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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Tue, 10 May 2022 15:18:40 +0200
Message-ID: <CAJfpegvBoYABebN2GD=ecu4gUsPZgiTksK6S8d3MA-1r1NgmMA@mail.gmail.com>
Subject: Re: [RFC PATCH] getting misc stats/attributes via xattr API
To:     Christian Brauner <brauner@kernel.org>
Cc:     linux-fsdevel@vger.kernel.org, Dave Chinner <david@fromorbit.com>,
        "Theodore Ts'o" <tytso@mit.edu>, Karel Zak <kzak@redhat.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org,
        Linux API <linux-api@vger.kernel.org>,
        linux-man <linux-man@vger.kernel.org>,
        LSM <linux-security-module@vger.kernel.org>,
        Ian Kent <raven@themaw.net>,
        David Howells <dhowells@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <christian@brauner.io>,
        Amir Goldstein <amir73il@gmail.com>,
        James Bottomley <James.Bottomley@hansenpartnership.com>
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On Tue, 10 May 2022 at 15:15, Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> On Tue, 10 May 2022 at 13:53, Christian Brauner <brauner@kernel.org> wrote:
>
> > > What exactly are the attributes that systemd requires?
> >
> > We keep a repo with ideas for (kernel) extensions - we should probably
> > publish that somewhere - but the list we used for a prototype roughly
> > contains:
> >
> > * mount flags MOUNT_ATTR_RDONLY etc.
> > * time flags MOUNT_ATTR_RELATIME etc. (could probably be combined with
> >   mount flags. We missed the opportunity to make them proper enums
> >   separate from other mount flags imho.)
> > * propagation "flags" (MS_SHARED)
> > * peer group
> > * mnt_id of the mount
> > * mnt_id of the mount's parent
> > * owning userns
>
> Sounds good thus far.   And hey, we don't even need a new syscall:
> statx(2) could handle these fine.

Oh, we need this indexed with a mount id, which statx can't do.  So
indeed, a new syscall may be the best choice.

Thanks,
Miklos