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Subject: Re: Reconsidering exportable UBIFS
From: Artem Bityutskiy <dedekind1@gmail.com>
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To: Richard Weinberger <richard@nod.at>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
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	Christoph Hellwig <hch@infradead.org>
Date: Mon, 18 Apr 2016 12:04:26 +0300
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On Tue, 2016-04-05 at 00:17 +0200, Richard Weinberger wrote:
> The biggest problem I see is that UBIFS does not really support
> telldir()
> and seekdir().
> Directory offsets in UBIFS are plain hash values, so
> telldir()/seekdir() won't
> correctly work if UBIFS faces hash collisions.
> Currently UBIFS implements a hack which stores the UBIFS dent object
> into
> file->private_data such that consecutive readdir()s are guaranteed to
> work.
> A comment on UBIFS's readdir states:
>  * This means that UBIFS cannot support NFS which requires full
>  * 'seekdir()'/'telldir()' support.

Richard, I do not remember much about NFS support. I can only say that
I never really put efforts into this, unfortunately.
Here is an old discussion which could give you some more hints:

http://marc.info/?l=linux-nfsv4&m=126480082613293&w=2

Artem.