JFFS2 an nodes checking

Artem B. Bityuckiy abityuckiy at yandex.ru
Tue Sep 28 13:15:46 EDT 2004



David Woodhouse wrote:
> Yeah, but we _know_ we're going to write to the flash when we write to
> regular files. That's not necessarily intuitively true for FIFOs. You
> expect your data to get to the other end of the FIFO... you don't
> necessarily expect anything to be written to the flash.
 >
Josh Boyer wrote:
 > Fifos don't really hold data, they are just named pipes.  When you write
 > to it, it's mostly handled by the VFS.  The actual data isn't written
 > out by JFFS2.  Except that we have to update st_ctime and st_mtime,
 > which causes more nodes.
Yes.. I thought in contents of the optimization I spoke about and tried 
to understand this problem in that context. I spoke about iget() delay. 
But the FIFO issue is another. Ok, thanks for reply!

David Woodhouse wrote:
 > On NOR we can scribble over the old nodes with the old mtime/ctime. On
 > NAND we can't so we end up with lots of nodes which are _potentially_
 > valid and which all have to be compared.
Josh Boyer wrote:
 > Because you can't directly obsolete a node on NAND flash (and some weird
 > versions of NOR flash as well).  So obsolete nodes are actually written
 > out to flash instead of just flipping a bit in the existing node.

Yes, I must have guess this myself. :-)

-- 
Best Regards,
Artem B. Bityuckiy,
St.-Petersburg, Russia.




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