PATCH] do_open(): Fix O_DIRECTORY

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Date:   Mon, 27 Mar 2023 21:13:18 +0100
From:   Pedro Falcato <pedro.falcato@...il.com>
To:     Christian Brauner <brauner@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Aleksa Sarai <cyphar@...har.com>
Subject: Re: [PATCH] do_open(): Fix O_DIRECTORY | O_CREAT behavior

On Tue, Mar 21, 2023 at 4:17 PM Christian Brauner <brauner@...nel.org> wrote:
> It would be very nice if we had tests for the new behavior. So if @Pedro
> would be up for it that would be highly appreciated. If not I'll put it
> on my ToDo...

Where do you want them? selftests? I have a relatively self-contained
""testsuite"" of namei stuff that could fit in there well, after some
cleanup.

> The expectation often is that this particular combination would create
> and open a directory. This suggests users who tried to use that
> combination would stumble upon the counterintuitive behavior no matter
> if pre-v5.7 or post v5.7 and quickly realize neither semantics give them
> what they want. For some examples see the code examples in [1] to [3]
> and the discussion in [4].

Ok so, silly question: Could it not be desirable to have these
semantics (open a dir or mkdir, atomically)?
It does seem to be why POSIX left this edge case implementation
defined, and if folks are asking for it, could it be the right move?

And yes, I do understand (from reading the room) that no one here is
too excited about this possibility.

-- 
Pedro