Re: [LSF/MM/BPF TOPIC] making O_TMPFILE more atomic

From: Miklos Szeredi <miklos@szeredi.hu>
To: Steve French <smfrench@gmail.com>
Cc: lsf-pc@lists.linux-foundation.org,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [LSF/MM/BPF TOPIC] making O_TMPFILE more atomic
Date: Tue, 3 May 2022 20:52:23 +0200	[thread overview]
Message-ID: <CAJfpegskJzpXXhWCdw6K9r2hKORiBdXfSrgpUhKqn9VVyuVuqw@mail.gmail.com> (raw)
In-Reply-To: <CAH2r5mv7Z7XmyWgp5K8ZshA1OiMBTNGU-v8FdmwwkZaNNe=4wA@mail.gmail.com>

On Thu, 24 Feb 2022 at 06:33, Steve French <smfrench@gmail.com> wrote:
>
> Currently creating tmpfiles on Linux can be problematic because the
> tmpfile is not created and opened at the same time  (vfs_tmpfile calls
> into the fs, then later vfs_open is called to open the tmpfile).   For
> some filesystems it would be more natural to create and open the
> tmpfile as one operation (because the action of creating the file on
> some filesystems returns an open handle, so closing it then reopening
> it would cause the tmpfile to be deleted).
>
> I would like to discuss whether the function do_tmpfile (which creates
> and then opens the tmpfile) could have an option for a filesystem to
> do this as one operation which would allow it to be more atomic and
> allow it to work on a wider variety of filesystems.

A related thread:

https://lore.kernel.org/all/20201109100343.3958378-3-chirantan@chromium.org/#r

There was no conclusion in the end. Not sure how hacky it would be to
store the open file in the inode...

Thanks,
Miklos