From: Christian Brauner <christian.brauner@ubuntu.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: David Howells <dhowells@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
dray@redhat.com, Karel Zak <kzak@redhat.com>,
Miklos Szeredi <mszeredi@redhat.com>,
Steven Whitehouse <swhiteho@redhat.com>,
Jeff Layton <jlayton@redhat.com>, Ian Kent <raven@themaw.net>,
andres@anarazel.de, keyrings@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Lennart Poettering <lennart@poettering.net>,
Aleksa Sarai <cyphar@cyphar.com>
Subject: Re: Upcoming: Notifications, FS notifications and fsinfo()
Date: Tue, 31 Mar 2020 08:15:07 +0000 [thread overview]
Message-ID: <20200331081507.f6an4x32cxwpxdpd@wittgenstein> (raw)
In-Reply-To: <CAJfpegtjmkJUSqORFv6jw-sYbqEMh9vJz64+dmzWhATYiBmzVQ@mail.gmail.com>
On Tue, Mar 31, 2020 at 07:11:11AM +0200, Miklos Szeredi wrote:
> On Mon, Mar 30, 2020 at 11:17 PM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
>
> > Fwiw, putting down my kernel hat and speaking as someone who maintains
> > two container runtimes and various other low-level bits and pieces in
> > userspace who'd make heavy use of this stuff I would prefer the fd-based
> > fsinfo() approach especially in the light of across namespace
> > operations, querying all properties of a mount atomically all-at-once,
>
> fsinfo(2) doesn't meet the atomically all-at-once requirement. Sure,
> it's possible to check the various change counters before and after a
> batch of calls to check that the result is consistent. Still, that's
> not an atomic all-at-once query, if you'd really require that, than
> fsinfo(2) as it currently stands would be inadequate.
It at all that's only true for batch requests.
>
> > and safe delegation through fds. Another heavy user of this would be
> > systemd (Cced Lennart who I've discussed this with) which would prefer
> > the fd-based approach as well. I think pulling this into a filesystem
> > and making userspace parse around in a filesystem tree to query mount
> > information is the wrong approach and will get messy pretty quickly
> > especially in the face of mount and user namespace interactions and
> > various other pitfalls.
>
> Have you actually looked at my proposed patch? Do you have concrete
Yes. So have others, Al actively disliked and nacked it and no-one got
excited about it.
> issues or just vague bad feelings?
We have had that discussion on-list where I made my "vague bad feelings"
clear where you responded with the same dismissive style so I don't see
the point in repeating this experience.
Again, I want to make it clear that here I'm stating my preference as a
user of this api and as such I don't want to have to parse through a
filesystem to get complex information about filesystems. We've had
fruitful discussions [1] around how fsinfo() ties in with supervised
mounts and the rest of the mount api and its clear and simple especially
in the face of namespaces and implements a nice delegation model. So +1
from me.
Christian
[1]: https://youtu.be/LN2CUgp8deo?th40
WARNING: multiple messages have this Message-ID (diff)
From: Christian Brauner <christian.brauner@ubuntu.com>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: David Howells <dhowells@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
dray@redhat.com, Karel Zak <kzak@redhat.com>,
Miklos Szeredi <mszeredi@redhat.com>,
Steven Whitehouse <swhiteho@redhat.com>,
Jeff Layton <jlayton@redhat.com>, Ian Kent <raven@themaw.net>,
andres@anarazel.de, keyrings@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Lennart Poettering <lennart@poettering.net>,
Aleksa Sarai <cyphar@cyphar.com>
Subject: Re: Upcoming: Notifications, FS notifications and fsinfo()
Date: Tue, 31 Mar 2020 10:15:07 +0200 [thread overview]
Message-ID: <20200331081507.f6an4x32cxwpxdpd@wittgenstein> (raw)
In-Reply-To: <CAJfpegtjmkJUSqORFv6jw-sYbqEMh9vJz64+dmzWhATYiBmzVQ@mail.gmail.com>
On Tue, Mar 31, 2020 at 07:11:11AM +0200, Miklos Szeredi wrote:
> On Mon, Mar 30, 2020 at 11:17 PM Christian Brauner
> <christian.brauner@ubuntu.com> wrote:
>
> > Fwiw, putting down my kernel hat and speaking as someone who maintains
> > two container runtimes and various other low-level bits and pieces in
> > userspace who'd make heavy use of this stuff I would prefer the fd-based
> > fsinfo() approach especially in the light of across namespace
> > operations, querying all properties of a mount atomically all-at-once,
>
> fsinfo(2) doesn't meet the atomically all-at-once requirement. Sure,
> it's possible to check the various change counters before and after a
> batch of calls to check that the result is consistent. Still, that's
> not an atomic all-at-once query, if you'd really require that, than
> fsinfo(2) as it currently stands would be inadequate.
