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JFFS2 not compressing things in 2.4.17 kernels?

To: linux-mips@oss.sgi.com
Subject: JFFS2 not compressing things in 2.4.17 kernels?
From: Stewart Brodie <stewart.brodie@pace.co.uk>
Date: Mon, 22 Jul 2002 11:40:50 +0100
Organization: Pace Micro Technology plc
Sender: owner-linux-mips@oss.sgi.com
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I have been having problems with mkfs.jffs2 (with the fs/jffs2 files from a
2.4.17 kernel) not compressing files as it constructs the filesystem image. 
I have no idea whether this will affect the run-time behaviour or not - I've
not got that far.  After inserting debugging into the compression routines,
it appears that streaming errors are occurring when the data is being passed
through zlib, and thus the simple rtime compression is being used instead.

It looks like mkfs.jffs2 is driving zlib's compression routines in a bizarre
way (c.f. the decompression which uses a trivial loop) passing only small
blocks of data at a time.  Is that loop correct?  Why is Z_PARTIAL_FLUSH
being used?  The errors I get are all "final deflate returned -2".

Any ideas?

-- 
Stewart Brodie, Senior Software Engineer
Pace Micro Technology PLC
645 Newmarket Road
Cambridge, CB5 8PB, United Kingdom         WWW: http://www.pacemicro.com/


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