From: Miklos Szeredi <miklos@szeredi.hu>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Jann Horn <jannh@google.com>,
Casey Schaufler <casey@schaufler-ca.com>,
Andy Lutomirski <luto@amacapital.net>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
David Howells <dhowells@redhat.com>, 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>,
Lennart Poettering <lennart@poettering.net>,
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: Wed, 12 Aug 2020 17:13:14 +0200 [thread overview]
Message-ID: <CAJfpegsQF1aN4XJ_8j977rnQESxc=Kcn7Z2C+LnVDWXo4PKhTQ@mail.gmail.com> (raw)
In-Reply-To: <20200812150807.GR1236603@ZenIV.linux.org.uk>
On Wed, Aug 12, 2020 at 5:08 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Wed, Aug 12, 2020 at 04:46:20PM +0200, Miklos Szeredi wrote:
>
> > > "Can those suckers be passed to
> > > ...at() as starting points?
> >
> > No.
>
> Lovely. And what of fchdir() to those?
Not allowed.
> Are they all non-directories?
> Because the starting point of ...at() can be simulated that way...
>
> > > Can they be bound in namespace?
> >
> > No.
> >
> > > Can something be bound *on* them?
> >
> > No.
> >
> > > What do they have for inodes
> > > and what maintains their inumbers (and st_dev, while we are at
> > > it)?
> >
> > Irrelevant. Can be some anon dev + shared inode.
> >
> > The only attribute of an attribute that I can think of that makes
> > sense would be st_size, but even that is probably unimportant.
> >
> > > Can _they_ have secondaries like that (sensu Swift)?
> >
> > Reference?
>
> http://www.online-literature.com/swift/3515/
> So, naturalists observe, a flea
> Has smaller fleas that on him prey;
> And these have smaller still to bite 'em,
> And so proceed ad infinitum.
> of course ;-)
> IOW, can the things in those trees have secondary trees on them, etc.?
> Not "will they have it in your originally intended use?" - "do we need
> the architecture of the entire thing to be capable to deal with that?"
No.
>
> > > Is that a flat space, or can they be directories?"
> >
> > Yes it has a directory tree. But you can't mkdir, rename, link,
> > symlink, etc on anything in there.
>
> That kills the "shared inode" part - you'll get deadlocks from
> hell that way.
No. The shared inode is not for lookup, just for the open file.
> "Can't mkdir" doesn't save you from that. BTW,
> what of unlink()? If the tree shape is not a hardwired constant,
> you get to decide how it's initially populated...
>
> Next: what will that tree be attached to? As in, "what's the parent
> of its root"? And while we are at it, what will be the struct mount
> used with those - same as the original file, something different
> attached to it, something created on the fly for each pathwalk and
> lazy-umounted? And see above re fchdir() - if they can be directories,
> it's very much in the game.
Why does it have to have a struct mount? It does not have to use
dentry/mount based path lookup.
Thanks,
Miklos
next prev parent reply other threads:[~2020-08-12 15:13 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
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 [this message]
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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