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Re: [PATCH 3/9] VFS: Introduce a mount context

From Miklos Szeredi <mszeredi@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH 3/9] VFS: Introduce a mount context
Date 2017-05-09 14:40 +0200
Message-ID <tFcAP-1J6-33@gated-at.bofh.it> (permalink)
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On Tue, May 9, 2017 at 11:56 AM, David Howells <dhowells@redhat.com> wrote:
> Miklos Szeredi <mszeredi@redhat.com> wrote:
>
>> So say we have commands like
>>
>> "o+ foo"
>> "o- bar"
>
> The convention seems to be to prepend "no" to things you want to disable, so
> let's stick with that, e.g.:
>
>         "o foo"
>         "o nobar"
>
> otherwise we will have to have separate parsers for old mount() and the new sb
> config code - and not just for NFS, but at least for ext2/3/4 also.
>
> Further, we can only publish one format in /proc/mounts - and we cannot change
> that from the foo/nofoo standard we already use as it's part of the UAPI.

You're right, that this is a complicated issue and worth more
discussion.  And also you are right that we cannot change existing
UAPI, which is going to cause some headaches.

But that doesn't mean the new UAPI must follow the conventions of the
badly defined existing UAPI.

And the "no*" convention is anything but well defined, so we cannot
just stick it into generic code, because you'll find exceptions
everywhere.

And one more reason to have a new, unambiguous UAPI for retrieving
superblock options.

>
>> The generic option parser would just add or remove the option in the
>> current set of options,
>
> It sounds like you want to build up a string of "opt1,opt2,opt3" then have the
> VFS add and remove things from it and then parse it into the filesystem's
> internal structures on "commit".

That would be the default operation, if the filesystem doesn't define
its own parser.

>> and commit would just call ->remount_fs() with the new set of options.
>
> You're defining "commit" to do different things depending on the situation.
> You need a separation between "commit create" and "commit update".

It would be different, yes, at least until the superblock creation api
is completely transformed, at which point it may actually become the
same thing.  But lets not jump ahead.

>> It would probably not work for the NFS case, but that's okay, NFS can
>> implement its own option parsing.
>
> If NFS has to implement its own option parsing, we've done it wrong.

My above sentence was not clear.  What I meant to say that NFS needs
to implement the non-generic option parsing function in order to be
able to handle the case of "you can't change the server IP address".
Which it would want to do anyway, since it will result in cleaner
code.

