From: Lennart Poettering <mzxreary@0pointer.de>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
David Howells <dhowells@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>, Karel Zak <kzak@redhat.com>,
Jeff Layton <jlayton@redhat.com>,
Miklos Szeredi <mszeredi@redhat.com>,
Nicolas Dichtel <nicolas.dichtel@6wind.com>,
Christian Brauner <christian@brauner.io>,
Linux API <linux-api@vger.kernel.org>,
Ian Kent <raven@themaw.net>,
LSM <linux-security-module@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: file metadata via fs API (was: [GIT PULL] Filesystem Information)
Date: Tue, 11 Aug 2020 21:31:05 +0200 [thread overview]
Message-ID: <20200811193105.GA228302@gardel-login> (raw)
In-Reply-To: <CAJfpeguo5nAWcmduX4frknQGiRJeaj9Rdj018xUBrwqOJhVufw@mail.gmail.com>
On Di, 11.08.20 20:49, Miklos Szeredi (miklos@szeredi.hu) wrote:
> On Tue, Aug 11, 2020 at 6:05 PM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>
> > and then people do "$(srctree)/". If you haven't seen that kind of
> > pattern where the pathname has two (or sometimes more!) slashes in the
> > middle, you've led a very sheltered life.
>
> Oh, I have. That's why I opted for triple slashes, since that should
> work most of the time even in those concatenated cases. And yes, I
> know, most is not always, and this might just be hiding bugs, etc...
> I think the pragmatic approach would be to try this and see how many
> triple slash hits a normal workload gets and if it's reasonably low,
> then hopefully that together with warnings for O_ALT would be enough.
There's no point. Userspace relies on the current meaning of triple
slashes. It really does.
I know many places in systemd where we might end up with a triple
slash. Here's a real-life example: some code wants to access the
cgroup attribute 'cgroup.controllers' of the root cgroup. It thus
generates the right path in the fs for it, which is the concatenation of
"/sys/fs/cgroup/" (because that's where cgroupfs is mounted), of "/"
(i.e. for the root cgroup) and of "/cgroup.controllers" (as that's the
file the attribute is exposed under).
And there you go:
"/sys/fs/cgroup/" + "/" + "/cgroup.controllers" → "/sys/fs/cgroup///cgroup.controllers"
This is a real-life thing. Don't break this please.
Lennart
--
Lennart Poettering, Berlin
next prev parent reply other threads:[~2020-08-11 19:40 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-03 15:27 [GIT PULL] Mount notifications David Howells
2020-08-03 15:49 ` [GIT PULL] Filesystem Information David Howells
2020-08-03 16:42 ` Miklos Szeredi
2020-08-04 2:15 ` Ian Kent
2020-08-04 14:36 ` Miklos Szeredi
2020-08-05 1:33 ` Ian Kent
2020-08-05 8:00 ` Miklos Szeredi
2020-08-05 11:13 ` Ian Kent
2020-08-05 8:24 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Miklos Szeredi
2020-08-11 13:54 ` Miklos Szeredi
2020-08-11 14:08 ` Al Viro
2020-08-11 14:22 ` Miklos Szeredi
2020-08-11 14:31 ` Al Viro
[not found] ` <CAAgocE07=vVKpQhG+rjEGO=NEBKZ02gjg4TRPxECAc+RKrzn=Q@mail.gmail.com>
2020-08-11 14:36 ` Al Viro
2020-08-11 14:36 ` Miklos Szeredi
2020-08-11 14:42 ` Al Viro
2020-08-11 14:47 ` Miklos Szeredi
2020-08-11 15:20 ` Linus Torvalds
2020-08-11 15:30 ` Miklos Szeredi
2020-08-11 16:05 ` Linus Torvalds
2020-08-11 18:49 ` Miklos Szeredi
2020-08-11 19:31 ` Lennart Poettering [this message]
2020-08-11 19:50 ` Christian Brauner
2020-08-11 19:39 ` Christian Brauner
2020-08-12 0:53 ` Ian Kent
2020-08-11 15:39 ` Andy Lutomirski
2020-08-11 16:17 ` Casey Schaufler
2020-08-11 16:30 ` Linus Torvalds
2020-08-11 20:28 ` Miklos Szeredi
2020-08-11 20:36 ` Jann Horn
2020-08-11 20:56 ` Miklos Szeredi
2020-08-11 21:17 ` Andy Lutomirski
2020-08-11 21:18 ` Linus Torvalds
2020-08-12 7:23 ` Miklos Szeredi
2020-08-12 14:39 ` Al Viro
2020-08-12 14:46 ` Miklos Szeredi
2020-08-12 15:08 ` Al Viro
2020-08-12 15:13 ` Miklos Szeredi
2020-08-12 16:33 ` Al Viro
2020-08-12 17:16 ` Miklos Szeredi
2020-08-12 17:39 ` Al Viro
2020-08-12 18:33 ` Al Viro
2020-08-12 21:30 ` Al Viro
2020-08-18 9:41 ` Miklos Szeredi
2020-08-18 9:30 ` Miklos Szeredi
2020-08-12 15:22 ` David Howells
2020-08-11 21:20 ` Al Viro
2020-08-11 21:35 ` Casey Schaufler
2020-08-11 16:05 ` Al Viro
2020-08-11 16:09 ` Linus Torvalds
2020-08-11 16:39 ` Al Viro
2020-08-12 10:14 ` Karel Zak
2020-08-12 13:09 ` Miklos Szeredi
2020-08-12 13:33 ` David Howells
2020-08-12 13:54 ` Miklos Szeredi
2020-08-12 0:05 ` David Howells
2020-08-12 7:55 ` Miklos Szeredi
2020-08-12 8:29 ` David Howells
2020-08-12 8:37 ` Miklos Szeredi
2020-08-12 9:43 ` file metadata via fs API Steven Whitehouse
2020-08-12 10:04 ` Miklos Szeredi
2020-08-12 11:28 ` Karel Zak
2020-08-12 12:43 ` Miklos Szeredi
2020-08-13 8:52 ` Karel Zak
2020-08-12 13:06 ` David Howells
2020-08-13 1:01 ` Ian Kent
2020-08-12 18:18 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Linus Torvalds
2020-08-12 19:34 ` file metadata via fs API Steven Whitehouse
2020-08-12 19:50 ` Linus Torvalds
2020-08-13 3:44 ` Ian Kent
2020-08-13 10:36 ` Karel Zak
2020-08-14 7:58 ` Lennart Poettering
2020-08-17 11:32 ` Steven Whitehouse
2020-08-17 17:15 ` Linus Torvalds
2020-08-17 22:44 ` Linus Torvalds
2020-08-18 12:50 ` Miklos Szeredi
2020-08-18 18:51 ` Linus Torvalds
2020-08-18 20:18 ` Miklos Szeredi
2020-08-18 20:53 ` Linus Torvalds
2020-08-21 13:17 ` Miklos Szeredi
2020-08-19 2:29 ` Al Viro
2020-08-13 3:53 ` file metadata via fs API (was: [GIT PULL] Filesystem Information) Jeffrey E Altman
2020-08-14 17:05 ` Linus Torvalds
2020-08-18 15:01 ` Jeffrey E Altman
2020-08-14 8:06 ` Lennart Poettering
2020-08-12 13:54 ` David Howells
2020-08-12 14:10 ` Miklos Szeredi
2020-08-12 14:23 ` David Howells
2020-08-03 22:48 ` [GIT PULL] Mount notifications Ian Kent
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