From: Al Viro <viro@zeniv.linux.org.uk>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Matthew Wilcox <willy@infradead.org>,
Dave Chinner <david@fromorbit.com>,
Christian Schoenebeck <qemu_oss@crudebyte.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Greg Kurz <groug@kaod.org>,
linux-fsdevel@vger.kernel.org,
Stefan Hajnoczi <stefanha@redhat.com>,
Miklos Szeredi <mszeredi@redhat.com>,
Vivek Goyal <vgoyal@redhat.com>,
Giuseppe Scrivano <gscrivan@redhat.com>,
Daniel J Walsh <dwalsh@redhat.com>,
Chirantan Ekbote <chirantan@chromium.org>
Subject: Re: xattr names for unprivileged stacking?
Date: Sat, 29 Aug 2020 19:04:48 +0100 [thread overview]
Message-ID: <20200829180448.GQ1236603@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAJfpegu2R21CF9PEoj2Cw6x01xmJ+qsff5QTcOcY4G5KEY3R0w@mail.gmail.com>
On Sat, Aug 29, 2020 at 07:51:47PM +0200, Miklos Szeredi wrote:
> On Sat, Aug 29, 2020 at 6:14 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > On Sat, Aug 29, 2020 at 05:07:17PM +0100, Matthew Wilcox wrote:
> >
>
> > > > The fact that ADS inodes would not be in the dentry cache and hence
> > > > not visible to pathwalks at all then means that all of the issues
> > > > such as mounting over them, chroot, etc don't exist in the first
> > > > place...
> > >
> > > Wait, you've now switched from "this is dentry cache infrastructure"
> > > to "it should not be in the dentry cache". So I don't understand what
> > > you're arguing for.
> >
> > Bloody wonderful, that. So now we have struct file instances with no dentry
> > associated with them? Which would have to be taken into account all over
> > the place...
>
> It could have a temporary dentry allocated for the lifetime of the
> file and dropped on last dput. I.e. there's a dentry, but no cache.
> Yeah, yeah, d_path() issues, however that one will have to be special
> cased anyway.
d_path() is the least of the problems, actually. Directory tree structure on
those, OTOH, is a serious problem. If you want to have getdents(2) on that
shite, you want an opened descriptor that looks like a directory. And _that_
opens a large can of worms. Because now you have fchdir(2) to cope with,
lookups going through /proc/self/fd/<n>/..., etc., etc.
Al, fully expecting "we'll special-case our way out of everything - how hard
could that be?" in response...
next prev parent reply other threads:[~2020-08-29 18:04 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 10:55 xattr names for unprivileged stacking? Dr. David Alan Gilbert
2020-07-28 13:08 ` Greg Kurz
2020-07-28 13:55 ` Christian Schoenebeck
2020-08-04 11:28 ` Dr. David Alan Gilbert
2020-08-04 13:51 ` Christian Schoenebeck
2020-08-12 11:18 ` Dr. David Alan Gilbert
2020-08-12 13:34 ` Christian Schoenebeck
2020-08-12 14:33 ` Dr. David Alan Gilbert
2020-08-13 9:01 ` Christian Schoenebeck
2020-08-16 22:56 ` Dave Chinner
2020-08-16 23:09 ` Matthew Wilcox
2020-08-17 0:29 ` Dave Chinner
2020-08-17 10:37 ` file forks vs. xattr (was: xattr names for unprivileged stacking?) Christian Schoenebeck
2020-08-23 23:40 ` Dave Chinner
2020-08-24 15:30 ` Christian Schoenebeck
2020-08-24 20:01 ` Miklos Szeredi
2020-08-24 21:26 ` Frank van der Linden
2020-08-24 22:29 ` Theodore Y. Ts'o
2020-08-25 15:12 ` Christian Schoenebeck
2020-08-25 15:32 ` Miklos Szeredi
2020-08-27 12:02 ` Christian Schoenebeck
2020-08-27 12:25 ` Matthew Wilcox
2020-08-27 13:48 ` Christian Schoenebeck
2020-08-27 14:01 ` Matthew Wilcox
2020-08-27 14:23 ` Christian Schoenebeck
2020-08-27 14:25 ` Matthew Wilcox
2020-08-27 14:44 ` Al Viro
2020-08-27 16:29 ` Dr. David Alan Gilbert
2020-08-27 16:35 ` Matthew Wilcox
2020-08-28 9:11 ` Christian Schoenebeck
2020-08-28 14:46 ` Theodore Y. Ts'o
2020-08-27 15:22 ` xattr names for unprivileged stacking? Matthew Wilcox
2020-08-27 22:24 ` Dave Chinner
2020-08-29 16:07 ` Matthew Wilcox
2020-08-29 16:13 ` Al Viro
2020-08-29 17:51 ` Miklos Szeredi
2020-08-29 18:04 ` Al Viro [this message]
2020-08-29 18:22 ` Christian Schoenebeck
2020-08-29 19:13 ` Miklos Szeredi
2020-08-29 19:25 ` Al Viro
2020-08-30 19:05 ` Miklos Szeredi
2020-08-30 19:10 ` Matthew Wilcox
2020-08-31 7:34 ` Miklos Szeredi
2020-08-31 11:37 ` Matthew Wilcox
2020-08-31 11:51 ` Miklos Szeredi
2020-08-31 13:23 ` Matthew Wilcox
2020-08-31 14:21 ` Miklos Szeredi
2020-08-31 14:25 ` Theodore Y. Ts'o
2020-08-31 14:45 ` Matthew Wilcox
2020-08-31 14:49 ` Miklos Szeredi
2020-09-01 3:34 ` Dave Chinner
2020-09-01 14:52 ` Theodore Y. Ts'o
2020-09-01 15:14 ` Theodore Y. Ts'o
2020-09-02 5:19 ` Dave Chinner
2020-08-31 18:02 ` Andreas Dilger
2020-09-01 3:48 ` Dave Chinner
2020-08-29 19:17 ` Matthew Wilcox
2020-08-29 19:40 ` Al Viro
2020-08-29 20:12 ` Matthew Wilcox
2020-08-31 14:23 ` Theodore Y. Ts'o
2020-08-31 14:40 ` Matthew Wilcox
2020-08-31 16:11 ` Christian Schoenebeck
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