JFFS2 OOPS in 2.6.20

Jörn Engel joern at lazybastard.org
Fri Mar 9 08:11:45 EST 2007

On Fri, 9 March 2007 11:56:20 +0100, Joakim Tjernlund wrote:
> Yeah, but I figured that changing seed was less intrusive. Not 
> sure how good Alder32 is but if we make an incompatible change we
> could change it to something else than crc32. We should measure if 
> how much faster Adler32 is first though.
> You think such a change is worthwhile?

Last time we discussed this, crc32 looked better.  It may be a bit
slower (not much, iirc), but it will catch _all_ 1-bit, 2-bit and 3-bit
errors and has a 1:2^32 change of missing n-bit errors with n>3.

Adler, if memory serves, can only guarantee all 1-bit errors and a
1:2^30 or so chance for n-bit errors, if the buffer is long enough.
"Long enough" is ~1000 bytes.  Below that, chances of getting false
positives are getting higher.

You can check the archives for this.  It might have been 2004 as well.


There are two ways of constructing a software design: one way is to make
it so simple that there are obviously no deficiencies, and the other is
to make it so complicated that there are no obvious deficiencies.
-- C. A. R. Hoare

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