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Re: [PATCH 4/9] Implement fsopen() to prepare for a mount

From David Howells <dhowells@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH 4/9] Implement fsopen() to prepare for a mount
Date 2017-05-04 15:10 +0200
Message-ID <tDoG5-3Su-7@gated-at.bofh.it> (permalink)
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Karel Zak <kzak@redhat.com> wrote:

> > 	write(mfd, "d /dev/sdb1"); // note I'm ignoring write's length arg
> 
> Not sure about 'd', in many cases it is not device, for mount(2)
> syscall we call it "source".

sys_mount() calls it devname.  But whatever - I'm not particularly attached to
the letter 'd' for this.

> The very basic mount(2) problem is that you have to parse
> /proc/self/mountinfo to get information about the mounted filesystem.
> It seems that your read() is also one way communication.
> 
> What we really need is to have a way how to specify *what* you want to
> read. The error message is not enough, I want to know the finally used
> mount options, mount ID, etc. It would be nice to have something like
> 
> 
>    fsmount(mfd, AT_FDCWD, "/mnt", 0);
> 
>    write(mfd, "o");
>    read(mfd, ....);     // read mount options
> 
>    write(mdf, "i");
>    read(mfd, ....);     // read mount ID
> 
> 
> but it seems ugly. Maybe introduce another function like 
> 
>     fsinfo(mdf, "o", buf, bufsz)
> 
> to get mount options (etc.) and to avoid separate write & read.

What is it you're trying to do?  Just read back the state of the new mount?
Or read back the state of a specified extant mount?

David

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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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