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Re: [RFC PATCH 1/2] Union Mount: glibc readdir support
- From: Bharata B Rao <bharata at linux dot vnet dot ibm dot com>
- To: David Newall <davidn at davidnewall dot com>
- Cc: Ulrich Drepper <drepper at redhat dot com>, bsn dot 0007 at gmail dot com, libc-alpha at sourceware dot org, Jan Blunck <jblunck at suse dot de>, Erez Zadok <ezk at cs dot sunysb dot edu>, linux-kernel at vger dot kernel dot org, linux-fsdevel at vger dot kernel dot org, viro at zeniv dot linux dot org dot uk, Christoph Hellwig <hch at lst dot de>, Mingming Cao <cmm at us dot ibm dot com>, Dave Hansen <haveblue at us dot ibm dot com>, Trond Myklebust <trond dot myklebust at fys dot uio dot no>, David Woodhouse <dwmw2 at infradead dot org>
- Date: Mon, 12 May 2008 09:13:41 +0530
- Subject: Re: [RFC PATCH 1/2] Union Mount: glibc readdir support
- References: <20080429133201.GA9938@localhost.localdomain> <20080429133346.GB9938@localhost.localdomain> <48195E69.3030701@redhat.com> <20080506042117.GA29298@in.ibm.com> <482058C4.8010104@davidnewall.com>
- Reply-to: bharata at linux dot vnet dot ibm dot com
On Tue, May 06, 2008 at 10:40:28PM +0930, David Newall wrote:
> Bharata B Rao wrote:
> > Is dis-allowing NFS-exporting of unions an option ?
>
> Is it that simple? What about a union further in an NFS export? What
> about union-mounting after the tree has been NFS-exported?
Ok I am realizing that it is not simple. I am actually reading up NFS
code to understand how it supports crossing of mountpoints. I see that
one can mount a filesystem within a NFS export and NFS server would be
able to cross over to that filesystem and provide those contents to the
client. Acutally Union Mount maintains union stack very similar to the
mount stack, but here we walk the union stack down. So I am checking if
something similar to mountpoint crossing would be able to solve the
problem of fetching all the contents of the NFS-exported union.
Answering my question to Erez that I raised in another thread, I see
that Unionfs doesn't set the export_operations in it's superblock and
hence I believe unions created by Unionfs aren't NFS-exportable as of
know. Erez, correct me if I got it wrong.
Regards,
Bharata.