It at all that's only true for batch requests.
>
> > and safe delegation through fds. Another heavy user of this would be
> > systemd (Cced Lennart who I've discussed this with) which would prefer
> > the fd-based approach as well. I think pulling this into a filesystem
> > and making userspace parse around in a filesystem tree to query mount
> > information is the wrong approach and will get messy pretty quickly
> > especially in the face of mount and user namespace interactions and
> > various other pitfalls.
>
> Have you actually looked at my proposed patch? Do you have concrete
Yes. So have others, Al actively disliked and nacked it and no-one got
excited about it.
> issues or just vague bad feelings?
We have had that discussion on-list where I made my "vague bad feelings"
clear where you responded with the same dismissive style so I don't see
the point in repeating this experience.
Again, I want to make it clear that here I'm stating my preference as a
user of this api and as such I don't want to have to parse through a
filesystem to get complex information about filesystems. We've had
fruitful discussions [1] around how fsinfo() ties in with supervised
mounts and the rest of the mount api and its clear and simple especially
in the face of namespaces and implements a nice delegation model. So +1
from me.
Christian
[1]: https://youtu.be/LN2CUgp8deo?t=6840
next prev parent reply other threads:[~2020-03-31 8:15 UTC|newest]
Thread overview: 199+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 13:58 Upcoming: Notifications, FS notifications and fsinfo() David Howells
2020-03-30 13:58 ` David Howells
2020-03-30 14:31 ` [GIT PULL] General notification queue and key notifications David Howells
2020-03-30 14:31 ` David Howells
2020-03-31 6:51 ` Stephen Rothwell
2020-03-31 6:51 ` Stephen Rothwell
2020-06-02 15:55 ` David Howells
2020-06-02 15:55 ` David Howells
2020-06-03 2:15 ` Ian Kent
2020-06-03 2:15 ` Ian Kent
2020-06-08 0:49 ` Ian Kent
2020-06-08 0:49 ` Ian Kent
2020-06-10 9:56 ` Christian Brauner
2020-06-10 9:56 ` Christian Brauner
2020-06-10 11:12 ` Karel Zak
2020-06-10 11:12 ` Karel Zak
2020-06-12 21:32 ` Linus Torvalds
2020-06-12 21:32 ` Linus Torvalds
2020-06-12 22:01 ` Linus Torvalds
2020-06-12 22:01 ` Linus Torvalds
2020-06-13 13:04 ` David Howells
2020-06-13 13:04 ` David Howells
2020-06-13 16:47 ` Linus Torvalds
2020-06-13 16:47 ` Linus Torvalds
2020-06-13 17:03 ` Linus Torvalds
2020-06-13 17:03 ` Linus Torvalds
2020-06-13 19:22 ` Miklos Szeredi
2020-06-13 19:22 ` Miklos Szeredi
2020-06-13 13:24 ` David Howells
2020-06-13 13:24 ` David Howells
2020-06-13 18:00 ` pr-tracker-bot
2020-06-13 18:00 ` pr-tracker-bot
2020-06-17 1:15 ` Williams, Dan J
2020-06-17 1:15 ` Williams, Dan J
2020-06-17 1:15 ` Williams, Dan J
2020-06-23 23:38 ` Dan Williams
2020-06-23 23:38 ` Dan Williams
