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From: Christian Schoenebeck <qemu_oss@crudebyte.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	Frank van der Linden <fllinden@amazon.com>,
	Dave Chinner <david@fromorbit.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: file forks vs. xattr (was: xattr names for unprivileged stacking?)
Date: Thu, 27 Aug 2020 15:48:57 +0200	[thread overview]
Message-ID: <3331978.UQhOATu6MC@silver> (raw)
In-Reply-To: <20200827122555.GD14765@casper.infradead.org>

On Donnerstag, 27. August 2020 14:25:55 CEST Matthew Wilcox wrote:
> On Thu, Aug 27, 2020 at 02:02:42PM +0200, Christian Schoenebeck wrote:
> > What I could imagine as delimiter instead; slash-caret:
> >     /var/foo.pdf/^/forkname
> 
> Any ascii character is going to be used in some actual customer workload.

Not exactly. "/foo/^/bar" is already a valid path today. So every Linux system 
(incl. all libs/apps) must be capable to deal with that path already, so it 
would not introduce a tokenization problem.

The caret character is not reserved by any filesystem either:
https://en.wikipedia.org/wiki/Filename

The only change a caret delimiter would bring, is a very minor change in 
semantic: apps would no longer be allowed to create dirs/files named exactly 
"^". But I find that a very small restriction compared to the negative impact 
of other delimiter options, i.e.:

	touch /some/where/^          # error if forks enabled, OK otherwise
	touch /some/where/^whatever  # always OK

So if you have apps that need to access dirs/files called *exactly* "^", that 
would be easy to fix. And if you don't want to, you just keep kernel's support 
for forks disabled and preserve old semantic of "^".

> I suggest we use a unicode character instead.
> 
> /var/foo.pdf/💩/badidea

Like I mentioned before, if you'd pick a unicode character (or binary), then 
each shell will map their own ASCII-sequence on top of that. Because shell 
users want ASCII. Which would defeat the primary purpose: a unified path 
resolution.

Then even if you'd pick unicode, that would raise new questions and problems; 
e.g. utf-8, utf-16, utf-32? Character normalization required? How do you 
ensure each layer will use the same encoding?

Best regards,
Christian Schoenebeck



  reply	other threads:[~2020-08-27 14:11 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 [this message]
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
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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