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From:   Miklos Szeredi <miklos@szeredi.hu>
Date:   Tue, 3 May 2022 17:04:06 +0200
Message-ID: <CAJfpegtZjRca5QPm2QgPtPG0-BJ=15Vtd48OTnRnr5G7ggAtmA@mail.gmail.com>
Subject: Re: [RFC PATCH] getting misc stats/attributes via xattr API
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Amir Goldstein <amir73il@gmail.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Dave Chinner <david@fromorbit.com>,
        "Theodore Ts'o" <tytso@mit.edu>, Karel Zak <kzak@redhat.com>,
        Christian Brauner <brauner@kernel.org>,
        linux-kernel <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>,
        James Bottomley <James.Bottomley@hansenpartnership.com>
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On Tue, 3 May 2022 at 16:53, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Tue, May 03, 2022 at 05:39:46PM +0300, Amir Goldstein wrote:

> > It should be noted that while this API mandates text keys,
> > it does not mandate text values, so for example, sb iostats could be
> > exported as text or as binary struct, or as individual text/binary records or
> > all of the above.
>
> Ugh, no, that would be a total mess.  Don't go exporting random binary
> structs depending on the file, that's going to be completely
> unmaintainable.  As it is, this is going to be hard enough with random
> text fields.
>
> As for this format, it needs to be required to be documented in
> Documentation/ABI/ for each entry and key type so that we have a chance
> of knowing what is going on and tracking how things are working and
> validating stuff.

My preference would be a single text value for each key.

Contents of ":mnt:info" contradicts that, but mountinfo has a long
established, well documented format, and nothing prevents exporting
individual attributes with separate names as well (the getvalues(2)
patch did exactly that).

Thanks,
Miklos