Wear Leveling in JFFS2 NOT working!(?)

David Woodhouse dwmw2 at infradead.org
Tue May 1 03:21:16 EDT 2001

Tim at Rikers.org said:
> Providing n is random, this is a good solution. Can the list be hacked
> to change the top/bottom without actually walking through n blocks and
> moving them? I have not looked at the source, but for a linked list
> you could join top and bottom entries and then break n and n-1 nodes
> and start becomes n, end becomes n-1, etc.

Yep, hacking the list is fairly easy. Coming up with a pseudo-random number 
of reasonable quality at boot time when the entropy pool is empty is the 
more interesting bit. The 'jiffies mod' trick would give repeatable

Just to restate the obvious - it doesn't have to be _random_, just evenly 

> This will still be somewhat pattern oriented. last blocks scanned will
> be either at front or back so I suspect wear numbers will increase
> towards the end of scanned blocks. ie: first scanned blocks would never
> be on the end of the dirty list.



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