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

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Message-ID: <Pine.LNX.4.61.0704101750420.21664@yvahk01.tjqt.qr>
Date:	Tue, 10 Apr 2007 17:54:54 +0200 (MEST)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.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>,
	Neil Brown <neilb@...e.de>
Subject: Re: If not readdir() then what?


On Apr 10 2007 10:37, Trond Myklebust wrote:
>
>NFS, OTOH, simply could not work without that requirement, since there
>exists no file pointer to tell you where you are in a stream beyond
>whatever the server manages to encode inside the opaque cookie+verifier.
>
>> But the fact of the matter is that if NFS protocols demands that a
>> per-directory entry cookie can be uniquely and permanently (including
>> across server reboots) identified with a small integer number, it's
>> dreaming.  Filesystem authors will cheat one way or another, because
>> there's nothing else for them to do.  
>
>Few people in the NFS community would disagree that the design of
>READDIR sucks (personally, I consider it to be one of the biggest
>scalability issues we have).
>The problem is that it is extremely hard to come up with an alternative
>that doesn't impose new conditions on what filesystems you can support.

I had a thought, but I think it's not quite ripe..

NFS server sends the whole directory contents on NFS client opendir,
so that the whole readdir/telldir/seekdir magic can happen on the
client only... which would perhaps also enable a cheap telldir/seekdir,
and would also give a 'fixed view' when adding/deleting files
during readdir.


Jan
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