linux-kernel - Re: If not readdir() then what?

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Message-ID: <17948.916.464492.881283@notabene.brown>
Date:	Wed, 11 Apr 2007 07:37:24 +1000
From:	Neil Brown <neilb@...e.de>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Theodore Tso <tytso@....edu>,
	Jörn Engel <joern@...ybastard.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Christoph Hellwig <hch@...radead.org>,
	Ulrich Drepper <drepper@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: If not readdir() then what?

On Tuesday April 10, trond.myklebust@....uio.no wrote:
> On Wed, 2007-04-11 at 07:12 +1000, Neil Brown wrote:
> > 
> > Is there something that makes that interface problematic?
> 
> File deletions...

How are they a problem ?

There are only two ways to organise a directory.
1/ Unsorted linear list of entries in which no repacking is ever done.
2/ Some data structure using an ordered search key that is based on
  the filename (e.g. a B-tree with a search key that is a hash of the
  filename). 

In the first case, you just use a fixed opaque cookie for location in
a directory.
In the second you use the filename.  If the file has been deleted,
that shouldn't stop you finding the place where it would have been in
the overall sort order.

NeilBrown
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