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Re: Proposal: Improved locking implementation for fsfs

From: Peter N. Lundblad <peter_at_famlundblad.se>
Date: 2004-12-21 23:43:43 CET

On Tue, 20 Dec 2004 kfogel@collab.net wrote:

> "Brian W. Fitzpatrick" <fitz@collab.net> writes:
> > Variation A: The Hash/ASCII Experiment
> >
> > Summary: Force each path component to some 127bit ASCII representation
> > and store locks the filesystem under a lowercase "ASCII-ized" name.
> > Use a hash for names that can't be efficiently "ASCII-ized".
> >
> > Details:
> >
> > The path to a lock is broken into its components, and each path
> > component is translated into its lowercase ASCII equivalent (Using the
> > 4 character hex code) for non-ASCII characters. If the resulting
> > "ASCII-ized" string is both a)longer than 16 characters and b) greater
> > than 1.5x times the length of the original string, we fall back onto
> > the 16 byte MD5 hash as described in the main proposal.
>
> I like Variation A, despite its slightly greater complexity.
>
I don't think it is essential, since you can use grep for debugging, but
I'm not against it either. Just be careful with device names on Windows.
(See r9895).

> Note that since we have a collision-resolution mechanism anyway, we
> have some flexibility in our hash function. We needn't encode all
> non-ASCII as 4 character hex codes; we could encode them in some more
> friendly way. Specifically, for certain common non-ASCII characters
> (e.g., most of those representable in ISO-8859-*), we could use an
> encoding that reads more intuitively to a human:
>
Yes, we can, but I see even less value in this. You know, 8859-1 is common
in one part of the world... ASCII is ASCII, but going further becomes
quite arbitrary IMO

Regards,
//Peter

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Received on Tue Dec 21 23:43:40 2004

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