Re: [RFC PATCH] getting misc stats/attributes via xattr API

From: Amir Goldstein <amir73il@gmail.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Greg KH <gregkh@linuxfoundation.org>,
	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>
Subject: Re: [RFC PATCH] getting misc stats/attributes via xattr API
Date: Tue, 3 May 2022 18:14:31 +0300	[thread overview]
Message-ID: <CAOQ4uxiBsQXbxQJf7Az3T+gq7Oph4joykqMB0EP87U=bj4LvSg@mail.gmail.com> (raw)
In-Reply-To: <CAJfpegtZjRca5QPm2QgPtPG0-BJ=15Vtd48OTnRnr5G7ggAtmA@mail.gmail.com>

On Tue, May 3, 2022 at 6:04 PM Miklos Szeredi <miklos@szeredi.hu> wrote:
>
> 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).
>

Right, the fun is that ":mnt:info" and ":mnt:info:" can co-exist.

Thanks,
Amir.