linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
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: Tue, 18 Aug 2020 11:41:29 +0200	[thread overview]
Message-ID: <CAJfpeguyQhfxrSnaH1mZkncgfiLFB2yM2ZgdMBzuhAdKdmmuxA@mail.gmail.com> (raw)
In-Reply-To: <20200812213041.GV1236603@ZenIV.linux.org.uk>

On Wed, Aug 12, 2020 at 11:30 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> On Wed, Aug 12, 2020 at 07:33:26PM +0100, Al Viro wrote:
>
> > BTW, what would such opened files look like from /proc/*/fd/* POV?  And
> > what would happen if you walk _through_ that symlink, with e.g. ".."
> > following it?  Or with names of those attributes, for that matter...
> > What about a normal open() of such a sucker?  It won't know where to
> > look for your ->private_data...
> >
> > FWIW, you keep refering to regularity of this stuff from the syscall
> > POV, but it looks like you have no real idea of what subset of the
> > things available for normal descriptors will be available for those.
>
> Another question: what should happen with that sucker on umount of
> the filesystem holding the underlying object?  Should it be counted
> as pinning that fs?

Obviously yes.

> Who controls what's in that tree?

It could be several entities:

 - global (like mount info)
 - per inode (like xattr)
 - per fs (fs specific inode attributes)
 - etc..

>  If we plan to have xattrs there,
> will they be in a flat tree, or should it mirror the hierarchy of
> xattrs?  When is it populated?  open() time?  What happens if we
> add/remove an xattr after that point?

From the interface perspective it would be dynamic (i.e. would get
updated on open or read).  From an implementation POV it could have
caching, but that's not how I'd start out.

> If we open the same file several times, what should we get?  A full
> copy of the tree every time, with all coherency being up to whatever's
> putting attributes there?
>
> What are the permissions needed to do lookups in that thing?

That would depend on what would need to be looked up.  Top level would
be world readable, otherwise it would be up to the attribute/group.

>
> All of that is about semantics and the answers are needed before we
> start looking into implementations.  "Whatever my implementation
> does" is _not_ a good way to go, especially since that'll be cast
> in stone as soon as API becomes exposed to userland...

Fine.

Thanks,
Miklos

  reply	other threads:[~2020-08-18  9:41 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
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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAJfpeguyQhfxrSnaH1mZkncgfiLFB2yM2ZgdMBzuhAdKdmmuxA@mail.gmail.com \
    --to=miklos@szeredi.hu \
    --cc=casey@schaufler-ca.com \
    --cc=christian@brauner.io \
    --cc=dhowells@redhat.com \
    --cc=jannh@google.com \
    --cc=jlayton@redhat.com \
    --cc=kzak@redhat.com \
    --cc=lennart@poettering.net \
    --cc=linux-api@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-security-module@vger.kernel.org \
    --cc=luto@amacapital.net \
    --cc=mszeredi@redhat.com \
    --cc=nicolas.dichtel@6wind.com \
    --cc=raven@themaw.net \
    --cc=torvalds@linux-foundation.org \
    --cc=viro@zeniv.linux.org.uk \
    --subject='Re: file metadata via fs API (was: [GIT PULL] Filesystem Information)' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).