2020-06-23 23:38 ` Dan Williams
2020-06-24 0:55 ` David Howells
2020-06-24 0:55 ` David Howells
2020-06-24 0:55 ` David Howells
2020-06-24 1:03 ` Dan Williams
2020-06-24 1:03 ` Dan Williams
2020-06-24 1:03 ` Dan Williams
2020-06-24 1:17 ` David Howells
2020-06-24 1:17 ` David Howells
2020-06-24 1:17 ` David Howells
2020-03-30 14:36 ` [GIT PULL] Mount and superblock notifications David Howells
2020-03-30 14:36 ` David Howells
2020-04-04 21:13 ` Linus Torvalds
2020-04-04 21:13 ` Linus Torvalds
2020-04-05 22:52 ` Andres Freund
2020-04-05 22:52 ` Andres Freund
2020-03-30 14:43 ` [GIT PULL] fsinfo: Filesystem information query David Howells
2020-03-30 14:43 ` David Howells
2020-03-30 20:28 ` Upcoming: Notifications, FS notifications and fsinfo() Miklos Szeredi
2020-03-30 20:28 ` Miklos Szeredi
2020-03-31 9:21 ` Karel Zak
2020-03-31 9:21 ` Karel Zak
2020-03-30 21:17 ` Christian Brauner
2020-03-30 21:17 ` Christian Brauner
2020-03-31 5:11 ` Miklos Szeredi
2020-03-31 5:11 ` Miklos Szeredi
2020-03-31 8:15 ` Christian Brauner [this message]
2020-03-31 8:15 ` Christian Brauner
2020-03-31 8:34 ` Miklos Szeredi
2020-03-31 8:34 ` Miklos Szeredi
2020-03-31 8:34 ` Karel Zak
2020-03-31 8:34 ` Karel Zak
2020-03-31 8:56 ` Miklos Szeredi
2020-03-31 8:56 ` Miklos Szeredi
2020-03-31 9:49 ` Karel Zak
2020-03-31 9:49 ` Karel Zak
2020-03-31 12:25 ` Lennart Poettering
2020-03-31 12:25 ` Lennart Poettering
2020-03-31 15:10 ` Miklos Szeredi
2020-03-31 15:10 ` Miklos Szeredi
2020-03-31 15:24 ` Lennart Poettering
2020-03-31 15:24 ` Lennart Poettering
2020-03-31 21:56 ` David Howells
2020-03-31 21:56 ` David Howells
2020-03-31 21:54 ` David Howells
2020-03-31 21:54 ` David Howells
2020-04-01 8:43 ` Karel Zak
2020-04-01 8:43 ` Karel Zak
2020-03-31 7:22 ` Lennart Poettering
2020-03-31 7:22 ` Lennart Poettering
2020-03-31 17:31 ` David Howells
2020-03-31 17:31 ` David Howells
2020-03-31 19:42 ` Miklos Szeredi
2020-03-31 19:42 ` Miklos Szeredi
2020-03-31 19:47 ` David Howells
2020-03-31 19:47 ` David Howells
2020-03-31 21:14 ` David Howells
2020-03-31 21:14 ` David Howells
2020-03-31 21:23 ` David Howells
2020-03-31 21:23 ` David Howells
2020-03-31 21:52 ` David Howells
2020-03-31 21:52 ` David Howells
2020-04-01 9:04 ` Karel Zak
2020-04-01 9:04 ` Karel Zak
2020-04-01 13:34 ` Miklos Szeredi
2020-04-01 13:34 ` Miklos Szeredi
2020-04-01 13:55 ` David Howells
2020-04-01 13:55 ` David Howells
2020-04-01 13:58 ` David Howells
2020-04-01 13:58 ` David Howells
2020-04-01 15:25 ` Miklos Szeredi
2020-04-01 15:25 ` Miklos Szeredi
2020-04-03 9:11 ` Karel Zak
2020-04-03 9:11 ` Karel Zak
2020-04-01 16:01 ` David Howells
2020-04-01 16:01 ` David Howells
2020-04-01 16:30 ` Miklos Szeredi
2020-04-01 16:30 ` Miklos Szeredi
2020-04-02 15:22 ` David Howells
2020-04-02 15:22 ` David Howells
2020-04-02 15:24 ` Miklos Szeredi
