Re: [PATCH 2.6.21] cramfs: add cramfs Linear XIP

On Thu, Jun 07, 2007 at 02:11:44PM -0700, Jared Hulbert wrote:
that even more important doesn't require pulling in
the whole block layer which is especially important for embedded
devices at the lower end of the scala.

Good point. That is a big oversight. Though I would prefer to handle
that in the same fs rather than fork.

If if were actually talking about complex filesystem I'd agree. But
the cramfs xip patch posted here touches about 2/3 of the number of
lines that cramfs has in total. And cramfs is not exactly the best
base to start with..

I still think it'd be even better to just
hook xip support into jffs or logfs because they give you a full
featured flash filesystem for all needs without the complexity
of strictly partitioning between xip-capable and write parts
of your storage.

This is nirvana. But it is not the goal of the patches in question.
In fact there are several use cases that don't need and don't value
the writeability and don't need therefore the overhead. It is a long
term goal never the less.

With the filemap_xip.c helpers adding xip support to any filesystem
is pretty trivial for the highlevel filesystem operations. The only
interesting bit is the lowlevel code (the get_xip_page method and
the others Carsten mentioned), but we need to do these lowlevel
code in a generic and proper way anyway.

I'll try to hack up an xip prototype for jffs2 next week.
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