linux-kernel - file metadata via fs API (was: [GIT PULL] Filesystem Information)

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Message-ID: <CAJfpegtNP8rQSS4Z14Ja4x-TOnejdhDRTsmmDD-Cccy2pkfVVw@mail.gmail.com>
Date:   Wed, 5 Aug 2020 10:24:23 +0200
From:   Miklos Szeredi <miklos@...redi.hu>
To:     Ian Kent <raven@...maw.net>
Cc:     David Howells <dhowells@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>, Karel Zak <kzak@...hat.com>,
        Jeff Layton <jlayton@...hat.com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>,
        Christian Brauner <christian@...uner.io>,
        Lennart Poettering <lennart@...ttering.net>,
        Linux API <linux-api@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org,
        LSM <linux-security-module@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: file metadata via fs API (was: [GIT PULL] Filesystem Information)

On Tue, Aug 4, 2020 at 4:36 PM Miklos Szeredi <miklos@...redi.hu> wrote:

> I think we already lost that with the xattr API, that should have been
> done in a way that fits this philosophy.  But given that we  have "/"
> as the only special purpose char in filenames, and even repetitions
> are allowed, it's hard to think of a good way to do that.  Pity.

One way this could be solved is to allow opting into an alternative
path resolution mode.

E.g.
  openat(AT_FDCWD, "foo/bar//mnt/info", O_RDONLY | O_ALT);

Yes, the implementation might be somewhat tricky, but that's another
question.  Also I'm pretty sure that we should be reducing the
POSIX-ness of anything below "//" to the bare minimum.  No seeking,
etc....

I think this would open up some nice possibilities beyond the fsinfo thing.

Thanks,
Miklos