2020-04-02 15:24 ` Miklos Szeredi
2020-04-02 15:42 ` David Howells
2020-04-02 15:42 ` David Howells
2020-04-02 15:24 ` David Howells
2020-04-02 15:24 ` David Howells
2020-04-01 14:41 ` Lennart Poettering
2020-04-01 14:41 ` Lennart Poettering
2020-04-01 15:33 ` Miklos Szeredi
2020-04-01 15:33 ` Miklos Szeredi
2020-04-01 16:06 ` David Howells
2020-04-01 16:06 ` David Howells
2020-04-01 16:40 ` Miklos Szeredi
2020-04-01 16:40 ` Miklos Szeredi
2020-04-02 2:52 ` Ian Kent
2020-04-02 2:52 ` Ian Kent
2020-04-02 13:52 ` Miklos Szeredi
2020-04-02 13:52 ` Miklos Szeredi
2020-04-02 14:36 ` Lennart Poettering
2020-04-02 14:36 ` Lennart Poettering
2020-04-02 15:22 ` Miklos Szeredi
2020-04-02 15:22 ` Miklos Szeredi
2020-04-02 15:28 ` Lennart Poettering
2020-04-02 15:28 ` Lennart Poettering
2020-04-02 15:35 ` Miklos Szeredi
2020-04-02 15:35 ` Miklos Szeredi
2020-04-02 15:50 ` Lennart Poettering
2020-04-02 15:50 ` Lennart Poettering
2020-04-02 17:20 ` Miklos Szeredi
2020-04-02 17:20 ` Miklos Szeredi
2020-04-03 11:08 ` Lennart Poettering
2020-04-03 11:08 ` Lennart Poettering
2020-04-03 11:48 ` Miklos Szeredi
2020-04-03 11:48 ` Miklos Szeredi
2020-04-03 15:01 ` Lennart Poettering
2020-04-03 15:01 ` Lennart Poettering
2020-04-06 9:22 ` Miklos Szeredi
2020-04-06 9:22 ` Miklos Szeredi
2020-04-06 17:29 ` Lennart Poettering
2020-04-06 17:29 ` Lennart Poettering
2020-04-07 2:21 ` Ian Kent
2020-04-07 2:21 ` Ian Kent
2020-04-07 13:59 ` Miklos Szeredi
2020-04-07 13:59 ` Miklos Szeredi
2020-04-07 15:53 ` Lennart Poettering
2020-04-07 15:53 ` Lennart Poettering
2020-04-07 16:06 ` Miklos Szeredi
2020-04-07 16:06 ` Miklos Szeredi
2020-04-02 15:51 ` David Howells
2020-04-02 15:51 ` David Howells
2020-04-02 15:56 ` David Howells
2020-04-02 15:56 ` David Howells
2020-04-03 1:44 ` Ian Kent
2020-04-03 1:44 ` Ian Kent
2020-04-03 11:11 ` Lennart Poettering
2020-04-03 11:11 ` Lennart Poettering
2020-04-03 11:38 ` Miklos Szeredi
2020-04-03 11:38 ` Miklos Szeredi
2020-04-03 12:05 ` Richard Weinberger
2020-04-03 12:05 ` Richard Weinberger
2020-04-03 15:12 ` Lennart Poettering
2020-04-03 15:12 ` Lennart Poettering
2020-04-03 20:30 ` J. Bruce Fields
2020-04-03 20:30 ` J. Bruce Fields
2020-04-06 8:35 ` Miklos Szeredi
2020-04-06 8:35 ` Miklos Szeredi
2020-04-06 16:07 ` J. Bruce Fields
2020-04-06 16:07 ` J. Bruce Fields
2020-04-06 9:17 ` Karel Zak
2020-04-06 9:17 ` Karel Zak
2020-04-06 16:34 ` Linus Torvalds
2020-04-06 16:34 ` Linus Torvalds
2020-04-06 18:46 ` J. Bruce Fields
2020-04-06 18:46 ` J. Bruce Fields
2020-04-06 18:48 ` Lennart Poettering
2020-04-06 18:48 ` Lennart Poettering
2020-04-08 3:36 ` Linus Torvalds
2020-04-08 3:36 ` Linus Torvalds
2020-04-03 15:36 ` David Howells
2020-04-03 15:36 ` David Howells
2020-04-03 15:41 ` Lennart Poettering
2020-04-03 15:41 ` Lennart Poettering
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