From: Bernd Schubert <bernd-schubert@web.de>
Subject: Re: directory depth limit?
Date: Fri, 8 Aug 2003 09:48:58 +0200
Sender: nfs-admin@lists.sourceforge.net
Message-ID: <200308080948.59738.bernd-schubert@web.de>
References: <20030807205633.DC0861833A@zachs.place.org>
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To: Paul Jimenez <pj@place.org>,
 nfs@lists.sourceforge.net
In-Reply-To: <20030807205633.DC0861833A@zachs.place.org>
Errors-To: nfs-admin@lists.sourceforge.net

On Thursday 07 August 2003 22:56, Paul Jimenez wrote:
> Hi,
>
>   I'm using kernel 2.4.20 under debian stable ('woody') and the
> user-land nfs server, and I can't seem to traverse more than about 23 or
> 24 levels deep into a directory structure over NFS.  Works fine on a local
> ext2 or ext3 fs, but not when that fs is exported via the abovementioned
> userland server.  And it's definitely related to directory depth and
> not PATHLEN because it fails even with single-char directory names for
> the entire depth.  So is this limit on the client, the server, or in the
> protocol?  And is it a bug or just a design limit?
>
> Thanks for your help,
>

Hi,

nfsv2 (nfsv3 is not supported by unfsd!) only allows 32 byte to decode the 
entire nfs-filehandle, so if one would use the pathname encoded by characters 
this would fail rather fast. IMHO all nfs-server use the inodes for 
encrypting the path.
Well, unfsd has 28 bytes to encrypt the complete pathname via inodes (32 bit) 
and hashtable into those 28 bytes. I guess that you have reached the 
unfsd-limit.

The knfsd does different, as far as I understand it, the file handle only 
consist of the file inode, the inode of the parent directory, a file creation 
number and I think some other stuff. Anyway the 32 byte are sufficient here 
to encode the pathname. 

NFS-experts, please correct me if I'm wrong. Btw, I still don't understand how 
the knfs-algorithm works, if the dentry-cache has no information about 
parent-inode/inode (e.g. after a server reboot). How does the kernel figures 
out the proper path in that case?

Best regards,
	Bernd

PS: Paul, why do you insist on using unfsd. Knfsd does a much better job! 
Well, there are a few exception for using unfsd, ClusterNFS is one of them, 
but you have to be very carefull on using of it.


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