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Re: [RFC PATCH 0/2] Union Mount: Directory listing in glibc
- From: "NAGABHUSHAN BS" <bsn dot 0007 at gmail dot com>
- To: "Jan Blunck" <jblunck at suse dot de>
- Cc: libc-alpha at sourceware dot org, "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>, "Ulrich Drepper" <drepper at redhat dot com>, "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>, bharata at linux dot vnet dot ibm dot com, "David Woodhouse" <dwmw2 at infradead dot org>
- Date: Wed, 30 Apr 2008 11:48:06 +0530
- Subject: Re: [RFC PATCH 0/2] Union Mount: Directory listing in glibc
- References: <20080429133201.GA9938@localhost.localdomain> <20080429160431.GY30780@bolzano.suse.de>
On Tue, Apr 29, 2008 at 9:34 PM, Jan Blunck <jblunck@suse.de> wrote:
> On Tue, Apr 29, bsn.0007@gmail.com wrote:
>
> > The RFC discussed about the information glibc readdir needs to get about
> > union mounted directories and I have assumed the following information
> > to be available from the kernel for this implementation.
> >
> > - Kernel would return all the dirents (including duplicates and whiteouts)
> > starting from the topmost directory of the union.
> >
> > - Indication that this directory is a union mounted directory
> > I have assumed that kernel would return a "." whiteout as the first
> > directory entry of the union. This would tell glibc readdir(3) that it is
> > working with a union mounted directory and it needs to do duplicate
> > elimination and whiteout suppression. It starts building a dirent cache
> > for this purpose.
>
> IIRC the intention was to emit a "." whiteout when "changing" from one
> directory to the next. That means when the first directory is completely read
> the whiteout is emitted. After that glibc knows to start duplicate
> removal.
>
Yes the intention was to get a "." whiteout when changing from one
directory to next and thats essentially what i have assumed, for
starting duplicate elimination.
Along with that i have also assumed to get a "." whiteout as the first
directory entry of the union, so as to indicate to glibc that the
directory is a union mounted directory.
Regards
Nagabhushan