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Date: Wed, 30 Apr 2008 11:37:10 +0530
From: "NAGABHUSHAN BS" <bsn.0007@gmail.com>
To: "Erez Zadok" <ezk@cs.sunysb.edu>
Subject: Re: [RFC PATCH 0/2] Union Mount: Directory listing in glibc
Cc: libc-alpha@sourceware.org, "Jan Blunck" <jblunck@suse.de>,
       linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
       viro@zeniv.linux.org.uk, "Christoph Hellwig" <hch@lst.de>,
       "Ulrich Drepper" <drepper@redhat.com>, "Mingming Cao" <cmm@us.ibm.com>,
       "Dave Hansen" <haveblue@us.ibm.com>,
       "Trond Myklebust" <trond.myklebust@fys.uio.no>,
       bharata@linux.vnet.ibm.com, "David Woodhouse" <dwmw2@infradead.org>
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On Tue, Apr 29, 2008 at 9:19 PM, Erez Zadok <ezk@cs.sunysb.edu> wrote:
> In message <20080429133201.GA9938@localhost.localdomain>, bsn.0007@gmail.com writes:
>  > Hi,
>  >
>  > I went through Bharata's RFC post on glibc based Union Mount readdir solution
>  > (http://lkml.org/lkml/2008/3/11/34) and have come up with patches
>  > against glibc to implement the same.
>  [...]
>
>  The last set of discussions on glibc support ended, as I understood it, with
>  the glibc people objecting to such "special-purpose" code in glibc.  See
>  <http://lkml.org/lkml/2008/3/11/66>.  So has anything changed behind the
>  scenes, or is this idea unlikely to be merged into glibc any time soon, if
>  ever.  (Personally I'd love to rip out the readdir-related code from unionfs
>  if glibc supported the same.)
>
>
>  > Patch 1. readdir support for union mounted directories.
>  >       I am caching the dirent names in a list to aid duplicate elimination.
>  > And this cache is stored in DIRP. For duplicate elimination I am using
>  > strcmp(). I am not sure if this works universally with different types
>  > of filesystems. Any suggestions here would be welcome.
>  [...]
>
>  You might consider using a hash table instead of a list; it'll be faster in
>  case where there are a lot of whiteouts/duplicates to process.
>

Yes, hash table was one of the things i had considered  to use as a
cache. But i am not completely sure how this would support seekdir.
Any suggestions are greatly welcome.

Regards Nagabhushan