From: Miklos Szeredi <miklos@szeredi.hu>
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>
Subject: Re: [RFC PATCH] getting misc stats/attributes via xattr API
Date: Tue, 10 May 2022 15:15:05 +0200 [thread overview]
Message-ID: <CAJfpegtVgyumJiFM_ujjuRTjg07vwOd4h9AT+mbh+n1Qn-LqqA@mail.gmail.com> (raw)
In-Reply-To: <20220510115316.acr6gl5ayqszada6@wittgenstein>
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.
> There's a bit more advanced stuff systemd would really want but which I
> think is misplaced in a mountinfo system call including:
> * list of primary and auxiliary block device major/minor
It's when you need to return variable size arrays or list of strings
that the statx kind of interface falls down.
For that a hierarchical namespace is a much better choice, as it can
represent arbitrary levels of arrays, while doing that with a
specialized syscall is going to be cumbersome.
> I just have a really hard time understanding how this belongs into the
> (f)getxattr() system call family and why it would be a big deal to just
> make this a separate system call.
Fragmenting syntactically equivalent interfaces is bad, unifying them
is good. Dave's example of adding a new syscall for retrieving
multiple xattrs is a prime example.
Thanks,
Miklos
next prev parent reply other threads:[~2022-05-10 13:21 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-03 12:23 [RFC PATCH] getting misc stats/attributes via xattr API Miklos Szeredi
2022-05-03 14:39 ` Amir Goldstein
2022-05-03 14:53 ` Greg KH
2022-05-03 15:04 ` Miklos Szeredi
2022-05-03 15:14 ` Amir Goldstein
2022-05-03 16:54 ` Greg KH
2022-05-03 22:43 ` Dave Chinner
2022-05-04 7:18 ` Miklos Szeredi
2022-05-04 14:22 ` Amir Goldstein
2022-05-05 12:30 ` Karel Zak
2022-05-05 13:59 ` Miklos Szeredi
2022-05-05 23:38 ` tytso
2022-05-06 0:06 ` Amir Goldstein
2022-05-07 0:32 ` Dave Chinner
2022-05-09 12:48 ` Christian Brauner
2022-05-09 14:20 ` Amir Goldstein
2022-05-09 15:08 ` Christian Brauner
2022-05-09 17:07 ` Amir Goldstein
2022-05-09 21:42 ` Vivek Goyal
2022-05-10 3:34 ` Ian Kent
2022-05-10 0:55 ` Dave Chinner
2022-05-10 12:40 ` Christian Brauner
2022-05-11 0:42 ` Dave Chinner
2022-05-11 9:16 ` Christian Brauner
2022-05-10 12:45 ` Florian Weimer
2022-05-10 23:04 ` Dave Chinner
2022-05-10 3:49 ` Miklos Szeredi
2022-05-10 4:27 ` Ian Kent
2022-05-10 8:06 ` Miklos Szeredi
2022-05-10 8:07 ` Miklos Szeredi
2022-05-10 11:53 ` Christian Brauner
2022-05-10 13:15 ` Miklos Szeredi [this message]
2022-05-10 13:18 ` Miklos Szeredi
2022-05-10 14:19 ` Christian Brauner
2022-05-10 14:41 ` Miklos Szeredi
2022-05-10 15:30 ` Christian Brauner
2022-05-10 15:47 ` Miklos Szeredi
2022-05-10 15:53 ` Christian Brauner
2022-05-10 12:35 ` Karel Zak
2022-05-10 23:25 ` Dave Chinner
2022-05-11 8:58 ` Karel Zak
2022-11-14 9:00 ` Abel Wu
2022-11-14 12:35 ` Miklos Szeredi
2022-11-15 3:39 ` Abel Wu
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