Thanks,
Miklos

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Thread

[RFC][PATCH 0/9] VFS: Introduce mount context David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
  [PATCH 1/9] Provide a function to create a NUL-terminated string  from unterminated data David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
    Re: [PATCH 1/9] Provide a function to create a NUL-terminated  string from unterminated data Jeff Layton <jlayton@poochiereds.net> - 2017-05-03 19:00 +0200
    Re: [PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2017-05-03 21:30 +0200
      Re: [PATCH 1/9] Provide a function to create a NUL-terminated string from unterminated data David Howells <dhowells@redhat.com> - 2017-05-03 22:20 +0200
  [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
    Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Jeff Layton <jlayton@poochiereds.net> - 2017-05-03 20:40 +0200
      Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-03 20:50 +0200
    Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2017-05-03 22:50 +0200
      Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-04 15:00 +0200
      Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-04 15:00 +0200
    Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Karel Zak <kzak@redhat.com> - 2017-05-04 12:50 +0200
      Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-04 15:10 +0200
        Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Karel Zak <kzak@redhat.com> - 2017-05-04 15:40 +0200
          Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Jeff Layton <jlayton@redhat.com> - 2017-05-09 20:50 +0200
    Re: [PATCH 4/9] Implement fsopen() to prepare for a mount Miklos Szeredi <mszeredi@redhat.com> - 2017-05-08 17:20 +0200
      Re: [PATCH 4/9] Implement fsopen() to prepare for a mount David Howells <dhowells@redhat.com> - 2017-05-09 01:20 +0200
  [PATCH 5/9] Implement fsmount() to effect a pre-configured mount David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
  [PATCH 2/9] Clean up whitespace in fs/namespace.c David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
  [PATCH 8/9] proc: Support the mount context in procfs David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
  [PATCH 7/9] procfs: Move proc_fill_super() to fs/proc/root.c David Howells <dhowells@redhat.com> - 2017-05-03 18:10 +0200
  Re: [RFC][PATCH 0/9] VFS: Introduce mount context Jeff Layton <jlayton@poochiereds.net> - 2017-05-03 18:50 +0200
    Re: [RFC][PATCH 0/9] VFS: Introduce mount context David Howells <dhowells@redhat.com> - 2017-05-03 19:00 +0200
      Re: [RFC][PATCH 0/9] VFS: Introduce mount context Jeff Layton <jlayton@poochiereds.net> - 2017-05-03 19:30 +0200
  Re: [PATCH 3/9] VFS: Introduce a mount context Joe Perches <joe@perches.com> - 2017-05-03 20:30 +0200
    Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-03 20:40 +0200
      Re: [PATCH 3/9] VFS: Introduce a mount context Joe Perches <joe@perches.com> - 2017-05-03 20:50 +0200
        Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-03 22:20 +0200
    Re: [PATCH 3/9] VFS: Introduce a mount context Matthew Wilcox <willy@infradead.org> - 2017-05-03 22:40 +0200
      Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-03 23:20 +0200
      Re: [PATCH 3/9] VFS: Introduce a mount context Joe Perches <joe@perches.com> - 2017-05-03 23:40 +0200
        Re: [PATCH 3/9] VFS: Introduce a mount context Julia Lawall <julia.lawall@lip6.fr> - 2017-05-04 08:30 +0200
    Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-04 11:30 +0200
      Re: [PATCH 3/9] VFS: Introduce a mount context Joe Perches <joe@perches.com> - 2017-05-04 16:40 +0200
  Re: [PATCH 3/9] VFS: Introduce a mount context Rasmus Villemoes <linux@rasmusvillemoes.dk> - 2017-05-03 23:50 +0200
    Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-04 12:30 +0200
  Re: [RFC][PATCH 0/9] VFS: Introduce mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-05 16:40 +0200
    Re: [RFC][PATCH 0/9] VFS: Introduce mount context David Howells <dhowells@redhat.com> - 2017-05-05 17:50 +0200
      Re: [RFC][PATCH 0/9] VFS: Introduce mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-08 10:30 +0200
      Re: [RFC][PATCH 0/9] VFS: Introduce mount context David Howells <dhowells@redhat.com> - 2017-05-08 10:40 +0200
        Re: [RFC][PATCH 0/9] VFS: Introduce mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-08 10:50 +0200
  Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-08 17:10 +0200
    Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-09 01:00 +0200
      Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-09 10:10 +0200
        Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-09 11:40 +0200
          Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-09 13:10 +0200
        Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-09 11:50 +0200
          Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-09 14:10 +0200
            Re: [PATCH 3/9] VFS: Introduce a mount context Jeff Layton <jlayton@redhat.com> - 2017-05-09 21:00 +0200
              Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-10 09:30 +0200
                Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-10 10:10 +0200
                Re: [PATCH 3/9] VFS: Introduce a mount context Jeff Layton <jlayton@redhat.com> - 2017-05-10 15:30 +0200
                Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-10 15:40 +0200
                Re: [PATCH 3/9] VFS: Introduce a mount context Jeff Layton <jlayton@redhat.com> - 2017-05-10 15:40 +0200
                Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-10 15:40 +0200
                Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-10 15:40 +0200
                Re: [PATCH 3/9] VFS: Introduce a mount context Jeff Layton <jlayton@redhat.com> - 2017-05-10 15:50 +0200
        Re: [PATCH 3/9] VFS: Introduce a mount context David Howells <dhowells@redhat.com> - 2017-05-09 12:00 +0200
          Re: [PATCH 3/9] VFS: Introduce a mount context Miklos Szeredi <mszeredi@redhat.com> - 2017-05-09 14:40 +0200
        Re: [PATCH 3/9] VFS: Introduce a mount context Karel Zak <kzak@redhat.com> - 2017-05-10 14:50 +0200
  Re: [RFC][PATCH 0/9] VFS: Introduce mount context Djalal Harouni <tixxdz@gmail.com> - 2017-05-08 19:10 +0200

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