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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