From: Trond Myklebust <trond.myklebust@fys.uio.no>
To: Aurelien Degremont <aurelien.degremont@cea.fr>
Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, nfs@lists.sourceforge.net,
Jacques-Charles Lafoucriere <jc.lafoucriere@cea.fr>
Subject: Re: NFS superblock sharing implies mount flags bug
Date: Mon, 20 Mar 2006 13:05:46 -0500 [thread overview]
Message-ID: <1142877946.7991.2.camel@lade.trondhjem.org> (raw)
In-Reply-To: <441EAC05.7020903@cea.fr>
On Mon, 2006-03-20 at 14:20 +0100, Aurelien Degremont wrote:
> Nobody is interested by this issue ?
> It could be easily reproduced. All recent versions are concerned.
>
> Aurelien
Check the linux-fsdevel and lkml archives.
There has been plenty of work on this issue both by Herbert Poetzl and
(more recently) by Christoph Hellwig.
Cheers,
Trond
> Aurelien Degremont wrote:
> > Hello
> >
> > I'm facing incorrect using of mount flags when dealing with NFS mounts
> > and I think it could be seen as a bug.
> >
> > The error occurs when mounting the same NFS export many times, on the
> > same machine but *with different mount flags*, particularly concerning
> > RO/RW flags.
> >
> > As the NFS client code re-uses superblocks when it detects that it is
> > the same export (same server/same port/same exported directory) and that
> > the read-only flag is managed as a per-superblock flag, if a NFS exports
> > is mounted a second time, the superblock of the first mount is re-used
> > and the specified mount flag is ignored.
> >
> > # mount foo:/bar /bar_ro -o ro
> > # mount foo:/bar /bar_rw -o rw
> > $ touch /bar_rw/bar
> > touch: cannot touch `/bar_rw/bar': Read-only file system
> >
> > Ideally, the best solution to fix this is to move the RDONLY flag from
> > its per-superblock basis to a per-mountpoint (vfsmount) basis. I do not
> > know is there is a something that prevent that except that this implies
> > many changes as many codes do not use macros but access s_flags directly.
> >
> > It seems quite clear that the superblock sharing couldn't be changed (to
> > avoid incoherency, inode aliasing and so on...) ?
> >
> > Do you have a (better) solution ?
> > I can help if needed.
> >
> >
> > Cordially
> >
>
>
prev parent reply other threads:[~2006-03-20 18:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-03-15 10:37 NFS superblock sharing implies mount flags bug Aurelien Degremont
2006-03-20 13:20 ` Aurelien Degremont
2006-03-20 18:05 ` Trond Myklebust [this message]
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